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 @copyright{} 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''.
117 @title Using @value{AS}
118 @subtitle The @sc{gnu} Assembler
120 @subtitle for the @value{TARGET} family
122 @ifset VERSION_PACKAGE
124 @subtitle @value{VERSION_PACKAGE}
127 @subtitle Version @value{VERSION}
130 The Free Software Foundation Inc.@: thanks The Nice Computer
131 Company of Australia for loaning Dean Elsner to write the
132 first (Vax) version of @command{as} for Project @sc{gnu}.
133 The proprietors, management and staff of TNCCA thank FSF for
134 distracting the boss while they got some work
137 @author Dean Elsner, Jay Fenlason & friends
141 \hfill {\it Using {\tt @value{AS}}}\par
142 \hfill Edited by Cygnus Support\par
144 %"boxit" macro for figures:
145 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
146 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
147 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
148 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
149 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
152 @vskip 0pt plus 1filll
153 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002,
154 2006, 2007 Free Software Foundation, Inc.
156 Permission is granted to copy, distribute and/or modify this document
157 under the terms of the GNU Free Documentation License, Version 1.1
158 or any later version published by the Free Software Foundation;
159 with no Invariant Sections, with no Front-Cover Texts, and with no
160 Back-Cover Texts. A copy of the license is included in the
161 section entitled ``GNU Free Documentation License''.
168 @top Using @value{AS}
170 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
171 @ifset VERSION_PACKAGE
172 @value{VERSION_PACKAGE}
174 version @value{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} [@b{-mvxworks-pic}]
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 [simple]}, @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 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
3883 * Rept:: @code{.rept @var{count}}
3884 * Sbttl:: @code{.sbttl "@var{subheading}"}
3886 * Scl:: @code{.scl @var{class}}
3889 * Section:: @code{.section @var{name}}
3892 * Set:: @code{.set @var{symbol}, @var{expression}}
3893 * Short:: @code{.short @var{expressions}}
3894 * Single:: @code{.single @var{flonums}}
3896 * Size:: @code{.size [@var{name} , @var{expression}]}
3899 * Skip:: @code{.skip @var{size} , @var{fill}}
3900 * Sleb128:: @code{.sleb128 @var{expressions}}
3901 * Space:: @code{.space @var{size} , @var{fill}}
3903 * Stab:: @code{.stabd, .stabn, .stabs}
3906 * String:: @code{.string "@var{str}"}
3907 * Struct:: @code{.struct @var{expression}}
3909 * SubSection:: @code{.subsection}
3910 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3914 * Tag:: @code{.tag @var{structname}}
3917 * Text:: @code{.text @var{subsection}}
3918 * Title:: @code{.title "@var{heading}"}
3920 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
3923 * Uleb128:: @code{.uleb128 @var{expressions}}
3925 * Val:: @code{.val @var{addr}}
3929 * Version:: @code{.version "@var{string}"}
3930 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
3931 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
3934 * Warning:: @code{.warning @var{string}}
3935 * Weak:: @code{.weak @var{names}}
3936 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
3937 * Word:: @code{.word @var{expressions}}
3938 * Deprecated:: Deprecated Directives
3942 @section @code{.abort}
3944 @cindex @code{abort} directive
3945 @cindex stopping the assembly
3946 This directive stops the assembly immediately. It is for
3947 compatibility with other assemblers. The original idea was that the
3948 assembly language source would be piped into the assembler. If the sender
3949 of the source quit, it could use this directive tells @command{@value{AS}} to
3950 quit also. One day @code{.abort} will not be supported.
3954 @section @code{.ABORT} (COFF)
3956 @cindex @code{ABORT} directive
3957 When producing COFF output, @command{@value{AS}} accepts this directive as a
3958 synonym for @samp{.abort}.
3961 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
3967 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3969 @cindex padding the location counter
3970 @cindex @code{align} directive
3971 Pad the location counter (in the current subsection) to a particular storage
3972 boundary. The first expression (which must be absolute) is the alignment
3973 required, as described below.
3975 The second expression (also absolute) gives the fill value to be stored in the
3976 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3977 padding bytes are normally zero. However, on some systems, if the section is
3978 marked as containing code and the fill value is omitted, the space is filled
3979 with no-op instructions.
3981 The third expression is also absolute, and is also optional. If it is present,
3982 it is the maximum number of bytes that should be skipped by this alignment
3983 directive. If doing the alignment would require skipping more bytes than the
3984 specified maximum, then the alignment is not done at all. You can omit the
3985 fill value (the second argument) entirely by simply using two commas after the
3986 required alignment; this can be useful if you want the alignment to be filled
3987 with no-op instructions when appropriate.
3989 The way the required alignment is specified varies from system to system.
3990 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
3991 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
3992 alignment request in bytes. For example @samp{.align 8} advances
3993 the location counter until it is a multiple of 8. If the location counter
3994 is already a multiple of 8, no change is needed. For the tic54x, the
3995 first expression is the alignment request in words.
3997 For other systems, including the i386 using a.out format, and the arm and
3998 strongarm, it is the
3999 number of low-order zero bits the location counter must have after
4000 advancement. For example @samp{.align 3} advances the location
4001 counter until it a multiple of 8. If the location counter is already a
4002 multiple of 8, no change is needed.
4004 This inconsistency is due to the different behaviors of the various
4005 native assemblers for these systems which GAS must emulate.
4006 GAS also provides @code{.balign} and @code{.p2align} directives,
4007 described later, which have a consistent behavior across all
4008 architectures (but are specific to GAS).
4011 @section @code{.ascii "@var{string}"}@dots{}
4013 @cindex @code{ascii} directive
4014 @cindex string literals
4015 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4016 separated by commas. It assembles each string (with no automatic
4017 trailing zero byte) into consecutive addresses.
4020 @section @code{.asciz "@var{string}"}@dots{}
4022 @cindex @code{asciz} directive
4023 @cindex zero-terminated strings
4024 @cindex null-terminated strings
4025 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4026 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4029 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4031 @cindex padding the location counter given number of bytes
4032 @cindex @code{balign} directive
4033 Pad the location counter (in the current subsection) to a particular
4034 storage boundary. The first expression (which must be absolute) is the
4035 alignment request in bytes. For example @samp{.balign 8} advances
4036 the location counter until it is a multiple of 8. If the location counter
4037 is already a multiple of 8, no change is needed.
4039 The second expression (also absolute) gives the fill value to be stored in the
4040 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4041 padding bytes are normally zero. However, on some systems, if the section is
4042 marked as containing code and the fill value is omitted, the space is filled
4043 with no-op instructions.
4045 The third expression is also absolute, and is also optional. If it is present,
4046 it is the maximum number of bytes that should be skipped by this alignment
4047 directive. If doing the alignment would require skipping more bytes than the
4048 specified maximum, then the alignment is not done at all. You can omit the
4049 fill value (the second argument) entirely by simply using two commas after the
4050 required alignment; this can be useful if you want the alignment to be filled
4051 with no-op instructions when appropriate.
4053 @cindex @code{balignw} directive
4054 @cindex @code{balignl} directive
4055 The @code{.balignw} and @code{.balignl} directives are variants of the
4056 @code{.balign} directive. The @code{.balignw} directive treats the fill
4057 pattern as a two byte word value. The @code{.balignl} directives treats the
4058 fill pattern as a four byte longword value. For example, @code{.balignw
4059 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4060 filled in with the value 0x368d (the exact placement of the bytes depends upon
4061 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4065 @section @code{.byte @var{expressions}}
4067 @cindex @code{byte} directive
4068 @cindex integers, one byte
4069 @code{.byte} expects zero or more expressions, separated by commas.
4070 Each expression is assembled into the next byte.
4073 @section @code{.comm @var{symbol} , @var{length} }
4075 @cindex @code{comm} directive
4076 @cindex symbol, common
4077 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4078 common symbol in one object file may be merged with a defined or common symbol
4079 of the same name in another object file. If @code{@value{LD}} does not see a
4080 definition for the symbol--just one or more common symbols--then it will
4081 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4082 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4083 the same name, and they do not all have the same size, it will allocate space
4084 using the largest size.
4087 When using ELF, the @code{.comm} directive takes an optional third argument.
4088 This is the desired alignment of the symbol, specified as a byte boundary (for
4089 example, an alignment of 16 means that the least significant 4 bits of the
4090 address should be zero). The alignment must be an absolute expression, and it
4091 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
4092 for the common symbol, it will use the alignment when placing the symbol. If
4093 no alignment is specified, @command{@value{AS}} will set the alignment to the
4094 largest power of two less than or equal to the size of the symbol, up to a
4099 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4100 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4103 @node CFI directives
4104 @section @code{.cfi_startproc [simple]}
4105 @cindex @code{cfi_startproc} directive
4106 @code{.cfi_startproc} is used at the beginning of each function that
4107 should have an entry in @code{.eh_frame}. It initializes some internal
4108 data structures. Don't forget to close the function by
4109 @code{.cfi_endproc}.
4111 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4112 it also emits some architecture dependent initial CFI instructions.
4114 @section @code{.cfi_endproc}
4115 @cindex @code{cfi_endproc} directive
4116 @code{.cfi_endproc} is used at the end of a function where it closes its
4117 unwind entry previously opened by
4118 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4120 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4121 @code{.cfi_personality} defines personality routine and its encoding.
4122 @var{encoding} must be a constant determining how the personality
4123 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4124 argument is not present, otherwise second argument should be
4125 a constant or a symbol name. When using indirect encodings,
4126 the symbol provided should be the location where personality
4127 can be loaded from, not the personality routine itself.
4128 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4129 no personality routine.
4131 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4132 @code{.cfi_lsda} defines LSDA and its encoding.
4133 @var{encoding} must be a constant determining how the LSDA
4134 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4135 argument is not present, otherwise second argument should be a constant
4136 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4139 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4140 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4141 address from @var{register} and add @var{offset} to it}.
4143 @section @code{.cfi_def_cfa_register @var{register}}
4144 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4145 now on @var{register} will be used instead of the old one. Offset
4148 @section @code{.cfi_def_cfa_offset @var{offset}}
4149 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4150 remains the same, but @var{offset} is new. Note that it is the
4151 absolute offset that will be added to a defined register to compute
4154 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4155 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4156 value that is added/substracted from the previous offset.
