1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
4 @c Free Software Foundation, Inc.
5 @c UPDATE!! On future updates--
6 @c (1) check for new machine-dep cmdline options in
7 @c md_parse_option definitions in config/tc-*.c
8 @c (2) for platform-specific directives, examine md_pseudo_op
10 @c (3) for object-format specific directives, examine obj_pseudo_op
12 @c (4) portable directives in potable[] in read.c
16 @macro gcctabopt{body}
19 @c defaults, config file may override:
22 @include asconfig.texi
27 @c Configure for the generation of man pages
64 @c common OR combinations of conditions
84 @set abnormal-separator
88 @settitle Using @value{AS}
91 @settitle Using @value{AS} (@value{TARGET})
93 @setchapternewpage odd
98 @c WARE! Some of the machine-dependent sections contain tables of machine
99 @c instructions. Except in multi-column format, these tables look silly.
100 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
101 @c the multi-col format is faked within @example sections.
103 @c Again unfortunately, the natural size that fits on a page, for these tables,
104 @c is different depending on whether or not smallbook is turned on.
105 @c This matters, because of order: text flow switches columns at each page
108 @c The format faked in this source works reasonably well for smallbook,
109 @c not well for the default large-page format. This manual expects that if you
110 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
111 @c tables in question. You can turn on one without the other at your
112 @c discretion, of course.
115 @c the insn tables look just as silly in info files regardless of smallbook,
116 @c might as well show 'em anyways.
122 * As: (as). The GNU assembler.
123 * Gas: (as). The GNU assembler.
132 This file documents the GNU Assembler "@value{AS}".
134 @c man begin COPYRIGHT
135 Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002 Free Software Foundation, Inc.
137 Permission is granted to copy, distribute and/or modify this document
138 under the terms of the GNU Free Documentation License, Version 1.1
139 or any later version published by the Free Software Foundation;
140 with no Invariant Sections, with no Front-Cover Texts, and with no
141 Back-Cover Texts. A copy of the license is included in the
142 section entitled "GNU Free Documentation License".
147 Permission is granted to process this file through Tex and print the
148 results, provided the printed document carries copying permission
149 notice identical to this one except for the removal of this paragraph
150 (this paragraph not being relevant to the printed manual).
156 @title Using @value{AS}
157 @subtitle The @sc{gnu} Assembler
159 @subtitle for the @value{TARGET} family
162 @subtitle Version @value{VERSION}
165 The Free Software Foundation Inc. thanks The Nice Computer
166 Company of Australia for loaning Dean Elsner to write the
167 first (Vax) version of @command{as} for Project @sc{gnu}.
168 The proprietors, management and staff of TNCCA thank FSF for
169 distracting the boss while they got some work
172 @author Dean Elsner, Jay Fenlason & friends
176 \hfill {\it Using {\tt @value{AS}}}\par
177 \hfill Edited by Cygnus Support\par
179 %"boxit" macro for figures:
180 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
181 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
182 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
183 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
184 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
187 @vskip 0pt plus 1filll
188 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002 Free Software Foundation, Inc.
190 Permission is granted to copy, distribute and/or modify this document
191 under the terms of the GNU Free Documentation License, Version 1.1
192 or any later version published by the Free Software Foundation;
193 with no Invariant Sections, with no Front-Cover Texts, and with no
194 Back-Cover Texts. A copy of the license is included in the
195 section entitled "GNU Free Documentation License".
201 @top Using @value{AS}
203 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}} version
206 This version of the file describes @command{@value{AS}} configured to generate
207 code for @value{TARGET} architectures.
210 This document is distributed under the terms of the GNU Free
211 Documentation License. A copy of the license is included in the
212 section entitled "GNU Free Documentation License".
215 * Overview:: Overview
216 * Invoking:: Command-Line Options
218 * Sections:: Sections and Relocation
220 * Expressions:: Expressions
221 * Pseudo Ops:: Assembler Directives
222 * Machine Dependencies:: Machine Dependent Features
223 * Reporting Bugs:: Reporting Bugs
224 * Acknowledgements:: Who Did What
225 * GNU Free Documentation License:: GNU Free Documentation License
233 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
235 This version of the manual describes @command{@value{AS}} configured to generate
236 code for @value{TARGET} architectures.
240 @cindex invocation summary
241 @cindex option summary
242 @cindex summary of options
243 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
244 @pxref{Invoking,,Command-Line Options}.
246 @c man title AS the portable GNU assembler.
250 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
254 @c We don't use deffn and friends for the following because they seem
255 @c to be limited to one line for the header.
257 @c man begin SYNOPSIS
258 @value{AS} [@b{-a}[@b{cdhlns}][=@var{file}]] [@b{-D}] [@b{--defsym} @var{sym}=@var{val}]
259 [@b{-f}] [@b{--gstabs}] [@b{--gdwarf2}] [@b{--help}] [@b{-I} @var{dir}]
260 [@b{-J}] [@b{-K}] [@b{-L}]
261 [@b{--listing-lhs-width}=@var{NUM}] [@b{--listing-lhs-width2}=@var{NUM}]
262 [@b{--listing-rhs-width}=@var{NUM}] [@b{--listing-cont-lines}=@var{NUM}]
263 [@b{--keep-locals}] [@b{-o} @var{objfile}] [@b{-R}] [@b{--statistics}] [@b{-v}]
264 [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}] [@b{--fatal-warnings}]
265 [@b{-w}] [@b{-x}] [@b{-Z}] [@b{--target-help}] [@var{target-options}]
266 [@b{--}|@var{files} @dots{}]
268 @c Target dependent options are listed below. Keep the list sorted.
269 @c Add an empty line for separation.
271 @c am29k has no machine-dependent assembler options
275 @emph{Target Alpha options:}
277 [@b{-mdebug} | @b{-no-mdebug}]
278 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
279 [@b{-F}] [@b{-32addr}]
283 @emph{Target ARC options:}
289 @emph{Target ARM options:}
290 @c Don't document the deprecated options
291 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
292 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
293 [@b{-mfpu}=@var{floating-point-fromat}]
296 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
297 @b{-mapcs-reentrant}]
298 [@b{-mthumb-interwork}] [@b{-moabi}] [@b{-k}]
302 @emph{Target CRIS options:}
303 [@b{--underscore} | @b{--no-underscore}]
305 [@b{--emulation=criself} | @b{--emulation=crisaout}]
306 @c Deprecated -- deliberately not documented.
311 @emph{Target D10V options:}
316 @emph{Target D30V options:}
317 [@b{-O}|@b{-n}|@b{-N}]
320 @c Hitachi family chips have no machine-dependent assembler options
323 @c HPPA has no machine-dependent assembler options (yet).
327 @emph{Target i386 options:}
332 @emph{Target i960 options:}
333 @c see md_parse_option in tc-i960.c
334 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
336 [@b{-b}] [@b{-no-relax}]
340 @emph{Target IA-64 options:}
341 [@b{-mconstant-gp}|@b{-mauto-pic}]
342 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
344 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
348 @emph{Target IP2K options:}
349 [@b{-mip2022}|@b{-mip2022ext}]
353 @emph{Target M32R options:}
354 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
359 @emph{Target M680X0 options:}
360 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
364 @emph{Target M68HC11 options:}
365 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}]
366 [@b{-mshort}|@b{-mlong}]
367 [@b{-mshort-double}|@b{-mlong-double}]
368 [@b{--force-long-branchs}] [@b{--short-branchs}]
369 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
370 [@b{--print-opcodes}] [@b{--generate-example}]
374 @emph{Target MCORE options:}
375 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
376 [@b{-mcpu=[210|340]}]
380 @emph{Target MIPS options:}
381 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-n}] [@b{-O}[@var{optimization level}]]
382 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
383 [@b{-non_shared}] [@b{-xgot}] [@b{--membedded-pic}]
384 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
385 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
386 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
388 [@b{-construct-floats}] [@b{-no-construct-floats}]
389 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
390 [@b{-mfix7000}] [@b{-mno-fix7000}]
391 [@b{-mips16}] [@b{-no-mips16}]
392 [@b{-mips3d}] [@b{-no-mips3d}]
393 [@b{-mdmx}] [@b{-no-mdmx}]
394 [@b{-mdebug}] [@b{-no-mdebug}]
398 @emph{Target MMIX options:}
399 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
400 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
401 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
402 [@b{--linker-allocated-gregs}]
406 @emph{Target PDP11 options:}
407 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
408 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
409 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
413 @emph{Target picoJava options:}
418 @emph{Target PowerPC options:}
419 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|
420 @b{-m403}|@b{-m405}|@b{-mppc64}|@b{-m620}|@b{-mppc64bridge}|@b{-mbooke}|
421 @b{-mbooke32}|@b{-mbooke64}]
422 [@b{-mcom}|@b{-many}|@b{-maltivec}] [@b{-memb}]
423 [@b{-mregnames}|@b{-mno-regnames}]
424 [@b{-mrelocatable}|@b{-mrelocatable-lib}]
425 [@b{-mlittle}|@b{-mlittle-endian}|@b{-mbig}|@b{-mbig-endian}]
426 [@b{-msolaris}|@b{-mno-solaris}]
430 @emph{Target SPARC options:}
431 @c The order here is important. See c-sparc.texi.
432 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
433 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
434 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
439 @emph{Target TIC54X options:}
440 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
441 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
444 @c Z8000 has no machine-dependent assembler options
453 Turn on listings, in any of a variety of ways:
457 omit false conditionals
460 omit debugging directives
463 include high-level source
469 include macro expansions
472 omit forms processing
478 set the name of the listing file
481 You may combine these options; for example, use @samp{-aln} for assembly
482 listing without forms processing. The @samp{=file} option, if used, must be
483 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
486 Ignored. This option is accepted for script compatibility with calls to
489 @item --defsym @var{sym}=@var{value}
490 Define the symbol @var{sym} to be @var{value} before assembling the input file.
491 @var{value} must be an integer constant. As in C, a leading @samp{0x}
492 indicates a hexadecimal value, and a leading @samp{0} indicates an octal value.
495 ``fast''---skip whitespace and comment preprocessing (assume source is
499 Generate stabs debugging information for each assembler line. This
500 may help debugging assembler code, if the debugger can handle it.
503 Generate DWARF2 debugging information for each assembler line. This
504 may help debugging assembler code, if the debugger can handle it. Note - this
505 option is only supported by some targets, not all of them.
508 Print a summary of the command line options and exit.
511 Print a summary of all target specific options and exit.
514 Add directory @var{dir} to the search list for @code{.include} directives.
517 Don't warn about signed overflow.
520 @ifclear DIFF-TBL-KLUGE
521 This option is accepted but has no effect on the @value{TARGET} family.
523 @ifset DIFF-TBL-KLUGE
524 Issue warnings when difference tables altered for long displacements.
529 Keep (in the symbol table) local symbols. On traditional a.out systems
530 these start with @samp{L}, but different systems have different local
533 @item --listing-lhs-width=@var{number}
534 Set the maximum width, in words, of the output data column for an assembler
535 listing to @var{number}.
537 @item --listing-lhs-width2=@var{number}
538 Set the maximum width, in words, of the output data column for continuation
539 lines in an assembler listing to @var{number}.
541 @item --listing-rhs-width=@var{number}
542 Set the maximum width of an input source line, as displayed in a listing, to
545 @item --listing-cont-lines=@var{number}
546 Set the maximum number of lines printed in a listing for a single line of input
549 @item -o @var{objfile}
550 Name the object-file output from @command{@value{AS}} @var{objfile}.
553 Fold the data section into the text section.
556 Print the maximum space (in bytes) and total time (in seconds) used by
559 @item --strip-local-absolute
560 Remove local absolute symbols from the outgoing symbol table.
564 Print the @command{as} version.
567 Print the @command{as} version and exit.
571 Suppress warning messages.
573 @item --fatal-warnings
574 Treat warnings as errors.
577 Don't suppress warning messages or treat them as errors.
586 Generate an object file even after errors.
588 @item -- | @var{files} @dots{}
589 Standard input, or source files to assemble.
594 The following options are available when @value{AS} is configured for
599 This option selects the core processor variant.
601 Select either big-endian (-EB) or little-endian (-EL) output.
606 The following options are available when @value{AS} is configured for the ARM
610 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
611 Specify which ARM processor variant is the target.
612 @item -march=@var{architecture}[+@var{extension}@dots{}]
613 Specify which ARM architecture variant is used by the target.
614 @item -mfpu=@var{floating-point-format}
615 Select which Floating Point architecture is the target.
617 Enable Thumb only instruction decoding.
618 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant | -moabi
619 Select which procedure calling convention is in use.
621 Select either big-endian (-EB) or little-endian (-EL) output.
622 @item -mthumb-interwork
623 Specify that the code has been generated with interworking between Thumb and
626 Specify that PIC code has been generated.
631 See the info pages for documentation of the CRIS-specific options.
635 The following options are available when @value{AS} is configured for
638 @cindex D10V optimization
639 @cindex optimization, D10V
641 Optimize output by parallelizing instructions.
646 The following options are available when @value{AS} is configured for a D30V
649 @cindex D30V optimization
650 @cindex optimization, D30V
652 Optimize output by parallelizing instructions.
656 Warn when nops are generated.
658 @cindex D30V nops after 32-bit multiply
660 Warn when a nop after a 32-bit multiply instruction is generated.
665 The following options are available when @value{AS} is configured for the
666 Intel 80960 processor.
669 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
670 Specify which variant of the 960 architecture is the target.
673 Add code to collect statistics about branches taken.
676 Do not alter compare-and-branch instructions for long displacements;
683 The following options are available when @value{AS} is configured for the
689 Specifies that the extended IP2022 instructions are allowed.
692 Restores the default behaviour, which restricts the permitted instructions to
693 just the basic IP2022 ones.
699 The following options are available when @value{AS} is configured for the
700 Mitsubishi M32R series.
705 Specify which processor in the M32R family is the target. The default
706 is normally the M32R, but this option changes it to the M32RX.
708 @item --warn-explicit-parallel-conflicts or --Wp
709 Produce warning messages when questionable parallel constructs are
712 @item --no-warn-explicit-parallel-conflicts or --Wnp
713 Do not produce warning messages when questionable parallel constructs are
720 The following options are available when @value{AS} is configured for the
721 Motorola 68000 series.
726 Shorten references to undefined symbols, to one word instead of two.
728 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
729 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
730 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
731 Specify what processor in the 68000 family is the target. The default
732 is normally the 68020, but this can be changed at configuration time.
734 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
735 The target machine does (or does not) have a floating-point coprocessor.
736 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
737 the basic 68000 is not compatible with the 68881, a combination of the
738 two can be specified, since it's possible to do emulation of the
739 coprocessor instructions with the main processor.
741 @item -m68851 | -mno-68851
742 The target machine does (or does not) have a memory-management
743 unit coprocessor. The default is to assume an MMU for 68020 and up.
750 For details about the PDP-11 machine dependent features options,
751 see @ref{PDP-11-Options}.
754 @item -mpic | -mno-pic
755 Generate position-independent (or position-dependent) code. The
756 default is @option{-mpic}.
759 @itemx -mall-extensions
760 Enable all instruction set extensions. This is the default.
762 @item -mno-extensions
763 Disable all instruction set extensions.
765 @item -m@var{extension} | -mno-@var{extension}
766 Enable (or disable) a particular instruction set extension.
769 Enable the instruction set extensions supported by a particular CPU, and
770 disable all other extensions.
772 @item -m@var{machine}
773 Enable the instruction set extensions supported by a particular machine
774 model, and disable all other extensions.
780 The following options are available when @value{AS} is configured for
781 a picoJava processor.
785 @cindex PJ endianness
786 @cindex endianness, PJ
787 @cindex big endian output, PJ
789 Generate ``big endian'' format output.
791 @cindex little endian output, PJ
793 Generate ``little endian'' format output.
799 The following options are available when @value{AS} is configured for the
800 Motorola 68HC11 or 68HC12 series.
804 @item -m68hc11 | -m68hc12 | -m68hcs12
805 Specify what processor is the target. The default is
806 defined by the configuration option when building the assembler.
809 Specify to use the 16-bit integer ABI.
812 Specify to use the 32-bit integer ABI.
815 Specify to use the 32-bit double ABI.
818 Specify to use the 64-bit double ABI.
820 @item --force-long-branchs
821 Relative branches are turned into absolute ones. This concerns
822 conditional branches, unconditional branches and branches to a
825 @item -S | --short-branchs
826 Do not turn relative branchs into absolute ones
827 when the offset is out of range.
829 @item --strict-direct-mode
830 Do not turn the direct addressing mode into extended addressing mode
831 when the instruction does not support direct addressing mode.
833 @item --print-insn-syntax
834 Print the syntax of instruction in case of error.
836 @item --print-opcodes
837 print the list of instructions with syntax and then exit.
839 @item --generate-example
840 print an example of instruction for each possible instruction and then exit.
841 This option is only useful for testing @command{@value{AS}}.
847 The following options are available when @command{@value{AS}} is configured
848 for the SPARC architecture:
851 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
852 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
853 Explicitly select a variant of the SPARC architecture.
855 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
856 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
858 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
859 UltraSPARC extensions.
861 @item -xarch=v8plus | -xarch=v8plusa
862 For compatibility with the Solaris v9 assembler. These options are
863 equivalent to -Av8plus and -Av8plusa, respectively.
866 Warn when the assembler switches to another architecture.
871 The following options are available when @value{AS} is configured for the 'c54x
876 Enable extended addressing mode. All addresses and relocations will assume
877 extended addressing (usually 23 bits).
878 @item -mcpu=@var{CPU_VERSION}
879 Sets the CPU version being compiled for.
880 @item -merrors-to-file @var{FILENAME}
881 Redirect error output to a file, for broken systems which don't support such
882 behaviour in the shell.
887 The following options are available when @value{AS} is configured for
888 a @sc{mips} processor.
892 This option sets the largest size of an object that can be referenced
893 implicitly with the @code{gp} register. It is only accepted for targets that
894 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
896 @cindex MIPS endianness
897 @cindex endianness, MIPS
898 @cindex big endian output, MIPS
900 Generate ``big endian'' format output.
902 @cindex little endian output, MIPS
904 Generate ``little endian'' format output.
915 Generate code for a particular @sc{mips} Instruction Set Architecture level.
916 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
917 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
918 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
919 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, and @samp{-mips64}
920 correspond to generic
921 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, and
922 @samp{MIPS64} ISA processors,
925 @item -march=@var{CPU}
926 Generate code for a particular @sc{mips} cpu.
928 @item -mtune=@var{cpu}
929 Schedule and tune for a particular @sc{mips} cpu.
933 Cause nops to be inserted if the read of the destination register
934 of an mfhi or mflo instruction occurs in the following two instructions.
938 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
939 section instead of the standard ELF .stabs sections.
943 The register sizes are normally inferred from the ISA and ABI, but these
944 flags force a certain group of registers to be treated as 32 bits wide at
945 all times. @samp{-mgp32} controls the size of general-purpose registers
946 and @samp{-mfp32} controls the size of floating-point registers.
950 Generate code for the MIPS 16 processor. This is equivalent to putting
951 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
952 turns off this option.
956 Generate code for the MIPS-3D Application Specific Extension.
957 This tells the assembler to accept MIPS-3D instructions.
958 @samp{-no-mips3d} turns off this option.
962 Generate code for the MDMX Application Specific Extension.
963 This tells the assembler to accept MDMX instructions.
964 @samp{-no-mdmx} turns off this option.
966 @item --construct-floats
967 @itemx --no-construct-floats
968 The @samp{--no-construct-floats} option disables the construction of
969 double width floating point constants by loading the two halves of the
970 value into the two single width floating point registers that make up
971 the double width register. By default @samp{--construct-floats} is
972 selected, allowing construction of these floating point constants.
975 @item --emulation=@var{name}
976 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
977 for some other target, in all respects, including output format (choosing
978 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
979 debugging information or store symbol table information, and default
980 endianness. The available configuration names are: @samp{mipsecoff},
981 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
982 @samp{mipsbelf}. The first two do not alter the default endianness from that
983 of the primary target for which the assembler was configured; the others change
984 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
985 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
986 selection in any case.
988 This option is currently supported only when the primary target
989 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
990 Furthermore, the primary target or others specified with
991 @samp{--enable-targets=@dots{}} at configuration time must include support for
992 the other format, if both are to be available. For example, the Irix 5
993 configuration includes support for both.
995 Eventually, this option will support more configurations, with more
996 fine-grained control over the assembler's behavior, and will be supported for
1000 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1007 Control how to deal with multiplication overflow and division by zero.
1008 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1009 (and only work for Instruction Set Architecture level 2 and higher);
1010 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1014 When this option is used, @command{@value{AS}} will issue a warning every
1015 time it generates a nop instruction from a macro.
