1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
4 @c Free Software Foundation, Inc.
5 @c UPDATE!! On future updates--
6 @c (1) check for new machine-dep cmdline options in
7 @c md_parse_option definitions in config/tc-*.c
8 @c (2) for platform-specific directives, examine md_pseudo_op
10 @c (3) for object-format specific directives, examine obj_pseudo_op
12 @c (4) portable directives in potable[] in read.c
16 @macro gcctabopt{body}
19 @c defaults, config file may override:
22 @include asconfig.texi
27 @c Configure for the generation of man pages
65 @c common OR combinations of conditions
91 @set abnormal-separator
95 @settitle Using @value{AS}
98 @settitle Using @value{AS} (@value{TARGET})
100 @setchapternewpage odd
105 @c WARE! Some of the machine-dependent sections contain tables of machine
106 @c instructions. Except in multi-column format, these tables look silly.
107 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
108 @c the multi-col format is faked within @example sections.
110 @c Again unfortunately, the natural size that fits on a page, for these tables,
111 @c is different depending on whether or not smallbook is turned on.
112 @c This matters, because of order: text flow switches columns at each page
115 @c The format faked in this source works reasonably well for smallbook,
116 @c not well for the default large-page format. This manual expects that if you
117 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
118 @c tables in question. You can turn on one without the other at your
119 @c discretion, of course.
122 @c the insn tables look just as silly in info files regardless of smallbook,
123 @c might as well show 'em anyways.
129 * As: (as). The GNU assembler.
130 * Gas: (as). The GNU assembler.
139 This file documents the GNU Assembler "@value{AS}".
141 @c man begin COPYRIGHT
142 Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002 Free Software Foundation, Inc.
144 Permission is granted to copy, distribute and/or modify this document
145 under the terms of the GNU Free Documentation License, Version 1.1
146 or any later version published by the Free Software Foundation;
147 with no Invariant Sections, with no Front-Cover Texts, and with no
148 Back-Cover Texts. A copy of the license is included in the
149 section entitled ``GNU Free Documentation License''.
154 Permission is granted to process this file through Tex and print the
155 results, provided the printed document carries copying permission
156 notice identical to this one except for the removal of this paragraph
157 (this paragraph not being relevant to the printed manual).
163 @title Using @value{AS}
164 @subtitle The @sc{gnu} Assembler
166 @subtitle for the @value{TARGET} family
169 @subtitle Version @value{VERSION}
172 The Free Software Foundation Inc. thanks The Nice Computer
173 Company of Australia for loaning Dean Elsner to write the
174 first (Vax) version of @command{as} for Project @sc{gnu}.
175 The proprietors, management and staff of TNCCA thank FSF for
176 distracting the boss while they got some work
179 @author Dean Elsner, Jay Fenlason & friends
183 \hfill {\it Using {\tt @value{AS}}}\par
184 \hfill Edited by Cygnus Support\par
186 %"boxit" macro for figures:
187 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
188 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
189 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
190 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
191 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
194 @vskip 0pt plus 1filll
195 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002 Free Software Foundation, Inc.
197 Permission is granted to copy, distribute and/or modify this document
198 under the terms of the GNU Free Documentation License, Version 1.1
199 or any later version published by the Free Software Foundation;
200 with no Invariant Sections, with no Front-Cover Texts, and with no
201 Back-Cover Texts. A copy of the license is included in the
202 section entitled ``GNU Free Documentation License''.
208 @top Using @value{AS}
210 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}} version
213 This version of the file describes @command{@value{AS}} configured to generate
214 code for @value{TARGET} architectures.
217 This document is distributed under the terms of the GNU Free
218 Documentation License. A copy of the license is included in the
219 section entitled ``GNU Free Documentation License''.
222 * Overview:: Overview
223 * Invoking:: Command-Line Options
225 * Sections:: Sections and Relocation
227 * Expressions:: Expressions
228 * Pseudo Ops:: Assembler Directives
229 * Machine Dependencies:: Machine Dependent Features
230 * Reporting Bugs:: Reporting Bugs
231 * Acknowledgements:: Who Did What
232 * GNU Free Documentation License:: GNU Free Documentation License
240 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
242 This version of the manual describes @command{@value{AS}} configured to generate
243 code for @value{TARGET} architectures.
247 @cindex invocation summary
248 @cindex option summary
249 @cindex summary of options
250 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
251 @pxref{Invoking,,Command-Line Options}.
253 @c man title AS the portable GNU assembler.
257 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
261 @c We don't use deffn and friends for the following because they seem
262 @c to be limited to one line for the header.
264 @c man begin SYNOPSIS
265 @value{AS} [@b{-a}[@b{cdhlns}][=@var{file}]] [@b{-D}] [@b{--defsym} @var{sym}=@var{val}]
266 [@b{-f}] [@b{--gstabs}] [@b{--gdwarf2}] [@b{--help}] [@b{-I} @var{dir}]
267 [@b{-J}] [@b{-K}] [@b{-L}]
268 [@b{--listing-lhs-width}=@var{NUM}] [@b{--listing-lhs-width2}=@var{NUM}]
269 [@b{--listing-rhs-width}=@var{NUM}] [@b{--listing-cont-lines}=@var{NUM}]
270 [@b{--keep-locals}] [@b{-o} @var{objfile}] [@b{-R}] [@b{--statistics}] [@b{-v}]
271 [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}] [@b{--fatal-warnings}]
272 [@b{-w}] [@b{-x}] [@b{-Z}] [@b{--target-help}] [@var{target-options}]
273 [@b{--}|@var{files} @dots{}]
275 @c Target dependent options are listed below. Keep the list sorted.
276 @c Add an empty line for separation.
278 @c am29k has no machine-dependent assembler options
282 @emph{Target Alpha options:}
284 [@b{-mdebug} | @b{-no-mdebug}]
285 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
286 [@b{-F}] [@b{-32addr}]
290 @emph{Target ARC options:}
296 @emph{Target ARM options:}
297 @c Don't document the deprecated options
298 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
299 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
300 [@b{-mfpu}=@var{floating-point-fromat}]
303 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
304 @b{-mapcs-reentrant}]
305 [@b{-mthumb-interwork}] [@b{-moabi}] [@b{-k}]
309 @emph{Target CRIS options:}
310 [@b{--underscore} | @b{--no-underscore}]
312 [@b{--emulation=criself} | @b{--emulation=crisaout}]
313 @c Deprecated -- deliberately not documented.
318 @emph{Target D10V options:}
323 @emph{Target D30V options:}
324 [@b{-O}|@b{-n}|@b{-N}]
327 @c Renesas family chips have no machine-dependent assembler options
330 @c HPPA has no machine-dependent assembler options (yet).
334 @emph{Target i386 options:}
335 [@b{--32}|@b{--64}] [@b{-n}]
339 @emph{Target i960 options:}
340 @c see md_parse_option in tc-i960.c
341 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
343 [@b{-b}] [@b{-no-relax}]
347 @emph{Target IA-64 options:}
348 [@b{-mconstant-gp}|@b{-mauto-pic}]
349 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
351 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
355 @emph{Target IP2K options:}
356 [@b{-mip2022}|@b{-mip2022ext}]
360 @emph{Target M32R options:}
361 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
366 @emph{Target M680X0 options:}
367 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
371 @emph{Target M68HC11 options:}
372 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}]
373 [@b{-mshort}|@b{-mlong}]
374 [@b{-mshort-double}|@b{-mlong-double}]
375 [@b{--force-long-branchs}] [@b{--short-branchs}]
376 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
377 [@b{--print-opcodes}] [@b{--generate-example}]
381 @emph{Target MCORE options:}
382 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
383 [@b{-mcpu=[210|340]}]
387 @emph{Target MIPS options:}
388 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-n}] [@b{-O}[@var{optimization level}]]
389 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
390 [@b{-non_shared}] [@b{-xgot}] [@b{--membedded-pic}]
391 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
392 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
393 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
395 [@b{-construct-floats}] [@b{-no-construct-floats}]
396 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
397 [@b{-mfix7000}] [@b{-mno-fix7000}]
398 [@b{-mips16}] [@b{-no-mips16}]
399 [@b{-mips3d}] [@b{-no-mips3d}]
400 [@b{-mdmx}] [@b{-no-mdmx}]
401 [@b{-mdebug}] [@b{-no-mdebug}]
402 [@b{-mpdr}] [@b{-mno-pdr}]
406 @emph{Target MMIX options:}
407 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
408 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
409 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
410 [@b{--linker-allocated-gregs}]
414 @emph{Target PDP11 options:}
415 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
416 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
417 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
421 @emph{Target picoJava options:}
426 @emph{Target PowerPC options:}
427 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|
428 @b{-m403}|@b{-m405}|@b{-mppc64}|@b{-m620}|@b{-mppc64bridge}|@b{-mbooke}|
429 @b{-mbooke32}|@b{-mbooke64}]
430 [@b{-mcom}|@b{-many}|@b{-maltivec}] [@b{-memb}]
431 [@b{-mregnames}|@b{-mno-regnames}]
432 [@b{-mrelocatable}|@b{-mrelocatable-lib}]
433 [@b{-mlittle}|@b{-mlittle-endian}|@b{-mbig}|@b{-mbig-endian}]
434 [@b{-msolaris}|@b{-mno-solaris}]
438 @emph{Target SPARC options:}
439 @c The order here is important. See c-sparc.texi.
440 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
441 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
442 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
447 @emph{Target TIC54X options:}
448 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
449 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
452 @c Z8000 has no machine-dependent assembler options
456 @emph{Target Xtensa options:}
457 [@b{--[no-]density}] [@b{--[no-]relax}] [@b{--[no-]generics}]
458 [@b{--[no-]text-section-literals}]
459 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
468 Turn on listings, in any of a variety of ways:
472 omit false conditionals
475 omit debugging directives
478 include high-level source
484 include macro expansions
487 omit forms processing
493 set the name of the listing file
496 You may combine these options; for example, use @samp{-aln} for assembly
497 listing without forms processing. The @samp{=file} option, if used, must be
498 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
501 Ignored. This option is accepted for script compatibility with calls to
504 @item --defsym @var{sym}=@var{value}
505 Define the symbol @var{sym} to be @var{value} before assembling the input file.
506 @var{value} must be an integer constant. As in C, a leading @samp{0x}
507 indicates a hexadecimal value, and a leading @samp{0} indicates an octal value.
510 ``fast''---skip whitespace and comment preprocessing (assume source is
514 Generate stabs debugging information for each assembler line. This
515 may help debugging assembler code, if the debugger can handle it.
518 Generate DWARF2 debugging information for each assembler line. This
519 may help debugging assembler code, if the debugger can handle it. Note---this
520 option is only supported by some targets, not all of them.
523 Print a summary of the command line options and exit.
526 Print a summary of all target specific options and exit.
529 Add directory @var{dir} to the search list for @code{.include} directives.
532 Don't warn about signed overflow.
535 @ifclear DIFF-TBL-KLUGE
536 This option is accepted but has no effect on the @value{TARGET} family.
538 @ifset DIFF-TBL-KLUGE
539 Issue warnings when difference tables altered for long displacements.
544 Keep (in the symbol table) local symbols. On traditional a.out systems
545 these start with @samp{L}, but different systems have different local
548 @item --listing-lhs-width=@var{number}
549 Set the maximum width, in words, of the output data column for an assembler
550 listing to @var{number}.
552 @item --listing-lhs-width2=@var{number}
553 Set the maximum width, in words, of the output data column for continuation
554 lines in an assembler listing to @var{number}.
556 @item --listing-rhs-width=@var{number}
557 Set the maximum width of an input source line, as displayed in a listing, to
560 @item --listing-cont-lines=@var{number}
561 Set the maximum number of lines printed in a listing for a single line of input
564 @item -o @var{objfile}
565 Name the object-file output from @command{@value{AS}} @var{objfile}.
568 Fold the data section into the text section.
571 Print the maximum space (in bytes) and total time (in seconds) used by
574 @item --strip-local-absolute
575 Remove local absolute symbols from the outgoing symbol table.
579 Print the @command{as} version.
582 Print the @command{as} version and exit.
586 Suppress warning messages.
588 @item --fatal-warnings
589 Treat warnings as errors.
592 Don't suppress warning messages or treat them as errors.
601 Generate an object file even after errors.
603 @item -- | @var{files} @dots{}
604 Standard input, or source files to assemble.
609 The following options are available when @value{AS} is configured for
614 This option selects the core processor variant.
616 Select either big-endian (-EB) or little-endian (-EL) output.
621 The following options are available when @value{AS} is configured for the ARM
625 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
626 Specify which ARM processor variant is the target.
627 @item -march=@var{architecture}[+@var{extension}@dots{}]
628 Specify which ARM architecture variant is used by the target.
629 @item -mfpu=@var{floating-point-format}
630 Select which Floating Point architecture is the target.
632 Enable Thumb only instruction decoding.
633 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant | -moabi
634 Select which procedure calling convention is in use.
636 Select either big-endian (-EB) or little-endian (-EL) output.
637 @item -mthumb-interwork
638 Specify that the code has been generated with interworking between Thumb and
641 Specify that PIC code has been generated.
646 See the info pages for documentation of the CRIS-specific options.
650 The following options are available when @value{AS} is configured for
653 @cindex D10V optimization
654 @cindex optimization, D10V
656 Optimize output by parallelizing instructions.
661 The following options are available when @value{AS} is configured for a D30V
664 @cindex D30V optimization
665 @cindex optimization, D30V
667 Optimize output by parallelizing instructions.
671 Warn when nops are generated.
673 @cindex D30V nops after 32-bit multiply
675 Warn when a nop after a 32-bit multiply instruction is generated.
680 The following options are available when @value{AS} is configured for the
681 Intel 80960 processor.
684 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
685 Specify which variant of the 960 architecture is the target.
688 Add code to collect statistics about branches taken.
691 Do not alter compare-and-branch instructions for long displacements;
698 The following options are available when @value{AS} is configured for the
704 Specifies that the extended IP2022 instructions are allowed.
707 Restores the default behaviour, which restricts the permitted instructions to
708 just the basic IP2022 ones.
714 The following options are available when @value{AS} is configured for the
715 Renesas M32R (formerly Mitsubishi M32R) series.
720 Specify which processor in the M32R family is the target. The default
721 is normally the M32R, but this option changes it to the M32RX.
723 @item --warn-explicit-parallel-conflicts or --Wp
724 Produce warning messages when questionable parallel constructs are
727 @item --no-warn-explicit-parallel-conflicts or --Wnp
728 Do not produce warning messages when questionable parallel constructs are
735 The following options are available when @value{AS} is configured for the
736 Motorola 68000 series.
741 Shorten references to undefined symbols, to one word instead of two.
743 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
744 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
745 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
746 Specify what processor in the 68000 family is the target. The default
747 is normally the 68020, but this can be changed at configuration time.
749 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
750 The target machine does (or does not) have a floating-point coprocessor.
751 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
752 the basic 68000 is not compatible with the 68881, a combination of the
753 two can be specified, since it's possible to do emulation of the
754 coprocessor instructions with the main processor.
756 @item -m68851 | -mno-68851
757 The target machine does (or does not) have a memory-management
758 unit coprocessor. The default is to assume an MMU for 68020 and up.
765 For details about the PDP-11 machine dependent features options,
766 see @ref{PDP-11-Options}.
769 @item -mpic | -mno-pic
770 Generate position-independent (or position-dependent) code. The
771 default is @option{-mpic}.
774 @itemx -mall-extensions
775 Enable all instruction set extensions. This is the default.
777 @item -mno-extensions
778 Disable all instruction set extensions.
780 @item -m@var{extension} | -mno-@var{extension}
781 Enable (or disable) a particular instruction set extension.
784 Enable the instruction set extensions supported by a particular CPU, and
785 disable all other extensions.
787 @item -m@var{machine}
788 Enable the instruction set extensions supported by a particular machine
789 model, and disable all other extensions.
795 The following options are available when @value{AS} is configured for
796 a picoJava processor.
800 @cindex PJ endianness
801 @cindex endianness, PJ
802 @cindex big endian output, PJ
804 Generate ``big endian'' format output.
806 @cindex little endian output, PJ
808 Generate ``little endian'' format output.
814 The following options are available when @value{AS} is configured for the
815 Motorola 68HC11 or 68HC12 series.
819 @item -m68hc11 | -m68hc12 | -m68hcs12
820 Specify what processor is the target. The default is
821 defined by the configuration option when building the assembler.
824 Specify to use the 16-bit integer ABI.
827 Specify to use the 32-bit integer ABI.
830 Specify to use the 32-bit double ABI.
833 Specify to use the 64-bit double ABI.
835 @item --force-long-branchs
836 Relative branches are turned into absolute ones. This concerns
837 conditional branches, unconditional branches and branches to a
840 @item -S | --short-branchs
841 Do not turn relative branchs into absolute ones
842 when the offset is out of range.
844 @item --strict-direct-mode
845 Do not turn the direct addressing mode into extended addressing mode
846 when the instruction does not support direct addressing mode.
848 @item --print-insn-syntax
849 Print the syntax of instruction in case of error.
851 @item --print-opcodes
852 print the list of instructions with syntax and then exit.
854 @item --generate-example
855 print an example of instruction for each possible instruction and then exit.
856 This option is only useful for testing @command{@value{AS}}.
862 The following options are available when @command{@value{AS}} is configured
863 for the SPARC architecture:
866 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
867 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
868 Explicitly select a variant of the SPARC architecture.
870 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
871 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
873 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
874 UltraSPARC extensions.
876 @item -xarch=v8plus | -xarch=v8plusa
877 For compatibility with the Solaris v9 assembler. These options are
878 equivalent to -Av8plus and -Av8plusa, respectively.
881 Warn when the assembler switches to another architecture.
886 The following options are available when @value{AS} is configured for the 'c54x
891 Enable extended addressing mode. All addresses and relocations will assume
892 extended addressing (usually 23 bits).
893 @item -mcpu=@var{CPU_VERSION}
894 Sets the CPU version being compiled for.
895 @item -merrors-to-file @var{FILENAME}
896 Redirect error output to a file, for broken systems which don't support such
897 behaviour in the shell.
902 The following options are available when @value{AS} is configured for
903 a @sc{mips} processor.
907 This option sets the largest size of an object that can be referenced
908 implicitly with the @code{gp} register. It is only accepted for targets that
909 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
911 @cindex MIPS endianness
912 @cindex endianness, MIPS
913 @cindex big endian output, MIPS
915 Generate ``big endian'' format output.
917 @cindex little endian output, MIPS
919 Generate ``little endian'' format output.
930 Generate code for a particular @sc{mips} Instruction Set Architecture level.
931 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
932 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
933 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
934 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, and @samp{-mips64}
935 correspond to generic
936 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, and
937 @samp{MIPS64} ISA processors,
940 @item -march=@var{CPU}
941 Generate code for a particular @sc{mips} cpu.
943 @item -mtune=@var{cpu}
944 Schedule and tune for a particular @sc{mips} cpu.
948 Cause nops to be inserted if the read of the destination register
949 of an mfhi or mflo instruction occurs in the following two instructions.
953 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
954 section instead of the standard ELF .stabs sections.
958 Control generation of @code{.pdr} sections.
962 The register sizes are normally inferred from the ISA and ABI, but these
963 flags force a certain group of registers to be treated as 32 bits wide at
964 all times. @samp{-mgp32} controls the size of general-purpose registers
965 and @samp{-mfp32} controls the size of floating-point registers.
969 Generate code for the MIPS 16 processor. This is equivalent to putting
970 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
971 turns off this option.
975 Generate code for the MIPS-3D Application Specific Extension.
976 This tells the assembler to accept MIPS-3D instructions.
977 @samp{-no-mips3d} turns off this option.
981 Generate code for the MDMX Application Specific Extension.
982 This tells the assembler to accept MDMX instructions.
983 @samp{-no-mdmx} turns off this option.
985 @item --construct-floats
986 @itemx --no-construct-floats
987 The @samp{--no-construct-floats} option disables the construction of
988 double width floating point constants by loading the two halves of the
989 value into the two single width floating point registers that make up
990 the double width register. By default @samp{--construct-floats} is
991 selected, allowing construction of these floating point constants.
994 @item --emulation=@var{name}
995 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
996 for some other target, in all respects, including output format (choosing
997 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
998 debugging information or store symbol table information, and default
999 endianness. The available configuration names are: @samp{mipsecoff},
1000 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1001 @samp{mipsbelf}. The first two do not alter the default endianness from that
1002 of the primary target for which the assembler was configured; the others change
1003 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1004 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1005 selection in any case.
