1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (c) 1991, 92, 93, 94, 95, 96, 97, 1998
3 @c Free Software Foundation, Inc.
4 @c UPDATE!! On future updates--
5 @c (1) check for new machine-dep cmdline options in
6 @c md_parse_option definitions in config/tc-*.c
7 @c (2) for platform-specific directives, examine md_pseudo_op
9 @c (3) for object-format specific directives, examine obj_pseudo_op
11 @c (4) portable directives in potable[] in read.c
15 @c defaults, config file may override:
18 @include asconfig.texi
20 @c common OR combinations of conditions
40 @set abnormal-separator
44 @settitle Using @value{AS}
47 @settitle Using @value{AS} (@value{TARGET})
49 @setchapternewpage odd
54 @c WARE! Some of the machine-dependent sections contain tables of machine
55 @c instructions. Except in multi-column format, these tables look silly.
56 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
57 @c the multi-col format is faked within @example sections.
59 @c Again unfortunately, the natural size that fits on a page, for these tables,
60 @c is different depending on whether or not smallbook is turned on.
61 @c This matters, because of order: text flow switches columns at each page
64 @c The format faked in this source works reasonably well for smallbook,
65 @c not well for the default large-page format. This manual expects that if you
66 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
67 @c tables in question. You can turn on one without the other at your
68 @c discretion, of course.
71 @c the insn tables look just as silly in info files regardless of smallbook,
72 @c might as well show 'em anyways.
78 * As: (as). The GNU assembler.
87 This file documents the GNU Assembler "@value{AS}".
89 Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 1998 Free Software Foundation, Inc.
91 Permission is granted to make and distribute verbatim copies of
92 this manual provided the copyright notice and this permission notice
93 are preserved on all copies.
96 Permission is granted to process this file through Tex and print the
97 results, provided the printed document carries copying permission
98 notice identical to this one except for the removal of this paragraph
99 (this paragraph not being relevant to the printed manual).
102 Permission is granted to copy and distribute modified versions of this manual
103 under the conditions for verbatim copying, provided that the entire resulting
104 derived work is distributed under the terms of a permission notice identical to
107 Permission is granted to copy and distribute translations of this manual
108 into another language, under the above conditions for modified versions.
112 @title Using @value{AS}
113 @subtitle The @sc{gnu} Assembler
115 @subtitle for the @value{TARGET} family
118 @subtitle January 1994
121 The Free Software Foundation Inc. thanks The Nice Computer
122 Company of Australia for loaning Dean Elsner to write the
123 first (Vax) version of @code{as} for Project @sc{gnu}.
124 The proprietors, management and staff of TNCCA thank FSF for
125 distracting the boss while they got some work
128 @author Dean Elsner, Jay Fenlason & friends
132 \hfill {\it Using {\tt @value{AS}}}\par
133 \hfill Edited by Cygnus Support\par
135 %"boxit" macro for figures:
136 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
137 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
138 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
139 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
140 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
143 @vskip 0pt plus 1filll
144 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 1998 Free Software Foundation, Inc.
146 Permission is granted to make and distribute verbatim copies of
147 this manual provided the copyright notice and this permission notice
148 are preserved on all copies.
150 Permission is granted to copy and distribute modified versions of this manual
151 under the conditions for verbatim copying, provided that the entire resulting
152 derived work is distributed under the terms of a permission notice identical to
155 Permission is granted to copy and distribute translations of this manual
156 into another language, under the above conditions for modified versions.
161 @top Using @value{AS}
163 This file is a user guide to the @sc{gnu} assembler @code{@value{AS}}.
165 This version of the file describes @code{@value{AS}} configured to generate
166 code for @value{TARGET} architectures.
169 * Overview:: Overview
170 * Invoking:: Command-Line Options
172 * Sections:: Sections and Relocation
174 * Expressions:: Expressions
175 * Pseudo Ops:: Assembler Directives
176 * Machine Dependencies:: Machine Dependent Features
177 * Reporting Bugs:: Reporting Bugs
178 * Acknowledgements:: Who Did What
186 This manual is a user guide to the @sc{gnu} assembler @code{@value{AS}}.
188 This version of the manual describes @code{@value{AS}} configured to generate
189 code for @value{TARGET} architectures.
193 @cindex invocation summary
194 @cindex option summary
195 @cindex summary of options
196 Here is a brief summary of how to invoke @code{@value{AS}}. For details,
197 @pxref{Invoking,,Comand-Line Options}.
199 @c We don't use deffn and friends for the following because they seem
200 @c to be limited to one line for the header.
202 @value{AS} [ -a[cdhlns][=file] ] [ -D ] [ --defsym @var{sym}=@var{val} ]
203 [ -f ] [ --gstabs ] [ --help ] [ -I @var{dir} ] [ -J ] [ -K ] [ -L ]
204 [ --keep-locals ] [ -o @var{objfile} ] [ -R ] [ --statistics ] [ -v ]
205 [ -version ] [ --version ] [ -W ] [ -w ] [ -x ] [ -Z ]
207 @c am29k has no machine-dependent assembler options
210 [ -mbig-endian | -mlittle-endian ]
213 [ -m[arm]1 | -m[arm]2 | -m[arm]250 | -m[arm]3 | -m[arm]6 | -m[arm]7[t][[d]m[i]] ]
214 [ -m[arm]v2 | -m[arm]v2a | -m[arm]v3 | -m[arm]v3m | -m[arm]v4 | -m[arm]v4t ]
216 [ -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu ]
218 [ -mapcs-32 | -mapcs-26 ]
223 @c start-sanitize-d30v
229 @c Hitachi family chips have no machine-dependent assembler options
232 @c HPPA has no machine-dependent assembler options (yet).
235 @c The order here is important. See c-sparc.texi.
236 [ -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
237 -Av8plus | -Av8plusa | -Av9 | -Av9a ]
238 [ -xarch=v8plus | -xarch=v8plusa ] [ -bump ] [ -32 | -64 ]
241 @c Z8000 has no machine-dependent assembler options
244 @c see md_parse_option in tc-i960.c
245 [ -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC ]
248 @c start-sanitize-m32rx
250 [ --m32rx | --[no-]warn-explicit-parallel-conflicts ]
252 @c end-sanitize-m32rx
254 [ -l ] [ -m68000 | -m68010 | -m68020 | ... ]
257 [ -nocpp ] [ -EL ] [ -EB ] [ -G @var{num} ] [ -mcpu=@var{CPU} ]
258 [ -mips1 ] [ -mips2 ] [ -mips3 ] [ -m4650 ] [ -no-m4650 ]
259 [ --trap ] [ --break ]
260 [ --emulation=@var{name} ]
262 [ -- | @var{files} @dots{} ]
267 Turn on listings, in any of a variety of ways:
271 omit false conditionals
274 omit debugging directives
277 include high-level source
283 include macro expansions
286 omit forms processing
292 set the name of the listing file
295 You may combine these options; for example, use @samp{-aln} for assembly
296 listing without forms processing. The @samp{=file} option, if used, must be
297 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
300 Ignored. This option is accepted for script compatibility with calls to
303 @item --defsym @var{sym}=@var{value}
304 Define the symbol @var{sym} to be @var{value} before assembling the input file.
305 @var{value} must be an integer constant. As in C, a leading @samp{0x}
306 indicates a hexadecimal value, and a leading @samp{0} indicates an octal value.
309 ``fast''---skip whitespace and comment preprocessing (assume source is
313 Generate stabs debugging information for each assembler line. This
314 may help debugging assembler code, if the debugger can handle it.
317 Print a summary of the command line options and exit.
320 Add directory @var{dir} to the search list for @code{.include} directives.
323 Don't warn about signed overflow.
326 @ifclear DIFF-TBL-KLUGE
327 This option is accepted but has no effect on the @value{TARGET} family.
329 @ifset DIFF-TBL-KLUGE
330 Issue warnings when difference tables altered for long displacements.
335 Keep (in the symbol table) local symbols. On traditional a.out systems
336 these start with @samp{L}, but different systems have different local
339 @item -o @var{objfile}
340 Name the object-file output from @code{@value{AS}} @var{objfile}.
343 Fold the data section into the text section.
346 Print the maximum space (in bytes) and total time (in seconds) used by
349 @item --strip-local-absolute
350 Remove local absolute symbols from the outgoing symbol table.
354 Print the @code{as} version.
357 Print the @code{as} version and exit.
360 Suppress warning messages.
369 Generate an object file even after errors.
371 @item -- | @var{files} @dots{}
372 Standard input, or source files to assemble.
377 The following options are available when @value{AS} is configured for
382 @cindex ARC endianness
383 @cindex endianness, ARC
384 @cindex big endian output, ARC
386 Generate ``big endian'' format output.
388 @cindex little endian output, ARC
389 @item -mlittle-endian
390 Generate ``little endian'' format output.
396 The following options are available when @value{AS} is configured for the ARM
400 @item -m[arm]1 | -m[arm]2 | -m[arm]250 | -m[arm]3 | -m[arm]6 | -m[arm]7[t][[d]m] | -m[arm]v2 | -m[arm]v2a | -m[arm]v3 | -m[arm]v3m | -m[arm]v4 | -m[arm]v4t
401 Specify which variant of the ARM architecture is the target.
402 @item -mthumb | -mall
403 Enable or disable Thumb only instruction decoding.
404 @item -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu
405 Select which Floating Point architcture is the target.
406 @item -mapcs-32 | -mapcs-26
407 Select which procedure calling convention is in use.
409 Select either big-endian (-EB) or little-endian (-EL) output.
414 The following options are available when @value{AS} is configured for
417 @cindex D10V optimization
418 @cindex optimization, D10V
420 Optimize output by parallelizing instructions.
424 @c start-sanitize-d30v
426 The following options are available when @value{AS} is configured for a D30V
429 @cindex D30V optimization
430 @cindex optimization, D30V
432 Optimize output by parallelizing instructions.
436 Warn when nops are generated.
438 @cindex D30V nops after 32-bit multiply
440 Warn when a nop after a 32-bit multiply instruction is generated.
446 The following options are available when @value{AS} is configured for the
447 Intel 80960 processor.
450 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
451 Specify which variant of the 960 architecture is the target.
454 Add code to collect statistics about branches taken.
457 Do not alter compare-and-branch instructions for long displacements;
463 @c start-sanitize-m32rx
465 The following options are available when @value{AS} is configured for the
466 Mitsubishi M32R series.
471 Specify which processor in the M32R family is the target. The default
472 is normally the M32R, but this option changes it to the M32RX.
474 @item --warn-explicit-parallel-conflicts
475 Produce warning messages when questionable parallel constructs are
478 @item --no-warn-explicit-parallel-conflicts
479 Do not produce warning messages when questionable parallel constructs are
484 @c end-sanitize-m32rx
487 The following options are available when @value{AS} is configured for the
488 Motorola 68000 series.
493 Shorten references to undefined symbols, to one word instead of two.
495 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030 | -m68040 | -m68060
496 @itemx | -m68302 | -m68331 | -m68332 | -m68333 | -m68340 | -mcpu32 | -m5200
497 Specify what processor in the 68000 family is the target. The default
498 is normally the 68020, but this can be changed at configuration time.
500 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
501 The target machine does (or does not) have a floating-point coprocessor.
502 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
503 the basic 68000 is not compatible with the 68881, a combination of the
504 two can be specified, since it's possible to do emulation of the
505 coprocessor instructions with the main processor.
507 @item -m68851 | -mno-68851
508 The target machine does (or does not) have a memory-management
509 unit coprocessor. The default is to assume an MMU for 68020 and up.
515 The following options are available when @code{@value{AS}} is configured
516 for the SPARC architecture:
519 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
520 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
521 Explicitly select a variant of the SPARC architecture.
523 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
524 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
526 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
527 UltraSPARC extensions.
529 @item -xarch=v8plus | -xarch=v8plusa
530 For compatibility with the Solaris v9 assembler. These options are
531 equivalent to -Av8plus and -Av8plusa, respectively.
534 Warn when the assembler switches to another architecture.
539 The following options are available when @value{AS} is configured for
544 This option sets the largest size of an object that can be referenced
545 implicitly with the @code{gp} register. It is only accepted for targets that
546 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
548 @cindex MIPS endianness
549 @cindex endianness, MIPS
550 @cindex big endian output, MIPS
552 Generate ``big endian'' format output.
554 @cindex little endian output, MIPS
556 Generate ``little endian'' format output.
562 Generate code for a particular MIPS Instruction Set Architecture level.
563 @samp{-mips1} corresponds to the @sc{r2000} and @sc{r3000} processors,
564 @samp{-mips2} to the @sc{r6000} processor, and @samp{-mips3} to the @sc{r4000}
569 Generate code for the MIPS @sc{r4650} chip. This tells the assembler to accept
570 the @samp{mad} and @samp{madu} instruction, and to not schedule @samp{nop}
571 instructions around accesses to the @samp{HI} and @samp{LO} registers.
572 @samp{-no-m4650} turns off this option.
574 @item -mcpu=@var{CPU}
575 Generate code for a particular MIPS cpu. This has little effect on the
576 assembler, but it is passed by @code{@value{GCC}}.
579 @item --emulation=@var{name}
580 This option causes @code{@value{AS}} to emulate @code{@value{AS}} configured
581 for some other target, in all respects, including output format (choosing
582 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
583 debugging information or store symbol table information, and default
584 endianness. The available configuration names are: @samp{mipsecoff},
585 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
586 @samp{mipsbelf}. The first two do not alter the default endianness from that
587 of the primary target for which the assembler was configured; the others change
588 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
589 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
590 selection in any case.
592 This option is currently supported only when the primary target
593 @code{@value{AS}} is configured for is a MIPS ELF or ECOFF target.
594 Furthermore, the primary target or others specified with
595 @samp{--enable-targets=@dots{}} at configuration time must include support for
596 the other format, if both are to be available. For example, the Irix 5
597 configuration includes support for both.
599 Eventually, this option will support more configurations, with more
600 fine-grained control over the assembler's behavior, and will be supported for
604 @code{@value{AS}} ignores this option. It is accepted for compatibility with
612 Control how to deal with multiplication overflow and division by zero.
613 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
614 (and only work for Instruction Set Architecture level 2 and higher);
615 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
621 * Manual:: Structure of this Manual
622 * GNU Assembler:: The GNU Assembler
623 * Object Formats:: Object File Formats
624 * Command Line:: Command Line
625 * Input Files:: Input Files
626 * Object:: Output (Object) File
627 * Errors:: Error and Warning Messages
631 @section Structure of this Manual
633 @cindex manual, structure and purpose
634 This manual is intended to describe what you need to know to use
635 @sc{gnu} @code{@value{AS}}. We cover the syntax expected in source files, including
636 notation for symbols, constants, and expressions; the directives that
637 @code{@value{AS}} understands; and of course how to invoke @code{@value{AS}}.
640 We also cover special features in the @value{TARGET}
641 configuration of @code{@value{AS}}, including assembler directives.
644 This manual also describes some of the machine-dependent features of
645 various flavors of the assembler.
648 @cindex machine instructions (not covered)
649 On the other hand, this manual is @emph{not} intended as an introduction
650 to programming in assembly language---let alone programming in general!
651 In a similar vein, we make no attempt to introduce the machine
652 architecture; we do @emph{not} describe the instruction set, standard
653 mnemonics, registers or addressing modes that are standard to a
654 particular architecture.
656 You may want to consult the manufacturer's
657 machine architecture manual for this information.
661 For information on the H8/300 machine instruction set, see @cite{H8/300
662 Series Programming Manual} (Hitachi ADE--602--025). For the H8/300H,
663 see @cite{H8/300H Series Programming Manual} (Hitachi).
666 For information on the H8/500 machine instruction set, see @cite{H8/500
667 Series Programming Manual} (Hitachi M21T001).
670 For information on the Hitachi SH machine instruction set, see
671 @cite{SH-Microcomputer User's Manual} (Hitachi Micro Systems, Inc.).
674 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
678 @c I think this is premature---doc@cygnus.com, 17jan1991
680 Throughout this manual, we assume that you are running @dfn{GNU},
681 the portable operating system from the @dfn{Free Software
682 Foundation, Inc.}. This restricts our attention to certain kinds of
683 computer (in particular, the kinds of computers that @sc{gnu} can run on);
684 once this assumption is granted examples and definitions need less
687 @code{@value{AS}} is part of a team of programs that turn a high-level
688 human-readable series of instructions into a low-level
689 computer-readable series of instructions. Different versions of
690 @code{@value{AS}} are used for different kinds of computer.
693 @c There used to be a section "Terminology" here, which defined
694 @c "contents", "byte", "word", and "long". Defining "word" to any
695 @c particular size is confusing when the .word directive may generate 16
696 @c bits on one machine and 32 bits on another; in general, for the user
697 @c version of this manual, none of these terms seem essential to define.
698 @c They were used very little even in the former draft of the manual;
699 @c this draft makes an effort to avoid them (except in names of
703 @section The GNU Assembler
705 @sc{gnu} @code{as} is really a family of assemblers.
707 This manual describes @code{@value{AS}}, a member of that family which is
708 configured for the @value{TARGET} architectures.
710 If you use (or have used) the @sc{gnu} assembler on one architecture, you
711 should find a fairly similar environment when you use it on another
712 architecture. Each version has much in common with the others,
713 including object file formats, most assembler directives (often called
714 @dfn{pseudo-ops}) and assembler syntax.@refill
716 @cindex purpose of @sc{gnu} assembler
717 @code{@value{AS}} is primarily intended to assemble the output of the
718 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
719 @code{@value{LD}}. Nevertheless, we've tried to make @code{@value{AS}}
720 assemble correctly everything that other assemblers for the same
721 machine would assemble.
723 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
726 @c This remark should appear in generic version of manual; assumption
727 @c here is that generic version sets M680x0.