1020 The following options are available when @value{AS} is configured for
1026 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1027 The command line option @samp{-nojsri2bsr} can be used to disable it.
1031 Enable or disable the silicon filter behaviour. By default this is disabled.
1032 The default can be overridden by the @samp{-sifilter} command line option.
1035 Alter jump instructions for long displacements.
1037 @item -mcpu=[210|340]
1038 Select the cpu type on the target hardware. This controls which instructions
1042 Assemble for a big endian target.
1045 Assemble for a little endian target.
1051 See the info pages for documentation of the MMIX-specific options.
1057 * Manual:: Structure of this Manual
1058 * GNU Assembler:: The GNU Assembler
1059 * Object Formats:: Object File Formats
1060 * Command Line:: Command Line
1061 * Input Files:: Input Files
1062 * Object:: Output (Object) File
1063 * Errors:: Error and Warning Messages
1067 @section Structure of this Manual
1069 @cindex manual, structure and purpose
1070 This manual is intended to describe what you need to know to use
1071 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1072 notation for symbols, constants, and expressions; the directives that
1073 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1076 We also cover special features in the @value{TARGET}
1077 configuration of @command{@value{AS}}, including assembler directives.
1080 This manual also describes some of the machine-dependent features of
1081 various flavors of the assembler.
1084 @cindex machine instructions (not covered)
1085 On the other hand, this manual is @emph{not} intended as an introduction
1086 to programming in assembly language---let alone programming in general!
1087 In a similar vein, we make no attempt to introduce the machine
1088 architecture; we do @emph{not} describe the instruction set, standard
1089 mnemonics, registers or addressing modes that are standard to a
1090 particular architecture.
1092 You may want to consult the manufacturer's
1093 machine architecture manual for this information.
1097 For information on the H8/300 machine instruction set, see @cite{H8/300
1098 Series Programming Manual} (Hitachi ADE--602--025). For the H8/300H,
1099 see @cite{H8/300H Series Programming Manual} (Hitachi).
1102 For information on the H8/500 machine instruction set, see @cite{H8/500
1103 Series Programming Manual} (Hitachi M21T001).
1106 For information on the Hitachi SH machine instruction set, see
1107 @cite{SH-Microcomputer User's Manual} (Hitachi Micro Systems, Inc.).
1110 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1114 @c I think this is premature---doc@cygnus.com, 17jan1991
1116 Throughout this manual, we assume that you are running @dfn{GNU},
1117 the portable operating system from the @dfn{Free Software
1118 Foundation, Inc.}. This restricts our attention to certain kinds of
1119 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1120 once this assumption is granted examples and definitions need less
1123 @command{@value{AS}} is part of a team of programs that turn a high-level
1124 human-readable series of instructions into a low-level
1125 computer-readable series of instructions. Different versions of
1126 @command{@value{AS}} are used for different kinds of computer.
1129 @c There used to be a section "Terminology" here, which defined
1130 @c "contents", "byte", "word", and "long". Defining "word" to any
1131 @c particular size is confusing when the .word directive may generate 16
1132 @c bits on one machine and 32 bits on another; in general, for the user
1133 @c version of this manual, none of these terms seem essential to define.
1134 @c They were used very little even in the former draft of the manual;
1135 @c this draft makes an effort to avoid them (except in names of
1139 @section The GNU Assembler
1141 @c man begin DESCRIPTION
1143 @sc{gnu} @command{as} is really a family of assemblers.
1145 This manual describes @command{@value{AS}}, a member of that family which is
1146 configured for the @value{TARGET} architectures.
1148 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1149 should find a fairly similar environment when you use it on another
1150 architecture. Each version has much in common with the others,
1151 including object file formats, most assembler directives (often called
1152 @dfn{pseudo-ops}) and assembler syntax.@refill
1154 @cindex purpose of @sc{gnu} assembler
1155 @command{@value{AS}} is primarily intended to assemble the output of the
1156 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1157 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1158 assemble correctly everything that other assemblers for the same
1159 machine would assemble.
1161 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1164 @c This remark should appear in generic version of manual; assumption
1165 @c here is that generic version sets M680x0.
1166 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1167 assembler for the same architecture; for example, we know of several
1168 incompatible versions of 680x0 assembly language syntax.
1173 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1174 program in one pass of the source file. This has a subtle impact on the
1175 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1177 @node Object Formats
1178 @section Object File Formats
1180 @cindex object file format
1181 The @sc{gnu} assembler can be configured to produce several alternative
1182 object file formats. For the most part, this does not affect how you
1183 write assembly language programs; but directives for debugging symbols
1184 are typically different in different file formats. @xref{Symbol
1185 Attributes,,Symbol Attributes}.
1188 On the @value{TARGET}, @command{@value{AS}} is configured to produce
1189 @value{OBJ-NAME} format object files.
1191 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1193 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1194 @code{a.out} or COFF format object files.
1197 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1198 @code{b.out} or COFF format object files.
1201 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1202 SOM or ELF format object files.
1207 @section Command Line
1209 @cindex command line conventions
1211 After the program name @command{@value{AS}}, the command line may contain
1212 options and file names. Options may appear in any order, and may be
1213 before, after, or between file names. The order of file names is
1216 @cindex standard input, as input file
1218 @file{--} (two hyphens) by itself names the standard input file
1219 explicitly, as one of the files for @command{@value{AS}} to assemble.
1221 @cindex options, command line
1222 Except for @samp{--} any command line argument that begins with a
1223 hyphen (@samp{-}) is an option. Each option changes the behavior of
1224 @command{@value{AS}}. No option changes the way another option works. An
1225 option is a @samp{-} followed by one or more letters; the case of
1226 the letter is important. All options are optional.
1228 Some options expect exactly one file name to follow them. The file
1229 name may either immediately follow the option's letter (compatible
1230 with older assemblers) or it may be the next command argument (@sc{gnu}
1231 standard). These two command lines are equivalent:
1234 @value{AS} -o my-object-file.o mumble.s
1235 @value{AS} -omy-object-file.o mumble.s
1239 @section Input Files
1242 @cindex source program
1243 @cindex files, input
1244 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1245 describe the program input to one run of @command{@value{AS}}. The program may
1246 be in one or more files; how the source is partitioned into files
1247 doesn't change the meaning of the source.
1249 @c I added "con" prefix to "catenation" just to prove I can overcome my
1250 @c APL training... doc@cygnus.com
1251 The source program is a concatenation of the text in all the files, in the
1254 @c man begin DESCRIPTION
1255 Each time you run @command{@value{AS}} it assembles exactly one source
1256 program. The source program is made up of one or more files.
1257 (The standard input is also a file.)
1259 You give @command{@value{AS}} a command line that has zero or more input file
1260 names. The input files are read (from left file name to right). A
1261 command line argument (in any position) that has no special meaning
1262 is taken to be an input file name.
1264 If you give @command{@value{AS}} no file names it attempts to read one input file
1265 from the @command{@value{AS}} standard input, which is normally your terminal. You
1266 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1269 Use @samp{--} if you need to explicitly name the standard input file
1270 in your command line.
1272 If the source is empty, @command{@value{AS}} produces a small, empty object
1277 @subheading Filenames and Line-numbers
1279 @cindex input file linenumbers
1280 @cindex line numbers, in input files
1281 There are two ways of locating a line in the input file (or files) and
1282 either may be used in reporting error messages. One way refers to a line
1283 number in a physical file; the other refers to a line number in a
1284 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1286 @dfn{Physical files} are those files named in the command line given
1287 to @command{@value{AS}}.
1289 @dfn{Logical files} are simply names declared explicitly by assembler
1290 directives; they bear no relation to physical files. Logical file names help
1291 error messages reflect the original source file, when @command{@value{AS}} source
1292 is itself synthesized from other files. @command{@value{AS}} understands the
1293 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1294 @ref{File,,@code{.file}}.
1297 @section Output (Object) File
1303 Every time you run @command{@value{AS}} it produces an output file, which is
1304 your assembly language program translated into numbers. This file
1305 is the object file. Its default name is
1313 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1315 You can give it another name by using the @option{-o} option. Conventionally,
1316 object file names end with @file{.o}. The default name is used for historical
1317 reasons: older assemblers were capable of assembling self-contained programs
1318 directly into a runnable program. (For some formats, this isn't currently
1319 possible, but it can be done for the @code{a.out} format.)
1323 The object file is meant for input to the linker @code{@value{LD}}. It contains
1324 assembled program code, information to help @code{@value{LD}} integrate
1325 the assembled program into a runnable file, and (optionally) symbolic
1326 information for the debugger.
1328 @c link above to some info file(s) like the description of a.out.
1329 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1332 @section Error and Warning Messages
1334 @c man begin DESCRIPTION
1336 @cindex error messages
1337 @cindex warning messages
1338 @cindex messages from assembler
1339 @command{@value{AS}} may write warnings and error messages to the standard error
1340 file (usually your terminal). This should not happen when a compiler
1341 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1342 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1343 grave problem that stops the assembly.
1347 @cindex format of warning messages
1348 Warning messages have the format
1351 file_name:@b{NNN}:Warning Message Text
1355 @cindex line numbers, in warnings/errors
1356 (where @b{NNN} is a line number). If a logical file name has been given
1357 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1358 the current input file is used. If a logical line number was given
1360 (@pxref{Line,,@code{.line}})
1364 (@pxref{Line,,@code{.line}})
1367 (@pxref{Ln,,@code{.ln}})
1370 then it is used to calculate the number printed,
1371 otherwise the actual line in the current source file is printed. The
1372 message text is intended to be self explanatory (in the grand Unix
1375 @cindex format of error messages
1376 Error messages have the format
1378 file_name:@b{NNN}:FATAL:Error Message Text
1380 The file name and line number are derived as for warning
1381 messages. The actual message text may be rather less explanatory
1382 because many of them aren't supposed to happen.
1385 @chapter Command-Line Options
1387 @cindex options, all versions of assembler
1388 This chapter describes command-line options available in @emph{all}
1389 versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
1391 to the @value{TARGET}.
1394 to particular machine architectures.
1397 @c man begin DESCRIPTION
1399 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler (version 2),
1400 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1401 The assembler arguments must be separated from each other (and the @samp{-Wa})
1402 by commas. For example:
1405 gcc -c -g -O -Wa,-alh,-L file.c
1409 This passes two options to the assembler: @samp{-alh} (emit a listing to
1410 standard output with high-level and assembly source) and @samp{-L} (retain
1411 local symbols in the symbol table).
1413 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1414 command-line options are automatically passed to the assembler by the compiler.
1415 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1416 precisely what options it passes to each compilation pass, including the
1422 * a:: -a[cdhlns] enable listings
1423 * D:: -D for compatibility
1424 * f:: -f to work faster
1425 * I:: -I for .include search path
1426 @ifclear DIFF-TBL-KLUGE
1427 * K:: -K for compatibility
1429 @ifset DIFF-TBL-KLUGE
1430 * K:: -K for difference tables
1433 * L:: -L to retain local labels
1434 * listing:: --listing-XXX to configure listing output
1435 * M:: -M or --mri to assemble in MRI compatibility mode
1436 * MD:: --MD for dependency tracking
1437 * o:: -o to name the object file
1438 * R:: -R to join data and text sections
1439 * statistics:: --statistics to see statistics about assembly
1440 * traditional-format:: --traditional-format for compatible output
1441 * v:: -v to announce version
1442 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1443 * Z:: -Z to make object file even after errors
1447 @section Enable Listings: @option{-a[cdhlns]}
1456 @cindex listings, enabling
1457 @cindex assembly listings, enabling
1459 These options enable listing output from the assembler. By itself,
1460 @samp{-a} requests high-level, assembly, and symbols listing.
1461 You can use other letters to select specific options for the list:
1462 @samp{-ah} requests a high-level language listing,
1463 @samp{-al} requests an output-program assembly listing, and
1464 @samp{-as} requests a symbol table listing.
1465 High-level listings require that a compiler debugging option like
1466 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1469 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1470 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1471 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1472 omitted from the listing.
1474 Use the @samp{-ad} option to omit debugging directives from the
1477 Once you have specified one of these options, you can further control
1478 listing output and its appearance using the directives @code{.list},
1479 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1481 The @samp{-an} option turns off all forms processing.
1482 If you do not request listing output with one of the @samp{-a} options, the
1483 listing-control directives have no effect.
1485 The letters after @samp{-a} may be combined into one option,
1486 @emph{e.g.}, @samp{-aln}.
1488 Note if the assembler source is coming from the standard input (eg because it
1489 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1490 is being used) then the listing will not contain any comments or preprocessor
1491 directives. This is because the listing code buffers input source lines from
1492 stdin only after they have been preprocessed by the assembler. This reduces
1493 memory usage and makes the code more efficient.
1496 @section @option{-D}
1499 This option has no effect whatsoever, but it is accepted to make it more
1500 likely that scripts written for other assemblers also work with
1501 @command{@value{AS}}.
1504 @section Work Faster: @option{-f}
1507 @cindex trusted compiler
1508 @cindex faster processing (@option{-f})
1509 @samp{-f} should only be used when assembling programs written by a
1510 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1511 and comment preprocessing on
1512 the input file(s) before assembling them. @xref{Preprocessing,
1516 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1517 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1522 @section @code{.include} search path: @option{-I} @var{path}
1524 @kindex -I @var{path}
1525 @cindex paths for @code{.include}
1526 @cindex search path for @code{.include}
1527 @cindex @code{include} directive search path
1528 Use this option to add a @var{path} to the list of directories
1529 @command{@value{AS}} searches for files specified in @code{.include}
1530 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1531 many times as necessary to include a variety of paths. The current
1532 working directory is always searched first; after that, @command{@value{AS}}
1533 searches any @samp{-I} directories in the same order as they were
1534 specified (left to right) on the command line.
1537 @section Difference Tables: @option{-K}
1540 @ifclear DIFF-TBL-KLUGE
1541 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1542 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1543 where it can be used to warn when the assembler alters the machine code
1544 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1545 family does not have the addressing limitations that sometimes lead to this
1546 alteration on other platforms.
1549 @ifset DIFF-TBL-KLUGE
1550 @cindex difference tables, warning
1551 @cindex warning for altered difference tables
1552 @command{@value{AS}} sometimes alters the code emitted for directives of the form
1553 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
1554 You can use the @samp{-K} option if you want a warning issued when this
1559 @section Include Local Labels: @option{-L}
1562 @cindex local labels, retaining in output
1563 Labels beginning with @samp{L} (upper case only) are called @dfn{local
1564 labels}. @xref{Symbol Names}. Normally you do not see such labels when
1565 debugging, because they are intended for the use of programs (like
1566 compilers) that compose assembler programs, not for your notice.
1567 Normally both @command{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
1568 normally debug with them.
1570 This option tells @command{@value{AS}} to retain those @samp{L@dots{}} symbols
1571 in the object file. Usually if you do this you also tell the linker
1572 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
1574 By default, a local label is any label beginning with @samp{L}, but each
1575 target is allowed to redefine the local label prefix.
1577 On the HPPA local labels begin with @samp{L$}.
1581 @section Configuring listing output: @option{--listing}
1583 The listing feature of the assembler can be enabled via the command line switch
1584 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1585 hex dump of the corresponding locations in the output object file, and displays
1586 them as a listing file. The format of this listing can be controlled by pseudo
1587 ops inside the assembler source (@pxref{List} @pxref{Title} @pxref{Sbttl}
1588 @pxref{Psize} @pxref{Eject}) and also by the following switches:
1591 @item --listing-lhs-width=@samp{number}
1592 @kindex --listing-lhs-width
1593 @cindex Width of first line disassembly output
1594 Sets the maximum width, in words, of the first line of the hex byte dump. This
1595 dump appears on the left hand side of the listing output.
1597 @item --listing-lhs-width2=@samp{number}
1598 @kindex --listing-lhs-width2
1599 @cindex Width of continuation lines of disassembly output
1600 Sets the maximum width, in words, of any further lines of the hex byte dump for
1601 a given input source line. If this value is not specified, it defaults to being
1602 the same as the value specified for @samp{--listing-lhs-width}. If neither
1603 switch is used the default is to one.
1605 @item --listing-rhs-width=@samp{number}
1606 @kindex --listing-rhs-width
1607 @cindex Width of source line output
1608 Sets the maximum width, in characters, of the source line that is displayed
1609 alongside the hex dump. The default value for this parameter is 100. The
1610 source line is displayed on the right hand side of the listing output.
1612 @item --listing-cont-lines=@samp{number}
1613 @kindex --listing-cont-lines
1614 @cindex Maximum number of continuation lines
1615 Sets the maximum number of continuation lines of hex dump that will be
1616 displayed for a given single line of source input. The default value is 4.
1620 @section Assemble in MRI Compatibility Mode: @option{-M}
1623 @cindex MRI compatibility mode
1624 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1625 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1626 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1627 configured target) assembler from Microtec Research. The exact nature of the
1628 MRI syntax will not be documented here; see the MRI manuals for more
1629 information. Note in particular that the handling of macros and macro
1630 arguments is somewhat different. The purpose of this option is to permit
1631 assembling existing MRI assembler code using @command{@value{AS}}.
1633 The MRI compatibility is not complete. Certain operations of the MRI assembler
1634 depend upon its object file format, and can not be supported using other object
1635 file formats. Supporting these would require enhancing each object file format
1636 individually. These are:
1639 @item global symbols in common section
1641 The m68k MRI assembler supports common sections which are merged by the linker.
1642 Other object file formats do not support this. @command{@value{AS}} handles
1643 common sections by treating them as a single common symbol. It permits local
1644 symbols to be defined within a common section, but it can not support global
1645 symbols, since it has no way to describe them.
1647 @item complex relocations
1649 The MRI assemblers support relocations against a negated section address, and
1650 relocations which combine the start addresses of two or more sections. These
1651 are not support by other object file formats.
1653 @item @code{END} pseudo-op specifying start address
1655 The MRI @code{END} pseudo-op permits the specification of a start address.
1656 This is not supported by other object file formats. The start address may
1657 instead be specified using the @option{-e} option to the linker, or in a linker
1660 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1662 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1663 name to the output file. This is not supported by other object file formats.
1665 @item @code{ORG} pseudo-op
1667 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1668 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
1669 which changes the location within the current section. Absolute sections are
1670 not supported by other object file formats. The address of a section may be
1671 assigned within a linker script.
1674 There are some other features of the MRI assembler which are not supported by
1675 @command{@value{AS}}, typically either because they are difficult or because they
1676 seem of little consequence. Some of these may be supported in future releases.
1680 @item EBCDIC strings
1682 EBCDIC strings are not supported.
1684 @item packed binary coded decimal
1686 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1687 and @code{DCB.P} pseudo-ops are not supported.
1689 @item @code{FEQU} pseudo-op
1691 The m68k @code{FEQU} pseudo-op is not supported.
1693 @item @code{NOOBJ} pseudo-op
1695 The m68k @code{NOOBJ} pseudo-op is not supported.
1697 @item @code{OPT} branch control options
1699 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1700 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
1701 relaxes all branches, whether forward or backward, to an appropriate size, so
1702 these options serve no purpose.
1704 @item @code{OPT} list control options
1706 The following m68k @code{OPT} list control options are ignored: @code{C},
1707 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1708 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1710 @item other @code{OPT} options
1712 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1713 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1715 @item @code{OPT} @code{D} option is default
1717 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1718 @code{OPT NOD} may be used to turn it off.
1720 @item @code{XREF} pseudo-op.
1722 The m68k @code{XREF} pseudo-op is ignored.
1724 @item @code{.debug} pseudo-op
1726 The i960 @code{.debug} pseudo-op is not supported.
1728 @item @code{.extended} pseudo-op
1730 The i960 @code{.extended} pseudo-op is not supported.
1732 @item @code{.list} pseudo-op.
1734 The various options of the i960 @code{.list} pseudo-op are not supported.
1736 @item @code{.optimize} pseudo-op
1738 The i960 @code{.optimize} pseudo-op is not supported.
1740 @item @code{.output} pseudo-op
1742 The i960 @code{.output} pseudo-op is not supported.
1744 @item @code{.setreal} pseudo-op
1746 The i960 @code{.setreal} pseudo-op is not supported.
1751 @section Dependency tracking: @option{--MD}
1754 @cindex dependency tracking
1757 @command{@value{AS}} can generate a dependency file for the file it creates. This
1758 file consists of a single rule suitable for @code{make} describing the
1759 dependencies of the main source file.