1007 This option is currently supported only when the primary target
1008 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1009 Furthermore, the primary target or others specified with
1010 @samp{--enable-targets=@dots{}} at configuration time must include support for
1011 the other format, if both are to be available. For example, the Irix 5
1012 configuration includes support for both.
1014 Eventually, this option will support more configurations, with more
1015 fine-grained control over the assembler's behavior, and will be supported for
1019 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1026 Control how to deal with multiplication overflow and division by zero.
1027 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1028 (and only work for Instruction Set Architecture level 2 and higher);
1029 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1033 When this option is used, @command{@value{AS}} will issue a warning every
1034 time it generates a nop instruction from a macro.
1039 The following options are available when @value{AS} is configured for
1045 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1046 The command line option @samp{-nojsri2bsr} can be used to disable it.
1050 Enable or disable the silicon filter behaviour. By default this is disabled.
1051 The default can be overridden by the @samp{-sifilter} command line option.
1054 Alter jump instructions for long displacements.
1056 @item -mcpu=[210|340]
1057 Select the cpu type on the target hardware. This controls which instructions
1061 Assemble for a big endian target.
1064 Assemble for a little endian target.
1070 See the info pages for documentation of the MMIX-specific options.
1074 The following options are available when @value{AS} is configured for
1075 an Xtensa processor.
1078 @item --density | --no-density
1079 Enable or disable use of instructions from the Xtensa code density
1080 option. This is enabled by default when the Xtensa processor supports
1081 the code density option.
1083 @item --relax | --no-relax
1084 Enable or disable instruction relaxation. This is enabled by default.
1085 Note: In the current implementation, these options also control whether
1086 assembler optimizations are performed, making these options equivalent
1087 to @option{--generics} and @option{--no-generics}.
1089 @item --generics | --no-generics
1090 Enable or disable all assembler transformations of Xtensa instructions.
1091 The default is @option{--generics};
1092 @option{--no-generics} should be used only in the rare cases when the
1093 instructions must be exactly as specified in the assembly source.
1095 @item --text-section-literals | --no-text-section-literals
1096 With @option{--text-@-section-@-literals}, literal pools are interspersed
1097 in the text section. The default is
1098 @option{--no-@-text-@-section-@-literals}, which places literals in a
1099 separate section in the output file.
1101 @item --target-align | --no-target-align
1102 Enable or disable automatic alignment to reduce branch penalties at the
1103 expense of some code density. The default is @option{--target-@-align}.
1105 @item --longcalls | --no-longcalls
1106 Enable or disable transformation of call instructions to allow calls
1107 across a greater range of addresses. The default is
1108 @option{--no-@-longcalls}.
1115 * Manual:: Structure of this Manual
1116 * GNU Assembler:: The GNU Assembler
1117 * Object Formats:: Object File Formats
1118 * Command Line:: Command Line
1119 * Input Files:: Input Files
1120 * Object:: Output (Object) File
1121 * Errors:: Error and Warning Messages
1125 @section Structure of this Manual
1127 @cindex manual, structure and purpose
1128 This manual is intended to describe what you need to know to use
1129 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1130 notation for symbols, constants, and expressions; the directives that
1131 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1134 We also cover special features in the @value{TARGET}
1135 configuration of @command{@value{AS}}, including assembler directives.
1138 This manual also describes some of the machine-dependent features of
1139 various flavors of the assembler.
1142 @cindex machine instructions (not covered)
1143 On the other hand, this manual is @emph{not} intended as an introduction
1144 to programming in assembly language---let alone programming in general!
1145 In a similar vein, we make no attempt to introduce the machine
1146 architecture; we do @emph{not} describe the instruction set, standard
1147 mnemonics, registers or addressing modes that are standard to a
1148 particular architecture.
1150 You may want to consult the manufacturer's
1151 machine architecture manual for this information.
1155 For information on the H8/300 machine instruction set, see @cite{H8/300
1156 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1157 Programming Manual} (Renesas).
1160 For information on the H8/500 machine instruction set, see @cite{H8/500
1161 Series Programming Manual} (Renesas M21T001).
1164 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1165 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1166 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1167 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1170 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1174 @c I think this is premature---doc@cygnus.com, 17jan1991
1176 Throughout this manual, we assume that you are running @dfn{GNU},
1177 the portable operating system from the @dfn{Free Software
1178 Foundation, Inc.}. This restricts our attention to certain kinds of
1179 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1180 once this assumption is granted examples and definitions need less
1183 @command{@value{AS}} is part of a team of programs that turn a high-level
1184 human-readable series of instructions into a low-level
1185 computer-readable series of instructions. Different versions of
1186 @command{@value{AS}} are used for different kinds of computer.
1189 @c There used to be a section "Terminology" here, which defined
1190 @c "contents", "byte", "word", and "long". Defining "word" to any
1191 @c particular size is confusing when the .word directive may generate 16
1192 @c bits on one machine and 32 bits on another; in general, for the user
1193 @c version of this manual, none of these terms seem essential to define.
1194 @c They were used very little even in the former draft of the manual;
1195 @c this draft makes an effort to avoid them (except in names of
1199 @section The GNU Assembler
1201 @c man begin DESCRIPTION
1203 @sc{gnu} @command{as} is really a family of assemblers.
1205 This manual describes @command{@value{AS}}, a member of that family which is
1206 configured for the @value{TARGET} architectures.
1208 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1209 should find a fairly similar environment when you use it on another
1210 architecture. Each version has much in common with the others,
1211 including object file formats, most assembler directives (often called
1212 @dfn{pseudo-ops}) and assembler syntax.@refill
1214 @cindex purpose of @sc{gnu} assembler
1215 @command{@value{AS}} is primarily intended to assemble the output of the
1216 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1217 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1218 assemble correctly everything that other assemblers for the same
1219 machine would assemble.
1221 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1224 @c This remark should appear in generic version of manual; assumption
1225 @c here is that generic version sets M680x0.
1226 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1227 assembler for the same architecture; for example, we know of several
1228 incompatible versions of 680x0 assembly language syntax.
1233 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1234 program in one pass of the source file. This has a subtle impact on the
1235 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1237 @node Object Formats
1238 @section Object File Formats
1240 @cindex object file format
1241 The @sc{gnu} assembler can be configured to produce several alternative
1242 object file formats. For the most part, this does not affect how you
1243 write assembly language programs; but directives for debugging symbols
1244 are typically different in different file formats. @xref{Symbol
1245 Attributes,,Symbol Attributes}.
1248 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1249 @value{OBJ-NAME} format object files.
1251 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1253 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1254 @code{a.out} or COFF format object files.
1257 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1258 @code{b.out} or COFF format object files.
1261 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1262 SOM or ELF format object files.
1267 @section Command Line
1269 @cindex command line conventions
1271 After the program name @command{@value{AS}}, the command line may contain
1272 options and file names. Options may appear in any order, and may be
1273 before, after, or between file names. The order of file names is
1276 @cindex standard input, as input file
1278 @file{--} (two hyphens) by itself names the standard input file
1279 explicitly, as one of the files for @command{@value{AS}} to assemble.
1281 @cindex options, command line
1282 Except for @samp{--} any command line argument that begins with a
1283 hyphen (@samp{-}) is an option. Each option changes the behavior of
1284 @command{@value{AS}}. No option changes the way another option works. An
1285 option is a @samp{-} followed by one or more letters; the case of
1286 the letter is important. All options are optional.
1288 Some options expect exactly one file name to follow them. The file
1289 name may either immediately follow the option's letter (compatible
1290 with older assemblers) or it may be the next command argument (@sc{gnu}
1291 standard). These two command lines are equivalent:
1294 @value{AS} -o my-object-file.o mumble.s
1295 @value{AS} -omy-object-file.o mumble.s
1299 @section Input Files
1302 @cindex source program
1303 @cindex files, input
1304 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1305 describe the program input to one run of @command{@value{AS}}. The program may
1306 be in one or more files; how the source is partitioned into files
1307 doesn't change the meaning of the source.
1309 @c I added "con" prefix to "catenation" just to prove I can overcome my
1310 @c APL training... doc@cygnus.com
1311 The source program is a concatenation of the text in all the files, in the
1314 @c man begin DESCRIPTION
1315 Each time you run @command{@value{AS}} it assembles exactly one source
1316 program. The source program is made up of one or more files.
1317 (The standard input is also a file.)
1319 You give @command{@value{AS}} a command line that has zero or more input file
1320 names. The input files are read (from left file name to right). A
1321 command line argument (in any position) that has no special meaning
1322 is taken to be an input file name.
1324 If you give @command{@value{AS}} no file names it attempts to read one input file
1325 from the @command{@value{AS}} standard input, which is normally your terminal. You
1326 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1329 Use @samp{--} if you need to explicitly name the standard input file
1330 in your command line.
1332 If the source is empty, @command{@value{AS}} produces a small, empty object
1337 @subheading Filenames and Line-numbers
1339 @cindex input file linenumbers
1340 @cindex line numbers, in input files
1341 There are two ways of locating a line in the input file (or files) and
1342 either may be used in reporting error messages. One way refers to a line
1343 number in a physical file; the other refers to a line number in a
1344 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1346 @dfn{Physical files} are those files named in the command line given
1347 to @command{@value{AS}}.
1349 @dfn{Logical files} are simply names declared explicitly by assembler
1350 directives; they bear no relation to physical files. Logical file names help
1351 error messages reflect the original source file, when @command{@value{AS}} source
1352 is itself synthesized from other files. @command{@value{AS}} understands the
1353 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1354 @ref{File,,@code{.file}}.
1357 @section Output (Object) File
1363 Every time you run @command{@value{AS}} it produces an output file, which is
1364 your assembly language program translated into numbers. This file
1365 is the object file. Its default name is
1373 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1375 You can give it another name by using the @option{-o} option. Conventionally,
1376 object file names end with @file{.o}. The default name is used for historical
1377 reasons: older assemblers were capable of assembling self-contained programs
1378 directly into a runnable program. (For some formats, this isn't currently
1379 possible, but it can be done for the @code{a.out} format.)
1383 The object file is meant for input to the linker @code{@value{LD}}. It contains
1384 assembled program code, information to help @code{@value{LD}} integrate
1385 the assembled program into a runnable file, and (optionally) symbolic
1386 information for the debugger.
1388 @c link above to some info file(s) like the description of a.out.
1389 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1392 @section Error and Warning Messages
1394 @c man begin DESCRIPTION
1396 @cindex error messages
1397 @cindex warning messages
1398 @cindex messages from assembler
1399 @command{@value{AS}} may write warnings and error messages to the standard error
1400 file (usually your terminal). This should not happen when a compiler
1401 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1402 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1403 grave problem that stops the assembly.
1407 @cindex format of warning messages
1408 Warning messages have the format
1411 file_name:@b{NNN}:Warning Message Text
1415 @cindex line numbers, in warnings/errors
1416 (where @b{NNN} is a line number). If a logical file name has been given
1417 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1418 the current input file is used. If a logical line number was given
1420 (@pxref{Line,,@code{.line}})
1424 (@pxref{Line,,@code{.line}})
1427 (@pxref{Ln,,@code{.ln}})
1430 then it is used to calculate the number printed,
1431 otherwise the actual line in the current source file is printed. The
1432 message text is intended to be self explanatory (in the grand Unix
1435 @cindex format of error messages
1436 Error messages have the format
1438 file_name:@b{NNN}:FATAL:Error Message Text
1440 The file name and line number are derived as for warning
1441 messages. The actual message text may be rather less explanatory
1442 because many of them aren't supposed to happen.
1445 @chapter Command-Line Options
1447 @cindex options, all versions of assembler
1448 This chapter describes command-line options available in @emph{all}
1449 versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
1451 to the @value{TARGET} target.
1454 to particular machine architectures.
1457 @c man begin DESCRIPTION
1459 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1460 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1461 The assembler arguments must be separated from each other (and the @samp{-Wa})
1462 by commas. For example:
1465 gcc -c -g -O -Wa,-alh,-L file.c
1469 This passes two options to the assembler: @samp{-alh} (emit a listing to
1470 standard output with high-level and assembly source) and @samp{-L} (retain
1471 local symbols in the symbol table).
1473 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1474 command-line options are automatically passed to the assembler by the compiler.
1475 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1476 precisely what options it passes to each compilation pass, including the
1482 * a:: -a[cdhlns] enable listings
1483 * D:: -D for compatibility
1484 * f:: -f to work faster
1485 * I:: -I for .include search path
1486 @ifclear DIFF-TBL-KLUGE
1487 * K:: -K for compatibility
1489 @ifset DIFF-TBL-KLUGE
1490 * K:: -K for difference tables
1493 * L:: -L to retain local labels
1494 * listing:: --listing-XXX to configure listing output
1495 * M:: -M or --mri to assemble in MRI compatibility mode
1496 * MD:: --MD for dependency tracking
1497 * o:: -o to name the object file
1498 * R:: -R to join data and text sections
1499 * statistics:: --statistics to see statistics about assembly
1500 * traditional-format:: --traditional-format for compatible output
1501 * v:: -v to announce version
1502 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1503 * Z:: -Z to make object file even after errors
1507 @section Enable Listings: @option{-a[cdhlns]}
1516 @cindex listings, enabling
1517 @cindex assembly listings, enabling
1519 These options enable listing output from the assembler. By itself,
1520 @samp{-a} requests high-level, assembly, and symbols listing.
1521 You can use other letters to select specific options for the list:
1522 @samp{-ah} requests a high-level language listing,
1523 @samp{-al} requests an output-program assembly listing, and
1524 @samp{-as} requests a symbol table listing.
1525 High-level listings require that a compiler debugging option like
1526 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1529 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1530 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1531 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1532 omitted from the listing.
1534 Use the @samp{-ad} option to omit debugging directives from the
1537 Once you have specified one of these options, you can further control
1538 listing output and its appearance using the directives @code{.list},
1539 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1541 The @samp{-an} option turns off all forms processing.
1542 If you do not request listing output with one of the @samp{-a} options, the
1543 listing-control directives have no effect.
1545 The letters after @samp{-a} may be combined into one option,
1546 @emph{e.g.}, @samp{-aln}.
1548 Note if the assembler source is coming from the standard input (eg because it
1549 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1550 is being used) then the listing will not contain any comments or preprocessor
1551 directives. This is because the listing code buffers input source lines from
1552 stdin only after they have been preprocessed by the assembler. This reduces
1553 memory usage and makes the code more efficient.
1556 @section @option{-D}
1559 This option has no effect whatsoever, but it is accepted to make it more
1560 likely that scripts written for other assemblers also work with
1561 @command{@value{AS}}.
1564 @section Work Faster: @option{-f}
1567 @cindex trusted compiler
1568 @cindex faster processing (@option{-f})
1569 @samp{-f} should only be used when assembling programs written by a
1570 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1571 and comment preprocessing on
1572 the input file(s) before assembling them. @xref{Preprocessing,
1576 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1577 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1582 @section @code{.include} Search Path: @option{-I} @var{path}
1584 @kindex -I @var{path}
1585 @cindex paths for @code{.include}
1586 @cindex search path for @code{.include}
1587 @cindex @code{include} directive search path
1588 Use this option to add a @var{path} to the list of directories
1589 @command{@value{AS}} searches for files specified in @code{.include}
1590 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1591 many times as necessary to include a variety of paths. The current
1592 working directory is always searched first; after that, @command{@value{AS}}
1593 searches any @samp{-I} directories in the same order as they were
1594 specified (left to right) on the command line.
1597 @section Difference Tables: @option{-K}
1600 @ifclear DIFF-TBL-KLUGE
1601 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1602 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1603 where it can be used to warn when the assembler alters the machine code
1604 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1605 family does not have the addressing limitations that sometimes lead to this
1606 alteration on other platforms.
1609 @ifset DIFF-TBL-KLUGE
1610 @cindex difference tables, warning
1611 @cindex warning for altered difference tables
1612 @command{@value{AS}} sometimes alters the code emitted for directives of the form
1613 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
1614 You can use the @samp{-K} option if you want a warning issued when this
1619 @section Include Local Labels: @option{-L}
1622 @cindex local labels, retaining in output
1623 Labels beginning with @samp{L} (upper case only) are called @dfn{local
1624 labels}. @xref{Symbol Names}. Normally you do not see such labels when
1625 debugging, because they are intended for the use of programs (like
1626 compilers) that compose assembler programs, not for your notice.
1627 Normally both @command{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
1628 normally debug with them.
1630 This option tells @command{@value{AS}} to retain those @samp{L@dots{}} symbols
1631 in the object file. Usually if you do this you also tell the linker
1632 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
1634 By default, a local label is any label beginning with @samp{L}, but each
1635 target is allowed to redefine the local label prefix.
1637 On the HPPA local labels begin with @samp{L$}.
1641 @section Configuring listing output: @option{--listing}
1643 The listing feature of the assembler can be enabled via the command line switch
1644 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1645 hex dump of the corresponding locations in the output object file, and displays
1646 them as a listing file. The format of this listing can be controlled by pseudo
1647 ops inside the assembler source (@pxref{List} @pxref{Title} @pxref{Sbttl}
1648 @pxref{Psize} @pxref{Eject}) and also by the following switches:
1651 @item --listing-lhs-width=@samp{number}
1652 @kindex --listing-lhs-width
1653 @cindex Width of first line disassembly output
1654 Sets the maximum width, in words, of the first line of the hex byte dump. This
1655 dump appears on the left hand side of the listing output.
1657 @item --listing-lhs-width2=@samp{number}
1658 @kindex --listing-lhs-width2
1659 @cindex Width of continuation lines of disassembly output
1660 Sets the maximum width, in words, of any further lines of the hex byte dump for
1661 a given input source line. If this value is not specified, it defaults to being
1662 the same as the value specified for @samp{--listing-lhs-width}. If neither
1663 switch is used the default is to one.
1665 @item --listing-rhs-width=@samp{number}
1666 @kindex --listing-rhs-width
1667 @cindex Width of source line output
1668 Sets the maximum width, in characters, of the source line that is displayed
1669 alongside the hex dump. The default value for this parameter is 100. The
1670 source line is displayed on the right hand side of the listing output.
1672 @item --listing-cont-lines=@samp{number}
1673 @kindex --listing-cont-lines
1674 @cindex Maximum number of continuation lines
1675 Sets the maximum number of continuation lines of hex dump that will be
1676 displayed for a given single line of source input. The default value is 4.
1680 @section Assemble in MRI Compatibility Mode: @option{-M}
1683 @cindex MRI compatibility mode
1684 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1685 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1686 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1687 configured target) assembler from Microtec Research. The exact nature of the
1688 MRI syntax will not be documented here; see the MRI manuals for more
1689 information. Note in particular that the handling of macros and macro
1690 arguments is somewhat different. The purpose of this option is to permit
1691 assembling existing MRI assembler code using @command{@value{AS}}.
1693 The MRI compatibility is not complete. Certain operations of the MRI assembler
1694 depend upon its object file format, and can not be supported using other object
1695 file formats. Supporting these would require enhancing each object file format
1696 individually. These are:
1699 @item global symbols in common section
1701 The m68k MRI assembler supports common sections which are merged by the linker.
1702 Other object file formats do not support this. @command{@value{AS}} handles
1703 common sections by treating them as a single common symbol. It permits local
1704 symbols to be defined within a common section, but it can not support global
1705 symbols, since it has no way to describe them.
1707 @item complex relocations
1709 The MRI assemblers support relocations against a negated section address, and
1710 relocations which combine the start addresses of two or more sections. These
1711 are not support by other object file formats.
1713 @item @code{END} pseudo-op specifying start address
1715 The MRI @code{END} pseudo-op permits the specification of a start address.
1716 This is not supported by other object file formats. The start address may
1717 instead be specified using the @option{-e} option to the linker, or in a linker
1720 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1722 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1723 name to the output file. This is not supported by other object file formats.
1725 @item @code{ORG} pseudo-op
1727 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1728 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
1729 which changes the location within the current section. Absolute sections are
1730 not supported by other object file formats. The address of a section may be
1731 assigned within a linker script.
1734 There are some other features of the MRI assembler which are not supported by
1735 @command{@value{AS}}, typically either because they are difficult or because they
1736 seem of little consequence. Some of these may be supported in future releases.
1740 @item EBCDIC strings
1742 EBCDIC strings are not supported.
1744 @item packed binary coded decimal
1746 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1747 and @code{DCB.P} pseudo-ops are not supported.