728 This doesn't mean @code{@value{AS}} always uses the same syntax as another
729 assembler for the same architecture; for example, we know of several
730 incompatible versions of 680x0 assembly language syntax.
733 Unlike older assemblers, @code{@value{AS}} is designed to assemble a source
734 program in one pass of the source file. This has a subtle impact on the
735 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
738 @section Object File Formats
740 @cindex object file format
741 The @sc{gnu} assembler can be configured to produce several alternative
742 object file formats. For the most part, this does not affect how you
743 write assembly language programs; but directives for debugging symbols
744 are typically different in different file formats. @xref{Symbol
745 Attributes,,Symbol Attributes}.
748 On the @value{TARGET}, @code{@value{AS}} is configured to produce
749 @value{OBJ-NAME} format object files.
751 @c The following should exhaust all configs that set MULTI-OBJ, ideally
753 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
754 @code{a.out} or COFF format object files.
757 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
758 @code{b.out} or COFF format object files.
761 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
762 SOM or ELF format object files.
767 @section Command Line
769 @cindex command line conventions
770 After the program name @code{@value{AS}}, the command line may contain
771 options and file names. Options may appear in any order, and may be
772 before, after, or between file names. The order of file names is
775 @cindex standard input, as input file
777 @file{--} (two hyphens) by itself names the standard input file
778 explicitly, as one of the files for @code{@value{AS}} to assemble.
780 @cindex options, command line
781 Except for @samp{--} any command line argument that begins with a
782 hyphen (@samp{-}) is an option. Each option changes the behavior of
783 @code{@value{AS}}. No option changes the way another option works. An
784 option is a @samp{-} followed by one or more letters; the case of
785 the letter is important. All options are optional.
787 Some options expect exactly one file name to follow them. The file
788 name may either immediately follow the option's letter (compatible
789 with older assemblers) or it may be the next command argument (@sc{gnu}
790 standard). These two command lines are equivalent:
793 @value{AS} -o my-object-file.o mumble.s
794 @value{AS} -omy-object-file.o mumble.s
801 @cindex source program
803 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
804 describe the program input to one run of @code{@value{AS}}. The program may
805 be in one or more files; how the source is partitioned into files
806 doesn't change the meaning of the source.
808 @c I added "con" prefix to "catenation" just to prove I can overcome my
809 @c APL training... doc@cygnus.com
810 The source program is a concatenation of the text in all the files, in the
813 Each time you run @code{@value{AS}} it assembles exactly one source
814 program. The source program is made up of one or more files.
815 (The standard input is also a file.)
817 You give @code{@value{AS}} a command line that has zero or more input file
818 names. The input files are read (from left file name to right). A
819 command line argument (in any position) that has no special meaning
820 is taken to be an input file name.
822 If you give @code{@value{AS}} no file names it attempts to read one input file
823 from the @code{@value{AS}} standard input, which is normally your terminal. You
824 may have to type @key{ctl-D} to tell @code{@value{AS}} there is no more program
827 Use @samp{--} if you need to explicitly name the standard input file
828 in your command line.
830 If the source is empty, @code{@value{AS}} produces a small, empty object
833 @subheading Filenames and Line-numbers
835 @cindex input file linenumbers
836 @cindex line numbers, in input files
837 There are two ways of locating a line in the input file (or files) and
838 either may be used in reporting error messages. One way refers to a line
839 number in a physical file; the other refers to a line number in a
840 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
842 @dfn{Physical files} are those files named in the command line given
843 to @code{@value{AS}}.
845 @dfn{Logical files} are simply names declared explicitly by assembler
846 directives; they bear no relation to physical files. Logical file names
847 help error messages reflect the original source file, when @code{@value{AS}}
848 source is itself synthesized from other files.
849 @xref{App-File,,@code{.app-file}}.
852 @section Output (Object) File
858 Every time you run @code{@value{AS}} it produces an output file, which is
859 your assembly language program translated into numbers. This file
860 is the object file. Its default name is
868 @code{b.out} when @code{@value{AS}} is configured for the Intel 80960.
870 You can give it another name by using the @code{-o} option. Conventionally,
871 object file names end with @file{.o}. The default name is used for historical
872 reasons: older assemblers were capable of assembling self-contained programs
873 directly into a runnable program. (For some formats, this isn't currently
874 possible, but it can be done for the @code{a.out} format.)
878 The object file is meant for input to the linker @code{@value{LD}}. It contains
879 assembled program code, information to help @code{@value{LD}} integrate
880 the assembled program into a runnable file, and (optionally) symbolic
881 information for the debugger.
883 @c link above to some info file(s) like the description of a.out.
884 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
887 @section Error and Warning Messages
889 @cindex error messsages
890 @cindex warning messages
891 @cindex messages from assembler
892 @code{@value{AS}} may write warnings and error messages to the standard error
893 file (usually your terminal). This should not happen when a compiler
894 runs @code{@value{AS}} automatically. Warnings report an assumption made so
895 that @code{@value{AS}} could keep assembling a flawed program; errors report a
896 grave problem that stops the assembly.
898 @cindex format of warning messages
899 Warning messages have the format
902 file_name:@b{NNN}:Warning Message Text
906 @cindex line numbers, in warnings/errors
907 (where @b{NNN} is a line number). If a logical file name has been given
908 (@pxref{App-File,,@code{.app-file}}) it is used for the filename,
909 otherwise the name of the current input file is used. If a logical line
912 (@pxref{Line,,@code{.line}})
916 (@pxref{Line,,@code{.line}})
919 (@pxref{Ln,,@code{.ln}})
922 then it is used to calculate the number printed,
923 otherwise the actual line in the current source file is printed. The
924 message text is intended to be self explanatory (in the grand Unix
927 @cindex format of error messages
928 Error messages have the format
930 file_name:@b{NNN}:FATAL:Error Message Text
932 The file name and line number are derived as for warning
933 messages. The actual message text may be rather less explanatory
934 because many of them aren't supposed to happen.
937 @chapter Command-Line Options
939 @cindex options, all versions of assembler
940 This chapter describes command-line options available in @emph{all}
941 versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
943 to the @value{TARGET}.
946 to particular machine architectures.
949 If you are invoking @code{@value{AS}} via the @sc{gnu} C compiler (version 2), you
950 can use the @samp{-Wa} option to pass arguments through to the
951 assembler. The assembler arguments must be separated from each other
952 (and the @samp{-Wa}) by commas. For example:
955 gcc -c -g -O -Wa,-alh,-L file.c
959 emits a listing to standard output with high-level
962 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
963 command-line options are automatically passed to the assembler by the compiler.
964 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
965 precisely what options it passes to each compilation pass, including the
969 * a:: -a[cdhlns] enable listings
970 * D:: -D for compatibility
971 * f:: -f to work faster
972 * I:: -I for .include search path
973 @ifclear DIFF-TBL-KLUGE
974 * K:: -K for compatibility
976 @ifset DIFF-TBL-KLUGE
977 * K:: -K for difference tables
980 * L:: -L to retain local labels
981 * M:: -M or --mri to assemble in MRI compatibility mode
982 * MD:: --MD for dependency tracking
983 * o:: -o to name the object file
984 * R:: -R to join data and text sections
985 * statistics:: --statistics to see statistics about assembly
986 * traditional-format:: --traditional-format for compatible output
987 * v:: -v to announce version
988 * W:: -W to suppress warnings
989 * Z:: -Z to make object file even after errors
993 @section Enable Listings: @code{-a[cdhlns]}
1002 @cindex listings, enabling
1003 @cindex assembly listings, enabling
1005 These options enable listing output from the assembler. By itself,
1006 @samp{-a} requests high-level, assembly, and symbols listing.
1007 You can use other letters to select specific options for the list:
1008 @samp{-ah} requests a high-level language listing,
1009 @samp{-al} requests an output-program assembly listing, and
1010 @samp{-as} requests a symbol table listing.
1011 High-level listings require that a compiler debugging option like
1012 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1015 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1016 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1017 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1018 omitted from the listing.
1020 Use the @samp{-ad} option to omit debugging directives from the
1023 Once you have specified one of these options, you can further control
1024 listing output and its appearance using the directives @code{.list},
1025 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1027 The @samp{-an} option turns off all forms processing.
1028 If you do not request listing output with one of the @samp{-a} options, the
1029 listing-control directives have no effect.
1031 The letters after @samp{-a} may be combined into one option,
1032 @emph{e.g.}, @samp{-aln}.
1038 This option has no effect whatsoever, but it is accepted to make it more
1039 likely that scripts written for other assemblers also work with
1043 @section Work Faster: @code{-f}
1046 @cindex trusted compiler
1047 @cindex faster processing (@code{-f})
1048 @samp{-f} should only be used when assembling programs written by a
1049 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1050 and comment preprocessing on
1051 the input file(s) before assembling them. @xref{Preprocessing,
1055 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1056 preprocessed (if they contain comments, for example), @code{@value{AS}} does
1061 @section @code{.include} search path: @code{-I} @var{path}
1063 @kindex -I @var{path}
1064 @cindex paths for @code{.include}
1065 @cindex search path for @code{.include}
1066 @cindex @code{include} directive search path
1067 Use this option to add a @var{path} to the list of directories
1068 @code{@value{AS}} searches for files specified in @code{.include}
1069 directives (@pxref{Include,,@code{.include}}). You may use @code{-I} as
1070 many times as necessary to include a variety of paths. The current
1071 working directory is always searched first; after that, @code{@value{AS}}
1072 searches any @samp{-I} directories in the same order as they were
1073 specified (left to right) on the command line.
1076 @section Difference Tables: @code{-K}
1079 @ifclear DIFF-TBL-KLUGE
1080 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1081 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1082 where it can be used to warn when the assembler alters the machine code
1083 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1084 family does not have the addressing limitations that sometimes lead to this
1085 alteration on other platforms.
1088 @ifset DIFF-TBL-KLUGE
1089 @cindex difference tables, warning
1090 @cindex warning for altered difference tables
1091 @code{@value{AS}} sometimes alters the code emitted for directives of the form
1092 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
1093 You can use the @samp{-K} option if you want a warning issued when this
1098 @section Include Local Labels: @code{-L}
1101 @cindex local labels, retaining in output
1102 Labels beginning with @samp{L} (upper case only) are called @dfn{local
1103 labels}. @xref{Symbol Names}. Normally you do not see such labels when
1104 debugging, because they are intended for the use of programs (like
1105 compilers) that compose assembler programs, not for your notice.
1106 Normally both @code{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
1107 normally debug with them.
1109 This option tells @code{@value{AS}} to retain those @samp{L@dots{}} symbols
1110 in the object file. Usually if you do this you also tell the linker
1111 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
1113 By default, a local label is any label beginning with @samp{L}, but each
1114 target is allowed to redefine the local label prefix.
1116 On the HPPA local labels begin with @samp{L$}.
1119 @samp{;} for the ARM family;
1123 @section Assemble in MRI Compatibility Mode: @code{-M}
1126 @cindex MRI compatibility mode
1127 The @code{-M} or @code{--mri} option selects MRI compatibility mode. This
1128 changes the syntax and pseudo-op handling of @code{@value{AS}} to make it
1129 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1130 configured target) assembler from Microtec Research. The exact nature of the
1131 MRI syntax will not be documented here; see the MRI manuals for more
1132 information. Note in particular that the handling of macros and macro
1133 arguments is somewhat different. The purpose of this option is to permit
1134 assembling existing MRI assembler code using @code{@value{AS}}.
1136 The MRI compatibility is not complete. Certain operations of the MRI assembler
1137 depend upon its object file format, and can not be supported using other object
1138 file formats. Supporting these would require enhancing each object file format
1139 individually. These are:
1142 @item global symbols in common section
1144 The m68k MRI assembler supports common sections which are merged by the linker.
1145 Other object file formats do not support this. @code{@value{AS}} handles
1146 common sections by treating them as a single common symbol. It permits local
1147 symbols to be defined within a common section, but it can not support global
1148 symbols, since it has no way to describe them.
1150 @item complex relocations
1152 The MRI assemblers support relocations against a negated section address, and
1153 relocations which combine the start addresses of two or more sections. These
1154 are not support by other object file formats.
1156 @item @code{END} pseudo-op specifying start address
1158 The MRI @code{END} pseudo-op permits the specification of a start address.
1159 This is not supported by other object file formats. The start address may
1160 instead be specified using the @code{-e} option to the linker, or in a linker
1163 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1165 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1166 name to the output file. This is not supported by other object file formats.
1168 @item @code{ORG} pseudo-op
1170 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1171 address. This differs from the usual @code{@value{AS}} @code{.org} pseudo-op,
1172 which changes the location within the current section. Absolute sections are
1173 not supported by other object file formats. The address of a section may be
1174 assigned within a linker script.
1177 There are some other features of the MRI assembler which are not supported by
1178 @code{@value{AS}}, typically either because they are difficult or because they
1179 seem of little consequence. Some of these may be supported in future releases.
1183 @item EBCDIC strings
1185 EBCDIC strings are not supported.
1187 @item packed binary coded decimal
1189 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1190 and @code{DCB.P} pseudo-ops are not supported.
1192 @item @code{FEQU} pseudo-op
1194 The m68k @code{FEQU} pseudo-op is not supported.
1196 @item @code{NOOBJ} pseudo-op
1198 The m68k @code{NOOBJ} pseudo-op is not supported.
1200 @item @code{OPT} branch control options
1202 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1203 @code{BRL}, and @code{BRW}---are ignored. @code{@value{AS}} automatically
1204 relaxes all branches, whether forward or backward, to an appropriate size, so
1205 these options serve no purpose.
1207 @item @code{OPT} list control options
1209 The following m68k @code{OPT} list control options are ignored: @code{C},
1210 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1211 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1213 @item other @code{OPT} options
1215 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1216 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1218 @item @code{OPT} @code{D} option is default
1220 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1221 @code{OPT NOD} may be used to turn it off.
1223 @item @code{XREF} pseudo-op.
1225 The m68k @code{XREF} pseudo-op is ignored.
1227 @item @code{.debug} pseudo-op
1229 The i960 @code{.debug} pseudo-op is not supported.
1231 @item @code{.extended} pseudo-op
1233 The i960 @code{.extended} pseudo-op is not supported.
1235 @item @code{.list} pseudo-op.
1237 The various options of the i960 @code{.list} pseudo-op are not supported.
1239 @item @code{.optimize} pseudo-op
1241 The i960 @code{.optimize} pseudo-op is not supported.
1243 @item @code{.output} pseudo-op
1245 The i960 @code{.output} pseudo-op is not supported.
1247 @item @code{.setreal} pseudo-op
1249 The i960 @code{.setreal} pseudo-op is not supported.
1254 @section Dependency tracking: @code{--MD}
1257 @cindex dependency tracking
1260 @code{@value{AS}} can generate a dependency file for the file it creates. This
1261 file consists of a single rule suitable for @code{make} describing the
1262 dependencies of the main source file.
1264 The rule is written to the file named in its argument.
1266 This feature is used in the automatic updating of makefiles.
1269 @section Name the Object File: @code{-o}
1272 @cindex naming object file
1273 @cindex object file name
1274 There is always one object file output when you run @code{@value{AS}}. By
1275 default it has the name
1278 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1292 You use this option (which takes exactly one filename) to give the
1293 object file a different name.
1295 Whatever the object file is called, @code{@value{AS}} overwrites any
1296 existing file of the same name.
1299 @section Join Data and Text Sections: @code{-R}
1302 @cindex data and text sections, joining
1303 @cindex text and data sections, joining
1304 @cindex joining text and data sections
1305 @cindex merging text and data sections
1306 @code{-R} tells @code{@value{AS}} to write the object file as if all
1307 data-section data lives in the text section. This is only done at
1308 the very last moment: your binary data are the same, but data
1309 section parts are relocated differently. The data section part of
1310 your object file is zero bytes long because all its bytes are
1311 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1313 When you specify @code{-R} it would be possible to generate shorter
1314 address displacements (because we do not have to cross between text and
1315 data section). We refrain from doing this simply for compatibility with
1316 older versions of @code{@value{AS}}. In future, @code{-R} may work this way.
1319 When @code{@value{AS}} is configured for COFF output,
1320 this option is only useful if you use sections named @samp{.text} and
1325 @code{-R} is not supported for any of the HPPA targets. Using
1326 @code{-R} generates a warning from @code{@value{AS}}.
1330 @section Display Assembly Statistics: @code{--statistics}
1332 @kindex --statistics
1333 @cindex statistics, about assembly
1334 @cindex time, total for assembly
1335 @cindex space used, maximum for assembly
1336 Use @samp{--statistics} to display two statistics about the resources used by
1337 @code{@value{AS}}: the maximum amount of space allocated during the assembly
1338 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1341 @node traditional-format
1342 @section Compatible output: @code{--traditional-format}
1344 @kindex --traditional-format
1345 For some targets, the output of @code{@value{AS}} is different in some ways
1346 from the output of some existing assembler. This switch requests
1347 @code{@value{AS}} to use the traditional format instead.
1349 For example, it disables the exception frame optimizations which
1350 @code{@value{AS}} normally does by default on @code{@value{GCC}} output.
1353 @section Announce Version: @code{-v}
1357 @cindex assembler version
1358 @cindex version of assembler
1359 You can find out what version of as is running by including the
1360 option @samp{-v} (which you can also spell as @samp{-version}) on the
1364 @section Suppress Warnings: @code{-W}
1367 @cindex suppressing warnings
1368 @cindex warnings, suppressing
1369 @code{@value{AS}} should never give a warning or error message when
1370 assembling compiler output. But programs written by people often
1371 cause @code{@value{AS}} to give a warning that a particular assumption was
1372 made. All such warnings are directed to the standard error file.