1761 The rule is written to the file named in its argument.
1763 This feature is used in the automatic updating of makefiles.
1766 @section Name the Object File: @option{-o}
1769 @cindex naming object file
1770 @cindex object file name
1771 There is always one object file output when you run @command{@value{AS}}. By
1772 default it has the name
1775 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1789 You use this option (which takes exactly one filename) to give the
1790 object file a different name.
1792 Whatever the object file is called, @command{@value{AS}} overwrites any
1793 existing file of the same name.
1796 @section Join Data and Text Sections: @option{-R}
1799 @cindex data and text sections, joining
1800 @cindex text and data sections, joining
1801 @cindex joining text and data sections
1802 @cindex merging text and data sections
1803 @option{-R} tells @command{@value{AS}} to write the object file as if all
1804 data-section data lives in the text section. This is only done at
1805 the very last moment: your binary data are the same, but data
1806 section parts are relocated differently. The data section part of
1807 your object file is zero bytes long because all its bytes are
1808 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1810 When you specify @option{-R} it would be possible to generate shorter
1811 address displacements (because we do not have to cross between text and
1812 data section). We refrain from doing this simply for compatibility with
1813 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
1816 When @command{@value{AS}} is configured for COFF output,
1817 this option is only useful if you use sections named @samp{.text} and
1822 @option{-R} is not supported for any of the HPPA targets. Using
1823 @option{-R} generates a warning from @command{@value{AS}}.
1827 @section Display Assembly Statistics: @option{--statistics}
1829 @kindex --statistics
1830 @cindex statistics, about assembly
1831 @cindex time, total for assembly
1832 @cindex space used, maximum for assembly
1833 Use @samp{--statistics} to display two statistics about the resources used by
1834 @command{@value{AS}}: the maximum amount of space allocated during the assembly
1835 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1838 @node traditional-format
1839 @section Compatible output: @option{--traditional-format}
1841 @kindex --traditional-format
1842 For some targets, the output of @command{@value{AS}} is different in some ways
1843 from the output of some existing assembler. This switch requests
1844 @command{@value{AS}} to use the traditional format instead.
1846 For example, it disables the exception frame optimizations which
1847 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
1850 @section Announce Version: @option{-v}
1854 @cindex assembler version
1855 @cindex version of assembler
1856 You can find out what version of as is running by including the
1857 option @samp{-v} (which you can also spell as @samp{-version}) on the
1861 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
1863 @command{@value{AS}} should never give a warning or error message when
1864 assembling compiler output. But programs written by people often
1865 cause @command{@value{AS}} to give a warning that a particular assumption was
1866 made. All such warnings are directed to the standard error file.
1869 @kindex @samp{--no-warn}
1870 @cindex suppressing warnings
1871 @cindex warnings, suppressing
1872 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
1873 This only affects the warning messages: it does not change any particular of
1874 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
1877 @kindex @samp{--fatal-warnings}
1878 @cindex errors, caused by warnings
1879 @cindex warnings, causing error
1880 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
1881 files that generate warnings to be in error.
1883 @kindex @samp{--warn}
1884 @cindex warnings, switching on
1885 You can switch these options off again by specifying @option{--warn}, which
1886 causes warnings to be output as usual.
1889 @section Generate Object File in Spite of Errors: @option{-Z}
1890 @cindex object file, after errors
1891 @cindex errors, continuing after
1892 After an error message, @command{@value{AS}} normally produces no output. If for
1893 some reason you are interested in object file output even after
1894 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
1895 option. If there are any errors, @command{@value{AS}} continues anyways, and
1896 writes an object file after a final warning message of the form @samp{@var{n}
1897 errors, @var{m} warnings, generating bad object file.}
1902 @cindex machine-independent syntax
1903 @cindex syntax, machine-independent
1904 This chapter describes the machine-independent syntax allowed in a
1905 source file. @command{@value{AS}} syntax is similar to what many other
1906 assemblers use; it is inspired by the BSD 4.2
1911 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
1915 * Preprocessing:: Preprocessing
1916 * Whitespace:: Whitespace
1917 * Comments:: Comments
1918 * Symbol Intro:: Symbols
1919 * Statements:: Statements
1920 * Constants:: Constants
1924 @section Preprocessing
1926 @cindex preprocessing
1927 The @command{@value{AS}} internal preprocessor:
1929 @cindex whitespace, removed by preprocessor
1931 adjusts and removes extra whitespace. It leaves one space or tab before
1932 the keywords on a line, and turns any other whitespace on the line into
1935 @cindex comments, removed by preprocessor
1937 removes all comments, replacing them with a single space, or an
1938 appropriate number of newlines.
1940 @cindex constants, converted by preprocessor
1942 converts character constants into the appropriate numeric values.
1945 It does not do macro processing, include file handling, or
1946 anything else you may get from your C compiler's preprocessor. You can
1947 do include file processing with the @code{.include} directive
1948 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
1949 to get other ``CPP'' style preprocessing, by giving the input file a
1950 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
1951 Output, gcc.info, Using GNU CC}.
1953 Excess whitespace, comments, and character constants
1954 cannot be used in the portions of the input text that are not
1957 @cindex turning preprocessing on and off
1958 @cindex preprocessing, turning on and off
1961 If the first line of an input file is @code{#NO_APP} or if you use the
1962 @samp{-f} option, whitespace and comments are not removed from the input file.
1963 Within an input file, you can ask for whitespace and comment removal in
1964 specific portions of the by putting a line that says @code{#APP} before the
1965 text that may contain whitespace or comments, and putting a line that says
1966 @code{#NO_APP} after this text. This feature is mainly intend to support
1967 @code{asm} statements in compilers whose output is otherwise free of comments
1974 @dfn{Whitespace} is one or more blanks or tabs, in any order.
1975 Whitespace is used to separate symbols, and to make programs neater for
1976 people to read. Unless within character constants
1977 (@pxref{Characters,,Character Constants}), any whitespace means the same
1978 as exactly one space.
1984 There are two ways of rendering comments to @command{@value{AS}}. In both
1985 cases the comment is equivalent to one space.
1987 Anything from @samp{/*} through the next @samp{*/} is a comment.
1988 This means you may not nest these comments.
1992 The only way to include a newline ('\n') in a comment
1993 is to use this sort of comment.
1996 /* This sort of comment does not nest. */
1999 @cindex line comment character
2000 Anything from the @dfn{line comment} character to the next newline
2001 is considered a comment and is ignored. The line comment character is
2003 @samp{;} for the AMD 29K family;
2006 @samp{;} on the ARC;
2009 @samp{@@} on the ARM;
2012 @samp{;} for the H8/300 family;
2015 @samp{!} for the H8/500 family;
2018 @samp{;} for the HPPA;
2021 @samp{#} on the i386 and x86-64;
2024 @samp{#} on the i960;
2027 @samp{;} for the PDP-11;
2030 @samp{;} for picoJava;
2033 @samp{;} for Motorola PowerPC;
2036 @samp{!} for the Hitachi SH;
2039 @samp{!} on the SPARC;
2042 @samp{#} on the ip2k;
2045 @samp{#} on the m32r;
2048 @samp{|} on the 680x0;
2051 @samp{#} on the 68HC11 and 68HC12;
2054 @samp{;} on the M880x0;
2057 @samp{#} on the Vax;
2060 @samp{!} for the Z8000;
2063 @samp{#} on the V850;
2065 see @ref{Machine Dependencies}. @refill
2066 @c FIXME What about i860?
2069 On some machines there are two different line comment characters. One
2070 character only begins a comment if it is the first non-whitespace character on
2071 a line, while the other always begins a comment.
2075 The V850 assembler also supports a double dash as starting a comment that
2076 extends to the end of the line.
2082 @cindex lines starting with @code{#}
2083 @cindex logical line numbers
2084 To be compatible with past assemblers, lines that begin with @samp{#} have a
2085 special interpretation. Following the @samp{#} should be an absolute
2086 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2087 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
2088 new logical file name. The rest of the line, if any, should be whitespace.
2090 If the first non-whitespace characters on the line are not numeric,
2091 the line is ignored. (Just like a comment.)
2094 # This is an ordinary comment.
2095 # 42-6 "new_file_name" # New logical file name
2096 # This is logical line # 36.
2098 This feature is deprecated, and may disappear from future versions
2099 of @command{@value{AS}}.
2104 @cindex characters used in symbols
2105 @ifclear SPECIAL-SYMS
2106 A @dfn{symbol} is one or more characters chosen from the set of all
2107 letters (both upper and lower case), digits and the three characters
2113 A @dfn{symbol} is one or more characters chosen from the set of all
2114 letters (both upper and lower case), digits and the three characters
2115 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2121 On most machines, you can also use @code{$} in symbol names; exceptions
2122 are noted in @ref{Machine Dependencies}.
2124 No symbol may begin with a digit. Case is significant.
2125 There is no length limit: all characters are significant. Symbols are
2126 delimited by characters not in that set, or by the beginning of a file
2127 (since the source program must end with a newline, the end of a file is
2128 not a possible symbol delimiter). @xref{Symbols}.
2129 @cindex length of symbols
2134 @cindex statements, structure of
2135 @cindex line separator character
2136 @cindex statement separator character
2138 @ifclear abnormal-separator
2139 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
2140 semicolon (@samp{;}). The newline or semicolon is considered part of
2141 the preceding statement. Newlines and semicolons within character
2142 constants are an exception: they do not end statements.
2144 @ifset abnormal-separator
2146 A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at''
2147 sign (@samp{@@}). The newline or at sign is considered part of the
2148 preceding statement. Newlines and at signs within character constants
2149 are an exception: they do not end statements.
2152 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
2153 point (@samp{!}). The newline or exclamation point is considered part of the
2154 preceding statement. Newlines and exclamation points within character
2155 constants are an exception: they do not end statements.
2158 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
2159 H8/300) a dollar sign (@samp{$}); or (for the
2162 (@samp{;}). The newline or separator character is considered part of
2163 the preceding statement. Newlines and separators within character
2164 constants are an exception: they do not end statements.
2169 A @dfn{statement} ends at a newline character (@samp{\n}) or line
2170 separator character. (The line separator is usually @samp{;}, unless
2171 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
2172 newline or separator character is considered part of the preceding
2173 statement. Newlines and separators within character constants are an
2174 exception: they do not end statements.
2177 @cindex newline, required at file end
2178 @cindex EOF, newline must precede
2179 It is an error to end any statement with end-of-file: the last
2180 character of any input file should be a newline.@refill
2182 An empty statement is allowed, and may include whitespace. It is ignored.
2184 @cindex instructions and directives
2185 @cindex directives and instructions
2186 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2187 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2189 A statement begins with zero or more labels, optionally followed by a
2190 key symbol which determines what kind of statement it is. The key
2191 symbol determines the syntax of the rest of the statement. If the
2192 symbol begins with a dot @samp{.} then the statement is an assembler
2193 directive: typically valid for any computer. If the symbol begins with
2194 a letter the statement is an assembly language @dfn{instruction}: it
2195 assembles into a machine language instruction.
2197 Different versions of @command{@value{AS}} for different computers
2198 recognize different instructions. In fact, the same symbol may
2199 represent a different instruction in a different computer's assembly
2203 @cindex @code{:} (label)
2204 @cindex label (@code{:})
2205 A label is a symbol immediately followed by a colon (@code{:}).
2206 Whitespace before a label or after a colon is permitted, but you may not
2207 have whitespace between a label's symbol and its colon. @xref{Labels}.
2210 For HPPA targets, labels need not be immediately followed by a colon, but
2211 the definition of a label must begin in column zero. This also implies that
2212 only one label may be defined on each line.
2216 label: .directive followed by something
2217 another_label: # This is an empty statement.
2218 instruction operand_1, operand_2, @dots{}
2225 A constant is a number, written so that its value is known by
2226 inspection, without knowing any context. Like this:
2229 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2230 .ascii "Ring the bell\7" # A string constant.
2231 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2232 .float 0f-314159265358979323846264338327\
2233 95028841971.693993751E-40 # - pi, a flonum.
2238 * Characters:: Character Constants
2239 * Numbers:: Number Constants
2243 @subsection Character Constants
2245 @cindex character constants
2246 @cindex constants, character
2247 There are two kinds of character constants. A @dfn{character} stands
2248 for one character in one byte and its value may be used in
2249 numeric expressions. String constants (properly called string
2250 @emph{literals}) are potentially many bytes and their values may not be
2251 used in arithmetic expressions.
2255 * Chars:: Characters
2259 @subsubsection Strings
2261 @cindex string constants
2262 @cindex constants, string
2263 A @dfn{string} is written between double-quotes. It may contain
2264 double-quotes or null characters. The way to get special characters
2265 into a string is to @dfn{escape} these characters: precede them with
2266 a backslash @samp{\} character. For example @samp{\\} represents
2267 one backslash: the first @code{\} is an escape which tells
2268 @command{@value{AS}} to interpret the second character literally as a backslash
2269 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2270 escape character). The complete list of escapes follows.
2272 @cindex escape codes, character
2273 @cindex character escape codes
2276 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2278 @cindex @code{\b} (backspace character)
2279 @cindex backspace (@code{\b})
2281 Mnemonic for backspace; for ASCII this is octal code 010.
2284 @c Mnemonic for EOText; for ASCII this is octal code 004.
2286 @cindex @code{\f} (formfeed character)
2287 @cindex formfeed (@code{\f})
2289 Mnemonic for FormFeed; for ASCII this is octal code 014.
2291 @cindex @code{\n} (newline character)
2292 @cindex newline (@code{\n})
2294 Mnemonic for newline; for ASCII this is octal code 012.
2297 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2299 @cindex @code{\r} (carriage return character)
2300 @cindex carriage return (@code{\r})
2302 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2305 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2306 @c other assemblers.
2308 @cindex @code{\t} (tab)
2309 @cindex tab (@code{\t})
2311 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2314 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2315 @c @item \x @var{digit} @var{digit} @var{digit}
2316 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2318 @cindex @code{\@var{ddd}} (octal character code)
2319 @cindex octal character code (@code{\@var{ddd}})
2320 @item \ @var{digit} @var{digit} @var{digit}
2321 An octal character code. The numeric code is 3 octal digits.
2322 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2323 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2325 @cindex @code{\@var{xd...}} (hex character code)
2326 @cindex hex character code (@code{\@var{xd...}})
2327 @item \@code{x} @var{hex-digits...}
2328 A hex character code. All trailing hex digits are combined. Either upper or
2329 lower case @code{x} works.
2331 @cindex @code{\\} (@samp{\} character)
2332 @cindex backslash (@code{\\})
2334 Represents one @samp{\} character.
2337 @c Represents one @samp{'} (accent acute) character.
2338 @c This is needed in single character literals
2339 @c (@xref{Characters,,Character Constants}.) to represent
2342 @cindex @code{\"} (doublequote character)
2343 @cindex doublequote (@code{\"})
2345 Represents one @samp{"} character. Needed in strings to represent
2346 this character, because an unescaped @samp{"} would end the string.
2348 @item \ @var{anything-else}
2349 Any other character when escaped by @kbd{\} gives a warning, but
2350 assembles as if the @samp{\} was not present. The idea is that if
2351 you used an escape sequence you clearly didn't want the literal
2352 interpretation of the following character. However @command{@value{AS}} has no
2353 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2354 code and warns you of the fact.
2357 Which characters are escapable, and what those escapes represent,
2358 varies widely among assemblers. The current set is what we think
2359 the BSD 4.2 assembler recognizes, and is a subset of what most C
2360 compilers recognize. If you are in doubt, do not use an escape
2364 @subsubsection Characters
2366 @cindex single character constant
2367 @cindex character, single
2368 @cindex constant, single character
2369 A single character may be written as a single quote immediately
2370 followed by that character. The same escapes apply to characters as
2371 to strings. So if you want to write the character backslash, you
2372 must write @kbd{'\\} where the first @code{\} escapes the second
2373 @code{\}. As you can see, the quote is an acute accent, not a
2374 grave accent. A newline
2376 @ifclear abnormal-separator
2377 (or semicolon @samp{;})
2379 @ifset abnormal-separator
2381 (or at sign @samp{@@})
2384 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2390 immediately following an acute accent is taken as a literal character
2391 and does not count as the end of a statement. The value of a character
2392 constant in a numeric expression is the machine's byte-wide code for
2393 that character. @command{@value{AS}} assumes your character code is ASCII:
2394 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2397 @subsection Number Constants
2399 @cindex constants, number
2400 @cindex number constants
2401 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2402 are stored in the target machine. @emph{Integers} are numbers that
2403 would fit into an @code{int} in the C language. @emph{Bignums} are
2404 integers, but they are stored in more than 32 bits. @emph{Flonums}
2405 are floating point numbers, described below.
2408 * Integers:: Integers
2413 * Bit Fields:: Bit Fields
2419 @subsubsection Integers
2421 @cindex constants, integer
2423 @cindex binary integers
2424 @cindex integers, binary
2425 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2426 the binary digits @samp{01}.
2428 @cindex octal integers
2429 @cindex integers, octal
2430 An octal integer is @samp{0} followed by zero or more of the octal
2431 digits (@samp{01234567}).
2433 @cindex decimal integers
2434 @cindex integers, decimal
2435 A decimal integer starts with a non-zero digit followed by zero or
2436 more digits (@samp{0123456789}).
2438 @cindex hexadecimal integers
2439 @cindex integers, hexadecimal
2440 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2441 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2443 Integers have the usual values. To denote a negative integer, use
2444 the prefix operator @samp{-} discussed under expressions
2445 (@pxref{Prefix Ops,,Prefix Operators}).
2448 @subsubsection Bignums
2451 @cindex constants, bignum
2452 A @dfn{bignum} has the same syntax and semantics as an integer
2453 except that the number (or its negative) takes more than 32 bits to
2454 represent in binary. The distinction is made because in some places
2455 integers are permitted while bignums are not.
2458 @subsubsection Flonums
2460 @cindex floating point numbers
2461 @cindex constants, floating point
2463 @cindex precision, floating point
2464 A @dfn{flonum} represents a floating point number. The translation is
2465 indirect: a decimal floating point number from the text is converted by
2466 @command{@value{AS}} to a generic binary floating point number of more than
2467 sufficient precision. This generic floating point number is converted
2468 to a particular computer's floating point format (or formats) by a
2469 portion of @command{@value{AS}} specialized to that computer.
2471 A flonum is written by writing (in order)
2476 (@samp{0} is optional on the HPPA.)
2480 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2482 @kbd{e} is recommended. Case is not important.
2484 @c FIXME: verify if flonum syntax really this vague for most cases
2485 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2486 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2489 On the H8/300, H8/500,
2491 and AMD 29K architectures, the letter must be
2492 one of the letters @samp{DFPRSX} (in upper or lower case).
2494 On the ARC, the letter must be one of the letters @samp{DFRS}
2495 (in upper or lower case).
2497 On the Intel 960 architecture, the letter must be
2498 one of the letters @samp{DFT} (in upper or lower case).
2500 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2504 One of the letters @samp{DFPRSX} (in upper or lower case).
2507 One of the letters @samp{DFRS} (in upper or lower case).
2510 One of the letters @samp{DFPRSX} (in upper or lower case).
2513 The letter @samp{E} (upper case only).
2516 One of the letters @samp{DFT} (in upper or lower case).
2521 An optional sign: either @samp{+} or @samp{-}.
2524 An optional @dfn{integer part}: zero or more decimal digits.
2527 An optional @dfn{fractional part}: @samp{.} followed by zero
2528 or more decimal digits.
2531 An optional exponent, consisting of:
2535 An @samp{E} or @samp{e}.
2536 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2537 @c principle this can perfectly well be different on different targets.
2539 Optional sign: either @samp{+} or @samp{-}.
2541 One or more decimal digits.
2546 At least one of the integer part or the fractional part must be
2547 present. The floating point number has the usual base-10 value.
2549 @command{@value{AS}} does all processing using integers. Flonums are computed
2550 independently of any floating point hardware in the computer running
2551 @command{@value{AS}}.
2555 @c Bit fields are written as a general facility but are also controlled
2556 @c by a conditional-compilation flag---which is as of now (21mar91)
2557 @c turned on only by the i960 config of GAS.
2559 @subsubsection Bit Fields
2562 @cindex constants, bit field
2563 You can also define numeric constants as @dfn{bit fields}.
2564 specify two numbers separated by a colon---
2566 @var{mask}:@var{value}
2569 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2572 The resulting number is then packed
2574 @c this conditional paren in case bit fields turned on elsewhere than 960
2575 (in host-dependent byte order)
2577 into a field whose width depends on which assembler directive has the
2578 bit-field as its argument. Overflow (a result from the bitwise and
2579 requiring more binary digits to represent) is not an error; instead,
2580 more constants are generated, of the specified width, beginning with the
2581 least significant digits.@refill
2583 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2584 @code{.short}, and @code{.word} accept bit-field arguments.