4158 @section @code{.cfi_offset @var{register}, @var{offset}}
4159 Previous value of @var{register} is saved at offset @var{offset} from
4162 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4163 Previous value of @var{register} is saved at offset @var{offset} from
4164 the current CFA register. This is transformed to @code{.cfi_offset}
4165 using the known displacement of the CFA register from the CFA.
4166 This is often easier to use, because the number will match the
4167 code it's annotating.
4169 @section @code{.cfi_register @var{register1}, @var{register2}}
4170 Previous value of @var{register1} is saved in register @var{register2}.
4172 @section @code{.cfi_restore @var{register}}
4173 @code{.cfi_restore} says that the rule for @var{register} is now the
4174 same as it was at the beginning of the function, after all initial
4175 instruction added by @code{.cfi_startproc} were executed.
4177 @section @code{.cfi_undefined @var{register}}
4178 From now on the previous value of @var{register} can't be restored anymore.
4180 @section @code{.cfi_same_value @var{register}}
4181 Current value of @var{register} is the same like in the previous frame,
4182 i.e. no restoration needed.
4184 @section @code{.cfi_remember_state},
4185 First save all current rules for all registers by @code{.cfi_remember_state},
4186 then totally screw them up by subsequent @code{.cfi_*} directives and when
4187 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4188 the previous saved state.
4190 @section @code{.cfi_return_column @var{register}}
4191 Change return column @var{register}, i.e. the return address is either
4192 directly in @var{register} or can be accessed by rules for @var{register}.
4194 @section @code{.cfi_signal_frame}
4195 Mark current function as signal trampoline.
4197 @section @code{.cfi_window_save}
4198 SPARC register window has been saved.
4200 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4201 Allows the user to add arbitrary bytes to the unwind info. One
4202 might use this to add OS-specific CFI opcodes, or generic CFI
4203 opcodes that GAS does not yet support.
4205 @node LNS directives
4206 @section @code{.file @var{fileno} @var{filename}}
4207 @cindex @code{file} directive
4208 When emitting dwarf2 line number information @code{.file} assigns filenames
4209 to the @code{.debug_line} file name table. The @var{fileno} operand should
4210 be a unique positive integer to use as the index of the entry in the table.
4211 The @var{filename} operand is a C string literal.
4213 The detail of filename indices is exposed to the user because the filename
4214 table is shared with the @code{.debug_info} section of the dwarf2 debugging
4215 information, and thus the user must know the exact indices that table
4218 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
4219 @cindex @code{loc} directive
4220 The @code{.loc} directive will add row to the @code{.debug_line} line
4221 number matrix corresponding to the immediately following assembly
4222 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
4223 arguments will be applied to the @code{.debug_line} state machine before
4226 The @var{options} are a sequence of the following tokens in any order:
4230 This option will set the @code{basic_block} register in the
4231 @code{.debug_line} state machine to @code{true}.
4234 This option will set the @code{prologue_end} register in the
4235 @code{.debug_line} state machine to @code{true}.
4237 @item epilogue_begin
4238 This option will set the @code{epilogue_begin} register in the
4239 @code{.debug_line} state machine to @code{true}.
4241 @item is_stmt @var{value}
4242 This option will set the @code{is_stmt} register in the
4243 @code{.debug_line} state machine to @code{value}, which must be
4246 @item isa @var{value}
4247 This directive will set the @code{isa} register in the @code{.debug_line}
4248 state machine to @var{value}, which must be an unsigned integer.
4252 @section @code{.loc_mark_blocks @var{enable}}
4253 @cindex @code{loc_mark_blocks} directive
4254 The @code{.loc_mark_blocks} directive makes the assembler emit an entry
4255 to the @code{.debug_line} line number matrix with the @code{basic_block}
4256 register in the state machine set whenever a code label is seen.
4257 The @var{enable} argument should be either 1 or 0, to enable or disable
4258 this function respectively.
4261 @section @code{.data @var{subsection}}
4263 @cindex @code{data} directive
4264 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4265 end of the data subsection numbered @var{subsection} (which is an
4266 absolute expression). If @var{subsection} is omitted, it defaults
4271 @section @code{.def @var{name}}
4273 @cindex @code{def} directive
4274 @cindex COFF symbols, debugging
4275 @cindex debugging COFF symbols
4276 Begin defining debugging information for a symbol @var{name}; the
4277 definition extends until the @code{.endef} directive is encountered.
4280 This directive is only observed when @command{@value{AS}} is configured for COFF
4281 format output; when producing @code{b.out}, @samp{.def} is recognized,
4288 @section @code{.desc @var{symbol}, @var{abs-expression}}
4290 @cindex @code{desc} directive
4291 @cindex COFF symbol descriptor
4292 @cindex symbol descriptor, COFF
4293 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4294 to the low 16 bits of an absolute expression.
4297 The @samp{.desc} directive is not available when @command{@value{AS}} is
4298 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4299 object format. For the sake of compatibility, @command{@value{AS}} accepts
4300 it, but produces no output, when configured for COFF.
4306 @section @code{.dim}
4308 @cindex @code{dim} directive
4309 @cindex COFF auxiliary symbol information
4310 @cindex auxiliary symbol information, COFF
4311 This directive is generated by compilers to include auxiliary debugging
4312 information in the symbol table. It is only permitted inside
4313 @code{.def}/@code{.endef} pairs.
4316 @samp{.dim} is only meaningful when generating COFF format output; when
4317 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4323 @section @code{.double @var{flonums}}
4325 @cindex @code{double} directive
4326 @cindex floating point numbers (double)
4327 @code{.double} expects zero or more flonums, separated by commas. It
4328 assembles floating point numbers.
4330 The exact kind of floating point numbers emitted depends on how
4331 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4335 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4336 in @sc{ieee} format.
4341 @section @code{.eject}
4343 @cindex @code{eject} directive
4344 @cindex new page, in listings
4345 @cindex page, in listings
4346 @cindex listing control: new page
4347 Force a page break at this point, when generating assembly listings.
4350 @section @code{.else}
4352 @cindex @code{else} directive
4353 @code{.else} is part of the @command{@value{AS}} support for conditional
4354 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4355 of code to be assembled if the condition for the preceding @code{.if}
4359 @section @code{.elseif}
4361 @cindex @code{elseif} directive
4362 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4363 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4364 @code{.if} block that would otherwise fill the entire @code{.else} section.
4367 @section @code{.end}
4369 @cindex @code{end} directive
4370 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4371 process anything in the file past the @code{.end} directive.
4375 @section @code{.endef}
4377 @cindex @code{endef} directive
4378 This directive flags the end of a symbol definition begun with
4382 @samp{.endef} is only meaningful when generating COFF format output; if
4383 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4384 directive but ignores it.
4389 @section @code{.endfunc}
4390 @cindex @code{endfunc} directive
4391 @code{.endfunc} marks the end of a function specified with @code{.func}.
4394 @section @code{.endif}
4396 @cindex @code{endif} directive
4397 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4398 it marks the end of a block of code that is only assembled
4399 conditionally. @xref{If,,@code{.if}}.
4402 @section @code{.equ @var{symbol}, @var{expression}}
4404 @cindex @code{equ} directive
4405 @cindex assigning values to symbols
4406 @cindex symbols, assigning values to
4407 This directive sets the value of @var{symbol} to @var{expression}.
4408 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4411 The syntax for @code{equ} on the HPPA is
4412 @samp{@var{symbol} .equ @var{expression}}.
4416 The syntax for @code{equ} on the Z80 is
4417 @samp{@var{symbol} equ @var{expression}}.
4418 On the Z80 it is an eror if @var{symbol} is already defined,
4419 but the symbol is not protected from later redefinition.
4420 Compare @ref{Equiv}.
4424 @section @code{.equiv @var{symbol}, @var{expression}}
4425 @cindex @code{equiv} directive
4426 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4427 the assembler will signal an error if @var{symbol} is already defined. Note a
4428 symbol which has been referenced but not actually defined is considered to be
4431 Except for the contents of the error message, this is roughly equivalent to
4438 plus it protects the symbol from later redefinition.
4441 @section @code{.eqv @var{symbol}, @var{expression}}
4442 @cindex @code{eqv} directive
4443 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4444 evaluate the expression or any part of it immediately. Instead each time
4445 the resulting symbol is used in an expression, a snapshot of its current
4449 @section @code{.err}
4450 @cindex @code{err} directive
4451 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4452 message and, unless the @option{-Z} option was used, it will not generate an
4453 object file. This can be used to signal an error in conditionally compiled code.
4456 @section @code{.error "@var{string}"}
4457 @cindex error directive
4459 Similarly to @code{.err}, this directive emits an error, but you can specify a
4460 string that will be emitted as the error message. If you don't specify the
4461 message, it defaults to @code{".error directive invoked in source file"}.
4462 @xref{Errors, ,Error and Warning Messages}.
4465 .error "This code has not been assembled and tested."
4469 @section @code{.exitm}
4470 Exit early from the current macro definition. @xref{Macro}.
4473 @section @code{.extern}
4475 @cindex @code{extern} directive
4476 @code{.extern} is accepted in the source program---for compatibility
4477 with other assemblers---but it is ignored. @command{@value{AS}} treats
4478 all undefined symbols as external.
4481 @section @code{.fail @var{expression}}
4483 @cindex @code{fail} directive
4484 Generates an error or a warning. If the value of the @var{expression} is 500
4485 or more, @command{@value{AS}} will print a warning message. If the value is less
4486 than 500, @command{@value{AS}} will print an error message. The message will
4487 include the value of @var{expression}. This can occasionally be useful inside
4488 complex nested macros or conditional assembly.
4490 @ifclear no-file-dir
4492 @section @code{.file @var{string}}
4494 @cindex @code{file} directive
4495 @cindex logical file name
4496 @cindex file name, logical
4497 @code{.file} tells @command{@value{AS}} that we are about to start a new logical
4498 file. @var{string} is the new file name. In general, the filename is
4499 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4500 to specify an empty file name, you must give the quotes--@code{""}. This
4501 statement may go away in future: it is only recognized to be compatible with
4502 old @command{@value{AS}} programs.
4506 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4508 @cindex @code{fill} directive
4509 @cindex writing patterns in memory
4510 @cindex patterns, writing in memory
4511 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4512 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4513 may be zero or more. @var{Size} may be zero or more, but if it is
4514 more than 8, then it is deemed to have the value 8, compatible with
4515 other people's assemblers. The contents of each @var{repeat} bytes
4516 is taken from an 8-byte number. The highest order 4 bytes are
4517 zero. The lowest order 4 bytes are @var{value} rendered in the
4518 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4519 Each @var{size} bytes in a repetition is taken from the lowest order
4520 @var{size} bytes of this number. Again, this bizarre behavior is
4521 compatible with other people's assemblers.
4523 @var{size} and @var{value} are optional.
4524 If the second comma and @var{value} are absent, @var{value} is
4525 assumed zero. If the first comma and following tokens are absent,
4526 @var{size} is assumed to be 1.
4529 @section @code{.float @var{flonums}}
4531 @cindex floating point numbers (single)
4532 @cindex @code{float} directive
4533 This directive assembles zero or more flonums, separated by commas. It
4534 has the same effect as @code{.single}.
4536 The exact kind of floating point numbers emitted depends on how
4537 @command{@value{AS}} is configured.
4538 @xref{Machine Dependencies}.
4542 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4543 in @sc{ieee} format.
4548 @section @code{.func @var{name}[,@var{label}]}
4549 @cindex @code{func} directive
4550 @code{.func} emits debugging information to denote function @var{name}, and
4551 is ignored unless the file is assembled with debugging enabled.
4552 Only @samp{--gstabs[+]} is currently supported.
4553 @var{label} is the entry point of the function and if omitted @var{name}
4554 prepended with the @samp{leading char} is used.
4555 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4556 All functions are currently defined to have @code{void} return type.
4557 The function must be terminated with @code{.endfunc}.
4560 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4562 @cindex @code{global} directive
4563 @cindex symbol, making visible to linker
4564 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4565 @var{symbol} in your partial program, its value is made available to
4566 other partial programs that are linked with it. Otherwise,
4567 @var{symbol} takes its attributes from a symbol of the same name
4568 from another file linked into the same program.
4570 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4571 compatibility with other assemblers.
4574 On the HPPA, @code{.global} is not always enough to make it accessible to other
4575 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4576 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4581 @section @code{.hidden @var{names}}
4583 @cindex @code{hidden} directive
4585 This is one of the ELF visibility directives. The other two are
4586 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4587 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4589 This directive overrides the named symbols default visibility (which is set by
4590 their binding: local, global or weak). The directive sets the visibility to
4591 @code{hidden} which means that the symbols are not visible to other components.
4592 Such symbols are always considered to be @code{protected} as well.
4596 @section @code{.hword @var{expressions}}
4598 @cindex @code{hword} directive
4599 @cindex integers, 16-bit
4600 @cindex numbers, 16-bit
4601 @cindex sixteen bit integers
4602 This expects zero or more @var{expressions}, and emits
4603 a 16 bit number for each.
4606 This directive is a synonym for @samp{.short}; depending on the target
4607 architecture, it may also be a synonym for @samp{.word}.
4611 This directive is a synonym for @samp{.short}.
4614 This directive is a synonym for both @samp{.short} and @samp{.word}.
4619 @section @code{.ident}
4621 @cindex @code{ident} directive
4623 This directive is used by some assemblers to place tags in object files. The
4624 behavior of this directive varies depending on the target. When using the
4625 a.out object file format, @command{@value{AS}} simply accepts the directive for
4626 source-file compatibility with existing assemblers, but does not emit anything
4627 for it. When using COFF, comments are emitted to the @code{.comment} or
4628 @code{.rdata} section, depending on the target. When using ELF, comments are
4629 emitted to the @code{.comment} section.
4632 @section @code{.if @var{absolute expression}}
4634 @cindex conditional assembly
4635 @cindex @code{if} directive
4636 @code{.if} marks the beginning of a section of code which is only
4637 considered part of the source program being assembled if the argument
4638 (which must be an @var{absolute expression}) is non-zero. The end of
4639 the conditional section of code must be marked by @code{.endif}
4640 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4641 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4642 If you have several conditions to check, @code{.elseif} may be used to avoid
4643 nesting blocks if/else within each subsequent @code{.else} block.
4645 The following variants of @code{.if} are also supported:
4647 @cindex @code{ifdef} directive
4648 @item .ifdef @var{symbol}
4649 Assembles the following section of code if the specified @var{symbol}
4650 has been defined. Note a symbol which has been referenced but not yet defined
4651 is considered to be undefined.
4653 @cindex @code{ifb} directive
4654 @item .ifb @var{text}
4655 Assembles the following section of code if the operand is blank (empty).
4657 @cindex @code{ifc} directive
4658 @item .ifc @var{string1},@var{string2}
4659 Assembles the following section of code if the two strings are the same. The
4660 strings may be optionally quoted with single quotes. If they are not quoted,
4661 the first string stops at the first comma, and the second string stops at the
4662 end of the line. Strings which contain whitespace should be quoted. The
4663 string comparison is case sensitive.
4665 @cindex @code{ifeq} directive
4666 @item .ifeq @var{absolute expression}
4667 Assembles the following section of code if the argument is zero.
4669 @cindex @code{ifeqs} directive
4670 @item .ifeqs @var{string1},@var{string2}
4671 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4673 @cindex @code{ifge} directive
4674 @item .ifge @var{absolute expression}
4675 Assembles the following section of code if the argument is greater than or
4678 @cindex @code{ifgt} directive
4679 @item .ifgt @var{absolute expression}
4680 Assembles the following section of code if the argument is greater than zero.
4682 @cindex @code{ifle} directive
4683 @item .ifle @var{absolute expression}
4684 Assembles the following section of code if the argument is less than or equal
4687 @cindex @code{iflt} directive
4688 @item .iflt @var{absolute expression}
4689 Assembles the following section of code if the argument is less than zero.
4691 @cindex @code{ifnb} directive
4692 @item .ifnb @var{text}
4693 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
4694 following section of code if the operand is non-blank (non-empty).
4696 @cindex @code{ifnc} directive
4697 @item .ifnc @var{string1},@var{string2}.
4698 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4699 following section of code if the two strings are not the same.
4701 @cindex @code{ifndef} directive
4702 @cindex @code{ifnotdef} directive
4703 @item .ifndef @var{symbol}
4704 @itemx .ifnotdef @var{symbol}
4705 Assembles the following section of code if the specified @var{symbol}
4706 has not been defined. Both spelling variants are equivalent. Note a symbol
4707 which has been referenced but not yet defined is considered to be undefined.
4709 @cindex @code{ifne} directive
4710 @item .ifne @var{absolute expression}
4711 Assembles the following section of code if the argument is not equal to zero
4712 (in other words, this is equivalent to @code{.if}).
4714 @cindex @code{ifnes} directive
4715 @item .ifnes @var{string1},@var{string2}
4716 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4717 following section of code if the two strings are not the same.
4721 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4723 @cindex @code{incbin} directive
4724 @cindex binary files, including
4725 The @code{incbin} directive includes @var{file} verbatim at the current
4726 location. You can control the search paths used with the @samp{-I} command-line
4727 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4730 The @var{skip} argument skips a number of bytes from the start of the
4731 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4732 read. Note that the data is not aligned in any way, so it is the user's
4733 responsibility to make sure that proper alignment is provided both before and
4734 after the @code{incbin} directive.
4737 @section @code{.include "@var{file}"}
4739 @cindex @code{include} directive
4740 @cindex supporting files, including
4741 @cindex files, including
4742 This directive provides a way to include supporting files at specified
4743 points in your source program. The code from @var{file} is assembled as
4744 if it followed the point of the @code{.include}; when the end of the
4745 included file is reached, assembly of the original file continues. You
4746 can control the search paths used with the @samp{-I} command-line option
4747 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4751 @section @code{.int @var{expressions}}
4753 @cindex @code{int} directive
4754 @cindex integers, 32-bit
4755 Expect zero or more @var{expressions}, of any section, separated by commas.
4756 For each expression, emit a number that, at run time, is the value of that
4757 expression. The byte order and bit size of the number depends on what kind
4758 of target the assembly is for.
4762 On most forms of the H8/300, @code{.int} emits 16-bit
4763 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
4770 @section @code{.internal @var{names}}
4772 @cindex @code{internal} directive
4774 This is one of the ELF visibility directives. The other two are
4775 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4776 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4778 This directive overrides the named symbols default visibility (which is set by
4779 their binding: local, global or weak). The directive sets the visibility to
4780 @code{internal} which means that the symbols are considered to be @code{hidden}
4781 (i.e., not visible to other components), and that some extra, processor specific
4782 processing must also be performed upon the symbols as well.
4786 @section @code{.irp @var{symbol},@var{values}}@dots{}
4788 @cindex @code{irp} directive
4789 Evaluate a sequence of statements assigning different values to @var{symbol}.
4790 The sequence of statements starts at the @code{.irp} directive, and is
4791 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4792 set to @var{value}, and the sequence of statements is assembled. If no
4793 @var{value} is listed, the sequence of statements is assembled once, with
4794 @var{symbol} set to the null string. To refer to @var{symbol} within the
4795 sequence of statements, use @var{\symbol}.
4797 For example, assembling
4805 is equivalent to assembling
4813 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
4816 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4818 @cindex @code{irpc} directive
4819 Evaluate a sequence of statements assigning different values to @var{symbol}.
4820 The sequence of statements starts at the @code{.irpc} directive, and is
4821 terminated by an @code{.endr} directive. For each character in @var{value},
4822 @var{symbol} is set to the character, and the sequence of statements is
4823 assembled. If no @var{value} is listed, the sequence of statements is
4824 assembled once, with @var{symbol} set to the null string. To refer to
4825 @var{symbol} within the sequence of statements, use @var{\symbol}.
4827 For example, assembling
4835 is equivalent to assembling
4843 For some caveats with the spelling of @var{symbol}, see also the discussion
4847 @section @code{.lcomm @var{symbol} , @var{length}}
4849 @cindex @code{lcomm} directive
4850 @cindex local common symbols
4851 @cindex symbols, local common
4852 Reserve @var{length} (an absolute expression) bytes for a local common
4853 denoted by @var{symbol}. The section and value of @var{symbol} are
4854 those of the new local common. The addresses are allocated in the bss
4855 section, so that at run-time the bytes start off zeroed. @var{Symbol}
4856 is not declared global (@pxref{Global,,@code{.global}}), so is normally
4857 not visible to @code{@value{LD}}.