1373 If you use this option, no warnings are issued. This option only
1374 affects the warning messages: it does not change any particular of how
1375 @code{@value{AS}} assembles your file. Errors, which stop the assembly, are
1379 @section Generate Object File in Spite of Errors: @code{-Z}
1380 @cindex object file, after errors
1381 @cindex errors, continuing after
1382 After an error message, @code{@value{AS}} normally produces no output. If for
1383 some reason you are interested in object file output even after
1384 @code{@value{AS}} gives an error message on your program, use the @samp{-Z}
1385 option. If there are any errors, @code{@value{AS}} continues anyways, and
1386 writes an object file after a final warning message of the form @samp{@var{n}
1387 errors, @var{m} warnings, generating bad object file.}
1392 @cindex machine-independent syntax
1393 @cindex syntax, machine-independent
1394 This chapter describes the machine-independent syntax allowed in a
1395 source file. @code{@value{AS}} syntax is similar to what many other
1396 assemblers use; it is inspired by the BSD 4.2
1401 assembler, except that @code{@value{AS}} does not assemble Vax bit-fields.
1405 * Preprocessing:: Preprocessing
1406 * Whitespace:: Whitespace
1407 * Comments:: Comments
1408 * Symbol Intro:: Symbols
1409 * Statements:: Statements
1410 * Constants:: Constants
1414 @section Preprocessing
1416 @cindex preprocessing
1417 The @code{@value{AS}} internal preprocessor:
1419 @cindex whitespace, removed by preprocessor
1421 adjusts and removes extra whitespace. It leaves one space or tab before
1422 the keywords on a line, and turns any other whitespace on the line into
1425 @cindex comments, removed by preprocessor
1427 removes all comments, replacing them with a single space, or an
1428 appropriate number of newlines.
1430 @cindex constants, converted by preprocessor
1432 converts character constants into the appropriate numeric values.
1435 It does not do macro processing, include file handling, or
1436 anything else you may get from your C compiler's preprocessor. You can
1437 do include file processing with the @code{.include} directive
1438 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
1439 to get other ``CPP'' style preprocessing, by giving the input file a
1440 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
1441 Output, gcc.info, Using GNU CC}.
1443 Excess whitespace, comments, and character constants
1444 cannot be used in the portions of the input text that are not
1447 @cindex turning preprocessing on and off
1448 @cindex preprocessing, turning on and off
1451 If the first line of an input file is @code{#NO_APP} or if you use the
1452 @samp{-f} option, whitespace and comments are not removed from the input file.
1453 Within an input file, you can ask for whitespace and comment removal in
1454 specific portions of the by putting a line that says @code{#APP} before the
1455 text that may contain whitespace or comments, and putting a line that says
1456 @code{#NO_APP} after this text. This feature is mainly intend to support
1457 @code{asm} statements in compilers whose output is otherwise free of comments
1464 @dfn{Whitespace} is one or more blanks or tabs, in any order.
1465 Whitespace is used to separate symbols, and to make programs neater for
1466 people to read. Unless within character constants
1467 (@pxref{Characters,,Character Constants}), any whitespace means the same
1468 as exactly one space.
1474 There are two ways of rendering comments to @code{@value{AS}}. In both
1475 cases the comment is equivalent to one space.
1477 Anything from @samp{/*} through the next @samp{*/} is a comment.
1478 This means you may not nest these comments.
1482 The only way to include a newline ('\n') in a comment
1483 is to use this sort of comment.
1486 /* This sort of comment does not nest. */
1489 @cindex line comment character
1490 Anything from the @dfn{line comment} character to the next newline
1491 is considered a comment and is ignored. The line comment character is
1493 @samp{;} for the AMD 29K family;
1496 @samp{;} on the ARC;
1499 @samp{;} for the H8/300 family;
1502 @samp{!} for the H8/500 family;
1505 @samp{;} for the HPPA;
1508 @samp{#} on the i960;
1511 @samp{!} for the Hitachi SH;
1514 @samp{!} on the SPARC;
1517 @samp{#} on the m32r;
1520 @samp{|} on the 680x0;
1523 @samp{#} on the Vax;
1526 @samp{!} for the Z8000;
1529 @samp{#} on the V850;
1531 see @ref{Machine Dependencies}. @refill
1532 @c FIXME What about i386, m88k, i860?
1535 On some machines there are two different line comment characters. One
1536 character only begins a comment if it is the first non-whitespace character on
1537 a line, while the other always begins a comment.
1541 The V850 assembler also supports a double dash as starting a comment that
1542 extends to the end of the line.
1548 @cindex lines starting with @code{#}
1549 @cindex logical line numbers
1550 To be compatible with past assemblers, lines that begin with @samp{#} have a
1551 special interpretation. Following the @samp{#} should be an absolute
1552 expression (@pxref{Expressions}): the logical line number of the @emph{next}
1553 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
1554 new logical file name. The rest of the line, if any, should be whitespace.
1556 If the first non-whitespace characters on the line are not numeric,
1557 the line is ignored. (Just like a comment.)
1560 # This is an ordinary comment.
1561 # 42-6 "new_file_name" # New logical file name
1562 # This is logical line # 36.
1564 This feature is deprecated, and may disappear from future versions
1565 of @code{@value{AS}}.
1570 @cindex characters used in symbols
1571 @ifclear SPECIAL-SYMS
1572 A @dfn{symbol} is one or more characters chosen from the set of all
1573 letters (both upper and lower case), digits and the three characters
1579 A @dfn{symbol} is one or more characters chosen from the set of all
1580 letters (both upper and lower case), digits and the three characters
1581 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
1587 On most machines, you can also use @code{$} in symbol names; exceptions
1588 are noted in @ref{Machine Dependencies}.
1590 No symbol may begin with a digit. Case is significant.
1591 There is no length limit: all characters are significant. Symbols are
1592 delimited by characters not in that set, or by the beginning of a file
1593 (since the source program must end with a newline, the end of a file is
1594 not a possible symbol delimiter). @xref{Symbols}.
1595 @cindex length of symbols
1600 @cindex statements, structure of
1601 @cindex line separator character
1602 @cindex statement separator character
1604 @ifclear abnormal-separator
1605 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
1606 semicolon (@samp{;}). The newline or semicolon is considered part of
1607 the preceding statement. Newlines and semicolons within character
1608 constants are an exception: they do not end statements.
1610 @ifset abnormal-separator
1612 A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at''
1613 sign (@samp{@@}). The newline or at sign is considered part of the
1614 preceding statement. Newlines and at signs within character constants
1615 are an exception: they do not end statements.
1618 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
1619 point (@samp{!}). The newline or exclamation point is considered part of the
1620 preceding statement. Newlines and exclamation points within character
1621 constants are an exception: they do not end statements.
1624 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
1625 H8/300) a dollar sign (@samp{$}); or (for the
1628 (@samp{;}). The newline or separator character is considered part of
1629 the preceding statement. Newlines and separators within character
1630 constants are an exception: they do not end statements.
1635 A @dfn{statement} ends at a newline character (@samp{\n}) or line
1636 separator character. (The line separator is usually @samp{;}, unless
1637 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
1638 newline or separator character is considered part of the preceding
1639 statement. Newlines and separators within character constants are an
1640 exception: they do not end statements.
1643 @cindex newline, required at file end
1644 @cindex EOF, newline must precede
1645 It is an error to end any statement with end-of-file: the last
1646 character of any input file should be a newline.@refill
1648 @cindex continuing statements
1649 @cindex multi-line statements
1650 @cindex statement on multiple lines
1651 You may write a statement on more than one line if you put a
1652 backslash (@kbd{\}) immediately in front of any newlines within the
1653 statement. When @code{@value{AS}} reads a backslashed newline both
1654 characters are ignored. You can even put backslashed newlines in
1655 the middle of symbol names without changing the meaning of your
1658 An empty statement is allowed, and may include whitespace. It is ignored.
1660 @cindex instructions and directives
1661 @cindex directives and instructions
1662 @c "key symbol" is not used elsewhere in the document; seems pedantic to
1663 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
1665 A statement begins with zero or more labels, optionally followed by a
1666 key symbol which determines what kind of statement it is. The key
1667 symbol determines the syntax of the rest of the statement. If the
1668 symbol begins with a dot @samp{.} then the statement is an assembler
1669 directive: typically valid for any computer. If the symbol begins with
1670 a letter the statement is an assembly language @dfn{instruction}: it
1671 assembles into a machine language instruction.
1673 Different versions of @code{@value{AS}} for different computers
1674 recognize different instructions. In fact, the same symbol may
1675 represent a different instruction in a different computer's assembly
1679 @cindex @code{:} (label)
1680 @cindex label (@code{:})
1681 A label is a symbol immediately followed by a colon (@code{:}).
1682 Whitespace before a label or after a colon is permitted, but you may not
1683 have whitespace between a label's symbol and its colon. @xref{Labels}.
1686 For HPPA targets, labels need not be immediately followed by a colon, but
1687 the definition of a label must begin in column zero. This also implies that
1688 only one label may be defined on each line.
1692 label: .directive followed by something
1693 another_label: # This is an empty statement.
1694 instruction operand_1, operand_2, @dots{}
1701 A constant is a number, written so that its value is known by
1702 inspection, without knowing any context. Like this:
1705 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
1706 .ascii "Ring the bell\7" # A string constant.
1707 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
1708 .float 0f-314159265358979323846264338327\
1709 95028841971.693993751E-40 # - pi, a flonum.
1714 * Characters:: Character Constants
1715 * Numbers:: Number Constants
1719 @subsection Character Constants
1721 @cindex character constants
1722 @cindex constants, character
1723 There are two kinds of character constants. A @dfn{character} stands
1724 for one character in one byte and its value may be used in
1725 numeric expressions. String constants (properly called string
1726 @emph{literals}) are potentially many bytes and their values may not be
1727 used in arithmetic expressions.
1731 * Chars:: Characters
1735 @subsubsection Strings
1737 @cindex string constants
1738 @cindex constants, string
1739 A @dfn{string} is written between double-quotes. It may contain
1740 double-quotes or null characters. The way to get special characters
1741 into a string is to @dfn{escape} these characters: precede them with
1742 a backslash @samp{\} character. For example @samp{\\} represents
1743 one backslash: the first @code{\} is an escape which tells
1744 @code{@value{AS}} to interpret the second character literally as a backslash
1745 (which prevents @code{@value{AS}} from recognizing the second @code{\} as an
1746 escape character). The complete list of escapes follows.
1748 @cindex escape codes, character
1749 @cindex character escape codes
1752 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
1754 @cindex @code{\b} (backspace character)
1755 @cindex backspace (@code{\b})
1757 Mnemonic for backspace; for ASCII this is octal code 010.
1760 @c Mnemonic for EOText; for ASCII this is octal code 004.
1762 @cindex @code{\f} (formfeed character)
1763 @cindex formfeed (@code{\f})
1765 Mnemonic for FormFeed; for ASCII this is octal code 014.
1767 @cindex @code{\n} (newline character)
1768 @cindex newline (@code{\n})
1770 Mnemonic for newline; for ASCII this is octal code 012.
1773 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
1775 @cindex @code{\r} (carriage return character)
1776 @cindex carriage return (@code{\r})
1778 Mnemonic for carriage-Return; for ASCII this is octal code 015.
1781 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
1782 @c other assemblers.
1784 @cindex @code{\t} (tab)
1785 @cindex tab (@code{\t})
1787 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
1790 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
1791 @c @item \x @var{digit} @var{digit} @var{digit}
1792 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
1794 @cindex @code{\@var{ddd}} (octal character code)
1795 @cindex octal character code (@code{\@var{ddd}})
1796 @item \ @var{digit} @var{digit} @var{digit}
1797 An octal character code. The numeric code is 3 octal digits.
1798 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
1799 for example, @code{\008} has the value 010, and @code{\009} the value 011.
1801 @cindex @code{\@var{xd...}} (hex character code)
1802 @cindex hex character code (@code{\@var{xd...}})
1803 @item \@code{x} @var{hex-digits...}
1804 A hex character code. All trailing hex digits are combined. Either upper or
1805 lower case @code{x} works.
1807 @cindex @code{\\} (@samp{\} character)
1808 @cindex backslash (@code{\\})
1810 Represents one @samp{\} character.
1813 @c Represents one @samp{'} (accent acute) character.
1814 @c This is needed in single character literals
1815 @c (@xref{Characters,,Character Constants}.) to represent
1818 @cindex @code{\"} (doublequote character)
1819 @cindex doublequote (@code{\"})
1821 Represents one @samp{"} character. Needed in strings to represent
1822 this character, because an unescaped @samp{"} would end the string.
1824 @item \ @var{anything-else}
1825 Any other character when escaped by @kbd{\} gives a warning, but
1826 assembles as if the @samp{\} was not present. The idea is that if
1827 you used an escape sequence you clearly didn't want the literal
1828 interpretation of the following character. However @code{@value{AS}} has no
1829 other interpretation, so @code{@value{AS}} knows it is giving you the wrong
1830 code and warns you of the fact.
1833 Which characters are escapable, and what those escapes represent,
1834 varies widely among assemblers. The current set is what we think
1835 the BSD 4.2 assembler recognizes, and is a subset of what most C
1836 compilers recognize. If you are in doubt, do not use an escape
1840 @subsubsection Characters
1842 @cindex single character constant
1843 @cindex character, single
1844 @cindex constant, single character
1845 A single character may be written as a single quote immediately
1846 followed by that character. The same escapes apply to characters as
1847 to strings. So if you want to write the character backslash, you
1848 must write @kbd{'\\} where the first @code{\} escapes the second
1849 @code{\}. As you can see, the quote is an acute accent, not a
1850 grave accent. A newline
1852 @ifclear abnormal-separator
1853 (or semicolon @samp{;})
1855 @ifset abnormal-separator
1857 (or at sign @samp{@@})
1860 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
1866 immediately following an acute accent is taken as a literal character
1867 and does not count as the end of a statement. The value of a character
1868 constant in a numeric expression is the machine's byte-wide code for
1869 that character. @code{@value{AS}} assumes your character code is ASCII:
1870 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
1873 @subsection Number Constants
1875 @cindex constants, number
1876 @cindex number constants
1877 @code{@value{AS}} distinguishes three kinds of numbers according to how they
1878 are stored in the target machine. @emph{Integers} are numbers that
1879 would fit into an @code{int} in the C language. @emph{Bignums} are
1880 integers, but they are stored in more than 32 bits. @emph{Flonums}
1881 are floating point numbers, described below.
1884 * Integers:: Integers
1889 * Bit Fields:: Bit Fields
1895 @subsubsection Integers
1897 @cindex constants, integer
1899 @cindex binary integers
1900 @cindex integers, binary
1901 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
1902 the binary digits @samp{01}.
1904 @cindex octal integers
1905 @cindex integers, octal
1906 An octal integer is @samp{0} followed by zero or more of the octal
1907 digits (@samp{01234567}).
1909 @cindex decimal integers
1910 @cindex integers, decimal
1911 A decimal integer starts with a non-zero digit followed by zero or
1912 more digits (@samp{0123456789}).
1914 @cindex hexadecimal integers
1915 @cindex integers, hexadecimal
1916 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
1917 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
1919 Integers have the usual values. To denote a negative integer, use
1920 the prefix operator @samp{-} discussed under expressions
1921 (@pxref{Prefix Ops,,Prefix Operators}).
1924 @subsubsection Bignums
1927 @cindex constants, bignum
1928 A @dfn{bignum} has the same syntax and semantics as an integer
1929 except that the number (or its negative) takes more than 32 bits to
1930 represent in binary. The distinction is made because in some places
1931 integers are permitted while bignums are not.
1934 @subsubsection Flonums
1936 @cindex floating point numbers
1937 @cindex constants, floating point
1939 @cindex precision, floating point
1940 A @dfn{flonum} represents a floating point number. The translation is
1941 indirect: a decimal floating point number from the text is converted by
1942 @code{@value{AS}} to a generic binary floating point number of more than
1943 sufficient precision. This generic floating point number is converted
1944 to a particular computer's floating point format (or formats) by a
1945 portion of @code{@value{AS}} specialized to that computer.
1947 A flonum is written by writing (in order)
1952 (@samp{0} is optional on the HPPA.)
1956 A letter, to tell @code{@value{AS}} the rest of the number is a flonum.
1958 @kbd{e} is recommended. Case is not important.
1960 @c FIXME: verify if flonum syntax really this vague for most cases
1961 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
1962 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
1965 On the H8/300, H8/500,
1967 and AMD 29K architectures, the letter must be
1968 one of the letters @samp{DFPRSX} (in upper or lower case).
1970 On the ARC, the letter must be one of the letters @samp{DFRS}
1971 (in upper or lower case).
1973 On the Intel 960 architecture, the letter must be
1974 one of the letters @samp{DFT} (in upper or lower case).
1976 On the HPPA architecture, the letter must be @samp{E} (upper case only).
1980 One of the letters @samp{DFPRSX} (in upper or lower case).
1983 One of the letters @samp{DFRS} (in upper or lower case).
1986 One of the letters @samp{DFPRSX} (in upper or lower case).
1989 The letter @samp{E} (upper case only).
1992 One of the letters @samp{DFT} (in upper or lower case).
1997 An optional sign: either @samp{+} or @samp{-}.
2000 An optional @dfn{integer part}: zero or more decimal digits.
2003 An optional @dfn{fractional part}: @samp{.} followed by zero
2004 or more decimal digits.
2007 An optional exponent, consisting of:
2011 An @samp{E} or @samp{e}.
2012 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2013 @c principle this can perfectly well be different on different targets.
2015 Optional sign: either @samp{+} or @samp{-}.
2017 One or more decimal digits.
2022 At least one of the integer part or the fractional part must be
2023 present. The floating point number has the usual base-10 value.
2025 @code{@value{AS}} does all processing using integers. Flonums are computed
2026 independently of any floating point hardware in the computer running
2031 @c Bit fields are written as a general facility but are also controlled
2032 @c by a conditional-compilation flag---which is as of now (21mar91)
2033 @c turned on only by the i960 config of GAS.
2035 @subsubsection Bit Fields
2038 @cindex constants, bit field
2039 You can also define numeric constants as @dfn{bit fields}.
2040 specify two numbers separated by a colon---
2042 @var{mask}:@var{value}
2045 @code{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2048 The resulting number is then packed
2050 @c this conditional paren in case bit fields turned on elsewhere than 960
2051 (in host-dependent byte order)
2053 into a field whose width depends on which assembler directive has the
2054 bit-field as its argument. Overflow (a result from the bitwise and
2055 requiring more binary digits to represent) is not an error; instead,
2056 more constants are generated, of the specified width, beginning with the
2057 least significant digits.@refill
2059 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2060 @code{.short}, and @code{.word} accept bit-field arguments.
2065 @chapter Sections and Relocation
2070 * Secs Background:: Background
2071 * Ld Sections:: Linker Sections
2072 * As Sections:: Assembler Internal Sections
2073 * Sub-Sections:: Sub-Sections
2077 @node Secs Background
2080 Roughly, a section is a range of addresses, with no gaps; all data
2081 ``in'' those addresses is treated the same for some particular purpose.
2082 For example there may be a ``read only'' section.
2084 @cindex linker, and assembler
2085 @cindex assembler, and linker
2086 The linker @code{@value{LD}} reads many object files (partial programs) and
2087 combines their contents to form a runnable program. When @code{@value{AS}}
2088 emits an object file, the partial program is assumed to start at address 0.
2089 @code{@value{LD}} assigns the final addresses for the partial program, so that
2090 different partial programs do not overlap. This is actually an
2091 oversimplification, but it suffices to explain how @code{@value{AS}} uses
2094 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2095 addresses. These blocks slide to their run-time addresses as rigid
2096 units; their length does not change and neither does the order of bytes
2097 within them. Such a rigid unit is called a @emph{section}. Assigning
2098 run-time addresses to sections is called @dfn{relocation}. It includes
2099 the task of adjusting mentions of object-file addresses so they refer to
2100 the proper run-time addresses.
2102 For the H8/300 and H8/500,
2103 and for the Hitachi SH,
2104 @code{@value{AS}} pads sections if needed to
2105 ensure they end on a word (sixteen bit) boundary.
2108 @cindex standard assembler sections
2109 An object file written by @code{@value{AS}} has at least three sections, any
2110 of which may be empty. These are named @dfn{text}, @dfn{data} and
2115 When it generates COFF output,
2117 @code{@value{AS}} can also generate whatever other named sections you specify
2118 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2119 If you do not use any directives that place output in the @samp{.text}
2120 or @samp{.data} sections, these sections still exist, but are empty.
2125 When @code{@value{AS}} generates SOM or ELF output for the HPPA,
2127 @code{@value{AS}} can also generate whatever other named sections you
2128 specify using the @samp{.space} and @samp{.subspace} directives. See
2129 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2130 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2131 assembler directives.
2134 Additionally, @code{@value{AS}} uses different names for the standard
2135 text, data, and bss sections when generating SOM output. Program text
2136 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2137 BSS into @samp{$BSS$}.
2141 Within the object file, the text section starts at address @code{0}, the
2142 data section follows, and the bss section follows the data section.
2145 When generating either SOM or ELF output files on the HPPA, the text
2146 section starts at address @code{0}, the data section at address
2147 @code{0x4000000}, and the bss section follows the data section.
2150 To let @code{@value{LD}} know which data changes when the sections are
2151 relocated, and how to change that data, @code{@value{AS}} also writes to the
2152 object file details of the relocation needed. To perform relocation
2153 @code{@value{LD}} must know, each time an address in the object
2157 Where in the object file is the beginning of this reference to
2160 How long (in bytes) is this reference?
2162 Which section does the address refer to? What is the numeric value of
2164 (@var{address}) @minus{} (@var{start-address of section})?
2167 Is the reference to an address ``Program-Counter relative''?
2170 @cindex addresses, format of
2171 @cindex section-relative addressing
2172 In fact, every address @code{@value{AS}} ever uses is expressed as
2174 (@var{section}) + (@var{offset into section})
2177 Further, most expressions @code{@value{AS}} computes have this section-relative
2180 (For some object formats, such as SOM for the HPPA, some expressions are
2181 symbol-relative instead.)
2184 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2185 @var{N} into section @var{secname}.''
2187 Apart from text, data and bss sections you need to know about the
2188 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2189 addresses in the absolute section remain unchanged. For example, address
2190 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2191 @code{@value{LD}}. Although the linker never arranges two partial programs'
2192 data sections with overlapping addresses after linking, @emph{by definition}
2193 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2194 part of a program is always the same address when the program is running as
2195 address @code{@{absolute@ 239@}} in any other part of the program.
2197 The idea of sections is extended to the @dfn{undefined} section. Any
2198 address whose section is unknown at assembly time is by definition
2199 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2200 Since numbers are always defined, the only way to generate an undefined
2201 address is to mention an undefined symbol. A reference to a named
2202 common block would be such a symbol: its value is unknown at assembly
2203 time so it has section @emph{undefined}.
2205 By analogy the word @emph{section} is used to describe groups of sections in
2206 the linked program. @code{@value{LD}} puts all partial programs' text
2207 sections in contiguous addresses in the linked program. It is
2208 customary to refer to the @emph{text section} of a program, meaning all
2209 the addresses of all partial programs' text sections. Likewise for
2210 data and bss sections.
2212 Some sections are manipulated by @code{@value{LD}}; others are invented for
2213 use of @code{@value{AS}} and have no meaning except during assembly.
2216 @section Linker Sections
2217 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2222 @cindex named sections
2223 @cindex sections, named
2224 @item named sections
2227 @cindex text section
2228 @cindex data section
2232 These sections hold your program. @code{@value{AS}} and @code{@value{LD}} treat them as
2233 separate but equal sections. Anything you can say of one section is
2236 When the program is running, however, it is
2237 customary for the text section to be unalterable. The
2238 text section is often shared among processes: it contains
2239 instructions, constants and the like. The data section of a running
2240 program is usually alterable: for example, C variables would be stored
2241 in the data section.
2246 This section contains zeroed bytes when your program begins running. It
2247 is used to hold unitialized variables or common storage. The length of
2248 each partial program's bss section is important, but because it starts
2249 out containing zeroed bytes there is no need to store explicit zero
2250 bytes in the object file. The bss section was invented to eliminate
2251 those explicit zeros from object files.
2253 @cindex absolute section
2254 @item absolute section
2255 Address 0 of this section is always ``relocated'' to runtime address 0.
2256 This is useful if you want to refer to an address that @code{@value{LD}} must
2257 not change when relocating. In this sense we speak of absolute
2258 addresses being ``unrelocatable'': they do not change during relocation.
2260 @cindex undefined section
2261 @item undefined section
2262 This ``section'' is a catch-all for address references to objects not in
2263 the preceding sections.
2264 @c FIXME: ref to some other doc on obj-file formats could go here.
2267 @cindex relocation example
2268 An idealized example of three relocatable sections follows.
2270 The example uses the traditional section names @samp{.text} and @samp{.data}.
2272 Memory addresses are on the horizontal axis.
2276 @c END TEXI2ROFF-KILL
2279 partial program # 1: |ttttt|dddd|00|
2286 partial program # 2: |TTT|DDD|000|
2289 +--+---+-----+--+----+---+-----+~~
2290 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2291 +--+---+-----+--+----+---+-----+~~
2293 addresses: 0 @dots{}
2300 \line{\it Partial program \#1: \hfil}
2301 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2302 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2304 \line{\it Partial program \#2: \hfil}
2305 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2306 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2308 \line{\it linked program: \hfil}
2309 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2310 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2311 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2312 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2314 \line{\it addresses: \hfil}
2318 @c END TEXI2ROFF-KILL
2321 @section Assembler Internal Sections
2323 @cindex internal assembler sections
2324 @cindex sections in messages, internal
2325 These sections are meant only for the internal use of @code{@value{AS}}. They
2326 have no meaning at run-time. You do not really need to know about these
2327 sections for most purposes; but they can be mentioned in @code{@value{AS}}
2328 warning messages, so it might be helpful to have an idea of their
2329 meanings to @code{@value{AS}}. These sections are used to permit the
2330 value of every expression in your assembly language program to be a
2331 section-relative address.
2334 @cindex assembler internal logic error
2335 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2336 An internal assembler logic error has been found. This means there is a
2337 bug in the assembler.
2339 @cindex expr (internal section)
2341 The assembler stores complex expression internally as combinations of
2342 symbols. When it needs to represent an expression as a symbol, it puts
2343 it in the expr section.
2345 @c FIXME item transfer[t] vector preload
2346 @c FIXME item transfer[t] vector postload
2347 @c FIXME item register
2351 @section Sub-Sections
2353 @cindex numbered subsections
2354 @cindex grouping data
2360 fall into two sections: text and data.
2362 You may have separate groups of
2364 data in named sections
2368 data in named sections
2374 that you want to end up near to each other in the object file, even though they
2375 are not contiguous in the assembler source. @code{@value{AS}} allows you to
2376 use @dfn{subsections} for this purpose. Within each section, there can be
2377 numbered subsections with values from 0 to 8192. Objects assembled into the
2378 same subsection go into the object file together with other objects in the same
2379 subsection. For example, a compiler might want to store constants in the text
2380 section, but might not want to have them interspersed with the program being
2381 assembled. In this case, the compiler could issue a @samp{.text 0} before each
2382 section of code being output, and a @samp{.text 1} before each group of
2383 constants being output.
2385 Subsections are optional. If you do not use subsections, everything
2386 goes in subsection number zero.
2389 Each subsection is zero-padded up to a multiple of four bytes.
2390 (Subsections may be padded a different amount on different flavors
2391 of @code{@value{AS}}.)
2395 On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word
2396 boundary (two bytes).
2397 The same is true on the Hitachi SH.
2400 @c FIXME section padding (alignment)?
2401 @c Rich Pixley says padding here depends on target obj code format; that
2402 @c doesn't seem particularly useful to say without further elaboration,
2403 @c so for now I say nothing about it. If this is a generic BFD issue,
2404 @c these paragraphs might need to vanish from this manual, and be
2405 @c discussed in BFD chapter of binutils (or some such).
2408 On the AMD 29K family, no particular padding is added to section or
2409 subsection sizes; @value{AS} forces no alignment on this platform.
2413 Subsections appear in your object file in numeric order, lowest numbered
2414 to highest. (All this to be compatible with other people's assemblers.)
2415 The object file contains no representation of subsections; @code{@value{LD}} and
2416 other programs that manipulate object files see no trace of them.
2417 They just see all your text subsections as a text section, and all your
2418 data subsections as a data section.
2420 To specify which subsection you want subsequent statements assembled
2421 into, use a numeric argument to specify it, in a @samp{.text
2422 @var{expression}} or a @samp{.data @var{expression}} statement.
2425 When generating COFF output, you
2430 can also use an extra subsection
2431 argument with arbitrary named sections: @samp{.section @var{name},
2434 @var{Expression} should be an absolute expression.
2435 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
2436 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
2437 begins in @code{text 0}. For instance:
2439 .text 0 # The default subsection is text 0 anyway.
2440 .ascii "This lives in the first text subsection. *"
2442 .ascii "But this lives in the second text subsection."
2444 .ascii "This lives in the data section,"
2445 .ascii "in the first data subsection."
2447 .ascii "This lives in the first text section,"
2448 .ascii "immediately following the asterisk (*)."
2451 Each section has a @dfn{location counter} incremented by one for every byte
2452 assembled into that section. Because subsections are merely a convenience
2453 restricted to @code{@value{AS}} there is no concept of a subsection location
2454 counter. There is no way to directly manipulate a location counter---but the
2455 @code{.align} directive changes it, and any label definition captures its
2456 current value. The location counter of the section where statements are being
2457 assembled is said to be the @dfn{active} location counter.
2460 @section bss Section
2463 @cindex common variable storage
2464 The bss section is used for local common variable storage.
2465 You may allocate address space in the bss section, but you may
2466 not dictate data to load into it before your program executes. When
2467 your program starts running, all the contents of the bss
2468 section are zeroed bytes.
2470 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
2471 @ref{Lcomm,,@code{.lcomm}}.
2473 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
2474 another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}.
2477 When assembling for a target which supports multiple sections, such as ELF or
2478 COFF, you may switch into the @code{.bss} section and define symbols as usual;
2479 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
2480 section. Typically the section will only contain symbol definitions and
2481 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
2488 Symbols are a central concept: the programmer uses symbols to name
2489 things, the linker uses symbols to link, and the debugger uses symbols
2493 @cindex debuggers, and symbol order
2494 @emph{Warning:} @code{@value{AS}} does not place symbols in the object file in
2495 the same order they were declared. This may break some debuggers.
2500 * Setting Symbols:: Giving Symbols Other Values
2501 * Symbol Names:: Symbol Names
2502 * Dot:: The Special Dot Symbol
2503 * Symbol Attributes:: Symbol Attributes
2510 A @dfn{label} is written as a symbol immediately followed by a colon
2511 @samp{:}. The symbol then represents the current value of the
2512 active location counter, and is, for example, a suitable instruction
2513 operand. You are warned if you use the same symbol to represent two
2514 different locations: the first definition overrides any other
2518 On the HPPA, the usual form for a label need not be immediately followed by a
2519 colon, but instead must start in column zero. Only one label may be defined on
2520 a single line. To work around this, the HPPA version of @code{@value{AS}} also
2521 provides a special directive @code{.label} for defining labels more flexibly.
2524 @node Setting Symbols
2525 @section Giving Symbols Other Values
2527 @cindex assigning values to symbols
2528 @cindex symbol values, assigning
2529 A symbol can be given an arbitrary value by writing a symbol, followed
2530 by an equals sign @samp{=}, followed by an expression
2531 (@pxref{Expressions}). This is equivalent to using the @code{.set}
2532 directive. @xref{Set,,@code{.set}}.
2535 @section Symbol Names
2537 @cindex symbol names
2538 @cindex names, symbol
2539 @ifclear SPECIAL-SYMS
2540 Symbol names begin with a letter or with one of @samp{._}. On most
2541 machines, you can also use @code{$} in symbol names; exceptions are
2542 noted in @ref{Machine Dependencies}. That character may be followed by any
2543 string of digits, letters, dollar signs (unless otherwise noted in
2544 @ref{Machine Dependencies}), and underscores.
2547 For the AMD 29K family, @samp{?} is also allowed in the
2548 body of a symbol name, though not at its beginning.
2553 Symbol names begin with a letter or with one of @samp{._}. On the
2555 H8/500, you can also use @code{$} in symbol names. That character may
2556 be followed by any string of digits, letters, dollar signs (save on the
2557 H8/300), and underscores.
2561 Case of letters is significant: @code{foo} is a different symbol name
2564 Each symbol has exactly one name. Each name in an assembly language program
2565 refers to exactly one symbol. You may use that symbol name any number of times
2568 @subheading Local Symbol Names
2570 @cindex local symbol names
2571 @cindex symbol names, local
2572 @cindex temporary symbol names
2573 @cindex symbol names, temporary
2574 Local symbols help compilers and programmers use names temporarily.
2575 There are ten local symbol names, which are re-used throughout the
2576 program. You may refer to them using the names @samp{0} @samp{1}
2577 @dots{} @samp{9}. To define a local symbol, write a label of the form
2578 @samp{@b{N}:} (where @b{N} represents any digit). To refer to the most
2579 recent previous definition of that symbol write @samp{@b{N}b}, using the
2580 same digit as when you defined the label. To refer to the next
2581 definition of a local label, write @samp{@b{N}f}---where @b{N} gives you
2582 a choice of 10 forward references. The @samp{b} stands for
2583 ``backwards'' and the @samp{f} stands for ``forwards''.
2585 Local symbols are not emitted by the current @sc{gnu} C compiler.
2587 There is no restriction on how you can use these labels, but
2588 remember that at any point in the assembly you can refer to at most
2589 10 prior local labels and to at most 10 forward local labels.
2591 Local symbol names are only a notation device. They are immediately
2592 transformed into more conventional symbol names before the assembler
2593 uses them. The symbol names stored in the symbol table, appearing in
2594 error messages and optionally emitted to the object file have these
2599 All local labels begin with @samp{L}. Normally both @code{@value{AS}} and
2600 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
2601 used for symbols you are never intended to see. If you use the
2602 @samp{-L} option then @code{@value{AS}} retains these symbols in the
2603 object file. If you also instruct @code{@value{LD}} to retain these symbols,
2604 you may use them in debugging.
2607 If the label is written @samp{0:} then the digit is @samp{0}.
2608 If the label is written @samp{1:} then the digit is @samp{1}.
2609 And so on up through @samp{9:}.
2612 This unusual character is included so you do not accidentally invent
2613 a symbol of the same name. The character has ASCII value
2616 @item @emph{ordinal number}
2617 This is a serial number to keep the labels distinct. The first
2618 @samp{0:} gets the number @samp{1}; The 15th @samp{0:} gets the
2619 number @samp{15}; @emph{etc.}. Likewise for the other labels @samp{1:}
2623 For instance, the first @code{1:} is named @code{L1@kbd{C-A}1}, the 44th
2624 @code{3:} is named @code{L3@kbd{C-A}44}.
2627 @section The Special Dot Symbol
2629 @cindex dot (symbol)
2630 @cindex @code{.} (symbol)
2631 @cindex current address
2632 @cindex location counter
2633 The special symbol @samp{.} refers to the current address that
2634 @code{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
2635 .long .} defines @code{melvin} to contain its own address.
2636 Assigning a value to @code{.} is treated the same as a @code{.org}
2637 directive. Thus, the expression @samp{.=.+4} is the same as saying
2638 @ifclear no-space-dir
2647 @node Symbol Attributes
2648 @section Symbol Attributes
2650 @cindex symbol attributes
2651 @cindex attributes, symbol
2652 Every symbol has, as well as its name, the attributes ``Value'' and
2653 ``Type''. Depending on output format, symbols can also have auxiliary
2656 The detailed definitions are in @file{a.out.h}.
2659 If you use a symbol without defining it, @code{@value{AS}} assumes zero for
2660 all these attributes, and probably won't warn you. This makes the
2661 symbol an externally defined symbol, which is generally what you
2665 * Symbol Value:: Value
2666 * Symbol Type:: Type
2669 * a.out Symbols:: Symbol Attributes: @code{a.out}
2673 * a.out Symbols:: Symbol Attributes: @code{a.out}
2676 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
2681 * COFF Symbols:: Symbol Attributes for COFF
2684 * SOM Symbols:: Symbol Attributes for SOM
2691 @cindex value of a symbol
2692 @cindex symbol value
2693 The value of a symbol is (usually) 32 bits. For a symbol which labels a
2694 location in the text, data, bss or absolute sections the value is the
2695 number of addresses from the start of that section to the label.
2696 Naturally for text, data and bss sections the value of a symbol changes
2697 as @code{@value{LD}} changes section base addresses during linking. Absolute
2698 symbols' values do not change during linking: that is why they are
2701 The value of an undefined symbol is treated in a special way. If it is
2702 0 then the symbol is not defined in this assembler source file, and
2703 @code{@value{LD}} tries to determine its value from other files linked into the
2704 same program. You make this kind of symbol simply by mentioning a symbol
2705 name without defining it. A non-zero value represents a @code{.comm}
2706 common declaration. The value is how much common storage to reserve, in
2707 bytes (addresses). The symbol refers to the first address of the
2713 @cindex type of a symbol
2715 The type attribute of a symbol contains relocation (section)
2716 information, any flag settings indicating that a symbol is external, and
2717 (optionally), other information for linkers and debuggers. The exact
2718 format depends on the object-code output format in use.
2723 @c The following avoids a "widow" subsection title. @group would be
2724 @c better if it were available outside examples.
2727 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
2729 @cindex @code{b.out} symbol attributes
2730 @cindex symbol attributes, @code{b.out}
2731 These symbol attributes appear only when @code{@value{AS}} is configured for
2732 one of the Berkeley-descended object output formats---@code{a.out} or
2738 @subsection Symbol Attributes: @code{a.out}
2740 @cindex @code{a.out} symbol attributes
2741 @cindex symbol attributes, @code{a.out}
2747 @subsection Symbol Attributes: @code{a.out}
2749 @cindex @code{a.out} symbol attributes
2750 @cindex symbol attributes, @code{a.out}
2754 * Symbol Desc:: Descriptor
2755 * Symbol Other:: Other
2759 @subsubsection Descriptor
2761 @cindex descriptor, of @code{a.out} symbol
2762 This is an arbitrary 16-bit value. You may establish a symbol's
2763 descriptor value by using a @code{.desc} statement
2764 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
2768 @subsubsection Other
2770 @cindex other attribute, of @code{a.out} symbol
2771 This is an arbitrary 8-bit value. It means nothing to @code{@value{AS}}.
2776 @subsection Symbol Attributes for COFF
2778 @cindex COFF symbol attributes
2779 @cindex symbol attributes, COFF
2781 The COFF format supports a multitude of auxiliary symbol attributes;
2782 like the primary symbol attributes, they are set between @code{.def} and
2783 @code{.endef} directives.
2785 @subsubsection Primary Attributes
2787 @cindex primary attributes, COFF symbols
2788 The symbol name is set with @code{.def}; the value and type,
2789 respectively, with @code{.val} and @code{.type}.
2791 @subsubsection Auxiliary Attributes
2793 @cindex auxiliary attributes, COFF symbols
2794 The @code{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
2795 @code{.size}, and @code{.tag} can generate auxiliary symbol table
2796 information for COFF.
2801 @subsection Symbol Attributes for SOM
2803 @cindex SOM symbol attributes
2804 @cindex symbol attributes, SOM
2806 The SOM format for the HPPA supports a multitude of symbol attributes set with
2807 the @code{.EXPORT} and @code{.IMPORT} directives.
2809 The attributes are described in @cite{HP9000 Series 800 Assembly
2810 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
2811 @code{EXPORT} assembler directive documentation.
2815 @chapter Expressions
2819 @cindex numeric values
2820 An @dfn{expression} specifies an address or numeric value.
2821 Whitespace may precede and/or follow an expression.
2823 The result of an expression must be an absolute number, or else an offset into
2824 a particular section. If an expression is not absolute, and there is not
2825 enough information when @code{@value{AS}} sees the expression to know its
2826 section, a second pass over the source program might be necessary to interpret
2827 the expression---but the second pass is currently not implemented.
2828 @code{@value{AS}} aborts with an error message in this situation.
2831 * Empty Exprs:: Empty Expressions
2832 * Integer Exprs:: Integer Expressions
2836 @section Empty Expressions
2838 @cindex empty expressions
2839 @cindex expressions, empty
2840 An empty expression has no value: it is just whitespace or null.
2841 Wherever an absolute expression is required, you may omit the
2842 expression, and @code{@value{AS}} assumes a value of (absolute) 0. This
2843 is compatible with other assemblers.
2846 @section Integer Expressions
2848 @cindex integer expressions
2849 @cindex expressions, integer
2850 An @dfn{integer expression} is one or more @emph{arguments} delimited
2851 by @emph{operators}.
2854 * Arguments:: Arguments
2855 * Operators:: Operators
2856 * Prefix Ops:: Prefix Operators
2857 * Infix Ops:: Infix Operators
2861 @subsection Arguments
2863 @cindex expression arguments
2864 @cindex arguments in expressions
2865 @cindex operands in expressions
2866 @cindex arithmetic operands
2867 @dfn{Arguments} are symbols, numbers or subexpressions. In other
2868 contexts arguments are sometimes called ``arithmetic operands''. In
2869 this manual, to avoid confusing them with the ``instruction operands'' of
2870 the machine language, we use the term ``argument'' to refer to parts of
2871 expressions only, reserving the word ``operand'' to refer only to machine
2872 instruction operands.
2874 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
2875 @var{section} is one of text, data, bss, absolute,
2876 or undefined. @var{NNN} is a signed, 2's complement 32 bit
2879 Numbers are usually integers.
2881 A number can be a flonum or bignum. In this case, you are warned
2882 that only the low order 32 bits are used, and @code{@value{AS}} pretends
2883 these 32 bits are an integer. You may write integer-manipulating
2884 instructions that act on exotic constants, compatible with other
2887 @cindex subexpressions
2888 Subexpressions are a left parenthesis @samp{(} followed by an integer
2889 expression, followed by a right parenthesis @samp{)}; or a prefix
2890 operator followed by an argument.
2893 @subsection Operators
2895 @cindex operators, in expressions
2896 @cindex arithmetic functions
2897 @cindex functions, in expressions
2898 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
2899 operators are followed by an argument. Infix operators appear
2900 between their arguments. Operators may be preceded and/or followed by
2904 @subsection Prefix Operator
2906 @cindex prefix operators
2907 @code{@value{AS}} has the following @dfn{prefix operators}. They each take
2908 one argument, which must be absolute.
2910 @c the tex/end tex stuff surrounding this small table is meant to make
2911 @c it align, on the printed page, with the similar table in the next
2912 @c section (which is inside an enumerate).
2914 \global\advance\leftskip by \itemindent
2919 @dfn{Negation}. Two's complement negation.
2921 @dfn{Complementation}. Bitwise not.
2925 \global\advance\leftskip by -\itemindent
2929 @subsection Infix Operators
2931 @cindex infix operators
2932 @cindex operators, permitted arguments
2933 @dfn{Infix operators} take two arguments, one on either side. Operators
2934 have precedence, but operations with equal precedence are performed left
2935 to right. Apart from @code{+} or @code{-}, both arguments must be
2936 absolute, and the result is absolute.
2939 @cindex operator precedence
2940 @cindex precedence of operators
2947 @dfn{Multiplication}.
2950 @dfn{Division}. Truncation is the same as the C operator @samp{/}
2957 @dfn{Shift Left}. Same as the C operator @samp{<<}.
2961 @dfn{Shift Right}. Same as the C operator @samp{>>}.
2965 Intermediate precedence
2970 @dfn{Bitwise Inclusive Or}.
2976 @dfn{Bitwise Exclusive Or}.
2979 @dfn{Bitwise Or Not}.
2986 @cindex addition, permitted arguments
2987 @cindex plus, permitted arguments
2988 @cindex arguments for addition
2990 @dfn{Addition}. If either argument is absolute, the result has the section of
2991 the other argument. You may not add together arguments from different
2994 @cindex subtraction, permitted arguments
2995 @cindex minus, permitted arguments
2996 @cindex arguments for subtraction
2998 @dfn{Subtraction}. If the right argument is absolute, the
2999 result has the section of the left argument.
3000 If both arguments are in the same section, the result is absolute.
3001 You may not subtract arguments from different sections.
3002 @c FIXME is there still something useful to say about undefined - undefined ?
3006 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3007 address; you can only have a defined section in one of the two arguments.
3010 @chapter Assembler Directives
3012 @cindex directives, machine independent
3013 @cindex pseudo-ops, machine independent
3014 @cindex machine independent directives
3015 All assembler directives have names that begin with a period (@samp{.}).
3016 The rest of the name is letters, usually in lower case.
3018 This chapter discusses directives that are available regardless of the
3019 target machine configuration for the @sc{gnu} assembler.
3021 Some machine configurations provide additional directives.
3022 @xref{Machine Dependencies}.
3025 @ifset machine-directives
3026 @xref{Machine Dependencies} for additional directives.
3031 * Abort:: @code{.abort}
3033 * ABORT:: @code{.ABORT}
3036 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3037 * App-File:: @code{.app-file @var{string}}
3038 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3039 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3040 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3041 * Byte:: @code{.byte @var{expressions}}
3042 * Comm:: @code{.comm @var{symbol} , @var{length} }
3043 * Data:: @code{.data @var{subsection}}
3045 * Def:: @code{.def @var{name}}
3048 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3054 * Double:: @code{.double @var{flonums}}
3055 * Eject:: @code{.eject}
3056 * Else:: @code{.else}
3058 * Endef:: @code{.endef}
3061 * Endif:: @code{.endif}
3062 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3063 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3065 * Extern:: @code{.extern}
3066 @ifclear no-file-dir
3067 * File:: @code{.file @var{string}}
3070 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3071 * Float:: @code{.float @var{flonums}}
3072 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3073 * hword:: @code{.hword @var{expressions}}
3074 * Ident:: @code{.ident}
3075 * If:: @code{.if @var{absolute expression}}
3076 * Include:: @code{.include "@var{file}"}
3077 * Int:: @code{.int @var{expressions}}
3078 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3079 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3080 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3081 * Lflags:: @code{.lflags}
3082 @ifclear no-line-dir
3083 * Line:: @code{.line @var{line-number}}
3086 * Ln:: @code{.ln @var{line-number}}
3087 * Linkonce:: @code{.linkonce [@var{type}]}
3088 * List:: @code{.list}
3089 * Long:: @code{.long @var{expressions}}
3091 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3094 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3095 * MRI:: @code{.mri @var{val}}
3097 * Nolist:: @code{.nolist}
3098 * Octa:: @code{.octa @var{bignums}}
3099 * Org:: @code{.org @var{new-lc} , @var{fill}}
3100 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
3101 * Psize:: @code{.psize @var{lines}, @var{columns}}
3102 * Quad:: @code{.quad @var{bignums}}
3103 * Rept:: @code{.rept @var{count}}
3104 * Sbttl:: @code{.sbttl "@var{subheading}"}
3106 * Scl:: @code{.scl @var{class}}
3107 * Section:: @code{.section @var{name}, @var{subsection}}
3110 * Set:: @code{.set @var{symbol}, @var{expression}}
3111 * Short:: @code{.short @var{expressions}}
3112 * Single:: @code{.single @var{flonums}}
3114 * Size:: @code{.size}
3117 * Skip:: @code{.skip @var{size} , @var{fill}}
3118 * Sleb128:: @code{.sleb128 @var{expressions}}
3119 * Space:: @code{.space @var{size} , @var{fill}}
3121 * Stab:: @code{.stabd, .stabn, .stabs}
3124 * String:: @code{.string "@var{str}"}
3126 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3129 * Tag:: @code{.tag @var{structname}}
3132 * Text:: @code{.text @var{subsection}}
3133 * Title:: @code{.title "@var{heading}"}
3135 * Type:: @code{.type @var{int}}
3136 * Val:: @code{.val @var{addr}}
3139 * Uleb128:: @code{.uleb128 @var{expressions}}
3140 * Word:: @code{.word @var{expressions}}
3141 * Deprecated:: Deprecated Directives
3145 @section @code{.abort}
3147 @cindex @code{abort} directive
3148 @cindex stopping the assembly
3149 This directive stops the assembly immediately. It is for
3150 compatibility with other assemblers. The original idea was that the
3151 assembly language source would be piped into the assembler. If the sender
3152 of the source quit, it could use this directive tells @code{@value{AS}} to
3153 quit also. One day @code{.abort} will not be supported.
3157 @section @code{.ABORT}
3159 @cindex @code{ABORT} directive
3160 When producing COFF output, @code{@value{AS}} accepts this directive as a
3161 synonym for @samp{.abort}.
3164 When producing @code{b.out} output, @code{@value{AS}} accepts this directive,
3170 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3172 @cindex padding the location counter
3173 @cindex @code{align} directive
3174 Pad the location counter (in the current subsection) to a particular storage
3175 boundary. The first expression (which must be absolute) is the alignment
3176 required, as described below.
3178 The second expression (also absolute) gives the fill value to be stored in the
3179 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3180 padding bytes are normally zero. However, on some systems, if the section is
3181 marked as containing code and the fill value is omitted, the space is filled
3182 with no-op instructions.
3184 The third expression is also absolute, and is also optional. If it is present,
3185 it is the maximum number of bytes that should be skipped by this alignment
3186 directive. If doing the alignment would require skipping more bytes than the
3187 specified maximum, then the alignment is not done at all. You can omit the
3188 fill value (the second argument) entirely by simply using two commas after the
3189 required alignment; this can be useful if you want the alignment to be filled
3190 with no-op instructions when appropriate.
3192 The way the required alignment is specified varies from system to system.
3193 For the a29k, hppa, m68k, m88k, w65, sparc, and Hitachi SH, and i386 using ELF
3195 the first expression is the
3196 alignment request in bytes. For example @samp{.align 8} advances
3197 the location counter until it is a multiple of 8. If the location counter
3198 is already a multiple of 8, no change is needed.
3200 For other systems, including the i386 using a.out format, it is the
3201 number of low-order zero bits the location counter must have after
3202 advancement. For example @samp{.align 3} advances the location
3203 counter until it a multiple of 8. If the location counter is already a
3204 multiple of 8, no change is needed.
3206 This inconsistency is due to the different behaviors of the various
3207 native assemblers for these systems which GAS must emulate.
3208 GAS also provides @code{.balign} and @code{.p2align} directives,
3209 described later, which have a consistent behavior across all
3210 architectures (but are specific to GAS).
3213 @section @code{.app-file @var{string}}
3215 @cindex logical file name
3216 @cindex file name, logical
3217 @cindex @code{app-file} directive
3219 @ifclear no-file-dir
3220 (which may also be spelled @samp{.file})
3222 tells @code{@value{AS}} that we are about to start a new
3223 logical file. @var{string} is the new file name. In general, the
3224 filename is recognized whether or not it is surrounded by quotes @samp{"};
3225 but if you wish to specify an empty file name is permitted,
3226 you must give the quotes--@code{""}. This statement may go away in
3227 future: it is only recognized to be compatible with old @code{@value{AS}}
3231 @section @code{.ascii "@var{string}"}@dots{}
3233 @cindex @code{ascii} directive
3234 @cindex string literals
3235 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3236 separated by commas. It assembles each string (with no automatic
3237 trailing zero byte) into consecutive addresses.
3240 @section @code{.asciz "@var{string}"}@dots{}
3242 @cindex @code{asciz} directive
3243 @cindex zero-terminated strings
3244 @cindex null-terminated strings
3245 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3246 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3249 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3251 @cindex padding the location counter given number of bytes
3252 @cindex @code{balign} directive
3253 Pad the location counter (in the current subsection) to a particular
3254 storage boundary. The first expression (which must be absolute) is the
3255 alignment request in bytes. For example @samp{.balign 8} advances
3256 the location counter until it is a multiple of 8. If the location counter
3257 is already a multiple of 8, no change is needed.
3259 The second expression (also absolute) gives the fill value to be stored in the
3260 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3261 padding bytes are normally zero. However, on some systems, if the section is
3262 marked as containing code and the fill value is omitted, the space is filled
3263 with no-op instructions.
3265 The third expression is also absolute, and is also optional. If it is present,
3266 it is the maximum number of bytes that should be skipped by this alignment
3267 directive. If doing the alignment would require skipping more bytes than the
3268 specified maximum, then the alignment is not done at all. You can omit the
3269 fill value (the second argument) entirely by simply using two commas after the
3270 required alignment; this can be useful if you want the alignment to be filled
3271 with no-op instructions when appropriate.
3273 @cindex @code{balignw} directive
3274 @cindex @code{balignl} directive
3275 The @code{.balignw} and @code{.balignl} directives are variants of the
3276 @code{.balign} directive. The @code{.balignw} directive treats the fill
3277 pattern as a two byte word value. The @code{.balignl} directives treats the
3278 fill pattern as a four byte longword value. For example, @code{.balignw
3279 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3280 filled in with the value 0x368d (the exact placement of the bytes depends upon
3281 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3285 @section @code{.byte @var{expressions}}
3287 @cindex @code{byte} directive
3288 @cindex integers, one byte
3289 @code{.byte} expects zero or more expressions, separated by commas.
3290 Each expression is assembled into the next byte.
3293 @section @code{.comm @var{symbol} , @var{length} }
3295 @cindex @code{comm} directive
3296 @cindex symbol, common
3297 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
3298 common symbol in one object file may be merged with a defined or common symbol
3299 of the same name in another object file. If @code{@value{LD}} does not see a
3300 definition for the symbol--just one or more common symbols--then it will
3301 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
3302 absolute expression. If @code{@value{LD}} sees multiple common symbols with
3303 the same name, and they do not all have the same size, it will allocate space
3304 using the largest size.
3307 When using ELF, the @code{.comm} directive takes an optional third argument.
3308 This is the desired alignment of the symbol, specified as a byte boundary (for
3309 example, an alignment of 16 means that the least significant 4 bits of the
3310 address should be zero). The alignment must be an absolute expression, and it
3311 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
3312 for the common symbol, it will use the alignment when placing the symbol. If
3313 no alignment is specified, @code{@value{AS}} will set the alignment to the
3314 largest power of two less than or equal to the size of the symbol, up to a
3319 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
3320 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
3324 @section @code{.data @var{subsection}}
3326 @cindex @code{data} directive
3327 @code{.data} tells @code{@value{AS}} to assemble the following statements onto the
3328 end of the data subsection numbered @var{subsection} (which is an
3329 absolute expression). If @var{subsection} is omitted, it defaults
3334 @section @code{.def @var{name}}
3336 @cindex @code{def} directive
3337 @cindex COFF symbols, debugging
3338 @cindex debugging COFF symbols
3339 Begin defining debugging information for a symbol @var{name}; the
3340 definition extends until the @code{.endef} directive is encountered.
3343 This directive is only observed when @code{@value{AS}} is configured for COFF
3344 format output; when producing @code{b.out}, @samp{.def} is recognized,
3351 @section @code{.desc @var{symbol}, @var{abs-expression}}
3353 @cindex @code{desc} directive
3354 @cindex COFF symbol descriptor
3355 @cindex symbol descriptor, COFF
3356 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
3357 to the low 16 bits of an absolute expression.
3360 The @samp{.desc} directive is not available when @code{@value{AS}} is
3361 configured for COFF output; it is only for @code{a.out} or @code{b.out}
3362 object format. For the sake of compatibility, @code{@value{AS}} accepts
3363 it, but produces no output, when configured for COFF.
3369 @section @code{.dim}
3371 @cindex @code{dim} directive
3372 @cindex COFF auxiliary symbol information
3373 @cindex auxiliary symbol information, COFF
3374 This directive is generated by compilers to include auxiliary debugging
3375 information in the symbol table. It is only permitted inside
3376 @code{.def}/@code{.endef} pairs.
3379 @samp{.dim} is only meaningful when generating COFF format output; when
3380 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
3386 @section @code{.double @var{flonums}}
3388 @cindex @code{double} directive
3389 @cindex floating point numbers (double)
3390 @code{.double} expects zero or more flonums, separated by commas. It
3391 assembles floating point numbers.
3393 The exact kind of floating point numbers emitted depends on how
3394 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
3398 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
3399 in @sc{ieee} format.
3404 @section @code{.eject}
3406 @cindex @code{eject} directive
3407 @cindex new page, in listings
3408 @cindex page, in listings
3409 @cindex listing control: new page
3410 Force a page break at this point, when generating assembly listings.
3413 @section @code{.else}
3415 @cindex @code{else} directive
3416 @code{.else} is part of the @code{@value{AS}} support for conditional
3417 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
3418 of code to be assembled if the condition for the preceding @code{.if}
3422 @node End, Endef, Else, Pseudo Ops
3423 @section @code{.end}
3425 @cindex @code{end} directive
3426 This doesn't do anything---but isn't an s_ignore, so I suspect it's
3427 meant to do something eventually (which is why it isn't documented here
3428 as "for compatibility with blah").
3433 @section @code{.endef}
3435 @cindex @code{endef} directive
3436 This directive flags the end of a symbol definition begun with
3440 @samp{.endef} is only meaningful when generating COFF format output; if
3441 @code{@value{AS}} is configured to generate @code{b.out}, it accepts this
3442 directive but ignores it.
3447 @section @code{.endif}
3449 @cindex @code{endif} directive
3450 @code{.endif} is part of the @code{@value{AS}} support for conditional assembly;
3451 it marks the end of a block of code that is only assembled
3452 conditionally. @xref{If,,@code{.if}}.
3455 @section @code{.equ @var{symbol}, @var{expression}}
3457 @cindex @code{equ} directive
3458 @cindex assigning values to symbols
3459 @cindex symbols, assigning values to
3460 This directive sets the value of @var{symbol} to @var{expression}.
3461 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
3464 The syntax for @code{equ} on the HPPA is
3465 @samp{@var{symbol} .equ @var{expression}}.
3469 @section @code{.equiv @var{symbol}, @var{expression}}
3470 @cindex @code{equiv} directive
3471 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
3472 the assembler will signal an error if @var{symbol} is already defined.
3474 Except for the contents of the error message, this is roughly equivalent to
3483 @section @code{.err}
3484 @cindex @code{err} directive
3485 If @code{@value{AS}} assembles a @code{.err} directive, it will print an error
3486 message and, unless the @code{-Z} option was used, it will not generate an
3487 object file. This can be used to signal error an conditionally compiled code.
3490 @section @code{.extern}
3492 @cindex @code{extern} directive
3493 @code{.extern} is accepted in the source program---for compatibility
3494 with other assemblers---but it is ignored. @code{@value{AS}} treats
3495 all undefined symbols as external.
3497 @ifclear no-file-dir
3499 @section @code{.file @var{string}}
3501 @cindex @code{file} directive
3502 @cindex logical file name
3503 @cindex file name, logical
3504 @code{.file} (which may also be spelled @samp{.app-file}) tells
3505 @code{@value{AS}} that we are about to start a new logical file.
3506 @var{string} is the new file name. In general, the filename is
3507 recognized whether or not it is surrounded by quotes @samp{"}; but if
3508 you wish to specify an empty file name, you must give the
3509 quotes--@code{""}. This statement may go away in future: it is only
3510 recognized to be compatible with old @code{@value{AS}} programs.
3512 In some configurations of @code{@value{AS}}, @code{.file} has already been
3513 removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}.
3518 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
3520 @cindex @code{fill} directive
3521 @cindex writing patterns in memory
3522 @cindex patterns, writing in memory
3523 @var{result}, @var{size} and @var{value} are absolute expressions.
3524 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
3525 may be zero or more. @var{Size} may be zero or more, but if it is
3526 more than 8, then it is deemed to have the value 8, compatible with
3527 other people's assemblers. The contents of each @var{repeat} bytes
3528 is taken from an 8-byte number. The highest order 4 bytes are
3529 zero. The lowest order 4 bytes are @var{value} rendered in the
3530 byte-order of an integer on the computer @code{@value{AS}} is assembling for.
3531 Each @var{size} bytes in a repetition is taken from the lowest order
3532 @var{size} bytes of this number. Again, this bizarre behavior is
3533 compatible with other people's assemblers.
3535 @var{size} and @var{value} are optional.
3536 If the second comma and @var{value} are absent, @var{value} is
3537 assumed zero. If the first comma and following tokens are absent,
3538 @var{size} is assumed to be 1.
3541 @section @code{.float @var{flonums}}
3543 @cindex floating point numbers (single)
3544 @cindex @code{float} directive
3545 This directive assembles zero or more flonums, separated by commas. It
3546 has the same effect as @code{.single}.
3548 The exact kind of floating point numbers emitted depends on how
3549 @code{@value{AS}} is configured.
3550 @xref{Machine Dependencies}.
3554 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
3555 in @sc{ieee} format.
3560 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3562 @cindex @code{global} directive
3563 @cindex symbol, making visible to linker
3564 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
3565 @var{symbol} in your partial program, its value is made available to
3566 other partial programs that are linked with it. Otherwise,
3567 @var{symbol} takes its attributes from a symbol of the same name
3568 from another file linked into the same program.
3570 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
3571 compatibility with other assemblers.
3574 On the HPPA, @code{.global} is not always enough to make it accessible to other
3575 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
3576 @xref{HPPA Directives,, HPPA Assembler Directives}.
3580 @section @code{.hword @var{expressions}}
3582 @cindex @code{hword} directive
3583 @cindex integers, 16-bit
3584 @cindex numbers, 16-bit
3585 @cindex sixteen bit integers
3586 This expects zero or more @var{expressions}, and emits
3587 a 16 bit number for each.
3590 This directive is a synonym for @samp{.short}; depending on the target
3591 architecture, it may also be a synonym for @samp{.word}.
3595 This directive is a synonym for @samp{.short}.
3598 This directive is a synonym for both @samp{.short} and @samp{.word}.
3603 @section @code{.ident}
3605 @cindex @code{ident} directive
3606 This directive is used by some assemblers to place tags in object files.
3607 @code{@value{AS}} simply accepts the directive for source-file
3608 compatibility with such assemblers, but does not actually emit anything
3612 @section @code{.if @var{absolute expression}}
3614 @cindex conditional assembly
3615 @cindex @code{if} directive
3616 @code{.if} marks the beginning of a section of code which is only
3617 considered part of the source program being assembled if the argument
3618 (which must be an @var{absolute expression}) is non-zero. The end of
3619 the conditional section of code must be marked by @code{.endif}
3620 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
3621 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
3623 The following variants of @code{.if} are also supported:
3625 @cindex @code{ifdef} directive
3626 @item .ifdef @var{symbol}
3627 Assembles the following section of code if the specified @var{symbol}
3631 @cindex @code{ifeqs} directive
3633 Not yet implemented.
3636 @cindex @code{ifndef} directive
3637 @cindex @code{ifnotdef} directive
3638 @item .ifndef @var{symbol}
3639 @itemx .ifnotdef @var{symbol}
3640 Assembles the following section of code if the specified @var{symbol}
3641 has not been defined. Both spelling variants are equivalent.
3645 Not yet implemented.
3650 @section @code{.include "@var{file}"}
3652 @cindex @code{include} directive
3653 @cindex supporting files, including
3654 @cindex files, including
3655 This directive provides a way to include supporting files at specified
3656 points in your source program. The code from @var{file} is assembled as
3657 if it followed the point of the @code{.include}; when the end of the
3658 included file is reached, assembly of the original file continues. You
3659 can control the search paths used with the @samp{-I} command-line option
3660 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
3664 @section @code{.int @var{expressions}}
3666 @cindex @code{int} directive
3667 @cindex integers, 32-bit
3668 Expect zero or more @var{expressions}, of any section, separated by commas.
3669 For each expression, emit a number that, at run time, is the value of that
3670 expression. The byte order and bit size of the number depends on what kind
3671 of target the assembly is for.
3675 On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit
3676 integers. On the H8/300H and the Hitachi SH, however, @code{.int} emits
3682 @section @code{.irp @var{symbol},@var{values}}@dots{}
3684 @cindex @code{irp} directive
3685 Evaluate a sequence of statements assigning different values to @var{symbol}.
3686 The sequence of statements starts at the @code{.irp} directive, and is
3687 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
3688 set to @var{value}, and the sequence of statements is assembled. If no
3689 @var{value} is listed, the sequence of statements is assembled once, with
3690 @var{symbol} set to the null string. To refer to @var{symbol} within the
3691 sequence of statements, use @var{\symbol}.
3693 For example, assembling
3701 is equivalent to assembling
3710 @section @code{.irpc @var{symbol},@var{values}}@dots{}
3712 @cindex @code{irpc} directive
3713 Evaluate a sequence of statements assigning different values to @var{symbol}.
3714 The sequence of statements starts at the @code{.irpc} directive, and is
3715 terminated by an @code{.endr} directive. For each character in @var{value},
3716 @var{symbol} is set to the character, and the sequence of statements is
3717 assembled. If no @var{value} is listed, the sequence of statements is
3718 assembled once, with @var{symbol} set to the null string. To refer to
3719 @var{symbol} within the sequence of statements, use @var{\symbol}.
3721 For example, assembling
3729 is equivalent to assembling
3738 @section @code{.lcomm @var{symbol} , @var{length}}
3740 @cindex @code{lcomm} directive
3741 @cindex local common symbols
3742 @cindex symbols, local common
3743 Reserve @var{length} (an absolute expression) bytes for a local common
3744 denoted by @var{symbol}. The section and value of @var{symbol} are
3745 those of the new local common. The addresses are allocated in the bss
3746 section, so that at run-time the bytes start off zeroed. @var{Symbol}
3747 is not declared global (@pxref{Global,,@code{.global}}), so is normally
3748 not visible to @code{@value{LD}}.
3751 Some targets permit a third argument to be used with @code{.lcomm}. This
3752 argument specifies the desired alignment of the symbol in the bss section.
3756 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
3757 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
3761 @section @code{.lflags}
3763 @cindex @code{lflags} directive (ignored)
3764 @code{@value{AS}} accepts this directive, for compatibility with other
3765 assemblers, but ignores it.
3767 @ifclear no-line-dir
3769 @section @code{.line @var{line-number}}
3771 @cindex @code{line} directive
3775 @section @code{.ln @var{line-number}}
3777 @cindex @code{ln} directive
3779 @cindex logical line number
3781 Change the logical line number. @var{line-number} must be an absolute
3782 expression. The next line has that logical line number. Therefore any other
3783 statements on the current line (after a statement separator character) are
3784 reported as on logical line number @var{line-number} @minus{} 1. One day
3785 @code{@value{AS}} will no longer support this directive: it is recognized only
3786 for compatibility with existing assembler programs.
3790 @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is
3791 not available; use the synonym @code{.ln} in that context.
3796 @ifclear no-line-dir
3797 Even though this is a directive associated with the @code{a.out} or
3798 @code{b.out} object-code formats, @code{@value{AS}} still recognizes it
3799 when producing COFF output, and treats @samp{.line} as though it
3800 were the COFF @samp{.ln} @emph{if} it is found outside a
3801 @code{.def}/@code{.endef} pair.
3803 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
3804 used by compilers to generate auxiliary symbol information for
3809 @section @code{.linkonce [@var{type}]}
3811 @cindex @code{linkonce} directive
3812 @cindex common sections
3813 Mark the current section so that the linker only includes a single copy of it.
3814 This may be used to include the same section in several different object files,
3815 but ensure that the linker will only include it once in the final output file.
3816 The @code{.linkonce} pseudo-op must be used for each instance of the section.
3817 Duplicate sections are detected based on the section name, so it should be
3820 This directive is only supported by a few object file formats; as of this
3821 writing, the only object file format which supports it is the Portable
3822 Executable format used on Windows NT.
3824 The @var{type} argument is optional. If specified, it must be one of the
3825 following strings. For example:
3829 Not all types may be supported on all object file formats.
3833 Silently discard duplicate sections. This is the default.
3836 Warn if there are duplicate sections, but still keep only one copy.
3839 Warn if any of the duplicates have different sizes.
3842 Warn if any of the duplicates do not have exactly the same contents.
3846 @section @code{.ln @var{line-number}}
3848 @cindex @code{ln} directive
3849 @ifclear no-line-dir
3850 @samp{.ln} is a synonym for @samp{.line}.
3853 Tell @code{@value{AS}} to change the logical line number. @var{line-number}
3854 must be an absolute expression. The next line has that logical
3855 line number, so any other statements on the current line (after a
3856 statement separator character @code{;}) are reported as on logical
3857 line number @var{line-number} @minus{} 1.
3860 This directive is accepted, but ignored, when @code{@value{AS}} is
3861 configured for @code{b.out}; its effect is only associated with COFF
3867 @section @code{.mri @var{val}}
3869 @cindex @code{mri} directive
3870 @cindex MRI mode, temporarily
3871 If @var{val} is non-zero, this tells @code{@value{AS}} to enter MRI mode. If
3872 @var{val} is zero, this tells @code{@value{AS}} to exit MRI mode. This change
3873 affects code assembled until the next @code{.mri} directive, or until the end
3874 of the file. @xref{M, MRI mode, MRI mode}.
3877 @section @code{.list}
3879 @cindex @code{list} directive
3880 @cindex listing control, turning on
3881 Control (in conjunction with the @code{.nolist} directive) whether or
3882 not assembly listings are generated. These two directives maintain an
3883 internal counter (which is zero initially). @code{.list} increments the
3884 counter, and @code{.nolist} decrements it. Assembly listings are
3885 generated whenever the counter is greater than zero.
3887 By default, listings are disabled. When you enable them (with the
3888 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
3889 the initial value of the listing counter is one.
3892 @section @code{.long @var{expressions}}
3894 @cindex @code{long} directive
3895 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
3898 @c no one seems to know what this is for or whether this description is
3899 @c what it really ought to do
3901 @section @code{.lsym @var{symbol}, @var{expression}}
3903 @cindex @code{lsym} directive
3904 @cindex symbol, not referenced in assembly
3905 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
3906 the hash table, ensuring it cannot be referenced by name during the
3907 rest of the assembly. This sets the attributes of the symbol to be
3908 the same as the expression value:
3910 @var{other} = @var{descriptor} = 0
3911 @var{type} = @r{(section of @var{expression})}
3912 @var{value} = @var{expression}
3915 The new symbol is not flagged as external.
3919 @section @code{.macro}
3922 The commands @code{.macro} and @code{.endm} allow you to define macros that
3923 generate assembly output. For example, this definition specifies a macro
3924 @code{sum} that puts a sequence of numbers into memory:
3927 .macro sum from=0, to=5
3936 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
3948 @item .macro @var{macname}
3949 @itemx .macro @var{macname} @var{macargs} @dots{}
3950 @cindex @code{macro} directive
3951 Begin the definition of a macro called @var{macname}. If your macro
3952 definition requires arguments, specify their names after the macro name,
3953 separated by commas or spaces. You can supply a default value for any
3954 macro argument by following the name with @samp{=@var{deflt}}. For
3955 example, these are all valid @code{.macro} statements:
3959 Begin the definition of a macro called @code{comm}, which takes no
3962 @item .macro plus1 p, p1
3963 @itemx .macro plus1 p p1
3964 Either statement begins the definition of a macro called @code{plus1},
3965 which takes two arguments; within the macro definition, write
3966 @samp{\p} or @samp{\p1} to evaluate the arguments.
3968 @item .macro reserve_str p1=0 p2
3969 Begin the definition of a macro called @code{reserve_str}, with two
3970 arguments. The first argument has a default value, but not the second.
3971 After the definition is complete, you can call the macro either as
3972 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
3973 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
3974 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
3975 @samp{0}, and @samp{\p2} evaluating to @var{b}).
3978 When you call a macro, you can specify the argument values either by
3979 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
3980 @samp{sum to=17, from=9}.
3983 @cindex @code{endm} directive
3984 Mark the end of a macro definition.
3987 @cindex @code{exitm} directive
3988 Exit early from the current macro definition.
3990 @cindex number of macros executed
3991 @cindex macros, count executed
3993 @code{@value{AS}} maintains a counter of how many macros it has
3994 executed in this pseudo-variable; you can copy that number to your
3995 output with @samp{\@@}, but @emph{only within a macro definition}.
3998 @item LOCAL @var{name} [ , @dots{} ]
3999 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
4000 macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,,
4001 Alternate macro syntax}.
4003 Generate a string replacement for each of the @var{name} arguments, and
4004 replace any instances of @var{name} in each macro expansion. The
4005 replacement string is unique in the assembly, and different for each
4006 separate macro expansion. @code{LOCAL} allows you to write macros that
4007 define symbols, without fear of conflict between separate macro expansions.
4012 @section @code{.nolist}
4014 @cindex @code{nolist} directive
4015 @cindex listing control, turning off
4016 Control (in conjunction with the @code{.list} directive) whether or
4017 not assembly listings are generated. These two directives maintain an
4018 internal counter (which is zero initially). @code{.list} increments the
4019 counter, and @code{.nolist} decrements it. Assembly listings are
4020 generated whenever the counter is greater than zero.
4023 @section @code{.octa @var{bignums}}
4025 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
4026 @cindex @code{octa} directive
4027 @cindex integer, 16-byte
4028 @cindex sixteen byte integer
4029 This directive expects zero or more bignums, separated by commas. For each
4030 bignum, it emits a 16-byte integer.
4032 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
4033 hence @emph{octa}-word for 16 bytes.
4036 @section @code{.org @var{new-lc} , @var{fill}}
4038 @cindex @code{org} directive
4039 @cindex location counter, advancing
4040 @cindex advancing location counter
4041 @cindex current address, advancing
4042 Advance the location counter of the current section to
4043 @var{new-lc}. @var{new-lc} is either an absolute expression or an
4044 expression with the same section as the current subsection. That is,
4045 you can't use @code{.org} to cross sections: if @var{new-lc} has the
4046 wrong section, the @code{.org} directive is ignored. To be compatible
4047 with former assemblers, if the section of @var{new-lc} is absolute,
4048 @code{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
4049 is the same as the current subsection.
4051 @code{.org} may only increase the location counter, or leave it
4052 unchanged; you cannot use @code{.org} to move the location counter
4055 @c double negative used below "not undefined" because this is a specific
4056 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
4057 @c section. doc@cygnus.com 18feb91
4058 Because @code{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
4059 may not be undefined. If you really detest this restriction we eagerly await
4060 a chance to share your improved assembler.
4062 Beware that the origin is relative to the start of the section, not
4063 to the start of the subsection. This is compatible with other
4064 people's assemblers.
4066 When the location counter (of the current subsection) is advanced, the
4067 intervening bytes are filled with @var{fill} which should be an
4068 absolute expression. If the comma and @var{fill} are omitted,
4069 @var{fill} defaults to zero.
4072 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4074 @cindex padding the location counter given a power of two
4075 @cindex @code{p2align} directive
4076 Pad the location counter (in the current subsection) to a particular
4077 storage boundary. The first expression (which must be absolute) is the
4078 number of low-order zero bits the location counter must have after
4079 advancement. For example @samp{.p2align 3} advances the location
4080 counter until it a multiple of 8. If the location counter is already a
4081 multiple of 8, no change is needed.
4083 The second expression (also absolute) gives the fill value to be stored in the
4084 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4085 padding bytes are normally zero. However, on some systems, if the section is
4086 marked as containing code and the fill value is omitted, the space is filled
4087 with no-op instructions.
4089 The third expression is also absolute, and is also optional. If it is present,
4090 it is the maximum number of bytes that should be skipped by this alignment
4091 directive. If doing the alignment would require skipping more bytes than the
4092 specified maximum, then the alignment is not done at all. You can omit the
4093 fill value (the second argument) entirely by simply using two commas after the
4094 required alignment; this can be useful if you want the alignment to be filled
4095 with no-op instructions when appropriate.
4097 @cindex @code{p2alignw} directive
4098 @cindex @code{p2alignl} directive
4099 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
4100 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
4101 pattern as a two byte word value. The @code{.p2alignl} directives treats the
4102 fill pattern as a four byte longword value. For example, @code{.p2alignw
4103 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4104 filled in with the value 0x368d (the exact placement of the bytes depends upon
4105 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4109 @section @code{.psize @var{lines} , @var{columns}}
4111 @cindex @code{psize} directive
4112 @cindex listing control: paper size
4113 @cindex paper size, for listings
4114 Use this directive to declare the number of lines---and, optionally, the
4115 number of columns---to use for each page, when generating listings.
4117 If you do not use @code{.psize}, listings use a default line-count
4118 of 60. You may omit the comma and @var{columns} specification; the
4119 default width is 200 columns.
4121 @code{@value{AS}} generates formfeeds whenever the specified number of
4122 lines is exceeded (or whenever you explicitly request one, using
4125 If you specify @var{lines} as @code{0}, no formfeeds are generated save
4126 those explicitly specified with @code{.eject}.
4129 @section @code{.quad @var{bignums}}
4131 @cindex @code{quad} directive
4132 @code{.quad} expects zero or more bignums, separated by commas. For
4133 each bignum, it emits
4135 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
4136 warning message; and just takes the lowest order 8 bytes of the bignum.
4137 @cindex eight-byte integer
4138 @cindex integer, 8-byte
4140 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
4141 hence @emph{quad}-word for 8 bytes.
4144 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
4145 warning message; and just takes the lowest order 16 bytes of the bignum.
4146 @cindex sixteen-byte integer
4147 @cindex integer, 16-byte
4151 @section @code{.rept @var{count}}
4153 @cindex @code{rept} directive
4154 Repeat the sequence of lines between the @code{.rept} directive and the next
4155 @code{.endr} directive @var{count} times.
4157 For example, assembling
4165 is equivalent to assembling
4174 @section @code{.sbttl "@var{subheading}"}
4176 @cindex @code{sbttl} directive
4177 @cindex subtitles for listings
4178 @cindex listing control: subtitle
4179 Use @var{subheading} as the title (third line, immediately after the
4180 title line) when generating assembly listings.
4182 This directive affects subsequent pages, as well as the current page if
4183 it appears within ten lines of the top of a page.
4187 @section @code{.scl @var{class}}
4189 @cindex @code{scl} directive
4190 @cindex symbol storage class (COFF)
4191 @cindex COFF symbol storage class
4192 Set the storage-class value for a symbol. This directive may only be
4193 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
4194 whether a symbol is static or external, or it may record further
4195 symbolic debugging information.
4198 The @samp{.scl} directive is primarily associated with COFF output; when
4199 configured to generate @code{b.out} output format, @code{@value{AS}}
4200 accepts this directive but ignores it.
4205 @section @code{.section @var{name}}
4207 @cindex @code{section} directive
4208 @cindex named section
4209 Use the @code{.section} directive to assemble the following code into a section
4212 This directive is only supported for targets that actually support arbitrarily
4213 named sections; on @code{a.out} targets, for example, it is not accepted, even
4214 with a standard @code{a.out} section name.
4217 For COFF targets, the @code{.section} directive is used in one of the following
4220 .section @var{name}[, "@var{flags}"]
4221 .section @var{name}[, @var{subsegment}]
4224 If the optional argument is quoted, it is taken as flags to use for the
4225 section. Each flag is a single character. The following flags are recognized:
4228 bss section (uninitialized data)
4230 section is not loaded
4241 If no flags are specified, the default flags depend upon the section name. If
4242 the section name is not recognized, the default will be for the section to be
4243 loaded and writable.
4245 If the optional argument to the @code{.section} directive is not quoted, it is
4246 taken as a subsegment number (@pxref{Sub-Sections}).
4250 For ELF targets, the @code{.section} directive is used like this:
4252 .section @var{name}[, "@var{flags}"[, @@@var{type}]]
4254 The optional @var{flags} argument is a quoted string which may contain any
4255 combintion of the following characters:
4258 section is allocatable
4262 section is executable
4265 The optional @var{type} argument may contain one of the following constants:
4268 section contains data
4270 section does not contain data (i.e., section only occupies space)
4273 If no flags are specified, the default flags depend upon the section name. If
4274 the section name is not recognized, the default will be for the section to have
4275 none of the above flags: it will not be allocated in memory, nor writable, nor
4276 executable. The section will contain data.
4278 For ELF targets, the assembler supports another type of @code{.section}
4279 directive for compatibility with the Solaris assembler:
4281 .section "@var{name}"[, @var{flags}...]
4283 Note that the section name is quoted. There may be a sequence of comma
4287 section is allocatable
4291 section is executable
4296 @section @code{.set @var{symbol}, @var{expression}}
4298 @cindex @code{set} directive
4299 @cindex symbol value, setting
4300 Set the value of @var{symbol} to @var{expression}. This
4301 changes @var{symbol}'s value and type to conform to
4302 @var{expression}. If @var{symbol} was flagged as external, it remains
4303 flagged (@pxref{Symbol Attributes}).
4305 You may @code{.set} a symbol many times in the same assembly.
4307 If you @code{.set} a global symbol, the value stored in the object
4308 file is the last value stored into it.
4311 The syntax for @code{set} on the HPPA is
4312 @samp{@var{symbol} .set @var{expression}}.
4316 @section @code{.short @var{expressions}}
4318 @cindex @code{short} directive
4320 @code{.short} is normally the same as @samp{.word}.
4321 @xref{Word,,@code{.word}}.
4323 In some configurations, however, @code{.short} and @code{.word} generate
4324 numbers of different lengths; @pxref{Machine Dependencies}.
4328 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
4331 This expects zero or more @var{expressions}, and emits
4332 a 16 bit number for each.
4337 @section @code{.single @var{flonums}}
4339 @cindex @code{single} directive
4340 @cindex floating point numbers (single)
4341 This directive assembles zero or more flonums, separated by commas. It
4342 has the same effect as @code{.float}.
4344 The exact kind of floating point numbers emitted depends on how
4345 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
4349 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
4350 numbers in @sc{ieee} format.
4356 @section @code{.size}
4358 @cindex @code{size} directive
4359 This directive is generated by compilers to include auxiliary debugging
4360 information in the symbol table. It is only permitted inside
4361 @code{.def}/@code{.endef} pairs.
4364 @samp{.size} is only meaningful when generating COFF format output; when
4365 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
4371 @section @code{.sleb128 @var{expressions}}
4373 @cindex @code{sleb128} directive
4374 @var{sleb128} stands for ``signed little endian base 128.'' This is a
4375 compact, variable length representation of numbers used by the DWARF
4376 symbolic debugging format. @xref{Uleb128,@code{.uleb128}}.
4378 @ifclear no-space-dir
4380 @section @code{.skip @var{size} , @var{fill}}
4382 @cindex @code{skip} directive
4383 @cindex filling memory
4384 This directive emits @var{size} bytes, each of value @var{fill}. Both
4385 @var{size} and @var{fill} are absolute expressions. If the comma and
4386 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
4390 @section @code{.space @var{size} , @var{fill}}
4392 @cindex @code{space} directive
4393 @cindex filling memory
4394 This directive emits @var{size} bytes, each of value @var{fill}. Both
4395 @var{size} and @var{fill} are absolute expressions. If the comma
4396 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
4401 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
4402 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
4403 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
4404 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
4413 @section @code{.space}
4414 @cindex @code{space} directive
4416 On the AMD 29K, this directive is ignored; it is accepted for
4417 compatibility with other AMD 29K assemblers.
4420 @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive
4421 @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}.
4427 @section @code{.stabd, .stabn, .stabs}
4429 @cindex symbolic debuggers, information for
4430 @cindex @code{stab@var{x}} directives
4431 There are three directives that begin @samp{.stab}.
4432 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
4433 The symbols are not entered in the @code{@value{AS}} hash table: they
4434 cannot be referenced elsewhere in the source file.
4435 Up to five fields are required:
4439 This is the symbol's name. It may contain any character except
4440 @samp{\000}, so is more general than ordinary symbol names. Some
4441 debuggers used to code arbitrarily complex structures into symbol names
4445 An absolute expression. The symbol's type is set to the low 8 bits of
4446 this expression. Any bit pattern is permitted, but @code{@value{LD}}
4447 and debuggers choke on silly bit patterns.
4450 An absolute expression. The symbol's ``other'' attribute is set to the
4451 low 8 bits of this expression.
4454 An absolute expression. The symbol's descriptor is set to the low 16
4455 bits of this expression.
4458 An absolute expression which becomes the symbol's value.
4461 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
4462 or @code{.stabs} statement, the symbol has probably already been created;
4463 you get a half-formed symbol in your object file. This is
4464 compatible with earlier assemblers!
4467 @cindex @code{stabd} directive
4468 @item .stabd @var{type} , @var{other} , @var{desc}
4470 The ``name'' of the symbol generated is not even an empty string.
4471 It is a null pointer, for compatibility. Older assemblers used a
4472 null pointer so they didn't waste space in object files with empty
4475 The symbol's value is set to the location counter,
4476 relocatably. When your program is linked, the value of this symbol
4477 is the address of the location counter when the @code{.stabd} was
4480 @cindex @code{stabn} directive
4481 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
4482 The name of the symbol is set to the empty string @code{""}.
4484 @cindex @code{stabs} directive
4485 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
4486 All five fields are specified.
4492 @section @code{.string} "@var{str}"
4494 @cindex string, copying to object file
4495 @cindex @code{string} directive
4497 Copy the characters in @var{str} to the object file. You may specify more than
4498 one string to copy, separated by commas. Unless otherwise specified for a
4499 particular machine, the assembler marks the end of each string with a 0 byte.
4500 You can use any of the escape sequences described in @ref{Strings,,Strings}.
4504 @section @code{.symver}
4505 @cindex @code{symver} directive
4506 @cindex symbol versioning
4507 @cindex versions of symbols
4508 Use the @code{.symver} directive to bind symbols to specific version nodes
4509 within a source file. This is only supported on ELF platforms, and is
4510 typically used when assembling files to be linked into a shared library.
4511 There are cases where it may make sense to use this in objects to be bound
4512 into an application itself so as to override a versioned symbol from a
4515 For ELF targets, the @code{.symver} directive is used like this:
4517 .symver @var{name}, @var{name2@@nodename}
4519 In this case, the symbol @var{name} must exist and be defined within the file
4520 being assembled. The @code{.versym} directive effectively creates a symbol
4521 alias with the name @var{name2@@nodename}, and in fact the main reason that we
4522 just don't try and create a regular alias is that the @var{@@} character isn't
4523 permitted in symbol names. The @var{name2} part of the name is the actual name
4524 of the symbol by which it will be externally referenced. The name @var{name}
4525 itself is merely a name of convenience that is used so that it is possible to
4526 have definitions for multiple versions of a function within a single source
4527 file, and so that the compiler can unambiguously know which version of a
4528 function is being mentioned. The @var{nodename} portion of the alias should be
4529 the name of a node specified in the version script supplied to the linker when
4530 building a shared library. If you are attempting to override a versioned
4531 symbol from a shared library, then @var{nodename} should correspond to the
4532 nodename of the symbol you are trying to override.
4537 @section @code{.tag @var{structname}}
4539 @cindex COFF structure debugging
4540 @cindex structure debugging, COFF
4541 @cindex @code{tag} directive
4542 This directive is generated by compilers to include auxiliary debugging
4543 information in the symbol table. It is only permitted inside
4544 @code{.def}/@code{.endef} pairs. Tags are used to link structure
4545 definitions in the symbol table with instances of those structures.
4548 @samp{.tag} is only used when generating COFF format output; when
4549 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
4555 @section @code{.text @var{subsection}}
4557 @cindex @code{text} directive
4558 Tells @code{@value{AS}} to assemble the following statements onto the end of
4559 the text subsection numbered @var{subsection}, which is an absolute
4560 expression. If @var{subsection} is omitted, subsection number zero
4564 @section @code{.title "@var{heading}"}
4566 @cindex @code{title} directive
4567 @cindex listing control: title line
4568 Use @var{heading} as the title (second line, immediately after the
4569 source file name and pagenumber) when generating assembly listings.
4571 This directive affects subsequent pages, as well as the current page if
4572 it appears within ten lines of the top of a page.
4576 @section @code{.type @var{int}}
4578 @cindex COFF symbol type
4579 @cindex symbol type, COFF
4580 @cindex @code{type} directive
4581 This directive, permitted only within @code{.def}/@code{.endef} pairs,
4582 records the integer @var{int} as the type attribute of a symbol table entry.
4585 @samp{.type} is associated only with COFF format output; when
4586 @code{@value{AS}} is configured for @code{b.out} output, it accepts this
4587 directive but ignores it.
4593 @section @code{.val @var{addr}}
4595 @cindex @code{val} directive
4596 @cindex COFF value attribute
4597 @cindex value attribute, COFF
4598 This directive, permitted only within @code{.def}/@code{.endef} pairs,
4599 records the address @var{addr} as the value attribute of a symbol table
4603 @samp{.val} is used only for COFF output; when @code{@value{AS}} is
4604 configured for @code{b.out}, it accepts this directive but ignores it.
4609 @section @code{.uleb128 @var{expressions}}
4611 @cindex @code{uleb128} directive
4612 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
4613 compact, variable length representation of numbers used by the DWARF
4614 symbolic debugging format. @xref{Sleb128,@code{.sleb128}}.
4617 @section @code{.word @var{expressions}}
4619 @cindex @code{word} directive
4620 This directive expects zero or more @var{expressions}, of any section,
4621 separated by commas.
4624 For each expression, @code{@value{AS}} emits a 32-bit number.
4627 For each expression, @code{@value{AS}} emits a 16-bit number.
4632 The size of the number emitted, and its byte order,
4633 depend on what target computer the assembly is for.
4636 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
4637 @c happen---32-bit addressability, period; no long/short jumps.
4638 @ifset DIFF-TBL-KLUGE
4639 @cindex difference tables altered
4640 @cindex altered difference tables
4642 @emph{Warning: Special Treatment to support Compilers}
4646 Machines with a 32-bit address space, but that do less than 32-bit
4647 addressing, require the following special treatment. If the machine of
4648 interest to you does 32-bit addressing (or doesn't require it;
4649 @pxref{Machine Dependencies}), you can ignore this issue.
4652 In order to assemble compiler output into something that works,
4653 @code{@value{AS}} occasionlly does strange things to @samp{.word} directives.
4654 Directives of the form @samp{.word sym1-sym2} are often emitted by
4655 compilers as part of jump tables. Therefore, when @code{@value{AS}} assembles a
4656 directive of the form @samp{.word sym1-sym2}, and the difference between
4657 @code{sym1} and @code{sym2} does not fit in 16 bits, @code{@value{AS}}
4658 creates a @dfn{secondary jump table}, immediately before the next label.
4659 This secondary jump table is preceded by a short-jump to the
4660 first byte after the secondary table. This short-jump prevents the flow
4661 of control from accidentally falling into the new table. Inside the
4662 table is a long-jump to @code{sym2}. The original @samp{.word}
4663 contains @code{sym1} minus the address of the long-jump to
4666 If there were several occurrences of @samp{.word sym1-sym2} before the
4667 secondary jump table, all of them are adjusted. If there was a
4668 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
4669 long-jump to @code{sym4} is included in the secondary jump table,
4670 and the @code{.word} directives are adjusted to contain @code{sym3}
4671 minus the address of the long-jump to @code{sym4}; and so on, for as many
4672 entries in the original jump table as necessary.
4675 @emph{This feature may be disabled by compiling @code{@value{AS}} with the
4676 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
4677 assembly language programmers.
4680 @c end DIFF-TBL-KLUGE
4683 @section Deprecated Directives
4685 @cindex deprecated directives
4686 @cindex obsolescent directives
4687 One day these directives won't work.
4688 They are included for compatibility with older assemblers.
4696 @node Machine Dependencies
4697 @chapter Machine Dependent Features
4699 @cindex machine dependencies
4700 The machine instruction sets are (almost by definition) different on
4701 each machine where @code{@value{AS}} runs. Floating point representations
4702 vary as well, and @code{@value{AS}} often supports a few additional
4703 directives or command-line options for compatibility with other
4704 assemblers on a particular platform. Finally, some versions of
4705 @code{@value{AS}} support special pseudo-instructions for branch
4708 This chapter discusses most of these differences, though it does not
4709 include details on any machine's instruction set. For details on that
4710 subject, see the hardware manufacturer's manual.
4714 * AMD29K-Dependent:: AMD 29K Dependent Features
4717 * ARC-Dependent:: ARC Dependent Features
4720 * ARM-Dependent:: ARM Dependent Features
4723 * D10V-Dependent:: D10V Dependent Features
4725 @c start-sanitize-d30v
4727 * D30V-Dependent:: D30V Dependent Features
4729 @c end-sanitize-d30v
4731 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
4734 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
4737 * HPPA-Dependent:: HPPA Dependent Features
4740 * i386-Dependent:: Intel 80386 Dependent Features
4743 * i960-Dependent:: Intel 80960 Dependent Features
4745 @c start-sanitize-m32rx
4747 * M32R-Dependent:: M32R Dependent Features
4749 @c end-sanitize-m32rx
4751 * M68K-Dependent:: M680x0 Dependent Features
4754 * MIPS-Dependent:: MIPS Dependent Features
4757 * SH-Dependent:: Hitachi SH Dependent Features
4760 * Sparc-Dependent:: SPARC Dependent Features
4763 * V850-Dependent:: V850 Dependent Features
4766 * Z8000-Dependent:: Z8000 Dependent Features
4769 * Vax-Dependent:: VAX Dependent Features
4776 @c The following major nodes are *sections* in the GENERIC version, *chapters*
4777 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
4778 @c peculiarity: to preserve cross-references, there must be a node called
4779 @c "Machine Dependencies". Hence the conditional nodenames in each
4780 @c major node below. Node defaulting in makeinfo requires adjacency of
4781 @c node and sectioning commands; hence the repetition of @chapter BLAH
4782 @c in both conditional blocks.
4788 @chapter ARC Dependent Features
4791 @node Machine Dependencies
4792 @chapter ARC Dependent Features
4797 * ARC-Opts:: Options
4798 * ARC-Float:: Floating Point
4799 * ARC-Directives:: Sparc Machine Directives
4805 @cindex options for ARC
4807 @cindex architectures, ARC
4808 @cindex ARC architectures
4809 The ARC chip family includes several successive levels (or other
4810 variants) of chip, using the same core instruction set, but including
4811 a few additional instructions at each level.
4813 By default, @code{@value{AS}} assumes the core instruction set (ARC
4814 base). The @code{.cpu} pseudo-op is intended to be used to select
4818 @cindex @code{-mbig-endian} option (ARC)
4819 @cindex @code{-mlittle-endian} option (ARC)
4820 @cindex ARC big-endian output
4821 @cindex ARC little-endian output
4822 @cindex big-endian output, ARC
4823 @cindex little-endian output, ARC
4825 @itemx -mlittle-endian
4826 Any @sc{arc} configuration of @code{@value{AS}} can select big-endian or
4827 little-endian output at run time (unlike most other @sc{gnu} development
4828 tools, which must be configured for one or the other). Use
4829 @samp{-mbig-endian} to select big-endian output, and @samp{-mlittle-endian}
4834 @section Floating Point
4836 @cindex floating point, ARC (@sc{ieee})
4837 @cindex ARC floating point (@sc{ieee})
4838 The ARC cpu family currently does not have hardware floating point
4839 support. Software floating point support is provided by @code{GCC}
4840 and uses @sc{ieee} floating-point numbers.
4842 @node ARC-Directives
4843 @section ARC Machine Directives
4845 @cindex ARC machine directives
4846 @cindex machine directives, ARC
4847 The ARC version of @code{@value{AS}} supports the following additional
4852 @cindex @code{cpu} directive, SPARC
4853 This must be followed by the desired cpu.
4854 The ARC is intended to be customizable, @code{.cpu} is used to
4855 select the desired variant [though currently there are none].
4862 @include c-a29k.texi
4871 @node Machine Dependencies
4872 @chapter Machine Dependent Features
4874 The machine instruction sets are different on each Hitachi chip family,
4875 and there are also some syntax differences among the families. This
4876 chapter describes the specific @code{@value{AS}} features for each
4880 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
4881 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
4882 * SH-Dependent:: Hitachi SH Dependent Features
4889 @include c-d10v.texi
4892 @c start-sanitize-d30v
4894 @include c-d30v.texi
4896 @c end-sanitize-d30v
4899 @include c-h8300.texi
4903 @include c-h8500.texi
4907 @include c-hppa.texi
4911 @include c-i386.texi
4915 @include c-i960.texi
4918 @c start-sanitize-m32rx
4920 @include c-m32r.texi
4922 @c end-sanitize-m32rx
4925 @include c-m68k.texi
4929 @include c-mips.texi
4933 @include c-ns32k.texi
4941 @include c-sparc.texi
4953 @include c-v850.texi
4957 @c reverse effect of @down at top of generic Machine-Dep chapter
4961 @node Reporting Bugs
4962 @chapter Reporting Bugs
4963 @cindex bugs in assembler
4964 @cindex reporting bugs in assembler
4966 Your bug reports play an essential role in making @code{@value{AS}} reliable.
4968 Reporting a bug may help you by bringing a solution to your problem, or it may
4969 not. But in any case the principal function of a bug report is to help the
4970 entire community by making the next version of @code{@value{AS}} work better.
4971 Bug reports are your contribution to the maintenance of @code{@value{AS}}.
4973 In order for a bug report to serve its purpose, you must include the
4974 information that enables us to fix the bug.
4977 * Bug Criteria:: Have you found a bug?
4978 * Bug Reporting:: How to report bugs
4982 @section Have you found a bug?
4983 @cindex bug criteria
4985 If you are not sure whether you have found a bug, here are some guidelines:
4988 @cindex fatal signal
4989 @cindex assembler crash
4990 @cindex crash of assembler
4992 If the assembler gets a fatal signal, for any input whatever, that is a
4993 @code{@value{AS}} bug. Reliable assemblers never crash.
4995 @cindex error on valid input
4997 If @code{@value{AS}} produces an error message for valid input, that is a bug.
4999 @cindex invalid input
5001 If @code{@value{AS}} does not produce an error message for invalid input, that
5002 is a bug. However, you should note that your idea of ``invalid input'' might
5003 be our idea of ``an extension'' or ``support for traditional practice''.
5006 If you are an experienced user of assemblers, your suggestions for improvement
5007 of @code{@value{AS}} are welcome in any case.
5011 @section How to report bugs
5013 @cindex assembler bugs, reporting
5015 A number of companies and individuals offer support for @sc{gnu} products. If
5016 you obtained @code{@value{AS}} from a support organization, we recommend you
5017 contact that organization first.
5019 You can find contact information for many support companies and
5020 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
5023 In any event, we also recommend that you send bug reports for @code{@value{AS}}
5024 to @samp{bug-gnu-utils@@prep.ai.mit.edu}.
5026 The fundamental principle of reporting bugs usefully is this:
5027 @strong{report all the facts}. If you are not sure whether to state a
5028 fact or leave it out, state it!
5030 Often people omit facts because they think they know what causes the problem
5031 and assume that some details do not matter. Thus, you might assume that the
5032 name of a symbol you use in an example does not matter. Well, probably it does
5033 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
5034 happens to fetch from the location where that name is stored in memory;
5035 perhaps, if the name were different, the contents of that location would fool
5036 the assembler into doing the right thing despite the bug. Play it safe and
5037 give a specific, complete example. That is the easiest thing for you to do,
5038 and the most helpful.
5040 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
5041 it is new to us. Therefore, always write your bug reports on the assumption
5042 that the bug has not been reported previously.
5044 Sometimes people give a few sketchy facts and ask, ``Does this ring a
5045 bell?'' Those bug reports are useless, and we urge everyone to
5046 @emph{refuse to respond to them} except to chide the sender to report
5049 To enable us to fix the bug, you should include all these things:
5053 The version of @code{@value{AS}}. @code{@value{AS}} announces it if you start
5054 it with the @samp{--version} argument.
5056 Without this, we will not know whether there is any point in looking for
5057 the bug in the current version of @code{@value{AS}}.
5060 Any patches you may have applied to the @code{@value{AS}} source.
5063 The type of machine you are using, and the operating system name and
5067 What compiler (and its version) was used to compile @code{@value{AS}}---e.g.
5071 The command arguments you gave the assembler to assemble your example and
5072 observe the bug. To guarantee you will not omit something important, list them
5073 all. A copy of the Makefile (or the output from make) is sufficient.
5075 If we were to try to guess the arguments, we would probably guess wrong
5076 and then we might not encounter the bug.
5079 A complete input file that will reproduce the bug. If the bug is observed when
5080 the assembler is invoked via a compiler, send the assembler source, not the
5081 high level language source. Most compilers will produce the assembler source
5082 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
5083 the options @samp{-v --save-temps}; this will save the assembler source in a
5084 file with an extension of @file{.s}, and also show you exactly how
5085 @code{@value{AS}} is being run.
5088 A description of what behavior you observe that you believe is
5089 incorrect. For example, ``It gets a fatal signal.''
5091 Of course, if the bug is that @code{@value{AS}} gets a fatal signal, then we
5092 will certainly notice it. But if the bug is incorrect output, we might not
5093 notice unless it is glaringly wrong. You might as well not give us a chance to
5096 Even if the problem you experience is a fatal signal, you should still say so
5097 explicitly. Suppose something strange is going on, such as, your copy of
5098 @code{@value{AS}} is out of synch, or you have encountered a bug in the C
5099 library on your system. (This has happened!) Your copy might crash and ours
5100 would not. If you told us to expect a crash, then when ours fails to crash, we
5101 would know that the bug was not happening for us. If you had not told us to
5102 expect a crash, then we would not be able to draw any conclusion from our
5106 If you wish to suggest changes to the @code{@value{AS}} source, send us context
5107 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
5108 option. Always send diffs from the old file to the new file. If you even
5109 discuss something in the @code{@value{AS}} source, refer to it by context, not
5112 The line numbers in our development sources will not match those in your
5113 sources. Your line numbers would convey no useful information to us.
5116 Here are some things that are not necessary:
5120 A description of the envelope of the bug.
5122 Often people who encounter a bug spend a lot of time investigating
5123 which changes to the input file will make the bug go away and which
5124 changes will not affect it.
5126 This is often time consuming and not very useful, because the way we
5127 will find the bug is by running a single example under the debugger
5128 with breakpoints, not by pure deduction from a series of examples.
5129 We recommend that you save your time for something else.
5131 Of course, if you can find a simpler example to report @emph{instead}
5132 of the original one, that is a convenience for us. Errors in the
5133 output will be easier to spot, running under the debugger will take
5134 less time, and so on.
5136 However, simplification is not vital; if you do not want to do this,
5137 report the bug anyway and send us the entire test case you used.
5140 A patch for the bug.
5142 A patch for the bug does help us if it is a good one. But do not omit
5143 the necessary information, such as the test case, on the assumption that
5144 a patch is all we need. We might see problems with your patch and decide
5145 to fix the problem another way, or we might not understand it at all.
5147 Sometimes with a program as complicated as @code{@value{AS}} it is very hard to
5148 construct an example that will make the program follow a certain path through
5149 the code. If you do not send us the example, we will not be able to construct
5150 one, so we will not be able to verify that the bug is fixed.
5152 And if we cannot understand what bug you are trying to fix, or why your
5153 patch should be an improvement, we will not install it. A test case will
5154 help us to understand.
5157 A guess about what the bug is or what it depends on.
5159 Such guesses are usually wrong. Even we cannot guess right about such
5160 things without first using the debugger to find the facts.
5163 @node Acknowledgements
5164 @chapter Acknowledgements
5166 If you have contributed to @code{@value{AS}} and your name isn't listed here,
5167 it is not meant as a slight. We just don't know about it. Send mail to the
5168 maintainer, and we'll correct the situation. Currently
5170 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
5172 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
5175 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
5176 information and the 68k series machines, most of the preprocessing pass, and
5177 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
5179 K. Richard Pixley maintained GAS for a while, adding various enhancements and
5180 many bug fixes, including merging support for several processors, breaking GAS
5181 up to handle multiple object file format back ends (including heavy rewrite,
5182 testing, an integration of the coff and b.out back ends), adding configuration
5183 including heavy testing and verification of cross assemblers and file splits
5184 and renaming, converted GAS to strictly ANSI C including full prototypes, added
5185 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
5186 port (including considerable amounts of reverse engineering), a SPARC opcode
5187 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
5188 assertions and made them work, much other reorganization, cleanup, and lint.
5190 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
5191 in format-specific I/O modules.
5193 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
5194 has done much work with it since.
5196 The Intel 80386 machine description was written by Eliot Dresselhaus.
5198 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
5200 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
5201 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
5203 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
5204 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
5205 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
5206 support a.out format.
5208 Support for the Zilog Z8k and Hitachi H8/300 and H8/500 processors (tc-z8k,
5209 tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by
5210 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
5211 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
5214 John Gilmore built the AMD 29000 support, added @code{.include} support, and
5215 simplified the configuration of which versions accept which directives. He
5216 updated the 68k machine description so that Motorola's opcodes always produced
5217 fixed-size instructions (e.g. @code{jsr}), while synthetic instructions
5218 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
5219 cross-compilation support, and one bug in relaxation that took a week and
5220 required the proverbial one-bit fix.
5222 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
5223 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
5224 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
5225 PowerPC assembler, and made a few other minor patches.
5227 Steve Chamberlain made @code{@value{AS}} able to generate listings.
5229 Hewlett-Packard contributed support for the HP9000/300.
5231 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
5232 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
5233 formats). This work was supported by both the Center for Software Science at
5234 the University of Utah and Cygnus Support.
5236 Support for ELF format files has been worked on by Mark Eichin of Cygnus
5237 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
5238 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
5239 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
5240 and some initial 64-bit support).
5242 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
5243 support for openVMS/Alpha.
5245 Several engineers at Cygnus Support have also provided many small bug fixes and
5246 configuration enhancements.
5248 Many others have contributed large or small bugfixes and enhancements. If
5249 you have contributed significant work and are not mentioned on this list, and
5250 want to be, let us know. Some of the history has been lost; we are not
5251 intentionally leaving anyone out.