2589 @chapter Sections and Relocation
2594 * Secs Background:: Background
2595 * Ld Sections:: Linker Sections
2596 * As Sections:: Assembler Internal Sections
2597 * Sub-Sections:: Sub-Sections
2601 @node Secs Background
2604 Roughly, a section is a range of addresses, with no gaps; all data
2605 ``in'' those addresses is treated the same for some particular purpose.
2606 For example there may be a ``read only'' section.
2608 @cindex linker, and assembler
2609 @cindex assembler, and linker
2610 The linker @code{@value{LD}} reads many object files (partial programs) and
2611 combines their contents to form a runnable program. When @command{@value{AS}}
2612 emits an object file, the partial program is assumed to start at address 0.
2613 @code{@value{LD}} assigns the final addresses for the partial program, so that
2614 different partial programs do not overlap. This is actually an
2615 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2618 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2619 addresses. These blocks slide to their run-time addresses as rigid
2620 units; their length does not change and neither does the order of bytes
2621 within them. Such a rigid unit is called a @emph{section}. Assigning
2622 run-time addresses to sections is called @dfn{relocation}. It includes
2623 the task of adjusting mentions of object-file addresses so they refer to
2624 the proper run-time addresses.
2626 For the H8/300 and H8/500,
2627 and for the Hitachi SH,
2628 @command{@value{AS}} pads sections if needed to
2629 ensure they end on a word (sixteen bit) boundary.
2632 @cindex standard assembler sections
2633 An object file written by @command{@value{AS}} has at least three sections, any
2634 of which may be empty. These are named @dfn{text}, @dfn{data} and
2639 When it generates COFF output,
2641 @command{@value{AS}} can also generate whatever other named sections you specify
2642 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2643 If you do not use any directives that place output in the @samp{.text}
2644 or @samp{.data} sections, these sections still exist, but are empty.
2649 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2651 @command{@value{AS}} can also generate whatever other named sections you
2652 specify using the @samp{.space} and @samp{.subspace} directives. See
2653 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2654 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2655 assembler directives.
2658 Additionally, @command{@value{AS}} uses different names for the standard
2659 text, data, and bss sections when generating SOM output. Program text
2660 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2661 BSS into @samp{$BSS$}.
2665 Within the object file, the text section starts at address @code{0}, the
2666 data section follows, and the bss section follows the data section.
2669 When generating either SOM or ELF output files on the HPPA, the text
2670 section starts at address @code{0}, the data section at address
2671 @code{0x4000000}, and the bss section follows the data section.
2674 To let @code{@value{LD}} know which data changes when the sections are
2675 relocated, and how to change that data, @command{@value{AS}} also writes to the
2676 object file details of the relocation needed. To perform relocation
2677 @code{@value{LD}} must know, each time an address in the object
2681 Where in the object file is the beginning of this reference to
2684 How long (in bytes) is this reference?
2686 Which section does the address refer to? What is the numeric value of
2688 (@var{address}) @minus{} (@var{start-address of section})?
2691 Is the reference to an address ``Program-Counter relative''?
2694 @cindex addresses, format of
2695 @cindex section-relative addressing
2696 In fact, every address @command{@value{AS}} ever uses is expressed as
2698 (@var{section}) + (@var{offset into section})
2701 Further, most expressions @command{@value{AS}} computes have this section-relative
2704 (For some object formats, such as SOM for the HPPA, some expressions are
2705 symbol-relative instead.)
2708 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2709 @var{N} into section @var{secname}.''
2711 Apart from text, data and bss sections you need to know about the
2712 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2713 addresses in the absolute section remain unchanged. For example, address
2714 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2715 @code{@value{LD}}. Although the linker never arranges two partial programs'
2716 data sections with overlapping addresses after linking, @emph{by definition}
2717 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2718 part of a program is always the same address when the program is running as
2719 address @code{@{absolute@ 239@}} in any other part of the program.
2721 The idea of sections is extended to the @dfn{undefined} section. Any
2722 address whose section is unknown at assembly time is by definition
2723 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2724 Since numbers are always defined, the only way to generate an undefined
2725 address is to mention an undefined symbol. A reference to a named
2726 common block would be such a symbol: its value is unknown at assembly
2727 time so it has section @emph{undefined}.
2729 By analogy the word @emph{section} is used to describe groups of sections in
2730 the linked program. @code{@value{LD}} puts all partial programs' text
2731 sections in contiguous addresses in the linked program. It is
2732 customary to refer to the @emph{text section} of a program, meaning all
2733 the addresses of all partial programs' text sections. Likewise for
2734 data and bss sections.
2736 Some sections are manipulated by @code{@value{LD}}; others are invented for
2737 use of @command{@value{AS}} and have no meaning except during assembly.
2740 @section Linker Sections
2741 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2746 @cindex named sections
2747 @cindex sections, named
2748 @item named sections
2751 @cindex text section
2752 @cindex data section
2756 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
2757 separate but equal sections. Anything you can say of one section is
2760 When the program is running, however, it is
2761 customary for the text section to be unalterable. The
2762 text section is often shared among processes: it contains
2763 instructions, constants and the like. The data section of a running
2764 program is usually alterable: for example, C variables would be stored
2765 in the data section.
2770 This section contains zeroed bytes when your program begins running. It
2771 is used to hold uninitialized variables or common storage. The length of
2772 each partial program's bss section is important, but because it starts
2773 out containing zeroed bytes there is no need to store explicit zero
2774 bytes in the object file. The bss section was invented to eliminate
2775 those explicit zeros from object files.
2777 @cindex absolute section
2778 @item absolute section
2779 Address 0 of this section is always ``relocated'' to runtime address 0.
2780 This is useful if you want to refer to an address that @code{@value{LD}} must
2781 not change when relocating. In this sense we speak of absolute
2782 addresses being ``unrelocatable'': they do not change during relocation.
2784 @cindex undefined section
2785 @item undefined section
2786 This ``section'' is a catch-all for address references to objects not in
2787 the preceding sections.
2788 @c FIXME: ref to some other doc on obj-file formats could go here.
2791 @cindex relocation example
2792 An idealized example of three relocatable sections follows.
2794 The example uses the traditional section names @samp{.text} and @samp{.data}.
2796 Memory addresses are on the horizontal axis.
2800 @c END TEXI2ROFF-KILL
2803 partial program # 1: |ttttt|dddd|00|
2810 partial program # 2: |TTT|DDD|000|
2813 +--+---+-----+--+----+---+-----+~~
2814 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2815 +--+---+-----+--+----+---+-----+~~
2817 addresses: 0 @dots{}
2824 \line{\it Partial program \#1: \hfil}
2825 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2826 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2828 \line{\it Partial program \#2: \hfil}
2829 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2830 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2832 \line{\it linked program: \hfil}
2833 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2834 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2835 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2836 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2838 \line{\it addresses: \hfil}
2842 @c END TEXI2ROFF-KILL
2845 @section Assembler Internal Sections
2847 @cindex internal assembler sections
2848 @cindex sections in messages, internal
2849 These sections are meant only for the internal use of @command{@value{AS}}. They
2850 have no meaning at run-time. You do not really need to know about these
2851 sections for most purposes; but they can be mentioned in @command{@value{AS}}
2852 warning messages, so it might be helpful to have an idea of their
2853 meanings to @command{@value{AS}}. These sections are used to permit the
2854 value of every expression in your assembly language program to be a
2855 section-relative address.
2858 @cindex assembler internal logic error
2859 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2860 An internal assembler logic error has been found. This means there is a
2861 bug in the assembler.
2863 @cindex expr (internal section)
2865 The assembler stores complex expression internally as combinations of
2866 symbols. When it needs to represent an expression as a symbol, it puts
2867 it in the expr section.
2869 @c FIXME item transfer[t] vector preload
2870 @c FIXME item transfer[t] vector postload
2871 @c FIXME item register
2875 @section Sub-Sections
2877 @cindex numbered subsections
2878 @cindex grouping data
2884 fall into two sections: text and data.
2886 You may have separate groups of
2888 data in named sections
2892 data in named sections
2898 that you want to end up near to each other in the object file, even though they
2899 are not contiguous in the assembler source. @command{@value{AS}} allows you to
2900 use @dfn{subsections} for this purpose. Within each section, there can be
2901 numbered subsections with values from 0 to 8192. Objects assembled into the
2902 same subsection go into the object file together with other objects in the same
2903 subsection. For example, a compiler might want to store constants in the text
2904 section, but might not want to have them interspersed with the program being
2905 assembled. In this case, the compiler could issue a @samp{.text 0} before each
2906 section of code being output, and a @samp{.text 1} before each group of
2907 constants being output.
2909 Subsections are optional. If you do not use subsections, everything
2910 goes in subsection number zero.
2913 Each subsection is zero-padded up to a multiple of four bytes.
2914 (Subsections may be padded a different amount on different flavors
2915 of @command{@value{AS}}.)
2919 On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word
2920 boundary (two bytes).
2921 The same is true on the Hitachi SH.
2924 @c FIXME section padding (alignment)?
2925 @c Rich Pixley says padding here depends on target obj code format; that
2926 @c doesn't seem particularly useful to say without further elaboration,
2927 @c so for now I say nothing about it. If this is a generic BFD issue,
2928 @c these paragraphs might need to vanish from this manual, and be
2929 @c discussed in BFD chapter of binutils (or some such).
2932 On the AMD 29K family, no particular padding is added to section or
2933 subsection sizes; @value{AS} forces no alignment on this platform.
2937 Subsections appear in your object file in numeric order, lowest numbered
2938 to highest. (All this to be compatible with other people's assemblers.)
2939 The object file contains no representation of subsections; @code{@value{LD}} and
2940 other programs that manipulate object files see no trace of them.
2941 They just see all your text subsections as a text section, and all your
2942 data subsections as a data section.
2944 To specify which subsection you want subsequent statements assembled
2945 into, use a numeric argument to specify it, in a @samp{.text
2946 @var{expression}} or a @samp{.data @var{expression}} statement.
2949 When generating COFF output, you
2954 can also use an extra subsection
2955 argument with arbitrary named sections: @samp{.section @var{name},
2958 @var{Expression} should be an absolute expression.
2959 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
2960 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
2961 begins in @code{text 0}. For instance:
2963 .text 0 # The default subsection is text 0 anyway.
2964 .ascii "This lives in the first text subsection. *"
2966 .ascii "But this lives in the second text subsection."
2968 .ascii "This lives in the data section,"
2969 .ascii "in the first data subsection."
2971 .ascii "This lives in the first text section,"
2972 .ascii "immediately following the asterisk (*)."
2975 Each section has a @dfn{location counter} incremented by one for every byte
2976 assembled into that section. Because subsections are merely a convenience
2977 restricted to @command{@value{AS}} there is no concept of a subsection location
2978 counter. There is no way to directly manipulate a location counter---but the
2979 @code{.align} directive changes it, and any label definition captures its
2980 current value. The location counter of the section where statements are being
2981 assembled is said to be the @dfn{active} location counter.
2984 @section bss Section
2987 @cindex common variable storage
2988 The bss section is used for local common variable storage.
2989 You may allocate address space in the bss section, but you may
2990 not dictate data to load into it before your program executes. When
2991 your program starts running, all the contents of the bss
2992 section are zeroed bytes.
2994 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
2995 @ref{Lcomm,,@code{.lcomm}}.
2997 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
2998 another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}.
3001 When assembling for a target which supports multiple sections, such as ELF or
3002 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3003 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3004 section. Typically the section will only contain symbol definitions and
3005 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3012 Symbols are a central concept: the programmer uses symbols to name
3013 things, the linker uses symbols to link, and the debugger uses symbols
3017 @cindex debuggers, and symbol order
3018 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3019 the same order they were declared. This may break some debuggers.
3024 * Setting Symbols:: Giving Symbols Other Values
3025 * Symbol Names:: Symbol Names
3026 * Dot:: The Special Dot Symbol
3027 * Symbol Attributes:: Symbol Attributes
3034 A @dfn{label} is written as a symbol immediately followed by a colon
3035 @samp{:}. The symbol then represents the current value of the
3036 active location counter, and is, for example, a suitable instruction
3037 operand. You are warned if you use the same symbol to represent two
3038 different locations: the first definition overrides any other
3042 On the HPPA, the usual form for a label need not be immediately followed by a
3043 colon, but instead must start in column zero. Only one label may be defined on
3044 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3045 provides a special directive @code{.label} for defining labels more flexibly.
3048 @node Setting Symbols
3049 @section Giving Symbols Other Values
3051 @cindex assigning values to symbols
3052 @cindex symbol values, assigning
3053 A symbol can be given an arbitrary value by writing a symbol, followed
3054 by an equals sign @samp{=}, followed by an expression
3055 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3056 directive. @xref{Set,,@code{.set}}.
3059 @section Symbol Names
3061 @cindex symbol names
3062 @cindex names, symbol
3063 @ifclear SPECIAL-SYMS
3064 Symbol names begin with a letter or with one of @samp{._}. On most
3065 machines, you can also use @code{$} in symbol names; exceptions are
3066 noted in @ref{Machine Dependencies}. That character may be followed by any
3067 string of digits, letters, dollar signs (unless otherwise noted in
3068 @ref{Machine Dependencies}), and underscores.
3071 For the AMD 29K family, @samp{?} is also allowed in the
3072 body of a symbol name, though not at its beginning.
3077 Symbol names begin with a letter or with one of @samp{._}. On the
3079 H8/500, you can also use @code{$} in symbol names. That character may
3080 be followed by any string of digits, letters, dollar signs (save on the
3081 H8/300), and underscores.
3085 Case of letters is significant: @code{foo} is a different symbol name
3088 Each symbol has exactly one name. Each name in an assembly language program
3089 refers to exactly one symbol. You may use that symbol name any number of times
3092 @subheading Local Symbol Names
3094 @cindex local symbol names
3095 @cindex symbol names, local
3096 @cindex temporary symbol names
3097 @cindex symbol names, temporary
3098 Local symbols help compilers and programmers use names temporarily.
3099 They create symbols which are guaranteed to be unique over the entire scope of
3100 the input source code and which can be referred to by a simple notation.
3101 To define a local symbol, write a label of the form @samp{@b{N}:} (where @b{N}
3102 represents any positive integer). To refer to the most recent previous
3103 definition of that symbol write @samp{@b{N}b}, using the same number as when
3104 you defined the label. To refer to the next definition of a local label, write
3105 @samp{@b{N}f}--- The @samp{b} stands for``backwards'' and the @samp{f} stands
3108 There is no restriction on how you can use these labels, and you can reuse them
3109 too. So that it is possible to repeatedly define the same local label (using
3110 the same number @samp{@b{N}}), although you can only refer to the most recently
3111 defined local label of that number (for a backwards reference) or the next
3112 definition of a specific local label for a forward reference. It is also worth
3113 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3114 implemented in a slightly more efficient manner than the others.
3125 Which is the equivalent of:
3128 label_1: branch label_3
3129 label_2: branch label_1
3130 label_3: branch label_4
3131 label_4: branch label_3
3134 Local symbol names are only a notational device. They are immediately
3135 transformed into more conventional symbol names before the assembler uses them.
3136 The symbol names stored in the symbol table, appearing in error messages and
3137 optionally emitted to the object file. The names are constructed using these
3142 All local labels begin with @samp{L}. Normally both @command{@value{AS}} and
3143 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
3144 used for symbols you are never intended to see. If you use the
3145 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3146 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3147 you may use them in debugging.
3150 This is the number that was used in the local label definition. So if the
3151 label is written @samp{55:} then the number is @samp{55}.
3154 This unusual character is included so you do not accidentally invent a symbol
3155 of the same name. The character has ASCII value of @samp{\002} (control-B).
3157 @item @emph{ordinal number}
3158 This is a serial number to keep the labels distinct. The first definition of
3159 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3160 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3161 the number @samp{1} and its 15th defintion gets @samp{15} as well.
3164 So for example, the first @code{1:} is named @code{L1@kbd{C-B}1}, the 44th
3165 @code{3:} is named @code{L3@kbd{C-B}44}.
3167 @subheading Dollar Local Labels
3168 @cindex dollar local symbols
3170 @code{@value{AS}} also supports an even more local form of local labels called
3171 dollar labels. These labels go out of scope (ie they become undefined) as soon
3172 as a non-local label is defined. Thus they remain valid for only a small
3173 region of the input source code. Normal local labels, by contrast, remain in
3174 scope for the entire file, or until they are redefined by another occurrence of
3175 the same local label.
3177 Dollar labels are defined in exactly the same way as ordinary local labels,
3178 except that instead of being terminated by a colon, they are terminated by a
3179 dollar sign. eg @samp{@b{55$}}.
3181 They can also be distinguished from ordinary local labels by their transformed
3182 name which uses ASCII character @samp{\001} (control-A) as the magic character
3183 to distinguish them from ordinary labels. Thus the 5th defintion of @samp{6$}
3184 is named @samp{L6@kbd{C-A}5}.
3187 @section The Special Dot Symbol
3189 @cindex dot (symbol)
3190 @cindex @code{.} (symbol)
3191 @cindex current address
3192 @cindex location counter
3193 The special symbol @samp{.} refers to the current address that
3194 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3195 .long .} defines @code{melvin} to contain its own address.
3196 Assigning a value to @code{.} is treated the same as a @code{.org}
3197 directive. Thus, the expression @samp{.=.+4} is the same as saying
3198 @ifclear no-space-dir
3207 @node Symbol Attributes
3208 @section Symbol Attributes
3210 @cindex symbol attributes
3211 @cindex attributes, symbol
3212 Every symbol has, as well as its name, the attributes ``Value'' and
3213 ``Type''. Depending on output format, symbols can also have auxiliary
3216 The detailed definitions are in @file{a.out.h}.
3219 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3220 all these attributes, and probably won't warn you. This makes the
3221 symbol an externally defined symbol, which is generally what you
3225 * Symbol Value:: Value
3226 * Symbol Type:: Type
3229 * a.out Symbols:: Symbol Attributes: @code{a.out}
3233 * a.out Symbols:: Symbol Attributes: @code{a.out}
3236 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3241 * COFF Symbols:: Symbol Attributes for COFF
3244 * SOM Symbols:: Symbol Attributes for SOM
3251 @cindex value of a symbol
3252 @cindex symbol value
3253 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3254 location in the text, data, bss or absolute sections the value is the
3255 number of addresses from the start of that section to the label.
3256 Naturally for text, data and bss sections the value of a symbol changes
3257 as @code{@value{LD}} changes section base addresses during linking. Absolute
3258 symbols' values do not change during linking: that is why they are
3261 The value of an undefined symbol is treated in a special way. If it is
3262 0 then the symbol is not defined in this assembler source file, and
3263 @code{@value{LD}} tries to determine its value from other files linked into the
3264 same program. You make this kind of symbol simply by mentioning a symbol
3265 name without defining it. A non-zero value represents a @code{.comm}
3266 common declaration. The value is how much common storage to reserve, in
3267 bytes (addresses). The symbol refers to the first address of the
3273 @cindex type of a symbol
3275 The type attribute of a symbol contains relocation (section)
3276 information, any flag settings indicating that a symbol is external, and
3277 (optionally), other information for linkers and debuggers. The exact
3278 format depends on the object-code output format in use.
3283 @c The following avoids a "widow" subsection title. @group would be
3284 @c better if it were available outside examples.
3287 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3289 @cindex @code{b.out} symbol attributes
3290 @cindex symbol attributes, @code{b.out}
3291 These symbol attributes appear only when @command{@value{AS}} is configured for
3292 one of the Berkeley-descended object output formats---@code{a.out} or
3298 @subsection Symbol Attributes: @code{a.out}
3300 @cindex @code{a.out} symbol attributes
3301 @cindex symbol attributes, @code{a.out}
3307 @subsection Symbol Attributes: @code{a.out}
3309 @cindex @code{a.out} symbol attributes
3310 @cindex symbol attributes, @code{a.out}
3314 * Symbol Desc:: Descriptor
3315 * Symbol Other:: Other
3319 @subsubsection Descriptor
3321 @cindex descriptor, of @code{a.out} symbol
3322 This is an arbitrary 16-bit value. You may establish a symbol's
3323 descriptor value by using a @code{.desc} statement
3324 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3325 @command{@value{AS}}.
3328 @subsubsection Other
3330 @cindex other attribute, of @code{a.out} symbol
3331 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3336 @subsection Symbol Attributes for COFF
3338 @cindex COFF symbol attributes
3339 @cindex symbol attributes, COFF
3341 The COFF format supports a multitude of auxiliary symbol attributes;
3342 like the primary symbol attributes, they are set between @code{.def} and
3343 @code{.endef} directives.