4860 Some targets permit a third argument to be used with @code{.lcomm}. This
4861 argument specifies the desired alignment of the symbol in the bss section.
4865 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
4866 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
4870 @section @code{.lflags}
4872 @cindex @code{lflags} directive (ignored)
4873 @command{@value{AS}} accepts this directive, for compatibility with other
4874 assemblers, but ignores it.
4876 @ifclear no-line-dir
4878 @section @code{.line @var{line-number}}
4880 @cindex @code{line} directive
4884 @section @code{.ln @var{line-number}}
4886 @cindex @code{ln} directive
4888 @cindex logical line number
4890 Change the logical line number. @var{line-number} must be an absolute
4891 expression. The next line has that logical line number. Therefore any other
4892 statements on the current line (after a statement separator character) are
4893 reported as on logical line number @var{line-number} @minus{} 1. One day
4894 @command{@value{AS}} will no longer support this directive: it is recognized only
4895 for compatibility with existing assembler programs.
4899 @ifclear no-line-dir
4900 Even though this is a directive associated with the @code{a.out} or
4901 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
4902 when producing COFF output, and treats @samp{.line} as though it
4903 were the COFF @samp{.ln} @emph{if} it is found outside a
4904 @code{.def}/@code{.endef} pair.
4906 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
4907 used by compilers to generate auxiliary symbol information for
4912 @section @code{.linkonce [@var{type}]}
4914 @cindex @code{linkonce} directive
4915 @cindex common sections
4916 Mark the current section so that the linker only includes a single copy of it.
4917 This may be used to include the same section in several different object files,
4918 but ensure that the linker will only include it once in the final output file.
4919 The @code{.linkonce} pseudo-op must be used for each instance of the section.
4920 Duplicate sections are detected based on the section name, so it should be
4923 This directive is only supported by a few object file formats; as of this
4924 writing, the only object file format which supports it is the Portable
4925 Executable format used on Windows NT.
4927 The @var{type} argument is optional. If specified, it must be one of the
4928 following strings. For example:
4932 Not all types may be supported on all object file formats.
4936 Silently discard duplicate sections. This is the default.
4939 Warn if there are duplicate sections, but still keep only one copy.
4942 Warn if any of the duplicates have different sizes.
4945 Warn if any of the duplicates do not have exactly the same contents.
4949 @section @code{.ln @var{line-number}}
4951 @cindex @code{ln} directive
4952 @ifclear no-line-dir
4953 @samp{.ln} is a synonym for @samp{.line}.
4956 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
4957 must be an absolute expression. The next line has that logical
4958 line number, so any other statements on the current line (after a
4959 statement separator character @code{;}) are reported as on logical
4960 line number @var{line-number} @minus{} 1.
4963 This directive is accepted, but ignored, when @command{@value{AS}} is
4964 configured for @code{b.out}; its effect is only associated with COFF
4970 @section @code{.mri @var{val}}
4972 @cindex @code{mri} directive
4973 @cindex MRI mode, temporarily
4974 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
4975 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
4976 affects code assembled until the next @code{.mri} directive, or until the end
4977 of the file. @xref{M, MRI mode, MRI mode}.
4980 @section @code{.list}
4982 @cindex @code{list} directive
4983 @cindex listing control, turning on
4984 Control (in conjunction with the @code{.nolist} directive) whether or
4985 not assembly listings are generated. These two directives maintain an
4986 internal counter (which is zero initially). @code{.list} increments the
4987 counter, and @code{.nolist} decrements it. Assembly listings are
4988 generated whenever the counter is greater than zero.
4990 By default, listings are disabled. When you enable them (with the
4991 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
4992 the initial value of the listing counter is one.
4995 @section @code{.long @var{expressions}}
4997 @cindex @code{long} directive
4998 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5001 @c no one seems to know what this is for or whether this description is
5002 @c what it really ought to do
5004 @section @code{.lsym @var{symbol}, @var{expression}}
5006 @cindex @code{lsym} directive
5007 @cindex symbol, not referenced in assembly
5008 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5009 the hash table, ensuring it cannot be referenced by name during the
5010 rest of the assembly. This sets the attributes of the symbol to be
5011 the same as the expression value:
5013 @var{other} = @var{descriptor} = 0
5014 @var{type} = @r{(section of @var{expression})}
5015 @var{value} = @var{expression}
5018 The new symbol is not flagged as external.
5022 @section @code{.macro}
5025 The commands @code{.macro} and @code{.endm} allow you to define macros that
5026 generate assembly output. For example, this definition specifies a macro
5027 @code{sum} that puts a sequence of numbers into memory:
5030 .macro sum from=0, to=5
5039 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5051 @item .macro @var{macname}
5052 @itemx .macro @var{macname} @var{macargs} @dots{}
5053 @cindex @code{macro} directive
5054 Begin the definition of a macro called @var{macname}. If your macro
5055 definition requires arguments, specify their names after the macro name,
5056 separated by commas or spaces. You can qualify the macro argument to
5057 indicate whether all invocations must specify a non-blank value (through
5058 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5059 (through @samp{:@code{vararg}}). You can supply a default value for any
5060 macro argument by following the name with @samp{=@var{deflt}}. You
5061 cannot define two macros with the same @var{macname} unless it has been
5062 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5063 definitions. For example, these are all valid @code{.macro} statements:
5067 Begin the definition of a macro called @code{comm}, which takes no
5070 @item .macro plus1 p, p1
5071 @itemx .macro plus1 p p1
5072 Either statement begins the definition of a macro called @code{plus1},
5073 which takes two arguments; within the macro definition, write
5074 @samp{\p} or @samp{\p1} to evaluate the arguments.
5076 @item .macro reserve_str p1=0 p2
5077 Begin the definition of a macro called @code{reserve_str}, with two
5078 arguments. The first argument has a default value, but not the second.
5079 After the definition is complete, you can call the macro either as
5080 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5081 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5082 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5083 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5085 @item .macro m p1:req, p2=0, p3:vararg
5086 Begin the definition of a macro called @code{m}, with at least three
5087 arguments. The first argument must always have a value specified, but
5088 not the second, which instead has a default value. The third formal
5089 will get assigned all remaining arguments specified at invocation time.
5091 When you call a macro, you can specify the argument values either by
5092 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5093 @samp{sum to=17, from=9}.
5097 Note that since each of the @var{macargs} can be an identifier exactly
5098 as any other one permitted by the target architecture, there may be
5099 occasional problems if the target hand-crafts special meanings to certain
5100 characters when they occur in a special position. For example, if the colon
5101 (@code{:}) is generally permitted to be part of a symbol name, but the
5102 architecture specific code special-cases it when occurring as the final
5103 character of a symbol (to denote a label), then the macro parameter
5104 replacement code will have no way of knowing that and consider the whole
5105 construct (including the colon) an identifier, and check only this
5106 identifier for being the subject to parameter substitution. So for example
5107 this macro definition:
5115 might not work as expected. Invoking @samp{label foo} might not create a label
5116 called @samp{foo} but instead just insert the text @samp{\l:} into the
5117 assembler source, probably generating an error about an unrecognised
5120 Similarly problems might occur with the period character (@samp{.})
5121 which is often allowed inside opcode names (and hence identifier names). So
5122 for example constructing a macro to build an opcode from a base name and a
5123 length specifier like this:
5126 .macro opcode base length
5131 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5132 instruction but instead generate some kind of error as the assembler tries to
5133 interpret the text @samp{\base.\length}.
5135 There are several possible ways around this problem:
5138 @item Insert white space
5139 If it is possible to use white space characters then this is the simplest
5148 @item Use @samp{\()}
5149 The string @samp{\()} can be used to separate the end of a macro argument from
5150 the following text. eg:
5153 .macro opcode base length
5158 @item Use the alternate macro syntax mode
5159 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5160 used as a separator. eg:
5170 Note: this problem of correctly identifying string parameters to pseudo ops
5171 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5172 and @code{.irpc} (@pxref{Irpc}) as well.
5175 @cindex @code{endm} directive
5176 Mark the end of a macro definition.
5179 @cindex @code{exitm} directive
5180 Exit early from the current macro definition.
5182 @cindex number of macros executed
5183 @cindex macros, count executed
5185 @command{@value{AS}} maintains a counter of how many macros it has
5186 executed in this pseudo-variable; you can copy that number to your
5187 output with @samp{\@@}, but @emph{only within a macro definition}.
5189 @item LOCAL @var{name} [ , @dots{} ]
5190 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5191 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5192 @xref{Altmacro,,@code{.altmacro}}.
5196 @section @code{.altmacro}
5197 Enable alternate macro mode, enabling:
5200 @item LOCAL @var{name} [ , @dots{} ]
5201 One additional directive, @code{LOCAL}, is available. It is used to
5202 generate a string replacement for each of the @var{name} arguments, and
5203 replace any instances of @var{name} in each macro expansion. The
5204 replacement string is unique in the assembly, and different for each
5205 separate macro expansion. @code{LOCAL} allows you to write macros that
5206 define symbols, without fear of conflict between separate macro expansions.
5208 @item String delimiters
5209 You can write strings delimited in these other ways besides
5210 @code{"@var{string}"}:
5213 @item '@var{string}'
5214 You can delimit strings with single-quote characters.
5216 @item <@var{string}>
5217 You can delimit strings with matching angle brackets.
5220 @item single-character string escape
5221 To include any single character literally in a string (even if the
5222 character would otherwise have some special meaning), you can prefix the
5223 character with @samp{!} (an exclamation mark). For example, you can
5224 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
5226 @item Expression results as strings
5227 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
5228 and use the result as a string.
5232 @section @code{.noaltmacro}
5233 Disable alternate macro mode. @xref{Altmacro}.
5236 @section @code{.nolist}
5238 @cindex @code{nolist} directive
5239 @cindex listing control, turning off
5240 Control (in conjunction with the @code{.list} directive) whether or
5241 not assembly listings are generated. These two directives maintain an
5242 internal counter (which is zero initially). @code{.list} increments the
5243 counter, and @code{.nolist} decrements it. Assembly listings are
5244 generated whenever the counter is greater than zero.