1749 @item @code{FEQU} pseudo-op
1751 The m68k @code{FEQU} pseudo-op is not supported.
1753 @item @code{NOOBJ} pseudo-op
1755 The m68k @code{NOOBJ} pseudo-op is not supported.
1757 @item @code{OPT} branch control options
1759 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1760 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
1761 relaxes all branches, whether forward or backward, to an appropriate size, so
1762 these options serve no purpose.
1764 @item @code{OPT} list control options
1766 The following m68k @code{OPT} list control options are ignored: @code{C},
1767 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1768 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1770 @item other @code{OPT} options
1772 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1773 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1775 @item @code{OPT} @code{D} option is default
1777 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1778 @code{OPT NOD} may be used to turn it off.
1780 @item @code{XREF} pseudo-op.
1782 The m68k @code{XREF} pseudo-op is ignored.
1784 @item @code{.debug} pseudo-op
1786 The i960 @code{.debug} pseudo-op is not supported.
1788 @item @code{.extended} pseudo-op
1790 The i960 @code{.extended} pseudo-op is not supported.
1792 @item @code{.list} pseudo-op.
1794 The various options of the i960 @code{.list} pseudo-op are not supported.
1796 @item @code{.optimize} pseudo-op
1798 The i960 @code{.optimize} pseudo-op is not supported.
1800 @item @code{.output} pseudo-op
1802 The i960 @code{.output} pseudo-op is not supported.
1804 @item @code{.setreal} pseudo-op
1806 The i960 @code{.setreal} pseudo-op is not supported.
1811 @section Dependency Tracking: @option{--MD}
1814 @cindex dependency tracking
1817 @command{@value{AS}} can generate a dependency file for the file it creates. This
1818 file consists of a single rule suitable for @code{make} describing the
1819 dependencies of the main source file.
1821 The rule is written to the file named in its argument.
1823 This feature is used in the automatic updating of makefiles.
1826 @section Name the Object File: @option{-o}
1829 @cindex naming object file
1830 @cindex object file name
1831 There is always one object file output when you run @command{@value{AS}}. By
1832 default it has the name
1835 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1849 You use this option (which takes exactly one filename) to give the
1850 object file a different name.
1852 Whatever the object file is called, @command{@value{AS}} overwrites any
1853 existing file of the same name.
1856 @section Join Data and Text Sections: @option{-R}
1859 @cindex data and text sections, joining
1860 @cindex text and data sections, joining
1861 @cindex joining text and data sections
1862 @cindex merging text and data sections
1863 @option{-R} tells @command{@value{AS}} to write the object file as if all
1864 data-section data lives in the text section. This is only done at
1865 the very last moment: your binary data are the same, but data
1866 section parts are relocated differently. The data section part of
1867 your object file is zero bytes long because all its bytes are
1868 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1870 When you specify @option{-R} it would be possible to generate shorter
1871 address displacements (because we do not have to cross between text and
1872 data section). We refrain from doing this simply for compatibility with
1873 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
1876 When @command{@value{AS}} is configured for COFF or ELF output,
1877 this option is only useful if you use sections named @samp{.text} and
1882 @option{-R} is not supported for any of the HPPA targets. Using
1883 @option{-R} generates a warning from @command{@value{AS}}.
1887 @section Display Assembly Statistics: @option{--statistics}
1889 @kindex --statistics
1890 @cindex statistics, about assembly
1891 @cindex time, total for assembly
1892 @cindex space used, maximum for assembly
1893 Use @samp{--statistics} to display two statistics about the resources used by
1894 @command{@value{AS}}: the maximum amount of space allocated during the assembly
1895 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1898 @node traditional-format
1899 @section Compatible Output: @option{--traditional-format}
1901 @kindex --traditional-format
1902 For some targets, the output of @command{@value{AS}} is different in some ways
1903 from the output of some existing assembler. This switch requests
1904 @command{@value{AS}} to use the traditional format instead.
1906 For example, it disables the exception frame optimizations which
1907 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
1910 @section Announce Version: @option{-v}
1914 @cindex assembler version
1915 @cindex version of assembler
1916 You can find out what version of as is running by including the
1917 option @samp{-v} (which you can also spell as @samp{-version}) on the
1921 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
1923 @command{@value{AS}} should never give a warning or error message when
1924 assembling compiler output. But programs written by people often
1925 cause @command{@value{AS}} to give a warning that a particular assumption was
1926 made. All such warnings are directed to the standard error file.
1930 @cindex suppressing warnings
1931 @cindex warnings, suppressing
1932 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
1933 This only affects the warning messages: it does not change any particular of
1934 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
1937 @kindex --fatal-warnings
1938 @cindex errors, caused by warnings
1939 @cindex warnings, causing error
1940 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
1941 files that generate warnings to be in error.
1944 @cindex warnings, switching on
1945 You can switch these options off again by specifying @option{--warn}, which
1946 causes warnings to be output as usual.
1949 @section Generate Object File in Spite of Errors: @option{-Z}
1950 @cindex object file, after errors
1951 @cindex errors, continuing after
1952 After an error message, @command{@value{AS}} normally produces no output. If for
1953 some reason you are interested in object file output even after
1954 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
1955 option. If there are any errors, @command{@value{AS}} continues anyways, and
1956 writes an object file after a final warning message of the form @samp{@var{n}
1957 errors, @var{m} warnings, generating bad object file.}
1962 @cindex machine-independent syntax
1963 @cindex syntax, machine-independent
1964 This chapter describes the machine-independent syntax allowed in a
1965 source file. @command{@value{AS}} syntax is similar to what many other
1966 assemblers use; it is inspired by the BSD 4.2
1971 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
1975 * Preprocessing:: Preprocessing
1976 * Whitespace:: Whitespace
1977 * Comments:: Comments
1978 * Symbol Intro:: Symbols
1979 * Statements:: Statements
1980 * Constants:: Constants
1984 @section Preprocessing
1986 @cindex preprocessing
1987 The @command{@value{AS}} internal preprocessor:
1989 @cindex whitespace, removed by preprocessor
1991 adjusts and removes extra whitespace. It leaves one space or tab before
1992 the keywords on a line, and turns any other whitespace on the line into
1995 @cindex comments, removed by preprocessor
1997 removes all comments, replacing them with a single space, or an
1998 appropriate number of newlines.
2000 @cindex constants, converted by preprocessor
2002 converts character constants into the appropriate numeric values.
2005 It does not do macro processing, include file handling, or
2006 anything else you may get from your C compiler's preprocessor. You can
2007 do include file processing with the @code{.include} directive
2008 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2009 to get other ``CPP'' style preprocessing by giving the input file a
2010 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
2011 Output, gcc.info, Using GNU CC}.
2013 Excess whitespace, comments, and character constants
2014 cannot be used in the portions of the input text that are not
2017 @cindex turning preprocessing on and off
2018 @cindex preprocessing, turning on and off
2021 If the first line of an input file is @code{#NO_APP} or if you use the
2022 @samp{-f} option, whitespace and comments are not removed from the input file.
2023 Within an input file, you can ask for whitespace and comment removal in
2024 specific portions of the by putting a line that says @code{#APP} before the
2025 text that may contain whitespace or comments, and putting a line that says
2026 @code{#NO_APP} after this text. This feature is mainly intend to support
2027 @code{asm} statements in compilers whose output is otherwise free of comments
2034 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2035 Whitespace is used to separate symbols, and to make programs neater for
2036 people to read. Unless within character constants
2037 (@pxref{Characters,,Character Constants}), any whitespace means the same
2038 as exactly one space.
2044 There are two ways of rendering comments to @command{@value{AS}}. In both
2045 cases the comment is equivalent to one space.
2047 Anything from @samp{/*} through the next @samp{*/} is a comment.
2048 This means you may not nest these comments.
2052 The only way to include a newline ('\n') in a comment
2053 is to use this sort of comment.
2056 /* This sort of comment does not nest. */
2059 @cindex line comment character
2060 Anything from the @dfn{line comment} character to the next newline
2061 is considered a comment and is ignored. The line comment character is
2063 @samp{;} for the AMD 29K family;
2066 @samp{;} on the ARC;
2069 @samp{@@} on the ARM;
2072 @samp{;} for the H8/300 family;
2075 @samp{!} for the H8/500 family;
2078 @samp{;} for the HPPA;
2081 @samp{#} on the i386 and x86-64;
2084 @samp{#} on the i960;
2087 @samp{;} for the PDP-11;
2090 @samp{;} for picoJava;
2093 @samp{;} for Motorola PowerPC;
2096 @samp{!} for the Renesas / SuperH SH;
2099 @samp{!} on the SPARC;
2102 @samp{#} on the ip2k;
2105 @samp{#} on the m32r;
2108 @samp{|} on the 680x0;
2111 @samp{#} on the 68HC11 and 68HC12;
2114 @samp{;} on the M880x0;
2117 @samp{#} on the Vax;
2120 @samp{!} for the Z8000;
2123 @samp{#} on the V850;
2126 @samp{#} for Xtensa systems;
2128 see @ref{Machine Dependencies}. @refill
2129 @c FIXME What about i860?
2132 On some machines there are two different line comment characters. One
2133 character only begins a comment if it is the first non-whitespace character on
2134 a line, while the other always begins a comment.
2138 The V850 assembler also supports a double dash as starting a comment that
2139 extends to the end of the line.
2145 @cindex lines starting with @code{#}
2146 @cindex logical line numbers
2147 To be compatible with past assemblers, lines that begin with @samp{#} have a
2148 special interpretation. Following the @samp{#} should be an absolute
2149 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2150 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
2151 new logical file name. The rest of the line, if any, should be whitespace.
2153 If the first non-whitespace characters on the line are not numeric,
2154 the line is ignored. (Just like a comment.)
2157 # This is an ordinary comment.
2158 # 42-6 "new_file_name" # New logical file name
2159 # This is logical line # 36.
2161 This feature is deprecated, and may disappear from future versions
2162 of @command{@value{AS}}.
2167 @cindex characters used in symbols
2168 @ifclear SPECIAL-SYMS
2169 A @dfn{symbol} is one or more characters chosen from the set of all
2170 letters (both upper and lower case), digits and the three characters
2176 A @dfn{symbol} is one or more characters chosen from the set of all
2177 letters (both upper and lower case), digits and the three characters
2178 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2184 On most machines, you can also use @code{$} in symbol names; exceptions
2185 are noted in @ref{Machine Dependencies}.
2187 No symbol may begin with a digit. Case is significant.
2188 There is no length limit: all characters are significant. Symbols are
2189 delimited by characters not in that set, or by the beginning of a file
2190 (since the source program must end with a newline, the end of a file is
2191 not a possible symbol delimiter). @xref{Symbols}.
2192 @cindex length of symbols
2197 @cindex statements, structure of
2198 @cindex line separator character
2199 @cindex statement separator character
2201 @ifclear abnormal-separator
2202 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
2203 semicolon (@samp{;}). The newline or semicolon is considered part of
2204 the preceding statement. Newlines and semicolons within character
2205 constants are an exception: they do not end statements.
2207 @ifset abnormal-separator
2209 A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at''
2210 sign (@samp{@@}). The newline or at sign is considered part of the
2211 preceding statement. Newlines and at signs within character constants
2212 are an exception: they do not end statements.
2215 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
2216 point (@samp{!}). The newline or exclamation point is considered part of the
2217 preceding statement. Newlines and exclamation points within character
2218 constants are an exception: they do not end statements.
2221 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
2222 H8/300) a dollar sign (@samp{$}); or (for the
2225 (@samp{;}). The newline or separator character is considered part of
2226 the preceding statement. Newlines and separators within character
2227 constants are an exception: they do not end statements.
2232 A @dfn{statement} ends at a newline character (@samp{\n}) or line
2233 separator character. (The line separator is usually @samp{;}, unless
2234 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
2235 newline or separator character is considered part of the preceding
2236 statement. Newlines and separators within character constants are an
2237 exception: they do not end statements.
2240 @cindex newline, required at file end
2241 @cindex EOF, newline must precede
2242 It is an error to end any statement with end-of-file: the last
2243 character of any input file should be a newline.@refill
2245 An empty statement is allowed, and may include whitespace. It is ignored.
2247 @cindex instructions and directives
2248 @cindex directives and instructions
2249 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2250 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2252 A statement begins with zero or more labels, optionally followed by a
2253 key symbol which determines what kind of statement it is. The key
2254 symbol determines the syntax of the rest of the statement. If the
2255 symbol begins with a dot @samp{.} then the statement is an assembler
2256 directive: typically valid for any computer. If the symbol begins with
2257 a letter the statement is an assembly language @dfn{instruction}: it
2258 assembles into a machine language instruction.
2260 Different versions of @command{@value{AS}} for different computers
2261 recognize different instructions. In fact, the same symbol may
2262 represent a different instruction in a different computer's assembly
2266 @cindex @code{:} (label)
2267 @cindex label (@code{:})
2268 A label is a symbol immediately followed by a colon (@code{:}).
2269 Whitespace before a label or after a colon is permitted, but you may not
2270 have whitespace between a label's symbol and its colon. @xref{Labels}.
2273 For HPPA targets, labels need not be immediately followed by a colon, but
2274 the definition of a label must begin in column zero. This also implies that
2275 only one label may be defined on each line.
2279 label: .directive followed by something
2280 another_label: # This is an empty statement.
2281 instruction operand_1, operand_2, @dots{}
2288 A constant is a number, written so that its value is known by
2289 inspection, without knowing any context. Like this:
2292 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2293 .ascii "Ring the bell\7" # A string constant.
2294 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2295 .float 0f-314159265358979323846264338327\
2296 95028841971.693993751E-40 # - pi, a flonum.
2301 * Characters:: Character Constants
2302 * Numbers:: Number Constants
2306 @subsection Character Constants
2308 @cindex character constants
2309 @cindex constants, character
2310 There are two kinds of character constants. A @dfn{character} stands
2311 for one character in one byte and its value may be used in
2312 numeric expressions. String constants (properly called string
2313 @emph{literals}) are potentially many bytes and their values may not be
2314 used in arithmetic expressions.
2318 * Chars:: Characters
2322 @subsubsection Strings
2324 @cindex string constants
2325 @cindex constants, string
2326 A @dfn{string} is written between double-quotes. It may contain
2327 double-quotes or null characters. The way to get special characters
2328 into a string is to @dfn{escape} these characters: precede them with
2329 a backslash @samp{\} character. For example @samp{\\} represents
2330 one backslash: the first @code{\} is an escape which tells
2331 @command{@value{AS}} to interpret the second character literally as a backslash
2332 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2333 escape character). The complete list of escapes follows.
2335 @cindex escape codes, character
2336 @cindex character escape codes
2339 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2341 @cindex @code{\b} (backspace character)
2342 @cindex backspace (@code{\b})
2344 Mnemonic for backspace; for ASCII this is octal code 010.
2347 @c Mnemonic for EOText; for ASCII this is octal code 004.
2349 @cindex @code{\f} (formfeed character)
2350 @cindex formfeed (@code{\f})
2352 Mnemonic for FormFeed; for ASCII this is octal code 014.
2354 @cindex @code{\n} (newline character)
2355 @cindex newline (@code{\n})
2357 Mnemonic for newline; for ASCII this is octal code 012.
2360 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2362 @cindex @code{\r} (carriage return character)
2363 @cindex carriage return (@code{\r})
2365 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2368 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2369 @c other assemblers.
2371 @cindex @code{\t} (tab)
2372 @cindex tab (@code{\t})
2374 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2377 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2378 @c @item \x @var{digit} @var{digit} @var{digit}
2379 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2381 @cindex @code{\@var{ddd}} (octal character code)
2382 @cindex octal character code (@code{\@var{ddd}})
2383 @item \ @var{digit} @var{digit} @var{digit}
2384 An octal character code. The numeric code is 3 octal digits.
2385 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2386 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2388 @cindex @code{\@var{xd...}} (hex character code)
2389 @cindex hex character code (@code{\@var{xd...}})
2390 @item \@code{x} @var{hex-digits...}
2391 A hex character code. All trailing hex digits are combined. Either upper or
2392 lower case @code{x} works.
2394 @cindex @code{\\} (@samp{\} character)
2395 @cindex backslash (@code{\\})
2397 Represents one @samp{\} character.
2400 @c Represents one @samp{'} (accent acute) character.
2401 @c This is needed in single character literals
2402 @c (@xref{Characters,,Character Constants}.) to represent
2405 @cindex @code{\"} (doublequote character)
2406 @cindex doublequote (@code{\"})
2408 Represents one @samp{"} character. Needed in strings to represent
2409 this character, because an unescaped @samp{"} would end the string.
2411 @item \ @var{anything-else}
2412 Any other character when escaped by @kbd{\} gives a warning, but
2413 assembles as if the @samp{\} was not present. The idea is that if
2414 you used an escape sequence you clearly didn't want the literal
2415 interpretation of the following character. However @command{@value{AS}} has no
2416 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2417 code and warns you of the fact.
2420 Which characters are escapable, and what those escapes represent,
2421 varies widely among assemblers. The current set is what we think
2422 the BSD 4.2 assembler recognizes, and is a subset of what most C
2423 compilers recognize. If you are in doubt, do not use an escape
2427 @subsubsection Characters
2429 @cindex single character constant
2430 @cindex character, single
2431 @cindex constant, single character
2432 A single character may be written as a single quote immediately
2433 followed by that character. The same escapes apply to characters as
2434 to strings. So if you want to write the character backslash, you
2435 must write @kbd{'\\} where the first @code{\} escapes the second
2436 @code{\}. As you can see, the quote is an acute accent, not a
2437 grave accent. A newline
2439 @ifclear abnormal-separator
2440 (or semicolon @samp{;})
2442 @ifset abnormal-separator
2444 (or at sign @samp{@@})
2447 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2448 Renesas SH or H8/500)
2452 immediately following an acute accent is taken as a literal character
2453 and does not count as the end of a statement. The value of a character
2454 constant in a numeric expression is the machine's byte-wide code for
2455 that character. @command{@value{AS}} assumes your character code is ASCII:
2456 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2459 @subsection Number Constants
2461 @cindex constants, number
2462 @cindex number constants
2463 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2464 are stored in the target machine. @emph{Integers} are numbers that
2465 would fit into an @code{int} in the C language. @emph{Bignums} are
2466 integers, but they are stored in more than 32 bits. @emph{Flonums}
2467 are floating point numbers, described below.
2470 * Integers:: Integers
2475 * Bit Fields:: Bit Fields
2481 @subsubsection Integers
2483 @cindex constants, integer
2485 @cindex binary integers
2486 @cindex integers, binary
2487 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2488 the binary digits @samp{01}.
2490 @cindex octal integers
2491 @cindex integers, octal
2492 An octal integer is @samp{0} followed by zero or more of the octal
2493 digits (@samp{01234567}).
2495 @cindex decimal integers
2496 @cindex integers, decimal
2497 A decimal integer starts with a non-zero digit followed by zero or
2498 more digits (@samp{0123456789}).
2500 @cindex hexadecimal integers
2501 @cindex integers, hexadecimal
2502 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2503 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2505 Integers have the usual values. To denote a negative integer, use
2506 the prefix operator @samp{-} discussed under expressions
2507 (@pxref{Prefix Ops,,Prefix Operators}).
2510 @subsubsection Bignums
2513 @cindex constants, bignum
2514 A @dfn{bignum} has the same syntax and semantics as an integer
2515 except that the number (or its negative) takes more than 32 bits to
2516 represent in binary. The distinction is made because in some places
2517 integers are permitted while bignums are not.
2520 @subsubsection Flonums
2522 @cindex floating point numbers
2523 @cindex constants, floating point
2525 @cindex precision, floating point
2526 A @dfn{flonum} represents a floating point number. The translation is
2527 indirect: a decimal floating point number from the text is converted by
2528 @command{@value{AS}} to a generic binary floating point number of more than
2529 sufficient precision. This generic floating point number is converted
2530 to a particular computer's floating point format (or formats) by a
2531 portion of @command{@value{AS}} specialized to that computer.
2533 A flonum is written by writing (in order)
2538 (@samp{0} is optional on the HPPA.)
2542 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2544 @kbd{e} is recommended. Case is not important.
2546 @c FIXME: verify if flonum syntax really this vague for most cases
2547 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2548 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2551 On the H8/300, H8/500,
2552 Renesas / SuperH SH,
2553 and AMD 29K architectures, the letter must be
2554 one of the letters @samp{DFPRSX} (in upper or lower case).
2556 On the ARC, the letter must be one of the letters @samp{DFRS}
2557 (in upper or lower case).
2559 On the Intel 960 architecture, the letter must be
2560 one of the letters @samp{DFT} (in upper or lower case).
2562 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2566 One of the letters @samp{DFPRSX} (in upper or lower case).
2569 One of the letters @samp{DFRS} (in upper or lower case).
2572 One of the letters @samp{DFPRSX} (in upper or lower case).
2575 The letter @samp{E} (upper case only).
2578 One of the letters @samp{DFT} (in upper or lower case).
2583 An optional sign: either @samp{+} or @samp{-}.
2586 An optional @dfn{integer part}: zero or more decimal digits.
2589 An optional @dfn{fractional part}: @samp{.} followed by zero
2590 or more decimal digits.
2593 An optional exponent, consisting of:
2597 An @samp{E} or @samp{e}.
2598 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2599 @c principle this can perfectly well be different on different targets.
2601 Optional sign: either @samp{+} or @samp{-}.
2603 One or more decimal digits.
2608 At least one of the integer part or the fractional part must be
2609 present. The floating point number has the usual base-10 value.
2611 @command{@value{AS}} does all processing using integers. Flonums are computed
2612 independently of any floating point hardware in the computer running
2613 @command{@value{AS}}.
2617 @c Bit fields are written as a general facility but are also controlled
2618 @c by a conditional-compilation flag---which is as of now (21mar91)
2619 @c turned on only by the i960 config of GAS.
2621 @subsubsection Bit Fields
2624 @cindex constants, bit field
2625 You can also define numeric constants as @dfn{bit fields}.
2626 specify two numbers separated by a colon---
2628 @var{mask}:@var{value}
2631 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2634 The resulting number is then packed
2636 @c this conditional paren in case bit fields turned on elsewhere than 960
2637 (in host-dependent byte order)
2639 into a field whose width depends on which assembler directive has the
2640 bit-field as its argument. Overflow (a result from the bitwise and
2641 requiring more binary digits to represent) is not an error; instead,
2642 more constants are generated, of the specified width, beginning with the
2643 least significant digits.@refill
2645 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2646 @code{.short}, and @code{.word} accept bit-field arguments.
2651 @chapter Sections and Relocation
2656 * Secs Background:: Background
2657 * Ld Sections:: Linker Sections
2658 * As Sections:: Assembler Internal Sections
2659 * Sub-Sections:: Sub-Sections
2663 @node Secs Background
2666 Roughly, a section is a range of addresses, with no gaps; all data
2667 ``in'' those addresses is treated the same for some particular purpose.
2668 For example there may be a ``read only'' section.
2670 @cindex linker, and assembler
2671 @cindex assembler, and linker
2672 The linker @code{@value{LD}} reads many object files (partial programs) and
2673 combines their contents to form a runnable program. When @command{@value{AS}}
2674 emits an object file, the partial program is assumed to start at address 0.
2675 @code{@value{LD}} assigns the final addresses for the partial program, so that
2676 different partial programs do not overlap. This is actually an
2677 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2680 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2681 addresses. These blocks slide to their run-time addresses as rigid
2682 units; their length does not change and neither does the order of bytes
2683 within them. Such a rigid unit is called a @emph{section}. Assigning
2684 run-time addresses to sections is called @dfn{relocation}. It includes
2685 the task of adjusting mentions of object-file addresses so they refer to
2686 the proper run-time addresses.
2688 For the H8/300 and H8/500,
2689 and for the Renesas / SuperH SH,
2690 @command{@value{AS}} pads sections if needed to
2691 ensure they end on a word (sixteen bit) boundary.
2694 @cindex standard assembler sections
2695 An object file written by @command{@value{AS}} has at least three sections, any
2696 of which may be empty. These are named @dfn{text}, @dfn{data} and
2701 When it generates COFF or ELF output,
2703 @command{@value{AS}} can also generate whatever other named sections you specify
2704 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2705 If you do not use any directives that place output in the @samp{.text}
2706 or @samp{.data} sections, these sections still exist, but are empty.
2711 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2713 @command{@value{AS}} can also generate whatever other named sections you
2714 specify using the @samp{.space} and @samp{.subspace} directives. See
2715 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2716 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2717 assembler directives.
2720 Additionally, @command{@value{AS}} uses different names for the standard
2721 text, data, and bss sections when generating SOM output. Program text
2722 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2723 BSS into @samp{$BSS$}.
2727 Within the object file, the text section starts at address @code{0}, the
2728 data section follows, and the bss section follows the data section.
2731 When generating either SOM or ELF output files on the HPPA, the text
2732 section starts at address @code{0}, the data section at address
2733 @code{0x4000000}, and the bss section follows the data section.
2736 To let @code{@value{LD}} know which data changes when the sections are
2737 relocated, and how to change that data, @command{@value{AS}} also writes to the
2738 object file details of the relocation needed. To perform relocation
2739 @code{@value{LD}} must know, each time an address in the object
2743 Where in the object file is the beginning of this reference to
2746 How long (in bytes) is this reference?
2748 Which section does the address refer to? What is the numeric value of
2750 (@var{address}) @minus{} (@var{start-address of section})?
2753 Is the reference to an address ``Program-Counter relative''?
2756 @cindex addresses, format of
2757 @cindex section-relative addressing
2758 In fact, every address @command{@value{AS}} ever uses is expressed as
2760 (@var{section}) + (@var{offset into section})
2763 Further, most expressions @command{@value{AS}} computes have this section-relative
2766 (For some object formats, such as SOM for the HPPA, some expressions are
2767 symbol-relative instead.)
2770 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2771 @var{N} into section @var{secname}.''
2773 Apart from text, data and bss sections you need to know about the
2774 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2775 addresses in the absolute section remain unchanged. For example, address
2776 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2777 @code{@value{LD}}. Although the linker never arranges two partial programs'
2778 data sections with overlapping addresses after linking, @emph{by definition}
2779 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2780 part of a program is always the same address when the program is running as
2781 address @code{@{absolute@ 239@}} in any other part of the program.
2783 The idea of sections is extended to the @dfn{undefined} section. Any
2784 address whose section is unknown at assembly time is by definition
2785 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2786 Since numbers are always defined, the only way to generate an undefined
2787 address is to mention an undefined symbol. A reference to a named
2788 common block would be such a symbol: its value is unknown at assembly
2789 time so it has section @emph{undefined}.
2791 By analogy the word @emph{section} is used to describe groups of sections in
2792 the linked program. @code{@value{LD}} puts all partial programs' text
2793 sections in contiguous addresses in the linked program. It is
2794 customary to refer to the @emph{text section} of a program, meaning all
2795 the addresses of all partial programs' text sections. Likewise for
2796 data and bss sections.
2798 Some sections are manipulated by @code{@value{LD}}; others are invented for
2799 use of @command{@value{AS}} and have no meaning except during assembly.
2802 @section Linker Sections
2803 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2808 @cindex named sections
2809 @cindex sections, named
2810 @item named sections
2813 @cindex text section
2814 @cindex data section
2818 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
2819 separate but equal sections. Anything you can say of one section is
2822 When the program is running, however, it is
2823 customary for the text section to be unalterable. The
2824 text section is often shared among processes: it contains
2825 instructions, constants and the like. The data section of a running
2826 program is usually alterable: for example, C variables would be stored
2827 in the data section.
2832 This section contains zeroed bytes when your program begins running. It
2833 is used to hold uninitialized variables or common storage. The length of
2834 each partial program's bss section is important, but because it starts
2835 out containing zeroed bytes there is no need to store explicit zero
2836 bytes in the object file. The bss section was invented to eliminate
2837 those explicit zeros from object files.
2839 @cindex absolute section
2840 @item absolute section
2841 Address 0 of this section is always ``relocated'' to runtime address 0.
2842 This is useful if you want to refer to an address that @code{@value{LD}} must
2843 not change when relocating. In this sense we speak of absolute
2844 addresses being ``unrelocatable'': they do not change during relocation.
2846 @cindex undefined section
2847 @item undefined section
2848 This ``section'' is a catch-all for address references to objects not in
2849 the preceding sections.
2850 @c FIXME: ref to some other doc on obj-file formats could go here.
2853 @cindex relocation example
2854 An idealized example of three relocatable sections follows.
2856 The example uses the traditional section names @samp{.text} and @samp{.data}.
2858 Memory addresses are on the horizontal axis.
2862 @c END TEXI2ROFF-KILL
2865 partial program # 1: |ttttt|dddd|00|
2872 partial program # 2: |TTT|DDD|000|
2875 +--+---+-----+--+----+---+-----+~~
2876 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2877 +--+---+-----+--+----+---+-----+~~
2879 addresses: 0 @dots{}
2886 \line{\it Partial program \#1: \hfil}
2887 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2888 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2890 \line{\it Partial program \#2: \hfil}
2891 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2892 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2894 \line{\it linked program: \hfil}
2895 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2896 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2897 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2898 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2900 \line{\it addresses: \hfil}
2904 @c END TEXI2ROFF-KILL
2907 @section Assembler Internal Sections
2909 @cindex internal assembler sections
2910 @cindex sections in messages, internal
2911 These sections are meant only for the internal use of @command{@value{AS}}. They
2912 have no meaning at run-time. You do not really need to know about these
2913 sections for most purposes; but they can be mentioned in @command{@value{AS}}
2914 warning messages, so it might be helpful to have an idea of their
2915 meanings to @command{@value{AS}}. These sections are used to permit the
2916 value of every expression in your assembly language program to be a
2917 section-relative address.
2920 @cindex assembler internal logic error
2921 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2922 An internal assembler logic error has been found. This means there is a
2923 bug in the assembler.
2925 @cindex expr (internal section)
2927 The assembler stores complex expression internally as combinations of
2928 symbols. When it needs to represent an expression as a symbol, it puts
2929 it in the expr section.
2931 @c FIXME item transfer[t] vector preload
2932 @c FIXME item transfer[t] vector postload
2933 @c FIXME item register
2937 @section Sub-Sections
2939 @cindex numbered subsections
2940 @cindex grouping data
2946 fall into two sections: text and data.
2948 You may have separate groups of
2950 data in named sections
2954 data in named sections
2960 that you want to end up near to each other in the object file, even though they
2961 are not contiguous in the assembler source. @command{@value{AS}} allows you to
2962 use @dfn{subsections} for this purpose. Within each section, there can be
2963 numbered subsections with values from 0 to 8192. Objects assembled into the
2964 same subsection go into the object file together with other objects in the same
2965 subsection. For example, a compiler might want to store constants in the text
2966 section, but might not want to have them interspersed with the program being
2967 assembled. In this case, the compiler could issue a @samp{.text 0} before each
2968 section of code being output, and a @samp{.text 1} before each group of
2969 constants being output.
2971 Subsections are optional. If you do not use subsections, everything
2972 goes in subsection number zero.
2975 Each subsection is zero-padded up to a multiple of four bytes.
2976 (Subsections may be padded a different amount on different flavors
2977 of @command{@value{AS}}.)
2981 On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word
2982 boundary (two bytes).
2983 The same is true on the Renesas SH.
2986 @c FIXME section padding (alignment)?
2987 @c Rich Pixley says padding here depends on target obj code format; that
2988 @c doesn't seem particularly useful to say without further elaboration,
2989 @c so for now I say nothing about it. If this is a generic BFD issue,
2990 @c these paragraphs might need to vanish from this manual, and be
2991 @c discussed in BFD chapter of binutils (or some such).
2994 On the AMD 29K family, no particular padding is added to section or
2995 subsection sizes; @value{AS} forces no alignment on this platform.
2999 Subsections appear in your object file in numeric order, lowest numbered
3000 to highest. (All this to be compatible with other people's assemblers.)
3001 The object file contains no representation of subsections; @code{@value{LD}} and
3002 other programs that manipulate object files see no trace of them.
3003 They just see all your text subsections as a text section, and all your
3004 data subsections as a data section.
3006 To specify which subsection you want subsequent statements assembled
3007 into, use a numeric argument to specify it, in a @samp{.text
3008 @var{expression}} or a @samp{.data @var{expression}} statement.
3011 When generating COFF or ELF output, you
3016 can also use an extra subsection
3017 argument with arbitrary named sections: @samp{.section @var{name},
3020 @var{Expression} should be an absolute expression.
3021 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
3022 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3023 begins in @code{text 0}. For instance:
3025 .text 0 # The default subsection is text 0 anyway.
3026 .ascii "This lives in the first text subsection. *"
3028 .ascii "But this lives in the second text subsection."
3030 .ascii "This lives in the data section,"
3031 .ascii "in the first data subsection."
3033 .ascii "This lives in the first text section,"
3034 .ascii "immediately following the asterisk (*)."
3037 Each section has a @dfn{location counter} incremented by one for every byte
3038 assembled into that section. Because subsections are merely a convenience
3039 restricted to @command{@value{AS}} there is no concept of a subsection location
3040 counter. There is no way to directly manipulate a location counter---but the
3041 @code{.align} directive changes it, and any label definition captures its
3042 current value. The location counter of the section where statements are being
3043 assembled is said to be the @dfn{active} location counter.
3046 @section bss Section
3049 @cindex common variable storage
3050 The bss section is used for local common variable storage.
3051 You may allocate address space in the bss section, but you may
3052 not dictate data to load into it before your program executes. When
3053 your program starts running, all the contents of the bss
3054 section are zeroed bytes.
3056 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3057 @ref{Lcomm,,@code{.lcomm}}.
3059 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3060 another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}.
3063 When assembling for a target which supports multiple sections, such as ELF or
3064 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3065 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3066 section. Typically the section will only contain symbol definitions and
3067 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3074 Symbols are a central concept: the programmer uses symbols to name
3075 things, the linker uses symbols to link, and the debugger uses symbols
3079 @cindex debuggers, and symbol order
3080 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3081 the same order they were declared. This may break some debuggers.
3086 * Setting Symbols:: Giving Symbols Other Values
3087 * Symbol Names:: Symbol Names
3088 * Dot:: The Special Dot Symbol
3089 * Symbol Attributes:: Symbol Attributes
3096 A @dfn{label} is written as a symbol immediately followed by a colon
3097 @samp{:}. The symbol then represents the current value of the
3098 active location counter, and is, for example, a suitable instruction
3099 operand. You are warned if you use the same symbol to represent two
3100 different locations: the first definition overrides any other
3104 On the HPPA, the usual form for a label need not be immediately followed by a
3105 colon, but instead must start in column zero. Only one label may be defined on
3106 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3107 provides a special directive @code{.label} for defining labels more flexibly.
3110 @node Setting Symbols
3111 @section Giving Symbols Other Values
3113 @cindex assigning values to symbols
3114 @cindex symbol values, assigning
3115 A symbol can be given an arbitrary value by writing a symbol, followed
3116 by an equals sign @samp{=}, followed by an expression
3117 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3118 directive. @xref{Set,,@code{.set}}.
3121 @section Symbol Names
3123 @cindex symbol names
3124 @cindex names, symbol
3125 @ifclear SPECIAL-SYMS
3126 Symbol names begin with a letter or with one of @samp{._}. On most
3127 machines, you can also use @code{$} in symbol names; exceptions are
3128 noted in @ref{Machine Dependencies}. That character may be followed by any
3129 string of digits, letters, dollar signs (unless otherwise noted in
3130 @ref{Machine Dependencies}), and underscores.
3133 For the AMD 29K family, @samp{?} is also allowed in the
3134 body of a symbol name, though not at its beginning.
3139 Symbol names begin with a letter or with one of @samp{._}. On the
3140 Renesas SH or the H8/500, you can also use @code{$} in symbol names. That
3141 character may be followed by any string of digits, letters, dollar signs (save
3142 on the H8/300), and underscores.
3146 Case of letters is significant: @code{foo} is a different symbol name
3149 Each symbol has exactly one name. Each name in an assembly language program
3150 refers to exactly one symbol. You may use that symbol name any number of times
3153 @subheading Local Symbol Names
3155 @cindex local symbol names
3156 @cindex symbol names, local
3157 @cindex temporary symbol names
3158 @cindex symbol names, temporary
3159 Local symbols help compilers and programmers use names temporarily.
3160 They create symbols which are guaranteed to be unique over the entire scope of
3161 the input source code and which can be referred to by a simple notation.
3162 To define a local symbol, write a label of the form @samp{@b{N}:} (where @b{N}
3163 represents any positive integer). To refer to the most recent previous
3164 definition of that symbol write @samp{@b{N}b}, using the same number as when
3165 you defined the label. To refer to the next definition of a local label, write
3166 @samp{@b{N}f}--- The @samp{b} stands for``backwards'' and the @samp{f} stands
3169 There is no restriction on how you can use these labels, and you can reuse them
3170 too. So that it is possible to repeatedly define the same local label (using
3171 the same number @samp{@b{N}}), although you can only refer to the most recently
3172 defined local label of that number (for a backwards reference) or the next
3173 definition of a specific local label for a forward reference. It is also worth
3174 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3175 implemented in a slightly more efficient manner than the others.
3186 Which is the equivalent of:
3189 label_1: branch label_3
3190 label_2: branch label_1
3191 label_3: branch label_4
3192 label_4: branch label_3
3195 Local symbol names are only a notational device. They are immediately
3196 transformed into more conventional symbol names before the assembler uses them.
3197 The symbol names stored in the symbol table, appearing in error messages and
3198 optionally emitted to the object file. The names are constructed using these
3203 All local labels begin with @samp{L}. Normally both @command{@value{AS}} and
3204 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
3205 used for symbols you are never intended to see. If you use the
3206 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3207 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3208 you may use them in debugging.
3211 This is the number that was used in the local label definition. So if the
3212 label is written @samp{55:} then the number is @samp{55}.
3215 This unusual character is included so you do not accidentally invent a symbol
3216 of the same name. The character has ASCII value of @samp{\002} (control-B).
3218 @item @emph{ordinal number}
3219 This is a serial number to keep the labels distinct. The first definition of
3220 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3221 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3222 the number @samp{1} and its 15th defintion gets @samp{15} as well.
3225 So for example, the first @code{1:} is named @code{L1@kbd{C-B}1}, the 44th
3226 @code{3:} is named @code{L3@kbd{C-B}44}.
3228 @subheading Dollar Local Labels
3229 @cindex dollar local symbols
3231 @code{@value{AS}} also supports an even more local form of local labels called
3232 dollar labels. These labels go out of scope (ie they become undefined) as soon
3233 as a non-local label is defined. Thus they remain valid for only a small
3234 region of the input source code. Normal local labels, by contrast, remain in
3235 scope for the entire file, or until they are redefined by another occurrence of
3236 the same local label.
3238 Dollar labels are defined in exactly the same way as ordinary local labels,
3239 except that instead of being terminated by a colon, they are terminated by a
3240 dollar sign. eg @samp{@b{55$}}.
3242 They can also be distinguished from ordinary local labels by their transformed
3243 name which uses ASCII character @samp{\001} (control-A) as the magic character
3244 to distinguish them from ordinary labels. Thus the 5th defintion of @samp{6$}
3245 is named @samp{L6@kbd{C-A}5}.
3248 @section The Special Dot Symbol
3250 @cindex dot (symbol)
3251 @cindex @code{.} (symbol)
3252 @cindex current address
3253 @cindex location counter
3254 The special symbol @samp{.} refers to the current address that
3255 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3256 .long .} defines @code{melvin} to contain its own address.
3257 Assigning a value to @code{.} is treated the same as a @code{.org}
3258 directive. Thus, the expression @samp{.=.+4} is the same as saying
3259 @ifclear no-space-dir
3268 @node Symbol Attributes
3269 @section Symbol Attributes
3271 @cindex symbol attributes
3272 @cindex attributes, symbol
3273 Every symbol has, as well as its name, the attributes ``Value'' and
3274 ``Type''. Depending on output format, symbols can also have auxiliary
3277 The detailed definitions are in @file{a.out.h}.
3280 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3281 all these attributes, and probably won't warn you. This makes the
3282 symbol an externally defined symbol, which is generally what you
3286 * Symbol Value:: Value
3287 * Symbol Type:: Type
3290 * a.out Symbols:: Symbol Attributes: @code{a.out}
3294 * a.out Symbols:: Symbol Attributes: @code{a.out}
3297 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3302 * COFF Symbols:: Symbol Attributes for COFF
3305 * SOM Symbols:: Symbol Attributes for SOM
3312 @cindex value of a symbol
3313 @cindex symbol value
3314 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3315 location in the text, data, bss or absolute sections the value is the
3316 number of addresses from the start of that section to the label.
3317 Naturally for text, data and bss sections the value of a symbol changes
3318 as @code{@value{LD}} changes section base addresses during linking. Absolute
3319 symbols' values do not change during linking: that is why they are
3322 The value of an undefined symbol is treated in a special way. If it is
3323 0 then the symbol is not defined in this assembler source file, and
3324 @code{@value{LD}} tries to determine its value from other files linked into the
3325 same program. You make this kind of symbol simply by mentioning a symbol
3326 name without defining it. A non-zero value represents a @code{.comm}
3327 common declaration. The value is how much common storage to reserve, in
3328 bytes (addresses). The symbol refers to the first address of the
3334 @cindex type of a symbol
3336 The type attribute of a symbol contains relocation (section)
3337 information, any flag settings indicating that a symbol is external, and
3338 (optionally), other information for linkers and debuggers. The exact
3339 format depends on the object-code output format in use.
3344 @c The following avoids a "widow" subsection title. @group would be
3345 @c better if it were available outside examples.
3348 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3350 @cindex @code{b.out} symbol attributes
3351 @cindex symbol attributes, @code{b.out}
3352 These symbol attributes appear only when @command{@value{AS}} is configured for
3353 one of the Berkeley-descended object output formats---@code{a.out} or
3359 @subsection Symbol Attributes: @code{a.out}
3361 @cindex @code{a.out} symbol attributes
3362 @cindex symbol attributes, @code{a.out}
3368 @subsection Symbol Attributes: @code{a.out}
3370 @cindex @code{a.out} symbol attributes
3371 @cindex symbol attributes, @code{a.out}
3375 * Symbol Desc:: Descriptor
3376 * Symbol Other:: Other
3380 @subsubsection Descriptor
3382 @cindex descriptor, of @code{a.out} symbol
3383 This is an arbitrary 16-bit value. You may establish a symbol's
3384 descriptor value by using a @code{.desc} statement
3385 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3386 @command{@value{AS}}.
3389 @subsubsection Other
3391 @cindex other attribute, of @code{a.out} symbol
3392 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3397 @subsection Symbol Attributes for COFF
3399 @cindex COFF symbol attributes
3400 @cindex symbol attributes, COFF
3402 The COFF format supports a multitude of auxiliary symbol attributes;
3403 like the primary symbol attributes, they are set between @code{.def} and
3404 @code{.endef} directives.
3406 @subsubsection Primary Attributes
3408 @cindex primary attributes, COFF symbols
3409 The symbol name is set with @code{.def}; the value and type,
3410 respectively, with @code{.val} and @code{.type}.
3412 @subsubsection Auxiliary Attributes
3414 @cindex auxiliary attributes, COFF symbols
3415 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3416 @code{.size}, and @code{.tag} can generate auxiliary symbol table
3417 information for COFF.
3422 @subsection Symbol Attributes for SOM
3424 @cindex SOM symbol attributes
3425 @cindex symbol attributes, SOM
3427 The SOM format for the HPPA supports a multitude of symbol attributes set with
3428 the @code{.EXPORT} and @code{.IMPORT} directives.
3430 The attributes are described in @cite{HP9000 Series 800 Assembly
3431 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3432 @code{EXPORT} assembler directive documentation.
3436 @chapter Expressions
3440 @cindex numeric values
3441 An @dfn{expression} specifies an address or numeric value.
3442 Whitespace may precede and/or follow an expression.
3444 The result of an expression must be an absolute number, or else an offset into
3445 a particular section. If an expression is not absolute, and there is not
3446 enough information when @command{@value{AS}} sees the expression to know its
3447 section, a second pass over the source program might be necessary to interpret
3448 the expression---but the second pass is currently not implemented.
3449 @command{@value{AS}} aborts with an error message in this situation.
3452 * Empty Exprs:: Empty Expressions
3453 * Integer Exprs:: Integer Expressions
3457 @section Empty Expressions
3459 @cindex empty expressions
3460 @cindex expressions, empty
3461 An empty expression has no value: it is just whitespace or null.
3462 Wherever an absolute expression is required, you may omit the
3463 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3464 is compatible with other assemblers.
3467 @section Integer Expressions
3469 @cindex integer expressions
3470 @cindex expressions, integer
3471 An @dfn{integer expression} is one or more @emph{arguments} delimited
3472 by @emph{operators}.
3475 * Arguments:: Arguments
3476 * Operators:: Operators
3477 * Prefix Ops:: Prefix Operators
3478 * Infix Ops:: Infix Operators
3482 @subsection Arguments
3484 @cindex expression arguments
3485 @cindex arguments in expressions
3486 @cindex operands in expressions
3487 @cindex arithmetic operands
3488 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3489 contexts arguments are sometimes called ``arithmetic operands''. In
3490 this manual, to avoid confusing them with the ``instruction operands'' of
3491 the machine language, we use the term ``argument'' to refer to parts of
3492 expressions only, reserving the word ``operand'' to refer only to machine
3493 instruction operands.
3495 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3496 @var{section} is one of text, data, bss, absolute,
3497 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3500 Numbers are usually integers.
3502 A number can be a flonum or bignum. In this case, you are warned
3503 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3504 these 32 bits are an integer. You may write integer-manipulating
3505 instructions that act on exotic constants, compatible with other
3508 @cindex subexpressions
3509 Subexpressions are a left parenthesis @samp{(} followed by an integer
3510 expression, followed by a right parenthesis @samp{)}; or a prefix
3511 operator followed by an argument.
3514 @subsection Operators
3516 @cindex operators, in expressions
3517 @cindex arithmetic functions
3518 @cindex functions, in expressions
3519 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3520 operators are followed by an argument. Infix operators appear
3521 between their arguments. Operators may be preceded and/or followed by
3525 @subsection Prefix Operator
3527 @cindex prefix operators
3528 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3529 one argument, which must be absolute.
3531 @c the tex/end tex stuff surrounding this small table is meant to make
3532 @c it align, on the printed page, with the similar table in the next
3533 @c section (which is inside an enumerate).
3535 \global\advance\leftskip by \itemindent
3540 @dfn{Negation}. Two's complement negation.
3542 @dfn{Complementation}. Bitwise not.
3546 \global\advance\leftskip by -\itemindent
3550 @subsection Infix Operators
3552 @cindex infix operators
3553 @cindex operators, permitted arguments
3554 @dfn{Infix operators} take two arguments, one on either side. Operators
3555 have precedence, but operations with equal precedence are performed left
3556 to right. Apart from @code{+} or @option{-}, both arguments must be
3557 absolute, and the result is absolute.
3560 @cindex operator precedence
3561 @cindex precedence of operators
3568 @dfn{Multiplication}.
3571 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3578 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3582 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3586 Intermediate precedence
3591 @dfn{Bitwise Inclusive Or}.
3597 @dfn{Bitwise Exclusive Or}.
3600 @dfn{Bitwise Or Not}.
3607 @cindex addition, permitted arguments
3608 @cindex plus, permitted arguments
3609 @cindex arguments for addition
3611 @dfn{Addition}. If either argument is absolute, the result has the section of
3612 the other argument. You may not add together arguments from different
3615 @cindex subtraction, permitted arguments
3616 @cindex minus, permitted arguments
3617 @cindex arguments for subtraction
3619 @dfn{Subtraction}. If the right argument is absolute, the
3620 result has the section of the left argument.
3621 If both arguments are in the same section, the result is absolute.
3622 You may not subtract arguments from different sections.
3623 @c FIXME is there still something useful to say about undefined - undefined ?
3625 @cindex comparison expressions
3626 @cindex expressions, comparison
3630 @dfn{Is Not Equal To}
3634 @dfn{Is Greater Than}
3636 @dfn{Is Greater Than Or Equal To}
3638 @dfn{Is Less Than Or Equal To}
3640 The comparison operators can be used as infix operators. A true results has a
3641 value of -1 whereas a false result has a value of 0. Note, these operators
3642 perform signed comparisons.
3645 @item Lowest Precedence
3654 These two logical operations can be used to combine the results of sub
3655 expressions. Note, unlike the comparison operators a true result returns a
3656 value of 1 but a false results does still return 0. Also note that the logical
3657 or operator has a slightly lower precedence than logical and.
3662 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3663 address; you can only have a defined section in one of the two arguments.
3666 @chapter Assembler Directives
3668 @cindex directives, machine independent
3669 @cindex pseudo-ops, machine independent
3670 @cindex machine independent directives
3671 All assembler directives have names that begin with a period (@samp{.}).
3672 The rest of the name is letters, usually in lower case.
3674 This chapter discusses directives that are available regardless of the
3675 target machine configuration for the @sc{gnu} assembler.
3677 Some machine configurations provide additional directives.
3678 @xref{Machine Dependencies}.
3681 @ifset machine-directives
3682 @xref{Machine Dependencies} for additional directives.
3687 * Abort:: @code{.abort}
3689 * ABORT:: @code{.ABORT}
3692 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3693 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3694 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3695 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3696 * Byte:: @code{.byte @var{expressions}}
3697 * Comm:: @code{.comm @var{symbol} , @var{length} }
3699 * CFI directives:: @code{.cfi_startproc}, @code{.cfi_endproc}, etc.
3701 * Data:: @code{.data @var{subsection}}
3703 * Def:: @code{.def @var{name}}
3706 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3712 * Double:: @code{.double @var{flonums}}
3713 * Eject:: @code{.eject}
3714 * Else:: @code{.else}
3715 * Elseif:: @code{.elseif}
3718 * Endef:: @code{.endef}
3721 * Endfunc:: @code{.endfunc}
3722 * Endif:: @code{.endif}
3723 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3724 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3726 * Exitm:: @code{.exitm}
3727 * Extern:: @code{.extern}
3728 * Fail:: @code{.fail}
3729 @ifclear no-file-dir
3730 * File:: @code{.file @var{string}}
3733 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3734 * Float:: @code{.float @var{flonums}}
3735 * Func:: @code{.func}
3736 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3738 * Hidden:: @code{.hidden @var{names}}
3741 * hword:: @code{.hword @var{expressions}}
3742 * Ident:: @code{.ident}
3743 * If:: @code{.if @var{absolute expression}}
3744 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
3745 * Include:: @code{.include "@var{file}"}
3746 * Int:: @code{.int @var{expressions}}
3748 * Internal:: @code{.internal @var{names}}
3751 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3752 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3753 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3754 * Lflags:: @code{.lflags}
3755 @ifclear no-line-dir
3756 * Line:: @code{.line @var{line-number}}
3759 * Ln:: @code{.ln @var{line-number}}
3760 * Linkonce:: @code{.linkonce [@var{type}]}
3761 * List:: @code{.list}
3762 * Long:: @code{.long @var{expressions}}
3764 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3767 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3768 * MRI:: @code{.mri @var{val}}
3769 * Nolist:: @code{.nolist}
3770 * Octa:: @code{.octa @var{bignums}}
3771 * Org:: @code{.org @var{new-lc} , @var{fill}}
3772 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
3774 * PopSection:: @code{.popsection}
3775 * Previous:: @code{.previous}
3778 * Print:: @code{.print @var{string}}
3780 * Protected:: @code{.protected @var{names}}
3783 * Psize:: @code{.psize @var{lines}, @var{columns}}
3784 * Purgem:: @code{.purgem @var{name}}
3786 * PushSection:: @code{.pushsection @var{name}}
3789 * Quad:: @code{.quad @var{bignums}}
3790 * Rept:: @code{.rept @var{count}}
3791 * Sbttl:: @code{.sbttl "@var{subheading}"}
3793 * Scl:: @code{.scl @var{class}}
3796 * Section:: @code{.section @var{name}}
3799 * Set:: @code{.set @var{symbol}, @var{expression}}
3800 * Short:: @code{.short @var{expressions}}
3801 * Single:: @code{.single @var{flonums}}
3803 * Size:: @code{.size [@var{name} , @var{expression}]}
3806 * Skip:: @code{.skip @var{size} , @var{fill}}
3807 * Sleb128:: @code{.sleb128 @var{expressions}}
3808 * Space:: @code{.space @var{size} , @var{fill}}
3810 * Stab:: @code{.stabd, .stabn, .stabs}
3813 * String:: @code{.string "@var{str}"}
3814 * Struct:: @code{.struct @var{expression}}
3816 * SubSection:: @code{.subsection}
3817 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3821 * Tag:: @code{.tag @var{structname}}
3824 * Text:: @code{.text @var{subsection}}
3825 * Title:: @code{.title "@var{heading}"}
3827 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
3830 * Uleb128:: @code{.uleb128 @var{expressions}}
3832 * Val:: @code{.val @var{addr}}
3836 * Version:: @code{.version "@var{string}"}
3837 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
3838 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
3839 * Weak:: @code{.weak @var{names}}
3842 * Word:: @code{.word @var{expressions}}
3843 * Deprecated:: Deprecated Directives
3847 @section @code{.abort}
3849 @cindex @code{abort} directive
3850 @cindex stopping the assembly
3851 This directive stops the assembly immediately. It is for
3852 compatibility with other assemblers. The original idea was that the
3853 assembly language source would be piped into the assembler. If the sender
3854 of the source quit, it could use this directive tells @command{@value{AS}} to
3855 quit also. One day @code{.abort} will not be supported.
3859 @section @code{.ABORT}
3861 @cindex @code{ABORT} directive
3862 When producing COFF output, @command{@value{AS}} accepts this directive as a
3863 synonym for @samp{.abort}.
3866 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
3872 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3874 @cindex padding the location counter
3875 @cindex @code{align} directive
3876 Pad the location counter (in the current subsection) to a particular storage
3877 boundary. The first expression (which must be absolute) is the alignment
3878 required, as described below.
3880 The second expression (also absolute) gives the fill value to be stored in the
3881 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3882 padding bytes are normally zero. However, on some systems, if the section is
3883 marked as containing code and the fill value is omitted, the space is filled
3884 with no-op instructions.
3886 The third expression is also absolute, and is also optional. If it is present,
3887 it is the maximum number of bytes that should be skipped by this alignment
3888 directive. If doing the alignment would require skipping more bytes than the
3889 specified maximum, then the alignment is not done at all. You can omit the
3890 fill value (the second argument) entirely by simply using two commas after the
3891 required alignment; this can be useful if you want the alignment to be filled
3892 with no-op instructions when appropriate.
3894 The way the required alignment is specified varies from system to system.
3895 For the a29k, hppa, m68k, m88k, w65, sparc, Xtensa, and Renesas / SuperH SH,
3896 and i386 using ELF format,
3897 the first expression is the
3898 alignment request in bytes. For example @samp{.align 8} advances
3899 the location counter until it is a multiple of 8. If the location counter
3900 is already a multiple of 8, no change is needed.
3902 For other systems, including the i386 using a.out format, and the arm and
3903 strongarm, it is the
3904 number of low-order zero bits the location counter must have after
3905 advancement. For example @samp{.align 3} advances the location
3906 counter until it a multiple of 8. If the location counter is already a
3907 multiple of 8, no change is needed.
3909 This inconsistency is due to the different behaviors of the various
3910 native assemblers for these systems which GAS must emulate.
3911 GAS also provides @code{.balign} and @code{.p2align} directives,
3912 described later, which have a consistent behavior across all
3913 architectures (but are specific to GAS).
3916 @section @code{.ascii "@var{string}"}@dots{}
3918 @cindex @code{ascii} directive
3919 @cindex string literals
3920 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3921 separated by commas. It assembles each string (with no automatic
3922 trailing zero byte) into consecutive addresses.
3925 @section @code{.asciz "@var{string}"}@dots{}
3927 @cindex @code{asciz} directive
3928 @cindex zero-terminated strings
3929 @cindex null-terminated strings
3930 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3931 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3934 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3936 @cindex padding the location counter given number of bytes
3937 @cindex @code{balign} directive
3938 Pad the location counter (in the current subsection) to a particular
3939 storage boundary. The first expression (which must be absolute) is the
3940 alignment request in bytes. For example @samp{.balign 8} advances
3941 the location counter until it is a multiple of 8. If the location counter
3942 is already a multiple of 8, no change is needed.
3944 The second expression (also absolute) gives the fill value to be stored in the
3945 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3946 padding bytes are normally zero. However, on some systems, if the section is
3947 marked as containing code and the fill value is omitted, the space is filled
3948 with no-op instructions.
3950 The third expression is also absolute, and is also optional. If it is present,
3951 it is the maximum number of bytes that should be skipped by this alignment
3952 directive. If doing the alignment would require skipping more bytes than the
3953 specified maximum, then the alignment is not done at all. You can omit the
3954 fill value (the second argument) entirely by simply using two commas after the
3955 required alignment; this can be useful if you want the alignment to be filled
3956 with no-op instructions when appropriate.
3958 @cindex @code{balignw} directive
3959 @cindex @code{balignl} directive
3960 The @code{.balignw} and @code{.balignl} directives are variants of the
3961 @code{.balign} directive. The @code{.balignw} directive treats the fill
3962 pattern as a two byte word value. The @code{.balignl} directives treats the
3963 fill pattern as a four byte longword value. For example, @code{.balignw
3964 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3965 filled in with the value 0x368d (the exact placement of the bytes depends upon
3966 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3970 @section @code{.byte @var{expressions}}
3972 @cindex @code{byte} directive
3973 @cindex integers, one byte
3974 @code{.byte} expects zero or more expressions, separated by commas.
3975 Each expression is assembled into the next byte.
3978 @section @code{.comm @var{symbol} , @var{length} }
3980 @cindex @code{comm} directive
3981 @cindex symbol, common
3982 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
3983 common symbol in one object file may be merged with a defined or common symbol
3984 of the same name in another object file. If @code{@value{LD}} does not see a
3985 definition for the symbol--just one or more common symbols--then it will
3986 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
3987 absolute expression. If @code{@value{LD}} sees multiple common symbols with
3988 the same name, and they do not all have the same size, it will allocate space
3989 using the largest size.
3992 When using ELF, the @code{.comm} directive takes an optional third argument.
3993 This is the desired alignment of the symbol, specified as a byte boundary (for
3994 example, an alignment of 16 means that the least significant 4 bits of the
3995 address should be zero). The alignment must be an absolute expression, and it
3996 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
3997 for the common symbol, it will use the alignment when placing the symbol. If
3998 no alignment is specified, @command{@value{AS}} will set the alignment to the
3999 largest power of two less than or equal to the size of the symbol, up to a
4004 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4005 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4008 @node CFI directives
4009 @section @code{.cfi_startproc}
4010 @cindex @code{cfi_startproc} directive
4011 @code{.cfi_startproc} is used at the beginning of each function that
4012 should have an entry in @code{.eh_frame}. It initializes some internal
4013 data structures and emits architecture dependent initial CFI instructions.
4014 Don't forget to close the function by
4015 @code{.cfi_endproc}.
4017 @section @code{.cfi_endproc}
4018 @cindex @code{cfi_endproc} directive
4019 @code{.cfi_endproc} is used at the end of a function where it closes its
4020 unwind entry previously opened by
4021 @code{.cfi_startproc}. and emits it to @code{.eh_frame}.
4023 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4024 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4025 address from @var{register} and add @var{offset} to it}.
4027 @section @code{.cfi_def_cfa_register @var{register}}
4028 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4029 now on @var{register} will be used instead of the old one. Offset
4032 @section @code{.cfi_def_cfa_offset @var{offset}}
4033 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4034 remains the same, but @var{offset} is new. Note that it is the
4035 absolute offset that will be added to a defined register to compute
4038 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4039 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4040 value that is added/substracted from the previous offset.
4042 @section @code{.cfi_offset @var{register}, @var{offset}}
4043 Previous value of @var{register} is saved at offset @var{offset} from
4046 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4047 Previous value of @var{register} is saved at offset @var{offset} from
4048 the current CFA register. This is transformed to @code{.cfi_offset}
4049 using the known displacement of the CFA register from the CFA.
4050 This is often easier to use, because the number will match the
4051 code it's annotating.
4053 @section @code{.cfi_gnu_window_save}
4054 SPARC register window has been saved.
4056 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4057 Allows the user to add arbitrary bytes to the unwind info. One
4058 might use this to add OS-specific CFI opcodes, or generic CFI
4059 opcodes that GAS does not yet support.
4062 @section @code{.data @var{subsection}}
4064 @cindex @code{data} directive
4065 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4066 end of the data subsection numbered @var{subsection} (which is an
4067 absolute expression). If @var{subsection} is omitted, it defaults
4072 @section @code{.def @var{name}}
4074 @cindex @code{def} directive
4075 @cindex COFF symbols, debugging
4076 @cindex debugging COFF symbols
4077 Begin defining debugging information for a symbol @var{name}; the
4078 definition extends until the @code{.endef} directive is encountered.
4081 This directive is only observed when @command{@value{AS}} is configured for COFF
4082 format output; when producing @code{b.out}, @samp{.def} is recognized,
4089 @section @code{.desc @var{symbol}, @var{abs-expression}}
4091 @cindex @code{desc} directive
4092 @cindex COFF symbol descriptor
4093 @cindex symbol descriptor, COFF
4094 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4095 to the low 16 bits of an absolute expression.
4098 The @samp{.desc} directive is not available when @command{@value{AS}} is
4099 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4100 object format. For the sake of compatibility, @command{@value{AS}} accepts
4101 it, but produces no output, when configured for COFF.
4107 @section @code{.dim}
4109 @cindex @code{dim} directive
4110 @cindex COFF auxiliary symbol information
4111 @cindex auxiliary symbol information, COFF
4112 This directive is generated by compilers to include auxiliary debugging
4113 information in the symbol table. It is only permitted inside
4114 @code{.def}/@code{.endef} pairs.
4117 @samp{.dim} is only meaningful when generating COFF format output; when
4118 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4124 @section @code{.double @var{flonums}}
4126 @cindex @code{double} directive
4127 @cindex floating point numbers (double)
4128 @code{.double} expects zero or more flonums, separated by commas. It
4129 assembles floating point numbers.
4131 The exact kind of floating point numbers emitted depends on how
4132 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4136 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4137 in @sc{ieee} format.
4142 @section @code{.eject}
4144 @cindex @code{eject} directive
4145 @cindex new page, in listings
4146 @cindex page, in listings
4147 @cindex listing control: new page
4148 Force a page break at this point, when generating assembly listings.
4151 @section @code{.else}
4153 @cindex @code{else} directive
4154 @code{.else} is part of the @command{@value{AS}} support for conditional
4155 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
4156 of code to be assembled if the condition for the preceding @code{.if}
4160 @section @code{.elseif}
4162 @cindex @code{elseif} directive
4163 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4164 assembly; @pxref{If,,@code{.if}}. It is shorthand for beginning a new
4165 @code{.if} block that would otherwise fill the entire @code{.else} section.
4168 @section @code{.end}
4170 @cindex @code{end} directive
4171 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4172 process anything in the file past the @code{.end} directive.
4176 @section @code{.endef}
4178 @cindex @code{endef} directive
4179 This directive flags the end of a symbol definition begun with
4183 @samp{.endef} is only meaningful when generating COFF format output; if
4184 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4185 directive but ignores it.
4190 @section @code{.endfunc}
4191 @cindex @code{endfunc} directive
4192 @code{.endfunc} marks the end of a function specified with @code{.func}.
4195 @section @code{.endif}
4197 @cindex @code{endif} directive
4198 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4199 it marks the end of a block of code that is only assembled
4200 conditionally. @xref{If,,@code{.if}}.
4203 @section @code{.equ @var{symbol}, @var{expression}}
4205 @cindex @code{equ} directive
4206 @cindex assigning values to symbols
4207 @cindex symbols, assigning values to
4208 This directive sets the value of @var{symbol} to @var{expression}.
4209 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
4212 The syntax for @code{equ} on the HPPA is
4213 @samp{@var{symbol} .equ @var{expression}}.
4217 @section @code{.equiv @var{symbol}, @var{expression}}
4218 @cindex @code{equiv} directive
4219 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4220 the assembler will signal an error if @var{symbol} is already defined. Note a
4221 symbol which has been referenced but not actually defined is considered to be
4224 Except for the contents of the error message, this is roughly equivalent to
4233 @section @code{.err}
4234 @cindex @code{err} directive
4235 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4236 message and, unless the @option{-Z} option was used, it will not generate an
4237 object file. This can be used to signal error an conditionally compiled code.
4240 @section @code{.exitm}
4241 Exit early from the current macro definition. @xref{Macro}.
4244 @section @code{.extern}
4246 @cindex @code{extern} directive
4247 @code{.extern} is accepted in the source program---for compatibility
4248 with other assemblers---but it is ignored. @command{@value{AS}} treats
4249 all undefined symbols as external.
4252 @section @code{.fail @var{expression}}
4254 @cindex @code{fail} directive
4255 Generates an error or a warning. If the value of the @var{expression} is 500
4256 or more, @command{@value{AS}} will print a warning message. If the value is less
4257 than 500, @command{@value{AS}} will print an error message. The message will
4258 include the value of @var{expression}. This can occasionally be useful inside
4259 complex nested macros or conditional assembly.
4261 @ifclear no-file-dir
4263 @section @code{.file @var{string}}
4265 @cindex @code{file} directive
4266 @cindex logical file name
4267 @cindex file name, logical
4268 @code{.file} tells @command{@value{AS}} that we are about to start a new logical
4269 file. @var{string} is the new file name. In general, the filename is
4270 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4271 to specify an empty file name, you must give the quotes--@code{""}. This
4272 statement may go away in future: it is only recognized to be compatible with
4273 old @command{@value{AS}} programs.
4275 In some configurations of @command{@value{AS}}, @code{.file} has already been
4276 removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}.
4281 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4283 @cindex @code{fill} directive
4284 @cindex writing patterns in memory
4285 @cindex patterns, writing in memory
4286 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4287 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4288 may be zero or more. @var{Size} may be zero or more, but if it is
4289 more than 8, then it is deemed to have the value 8, compatible with
4290 other people's assemblers. The contents of each @var{repeat} bytes
4291 is taken from an 8-byte number. The highest order 4 bytes are
4292 zero. The lowest order 4 bytes are @var{value} rendered in the
4293 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4294 Each @var{size} bytes in a repetition is taken from the lowest order
4295 @var{size} bytes of this number. Again, this bizarre behavior is
4296 compatible with other people's assemblers.
4298 @var{size} and @var{value} are optional.
4299 If the second comma and @var{value} are absent, @var{value} is
4300 assumed zero. If the first comma and following tokens are absent,
4301 @var{size} is assumed to be 1.
4304 @section @code{.float @var{flonums}}
4306 @cindex floating point numbers (single)
4307 @cindex @code{float} directive
4308 This directive assembles zero or more flonums, separated by commas. It
4309 has the same effect as @code{.single}.
4311 The exact kind of floating point numbers emitted depends on how
4312 @command{@value{AS}} is configured.
4313 @xref{Machine Dependencies}.
4317 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4318 in @sc{ieee} format.
4323 @section @code{.func @var{name}[,@var{label}]}
4324 @cindex @code{func} directive
4325 @code{.func} emits debugging information to denote function @var{name}, and
4326 is ignored unless the file is assembled with debugging enabled.
4327 Only @samp{--gstabs} is currently supported.
4328 @var{label} is the entry point of the function and if omitted @var{name}
4329 prepended with the @samp{leading char} is used.
4330 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4331 All functions are currently defined to have @code{void} return type.
4332 The function must be terminated with @code{.endfunc}.
4335 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4337 @cindex @code{global} directive
4338 @cindex symbol, making visible to linker
4339 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4340 @var{symbol} in your partial program, its value is made available to
4341 other partial programs that are linked with it. Otherwise,
4342 @var{symbol} takes its attributes from a symbol of the same name
4343 from another file linked into the same program.
4345 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4346 compatibility with other assemblers.
4349 On the HPPA, @code{.global} is not always enough to make it accessible to other
4350 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4351 @xref{HPPA Directives,, HPPA Assembler Directives}.
4356 @section @code{.hidden @var{names}}
4358 @cindex @code{hidden} directive
4360 This one of the ELF visibility directives. The other two are
4361 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4362 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4364 This directive overrides the named symbols default visibility (which is set by
4365 their binding: local, global or weak). The directive sets the visibility to
4366 @code{hidden} which means that the symbols are not visible to other components.
4367 Such symbols are always considered to be @code{protected} as well.
4371 @section @code{.hword @var{expressions}}
4373 @cindex @code{hword} directive
4374 @cindex integers, 16-bit
4375 @cindex numbers, 16-bit
4376 @cindex sixteen bit integers
4377 This expects zero or more @var{expressions}, and emits
4378 a 16 bit number for each.
4381 This directive is a synonym for @samp{.short}; depending on the target
4382 architecture, it may also be a synonym for @samp{.word}.
4386 This directive is a synonym for @samp{.short}.
4389 This directive is a synonym for both @samp{.short} and @samp{.word}.
4394 @section @code{.ident}
4396 @cindex @code{ident} directive
4397 This directive is used by some assemblers to place tags in object files.
4398 @command{@value{AS}} simply accepts the directive for source-file
4399 compatibility with such assemblers, but does not actually emit anything
4403 @section @code{.if @var{absolute expression}}
4405 @cindex conditional assembly
4406 @cindex @code{if} directive
4407 @code{.if} marks the beginning of a section of code which is only
4408 considered part of the source program being assembled if the argument
4409 (which must be an @var{absolute expression}) is non-zero. The end of
4410 the conditional section of code must be marked by @code{.endif}
4411 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4412 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4413 If you have several conditions to check, @code{.elseif} may be used to avoid
4414 nesting blocks if/else within each subsequent @code{.else} block.
4416 The following variants of @code{.if} are also supported:
4418 @cindex @code{ifdef} directive
4419 @item .ifdef @var{symbol}
4420 Assembles the following section of code if the specified @var{symbol}
4421 has been defined. Note a symbol which has been referenced but not yet defined
4422 is considered to be undefined.
4424 @cindex @code{ifc} directive
4425 @item .ifc @var{string1},@var{string2}
4426 Assembles the following section of code if the two strings are the same. The
4427 strings may be optionally quoted with single quotes. If they are not quoted,
4428 the first string stops at the first comma, and the second string stops at the
4429 end of the line. Strings which contain whitespace should be quoted. The
4430 string comparison is case sensitive.
4432 @cindex @code{ifeq} directive
4433 @item .ifeq @var{absolute expression}
4434 Assembles the following section of code if the argument is zero.
4436 @cindex @code{ifeqs} directive
4437 @item .ifeqs @var{string1},@var{string2}
4438 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4440 @cindex @code{ifge} directive
4441 @item .ifge @var{absolute expression}
4442 Assembles the following section of code if the argument is greater than or
4445 @cindex @code{ifgt} directive
4446 @item .ifgt @var{absolute expression}
4447 Assembles the following section of code if the argument is greater than zero.
4449 @cindex @code{ifle} directive
4450 @item .ifle @var{absolute expression}
4451 Assembles the following section of code if the argument is less than or equal
4454 @cindex @code{iflt} directive
4455 @item .iflt @var{absolute expression}
4456 Assembles the following section of code if the argument is less than zero.
4458 @cindex @code{ifnc} directive
4459 @item .ifnc @var{string1},@var{string2}.
4460 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4461 following section of code if the two strings are not the same.
4463 @cindex @code{ifndef} directive
4464 @cindex @code{ifnotdef} directive
4465 @item .ifndef @var{symbol}
4466 @itemx .ifnotdef @var{symbol}
4467 Assembles the following section of code if the specified @var{symbol}
4468 has not been defined. Both spelling variants are equivalent. Note a symbol
4469 which has been referenced but not yet defined is considered to be undefined.
4471 @cindex @code{ifne} directive
4472 @item .ifne @var{absolute expression}
4473 Assembles the following section of code if the argument is not equal to zero
4474 (in other words, this is equivalent to @code{.if}).
4476 @cindex @code{ifnes} directive
4477 @item .ifnes @var{string1},@var{string2}
4478 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4479 following section of code if the two strings are not the same.
4483 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4485 @cindex @code{incbin} directive
4486 @cindex binary files, including
4487 The @code{incbin} directive includes @var{file} verbatim at the current
4488 location. You can control the search paths used with the @samp{-I} command-line
4489 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4492 The @var{skip} argument skips a number of bytes from the start of the
4493 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4494 read. Note that the data is not aligned in any way, so it is the user's
4495 responsibility to make sure that proper alignment is provided both before and
4496 after the @code{incbin} directive.
4499 @section @code{.include "@var{file}"}
4501 @cindex @code{include} directive
4502 @cindex supporting files, including
4503 @cindex files, including
4504 This directive provides a way to include supporting files at specified
4505 points in your source program. The code from @var{file} is assembled as
4506 if it followed the point of the @code{.include}; when the end of the
4507 included file is reached, assembly of the original file continues. You
4508 can control the search paths used with the @samp{-I} command-line option
4509 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4513 @section @code{.int @var{expressions}}
4515 @cindex @code{int} directive
4516 @cindex integers, 32-bit
4517 Expect zero or more @var{expressions}, of any section, separated by commas.
4518 For each expression, emit a number that, at run time, is the value of that
4519 expression. The byte order and bit size of the number depends on what kind
4520 of target the assembly is for.
4524 On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit
4525 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
4532 @section @code{.internal @var{names}}
4534 @cindex @code{internal} directive
4536 This one of the ELF visibility directives. The other two are
4537 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4538 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4540 This directive overrides the named symbols default visibility (which is set by
4541 their binding: local, global or weak). The directive sets the visibility to
4542 @code{internal} which means that the symbols are considered to be @code{hidden}
4543 (i.e., not visible to other components), and that some extra, processor specific
4544 processing must also be performed upon the symbols as well.
4548 @section @code{.irp @var{symbol},@var{values}}@dots{}
4550 @cindex @code{irp} directive
4551 Evaluate a sequence of statements assigning different values to @var{symbol}.
4552 The sequence of statements starts at the @code{.irp} directive, and is
4553 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4554 set to @var{value}, and the sequence of statements is assembled. If no
4555 @var{value} is listed, the sequence of statements is assembled once, with
4556 @var{symbol} set to the null string. To refer to @var{symbol} within the
4557 sequence of statements, use @var{\symbol}.
4559 For example, assembling
4567 is equivalent to assembling
4576 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4578 @cindex @code{irpc} directive
4579 Evaluate a sequence of statements assigning different values to @var{symbol}.
4580 The sequence of statements starts at the @code{.irpc} directive, and is
4581 terminated by an @code{.endr} directive. For each character in @var{value},
4582 @var{symbol} is set to the character, and the sequence of statements is
4583 assembled. If no @var{value} is listed, the sequence of statements is
4584 assembled once, with @var{symbol} set to the null string. To refer to
4585 @var{symbol} within the sequence of statements, use @var{\symbol}.
4587 For example, assembling
4595 is equivalent to assembling
4604 @section @code{.lcomm @var{symbol} , @var{length}}
4606 @cindex @code{lcomm} directive
4607 @cindex local common symbols
4608 @cindex symbols, local common
4609 Reserve @var{length} (an absolute expression) bytes for a local common
4610 denoted by @var{symbol}. The section and value of @var{symbol} are
4611 those of the new local common. The addresses are allocated in the bss
4612 section, so that at run-time the bytes start off zeroed. @var{Symbol}
4613 is not declared global (@pxref{Global,,@code{.global}}), so is normally
4614 not visible to @code{@value{LD}}.
4617 Some targets permit a third argument to be used with @code{.lcomm}. This
4618 argument specifies the desired alignment of the symbol in the bss section.
4622 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
4623 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
4627 @section @code{.lflags}
4629 @cindex @code{lflags} directive (ignored)
4630 @command{@value{AS}} accepts this directive, for compatibility with other
4631 assemblers, but ignores it.
4633 @ifclear no-line-dir
4635 @section @code{.line @var{line-number}}
4637 @cindex @code{line} directive
4641 @section @code{.ln @var{line-number}}
4643 @cindex @code{ln} directive
4645 @cindex logical line number
4647 Change the logical line number. @var{line-number} must be an absolute
4648 expression. The next line has that logical line number. Therefore any other
4649 statements on the current line (after a statement separator character) are
4650 reported as on logical line number @var{line-number} @minus{} 1. One day
4651 @command{@value{AS}} will no longer support this directive: it is recognized only
4652 for compatibility with existing assembler programs.
4656 @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is
4657 not available; use the synonym @code{.ln} in that context.
4662 @ifclear no-line-dir
4663 Even though this is a directive associated with the @code{a.out} or
4664 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
4665 when producing COFF output, and treats @samp{.line} as though it
4666 were the COFF @samp{.ln} @emph{if} it is found outside a
4667 @code{.def}/@code{.endef} pair.
4669 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
4670 used by compilers to generate auxiliary symbol information for
4675 @section @code{.linkonce [@var{type}]}
4677 @cindex @code{linkonce} directive
4678 @cindex common sections
4679 Mark the current section so that the linker only includes a single copy of it.
4680 This may be used to include the same section in several different object files,
4681 but ensure that the linker will only include it once in the final output file.
4682 The @code{.linkonce} pseudo-op must be used for each instance of the section.
4683 Duplicate sections are detected based on the section name, so it should be
4686 This directive is only supported by a few object file formats; as of this
4687 writing, the only object file format which supports it is the Portable
4688 Executable format used on Windows NT.
4690 The @var{type} argument is optional. If specified, it must be one of the
4691 following strings. For example:
4695 Not all types may be supported on all object file formats.
4699 Silently discard duplicate sections. This is the default.
4702 Warn if there are duplicate sections, but still keep only one copy.
4705 Warn if any of the duplicates have different sizes.
4708 Warn if any of the duplicates do not have exactly the same contents.
4712 @section @code{.ln @var{line-number}}
4714 @cindex @code{ln} directive
4715 @ifclear no-line-dir
4716 @samp{.ln} is a synonym for @samp{.line}.
4719 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
4720 must be an absolute expression. The next line has that logical
4721 line number, so any other statements on the current line (after a
4722 statement separator character @code{;}) are reported as on logical
4723 line number @var{line-number} @minus{} 1.
4726 This directive is accepted, but ignored, when @command{@value{AS}} is
4727 configured for @code{b.out}; its effect is only associated with COFF
4733 @section @code{.mri @var{val}}
4735 @cindex @code{mri} directive
4736 @cindex MRI mode, temporarily
4737 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
4738 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
4739 affects code assembled until the next @code{.mri} directive, or until the end
4740 of the file. @xref{M, MRI mode, MRI mode}.
4743 @section @code{.list}
4745 @cindex @code{list} directive
4746 @cindex listing control, turning on
4747 Control (in conjunction with the @code{.nolist} directive) whether or
4748 not assembly listings are generated. These two directives maintain an
4749 internal counter (which is zero initially). @code{.list} increments the
4750 counter, and @code{.nolist} decrements it. Assembly listings are
4751 generated whenever the counter is greater than zero.
4753 By default, listings are disabled. When you enable them (with the
4754 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
4755 the initial value of the listing counter is one.
4758 @section @code{.long @var{expressions}}
4760 @cindex @code{long} directive
4761 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
4764 @c no one seems to know what this is for or whether this description is
4765 @c what it really ought to do
4767 @section @code{.lsym @var{symbol}, @var{expression}}
4769 @cindex @code{lsym} directive
4770 @cindex symbol, not referenced in assembly
4771 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
4772 the hash table, ensuring it cannot be referenced by name during the
4773 rest of the assembly. This sets the attributes of the symbol to be
4774 the same as the expression value:
4776 @var{other} = @var{descriptor} = 0
4777 @var{type} = @r{(section of @var{expression})}
4778 @var{value} = @var{expression}
4781 The new symbol is not flagged as external.
4785 @section @code{.macro}
4788 The commands @code{.macro} and @code{.endm} allow you to define macros that
4789 generate assembly output. For example, this definition specifies a macro
4790 @code{sum} that puts a sequence of numbers into memory:
4793 .macro sum from=0, to=5
4802 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
4814 @item .macro @var{macname}
4815 @itemx .macro @var{macname} @var{macargs} @dots{}
4816 @cindex @code{macro} directive
4817 Begin the definition of a macro called @var{macname}. If your macro
4818 definition requires arguments, specify their names after the macro name,
4819 separated by commas or spaces. You can supply a default value for any
4820 macro argument by following the name with @samp{=@var{deflt}}. For
4821 example, these are all valid @code{.macro} statements:
4825 Begin the definition of a macro called @code{comm}, which takes no
4828 @item .macro plus1 p, p1
4829 @itemx .macro plus1 p p1
4830 Either statement begins the definition of a macro called @code{plus1},
4831 which takes two arguments; within the macro definition, write
4832 @samp{\p} or @samp{\p1} to evaluate the arguments.
4834 @item .macro reserve_str p1=0 p2
4835 Begin the definition of a macro called @code{reserve_str}, with two
4836 arguments. The first argument has a default value, but not the second.
4837 After the definition is complete, you can call the macro either as
4838 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
4839 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
4840 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
4841 @samp{0}, and @samp{\p2} evaluating to @var{b}).
4844 When you call a macro, you can specify the argument values either by
4845 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
4846 @samp{sum to=17, from=9}.
4849 @cindex @code{endm} directive
4850 Mark the end of a macro definition.
4853 @cindex @code{exitm} directive
4854 Exit early from the current macro definition.
4856 @cindex number of macros executed
4857 @cindex macros, count executed
4859 @command{@value{AS}} maintains a counter of how many macros it has
4860 executed in this pseudo-variable; you can copy that number to your
4861 output with @samp{\@@}, but @emph{only within a macro definition}.
4864 @item LOCAL @var{name} [ , @dots{} ]
4865 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
4866 macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,,
4867 Alternate macro syntax}.
4869 Generate a string replacement for each of the @var{name} arguments, and
4870 replace any instances of @var{name} in each macro expansion. The
4871 replacement string is unique in the assembly, and different for each
4872 separate macro expansion. @code{LOCAL} allows you to write macros that
4873 define symbols, without fear of conflict between separate macro expansions.
4878 @section @code{.nolist}
4880 @cindex @code{nolist} directive
4881 @cindex listing control, turning off
4882 Control (in conjunction with the @code{.list} directive) whether or
4883 not assembly listings are generated. These two directives maintain an
4884 internal counter (which is zero initially). @code{.list} increments the
4885 counter, and @code{.nolist} decrements it. Assembly listings are
4886 generated whenever the counter is greater than zero.
4889 @section @code{.octa @var{bignums}}
4891 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
4892 @cindex @code{octa} directive
4893 @cindex integer, 16-byte
4894 @cindex sixteen byte integer
4895 This directive expects zero or more bignums, separated by commas. For each
4896 bignum, it emits a 16-byte integer.
4898 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
4899 hence @emph{octa}-word for 16 bytes.
4902 @section @code{.org @var{new-lc} , @var{fill}}
4904 @cindex @code{org} directive
4905 @cindex location counter, advancing
4906 @cindex advancing location counter
4907 @cindex current address, advancing
4908 Advance the location counter of the current section to
4909 @var{new-lc}. @var{new-lc} is either an absolute expression or an
4910 expression with the same section as the current subsection. That is,
4911 you can't use @code{.org} to cross sections: if @var{new-lc} has the
4912 wrong section, the @code{.org} directive is ignored. To be compatible
4913 with former assemblers, if the section of @var{new-lc} is absolute,
4914 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
4915 is the same as the current subsection.
4917 @code{.org} may only increase the location counter, or leave it
4918 unchanged; you cannot use @code{.org} to move the location counter
4921 @c double negative used below "not undefined" because this is a specific
4922 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
4923 @c section. doc@cygnus.com 18feb91
4924 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
4925 may not be undefined. If you really detest this restriction we eagerly await
4926 a chance to share your improved assembler.
4928 Beware that the origin is relative to the start of the section, not
4929 to the start of the subsection. This is compatible with other
4930 people's assemblers.
4932 When the location counter (of the current subsection) is advanced, the
4933 intervening bytes are filled with @var{fill} which should be an
4934 absolute expression. If the comma and @var{fill} are omitted,
4935 @var{fill} defaults to zero.
4938 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4940 @cindex padding the location counter given a power of two
4941 @cindex @code{p2align} directive
4942 Pad the location counter (in the current subsection) to a particular
4943 storage boundary. The first expression (which must be absolute) is the
4944 number of low-order zero bits the location counter must have after
4945 advancement. For example @samp{.p2align 3} advances the location
4946 counter until it a multiple of 8. If the location counter is already a
4947 multiple of 8, no change is needed.
4949 The second expression (also absolute) gives the fill value to be stored in the
4950 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4951 padding bytes are normally zero. However, on some systems, if the section is
4952 marked as containing code and the fill value is omitted, the space is filled
4953 with no-op instructions.
4955 The third expression is also absolute, and is also optional. If it is present,
4956 it is the maximum number of bytes that should be skipped by this alignment
4957 directive. If doing the alignment would require skipping more bytes than the
4958 specified maximum, then the alignment is not done at all. You can omit the
4959 fill value (the second argument) entirely by simply using two commas after the
4960 required alignment; this can be useful if you want the alignment to be filled
4961 with no-op instructions when appropriate.
4963 @cindex @code{p2alignw} directive
4964 @cindex @code{p2alignl} directive
4965 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
4966 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
4967 pattern as a two byte word value. The @code{.p2alignl} directives treats the
4968 fill pattern as a four byte longword value. For example, @code{.p2alignw
4969 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4970 filled in with the value 0x368d (the exact placement of the bytes depends upon
4971 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4976 @section @code{.previous}
4978 @cindex @code{previous} directive
4979 @cindex Section Stack
4980 This is one of the ELF section stack manipulation directives. The others are
4981 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4982 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
4983 (@pxref{PopSection}).
4985 This directive swaps the current section (and subsection) with most recently
4986 referenced section (and subsection) prior to this one. Multiple
4987 @code{.previous} directives in a row will flip between two sections (and their
4990 In terms of the section stack, this directive swaps the current section with
4991 the top section on the section stack.
4996 @section @code{.popsection}
4998 @cindex @code{popsection} directive
4999 @cindex Section Stack
5000 This is one of the ELF section stack manipulation directives. The others are
5001 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5002 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5005 This directive replaces the current section (and subsection) with the top
5006 section (and subsection) on the section stack. This section is popped off the
5011 @section @code{.print @var{string}}
5013 @cindex @code{print} directive
5014 @command{@value{AS}} will print @var{string} on the standard output during
5015 assembly. You must put @var{string} in double quotes.
5019 @section @code{.protected @var{names}}
5021 @cindex @code{protected} directive
5023 This one of the ELF visibility directives. The other two are
5024 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5026 This directive overrides the named symbols default visibility (which is set by
5027 their binding: local, global or weak). The directive sets the visibility to
5028 @code{protected} which means that any references to the symbols from within the
5029 components that defines them must be resolved to the definition in that
5030 component, even if a definition in another component would normally preempt
5035 @section @code{.psize @var{lines} , @var{columns}}
5037 @cindex @code{psize} directive
5038 @cindex listing control: paper size
5039 @cindex paper size, for listings
5040 Use this directive to declare the number of lines---and, optionally, the
5041 number of columns---to use for each page, when generating listings.
5043 If you do not use @code{.psize}, listings use a default line-count
5044 of 60. You may omit the comma and @var{columns} specification; the
5045 default width is 200 columns.
5047 @command{@value{AS}} generates formfeeds whenever the specified number of
5048 lines is exceeded (or whenever you explicitly request one, using
5051 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5052 those explicitly specified with @code{.eject}.
5055 @section @code{.purgem @var{name}}
5057 @cindex @code{purgem} directive
5058 Undefine the macro @var{name}, so that later uses of the string will not be
5059 expanded. @xref{Macro}.
5063 @section @code{.pushsection @var{name} , @var{subsection}}
5065 @cindex @code{pushsection} directive
5066 @cindex Section Stack
5067 This is one of the ELF section stack manipulation directives. The others are
5068 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5069 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5072 This directive is a synonym for @code{.section}. It pushes the current section
5073 (and subsection) onto the top of the section stack, and then replaces the
5074 current section and subsection with @code{name} and @code{subsection}.
5078 @section @code{.quad @var{bignums}}
5080 @cindex @code{quad} directive
5081 @code{.quad} expects zero or more bignums, separated by commas. For
5082 each bignum, it emits
5084 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5085 warning message; and just takes the lowest order 8 bytes of the bignum.
5086 @cindex eight-byte integer
5087 @cindex integer, 8-byte
5089 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5090 hence @emph{quad}-word for 8 bytes.
5093 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5094 warning message; and just takes the lowest order 16 bytes of the bignum.
5095 @cindex sixteen-byte integer
5096 @cindex integer, 16-byte
5100 @section @code{.rept @var{count}}
5102 @cindex @code{rept} directive
5103 Repeat the sequence of lines between the @code{.rept} directive and the next
5104 @code{.endr} directive @var{count} times.
5106 For example, assembling
5114 is equivalent to assembling
5123 @section @code{.sbttl "@var{subheading}"}
5125 @cindex @code{sbttl} directive
5126 @cindex subtitles for listings
5127 @cindex listing control: subtitle
5128 Use @var{subheading} as the title (third line, immediately after the
5129 title line) when generating assembly listings.
5131 This directive affects subsequent pages, as well as the current page if
5132 it appears within ten lines of the top of a page.
5136 @section @code{.scl @var{class}}
5138 @cindex @code{scl} directive
5139 @cindex symbol storage class (COFF)
5140 @cindex COFF symbol storage class
5141 Set the storage-class value for a symbol. This directive may only be
5142 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5143 whether a symbol is static or external, or it may record further
5144 symbolic debugging information.
5147 The @samp{.scl} directive is primarily associated with COFF output; when
5148 configured to generate @code{b.out} output format, @command{@value{AS}}
5149 accepts this directive but ignores it.
5155 @section @code{.section @var{name}}
5157 @cindex named section
5158 Use the @code{.section} directive to assemble the following code into a section
5161 This directive is only supported for targets that actually support arbitrarily
5162 named sections; on @code{a.out} targets, for example, it is not accepted, even
5163 with a standard @code{a.out} section name.
5167 @c only print the extra heading if both COFF and ELF are set
5168 @subheading COFF Version
5171 @cindex @code{section} directive (COFF version)
5172 For COFF targets, the @code{.section} directive is used in one of the following
5176 .section @var{name}[, "@var{flags}"]
5177 .section @var{name}[, @var{subsegment}]
5180 If the optional argument is quoted, it is taken as flags to use for the
5181 section. Each flag is a single character. The following flags are recognized:
5184 bss section (uninitialized data)
5186 section is not loaded
5196 shared section (meaningful for PE targets)
5198 ignored. (For compatibility with the ELF version)
5201 If no flags are specified, the default flags depend upon the section name. If
5202 the section name is not recognized, the default will be for the section to be
5203 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5204 from the section, rather than adding them, so if they are used on their own it
5205 will be as if no flags had been specified at all.
5207 If the optional argument to the @code{.section} directive is not quoted, it is
5208 taken as a subsegment number (@pxref{Sub-Sections}).
5213 @c only print the extra heading if both COFF and ELF are set
5214 @subheading ELF Version
5217 @cindex Section Stack
5218 This is one of the ELF section stack manipulation directives. The others are
5219 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5220 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5221 @code{.previous} (@pxref{Previous}).
5223 @cindex @code{section} directive (ELF version)
5224 For ELF targets, the @code{.section} directive is used like this:
5227 .section @var{name} [, "@var{flags}"[, @@@var{type}[, @@@var{entsize}]]]
5230 The optional @var{flags} argument is a quoted string which may contain any
5231 combination of the following characters:
5234 section is allocatable
5238 section is executable
5240 section is mergeable
5242 section contains zero terminated strings
5245 The optional @var{type} argument may contain one of the following constants:
5248 section contains data
5250 section does not contain data (i.e., section only occupies space)
5253 Note on targets where the @code{@@} character is the start of a comment (eg
5254 ARM) then another character is used instead. For example the ARM port uses the
5257 If @var{flags} contains @code{M} flag, @var{type} argument must be specified
5258 as well as @var{entsize} argument. Sections with @code{M} flag but not
5259 @code{S} flag must contain fixed size constants, each @var{entsize} octets
5260 long. Sections with both @code{M} and @code{S} must contain zero terminated
5261 strings where each character is @var{entsize} bytes long. The linker may remove
5262 duplicates within sections with the same name, same entity size and same flags.
5264 If no flags are specified, the default flags depend upon the section name. If
5265 the section name is not recognized, the default will be for the section to have
5266 none of the above flags: it will not be allocated in memory, nor writable, nor
5267 executable. The section will contain data.
5269 For ELF targets, the assembler supports another type of @code{.section}
5270 directive for compatibility with the Solaris assembler:
5273 .section "@var{name}"[, @var{flags}...]
5276 Note that the section name is quoted. There may be a sequence of comma
5280 section is allocatable
5284 section is executable
5287 This directive replaces the current section and subsection. The replaced
5288 section and subsection are pushed onto the section stack. See the contents of
5289 the gas testsuite directory @code{gas/testsuite/gas/elf} for some examples of
5290 how this directive and the other section stack directives work.
5295 @section @code{.set @var{symbol}, @var{expression}}
5297 @cindex @code{set} directive
5298 @cindex symbol value, setting
5299 Set the value of @var{symbol} to @var{expression}. This
5300 changes @var{symbol}'s value and type to conform to
5301 @var{expression}. If @var{symbol} was flagged as external, it remains
5302 flagged (@pxref{Symbol Attributes}).
5304 You may @code{.set} a symbol many times in the same assembly.
5306 If you @code{.set} a global symbol, the value stored in the object
5307 file is the last value stored into it.
5310 The syntax for @code{set} on the HPPA is
5311 @samp{@var{symbol} .set @var{expression}}.
5315 @section @code{.short @var{expressions}}
5317 @cindex @code{short} directive
5319 @code{.short} is normally the same as @samp{.word}.
5320 @xref{Word,,@code{.word}}.
5322 In some configurations, however, @code{.short} and @code{.word} generate
5323 numbers of different lengths; @pxref{Machine Dependencies}.
5327 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
5330 This expects zero or more @var{expressions}, and emits
5331 a 16 bit number for each.
5336 @section @code{.single @var{flonums}}
5338 @cindex @code{single} directive
5339 @cindex floating point numbers (single)
5340 This directive assembles zero or more flonums, separated by commas. It
5341 has the same effect as @code{.float}.
5343 The exact kind of floating point numbers emitted depends on how
5344 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5348 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
5349 numbers in @sc{ieee} format.
5355 @section @code{.size}
5357 This directive is used to set the size associated with a symbol.
5361 @c only print the extra heading if both COFF and ELF are set
5362 @subheading COFF Version
5365 @cindex @code{size} directive (COFF version)
5366 For COFF targets, the @code{.size} directive is only permitted inside
5367 @code{.def}/@code{.endef} pairs. It is used like this:
5370 .size @var{expression}
5374 @samp{.size} is only meaningful when generating COFF format output; when
5375 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5382 @c only print the extra heading if both COFF and ELF are set
5383 @subheading ELF Version
5386 @cindex @code{size} directive (ELF version)
5387 For ELF targets, the @code{.size} directive is used like this:
5390 .size @var{name} , @var{expression}
5393 This directive sets the size associated with a symbol @var{name}.
5394 The size in bytes is computed from @var{expression} which can make use of label
5395 arithmetic. This directive is typically used to set the size of function
5401 @section @code{.sleb128 @var{expressions}}
5403 @cindex @code{sleb128} directive
5404 @var{sleb128} stands for ``signed little endian base 128.'' This is a
5405 compact, variable length representation of numbers used by the DWARF
5406 symbolic debugging format. @xref{Uleb128,@code{.uleb128}}.
5408 @ifclear no-space-dir
5410 @section @code{.skip @var{size} , @var{fill}}
5412 @cindex @code{skip} directive
5413 @cindex filling memory
5414 This directive emits @var{size} bytes, each of value @var{fill}. Both
5415 @var{size} and @var{fill} are absolute expressions. If the comma and
5416 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
5420 @section @code{.space @var{size} , @var{fill}}
5422 @cindex @code{space} directive
5423 @cindex filling memory
5424 This directive emits @var{size} bytes, each of value @var{fill}. Both
5425 @var{size} and @var{fill} are absolute expressions. If the comma
5426 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
5431 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
5432 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
5433 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
5434 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
5443 @section @code{.space}
5444 @cindex @code{space} directive
5446 On the AMD 29K, this directive is ignored; it is accepted for
5447 compatibility with other AMD 29K assemblers.
5450 @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive
5451 @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}.
5457 @section @code{.stabd, .stabn, .stabs}
5459 @cindex symbolic debuggers, information for
5460 @cindex @code{stab@var{x}} directives
5461 There are three directives that begin @samp{.stab}.
5462 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
5463 The symbols are not entered in the @command{@value{AS}} hash table: they
5464 cannot be referenced elsewhere in the source file.
5465 Up to five fields are required:
5469 This is the symbol's name. It may contain any character except
5470 @samp{\000}, so is more general than ordinary symbol names. Some
5471 debuggers used to code arbitrarily complex structures into symbol names
5475 An absolute expression. The symbol's type is set to the low 8 bits of
5476 this expression. Any bit pattern is permitted, but @code{@value{LD}}
5477 and debuggers choke on silly bit patterns.
5480 An absolute expression. The symbol's ``other'' attribute is set to the
5481 low 8 bits of this expression.
5484 An absolute expression. The symbol's descriptor is set to the low 16
5485 bits of this expression.
5488 An absolute expression which becomes the symbol's value.
5491 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
5492 or @code{.stabs} statement, the symbol has probably already been created;
5493 you get a half-formed symbol in your object file. This is
5494 compatible with earlier assemblers!
5497 @cindex @code{stabd} directive
5498 @item .stabd @var{type} , @var{other} , @var{desc}
5500 The ``name'' of the symbol generated is not even an empty string.
5501 It is a null pointer, for compatibility. Older assemblers used a
5502 null pointer so they didn't waste space in object files with empty
5505 The symbol's value is set to the location counter,
5506 relocatably. When your program is linked, the value of this symbol
5507 is the address of the location counter when the @code{.stabd} was
5510 @cindex @code{stabn} directive
5511 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
5512 The name of the symbol is set to the empty string @code{""}.
5514 @cindex @code{stabs} directive
5515 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
5516 All five fields are specified.
5522 @section @code{.string} "@var{str}"
5524 @cindex string, copying to object file
5525 @cindex @code{string} directive
5527 Copy the characters in @var{str} to the object file. You may specify more than
5528 one string to copy, separated by commas. Unless otherwise specified for a
5529 particular machine, the assembler marks the end of each string with a 0 byte.
5530 You can use any of the escape sequences described in @ref{Strings,,Strings}.
5533 @section @code{.struct @var{expression}}
5535 @cindex @code{struct} directive
5536 Switch to the absolute section, and set the section offset to @var{expression},
5537 which must be an absolute expression. You might use this as follows:
5546 This would define the symbol @code{field1} to have the value 0, the symbol
5547 @code{field2} to have the value 4, and the symbol @code{field3} to have the
5548 value 8. Assembly would be left in the absolute section, and you would need to
5549 use a @code{.section} directive of some sort to change to some other section
5550 before further assembly.
5554 @section @code{.subsection @var{name}}
5556 @cindex @code{subsection} directive
5557 @cindex Section Stack
5558 This is one of the ELF section stack manipulation directives. The others are
5559 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
5560 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5563 This directive replaces the current subsection with @code{name}. The current
5564 section is not changed. The replaced subsection is put onto the section stack
5565 in place of the then current top of stack subsection.
5570 @section @code{.symver}
5571 @cindex @code{symver} directive
5572 @cindex symbol versioning
5573 @cindex versions of symbols
5574 Use the @code{.symver} directive to bind symbols to specific version nodes
5575 within a source file. This is only supported on ELF platforms, and is
5576 typically used when assembling files to be linked into a shared library.
5577 There are cases where it may make sense to use this in objects to be bound
5578 into an application itself so as to override a versioned symbol from a
5581 For ELF targets, the @code{.symver} directive can be used like this:
5583 .symver @var{name}, @var{name2@@nodename}
5585 If the symbol @var{name} is defined within the file
5586 being assembled, the @code{.symver} directive effectively creates a symbol
5587 alias with the name @var{name2@@nodename}, and in fact the main reason that we
5588 just don't try and create a regular alias is that the @var{@@} character isn't
5589 permitted in symbol names. The @var{name2} part of the name is the actual name
5590 of the symbol by which it will be externally referenced. The name @var{name}
5591 itself is merely a name of convenience that is used so that it is possible to
5592 have definitions for multiple versions of a function within a single source
5593 file, and so that the compiler can unambiguously know which version of a
5594 function is being mentioned. The @var{nodename} portion of the alias should be
5595 the name of a node specified in the version script supplied to the linker when
5596 building a shared library. If you are attempting to override a versioned
5597 symbol from a shared library, then @var{nodename} should correspond to the
5598 nodename of the symbol you are trying to override.
5600 If the symbol @var{name} is not defined within the file being assembled, all
5601 references to @var{name} will be changed to @var{name2@@nodename}. If no
5602 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
5605 Another usage of the @code{.symver} directive is:
5607 .symver @var{name}, @var{name2@@@@nodename}
5609 In this case, the symbol @var{name} must exist and be defined within
5610 the file being assembled. It is similar to @var{name2@@nodename}. The
5611 difference is @var{name2@@@@nodename} will also be used to resolve
5612 references to @var{name2} by the linker.
5614 The third usage of the @code{.symver} directive is:
5616 .symver @var{name}, @var{name2@@@@@@nodename}
5618 When @var{name} is not defined within the
5619 file being assembled, it is treated as @var{name2@@nodename}. When
5620 @var{name} is defined within the file being assembled, the symbol
5621 name, @var{name}, will be changed to @var{name2@@@@nodename}.
5626 @section @code{.tag @var{structname}}
5628 @cindex COFF structure debugging
5629 @cindex structure debugging, COFF
5630 @cindex @code{tag} directive
5631 This directive is generated by compilers to include auxiliary debugging
5632 information in the symbol table. It is only permitted inside
5633 @code{.def}/@code{.endef} pairs. Tags are used to link structure
5634 definitions in the symbol table with instances of those structures.
5637 @samp{.tag} is only used when generating COFF format output; when
5638 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5644 @section @code{.text @var{subsection}}
5646 @cindex @code{text} directive
5647 Tells @command{@value{AS}} to assemble the following statements onto the end of
5648 the text subsection numbered @var{subsection}, which is an absolute
5649 expression. If @var{subsection} is omitted, subsection number zero
5653 @section @code{.title "@var{heading}"}
5655 @cindex @code{title} directive
5656 @cindex listing control: title line
5657 Use @var{heading} as the title (second line, immediately after the
5658 source file name and pagenumber) when generating assembly listings.
5660 This directive affects subsequent pages, as well as the current page if
5661 it appears within ten lines of the top of a page.
5665 @section @code{.type}
5667 This directive is used to set the type of a symbol.
5671 @c only print the extra heading if both COFF and ELF are set
5672 @subheading COFF Version
5675 @cindex COFF symbol type
5676 @cindex symbol type, COFF
5677 @cindex @code{type} directive (COFF version)
5678 For COFF targets, this directive is permitted only within
5679 @code{.def}/@code{.endef} pairs. It is used like this:
5685 This records the integer @var{int} as the type attribute of a symbol table
5689 @samp{.type} is associated only with COFF format output; when
5690 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
5691 directive but ignores it.
5697 @c only print the extra heading if both COFF and ELF are set
5698 @subheading ELF Version
5701 @cindex ELF symbol type
5702 @cindex symbol type, ELF
5703 @cindex @code{type} directive (ELF version)
5704 For ELF targets, the @code{.type} directive is used like this:
5707 .type @var{name} , @var{type description}
5710 This sets the type of symbol @var{name} to be either a
5711 function symbol or an object symbol. There are five different syntaxes
5712 supported for the @var{type description} field, in order to provide
5713 compatibility with various other assemblers. The syntaxes supported are:
5716 .type <name>,#function
5717 .type <name>,#object
5719 .type <name>,@@function
5720 .type <name>,@@object
5722 .type <name>,%function
5723 .type <name>,%object
5725 .type <name>,"function"
5726 .type <name>,"object"
5728 .type <name> STT_FUNCTION
5729 .type <name> STT_OBJECT
5735 @section @code{.uleb128 @var{expressions}}
5737 @cindex @code{uleb128} directive
5738 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
5739 compact, variable length representation of numbers used by the DWARF
5740 symbolic debugging format. @xref{Sleb128,@code{.sleb128}}.
5744 @section @code{.val @var{addr}}
5746 @cindex @code{val} directive
5747 @cindex COFF value attribute
5748 @cindex value attribute, COFF
5749 This directive, permitted only within @code{.def}/@code{.endef} pairs,
5750 records the address @var{addr} as the value attribute of a symbol table
5754 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
5755 configured for @code{b.out}, it accepts this directive but ignores it.
5761 @section @code{.version "@var{string}"}
5763 @cindex @code{version} directive
5764 This directive creates a @code{.note} section and places into it an ELF
5765 formatted note of type NT_VERSION. The note's name is set to @code{string}.
5770 @section @code{.vtable_entry @var{table}, @var{offset}}
5772 @cindex @code{vtable_entry}
5773 This directive finds or creates a symbol @code{table} and creates a
5774 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
5777 @section @code{.vtable_inherit @var{child}, @var{parent}}
5779 @cindex @code{vtable_inherit}
5780 This directive finds the symbol @code{child} and finds or creates the symbol
5781 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
5782 parent whose addend is the value of the child symbol. As a special case the
5783 parent name of @code{0} is treated as refering the @code{*ABS*} section.
5788 @section @code{.weak @var{names}}
5790 @cindex @code{weak} directive
5791 This directive sets the weak attribute on the comma separated list of symbol
5792 @code{names}. If the symbols do not already exist, they will be created.
5796 @section @code{.word @var{expressions}}
5798 @cindex @code{word} directive
5799 This directive expects zero or more @var{expressions}, of any section,
5800 separated by commas.
5803 For each expression, @command{@value{AS}} emits a 32-bit number.
5806 For each expression, @command{@value{AS}} emits a 16-bit number.
5811 The size of the number emitted, and its byte order,
5812 depend on what target computer the assembly is for.
5815 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
5816 @c happen---32-bit addressability, period; no long/short jumps.
5817 @ifset DIFF-TBL-KLUGE
5818 @cindex difference tables altered
5819 @cindex altered difference tables
5821 @emph{Warning: Special Treatment to support Compilers}
5825 Machines with a 32-bit address space, but that do less than 32-bit
5826 addressing, require the following special treatment. If the machine of
5827 interest to you does 32-bit addressing (or doesn't require it;
5828 @pxref{Machine Dependencies}), you can ignore this issue.
5831 In order to assemble compiler output into something that works,
5832 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
5833 Directives of the form @samp{.word sym1-sym2} are often emitted by
5834 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
5835 directive of the form @samp{.word sym1-sym2}, and the difference between
5836 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
5837 creates a @dfn{secondary jump table}, immediately before the next label.
5838 This secondary jump table is preceded by a short-jump to the
5839 first byte after the secondary table. This short-jump prevents the flow
5840 of control from accidentally falling into the new table. Inside the
5841 table is a long-jump to @code{sym2}. The original @samp{.word}
5842 contains @code{sym1} minus the address of the long-jump to
5845 If there were several occurrences of @samp{.word sym1-sym2} before the
5846 secondary jump table, all of them are adjusted. If there was a
5847 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
5848 long-jump to @code{sym4} is included in the secondary jump table,
5849 and the @code{.word} directives are adjusted to contain @code{sym3}
5850 minus the address of the long-jump to @code{sym4}; and so on, for as many
5851 entries in the original jump table as necessary.
5854 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
5855 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
5856 assembly language programmers.
5859 @c end DIFF-TBL-KLUGE
5862 @section Deprecated Directives
5864 @cindex deprecated directives
5865 @cindex obsolescent directives
5866 One day these directives won't work.
5867 They are included for compatibility with older assemblers.
5874 @node Machine Dependencies
5875 @chapter Machine Dependent Features
5877 @cindex machine dependencies
5878 The machine instruction sets are (almost by definition) different on
5879 each machine where @command{@value{AS}} runs. Floating point representations
5880 vary as well, and @command{@value{AS}} often supports a few additional
5881 directives or command-line options for compatibility with other
5882 assemblers on a particular platform. Finally, some versions of
5883 @command{@value{AS}} support special pseudo-instructions for branch
5886 This chapter discusses most of these differences, though it does not
5887 include details on any machine's instruction set. For details on that
5888 subject, see the hardware manufacturer's manual.
5892 * AMD29K-Dependent:: AMD 29K Dependent Features
5895 * Alpha-Dependent:: Alpha Dependent Features
5898 * ARC-Dependent:: ARC Dependent Features
5901 * ARM-Dependent:: ARM Dependent Features
5904 * CRIS-Dependent:: CRIS Dependent Features
5907 * D10V-Dependent:: D10V Dependent Features
5910 * D30V-Dependent:: D30V Dependent Features
5913 * H8/300-Dependent:: Renesas H8/300 Dependent Features
5916 * H8/500-Dependent:: Renesas H8/500 Dependent Features
5919 * HPPA-Dependent:: HPPA Dependent Features
5922 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
5925 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
5928 * i860-Dependent:: Intel 80860 Dependent Features
5931 * i960-Dependent:: Intel 80960 Dependent Features
5934 * IP2K-Dependent:: IP2K Dependent Features
5937 * M32R-Dependent:: M32R Dependent Features
5940 * M68K-Dependent:: M680x0 Dependent Features
5943 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
5946 * M88K-Dependent:: M880x0 Dependent Features
5949 * MIPS-Dependent:: MIPS Dependent Features
5952 * MMIX-Dependent:: MMIX Dependent Features
5955 * MSP430-Dependent:: MSP430 Dependent Features
5958 * SH-Dependent:: Renesas / SuperH SH Dependent Features
5959 * SH64-Dependent:: SuperH SH64 Dependent Features
5962 * PDP-11-Dependent:: PDP-11 Dependent Features
5965 * PJ-Dependent:: picoJava Dependent Features
5968 * PPC-Dependent:: PowerPC Dependent Features
5971 * Sparc-Dependent:: SPARC Dependent Features
5974 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
5977 * V850-Dependent:: V850 Dependent Features
5980 * Xtensa-Dependent:: Xtensa Dependent Features
5983 * Z8000-Dependent:: Z8000 Dependent Features
5986 * Vax-Dependent:: VAX Dependent Features
5993 @c The following major nodes are *sections* in the GENERIC version, *chapters*
5994 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
5995 @c peculiarity: to preserve cross-references, there must be a node called
5996 @c "Machine Dependencies". Hence the conditional nodenames in each
5997 @c major node below. Node defaulting in makeinfo requires adjacency of
5998 @c node and sectioning commands; hence the repetition of @chapter BLAH
5999 @c in both conditional blocks.
6002 @include c-a29k.texi
6006 @include c-alpha.texi
6018 @include c-cris.texi
6023 @node Machine Dependencies
6024 @chapter Machine Dependent Features
6026 The machine instruction sets are different on each Renesas chip family,
6027 and there are also some syntax differences among the families. This
6028 chapter describes the specific @command{@value{AS}} features for each
6032 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6033 * H8/500-Dependent:: Renesas H8/500 Dependent Features
6034 * SH-Dependent:: Renesas SH Dependent Features
6041 @include c-d10v.texi
6045 @include c-d30v.texi
6049 @include c-h8300.texi
6053 @include c-h8500.texi
6057 @include c-hppa.texi
6061 @include c-i370.texi
6065 @include c-i386.texi
6069 @include c-i860.texi
6073 @include c-i960.texi
6077 @include c-ia64.texi
6081 @include c-ip2k.texi
6085 @include c-m32r.texi
6089 @include c-m68k.texi
6093 @include c-m68hc11.texi
6097 @include c-m88k.texi
6101 @include c-mips.texi
6105 @include c-mmix.texi
6109 @include c-msp430.texi
6113 @include c-ns32k.texi
6117 @include c-pdp11.texi
6130 @include c-sh64.texi
6134 @include c-sparc.texi
6138 @include c-tic54x.texi
6150 @include c-v850.texi
6154 @include c-xtensa.texi
6158 @c reverse effect of @down at top of generic Machine-Dep chapter
6162 @node Reporting Bugs
6163 @chapter Reporting Bugs
6164 @cindex bugs in assembler
6165 @cindex reporting bugs in assembler
6167 Your bug reports play an essential role in making @command{@value{AS}} reliable.
6169 Reporting a bug may help you by bringing a solution to your problem, or it may
6170 not. But in any case the principal function of a bug report is to help the
6171 entire community by making the next version of @command{@value{AS}} work better.
6172 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
6174 In order for a bug report to serve its purpose, you must include the
6175 information that enables us to fix the bug.
6178 * Bug Criteria:: Have you found a bug?
6179 * Bug Reporting:: How to report bugs
6183 @section Have You Found a Bug?
6184 @cindex bug criteria
6186 If you are not sure whether you have found a bug, here are some guidelines:
6189 @cindex fatal signal
6190 @cindex assembler crash
6191 @cindex crash of assembler
6193 If the assembler gets a fatal signal, for any input whatever, that is a
6194 @command{@value{AS}} bug. Reliable assemblers never crash.
6196 @cindex error on valid input
6198 If @command{@value{AS}} produces an error message for valid input, that is a bug.
6200 @cindex invalid input
6202 If @command{@value{AS}} does not produce an error message for invalid input, that
6203 is a bug. However, you should note that your idea of ``invalid input'' might
6204 be our idea of ``an extension'' or ``support for traditional practice''.
6207 If you are an experienced user of assemblers, your suggestions for improvement
6208 of @command{@value{AS}} are welcome in any case.
6212 @section How to Report Bugs
6214 @cindex assembler bugs, reporting
6216 A number of companies and individuals offer support for @sc{gnu} products. If
6217 you obtained @command{@value{AS}} from a support organization, we recommend you
6218 contact that organization first.
6220 You can find contact information for many support companies and
6221 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
6224 In any event, we also recommend that you send bug reports for @command{@value{AS}}
6225 to @samp{bug-binutils@@gnu.org}.
6227 The fundamental principle of reporting bugs usefully is this:
6228 @strong{report all the facts}. If you are not sure whether to state a
6229 fact or leave it out, state it!
6231 Often people omit facts because they think they know what causes the problem
6232 and assume that some details do not matter. Thus, you might assume that the
6233 name of a symbol you use in an example does not matter. Well, probably it does
6234 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
6235 happens to fetch from the location where that name is stored in memory;
6236 perhaps, if the name were different, the contents of that location would fool
6237 the assembler into doing the right thing despite the bug. Play it safe and
6238 give a specific, complete example. That is the easiest thing for you to do,
6239 and the most helpful.
6241 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
6242 it is new to us. Therefore, always write your bug reports on the assumption
6243 that the bug has not been reported previously.
6245 Sometimes people give a few sketchy facts and ask, ``Does this ring a
6246 bell?'' This cannot help us fix a bug, so it is basically useless. We
6247 respond by asking for enough details to enable us to investigate.
6248 You might as well expedite matters by sending them to begin with.
6250 To enable us to fix the bug, you should include all these things:
6254 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
6255 it with the @samp{--version} argument.
6257 Without this, we will not know whether there is any point in looking for
6258 the bug in the current version of @command{@value{AS}}.
6261 Any patches you may have applied to the @command{@value{AS}} source.
6264 The type of machine you are using, and the operating system name and
6268 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
6272 The command arguments you gave the assembler to assemble your example and
6273 observe the bug. To guarantee you will not omit something important, list them
6274 all. A copy of the Makefile (or the output from make) is sufficient.
6276 If we were to try to guess the arguments, we would probably guess wrong
6277 and then we might not encounter the bug.
6280 A complete input file that will reproduce the bug. If the bug is observed when
6281 the assembler is invoked via a compiler, send the assembler source, not the
6282 high level language source. Most compilers will produce the assembler source
6283 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
6284 the options @samp{-v --save-temps}; this will save the assembler source in a
6285 file with an extension of @file{.s}, and also show you exactly how
6286 @command{@value{AS}} is being run.
6289 A description of what behavior you observe that you believe is
6290 incorrect. For example, ``It gets a fatal signal.''
6292 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
6293 will certainly notice it. But if the bug is incorrect output, we might not
6294 notice unless it is glaringly wrong. You might as well not give us a chance to
6297 Even if the problem you experience is a fatal signal, you should still say so
6298 explicitly. Suppose something strange is going on, such as, your copy of
6299 @command{@value{AS}} is out of synch, or you have encountered a bug in the C
6300 library on your system. (This has happened!) Your copy might crash and ours
6301 would not. If you told us to expect a crash, then when ours fails to crash, we
6302 would know that the bug was not happening for us. If you had not told us to
6303 expect a crash, then we would not be able to draw any conclusion from our
6307 If you wish to suggest changes to the @command{@value{AS}} source, send us context
6308 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
6309 option. Always send diffs from the old file to the new file. If you even
6310 discuss something in the @command{@value{AS}} source, refer to it by context, not
6313 The line numbers in our development sources will not match those in your
6314 sources. Your line numbers would convey no useful information to us.
6317 Here are some things that are not necessary:
6321 A description of the envelope of the bug.
6323 Often people who encounter a bug spend a lot of time investigating
6324 which changes to the input file will make the bug go away and which
6325 changes will not affect it.
6327 This is often time consuming and not very useful, because the way we
6328 will find the bug is by running a single example under the debugger
6329 with breakpoints, not by pure deduction from a series of examples.
6330 We recommend that you save your time for something else.
6332 Of course, if you can find a simpler example to report @emph{instead}
6333 of the original one, that is a convenience for us. Errors in the
6334 output will be easier to spot, running under the debugger will take
6335 less time, and so on.
6337 However, simplification is not vital; if you do not want to do this,
6338 report the bug anyway and send us the entire test case you used.
6341 A patch for the bug.
6343 A patch for the bug does help us if it is a good one. But do not omit
6344 the necessary information, such as the test case, on the assumption that
6345 a patch is all we need. We might see problems with your patch and decide
6346 to fix the problem another way, or we might not understand it at all.
6348 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
6349 construct an example that will make the program follow a certain path through
6350 the code. If you do not send us the example, we will not be able to construct
6351 one, so we will not be able to verify that the bug is fixed.
6353 And if we cannot understand what bug you are trying to fix, or why your
6354 patch should be an improvement, we will not install it. A test case will
6355 help us to understand.
6358 A guess about what the bug is or what it depends on.
6360 Such guesses are usually wrong. Even we cannot guess right about such
6361 things without first using the debugger to find the facts.
6364 @node Acknowledgements
6365 @chapter Acknowledgements
6367 If you have contributed to @command{@value{AS}} and your name isn't listed here,
6368 it is not meant as a slight. We just don't know about it. Send mail to the
6369 maintainer, and we'll correct the situation. Currently
6371 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
6373 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
6376 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
6377 information and the 68k series machines, most of the preprocessing pass, and
6378 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
6380 K. Richard Pixley maintained GAS for a while, adding various enhancements and
6381 many bug fixes, including merging support for several processors, breaking GAS
6382 up to handle multiple object file format back ends (including heavy rewrite,
6383 testing, an integration of the coff and b.out back ends), adding configuration
6384 including heavy testing and verification of cross assemblers and file splits
6385 and renaming, converted GAS to strictly ANSI C including full prototypes, added
6386 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
6387 port (including considerable amounts of reverse engineering), a SPARC opcode
6388 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
6389 assertions and made them work, much other reorganization, cleanup, and lint.
6391 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
6392 in format-specific I/O modules.
6394 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
6395 has done much work with it since.
6397 The Intel 80386 machine description was written by Eliot Dresselhaus.
6399 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
6401 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
6402 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
6404 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
6405 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
6406 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
6407 support a.out format.
6409 Support for the Zilog Z8k and Renesas H8/300 and H8/500 processors (tc-z8k,
6410 tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by
6411 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
6412 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
6415 John Gilmore built the AMD 29000 support, added @code{.include} support, and
6416 simplified the configuration of which versions accept which directives. He
6417 updated the 68k machine description so that Motorola's opcodes always produced
6418 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
6419 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
6420 cross-compilation support, and one bug in relaxation that took a week and
6421 required the proverbial one-bit fix.
6423 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
6424 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
6425 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
6426 PowerPC assembler, and made a few other minor patches.
6428 Steve Chamberlain made @command{@value{AS}} able to generate listings.
6430 Hewlett-Packard contributed support for the HP9000/300.
6432 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
6433 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
6434 formats). This work was supported by both the Center for Software Science at
6435 the University of Utah and Cygnus Support.
6437 Support for ELF format files has been worked on by Mark Eichin of Cygnus
6438 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
6439 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
6440 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
6441 and some initial 64-bit support).
6443 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
6445 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
6446 support for openVMS/Alpha.
6448 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
6451 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
6452 Inc. added support for Xtensa processors.
6454 Several engineers at Cygnus Support have also provided many small bug fixes and
6455 configuration enhancements.
6457 Many others have contributed large or small bugfixes and enhancements. If
6458 you have contributed significant work and are not mentioned on this list, and
6459 want to be, let us know. Some of the history has been lost; we are not
6460 intentionally leaving anyone out.
projects / deliverable / binutils-gdb.git / blob