3345 @subsubsection Primary Attributes
3347 @cindex primary attributes, COFF symbols
3348 The symbol name is set with @code{.def}; the value and type,
3349 respectively, with @code{.val} and @code{.type}.
3351 @subsubsection Auxiliary Attributes
3353 @cindex auxiliary attributes, COFF symbols
3354 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3355 @code{.size}, and @code{.tag} can generate auxiliary symbol table
3356 information for COFF.
3361 @subsection Symbol Attributes for SOM
3363 @cindex SOM symbol attributes
3364 @cindex symbol attributes, SOM
3366 The SOM format for the HPPA supports a multitude of symbol attributes set with
3367 the @code{.EXPORT} and @code{.IMPORT} directives.
3369 The attributes are described in @cite{HP9000 Series 800 Assembly
3370 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3371 @code{EXPORT} assembler directive documentation.
3375 @chapter Expressions
3379 @cindex numeric values
3380 An @dfn{expression} specifies an address or numeric value.
3381 Whitespace may precede and/or follow an expression.
3383 The result of an expression must be an absolute number, or else an offset into
3384 a particular section. If an expression is not absolute, and there is not
3385 enough information when @command{@value{AS}} sees the expression to know its
3386 section, a second pass over the source program might be necessary to interpret
3387 the expression---but the second pass is currently not implemented.
3388 @command{@value{AS}} aborts with an error message in this situation.
3391 * Empty Exprs:: Empty Expressions
3392 * Integer Exprs:: Integer Expressions
3396 @section Empty Expressions
3398 @cindex empty expressions
3399 @cindex expressions, empty
3400 An empty expression has no value: it is just whitespace or null.
3401 Wherever an absolute expression is required, you may omit the
3402 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3403 is compatible with other assemblers.
3406 @section Integer Expressions
3408 @cindex integer expressions
3409 @cindex expressions, integer
3410 An @dfn{integer expression} is one or more @emph{arguments} delimited
3411 by @emph{operators}.
3414 * Arguments:: Arguments
3415 * Operators:: Operators
3416 * Prefix Ops:: Prefix Operators
3417 * Infix Ops:: Infix Operators
3421 @subsection Arguments
3423 @cindex expression arguments
3424 @cindex arguments in expressions
3425 @cindex operands in expressions
3426 @cindex arithmetic operands
3427 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3428 contexts arguments are sometimes called ``arithmetic operands''. In
3429 this manual, to avoid confusing them with the ``instruction operands'' of
3430 the machine language, we use the term ``argument'' to refer to parts of
3431 expressions only, reserving the word ``operand'' to refer only to machine
3432 instruction operands.
3434 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3435 @var{section} is one of text, data, bss, absolute,
3436 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3439 Numbers are usually integers.
3441 A number can be a flonum or bignum. In this case, you are warned
3442 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3443 these 32 bits are an integer. You may write integer-manipulating
3444 instructions that act on exotic constants, compatible with other
3447 @cindex subexpressions
3448 Subexpressions are a left parenthesis @samp{(} followed by an integer
3449 expression, followed by a right parenthesis @samp{)}; or a prefix
3450 operator followed by an argument.
3453 @subsection Operators
3455 @cindex operators, in expressions
3456 @cindex arithmetic functions
3457 @cindex functions, in expressions
3458 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3459 operators are followed by an argument. Infix operators appear
3460 between their arguments. Operators may be preceded and/or followed by
3464 @subsection Prefix Operator
3466 @cindex prefix operators
3467 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3468 one argument, which must be absolute.
3470 @c the tex/end tex stuff surrounding this small table is meant to make
3471 @c it align, on the printed page, with the similar table in the next
3472 @c section (which is inside an enumerate).
3474 \global\advance\leftskip by \itemindent
3479 @dfn{Negation}. Two's complement negation.
3481 @dfn{Complementation}. Bitwise not.
3485 \global\advance\leftskip by -\itemindent
3489 @subsection Infix Operators
3491 @cindex infix operators
3492 @cindex operators, permitted arguments
3493 @dfn{Infix operators} take two arguments, one on either side. Operators
3494 have precedence, but operations with equal precedence are performed left
3495 to right. Apart from @code{+} or @option{-}, both arguments must be
3496 absolute, and the result is absolute.
3499 @cindex operator precedence
3500 @cindex precedence of operators
3507 @dfn{Multiplication}.
3510 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3517 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3521 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3525 Intermediate precedence
3530 @dfn{Bitwise Inclusive Or}.
3536 @dfn{Bitwise Exclusive Or}.
3539 @dfn{Bitwise Or Not}.
3546 @cindex addition, permitted arguments
3547 @cindex plus, permitted arguments
3548 @cindex arguments for addition
3550 @dfn{Addition}. If either argument is absolute, the result has the section of
3551 the other argument. You may not add together arguments from different
3554 @cindex subtraction, permitted arguments
3555 @cindex minus, permitted arguments
3556 @cindex arguments for subtraction
3558 @dfn{Subtraction}. If the right argument is absolute, the
3559 result has the section of the left argument.
3560 If both arguments are in the same section, the result is absolute.
3561 You may not subtract arguments from different sections.
3562 @c FIXME is there still something useful to say about undefined - undefined ?
3564 @cindex comparison expressions
3565 @cindex expressions, comparison
3569 @dfn{Is Not Equal To}
3573 @dfn{Is Greater Than}
3575 @dfn{Is Greater Than Or Equal To}
3577 @dfn{Is Less Than Or Equal To}
3579 The comparison operators can be used as infix operators. A true results has a
3580 value of -1 whereas a false result has a value of 0. Note, these operators
3581 perform signed comparisons.
3584 @item Lowest Precedence
3593 These two logical operations can be used to combine the results of sub
3594 expressions. Note, unlike the comparison operators a true result returns a
3595 value of 1 but a false results does still return 0. Also note that the logical
3596 or operator has a slightly lower precedence than logical and.
3601 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3602 address; you can only have a defined section in one of the two arguments.
3605 @chapter Assembler Directives
3607 @cindex directives, machine independent
3608 @cindex pseudo-ops, machine independent
3609 @cindex machine independent directives
3610 All assembler directives have names that begin with a period (@samp{.}).
3611 The rest of the name is letters, usually in lower case.
3613 This chapter discusses directives that are available regardless of the
3614 target machine configuration for the @sc{gnu} assembler.
3616 Some machine configurations provide additional directives.
3617 @xref{Machine Dependencies}.
3620 @ifset machine-directives
3621 @xref{Machine Dependencies} for additional directives.
3626 * Abort:: @code{.abort}
3628 * ABORT:: @code{.ABORT}
3631 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3632 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3633 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3634 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3635 * Byte:: @code{.byte @var{expressions}}
3636 * Comm:: @code{.comm @var{symbol} , @var{length} }
3637 * Data:: @code{.data @var{subsection}}
3639 * Def:: @code{.def @var{name}}
3642 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3648 * Double:: @code{.double @var{flonums}}
3649 * Eject:: @code{.eject}
3650 * Else:: @code{.else}
3651 * Elseif:: @code{.elseif}
3654 * Endef:: @code{.endef}
3657 * Endfunc:: @code{.endfunc}
3658 * Endif:: @code{.endif}
3659 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3660 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3662 * Exitm:: @code{.exitm}
3663 * Extern:: @code{.extern}
3664 * Fail:: @code{.fail}
3665 @ifclear no-file-dir
3666 * File:: @code{.file @var{string}}
3669 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3670 * Float:: @code{.float @var{flonums}}
3671 * Func:: @code{.func}
3672 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3674 * Hidden:: @code{.hidden @var{names}}
3677 * hword:: @code{.hword @var{expressions}}
3678 * Ident:: @code{.ident}
3679 * If:: @code{.if @var{absolute expression}}
3680 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
3681 * Include:: @code{.include "@var{file}"}
3682 * Int:: @code{.int @var{expressions}}
3684 * Internal:: @code{.internal @var{names}}
3687 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3688 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3689 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3690 * Lflags:: @code{.lflags}
3691 @ifclear no-line-dir
3692 * Line:: @code{.line @var{line-number}}
3695 * Ln:: @code{.ln @var{line-number}}
3696 * Linkonce:: @code{.linkonce [@var{type}]}
3697 * List:: @code{.list}
3698 * Long:: @code{.long @var{expressions}}
3700 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3703 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3704 * MRI:: @code{.mri @var{val}}
3705 * Nolist:: @code{.nolist}
3706 * Octa:: @code{.octa @var{bignums}}
3707 * Org:: @code{.org @var{new-lc} , @var{fill}}
3708 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
3710 * PopSection:: @code{.popsection}
3711 * Previous:: @code{.previous}
3714 * Print:: @code{.print @var{string}}
3716 * Protected:: @code{.protected @var{names}}
3719 * Psize:: @code{.psize @var{lines}, @var{columns}}
3720 * Purgem:: @code{.purgem @var{name}}
3722 * PushSection:: @code{.pushsection @var{name}}
3725 * Quad:: @code{.quad @var{bignums}}
3726 * Rept:: @code{.rept @var{count}}
3727 * Sbttl:: @code{.sbttl "@var{subheading}"}
3729 * Scl:: @code{.scl @var{class}}
3730 * Section:: @code{.section @var{name}, @var{subsection}}
3733 * Set:: @code{.set @var{symbol}, @var{expression}}
3734 * Short:: @code{.short @var{expressions}}
3735 * Single:: @code{.single @var{flonums}}
3736 * Size:: @code{.size [@var{name} , @var{expression}]}
3737 * Skip:: @code{.skip @var{size} , @var{fill}}
3738 * Sleb128:: @code{.sleb128 @var{expressions}}
3739 * Space:: @code{.space @var{size} , @var{fill}}
3741 * Stab:: @code{.stabd, .stabn, .stabs}
3744 * String:: @code{.string "@var{str}"}
3745 * Struct:: @code{.struct @var{expression}}
3747 * SubSection:: @code{.subsection}
3748 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3752 * Tag:: @code{.tag @var{structname}}
3755 * Text:: @code{.text @var{subsection}}
3756 * Title:: @code{.title "@var{heading}"}
3757 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
3758 * Uleb128:: @code{.uleb128 @var{expressions}}
3760 * Val:: @code{.val @var{addr}}
3764 * Version:: @code{.version "@var{string}"}
3765 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
3766 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
3767 * Weak:: @code{.weak @var{names}}
3770 * Word:: @code{.word @var{expressions}}
3771 * Deprecated:: Deprecated Directives
3775 @section @code{.abort}
3777 @cindex @code{abort} directive
3778 @cindex stopping the assembly
3779 This directive stops the assembly immediately. It is for
3780 compatibility with other assemblers. The original idea was that the
3781 assembly language source would be piped into the assembler. If the sender
3782 of the source quit, it could use this directive tells @command{@value{AS}} to
3783 quit also. One day @code{.abort} will not be supported.
3787 @section @code{.ABORT}
3789 @cindex @code{ABORT} directive
3790 When producing COFF output, @command{@value{AS}} accepts this directive as a
3791 synonym for @samp{.abort}.
3794 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
3800 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3802 @cindex padding the location counter
3803 @cindex @code{align} directive
3804 Pad the location counter (in the current subsection) to a particular storage
3805 boundary. The first expression (which must be absolute) is the alignment
3806 required, as described below.
3808 The second expression (also absolute) gives the fill value to be stored in the
3809 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3810 padding bytes are normally zero. However, on some systems, if the section is
3811 marked as containing code and the fill value is omitted, the space is filled
3812 with no-op instructions.
3814 The third expression is also absolute, and is also optional. If it is present,
3815 it is the maximum number of bytes that should be skipped by this alignment
3816 directive. If doing the alignment would require skipping more bytes than the
3817 specified maximum, then the alignment is not done at all. You can omit the
3818 fill value (the second argument) entirely by simply using two commas after the
3819 required alignment; this can be useful if you want the alignment to be filled
3820 with no-op instructions when appropriate.
3822 The way the required alignment is specified varies from system to system.
3823 For the a29k, hppa, m68k, m88k, w65, sparc, and Hitachi SH, and i386 using ELF
3825 the first expression is the
3826 alignment request in bytes. For example @samp{.align 8} advances
3827 the location counter until it is a multiple of 8. If the location counter
3828 is already a multiple of 8, no change is needed.
3830 For other systems, including the i386 using a.out format, and the arm and
3831 strongarm, it is the
3832 number of low-order zero bits the location counter must have after
3833 advancement. For example @samp{.align 3} advances the location
3834 counter until it a multiple of 8. If the location counter is already a
3835 multiple of 8, no change is needed.
3837 This inconsistency is due to the different behaviors of the various
3838 native assemblers for these systems which GAS must emulate.
3839 GAS also provides @code{.balign} and @code{.p2align} directives,
3840 described later, which have a consistent behavior across all
3841 architectures (but are specific to GAS).
3844 @section @code{.ascii "@var{string}"}@dots{}
3846 @cindex @code{ascii} directive
3847 @cindex string literals
3848 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3849 separated by commas. It assembles each string (with no automatic
3850 trailing zero byte) into consecutive addresses.
3853 @section @code{.asciz "@var{string}"}@dots{}
3855 @cindex @code{asciz} directive
3856 @cindex zero-terminated strings
3857 @cindex null-terminated strings
3858 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3859 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3862 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3864 @cindex padding the location counter given number of bytes
3865 @cindex @code{balign} directive
3866 Pad the location counter (in the current subsection) to a particular
3867 storage boundary. The first expression (which must be absolute) is the
3868 alignment request in bytes. For example @samp{.balign 8} advances
3869 the location counter until it is a multiple of 8. If the location counter
3870 is already a multiple of 8, no change is needed.
3872 The second expression (also absolute) gives the fill value to be stored in the
3873 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3874 padding bytes are normally zero. However, on some systems, if the section is
3875 marked as containing code and the fill value is omitted, the space is filled
3876 with no-op instructions.
3878 The third expression is also absolute, and is also optional. If it is present,
3879 it is the maximum number of bytes that should be skipped by this alignment
3880 directive. If doing the alignment would require skipping more bytes than the
3881 specified maximum, then the alignment is not done at all. You can omit the
3882 fill value (the second argument) entirely by simply using two commas after the
3883 required alignment; this can be useful if you want the alignment to be filled
3884 with no-op instructions when appropriate.
3886 @cindex @code{balignw} directive
3887 @cindex @code{balignl} directive
3888 The @code{.balignw} and @code{.balignl} directives are variants of the
3889 @code{.balign} directive. The @code{.balignw} directive treats the fill
3890 pattern as a two byte word value. The @code{.balignl} directives treats the
3891 fill pattern as a four byte longword value. For example, @code{.balignw
3892 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3893 filled in with the value 0x368d (the exact placement of the bytes depends upon
3894 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3898 @section @code{.byte @var{expressions}}
3900 @cindex @code{byte} directive
3901 @cindex integers, one byte
3902 @code{.byte} expects zero or more expressions, separated by commas.
3903 Each expression is assembled into the next byte.
3906 @section @code{.comm @var{symbol} , @var{length} }
3908 @cindex @code{comm} directive
3909 @cindex symbol, common
3910 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
3911 common symbol in one object file may be merged with a defined or common symbol
3912 of the same name in another object file. If @code{@value{LD}} does not see a
3913 definition for the symbol--just one or more common symbols--then it will
3914 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
3915 absolute expression. If @code{@value{LD}} sees multiple common symbols with
3916 the same name, and they do not all have the same size, it will allocate space
3917 using the largest size.
3920 When using ELF, the @code{.comm} directive takes an optional third argument.
3921 This is the desired alignment of the symbol, specified as a byte boundary (for
3922 example, an alignment of 16 means that the least significant 4 bits of the
3923 address should be zero). The alignment must be an absolute expression, and it
3924 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
3925 for the common symbol, it will use the alignment when placing the symbol. If
3926 no alignment is specified, @command{@value{AS}} will set the alignment to the
3927 largest power of two less than or equal to the size of the symbol, up to a
3932 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
3933 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
3937 @section @code{.data @var{subsection}}
3939 @cindex @code{data} directive
3940 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
3941 end of the data subsection numbered @var{subsection} (which is an
3942 absolute expression). If @var{subsection} is omitted, it defaults
3947 @section @code{.def @var{name}}
3949 @cindex @code{def} directive
3950 @cindex COFF symbols, debugging
3951 @cindex debugging COFF symbols
3952 Begin defining debugging information for a symbol @var{name}; the
3953 definition extends until the @code{.endef} directive is encountered.
3956 This directive is only observed when @command{@value{AS}} is configured for COFF
3957 format output; when producing @code{b.out}, @samp{.def} is recognized,
3964 @section @code{.desc @var{symbol}, @var{abs-expression}}
3966 @cindex @code{desc} directive
3967 @cindex COFF symbol descriptor
3968 @cindex symbol descriptor, COFF
3969 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
3970 to the low 16 bits of an absolute expression.
3973 The @samp{.desc} directive is not available when @command{@value{AS}} is
3974 configured for COFF output; it is only for @code{a.out} or @code{b.out}
3975 object format. For the sake of compatibility, @command{@value{AS}} accepts
3976 it, but produces no output, when configured for COFF.
3982 @section @code{.dim}
3984 @cindex @code{dim} directive
3985 @cindex COFF auxiliary symbol information
3986 @cindex auxiliary symbol information, COFF
3987 This directive is generated by compilers to include auxiliary debugging
3988 information in the symbol table. It is only permitted inside
3989 @code{.def}/@code{.endef} pairs.
3992 @samp{.dim} is only meaningful when generating COFF format output; when
3993 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
3999 @section @code{.double @var{flonums}}
4001 @cindex @code{double} directive
4002 @cindex floating point numbers (double)
4003 @code{.double} expects zero or more flonums, separated by commas. It
4004 assembles floating point numbers.
4006 The exact kind of floating point numbers emitted depends on how
4007 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4011 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4012 in @sc{ieee} format.
4017 @section @code{.eject}
4019 @cindex @code{eject} directive
4020 @cindex new page, in listings
4021 @cindex page, in listings
4022 @cindex listing control: new page
4023 Force a page break at this point, when generating assembly listings.
4026 @section @code{.else}
4028 @cindex @code{else} directive
4029 @code{.else} is part of the @command{@value{AS}} support for conditional
4030 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
4031 of code to be assembled if the condition for the preceding @code{.if}
4035 @section @code{.elseif}
4037 @cindex @code{elseif} directive
4038 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4039 assembly; @pxref{If,,@code{.if}}. It is shorthand for beginning a new
4040 @code{.if} block that would otherwise fill the entire @code{.else} section.
4043 @section @code{.end}
4045 @cindex @code{end} directive
4046 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4047 process anything in the file past the @code{.end} directive.
4051 @section @code{.endef}
4053 @cindex @code{endef} directive
4054 This directive flags the end of a symbol definition begun with
4058 @samp{.endef} is only meaningful when generating COFF format output; if
4059 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4060 directive but ignores it.
4065 @section @code{.endfunc}
4066 @cindex @code{endfunc} directive
4067 @code{.endfunc} marks the end of a function specified with @code{.func}.
4070 @section @code{.endif}
4072 @cindex @code{endif} directive
4073 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4074 it marks the end of a block of code that is only assembled
4075 conditionally. @xref{If,,@code{.if}}.
4078 @section @code{.equ @var{symbol}, @var{expression}}
4080 @cindex @code{equ} directive
4081 @cindex assigning values to symbols
4082 @cindex symbols, assigning values to
4083 This directive sets the value of @var{symbol} to @var{expression}.
4084 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
4087 The syntax for @code{equ} on the HPPA is
4088 @samp{@var{symbol} .equ @var{expression}}.
4092 @section @code{.equiv @var{symbol}, @var{expression}}
4093 @cindex @code{equiv} directive
4094 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4095 the assembler will signal an error if @var{symbol} is already defined. Note a
4096 symbol which has been referenced but not actually defined is considered to be
4099 Except for the contents of the error message, this is roughly equivalent to
4108 @section @code{.err}
4109 @cindex @code{err} directive
4110 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4111 message and, unless the @option{-Z} option was used, it will not generate an
4112 object file. This can be used to signal error an conditionally compiled code.
4115 @section @code{.exitm}
4116 Exit early from the current macro definition. @xref{Macro}.
4119 @section @code{.extern}
4121 @cindex @code{extern} directive
4122 @code{.extern} is accepted in the source program---for compatibility
4123 with other assemblers---but it is ignored. @command{@value{AS}} treats
4124 all undefined symbols as external.
4127 @section @code{.fail @var{expression}}
4129 @cindex @code{fail} directive
4130 Generates an error or a warning. If the value of the @var{expression} is 500
4131 or more, @command{@value{AS}} will print a warning message. If the value is less
4132 than 500, @command{@value{AS}} will print an error message. The message will
4133 include the value of @var{expression}. This can occasionally be useful inside
4134 complex nested macros or conditional assembly.
4136 @ifclear no-file-dir
4138 @section @code{.file @var{string}}
4140 @cindex @code{file} directive
4141 @cindex logical file name
4142 @cindex file name, logical
4143 @code{.file} tells @command{@value{AS}} that we are about to start a new logical
4144 file. @var{string} is the new file name. In general, the filename is
4145 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4146 to specify an empty file name, you must give the quotes--@code{""}. This
4147 statement may go away in future: it is only recognized to be compatible with
4148 old @command{@value{AS}} programs.
4150 In some configurations of @command{@value{AS}}, @code{.file} has already been
4151 removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}.
4156 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4158 @cindex @code{fill} directive
4159 @cindex writing patterns in memory
4160 @cindex patterns, writing in memory
4161 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4162 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4163 may be zero or more. @var{Size} may be zero or more, but if it is
4164 more than 8, then it is deemed to have the value 8, compatible with
4165 other people's assemblers. The contents of each @var{repeat} bytes
4166 is taken from an 8-byte number. The highest order 4 bytes are
4167 zero. The lowest order 4 bytes are @var{value} rendered in the
4168 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4169 Each @var{size} bytes in a repetition is taken from the lowest order
4170 @var{size} bytes of this number. Again, this bizarre behavior is
4171 compatible with other people's assemblers.
4173 @var{size} and @var{value} are optional.
4174 If the second comma and @var{value} are absent, @var{value} is
4175 assumed zero. If the first comma and following tokens are absent,
4176 @var{size} is assumed to be 1.
4179 @section @code{.float @var{flonums}}
4181 @cindex floating point numbers (single)
4182 @cindex @code{float} directive
4183 This directive assembles zero or more flonums, separated by commas. It
4184 has the same effect as @code{.single}.
4186 The exact kind of floating point numbers emitted depends on how
4187 @command{@value{AS}} is configured.
4188 @xref{Machine Dependencies}.
4192 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4193 in @sc{ieee} format.
4198 @section @code{.func @var{name}[,@var{label}]}
4199 @cindex @code{func} directive
4200 @code{.func} emits debugging information to denote function @var{name}, and
4201 is ignored unless the file is assembled with debugging enabled.
4202 Only @samp{--gstabs} is currently supported.
4203 @var{label} is the entry point of the function and if omitted @var{name}
4204 prepended with the @samp{leading char} is used.
4205 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4206 All functions are currently defined to have @code{void} return type.
4207 The function must be terminated with @code{.endfunc}.
4210 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4212 @cindex @code{global} directive
4213 @cindex symbol, making visible to linker
4214 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4215 @var{symbol} in your partial program, its value is made available to
4216 other partial programs that are linked with it. Otherwise,
4217 @var{symbol} takes its attributes from a symbol of the same name
4218 from another file linked into the same program.
4220 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4221 compatibility with other assemblers.
4224 On the HPPA, @code{.global} is not always enough to make it accessible to other
4225 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4226 @xref{HPPA Directives,, HPPA Assembler Directives}.
4231 @section @code{.hidden @var{names}}
4233 @cindex @code{.hidden} directive
4235 This one of the ELF visibility directives. The other two are
4236 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4237 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4239 This directive overrides the named symbols default visibility (which is set by
4240 their binding: local, global or weak). The directive sets the visibility to
4241 @code{hidden} which means that the symbols are not visible to other components.
4242 Such symbols are always considered to be @code{protected} as well.
4246 @section @code{.hword @var{expressions}}
4248 @cindex @code{hword} directive
4249 @cindex integers, 16-bit
4250 @cindex numbers, 16-bit
4251 @cindex sixteen bit integers
4252 This expects zero or more @var{expressions}, and emits
4253 a 16 bit number for each.
4256 This directive is a synonym for @samp{.short}; depending on the target
4257 architecture, it may also be a synonym for @samp{.word}.
4261 This directive is a synonym for @samp{.short}.
4264 This directive is a synonym for both @samp{.short} and @samp{.word}.
4269 @section @code{.ident}
4271 @cindex @code{ident} directive
4272 This directive is used by some assemblers to place tags in object files.
4273 @command{@value{AS}} simply accepts the directive for source-file
4274 compatibility with such assemblers, but does not actually emit anything
4278 @section @code{.if @var{absolute expression}}
4280 @cindex conditional assembly
4281 @cindex @code{if} directive
4282 @code{.if} marks the beginning of a section of code which is only
4283 considered part of the source program being assembled if the argument
4284 (which must be an @var{absolute expression}) is non-zero. The end of
4285 the conditional section of code must be marked by @code{.endif}
4286 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4287 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4288 If you have several conditions to check, @code{.elseif} may be used to avoid
4289 nesting blocks if/else within each subsequent @code{.else} block.
4291 The following variants of @code{.if} are also supported:
4293 @cindex @code{ifdef} directive
4294 @item .ifdef @var{symbol}
4295 Assembles the following section of code if the specified @var{symbol}
4296 has been defined. Note a symbol which has been referenced but not yet defined
4297 is considered to be undefined.
4299 @cindex @code{ifc} directive
4300 @item .ifc @var{string1},@var{string2}
4301 Assembles the following section of code if the two strings are the same. The
4302 strings may be optionally quoted with single quotes. If they are not quoted,
4303 the first string stops at the first comma, and the second string stops at the
4304 end of the line. Strings which contain whitespace should be quoted. The
4305 string comparison is case sensitive.
4307 @cindex @code{ifeq} directive
4308 @item .ifeq @var{absolute expression}
4309 Assembles the following section of code if the argument is zero.
4311 @cindex @code{ifeqs} directive
4312 @item .ifeqs @var{string1},@var{string2}
4313 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4315 @cindex @code{ifge} directive
4316 @item .ifge @var{absolute expression}
4317 Assembles the following section of code if the argument is greater than or
4320 @cindex @code{ifgt} directive
4321 @item .ifgt @var{absolute expression}
4322 Assembles the following section of code if the argument is greater than zero.
4324 @cindex @code{ifle} directive
4325 @item .ifle @var{absolute expression}
4326 Assembles the following section of code if the argument is less than or equal
4329 @cindex @code{iflt} directive
4330 @item .iflt @var{absolute expression}
4331 Assembles the following section of code if the argument is less than zero.
4333 @cindex @code{ifnc} directive
4334 @item .ifnc @var{string1},@var{string2}.
4335 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4336 following section of code if the two strings are not the same.
4338 @cindex @code{ifndef} directive
4339 @cindex @code{ifnotdef} directive
4340 @item .ifndef @var{symbol}
4341 @itemx .ifnotdef @var{symbol}
4342 Assembles the following section of code if the specified @var{symbol}
4343 has not been defined. Both spelling variants are equivalent. Note a symbol
4344 which has been referenced but not yet defined is considered to be undefined.
4346 @cindex @code{ifne} directive
4347 @item .ifne @var{absolute expression}
4348 Assembles the following section of code if the argument is not equal to zero
4349 (in other words, this is equivalent to @code{.if}).
4351 @cindex @code{ifnes} directive
4352 @item .ifnes @var{string1},@var{string2}
4353 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4354 following section of code if the two strings are not the same.
4358 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4360 @cindex @code{incbin} directive
4361 @cindex binary files, including
4362 The @code{incbin} directive includes @var{file} verbatim at the current
4363 location. You can control the search paths used with the @samp{-I} command-line
4364 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4367 The @var{skip} argument skips a number of bytes from the start of the
4368 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4369 read. Note that the data is not aligned in any way, so it is the user's
4370 responsibility to make sure that proper alignment is provided both before and
4371 after the @code{incbin} directive.
4374 @section @code{.include "@var{file}"}
4376 @cindex @code{include} directive
4377 @cindex supporting files, including
4378 @cindex files, including
4379 This directive provides a way to include supporting files at specified
4380 points in your source program. The code from @var{file} is assembled as
4381 if it followed the point of the @code{.include}; when the end of the
4382 included file is reached, assembly of the original file continues. You
4383 can control the search paths used with the @samp{-I} command-line option
4384 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4388 @section @code{.int @var{expressions}}
4390 @cindex @code{int} directive
4391 @cindex integers, 32-bit
4392 Expect zero or more @var{expressions}, of any section, separated by commas.
4393 For each expression, emit a number that, at run time, is the value of that
4394 expression. The byte order and bit size of the number depends on what kind
4395 of target the assembly is for.
4399 On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit
4400 integers. On the H8/300H and the Hitachi SH, however, @code{.int} emits
4407 @section @code{.internal @var{names}}
4409 @cindex @code{.internal} directive
4411 This one of the ELF visibility directives. The other two are
4412 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4413 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4415 This directive overrides the named symbols default visibility (which is set by
4416 their binding: local, global or weak). The directive sets the visibility to
4417 @code{internal} which means that the symbols are considered to be @code{hidden}
4418 (ie not visible to other components), and that some extra, processor specific
4419 processing must also be performed upon the symbols as well.
4423 @section @code{.irp @var{symbol},@var{values}}@dots{}
4425 @cindex @code{irp} directive
4426 Evaluate a sequence of statements assigning different values to @var{symbol}.
4427 The sequence of statements starts at the @code{.irp} directive, and is
4428 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4429 set to @var{value}, and the sequence of statements is assembled. If no
4430 @var{value} is listed, the sequence of statements is assembled once, with
4431 @var{symbol} set to the null string. To refer to @var{symbol} within the
4432 sequence of statements, use @var{\symbol}.
4434 For example, assembling
4442 is equivalent to assembling
4451 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4453 @cindex @code{irpc} directive
4454 Evaluate a sequence of statements assigning different values to @var{symbol}.
4455 The sequence of statements starts at the @code{.irpc} directive, and is
4456 terminated by an @code{.endr} directive. For each character in @var{value},
4457 @var{symbol} is set to the character, and the sequence of statements is
4458 assembled. If no @var{value} is listed, the sequence of statements is
4459 assembled once, with @var{symbol} set to the null string. To refer to
4460 @var{symbol} within the sequence of statements, use @var{\symbol}.
4462 For example, assembling
4470 is equivalent to assembling
4479 @section @code{.lcomm @var{symbol} , @var{length}}
4481 @cindex @code{lcomm} directive
4482 @cindex local common symbols
4483 @cindex symbols, local common
4484 Reserve @var{length} (an absolute expression) bytes for a local common
4485 denoted by @var{symbol}. The section and value of @var{symbol} are
4486 those of the new local common. The addresses are allocated in the bss
4487 section, so that at run-time the bytes start off zeroed. @var{Symbol}
4488 is not declared global (@pxref{Global,,@code{.global}}), so is normally
4489 not visible to @code{@value{LD}}.
4492 Some targets permit a third argument to be used with @code{.lcomm}. This
4493 argument specifies the desired alignment of the symbol in the bss section.
4497 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
4498 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
4502 @section @code{.lflags}
4504 @cindex @code{lflags} directive (ignored)
4505 @command{@value{AS}} accepts this directive, for compatibility with other
4506 assemblers, but ignores it.
4508 @ifclear no-line-dir
4510 @section @code{.line @var{line-number}}
4512 @cindex @code{line} directive
4516 @section @code{.ln @var{line-number}}
4518 @cindex @code{ln} directive
4520 @cindex logical line number
4522 Change the logical line number. @var{line-number} must be an absolute
4523 expression. The next line has that logical line number. Therefore any other
4524 statements on the current line (after a statement separator character) are
4525 reported as on logical line number @var{line-number} @minus{} 1. One day
4526 @command{@value{AS}} will no longer support this directive: it is recognized only
4527 for compatibility with existing assembler programs.
4531 @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is
4532 not available; use the synonym @code{.ln} in that context.
4537 @ifclear no-line-dir
4538 Even though this is a directive associated with the @code{a.out} or
4539 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
4540 when producing COFF output, and treats @samp{.line} as though it
4541 were the COFF @samp{.ln} @emph{if} it is found outside a
4542 @code{.def}/@code{.endef} pair.
4544 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
4545 used by compilers to generate auxiliary symbol information for
4550 @section @code{.linkonce [@var{type}]}
4552 @cindex @code{linkonce} directive
4553 @cindex common sections
4554 Mark the current section so that the linker only includes a single copy of it.
4555 This may be used to include the same section in several different object files,
4556 but ensure that the linker will only include it once in the final output file.
4557 The @code{.linkonce} pseudo-op must be used for each instance of the section.
4558 Duplicate sections are detected based on the section name, so it should be
4561 This directive is only supported by a few object file formats; as of this
4562 writing, the only object file format which supports it is the Portable
4563 Executable format used on Windows NT.
4565 The @var{type} argument is optional. If specified, it must be one of the
4566 following strings. For example:
4570 Not all types may be supported on all object file formats.
4574 Silently discard duplicate sections. This is the default.
4577 Warn if there are duplicate sections, but still keep only one copy.
4580 Warn if any of the duplicates have different sizes.
4583 Warn if any of the duplicates do not have exactly the same contents.
4587 @section @code{.ln @var{line-number}}
4589 @cindex @code{ln} directive
4590 @ifclear no-line-dir
4591 @samp{.ln} is a synonym for @samp{.line}.
4594 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
4595 must be an absolute expression. The next line has that logical
4596 line number, so any other statements on the current line (after a
4597 statement separator character @code{;}) are reported as on logical
4598 line number @var{line-number} @minus{} 1.
4601 This directive is accepted, but ignored, when @command{@value{AS}} is
4602 configured for @code{b.out}; its effect is only associated with COFF
4608 @section @code{.mri @var{val}}
4610 @cindex @code{mri} directive
4611 @cindex MRI mode, temporarily
4612 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
4613 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
4614 affects code assembled until the next @code{.mri} directive, or until the end
4615 of the file. @xref{M, MRI mode, MRI mode}.
4618 @section @code{.list}
4620 @cindex @code{list} directive
4621 @cindex listing control, turning on
4622 Control (in conjunction with the @code{.nolist} directive) whether or
4623 not assembly listings are generated. These two directives maintain an
4624 internal counter (which is zero initially). @code{.list} increments the
4625 counter, and @code{.nolist} decrements it. Assembly listings are
4626 generated whenever the counter is greater than zero.
4628 By default, listings are disabled. When you enable them (with the
4629 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
4630 the initial value of the listing counter is one.
4633 @section @code{.long @var{expressions}}
4635 @cindex @code{long} directive
4636 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
4639 @c no one seems to know what this is for or whether this description is
4640 @c what it really ought to do
4642 @section @code{.lsym @var{symbol}, @var{expression}}
4644 @cindex @code{lsym} directive
4645 @cindex symbol, not referenced in assembly
4646 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
4647 the hash table, ensuring it cannot be referenced by name during the
4648 rest of the assembly. This sets the attributes of the symbol to be
4649 the same as the expression value:
4651 @var{other} = @var{descriptor} = 0
4652 @var{type} = @r{(section of @var{expression})}
4653 @var{value} = @var{expression}
4656 The new symbol is not flagged as external.
4660 @section @code{.macro}
4663 The commands @code{.macro} and @code{.endm} allow you to define macros that
4664 generate assembly output. For example, this definition specifies a macro
4665 @code{sum} that puts a sequence of numbers into memory:
4668 .macro sum from=0, to=5
4677 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
4689 @item .macro @var{macname}
4690 @itemx .macro @var{macname} @var{macargs} @dots{}
4691 @cindex @code{macro} directive
4692 Begin the definition of a macro called @var{macname}. If your macro
4693 definition requires arguments, specify their names after the macro name,
4694 separated by commas or spaces. You can supply a default value for any
4695 macro argument by following the name with @samp{=@var{deflt}}. For
4696 example, these are all valid @code{.macro} statements:
4700 Begin the definition of a macro called @code{comm}, which takes no
4703 @item .macro plus1 p, p1
4704 @itemx .macro plus1 p p1
4705 Either statement begins the definition of a macro called @code{plus1},
4706 which takes two arguments; within the macro definition, write
4707 @samp{\p} or @samp{\p1} to evaluate the arguments.
4709 @item .macro reserve_str p1=0 p2
4710 Begin the definition of a macro called @code{reserve_str}, with two
4711 arguments. The first argument has a default value, but not the second.
4712 After the definition is complete, you can call the macro either as
4713 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
4714 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
4715 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
4716 @samp{0}, and @samp{\p2} evaluating to @var{b}).
4719 When you call a macro, you can specify the argument values either by
4720 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
4721 @samp{sum to=17, from=9}.
4724 @cindex @code{endm} directive
4725 Mark the end of a macro definition.
4728 @cindex @code{exitm} directive
4729 Exit early from the current macro definition.
4731 @cindex number of macros executed
4732 @cindex macros, count executed
4734 @command{@value{AS}} maintains a counter of how many macros it has
4735 executed in this pseudo-variable; you can copy that number to your
4736 output with @samp{\@@}, but @emph{only within a macro definition}.
4739 @item LOCAL @var{name} [ , @dots{} ]
4740 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
4741 macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,,
4742 Alternate macro syntax}.
4744 Generate a string replacement for each of the @var{name} arguments, and
4745 replace any instances of @var{name} in each macro expansion. The
4746 replacement string is unique in the assembly, and different for each
4747 separate macro expansion. @code{LOCAL} allows you to write macros that
4748 define symbols, without fear of conflict between separate macro expansions.
4753 @section @code{.nolist}
4755 @cindex @code{nolist} directive
4756 @cindex listing control, turning off
4757 Control (in conjunction with the @code{.list} directive) whether or
4758 not assembly listings are generated. These two directives maintain an
4759 internal counter (which is zero initially). @code{.list} increments the
4760 counter, and @code{.nolist} decrements it. Assembly listings are
4761 generated whenever the counter is greater than zero.
4764 @section @code{.octa @var{bignums}}
4766 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
4767 @cindex @code{octa} directive
4768 @cindex integer, 16-byte
4769 @cindex sixteen byte integer
4770 This directive expects zero or more bignums, separated by commas. For each
4771 bignum, it emits a 16-byte integer.
4773 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
4774 hence @emph{octa}-word for 16 bytes.
4777 @section @code{.org @var{new-lc} , @var{fill}}
4779 @cindex @code{org} directive
4780 @cindex location counter, advancing
4781 @cindex advancing location counter
4782 @cindex current address, advancing
4783 Advance the location counter of the current section to
4784 @var{new-lc}. @var{new-lc} is either an absolute expression or an
4785 expression with the same section as the current subsection. That is,
4786 you can't use @code{.org} to cross sections: if @var{new-lc} has the
4787 wrong section, the @code{.org} directive is ignored. To be compatible
4788 with former assemblers, if the section of @var{new-lc} is absolute,
4789 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
4790 is the same as the current subsection.
4792 @code{.org} may only increase the location counter, or leave it
4793 unchanged; you cannot use @code{.org} to move the location counter
4796 @c double negative used below "not undefined" because this is a specific
4797 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
4798 @c section. doc@cygnus.com 18feb91
4799 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
4800 may not be undefined. If you really detest this restriction we eagerly await
4801 a chance to share your improved assembler.
4803 Beware that the origin is relative to the start of the section, not
4804 to the start of the subsection. This is compatible with other
4805 people's assemblers.
4807 When the location counter (of the current subsection) is advanced, the
4808 intervening bytes are filled with @var{fill} which should be an
4809 absolute expression. If the comma and @var{fill} are omitted,
4810 @var{fill} defaults to zero.
4813 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4815 @cindex padding the location counter given a power of two
4816 @cindex @code{p2align} directive
4817 Pad the location counter (in the current subsection) to a particular
4818 storage boundary. The first expression (which must be absolute) is the
4819 number of low-order zero bits the location counter must have after
4820 advancement. For example @samp{.p2align 3} advances the location
4821 counter until it a multiple of 8. If the location counter is already a
4822 multiple of 8, no change is needed.
4824 The second expression (also absolute) gives the fill value to be stored in the
4825 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4826 padding bytes are normally zero. However, on some systems, if the section is
4827 marked as containing code and the fill value is omitted, the space is filled
4828 with no-op instructions.
4830 The third expression is also absolute, and is also optional. If it is present,
4831 it is the maximum number of bytes that should be skipped by this alignment
4832 directive. If doing the alignment would require skipping more bytes than the
4833 specified maximum, then the alignment is not done at all. You can omit the
4834 fill value (the second argument) entirely by simply using two commas after the
4835 required alignment; this can be useful if you want the alignment to be filled
4836 with no-op instructions when appropriate.
4838 @cindex @code{p2alignw} directive
4839 @cindex @code{p2alignl} directive
4840 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
4841 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
4842 pattern as a two byte word value. The @code{.p2alignl} directives treats the
4843 fill pattern as a four byte longword value. For example, @code{.p2alignw
4844 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4845 filled in with the value 0x368d (the exact placement of the bytes depends upon
4846 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4851 @section @code{.previous}
4853 @cindex @code{.previous} directive
4854 @cindex Section Stack
4855 This is one of the ELF section stack manipulation directives. The others are
4856 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4857 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
4858 (@pxref{PopSection}).
4860 This directive swaps the current section (and subsection) with most recently
4861 referenced section (and subsection) prior to this one. Multiple
4862 @code{.previous} directives in a row will flip between two sections (and their
4865 In terms of the section stack, this directive swaps the current section with
4866 the top section on the section stack.
4871 @section @code{.popsection}
4873 @cindex @code{.popsection} directive
4874 @cindex Section Stack
4875 This is one of the ELF section stack manipulation directives. The others are
4876 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4877 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
4880 This directive replaces the current section (and subsection) with the top
4881 section (and subsection) on the section stack. This section is popped off the
4886 @section @code{.print @var{string}}
4888 @cindex @code{print} directive
4889 @command{@value{AS}} will print @var{string} on the standard output during
4890 assembly. You must put @var{string} in double quotes.
4894 @section @code{.protected @var{names}}
4896 @cindex @code{.protected} directive
4898 This one of the ELF visibility directives. The other two are
4899 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
4901 This directive overrides the named symbols default visibility (which is set by
4902 their binding: local, global or weak). The directive sets the visibility to
4903 @code{protected} which means that any references to the symbols from within the
4904 components that defines them must be resolved to the definition in that
4905 component, even if a definition in another component would normally preempt
4910 @section @code{.psize @var{lines} , @var{columns}}
4912 @cindex @code{psize} directive
4913 @cindex listing control: paper size
4914 @cindex paper size, for listings
4915 Use this directive to declare the number of lines---and, optionally, the
4916 number of columns---to use for each page, when generating listings.
4918 If you do not use @code{.psize}, listings use a default line-count
4919 of 60. You may omit the comma and @var{columns} specification; the
4920 default width is 200 columns.
4922 @command{@value{AS}} generates formfeeds whenever the specified number of
4923 lines is exceeded (or whenever you explicitly request one, using
4926 If you specify @var{lines} as @code{0}, no formfeeds are generated save
4927 those explicitly specified with @code{.eject}.
4930 @section @code{.purgem @var{name}}
4932 @cindex @code{purgem} directive
4933 Undefine the macro @var{name}, so that later uses of the string will not be
4934 expanded. @xref{Macro}.
4938 @section @code{.pushsection @var{name} , @var{subsection}}
4940 @cindex @code{.pushsection} directive
4941 @cindex Section Stack
4942 This is one of the ELF section stack manipulation directives. The others are
4943 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4944 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
4947 This directive is a synonym for @code{.section}. It pushes the current section
4948 (and subsection) onto the top of the section stack, and then replaces the
4949 current section and subsection with @code{name} and @code{subsection}.
4953 @section @code{.quad @var{bignums}}
4955 @cindex @code{quad} directive
4956 @code{.quad} expects zero or more bignums, separated by commas. For
4957 each bignum, it emits
4959 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
4960 warning message; and just takes the lowest order 8 bytes of the bignum.
4961 @cindex eight-byte integer
4962 @cindex integer, 8-byte
4964 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
4965 hence @emph{quad}-word for 8 bytes.
4968 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
4969 warning message; and just takes the lowest order 16 bytes of the bignum.
4970 @cindex sixteen-byte integer
4971 @cindex integer, 16-byte
4975 @section @code{.rept @var{count}}
4977 @cindex @code{rept} directive
4978 Repeat the sequence of lines between the @code{.rept} directive and the next
4979 @code{.endr} directive @var{count} times.
4981 For example, assembling
4989 is equivalent to assembling
4998 @section @code{.sbttl "@var{subheading}"}
5000 @cindex @code{sbttl} directive
5001 @cindex subtitles for listings
5002 @cindex listing control: subtitle
5003 Use @var{subheading} as the title (third line, immediately after the
5004 title line) when generating assembly listings.
5006 This directive affects subsequent pages, as well as the current page if
5007 it appears within ten lines of the top of a page.
5011 @section @code{.scl @var{class}}
5013 @cindex @code{scl} directive
5014 @cindex symbol storage class (COFF)
5015 @cindex COFF symbol storage class
5016 Set the storage-class value for a symbol. This directive may only be
5017 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5018 whether a symbol is static or external, or it may record further
5019 symbolic debugging information.
5022 The @samp{.scl} directive is primarily associated with COFF output; when
5023 configured to generate @code{b.out} output format, @command{@value{AS}}
5024 accepts this directive but ignores it.
5029 @section @code{.section @var{name}} (COFF version)
5031 @cindex @code{section} directive
5032 @cindex named section
5033 Use the @code{.section} directive to assemble the following code into a section
5036 This directive is only supported for targets that actually support arbitrarily
5037 named sections; on @code{a.out} targets, for example, it is not accepted, even
5038 with a standard @code{a.out} section name.
5040 For COFF targets, the @code{.section} directive is used in one of the following
5044 .section @var{name}[, "@var{flags}"]
5045 .section @var{name}[, @var{subsegment}]
5048 If the optional argument is quoted, it is taken as flags to use for the
5049 section. Each flag is a single character. The following flags are recognized:
5052 bss section (uninitialized data)
5054 section is not loaded
5064 shared section (meaningful for PE targets)
5066 ignored. (For compatibility with the ELF version)
5069 If no flags are specified, the default flags depend upon the section name. If
5070 the section name is not recognized, the default will be for the section to be
5071 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5072 from the section, rather than adding them, so if they are used on their own it
5073 will be as if no flags had been specified at all.
5075 If the optional argument to the @code{.section} directive is not quoted, it is
5076 taken as a subsegment number (@pxref{Sub-Sections}).
5079 @section @code{.section @var{name}} (ELF version)
5081 @cindex @code{section} directive
5082 @cindex named section
5084 @cindex Section Stack
5085 This is one of the ELF section stack manipulation directives. The others are
5086 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5087 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5088 @code{.previous} (@pxref{Previous}).
5091 For ELF targets, the @code{.section} directive is used like this:
5094 .section @var{name} [, "@var{flags}"[, @@@var{type}[, @@@var{entsize}]]]
5097 The optional @var{flags} argument is a quoted string which may contain any
5098 combination of the following characters:
5101 section is allocatable
5105 section is executable
5107 section is mergeable
5109 section contains zero terminated strings
5112 The optional @var{type} argument may contain one of the following constants:
5115 section contains data
5117 section does not contain data (i.e., section only occupies space)
5120 Note on targets where the @code{@@} character is the start of a comment (eg
5121 ARM) then another character is used instead. For example the ARM port uses the
5124 If @var{flags} contains @code{M} flag, @var{type} argument must be specified
5125 as well as @var{entsize} argument. Sections with @code{M} flag but not
5126 @code{S} flag must contain fixed size constants, each @var{entsize} octets
5127 long. Sections with both @code{M} and @code{S} must contain zero terminated
5128 strings where each character is @var{entsize} bytes long. The linker may remove
5129 duplicates within sections with the same name, same entity size and same flags.
5131 If no flags are specified, the default flags depend upon the section name. If
5132 the section name is not recognized, the default will be for the section to have
5133 none of the above flags: it will not be allocated in memory, nor writable, nor
5134 executable. The section will contain data.
5136 For ELF targets, the assembler supports another type of @code{.section}
5137 directive for compatibility with the Solaris assembler:
5140 .section "@var{name}"[, @var{flags}...]
5143 Note that the section name is quoted. There may be a sequence of comma
5147 section is allocatable
5151 section is executable
5154 This directive replaces the current section and subsection. The replaced
5155 section and subsection are pushed onto the section stack. See the contents of
5156 the gas testsuite directory @code{gas/testsuite/gas/elf} for some examples of
5157 how this directive and the other section stack directives work.
5160 @section @code{.set @var{symbol}, @var{expression}}
5162 @cindex @code{set} directive
5163 @cindex symbol value, setting
5164 Set the value of @var{symbol} to @var{expression}. This
5165 changes @var{symbol}'s value and type to conform to
5166 @var{expression}. If @var{symbol} was flagged as external, it remains
5167 flagged (@pxref{Symbol Attributes}).
5169 You may @code{.set} a symbol many times in the same assembly.
5171 If you @code{.set} a global symbol, the value stored in the object
5172 file is the last value stored into it.
5175 The syntax for @code{set} on the HPPA is
5176 @samp{@var{symbol} .set @var{expression}}.
5180 @section @code{.short @var{expressions}}
5182 @cindex @code{short} directive
5184 @code{.short} is normally the same as @samp{.word}.
5185 @xref{Word,,@code{.word}}.
5187 In some configurations, however, @code{.short} and @code{.word} generate
5188 numbers of different lengths; @pxref{Machine Dependencies}.
5192 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
5195 This expects zero or more @var{expressions}, and emits
5196 a 16 bit number for each.
5201 @section @code{.single @var{flonums}}
5203 @cindex @code{single} directive
5204 @cindex floating point numbers (single)
5205 This directive assembles zero or more flonums, separated by commas. It
5206 has the same effect as @code{.float}.
5208 The exact kind of floating point numbers emitted depends on how
5209 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5213 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
5214 numbers in @sc{ieee} format.
5219 @section @code{.size} (COFF version)
5221 @cindex @code{size} directive
5222 This directive is generated by compilers to include auxiliary debugging
5223 information in the symbol table. It is only permitted inside
5224 @code{.def}/@code{.endef} pairs.
5227 @samp{.size} is only meaningful when generating COFF format output; when
5228 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5232 @section @code{.size @var{name} , @var{expression}} (ELF version)
5233 @cindex @code{size} directive
5235 This directive is used to set the size associated with a symbol @var{name}.
5236 The size in bytes is computed from @var{expression} which can make use of label
5237 arithmetic. This directive is typically used to set the size of function
5241 @section @code{.sleb128 @var{expressions}}
5243 @cindex @code{sleb128} directive
5244 @var{sleb128} stands for ``signed little endian base 128.'' This is a
5245 compact, variable length representation of numbers used by the DWARF
5246 symbolic debugging format. @xref{Uleb128,@code{.uleb128}}.
5248 @ifclear no-space-dir
5250 @section @code{.skip @var{size} , @var{fill}}
5252 @cindex @code{skip} directive
5253 @cindex filling memory
5254 This directive emits @var{size} bytes, each of value @var{fill}. Both
5255 @var{size} and @var{fill} are absolute expressions. If the comma and
5256 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
5260 @section @code{.space @var{size} , @var{fill}}
5262 @cindex @code{space} directive
5263 @cindex filling memory
5264 This directive emits @var{size} bytes, each of value @var{fill}. Both
5265 @var{size} and @var{fill} are absolute expressions. If the comma
5266 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
5271 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
5272 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
5273 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
5274 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
5283 @section @code{.space}
5284 @cindex @code{space} directive
5286 On the AMD 29K, this directive is ignored; it is accepted for
5287 compatibility with other AMD 29K assemblers.
5290 @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive
5291 @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}.
5297 @section @code{.stabd, .stabn, .stabs}
5299 @cindex symbolic debuggers, information for
5300 @cindex @code{stab@var{x}} directives
5301 There are three directives that begin @samp{.stab}.
5302 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
5303 The symbols are not entered in the @command{@value{AS}} hash table: they
5304 cannot be referenced elsewhere in the source file.
5305 Up to five fields are required:
5309 This is the symbol's name. It may contain any character except
5310 @samp{\000}, so is more general than ordinary symbol names. Some
5311 debuggers used to code arbitrarily complex structures into symbol names
5315 An absolute expression. The symbol's type is set to the low 8 bits of
5316 this expression. Any bit pattern is permitted, but @code{@value{LD}}
5317 and debuggers choke on silly bit patterns.
5320 An absolute expression. The symbol's ``other'' attribute is set to the
5321 low 8 bits of this expression.
5324 An absolute expression. The symbol's descriptor is set to the low 16
5325 bits of this expression.
5328 An absolute expression which becomes the symbol's value.
5331 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
5332 or @code{.stabs} statement, the symbol has probably already been created;
5333 you get a half-formed symbol in your object file. This is
5334 compatible with earlier assemblers!
5337 @cindex @code{stabd} directive
5338 @item .stabd @var{type} , @var{other} , @var{desc}
5340 The ``name'' of the symbol generated is not even an empty string.
5341 It is a null pointer, for compatibility. Older assemblers used a
5342 null pointer so they didn't waste space in object files with empty
5345 The symbol's value is set to the location counter,
5346 relocatably. When your program is linked, the value of this symbol
5347 is the address of the location counter when the @code{.stabd} was
5350 @cindex @code{stabn} directive
5351 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
5352 The name of the symbol is set to the empty string @code{""}.
5354 @cindex @code{stabs} directive
5355 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
5356 All five fields are specified.
5362 @section @code{.string} "@var{str}"
5364 @cindex string, copying to object file
5365 @cindex @code{string} directive
5367 Copy the characters in @var{str} to the object file. You may specify more than
5368 one string to copy, separated by commas. Unless otherwise specified for a
5369 particular machine, the assembler marks the end of each string with a 0 byte.
5370 You can use any of the escape sequences described in @ref{Strings,,Strings}.
5373 @section @code{.struct @var{expression}}
5375 @cindex @code{struct} directive
5376 Switch to the absolute section, and set the section offset to @var{expression},
5377 which must be an absolute expression. You might use this as follows:
5386 This would define the symbol @code{field1} to have the value 0, the symbol
5387 @code{field2} to have the value 4, and the symbol @code{field3} to have the
5388 value 8. Assembly would be left in the absolute section, and you would need to
5389 use a @code{.section} directive of some sort to change to some other section
5390 before further assembly.
5394 @section @code{.subsection @var{name}}
5396 @cindex @code{.subsection} directive
5397 @cindex Section Stack
5398 This is one of the ELF section stack manipulation directives. The others are
5399 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
5400 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5403 This directive replaces the current subsection with @code{name}. The current
5404 section is not changed. The replaced subsection is put onto the section stack
5405 in place of the then current top of stack subsection.
5410 @section @code{.symver}
5411 @cindex @code{symver} directive
5412 @cindex symbol versioning
5413 @cindex versions of symbols
5414 Use the @code{.symver} directive to bind symbols to specific version nodes
5415 within a source file. This is only supported on ELF platforms, and is
5416 typically used when assembling files to be linked into a shared library.
5417 There are cases where it may make sense to use this in objects to be bound
5418 into an application itself so as to override a versioned symbol from a
5421 For ELF targets, the @code{.symver} directive can be used like this:
5423 .symver @var{name}, @var{name2@@nodename}
5425 If the symbol @var{name} is defined within the file
5426 being assembled, the @code{.symver} directive effectively creates a symbol
5427 alias with the name @var{name2@@nodename}, and in fact the main reason that we
5428 just don't try and create a regular alias is that the @var{@@} character isn't
5429 permitted in symbol names. The @var{name2} part of the name is the actual name
5430 of the symbol by which it will be externally referenced. The name @var{name}
5431 itself is merely a name of convenience that is used so that it is possible to
5432 have definitions for multiple versions of a function within a single source
5433 file, and so that the compiler can unambiguously know which version of a
5434 function is being mentioned. The @var{nodename} portion of the alias should be
5435 the name of a node specified in the version script supplied to the linker when
5436 building a shared library. If you are attempting to override a versioned
5437 symbol from a shared library, then @var{nodename} should correspond to the
5438 nodename of the symbol you are trying to override.
5440 If the symbol @var{name} is not defined within the file being assembled, all
5441 references to @var{name} will be changed to @var{name2@@nodename}. If no
5442 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
5445 Another usage of the @code{.symver} directive is:
5447 .symver @var{name}, @var{name2@@@@nodename}
5449 In this case, the symbol @var{name} must exist and be defined within
5450 the file being assembled. It is similar to @var{name2@@nodename}. The
5451 difference is @var{name2@@@@nodename} will also be used to resolve
5452 references to @var{name2} by the linker.
5454 The third usage of the @code{.symver} directive is:
5456 .symver @var{name}, @var{name2@@@@@@nodename}
5458 When @var{name} is not defined within the
5459 file being assembled, it is treated as @var{name2@@nodename}. When
5460 @var{name} is defined within the file being assembled, the symbol
5461 name, @var{name}, will be changed to @var{name2@@@@nodename}.
5466 @section @code{.tag @var{structname}}
5468 @cindex COFF structure debugging
5469 @cindex structure debugging, COFF
5470 @cindex @code{tag} directive
5471 This directive is generated by compilers to include auxiliary debugging
5472 information in the symbol table. It is only permitted inside
5473 @code{.def}/@code{.endef} pairs. Tags are used to link structure
5474 definitions in the symbol table with instances of those structures.
5477 @samp{.tag} is only used when generating COFF format output; when
5478 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5484 @section @code{.text @var{subsection}}
5486 @cindex @code{text} directive
5487 Tells @command{@value{AS}} to assemble the following statements onto the end of
5488 the text subsection numbered @var{subsection}, which is an absolute
5489 expression. If @var{subsection} is omitted, subsection number zero
5493 @section @code{.title "@var{heading}"}
5495 @cindex @code{title} directive
5496 @cindex listing control: title line
5497 Use @var{heading} as the title (second line, immediately after the
5498 source file name and pagenumber) when generating assembly listings.
5500 This directive affects subsequent pages, as well as the current page if
5501 it appears within ten lines of the top of a page.
5504 @section @code{.type @var{int}} (COFF version)
5506 @cindex COFF symbol type
5507 @cindex symbol type, COFF
5508 @cindex @code{type} directive
5509 This directive, permitted only within @code{.def}/@code{.endef} pairs,
5510 records the integer @var{int} as the type attribute of a symbol table entry.
5513 @samp{.type} is associated only with COFF format output; when
5514 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
5515 directive but ignores it.
5518 @section @code{.type @var{name} , @var{type description}} (ELF version)
5520 @cindex ELF symbol type
5521 @cindex symbol type, ELF
5522 @cindex @code{type} directive
5523 This directive is used to set the type of symbol @var{name} to be either a
5524 function symbol or an object symbol. There are five different syntaxes
5525 supported for the @var{type description} field, in order to provide
5526 compatibility with various other assemblers. The syntaxes supported are:
5529 .type <name>,#function
5530 .type <name>,#object
5532 .type <name>,@@function
5533 .type <name>,@@object
5535 .type <name>,%function
5536 .type <name>,%object
5538 .type <name>,"function"
5539 .type <name>,"object"
5541 .type <name> STT_FUNCTION
5542 .type <name> STT_OBJECT
5546 @section @code{.uleb128 @var{expressions}}
5548 @cindex @code{uleb128} directive
5549 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
5550 compact, variable length representation of numbers used by the DWARF
5551 symbolic debugging format. @xref{Sleb128,@code{.sleb128}}.
5555 @section @code{.val @var{addr}}
5557 @cindex @code{val} directive
5558 @cindex COFF value attribute
5559 @cindex value attribute, COFF
5560 This directive, permitted only within @code{.def}/@code{.endef} pairs,
5561 records the address @var{addr} as the value attribute of a symbol table
5565 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
5566 configured for @code{b.out}, it accepts this directive but ignores it.
5572 @section @code{.version "@var{string}"}
5574 @cindex @code{.version}
5575 This directive creates a @code{.note} section and places into it an ELF
5576 formatted note of type NT_VERSION. The note's name is set to @code{string}.
5581 @section @code{.vtable_entry @var{table}, @var{offset}}
5583 @cindex @code{.vtable_entry}
5584 This directive finds or creates a symbol @code{table} and creates a
5585 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
5588 @section @code{.vtable_inherit @var{child}, @var{parent}}
5590 @cindex @code{.vtable_inherit}
5591 This directive finds the symbol @code{child} and finds or creates the symbol
5592 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
5593 parent whose addend is the value of the child symbol. As a special case the
5594 parent name of @code{0} is treated as refering the @code{*ABS*} section.
5599 @section @code{.weak @var{names}}
5601 @cindex @code{.weak}
5602 This directive sets the weak attribute on the comma separated list of symbol
5603 @code{names}. If the symbols do not already exist, they will be created.
5607 @section @code{.word @var{expressions}}
5609 @cindex @code{word} directive
5610 This directive expects zero or more @var{expressions}, of any section,
5611 separated by commas.
5614 For each expression, @command{@value{AS}} emits a 32-bit number.
5617 For each expression, @command{@value{AS}} emits a 16-bit number.
5622 The size of the number emitted, and its byte order,
5623 depend on what target computer the assembly is for.
5626 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
5627 @c happen---32-bit addressability, period; no long/short jumps.
5628 @ifset DIFF-TBL-KLUGE
5629 @cindex difference tables altered
5630 @cindex altered difference tables
5632 @emph{Warning: Special Treatment to support Compilers}
5636 Machines with a 32-bit address space, but that do less than 32-bit
5637 addressing, require the following special treatment. If the machine of
5638 interest to you does 32-bit addressing (or doesn't require it;
5639 @pxref{Machine Dependencies}), you can ignore this issue.
5642 In order to assemble compiler output into something that works,
5643 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
5644 Directives of the form @samp{.word sym1-sym2} are often emitted by
5645 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
5646 directive of the form @samp{.word sym1-sym2}, and the difference between
5647 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
5648 creates a @dfn{secondary jump table}, immediately before the next label.
5649 This secondary jump table is preceded by a short-jump to the
5650 first byte after the secondary table. This short-jump prevents the flow
5651 of control from accidentally falling into the new table. Inside the
5652 table is a long-jump to @code{sym2}. The original @samp{.word}
5653 contains @code{sym1} minus the address of the long-jump to
5656 If there were several occurrences of @samp{.word sym1-sym2} before the
5657 secondary jump table, all of them are adjusted. If there was a
5658 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
5659 long-jump to @code{sym4} is included in the secondary jump table,
5660 and the @code{.word} directives are adjusted to contain @code{sym3}
5661 minus the address of the long-jump to @code{sym4}; and so on, for as many
5662 entries in the original jump table as necessary.
5665 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
5666 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
5667 assembly language programmers.
5670 @c end DIFF-TBL-KLUGE
5673 @section Deprecated Directives
5675 @cindex deprecated directives
5676 @cindex obsolescent directives
5677 One day these directives won't work.
5678 They are included for compatibility with older assemblers.
5685 @node Machine Dependencies
5686 @chapter Machine Dependent Features
5688 @cindex machine dependencies
5689 The machine instruction sets are (almost by definition) different on
5690 each machine where @command{@value{AS}} runs. Floating point representations
5691 vary as well, and @command{@value{AS}} often supports a few additional
5692 directives or command-line options for compatibility with other
5693 assemblers on a particular platform. Finally, some versions of
5694 @command{@value{AS}} support special pseudo-instructions for branch
5697 This chapter discusses most of these differences, though it does not
5698 include details on any machine's instruction set. For details on that
5699 subject, see the hardware manufacturer's manual.
5703 * AMD29K-Dependent:: AMD 29K Dependent Features
5706 * Alpha-Dependent:: Alpha Dependent Features
5709 * ARC-Dependent:: ARC Dependent Features
5712 * ARM-Dependent:: ARM Dependent Features
5715 * CRIS-Dependent:: CRIS Dependent Features
5718 * D10V-Dependent:: D10V Dependent Features
5721 * D30V-Dependent:: D30V Dependent Features
5724 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
5727 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
5730 * HPPA-Dependent:: HPPA Dependent Features
5733 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
5736 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
5739 * i860-Dependent:: Intel 80860 Dependent Features
5742 * i960-Dependent:: Intel 80960 Dependent Features
5745 * IP2K-Dependent:: IP2K Dependent Features
5748 * M32R-Dependent:: M32R Dependent Features
5751 * M68K-Dependent:: M680x0 Dependent Features
5754 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
5757 * M88K-Dependent:: M880x0 Dependent Features
5760 * MIPS-Dependent:: MIPS Dependent Features
5763 * MMIX-Dependent:: MMIX Dependent Features
5766 * MSP430-Dependent:: MSP430 Dependent Features
5769 * SH-Dependent:: Hitachi SH Dependent Features
5770 * SH64-Dependent:: Hitachi SH64 Dependent Features
5773 * PDP-11-Dependent:: PDP-11 Dependent Features
5776 * PJ-Dependent:: picoJava Dependent Features
5779 * PPC-Dependent:: PowerPC Dependent Features
5782 * Sparc-Dependent:: SPARC Dependent Features
5785 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
5788 * V850-Dependent:: V850 Dependent Features
5791 * Z8000-Dependent:: Z8000 Dependent Features
5794 * Vax-Dependent:: VAX Dependent Features
5801 @c The following major nodes are *sections* in the GENERIC version, *chapters*
5802 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
5803 @c peculiarity: to preserve cross-references, there must be a node called
5804 @c "Machine Dependencies". Hence the conditional nodenames in each
5805 @c major node below. Node defaulting in makeinfo requires adjacency of
5806 @c node and sectioning commands; hence the repetition of @chapter BLAH
5807 @c in both conditional blocks.
5810 @include c-a29k.texi
5814 @include c-alpha.texi
5826 @include c-cris.texi
5831 @node Machine Dependencies
5832 @chapter Machine Dependent Features
5834 The machine instruction sets are different on each Hitachi chip family,
5835 and there are also some syntax differences among the families. This
5836 chapter describes the specific @command{@value{AS}} features for each
5840 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
5841 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
5842 * SH-Dependent:: Hitachi SH Dependent Features
5849 @include c-d10v.texi
5853 @include c-d30v.texi
5857 @include c-h8300.texi
5861 @include c-h8500.texi
5865 @include c-hppa.texi
5869 @include c-i370.texi
5873 @include c-i386.texi
5877 @include c-i860.texi
5881 @include c-i960.texi
5885 @include c-ia64.texi
5889 @include c-ip2k.texi
5893 @include c-m32r.texi
5897 @include c-m68k.texi
5901 @include c-m68hc11.texi
5905 @include c-m88k.texi
5909 @include c-mips.texi
5913 @include c-mmix.texi
5917 @include c-msp430.texi
5921 @include c-ns32k.texi
5925 @include c-pdp11.texi
5938 @include c-sh64.texi
5942 @include c-sparc.texi
5946 @include c-tic54x.texi
5958 @include c-v850.texi
5962 @c reverse effect of @down at top of generic Machine-Dep chapter
5966 @node Reporting Bugs
5967 @chapter Reporting Bugs
5968 @cindex bugs in assembler
5969 @cindex reporting bugs in assembler
5971 Your bug reports play an essential role in making @command{@value{AS}} reliable.
5973 Reporting a bug may help you by bringing a solution to your problem, or it may
5974 not. But in any case the principal function of a bug report is to help the
5975 entire community by making the next version of @command{@value{AS}} work better.
5976 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
5978 In order for a bug report to serve its purpose, you must include the
5979 information that enables us to fix the bug.
5982 * Bug Criteria:: Have you found a bug?
5983 * Bug Reporting:: How to report bugs
5987 @section Have you found a bug?
5988 @cindex bug criteria
5990 If you are not sure whether you have found a bug, here are some guidelines:
5993 @cindex fatal signal
5994 @cindex assembler crash
5995 @cindex crash of assembler
5997 If the assembler gets a fatal signal, for any input whatever, that is a
5998 @command{@value{AS}} bug. Reliable assemblers never crash.
6000 @cindex error on valid input
6002 If @command{@value{AS}} produces an error message for valid input, that is a bug.
6004 @cindex invalid input
6006 If @command{@value{AS}} does not produce an error message for invalid input, that
6007 is a bug. However, you should note that your idea of ``invalid input'' might
6008 be our idea of ``an extension'' or ``support for traditional practice''.
6011 If you are an experienced user of assemblers, your suggestions for improvement
6012 of @command{@value{AS}} are welcome in any case.
6016 @section How to report bugs
6018 @cindex assembler bugs, reporting
6020 A number of companies and individuals offer support for @sc{gnu} products. If
6021 you obtained @command{@value{AS}} from a support organization, we recommend you
6022 contact that organization first.
6024 You can find contact information for many support companies and
6025 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
6028 In any event, we also recommend that you send bug reports for @command{@value{AS}}
6029 to @samp{bug-binutils@@gnu.org}.
6031 The fundamental principle of reporting bugs usefully is this:
6032 @strong{report all the facts}. If you are not sure whether to state a
6033 fact or leave it out, state it!
6035 Often people omit facts because they think they know what causes the problem
6036 and assume that some details do not matter. Thus, you might assume that the
6037 name of a symbol you use in an example does not matter. Well, probably it does
6038 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
6039 happens to fetch from the location where that name is stored in memory;
6040 perhaps, if the name were different, the contents of that location would fool
6041 the assembler into doing the right thing despite the bug. Play it safe and
6042 give a specific, complete example. That is the easiest thing for you to do,
6043 and the most helpful.
6045 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
6046 it is new to us. Therefore, always write your bug reports on the assumption
6047 that the bug has not been reported previously.
6049 Sometimes people give a few sketchy facts and ask, ``Does this ring a
6050 bell?'' Those bug reports are useless, and we urge everyone to
6051 @emph{refuse to respond to them} except to chide the sender to report
6054 To enable us to fix the bug, you should include all these things:
6058 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
6059 it with the @samp{--version} argument.
6061 Without this, we will not know whether there is any point in looking for
6062 the bug in the current version of @command{@value{AS}}.
6065 Any patches you may have applied to the @command{@value{AS}} source.
6068 The type of machine you are using, and the operating system name and
6072 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
6076 The command arguments you gave the assembler to assemble your example and
6077 observe the bug. To guarantee you will not omit something important, list them
6078 all. A copy of the Makefile (or the output from make) is sufficient.
6080 If we were to try to guess the arguments, we would probably guess wrong
6081 and then we might not encounter the bug.
6084 A complete input file that will reproduce the bug. If the bug is observed when
6085 the assembler is invoked via a compiler, send the assembler source, not the
6086 high level language source. Most compilers will produce the assembler source
6087 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
6088 the options @samp{-v --save-temps}; this will save the assembler source in a
6089 file with an extension of @file{.s}, and also show you exactly how
6090 @command{@value{AS}} is being run.
6093 A description of what behavior you observe that you believe is
6094 incorrect. For example, ``It gets a fatal signal.''
6096 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
6097 will certainly notice it. But if the bug is incorrect output, we might not
6098 notice unless it is glaringly wrong. You might as well not give us a chance to
6101 Even if the problem you experience is a fatal signal, you should still say so
6102 explicitly. Suppose something strange is going on, such as, your copy of
6103 @command{@value{AS}} is out of synch, or you have encountered a bug in the C
6104 library on your system. (This has happened!) Your copy might crash and ours
6105 would not. If you told us to expect a crash, then when ours fails to crash, we
6106 would know that the bug was not happening for us. If you had not told us to
6107 expect a crash, then we would not be able to draw any conclusion from our
6111 If you wish to suggest changes to the @command{@value{AS}} source, send us context
6112 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
6113 option. Always send diffs from the old file to the new file. If you even
6114 discuss something in the @command{@value{AS}} source, refer to it by context, not
6117 The line numbers in our development sources will not match those in your
6118 sources. Your line numbers would convey no useful information to us.
6121 Here are some things that are not necessary:
6125 A description of the envelope of the bug.
6127 Often people who encounter a bug spend a lot of time investigating
6128 which changes to the input file will make the bug go away and which
6129 changes will not affect it.
6131 This is often time consuming and not very useful, because the way we
6132 will find the bug is by running a single example under the debugger
6133 with breakpoints, not by pure deduction from a series of examples.
6134 We recommend that you save your time for something else.
6136 Of course, if you can find a simpler example to report @emph{instead}
6137 of the original one, that is a convenience for us. Errors in the
6138 output will be easier to spot, running under the debugger will take
6139 less time, and so on.
6141 However, simplification is not vital; if you do not want to do this,
6142 report the bug anyway and send us the entire test case you used.
6145 A patch for the bug.
6147 A patch for the bug does help us if it is a good one. But do not omit
6148 the necessary information, such as the test case, on the assumption that
6149 a patch is all we need. We might see problems with your patch and decide
6150 to fix the problem another way, or we might not understand it at all.
6152 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
6153 construct an example that will make the program follow a certain path through
6154 the code. If you do not send us the example, we will not be able to construct
6155 one, so we will not be able to verify that the bug is fixed.
6157 And if we cannot understand what bug you are trying to fix, or why your
6158 patch should be an improvement, we will not install it. A test case will
6159 help us to understand.
6162 A guess about what the bug is or what it depends on.
6164 Such guesses are usually wrong. Even we cannot guess right about such
6165 things without first using the debugger to find the facts.
6168 @node Acknowledgements
6169 @chapter Acknowledgements
6171 If you have contributed to @command{@value{AS}} and your name isn't listed here,
6172 it is not meant as a slight. We just don't know about it. Send mail to the
6173 maintainer, and we'll correct the situation. Currently
6175 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
6177 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
6180 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
6181 information and the 68k series machines, most of the preprocessing pass, and
6182 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
6184 K. Richard Pixley maintained GAS for a while, adding various enhancements and
6185 many bug fixes, including merging support for several processors, breaking GAS
6186 up to handle multiple object file format back ends (including heavy rewrite,
6187 testing, an integration of the coff and b.out back ends), adding configuration
6188 including heavy testing and verification of cross assemblers and file splits
6189 and renaming, converted GAS to strictly ANSI C including full prototypes, added
6190 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
6191 port (including considerable amounts of reverse engineering), a SPARC opcode
6192 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
6193 assertions and made them work, much other reorganization, cleanup, and lint.
6195 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
6196 in format-specific I/O modules.
6198 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
6199 has done much work with it since.
6201 The Intel 80386 machine description was written by Eliot Dresselhaus.
6203 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
6205 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
6206 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
6208 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
6209 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
6210 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
6211 support a.out format.
6213 Support for the Zilog Z8k and Hitachi H8/300 and H8/500 processors (tc-z8k,
6214 tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by
6215 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
6216 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
6219 John Gilmore built the AMD 29000 support, added @code{.include} support, and
6220 simplified the configuration of which versions accept which directives. He
6221 updated the 68k machine description so that Motorola's opcodes always produced
6222 fixed-size instructions (e.g. @code{jsr}), while synthetic instructions
6223 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
6224 cross-compilation support, and one bug in relaxation that took a week and
6225 required the proverbial one-bit fix.
6227 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
6228 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
6229 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
6230 PowerPC assembler, and made a few other minor patches.
6232 Steve Chamberlain made @command{@value{AS}} able to generate listings.
6234 Hewlett-Packard contributed support for the HP9000/300.
6236 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
6237 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
6238 formats). This work was supported by both the Center for Software Science at
6239 the University of Utah and Cygnus Support.
6241 Support for ELF format files has been worked on by Mark Eichin of Cygnus
6242 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
6243 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
6244 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
6245 and some initial 64-bit support).
6247 Linas Vepstas added GAS support for the ESA/390 "IBM 370" architecture.
6249 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
6250 support for openVMS/Alpha.
6252 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
6255 Several engineers at Cygnus Support have also provided many small bug fixes and
6256 configuration enhancements.
6258 Many others have contributed large or small bugfixes and enhancements. If
6259 you have contributed significant work and are not mentioned on this list, and
6260 want to be, let us know. Some of the history has been lost; we are not
6261 intentionally leaving anyone out.
6263 @node GNU Free Documentation License
6264 @chapter GNU Free Documentation License
6266 GNU Free Documentation License
6268 Version 1.1, March 2000
6270 Copyright (C) 2000 Free Software Foundation, Inc.
6271 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
6273 Everyone is permitted to copy and distribute verbatim copies
6274 of this license document, but changing it is not allowed.
6279 The purpose of this License is to make a manual, textbook, or other
6280 written document "free" in the sense of freedom: to assure everyone
6281 the effective freedom to copy and redistribute it, with or without
6282 modifying it, either commercially or noncommercially. Secondarily,
6283 this License preserves for the author and publisher a way to get
6284 credit for their work, while not being considered responsible for
6285 modifications made by others.
6287 This License is a kind of "copyleft", which means that derivative
6288 works of the document must themselves be free in the same sense. It
6289 complements the GNU General Public License, which is a copyleft
6290 license designed for free software.
6292 We have designed this License in order to use it for manuals for free
6293 software, because free software needs free documentation: a free
6294 program should come with manuals providing the same freedoms that the
6295 software does. But this License is not limited to software manuals;
6296 it can be used for any textual work, regardless of subject matter or
6297 whether it is published as a printed book. We recommend this License
6298 principally for works whose purpose is instruction or reference.
6301 1. APPLICABILITY AND DEFINITIONS
6303 This License applies to any manual or other work that contains a
6304 notice placed by the copyright holder saying it can be distributed
6305 under the terms of this License. The "Document", below, refers to any
6306 such manual or work. Any member of the public is a licensee, and is
6309 A "Modified Version" of the Document means any work containing the
6310 Document or a portion of it, either copied verbatim, or with
6311 modifications and/or translated into another language.
6313 A "Secondary Section" is a named appendix or a front-matter section of
6314 the Document that deals exclusively with the relationship of the
6315 publishers or authors of the Document to the Document's overall subject
6316 (or to related matters) and contains nothing that could fall directly
6317 within that overall subject. (For example, if the Document is in part a
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6320 connection with the subject or with related matters, or of legal,
6321 commercial, philosophical, ethical or political position regarding
6324 The "Invariant Sections" are certain Secondary Sections whose titles
6325 are designated, as being those of Invariant Sections, in the notice
6326 that says that the Document is released under this License.
6328 The "Cover Texts" are certain short passages of text that are listed,
6329 as Front-Cover Texts or Back-Cover Texts, in the notice that says that
6330 the Document is released under this License.
6332 A "Transparent" copy of the Document means a machine-readable copy,
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6351 machine-generated HTML produced by some word processors for output
6354 The "Title Page" means, for a printed book, the title page itself,
6355 plus such following pages as are needed to hold, legibly, the material
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6358 the text near the most prominent appearance of the work's title,
6359 preceding the beginning of the body of the text.
6364 You may copy and distribute the Document in any medium, either
6365 commercially or noncommercially, provided that this License, the
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6371 compensation in exchange for copies. If you distribute a large enough
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6374 You may also lend copies, under the same conditions stated above, and
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6378 3. COPYING IN QUANTITY
6380 If you publish printed copies of the Document numbering more than 100,
6381 and the Document's license notice requires Cover Texts, you must enclose
6382 the copies in covers that carry, clearly and legibly, all these Cover
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6388 Copying with changes limited to the covers, as long as they preserve
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6392 If the required texts for either cover are too voluminous to fit
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6397 If you publish or distribute Opaque copies of the Document numbering
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6402 general network-using public has access to download anonymously at no
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6413 them a chance to provide you with an updated version of the Document.
6418 You may copy and distribute a Modified Version of the Document under
6419 the conditions of sections 2 and 3 above, provided that you release
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6430 B. List on the Title Page, as authors, one or more persons or entities
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6436 D. Preserve all the copyright notices of the Document.
6437 E. Add an appropriate copyright notice for your modifications
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6439 F. Include, immediately after the copyright notices, a license notice
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6446 it an item stating at least the title, year, new authors, and
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6466 M. Delete any section entitled "Endorsements". Such a section
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6471 If the Modified Version includes new front-matter sections or
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6476 These titles must be distinct from any other section titles.
6478 You may add a section entitled "Endorsements", provided it contains
6479 nothing but endorsements of your Modified Version by various
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6499 5. COMBINING DOCUMENTS
6501 You may combine the Document with other documents released under this
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6504 Invariant Sections of all of the original documents, unmodified, and
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6524 6. COLLECTIONS OF DOCUMENTS
6526 You may make a collection consisting of the Document and other documents
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6538 7. AGGREGATION WITH INDEPENDENT WORKS
6540 A compilation of the Document or its derivatives with other separate
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6572 You may not copy, modify, sublicense, or distribute the Document except
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6581 10. FUTURE REVISIONS OF THIS LICENSE
6583 The Free Software Foundation may publish new, revised versions
6584 of the GNU Free Documentation License from time to time. Such new
6585 versions will be similar in spirit to the present version, but may
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6599 ADDENDUM: How to use this License for your documents
6601 To use this License in a document you have written, include a copy of
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6606 Copyright (c) YEAR YOUR NAME.
6607 Permission is granted to copy, distribute and/or modify this document
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6609 or any later version published by the Free Software Foundation;
6610 with the Invariant Sections being LIST THEIR TITLES, with the
6611 Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
6612 A copy of the license is included in the section entitled "GNU
6613 Free Documentation License".
6616 If you have no Invariant Sections, write "with no Invariant Sections"
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6618 Front-Cover Texts, write "no Front-Cover Texts" instead of
6619 "Front-Cover Texts being LIST"; likewise for Back-Cover Texts.
6621 If your document contains nontrivial examples of program code, we
6622 recommend releasing these examples in parallel under your choice of
6623 free software license, such as the GNU General Public License,
6624 to permit their use in free software.
projects / platform / upstream / binutils.git / blob