5247 @section @code{.octa @var{bignums}}
5249 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5250 @cindex @code{octa} directive
5251 @cindex integer, 16-byte
5252 @cindex sixteen byte integer
5253 This directive expects zero or more bignums, separated by commas. For each
5254 bignum, it emits a 16-byte integer.
5256 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5257 hence @emph{octa}-word for 16 bytes.
5260 @section @code{.org @var{new-lc} , @var{fill}}
5262 @cindex @code{org} directive
5263 @cindex location counter, advancing
5264 @cindex advancing location counter
5265 @cindex current address, advancing
5266 Advance the location counter of the current section to
5267 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5268 expression with the same section as the current subsection. That is,
5269 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5270 wrong section, the @code{.org} directive is ignored. To be compatible
5271 with former assemblers, if the section of @var{new-lc} is absolute,
5272 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5273 is the same as the current subsection.
5275 @code{.org} may only increase the location counter, or leave it
5276 unchanged; you cannot use @code{.org} to move the location counter
5279 @c double negative used below "not undefined" because this is a specific
5280 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5281 @c section. doc@cygnus.com 18feb91
5282 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5283 may not be undefined. If you really detest this restriction we eagerly await
5284 a chance to share your improved assembler.
5286 Beware that the origin is relative to the start of the section, not
5287 to the start of the subsection. This is compatible with other
5288 people's assemblers.
5290 When the location counter (of the current subsection) is advanced, the
5291 intervening bytes are filled with @var{fill} which should be an
5292 absolute expression. If the comma and @var{fill} are omitted,
5293 @var{fill} defaults to zero.
5296 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5298 @cindex padding the location counter given a power of two
5299 @cindex @code{p2align} directive
5300 Pad the location counter (in the current subsection) to a particular
5301 storage boundary. The first expression (which must be absolute) is the
5302 number of low-order zero bits the location counter must have after
5303 advancement. For example @samp{.p2align 3} advances the location
5304 counter until it a multiple of 8. If the location counter is already a
5305 multiple of 8, no change is needed.
5307 The second expression (also absolute) gives the fill value to be stored in the
5308 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5309 padding bytes are normally zero. However, on some systems, if the section is
5310 marked as containing code and the fill value is omitted, the space is filled
5311 with no-op instructions.
5313 The third expression is also absolute, and is also optional. If it is present,
5314 it is the maximum number of bytes that should be skipped by this alignment
5315 directive. If doing the alignment would require skipping more bytes than the
5316 specified maximum, then the alignment is not done at all. You can omit the
5317 fill value (the second argument) entirely by simply using two commas after the
5318 required alignment; this can be useful if you want the alignment to be filled
5319 with no-op instructions when appropriate.
5321 @cindex @code{p2alignw} directive
5322 @cindex @code{p2alignl} directive
5323 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5324 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5325 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5326 fill pattern as a four byte longword value. For example, @code{.p2alignw
5327 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5328 filled in with the value 0x368d (the exact placement of the bytes depends upon
5329 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5334 @section @code{.previous}
5336 @cindex @code{previous} directive
5337 @cindex Section Stack
5338 This is one of the ELF section stack manipulation directives. The others are
5339 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5340 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5341 (@pxref{PopSection}).
5343 This directive swaps the current section (and subsection) with most recently
5344 referenced section (and subsection) prior to this one. Multiple
5345 @code{.previous} directives in a row will flip between two sections (and their
5348 In terms of the section stack, this directive swaps the current section with
5349 the top section on the section stack.
5354 @section @code{.popsection}
5356 @cindex @code{popsection} directive
5357 @cindex Section Stack
5358 This is one of the ELF section stack manipulation directives. The others are
5359 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5360 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5363 This directive replaces the current section (and subsection) with the top
5364 section (and subsection) on the section stack. This section is popped off the
5369 @section @code{.print @var{string}}
5371 @cindex @code{print} directive
5372 @command{@value{AS}} will print @var{string} on the standard output during
5373 assembly. You must put @var{string} in double quotes.
5377 @section @code{.protected @var{names}}
5379 @cindex @code{protected} directive
5381 This is one of the ELF visibility directives. The other two are
5382 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5384 This directive overrides the named symbols default visibility (which is set by
5385 their binding: local, global or weak). The directive sets the visibility to
5386 @code{protected} which means that any references to the symbols from within the
5387 components that defines them must be resolved to the definition in that
5388 component, even if a definition in another component would normally preempt
5393 @section @code{.psize @var{lines} , @var{columns}}
5395 @cindex @code{psize} directive
5396 @cindex listing control: paper size
5397 @cindex paper size, for listings
5398 Use this directive to declare the number of lines---and, optionally, the
5399 number of columns---to use for each page, when generating listings.
5401 If you do not use @code{.psize}, listings use a default line-count
5402 of 60. You may omit the comma and @var{columns} specification; the
5403 default width is 200 columns.
5405 @command{@value{AS}} generates formfeeds whenever the specified number of
5406 lines is exceeded (or whenever you explicitly request one, using
5409 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5410 those explicitly specified with @code{.eject}.
5413 @section @code{.purgem @var{name}}
5415 @cindex @code{purgem} directive
5416 Undefine the macro @var{name}, so that later uses of the string will not be
5417 expanded. @xref{Macro}.
5421 @section @code{.pushsection @var{name} , @var{subsection}}
5423 @cindex @code{pushsection} directive
5424 @cindex Section Stack
5425 This is one of the ELF section stack manipulation directives. The others are
5426 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5427 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5430 This directive pushes the current section (and subsection) onto the
5431 top of the section stack, and then replaces the current section and
5432 subsection with @code{name} and @code{subsection}.
5436 @section @code{.quad @var{bignums}}
5438 @cindex @code{quad} directive
5439 @code{.quad} expects zero or more bignums, separated by commas. For
5440 each bignum, it emits
5442 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5443 warning message; and just takes the lowest order 8 bytes of the bignum.
5444 @cindex eight-byte integer
5445 @cindex integer, 8-byte
5447 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5448 hence @emph{quad}-word for 8 bytes.
5451 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5452 warning message; and just takes the lowest order 16 bytes of the bignum.
5453 @cindex sixteen-byte integer
5454 @cindex integer, 16-byte
5458 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5460 @cindex @code{reloc} directive
5461 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5462 @var{expression}. If @var{offset} is a number, the relocation is generated in
5463 the current section. If @var{offset} is an expression that resolves to a
5464 symbol plus offset, the relocation is generated in the given symbol's section.
5465 @var{expression}, if present, must resolve to a symbol plus addend or to an
5466 absolute value, but note that not all targets support an addend. e.g. ELF REL
5467 targets such as i386 store an addend in the section contents rather than in the
5468 relocation. This low level interface does not support addends stored in the
5472 @section @code{.rept @var{count}}
5474 @cindex @code{rept} directive
5475 Repeat the sequence of lines between the @code{.rept} directive and the next
5476 @code{.endr} directive @var{count} times.
5478 For example, assembling
5486 is equivalent to assembling
5495 @section @code{.sbttl "@var{subheading}"}
5497 @cindex @code{sbttl} directive
5498 @cindex subtitles for listings
5499 @cindex listing control: subtitle
5500 Use @var{subheading} as the title (third line, immediately after the
5501 title line) when generating assembly listings.
5503 This directive affects subsequent pages, as well as the current page if
5504 it appears within ten lines of the top of a page.
5508 @section @code{.scl @var{class}}
5510 @cindex @code{scl} directive
5511 @cindex symbol storage class (COFF)
5512 @cindex COFF symbol storage class
5513 Set the storage-class value for a symbol. This directive may only be
5514 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5515 whether a symbol is static or external, or it may record further
5516 symbolic debugging information.
5519 The @samp{.scl} directive is primarily associated with COFF output; when
5520 configured to generate @code{b.out} output format, @command{@value{AS}}
5521 accepts this directive but ignores it.
5527 @section @code{.section @var{name}}
5529 @cindex named section
5530 Use the @code{.section} directive to assemble the following code into a section
5533 This directive is only supported for targets that actually support arbitrarily
5534 named sections; on @code{a.out} targets, for example, it is not accepted, even
5535 with a standard @code{a.out} section name.
5539 @c only print the extra heading if both COFF and ELF are set
5540 @subheading COFF Version
5543 @cindex @code{section} directive (COFF version)
5544 For COFF targets, the @code{.section} directive is used in one of the following
5548 .section @var{name}[, "@var{flags}"]
5549 .section @var{name}[, @var{subsegment}]
5552 If the optional argument is quoted, it is taken as flags to use for the
5553 section. Each flag is a single character. The following flags are recognized:
5556 bss section (uninitialized data)
5558 section is not loaded
5568 shared section (meaningful for PE targets)
5570 ignored. (For compatibility with the ELF version)
5573 If no flags are specified, the default flags depend upon the section name. If
5574 the section name is not recognized, the default will be for the section to be
5575 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5576 from the section, rather than adding them, so if they are used on their own it
5577 will be as if no flags had been specified at all.
5579 If the optional argument to the @code{.section} directive is not quoted, it is
5580 taken as a subsegment number (@pxref{Sub-Sections}).
5585 @c only print the extra heading if both COFF and ELF are set
5586 @subheading ELF Version
5589 @cindex Section Stack
5590 This is one of the ELF section stack manipulation directives. The others are
5591 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5592 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5593 @code{.previous} (@pxref{Previous}).
5595 @cindex @code{section} directive (ELF version)
5596 For ELF targets, the @code{.section} directive is used like this:
5599 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
5602 The optional @var{flags} argument is a quoted string which may contain any
5603 combination of the following characters:
5606 section is allocatable
5610 section is executable
5612 section is mergeable
5614 section contains zero terminated strings
5616 section is a member of a section group
5618 section is used for thread-local-storage
5621 The optional @var{type} argument may contain one of the following constants:
5624 section contains data
5626 section does not contain data (i.e., section only occupies space)
5628 section contains data which is used by things other than the program
5630 section contains an array of pointers to init functions
5632 section contains an array of pointers to finish functions
5633 @item @@preinit_array
5634 section contains an array of pointers to pre-init functions
5637 Many targets only support the first three section types.
5639 Note on targets where the @code{@@} character is the start of a comment (eg
5640 ARM) then another character is used instead. For example the ARM port uses the
5643 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
5644 be specified as well as an extra argument---@var{entsize}---like this:
5647 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
5650 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
5651 constants, each @var{entsize} octets long. Sections with both @code{M} and
5652 @code{S} must contain zero terminated strings where each character is
5653 @var{entsize} bytes long. The linker may remove duplicates within sections with
5654 the same name, same entity size and same flags. @var{entsize} must be an
5655 absolute expression.
5657 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
5658 be present along with an additional field like this:
5661 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
5664 The @var{GroupName} field specifies the name of the section group to which this
5665 particular section belongs. The optional linkage field can contain:
5668 indicates that only one copy of this section should be retained
5673 Note: if both the @var{M} and @var{G} flags are present then the fields for
5674 the Merge flag should come first, like this:
5677 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
5680 If no flags are specified, the default flags depend upon the section name. If
5681 the section name is not recognized, the default will be for the section to have
5682 none of the above flags: it will not be allocated in memory, nor writable, nor
5683 executable. The section will contain data.
5685 For ELF targets, the assembler supports another type of @code{.section}
5686 directive for compatibility with the Solaris assembler:
5689 .section "@var{name}"[, @var{flags}...]
5692 Note that the section name is quoted. There may be a sequence of comma
5696 section is allocatable
5700 section is executable
5702 section is used for thread local storage
5705 This directive replaces the current section and subsection. See the
5706 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
5707 some examples of how this directive and the other section stack directives
5713 @section @code{.set @var{symbol}, @var{expression}}
5715 @cindex @code{set} directive
5716 @cindex symbol value, setting
5717 Set the value of @var{symbol} to @var{expression}. This
5718 changes @var{symbol}'s value and type to conform to
5719 @var{expression}. If @var{symbol} was flagged as external, it remains
5720 flagged (@pxref{Symbol Attributes}).
5722 You may @code{.set} a symbol many times in the same assembly.
5724 If you @code{.set} a global symbol, the value stored in the object
5725 file is the last value stored into it.
5728 The syntax for @code{set} on the HPPA is
5729 @samp{@var{symbol} .set @var{expression}}.
5733 On Z80 @code{set} is a real instruction, use
5734 @samp{@var{symbol} defl @var{expression}} instead.
5738 @section @code{.short @var{expressions}}
5740 @cindex @code{short} directive
5742 @code{.short} is normally the same as @samp{.word}.
5743 @xref{Word,,@code{.word}}.
5745 In some configurations, however, @code{.short} and @code{.word} generate
5746 numbers of different lengths. @xref{Machine Dependencies}.
5750 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
5753 This expects zero or more @var{expressions}, and emits
5754 a 16 bit number for each.
5759 @section @code{.single @var{flonums}}
5761 @cindex @code{single} directive
5762 @cindex floating point numbers (single)
5763 This directive assembles zero or more flonums, separated by commas. It
5764 has the same effect as @code{.float}.
5766 The exact kind of floating point numbers emitted depends on how
5767 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5771 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
5772 numbers in @sc{ieee} format.
5778 @section @code{.size}
5780 This directive is used to set the size associated with a symbol.
5784 @c only print the extra heading if both COFF and ELF are set
5785 @subheading COFF Version
5788 @cindex @code{size} directive (COFF version)
5789 For COFF targets, the @code{.size} directive is only permitted inside
5790 @code{.def}/@code{.endef} pairs. It is used like this:
5793 .size @var{expression}
5797 @samp{.size} is only meaningful when generating COFF format output; when
5798 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5805 @c only print the extra heading if both COFF and ELF are set
5806 @subheading ELF Version
5809 @cindex @code{size} directive (ELF version)
5810 For ELF targets, the @code{.size} directive is used like this:
5813 .size @var{name} , @var{expression}
5816 This directive sets the size associated with a symbol @var{name}.
5817 The size in bytes is computed from @var{expression} which can make use of label
5818 arithmetic. This directive is typically used to set the size of function
5824 @section @code{.sleb128 @var{expressions}}
5826 @cindex @code{sleb128} directive
5827 @var{sleb128} stands for ``signed little endian base 128.'' This is a
5828 compact, variable length representation of numbers used by the DWARF
5829 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
5831 @ifclear no-space-dir
5833 @section @code{.skip @var{size} , @var{fill}}
5835 @cindex @code{skip} directive
5836 @cindex filling memory
5837 This directive emits @var{size} bytes, each of value @var{fill}. Both
5838 @var{size} and @var{fill} are absolute expressions. If the comma and
5839 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
5843 @section @code{.space @var{size} , @var{fill}}
5845 @cindex @code{space} directive
5846 @cindex filling memory
5847 This directive emits @var{size} bytes, each of value @var{fill}. Both
5848 @var{size} and @var{fill} are absolute expressions. If the comma
5849 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
5854 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
5855 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
5856 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
5857 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
5865 @section @code{.stabd, .stabn, .stabs}
5867 @cindex symbolic debuggers, information for
5868 @cindex @code{stab@var{x}} directives
5869 There are three directives that begin @samp{.stab}.
5870 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
5871 The symbols are not entered in the @command{@value{AS}} hash table: they
5872 cannot be referenced elsewhere in the source file.
5873 Up to five fields are required:
5877 This is the symbol's name. It may contain any character except
5878 @samp{\000}, so is more general than ordinary symbol names. Some
5879 debuggers used to code arbitrarily complex structures into symbol names
5883 An absolute expression. The symbol's type is set to the low 8 bits of
5884 this expression. Any bit pattern is permitted, but @code{@value{LD}}
5885 and debuggers choke on silly bit patterns.
5888 An absolute expression. The symbol's ``other'' attribute is set to the
5889 low 8 bits of this expression.
5892 An absolute expression. The symbol's descriptor is set to the low 16
5893 bits of this expression.
5896 An absolute expression which becomes the symbol's value.
5899 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
5900 or @code{.stabs} statement, the symbol has probably already been created;
5901 you get a half-formed symbol in your object file. This is
5902 compatible with earlier assemblers!
5905 @cindex @code{stabd} directive
5906 @item .stabd @var{type} , @var{other} , @var{desc}
5908 The ``name'' of the symbol generated is not even an empty string.
5909 It is a null pointer, for compatibility. Older assemblers used a
5910 null pointer so they didn't waste space in object files with empty
5913 The symbol's value is set to the location counter,
5914 relocatably. When your program is linked, the value of this symbol
5915 is the address of the location counter when the @code{.stabd} was
5918 @cindex @code{stabn} directive
5919 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
5920 The name of the symbol is set to the empty string @code{""}.
5922 @cindex @code{stabs} directive
5923 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
5924 All five fields are specified.
5930 @section @code{.string} "@var{str}"
5932 @cindex string, copying to object file
5933 @cindex @code{string} directive
5935 Copy the characters in @var{str} to the object file. You may specify more than
5936 one string to copy, separated by commas. Unless otherwise specified for a
5937 particular machine, the assembler marks the end of each string with a 0 byte.
5938 You can use any of the escape sequences described in @ref{Strings,,Strings}.
5941 @section @code{.struct @var{expression}}
5943 @cindex @code{struct} directive
5944 Switch to the absolute section, and set the section offset to @var{expression},
5945 which must be an absolute expression. You might use this as follows:
5954 This would define the symbol @code{field1} to have the value 0, the symbol
5955 @code{field2} to have the value 4, and the symbol @code{field3} to have the
5956 value 8. Assembly would be left in the absolute section, and you would need to
5957 use a @code{.section} directive of some sort to change to some other section
5958 before further assembly.
5962 @section @code{.subsection @var{name}}
5964 @cindex @code{subsection} directive
5965 @cindex Section Stack
5966 This is one of the ELF section stack manipulation directives. The others are
5967 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
5968 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5971 This directive replaces the current subsection with @code{name}. The current
5972 section is not changed. The replaced subsection is put onto the section stack
5973 in place of the then current top of stack subsection.
5978 @section @code{.symver}
5979 @cindex @code{symver} directive
5980 @cindex symbol versioning
5981 @cindex versions of symbols
5982 Use the @code{.symver} directive to bind symbols to specific version nodes
5983 within a source file. This is only supported on ELF platforms, and is
5984 typically used when assembling files to be linked into a shared library.
5985 There are cases where it may make sense to use this in objects to be bound
5986 into an application itself so as to override a versioned symbol from a
5989 For ELF targets, the @code{.symver} directive can be used like this:
5991 .symver @var{name}, @var{name2@@nodename}
5993 If the symbol @var{name} is defined within the file
5994 being assembled, the @code{.symver} directive effectively creates a symbol
5995 alias with the name @var{name2@@nodename}, and in fact the main reason that we
5996 just don't try and create a regular alias is that the @var{@@} character isn't
5997 permitted in symbol names. The @var{name2} part of the name is the actual name
5998 of the symbol by which it will be externally referenced. The name @var{name}
5999 itself is merely a name of convenience that is used so that it is possible to
6000 have definitions for multiple versions of a function within a single source
6001 file, and so that the compiler can unambiguously know which version of a
6002 function is being mentioned. The @var{nodename} portion of the alias should be
6003 the name of a node specified in the version script supplied to the linker when
6004 building a shared library. If you are attempting to override a versioned
6005 symbol from a shared library, then @var{nodename} should correspond to the
6006 nodename of the symbol you are trying to override.
6008 If the symbol @var{name} is not defined within the file being assembled, all
6009 references to @var{name} will be changed to @var{name2@@nodename}. If no
6010 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6013 Another usage of the @code{.symver} directive is:
6015 .symver @var{name}, @var{name2@@@@nodename}
6017 In this case, the symbol @var{name} must exist and be defined within
6018 the file being assembled. It is similar to @var{name2@@nodename}. The
6019 difference is @var{name2@@@@nodename} will also be used to resolve
6020 references to @var{name2} by the linker.
6022 The third usage of the @code{.symver} directive is:
6024 .symver @var{name}, @var{name2@@@@@@nodename}
6026 When @var{name} is not defined within the
6027 file being assembled, it is treated as @var{name2@@nodename}. When
6028 @var{name} is defined within the file being assembled, the symbol
6029 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6034 @section @code{.tag @var{structname}}
6036 @cindex COFF structure debugging
6037 @cindex structure debugging, COFF
6038 @cindex @code{tag} directive
6039 This directive is generated by compilers to include auxiliary debugging
6040 information in the symbol table. It is only permitted inside
6041 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6042 definitions in the symbol table with instances of those structures.
6045 @samp{.tag} is only used when generating COFF format output; when
6046 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6052 @section @code{.text @var{subsection}}
6054 @cindex @code{text} directive
6055 Tells @command{@value{AS}} to assemble the following statements onto the end of
6056 the text subsection numbered @var{subsection}, which is an absolute
6057 expression. If @var{subsection} is omitted, subsection number zero
6061 @section @code{.title "@var{heading}"}
6063 @cindex @code{title} directive
6064 @cindex listing control: title line
6065 Use @var{heading} as the title (second line, immediately after the
6066 source file name and pagenumber) when generating assembly listings.
6068 This directive affects subsequent pages, as well as the current page if
6069 it appears within ten lines of the top of a page.
6073 @section @code{.type}
6075 This directive is used to set the type of a symbol.
6079 @c only print the extra heading if both COFF and ELF are set
6080 @subheading COFF Version
6083 @cindex COFF symbol type
6084 @cindex symbol type, COFF
6085 @cindex @code{type} directive (COFF version)
6086 For COFF targets, this directive is permitted only within
6087 @code{.def}/@code{.endef} pairs. It is used like this:
6093 This records the integer @var{int} as the type attribute of a symbol table
6097 @samp{.type} is associated only with COFF format output; when
6098 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6099 directive but ignores it.
6105 @c only print the extra heading if both COFF and ELF are set
6106 @subheading ELF Version
6109 @cindex ELF symbol type
6110 @cindex symbol type, ELF
6111 @cindex @code{type} directive (ELF version)
6112 For ELF targets, the @code{.type} directive is used like this:
6115 .type @var{name} , @var{type description}
6118 This sets the type of symbol @var{name} to be either a
6119 function symbol or an object symbol. There are five different syntaxes
6120 supported for the @var{type description} field, in order to provide
6121 compatibility with various other assemblers.
6123 Because some of the characters used in these syntaxes (such as @samp{@@} and
6124 @samp{#}) are comment characters for some architectures, some of the syntaxes
6125 below do not work on all architectures. The first variant will be accepted by
6126 the GNU assembler on all architectures so that variant should be used for
6127 maximum portability, if you do not need to assemble your code with other
6130 The syntaxes supported are:
6133 .type <name> STT_FUNCTION
6134 .type <name> STT_OBJECT
6136 .type <name>,#function
6137 .type <name>,#object
6139 .type <name>,@@function
6140 .type <name>,@@object
6142 .type <name>,%function
6143 .type <name>,%object
6145 .type <name>,"function"
6146 .type <name>,"object"
6152 @section @code{.uleb128 @var{expressions}}
6154 @cindex @code{uleb128} directive
6155 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6156 compact, variable length representation of numbers used by the DWARF
6157 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6161 @section @code{.val @var{addr}}
6163 @cindex @code{val} directive
6164 @cindex COFF value attribute
6165 @cindex value attribute, COFF
6166 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6167 records the address @var{addr} as the value attribute of a symbol table
6171 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6172 configured for @code{b.out}, it accepts this directive but ignores it.
6178 @section @code{.version "@var{string}"}
6180 @cindex @code{version} directive
6181 This directive creates a @code{.note} section and places into it an ELF
6182 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6187 @section @code{.vtable_entry @var{table}, @var{offset}}
6189 @cindex @code{vtable_entry} directive
6190 This directive finds or creates a symbol @code{table} and creates a
6191 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6194 @section @code{.vtable_inherit @var{child}, @var{parent}}
6196 @cindex @code{vtable_inherit} directive
6197 This directive finds the symbol @code{child} and finds or creates the symbol
6198 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6199 parent whose addend is the value of the child symbol. As a special case the
6200 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6204 @section @code{.warning "@var{string}"}
6205 @cindex warning directive
6206 Similar to the directive @code{.error}
6207 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6210 @section @code{.weak @var{names}}
6212 @cindex @code{weak} directive
6213 This directive sets the weak attribute on the comma separated list of symbol
6214 @code{names}. If the symbols do not already exist, they will be created.
6216 On COFF targets other than PE, weak symbols are a GNU extension. This
6217 directive sets the weak attribute on the comma separated list of symbol
6218 @code{names}. If the symbols do not already exist, they will be created.
6220 On the PE target, weak symbols are supported natively as weak aliases.
6221 When a weak symbol is created that is not an alias, GAS creates an
6222 alternate symbol to hold the default value.
6225 @section @code{.weakref @var{alias}, @var{target}}
6227 @cindex @code{weakref} directive
6228 This directive creates an alias to the target symbol that enables the symbol to
6229 be referenced with weak-symbol semantics, but without actually making it weak.
6230 If direct references or definitions of the symbol are present, then the symbol
6231 will not be weak, but if all references to it are through weak references, the
6232 symbol will be marked as weak in the symbol table.
6234 The effect is equivalent to moving all references to the alias to a separate
6235 assembly source file, renaming the alias to the symbol in it, declaring the
6236 symbol as weak there, and running a reloadable link to merge the object files
6237 resulting from the assembly of the new source file and the old source file that
6238 had the references to the alias removed.
6240 The alias itself never makes to the symbol table, and is entirely handled
6241 within the assembler.
6244 @section @code{.word @var{expressions}}
6246 @cindex @code{word} directive
6247 This directive expects zero or more @var{expressions}, of any section,
6248 separated by commas.
6251 For each expression, @command{@value{AS}} emits a 32-bit number.
6254 For each expression, @command{@value{AS}} emits a 16-bit number.
6259 The size of the number emitted, and its byte order,
6260 depend on what target computer the assembly is for.
6263 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6264 @c happen---32-bit addressability, period; no long/short jumps.
6265 @ifset DIFF-TBL-KLUGE
6266 @cindex difference tables altered
6267 @cindex altered difference tables
6269 @emph{Warning: Special Treatment to support Compilers}
6273 Machines with a 32-bit address space, but that do less than 32-bit
6274 addressing, require the following special treatment. If the machine of
6275 interest to you does 32-bit addressing (or doesn't require it;
6276 @pxref{Machine Dependencies}), you can ignore this issue.
6279 In order to assemble compiler output into something that works,
6280 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6281 Directives of the form @samp{.word sym1-sym2} are often emitted by
6282 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6283 directive of the form @samp{.word sym1-sym2}, and the difference between
6284 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6285 creates a @dfn{secondary jump table}, immediately before the next label.
6286 This secondary jump table is preceded by a short-jump to the
6287 first byte after the secondary table. This short-jump prevents the flow
6288 of control from accidentally falling into the new table. Inside the
6289 table is a long-jump to @code{sym2}. The original @samp{.word}
6290 contains @code{sym1} minus the address of the long-jump to
6293 If there were several occurrences of @samp{.word sym1-sym2} before the
6294 secondary jump table, all of them are adjusted. If there was a
6295 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6296 long-jump to @code{sym4} is included in the secondary jump table,
6297 and the @code{.word} directives are adjusted to contain @code{sym3}
6298 minus the address of the long-jump to @code{sym4}; and so on, for as many
6299 entries in the original jump table as necessary.
6302 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6303 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6304 assembly language programmers.
6307 @c end DIFF-TBL-KLUGE
6310 @section Deprecated Directives
6312 @cindex deprecated directives
6313 @cindex obsolescent directives
6314 One day these directives won't work.
6315 They are included for compatibility with older assemblers.
6322 @node Machine Dependencies
6323 @chapter Machine Dependent Features
6325 @cindex machine dependencies
6326 The machine instruction sets are (almost by definition) different on
6327 each machine where @command{@value{AS}} runs. Floating point representations
6328 vary as well, and @command{@value{AS}} often supports a few additional
6329 directives or command-line options for compatibility with other
6330 assemblers on a particular platform. Finally, some versions of
6331 @command{@value{AS}} support special pseudo-instructions for branch
6334 This chapter discusses most of these differences, though it does not
6335 include details on any machine's instruction set. For details on that
6336 subject, see the hardware manufacturer's manual.
6340 * Alpha-Dependent:: Alpha Dependent Features
6343 * ARC-Dependent:: ARC Dependent Features
6346 * ARM-Dependent:: ARM Dependent Features
6349 * AVR-Dependent:: AVR Dependent Features
6352 * BFIN-Dependent:: BFIN Dependent Features
6355 * CRIS-Dependent:: CRIS Dependent Features
6358 * D10V-Dependent:: D10V Dependent Features
6361 * D30V-Dependent:: D30V Dependent Features
6364 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6367 * HPPA-Dependent:: HPPA Dependent Features
6370 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6373 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6376 * i860-Dependent:: Intel 80860 Dependent Features
6379 * i960-Dependent:: Intel 80960 Dependent Features
6382 * IA-64-Dependent:: Intel IA-64 Dependent Features
6385 * IP2K-Dependent:: IP2K Dependent Features
6388 * M32C-Dependent:: M32C Dependent Features
6391 * M32R-Dependent:: M32R Dependent Features
6394 * M68K-Dependent:: M680x0 Dependent Features
6397 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
6400 * MIPS-Dependent:: MIPS Dependent Features
6403 * MMIX-Dependent:: MMIX Dependent Features
6406 * MSP430-Dependent:: MSP430 Dependent Features
6409 * SH-Dependent:: Renesas / SuperH SH Dependent Features
6410 * SH64-Dependent:: SuperH SH64 Dependent Features
6413 * PDP-11-Dependent:: PDP-11 Dependent Features
6416 * PJ-Dependent:: picoJava Dependent Features
6419 * PPC-Dependent:: PowerPC Dependent Features
6422 * Sparc-Dependent:: SPARC Dependent Features
6425 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
6428 * V850-Dependent:: V850 Dependent Features
6431 * Xtensa-Dependent:: Xtensa Dependent Features
6434 * Z80-Dependent:: Z80 Dependent Features
6437 * Z8000-Dependent:: Z8000 Dependent Features
6440 * Vax-Dependent:: VAX Dependent Features
6447 @c The following major nodes are *sections* in the GENERIC version, *chapters*
6448 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
6449 @c peculiarity: to preserve cross-references, there must be a node called
6450 @c "Machine Dependencies". Hence the conditional nodenames in each
6451 @c major node below. Node defaulting in makeinfo requires adjacency of
6452 @c node and sectioning commands; hence the repetition of @chapter BLAH
6453 @c in both conditional blocks.
6456 @include c-alpha.texi
6472 @include c-bfin.texi
6476 @include c-cris.texi
6481 @node Machine Dependencies
6482 @chapter Machine Dependent Features
6484 The machine instruction sets are different on each Renesas chip family,
6485 and there are also some syntax differences among the families. This
6486 chapter describes the specific @command{@value{AS}} features for each
6490 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6491 * SH-Dependent:: Renesas SH Dependent Features
6498 @include c-d10v.texi
6502 @include c-d30v.texi
6506 @include c-h8300.texi
6510 @include c-hppa.texi
6514 @include c-i370.texi
6518 @include c-i386.texi
6522 @include c-i860.texi
6526 @include c-i960.texi
6530 @include c-ia64.texi
6534 @include c-ip2k.texi
6538 @include c-m32c.texi
6542 @include c-m32r.texi
6546 @include c-m68k.texi
6550 @include c-m68hc11.texi
6554 @include c-mips.texi
6558 @include c-mmix.texi
6562 @include c-msp430.texi
6566 @include c-ns32k.texi
6570 @include c-pdp11.texi
6583 @include c-sh64.texi
6587 @include c-sparc.texi
6591 @include c-tic54x.texi
6607 @include c-v850.texi
6611 @include c-xtensa.texi
6615 @c reverse effect of @down at top of generic Machine-Dep chapter
6619 @node Reporting Bugs
6620 @chapter Reporting Bugs
6621 @cindex bugs in assembler
6622 @cindex reporting bugs in assembler
6624 Your bug reports play an essential role in making @command{@value{AS}} reliable.
6626 Reporting a bug may help you by bringing a solution to your problem, or it may
6627 not. But in any case the principal function of a bug report is to help the
6628 entire community by making the next version of @command{@value{AS}} work better.
6629 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
6631 In order for a bug report to serve its purpose, you must include the
6632 information that enables us to fix the bug.
6635 * Bug Criteria:: Have you found a bug?
6636 * Bug Reporting:: How to report bugs
6640 @section Have You Found a Bug?
6641 @cindex bug criteria
6643 If you are not sure whether you have found a bug, here are some guidelines:
6646 @cindex fatal signal
6647 @cindex assembler crash
6648 @cindex crash of assembler
6650 If the assembler gets a fatal signal, for any input whatever, that is a
6651 @command{@value{AS}} bug. Reliable assemblers never crash.
6653 @cindex error on valid input
6655 If @command{@value{AS}} produces an error message for valid input, that is a bug.
6657 @cindex invalid input
6659 If @command{@value{AS}} does not produce an error message for invalid input, that
6660 is a bug. However, you should note that your idea of ``invalid input'' might
6661 be our idea of ``an extension'' or ``support for traditional practice''.
6664 If you are an experienced user of assemblers, your suggestions for improvement
6665 of @command{@value{AS}} are welcome in any case.
6669 @section How to Report Bugs
6671 @cindex assembler bugs, reporting
6673 A number of companies and individuals offer support for @sc{gnu} products. If
6674 you obtained @command{@value{AS}} from a support organization, we recommend you
6675 contact that organization first.
6677 You can find contact information for many support companies and
6678 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
6682 In any event, we also recommend that you send bug reports for @command{@value{AS}}
6686 The fundamental principle of reporting bugs usefully is this:
6687 @strong{report all the facts}. If you are not sure whether to state a
6688 fact or leave it out, state it!
6690 Often people omit facts because they think they know what causes the problem
6691 and assume that some details do not matter. Thus, you might assume that the
6692 name of a symbol you use in an example does not matter. Well, probably it does
6693 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
6694 happens to fetch from the location where that name is stored in memory;
6695 perhaps, if the name were different, the contents of that location would fool
6696 the assembler into doing the right thing despite the bug. Play it safe and
6697 give a specific, complete example. That is the easiest thing for you to do,
6698 and the most helpful.
6700 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
6701 it is new to us. Therefore, always write your bug reports on the assumption
6702 that the bug has not been reported previously.
6704 Sometimes people give a few sketchy facts and ask, ``Does this ring a
6705 bell?'' This cannot help us fix a bug, so it is basically useless. We
6706 respond by asking for enough details to enable us to investigate.
6707 You might as well expedite matters by sending them to begin with.
6709 To enable us to fix the bug, you should include all these things:
6713 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
6714 it with the @samp{--version} argument.
6716 Without this, we will not know whether there is any point in looking for
6717 the bug in the current version of @command{@value{AS}}.
6720 Any patches you may have applied to the @command{@value{AS}} source.
6723 The type of machine you are using, and the operating system name and
6727 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
6731 The command arguments you gave the assembler to assemble your example and
6732 observe the bug. To guarantee you will not omit something important, list them
6733 all. A copy of the Makefile (or the output from make) is sufficient.
6735 If we were to try to guess the arguments, we would probably guess wrong
6736 and then we might not encounter the bug.
6739 A complete input file that will reproduce the bug. If the bug is observed when
6740 the assembler is invoked via a compiler, send the assembler source, not the
6741 high level language source. Most compilers will produce the assembler source
6742 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
6743 the options @samp{-v --save-temps}; this will save the assembler source in a
6744 file with an extension of @file{.s}, and also show you exactly how
6745 @command{@value{AS}} is being run.
6748 A description of what behavior you observe that you believe is
6749 incorrect. For example, ``It gets a fatal signal.''
6751 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
6752 will certainly notice it. But if the bug is incorrect output, we might not
6753 notice unless it is glaringly wrong. You might as well not give us a chance to
6756 Even if the problem you experience is a fatal signal, you should still say so
6757 explicitly. Suppose something strange is going on, such as, your copy of
6758 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
6759 library on your system. (This has happened!) Your copy might crash and ours
6760 would not. If you told us to expect a crash, then when ours fails to crash, we
6761 would know that the bug was not happening for us. If you had not told us to
6762 expect a crash, then we would not be able to draw any conclusion from our
6766 If you wish to suggest changes to the @command{@value{AS}} source, send us context
6767 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
6768 option. Always send diffs from the old file to the new file. If you even
6769 discuss something in the @command{@value{AS}} source, refer to it by context, not
6772 The line numbers in our development sources will not match those in your
6773 sources. Your line numbers would convey no useful information to us.
6776 Here are some things that are not necessary:
6780 A description of the envelope of the bug.
6782 Often people who encounter a bug spend a lot of time investigating
6783 which changes to the input file will make the bug go away and which
6784 changes will not affect it.
6786 This is often time consuming and not very useful, because the way we
6787 will find the bug is by running a single example under the debugger
6788 with breakpoints, not by pure deduction from a series of examples.
6789 We recommend that you save your time for something else.
6791 Of course, if you can find a simpler example to report @emph{instead}
6792 of the original one, that is a convenience for us. Errors in the
6793 output will be easier to spot, running under the debugger will take
6794 less time, and so on.
6796 However, simplification is not vital; if you do not want to do this,
6797 report the bug anyway and send us the entire test case you used.
6800 A patch for the bug.
6802 A patch for the bug does help us if it is a good one. But do not omit
6803 the necessary information, such as the test case, on the assumption that
6804 a patch is all we need. We might see problems with your patch and decide
6805 to fix the problem another way, or we might not understand it at all.
6807 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
6808 construct an example that will make the program follow a certain path through
6809 the code. If you do not send us the example, we will not be able to construct
6810 one, so we will not be able to verify that the bug is fixed.
6812 And if we cannot understand what bug you are trying to fix, or why your
6813 patch should be an improvement, we will not install it. A test case will
6814 help us to understand.
6817 A guess about what the bug is or what it depends on.
6819 Such guesses are usually wrong. Even we cannot guess right about such
6820 things without first using the debugger to find the facts.
6823 @node Acknowledgements
6824 @chapter Acknowledgements
6826 If you have contributed to GAS and your name isn't listed here,
6827 it is not meant as a slight. We just don't know about it. Send mail to the
6828 maintainer, and we'll correct the situation. Currently
6830 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
6832 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
6835 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
6836 information and the 68k series machines, most of the preprocessing pass, and
6837 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
6839 K. Richard Pixley maintained GAS for a while, adding various enhancements and
6840 many bug fixes, including merging support for several processors, breaking GAS
6841 up to handle multiple object file format back ends (including heavy rewrite,
6842 testing, an integration of the coff and b.out back ends), adding configuration
6843 including heavy testing and verification of cross assemblers and file splits
6844 and renaming, converted GAS to strictly ANSI C including full prototypes, added
6845 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
6846 port (including considerable amounts of reverse engineering), a SPARC opcode
6847 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
6848 assertions and made them work, much other reorganization, cleanup, and lint.
6850 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
6851 in format-specific I/O modules.
6853 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
6854 has done much work with it since.
6856 The Intel 80386 machine description was written by Eliot Dresselhaus.
6858 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
6860 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
6861 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
6863 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
6864 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
6865 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
6866 support a.out format.
6868 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
6869 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
6870 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
6871 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
6874 John Gilmore built the AMD 29000 support, added @code{.include} support, and
6875 simplified the configuration of which versions accept which directives. He
6876 updated the 68k machine description so that Motorola's opcodes always produced
6877 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
6878 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
6879 cross-compilation support, and one bug in relaxation that took a week and
6880 required the proverbial one-bit fix.
6882 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
6883 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
6884 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
6885 PowerPC assembler, and made a few other minor patches.
6887 Steve Chamberlain made GAS able to generate listings.
6889 Hewlett-Packard contributed support for the HP9000/300.
6891 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
6892 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
6893 formats). This work was supported by both the Center for Software Science at
6894 the University of Utah and Cygnus Support.
6896 Support for ELF format files has been worked on by Mark Eichin of Cygnus
6897 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
6898 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
6899 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
6900 and some initial 64-bit support).
6902 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
6904 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
6905 support for openVMS/Alpha.
6907 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
6910 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
6911 Inc.@: added support for Xtensa processors.
6913 Several engineers at Cygnus Support have also provided many small bug fixes and
6914 configuration enhancements.
6916 Many others have contributed large or small bugfixes and enhancements. If
6917 you have contributed significant work and are not mentioned on this list, and
6918 want to be, let us know. Some of the history has been lost; we are not
6919 intentionally leaving anyone out.
6924 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob