1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
3 @c 2001, 2002, 2003, 2004, 2005, 2006, 2007
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:
24 @include asconfig.texi
29 @c common OR combinations of conditions
52 @set abnormal-separator
56 @settitle Using @value{AS}
59 @settitle Using @value{AS} (@value{TARGET})
61 @setchapternewpage odd
66 @c WARE! Some of the machine-dependent sections contain tables of machine
67 @c instructions. Except in multi-column format, these tables look silly.
68 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
69 @c the multi-col format is faked within @example sections.
71 @c Again unfortunately, the natural size that fits on a page, for these tables,
72 @c is different depending on whether or not smallbook is turned on.
73 @c This matters, because of order: text flow switches columns at each page
76 @c The format faked in this source works reasonably well for smallbook,
77 @c not well for the default large-page format. This manual expects that if you
78 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
79 @c tables in question. You can turn on one without the other at your
80 @c discretion, of course.
83 @c the insn tables look just as silly in info files regardless of smallbook,
84 @c might as well show 'em anyways.
90 * As: (as). The GNU assembler.
91 * Gas: (as). The GNU assembler.
100 This file documents the GNU Assembler "@value{AS}".
102 @c man begin COPYRIGHT
103 Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002,
104 2006, 2007 Free Software Foundation, Inc.
106 Permission is granted to copy, distribute and/or modify this document
107 under the terms of the GNU Free Documentation License, Version 1.1
108 or any later version published by the Free Software Foundation;
109 with no Invariant Sections, with no Front-Cover Texts, and with no
110 Back-Cover Texts. A copy of the license is included in the
111 section entitled ``GNU Free Documentation License''.
116 Permission is granted to process this file through Tex and print the
117 results, provided the printed document carries copying permission
118 notice identical to this one except for the removal of this paragraph
119 (this paragraph not being relevant to the printed manual).
125 @title Using @value{AS}
126 @subtitle The @sc{gnu} Assembler
128 @subtitle for the @value{TARGET} family
131 @subtitle Version @value{VERSION}
134 The Free Software Foundation Inc.@: thanks The Nice Computer
135 Company of Australia for loaning Dean Elsner to write the
136 first (Vax) version of @command{as} for Project @sc{gnu}.
137 The proprietors, management and staff of TNCCA thank FSF for
138 distracting the boss while they got some work
141 @author Dean Elsner, Jay Fenlason & friends
145 \hfill {\it Using {\tt @value{AS}}}\par
146 \hfill Edited by Cygnus Support\par
148 %"boxit" macro for figures:
149 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
150 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
151 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
152 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
153 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
156 @vskip 0pt plus 1filll
157 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002,
158 2006, 2007 Free Software Foundation, Inc.
160 Permission is granted to copy, distribute and/or modify this document
161 under the terms of the GNU Free Documentation License, Version 1.1
162 or any later version published by the Free Software Foundation;
163 with no Invariant Sections, with no Front-Cover Texts, and with no
164 Back-Cover Texts. A copy of the license is included in the
165 section entitled ``GNU Free Documentation License''.
171 @top Using @value{AS}
173 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}} version
176 This version of the file describes @command{@value{AS}} configured to generate
177 code for @value{TARGET} architectures.
180 This document is distributed under the terms of the GNU Free
181 Documentation License. A copy of the license is included in the
182 section entitled ``GNU Free Documentation License''.
185 * Overview:: Overview
186 * Invoking:: Command-Line Options
188 * Sections:: Sections and Relocation
190 * Expressions:: Expressions
191 * Pseudo Ops:: Assembler Directives
192 * Machine Dependencies:: Machine Dependent Features
193 * Reporting Bugs:: Reporting Bugs
194 * Acknowledgements:: Who Did What
195 * GNU Free Documentation License:: GNU Free Documentation License
196 * AS Index:: AS Index
203 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
205 This version of the manual describes @command{@value{AS}} configured to generate
206 code for @value{TARGET} architectures.
210 @cindex invocation summary
211 @cindex option summary
212 @cindex summary of options
213 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
214 see @ref{Invoking,,Command-Line Options}.
216 @c man title AS the portable GNU assembler.
220 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
224 @c We don't use deffn and friends for the following because they seem
225 @c to be limited to one line for the header.
227 @c man begin SYNOPSIS
228 @value{AS} [@b{-a}[@b{cdhlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
229 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
230 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
231 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
232 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
233 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}] [@b{-o}
234 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
235 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
236 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}]
237 [@b{--target-help}] [@var{target-options}]
238 [@b{--}|@var{files} @dots{}]
240 @c Target dependent options are listed below. Keep the list sorted.
241 @c Add an empty line for separation.
244 @emph{Target Alpha options:}
246 [@b{-mdebug} | @b{-no-mdebug}]
247 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
248 [@b{-F}] [@b{-32addr}]
252 @emph{Target ARC options:}
258 @emph{Target ARM options:}
259 @c Don't document the deprecated options
260 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
261 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
262 [@b{-mfpu}=@var{floating-point-format}]
263 [@b{-mfloat-abi}=@var{abi}]
264 [@b{-meabi}=@var{ver}]
267 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
268 @b{-mapcs-reentrant}]
269 [@b{-mthumb-interwork}] [@b{-k}]
273 @emph{Target CRIS options:}
274 [@b{--underscore} | @b{--no-underscore}]
276 [@b{--emulation=criself} | @b{--emulation=crisaout}]
277 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
278 @c Deprecated -- deliberately not documented.
283 @emph{Target D10V options:}
288 @emph{Target D30V options:}
289 [@b{-O}|@b{-n}|@b{-N}]
292 @c Renesas family chips have no machine-dependent assembler options
295 @c HPPA has no machine-dependent assembler options (yet).
299 @emph{Target i386 options:}
300 [@b{--32}|@b{--64}] [@b{-n}]
301 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}]
305 @emph{Target i960 options:}
306 @c see md_parse_option in tc-i960.c
307 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
309 [@b{-b}] [@b{-no-relax}]
313 @emph{Target IA-64 options:}
314 [@b{-mconstant-gp}|@b{-mauto-pic}]
315 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
317 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
318 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
319 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
320 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
324 @emph{Target IP2K options:}
325 [@b{-mip2022}|@b{-mip2022ext}]
329 @emph{Target M32C options:}
330 [@b{-m32c}|@b{-m16c}]
334 @emph{Target M32R options:}
335 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
340 @emph{Target M680X0 options:}
341 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
345 @emph{Target M68HC11 options:}
346 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}]
347 [@b{-mshort}|@b{-mlong}]
348 [@b{-mshort-double}|@b{-mlong-double}]
349 [@b{--force-long-branches}] [@b{--short-branches}]
350 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
351 [@b{--print-opcodes}] [@b{--generate-example}]
355 @emph{Target MCORE options:}
356 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
357 [@b{-mcpu=[210|340]}]
361 @emph{Target MIPS options:}
362 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
363 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
364 [@b{-non_shared}] [@b{-xgot}]
365 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
366 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
367 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
368 [@b{-mips64}] [@b{-mips64r2}]
369 [@b{-construct-floats}] [@b{-no-construct-floats}]
370 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
371 [@b{-mfix7000}] [@b{-mno-fix7000}]
372 [@b{-mips16}] [@b{-no-mips16}]
373 [@b{-msmartmips}] [@b{-mno-smartmips}]
374 [@b{-mips3d}] [@b{-no-mips3d}]
375 [@b{-mdmx}] [@b{-no-mdmx}]
376 [@b{-mdsp}] [@b{-mno-dsp}]
377 [@b{-mdspr2}] [@b{-mno-dspr2}]
378 [@b{-mmt}] [@b{-mno-mt}]
379 [@b{-mdebug}] [@b{-no-mdebug}]
380 [@b{-mpdr}] [@b{-mno-pdr}]
384 @emph{Target MMIX options:}
385 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
386 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
387 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
388 [@b{--linker-allocated-gregs}]
392 @emph{Target PDP11 options:}
393 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
394 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
395 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
399 @emph{Target picoJava options:}
404 @emph{Target PowerPC options:}
405 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|
406 @b{-m403}|@b{-m405}|@b{-mppc64}|@b{-m620}|@b{-mppc64bridge}|@b{-mbooke}|
407 @b{-mbooke32}|@b{-mbooke64}]
408 [@b{-mcom}|@b{-many}|@b{-maltivec}] [@b{-memb}]
409 [@b{-mregnames}|@b{-mno-regnames}]
410 [@b{-mrelocatable}|@b{-mrelocatable-lib}]
411 [@b{-mlittle}|@b{-mlittle-endian}|@b{-mbig}|@b{-mbig-endian}]
412 [@b{-msolaris}|@b{-mno-solaris}]
416 @emph{Target SPARC options:}
417 @c The order here is important. See c-sparc.texi.
418 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
419 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
420 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
425 @emph{Target TIC54X options:}
426 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
427 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
432 @emph{Target Z80 options:}
433 [@b{-z80}] [@b{-r800}]
434 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
435 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
436 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
437 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
438 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
439 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
443 @c Z8000 has no machine-dependent assembler options
447 @emph{Target Xtensa options:}
448 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
449 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
450 [@b{--[no-]transform}]
451 [@b{--rename-section} @var{oldname}=@var{newname}]
459 @include at-file.texi
462 Turn on listings, in any of a variety of ways:
466 omit false conditionals
469 omit debugging directives
472 include high-level source
478 include macro expansions
481 omit forms processing
487 set the name of the listing file
490 You may combine these options; for example, use @samp{-aln} for assembly
491 listing without forms processing. The @samp{=file} option, if used, must be
492 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
495 Begin in alternate macro mode.
497 @xref{Altmacro,,@code{.altmacro}}.
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
508 value. The value of the symbol can be overridden inside a source file via the
509 use of a @code{.set} pseudo-op.
512 ``fast''---skip whitespace and comment preprocessing (assume source is
517 Generate debugging information for each assembler source line using whichever
518 debug format is preferred by the target. This currently means either STABS,
522 Generate stabs debugging information for each assembler line. This
523 may help debugging assembler code, if the debugger can handle it.
526 Generate stabs debugging information for each assembler line, with GNU
527 extensions that probably only gdb can handle, and that could make other
528 debuggers crash or refuse to read your program. This
529 may help debugging assembler code. Currently the only GNU extension is
530 the location of the current working directory at assembling time.
533 Generate DWARF2 debugging information for each assembler line. This
534 may help debugging assembler code, if the debugger can handle it. Note---this
535 option is only supported by some targets, not all of them.
538 Print a summary of the command line options and exit.
541 Print a summary of all target specific options and exit.
544 Add directory @var{dir} to the search list for @code{.include} directives.
547 Don't warn about signed overflow.
550 @ifclear DIFF-TBL-KLUGE
551 This option is accepted but has no effect on the @value{TARGET} family.
553 @ifset DIFF-TBL-KLUGE
554 Issue warnings when difference tables altered for long displacements.
559 Keep (in the symbol table) local symbols. These symbols start with
560 system-specific local label prefixes, typically @samp{.L} for ELF systems
561 or @samp{L} for traditional a.out systems.
566 @item --listing-lhs-width=@var{number}
567 Set the maximum width, in words, of the output data column for an assembler
568 listing to @var{number}.
570 @item --listing-lhs-width2=@var{number}
571 Set the maximum width, in words, of the output data column for continuation
572 lines in an assembler listing to @var{number}.
574 @item --listing-rhs-width=@var{number}
575 Set the maximum width of an input source line, as displayed in a listing, to
578 @item --listing-cont-lines=@var{number}
579 Set the maximum number of lines printed in a listing for a single line of input
582 @item -o @var{objfile}
583 Name the object-file output from @command{@value{AS}} @var{objfile}.
586 Fold the data section into the text section.
588 @kindex --hash-size=@var{number}
589 Set the default size of GAS's hash tables to a prime number close to
590 @var{number}. Increasing this value can reduce the length of time it takes the
591 assembler to perform its tasks, at the expense of increasing the assembler's
592 memory requirements. Similarly reducing this value can reduce the memory
593 requirements at the expense of speed.
595 @item --reduce-memory-overheads
596 This option reduces GAS's memory requirements, at the expense of making the
597 assembly processes slower. Currently this switch is a synonym for
598 @samp{--hash-size=4051}, but in the future it may have other effects as well.
601 Print the maximum space (in bytes) and total time (in seconds) used by
604 @item --strip-local-absolute
605 Remove local absolute symbols from the outgoing symbol table.
609 Print the @command{as} version.
612 Print the @command{as} version and exit.
616 Suppress warning messages.
618 @item --fatal-warnings
619 Treat warnings as errors.
622 Don't suppress warning messages or treat them as errors.
631 Generate an object file even after errors.
633 @item -- | @var{files} @dots{}
634 Standard input, or source files to assemble.
639 The following options are available when @value{AS} is configured for
644 This option selects the core processor variant.
646 Select either big-endian (-EB) or little-endian (-EL) output.
651 The following options are available when @value{AS} is configured for the ARM
655 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
656 Specify which ARM processor variant is the target.
657 @item -march=@var{architecture}[+@var{extension}@dots{}]
658 Specify which ARM architecture variant is used by the target.
659 @item -mfpu=@var{floating-point-format}
660 Select which Floating Point architecture is the target.
661 @item -mfloat-abi=@var{abi}
662 Select which floating point ABI is in use.
664 Enable Thumb only instruction decoding.
665 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
666 Select which procedure calling convention is in use.
668 Select either big-endian (-EB) or little-endian (-EL) output.
669 @item -mthumb-interwork
670 Specify that the code has been generated with interworking between Thumb and
673 Specify that PIC code has been generated.
678 See the info pages for documentation of the CRIS-specific options.
682 The following options are available when @value{AS} is configured for
685 @cindex D10V optimization
686 @cindex optimization, D10V
688 Optimize output by parallelizing instructions.
693 The following options are available when @value{AS} is configured for a D30V
696 @cindex D30V optimization
697 @cindex optimization, D30V
699 Optimize output by parallelizing instructions.
703 Warn when nops are generated.
705 @cindex D30V nops after 32-bit multiply
707 Warn when a nop after a 32-bit multiply instruction is generated.
712 The following options are available when @value{AS} is configured for the
713 Intel 80960 processor.
716 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
717 Specify which variant of the 960 architecture is the target.
720 Add code to collect statistics about branches taken.
723 Do not alter compare-and-branch instructions for long displacements;
730 The following options are available when @value{AS} is configured for the
736 Specifies that the extended IP2022 instructions are allowed.
739 Restores the default behaviour, which restricts the permitted instructions to
740 just the basic IP2022 ones.
746 The following options are available when @value{AS} is configured for the
747 Renesas M32C and M16C processors.
752 Assemble M32C instructions.
755 Assemble M16C instructions (the default).
761 The following options are available when @value{AS} is configured for the
762 Renesas M32R (formerly Mitsubishi M32R) series.
767 Specify which processor in the M32R family is the target. The default
768 is normally the M32R, but this option changes it to the M32RX.
770 @item --warn-explicit-parallel-conflicts or --Wp
771 Produce warning messages when questionable parallel constructs are
774 @item --no-warn-explicit-parallel-conflicts or --Wnp
775 Do not produce warning messages when questionable parallel constructs are
782 The following options are available when @value{AS} is configured for the
783 Motorola 68000 series.
788 Shorten references to undefined symbols, to one word instead of two.
790 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
791 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
792 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
793 Specify what processor in the 68000 family is the target. The default
794 is normally the 68020, but this can be changed at configuration time.
796 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
797 The target machine does (or does not) have a floating-point coprocessor.
798 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
799 the basic 68000 is not compatible with the 68881, a combination of the
800 two can be specified, since it's possible to do emulation of the
801 coprocessor instructions with the main processor.
803 @item -m68851 | -mno-68851
804 The target machine does (or does not) have a memory-management
805 unit coprocessor. The default is to assume an MMU for 68020 and up.
812 For details about the PDP-11 machine dependent features options,
813 see @ref{PDP-11-Options}.
816 @item -mpic | -mno-pic
817 Generate position-independent (or position-dependent) code. The
818 default is @option{-mpic}.
821 @itemx -mall-extensions
822 Enable all instruction set extensions. This is the default.
824 @item -mno-extensions
825 Disable all instruction set extensions.
827 @item -m@var{extension} | -mno-@var{extension}
828 Enable (or disable) a particular instruction set extension.
831 Enable the instruction set extensions supported by a particular CPU, and
832 disable all other extensions.
834 @item -m@var{machine}
835 Enable the instruction set extensions supported by a particular machine
836 model, and disable all other extensions.
842 The following options are available when @value{AS} is configured for
843 a picoJava processor.
847 @cindex PJ endianness
848 @cindex endianness, PJ
849 @cindex big endian output, PJ
851 Generate ``big endian'' format output.
853 @cindex little endian output, PJ
855 Generate ``little endian'' format output.
861 The following options are available when @value{AS} is configured for the
862 Motorola 68HC11 or 68HC12 series.
866 @item -m68hc11 | -m68hc12 | -m68hcs12
867 Specify what processor is the target. The default is
868 defined by the configuration option when building the assembler.
871 Specify to use the 16-bit integer ABI.
874 Specify to use the 32-bit integer ABI.
877 Specify to use the 32-bit double ABI.
880 Specify to use the 64-bit double ABI.
882 @item --force-long-branches
883 Relative branches are turned into absolute ones. This concerns
884 conditional branches, unconditional branches and branches to a
887 @item -S | --short-branches
888 Do not turn relative branches into absolute ones
889 when the offset is out of range.
891 @item --strict-direct-mode
892 Do not turn the direct addressing mode into extended addressing mode
893 when the instruction does not support direct addressing mode.
895 @item --print-insn-syntax
896 Print the syntax of instruction in case of error.
898 @item --print-opcodes
899 print the list of instructions with syntax and then exit.
901 @item --generate-example
902 print an example of instruction for each possible instruction and then exit.
903 This option is only useful for testing @command{@value{AS}}.
909 The following options are available when @command{@value{AS}} is configured
910 for the SPARC architecture:
913 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
914 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
915 Explicitly select a variant of the SPARC architecture.
917 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
918 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
920 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
921 UltraSPARC extensions.
923 @item -xarch=v8plus | -xarch=v8plusa
924 For compatibility with the Solaris v9 assembler. These options are
925 equivalent to -Av8plus and -Av8plusa, respectively.
928 Warn when the assembler switches to another architecture.
933 The following options are available when @value{AS} is configured for the 'c54x
938 Enable extended addressing mode. All addresses and relocations will assume
939 extended addressing (usually 23 bits).
940 @item -mcpu=@var{CPU_VERSION}
941 Sets the CPU version being compiled for.
942 @item -merrors-to-file @var{FILENAME}
943 Redirect error output to a file, for broken systems which don't support such
944 behaviour in the shell.
949 The following options are available when @value{AS} is configured for
950 a @sc{mips} processor.
954 This option sets the largest size of an object that can be referenced
955 implicitly with the @code{gp} register. It is only accepted for targets that
956 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
958 @cindex MIPS endianness
959 @cindex endianness, MIPS
960 @cindex big endian output, MIPS
962 Generate ``big endian'' format output.
964 @cindex little endian output, MIPS
966 Generate ``little endian'' format output.
978 Generate code for a particular @sc{mips} Instruction Set Architecture level.
979 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
980 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
981 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
982 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
984 correspond to generic
985 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
986 and @samp{MIPS64 Release 2}
987 ISA processors, respectively.
989 @item -march=@var{CPU}
990 Generate code for a particular @sc{mips} cpu.
992 @item -mtune=@var{cpu}
993 Schedule and tune for a particular @sc{mips} cpu.
997 Cause nops to be inserted if the read of the destination register
998 of an mfhi or mflo instruction occurs in the following two instructions.
1002 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1003 section instead of the standard ELF .stabs sections.
1007 Control generation of @code{.pdr} sections.
1011 The register sizes are normally inferred from the ISA and ABI, but these
1012 flags force a certain group of registers to be treated as 32 bits wide at
1013 all times. @samp{-mgp32} controls the size of general-purpose registers
1014 and @samp{-mfp32} controls the size of floating-point registers.
1018 Generate code for the MIPS 16 processor. This is equivalent to putting
1019 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1020 turns off this option.
1023 @itemx -mno-smartmips
1024 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1025 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1026 @samp{-mno-smartmips} turns off this option.
1030 Generate code for the MIPS-3D Application Specific Extension.
1031 This tells the assembler to accept MIPS-3D instructions.
1032 @samp{-no-mips3d} turns off this option.
1036 Generate code for the MDMX Application Specific Extension.
1037 This tells the assembler to accept MDMX instructions.
1038 @samp{-no-mdmx} turns off this option.
1042 Generate code for the DSP Release 1 Application Specific Extension.
1043 This tells the assembler to accept DSP Release 1 instructions.
1044 @samp{-mno-dsp} turns off this option.
1048 Generate code for the DSP Release 2 Application Specific Extension.
1049 This option implies -mdsp.
1050 This tells the assembler to accept DSP Release 2 instructions.
1051 @samp{-mno-dspr2} turns off this option.
1055 Generate code for the MT Application Specific Extension.
1056 This tells the assembler to accept MT instructions.
1057 @samp{-mno-mt} turns off this option.
1059 @item --construct-floats
1060 @itemx --no-construct-floats
1061 The @samp{--no-construct-floats} option disables the construction of
1062 double width floating point constants by loading the two halves of the
1063 value into the two single width floating point registers that make up
1064 the double width register. By default @samp{--construct-floats} is
1065 selected, allowing construction of these floating point constants.
1068 @item --emulation=@var{name}
1069 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1070 for some other target, in all respects, including output format (choosing
1071 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1072 debugging information or store symbol table information, and default
1073 endianness. The available configuration names are: @samp{mipsecoff},
1074 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1075 @samp{mipsbelf}. The first two do not alter the default endianness from that
1076 of the primary target for which the assembler was configured; the others change
1077 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1078 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1079 selection in any case.
1081 This option is currently supported only when the primary target
1082 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1083 Furthermore, the primary target or others specified with
1084 @samp{--enable-targets=@dots{}} at configuration time must include support for
1085 the other format, if both are to be available. For example, the Irix 5
1086 configuration includes support for both.
1088 Eventually, this option will support more configurations, with more
1089 fine-grained control over the assembler's behavior, and will be supported for
1093 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1100 Control how to deal with multiplication overflow and division by zero.
1101 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1102 (and only work for Instruction Set Architecture level 2 and higher);
1103 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1107 When this option is used, @command{@value{AS}} will issue a warning every
1108 time it generates a nop instruction from a macro.
1113 The following options are available when @value{AS} is configured for
1119 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1120 The command line option @samp{-nojsri2bsr} can be used to disable it.
1124 Enable or disable the silicon filter behaviour. By default this is disabled.
1125 The default can be overridden by the @samp{-sifilter} command line option.
1128 Alter jump instructions for long displacements.
1130 @item -mcpu=[210|340]
1131 Select the cpu type on the target hardware. This controls which instructions
1135 Assemble for a big endian target.
1138 Assemble for a little endian target.
1144 See the info pages for documentation of the MMIX-specific options.
1148 The following options are available when @value{AS} is configured for
1149 an Xtensa processor.
1152 @item --text-section-literals | --no-text-section-literals
1153 With @option{--text-@-section-@-literals}, literal pools are interspersed
1154 in the text section. The default is
1155 @option{--no-@-text-@-section-@-literals}, which places literals in a
1156 separate section in the output file. These options only affect literals
1157 referenced via PC-relative @code{L32R} instructions; literals for
1158 absolute mode @code{L32R} instructions are handled separately.
1160 @item --absolute-literals | --no-absolute-literals
1161 Indicate to the assembler whether @code{L32R} instructions use absolute
1162 or PC-relative addressing. The default is to assume absolute addressing
1163 if the Xtensa processor includes the absolute @code{L32R} addressing
1164 option. Otherwise, only the PC-relative @code{L32R} mode can be used.
1166 @item --target-align | --no-target-align
1167 Enable or disable automatic alignment to reduce branch penalties at the
1168 expense of some code density. The default is @option{--target-@-align}.
1170 @item --longcalls | --no-longcalls
1171 Enable or disable transformation of call instructions to allow calls
1172 across a greater range of addresses. The default is
1173 @option{--no-@-longcalls}.
1175 @item --transform | --no-transform
1176 Enable or disable all assembler transformations of Xtensa instructions.
1177 The default is @option{--transform};
1178 @option{--no-transform} should be used only in the rare cases when the
1179 instructions must be exactly as specified in the assembly source.
1184 The following options are available when @value{AS} is configured for
1185 a Z80 family processor.
1188 Assemble for Z80 processor.
1190 Assemble for R800 processor.
1191 @item -ignore-undocumented-instructions
1193 Assemble undocumented Z80 instructions that also work on R800 without warning.
1194 @item -ignore-unportable-instructions
1196 Assemble all undocumented Z80 instructions without warning.
1197 @item -warn-undocumented-instructions
1199 Issue a warning for undocumented Z80 instructions that also work on R800.
1200 @item -warn-unportable-instructions
1202 Issue a warning for undocumented Z80 instructions that do not work on R800.
1203 @item -forbid-undocumented-instructions
1205 Treat all undocumented instructions as errors.
1206 @item -forbid-unportable-instructions
1208 Treat undocumented Z80 instructions that do not work on R800 as errors.
1215 * Manual:: Structure of this Manual
1216 * GNU Assembler:: The GNU Assembler
1217 * Object Formats:: Object File Formats
1218 * Command Line:: Command Line
1219 * Input Files:: Input Files
1220 * Object:: Output (Object) File
1221 * Errors:: Error and Warning Messages
1225 @section Structure of this Manual
1227 @cindex manual, structure and purpose
1228 This manual is intended to describe what you need to know to use
1229 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1230 notation for symbols, constants, and expressions; the directives that
1231 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1234 We also cover special features in the @value{TARGET}
1235 configuration of @command{@value{AS}}, including assembler directives.
1238 This manual also describes some of the machine-dependent features of
1239 various flavors of the assembler.
1242 @cindex machine instructions (not covered)
1243 On the other hand, this manual is @emph{not} intended as an introduction
1244 to programming in assembly language---let alone programming in general!
1245 In a similar vein, we make no attempt to introduce the machine
1246 architecture; we do @emph{not} describe the instruction set, standard
1247 mnemonics, registers or addressing modes that are standard to a
1248 particular architecture.
1250 You may want to consult the manufacturer's
1251 machine architecture manual for this information.
1255 For information on the H8/300 machine instruction set, see @cite{H8/300
1256 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1257 Programming Manual} (Renesas).
1260 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1261 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1262 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1263 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1266 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1270 @c I think this is premature---doc@cygnus.com, 17jan1991
1272 Throughout this manual, we assume that you are running @dfn{GNU},
1273 the portable operating system from the @dfn{Free Software
1274 Foundation, Inc.}. This restricts our attention to certain kinds of
1275 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1276 once this assumption is granted examples and definitions need less
1279 @command{@value{AS}} is part of a team of programs that turn a high-level
1280 human-readable series of instructions into a low-level
1281 computer-readable series of instructions. Different versions of
1282 @command{@value{AS}} are used for different kinds of computer.
1285 @c There used to be a section "Terminology" here, which defined
1286 @c "contents", "byte", "word", and "long". Defining "word" to any
1287 @c particular size is confusing when the .word directive may generate 16
1288 @c bits on one machine and 32 bits on another; in general, for the user
1289 @c version of this manual, none of these terms seem essential to define.
1290 @c They were used very little even in the former draft of the manual;
1291 @c this draft makes an effort to avoid them (except in names of
1295 @section The GNU Assembler
1297 @c man begin DESCRIPTION
1299 @sc{gnu} @command{as} is really a family of assemblers.
1301 This manual describes @command{@value{AS}}, a member of that family which is
1302 configured for the @value{TARGET} architectures.
1304 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1305 should find a fairly similar environment when you use it on another
1306 architecture. Each version has much in common with the others,
1307 including object file formats, most assembler directives (often called
1308 @dfn{pseudo-ops}) and assembler syntax.@refill
1310 @cindex purpose of @sc{gnu} assembler
1311 @command{@value{AS}} is primarily intended to assemble the output of the
1312 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1313 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1314 assemble correctly everything that other assemblers for the same
1315 machine would assemble.
1317 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1320 @c This remark should appear in generic version of manual; assumption
1321 @c here is that generic version sets M680x0.
1322 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1323 assembler for the same architecture; for example, we know of several
1324 incompatible versions of 680x0 assembly language syntax.
1329 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1330 program in one pass of the source file. This has a subtle impact on the
1331 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1333 @node Object Formats
1334 @section Object File Formats
1336 @cindex object file format
1337 The @sc{gnu} assembler can be configured to produce several alternative
1338 object file formats. For the most part, this does not affect how you
1339 write assembly language programs; but directives for debugging symbols
1340 are typically different in different file formats. @xref{Symbol
1341 Attributes,,Symbol Attributes}.
1344 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1345 @value{OBJ-NAME} format object files.
1347 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1349 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1350 @code{b.out} or COFF format object files.
1353 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1354 SOM or ELF format object files.
1359 @section Command Line
1361 @cindex command line conventions
1363 After the program name @command{@value{AS}}, the command line may contain
1364 options and file names. Options may appear in any order, and may be
1365 before, after, or between file names. The order of file names is
1368 @cindex standard input, as input file
1370 @file{--} (two hyphens) by itself names the standard input file
1371 explicitly, as one of the files for @command{@value{AS}} to assemble.
1373 @cindex options, command line
1374 Except for @samp{--} any command line argument that begins with a
1375 hyphen (@samp{-}) is an option. Each option changes the behavior of
1376 @command{@value{AS}}. No option changes the way another option works. An
1377 option is a @samp{-} followed by one or more letters; the case of
1378 the letter is important. All options are optional.
1380 Some options expect exactly one file name to follow them. The file
1381 name may either immediately follow the option's letter (compatible
1382 with older assemblers) or it may be the next command argument (@sc{gnu}
1383 standard). These two command lines are equivalent:
1386 @value{AS} -o my-object-file.o mumble.s
1387 @value{AS} -omy-object-file.o mumble.s
1391 @section Input Files
1394 @cindex source program
1395 @cindex files, input
1396 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1397 describe the program input to one run of @command{@value{AS}}. The program may
1398 be in one or more files; how the source is partitioned into files
1399 doesn't change the meaning of the source.
1401 @c I added "con" prefix to "catenation" just to prove I can overcome my
1402 @c APL training... doc@cygnus.com
1403 The source program is a concatenation of the text in all the files, in the
1406 @c man begin DESCRIPTION
1407 Each time you run @command{@value{AS}} it assembles exactly one source
1408 program. The source program is made up of one or more files.
1409 (The standard input is also a file.)
1411 You give @command{@value{AS}} a command line that has zero or more input file
1412 names. The input files are read (from left file name to right). A
1413 command line argument (in any position) that has no special meaning
1414 is taken to be an input file name.
1416 If you give @command{@value{AS}} no file names it attempts to read one input file
1417 from the @command{@value{AS}} standard input, which is normally your terminal. You
1418 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1421 Use @samp{--} if you need to explicitly name the standard input file
1422 in your command line.
1424 If the source is empty, @command{@value{AS}} produces a small, empty object
1429 @subheading Filenames and Line-numbers
1431 @cindex input file linenumbers
1432 @cindex line numbers, in input files
1433 There are two ways of locating a line in the input file (or files) and
1434 either may be used in reporting error messages. One way refers to a line
1435 number in a physical file; the other refers to a line number in a
1436 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1438 @dfn{Physical files} are those files named in the command line given
1439 to @command{@value{AS}}.
1441 @dfn{Logical files} are simply names declared explicitly by assembler
1442 directives; they bear no relation to physical files. Logical file names help
1443 error messages reflect the original source file, when @command{@value{AS}} source
1444 is itself synthesized from other files. @command{@value{AS}} understands the
1445 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1446 @ref{File,,@code{.file}}.
1449 @section Output (Object) File
1455 Every time you run @command{@value{AS}} it produces an output file, which is
1456 your assembly language program translated into numbers. This file
1457 is the object file. Its default name is
1465 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1467 You can give it another name by using the @option{-o} option. Conventionally,
1468 object file names end with @file{.o}. The default name is used for historical
1469 reasons: older assemblers were capable of assembling self-contained programs
1470 directly into a runnable program. (For some formats, this isn't currently
1471 possible, but it can be done for the @code{a.out} format.)
1475 The object file is meant for input to the linker @code{@value{LD}}. It contains
1476 assembled program code, information to help @code{@value{LD}} integrate
1477 the assembled program into a runnable file, and (optionally) symbolic
1478 information for the debugger.
1480 @c link above to some info file(s) like the description of a.out.
1481 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1484 @section Error and Warning Messages
1486 @c man begin DESCRIPTION
1488 @cindex error messages
1489 @cindex warning messages
1490 @cindex messages from assembler
1491 @command{@value{AS}} may write warnings and error messages to the standard error
1492 file (usually your terminal). This should not happen when a compiler
1493 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1494 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1495 grave problem that stops the assembly.
1499 @cindex format of warning messages
1500 Warning messages have the format
1503 file_name:@b{NNN}:Warning Message Text
1507 @cindex line numbers, in warnings/errors
1508 (where @b{NNN} is a line number). If a logical file name has been given
1509 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1510 the current input file is used. If a logical line number was given
1512 (@pxref{Line,,@code{.line}})
1514 then it is used to calculate the number printed,
1515 otherwise the actual line in the current source file is printed. The
1516 message text is intended to be self explanatory (in the grand Unix
1519 @cindex format of error messages
1520 Error messages have the format
1522 file_name:@b{NNN}:FATAL:Error Message Text
1524 The file name and line number are derived as for warning
1525 messages. The actual message text may be rather less explanatory
1526 because many of them aren't supposed to happen.
1529 @chapter Command-Line Options
1531 @cindex options, all versions of assembler
1532 This chapter describes command-line options available in @emph{all}
1533 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1534 for options specific
1536 to the @value{TARGET} target.
1539 to particular machine architectures.
1542 @c man begin DESCRIPTION
1544 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1545 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1546 The assembler arguments must be separated from each other (and the @samp{-Wa})
1547 by commas. For example:
1550 gcc -c -g -O -Wa,-alh,-L file.c
1554 This passes two options to the assembler: @samp{-alh} (emit a listing to
1555 standard output with high-level and assembly source) and @samp{-L} (retain
1556 local symbols in the symbol table).
1558 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1559 command-line options are automatically passed to the assembler by the compiler.
1560 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1561 precisely what options it passes to each compilation pass, including the
1567 * a:: -a[cdhlns] enable listings
1568 * alternate:: --alternate enable alternate macro syntax
1569 * D:: -D for compatibility
1570 * f:: -f to work faster
1571 * I:: -I for .include search path
1572 @ifclear DIFF-TBL-KLUGE
1573 * K:: -K for compatibility
1575 @ifset DIFF-TBL-KLUGE
1576 * K:: -K for difference tables
1579 * L:: -L to retain local symbols
1580 * listing:: --listing-XXX to configure listing output
1581 * M:: -M or --mri to assemble in MRI compatibility mode
1582 * MD:: --MD for dependency tracking
1583 * o:: -o to name the object file
1584 * R:: -R to join data and text sections
1585 * statistics:: --statistics to see statistics about assembly
1586 * traditional-format:: --traditional-format for compatible output
1587 * v:: -v to announce version
1588 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1589 * Z:: -Z to make object file even after errors
1593 @section Enable Listings: @option{-a[cdhlns]}
1602 @cindex listings, enabling
1603 @cindex assembly listings, enabling
1605 These options enable listing output from the assembler. By itself,
1606 @samp{-a} requests high-level, assembly, and symbols listing.
1607 You can use other letters to select specific options for the list:
1608 @samp{-ah} requests a high-level language listing,
1609 @samp{-al} requests an output-program assembly listing, and
1610 @samp{-as} requests a symbol table listing.
1611 High-level listings require that a compiler debugging option like
1612 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1615 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1616 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1617 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1618 omitted from the listing.
1620 Use the @samp{-ad} option to omit debugging directives from the
1623 Once you have specified one of these options, you can further control
1624 listing output and its appearance using the directives @code{.list},
1625 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1627 The @samp{-an} option turns off all forms processing.
1628 If you do not request listing output with one of the @samp{-a} options, the
1629 listing-control directives have no effect.
1631 The letters after @samp{-a} may be combined into one option,
1632 @emph{e.g.}, @samp{-aln}.
1634 Note if the assembler source is coming from the standard input (e.g.,
1636 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1637 is being used) then the listing will not contain any comments or preprocessor
1638 directives. This is because the listing code buffers input source lines from
1639 stdin only after they have been preprocessed by the assembler. This reduces
1640 memory usage and makes the code more efficient.
1643 @section @option{--alternate}
1646 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
1649 @section @option{-D}
1652 This option has no effect whatsoever, but it is accepted to make it more
1653 likely that scripts written for other assemblers also work with
1654 @command{@value{AS}}.
1657 @section Work Faster: @option{-f}
1660 @cindex trusted compiler
1661 @cindex faster processing (@option{-f})
1662 @samp{-f} should only be used when assembling programs written by a
1663 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1664 and comment preprocessing on
1665 the input file(s) before assembling them. @xref{Preprocessing,
1669 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1670 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1675 @section @code{.include} Search Path: @option{-I} @var{path}
1677 @kindex -I @var{path}
1678 @cindex paths for @code{.include}
1679 @cindex search path for @code{.include}
1680 @cindex @code{include} directive search path
1681 Use this option to add a @var{path} to the list of directories
1682 @command{@value{AS}} searches for files specified in @code{.include}
1683 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1684 many times as necessary to include a variety of paths. The current
1685 working directory is always searched first; after that, @command{@value{AS}}
1686 searches any @samp{-I} directories in the same order as they were
1687 specified (left to right) on the command line.
1690 @section Difference Tables: @option{-K}
1693 @ifclear DIFF-TBL-KLUGE
1694 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1695 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1696 where it can be used to warn when the assembler alters the machine code
1697 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1698 family does not have the addressing limitations that sometimes lead to this
1699 alteration on other platforms.
1702 @ifset DIFF-TBL-KLUGE
1703 @cindex difference tables, warning
1704 @cindex warning for altered difference tables
1705 @command{@value{AS}} sometimes alters the code emitted for directives of the
1706 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
1707 You can use the @samp{-K} option if you want a warning issued when this
1712 @section Include Local Symbols: @option{-L}
1715 @cindex local symbols, retaining in output
1716 Symbols beginning with system-specific local label prefixes, typically
1717 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
1718 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
1719 such symbols when debugging, because they are intended for the use of
1720 programs (like compilers) that compose assembler programs, not for your
1721 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
1722 such symbols, so you do not normally debug with them.
1724 This option tells @command{@value{AS}} to retain those local symbols
1725 in the object file. Usually if you do this you also tell the linker
1726 @code{@value{LD}} to preserve those symbols.
1729 @section Configuring listing output: @option{--listing}
1731 The listing feature of the assembler can be enabled via the command line switch
1732 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1733 hex dump of the corresponding locations in the output object file, and displays
1734 them as a listing file. The format of this listing can be controlled by
1735 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
1736 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
1737 @code{.psize} (@pxref{Psize}), and
1738 @code{.eject} (@pxref{Eject}) and also by the following switches:
1741 @item --listing-lhs-width=@samp{number}
1742 @kindex --listing-lhs-width
1743 @cindex Width of first line disassembly output
1744 Sets the maximum width, in words, of the first line of the hex byte dump. This
1745 dump appears on the left hand side of the listing output.
1747 @item --listing-lhs-width2=@samp{number}
1748 @kindex --listing-lhs-width2
1749 @cindex Width of continuation lines of disassembly output
1750 Sets the maximum width, in words, of any further lines of the hex byte dump for
1751 a given input source line. If this value is not specified, it defaults to being
1752 the same as the value specified for @samp{--listing-lhs-width}. If neither
1753 switch is used the default is to one.
1755 @item --listing-rhs-width=@samp{number}
1756 @kindex --listing-rhs-width
1757 @cindex Width of source line output
1758 Sets the maximum width, in characters, of the source line that is displayed
1759 alongside the hex dump. The default value for this parameter is 100. The
1760 source line is displayed on the right hand side of the listing output.
1762 @item --listing-cont-lines=@samp{number}
1763 @kindex --listing-cont-lines
1764 @cindex Maximum number of continuation lines
1765 Sets the maximum number of continuation lines of hex dump that will be
1766 displayed for a given single line of source input. The default value is 4.
1770 @section Assemble in MRI Compatibility Mode: @option{-M}
1773 @cindex MRI compatibility mode
1774 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1775 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1776 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1777 configured target) assembler from Microtec Research. The exact nature of the
1778 MRI syntax will not be documented here; see the MRI manuals for more
1779 information. Note in particular that the handling of macros and macro
1780 arguments is somewhat different. The purpose of this option is to permit
1781 assembling existing MRI assembler code using @command{@value{AS}}.
1783 The MRI compatibility is not complete. Certain operations of the MRI assembler
1784 depend upon its object file format, and can not be supported using other object
1785 file formats. Supporting these would require enhancing each object file format
1786 individually. These are:
1789 @item global symbols in common section
1791 The m68k MRI assembler supports common sections which are merged by the linker.
1792 Other object file formats do not support this. @command{@value{AS}} handles
1793 common sections by treating them as a single common symbol. It permits local
1794 symbols to be defined within a common section, but it can not support global
1795 symbols, since it has no way to describe them.
1797 @item complex relocations
1799 The MRI assemblers support relocations against a negated section address, and
1800 relocations which combine the start addresses of two or more sections. These
1801 are not support by other object file formats.
1803 @item @code{END} pseudo-op specifying start address
1805 The MRI @code{END} pseudo-op permits the specification of a start address.
1806 This is not supported by other object file formats. The start address may
1807 instead be specified using the @option{-e} option to the linker, or in a linker
1810 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1812 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1813 name to the output file. This is not supported by other object file formats.
1815 @item @code{ORG} pseudo-op
1817 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1818 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
1819 which changes the location within the current section. Absolute sections are
1820 not supported by other object file formats. The address of a section may be
1821 assigned within a linker script.
1824 There are some other features of the MRI assembler which are not supported by
1825 @command{@value{AS}}, typically either because they are difficult or because they
1826 seem of little consequence. Some of these may be supported in future releases.
1830 @item EBCDIC strings
1832 EBCDIC strings are not supported.
1834 @item packed binary coded decimal
1836 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1837 and @code{DCB.P} pseudo-ops are not supported.
1839 @item @code{FEQU} pseudo-op
1841 The m68k @code{FEQU} pseudo-op is not supported.
1843 @item @code{NOOBJ} pseudo-op
1845 The m68k @code{NOOBJ} pseudo-op is not supported.
1847 @item @code{OPT} branch control options
1849 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1850 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
1851 relaxes all branches, whether forward or backward, to an appropriate size, so
1852 these options serve no purpose.
1854 @item @code{OPT} list control options
1856 The following m68k @code{OPT} list control options are ignored: @code{C},
1857 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1858 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1860 @item other @code{OPT} options
1862 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1863 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1865 @item @code{OPT} @code{D} option is default
1867 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1868 @code{OPT NOD} may be used to turn it off.
1870 @item @code{XREF} pseudo-op.
1872 The m68k @code{XREF} pseudo-op is ignored.
1874 @item @code{.debug} pseudo-op
1876 The i960 @code{.debug} pseudo-op is not supported.
1878 @item @code{.extended} pseudo-op
1880 The i960 @code{.extended} pseudo-op is not supported.
1882 @item @code{.list} pseudo-op.
1884 The various options of the i960 @code{.list} pseudo-op are not supported.
1886 @item @code{.optimize} pseudo-op
1888 The i960 @code{.optimize} pseudo-op is not supported.
1890 @item @code{.output} pseudo-op
1892 The i960 @code{.output} pseudo-op is not supported.
1894 @item @code{.setreal} pseudo-op
1896 The i960 @code{.setreal} pseudo-op is not supported.
1901 @section Dependency Tracking: @option{--MD}
1904 @cindex dependency tracking
1907 @command{@value{AS}} can generate a dependency file for the file it creates. This
1908 file consists of a single rule suitable for @code{make} describing the
1909 dependencies of the main source file.
1911 The rule is written to the file named in its argument.
1913 This feature is used in the automatic updating of makefiles.
1916 @section Name the Object File: @option{-o}
1919 @cindex naming object file
1920 @cindex object file name
1921 There is always one object file output when you run @command{@value{AS}}. By
1922 default it has the name
1925 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1939 You use this option (which takes exactly one filename) to give the
1940 object file a different name.
1942 Whatever the object file is called, @command{@value{AS}} overwrites any
1943 existing file of the same name.
1946 @section Join Data and Text Sections: @option{-R}
1949 @cindex data and text sections, joining
1950 @cindex text and data sections, joining
1951 @cindex joining text and data sections
1952 @cindex merging text and data sections
1953 @option{-R} tells @command{@value{AS}} to write the object file as if all
1954 data-section data lives in the text section. This is only done at
1955 the very last moment: your binary data are the same, but data
1956 section parts are relocated differently. The data section part of
1957 your object file is zero bytes long because all its bytes are
1958 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1960 When you specify @option{-R} it would be possible to generate shorter
1961 address displacements (because we do not have to cross between text and
1962 data section). We refrain from doing this simply for compatibility with
1963 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
1966 When @command{@value{AS}} is configured for COFF or ELF output,
1967 this option is only useful if you use sections named @samp{.text} and
1972 @option{-R} is not supported for any of the HPPA targets. Using
1973 @option{-R} generates a warning from @command{@value{AS}}.
1977 @section Display Assembly Statistics: @option{--statistics}
1979 @kindex --statistics
1980 @cindex statistics, about assembly
1981 @cindex time, total for assembly
1982 @cindex space used, maximum for assembly
1983 Use @samp{--statistics} to display two statistics about the resources used by
1984 @command{@value{AS}}: the maximum amount of space allocated during the assembly
1985 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1988 @node traditional-format
1989 @section Compatible Output: @option{--traditional-format}
1991 @kindex --traditional-format
1992 For some targets, the output of @command{@value{AS}} is different in some ways
1993 from the output of some existing assembler. This switch requests
1994 @command{@value{AS}} to use the traditional format instead.
1996 For example, it disables the exception frame optimizations which
1997 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2000 @section Announce Version: @option{-v}
2004 @cindex assembler version
2005 @cindex version of assembler
2006 You can find out what version of as is running by including the
2007 option @samp{-v} (which you can also spell as @samp{-version}) on the
2011 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2013 @command{@value{AS}} should never give a warning or error message when
2014 assembling compiler output. But programs written by people often
2015 cause @command{@value{AS}} to give a warning that a particular assumption was
2016 made. All such warnings are directed to the standard error file.
2020 @cindex suppressing warnings
2021 @cindex warnings, suppressing
2022 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2023 This only affects the warning messages: it does not change any particular of
2024 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2027 @kindex --fatal-warnings
2028 @cindex errors, caused by warnings
2029 @cindex warnings, causing error
2030 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2031 files that generate warnings to be in error.
2034 @cindex warnings, switching on
2035 You can switch these options off again by specifying @option{--warn}, which
2036 causes warnings to be output as usual.
2039 @section Generate Object File in Spite of Errors: @option{-Z}
2040 @cindex object file, after errors
2041 @cindex errors, continuing after
2042 After an error message, @command{@value{AS}} normally produces no output. If for
2043 some reason you are interested in object file output even after
2044 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2045 option. If there are any errors, @command{@value{AS}} continues anyways, and
2046 writes an object file after a final warning message of the form @samp{@var{n}
2047 errors, @var{m} warnings, generating bad object file.}
2052 @cindex machine-independent syntax
2053 @cindex syntax, machine-independent
2054 This chapter describes the machine-independent syntax allowed in a
2055 source file. @command{@value{AS}} syntax is similar to what many other
2056 assemblers use; it is inspired by the BSD 4.2
2061 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2065 * Preprocessing:: Preprocessing
2066 * Whitespace:: Whitespace
2067 * Comments:: Comments
2068 * Symbol Intro:: Symbols
2069 * Statements:: Statements
2070 * Constants:: Constants
2074 @section Preprocessing
2076 @cindex preprocessing
2077 The @command{@value{AS}} internal preprocessor:
2079 @cindex whitespace, removed by preprocessor
2081 adjusts and removes extra whitespace. It leaves one space or tab before
2082 the keywords on a line, and turns any other whitespace on the line into
2085 @cindex comments, removed by preprocessor
2087 removes all comments, replacing them with a single space, or an
2088 appropriate number of newlines.
2090 @cindex constants, converted by preprocessor
2092 converts character constants into the appropriate numeric values.
2095 It does not do macro processing, include file handling, or
2096 anything else you may get from your C compiler's preprocessor. You can
2097 do include file processing with the @code{.include} directive
2098 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2099 to get other ``CPP'' style preprocessing by giving the input file a
2100 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2101 Output, gcc.info, Using GNU CC}.
2103 Excess whitespace, comments, and character constants
2104 cannot be used in the portions of the input text that are not
2107 @cindex turning preprocessing on and off
2108 @cindex preprocessing, turning on and off
2111 If the first line of an input file is @code{#NO_APP} or if you use the
2112 @samp{-f} option, whitespace and comments are not removed from the input file.
2113 Within an input file, you can ask for whitespace and comment removal in
2114 specific portions of the by putting a line that says @code{#APP} before the
2115 text that may contain whitespace or comments, and putting a line that says
2116 @code{#NO_APP} after this text. This feature is mainly intend to support
2117 @code{asm} statements in compilers whose output is otherwise free of comments
2124 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2125 Whitespace is used to separate symbols, and to make programs neater for
2126 people to read. Unless within character constants
2127 (@pxref{Characters,,Character Constants}), any whitespace means the same
2128 as exactly one space.
2134 There are two ways of rendering comments to @command{@value{AS}}. In both
2135 cases the comment is equivalent to one space.
2137 Anything from @samp{/*} through the next @samp{*/} is a comment.
2138 This means you may not nest these comments.
2142 The only way to include a newline ('\n') in a comment
2143 is to use this sort of comment.
2146 /* This sort of comment does not nest. */
2149 @cindex line comment character
2150 Anything from the @dfn{line comment} character to the next newline
2151 is considered a comment and is ignored. The line comment character is
2153 @samp{;} on the ARC;
2156 @samp{@@} on the ARM;
2159 @samp{;} for the H8/300 family;
2162 @samp{;} for the HPPA;
2165 @samp{#} on the i386 and x86-64;
2168 @samp{#} on the i960;
2171 @samp{;} for the PDP-11;
2174 @samp{;} for picoJava;
2177 @samp{#} for Motorola PowerPC;
2180 @samp{!} for the Renesas / SuperH SH;
2183 @samp{!} on the SPARC;
2186 @samp{#} on the ip2k;
2189 @samp{#} on the m32c;
2192 @samp{#} on the m32r;
2195 @samp{|} on the 680x0;
2198 @samp{#} on the 68HC11 and 68HC12;
2201 @samp{#} on the Vax;
2204 @samp{;} for the Z80;
2207 @samp{!} for the Z8000;
2210 @samp{#} on the V850;
2213 @samp{#} for Xtensa systems;
2215 see @ref{Machine Dependencies}. @refill
2216 @c FIXME What about i860?
2219 On some machines there are two different line comment characters. One
2220 character only begins a comment if it is the first non-whitespace character on
2221 a line, while the other always begins a comment.
2225 The V850 assembler also supports a double dash as starting a comment that
2226 extends to the end of the line.
2232 @cindex lines starting with @code{#}
2233 @cindex logical line numbers
2234 To be compatible with past assemblers, lines that begin with @samp{#} have a
2235 special interpretation. Following the @samp{#} should be an absolute
2236 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2237 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2238 new logical file name. The rest of the line, if any, should be whitespace.
2240 If the first non-whitespace characters on the line are not numeric,
2241 the line is ignored. (Just like a comment.)
2244 # This is an ordinary comment.
2245 # 42-6 "new_file_name" # New logical file name
2246 # This is logical line # 36.
2248 This feature is deprecated, and may disappear from future versions
2249 of @command{@value{AS}}.
2254 @cindex characters used in symbols
2255 @ifclear SPECIAL-SYMS
2256 A @dfn{symbol} is one or more characters chosen from the set of all
2257 letters (both upper and lower case), digits and the three characters
2263 A @dfn{symbol} is one or more characters chosen from the set of all
2264 letters (both upper and lower case), digits and the three characters
2265 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2271 On most machines, you can also use @code{$} in symbol names; exceptions
2272 are noted in @ref{Machine Dependencies}.
2274 No symbol may begin with a digit. Case is significant.
2275 There is no length limit: all characters are significant. Symbols are
2276 delimited by characters not in that set, or by the beginning of a file
2277 (since the source program must end with a newline, the end of a file is
2278 not a possible symbol delimiter). @xref{Symbols}.
2279 @cindex length of symbols
2284 @cindex statements, structure of
2285 @cindex line separator character
2286 @cindex statement separator character
2288 @ifclear abnormal-separator
2289 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
2290 semicolon (@samp{;}). The newline or semicolon is considered part of
2291 the preceding statement. Newlines and semicolons within character
2292 constants are an exception: they do not end statements.
2294 @ifset abnormal-separator
2296 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
2297 point (@samp{!}). The newline or exclamation point is considered part of the
2298 preceding statement. Newlines and exclamation points within character
2299 constants are an exception: they do not end statements.
2302 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
2303 H8/300) a dollar sign (@samp{$}); or (for the Renesas-SH) a semicolon
2304 (@samp{;}). The newline or separator character is considered part of
2305 the preceding statement. Newlines and separators within character
2306 constants are an exception: they do not end statements.
2311 A @dfn{statement} ends at a newline character (@samp{\n}) or line
2312 separator character. (The line separator is usually @samp{;}, unless this
2313 conflicts with the comment character; see @ref{Machine Dependencies}.) The
2314 newline or separator character is considered part of the preceding
2315 statement. Newlines and separators within character constants are an
2316 exception: they do not end statements.
2319 @cindex newline, required at file end
2320 @cindex EOF, newline must precede
2321 It is an error to end any statement with end-of-file: the last
2322 character of any input file should be a newline.@refill
2324 An empty statement is allowed, and may include whitespace. It is ignored.
2326 @cindex instructions and directives
2327 @cindex directives and instructions
2328 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2329 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2331 A statement begins with zero or more labels, optionally followed by a
2332 key symbol which determines what kind of statement it is. The key
2333 symbol determines the syntax of the rest of the statement. If the
2334 symbol begins with a dot @samp{.} then the statement is an assembler
2335 directive: typically valid for any computer. If the symbol begins with
2336 a letter the statement is an assembly language @dfn{instruction}: it
2337 assembles into a machine language instruction.
2339 Different versions of @command{@value{AS}} for different computers
2340 recognize different instructions. In fact, the same symbol may
2341 represent a different instruction in a different computer's assembly
2345 @cindex @code{:} (label)
2346 @cindex label (@code{:})
2347 A label is a symbol immediately followed by a colon (@code{:}).
2348 Whitespace before a label or after a colon is permitted, but you may not
2349 have whitespace between a label's symbol and its colon. @xref{Labels}.
2352 For HPPA targets, labels need not be immediately followed by a colon, but
2353 the definition of a label must begin in column zero. This also implies that
2354 only one label may be defined on each line.
2358 label: .directive followed by something
2359 another_label: # This is an empty statement.
2360 instruction operand_1, operand_2, @dots{}
2367 A constant is a number, written so that its value is known by
2368 inspection, without knowing any context. Like this:
2371 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2372 .ascii "Ring the bell\7" # A string constant.
2373 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2374 .float 0f-314159265358979323846264338327\
2375 95028841971.693993751E-40 # - pi, a flonum.
2380 * Characters:: Character Constants
2381 * Numbers:: Number Constants
2385 @subsection Character Constants
2387 @cindex character constants
2388 @cindex constants, character
2389 There are two kinds of character constants. A @dfn{character} stands
2390 for one character in one byte and its value may be used in
2391 numeric expressions. String constants (properly called string
2392 @emph{literals}) are potentially many bytes and their values may not be
2393 used in arithmetic expressions.
2397 * Chars:: Characters
2401 @subsubsection Strings
2403 @cindex string constants
2404 @cindex constants, string
2405 A @dfn{string} is written between double-quotes. It may contain
2406 double-quotes or null characters. The way to get special characters
2407 into a string is to @dfn{escape} these characters: precede them with
2408 a backslash @samp{\} character. For example @samp{\\} represents
2409 one backslash: the first @code{\} is an escape which tells
2410 @command{@value{AS}} to interpret the second character literally as a backslash
2411 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2412 escape character). The complete list of escapes follows.
2414 @cindex escape codes, character
2415 @cindex character escape codes
2418 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2420 @cindex @code{\b} (backspace character)
2421 @cindex backspace (@code{\b})
2423 Mnemonic for backspace; for ASCII this is octal code 010.
2426 @c Mnemonic for EOText; for ASCII this is octal code 004.
2428 @cindex @code{\f} (formfeed character)
2429 @cindex formfeed (@code{\f})
2431 Mnemonic for FormFeed; for ASCII this is octal code 014.
2433 @cindex @code{\n} (newline character)
2434 @cindex newline (@code{\n})
2436 Mnemonic for newline; for ASCII this is octal code 012.
2439 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2441 @cindex @code{\r} (carriage return character)
2442 @cindex carriage return (@code{\r})
2444 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2447 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2448 @c other assemblers.
2450 @cindex @code{\t} (tab)
2451 @cindex tab (@code{\t})
2453 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2456 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2457 @c @item \x @var{digit} @var{digit} @var{digit}
2458 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2460 @cindex @code{\@var{ddd}} (octal character code)
2461 @cindex octal character code (@code{\@var{ddd}})
2462 @item \ @var{digit} @var{digit} @var{digit}
2463 An octal character code. The numeric code is 3 octal digits.
2464 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2465 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2467 @cindex @code{\@var{xd...}} (hex character code)
2468 @cindex hex character code (@code{\@var{xd...}})
2469 @item \@code{x} @var{hex-digits...}
2470 A hex character code. All trailing hex digits are combined. Either upper or
2471 lower case @code{x} works.
2473 @cindex @code{\\} (@samp{\} character)
2474 @cindex backslash (@code{\\})
2476 Represents one @samp{\} character.
2479 @c Represents one @samp{'} (accent acute) character.
2480 @c This is needed in single character literals
2481 @c (@xref{Characters,,Character Constants}.) to represent
2484 @cindex @code{\"} (doublequote character)
2485 @cindex doublequote (@code{\"})
2487 Represents one @samp{"} character. Needed in strings to represent
2488 this character, because an unescaped @samp{"} would end the string.
2490 @item \ @var{anything-else}
2491 Any other character when escaped by @kbd{\} gives a warning, but
2492 assembles as if the @samp{\} was not present. The idea is that if
2493 you used an escape sequence you clearly didn't want the literal
2494 interpretation of the following character. However @command{@value{AS}} has no
2495 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2496 code and warns you of the fact.
2499 Which characters are escapable, and what those escapes represent,
2500 varies widely among assemblers. The current set is what we think
2501 the BSD 4.2 assembler recognizes, and is a subset of what most C
2502 compilers recognize. If you are in doubt, do not use an escape
2506 @subsubsection Characters
2508 @cindex single character constant
2509 @cindex character, single
2510 @cindex constant, single character
2511 A single character may be written as a single quote immediately
2512 followed by that character. The same escapes apply to characters as
2513 to strings. So if you want to write the character backslash, you
2514 must write @kbd{'\\} where the first @code{\} escapes the second
2515 @code{\}. As you can see, the quote is an acute accent, not a
2516 grave accent. A newline
2518 @ifclear abnormal-separator
2519 (or semicolon @samp{;})
2521 @ifset abnormal-separator
2523 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2528 immediately following an acute accent is taken as a literal character
2529 and does not count as the end of a statement. The value of a character
2530 constant in a numeric expression is the machine's byte-wide code for
2531 that character. @command{@value{AS}} assumes your character code is ASCII:
2532 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2535 @subsection Number Constants
2537 @cindex constants, number
2538 @cindex number constants
2539 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2540 are stored in the target machine. @emph{Integers} are numbers that
2541 would fit into an @code{int} in the C language. @emph{Bignums} are
2542 integers, but they are stored in more than 32 bits. @emph{Flonums}
2543 are floating point numbers, described below.
2546 * Integers:: Integers
2551 * Bit Fields:: Bit Fields
2557 @subsubsection Integers
2559 @cindex constants, integer
2561 @cindex binary integers
2562 @cindex integers, binary
2563 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2564 the binary digits @samp{01}.
2566 @cindex octal integers
2567 @cindex integers, octal
2568 An octal integer is @samp{0} followed by zero or more of the octal
2569 digits (@samp{01234567}).
2571 @cindex decimal integers
2572 @cindex integers, decimal
2573 A decimal integer starts with a non-zero digit followed by zero or
2574 more digits (@samp{0123456789}).
2576 @cindex hexadecimal integers
2577 @cindex integers, hexadecimal
2578 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2579 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2581 Integers have the usual values. To denote a negative integer, use
2582 the prefix operator @samp{-} discussed under expressions
2583 (@pxref{Prefix Ops,,Prefix Operators}).
2586 @subsubsection Bignums
2589 @cindex constants, bignum
2590 A @dfn{bignum} has the same syntax and semantics as an integer
2591 except that the number (or its negative) takes more than 32 bits to
2592 represent in binary. The distinction is made because in some places
2593 integers are permitted while bignums are not.
2596 @subsubsection Flonums
2598 @cindex floating point numbers
2599 @cindex constants, floating point
2601 @cindex precision, floating point
2602 A @dfn{flonum} represents a floating point number. The translation is
2603 indirect: a decimal floating point number from the text is converted by
2604 @command{@value{AS}} to a generic binary floating point number of more than
2605 sufficient precision. This generic floating point number is converted
2606 to a particular computer's floating point format (or formats) by a
2607 portion of @command{@value{AS}} specialized to that computer.
2609 A flonum is written by writing (in order)
2614 (@samp{0} is optional on the HPPA.)
2618 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2620 @kbd{e} is recommended. Case is not important.
2622 @c FIXME: verify if flonum syntax really this vague for most cases
2623 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2624 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2627 On the H8/300, Renesas / SuperH SH,
2628 and AMD 29K architectures, the letter must be
2629 one of the letters @samp{DFPRSX} (in upper or lower case).
2631 On the ARC, the letter must be one of the letters @samp{DFRS}
2632 (in upper or lower case).
2634 On the Intel 960 architecture, the letter must be
2635 one of the letters @samp{DFT} (in upper or lower case).
2637 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2641 One of the letters @samp{DFRS} (in upper or lower case).
2644 One of the letters @samp{DFPRSX} (in upper or lower case).
2647 The letter @samp{E} (upper case only).
2650 One of the letters @samp{DFT} (in upper or lower case).
2655 An optional sign: either @samp{+} or @samp{-}.
2658 An optional @dfn{integer part}: zero or more decimal digits.
2661 An optional @dfn{fractional part}: @samp{.} followed by zero
2662 or more decimal digits.
2665 An optional exponent, consisting of:
2669 An @samp{E} or @samp{e}.
2670 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2671 @c principle this can perfectly well be different on different targets.
2673 Optional sign: either @samp{+} or @samp{-}.
2675 One or more decimal digits.
2680 At least one of the integer part or the fractional part must be
2681 present. The floating point number has the usual base-10 value.
2683 @command{@value{AS}} does all processing using integers. Flonums are computed
2684 independently of any floating point hardware in the computer running
2685 @command{@value{AS}}.
2689 @c Bit fields are written as a general facility but are also controlled
2690 @c by a conditional-compilation flag---which is as of now (21mar91)
2691 @c turned on only by the i960 config of GAS.
2693 @subsubsection Bit Fields
2696 @cindex constants, bit field
2697 You can also define numeric constants as @dfn{bit fields}.
2698 Specify two numbers separated by a colon---
2700 @var{mask}:@var{value}
2703 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2706 The resulting number is then packed
2708 @c this conditional paren in case bit fields turned on elsewhere than 960
2709 (in host-dependent byte order)
2711 into a field whose width depends on which assembler directive has the
2712 bit-field as its argument. Overflow (a result from the bitwise and
2713 requiring more binary digits to represent) is not an error; instead,
2714 more constants are generated, of the specified width, beginning with the
2715 least significant digits.@refill
2717 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2718 @code{.short}, and @code{.word} accept bit-field arguments.
2723 @chapter Sections and Relocation
2728 * Secs Background:: Background
2729 * Ld Sections:: Linker Sections
2730 * As Sections:: Assembler Internal Sections
2731 * Sub-Sections:: Sub-Sections
2735 @node Secs Background
2738 Roughly, a section is a range of addresses, with no gaps; all data
2739 ``in'' those addresses is treated the same for some particular purpose.
2740 For example there may be a ``read only'' section.
2742 @cindex linker, and assembler
2743 @cindex assembler, and linker
2744 The linker @code{@value{LD}} reads many object files (partial programs) and
2745 combines their contents to form a runnable program. When @command{@value{AS}}
2746 emits an object file, the partial program is assumed to start at address 0.
2747 @code{@value{LD}} assigns the final addresses for the partial program, so that
2748 different partial programs do not overlap. This is actually an
2749 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2752 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2753 addresses. These blocks slide to their run-time addresses as rigid
2754 units; their length does not change and neither does the order of bytes
2755 within them. Such a rigid unit is called a @emph{section}. Assigning
2756 run-time addresses to sections is called @dfn{relocation}. It includes
2757 the task of adjusting mentions of object-file addresses so they refer to
2758 the proper run-time addresses.
2760 For the H8/300, and for the Renesas / SuperH SH,
2761 @command{@value{AS}} pads sections if needed to
2762 ensure they end on a word (sixteen bit) boundary.
2765 @cindex standard assembler sections
2766 An object file written by @command{@value{AS}} has at least three sections, any
2767 of which may be empty. These are named @dfn{text}, @dfn{data} and
2772 When it generates COFF or ELF output,
2774 @command{@value{AS}} can also generate whatever other named sections you specify
2775 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2776 If you do not use any directives that place output in the @samp{.text}
2777 or @samp{.data} sections, these sections still exist, but are empty.
2782 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2784 @command{@value{AS}} can also generate whatever other named sections you
2785 specify using the @samp{.space} and @samp{.subspace} directives. See
2786 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2787 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2788 assembler directives.
2791 Additionally, @command{@value{AS}} uses different names for the standard
2792 text, data, and bss sections when generating SOM output. Program text
2793 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2794 BSS into @samp{$BSS$}.
2798 Within the object file, the text section starts at address @code{0}, the
2799 data section follows, and the bss section follows the data section.
2802 When generating either SOM or ELF output files on the HPPA, the text
2803 section starts at address @code{0}, the data section at address
2804 @code{0x4000000}, and the bss section follows the data section.
2807 To let @code{@value{LD}} know which data changes when the sections are
2808 relocated, and how to change that data, @command{@value{AS}} also writes to the
2809 object file details of the relocation needed. To perform relocation
2810 @code{@value{LD}} must know, each time an address in the object
2814 Where in the object file is the beginning of this reference to
2817 How long (in bytes) is this reference?
2819 Which section does the address refer to? What is the numeric value of
2821 (@var{address}) @minus{} (@var{start-address of section})?
2824 Is the reference to an address ``Program-Counter relative''?
2827 @cindex addresses, format of
2828 @cindex section-relative addressing
2829 In fact, every address @command{@value{AS}} ever uses is expressed as
2831 (@var{section}) + (@var{offset into section})
2834 Further, most expressions @command{@value{AS}} computes have this section-relative
2837 (For some object formats, such as SOM for the HPPA, some expressions are
2838 symbol-relative instead.)
2841 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2842 @var{N} into section @var{secname}.''
2844 Apart from text, data and bss sections you need to know about the
2845 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2846 addresses in the absolute section remain unchanged. For example, address
2847 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2848 @code{@value{LD}}. Although the linker never arranges two partial programs'
2849 data sections with overlapping addresses after linking, @emph{by definition}
2850 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2851 part of a program is always the same address when the program is running as
2852 address @code{@{absolute@ 239@}} in any other part of the program.
2854 The idea of sections is extended to the @dfn{undefined} section. Any
2855 address whose section is unknown at assembly time is by definition
2856 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2857 Since numbers are always defined, the only way to generate an undefined
2858 address is to mention an undefined symbol. A reference to a named
2859 common block would be such a symbol: its value is unknown at assembly
2860 time so it has section @emph{undefined}.
2862 By analogy the word @emph{section} is used to describe groups of sections in
2863 the linked program. @code{@value{LD}} puts all partial programs' text
2864 sections in contiguous addresses in the linked program. It is
2865 customary to refer to the @emph{text section} of a program, meaning all
2866 the addresses of all partial programs' text sections. Likewise for
2867 data and bss sections.
2869 Some sections are manipulated by @code{@value{LD}}; others are invented for
2870 use of @command{@value{AS}} and have no meaning except during assembly.
2873 @section Linker Sections
2874 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2879 @cindex named sections
2880 @cindex sections, named
2881 @item named sections
2884 @cindex text section
2885 @cindex data section
2889 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
2890 separate but equal sections. Anything you can say of one section is
2893 When the program is running, however, it is
2894 customary for the text section to be unalterable. The
2895 text section is often shared among processes: it contains
2896 instructions, constants and the like. The data section of a running
2897 program is usually alterable: for example, C variables would be stored
2898 in the data section.
2903 This section contains zeroed bytes when your program begins running. It
2904 is used to hold uninitialized variables or common storage. The length of
2905 each partial program's bss section is important, but because it starts
2906 out containing zeroed bytes there is no need to store explicit zero
2907 bytes in the object file. The bss section was invented to eliminate
2908 those explicit zeros from object files.
2910 @cindex absolute section
2911 @item absolute section
2912 Address 0 of this section is always ``relocated'' to runtime address 0.
2913 This is useful if you want to refer to an address that @code{@value{LD}} must
2914 not change when relocating. In this sense we speak of absolute
2915 addresses being ``unrelocatable'': they do not change during relocation.
2917 @cindex undefined section
2918 @item undefined section
2919 This ``section'' is a catch-all for address references to objects not in
2920 the preceding sections.
2921 @c FIXME: ref to some other doc on obj-file formats could go here.
2924 @cindex relocation example
2925 An idealized example of three relocatable sections follows.
2927 The example uses the traditional section names @samp{.text} and @samp{.data}.
2929 Memory addresses are on the horizontal axis.
2933 @c END TEXI2ROFF-KILL
2936 partial program # 1: |ttttt|dddd|00|
2943 partial program # 2: |TTT|DDD|000|
2946 +--+---+-----+--+----+---+-----+~~
2947 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2948 +--+---+-----+--+----+---+-----+~~
2950 addresses: 0 @dots{}
2957 \line{\it Partial program \#1: \hfil}
2958 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2959 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2961 \line{\it Partial program \#2: \hfil}
2962 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2963 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2965 \line{\it linked program: \hfil}
2966 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2967 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2968 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2969 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2971 \line{\it addresses: \hfil}
2975 @c END TEXI2ROFF-KILL
2978 @section Assembler Internal Sections
2980 @cindex internal assembler sections
2981 @cindex sections in messages, internal
2982 These sections are meant only for the internal use of @command{@value{AS}}. They
2983 have no meaning at run-time. You do not really need to know about these
2984 sections for most purposes; but they can be mentioned in @command{@value{AS}}
2985 warning messages, so it might be helpful to have an idea of their
2986 meanings to @command{@value{AS}}. These sections are used to permit the
2987 value of every expression in your assembly language program to be a
2988 section-relative address.
2991 @cindex assembler internal logic error
2992 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2993 An internal assembler logic error has been found. This means there is a
2994 bug in the assembler.
2996 @cindex expr (internal section)
2998 The assembler stores complex expression internally as combinations of
2999 symbols. When it needs to represent an expression as a symbol, it puts
3000 it in the expr section.
3002 @c FIXME item transfer[t] vector preload
3003 @c FIXME item transfer[t] vector postload
3004 @c FIXME item register
3008 @section Sub-Sections
3010 @cindex numbered subsections
3011 @cindex grouping data
3017 fall into two sections: text and data.
3019 You may have separate groups of
3021 data in named sections
3025 data in named sections
3031 that you want to end up near to each other in the object file, even though they
3032 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3033 use @dfn{subsections} for this purpose. Within each section, there can be
3034 numbered subsections with values from 0 to 8192. Objects assembled into the
3035 same subsection go into the object file together with other objects in the same
3036 subsection. For example, a compiler might want to store constants in the text
3037 section, but might not want to have them interspersed with the program being
3038 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3039 section of code being output, and a @samp{.text 1} before each group of
3040 constants being output.
3042 Subsections are optional. If you do not use subsections, everything
3043 goes in subsection number zero.
3046 Each subsection is zero-padded up to a multiple of four bytes.
3047 (Subsections may be padded a different amount on different flavors
3048 of @command{@value{AS}}.)
3052 On the H8/300 platform, each subsection is zero-padded to a word
3053 boundary (two bytes).
3054 The same is true on the Renesas SH.
3057 @c FIXME section padding (alignment)?
3058 @c Rich Pixley says padding here depends on target obj code format; that
3059 @c doesn't seem particularly useful to say without further elaboration,
3060 @c so for now I say nothing about it. If this is a generic BFD issue,
3061 @c these paragraphs might need to vanish from this manual, and be
3062 @c discussed in BFD chapter of binutils (or some such).
3066 Subsections appear in your object file in numeric order, lowest numbered
3067 to highest. (All this to be compatible with other people's assemblers.)
3068 The object file contains no representation of subsections; @code{@value{LD}} and
3069 other programs that manipulate object files see no trace of them.
3070 They just see all your text subsections as a text section, and all your
3071 data subsections as a data section.
3073 To specify which subsection you want subsequent statements assembled
3074 into, use a numeric argument to specify it, in a @samp{.text
3075 @var{expression}} or a @samp{.data @var{expression}} statement.
3078 When generating COFF output, you
3083 can also use an extra subsection
3084 argument with arbitrary named sections: @samp{.section @var{name},
3089 When generating ELF output, you
3094 can also use the @code{.subsection} directive (@pxref{SubSection})
3095 to specify a subsection: @samp{.subsection @var{expression}}.
3097 @var{Expression} should be an absolute expression
3098 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3099 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3100 begins in @code{text 0}. For instance:
3102 .text 0 # The default subsection is text 0 anyway.
3103 .ascii "This lives in the first text subsection. *"
3105 .ascii "But this lives in the second text subsection."
3107 .ascii "This lives in the data section,"
3108 .ascii "in the first data subsection."
3110 .ascii "This lives in the first text section,"
3111 .ascii "immediately following the asterisk (*)."
3114 Each section has a @dfn{location counter} incremented by one for every byte
3115 assembled into that section. Because subsections are merely a convenience
3116 restricted to @command{@value{AS}} there is no concept of a subsection location
3117 counter. There is no way to directly manipulate a location counter---but the
3118 @code{.align} directive changes it, and any label definition captures its
3119 current value. The location counter of the section where statements are being
3120 assembled is said to be the @dfn{active} location counter.
3123 @section bss Section
3126 @cindex common variable storage
3127 The bss section is used for local common variable storage.
3128 You may allocate address space in the bss section, but you may
3129 not dictate data to load into it before your program executes. When
3130 your program starts running, all the contents of the bss
3131 section are zeroed bytes.
3133 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3134 @ref{Lcomm,,@code{.lcomm}}.
3136 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3137 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3140 When assembling for a target which supports multiple sections, such as ELF or
3141 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3142 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3143 section. Typically the section will only contain symbol definitions and
3144 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3151 Symbols are a central concept: the programmer uses symbols to name
3152 things, the linker uses symbols to link, and the debugger uses symbols
3156 @cindex debuggers, and symbol order
3157 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3158 the same order they were declared. This may break some debuggers.
3163 * Setting Symbols:: Giving Symbols Other Values
3164 * Symbol Names:: Symbol Names
3165 * Dot:: The Special Dot Symbol
3166 * Symbol Attributes:: Symbol Attributes
3173 A @dfn{label} is written as a symbol immediately followed by a colon
3174 @samp{:}. The symbol then represents the current value of the
3175 active location counter, and is, for example, a suitable instruction
3176 operand. You are warned if you use the same symbol to represent two
3177 different locations: the first definition overrides any other
3181 On the HPPA, the usual form for a label need not be immediately followed by a
3182 colon, but instead must start in column zero. Only one label may be defined on
3183 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3184 provides a special directive @code{.label} for defining labels more flexibly.
3187 @node Setting Symbols
3188 @section Giving Symbols Other Values
3190 @cindex assigning values to symbols
3191 @cindex symbol values, assigning
3192 A symbol can be given an arbitrary value by writing a symbol, followed
3193 by an equals sign @samp{=}, followed by an expression
3194 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3195 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3196 equals sign @samp{=}@samp{=} here represents an equivalent of the
3197 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3200 @section Symbol Names
3202 @cindex symbol names
3203 @cindex names, symbol
3204 @ifclear SPECIAL-SYMS
3205 Symbol names begin with a letter or with one of @samp{._}. On most
3206 machines, you can also use @code{$} in symbol names; exceptions are
3207 noted in @ref{Machine Dependencies}. That character may be followed by any
3208 string of digits, letters, dollar signs (unless otherwise noted for a
3209 particular target machine), and underscores.
3213 Symbol names begin with a letter or with one of @samp{._}. On the
3214 Renesas SH you can also use @code{$} in symbol names. That
3215 character may be followed by any string of digits, letters, dollar signs (save
3216 on the H8/300), and underscores.
3220 Case of letters is significant: @code{foo} is a different symbol name
3223 Each symbol has exactly one name. Each name in an assembly language program
3224 refers to exactly one symbol. You may use that symbol name any number of times
3227 @subheading Local Symbol Names
3229 @cindex local symbol names
3230 @cindex symbol names, local
3231 A local symbol is any symbol beginning with certain local label prefixes.
3232 By default, the local label prefix is @samp{.L} for ELF systems or
3233 @samp{L} for traditional a.out systems, but each target may have its own
3234 set of local label prefixes.
3236 On the HPPA local symbols begin with @samp{L$}.
3239 Local symbols are defined and used within the assembler, but they are
3240 normally not saved in object files. Thus, they are not visible when debugging.
3241 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3242 @option{-L}}) to retain the local symbols in the object files.
3244 @subheading Local Labels
3246 @cindex local labels
3247 @cindex temporary symbol names
3248 @cindex symbol names, temporary
3249 Local labels help compilers and programmers use names temporarily.
3250 They create symbols which are guaranteed to be unique over the entire scope of
3251 the input source code and which can be referred to by a simple notation.
3252 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3253 represents any positive integer). To refer to the most recent previous
3254 definition of that label write @samp{@b{N}b}, using the same number as when
3255 you defined the label. To refer to the next definition of a local label, write
3256 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3259 There is no restriction on how you can use these labels, and you can reuse them
3260 too. So that it is possible to repeatedly define the same local label (using
3261 the same number @samp{@b{N}}), although you can only refer to the most recently
3262 defined local label of that number (for a backwards reference) or the next
3263 definition of a specific local label for a forward reference. It is also worth
3264 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3265 implemented in a slightly more efficient manner than the others.
3276 Which is the equivalent of:
3279 label_1: branch label_3
3280 label_2: branch label_1
3281 label_3: branch label_4
3282 label_4: branch label_3
3285 Local label names are only a notational device. They are immediately
3286 transformed into more conventional symbol names before the assembler uses them.
3287 The symbol names are stored in the symbol table, appear in error messages, and
3288 are optionally emitted to the object file. The names are constructed using
3292 @item @emph{local label prefix}
3293 All local symbols begin with the system-specific local label prefix.
3294 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3295 that start with the local label prefix. These labels are
3296 used for symbols you are never intended to see. If you use the
3297 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3298 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3299 you may use them in debugging.
3302 This is the number that was used in the local label definition. So if the
3303 label is written @samp{55:} then the number is @samp{55}.
3306 This unusual character is included so you do not accidentally invent a symbol
3307 of the same name. The character has ASCII value of @samp{\002} (control-B).
3309 @item @emph{ordinal number}
3310 This is a serial number to keep the labels distinct. The first definition of
3311 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3312 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3313 the number @samp{1} and its 15th definition gets @samp{15} as well.
3316 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3317 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3319 @subheading Dollar Local Labels
3320 @cindex dollar local symbols
3322 @code{@value{AS}} also supports an even more local form of local labels called
3323 dollar labels. These labels go out of scope (i.e., they become undefined) as
3324 soon as a non-local label is defined. Thus they remain valid for only a small
3325 region of the input source code. Normal local labels, by contrast, remain in
3326 scope for the entire file, or until they are redefined by another occurrence of
3327 the same local label.
3329 Dollar labels are defined in exactly the same way as ordinary local labels,
3330 except that instead of being terminated by a colon, they are terminated by a
3331 dollar sign, e.g., @samp{@b{55$}}.
3333 They can also be distinguished from ordinary local labels by their transformed
3334 names which use ASCII character @samp{\001} (control-A) as the magic character
3335 to distinguish them from ordinary labels. For example, the fifth definition of
3336 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3339 @section The Special Dot Symbol
3341 @cindex dot (symbol)
3342 @cindex @code{.} (symbol)
3343 @cindex current address
3344 @cindex location counter
3345 The special symbol @samp{.} refers to the current address that
3346 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3347 .long .} defines @code{melvin} to contain its own address.
3348 Assigning a value to @code{.} is treated the same as a @code{.org}
3349 directive. Thus, the expression @samp{.=.+4} is the same as saying
3350 @ifclear no-space-dir
3354 @node Symbol Attributes
3355 @section Symbol Attributes
3357 @cindex symbol attributes
3358 @cindex attributes, symbol
3359 Every symbol has, as well as its name, the attributes ``Value'' and
3360 ``Type''. Depending on output format, symbols can also have auxiliary
3363 The detailed definitions are in @file{a.out.h}.
3366 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3367 all these attributes, and probably won't warn you. This makes the
3368 symbol an externally defined symbol, which is generally what you
3372 * Symbol Value:: Value
3373 * Symbol Type:: Type
3376 * a.out Symbols:: Symbol Attributes: @code{a.out}
3380 * a.out Symbols:: Symbol Attributes: @code{a.out}
3383 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3388 * COFF Symbols:: Symbol Attributes for COFF
3391 * SOM Symbols:: Symbol Attributes for SOM
3398 @cindex value of a symbol
3399 @cindex symbol value
3400 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3401 location in the text, data, bss or absolute sections the value is the
3402 number of addresses from the start of that section to the label.
3403 Naturally for text, data and bss sections the value of a symbol changes
3404 as @code{@value{LD}} changes section base addresses during linking. Absolute
3405 symbols' values do not change during linking: that is why they are
3408 The value of an undefined symbol is treated in a special way. If it is
3409 0 then the symbol is not defined in this assembler source file, and
3410 @code{@value{LD}} tries to determine its value from other files linked into the
3411 same program. You make this kind of symbol simply by mentioning a symbol
3412 name without defining it. A non-zero value represents a @code{.comm}
3413 common declaration. The value is how much common storage to reserve, in
3414 bytes (addresses). The symbol refers to the first address of the
3420 @cindex type of a symbol
3422 The type attribute of a symbol contains relocation (section)
3423 information, any flag settings indicating that a symbol is external, and
3424 (optionally), other information for linkers and debuggers. The exact
3425 format depends on the object-code output format in use.
3430 @c The following avoids a "widow" subsection title. @group would be
3431 @c better if it were available outside examples.
3434 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3436 @cindex @code{b.out} symbol attributes
3437 @cindex symbol attributes, @code{b.out}
3438 These symbol attributes appear only when @command{@value{AS}} is configured for
3439 one of the Berkeley-descended object output formats---@code{a.out} or
3445 @subsection Symbol Attributes: @code{a.out}
3447 @cindex @code{a.out} symbol attributes
3448 @cindex symbol attributes, @code{a.out}
3454 @subsection Symbol Attributes: @code{a.out}
3456 @cindex @code{a.out} symbol attributes
3457 @cindex symbol attributes, @code{a.out}
3461 * Symbol Desc:: Descriptor
3462 * Symbol Other:: Other
3466 @subsubsection Descriptor
3468 @cindex descriptor, of @code{a.out} symbol
3469 This is an arbitrary 16-bit value. You may establish a symbol's
3470 descriptor value by using a @code{.desc} statement
3471 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3472 @command{@value{AS}}.
3475 @subsubsection Other
3477 @cindex other attribute, of @code{a.out} symbol
3478 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3483 @subsection Symbol Attributes for COFF
3485 @cindex COFF symbol attributes
3486 @cindex symbol attributes, COFF
3488 The COFF format supports a multitude of auxiliary symbol attributes;
3489 like the primary symbol attributes, they are set between @code{.def} and
3490 @code{.endef} directives.
3492 @subsubsection Primary Attributes
3494 @cindex primary attributes, COFF symbols
3495 The symbol name is set with @code{.def}; the value and type,
3496 respectively, with @code{.val} and @code{.type}.
3498 @subsubsection Auxiliary Attributes
3500 @cindex auxiliary attributes, COFF symbols
3501 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3502 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3503 table information for COFF.
3508 @subsection Symbol Attributes for SOM
3510 @cindex SOM symbol attributes
3511 @cindex symbol attributes, SOM
3513 The SOM format for the HPPA supports a multitude of symbol attributes set with
3514 the @code{.EXPORT} and @code{.IMPORT} directives.
3516 The attributes are described in @cite{HP9000 Series 800 Assembly
3517 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3518 @code{EXPORT} assembler directive documentation.
3522 @chapter Expressions
3526 @cindex numeric values
3527 An @dfn{expression} specifies an address or numeric value.
3528 Whitespace may precede and/or follow an expression.
3530 The result of an expression must be an absolute number, or else an offset into
3531 a particular section. If an expression is not absolute, and there is not
3532 enough information when @command{@value{AS}} sees the expression to know its
3533 section, a second pass over the source program might be necessary to interpret
3534 the expression---but the second pass is currently not implemented.
3535 @command{@value{AS}} aborts with an error message in this situation.
3538 * Empty Exprs:: Empty Expressions
3539 * Integer Exprs:: Integer Expressions
3543 @section Empty Expressions
3545 @cindex empty expressions
3546 @cindex expressions, empty
3547 An empty expression has no value: it is just whitespace or null.
3548 Wherever an absolute expression is required, you may omit the
3549 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3550 is compatible with other assemblers.
3553 @section Integer Expressions
3555 @cindex integer expressions
3556 @cindex expressions, integer
3557 An @dfn{integer expression} is one or more @emph{arguments} delimited
3558 by @emph{operators}.
3561 * Arguments:: Arguments
3562 * Operators:: Operators
3563 * Prefix Ops:: Prefix Operators
3564 * Infix Ops:: Infix Operators
3568 @subsection Arguments
3570 @cindex expression arguments
3571 @cindex arguments in expressions
3572 @cindex operands in expressions
3573 @cindex arithmetic operands
3574 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3575 contexts arguments are sometimes called ``arithmetic operands''. In
3576 this manual, to avoid confusing them with the ``instruction operands'' of
3577 the machine language, we use the term ``argument'' to refer to parts of
3578 expressions only, reserving the word ``operand'' to refer only to machine
3579 instruction operands.
3581 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3582 @var{section} is one of text, data, bss, absolute,
3583 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3586 Numbers are usually integers.
3588 A number can be a flonum or bignum. In this case, you are warned
3589 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3590 these 32 bits are an integer. You may write integer-manipulating
3591 instructions that act on exotic constants, compatible with other
3594 @cindex subexpressions
3595 Subexpressions are a left parenthesis @samp{(} followed by an integer
3596 expression, followed by a right parenthesis @samp{)}; or a prefix
3597 operator followed by an argument.
3600 @subsection Operators
3602 @cindex operators, in expressions
3603 @cindex arithmetic functions
3604 @cindex functions, in expressions
3605 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3606 operators are followed by an argument. Infix operators appear
3607 between their arguments. Operators may be preceded and/or followed by
3611 @subsection Prefix Operator
3613 @cindex prefix operators
3614 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3615 one argument, which must be absolute.
3617 @c the tex/end tex stuff surrounding this small table is meant to make
3618 @c it align, on the printed page, with the similar table in the next
3619 @c section (which is inside an enumerate).
3621 \global\advance\leftskip by \itemindent
3626 @dfn{Negation}. Two's complement negation.
3628 @dfn{Complementation}. Bitwise not.
3632 \global\advance\leftskip by -\itemindent
3636 @subsection Infix Operators
3638 @cindex infix operators
3639 @cindex operators, permitted arguments
3640 @dfn{Infix operators} take two arguments, one on either side. Operators
3641 have precedence, but operations with equal precedence are performed left
3642 to right. Apart from @code{+} or @option{-}, both arguments must be
3643 absolute, and the result is absolute.
3646 @cindex operator precedence
3647 @cindex precedence of operators
3654 @dfn{Multiplication}.
3657 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3663 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3666 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3670 Intermediate precedence
3675 @dfn{Bitwise Inclusive Or}.
3681 @dfn{Bitwise Exclusive Or}.
3684 @dfn{Bitwise Or Not}.
3691 @cindex addition, permitted arguments
3692 @cindex plus, permitted arguments
3693 @cindex arguments for addition
3695 @dfn{Addition}. If either argument is absolute, the result has the section of
3696 the other argument. You may not add together arguments from different
3699 @cindex subtraction, permitted arguments
3700 @cindex minus, permitted arguments
3701 @cindex arguments for subtraction
3703 @dfn{Subtraction}. If the right argument is absolute, the
3704 result has the section of the left argument.
3705 If both arguments are in the same section, the result is absolute.
3706 You may not subtract arguments from different sections.
3707 @c FIXME is there still something useful to say about undefined - undefined ?
3709 @cindex comparison expressions
3710 @cindex expressions, comparison
3715 @dfn{Is Not Equal To}
3719 @dfn{Is Greater Than}
3721 @dfn{Is Greater Than Or Equal To}
3723 @dfn{Is Less Than Or Equal To}
3725 The comparison operators can be used as infix operators. A true results has a
3726 value of -1 whereas a false result has a value of 0. Note, these operators
3727 perform signed comparisons.
3730 @item Lowest Precedence
3739 These two logical operations can be used to combine the results of sub
3740 expressions. Note, unlike the comparison operators a true result returns a
3741 value of 1 but a false results does still return 0. Also note that the logical
3742 or operator has a slightly lower precedence than logical and.
3747 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3748 address; you can only have a defined section in one of the two arguments.
3751 @chapter Assembler Directives
3753 @cindex directives, machine independent
3754 @cindex pseudo-ops, machine independent
3755 @cindex machine independent directives
3756 All assembler directives have names that begin with a period (@samp{.}).
3757 The rest of the name is letters, usually in lower case.
3759 This chapter discusses directives that are available regardless of the
3760 target machine configuration for the @sc{gnu} assembler.
3762 Some machine configurations provide additional directives.
3763 @xref{Machine Dependencies}.
3766 @ifset machine-directives
3767 @xref{Machine Dependencies}, for additional directives.
3772 * Abort:: @code{.abort}
3774 * ABORT (COFF):: @code{.ABORT}
3777 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3778 * Altmacro:: @code{.altmacro}
3779 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3780 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3781 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3782 * Byte:: @code{.byte @var{expressions}}
3783 * Comm:: @code{.comm @var{symbol} , @var{length} }
3785 * CFI directives:: @code{.cfi_startproc}, @code{.cfi_endproc}, etc.
3787 * Data:: @code{.data @var{subsection}}
3789 * Def:: @code{.def @var{name}}
3792 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3798 * Double:: @code{.double @var{flonums}}
3799 * Eject:: @code{.eject}
3800 * Else:: @code{.else}
3801 * Elseif:: @code{.elseif}
3804 * Endef:: @code{.endef}
3807 * Endfunc:: @code{.endfunc}
3808 * Endif:: @code{.endif}
3809 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3810 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3811 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
3813 * Error:: @code{.error @var{string}}
3814 * Exitm:: @code{.exitm}
3815 * Extern:: @code{.extern}
3816 * Fail:: @code{.fail}
3817 @ifclear no-file-dir
3818 * File:: @code{.file @var{string}}
3821 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3822 * Float:: @code{.float @var{flonums}}
3823 * Func:: @code{.func}
3824 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3826 * Hidden:: @code{.hidden @var{names}}
3829 * hword:: @code{.hword @var{expressions}}
3830 * Ident:: @code{.ident}
3831 * If:: @code{.if @var{absolute expression}}
3832 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
3833 * Include:: @code{.include "@var{file}"}
3834 * Int:: @code{.int @var{expressions}}
3836 * Internal:: @code{.internal @var{names}}
3839 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3840 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3841 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3842 * Lflags:: @code{.lflags}
3843 @ifclear no-line-dir
3844 * Line:: @code{.line @var{line-number}}
3847 * Linkonce:: @code{.linkonce [@var{type}]}
3848 * List:: @code{.list}
3849 * Ln:: @code{.ln @var{line-number}}
3851 * LNS directives:: @code{.file}, @code{.loc}, etc.
3853 * Long:: @code{.long @var{expressions}}
3855 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3858 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3859 * MRI:: @code{.mri @var{val}}
3860 * Noaltmacro:: @code{.noaltmacro}
3861 * Nolist:: @code{.nolist}
3862 * Octa:: @code{.octa @var{bignums}}
3863 * Org:: @code{.org @var{new-lc}, @var{fill}}
3864 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3866 * PopSection:: @code{.popsection}
3867 * Previous:: @code{.previous}
3870 * Print:: @code{.print @var{string}}
3872 * Protected:: @code{.protected @var{names}}
3875 * Psize:: @code{.psize @var{lines}, @var{columns}}
3876 * Purgem:: @code{.purgem @var{name}}
3878 * PushSection:: @code{.pushsection @var{name}}
3881 * Quad:: @code{.quad @var{bignums}}
3882 * Rept:: @code{.rept @var{count}}
3883 * Sbttl:: @code{.sbttl "@var{subheading}"}
3885 * Scl:: @code{.scl @var{class}}
3888 * Section:: @code{.section @var{name}}
3891 * Set:: @code{.set @var{symbol}, @var{expression}}
3892 * Short:: @code{.short @var{expressions}}
3893 * Single:: @code{.single @var{flonums}}
3895 * Size:: @code{.size [@var{name} , @var{expression}]}
3898 * Skip:: @code{.skip @var{size} , @var{fill}}
3899 * Sleb128:: @code{.sleb128 @var{expressions}}
3900 * Space:: @code{.space @var{size} , @var{fill}}
3902 * Stab:: @code{.stabd, .stabn, .stabs}
3905 * String:: @code{.string "@var{str}"}
3906 * Struct:: @code{.struct @var{expression}}
3908 * SubSection:: @code{.subsection}
3909 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3913 * Tag:: @code{.tag @var{structname}}
3916 * Text:: @code{.text @var{subsection}}
3917 * Title:: @code{.title "@var{heading}"}
3919 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
3922 * Uleb128:: @code{.uleb128 @var{expressions}}
3924 * Val:: @code{.val @var{addr}}
3928 * Version:: @code{.version "@var{string}"}
3929 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
3930 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
3933 * Warning:: @code{.warning @var{string}}
3934 * Weak:: @code{.weak @var{names}}
3935 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
3936 * Word:: @code{.word @var{expressions}}
3937 * Deprecated:: Deprecated Directives
3941 @section @code{.abort}
3943 @cindex @code{abort} directive
3944 @cindex stopping the assembly
3945 This directive stops the assembly immediately. It is for
3946 compatibility with other assemblers. The original idea was that the
3947 assembly language source would be piped into the assembler. If the sender
3948 of the source quit, it could use this directive tells @command{@value{AS}} to
3949 quit also. One day @code{.abort} will not be supported.
3953 @section @code{.ABORT} (COFF)
3955 @cindex @code{ABORT} directive
3956 When producing COFF output, @command{@value{AS}} accepts this directive as a
3957 synonym for @samp{.abort}.
3960 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
3966 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3968 @cindex padding the location counter
3969 @cindex @code{align} directive
3970 Pad the location counter (in the current subsection) to a particular storage
3971 boundary. The first expression (which must be absolute) is the alignment
3972 required, as described below.
3974 The second expression (also absolute) gives the fill value to be stored in the
3975 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3976 padding bytes are normally zero. However, on some systems, if the section is
3977 marked as containing code and the fill value is omitted, the space is filled
3978 with no-op instructions.
3980 The third expression is also absolute, and is also optional. If it is present,
3981 it is the maximum number of bytes that should be skipped by this alignment
3982 directive. If doing the alignment would require skipping more bytes than the
3983 specified maximum, then the alignment is not done at all. You can omit the
3984 fill value (the second argument) entirely by simply using two commas after the
3985 required alignment; this can be useful if you want the alignment to be filled
3986 with no-op instructions when appropriate.
3988 The way the required alignment is specified varies from system to system.
3989 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
3990 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
3991 alignment request in bytes. For example @samp{.align 8} advances
3992 the location counter until it is a multiple of 8. If the location counter
3993 is already a multiple of 8, no change is needed. For the tic54x, the
3994 first expression is the alignment request in words.
3996 For other systems, including the i386 using a.out format, and the arm and
3997 strongarm, it is the
3998 number of low-order zero bits the location counter must have after
3999 advancement. For example @samp{.align 3} advances the location
4000 counter until it a multiple of 8. If the location counter is already a
4001 multiple of 8, no change is needed.
4003 This inconsistency is due to the different behaviors of the various
4004 native assemblers for these systems which GAS must emulate.
4005 GAS also provides @code{.balign} and @code{.p2align} directives,
4006 described later, which have a consistent behavior across all
4007 architectures (but are specific to GAS).
4010 @section @code{.ascii "@var{string}"}@dots{}
4012 @cindex @code{ascii} directive
4013 @cindex string literals
4014 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4015 separated by commas. It assembles each string (with no automatic
4016 trailing zero byte) into consecutive addresses.
4019 @section @code{.asciz "@var{string}"}@dots{}
4021 @cindex @code{asciz} directive
4022 @cindex zero-terminated strings
4023 @cindex null-terminated strings
4024 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4025 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4028 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4030 @cindex padding the location counter given number of bytes
4031 @cindex @code{balign} directive
4032 Pad the location counter (in the current subsection) to a particular
4033 storage boundary. The first expression (which must be absolute) is the
4034 alignment request in bytes. For example @samp{.balign 8} advances
4035 the location counter until it is a multiple of 8. If the location counter
4036 is already a multiple of 8, no change is needed.
4038 The second expression (also absolute) gives the fill value to be stored in the
4039 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4040 padding bytes are normally zero. However, on some systems, if the section is
4041 marked as containing code and the fill value is omitted, the space is filled
4042 with no-op instructions.
4044 The third expression is also absolute, and is also optional. If it is present,
4045 it is the maximum number of bytes that should be skipped by this alignment
4046 directive. If doing the alignment would require skipping more bytes than the
4047 specified maximum, then the alignment is not done at all. You can omit the
4048 fill value (the second argument) entirely by simply using two commas after the
4049 required alignment; this can be useful if you want the alignment to be filled
4050 with no-op instructions when appropriate.
4052 @cindex @code{balignw} directive
4053 @cindex @code{balignl} directive
4054 The @code{.balignw} and @code{.balignl} directives are variants of the
4055 @code{.balign} directive. The @code{.balignw} directive treats the fill
4056 pattern as a two byte word value. The @code{.balignl} directives treats the
4057 fill pattern as a four byte longword value. For example, @code{.balignw
4058 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4059 filled in with the value 0x368d (the exact placement of the bytes depends upon
4060 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4064 @section @code{.byte @var{expressions}}
4066 @cindex @code{byte} directive
4067 @cindex integers, one byte
4068 @code{.byte} expects zero or more expressions, separated by commas.
4069 Each expression is assembled into the next byte.
4072 @section @code{.comm @var{symbol} , @var{length} }
4074 @cindex @code{comm} directive
4075 @cindex symbol, common
4076 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4077 common symbol in one object file may be merged with a defined or common symbol
4078 of the same name in another object file. If @code{@value{LD}} does not see a
4079 definition for the symbol--just one or more common symbols--then it will
4080 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4081 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4082 the same name, and they do not all have the same size, it will allocate space
4083 using the largest size.
4086 When using ELF, the @code{.comm} directive takes an optional third argument.
4087 This is the desired alignment of the symbol, specified as a byte boundary (for
4088 example, an alignment of 16 means that the least significant 4 bits of the
4089 address should be zero). The alignment must be an absolute expression, and it
4090 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
4091 for the common symbol, it will use the alignment when placing the symbol. If
4092 no alignment is specified, @command{@value{AS}} will set the alignment to the
4093 largest power of two less than or equal to the size of the symbol, up to a
4098 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4099 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4102 @node CFI directives
4103 @section @code{.cfi_startproc}
4104 @cindex @code{cfi_startproc} directive
4105 @code{.cfi_startproc} is used at the beginning of each function that
4106 should have an entry in @code{.eh_frame}. It initializes some internal
4107 data structures and emits architecture dependent initial CFI instructions.
4108 Don't forget to close the function by
4109 @code{.cfi_endproc}.
4111 @section @code{.cfi_endproc}
4112 @cindex @code{cfi_endproc} directive
4113 @code{.cfi_endproc} is used at the end of a function where it closes its
4114 unwind entry previously opened by
4115 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4117 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4118 @code{.cfi_personality} defines personality routine and its encoding.
4119 @var{encoding} must be a constant determining how the personality
4120 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4121 argument is not present, otherwise second argument should be
4122 a constant or a symbol name. When using indirect encodings,
4123 the symbol provided should be the location where personality
4124 can be loaded from, not the personality routine itself.
4125 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4126 no personality routine.
4128 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4129 @code{.cfi_lsda} defines LSDA and its encoding.
4130 @var{encoding} must be a constant determining how the LSDA
4131 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4132 argument is not present, otherwise second argument should be a constant
4133 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4136 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4137 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4138 address from @var{register} and add @var{offset} to it}.
4140 @section @code{.cfi_def_cfa_register @var{register}}
4141 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4142 now on @var{register} will be used instead of the old one. Offset
4145 @section @code{.cfi_def_cfa_offset @var{offset}}
4146 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4147 remains the same, but @var{offset} is new. Note that it is the
4148 absolute offset that will be added to a defined register to compute
4151 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4152 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4153 value that is added/substracted from the previous offset.
4155 @section @code{.cfi_offset @var{register}, @var{offset}}
4156 Previous value of @var{register} is saved at offset @var{offset} from
4159 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4160 Previous value of @var{register} is saved at offset @var{offset} from
4161 the current CFA register. This is transformed to @code{.cfi_offset}
4162 using the known displacement of the CFA register from the CFA.
4163 This is often easier to use, because the number will match the
4164 code it's annotating.
4166 @section @code{.cfi_signal_frame}
4167 Mark current function as signal trampoline.
4169 @section @code{.cfi_window_save}
4170 SPARC register window has been saved.
4172 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4173 Allows the user to add arbitrary bytes to the unwind info. One
4174 might use this to add OS-specific CFI opcodes, or generic CFI
4175 opcodes that GAS does not yet support.
4177 @node LNS directives
4178 @section @code{.file @var{fileno} @var{filename}}
4179 @cindex @code{file} directive
4180 When emitting dwarf2 line number information @code{.file} assigns filenames
4181 to the @code{.debug_line} file name table. The @var{fileno} operand should
4182 be a unique positive integer to use as the index of the entry in the table.
4183 The @var{filename} operand is a C string literal.
4185 The detail of filename indices is exposed to the user because the filename
4186 table is shared with the @code{.debug_info} section of the dwarf2 debugging
4187 information, and thus the user must know the exact indices that table
4190 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
4191 @cindex @code{loc} directive
4192 The @code{.loc} directive will add row to the @code{.debug_line} line
4193 number matrix corresponding to the immediately following assembly
4194 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
4195 arguments will be applied to the @code{.debug_line} state machine before
4198 The @var{options} are a sequence of the following tokens in any order:
4202 This option will set the @code{basic_block} register in the
4203 @code{.debug_line} state machine to @code{true}.
4206 This option will set the @code{prologue_end} register in the
4207 @code{.debug_line} state machine to @code{true}.
4209 @item epilogue_begin
4210 This option will set the @code{epilogue_begin} register in the
4211 @code{.debug_line} state machine to @code{true}.
4213 @item is_stmt @var{value}
4214 This option will set the @code{is_stmt} register in the
4215 @code{.debug_line} state machine to @code{value}, which must be
4218 @item isa @var{value}
4219 This directive will set the @code{isa} register in the @code{.debug_line}
4220 state machine to @var{value}, which must be an unsigned integer.
4224 @section @code{.loc_mark_blocks @var{enable}}
4225 @cindex @code{loc_mark_blocks} directive
4226 The @code{.loc_mark_blocks} directive makes the assembler emit an entry
4227 to the @code{.debug_line} line number matrix with the @code{basic_block}
4228 register in the state machine set whenever a code label is seen.
4229 The @var{enable} argument should be either 1 or 0, to enable or disable
4230 this function respectively.
4233 @section @code{.data @var{subsection}}
4235 @cindex @code{data} directive
4236 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4237 end of the data subsection numbered @var{subsection} (which is an
4238 absolute expression). If @var{subsection} is omitted, it defaults
4243 @section @code{.def @var{name}}
4245 @cindex @code{def} directive
4246 @cindex COFF symbols, debugging
4247 @cindex debugging COFF symbols
4248 Begin defining debugging information for a symbol @var{name}; the
4249 definition extends until the @code{.endef} directive is encountered.
4252 This directive is only observed when @command{@value{AS}} is configured for COFF
4253 format output; when producing @code{b.out}, @samp{.def} is recognized,
4260 @section @code{.desc @var{symbol}, @var{abs-expression}}
4262 @cindex @code{desc} directive
4263 @cindex COFF symbol descriptor
4264 @cindex symbol descriptor, COFF
4265 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4266 to the low 16 bits of an absolute expression.
4269 The @samp{.desc} directive is not available when @command{@value{AS}} is
4270 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4271 object format. For the sake of compatibility, @command{@value{AS}} accepts
4272 it, but produces no output, when configured for COFF.
4278 @section @code{.dim}
4280 @cindex @code{dim} directive
4281 @cindex COFF auxiliary symbol information
4282 @cindex auxiliary symbol information, COFF
4283 This directive is generated by compilers to include auxiliary debugging
4284 information in the symbol table. It is only permitted inside
4285 @code{.def}/@code{.endef} pairs.
4288 @samp{.dim} is only meaningful when generating COFF format output; when
4289 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4295 @section @code{.double @var{flonums}}
4297 @cindex @code{double} directive
4298 @cindex floating point numbers (double)
4299 @code{.double} expects zero or more flonums, separated by commas. It
4300 assembles floating point numbers.
4302 The exact kind of floating point numbers emitted depends on how
4303 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4307 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4308 in @sc{ieee} format.
4313 @section @code{.eject}
4315 @cindex @code{eject} directive
4316 @cindex new page, in listings
4317 @cindex page, in listings
4318 @cindex listing control: new page
4319 Force a page break at this point, when generating assembly listings.
4322 @section @code{.else}
4324 @cindex @code{else} directive
4325 @code{.else} is part of the @command{@value{AS}} support for conditional
4326 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4327 of code to be assembled if the condition for the preceding @code{.if}
4331 @section @code{.elseif}
4333 @cindex @code{elseif} directive
4334 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4335 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4336 @code{.if} block that would otherwise fill the entire @code{.else} section.
4339 @section @code{.end}
4341 @cindex @code{end} directive
4342 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4343 process anything in the file past the @code{.end} directive.
4347 @section @code{.endef}
4349 @cindex @code{endef} directive
4350 This directive flags the end of a symbol definition begun with
4354 @samp{.endef} is only meaningful when generating COFF format output; if
4355 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4356 directive but ignores it.
4361 @section @code{.endfunc}
4362 @cindex @code{endfunc} directive
4363 @code{.endfunc} marks the end of a function specified with @code{.func}.
4366 @section @code{.endif}
4368 @cindex @code{endif} directive
4369 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4370 it marks the end of a block of code that is only assembled
4371 conditionally. @xref{If,,@code{.if}}.
4374 @section @code{.equ @var{symbol}, @var{expression}}
4376 @cindex @code{equ} directive
4377 @cindex assigning values to symbols
4378 @cindex symbols, assigning values to
4379 This directive sets the value of @var{symbol} to @var{expression}.
4380 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4383 The syntax for @code{equ} on the HPPA is
4384 @samp{@var{symbol} .equ @var{expression}}.
4388 The syntax for @code{equ} on the Z80 is
4389 @samp{@var{symbol} equ @var{expression}}.
4390 On the Z80 it is an eror if @var{symbol} is already defined,
4391 but the symbol is not protected from later redefinition.
4392 Compare @ref{Equiv}.
4396 @section @code{.equiv @var{symbol}, @var{expression}}
4397 @cindex @code{equiv} directive
4398 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4399 the assembler will signal an error if @var{symbol} is already defined. Note a
4400 symbol which has been referenced but not actually defined is considered to be
4403 Except for the contents of the error message, this is roughly equivalent to
4410 plus it protects the symbol from later redefinition.
4413 @section @code{.eqv @var{symbol}, @var{expression}}
4414 @cindex @code{eqv} directive
4415 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4416 evaluate the expression or any part of it immediately. Instead each time
4417 the resulting symbol is used in an expression, a snapshot of its current
4421 @section @code{.err}
4422 @cindex @code{err} directive
4423 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4424 message and, unless the @option{-Z} option was used, it will not generate an
4425 object file. This can be used to signal an error in conditionally compiled code.
4428 @section @code{.error "@var{string}"}
4429 @cindex error directive
4431 Similarly to @code{.err}, this directive emits an error, but you can specify a
4432 string that will be emitted as the error message. If you don't specify the
4433 message, it defaults to @code{".error directive invoked in source file"}.
4434 @xref{Errors, ,Error and Warning Messages}.
4437 .error "This code has not been assembled and tested."
4441 @section @code{.exitm}
4442 Exit early from the current macro definition. @xref{Macro}.
4445 @section @code{.extern}
4447 @cindex @code{extern} directive
4448 @code{.extern} is accepted in the source program---for compatibility
4449 with other assemblers---but it is ignored. @command{@value{AS}} treats
4450 all undefined symbols as external.
4453 @section @code{.fail @var{expression}}
4455 @cindex @code{fail} directive
4456 Generates an error or a warning. If the value of the @var{expression} is 500
4457 or more, @command{@value{AS}} will print a warning message. If the value is less
4458 than 500, @command{@value{AS}} will print an error message. The message will
4459 include the value of @var{expression}. This can occasionally be useful inside
4460 complex nested macros or conditional assembly.
4462 @ifclear no-file-dir
4464 @section @code{.file @var{string}}
4466 @cindex @code{file} directive
4467 @cindex logical file name
4468 @cindex file name, logical
4469 @code{.file} tells @command{@value{AS}} that we are about to start a new logical
4470 file. @var{string} is the new file name. In general, the filename is
4471 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4472 to specify an empty file name, you must give the quotes--@code{""}. This
4473 statement may go away in future: it is only recognized to be compatible with
4474 old @command{@value{AS}} programs.
4478 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4480 @cindex @code{fill} directive
4481 @cindex writing patterns in memory
4482 @cindex patterns, writing in memory
4483 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4484 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4485 may be zero or more. @var{Size} may be zero or more, but if it is
4486 more than 8, then it is deemed to have the value 8, compatible with
4487 other people's assemblers. The contents of each @var{repeat} bytes
4488 is taken from an 8-byte number. The highest order 4 bytes are
4489 zero. The lowest order 4 bytes are @var{value} rendered in the
4490 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4491 Each @var{size} bytes in a repetition is taken from the lowest order
4492 @var{size} bytes of this number. Again, this bizarre behavior is
4493 compatible with other people's assemblers.
4495 @var{size} and @var{value} are optional.
4496 If the second comma and @var{value} are absent, @var{value} is
4497 assumed zero. If the first comma and following tokens are absent,
4498 @var{size} is assumed to be 1.
4501 @section @code{.float @var{flonums}}
4503 @cindex floating point numbers (single)
4504 @cindex @code{float} directive
4505 This directive assembles zero or more flonums, separated by commas. It
4506 has the same effect as @code{.single}.
4508 The exact kind of floating point numbers emitted depends on how
4509 @command{@value{AS}} is configured.
4510 @xref{Machine Dependencies}.
4514 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4515 in @sc{ieee} format.
4520 @section @code{.func @var{name}[,@var{label}]}
4521 @cindex @code{func} directive
4522 @code{.func} emits debugging information to denote function @var{name}, and
4523 is ignored unless the file is assembled with debugging enabled.
4524 Only @samp{--gstabs[+]} is currently supported.
4525 @var{label} is the entry point of the function and if omitted @var{name}
4526 prepended with the @samp{leading char} is used.
4527 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4528 All functions are currently defined to have @code{void} return type.
4529 The function must be terminated with @code{.endfunc}.
4532 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4534 @cindex @code{global} directive
4535 @cindex symbol, making visible to linker
4536 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4537 @var{symbol} in your partial program, its value is made available to
4538 other partial programs that are linked with it. Otherwise,
4539 @var{symbol} takes its attributes from a symbol of the same name
4540 from another file linked into the same program.
4542 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4543 compatibility with other assemblers.
4546 On the HPPA, @code{.global} is not always enough to make it accessible to other
4547 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4548 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4553 @section @code{.hidden @var{names}}
4555 @cindex @code{hidden} directive
4557 This is one of the ELF visibility directives. The other two are
4558 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4559 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4561 This directive overrides the named symbols default visibility (which is set by
4562 their binding: local, global or weak). The directive sets the visibility to
4563 @code{hidden} which means that the symbols are not visible to other components.
4564 Such symbols are always considered to be @code{protected} as well.
4568 @section @code{.hword @var{expressions}}
4570 @cindex @code{hword} directive
4571 @cindex integers, 16-bit
4572 @cindex numbers, 16-bit
4573 @cindex sixteen bit integers
4574 This expects zero or more @var{expressions}, and emits
4575 a 16 bit number for each.
4578 This directive is a synonym for @samp{.short}; depending on the target
4579 architecture, it may also be a synonym for @samp{.word}.
4583 This directive is a synonym for @samp{.short}.
4586 This directive is a synonym for both @samp{.short} and @samp{.word}.
4591 @section @code{.ident}
4593 @cindex @code{ident} directive
4595 This directive is used by some assemblers to place tags in object files. The
4596 behavior of this directive varies depending on the target. When using the
4597 a.out object file format, @command{@value{AS}} simply accepts the directive for
4598 source-file compatibility with existing assemblers, but does not emit anything
4599 for it. When using COFF, comments are emitted to the @code{.comment} or
4600 @code{.rdata} section, depending on the target. When using ELF, comments are
4601 emitted to the @code{.comment} section.
4604 @section @code{.if @var{absolute expression}}
4606 @cindex conditional assembly
4607 @cindex @code{if} directive
4608 @code{.if} marks the beginning of a section of code which is only
4609 considered part of the source program being assembled if the argument
4610 (which must be an @var{absolute expression}) is non-zero. The end of
4611 the conditional section of code must be marked by @code{.endif}
4612 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4613 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4614 If you have several conditions to check, @code{.elseif} may be used to avoid
4615 nesting blocks if/else within each subsequent @code{.else} block.
4617 The following variants of @code{.if} are also supported:
4619 @cindex @code{ifdef} directive
4620 @item .ifdef @var{symbol}
4621 Assembles the following section of code if the specified @var{symbol}
4622 has been defined. Note a symbol which has been referenced but not yet defined
4623 is considered to be undefined.
4625 @cindex @code{ifb} directive
4626 @item .ifb @var{text}
4627 Assembles the following section of code if the operand is blank (empty).
4629 @cindex @code{ifc} directive
4630 @item .ifc @var{string1},@var{string2}
4631 Assembles the following section of code if the two strings are the same. The
4632 strings may be optionally quoted with single quotes. If they are not quoted,
4633 the first string stops at the first comma, and the second string stops at the
4634 end of the line. Strings which contain whitespace should be quoted. The
4635 string comparison is case sensitive.
4637 @cindex @code{ifeq} directive
4638 @item .ifeq @var{absolute expression}
4639 Assembles the following section of code if the argument is zero.
4641 @cindex @code{ifeqs} directive
4642 @item .ifeqs @var{string1},@var{string2}
4643 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4645 @cindex @code{ifge} directive
4646 @item .ifge @var{absolute expression}
4647 Assembles the following section of code if the argument is greater than or
4650 @cindex @code{ifgt} directive
4651 @item .ifgt @var{absolute expression}
4652 Assembles the following section of code if the argument is greater than zero.
4654 @cindex @code{ifle} directive
4655 @item .ifle @var{absolute expression}
4656 Assembles the following section of code if the argument is less than or equal
4659 @cindex @code{iflt} directive
4660 @item .iflt @var{absolute expression}
4661 Assembles the following section of code if the argument is less than zero.
4663 @cindex @code{ifnb} directive
4664 @item .ifnb @var{text}
4665 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
4666 following section of code if the operand is non-blank (non-empty).
4668 @cindex @code{ifnc} directive
4669 @item .ifnc @var{string1},@var{string2}.
4670 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4671 following section of code if the two strings are not the same.
4673 @cindex @code{ifndef} directive
4674 @cindex @code{ifnotdef} directive
4675 @item .ifndef @var{symbol}
4676 @itemx .ifnotdef @var{symbol}
4677 Assembles the following section of code if the specified @var{symbol}
4678 has not been defined. Both spelling variants are equivalent. Note a symbol
4679 which has been referenced but not yet defined is considered to be undefined.
4681 @cindex @code{ifne} directive
4682 @item .ifne @var{absolute expression}
4683 Assembles the following section of code if the argument is not equal to zero
4684 (in other words, this is equivalent to @code{.if}).
4686 @cindex @code{ifnes} directive
4687 @item .ifnes @var{string1},@var{string2}
4688 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4689 following section of code if the two strings are not the same.
4693 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4695 @cindex @code{incbin} directive
4696 @cindex binary files, including
4697 The @code{incbin} directive includes @var{file} verbatim at the current
4698 location. You can control the search paths used with the @samp{-I} command-line
4699 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4702 The @var{skip} argument skips a number of bytes from the start of the
4703 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4704 read. Note that the data is not aligned in any way, so it is the user's
4705 responsibility to make sure that proper alignment is provided both before and
4706 after the @code{incbin} directive.
4709 @section @code{.include "@var{file}"}
4711 @cindex @code{include} directive
4712 @cindex supporting files, including
4713 @cindex files, including
4714 This directive provides a way to include supporting files at specified
4715 points in your source program. The code from @var{file} is assembled as
4716 if it followed the point of the @code{.include}; when the end of the
4717 included file is reached, assembly of the original file continues. You
4718 can control the search paths used with the @samp{-I} command-line option
4719 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4723 @section @code{.int @var{expressions}}
4725 @cindex @code{int} directive
4726 @cindex integers, 32-bit
4727 Expect zero or more @var{expressions}, of any section, separated by commas.
4728 For each expression, emit a number that, at run time, is the value of that
4729 expression. The byte order and bit size of the number depends on what kind
4730 of target the assembly is for.
4734 On most forms of the H8/300, @code{.int} emits 16-bit
4735 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
4742 @section @code{.internal @var{names}}
4744 @cindex @code{internal} directive
4746 This is one of the ELF visibility directives. The other two are
4747 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4748 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4750 This directive overrides the named symbols default visibility (which is set by
4751 their binding: local, global or weak). The directive sets the visibility to
4752 @code{internal} which means that the symbols are considered to be @code{hidden}
4753 (i.e., not visible to other components), and that some extra, processor specific
4754 processing must also be performed upon the symbols as well.
4758 @section @code{.irp @var{symbol},@var{values}}@dots{}
4760 @cindex @code{irp} directive
4761 Evaluate a sequence of statements assigning different values to @var{symbol}.
4762 The sequence of statements starts at the @code{.irp} directive, and is
4763 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4764 set to @var{value}, and the sequence of statements is assembled. If no
4765 @var{value} is listed, the sequence of statements is assembled once, with
4766 @var{symbol} set to the null string. To refer to @var{symbol} within the
4767 sequence of statements, use @var{\symbol}.
4769 For example, assembling
4777 is equivalent to assembling
4785 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
4788 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4790 @cindex @code{irpc} directive
4791 Evaluate a sequence of statements assigning different values to @var{symbol}.
4792 The sequence of statements starts at the @code{.irpc} directive, and is
4793 terminated by an @code{.endr} directive. For each character in @var{value},
4794 @var{symbol} is set to the character, and the sequence of statements is
4795 assembled. If no @var{value} is listed, the sequence of statements is
4796 assembled once, with @var{symbol} set to the null string. To refer to
4797 @var{symbol} within the sequence of statements, use @var{\symbol}.
4799 For example, assembling
4807 is equivalent to assembling
4815 For some caveats with the spelling of @var{symbol}, see also the discussion
4819 @section @code{.lcomm @var{symbol} , @var{length}}
4821 @cindex @code{lcomm} directive
4822 @cindex local common symbols
4823 @cindex symbols, local common
4824 Reserve @var{length} (an absolute expression) bytes for a local common
4825 denoted by @var{symbol}. The section and value of @var{symbol} are
4826 those of the new local common. The addresses are allocated in the bss
4827 section, so that at run-time the bytes start off zeroed. @var{Symbol}
4828 is not declared global (@pxref{Global,,@code{.global}}), so is normally
4829 not visible to @code{@value{LD}}.
4832 Some targets permit a third argument to be used with @code{.lcomm}. This
4833 argument specifies the desired alignment of the symbol in the bss section.
4837 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
4838 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
4842 @section @code{.lflags}
4844 @cindex @code{lflags} directive (ignored)
4845 @command{@value{AS}} accepts this directive, for compatibility with other
4846 assemblers, but ignores it.
4848 @ifclear no-line-dir
4850 @section @code{.line @var{line-number}}
4852 @cindex @code{line} directive
4856 @section @code{.ln @var{line-number}}
4858 @cindex @code{ln} directive
4860 @cindex logical line number
4862 Change the logical line number. @var{line-number} must be an absolute
4863 expression. The next line has that logical line number. Therefore any other
4864 statements on the current line (after a statement separator character) are
4865 reported as on logical line number @var{line-number} @minus{} 1. One day
4866 @command{@value{AS}} will no longer support this directive: it is recognized only
4867 for compatibility with existing assembler programs.
4871 @ifclear no-line-dir
4872 Even though this is a directive associated with the @code{a.out} or
4873 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
4874 when producing COFF output, and treats @samp{.line} as though it
4875 were the COFF @samp{.ln} @emph{if} it is found outside a
4876 @code{.def}/@code{.endef} pair.
4878 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
4879 used by compilers to generate auxiliary symbol information for
4884 @section @code{.linkonce [@var{type}]}
4886 @cindex @code{linkonce} directive
4887 @cindex common sections
4888 Mark the current section so that the linker only includes a single copy of it.
4889 This may be used to include the same section in several different object files,
4890 but ensure that the linker will only include it once in the final output file.
4891 The @code{.linkonce} pseudo-op must be used for each instance of the section.
4892 Duplicate sections are detected based on the section name, so it should be
4895 This directive is only supported by a few object file formats; as of this
4896 writing, the only object file format which supports it is the Portable
4897 Executable format used on Windows NT.
4899 The @var{type} argument is optional. If specified, it must be one of the
4900 following strings. For example:
4904 Not all types may be supported on all object file formats.
4908 Silently discard duplicate sections. This is the default.
4911 Warn if there are duplicate sections, but still keep only one copy.
4914 Warn if any of the duplicates have different sizes.
4917 Warn if any of the duplicates do not have exactly the same contents.
4921 @section @code{.ln @var{line-number}}
4923 @cindex @code{ln} directive
4924 @ifclear no-line-dir
4925 @samp{.ln} is a synonym for @samp{.line}.
4928 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
4929 must be an absolute expression. The next line has that logical
4930 line number, so any other statements on the current line (after a
4931 statement separator character @code{;}) are reported as on logical
4932 line number @var{line-number} @minus{} 1.
4935 This directive is accepted, but ignored, when @command{@value{AS}} is
4936 configured for @code{b.out}; its effect is only associated with COFF
4942 @section @code{.mri @var{val}}
4944 @cindex @code{mri} directive
4945 @cindex MRI mode, temporarily
4946 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
4947 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
4948 affects code assembled until the next @code{.mri} directive, or until the end
4949 of the file. @xref{M, MRI mode, MRI mode}.
4952 @section @code{.list}
4954 @cindex @code{list} directive
4955 @cindex listing control, turning on
4956 Control (in conjunction with the @code{.nolist} directive) whether or
4957 not assembly listings are generated. These two directives maintain an
4958 internal counter (which is zero initially). @code{.list} increments the
4959 counter, and @code{.nolist} decrements it. Assembly listings are
4960 generated whenever the counter is greater than zero.
4962 By default, listings are disabled. When you enable them (with the
4963 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
4964 the initial value of the listing counter is one.
4967 @section @code{.long @var{expressions}}
4969 @cindex @code{long} directive
4970 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
4973 @c no one seems to know what this is for or whether this description is
4974 @c what it really ought to do
4976 @section @code{.lsym @var{symbol}, @var{expression}}
4978 @cindex @code{lsym} directive
4979 @cindex symbol, not referenced in assembly
4980 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
4981 the hash table, ensuring it cannot be referenced by name during the
4982 rest of the assembly. This sets the attributes of the symbol to be
4983 the same as the expression value:
4985 @var{other} = @var{descriptor} = 0
4986 @var{type} = @r{(section of @var{expression})}
4987 @var{value} = @var{expression}
4990 The new symbol is not flagged as external.
4994 @section @code{.macro}
4997 The commands @code{.macro} and @code{.endm} allow you to define macros that
4998 generate assembly output. For example, this definition specifies a macro
4999 @code{sum} that puts a sequence of numbers into memory:
5002 .macro sum from=0, to=5
5011 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5023 @item .macro @var{macname}
5024 @itemx .macro @var{macname} @var{macargs} @dots{}
5025 @cindex @code{macro} directive
5026 Begin the definition of a macro called @var{macname}. If your macro
5027 definition requires arguments, specify their names after the macro name,
5028 separated by commas or spaces. You can qualify the macro argument to
5029 indicate whether all invocations must specify a non-blank value (through
5030 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5031 (through @samp{:@code{vararg}}). You can supply a default value for any
5032 macro argument by following the name with @samp{=@var{deflt}}. You
5033 cannot define two macros with the same @var{macname} unless it has been
5034 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5035 definitions. For example, these are all valid @code{.macro} statements:
5039 Begin the definition of a macro called @code{comm}, which takes no
5042 @item .macro plus1 p, p1
5043 @itemx .macro plus1 p p1
5044 Either statement begins the definition of a macro called @code{plus1},
5045 which takes two arguments; within the macro definition, write
5046 @samp{\p} or @samp{\p1} to evaluate the arguments.
5048 @item .macro reserve_str p1=0 p2
5049 Begin the definition of a macro called @code{reserve_str}, with two
5050 arguments. The first argument has a default value, but not the second.
5051 After the definition is complete, you can call the macro either as
5052 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5053 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5054 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5055 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5057 @item .macro m p1:req, p2=0, p3:vararg
5058 Begin the definition of a macro called @code{m}, with at least three
5059 arguments. The first argument must always have a value specified, but
5060 not the second, which instead has a default value. The third formal
5061 will get assigned all remaining arguments specified at invocation time.
5063 When you call a macro, you can specify the argument values either by
5064 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5065 @samp{sum to=17, from=9}.
5069 Note that since each of the @var{macargs} can be an identifier exactly
5070 as any other one permitted by the target architecture, there may be
5071 occasional problems if the target hand-crafts special meanings to certain
5072 characters when they occur in a special position. For example, if the colon
5073 (@code{:}) is generally permitted to be part of a symbol name, but the
5074 architecture specific code special-cases it when occurring as the final
5075 character of a symbol (to denote a label), then the macro parameter
5076 replacement code will have no way of knowing that and consider the whole
5077 construct (including the colon) an identifier, and check only this
5078 identifier for being the subject to parameter substitution. So for example
5079 this macro definition:
5087 might not work as expected. Invoking @samp{label foo} might not create a label
5088 called @samp{foo} but instead just insert the text @samp{\l:} into the
5089 assembler source, probably generating an error about an unrecognised
5092 Similarly problems might occur with the period character (@samp{.})
5093 which is often allowed inside opcode names (and hence identifier names). So
5094 for example constructing a macro to build an opcode from a base name and a
5095 length specifier like this:
5098 .macro opcode base length
5103 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5104 instruction but instead generate some kind of error as the assembler tries to
5105 interpret the text @samp{\base.\length}.
5107 There are several possible ways around this problem:
5110 @item Insert white space
5111 If it is possible to use white space characters then this is the simplest
5120 @item Use @samp{\()}
5121 The string @samp{\()} can be used to separate the end of a macro argument from
5122 the following text. eg:
5125 .macro opcode base length
5130 @item Use the alternate macro syntax mode
5131 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5132 used as a separator. eg:
5142 Note: this problem of correctly identifying string parameters to pseudo ops
5143 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5144 and @code{.irpc} (@pxref{Irpc}) as well.
5147 @cindex @code{endm} directive
5148 Mark the end of a macro definition.
5151 @cindex @code{exitm} directive
5152 Exit early from the current macro definition.
5154 @cindex number of macros executed
5155 @cindex macros, count executed
5157 @command{@value{AS}} maintains a counter of how many macros it has
5158 executed in this pseudo-variable; you can copy that number to your
5159 output with @samp{\@@}, but @emph{only within a macro definition}.
5161 @item LOCAL @var{name} [ , @dots{} ]
5162 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5163 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5164 @xref{Altmacro,,@code{.altmacro}}.
5168 @section @code{.altmacro}
5169 Enable alternate macro mode, enabling:
5172 @item LOCAL @var{name} [ , @dots{} ]
5173 One additional directive, @code{LOCAL}, is available. It is used to
5174 generate a string replacement for each of the @var{name} arguments, and
5175 replace any instances of @var{name} in each macro expansion. The
5176 replacement string is unique in the assembly, and different for each
5177 separate macro expansion. @code{LOCAL} allows you to write macros that
5178 define symbols, without fear of conflict between separate macro expansions.
5180 @item String delimiters
5181 You can write strings delimited in these other ways besides
5182 @code{"@var{string}"}:
5185 @item '@var{string}'
5186 You can delimit strings with single-quote characters.
5188 @item <@var{string}>
5189 You can delimit strings with matching angle brackets.
5192 @item single-character string escape
5193 To include any single character literally in a string (even if the
5194 character would otherwise have some special meaning), you can prefix the
5195 character with @samp{!} (an exclamation mark). For example, you can
5196 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
5198 @item Expression results as strings
5199 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
5200 and use the result as a string.
5204 @section @code{.noaltmacro}
5205 Disable alternate macro mode. @xref{Altmacro}.
5208 @section @code{.nolist}
5210 @cindex @code{nolist} directive
5211 @cindex listing control, turning off
5212 Control (in conjunction with the @code{.list} directive) whether or
5213 not assembly listings are generated. These two directives maintain an
5214 internal counter (which is zero initially). @code{.list} increments the
5215 counter, and @code{.nolist} decrements it. Assembly listings are
5216 generated whenever the counter is greater than zero.
5219 @section @code{.octa @var{bignums}}
5221 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5222 @cindex @code{octa} directive
5223 @cindex integer, 16-byte
5224 @cindex sixteen byte integer
5225 This directive expects zero or more bignums, separated by commas. For each
5226 bignum, it emits a 16-byte integer.
5228 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5229 hence @emph{octa}-word for 16 bytes.
5232 @section @code{.org @var{new-lc} , @var{fill}}
5234 @cindex @code{org} directive
5235 @cindex location counter, advancing
5236 @cindex advancing location counter
5237 @cindex current address, advancing
5238 Advance the location counter of the current section to
5239 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5240 expression with the same section as the current subsection. That is,
5241 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5242 wrong section, the @code{.org} directive is ignored. To be compatible
5243 with former assemblers, if the section of @var{new-lc} is absolute,
5244 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5245 is the same as the current subsection.
5247 @code{.org} may only increase the location counter, or leave it
5248 unchanged; you cannot use @code{.org} to move the location counter
5251 @c double negative used below "not undefined" because this is a specific
5252 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5253 @c section. doc@cygnus.com 18feb91
5254 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5255 may not be undefined. If you really detest this restriction we eagerly await
5256 a chance to share your improved assembler.
5258 Beware that the origin is relative to the start of the section, not
5259 to the start of the subsection. This is compatible with other
5260 people's assemblers.
5262 When the location counter (of the current subsection) is advanced, the
5263 intervening bytes are filled with @var{fill} which should be an
5264 absolute expression. If the comma and @var{fill} are omitted,
5265 @var{fill} defaults to zero.
5268 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5270 @cindex padding the location counter given a power of two
5271 @cindex @code{p2align} directive
5272 Pad the location counter (in the current subsection) to a particular
5273 storage boundary. The first expression (which must be absolute) is the
5274 number of low-order zero bits the location counter must have after
5275 advancement. For example @samp{.p2align 3} advances the location
5276 counter until it a multiple of 8. If the location counter is already a
5277 multiple of 8, no change is needed.
5279 The second expression (also absolute) gives the fill value to be stored in the
5280 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5281 padding bytes are normally zero. However, on some systems, if the section is
5282 marked as containing code and the fill value is omitted, the space is filled
5283 with no-op instructions.
5285 The third expression is also absolute, and is also optional. If it is present,
5286 it is the maximum number of bytes that should be skipped by this alignment
5287 directive. If doing the alignment would require skipping more bytes than the
5288 specified maximum, then the alignment is not done at all. You can omit the
5289 fill value (the second argument) entirely by simply using two commas after the
5290 required alignment; this can be useful if you want the alignment to be filled
5291 with no-op instructions when appropriate.
5293 @cindex @code{p2alignw} directive
5294 @cindex @code{p2alignl} directive
5295 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5296 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5297 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5298 fill pattern as a four byte longword value. For example, @code{.p2alignw
5299 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5300 filled in with the value 0x368d (the exact placement of the bytes depends upon
5301 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5306 @section @code{.previous}
5308 @cindex @code{previous} directive
5309 @cindex Section Stack
5310 This is one of the ELF section stack manipulation directives. The others are
5311 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5312 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5313 (@pxref{PopSection}).
5315 This directive swaps the current section (and subsection) with most recently
5316 referenced section (and subsection) prior to this one. Multiple
5317 @code{.previous} directives in a row will flip between two sections (and their
5320 In terms of the section stack, this directive swaps the current section with
5321 the top section on the section stack.
5326 @section @code{.popsection}
5328 @cindex @code{popsection} directive
5329 @cindex Section Stack
5330 This is one of the ELF section stack manipulation directives. The others are
5331 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5332 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5335 This directive replaces the current section (and subsection) with the top
5336 section (and subsection) on the section stack. This section is popped off the
5341 @section @code{.print @var{string}}
5343 @cindex @code{print} directive
5344 @command{@value{AS}} will print @var{string} on the standard output during
5345 assembly. You must put @var{string} in double quotes.
5349 @section @code{.protected @var{names}}
5351 @cindex @code{protected} directive
5353 This is one of the ELF visibility directives. The other two are
5354 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5356 This directive overrides the named symbols default visibility (which is set by
5357 their binding: local, global or weak). The directive sets the visibility to
5358 @code{protected} which means that any references to the symbols from within the
5359 components that defines them must be resolved to the definition in that
5360 component, even if a definition in another component would normally preempt
5365 @section @code{.psize @var{lines} , @var{columns}}
5367 @cindex @code{psize} directive
5368 @cindex listing control: paper size
5369 @cindex paper size, for listings
5370 Use this directive to declare the number of lines---and, optionally, the
5371 number of columns---to use for each page, when generating listings.
5373 If you do not use @code{.psize}, listings use a default line-count
5374 of 60. You may omit the comma and @var{columns} specification; the
5375 default width is 200 columns.
5377 @command{@value{AS}} generates formfeeds whenever the specified number of
5378 lines is exceeded (or whenever you explicitly request one, using
5381 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5382 those explicitly specified with @code{.eject}.
5385 @section @code{.purgem @var{name}}
5387 @cindex @code{purgem} directive
5388 Undefine the macro @var{name}, so that later uses of the string will not be
5389 expanded. @xref{Macro}.
5393 @section @code{.pushsection @var{name} , @var{subsection}}
5395 @cindex @code{pushsection} directive
5396 @cindex Section Stack
5397 This is one of the ELF section stack manipulation directives. The others are
5398 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5399 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5402 This directive pushes the current section (and subsection) onto the
5403 top of the section stack, and then replaces the current section and
5404 subsection with @code{name} and @code{subsection}.
5408 @section @code{.quad @var{bignums}}
5410 @cindex @code{quad} directive
5411 @code{.quad} expects zero or more bignums, separated by commas. For
5412 each bignum, it emits
5414 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5415 warning message; and just takes the lowest order 8 bytes of the bignum.
5416 @cindex eight-byte integer
5417 @cindex integer, 8-byte
5419 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5420 hence @emph{quad}-word for 8 bytes.
5423 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5424 warning message; and just takes the lowest order 16 bytes of the bignum.
5425 @cindex sixteen-byte integer
5426 @cindex integer, 16-byte
5430 @section @code{.rept @var{count}}
5432 @cindex @code{rept} directive
5433 Repeat the sequence of lines between the @code{.rept} directive and the next
5434 @code{.endr} directive @var{count} times.
5436 For example, assembling
5444 is equivalent to assembling
5453 @section @code{.sbttl "@var{subheading}"}
5455 @cindex @code{sbttl} directive
5456 @cindex subtitles for listings
5457 @cindex listing control: subtitle
5458 Use @var{subheading} as the title (third line, immediately after the
5459 title line) when generating assembly listings.
5461 This directive affects subsequent pages, as well as the current page if
5462 it appears within ten lines of the top of a page.
5466 @section @code{.scl @var{class}}
5468 @cindex @code{scl} directive
5469 @cindex symbol storage class (COFF)
5470 @cindex COFF symbol storage class
5471 Set the storage-class value for a symbol. This directive may only be
5472 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5473 whether a symbol is static or external, or it may record further
5474 symbolic debugging information.
5477 The @samp{.scl} directive is primarily associated with COFF output; when
5478 configured to generate @code{b.out} output format, @command{@value{AS}}
5479 accepts this directive but ignores it.
5485 @section @code{.section @var{name}}
5487 @cindex named section
5488 Use the @code{.section} directive to assemble the following code into a section
5491 This directive is only supported for targets that actually support arbitrarily
5492 named sections; on @code{a.out} targets, for example, it is not accepted, even
5493 with a standard @code{a.out} section name.
5497 @c only print the extra heading if both COFF and ELF are set
5498 @subheading COFF Version
5501 @cindex @code{section} directive (COFF version)
5502 For COFF targets, the @code{.section} directive is used in one of the following
5506 .section @var{name}[, "@var{flags}"]
5507 .section @var{name}[, @var{subsegment}]
5510 If the optional argument is quoted, it is taken as flags to use for the
5511 section. Each flag is a single character. The following flags are recognized:
5514 bss section (uninitialized data)
5516 section is not loaded
5526 shared section (meaningful for PE targets)
5528 ignored. (For compatibility with the ELF version)
5531 If no flags are specified, the default flags depend upon the section name. If
5532 the section name is not recognized, the default will be for the section to be
5533 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5534 from the section, rather than adding them, so if they are used on their own it
5535 will be as if no flags had been specified at all.
5537 If the optional argument to the @code{.section} directive is not quoted, it is
5538 taken as a subsegment number (@pxref{Sub-Sections}).
5543 @c only print the extra heading if both COFF and ELF are set
5544 @subheading ELF Version
5547 @cindex Section Stack
5548 This is one of the ELF section stack manipulation directives. The others are
5549 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5550 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5551 @code{.previous} (@pxref{Previous}).
5553 @cindex @code{section} directive (ELF version)
5554 For ELF targets, the @code{.section} directive is used like this:
5557 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
5560 The optional @var{flags} argument is a quoted string which may contain any
5561 combination of the following characters:
5564 section is allocatable
5568 section is executable
5570 section is mergeable
5572 section contains zero terminated strings
5574 section is a member of a section group
5576 section is used for thread-local-storage
5579 The optional @var{type} argument may contain one of the following constants:
5582 section contains data
5584 section does not contain data (i.e., section only occupies space)
5586 section contains data which is used by things other than the program
5588 section contains an array of pointers to init functions
5590 section contains an array of pointers to finish functions
5591 @item @@preinit_array
5592 section contains an array of pointers to pre-init functions
5595 Many targets only support the first three section types.
5597 Note on targets where the @code{@@} character is the start of a comment (eg
5598 ARM) then another character is used instead. For example the ARM port uses the
5601 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
5602 be specified as well as an extra argument---@var{entsize}---like this:
5605 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
5608 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
5609 constants, each @var{entsize} octets long. Sections with both @code{M} and
5610 @code{S} must contain zero terminated strings where each character is
5611 @var{entsize} bytes long. The linker may remove duplicates within sections with
5612 the same name, same entity size and same flags. @var{entsize} must be an
5613 absolute expression.
5615 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
5616 be present along with an additional field like this:
5619 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
5622 The @var{GroupName} field specifies the name of the section group to which this
5623 particular section belongs. The optional linkage field can contain:
5626 indicates that only one copy of this section should be retained
5631 Note: if both the @var{M} and @var{G} flags are present then the fields for
5632 the Merge flag should come first, like this:
5635 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
5638 If no flags are specified, the default flags depend upon the section name. If
5639 the section name is not recognized, the default will be for the section to have
5640 none of the above flags: it will not be allocated in memory, nor writable, nor
5641 executable. The section will contain data.
5643 For ELF targets, the assembler supports another type of @code{.section}
5644 directive for compatibility with the Solaris assembler:
5647 .section "@var{name}"[, @var{flags}...]
5650 Note that the section name is quoted. There may be a sequence of comma
5654 section is allocatable
5658 section is executable
5660 section is used for thread local storage
5663 This directive replaces the current section and subsection. See the
5664 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
5665 some examples of how this directive and the other section stack directives
5671 @section @code{.set @var{symbol}, @var{expression}}
5673 @cindex @code{set} directive
5674 @cindex symbol value, setting
5675 Set the value of @var{symbol} to @var{expression}. This
5676 changes @var{symbol}'s value and type to conform to
5677 @var{expression}. If @var{symbol} was flagged as external, it remains
5678 flagged (@pxref{Symbol Attributes}).
5680 You may @code{.set} a symbol many times in the same assembly.
5682 If you @code{.set} a global symbol, the value stored in the object
5683 file is the last value stored into it.
5686 The syntax for @code{set} on the HPPA is
5687 @samp{@var{symbol} .set @var{expression}}.
5691 On Z80 @code{set} is a real instruction, use
5692 @samp{@var{symbol} defl @var{expression}} instead.
5696 @section @code{.short @var{expressions}}
5698 @cindex @code{short} directive
5700 @code{.short} is normally the same as @samp{.word}.
5701 @xref{Word,,@code{.word}}.
5703 In some configurations, however, @code{.short} and @code{.word} generate
5704 numbers of different lengths. @xref{Machine Dependencies}.
5708 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
5711 This expects zero or more @var{expressions}, and emits
5712 a 16 bit number for each.
5717 @section @code{.single @var{flonums}}
5719 @cindex @code{single} directive
5720 @cindex floating point numbers (single)
5721 This directive assembles zero or more flonums, separated by commas. It
5722 has the same effect as @code{.float}.
5724 The exact kind of floating point numbers emitted depends on how
5725 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5729 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
5730 numbers in @sc{ieee} format.
5736 @section @code{.size}
5738 This directive is used to set the size associated with a symbol.
5742 @c only print the extra heading if both COFF and ELF are set
5743 @subheading COFF Version
5746 @cindex @code{size} directive (COFF version)
5747 For COFF targets, the @code{.size} directive is only permitted inside
5748 @code{.def}/@code{.endef} pairs. It is used like this:
5751 .size @var{expression}
5755 @samp{.size} is only meaningful when generating COFF format output; when
5756 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5763 @c only print the extra heading if both COFF and ELF are set
5764 @subheading ELF Version
5767 @cindex @code{size} directive (ELF version)
5768 For ELF targets, the @code{.size} directive is used like this:
5771 .size @var{name} , @var{expression}
5774 This directive sets the size associated with a symbol @var{name}.
5775 The size in bytes is computed from @var{expression} which can make use of label
5776 arithmetic. This directive is typically used to set the size of function
5782 @section @code{.sleb128 @var{expressions}}
5784 @cindex @code{sleb128} directive
5785 @var{sleb128} stands for ``signed little endian base 128.'' This is a
5786 compact, variable length representation of numbers used by the DWARF
5787 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
5789 @ifclear no-space-dir
5791 @section @code{.skip @var{size} , @var{fill}}
5793 @cindex @code{skip} directive
5794 @cindex filling memory
5795 This directive emits @var{size} bytes, each of value @var{fill}. Both
5796 @var{size} and @var{fill} are absolute expressions. If the comma and
5797 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
5801 @section @code{.space @var{size} , @var{fill}}
5803 @cindex @code{space} directive
5804 @cindex filling memory
5805 This directive emits @var{size} bytes, each of value @var{fill}. Both
5806 @var{size} and @var{fill} are absolute expressions. If the comma
5807 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
5812 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
5813 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
5814 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
5815 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
5823 @section @code{.stabd, .stabn, .stabs}
5825 @cindex symbolic debuggers, information for
5826 @cindex @code{stab@var{x}} directives
5827 There are three directives that begin @samp{.stab}.
5828 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
5829 The symbols are not entered in the @command{@value{AS}} hash table: they
5830 cannot be referenced elsewhere in the source file.
5831 Up to five fields are required:
5835 This is the symbol's name. It may contain any character except
5836 @samp{\000}, so is more general than ordinary symbol names. Some
5837 debuggers used to code arbitrarily complex structures into symbol names
5841 An absolute expression. The symbol's type is set to the low 8 bits of
5842 this expression. Any bit pattern is permitted, but @code{@value{LD}}
5843 and debuggers choke on silly bit patterns.
5846 An absolute expression. The symbol's ``other'' attribute is set to the
5847 low 8 bits of this expression.
5850 An absolute expression. The symbol's descriptor is set to the low 16
5851 bits of this expression.
5854 An absolute expression which becomes the symbol's value.
5857 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
5858 or @code{.stabs} statement, the symbol has probably already been created;
5859 you get a half-formed symbol in your object file. This is
5860 compatible with earlier assemblers!
5863 @cindex @code{stabd} directive
5864 @item .stabd @var{type} , @var{other} , @var{desc}
5866 The ``name'' of the symbol generated is not even an empty string.
5867 It is a null pointer, for compatibility. Older assemblers used a
5868 null pointer so they didn't waste space in object files with empty
5871 The symbol's value is set to the location counter,
5872 relocatably. When your program is linked, the value of this symbol
5873 is the address of the location counter when the @code{.stabd} was
5876 @cindex @code{stabn} directive
5877 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
5878 The name of the symbol is set to the empty string @code{""}.
5880 @cindex @code{stabs} directive
5881 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
5882 All five fields are specified.
5888 @section @code{.string} "@var{str}"
5890 @cindex string, copying to object file
5891 @cindex @code{string} directive
5893 Copy the characters in @var{str} to the object file. You may specify more than
5894 one string to copy, separated by commas. Unless otherwise specified for a
5895 particular machine, the assembler marks the end of each string with a 0 byte.
5896 You can use any of the escape sequences described in @ref{Strings,,Strings}.
5899 @section @code{.struct @var{expression}}
5901 @cindex @code{struct} directive
5902 Switch to the absolute section, and set the section offset to @var{expression},
5903 which must be an absolute expression. You might use this as follows:
5912 This would define the symbol @code{field1} to have the value 0, the symbol
5913 @code{field2} to have the value 4, and the symbol @code{field3} to have the
5914 value 8. Assembly would be left in the absolute section, and you would need to
5915 use a @code{.section} directive of some sort to change to some other section
5916 before further assembly.
5920 @section @code{.subsection @var{name}}
5922 @cindex @code{subsection} directive
5923 @cindex Section Stack
5924 This is one of the ELF section stack manipulation directives. The others are
5925 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
5926 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5929 This directive replaces the current subsection with @code{name}. The current
5930 section is not changed. The replaced subsection is put onto the section stack
5931 in place of the then current top of stack subsection.
5936 @section @code{.symver}
5937 @cindex @code{symver} directive
5938 @cindex symbol versioning
5939 @cindex versions of symbols
5940 Use the @code{.symver} directive to bind symbols to specific version nodes
5941 within a source file. This is only supported on ELF platforms, and is
5942 typically used when assembling files to be linked into a shared library.
5943 There are cases where it may make sense to use this in objects to be bound
5944 into an application itself so as to override a versioned symbol from a
5947 For ELF targets, the @code{.symver} directive can be used like this:
5949 .symver @var{name}, @var{name2@@nodename}
5951 If the symbol @var{name} is defined within the file
5952 being assembled, the @code{.symver} directive effectively creates a symbol
5953 alias with the name @var{name2@@nodename}, and in fact the main reason that we
5954 just don't try and create a regular alias is that the @var{@@} character isn't
5955 permitted in symbol names. The @var{name2} part of the name is the actual name
5956 of the symbol by which it will be externally referenced. The name @var{name}
5957 itself is merely a name of convenience that is used so that it is possible to
5958 have definitions for multiple versions of a function within a single source
5959 file, and so that the compiler can unambiguously know which version of a
5960 function is being mentioned. The @var{nodename} portion of the alias should be
5961 the name of a node specified in the version script supplied to the linker when
5962 building a shared library. If you are attempting to override a versioned
5963 symbol from a shared library, then @var{nodename} should correspond to the
5964 nodename of the symbol you are trying to override.
5966 If the symbol @var{name} is not defined within the file being assembled, all
5967 references to @var{name} will be changed to @var{name2@@nodename}. If no
5968 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
5971 Another usage of the @code{.symver} directive is:
5973 .symver @var{name}, @var{name2@@@@nodename}
5975 In this case, the symbol @var{name} must exist and be defined within
5976 the file being assembled. It is similar to @var{name2@@nodename}. The
5977 difference is @var{name2@@@@nodename} will also be used to resolve
5978 references to @var{name2} by the linker.
5980 The third usage of the @code{.symver} directive is:
5982 .symver @var{name}, @var{name2@@@@@@nodename}
5984 When @var{name} is not defined within the
5985 file being assembled, it is treated as @var{name2@@nodename}. When
5986 @var{name} is defined within the file being assembled, the symbol
5987 name, @var{name}, will be changed to @var{name2@@@@nodename}.
5992 @section @code{.tag @var{structname}}
5994 @cindex COFF structure debugging
5995 @cindex structure debugging, COFF
5996 @cindex @code{tag} directive
5997 This directive is generated by compilers to include auxiliary debugging
5998 information in the symbol table. It is only permitted inside
5999 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6000 definitions in the symbol table with instances of those structures.
6003 @samp{.tag} is only used when generating COFF format output; when
6004 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6010 @section @code{.text @var{subsection}}
6012 @cindex @code{text} directive
6013 Tells @command{@value{AS}} to assemble the following statements onto the end of
6014 the text subsection numbered @var{subsection}, which is an absolute
6015 expression. If @var{subsection} is omitted, subsection number zero
6019 @section @code{.title "@var{heading}"}
6021 @cindex @code{title} directive
6022 @cindex listing control: title line
6023 Use @var{heading} as the title (second line, immediately after the
6024 source file name and pagenumber) when generating assembly listings.
6026 This directive affects subsequent pages, as well as the current page if
6027 it appears within ten lines of the top of a page.
6031 @section @code{.type}
6033 This directive is used to set the type of a symbol.
6037 @c only print the extra heading if both COFF and ELF are set
6038 @subheading COFF Version
6041 @cindex COFF symbol type
6042 @cindex symbol type, COFF
6043 @cindex @code{type} directive (COFF version)
6044 For COFF targets, this directive is permitted only within
6045 @code{.def}/@code{.endef} pairs. It is used like this:
6051 This records the integer @var{int} as the type attribute of a symbol table
6055 @samp{.type} is associated only with COFF format output; when
6056 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6057 directive but ignores it.
6063 @c only print the extra heading if both COFF and ELF are set
6064 @subheading ELF Version
6067 @cindex ELF symbol type
6068 @cindex symbol type, ELF
6069 @cindex @code{type} directive (ELF version)
6070 For ELF targets, the @code{.type} directive is used like this:
6073 .type @var{name} , @var{type description}
6076 This sets the type of symbol @var{name} to be either a
6077 function symbol or an object symbol. There are five different syntaxes
6078 supported for the @var{type description} field, in order to provide
6079 compatibility with various other assemblers.
6081 Because some of the characters used in these syntaxes (such as @samp{@@} and
6082 @samp{#}) are comment characters for some architectures, some of the syntaxes
6083 below do not work on all architectures. The first variant will be accepted by
6084 the GNU assembler on all architectures so that variant should be used for
6085 maximum portability, if you do not need to assemble your code with other
6088 The syntaxes supported are:
6091 .type <name> STT_FUNCTION
6092 .type <name> STT_OBJECT
6094 .type <name>,#function
6095 .type <name>,#object
6097 .type <name>,@@function
6098 .type <name>,@@object
6100 .type <name>,%function
6101 .type <name>,%object
6103 .type <name>,"function"
6104 .type <name>,"object"
6110 @section @code{.uleb128 @var{expressions}}
6112 @cindex @code{uleb128} directive
6113 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6114 compact, variable length representation of numbers used by the DWARF
6115 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6119 @section @code{.val @var{addr}}
6121 @cindex @code{val} directive
6122 @cindex COFF value attribute
6123 @cindex value attribute, COFF
6124 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6125 records the address @var{addr} as the value attribute of a symbol table
6129 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6130 configured for @code{b.out}, it accepts this directive but ignores it.
6136 @section @code{.version "@var{string}"}
6138 @cindex @code{version} directive
6139 This directive creates a @code{.note} section and places into it an ELF
6140 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6145 @section @code{.vtable_entry @var{table}, @var{offset}}
6147 @cindex @code{vtable_entry} directive
6148 This directive finds or creates a symbol @code{table} and creates a
6149 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6152 @section @code{.vtable_inherit @var{child}, @var{parent}}
6154 @cindex @code{vtable_inherit} directive
6155 This directive finds the symbol @code{child} and finds or creates the symbol
6156 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6157 parent whose addend is the value of the child symbol. As a special case the
6158 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6162 @section @code{.warning "@var{string}"}
6163 @cindex warning directive
6164 Similar to the directive @code{.error}
6165 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6168 @section @code{.weak @var{names}}
6170 @cindex @code{weak} directive
6171 This directive sets the weak attribute on the comma separated list of symbol
6172 @code{names}. If the symbols do not already exist, they will be created.
6174 On COFF targets other than PE, weak symbols are a GNU extension. This
6175 directive sets the weak attribute on the comma separated list of symbol
6176 @code{names}. If the symbols do not already exist, they will be created.
6178 On the PE target, weak symbols are supported natively as weak aliases.
6179 When a weak symbol is created that is not an alias, GAS creates an
6180 alternate symbol to hold the default value.
6183 @section @code{.weakref @var{alias}, @var{target}}
6185 @cindex @code{weakref} directive
6186 This directive creates an alias to the target symbol that enables the symbol to
6187 be referenced with weak-symbol semantics, but without actually making it weak.
6188 If direct references or definitions of the symbol are present, then the symbol
6189 will not be weak, but if all references to it are through weak references, the
6190 symbol will be marked as weak in the symbol table.
6192 The effect is equivalent to moving all references to the alias to a separate
6193 assembly source file, renaming the alias to the symbol in it, declaring the
6194 symbol as weak there, and running a reloadable link to merge the object files
6195 resulting from the assembly of the new source file and the old source file that
6196 had the references to the alias removed.
6198 The alias itself never makes to the symbol table, and is entirely handled
6199 within the assembler.
6202 @section @code{.word @var{expressions}}
6204 @cindex @code{word} directive
6205 This directive expects zero or more @var{expressions}, of any section,
6206 separated by commas.
6209 For each expression, @command{@value{AS}} emits a 32-bit number.
6212 For each expression, @command{@value{AS}} emits a 16-bit number.
6217 The size of the number emitted, and its byte order,
6218 depend on what target computer the assembly is for.
6221 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6222 @c happen---32-bit addressability, period; no long/short jumps.
6223 @ifset DIFF-TBL-KLUGE
6224 @cindex difference tables altered
6225 @cindex altered difference tables
6227 @emph{Warning: Special Treatment to support Compilers}
6231 Machines with a 32-bit address space, but that do less than 32-bit
6232 addressing, require the following special treatment. If the machine of
6233 interest to you does 32-bit addressing (or doesn't require it;
6234 @pxref{Machine Dependencies}), you can ignore this issue.
6237 In order to assemble compiler output into something that works,
6238 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6239 Directives of the form @samp{.word sym1-sym2} are often emitted by
6240 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6241 directive of the form @samp{.word sym1-sym2}, and the difference between
6242 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6243 creates a @dfn{secondary jump table}, immediately before the next label.
6244 This secondary jump table is preceded by a short-jump to the
6245 first byte after the secondary table. This short-jump prevents the flow
6246 of control from accidentally falling into the new table. Inside the
6247 table is a long-jump to @code{sym2}. The original @samp{.word}
6248 contains @code{sym1} minus the address of the long-jump to
6251 If there were several occurrences of @samp{.word sym1-sym2} before the
6252 secondary jump table, all of them are adjusted. If there was a
6253 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6254 long-jump to @code{sym4} is included in the secondary jump table,
6255 and the @code{.word} directives are adjusted to contain @code{sym3}
6256 minus the address of the long-jump to @code{sym4}; and so on, for as many
6257 entries in the original jump table as necessary.
6260 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6261 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6262 assembly language programmers.
6265 @c end DIFF-TBL-KLUGE
6268 @section Deprecated Directives
6270 @cindex deprecated directives
6271 @cindex obsolescent directives
6272 One day these directives won't work.
6273 They are included for compatibility with older assemblers.
6280 @node Machine Dependencies
6281 @chapter Machine Dependent Features
6283 @cindex machine dependencies
6284 The machine instruction sets are (almost by definition) different on
6285 each machine where @command{@value{AS}} runs. Floating point representations
6286 vary as well, and @command{@value{AS}} often supports a few additional
6287 directives or command-line options for compatibility with other
6288 assemblers on a particular platform. Finally, some versions of
6289 @command{@value{AS}} support special pseudo-instructions for branch
6292 This chapter discusses most of these differences, though it does not
6293 include details on any machine's instruction set. For details on that
6294 subject, see the hardware manufacturer's manual.
6298 * Alpha-Dependent:: Alpha Dependent Features
6301 * ARC-Dependent:: ARC Dependent Features
6304 * ARM-Dependent:: ARM Dependent Features
6307 * AVR-Dependent:: AVR Dependent Features
6310 * BFIN-Dependent:: BFIN Dependent Features
6313 * CRIS-Dependent:: CRIS Dependent Features
6316 * D10V-Dependent:: D10V Dependent Features
6319 * D30V-Dependent:: D30V Dependent Features
6322 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6325 * HPPA-Dependent:: HPPA Dependent Features
6328 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6331 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6334 * i860-Dependent:: Intel 80860 Dependent Features
6337 * i960-Dependent:: Intel 80960 Dependent Features
6340 * IA-64-Dependent:: Intel IA-64 Dependent Features
6343 * IP2K-Dependent:: IP2K Dependent Features
6346 * M32C-Dependent:: M32C Dependent Features
6349 * M32R-Dependent:: M32R Dependent Features
6352 * M68K-Dependent:: M680x0 Dependent Features
6355 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
6358 * MIPS-Dependent:: MIPS Dependent Features
6361 * MMIX-Dependent:: MMIX Dependent Features
6364 * MSP430-Dependent:: MSP430 Dependent Features
6367 * SH-Dependent:: Renesas / SuperH SH Dependent Features
6368 * SH64-Dependent:: SuperH SH64 Dependent Features
6371 * PDP-11-Dependent:: PDP-11 Dependent Features
6374 * PJ-Dependent:: picoJava Dependent Features
6377 * PPC-Dependent:: PowerPC Dependent Features
6380 * Sparc-Dependent:: SPARC Dependent Features
6383 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
6386 * V850-Dependent:: V850 Dependent Features
6389 * Xtensa-Dependent:: Xtensa Dependent Features
6392 * Z80-Dependent:: Z80 Dependent Features
6395 * Z8000-Dependent:: Z8000 Dependent Features
6398 * Vax-Dependent:: VAX Dependent Features
6405 @c The following major nodes are *sections* in the GENERIC version, *chapters*
6406 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
6407 @c peculiarity: to preserve cross-references, there must be a node called
6408 @c "Machine Dependencies". Hence the conditional nodenames in each
6409 @c major node below. Node defaulting in makeinfo requires adjacency of
6410 @c node and sectioning commands; hence the repetition of @chapter BLAH
6411 @c in both conditional blocks.
6414 @include c-alpha.texi
6430 @include c-bfin.texi
6434 @include c-cris.texi
6439 @node Machine Dependencies
6440 @chapter Machine Dependent Features
6442 The machine instruction sets are different on each Renesas chip family,
6443 and there are also some syntax differences among the families. This
6444 chapter describes the specific @command{@value{AS}} features for each
6448 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6449 * SH-Dependent:: Renesas SH Dependent Features
6456 @include c-d10v.texi
6460 @include c-d30v.texi
6464 @include c-h8300.texi
6468 @include c-hppa.texi
6472 @include c-i370.texi
6476 @include c-i386.texi
6480 @include c-i860.texi
6484 @include c-i960.texi
6488 @include c-ia64.texi
6492 @include c-ip2k.texi
6496 @include c-m32c.texi
6500 @include c-m32r.texi
6504 @include c-m68k.texi
6508 @include c-m68hc11.texi
6512 @include c-mips.texi
6516 @include c-mmix.texi
6520 @include c-msp430.texi
6524 @include c-ns32k.texi
6528 @include c-pdp11.texi
6541 @include c-sh64.texi
6545 @include c-sparc.texi
6549 @include c-tic54x.texi
6565 @include c-v850.texi
6569 @include c-xtensa.texi
6573 @c reverse effect of @down at top of generic Machine-Dep chapter
6577 @node Reporting Bugs
6578 @chapter Reporting Bugs
6579 @cindex bugs in assembler
6580 @cindex reporting bugs in assembler
6582 Your bug reports play an essential role in making @command{@value{AS}} reliable.
6584 Reporting a bug may help you by bringing a solution to your problem, or it may
6585 not. But in any case the principal function of a bug report is to help the
6586 entire community by making the next version of @command{@value{AS}} work better.
6587 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
6589 In order for a bug report to serve its purpose, you must include the
6590 information that enables us to fix the bug.
6593 * Bug Criteria:: Have you found a bug?
6594 * Bug Reporting:: How to report bugs
6598 @section Have You Found a Bug?
6599 @cindex bug criteria
6601 If you are not sure whether you have found a bug, here are some guidelines:
6604 @cindex fatal signal
6605 @cindex assembler crash
6606 @cindex crash of assembler
6608 If the assembler gets a fatal signal, for any input whatever, that is a
6609 @command{@value{AS}} bug. Reliable assemblers never crash.
6611 @cindex error on valid input
6613 If @command{@value{AS}} produces an error message for valid input, that is a bug.
6615 @cindex invalid input
6617 If @command{@value{AS}} does not produce an error message for invalid input, that
6618 is a bug. However, you should note that your idea of ``invalid input'' might
6619 be our idea of ``an extension'' or ``support for traditional practice''.
6622 If you are an experienced user of assemblers, your suggestions for improvement
6623 of @command{@value{AS}} are welcome in any case.
6627 @section How to Report Bugs
6629 @cindex assembler bugs, reporting
6631 A number of companies and individuals offer support for @sc{gnu} products. If
6632 you obtained @command{@value{AS}} from a support organization, we recommend you
6633 contact that organization first.
6635 You can find contact information for many support companies and
6636 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
6640 In any event, we also recommend that you send bug reports for @command{@value{AS}}
6644 The fundamental principle of reporting bugs usefully is this:
6645 @strong{report all the facts}. If you are not sure whether to state a
6646 fact or leave it out, state it!
6648 Often people omit facts because they think they know what causes the problem
6649 and assume that some details do not matter. Thus, you might assume that the
6650 name of a symbol you use in an example does not matter. Well, probably it does
6651 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
6652 happens to fetch from the location where that name is stored in memory;
6653 perhaps, if the name were different, the contents of that location would fool
6654 the assembler into doing the right thing despite the bug. Play it safe and
6655 give a specific, complete example. That is the easiest thing for you to do,
6656 and the most helpful.
6658 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
6659 it is new to us. Therefore, always write your bug reports on the assumption
6660 that the bug has not been reported previously.
6662 Sometimes people give a few sketchy facts and ask, ``Does this ring a
6663 bell?'' This cannot help us fix a bug, so it is basically useless. We
6664 respond by asking for enough details to enable us to investigate.
6665 You might as well expedite matters by sending them to begin with.
6667 To enable us to fix the bug, you should include all these things:
6671 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
6672 it with the @samp{--version} argument.
6674 Without this, we will not know whether there is any point in looking for
6675 the bug in the current version of @command{@value{AS}}.
6678 Any patches you may have applied to the @command{@value{AS}} source.
6681 The type of machine you are using, and the operating system name and
6685 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
6689 The command arguments you gave the assembler to assemble your example and
6690 observe the bug. To guarantee you will not omit something important, list them
6691 all. A copy of the Makefile (or the output from make) is sufficient.
6693 If we were to try to guess the arguments, we would probably guess wrong
6694 and then we might not encounter the bug.
6697 A complete input file that will reproduce the bug. If the bug is observed when
6698 the assembler is invoked via a compiler, send the assembler source, not the
6699 high level language source. Most compilers will produce the assembler source
6700 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
6701 the options @samp{-v --save-temps}; this will save the assembler source in a
6702 file with an extension of @file{.s}, and also show you exactly how
6703 @command{@value{AS}} is being run.
6706 A description of what behavior you observe that you believe is
6707 incorrect. For example, ``It gets a fatal signal.''
6709 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
6710 will certainly notice it. But if the bug is incorrect output, we might not
6711 notice unless it is glaringly wrong. You might as well not give us a chance to
6714 Even if the problem you experience is a fatal signal, you should still say so
6715 explicitly. Suppose something strange is going on, such as, your copy of
6716 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
6717 library on your system. (This has happened!) Your copy might crash and ours
6718 would not. If you told us to expect a crash, then when ours fails to crash, we
6719 would know that the bug was not happening for us. If you had not told us to
6720 expect a crash, then we would not be able to draw any conclusion from our
6724 If you wish to suggest changes to the @command{@value{AS}} source, send us context
6725 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
6726 option. Always send diffs from the old file to the new file. If you even
6727 discuss something in the @command{@value{AS}} source, refer to it by context, not
6730 The line numbers in our development sources will not match those in your
6731 sources. Your line numbers would convey no useful information to us.
6734 Here are some things that are not necessary:
6738 A description of the envelope of the bug.
6740 Often people who encounter a bug spend a lot of time investigating
6741 which changes to the input file will make the bug go away and which
6742 changes will not affect it.
6744 This is often time consuming and not very useful, because the way we
6745 will find the bug is by running a single example under the debugger
6746 with breakpoints, not by pure deduction from a series of examples.
6747 We recommend that you save your time for something else.
6749 Of course, if you can find a simpler example to report @emph{instead}
6750 of the original one, that is a convenience for us. Errors in the
6751 output will be easier to spot, running under the debugger will take
6752 less time, and so on.
6754 However, simplification is not vital; if you do not want to do this,
6755 report the bug anyway and send us the entire test case you used.
6758 A patch for the bug.
6760 A patch for the bug does help us if it is a good one. But do not omit
6761 the necessary information, such as the test case, on the assumption that
6762 a patch is all we need. We might see problems with your patch and decide
6763 to fix the problem another way, or we might not understand it at all.
6765 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
6766 construct an example that will make the program follow a certain path through
6767 the code. If you do not send us the example, we will not be able to construct
6768 one, so we will not be able to verify that the bug is fixed.
6770 And if we cannot understand what bug you are trying to fix, or why your
6771 patch should be an improvement, we will not install it. A test case will
6772 help us to understand.
6775 A guess about what the bug is or what it depends on.
6777 Such guesses are usually wrong. Even we cannot guess right about such
6778 things without first using the debugger to find the facts.
6781 @node Acknowledgements
6782 @chapter Acknowledgements
6784 If you have contributed to GAS and your name isn't listed here,
6785 it is not meant as a slight. We just don't know about it. Send mail to the
6786 maintainer, and we'll correct the situation. Currently
6788 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
6790 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
6793 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
6794 information and the 68k series machines, most of the preprocessing pass, and
6795 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
6797 K. Richard Pixley maintained GAS for a while, adding various enhancements and
6798 many bug fixes, including merging support for several processors, breaking GAS
6799 up to handle multiple object file format back ends (including heavy rewrite,
6800 testing, an integration of the coff and b.out back ends), adding configuration
6801 including heavy testing and verification of cross assemblers and file splits
6802 and renaming, converted GAS to strictly ANSI C including full prototypes, added
6803 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
6804 port (including considerable amounts of reverse engineering), a SPARC opcode
6805 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
6806 assertions and made them work, much other reorganization, cleanup, and lint.
6808 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
6809 in format-specific I/O modules.
6811 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
6812 has done much work with it since.
6814 The Intel 80386 machine description was written by Eliot Dresselhaus.
6816 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
6818 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
6819 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
6821 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
6822 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
6823 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
6824 support a.out format.
6826 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
6827 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
6828 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
6829 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
6832 John Gilmore built the AMD 29000 support, added @code{.include} support, and
6833 simplified the configuration of which versions accept which directives. He
6834 updated the 68k machine description so that Motorola's opcodes always produced
6835 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
6836 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
6837 cross-compilation support, and one bug in relaxation that took a week and
6838 required the proverbial one-bit fix.
6840 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
6841 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
6842 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
6843 PowerPC assembler, and made a few other minor patches.
6845 Steve Chamberlain made GAS able to generate listings.
6847 Hewlett-Packard contributed support for the HP9000/300.
6849 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
6850 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
6851 formats). This work was supported by both the Center for Software Science at
6852 the University of Utah and Cygnus Support.
6854 Support for ELF format files has been worked on by Mark Eichin of Cygnus
6855 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
6856 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
6857 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
6858 and some initial 64-bit support).
6860 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
6862 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
6863 support for openVMS/Alpha.
6865 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
6868 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
6869 Inc.@: added support for Xtensa processors.
6871 Several engineers at Cygnus Support have also provided many small bug fixes and
6872 configuration enhancements.
6874 Many others have contributed large or small bugfixes and enhancements. If
6875 you have contributed significant work and are not mentioned on this list, and
6876 want to be, let us know. Some of the history has been lost; we are not
6877 intentionally leaving anyone out.
6882 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob