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, 2008
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, 2008 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 1.3
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, 2008 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 1.3
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
193 * Object Attributes:: Object Attributes
195 * Machine Dependencies:: Machine Dependent Features
196 * Reporting Bugs:: Reporting Bugs
197 * Acknowledgements:: Who Did What
198 * GNU Free Documentation License:: GNU Free Documentation License
199 * AS Index:: AS Index
206 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
208 This version of the manual describes @command{@value{AS}} configured to generate
209 code for @value{TARGET} architectures.
213 @cindex invocation summary
214 @cindex option summary
215 @cindex summary of options
216 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
217 see @ref{Invoking,,Command-Line Options}.
219 @c man title AS the portable GNU assembler.
223 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
227 @c We don't use deffn and friends for the following because they seem
228 @c to be limited to one line for the header.
230 @c man begin SYNOPSIS
231 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
232 [@b{--debug-prefix-map} @var{old}=@var{new}]
233 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
234 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
235 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
236 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
237 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}] [@b{-o}
238 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
239 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
240 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}]
241 [@b{--target-help}] [@var{target-options}]
242 [@b{--}|@var{files} @dots{}]
244 @c Target dependent options are listed below. Keep the list sorted.
245 @c Add an empty line for separation.
248 @emph{Target Alpha options:}
250 [@b{-mdebug} | @b{-no-mdebug}]
251 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
252 [@b{-F}] [@b{-32addr}]
256 @emph{Target ARC options:}
262 @emph{Target ARM options:}
263 @c Don't document the deprecated options
264 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
265 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
266 [@b{-mfpu}=@var{floating-point-format}]
267 [@b{-mfloat-abi}=@var{abi}]
268 [@b{-meabi}=@var{ver}]
271 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
272 @b{-mapcs-reentrant}]
273 [@b{-mthumb-interwork}] [@b{-k}]
277 @emph{Target CRIS options:}
278 [@b{--underscore} | @b{--no-underscore}]
280 [@b{--emulation=criself} | @b{--emulation=crisaout}]
281 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
282 @c Deprecated -- deliberately not documented.
287 @emph{Target D10V options:}
292 @emph{Target D30V options:}
293 [@b{-O}|@b{-n}|@b{-N}]
297 @emph{Target H8/300 options:}
301 @c HPPA has no machine-dependent assembler options (yet).
305 @emph{Target i386 options:}
306 [@b{--32}|@b{--64}] [@b{-n}]
307 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
311 @emph{Target i960 options:}
312 @c see md_parse_option in tc-i960.c
313 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
315 [@b{-b}] [@b{-no-relax}]
319 @emph{Target IA-64 options:}
320 [@b{-mconstant-gp}|@b{-mauto-pic}]
321 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
323 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
324 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
325 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
326 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
330 @emph{Target IP2K options:}
331 [@b{-mip2022}|@b{-mip2022ext}]
335 @emph{Target M32C options:}
336 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
340 @emph{Target M32R options:}
341 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
346 @emph{Target M680X0 options:}
347 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
351 @emph{Target M68HC11 options:}
352 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}]
353 [@b{-mshort}|@b{-mlong}]
354 [@b{-mshort-double}|@b{-mlong-double}]
355 [@b{--force-long-branches}] [@b{--short-branches}]
356 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
357 [@b{--print-opcodes}] [@b{--generate-example}]
361 @emph{Target MCORE options:}
362 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
363 [@b{-mcpu=[210|340]}]
367 @emph{Target MIPS options:}
368 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
369 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
370 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
371 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
372 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
373 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
374 [@b{-mips64}] [@b{-mips64r2}]
375 [@b{-construct-floats}] [@b{-no-construct-floats}]
376 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
377 [@b{-mfix7000}] [@b{-mno-fix7000}]
378 [@b{-mips16}] [@b{-no-mips16}]
379 [@b{-msmartmips}] [@b{-mno-smartmips}]
380 [@b{-mips3d}] [@b{-no-mips3d}]
381 [@b{-mdmx}] [@b{-no-mdmx}]
382 [@b{-mdsp}] [@b{-mno-dsp}]
383 [@b{-mdspr2}] [@b{-mno-dspr2}]
384 [@b{-mmt}] [@b{-mno-mt}]
385 [@b{-mdebug}] [@b{-no-mdebug}]
386 [@b{-mpdr}] [@b{-mno-pdr}]
390 @emph{Target MMIX options:}
391 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
392 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
393 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
394 [@b{--linker-allocated-gregs}]
398 @emph{Target PDP11 options:}
399 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
400 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
401 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
405 @emph{Target picoJava options:}
410 @emph{Target PowerPC options:}
411 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|
412 @b{-m403}|@b{-m405}|@b{-mppc64}|@b{-m620}|@b{-mppc64bridge}|@b{-mbooke}]
413 [@b{-mcom}|@b{-many}|@b{-maltivec}|@b{-mvsx}] [@b{-memb}]
414 [@b{-mregnames}|@b{-mno-regnames}]
415 [@b{-mrelocatable}|@b{-mrelocatable-lib}]
416 [@b{-mlittle}|@b{-mlittle-endian}|@b{-mbig}|@b{-mbig-endian}]
417 [@b{-msolaris}|@b{-mno-solaris}]
421 @emph{Target s390 options:}
422 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
423 [@b{-mregnames}|@b{-mno-regnames}]
424 [@b{-mwarn-areg-zero}]
428 @emph{Target SPARC options:}
429 @c The order here is important. See c-sparc.texi.
430 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
431 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
432 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
437 @emph{Target TIC54X options:}
438 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
439 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
444 @emph{Target Z80 options:}
445 [@b{-z80}] [@b{-r800}]
446 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
447 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
448 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
449 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
450 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
451 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
455 @c Z8000 has no machine-dependent assembler options
459 @emph{Target Xtensa options:}
460 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
461 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
462 [@b{--[no-]transform}]
463 [@b{--rename-section} @var{oldname}=@var{newname}]
471 @include at-file.texi
474 Turn on listings, in any of a variety of ways:
478 omit false conditionals
481 omit debugging directives
484 include general information, like @value{AS} version and options passed
487 include high-level source
493 include macro expansions
496 omit forms processing
502 set the name of the listing file
505 You may combine these options; for example, use @samp{-aln} for assembly
506 listing without forms processing. The @samp{=file} option, if used, must be
507 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
510 Begin in alternate macro mode.
512 @xref{Altmacro,,@code{.altmacro}}.
516 Ignored. This option is accepted for script compatibility with calls to
519 @item --debug-prefix-map @var{old}=@var{new}
520 When assembling files in directory @file{@var{old}}, record debugging
521 information describing them as in @file{@var{new}} instead.
523 @item --defsym @var{sym}=@var{value}
524 Define the symbol @var{sym} to be @var{value} before assembling the input file.
525 @var{value} must be an integer constant. As in C, a leading @samp{0x}
526 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
527 value. The value of the symbol can be overridden inside a source file via the
528 use of a @code{.set} pseudo-op.
531 ``fast''---skip whitespace and comment preprocessing (assume source is
536 Generate debugging information for each assembler source line using whichever
537 debug format is preferred by the target. This currently means either STABS,
541 Generate stabs debugging information for each assembler line. This
542 may help debugging assembler code, if the debugger can handle it.
545 Generate stabs debugging information for each assembler line, with GNU
546 extensions that probably only gdb can handle, and that could make other
547 debuggers crash or refuse to read your program. This
548 may help debugging assembler code. Currently the only GNU extension is
549 the location of the current working directory at assembling time.
552 Generate DWARF2 debugging information for each assembler line. This
553 may help debugging assembler code, if the debugger can handle it. Note---this
554 option is only supported by some targets, not all of them.
557 Print a summary of the command line options and exit.
560 Print a summary of all target specific options and exit.
563 Add directory @var{dir} to the search list for @code{.include} directives.
566 Don't warn about signed overflow.
569 @ifclear DIFF-TBL-KLUGE
570 This option is accepted but has no effect on the @value{TARGET} family.
572 @ifset DIFF-TBL-KLUGE
573 Issue warnings when difference tables altered for long displacements.
578 Keep (in the symbol table) local symbols. These symbols start with
579 system-specific local label prefixes, typically @samp{.L} for ELF systems
580 or @samp{L} for traditional a.out systems.
585 @item --listing-lhs-width=@var{number}
586 Set the maximum width, in words, of the output data column for an assembler
587 listing to @var{number}.
589 @item --listing-lhs-width2=@var{number}
590 Set the maximum width, in words, of the output data column for continuation
591 lines in an assembler listing to @var{number}.
593 @item --listing-rhs-width=@var{number}
594 Set the maximum width of an input source line, as displayed in a listing, to
597 @item --listing-cont-lines=@var{number}
598 Set the maximum number of lines printed in a listing for a single line of input
601 @item -o @var{objfile}
602 Name the object-file output from @command{@value{AS}} @var{objfile}.
605 Fold the data section into the text section.
607 @kindex --hash-size=@var{number}
608 Set the default size of GAS's hash tables to a prime number close to
609 @var{number}. Increasing this value can reduce the length of time it takes the
610 assembler to perform its tasks, at the expense of increasing the assembler's
611 memory requirements. Similarly reducing this value can reduce the memory
612 requirements at the expense of speed.
614 @item --reduce-memory-overheads
615 This option reduces GAS's memory requirements, at the expense of making the
616 assembly processes slower. Currently this switch is a synonym for
617 @samp{--hash-size=4051}, but in the future it may have other effects as well.
620 Print the maximum space (in bytes) and total time (in seconds) used by
623 @item --strip-local-absolute
624 Remove local absolute symbols from the outgoing symbol table.
628 Print the @command{as} version.
631 Print the @command{as} version and exit.
635 Suppress warning messages.
637 @item --fatal-warnings
638 Treat warnings as errors.
641 Don't suppress warning messages or treat them as errors.
650 Generate an object file even after errors.
652 @item -- | @var{files} @dots{}
653 Standard input, or source files to assemble.
658 The following options are available when @value{AS} is configured for
663 This option selects the core processor variant.
665 Select either big-endian (-EB) or little-endian (-EL) output.
670 The following options are available when @value{AS} is configured for the ARM
674 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
675 Specify which ARM processor variant is the target.
676 @item -march=@var{architecture}[+@var{extension}@dots{}]
677 Specify which ARM architecture variant is used by the target.
678 @item -mfpu=@var{floating-point-format}
679 Select which Floating Point architecture is the target.
680 @item -mfloat-abi=@var{abi}
681 Select which floating point ABI is in use.
683 Enable Thumb only instruction decoding.
684 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
685 Select which procedure calling convention is in use.
687 Select either big-endian (-EB) or little-endian (-EL) output.
688 @item -mthumb-interwork
689 Specify that the code has been generated with interworking between Thumb and
692 Specify that PIC code has been generated.
697 See the info pages for documentation of the CRIS-specific options.
701 The following options are available when @value{AS} is configured for
704 @cindex D10V optimization
705 @cindex optimization, D10V
707 Optimize output by parallelizing instructions.
712 The following options are available when @value{AS} is configured for a D30V
715 @cindex D30V optimization
716 @cindex optimization, D30V
718 Optimize output by parallelizing instructions.
722 Warn when nops are generated.
724 @cindex D30V nops after 32-bit multiply
726 Warn when a nop after a 32-bit multiply instruction is generated.
731 The following options are available when @value{AS} is configured for the
732 Intel 80960 processor.
735 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
736 Specify which variant of the 960 architecture is the target.
739 Add code to collect statistics about branches taken.
742 Do not alter compare-and-branch instructions for long displacements;
749 The following options are available when @value{AS} is configured for the
755 Specifies that the extended IP2022 instructions are allowed.
758 Restores the default behaviour, which restricts the permitted instructions to
759 just the basic IP2022 ones.
765 The following options are available when @value{AS} is configured for the
766 Renesas M32C and M16C processors.
771 Assemble M32C instructions.
774 Assemble M16C instructions (the default).
777 Enable support for link-time relaxations.
780 Support H'00 style hex constants in addition to 0x00 style.
786 The following options are available when @value{AS} is configured for the
787 Renesas M32R (formerly Mitsubishi M32R) series.
792 Specify which processor in the M32R family is the target. The default
793 is normally the M32R, but this option changes it to the M32RX.
795 @item --warn-explicit-parallel-conflicts or --Wp
796 Produce warning messages when questionable parallel constructs are
799 @item --no-warn-explicit-parallel-conflicts or --Wnp
800 Do not produce warning messages when questionable parallel constructs are
807 The following options are available when @value{AS} is configured for the
808 Motorola 68000 series.
813 Shorten references to undefined symbols, to one word instead of two.
815 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
816 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
817 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
818 Specify what processor in the 68000 family is the target. The default
819 is normally the 68020, but this can be changed at configuration time.
821 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
822 The target machine does (or does not) have a floating-point coprocessor.
823 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
824 the basic 68000 is not compatible with the 68881, a combination of the
825 two can be specified, since it's possible to do emulation of the
826 coprocessor instructions with the main processor.
828 @item -m68851 | -mno-68851
829 The target machine does (or does not) have a memory-management
830 unit coprocessor. The default is to assume an MMU for 68020 and up.
837 For details about the PDP-11 machine dependent features options,
838 see @ref{PDP-11-Options}.
841 @item -mpic | -mno-pic
842 Generate position-independent (or position-dependent) code. The
843 default is @option{-mpic}.
846 @itemx -mall-extensions
847 Enable all instruction set extensions. This is the default.
849 @item -mno-extensions
850 Disable all instruction set extensions.
852 @item -m@var{extension} | -mno-@var{extension}
853 Enable (or disable) a particular instruction set extension.
856 Enable the instruction set extensions supported by a particular CPU, and
857 disable all other extensions.
859 @item -m@var{machine}
860 Enable the instruction set extensions supported by a particular machine
861 model, and disable all other extensions.
867 The following options are available when @value{AS} is configured for
868 a picoJava processor.
872 @cindex PJ endianness
873 @cindex endianness, PJ
874 @cindex big endian output, PJ
876 Generate ``big endian'' format output.
878 @cindex little endian output, PJ
880 Generate ``little endian'' format output.
886 The following options are available when @value{AS} is configured for the
887 Motorola 68HC11 or 68HC12 series.
891 @item -m68hc11 | -m68hc12 | -m68hcs12
892 Specify what processor is the target. The default is
893 defined by the configuration option when building the assembler.
896 Specify to use the 16-bit integer ABI.
899 Specify to use the 32-bit integer ABI.
902 Specify to use the 32-bit double ABI.
905 Specify to use the 64-bit double ABI.
907 @item --force-long-branches
908 Relative branches are turned into absolute ones. This concerns
909 conditional branches, unconditional branches and branches to a
912 @item -S | --short-branches
913 Do not turn relative branches into absolute ones
914 when the offset is out of range.
916 @item --strict-direct-mode
917 Do not turn the direct addressing mode into extended addressing mode
918 when the instruction does not support direct addressing mode.
920 @item --print-insn-syntax
921 Print the syntax of instruction in case of error.
923 @item --print-opcodes
924 print the list of instructions with syntax and then exit.
926 @item --generate-example
927 print an example of instruction for each possible instruction and then exit.
928 This option is only useful for testing @command{@value{AS}}.
934 The following options are available when @command{@value{AS}} is configured
935 for the SPARC architecture:
938 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
939 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
940 Explicitly select a variant of the SPARC architecture.
942 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
943 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
945 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
946 UltraSPARC extensions.
948 @item -xarch=v8plus | -xarch=v8plusa
949 For compatibility with the Solaris v9 assembler. These options are
950 equivalent to -Av8plus and -Av8plusa, respectively.
953 Warn when the assembler switches to another architecture.
958 The following options are available when @value{AS} is configured for the 'c54x
963 Enable extended addressing mode. All addresses and relocations will assume
964 extended addressing (usually 23 bits).
965 @item -mcpu=@var{CPU_VERSION}
966 Sets the CPU version being compiled for.
967 @item -merrors-to-file @var{FILENAME}
968 Redirect error output to a file, for broken systems which don't support such
969 behaviour in the shell.
974 The following options are available when @value{AS} is configured for
975 a @sc{mips} processor.
979 This option sets the largest size of an object that can be referenced
980 implicitly with the @code{gp} register. It is only accepted for targets that
981 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
983 @cindex MIPS endianness
984 @cindex endianness, MIPS
985 @cindex big endian output, MIPS
987 Generate ``big endian'' format output.
989 @cindex little endian output, MIPS
991 Generate ``little endian'' format output.
1003 Generate code for a particular @sc{mips} Instruction Set Architecture level.
1004 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1005 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1006 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1007 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1009 correspond to generic
1010 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
1011 and @samp{MIPS64 Release 2}
1012 ISA processors, respectively.
1014 @item -march=@var{CPU}
1015 Generate code for a particular @sc{mips} cpu.
1017 @item -mtune=@var{cpu}
1018 Schedule and tune for a particular @sc{mips} cpu.
1022 Cause nops to be inserted if the read of the destination register
1023 of an mfhi or mflo instruction occurs in the following two instructions.
1027 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1028 section instead of the standard ELF .stabs sections.
1032 Control generation of @code{.pdr} sections.
1036 The register sizes are normally inferred from the ISA and ABI, but these
1037 flags force a certain group of registers to be treated as 32 bits wide at
1038 all times. @samp{-mgp32} controls the size of general-purpose registers
1039 and @samp{-mfp32} controls the size of floating-point registers.
1043 Generate code for the MIPS 16 processor. This is equivalent to putting
1044 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1045 turns off this option.
1048 @itemx -mno-smartmips
1049 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1050 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1051 @samp{-mno-smartmips} turns off this option.
1055 Generate code for the MIPS-3D Application Specific Extension.
1056 This tells the assembler to accept MIPS-3D instructions.
1057 @samp{-no-mips3d} turns off this option.
1061 Generate code for the MDMX Application Specific Extension.
1062 This tells the assembler to accept MDMX instructions.
1063 @samp{-no-mdmx} turns off this option.
1067 Generate code for the DSP Release 1 Application Specific Extension.
1068 This tells the assembler to accept DSP Release 1 instructions.
1069 @samp{-mno-dsp} turns off this option.
1073 Generate code for the DSP Release 2 Application Specific Extension.
1074 This option implies -mdsp.
1075 This tells the assembler to accept DSP Release 2 instructions.
1076 @samp{-mno-dspr2} turns off this option.
1080 Generate code for the MT Application Specific Extension.
1081 This tells the assembler to accept MT instructions.
1082 @samp{-mno-mt} turns off this option.
1084 @item --construct-floats
1085 @itemx --no-construct-floats
1086 The @samp{--no-construct-floats} option disables the construction of
1087 double width floating point constants by loading the two halves of the
1088 value into the two single width floating point registers that make up
1089 the double width register. By default @samp{--construct-floats} is
1090 selected, allowing construction of these floating point constants.
1093 @item --emulation=@var{name}
1094 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1095 for some other target, in all respects, including output format (choosing
1096 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1097 debugging information or store symbol table information, and default
1098 endianness. The available configuration names are: @samp{mipsecoff},
1099 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1100 @samp{mipsbelf}. The first two do not alter the default endianness from that
1101 of the primary target for which the assembler was configured; the others change
1102 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1103 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1104 selection in any case.
1106 This option is currently supported only when the primary target
1107 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1108 Furthermore, the primary target or others specified with
1109 @samp{--enable-targets=@dots{}} at configuration time must include support for
1110 the other format, if both are to be available. For example, the Irix 5
1111 configuration includes support for both.
1113 Eventually, this option will support more configurations, with more
1114 fine-grained control over the assembler's behavior, and will be supported for
1118 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1125 Control how to deal with multiplication overflow and division by zero.
1126 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1127 (and only work for Instruction Set Architecture level 2 and higher);
1128 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1132 When this option is used, @command{@value{AS}} will issue a warning every
1133 time it generates a nop instruction from a macro.
1138 The following options are available when @value{AS} is configured for
1144 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1145 The command line option @samp{-nojsri2bsr} can be used to disable it.
1149 Enable or disable the silicon filter behaviour. By default this is disabled.
1150 The default can be overridden by the @samp{-sifilter} command line option.
1153 Alter jump instructions for long displacements.
1155 @item -mcpu=[210|340]
1156 Select the cpu type on the target hardware. This controls which instructions
1160 Assemble for a big endian target.
1163 Assemble for a little endian target.
1169 See the info pages for documentation of the MMIX-specific options.
1173 The following options are available when @value{AS} is configured for the s390
1179 Select the word size, either 31/32 bits or 64 bits.
1182 Select the architecture mode, either the Enterprise System
1183 Architecture (esa) or the z/Architecture mode (zarch).
1184 @item -march=@var{processor}
1185 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1186 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, or @samp{z10}.
1188 @itemx -mno-regnames
1189 Allow or disallow symbolic names for registers.
1190 @item -mwarn-areg-zero
1191 Warn whenever the operand for a base or index register has been specified
1192 but evaluates to zero.
1197 The following options are available when @value{AS} is configured for
1198 an Xtensa processor.
1201 @item --text-section-literals | --no-text-section-literals
1202 With @option{--text-@-section-@-literals}, literal pools are interspersed
1203 in the text section. The default is
1204 @option{--no-@-text-@-section-@-literals}, which places literals in a
1205 separate section in the output file. These options only affect literals
1206 referenced via PC-relative @code{L32R} instructions; literals for
1207 absolute mode @code{L32R} instructions are handled separately.
1209 @item --absolute-literals | --no-absolute-literals
1210 Indicate to the assembler whether @code{L32R} instructions use absolute
1211 or PC-relative addressing. The default is to assume absolute addressing
1212 if the Xtensa processor includes the absolute @code{L32R} addressing
1213 option. Otherwise, only the PC-relative @code{L32R} mode can be used.
1215 @item --target-align | --no-target-align
1216 Enable or disable automatic alignment to reduce branch penalties at the
1217 expense of some code density. The default is @option{--target-@-align}.
1219 @item --longcalls | --no-longcalls
1220 Enable or disable transformation of call instructions to allow calls
1221 across a greater range of addresses. The default is
1222 @option{--no-@-longcalls}.
1224 @item --transform | --no-transform
1225 Enable or disable all assembler transformations of Xtensa instructions.
1226 The default is @option{--transform};
1227 @option{--no-transform} should be used only in the rare cases when the
1228 instructions must be exactly as specified in the assembly source.
1230 @item --rename-section @var{oldname}=@var{newname}
1231 When generating output sections, rename the @var{oldname} section to
1237 The following options are available when @value{AS} is configured for
1238 a Z80 family processor.
1241 Assemble for Z80 processor.
1243 Assemble for R800 processor.
1244 @item -ignore-undocumented-instructions
1246 Assemble undocumented Z80 instructions that also work on R800 without warning.
1247 @item -ignore-unportable-instructions
1249 Assemble all undocumented Z80 instructions without warning.
1250 @item -warn-undocumented-instructions
1252 Issue a warning for undocumented Z80 instructions that also work on R800.
1253 @item -warn-unportable-instructions
1255 Issue a warning for undocumented Z80 instructions that do not work on R800.
1256 @item -forbid-undocumented-instructions
1258 Treat all undocumented instructions as errors.
1259 @item -forbid-unportable-instructions
1261 Treat undocumented Z80 instructions that do not work on R800 as errors.
1268 * Manual:: Structure of this Manual
1269 * GNU Assembler:: The GNU Assembler
1270 * Object Formats:: Object File Formats
1271 * Command Line:: Command Line
1272 * Input Files:: Input Files
1273 * Object:: Output (Object) File
1274 * Errors:: Error and Warning Messages
1278 @section Structure of this Manual
1280 @cindex manual, structure and purpose
1281 This manual is intended to describe what you need to know to use
1282 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1283 notation for symbols, constants, and expressions; the directives that
1284 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1287 We also cover special features in the @value{TARGET}
1288 configuration of @command{@value{AS}}, including assembler directives.
1291 This manual also describes some of the machine-dependent features of
1292 various flavors of the assembler.
1295 @cindex machine instructions (not covered)
1296 On the other hand, this manual is @emph{not} intended as an introduction
1297 to programming in assembly language---let alone programming in general!
1298 In a similar vein, we make no attempt to introduce the machine
1299 architecture; we do @emph{not} describe the instruction set, standard
1300 mnemonics, registers or addressing modes that are standard to a
1301 particular architecture.
1303 You may want to consult the manufacturer's
1304 machine architecture manual for this information.
1308 For information on the H8/300 machine instruction set, see @cite{H8/300
1309 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1310 Programming Manual} (Renesas).
1313 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1314 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1315 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1316 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1319 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1323 @c I think this is premature---doc@cygnus.com, 17jan1991
1325 Throughout this manual, we assume that you are running @dfn{GNU},
1326 the portable operating system from the @dfn{Free Software
1327 Foundation, Inc.}. This restricts our attention to certain kinds of
1328 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1329 once this assumption is granted examples and definitions need less
1332 @command{@value{AS}} is part of a team of programs that turn a high-level
1333 human-readable series of instructions into a low-level
1334 computer-readable series of instructions. Different versions of
1335 @command{@value{AS}} are used for different kinds of computer.
1338 @c There used to be a section "Terminology" here, which defined
1339 @c "contents", "byte", "word", and "long". Defining "word" to any
1340 @c particular size is confusing when the .word directive may generate 16
1341 @c bits on one machine and 32 bits on another; in general, for the user
1342 @c version of this manual, none of these terms seem essential to define.
1343 @c They were used very little even in the former draft of the manual;
1344 @c this draft makes an effort to avoid them (except in names of
1348 @section The GNU Assembler
1350 @c man begin DESCRIPTION
1352 @sc{gnu} @command{as} is really a family of assemblers.
1354 This manual describes @command{@value{AS}}, a member of that family which is
1355 configured for the @value{TARGET} architectures.
1357 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1358 should find a fairly similar environment when you use it on another
1359 architecture. Each version has much in common with the others,
1360 including object file formats, most assembler directives (often called
1361 @dfn{pseudo-ops}) and assembler syntax.@refill
1363 @cindex purpose of @sc{gnu} assembler
1364 @command{@value{AS}} is primarily intended to assemble the output of the
1365 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1366 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1367 assemble correctly everything that other assemblers for the same
1368 machine would assemble.
1370 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1373 @c This remark should appear in generic version of manual; assumption
1374 @c here is that generic version sets M680x0.
1375 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1376 assembler for the same architecture; for example, we know of several
1377 incompatible versions of 680x0 assembly language syntax.
1382 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1383 program in one pass of the source file. This has a subtle impact on the
1384 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1386 @node Object Formats
1387 @section Object File Formats
1389 @cindex object file format
1390 The @sc{gnu} assembler can be configured to produce several alternative
1391 object file formats. For the most part, this does not affect how you
1392 write assembly language programs; but directives for debugging symbols
1393 are typically different in different file formats. @xref{Symbol
1394 Attributes,,Symbol Attributes}.
1397 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1398 @value{OBJ-NAME} format object files.
1400 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1402 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1403 @code{b.out} or COFF format object files.
1406 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1407 SOM or ELF format object files.
1412 @section Command Line
1414 @cindex command line conventions
1416 After the program name @command{@value{AS}}, the command line may contain
1417 options and file names. Options may appear in any order, and may be
1418 before, after, or between file names. The order of file names is
1421 @cindex standard input, as input file
1423 @file{--} (two hyphens) by itself names the standard input file
1424 explicitly, as one of the files for @command{@value{AS}} to assemble.
1426 @cindex options, command line
1427 Except for @samp{--} any command line argument that begins with a
1428 hyphen (@samp{-}) is an option. Each option changes the behavior of
1429 @command{@value{AS}}. No option changes the way another option works. An
1430 option is a @samp{-} followed by one or more letters; the case of
1431 the letter is important. All options are optional.
1433 Some options expect exactly one file name to follow them. The file
1434 name may either immediately follow the option's letter (compatible
1435 with older assemblers) or it may be the next command argument (@sc{gnu}
1436 standard). These two command lines are equivalent:
1439 @value{AS} -o my-object-file.o mumble.s
1440 @value{AS} -omy-object-file.o mumble.s
1444 @section Input Files
1447 @cindex source program
1448 @cindex files, input
1449 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1450 describe the program input to one run of @command{@value{AS}}. The program may
1451 be in one or more files; how the source is partitioned into files
1452 doesn't change the meaning of the source.
1454 @c I added "con" prefix to "catenation" just to prove I can overcome my
1455 @c APL training... doc@cygnus.com
1456 The source program is a concatenation of the text in all the files, in the
1459 @c man begin DESCRIPTION
1460 Each time you run @command{@value{AS}} it assembles exactly one source
1461 program. The source program is made up of one or more files.
1462 (The standard input is also a file.)
1464 You give @command{@value{AS}} a command line that has zero or more input file
1465 names. The input files are read (from left file name to right). A
1466 command line argument (in any position) that has no special meaning
1467 is taken to be an input file name.
1469 If you give @command{@value{AS}} no file names it attempts to read one input file
1470 from the @command{@value{AS}} standard input, which is normally your terminal. You
1471 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1474 Use @samp{--} if you need to explicitly name the standard input file
1475 in your command line.
1477 If the source is empty, @command{@value{AS}} produces a small, empty object
1482 @subheading Filenames and Line-numbers
1484 @cindex input file linenumbers
1485 @cindex line numbers, in input files
1486 There are two ways of locating a line in the input file (or files) and
1487 either may be used in reporting error messages. One way refers to a line
1488 number in a physical file; the other refers to a line number in a
1489 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1491 @dfn{Physical files} are those files named in the command line given
1492 to @command{@value{AS}}.
1494 @dfn{Logical files} are simply names declared explicitly by assembler
1495 directives; they bear no relation to physical files. Logical file names help
1496 error messages reflect the original source file, when @command{@value{AS}} source
1497 is itself synthesized from other files. @command{@value{AS}} understands the
1498 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1499 @ref{File,,@code{.file}}.
1502 @section Output (Object) File
1508 Every time you run @command{@value{AS}} it produces an output file, which is
1509 your assembly language program translated into numbers. This file
1510 is the object file. Its default name is
1518 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1520 You can give it another name by using the @option{-o} option. Conventionally,
1521 object file names end with @file{.o}. The default name is used for historical
1522 reasons: older assemblers were capable of assembling self-contained programs
1523 directly into a runnable program. (For some formats, this isn't currently
1524 possible, but it can be done for the @code{a.out} format.)
1528 The object file is meant for input to the linker @code{@value{LD}}. It contains
1529 assembled program code, information to help @code{@value{LD}} integrate
1530 the assembled program into a runnable file, and (optionally) symbolic
1531 information for the debugger.
1533 @c link above to some info file(s) like the description of a.out.
1534 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1537 @section Error and Warning Messages
1539 @c man begin DESCRIPTION
1541 @cindex error messages
1542 @cindex warning messages
1543 @cindex messages from assembler
1544 @command{@value{AS}} may write warnings and error messages to the standard error
1545 file (usually your terminal). This should not happen when a compiler
1546 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1547 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1548 grave problem that stops the assembly.
1552 @cindex format of warning messages
1553 Warning messages have the format
1556 file_name:@b{NNN}:Warning Message Text
1560 @cindex line numbers, in warnings/errors
1561 (where @b{NNN} is a line number). If a logical file name has been given
1562 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1563 the current input file is used. If a logical line number was given
1565 (@pxref{Line,,@code{.line}})
1567 then it is used to calculate the number printed,
1568 otherwise the actual line in the current source file is printed. The
1569 message text is intended to be self explanatory (in the grand Unix
1572 @cindex format of error messages
1573 Error messages have the format
1575 file_name:@b{NNN}:FATAL:Error Message Text
1577 The file name and line number are derived as for warning
1578 messages. The actual message text may be rather less explanatory
1579 because many of them aren't supposed to happen.
1582 @chapter Command-Line Options
1584 @cindex options, all versions of assembler
1585 This chapter describes command-line options available in @emph{all}
1586 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1587 for options specific
1589 to the @value{TARGET} target.
1592 to particular machine architectures.
1595 @c man begin DESCRIPTION
1597 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1598 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1599 The assembler arguments must be separated from each other (and the @samp{-Wa})
1600 by commas. For example:
1603 gcc -c -g -O -Wa,-alh,-L file.c
1607 This passes two options to the assembler: @samp{-alh} (emit a listing to
1608 standard output with high-level and assembly source) and @samp{-L} (retain
1609 local symbols in the symbol table).
1611 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1612 command-line options are automatically passed to the assembler by the compiler.
1613 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1614 precisely what options it passes to each compilation pass, including the
1620 * a:: -a[cdghlns] enable listings
1621 * alternate:: --alternate enable alternate macro syntax
1622 * D:: -D for compatibility
1623 * f:: -f to work faster
1624 * I:: -I for .include search path
1625 @ifclear DIFF-TBL-KLUGE
1626 * K:: -K for compatibility
1628 @ifset DIFF-TBL-KLUGE
1629 * K:: -K for difference tables
1632 * L:: -L to retain local symbols
1633 * listing:: --listing-XXX to configure listing output
1634 * M:: -M or --mri to assemble in MRI compatibility mode
1635 * MD:: --MD for dependency tracking
1636 * o:: -o to name the object file
1637 * R:: -R to join data and text sections
1638 * statistics:: --statistics to see statistics about assembly
1639 * traditional-format:: --traditional-format for compatible output
1640 * v:: -v to announce version
1641 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1642 * Z:: -Z to make object file even after errors
1646 @section Enable Listings: @option{-a[cdghlns]}
1656 @cindex listings, enabling
1657 @cindex assembly listings, enabling
1659 These options enable listing output from the assembler. By itself,
1660 @samp{-a} requests high-level, assembly, and symbols listing.
1661 You can use other letters to select specific options for the list:
1662 @samp{-ah} requests a high-level language listing,
1663 @samp{-al} requests an output-program assembly listing, and
1664 @samp{-as} requests a symbol table listing.
1665 High-level listings require that a compiler debugging option like
1666 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1669 Use the @samp{-ag} option to print a first section with general assembly
1670 information, like @value{AS} version, switches passed, or time stamp.
1672 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1673 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1674 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1675 omitted from the listing.
1677 Use the @samp{-ad} option to omit debugging directives from the
1680 Once you have specified one of these options, you can further control
1681 listing output and its appearance using the directives @code{.list},
1682 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1684 The @samp{-an} option turns off all forms processing.
1685 If you do not request listing output with one of the @samp{-a} options, the
1686 listing-control directives have no effect.
1688 The letters after @samp{-a} may be combined into one option,
1689 @emph{e.g.}, @samp{-aln}.
1691 Note if the assembler source is coming from the standard input (e.g.,
1693 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1694 is being used) then the listing will not contain any comments or preprocessor
1695 directives. This is because the listing code buffers input source lines from
1696 stdin only after they have been preprocessed by the assembler. This reduces
1697 memory usage and makes the code more efficient.
1700 @section @option{--alternate}
1703 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
1706 @section @option{-D}
1709 This option has no effect whatsoever, but it is accepted to make it more
1710 likely that scripts written for other assemblers also work with
1711 @command{@value{AS}}.
1714 @section Work Faster: @option{-f}
1717 @cindex trusted compiler
1718 @cindex faster processing (@option{-f})
1719 @samp{-f} should only be used when assembling programs written by a
1720 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1721 and comment preprocessing on
1722 the input file(s) before assembling them. @xref{Preprocessing,
1726 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1727 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1732 @section @code{.include} Search Path: @option{-I} @var{path}
1734 @kindex -I @var{path}
1735 @cindex paths for @code{.include}
1736 @cindex search path for @code{.include}
1737 @cindex @code{include} directive search path
1738 Use this option to add a @var{path} to the list of directories
1739 @command{@value{AS}} searches for files specified in @code{.include}
1740 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1741 many times as necessary to include a variety of paths. The current
1742 working directory is always searched first; after that, @command{@value{AS}}
1743 searches any @samp{-I} directories in the same order as they were
1744 specified (left to right) on the command line.
1747 @section Difference Tables: @option{-K}
1750 @ifclear DIFF-TBL-KLUGE
1751 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1752 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1753 where it can be used to warn when the assembler alters the machine code
1754 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1755 family does not have the addressing limitations that sometimes lead to this
1756 alteration on other platforms.
1759 @ifset DIFF-TBL-KLUGE
1760 @cindex difference tables, warning
1761 @cindex warning for altered difference tables
1762 @command{@value{AS}} sometimes alters the code emitted for directives of the
1763 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
1764 You can use the @samp{-K} option if you want a warning issued when this
1769 @section Include Local Symbols: @option{-L}
1772 @cindex local symbols, retaining in output
1773 Symbols beginning with system-specific local label prefixes, typically
1774 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
1775 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
1776 such symbols when debugging, because they are intended for the use of
1777 programs (like compilers) that compose assembler programs, not for your
1778 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
1779 such symbols, so you do not normally debug with them.
1781 This option tells @command{@value{AS}} to retain those local symbols
1782 in the object file. Usually if you do this you also tell the linker
1783 @code{@value{LD}} to preserve those symbols.
1786 @section Configuring listing output: @option{--listing}
1788 The listing feature of the assembler can be enabled via the command line switch
1789 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1790 hex dump of the corresponding locations in the output object file, and displays
1791 them as a listing file. The format of this listing can be controlled by
1792 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
1793 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
1794 @code{.psize} (@pxref{Psize}), and
1795 @code{.eject} (@pxref{Eject}) and also by the following switches:
1798 @item --listing-lhs-width=@samp{number}
1799 @kindex --listing-lhs-width
1800 @cindex Width of first line disassembly output
1801 Sets the maximum width, in words, of the first line of the hex byte dump. This
1802 dump appears on the left hand side of the listing output.
1804 @item --listing-lhs-width2=@samp{number}
1805 @kindex --listing-lhs-width2
1806 @cindex Width of continuation lines of disassembly output
1807 Sets the maximum width, in words, of any further lines of the hex byte dump for
1808 a given input source line. If this value is not specified, it defaults to being
1809 the same as the value specified for @samp{--listing-lhs-width}. If neither
1810 switch is used the default is to one.
1812 @item --listing-rhs-width=@samp{number}
1813 @kindex --listing-rhs-width
1814 @cindex Width of source line output
1815 Sets the maximum width, in characters, of the source line that is displayed
1816 alongside the hex dump. The default value for this parameter is 100. The
1817 source line is displayed on the right hand side of the listing output.
1819 @item --listing-cont-lines=@samp{number}
1820 @kindex --listing-cont-lines
1821 @cindex Maximum number of continuation lines
1822 Sets the maximum number of continuation lines of hex dump that will be
1823 displayed for a given single line of source input. The default value is 4.
1827 @section Assemble in MRI Compatibility Mode: @option{-M}
1830 @cindex MRI compatibility mode
1831 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1832 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1833 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1834 configured target) assembler from Microtec Research. The exact nature of the
1835 MRI syntax will not be documented here; see the MRI manuals for more
1836 information. Note in particular that the handling of macros and macro
1837 arguments is somewhat different. The purpose of this option is to permit
1838 assembling existing MRI assembler code using @command{@value{AS}}.
1840 The MRI compatibility is not complete. Certain operations of the MRI assembler
1841 depend upon its object file format, and can not be supported using other object
1842 file formats. Supporting these would require enhancing each object file format
1843 individually. These are:
1846 @item global symbols in common section
1848 The m68k MRI assembler supports common sections which are merged by the linker.
1849 Other object file formats do not support this. @command{@value{AS}} handles
1850 common sections by treating them as a single common symbol. It permits local
1851 symbols to be defined within a common section, but it can not support global
1852 symbols, since it has no way to describe them.
1854 @item complex relocations
1856 The MRI assemblers support relocations against a negated section address, and
1857 relocations which combine the start addresses of two or more sections. These
1858 are not support by other object file formats.
1860 @item @code{END} pseudo-op specifying start address
1862 The MRI @code{END} pseudo-op permits the specification of a start address.
1863 This is not supported by other object file formats. The start address may
1864 instead be specified using the @option{-e} option to the linker, or in a linker
1867 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1869 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1870 name to the output file. This is not supported by other object file formats.
1872 @item @code{ORG} pseudo-op
1874 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1875 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
1876 which changes the location within the current section. Absolute sections are
1877 not supported by other object file formats. The address of a section may be
1878 assigned within a linker script.
1881 There are some other features of the MRI assembler which are not supported by
1882 @command{@value{AS}}, typically either because they are difficult or because they
1883 seem of little consequence. Some of these may be supported in future releases.
1887 @item EBCDIC strings
1889 EBCDIC strings are not supported.
1891 @item packed binary coded decimal
1893 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1894 and @code{DCB.P} pseudo-ops are not supported.
1896 @item @code{FEQU} pseudo-op
1898 The m68k @code{FEQU} pseudo-op is not supported.
1900 @item @code{NOOBJ} pseudo-op
1902 The m68k @code{NOOBJ} pseudo-op is not supported.
1904 @item @code{OPT} branch control options
1906 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1907 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
1908 relaxes all branches, whether forward or backward, to an appropriate size, so
1909 these options serve no purpose.
1911 @item @code{OPT} list control options
1913 The following m68k @code{OPT} list control options are ignored: @code{C},
1914 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1915 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1917 @item other @code{OPT} options
1919 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1920 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1922 @item @code{OPT} @code{D} option is default
1924 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1925 @code{OPT NOD} may be used to turn it off.
1927 @item @code{XREF} pseudo-op.
1929 The m68k @code{XREF} pseudo-op is ignored.
1931 @item @code{.debug} pseudo-op
1933 The i960 @code{.debug} pseudo-op is not supported.
1935 @item @code{.extended} pseudo-op
1937 The i960 @code{.extended} pseudo-op is not supported.
1939 @item @code{.list} pseudo-op.
1941 The various options of the i960 @code{.list} pseudo-op are not supported.
1943 @item @code{.optimize} pseudo-op
1945 The i960 @code{.optimize} pseudo-op is not supported.
1947 @item @code{.output} pseudo-op
1949 The i960 @code{.output} pseudo-op is not supported.
1951 @item @code{.setreal} pseudo-op
1953 The i960 @code{.setreal} pseudo-op is not supported.
1958 @section Dependency Tracking: @option{--MD}
1961 @cindex dependency tracking
1964 @command{@value{AS}} can generate a dependency file for the file it creates. This
1965 file consists of a single rule suitable for @code{make} describing the
1966 dependencies of the main source file.
1968 The rule is written to the file named in its argument.
1970 This feature is used in the automatic updating of makefiles.
1973 @section Name the Object File: @option{-o}
1976 @cindex naming object file
1977 @cindex object file name
1978 There is always one object file output when you run @command{@value{AS}}. By
1979 default it has the name
1982 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1996 You use this option (which takes exactly one filename) to give the
1997 object file a different name.
1999 Whatever the object file is called, @command{@value{AS}} overwrites any
2000 existing file of the same name.
2003 @section Join Data and Text Sections: @option{-R}
2006 @cindex data and text sections, joining
2007 @cindex text and data sections, joining
2008 @cindex joining text and data sections
2009 @cindex merging text and data sections
2010 @option{-R} tells @command{@value{AS}} to write the object file as if all
2011 data-section data lives in the text section. This is only done at
2012 the very last moment: your binary data are the same, but data
2013 section parts are relocated differently. The data section part of
2014 your object file is zero bytes long because all its bytes are
2015 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2017 When you specify @option{-R} it would be possible to generate shorter
2018 address displacements (because we do not have to cross between text and
2019 data section). We refrain from doing this simply for compatibility with
2020 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2023 When @command{@value{AS}} is configured for COFF or ELF output,
2024 this option is only useful if you use sections named @samp{.text} and
2029 @option{-R} is not supported for any of the HPPA targets. Using
2030 @option{-R} generates a warning from @command{@value{AS}}.
2034 @section Display Assembly Statistics: @option{--statistics}
2036 @kindex --statistics
2037 @cindex statistics, about assembly
2038 @cindex time, total for assembly
2039 @cindex space used, maximum for assembly
2040 Use @samp{--statistics} to display two statistics about the resources used by
2041 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2042 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2045 @node traditional-format
2046 @section Compatible Output: @option{--traditional-format}
2048 @kindex --traditional-format
2049 For some targets, the output of @command{@value{AS}} is different in some ways
2050 from the output of some existing assembler. This switch requests
2051 @command{@value{AS}} to use the traditional format instead.
2053 For example, it disables the exception frame optimizations which
2054 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2057 @section Announce Version: @option{-v}
2061 @cindex assembler version
2062 @cindex version of assembler
2063 You can find out what version of as is running by including the
2064 option @samp{-v} (which you can also spell as @samp{-version}) on the
2068 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2070 @command{@value{AS}} should never give a warning or error message when
2071 assembling compiler output. But programs written by people often
2072 cause @command{@value{AS}} to give a warning that a particular assumption was
2073 made. All such warnings are directed to the standard error file.
2077 @cindex suppressing warnings
2078 @cindex warnings, suppressing
2079 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2080 This only affects the warning messages: it does not change any particular of
2081 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2084 @kindex --fatal-warnings
2085 @cindex errors, caused by warnings
2086 @cindex warnings, causing error
2087 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2088 files that generate warnings to be in error.
2091 @cindex warnings, switching on
2092 You can switch these options off again by specifying @option{--warn}, which
2093 causes warnings to be output as usual.
2096 @section Generate Object File in Spite of Errors: @option{-Z}
2097 @cindex object file, after errors
2098 @cindex errors, continuing after
2099 After an error message, @command{@value{AS}} normally produces no output. If for
2100 some reason you are interested in object file output even after
2101 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2102 option. If there are any errors, @command{@value{AS}} continues anyways, and
2103 writes an object file after a final warning message of the form @samp{@var{n}
2104 errors, @var{m} warnings, generating bad object file.}
2109 @cindex machine-independent syntax
2110 @cindex syntax, machine-independent
2111 This chapter describes the machine-independent syntax allowed in a
2112 source file. @command{@value{AS}} syntax is similar to what many other
2113 assemblers use; it is inspired by the BSD 4.2
2118 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2122 * Preprocessing:: Preprocessing
2123 * Whitespace:: Whitespace
2124 * Comments:: Comments
2125 * Symbol Intro:: Symbols
2126 * Statements:: Statements
2127 * Constants:: Constants
2131 @section Preprocessing
2133 @cindex preprocessing
2134 The @command{@value{AS}} internal preprocessor:
2136 @cindex whitespace, removed by preprocessor
2138 adjusts and removes extra whitespace. It leaves one space or tab before
2139 the keywords on a line, and turns any other whitespace on the line into
2142 @cindex comments, removed by preprocessor
2144 removes all comments, replacing them with a single space, or an
2145 appropriate number of newlines.
2147 @cindex constants, converted by preprocessor
2149 converts character constants into the appropriate numeric values.
2152 It does not do macro processing, include file handling, or
2153 anything else you may get from your C compiler's preprocessor. You can
2154 do include file processing with the @code{.include} directive
2155 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2156 to get other ``CPP'' style preprocessing by giving the input file a
2157 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2158 Output, gcc.info, Using GNU CC}.
2160 Excess whitespace, comments, and character constants
2161 cannot be used in the portions of the input text that are not
2164 @cindex turning preprocessing on and off
2165 @cindex preprocessing, turning on and off
2168 If the first line of an input file is @code{#NO_APP} or if you use the
2169 @samp{-f} option, whitespace and comments are not removed from the input file.
2170 Within an input file, you can ask for whitespace and comment removal in
2171 specific portions of the by putting a line that says @code{#APP} before the
2172 text that may contain whitespace or comments, and putting a line that says
2173 @code{#NO_APP} after this text. This feature is mainly intend to support
2174 @code{asm} statements in compilers whose output is otherwise free of comments
2181 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2182 Whitespace is used to separate symbols, and to make programs neater for
2183 people to read. Unless within character constants
2184 (@pxref{Characters,,Character Constants}), any whitespace means the same
2185 as exactly one space.
2191 There are two ways of rendering comments to @command{@value{AS}}. In both
2192 cases the comment is equivalent to one space.
2194 Anything from @samp{/*} through the next @samp{*/} is a comment.
2195 This means you may not nest these comments.
2199 The only way to include a newline ('\n') in a comment
2200 is to use this sort of comment.
2203 /* This sort of comment does not nest. */
2206 @cindex line comment character
2207 Anything from the @dfn{line comment} character to the next newline
2208 is considered a comment and is ignored. The line comment character is
2210 @samp{;} on the ARC;
2213 @samp{@@} on the ARM;
2216 @samp{;} for the H8/300 family;
2219 @samp{;} for the HPPA;
2222 @samp{#} on the i386 and x86-64;
2225 @samp{#} on the i960;
2228 @samp{;} for the PDP-11;
2231 @samp{;} for picoJava;
2234 @samp{#} for Motorola PowerPC;
2237 @samp{#} for IBM S/390;
2240 @samp{!} for the Renesas / SuperH SH;
2243 @samp{!} on the SPARC;
2246 @samp{#} on the ip2k;
2249 @samp{#} on the m32c;
2252 @samp{#} on the m32r;
2255 @samp{|} on the 680x0;
2258 @samp{#} on the 68HC11 and 68HC12;
2261 @samp{#} on the Vax;
2264 @samp{;} for the Z80;
2267 @samp{!} for the Z8000;
2270 @samp{#} on the V850;
2273 @samp{#} for Xtensa systems;
2275 see @ref{Machine Dependencies}. @refill
2276 @c FIXME What about i860?
2279 On some machines there are two different line comment characters. One
2280 character only begins a comment if it is the first non-whitespace character on
2281 a line, while the other always begins a comment.
2285 The V850 assembler also supports a double dash as starting a comment that
2286 extends to the end of the line.
2292 @cindex lines starting with @code{#}
2293 @cindex logical line numbers
2294 To be compatible with past assemblers, lines that begin with @samp{#} have a
2295 special interpretation. Following the @samp{#} should be an absolute
2296 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2297 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2298 new logical file name. The rest of the line, if any, should be whitespace.
2300 If the first non-whitespace characters on the line are not numeric,
2301 the line is ignored. (Just like a comment.)
2304 # This is an ordinary comment.
2305 # 42-6 "new_file_name" # New logical file name
2306 # This is logical line # 36.
2308 This feature is deprecated, and may disappear from future versions
2309 of @command{@value{AS}}.
2314 @cindex characters used in symbols
2315 @ifclear SPECIAL-SYMS
2316 A @dfn{symbol} is one or more characters chosen from the set of all
2317 letters (both upper and lower case), digits and the three characters
2323 A @dfn{symbol} is one or more characters chosen from the set of all
2324 letters (both upper and lower case), digits and the three characters
2325 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2331 On most machines, you can also use @code{$} in symbol names; exceptions
2332 are noted in @ref{Machine Dependencies}.
2334 No symbol may begin with a digit. Case is significant.
2335 There is no length limit: all characters are significant. Symbols are
2336 delimited by characters not in that set, or by the beginning of a file
2337 (since the source program must end with a newline, the end of a file is
2338 not a possible symbol delimiter). @xref{Symbols}.
2339 @cindex length of symbols
2344 @cindex statements, structure of
2345 @cindex line separator character
2346 @cindex statement separator character
2348 @ifclear abnormal-separator
2349 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
2350 semicolon (@samp{;}). The newline or semicolon is considered part of
2351 the preceding statement. Newlines and semicolons within character
2352 constants are an exception: they do not end statements.
2354 @ifset abnormal-separator
2356 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
2357 point (@samp{!}). The newline or exclamation point is considered part of the
2358 preceding statement. Newlines and exclamation points within character
2359 constants are an exception: they do not end statements.
2362 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
2363 H8/300) a dollar sign (@samp{$}); or (for the Renesas-SH) a semicolon
2364 (@samp{;}). The newline or separator character is considered part of
2365 the preceding statement. Newlines and separators within character
2366 constants are an exception: they do not end statements.
2371 A @dfn{statement} ends at a newline character (@samp{\n}) or line
2372 separator character. (The line separator is usually @samp{;}, unless this
2373 conflicts with the comment character; see @ref{Machine Dependencies}.) The
2374 newline or separator character is considered part of the preceding
2375 statement. Newlines and separators within character constants are an
2376 exception: they do not end statements.
2379 @cindex newline, required at file end
2380 @cindex EOF, newline must precede
2381 It is an error to end any statement with end-of-file: the last
2382 character of any input file should be a newline.@refill
2384 An empty statement is allowed, and may include whitespace. It is ignored.
2386 @cindex instructions and directives
2387 @cindex directives and instructions
2388 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2389 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2391 A statement begins with zero or more labels, optionally followed by a
2392 key symbol which determines what kind of statement it is. The key
2393 symbol determines the syntax of the rest of the statement. If the
2394 symbol begins with a dot @samp{.} then the statement is an assembler
2395 directive: typically valid for any computer. If the symbol begins with
2396 a letter the statement is an assembly language @dfn{instruction}: it
2397 assembles into a machine language instruction.
2399 Different versions of @command{@value{AS}} for different computers
2400 recognize different instructions. In fact, the same symbol may
2401 represent a different instruction in a different computer's assembly
2405 @cindex @code{:} (label)
2406 @cindex label (@code{:})
2407 A label is a symbol immediately followed by a colon (@code{:}).
2408 Whitespace before a label or after a colon is permitted, but you may not
2409 have whitespace between a label's symbol and its colon. @xref{Labels}.
2412 For HPPA targets, labels need not be immediately followed by a colon, but
2413 the definition of a label must begin in column zero. This also implies that
2414 only one label may be defined on each line.
2418 label: .directive followed by something
2419 another_label: # This is an empty statement.
2420 instruction operand_1, operand_2, @dots{}
2427 A constant is a number, written so that its value is known by
2428 inspection, without knowing any context. Like this:
2431 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2432 .ascii "Ring the bell\7" # A string constant.
2433 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2434 .float 0f-314159265358979323846264338327\
2435 95028841971.693993751E-40 # - pi, a flonum.
2440 * Characters:: Character Constants
2441 * Numbers:: Number Constants
2445 @subsection Character Constants
2447 @cindex character constants
2448 @cindex constants, character
2449 There are two kinds of character constants. A @dfn{character} stands
2450 for one character in one byte and its value may be used in
2451 numeric expressions. String constants (properly called string
2452 @emph{literals}) are potentially many bytes and their values may not be
2453 used in arithmetic expressions.
2457 * Chars:: Characters
2461 @subsubsection Strings
2463 @cindex string constants
2464 @cindex constants, string
2465 A @dfn{string} is written between double-quotes. It may contain
2466 double-quotes or null characters. The way to get special characters
2467 into a string is to @dfn{escape} these characters: precede them with
2468 a backslash @samp{\} character. For example @samp{\\} represents
2469 one backslash: the first @code{\} is an escape which tells
2470 @command{@value{AS}} to interpret the second character literally as a backslash
2471 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2472 escape character). The complete list of escapes follows.
2474 @cindex escape codes, character
2475 @cindex character escape codes
2478 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2480 @cindex @code{\b} (backspace character)
2481 @cindex backspace (@code{\b})
2483 Mnemonic for backspace; for ASCII this is octal code 010.
2486 @c Mnemonic for EOText; for ASCII this is octal code 004.
2488 @cindex @code{\f} (formfeed character)
2489 @cindex formfeed (@code{\f})
2491 Mnemonic for FormFeed; for ASCII this is octal code 014.
2493 @cindex @code{\n} (newline character)
2494 @cindex newline (@code{\n})
2496 Mnemonic for newline; for ASCII this is octal code 012.
2499 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2501 @cindex @code{\r} (carriage return character)
2502 @cindex carriage return (@code{\r})
2504 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2507 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2508 @c other assemblers.
2510 @cindex @code{\t} (tab)
2511 @cindex tab (@code{\t})
2513 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2516 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2517 @c @item \x @var{digit} @var{digit} @var{digit}
2518 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2520 @cindex @code{\@var{ddd}} (octal character code)
2521 @cindex octal character code (@code{\@var{ddd}})
2522 @item \ @var{digit} @var{digit} @var{digit}
2523 An octal character code. The numeric code is 3 octal digits.
2524 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2525 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2527 @cindex @code{\@var{xd...}} (hex character code)
2528 @cindex hex character code (@code{\@var{xd...}})
2529 @item \@code{x} @var{hex-digits...}
2530 A hex character code. All trailing hex digits are combined. Either upper or
2531 lower case @code{x} works.
2533 @cindex @code{\\} (@samp{\} character)
2534 @cindex backslash (@code{\\})
2536 Represents one @samp{\} character.
2539 @c Represents one @samp{'} (accent acute) character.
2540 @c This is needed in single character literals
2541 @c (@xref{Characters,,Character Constants}.) to represent
2544 @cindex @code{\"} (doublequote character)
2545 @cindex doublequote (@code{\"})
2547 Represents one @samp{"} character. Needed in strings to represent
2548 this character, because an unescaped @samp{"} would end the string.
2550 @item \ @var{anything-else}
2551 Any other character when escaped by @kbd{\} gives a warning, but
2552 assembles as if the @samp{\} was not present. The idea is that if
2553 you used an escape sequence you clearly didn't want the literal
2554 interpretation of the following character. However @command{@value{AS}} has no
2555 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2556 code and warns you of the fact.
2559 Which characters are escapable, and what those escapes represent,
2560 varies widely among assemblers. The current set is what we think
2561 the BSD 4.2 assembler recognizes, and is a subset of what most C
2562 compilers recognize. If you are in doubt, do not use an escape
2566 @subsubsection Characters
2568 @cindex single character constant
2569 @cindex character, single
2570 @cindex constant, single character
2571 A single character may be written as a single quote immediately
2572 followed by that character. The same escapes apply to characters as
2573 to strings. So if you want to write the character backslash, you
2574 must write @kbd{'\\} where the first @code{\} escapes the second
2575 @code{\}. As you can see, the quote is an acute accent, not a
2576 grave accent. A newline
2578 @ifclear abnormal-separator
2579 (or semicolon @samp{;})
2581 @ifset abnormal-separator
2583 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2588 immediately following an acute accent is taken as a literal character
2589 and does not count as the end of a statement. The value of a character
2590 constant in a numeric expression is the machine's byte-wide code for
2591 that character. @command{@value{AS}} assumes your character code is ASCII:
2592 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2595 @subsection Number Constants
2597 @cindex constants, number
2598 @cindex number constants
2599 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2600 are stored in the target machine. @emph{Integers} are numbers that
2601 would fit into an @code{int} in the C language. @emph{Bignums} are
2602 integers, but they are stored in more than 32 bits. @emph{Flonums}
2603 are floating point numbers, described below.
2606 * Integers:: Integers
2611 * Bit Fields:: Bit Fields
2617 @subsubsection Integers
2619 @cindex constants, integer
2621 @cindex binary integers
2622 @cindex integers, binary
2623 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2624 the binary digits @samp{01}.
2626 @cindex octal integers
2627 @cindex integers, octal
2628 An octal integer is @samp{0} followed by zero or more of the octal
2629 digits (@samp{01234567}).
2631 @cindex decimal integers
2632 @cindex integers, decimal
2633 A decimal integer starts with a non-zero digit followed by zero or
2634 more digits (@samp{0123456789}).
2636 @cindex hexadecimal integers
2637 @cindex integers, hexadecimal
2638 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2639 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2641 Integers have the usual values. To denote a negative integer, use
2642 the prefix operator @samp{-} discussed under expressions
2643 (@pxref{Prefix Ops,,Prefix Operators}).
2646 @subsubsection Bignums
2649 @cindex constants, bignum
2650 A @dfn{bignum} has the same syntax and semantics as an integer
2651 except that the number (or its negative) takes more than 32 bits to
2652 represent in binary. The distinction is made because in some places
2653 integers are permitted while bignums are not.
2656 @subsubsection Flonums
2658 @cindex floating point numbers
2659 @cindex constants, floating point
2661 @cindex precision, floating point
2662 A @dfn{flonum} represents a floating point number. The translation is
2663 indirect: a decimal floating point number from the text is converted by
2664 @command{@value{AS}} to a generic binary floating point number of more than
2665 sufficient precision. This generic floating point number is converted
2666 to a particular computer's floating point format (or formats) by a
2667 portion of @command{@value{AS}} specialized to that computer.
2669 A flonum is written by writing (in order)
2674 (@samp{0} is optional on the HPPA.)
2678 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2680 @kbd{e} is recommended. Case is not important.
2682 @c FIXME: verify if flonum syntax really this vague for most cases
2683 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2684 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2687 On the H8/300, Renesas / SuperH SH,
2688 and AMD 29K architectures, the letter must be
2689 one of the letters @samp{DFPRSX} (in upper or lower case).
2691 On the ARC, the letter must be one of the letters @samp{DFRS}
2692 (in upper or lower case).
2694 On the Intel 960 architecture, the letter must be
2695 one of the letters @samp{DFT} (in upper or lower case).
2697 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2701 One of the letters @samp{DFRS} (in upper or lower case).
2704 One of the letters @samp{DFPRSX} (in upper or lower case).
2707 The letter @samp{E} (upper case only).
2710 One of the letters @samp{DFT} (in upper or lower case).
2715 An optional sign: either @samp{+} or @samp{-}.
2718 An optional @dfn{integer part}: zero or more decimal digits.
2721 An optional @dfn{fractional part}: @samp{.} followed by zero
2722 or more decimal digits.
2725 An optional exponent, consisting of:
2729 An @samp{E} or @samp{e}.
2730 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2731 @c principle this can perfectly well be different on different targets.
2733 Optional sign: either @samp{+} or @samp{-}.
2735 One or more decimal digits.
2740 At least one of the integer part or the fractional part must be
2741 present. The floating point number has the usual base-10 value.
2743 @command{@value{AS}} does all processing using integers. Flonums are computed
2744 independently of any floating point hardware in the computer running
2745 @command{@value{AS}}.
2749 @c Bit fields are written as a general facility but are also controlled
2750 @c by a conditional-compilation flag---which is as of now (21mar91)
2751 @c turned on only by the i960 config of GAS.
2753 @subsubsection Bit Fields
2756 @cindex constants, bit field
2757 You can also define numeric constants as @dfn{bit fields}.
2758 Specify two numbers separated by a colon---
2760 @var{mask}:@var{value}
2763 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2766 The resulting number is then packed
2768 @c this conditional paren in case bit fields turned on elsewhere than 960
2769 (in host-dependent byte order)
2771 into a field whose width depends on which assembler directive has the
2772 bit-field as its argument. Overflow (a result from the bitwise and
2773 requiring more binary digits to represent) is not an error; instead,
2774 more constants are generated, of the specified width, beginning with the
2775 least significant digits.@refill
2777 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2778 @code{.short}, and @code{.word} accept bit-field arguments.
2783 @chapter Sections and Relocation
2788 * Secs Background:: Background
2789 * Ld Sections:: Linker Sections
2790 * As Sections:: Assembler Internal Sections
2791 * Sub-Sections:: Sub-Sections
2795 @node Secs Background
2798 Roughly, a section is a range of addresses, with no gaps; all data
2799 ``in'' those addresses is treated the same for some particular purpose.
2800 For example there may be a ``read only'' section.
2802 @cindex linker, and assembler
2803 @cindex assembler, and linker
2804 The linker @code{@value{LD}} reads many object files (partial programs) and
2805 combines their contents to form a runnable program. When @command{@value{AS}}
2806 emits an object file, the partial program is assumed to start at address 0.
2807 @code{@value{LD}} assigns the final addresses for the partial program, so that
2808 different partial programs do not overlap. This is actually an
2809 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2812 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2813 addresses. These blocks slide to their run-time addresses as rigid
2814 units; their length does not change and neither does the order of bytes
2815 within them. Such a rigid unit is called a @emph{section}. Assigning
2816 run-time addresses to sections is called @dfn{relocation}. It includes
2817 the task of adjusting mentions of object-file addresses so they refer to
2818 the proper run-time addresses.
2820 For the H8/300, and for the Renesas / SuperH SH,
2821 @command{@value{AS}} pads sections if needed to
2822 ensure they end on a word (sixteen bit) boundary.
2825 @cindex standard assembler sections
2826 An object file written by @command{@value{AS}} has at least three sections, any
2827 of which may be empty. These are named @dfn{text}, @dfn{data} and
2832 When it generates COFF or ELF output,
2834 @command{@value{AS}} can also generate whatever other named sections you specify
2835 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2836 If you do not use any directives that place output in the @samp{.text}
2837 or @samp{.data} sections, these sections still exist, but are empty.
2842 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2844 @command{@value{AS}} can also generate whatever other named sections you
2845 specify using the @samp{.space} and @samp{.subspace} directives. See
2846 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2847 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2848 assembler directives.
2851 Additionally, @command{@value{AS}} uses different names for the standard
2852 text, data, and bss sections when generating SOM output. Program text
2853 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2854 BSS into @samp{$BSS$}.
2858 Within the object file, the text section starts at address @code{0}, the
2859 data section follows, and the bss section follows the data section.
2862 When generating either SOM or ELF output files on the HPPA, the text
2863 section starts at address @code{0}, the data section at address
2864 @code{0x4000000}, and the bss section follows the data section.
2867 To let @code{@value{LD}} know which data changes when the sections are
2868 relocated, and how to change that data, @command{@value{AS}} also writes to the
2869 object file details of the relocation needed. To perform relocation
2870 @code{@value{LD}} must know, each time an address in the object
2874 Where in the object file is the beginning of this reference to
2877 How long (in bytes) is this reference?
2879 Which section does the address refer to? What is the numeric value of
2881 (@var{address}) @minus{} (@var{start-address of section})?
2884 Is the reference to an address ``Program-Counter relative''?
2887 @cindex addresses, format of
2888 @cindex section-relative addressing
2889 In fact, every address @command{@value{AS}} ever uses is expressed as
2891 (@var{section}) + (@var{offset into section})
2894 Further, most expressions @command{@value{AS}} computes have this section-relative
2897 (For some object formats, such as SOM for the HPPA, some expressions are
2898 symbol-relative instead.)
2901 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2902 @var{N} into section @var{secname}.''
2904 Apart from text, data and bss sections you need to know about the
2905 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2906 addresses in the absolute section remain unchanged. For example, address
2907 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2908 @code{@value{LD}}. Although the linker never arranges two partial programs'
2909 data sections with overlapping addresses after linking, @emph{by definition}
2910 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2911 part of a program is always the same address when the program is running as
2912 address @code{@{absolute@ 239@}} in any other part of the program.
2914 The idea of sections is extended to the @dfn{undefined} section. Any
2915 address whose section is unknown at assembly time is by definition
2916 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2917 Since numbers are always defined, the only way to generate an undefined
2918 address is to mention an undefined symbol. A reference to a named
2919 common block would be such a symbol: its value is unknown at assembly
2920 time so it has section @emph{undefined}.
2922 By analogy the word @emph{section} is used to describe groups of sections in
2923 the linked program. @code{@value{LD}} puts all partial programs' text
2924 sections in contiguous addresses in the linked program. It is
2925 customary to refer to the @emph{text section} of a program, meaning all
2926 the addresses of all partial programs' text sections. Likewise for
2927 data and bss sections.
2929 Some sections are manipulated by @code{@value{LD}}; others are invented for
2930 use of @command{@value{AS}} and have no meaning except during assembly.
2933 @section Linker Sections
2934 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2939 @cindex named sections
2940 @cindex sections, named
2941 @item named sections
2944 @cindex text section
2945 @cindex data section
2949 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
2950 separate but equal sections. Anything you can say of one section is
2953 When the program is running, however, it is
2954 customary for the text section to be unalterable. The
2955 text section is often shared among processes: it contains
2956 instructions, constants and the like. The data section of a running
2957 program is usually alterable: for example, C variables would be stored
2958 in the data section.
2963 This section contains zeroed bytes when your program begins running. It
2964 is used to hold uninitialized variables or common storage. The length of
2965 each partial program's bss section is important, but because it starts
2966 out containing zeroed bytes there is no need to store explicit zero
2967 bytes in the object file. The bss section was invented to eliminate
2968 those explicit zeros from object files.
2970 @cindex absolute section
2971 @item absolute section
2972 Address 0 of this section is always ``relocated'' to runtime address 0.
2973 This is useful if you want to refer to an address that @code{@value{LD}} must
2974 not change when relocating. In this sense we speak of absolute
2975 addresses being ``unrelocatable'': they do not change during relocation.
2977 @cindex undefined section
2978 @item undefined section
2979 This ``section'' is a catch-all for address references to objects not in
2980 the preceding sections.
2981 @c FIXME: ref to some other doc on obj-file formats could go here.
2984 @cindex relocation example
2985 An idealized example of three relocatable sections follows.
2987 The example uses the traditional section names @samp{.text} and @samp{.data}.
2989 Memory addresses are on the horizontal axis.
2993 @c END TEXI2ROFF-KILL
2996 partial program # 1: |ttttt|dddd|00|
3003 partial program # 2: |TTT|DDD|000|
3006 +--+---+-----+--+----+---+-----+~~
3007 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3008 +--+---+-----+--+----+---+-----+~~
3010 addresses: 0 @dots{}
3017 \line{\it Partial program \#1: \hfil}
3018 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3019 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3021 \line{\it Partial program \#2: \hfil}
3022 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3023 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3025 \line{\it linked program: \hfil}
3026 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3027 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3028 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3029 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3031 \line{\it addresses: \hfil}
3035 @c END TEXI2ROFF-KILL
3038 @section Assembler Internal Sections
3040 @cindex internal assembler sections
3041 @cindex sections in messages, internal
3042 These sections are meant only for the internal use of @command{@value{AS}}. They
3043 have no meaning at run-time. You do not really need to know about these
3044 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3045 warning messages, so it might be helpful to have an idea of their
3046 meanings to @command{@value{AS}}. These sections are used to permit the
3047 value of every expression in your assembly language program to be a
3048 section-relative address.
3051 @cindex assembler internal logic error
3052 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3053 An internal assembler logic error has been found. This means there is a
3054 bug in the assembler.
3056 @cindex expr (internal section)
3058 The assembler stores complex expression internally as combinations of
3059 symbols. When it needs to represent an expression as a symbol, it puts
3060 it in the expr section.
3062 @c FIXME item transfer[t] vector preload
3063 @c FIXME item transfer[t] vector postload
3064 @c FIXME item register
3068 @section Sub-Sections
3070 @cindex numbered subsections
3071 @cindex grouping data
3077 fall into two sections: text and data.
3079 You may have separate groups of
3081 data in named sections
3085 data in named sections
3091 that you want to end up near to each other in the object file, even though they
3092 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3093 use @dfn{subsections} for this purpose. Within each section, there can be
3094 numbered subsections with values from 0 to 8192. Objects assembled into the
3095 same subsection go into the object file together with other objects in the same
3096 subsection. For example, a compiler might want to store constants in the text
3097 section, but might not want to have them interspersed with the program being
3098 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3099 section of code being output, and a @samp{.text 1} before each group of
3100 constants being output.
3102 Subsections are optional. If you do not use subsections, everything
3103 goes in subsection number zero.
3106 Each subsection is zero-padded up to a multiple of four bytes.
3107 (Subsections may be padded a different amount on different flavors
3108 of @command{@value{AS}}.)
3112 On the H8/300 platform, each subsection is zero-padded to a word
3113 boundary (two bytes).
3114 The same is true on the Renesas SH.
3117 @c FIXME section padding (alignment)?
3118 @c Rich Pixley says padding here depends on target obj code format; that
3119 @c doesn't seem particularly useful to say without further elaboration,
3120 @c so for now I say nothing about it. If this is a generic BFD issue,
3121 @c these paragraphs might need to vanish from this manual, and be
3122 @c discussed in BFD chapter of binutils (or some such).
3126 Subsections appear in your object file in numeric order, lowest numbered
3127 to highest. (All this to be compatible with other people's assemblers.)
3128 The object file contains no representation of subsections; @code{@value{LD}} and
3129 other programs that manipulate object files see no trace of them.
3130 They just see all your text subsections as a text section, and all your
3131 data subsections as a data section.
3133 To specify which subsection you want subsequent statements assembled
3134 into, use a numeric argument to specify it, in a @samp{.text
3135 @var{expression}} or a @samp{.data @var{expression}} statement.
3138 When generating COFF output, you
3143 can also use an extra subsection
3144 argument with arbitrary named sections: @samp{.section @var{name},
3149 When generating ELF output, you
3154 can also use the @code{.subsection} directive (@pxref{SubSection})
3155 to specify a subsection: @samp{.subsection @var{expression}}.
3157 @var{Expression} should be an absolute expression
3158 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3159 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3160 begins in @code{text 0}. For instance:
3162 .text 0 # The default subsection is text 0 anyway.
3163 .ascii "This lives in the first text subsection. *"
3165 .ascii "But this lives in the second text subsection."
3167 .ascii "This lives in the data section,"
3168 .ascii "in the first data subsection."
3170 .ascii "This lives in the first text section,"
3171 .ascii "immediately following the asterisk (*)."
3174 Each section has a @dfn{location counter} incremented by one for every byte
3175 assembled into that section. Because subsections are merely a convenience
3176 restricted to @command{@value{AS}} there is no concept of a subsection location
3177 counter. There is no way to directly manipulate a location counter---but the
3178 @code{.align} directive changes it, and any label definition captures its
3179 current value. The location counter of the section where statements are being
3180 assembled is said to be the @dfn{active} location counter.
3183 @section bss Section
3186 @cindex common variable storage
3187 The bss section is used for local common variable storage.
3188 You may allocate address space in the bss section, but you may
3189 not dictate data to load into it before your program executes. When
3190 your program starts running, all the contents of the bss
3191 section are zeroed bytes.
3193 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3194 @ref{Lcomm,,@code{.lcomm}}.
3196 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3197 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3200 When assembling for a target which supports multiple sections, such as ELF or
3201 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3202 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3203 section. Typically the section will only contain symbol definitions and
3204 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3211 Symbols are a central concept: the programmer uses symbols to name
3212 things, the linker uses symbols to link, and the debugger uses symbols
3216 @cindex debuggers, and symbol order
3217 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3218 the same order they were declared. This may break some debuggers.
3223 * Setting Symbols:: Giving Symbols Other Values
3224 * Symbol Names:: Symbol Names
3225 * Dot:: The Special Dot Symbol
3226 * Symbol Attributes:: Symbol Attributes
3233 A @dfn{label} is written as a symbol immediately followed by a colon
3234 @samp{:}. The symbol then represents the current value of the
3235 active location counter, and is, for example, a suitable instruction
3236 operand. You are warned if you use the same symbol to represent two
3237 different locations: the first definition overrides any other
3241 On the HPPA, the usual form for a label need not be immediately followed by a
3242 colon, but instead must start in column zero. Only one label may be defined on
3243 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3244 provides a special directive @code{.label} for defining labels more flexibly.
3247 @node Setting Symbols
3248 @section Giving Symbols Other Values
3250 @cindex assigning values to symbols
3251 @cindex symbol values, assigning
3252 A symbol can be given an arbitrary value by writing a symbol, followed
3253 by an equals sign @samp{=}, followed by an expression
3254 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3255 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3256 equals sign @samp{=}@samp{=} here represents an equivalent of the
3257 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3260 @section Symbol Names
3262 @cindex symbol names
3263 @cindex names, symbol
3264 @ifclear SPECIAL-SYMS
3265 Symbol names begin with a letter or with one of @samp{._}. On most
3266 machines, you can also use @code{$} in symbol names; exceptions are
3267 noted in @ref{Machine Dependencies}. That character may be followed by any
3268 string of digits, letters, dollar signs (unless otherwise noted for a
3269 particular target machine), and underscores.
3273 Symbol names begin with a letter or with one of @samp{._}. On the
3274 Renesas SH you can also use @code{$} in symbol names. That
3275 character may be followed by any string of digits, letters, dollar signs (save
3276 on the H8/300), and underscores.
3280 Case of letters is significant: @code{foo} is a different symbol name
3283 Each symbol has exactly one name. Each name in an assembly language program
3284 refers to exactly one symbol. You may use that symbol name any number of times
3287 @subheading Local Symbol Names
3289 @cindex local symbol names
3290 @cindex symbol names, local
3291 A local symbol is any symbol beginning with certain local label prefixes.
3292 By default, the local label prefix is @samp{.L} for ELF systems or
3293 @samp{L} for traditional a.out systems, but each target may have its own
3294 set of local label prefixes.
3296 On the HPPA local symbols begin with @samp{L$}.
3299 Local symbols are defined and used within the assembler, but they are
3300 normally not saved in object files. Thus, they are not visible when debugging.
3301 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3302 @option{-L}}) to retain the local symbols in the object files.
3304 @subheading Local Labels
3306 @cindex local labels
3307 @cindex temporary symbol names
3308 @cindex symbol names, temporary
3309 Local labels help compilers and programmers use names temporarily.
3310 They create symbols which are guaranteed to be unique over the entire scope of
3311 the input source code and which can be referred to by a simple notation.
3312 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3313 represents any positive integer). To refer to the most recent previous
3314 definition of that label write @samp{@b{N}b}, using the same number as when
3315 you defined the label. To refer to the next definition of a local label, write
3316 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3319 There is no restriction on how you can use these labels, and you can reuse them
3320 too. So that it is possible to repeatedly define the same local label (using
3321 the same number @samp{@b{N}}), although you can only refer to the most recently
3322 defined local label of that number (for a backwards reference) or the next
3323 definition of a specific local label for a forward reference. It is also worth
3324 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3325 implemented in a slightly more efficient manner than the others.
3336 Which is the equivalent of:
3339 label_1: branch label_3
3340 label_2: branch label_1
3341 label_3: branch label_4
3342 label_4: branch label_3
3345 Local label names are only a notational device. They are immediately
3346 transformed into more conventional symbol names before the assembler uses them.
3347 The symbol names are stored in the symbol table, appear in error messages, and
3348 are optionally emitted to the object file. The names are constructed using
3352 @item @emph{local label prefix}
3353 All local symbols begin with the system-specific local label prefix.
3354 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3355 that start with the local label prefix. These labels are
3356 used for symbols you are never intended to see. If you use the
3357 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3358 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3359 you may use them in debugging.
3362 This is the number that was used in the local label definition. So if the
3363 label is written @samp{55:} then the number is @samp{55}.
3366 This unusual character is included so you do not accidentally invent a symbol
3367 of the same name. The character has ASCII value of @samp{\002} (control-B).
3369 @item @emph{ordinal number}
3370 This is a serial number to keep the labels distinct. The first definition of
3371 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3372 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3373 the number @samp{1} and its 15th definition gets @samp{15} as well.
3376 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3377 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3379 @subheading Dollar Local Labels
3380 @cindex dollar local symbols
3382 @code{@value{AS}} also supports an even more local form of local labels called
3383 dollar labels. These labels go out of scope (i.e., they become undefined) as
3384 soon as a non-local label is defined. Thus they remain valid for only a small
3385 region of the input source code. Normal local labels, by contrast, remain in
3386 scope for the entire file, or until they are redefined by another occurrence of
3387 the same local label.
3389 Dollar labels are defined in exactly the same way as ordinary local labels,
3390 except that they have a dollar sign suffix to their numeric value, e.g.,
3393 They can also be distinguished from ordinary local labels by their transformed
3394 names which use ASCII character @samp{\001} (control-A) as the magic character
3395 to distinguish them from ordinary labels. For example, the fifth definition of
3396 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3399 @section The Special Dot Symbol
3401 @cindex dot (symbol)
3402 @cindex @code{.} (symbol)
3403 @cindex current address
3404 @cindex location counter
3405 The special symbol @samp{.} refers to the current address that
3406 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3407 .long .} defines @code{melvin} to contain its own address.
3408 Assigning a value to @code{.} is treated the same as a @code{.org}
3410 @ifclear no-space-dir
3411 Thus, the expression @samp{.=.+4} is the same as saying
3415 @node Symbol Attributes
3416 @section Symbol Attributes
3418 @cindex symbol attributes
3419 @cindex attributes, symbol
3420 Every symbol has, as well as its name, the attributes ``Value'' and
3421 ``Type''. Depending on output format, symbols can also have auxiliary
3424 The detailed definitions are in @file{a.out.h}.
3427 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3428 all these attributes, and probably won't warn you. This makes the
3429 symbol an externally defined symbol, which is generally what you
3433 * Symbol Value:: Value
3434 * Symbol Type:: Type
3437 * a.out Symbols:: Symbol Attributes: @code{a.out}
3441 * a.out Symbols:: Symbol Attributes: @code{a.out}
3444 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3449 * COFF Symbols:: Symbol Attributes for COFF
3452 * SOM Symbols:: Symbol Attributes for SOM
3459 @cindex value of a symbol
3460 @cindex symbol value
3461 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3462 location in the text, data, bss or absolute sections the value is the
3463 number of addresses from the start of that section to the label.
3464 Naturally for text, data and bss sections the value of a symbol changes
3465 as @code{@value{LD}} changes section base addresses during linking. Absolute
3466 symbols' values do not change during linking: that is why they are
3469 The value of an undefined symbol is treated in a special way. If it is
3470 0 then the symbol is not defined in this assembler source file, and
3471 @code{@value{LD}} tries to determine its value from other files linked into the
3472 same program. You make this kind of symbol simply by mentioning a symbol
3473 name without defining it. A non-zero value represents a @code{.comm}
3474 common declaration. The value is how much common storage to reserve, in
3475 bytes (addresses). The symbol refers to the first address of the
3481 @cindex type of a symbol
3483 The type attribute of a symbol contains relocation (section)
3484 information, any flag settings indicating that a symbol is external, and
3485 (optionally), other information for linkers and debuggers. The exact
3486 format depends on the object-code output format in use.
3491 @c The following avoids a "widow" subsection title. @group would be
3492 @c better if it were available outside examples.
3495 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3497 @cindex @code{b.out} symbol attributes
3498 @cindex symbol attributes, @code{b.out}
3499 These symbol attributes appear only when @command{@value{AS}} is configured for
3500 one of the Berkeley-descended object output formats---@code{a.out} or
3506 @subsection Symbol Attributes: @code{a.out}
3508 @cindex @code{a.out} symbol attributes
3509 @cindex symbol attributes, @code{a.out}
3515 @subsection Symbol Attributes: @code{a.out}
3517 @cindex @code{a.out} symbol attributes
3518 @cindex symbol attributes, @code{a.out}
3522 * Symbol Desc:: Descriptor
3523 * Symbol Other:: Other
3527 @subsubsection Descriptor
3529 @cindex descriptor, of @code{a.out} symbol
3530 This is an arbitrary 16-bit value. You may establish a symbol's
3531 descriptor value by using a @code{.desc} statement
3532 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3533 @command{@value{AS}}.
3536 @subsubsection Other
3538 @cindex other attribute, of @code{a.out} symbol
3539 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3544 @subsection Symbol Attributes for COFF
3546 @cindex COFF symbol attributes
3547 @cindex symbol attributes, COFF
3549 The COFF format supports a multitude of auxiliary symbol attributes;
3550 like the primary symbol attributes, they are set between @code{.def} and
3551 @code{.endef} directives.
3553 @subsubsection Primary Attributes
3555 @cindex primary attributes, COFF symbols
3556 The symbol name is set with @code{.def}; the value and type,
3557 respectively, with @code{.val} and @code{.type}.
3559 @subsubsection Auxiliary Attributes
3561 @cindex auxiliary attributes, COFF symbols
3562 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3563 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3564 table information for COFF.
3569 @subsection Symbol Attributes for SOM
3571 @cindex SOM symbol attributes
3572 @cindex symbol attributes, SOM
3574 The SOM format for the HPPA supports a multitude of symbol attributes set with
3575 the @code{.EXPORT} and @code{.IMPORT} directives.
3577 The attributes are described in @cite{HP9000 Series 800 Assembly
3578 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3579 @code{EXPORT} assembler directive documentation.
3583 @chapter Expressions
3587 @cindex numeric values
3588 An @dfn{expression} specifies an address or numeric value.
3589 Whitespace may precede and/or follow an expression.
3591 The result of an expression must be an absolute number, or else an offset into
3592 a particular section. If an expression is not absolute, and there is not
3593 enough information when @command{@value{AS}} sees the expression to know its
3594 section, a second pass over the source program might be necessary to interpret
3595 the expression---but the second pass is currently not implemented.
3596 @command{@value{AS}} aborts with an error message in this situation.
3599 * Empty Exprs:: Empty Expressions
3600 * Integer Exprs:: Integer Expressions
3604 @section Empty Expressions
3606 @cindex empty expressions
3607 @cindex expressions, empty
3608 An empty expression has no value: it is just whitespace or null.
3609 Wherever an absolute expression is required, you may omit the
3610 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3611 is compatible with other assemblers.
3614 @section Integer Expressions
3616 @cindex integer expressions
3617 @cindex expressions, integer
3618 An @dfn{integer expression} is one or more @emph{arguments} delimited
3619 by @emph{operators}.
3622 * Arguments:: Arguments
3623 * Operators:: Operators
3624 * Prefix Ops:: Prefix Operators
3625 * Infix Ops:: Infix Operators
3629 @subsection Arguments
3631 @cindex expression arguments
3632 @cindex arguments in expressions
3633 @cindex operands in expressions
3634 @cindex arithmetic operands
3635 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3636 contexts arguments are sometimes called ``arithmetic operands''. In
3637 this manual, to avoid confusing them with the ``instruction operands'' of
3638 the machine language, we use the term ``argument'' to refer to parts of
3639 expressions only, reserving the word ``operand'' to refer only to machine
3640 instruction operands.
3642 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3643 @var{section} is one of text, data, bss, absolute,
3644 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3647 Numbers are usually integers.
3649 A number can be a flonum or bignum. In this case, you are warned
3650 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3651 these 32 bits are an integer. You may write integer-manipulating
3652 instructions that act on exotic constants, compatible with other
3655 @cindex subexpressions
3656 Subexpressions are a left parenthesis @samp{(} followed by an integer
3657 expression, followed by a right parenthesis @samp{)}; or a prefix
3658 operator followed by an argument.
3661 @subsection Operators
3663 @cindex operators, in expressions
3664 @cindex arithmetic functions
3665 @cindex functions, in expressions
3666 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3667 operators are followed by an argument. Infix operators appear
3668 between their arguments. Operators may be preceded and/or followed by
3672 @subsection Prefix Operator
3674 @cindex prefix operators
3675 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3676 one argument, which must be absolute.
3678 @c the tex/end tex stuff surrounding this small table is meant to make
3679 @c it align, on the printed page, with the similar table in the next
3680 @c section (which is inside an enumerate).
3682 \global\advance\leftskip by \itemindent
3687 @dfn{Negation}. Two's complement negation.
3689 @dfn{Complementation}. Bitwise not.
3693 \global\advance\leftskip by -\itemindent
3697 @subsection Infix Operators
3699 @cindex infix operators
3700 @cindex operators, permitted arguments
3701 @dfn{Infix operators} take two arguments, one on either side. Operators
3702 have precedence, but operations with equal precedence are performed left
3703 to right. Apart from @code{+} or @option{-}, both arguments must be
3704 absolute, and the result is absolute.
3707 @cindex operator precedence
3708 @cindex precedence of operators
3715 @dfn{Multiplication}.
3718 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3724 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3727 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3731 Intermediate precedence
3736 @dfn{Bitwise Inclusive Or}.
3742 @dfn{Bitwise Exclusive Or}.
3745 @dfn{Bitwise Or Not}.
3752 @cindex addition, permitted arguments
3753 @cindex plus, permitted arguments
3754 @cindex arguments for addition
3756 @dfn{Addition}. If either argument is absolute, the result has the section of
3757 the other argument. You may not add together arguments from different
3760 @cindex subtraction, permitted arguments
3761 @cindex minus, permitted arguments
3762 @cindex arguments for subtraction
3764 @dfn{Subtraction}. If the right argument is absolute, the
3765 result has the section of the left argument.
3766 If both arguments are in the same section, the result is absolute.
3767 You may not subtract arguments from different sections.
3768 @c FIXME is there still something useful to say about undefined - undefined ?
3770 @cindex comparison expressions
3771 @cindex expressions, comparison
3776 @dfn{Is Not Equal To}
3780 @dfn{Is Greater Than}
3782 @dfn{Is Greater Than Or Equal To}
3784 @dfn{Is Less Than Or Equal To}
3786 The comparison operators can be used as infix operators. A true results has a
3787 value of -1 whereas a false result has a value of 0. Note, these operators
3788 perform signed comparisons.
3791 @item Lowest Precedence
3800 These two logical operations can be used to combine the results of sub
3801 expressions. Note, unlike the comparison operators a true result returns a
3802 value of 1 but a false results does still return 0. Also note that the logical
3803 or operator has a slightly lower precedence than logical and.
3808 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3809 address; you can only have a defined section in one of the two arguments.
3812 @chapter Assembler Directives
3814 @cindex directives, machine independent
3815 @cindex pseudo-ops, machine independent
3816 @cindex machine independent directives
3817 All assembler directives have names that begin with a period (@samp{.}).
3818 The rest of the name is letters, usually in lower case.
3820 This chapter discusses directives that are available regardless of the
3821 target machine configuration for the @sc{gnu} assembler.
3823 Some machine configurations provide additional directives.
3824 @xref{Machine Dependencies}.
3827 @ifset machine-directives
3828 @xref{Machine Dependencies}, for additional directives.
3833 * Abort:: @code{.abort}
3835 * ABORT (COFF):: @code{.ABORT}
3838 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3839 * Altmacro:: @code{.altmacro}
3840 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3841 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3842 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3843 * Byte:: @code{.byte @var{expressions}}
3844 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
3845 * Comm:: @code{.comm @var{symbol} , @var{length} }
3846 * Data:: @code{.data @var{subsection}}
3848 * Def:: @code{.def @var{name}}
3851 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3857 * Double:: @code{.double @var{flonums}}
3858 * Eject:: @code{.eject}
3859 * Else:: @code{.else}
3860 * Elseif:: @code{.elseif}
3863 * Endef:: @code{.endef}
3866 * Endfunc:: @code{.endfunc}
3867 * Endif:: @code{.endif}
3868 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3869 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3870 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
3872 * Error:: @code{.error @var{string}}
3873 * Exitm:: @code{.exitm}
3874 * Extern:: @code{.extern}
3875 * Fail:: @code{.fail}
3876 * File:: @code{.file}
3877 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3878 * Float:: @code{.float @var{flonums}}
3879 * Func:: @code{.func}
3880 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3882 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
3883 * Hidden:: @code{.hidden @var{names}}
3886 * hword:: @code{.hword @var{expressions}}
3887 * Ident:: @code{.ident}
3888 * If:: @code{.if @var{absolute expression}}
3889 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
3890 * Include:: @code{.include "@var{file}"}
3891 * Int:: @code{.int @var{expressions}}
3893 * Internal:: @code{.internal @var{names}}
3896 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3897 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3898 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3899 * Lflags:: @code{.lflags}
3900 @ifclear no-line-dir
3901 * Line:: @code{.line @var{line-number}}
3904 * Linkonce:: @code{.linkonce [@var{type}]}
3905 * List:: @code{.list}
3906 * Ln:: @code{.ln @var{line-number}}
3907 * Loc:: @code{.loc @var{fileno} @var{lineno}}
3908 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
3910 * Local:: @code{.local @var{names}}
3913 * Long:: @code{.long @var{expressions}}
3915 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3918 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3919 * MRI:: @code{.mri @var{val}}
3920 * Noaltmacro:: @code{.noaltmacro}
3921 * Nolist:: @code{.nolist}
3922 * Octa:: @code{.octa @var{bignums}}
3923 * Org:: @code{.org @var{new-lc}, @var{fill}}
3924 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3926 * PopSection:: @code{.popsection}
3927 * Previous:: @code{.previous}
3930 * Print:: @code{.print @var{string}}
3932 * Protected:: @code{.protected @var{names}}
3935 * Psize:: @code{.psize @var{lines}, @var{columns}}
3936 * Purgem:: @code{.purgem @var{name}}
3938 * PushSection:: @code{.pushsection @var{name}}
3941 * Quad:: @code{.quad @var{bignums}}
3942 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
3943 * Rept:: @code{.rept @var{count}}
3944 * Sbttl:: @code{.sbttl "@var{subheading}"}
3946 * Scl:: @code{.scl @var{class}}
3949 * Section:: @code{.section @var{name}[, @var{flags}]}
3952 * Set:: @code{.set @var{symbol}, @var{expression}}
3953 * Short:: @code{.short @var{expressions}}
3954 * Single:: @code{.single @var{flonums}}
3956 * Size:: @code{.size [@var{name} , @var{expression}]}
3958 @ifclear no-space-dir
3959 * Skip:: @code{.skip @var{size} , @var{fill}}
3962 * Sleb128:: @code{.sleb128 @var{expressions}}
3963 @ifclear no-space-dir
3964 * Space:: @code{.space @var{size} , @var{fill}}
3967 * Stab:: @code{.stabd, .stabn, .stabs}
3970 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
3971 * Struct:: @code{.struct @var{expression}}
3973 * SubSection:: @code{.subsection}
3974 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3978 * Tag:: @code{.tag @var{structname}}
3981 * Text:: @code{.text @var{subsection}}
3982 * Title:: @code{.title "@var{heading}"}
3984 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
3987 * Uleb128:: @code{.uleb128 @var{expressions}}
3989 * Val:: @code{.val @var{addr}}
3993 * Version:: @code{.version "@var{string}"}
3994 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
3995 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
3998 * Warning:: @code{.warning @var{string}}
3999 * Weak:: @code{.weak @var{names}}
4000 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4001 * Word:: @code{.word @var{expressions}}
4002 * Deprecated:: Deprecated Directives
4006 @section @code{.abort}
4008 @cindex @code{abort} directive
4009 @cindex stopping the assembly
4010 This directive stops the assembly immediately. It is for
4011 compatibility with other assemblers. The original idea was that the
4012 assembly language source would be piped into the assembler. If the sender
4013 of the source quit, it could use this directive tells @command{@value{AS}} to
4014 quit also. One day @code{.abort} will not be supported.
4018 @section @code{.ABORT} (COFF)
4020 @cindex @code{ABORT} directive
4021 When producing COFF output, @command{@value{AS}} accepts this directive as a
4022 synonym for @samp{.abort}.
4025 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4031 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4033 @cindex padding the location counter
4034 @cindex @code{align} directive
4035 Pad the location counter (in the current subsection) to a particular storage
4036 boundary. The first expression (which must be absolute) is the alignment
4037 required, as described below.
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 The way the required alignment is specified varies from system to system.
4054 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4055 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4056 alignment request in bytes. For example @samp{.align 8} advances
4057 the location counter until it is a multiple of 8. If the location counter
4058 is already a multiple of 8, no change is needed. For the tic54x, the
4059 first expression is the alignment request in words.
4061 For other systems, including ppc, i386 using a.out format, arm and
4062 strongarm, it is the
4063 number of low-order zero bits the location counter must have after
4064 advancement. For example @samp{.align 3} advances the location
4065 counter until it a multiple of 8. If the location counter is already a
4066 multiple of 8, no change is needed.
4068 This inconsistency is due to the different behaviors of the various
4069 native assemblers for these systems which GAS must emulate.
4070 GAS also provides @code{.balign} and @code{.p2align} directives,
4071 described later, which have a consistent behavior across all
4072 architectures (but are specific to GAS).
4075 @section @code{.altmacro}
4076 Enable alternate macro mode, enabling:
4079 @item LOCAL @var{name} [ , @dots{} ]
4080 One additional directive, @code{LOCAL}, is available. It is used to
4081 generate a string replacement for each of the @var{name} arguments, and
4082 replace any instances of @var{name} in each macro expansion. The
4083 replacement string is unique in the assembly, and different for each
4084 separate macro expansion. @code{LOCAL} allows you to write macros that
4085 define symbols, without fear of conflict between separate macro expansions.
4087 @item String delimiters
4088 You can write strings delimited in these other ways besides
4089 @code{"@var{string}"}:
4092 @item '@var{string}'
4093 You can delimit strings with single-quote characters.
4095 @item <@var{string}>
4096 You can delimit strings with matching angle brackets.
4099 @item single-character string escape
4100 To include any single character literally in a string (even if the
4101 character would otherwise have some special meaning), you can prefix the
4102 character with @samp{!} (an exclamation mark). For example, you can
4103 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4105 @item Expression results as strings
4106 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4107 and use the result as a string.
4111 @section @code{.ascii "@var{string}"}@dots{}
4113 @cindex @code{ascii} directive
4114 @cindex string literals
4115 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4116 separated by commas. It assembles each string (with no automatic
4117 trailing zero byte) into consecutive addresses.
4120 @section @code{.asciz "@var{string}"}@dots{}
4122 @cindex @code{asciz} directive
4123 @cindex zero-terminated strings
4124 @cindex null-terminated strings
4125 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4126 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4129 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4131 @cindex padding the location counter given number of bytes
4132 @cindex @code{balign} directive
4133 Pad the location counter (in the current subsection) to a particular
4134 storage boundary. The first expression (which must be absolute) is the
4135 alignment request in bytes. For example @samp{.balign 8} advances
4136 the location counter until it is a multiple of 8. If the location counter
4137 is already a multiple of 8, no change is needed.
4139 The second expression (also absolute) gives the fill value to be stored in the
4140 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4141 padding bytes are normally zero. However, on some systems, if the section is
4142 marked as containing code and the fill value is omitted, the space is filled
4143 with no-op instructions.
4145 The third expression is also absolute, and is also optional. If it is present,
4146 it is the maximum number of bytes that should be skipped by this alignment
4147 directive. If doing the alignment would require skipping more bytes than the
4148 specified maximum, then the alignment is not done at all. You can omit the
4149 fill value (the second argument) entirely by simply using two commas after the
4150 required alignment; this can be useful if you want the alignment to be filled
4151 with no-op instructions when appropriate.
4153 @cindex @code{balignw} directive
4154 @cindex @code{balignl} directive
4155 The @code{.balignw} and @code{.balignl} directives are variants of the
4156 @code{.balign} directive. The @code{.balignw} directive treats the fill
4157 pattern as a two byte word value. The @code{.balignl} directives treats the
4158 fill pattern as a four byte longword value. For example, @code{.balignw
4159 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4160 filled in with the value 0x368d (the exact placement of the bytes depends upon
4161 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4165 @section @code{.byte @var{expressions}}
4167 @cindex @code{byte} directive
4168 @cindex integers, one byte
4169 @code{.byte} expects zero or more expressions, separated by commas.
4170 Each expression is assembled into the next byte.
4172 @node CFI directives
4173 @section @code{.cfi_startproc [simple]}
4174 @cindex @code{cfi_startproc} directive
4175 @code{.cfi_startproc} is used at the beginning of each function that
4176 should have an entry in @code{.eh_frame}. It initializes some internal
4177 data structures. Don't forget to close the function by
4178 @code{.cfi_endproc}.
4180 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4181 it also emits some architecture dependent initial CFI instructions.
4183 @section @code{.cfi_endproc}
4184 @cindex @code{cfi_endproc} directive
4185 @code{.cfi_endproc} is used at the end of a function where it closes its
4186 unwind entry previously opened by
4187 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4189 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4190 @code{.cfi_personality} defines personality routine and its encoding.
4191 @var{encoding} must be a constant determining how the personality
4192 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4193 argument is not present, otherwise second argument should be
4194 a constant or a symbol name. When using indirect encodings,
4195 the symbol provided should be the location where personality
4196 can be loaded from, not the personality routine itself.
4197 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4198 no personality routine.
4200 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4201 @code{.cfi_lsda} defines LSDA and its encoding.
4202 @var{encoding} must be a constant determining how the LSDA
4203 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4204 argument is not present, otherwise second argument should be a constant
4205 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4208 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4209 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4210 address from @var{register} and add @var{offset} to it}.
4212 @section @code{.cfi_def_cfa_register @var{register}}
4213 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4214 now on @var{register} will be used instead of the old one. Offset
4217 @section @code{.cfi_def_cfa_offset @var{offset}}
4218 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4219 remains the same, but @var{offset} is new. Note that it is the
4220 absolute offset that will be added to a defined register to compute
4223 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4224 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4225 value that is added/substracted from the previous offset.
4227 @section @code{.cfi_offset @var{register}, @var{offset}}
4228 Previous value of @var{register} is saved at offset @var{offset} from
4231 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4232 Previous value of @var{register} is saved at offset @var{offset} from
4233 the current CFA register. This is transformed to @code{.cfi_offset}
4234 using the known displacement of the CFA register from the CFA.
4235 This is often easier to use, because the number will match the
4236 code it's annotating.
4238 @section @code{.cfi_register @var{register1}, @var{register2}}
4239 Previous value of @var{register1} is saved in register @var{register2}.
4241 @section @code{.cfi_restore @var{register}}
4242 @code{.cfi_restore} says that the rule for @var{register} is now the
4243 same as it was at the beginning of the function, after all initial
4244 instruction added by @code{.cfi_startproc} were executed.
4246 @section @code{.cfi_undefined @var{register}}
4247 From now on the previous value of @var{register} can't be restored anymore.
4249 @section @code{.cfi_same_value @var{register}}
4250 Current value of @var{register} is the same like in the previous frame,
4251 i.e. no restoration needed.
4253 @section @code{.cfi_remember_state},
4254 First save all current rules for all registers by @code{.cfi_remember_state},
4255 then totally screw them up by subsequent @code{.cfi_*} directives and when
4256 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4257 the previous saved state.
4259 @section @code{.cfi_return_column @var{register}}
4260 Change return column @var{register}, i.e. the return address is either
4261 directly in @var{register} or can be accessed by rules for @var{register}.
4263 @section @code{.cfi_signal_frame}
4264 Mark current function as signal trampoline.
4266 @section @code{.cfi_window_save}
4267 SPARC register window has been saved.
4269 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4270 Allows the user to add arbitrary bytes to the unwind info. One
4271 might use this to add OS-specific CFI opcodes, or generic CFI
4272 opcodes that GAS does not yet support.
4274 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4275 The current value of @var{register} is @var{label}. The value of @var{label}
4276 will be encoded in the output file according to @var{encoding}; see the
4277 description of @code{.cfi_personality} for details on this encoding.
4279 The usefulness of equating a register to a fixed label is probably
4280 limited to the return address register. Here, it can be useful to
4281 mark a code segment that has only one return address which is reached
4282 by a direct branch and no copy of the return address exists in memory
4283 or another register.
4286 @section @code{.comm @var{symbol} , @var{length} }
4288 @cindex @code{comm} directive
4289 @cindex symbol, common
4290 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4291 common symbol in one object file may be merged with a defined or common symbol
4292 of the same name in another object file. If @code{@value{LD}} does not see a
4293 definition for the symbol--just one or more common symbols--then it will
4294 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4295 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4296 the same name, and they do not all have the same size, it will allocate space
4297 using the largest size.
4300 When using ELF, the @code{.comm} directive takes an optional third argument.
4301 This is the desired alignment of the symbol, specified as a byte boundary (for
4302 example, an alignment of 16 means that the least significant 4 bits of the
4303 address should be zero). The alignment must be an absolute expression, and it
4304 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
4305 for the common symbol, it will use the alignment when placing the symbol. If
4306 no alignment is specified, @command{@value{AS}} will set the alignment to the
4307 largest power of two less than or equal to the size of the symbol, up to a
4312 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4313 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4317 @section @code{.data @var{subsection}}
4319 @cindex @code{data} directive
4320 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4321 end of the data subsection numbered @var{subsection} (which is an
4322 absolute expression). If @var{subsection} is omitted, it defaults
4327 @section @code{.def @var{name}}
4329 @cindex @code{def} directive
4330 @cindex COFF symbols, debugging
4331 @cindex debugging COFF symbols
4332 Begin defining debugging information for a symbol @var{name}; the
4333 definition extends until the @code{.endef} directive is encountered.
4336 This directive is only observed when @command{@value{AS}} is configured for COFF
4337 format output; when producing @code{b.out}, @samp{.def} is recognized,
4344 @section @code{.desc @var{symbol}, @var{abs-expression}}
4346 @cindex @code{desc} directive
4347 @cindex COFF symbol descriptor
4348 @cindex symbol descriptor, COFF
4349 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4350 to the low 16 bits of an absolute expression.
4353 The @samp{.desc} directive is not available when @command{@value{AS}} is
4354 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4355 object format. For the sake of compatibility, @command{@value{AS}} accepts
4356 it, but produces no output, when configured for COFF.
4362 @section @code{.dim}
4364 @cindex @code{dim} directive
4365 @cindex COFF auxiliary symbol information
4366 @cindex auxiliary symbol information, COFF
4367 This directive is generated by compilers to include auxiliary debugging
4368 information in the symbol table. It is only permitted inside
4369 @code{.def}/@code{.endef} pairs.
4372 @samp{.dim} is only meaningful when generating COFF format output; when
4373 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4379 @section @code{.double @var{flonums}}
4381 @cindex @code{double} directive
4382 @cindex floating point numbers (double)
4383 @code{.double} expects zero or more flonums, separated by commas. It
4384 assembles floating point numbers.
4386 The exact kind of floating point numbers emitted depends on how
4387 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4391 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4392 in @sc{ieee} format.
4397 @section @code{.eject}
4399 @cindex @code{eject} directive
4400 @cindex new page, in listings
4401 @cindex page, in listings
4402 @cindex listing control: new page
4403 Force a page break at this point, when generating assembly listings.
4406 @section @code{.else}
4408 @cindex @code{else} directive
4409 @code{.else} is part of the @command{@value{AS}} support for conditional
4410 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4411 of code to be assembled if the condition for the preceding @code{.if}
4415 @section @code{.elseif}
4417 @cindex @code{elseif} directive
4418 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4419 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4420 @code{.if} block that would otherwise fill the entire @code{.else} section.
4423 @section @code{.end}
4425 @cindex @code{end} directive
4426 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4427 process anything in the file past the @code{.end} directive.
4431 @section @code{.endef}
4433 @cindex @code{endef} directive
4434 This directive flags the end of a symbol definition begun with
4438 @samp{.endef} is only meaningful when generating COFF format output; if
4439 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4440 directive but ignores it.
4445 @section @code{.endfunc}
4446 @cindex @code{endfunc} directive
4447 @code{.endfunc} marks the end of a function specified with @code{.func}.
4450 @section @code{.endif}
4452 @cindex @code{endif} directive
4453 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4454 it marks the end of a block of code that is only assembled
4455 conditionally. @xref{If,,@code{.if}}.
4458 @section @code{.equ @var{symbol}, @var{expression}}
4460 @cindex @code{equ} directive
4461 @cindex assigning values to symbols
4462 @cindex symbols, assigning values to
4463 This directive sets the value of @var{symbol} to @var{expression}.
4464 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4467 The syntax for @code{equ} on the HPPA is
4468 @samp{@var{symbol} .equ @var{expression}}.
4472 The syntax for @code{equ} on the Z80 is
4473 @samp{@var{symbol} equ @var{expression}}.
4474 On the Z80 it is an eror if @var{symbol} is already defined,
4475 but the symbol is not protected from later redefinition.
4476 Compare @ref{Equiv}.
4480 @section @code{.equiv @var{symbol}, @var{expression}}
4481 @cindex @code{equiv} directive
4482 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4483 the assembler will signal an error if @var{symbol} is already defined. Note a
4484 symbol which has been referenced but not actually defined is considered to be
4487 Except for the contents of the error message, this is roughly equivalent to
4494 plus it protects the symbol from later redefinition.
4497 @section @code{.eqv @var{symbol}, @var{expression}}
4498 @cindex @code{eqv} directive
4499 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4500 evaluate the expression or any part of it immediately. Instead each time
4501 the resulting symbol is used in an expression, a snapshot of its current
4505 @section @code{.err}
4506 @cindex @code{err} directive
4507 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4508 message and, unless the @option{-Z} option was used, it will not generate an
4509 object file. This can be used to signal an error in conditionally compiled code.
4512 @section @code{.error "@var{string}"}
4513 @cindex error directive
4515 Similarly to @code{.err}, this directive emits an error, but you can specify a
4516 string that will be emitted as the error message. If you don't specify the
4517 message, it defaults to @code{".error directive invoked in source file"}.
4518 @xref{Errors, ,Error and Warning Messages}.
4521 .error "This code has not been assembled and tested."
4525 @section @code{.exitm}
4526 Exit early from the current macro definition. @xref{Macro}.
4529 @section @code{.extern}
4531 @cindex @code{extern} directive
4532 @code{.extern} is accepted in the source program---for compatibility
4533 with other assemblers---but it is ignored. @command{@value{AS}} treats
4534 all undefined symbols as external.
4537 @section @code{.fail @var{expression}}
4539 @cindex @code{fail} directive
4540 Generates an error or a warning. If the value of the @var{expression} is 500
4541 or more, @command{@value{AS}} will print a warning message. If the value is less
4542 than 500, @command{@value{AS}} will print an error message. The message will
4543 include the value of @var{expression}. This can occasionally be useful inside
4544 complex nested macros or conditional assembly.
4547 @section @code{.file}
4548 @cindex @code{file} directive
4550 @ifclear no-file-dir
4551 There are two different versions of the @code{.file} directive. Targets
4552 that support DWARF2 line number information use the DWARF2 version of
4553 @code{.file}. Other targets use the default version.
4555 @subheading Default Version
4557 @cindex logical file name
4558 @cindex file name, logical
4559 This version of the @code{.file} directive tells @command{@value{AS}} that we
4560 are about to start a new logical file. The syntax is:
4566 @var{string} is the new file name. In general, the filename is
4567 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4568 to specify an empty file name, you must give the quotes--@code{""}. This
4569 statement may go away in future: it is only recognized to be compatible with
4570 old @command{@value{AS}} programs.
4572 @subheading DWARF2 Version
4575 When emitting DWARF2 line number information, @code{.file} assigns filenames
4576 to the @code{.debug_line} file name table. The syntax is:
4579 .file @var{fileno} @var{filename}
4582 The @var{fileno} operand should be a unique positive integer to use as the
4583 index of the entry in the table. The @var{filename} operand is a C string
4586 The detail of filename indices is exposed to the user because the filename
4587 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4588 information, and thus the user must know the exact indices that table
4592 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4594 @cindex @code{fill} directive
4595 @cindex writing patterns in memory
4596 @cindex patterns, writing in memory
4597 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4598 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4599 may be zero or more. @var{Size} may be zero or more, but if it is
4600 more than 8, then it is deemed to have the value 8, compatible with
4601 other people's assemblers. The contents of each @var{repeat} bytes
4602 is taken from an 8-byte number. The highest order 4 bytes are
4603 zero. The lowest order 4 bytes are @var{value} rendered in the
4604 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4605 Each @var{size} bytes in a repetition is taken from the lowest order
4606 @var{size} bytes of this number. Again, this bizarre behavior is
4607 compatible with other people's assemblers.
4609 @var{size} and @var{value} are optional.
4610 If the second comma and @var{value} are absent, @var{value} is
4611 assumed zero. If the first comma and following tokens are absent,
4612 @var{size} is assumed to be 1.
4615 @section @code{.float @var{flonums}}
4617 @cindex floating point numbers (single)
4618 @cindex @code{float} directive
4619 This directive assembles zero or more flonums, separated by commas. It
4620 has the same effect as @code{.single}.
4622 The exact kind of floating point numbers emitted depends on how
4623 @command{@value{AS}} is configured.
4624 @xref{Machine Dependencies}.
4628 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4629 in @sc{ieee} format.
4634 @section @code{.func @var{name}[,@var{label}]}
4635 @cindex @code{func} directive
4636 @code{.func} emits debugging information to denote function @var{name}, and
4637 is ignored unless the file is assembled with debugging enabled.
4638 Only @samp{--gstabs[+]} is currently supported.
4639 @var{label} is the entry point of the function and if omitted @var{name}
4640 prepended with the @samp{leading char} is used.
4641 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4642 All functions are currently defined to have @code{void} return type.
4643 The function must be terminated with @code{.endfunc}.
4646 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4648 @cindex @code{global} directive
4649 @cindex symbol, making visible to linker
4650 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4651 @var{symbol} in your partial program, its value is made available to
4652 other partial programs that are linked with it. Otherwise,
4653 @var{symbol} takes its attributes from a symbol of the same name
4654 from another file linked into the same program.
4656 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4657 compatibility with other assemblers.
4660 On the HPPA, @code{.global} is not always enough to make it accessible to other
4661 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4662 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4667 @section @code{.gnu_attribute @var{tag},@var{value}}
4668 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4671 @section @code{.hidden @var{names}}
4673 @cindex @code{hidden} directive
4675 This is one of the ELF visibility directives. The other two are
4676 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4677 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4679 This directive overrides the named symbols default visibility (which is set by
4680 their binding: local, global or weak). The directive sets the visibility to
4681 @code{hidden} which means that the symbols are not visible to other components.
4682 Such symbols are always considered to be @code{protected} as well.
4686 @section @code{.hword @var{expressions}}
4688 @cindex @code{hword} directive
4689 @cindex integers, 16-bit
4690 @cindex numbers, 16-bit
4691 @cindex sixteen bit integers
4692 This expects zero or more @var{expressions}, and emits
4693 a 16 bit number for each.
4696 This directive is a synonym for @samp{.short}; depending on the target
4697 architecture, it may also be a synonym for @samp{.word}.
4701 This directive is a synonym for @samp{.short}.
4704 This directive is a synonym for both @samp{.short} and @samp{.word}.
4709 @section @code{.ident}
4711 @cindex @code{ident} directive
4713 This directive is used by some assemblers to place tags in object files. The
4714 behavior of this directive varies depending on the target. When using the
4715 a.out object file format, @command{@value{AS}} simply accepts the directive for
4716 source-file compatibility with existing assemblers, but does not emit anything
4717 for it. When using COFF, comments are emitted to the @code{.comment} or
4718 @code{.rdata} section, depending on the target. When using ELF, comments are
4719 emitted to the @code{.comment} section.
4722 @section @code{.if @var{absolute expression}}
4724 @cindex conditional assembly
4725 @cindex @code{if} directive
4726 @code{.if} marks the beginning of a section of code which is only
4727 considered part of the source program being assembled if the argument
4728 (which must be an @var{absolute expression}) is non-zero. The end of
4729 the conditional section of code must be marked by @code{.endif}
4730 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4731 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4732 If you have several conditions to check, @code{.elseif} may be used to avoid
4733 nesting blocks if/else within each subsequent @code{.else} block.
4735 The following variants of @code{.if} are also supported:
4737 @cindex @code{ifdef} directive
4738 @item .ifdef @var{symbol}
4739 Assembles the following section of code if the specified @var{symbol}
4740 has been defined. Note a symbol which has been referenced but not yet defined
4741 is considered to be undefined.
4743 @cindex @code{ifb} directive
4744 @item .ifb @var{text}
4745 Assembles the following section of code if the operand is blank (empty).
4747 @cindex @code{ifc} directive
4748 @item .ifc @var{string1},@var{string2}
4749 Assembles the following section of code if the two strings are the same. The
4750 strings may be optionally quoted with single quotes. If they are not quoted,
4751 the first string stops at the first comma, and the second string stops at the
4752 end of the line. Strings which contain whitespace should be quoted. The
4753 string comparison is case sensitive.
4755 @cindex @code{ifeq} directive
4756 @item .ifeq @var{absolute expression}
4757 Assembles the following section of code if the argument is zero.
4759 @cindex @code{ifeqs} directive
4760 @item .ifeqs @var{string1},@var{string2}
4761 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4763 @cindex @code{ifge} directive
4764 @item .ifge @var{absolute expression}
4765 Assembles the following section of code if the argument is greater than or
4768 @cindex @code{ifgt} directive
4769 @item .ifgt @var{absolute expression}
4770 Assembles the following section of code if the argument is greater than zero.
4772 @cindex @code{ifle} directive
4773 @item .ifle @var{absolute expression}
4774 Assembles the following section of code if the argument is less than or equal
4777 @cindex @code{iflt} directive
4778 @item .iflt @var{absolute expression}
4779 Assembles the following section of code if the argument is less than zero.
4781 @cindex @code{ifnb} directive
4782 @item .ifnb @var{text}
4783 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
4784 following section of code if the operand is non-blank (non-empty).
4786 @cindex @code{ifnc} directive
4787 @item .ifnc @var{string1},@var{string2}.
4788 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4789 following section of code if the two strings are not the same.
4791 @cindex @code{ifndef} directive
4792 @cindex @code{ifnotdef} directive
4793 @item .ifndef @var{symbol}
4794 @itemx .ifnotdef @var{symbol}
4795 Assembles the following section of code if the specified @var{symbol}
4796 has not been defined. Both spelling variants are equivalent. Note a symbol
4797 which has been referenced but not yet defined is considered to be undefined.
4799 @cindex @code{ifne} directive
4800 @item .ifne @var{absolute expression}
4801 Assembles the following section of code if the argument is not equal to zero
4802 (in other words, this is equivalent to @code{.if}).
4804 @cindex @code{ifnes} directive
4805 @item .ifnes @var{string1},@var{string2}
4806 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4807 following section of code if the two strings are not the same.
4811 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4813 @cindex @code{incbin} directive
4814 @cindex binary files, including
4815 The @code{incbin} directive includes @var{file} verbatim at the current
4816 location. You can control the search paths used with the @samp{-I} command-line
4817 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4820 The @var{skip} argument skips a number of bytes from the start of the
4821 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4822 read. Note that the data is not aligned in any way, so it is the user's
4823 responsibility to make sure that proper alignment is provided both before and
4824 after the @code{incbin} directive.
4827 @section @code{.include "@var{file}"}
4829 @cindex @code{include} directive
4830 @cindex supporting files, including
4831 @cindex files, including
4832 This directive provides a way to include supporting files at specified
4833 points in your source program. The code from @var{file} is assembled as
4834 if it followed the point of the @code{.include}; when the end of the
4835 included file is reached, assembly of the original file continues. You
4836 can control the search paths used with the @samp{-I} command-line option
4837 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4841 @section @code{.int @var{expressions}}
4843 @cindex @code{int} directive
4844 @cindex integers, 32-bit
4845 Expect zero or more @var{expressions}, of any section, separated by commas.
4846 For each expression, emit a number that, at run time, is the value of that
4847 expression. The byte order and bit size of the number depends on what kind
4848 of target the assembly is for.
4852 On most forms of the H8/300, @code{.int} emits 16-bit
4853 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
4860 @section @code{.internal @var{names}}
4862 @cindex @code{internal} directive
4864 This is one of the ELF visibility directives. The other two are
4865 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4866 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4868 This directive overrides the named symbols default visibility (which is set by
4869 their binding: local, global or weak). The directive sets the visibility to
4870 @code{internal} which means that the symbols are considered to be @code{hidden}
4871 (i.e., not visible to other components), and that some extra, processor specific
4872 processing must also be performed upon the symbols as well.
4876 @section @code{.irp @var{symbol},@var{values}}@dots{}
4878 @cindex @code{irp} directive
4879 Evaluate a sequence of statements assigning different values to @var{symbol}.
4880 The sequence of statements starts at the @code{.irp} directive, and is
4881 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4882 set to @var{value}, and the sequence of statements is assembled. If no
4883 @var{value} is listed, the sequence of statements is assembled once, with
4884 @var{symbol} set to the null string. To refer to @var{symbol} within the
4885 sequence of statements, use @var{\symbol}.
4887 For example, assembling
4895 is equivalent to assembling
4903 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
4906 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4908 @cindex @code{irpc} directive
4909 Evaluate a sequence of statements assigning different values to @var{symbol}.
4910 The sequence of statements starts at the @code{.irpc} directive, and is
4911 terminated by an @code{.endr} directive. For each character in @var{value},
4912 @var{symbol} is set to the character, and the sequence of statements is
4913 assembled. If no @var{value} is listed, the sequence of statements is
4914 assembled once, with @var{symbol} set to the null string. To refer to
4915 @var{symbol} within the sequence of statements, use @var{\symbol}.
4917 For example, assembling
4925 is equivalent to assembling
4933 For some caveats with the spelling of @var{symbol}, see also the discussion
4937 @section @code{.lcomm @var{symbol} , @var{length}}
4939 @cindex @code{lcomm} directive
4940 @cindex local common symbols
4941 @cindex symbols, local common
4942 Reserve @var{length} (an absolute expression) bytes for a local common
4943 denoted by @var{symbol}. The section and value of @var{symbol} are
4944 those of the new local common. The addresses are allocated in the bss
4945 section, so that at run-time the bytes start off zeroed. @var{Symbol}
4946 is not declared global (@pxref{Global,,@code{.global}}), so is normally
4947 not visible to @code{@value{LD}}.
4950 Some targets permit a third argument to be used with @code{.lcomm}. This
4951 argument specifies the desired alignment of the symbol in the bss section.
4955 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
4956 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
4960 @section @code{.lflags}
4962 @cindex @code{lflags} directive (ignored)
4963 @command{@value{AS}} accepts this directive, for compatibility with other
4964 assemblers, but ignores it.
4966 @ifclear no-line-dir
4968 @section @code{.line @var{line-number}}
4970 @cindex @code{line} directive
4971 @cindex logical line number
4973 Change the logical line number. @var{line-number} must be an absolute
4974 expression. The next line has that logical line number. Therefore any other
4975 statements on the current line (after a statement separator character) are
4976 reported as on logical line number @var{line-number} @minus{} 1. One day
4977 @command{@value{AS}} will no longer support this directive: it is recognized only
4978 for compatibility with existing assembler programs.
4981 Even though this is a directive associated with the @code{a.out} or
4982 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
4983 when producing COFF output, and treats @samp{.line} as though it
4984 were the COFF @samp{.ln} @emph{if} it is found outside a
4985 @code{.def}/@code{.endef} pair.
4987 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
4988 used by compilers to generate auxiliary symbol information for
4993 @section @code{.linkonce [@var{type}]}
4995 @cindex @code{linkonce} directive
4996 @cindex common sections
4997 Mark the current section so that the linker only includes a single copy of it.
4998 This may be used to include the same section in several different object files,
4999 but ensure that the linker will only include it once in the final output file.
5000 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5001 Duplicate sections are detected based on the section name, so it should be
5004 This directive is only supported by a few object file formats; as of this
5005 writing, the only object file format which supports it is the Portable
5006 Executable format used on Windows NT.
5008 The @var{type} argument is optional. If specified, it must be one of the
5009 following strings. For example:
5013 Not all types may be supported on all object file formats.
5017 Silently discard duplicate sections. This is the default.
5020 Warn if there are duplicate sections, but still keep only one copy.
5023 Warn if any of the duplicates have different sizes.
5026 Warn if any of the duplicates do not have exactly the same contents.
5030 @section @code{.list}
5032 @cindex @code{list} directive
5033 @cindex listing control, turning on
5034 Control (in conjunction with the @code{.nolist} directive) whether or
5035 not assembly listings are generated. These two directives maintain an
5036 internal counter (which is zero initially). @code{.list} increments the
5037 counter, and @code{.nolist} decrements it. Assembly listings are
5038 generated whenever the counter is greater than zero.
5040 By default, listings are disabled. When you enable them (with the
5041 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5042 the initial value of the listing counter is one.
5045 @section @code{.ln @var{line-number}}
5047 @cindex @code{ln} directive
5048 @ifclear no-line-dir
5049 @samp{.ln} is a synonym for @samp{.line}.
5052 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5053 must be an absolute expression. The next line has that logical
5054 line number, so any other statements on the current line (after a
5055 statement separator character @code{;}) are reported as on logical
5056 line number @var{line-number} @minus{} 1.
5059 This directive is accepted, but ignored, when @command{@value{AS}} is
5060 configured for @code{b.out}; its effect is only associated with COFF
5066 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5067 @cindex @code{loc} directive
5068 When emitting DWARF2 line number information,
5069 the @code{.loc} directive will add a row to the @code{.debug_line} line
5070 number matrix corresponding to the immediately following assembly
5071 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5072 arguments will be applied to the @code{.debug_line} state machine before
5075 The @var{options} are a sequence of the following tokens in any order:
5079 This option will set the @code{basic_block} register in the
5080 @code{.debug_line} state machine to @code{true}.
5083 This option will set the @code{prologue_end} register in the
5084 @code{.debug_line} state machine to @code{true}.
5086 @item epilogue_begin
5087 This option will set the @code{epilogue_begin} register in the
5088 @code{.debug_line} state machine to @code{true}.
5090 @item is_stmt @var{value}
5091 This option will set the @code{is_stmt} register in the
5092 @code{.debug_line} state machine to @code{value}, which must be
5095 @item isa @var{value}
5096 This directive will set the @code{isa} register in the @code{.debug_line}
5097 state machine to @var{value}, which must be an unsigned integer.
5101 @node Loc_mark_labels
5102 @section @code{.loc_mark_labels @var{enable}}
5103 @cindex @code{loc_mark_labels} directive
5104 When emitting DWARF2 line number information,
5105 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5106 to the @code{.debug_line} line number matrix with the @code{basic_block}
5107 register in the state machine set whenever a code label is seen.
5108 The @var{enable} argument should be either 1 or 0, to enable or disable
5109 this function respectively.
5113 @section @code{.local @var{names}}
5115 @cindex @code{local} directive
5116 This directive, which is available for ELF targets, marks each symbol in
5117 the comma-separated list of @code{names} as a local symbol so that it
5118 will not be externally visible. If the symbols do not already exist,
5119 they will be created.
5121 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5122 accept an alignment argument, which is the case for most ELF targets,
5123 the @code{.local} directive can be used in combination with @code{.comm}
5124 (@pxref{Comm}) to define aligned local common data.
5128 @section @code{.long @var{expressions}}
5130 @cindex @code{long} directive
5131 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5134 @c no one seems to know what this is for or whether this description is
5135 @c what it really ought to do
5137 @section @code{.lsym @var{symbol}, @var{expression}}
5139 @cindex @code{lsym} directive
5140 @cindex symbol, not referenced in assembly
5141 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5142 the hash table, ensuring it cannot be referenced by name during the
5143 rest of the assembly. This sets the attributes of the symbol to be
5144 the same as the expression value:
5146 @var{other} = @var{descriptor} = 0
5147 @var{type} = @r{(section of @var{expression})}
5148 @var{value} = @var{expression}
5151 The new symbol is not flagged as external.
5155 @section @code{.macro}
5158 The commands @code{.macro} and @code{.endm} allow you to define macros that
5159 generate assembly output. For example, this definition specifies a macro
5160 @code{sum} that puts a sequence of numbers into memory:
5163 .macro sum from=0, to=5
5172 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5184 @item .macro @var{macname}
5185 @itemx .macro @var{macname} @var{macargs} @dots{}
5186 @cindex @code{macro} directive
5187 Begin the definition of a macro called @var{macname}. If your macro
5188 definition requires arguments, specify their names after the macro name,
5189 separated by commas or spaces. You can qualify the macro argument to
5190 indicate whether all invocations must specify a non-blank value (through
5191 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5192 (through @samp{:@code{vararg}}). You can supply a default value for any
5193 macro argument by following the name with @samp{=@var{deflt}}. You
5194 cannot define two macros with the same @var{macname} unless it has been
5195 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5196 definitions. For example, these are all valid @code{.macro} statements:
5200 Begin the definition of a macro called @code{comm}, which takes no
5203 @item .macro plus1 p, p1
5204 @itemx .macro plus1 p p1
5205 Either statement begins the definition of a macro called @code{plus1},
5206 which takes two arguments; within the macro definition, write
5207 @samp{\p} or @samp{\p1} to evaluate the arguments.
5209 @item .macro reserve_str p1=0 p2
5210 Begin the definition of a macro called @code{reserve_str}, with two
5211 arguments. The first argument has a default value, but not the second.
5212 After the definition is complete, you can call the macro either as
5213 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5214 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5215 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5216 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5218 @item .macro m p1:req, p2=0, p3:vararg
5219 Begin the definition of a macro called @code{m}, with at least three
5220 arguments. The first argument must always have a value specified, but
5221 not the second, which instead has a default value. The third formal
5222 will get assigned all remaining arguments specified at invocation time.
5224 When you call a macro, you can specify the argument values either by
5225 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5226 @samp{sum to=17, from=9}.
5230 Note that since each of the @var{macargs} can be an identifier exactly
5231 as any other one permitted by the target architecture, there may be
5232 occasional problems if the target hand-crafts special meanings to certain
5233 characters when they occur in a special position. For example, if the colon
5234 (@code{:}) is generally permitted to be part of a symbol name, but the
5235 architecture specific code special-cases it when occurring as the final
5236 character of a symbol (to denote a label), then the macro parameter
5237 replacement code will have no way of knowing that and consider the whole
5238 construct (including the colon) an identifier, and check only this
5239 identifier for being the subject to parameter substitution. So for example
5240 this macro definition:
5248 might not work as expected. Invoking @samp{label foo} might not create a label
5249 called @samp{foo} but instead just insert the text @samp{\l:} into the
5250 assembler source, probably generating an error about an unrecognised
5253 Similarly problems might occur with the period character (@samp{.})
5254 which is often allowed inside opcode names (and hence identifier names). So
5255 for example constructing a macro to build an opcode from a base name and a
5256 length specifier like this:
5259 .macro opcode base length
5264 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5265 instruction but instead generate some kind of error as the assembler tries to
5266 interpret the text @samp{\base.\length}.
5268 There are several possible ways around this problem:
5271 @item Insert white space
5272 If it is possible to use white space characters then this is the simplest
5281 @item Use @samp{\()}
5282 The string @samp{\()} can be used to separate the end of a macro argument from
5283 the following text. eg:
5286 .macro opcode base length
5291 @item Use the alternate macro syntax mode
5292 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5293 used as a separator. eg:
5303 Note: this problem of correctly identifying string parameters to pseudo ops
5304 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5305 and @code{.irpc} (@pxref{Irpc}) as well.
5308 @cindex @code{endm} directive
5309 Mark the end of a macro definition.
5312 @cindex @code{exitm} directive
5313 Exit early from the current macro definition.
5315 @cindex number of macros executed
5316 @cindex macros, count executed
5318 @command{@value{AS}} maintains a counter of how many macros it has
5319 executed in this pseudo-variable; you can copy that number to your
5320 output with @samp{\@@}, but @emph{only within a macro definition}.
5322 @item LOCAL @var{name} [ , @dots{} ]
5323 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5324 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5325 @xref{Altmacro,,@code{.altmacro}}.
5329 @section @code{.mri @var{val}}
5331 @cindex @code{mri} directive
5332 @cindex MRI mode, temporarily
5333 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5334 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5335 affects code assembled until the next @code{.mri} directive, or until the end
5336 of the file. @xref{M, MRI mode, MRI mode}.
5339 @section @code{.noaltmacro}
5340 Disable alternate macro mode. @xref{Altmacro}.
5343 @section @code{.nolist}
5345 @cindex @code{nolist} directive
5346 @cindex listing control, turning off
5347 Control (in conjunction with the @code{.list} directive) whether or
5348 not assembly listings are generated. These two directives maintain an
5349 internal counter (which is zero initially). @code{.list} increments the
5350 counter, and @code{.nolist} decrements it. Assembly listings are
5351 generated whenever the counter is greater than zero.
5354 @section @code{.octa @var{bignums}}
5356 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5357 @cindex @code{octa} directive
5358 @cindex integer, 16-byte
5359 @cindex sixteen byte integer
5360 This directive expects zero or more bignums, separated by commas. For each
5361 bignum, it emits a 16-byte integer.
5363 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5364 hence @emph{octa}-word for 16 bytes.
5367 @section @code{.org @var{new-lc} , @var{fill}}
5369 @cindex @code{org} directive
5370 @cindex location counter, advancing
5371 @cindex advancing location counter
5372 @cindex current address, advancing
5373 Advance the location counter of the current section to
5374 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5375 expression with the same section as the current subsection. That is,
5376 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5377 wrong section, the @code{.org} directive is ignored. To be compatible
5378 with former assemblers, if the section of @var{new-lc} is absolute,
5379 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5380 is the same as the current subsection.
5382 @code{.org} may only increase the location counter, or leave it
5383 unchanged; you cannot use @code{.org} to move the location counter
5386 @c double negative used below "not undefined" because this is a specific
5387 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5388 @c section. doc@cygnus.com 18feb91
5389 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5390 may not be undefined. If you really detest this restriction we eagerly await
5391 a chance to share your improved assembler.
5393 Beware that the origin is relative to the start of the section, not
5394 to the start of the subsection. This is compatible with other
5395 people's assemblers.
5397 When the location counter (of the current subsection) is advanced, the
5398 intervening bytes are filled with @var{fill} which should be an
5399 absolute expression. If the comma and @var{fill} are omitted,
5400 @var{fill} defaults to zero.
5403 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5405 @cindex padding the location counter given a power of two
5406 @cindex @code{p2align} directive
5407 Pad the location counter (in the current subsection) to a particular
5408 storage boundary. The first expression (which must be absolute) is the
5409 number of low-order zero bits the location counter must have after
5410 advancement. For example @samp{.p2align 3} advances the location
5411 counter until it a multiple of 8. If the location counter is already a
5412 multiple of 8, no change is needed.
5414 The second expression (also absolute) gives the fill value to be stored in the
5415 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5416 padding bytes are normally zero. However, on some systems, if the section is
5417 marked as containing code and the fill value is omitted, the space is filled
5418 with no-op instructions.
5420 The third expression is also absolute, and is also optional. If it is present,
5421 it is the maximum number of bytes that should be skipped by this alignment
5422 directive. If doing the alignment would require skipping more bytes than the
5423 specified maximum, then the alignment is not done at all. You can omit the
5424 fill value (the second argument) entirely by simply using two commas after the
5425 required alignment; this can be useful if you want the alignment to be filled
5426 with no-op instructions when appropriate.
5428 @cindex @code{p2alignw} directive
5429 @cindex @code{p2alignl} directive
5430 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5431 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5432 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5433 fill pattern as a four byte longword value. For example, @code{.p2alignw
5434 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5435 filled in with the value 0x368d (the exact placement of the bytes depends upon
5436 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5441 @section @code{.popsection}
5443 @cindex @code{popsection} directive
5444 @cindex Section Stack
5445 This is one of the ELF section stack manipulation directives. The others are
5446 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5447 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5450 This directive replaces the current section (and subsection) with the top
5451 section (and subsection) on the section stack. This section is popped off the
5457 @section @code{.previous}
5459 @cindex @code{previous} directive
5460 @cindex Section Stack
5461 This is one of the ELF section stack manipulation directives. The others are
5462 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5463 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5464 (@pxref{PopSection}).
5466 This directive swaps the current section (and subsection) with most recently
5467 referenced section/subsection pair prior to this one. Multiple
5468 @code{.previous} directives in a row will flip between two sections (and their
5469 subsections). For example:
5481 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5487 # Now in section A subsection 1
5491 # Now in section B subsection 0
5494 # Now in section B subsection 1
5497 # Now in section B subsection 0
5501 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5502 section B and 0x9abc into subsection 1 of section B.
5504 In terms of the section stack, this directive swaps the current section with
5505 the top section on the section stack.
5509 @section @code{.print @var{string}}
5511 @cindex @code{print} directive
5512 @command{@value{AS}} will print @var{string} on the standard output during
5513 assembly. You must put @var{string} in double quotes.
5517 @section @code{.protected @var{names}}
5519 @cindex @code{protected} directive
5521 This is one of the ELF visibility directives. The other two are
5522 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5524 This directive overrides the named symbols default visibility (which is set by
5525 their binding: local, global or weak). The directive sets the visibility to
5526 @code{protected} which means that any references to the symbols from within the
5527 components that defines them must be resolved to the definition in that
5528 component, even if a definition in another component would normally preempt
5533 @section @code{.psize @var{lines} , @var{columns}}
5535 @cindex @code{psize} directive
5536 @cindex listing control: paper size
5537 @cindex paper size, for listings
5538 Use this directive to declare the number of lines---and, optionally, the
5539 number of columns---to use for each page, when generating listings.
5541 If you do not use @code{.psize}, listings use a default line-count
5542 of 60. You may omit the comma and @var{columns} specification; the
5543 default width is 200 columns.
5545 @command{@value{AS}} generates formfeeds whenever the specified number of
5546 lines is exceeded (or whenever you explicitly request one, using
5549 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5550 those explicitly specified with @code{.eject}.
5553 @section @code{.purgem @var{name}}
5555 @cindex @code{purgem} directive
5556 Undefine the macro @var{name}, so that later uses of the string will not be
5557 expanded. @xref{Macro}.
5561 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5563 @cindex @code{pushsection} directive
5564 @cindex Section Stack
5565 This is one of the ELF section stack manipulation directives. The others are
5566 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5567 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5570 This directive pushes the current section (and subsection) onto the
5571 top of the section stack, and then replaces the current section and
5572 subsection with @code{name} and @code{subsection}. The optional
5573 @code{flags}, @code{type} and @code{arguments} are treated the same
5574 as in the @code{.section} (@pxref{Section}) directive.
5578 @section @code{.quad @var{bignums}}
5580 @cindex @code{quad} directive
5581 @code{.quad} expects zero or more bignums, separated by commas. For
5582 each bignum, it emits
5584 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5585 warning message; and just takes the lowest order 8 bytes of the bignum.
5586 @cindex eight-byte integer
5587 @cindex integer, 8-byte
5589 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5590 hence @emph{quad}-word for 8 bytes.
5593 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5594 warning message; and just takes the lowest order 16 bytes of the bignum.
5595 @cindex sixteen-byte integer
5596 @cindex integer, 16-byte
5600 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5602 @cindex @code{reloc} directive
5603 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5604 @var{expression}. If @var{offset} is a number, the relocation is generated in
5605 the current section. If @var{offset} is an expression that resolves to a
5606 symbol plus offset, the relocation is generated in the given symbol's section.
5607 @var{expression}, if present, must resolve to a symbol plus addend or to an
5608 absolute value, but note that not all targets support an addend. e.g. ELF REL
5609 targets such as i386 store an addend in the section contents rather than in the
5610 relocation. This low level interface does not support addends stored in the
5614 @section @code{.rept @var{count}}
5616 @cindex @code{rept} directive
5617 Repeat the sequence of lines between the @code{.rept} directive and the next
5618 @code{.endr} directive @var{count} times.
5620 For example, assembling
5628 is equivalent to assembling
5637 @section @code{.sbttl "@var{subheading}"}
5639 @cindex @code{sbttl} directive
5640 @cindex subtitles for listings
5641 @cindex listing control: subtitle
5642 Use @var{subheading} as the title (third line, immediately after the
5643 title line) when generating assembly listings.
5645 This directive affects subsequent pages, as well as the current page if
5646 it appears within ten lines of the top of a page.
5650 @section @code{.scl @var{class}}
5652 @cindex @code{scl} directive
5653 @cindex symbol storage class (COFF)
5654 @cindex COFF symbol storage class
5655 Set the storage-class value for a symbol. This directive may only be
5656 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5657 whether a symbol is static or external, or it may record further
5658 symbolic debugging information.
5661 The @samp{.scl} directive is primarily associated with COFF output; when
5662 configured to generate @code{b.out} output format, @command{@value{AS}}
5663 accepts this directive but ignores it.
5669 @section @code{.section @var{name}}
5671 @cindex named section
5672 Use the @code{.section} directive to assemble the following code into a section
5675 This directive is only supported for targets that actually support arbitrarily
5676 named sections; on @code{a.out} targets, for example, it is not accepted, even
5677 with a standard @code{a.out} section name.
5681 @c only print the extra heading if both COFF and ELF are set
5682 @subheading COFF Version
5685 @cindex @code{section} directive (COFF version)
5686 For COFF targets, the @code{.section} directive is used in one of the following
5690 .section @var{name}[, "@var{flags}"]
5691 .section @var{name}[, @var{subsection}]
5694 If the optional argument is quoted, it is taken as flags to use for the
5695 section. Each flag is a single character. The following flags are recognized:
5698 bss section (uninitialized data)
5700 section is not loaded
5710 shared section (meaningful for PE targets)
5712 ignored. (For compatibility with the ELF version)
5715 If no flags are specified, the default flags depend upon the section name. If
5716 the section name is not recognized, the default will be for the section to be
5717 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5718 from the section, rather than adding them, so if they are used on their own it
5719 will be as if no flags had been specified at all.
5721 If the optional argument to the @code{.section} directive is not quoted, it is
5722 taken as a subsection number (@pxref{Sub-Sections}).
5727 @c only print the extra heading if both COFF and ELF are set
5728 @subheading ELF Version
5731 @cindex Section Stack
5732 This is one of the ELF section stack manipulation directives. The others are
5733 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5734 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5735 @code{.previous} (@pxref{Previous}).
5737 @cindex @code{section} directive (ELF version)
5738 For ELF targets, the @code{.section} directive is used like this:
5741 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
5744 The optional @var{flags} argument is a quoted string which may contain any
5745 combination of the following characters:
5748 section is allocatable
5752 section is executable
5754 section is mergeable
5756 section contains zero terminated strings
5758 section is a member of a section group
5760 section is used for thread-local-storage
5763 The optional @var{type} argument may contain one of the following constants:
5766 section contains data
5768 section does not contain data (i.e., section only occupies space)
5770 section contains data which is used by things other than the program
5772 section contains an array of pointers to init functions
5774 section contains an array of pointers to finish functions
5775 @item @@preinit_array
5776 section contains an array of pointers to pre-init functions
5779 Many targets only support the first three section types.
5781 Note on targets where the @code{@@} character is the start of a comment (eg
5782 ARM) then another character is used instead. For example the ARM port uses the
5785 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
5786 be specified as well as an extra argument---@var{entsize}---like this:
5789 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
5792 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
5793 constants, each @var{entsize} octets long. Sections with both @code{M} and
5794 @code{S} must contain zero terminated strings where each character is
5795 @var{entsize} bytes long. The linker may remove duplicates within sections with
5796 the same name, same entity size and same flags. @var{entsize} must be an
5797 absolute expression.
5799 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
5800 be present along with an additional field like this:
5803 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
5806 The @var{GroupName} field specifies the name of the section group to which this
5807 particular section belongs. The optional linkage field can contain:
5810 indicates that only one copy of this section should be retained
5815 Note: if both the @var{M} and @var{G} flags are present then the fields for
5816 the Merge flag should come first, like this:
5819 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
5822 If no flags are specified, the default flags depend upon the section name. If
5823 the section name is not recognized, the default will be for the section to have
5824 none of the above flags: it will not be allocated in memory, nor writable, nor
5825 executable. The section will contain data.
5827 For ELF targets, the assembler supports another type of @code{.section}
5828 directive for compatibility with the Solaris assembler:
5831 .section "@var{name}"[, @var{flags}...]
5834 Note that the section name is quoted. There may be a sequence of comma
5838 section is allocatable
5842 section is executable
5844 section is used for thread local storage
5847 This directive replaces the current section and subsection. See the
5848 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
5849 some examples of how this directive and the other section stack directives
5855 @section @code{.set @var{symbol}, @var{expression}}
5857 @cindex @code{set} directive
5858 @cindex symbol value, setting
5859 Set the value of @var{symbol} to @var{expression}. This
5860 changes @var{symbol}'s value and type to conform to
5861 @var{expression}. If @var{symbol} was flagged as external, it remains
5862 flagged (@pxref{Symbol Attributes}).
5864 You may @code{.set} a symbol many times in the same assembly.
5866 If you @code{.set} a global symbol, the value stored in the object
5867 file is the last value stored into it.
5870 The syntax for @code{set} on the HPPA is
5871 @samp{@var{symbol} .set @var{expression}}.
5875 On Z80 @code{set} is a real instruction, use
5876 @samp{@var{symbol} defl @var{expression}} instead.
5880 @section @code{.short @var{expressions}}
5882 @cindex @code{short} directive
5884 @code{.short} is normally the same as @samp{.word}.
5885 @xref{Word,,@code{.word}}.
5887 In some configurations, however, @code{.short} and @code{.word} generate
5888 numbers of different lengths. @xref{Machine Dependencies}.
5892 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
5895 This expects zero or more @var{expressions}, and emits
5896 a 16 bit number for each.
5901 @section @code{.single @var{flonums}}
5903 @cindex @code{single} directive
5904 @cindex floating point numbers (single)
5905 This directive assembles zero or more flonums, separated by commas. It
5906 has the same effect as @code{.float}.
5908 The exact kind of floating point numbers emitted depends on how
5909 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5913 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
5914 numbers in @sc{ieee} format.
5920 @section @code{.size}
5922 This directive is used to set the size associated with a symbol.
5926 @c only print the extra heading if both COFF and ELF are set
5927 @subheading COFF Version
5930 @cindex @code{size} directive (COFF version)
5931 For COFF targets, the @code{.size} directive is only permitted inside
5932 @code{.def}/@code{.endef} pairs. It is used like this:
5935 .size @var{expression}
5939 @samp{.size} is only meaningful when generating COFF format output; when
5940 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5947 @c only print the extra heading if both COFF and ELF are set
5948 @subheading ELF Version
5951 @cindex @code{size} directive (ELF version)
5952 For ELF targets, the @code{.size} directive is used like this:
5955 .size @var{name} , @var{expression}
5958 This directive sets the size associated with a symbol @var{name}.
5959 The size in bytes is computed from @var{expression} which can make use of label
5960 arithmetic. This directive is typically used to set the size of function
5965 @ifclear no-space-dir
5967 @section @code{.skip @var{size} , @var{fill}}
5969 @cindex @code{skip} directive
5970 @cindex filling memory
5971 This directive emits @var{size} bytes, each of value @var{fill}. Both
5972 @var{size} and @var{fill} are absolute expressions. If the comma and
5973 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
5978 @section @code{.sleb128 @var{expressions}}
5980 @cindex @code{sleb128} directive
5981 @var{sleb128} stands for ``signed little endian base 128.'' This is a
5982 compact, variable length representation of numbers used by the DWARF
5983 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
5985 @ifclear no-space-dir
5987 @section @code{.space @var{size} , @var{fill}}
5989 @cindex @code{space} directive
5990 @cindex filling memory
5991 This directive emits @var{size} bytes, each of value @var{fill}. Both
5992 @var{size} and @var{fill} are absolute expressions. If the comma
5993 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
5998 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
5999 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6000 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6001 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6009 @section @code{.stabd, .stabn, .stabs}
6011 @cindex symbolic debuggers, information for
6012 @cindex @code{stab@var{x}} directives
6013 There are three directives that begin @samp{.stab}.
6014 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6015 The symbols are not entered in the @command{@value{AS}} hash table: they
6016 cannot be referenced elsewhere in the source file.
6017 Up to five fields are required:
6021 This is the symbol's name. It may contain any character except
6022 @samp{\000}, so is more general than ordinary symbol names. Some
6023 debuggers used to code arbitrarily complex structures into symbol names
6027 An absolute expression. The symbol's type is set to the low 8 bits of
6028 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6029 and debuggers choke on silly bit patterns.
6032 An absolute expression. The symbol's ``other'' attribute is set to the
6033 low 8 bits of this expression.
6036 An absolute expression. The symbol's descriptor is set to the low 16
6037 bits of this expression.
6040 An absolute expression which becomes the symbol's value.
6043 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6044 or @code{.stabs} statement, the symbol has probably already been created;
6045 you get a half-formed symbol in your object file. This is
6046 compatible with earlier assemblers!
6049 @cindex @code{stabd} directive
6050 @item .stabd @var{type} , @var{other} , @var{desc}
6052 The ``name'' of the symbol generated is not even an empty string.
6053 It is a null pointer, for compatibility. Older assemblers used a
6054 null pointer so they didn't waste space in object files with empty
6057 The symbol's value is set to the location counter,
6058 relocatably. When your program is linked, the value of this symbol
6059 is the address of the location counter when the @code{.stabd} was
6062 @cindex @code{stabn} directive
6063 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6064 The name of the symbol is set to the empty string @code{""}.
6066 @cindex @code{stabs} directive
6067 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6068 All five fields are specified.
6074 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6075 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6077 @cindex string, copying to object file
6078 @cindex string8, copying to object file
6079 @cindex string16, copying to object file
6080 @cindex string32, copying to object file
6081 @cindex string64, copying to object file
6082 @cindex @code{string} directive
6083 @cindex @code{string8} directive
6084 @cindex @code{string16} directive
6085 @cindex @code{string32} directive
6086 @cindex @code{string64} directive
6088 Copy the characters in @var{str} to the object file. You may specify more than
6089 one string to copy, separated by commas. Unless otherwise specified for a
6090 particular machine, the assembler marks the end of each string with a 0 byte.
6091 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6093 The variants @code{string16}, @code{string32} and @code{string64} differ from
6094 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6095 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6096 are stored in target endianness byte order.
6102 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6103 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6108 @section @code{.struct @var{expression}}
6110 @cindex @code{struct} directive
6111 Switch to the absolute section, and set the section offset to @var{expression},
6112 which must be an absolute expression. You might use this as follows:
6121 This would define the symbol @code{field1} to have the value 0, the symbol
6122 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6123 value 8. Assembly would be left in the absolute section, and you would need to
6124 use a @code{.section} directive of some sort to change to some other section
6125 before further assembly.
6129 @section @code{.subsection @var{name}}
6131 @cindex @code{subsection} directive
6132 @cindex Section Stack
6133 This is one of the ELF section stack manipulation directives. The others are
6134 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6135 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6138 This directive replaces the current subsection with @code{name}. The current
6139 section is not changed. The replaced subsection is put onto the section stack
6140 in place of the then current top of stack subsection.
6145 @section @code{.symver}
6146 @cindex @code{symver} directive
6147 @cindex symbol versioning
6148 @cindex versions of symbols
6149 Use the @code{.symver} directive to bind symbols to specific version nodes
6150 within a source file. This is only supported on ELF platforms, and is
6151 typically used when assembling files to be linked into a shared library.
6152 There are cases where it may make sense to use this in objects to be bound
6153 into an application itself so as to override a versioned symbol from a
6156 For ELF targets, the @code{.symver} directive can be used like this:
6158 .symver @var{name}, @var{name2@@nodename}
6160 If the symbol @var{name} is defined within the file
6161 being assembled, the @code{.symver} directive effectively creates a symbol
6162 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6163 just don't try and create a regular alias is that the @var{@@} character isn't
6164 permitted in symbol names. The @var{name2} part of the name is the actual name
6165 of the symbol by which it will be externally referenced. The name @var{name}
6166 itself is merely a name of convenience that is used so that it is possible to
6167 have definitions for multiple versions of a function within a single source
6168 file, and so that the compiler can unambiguously know which version of a
6169 function is being mentioned. The @var{nodename} portion of the alias should be
6170 the name of a node specified in the version script supplied to the linker when
6171 building a shared library. If you are attempting to override a versioned
6172 symbol from a shared library, then @var{nodename} should correspond to the
6173 nodename of the symbol you are trying to override.
6175 If the symbol @var{name} is not defined within the file being assembled, all
6176 references to @var{name} will be changed to @var{name2@@nodename}. If no
6177 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6180 Another usage of the @code{.symver} directive is:
6182 .symver @var{name}, @var{name2@@@@nodename}
6184 In this case, the symbol @var{name} must exist and be defined within
6185 the file being assembled. It is similar to @var{name2@@nodename}. The
6186 difference is @var{name2@@@@nodename} will also be used to resolve
6187 references to @var{name2} by the linker.
6189 The third usage of the @code{.symver} directive is:
6191 .symver @var{name}, @var{name2@@@@@@nodename}
6193 When @var{name} is not defined within the
6194 file being assembled, it is treated as @var{name2@@nodename}. When
6195 @var{name} is defined within the file being assembled, the symbol
6196 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6201 @section @code{.tag @var{structname}}
6203 @cindex COFF structure debugging
6204 @cindex structure debugging, COFF
6205 @cindex @code{tag} directive
6206 This directive is generated by compilers to include auxiliary debugging
6207 information in the symbol table. It is only permitted inside
6208 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6209 definitions in the symbol table with instances of those structures.
6212 @samp{.tag} is only used when generating COFF format output; when
6213 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6219 @section @code{.text @var{subsection}}
6221 @cindex @code{text} directive
6222 Tells @command{@value{AS}} to assemble the following statements onto the end of
6223 the text subsection numbered @var{subsection}, which is an absolute
6224 expression. If @var{subsection} is omitted, subsection number zero
6228 @section @code{.title "@var{heading}"}
6230 @cindex @code{title} directive
6231 @cindex listing control: title line
6232 Use @var{heading} as the title (second line, immediately after the
6233 source file name and pagenumber) when generating assembly listings.
6235 This directive affects subsequent pages, as well as the current page if
6236 it appears within ten lines of the top of a page.
6240 @section @code{.type}
6242 This directive is used to set the type of a symbol.
6246 @c only print the extra heading if both COFF and ELF are set
6247 @subheading COFF Version
6250 @cindex COFF symbol type
6251 @cindex symbol type, COFF
6252 @cindex @code{type} directive (COFF version)
6253 For COFF targets, this directive is permitted only within
6254 @code{.def}/@code{.endef} pairs. It is used like this:
6260 This records the integer @var{int} as the type attribute of a symbol table
6264 @samp{.type} is associated only with COFF format output; when
6265 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6266 directive but ignores it.
6272 @c only print the extra heading if both COFF and ELF are set
6273 @subheading ELF Version
6276 @cindex ELF symbol type
6277 @cindex symbol type, ELF
6278 @cindex @code{type} directive (ELF version)
6279 For ELF targets, the @code{.type} directive is used like this:
6282 .type @var{name} , @var{type description}
6285 This sets the type of symbol @var{name} to be either a
6286 function symbol or an object symbol. There are five different syntaxes
6287 supported for the @var{type description} field, in order to provide
6288 compatibility with various other assemblers.
6290 Because some of the characters used in these syntaxes (such as @samp{@@} and
6291 @samp{#}) are comment characters for some architectures, some of the syntaxes
6292 below do not work on all architectures. The first variant will be accepted by
6293 the GNU assembler on all architectures so that variant should be used for
6294 maximum portability, if you do not need to assemble your code with other
6297 The syntaxes supported are:
6300 .type <name> STT_<TYPE_IN_UPPER_CASE>
6301 .type <name>,#<type>
6302 .type <name>,@@<type>
6303 .type <name>,%<type>
6304 .type <name>,"<type>"
6307 The types supported are:
6312 Mark the symbol as being a function name.
6316 Mark the symbol as being a data object.
6320 Mark the symbol as being a thead-local data object.
6324 Mark the symbol as being a common data object.
6328 Does not mark the symbol in any way. It is supported just for completeness.
6332 Note: Some targets support extra types in addition to those listed above.
6338 @section @code{.uleb128 @var{expressions}}
6340 @cindex @code{uleb128} directive
6341 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6342 compact, variable length representation of numbers used by the DWARF
6343 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6347 @section @code{.val @var{addr}}
6349 @cindex @code{val} directive
6350 @cindex COFF value attribute
6351 @cindex value attribute, COFF
6352 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6353 records the address @var{addr} as the value attribute of a symbol table
6357 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6358 configured for @code{b.out}, it accepts this directive but ignores it.
6364 @section @code{.version "@var{string}"}
6366 @cindex @code{version} directive
6367 This directive creates a @code{.note} section and places into it an ELF
6368 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6373 @section @code{.vtable_entry @var{table}, @var{offset}}
6375 @cindex @code{vtable_entry} directive
6376 This directive finds or creates a symbol @code{table} and creates a
6377 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6380 @section @code{.vtable_inherit @var{child}, @var{parent}}
6382 @cindex @code{vtable_inherit} directive
6383 This directive finds the symbol @code{child} and finds or creates the symbol
6384 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6385 parent whose addend is the value of the child symbol. As a special case the
6386 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6390 @section @code{.warning "@var{string}"}
6391 @cindex warning directive
6392 Similar to the directive @code{.error}
6393 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6396 @section @code{.weak @var{names}}
6398 @cindex @code{weak} directive
6399 This directive sets the weak attribute on the comma separated list of symbol
6400 @code{names}. If the symbols do not already exist, they will be created.
6402 On COFF targets other than PE, weak symbols are a GNU extension. This
6403 directive sets the weak attribute on the comma separated list of symbol
6404 @code{names}. If the symbols do not already exist, they will be created.
6406 On the PE target, weak symbols are supported natively as weak aliases.
6407 When a weak symbol is created that is not an alias, GAS creates an
6408 alternate symbol to hold the default value.
6411 @section @code{.weakref @var{alias}, @var{target}}
6413 @cindex @code{weakref} directive
6414 This directive creates an alias to the target symbol that enables the symbol to
6415 be referenced with weak-symbol semantics, but without actually making it weak.
6416 If direct references or definitions of the symbol are present, then the symbol
6417 will not be weak, but if all references to it are through weak references, the
6418 symbol will be marked as weak in the symbol table.
6420 The effect is equivalent to moving all references to the alias to a separate
6421 assembly source file, renaming the alias to the symbol in it, declaring the
6422 symbol as weak there, and running a reloadable link to merge the object files
6423 resulting from the assembly of the new source file and the old source file that
6424 had the references to the alias removed.
6426 The alias itself never makes to the symbol table, and is entirely handled
6427 within the assembler.
6430 @section @code{.word @var{expressions}}
6432 @cindex @code{word} directive
6433 This directive expects zero or more @var{expressions}, of any section,
6434 separated by commas.
6437 For each expression, @command{@value{AS}} emits a 32-bit number.
6440 For each expression, @command{@value{AS}} emits a 16-bit number.
6445 The size of the number emitted, and its byte order,
6446 depend on what target computer the assembly is for.
6449 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6450 @c happen---32-bit addressability, period; no long/short jumps.
6451 @ifset DIFF-TBL-KLUGE
6452 @cindex difference tables altered
6453 @cindex altered difference tables
6455 @emph{Warning: Special Treatment to support Compilers}
6459 Machines with a 32-bit address space, but that do less than 32-bit
6460 addressing, require the following special treatment. If the machine of
6461 interest to you does 32-bit addressing (or doesn't require it;
6462 @pxref{Machine Dependencies}), you can ignore this issue.
6465 In order to assemble compiler output into something that works,
6466 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6467 Directives of the form @samp{.word sym1-sym2} are often emitted by
6468 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6469 directive of the form @samp{.word sym1-sym2}, and the difference between
6470 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6471 creates a @dfn{secondary jump table}, immediately before the next label.
6472 This secondary jump table is preceded by a short-jump to the
6473 first byte after the secondary table. This short-jump prevents the flow
6474 of control from accidentally falling into the new table. Inside the
6475 table is a long-jump to @code{sym2}. The original @samp{.word}
6476 contains @code{sym1} minus the address of the long-jump to
6479 If there were several occurrences of @samp{.word sym1-sym2} before the
6480 secondary jump table, all of them are adjusted. If there was a
6481 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6482 long-jump to @code{sym4} is included in the secondary jump table,
6483 and the @code{.word} directives are adjusted to contain @code{sym3}
6484 minus the address of the long-jump to @code{sym4}; and so on, for as many
6485 entries in the original jump table as necessary.
6488 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6489 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6490 assembly language programmers.
6493 @c end DIFF-TBL-KLUGE
6496 @section Deprecated Directives
6498 @cindex deprecated directives
6499 @cindex obsolescent directives
6500 One day these directives won't work.
6501 They are included for compatibility with older assemblers.
6508 @node Object Attributes
6509 @chapter Object Attributes
6510 @cindex object attributes
6512 @command{@value{AS}} assembles source files written for a specific architecture
6513 into object files for that architecture. But not all object files are alike.
6514 Many architectures support incompatible variations. For instance, floating
6515 point arguments might be passed in floating point registers if the object file
6516 requires hardware floating point support---or floating point arguments might be
6517 passed in integer registers if the object file supports processors with no
6518 hardware floating point unit. Or, if two objects are built for different
6519 generations of the same architecture, the combination may require the
6520 newer generation at run-time.
6522 This information is useful during and after linking. At link time,
6523 @command{@value{LD}} can warn about incompatible object files. After link
6524 time, tools like @command{gdb} can use it to process the linked file
6527 Compatibility information is recorded as a series of object attributes. Each
6528 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6529 string, and indicates who sets the meaning of the tag. The tag is an integer,
6530 and indicates what property the attribute describes. The value may be a string
6531 or an integer, and indicates how the property affects this object. Missing
6532 attributes are the same as attributes with a zero value or empty string value.
6534 Object attributes were developed as part of the ABI for the ARM Architecture.
6535 The file format is documented in @cite{ELF for the ARM Architecture}.
6538 * GNU Object Attributes:: @sc{gnu} Object Attributes
6539 * Defining New Object Attributes:: Defining New Object Attributes
6542 @node GNU Object Attributes
6543 @section @sc{gnu} Object Attributes
6545 The @code{.gnu_attribute} directive records an object attribute
6546 with vendor @samp{gnu}.
6548 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6549 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6550 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6551 2} is set for architecture-independent attributes and clear for
6552 architecture-dependent ones.
6554 @subsection Common @sc{gnu} attributes
6556 These attributes are valid on all architectures.
6559 @item Tag_compatibility (32)
6560 The compatibility attribute takes an integer flag value and a vendor name. If
6561 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6562 then the file is only compatible with the named toolchain. If it is greater
6563 than 1, the file can only be processed by other toolchains under some private
6564 arrangement indicated by the flag value and the vendor name.
6567 @subsection MIPS Attributes
6570 @item Tag_GNU_MIPS_ABI_FP (4)
6571 The floating-point ABI used by this object file. The value will be:
6575 0 for files not affected by the floating-point ABI.
6577 1 for files using the hardware floating-point with a standard double-precision
6580 2 for files using the hardware floating-point ABI with a single-precision FPU.
6582 3 for files using the software floating-point ABI.
6584 4 for files using the hardware floating-point ABI with 64-bit wide
6585 double-precision floating-point registers and 32-bit wide general
6590 @subsection PowerPC Attributes
6593 @item Tag_GNU_Power_ABI_FP (4)
6594 The floating-point ABI used by this object file. The value will be:
6598 0 for files not affected by the floating-point ABI.
6600 1 for files using double-precision hardware floating-point ABI.
6602 2 for files using the software floating-point ABI.
6604 3 for files using single-precision hardware floating-point ABI.
6607 @item Tag_GNU_Power_ABI_Vector (8)
6608 The vector ABI used by this object file. The value will be:
6612 0 for files not affected by the vector ABI.
6614 1 for files using general purpose registers to pass vectors.
6616 2 for files using AltiVec registers to pass vectors.
6618 3 for files using SPE registers to pass vectors.
6622 @node Defining New Object Attributes
6623 @section Defining New Object Attributes
6625 If you want to define a new @sc{gnu} object attribute, here are the places you
6626 will need to modify. New attributes should be discussed on the @samp{binutils}
6631 This manual, which is the official register of attributes.
6633 The header for your architecture @file{include/elf}, to define the tag.
6635 The @file{bfd} support file for your architecture, to merge the attribute
6636 and issue any appropriate link warnings.
6638 Test cases in @file{ld/testsuite} for merging and link warnings.
6640 @file{binutils/readelf.c} to display your attribute.
6642 GCC, if you want the compiler to mark the attribute automatically.
6648 @node Machine Dependencies
6649 @chapter Machine Dependent Features
6651 @cindex machine dependencies
6652 The machine instruction sets are (almost by definition) different on
6653 each machine where @command{@value{AS}} runs. Floating point representations
6654 vary as well, and @command{@value{AS}} often supports a few additional
6655 directives or command-line options for compatibility with other
6656 assemblers on a particular platform. Finally, some versions of
6657 @command{@value{AS}} support special pseudo-instructions for branch
6660 This chapter discusses most of these differences, though it does not
6661 include details on any machine's instruction set. For details on that
6662 subject, see the hardware manufacturer's manual.
6666 * Alpha-Dependent:: Alpha Dependent Features
6669 * ARC-Dependent:: ARC Dependent Features
6672 * ARM-Dependent:: ARM Dependent Features
6675 * AVR-Dependent:: AVR Dependent Features
6678 * BFIN-Dependent:: BFIN Dependent Features
6681 * CR16-Dependent:: CR16 Dependent Features
6684 * CRIS-Dependent:: CRIS Dependent Features
6687 * D10V-Dependent:: D10V Dependent Features
6690 * D30V-Dependent:: D30V Dependent Features
6693 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6696 * HPPA-Dependent:: HPPA Dependent Features
6699 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6702 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6705 * i860-Dependent:: Intel 80860 Dependent Features
6708 * i960-Dependent:: Intel 80960 Dependent Features
6711 * IA-64-Dependent:: Intel IA-64 Dependent Features
6714 * IP2K-Dependent:: IP2K Dependent Features
6717 * LM32-Dependent:: LM32 Dependent Features
6720 * M32C-Dependent:: M32C Dependent Features
6723 * M32R-Dependent:: M32R Dependent Features
6726 * M68K-Dependent:: M680x0 Dependent Features
6729 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
6732 * MIPS-Dependent:: MIPS Dependent Features
6735 * MMIX-Dependent:: MMIX Dependent Features
6738 * MSP430-Dependent:: MSP430 Dependent Features
6741 * SH-Dependent:: Renesas / SuperH SH Dependent Features
6742 * SH64-Dependent:: SuperH SH64 Dependent Features
6745 * PDP-11-Dependent:: PDP-11 Dependent Features
6748 * PJ-Dependent:: picoJava Dependent Features
6751 * PPC-Dependent:: PowerPC Dependent Features
6754 * S/390-Dependent:: IBM S/390 Dependent Features
6757 * Sparc-Dependent:: SPARC Dependent Features
6760 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
6763 * V850-Dependent:: V850 Dependent Features
6766 * Xtensa-Dependent:: Xtensa Dependent Features
6769 * Z80-Dependent:: Z80 Dependent Features
6772 * Z8000-Dependent:: Z8000 Dependent Features
6775 * Vax-Dependent:: VAX Dependent Features
6782 @c The following major nodes are *sections* in the GENERIC version, *chapters*
6783 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
6784 @c peculiarity: to preserve cross-references, there must be a node called
6785 @c "Machine Dependencies". Hence the conditional nodenames in each
6786 @c major node below. Node defaulting in makeinfo requires adjacency of
6787 @c node and sectioning commands; hence the repetition of @chapter BLAH
6788 @c in both conditional blocks.
6791 @include c-alpha.texi
6807 @include c-bfin.texi
6811 @include c-cr16.texi
6815 @include c-cris.texi
6820 @node Machine Dependencies
6821 @chapter Machine Dependent Features
6823 The machine instruction sets are different on each Renesas chip family,
6824 and there are also some syntax differences among the families. This
6825 chapter describes the specific @command{@value{AS}} features for each
6829 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6830 * SH-Dependent:: Renesas SH Dependent Features
6837 @include c-d10v.texi
6841 @include c-d30v.texi
6845 @include c-h8300.texi
6849 @include c-hppa.texi
6853 @include c-i370.texi
6857 @include c-i386.texi
6861 @include c-i860.texi
6865 @include c-i960.texi
6869 @include c-ia64.texi
6873 @include c-ip2k.texi
6877 @include c-lm32.texi
6881 @include c-m32c.texi
6885 @include c-m32r.texi
6889 @include c-m68k.texi
6893 @include c-m68hc11.texi
6897 @include c-mips.texi
6901 @include c-mmix.texi
6905 @include c-msp430.texi
6909 @include c-ns32k.texi
6913 @include c-pdp11.texi
6925 @include c-s390.texi
6930 @include c-sh64.texi
6934 @include c-sparc.texi
6938 @include c-tic54x.texi
6954 @include c-v850.texi
6958 @include c-xtensa.texi
6962 @c reverse effect of @down at top of generic Machine-Dep chapter
6966 @node Reporting Bugs
6967 @chapter Reporting Bugs
6968 @cindex bugs in assembler
6969 @cindex reporting bugs in assembler
6971 Your bug reports play an essential role in making @command{@value{AS}} reliable.
6973 Reporting a bug may help you by bringing a solution to your problem, or it may
6974 not. But in any case the principal function of a bug report is to help the
6975 entire community by making the next version of @command{@value{AS}} work better.
6976 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
6978 In order for a bug report to serve its purpose, you must include the
6979 information that enables us to fix the bug.
6982 * Bug Criteria:: Have you found a bug?
6983 * Bug Reporting:: How to report bugs
6987 @section Have You Found a Bug?
6988 @cindex bug criteria
6990 If you are not sure whether you have found a bug, here are some guidelines:
6993 @cindex fatal signal
6994 @cindex assembler crash
6995 @cindex crash of assembler
6997 If the assembler gets a fatal signal, for any input whatever, that is a
6998 @command{@value{AS}} bug. Reliable assemblers never crash.
7000 @cindex error on valid input
7002 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7004 @cindex invalid input
7006 If @command{@value{AS}} does not produce an error message for invalid input, that
7007 is a bug. However, you should note that your idea of ``invalid input'' might
7008 be our idea of ``an extension'' or ``support for traditional practice''.
7011 If you are an experienced user of assemblers, your suggestions for improvement
7012 of @command{@value{AS}} are welcome in any case.
7016 @section How to Report Bugs
7018 @cindex assembler bugs, reporting
7020 A number of companies and individuals offer support for @sc{gnu} products. If
7021 you obtained @command{@value{AS}} from a support organization, we recommend you
7022 contact that organization first.
7024 You can find contact information for many support companies and
7025 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7029 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7033 The fundamental principle of reporting bugs usefully is this:
7034 @strong{report all the facts}. If you are not sure whether to state a
7035 fact or leave it out, state it!
7037 Often people omit facts because they think they know what causes the problem
7038 and assume that some details do not matter. Thus, you might assume that the
7039 name of a symbol you use in an example does not matter. Well, probably it does
7040 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7041 happens to fetch from the location where that name is stored in memory;
7042 perhaps, if the name were different, the contents of that location would fool
7043 the assembler into doing the right thing despite the bug. Play it safe and
7044 give a specific, complete example. That is the easiest thing for you to do,
7045 and the most helpful.
7047 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7048 it is new to us. Therefore, always write your bug reports on the assumption
7049 that the bug has not been reported previously.
7051 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7052 bell?'' This cannot help us fix a bug, so it is basically useless. We
7053 respond by asking for enough details to enable us to investigate.
7054 You might as well expedite matters by sending them to begin with.
7056 To enable us to fix the bug, you should include all these things:
7060 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7061 it with the @samp{--version} argument.
7063 Without this, we will not know whether there is any point in looking for
7064 the bug in the current version of @command{@value{AS}}.
7067 Any patches you may have applied to the @command{@value{AS}} source.
7070 The type of machine you are using, and the operating system name and
7074 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7078 The command arguments you gave the assembler to assemble your example and
7079 observe the bug. To guarantee you will not omit something important, list them
7080 all. A copy of the Makefile (or the output from make) is sufficient.
7082 If we were to try to guess the arguments, we would probably guess wrong
7083 and then we might not encounter the bug.
7086 A complete input file that will reproduce the bug. If the bug is observed when
7087 the assembler is invoked via a compiler, send the assembler source, not the
7088 high level language source. Most compilers will produce the assembler source
7089 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7090 the options @samp{-v --save-temps}; this will save the assembler source in a
7091 file with an extension of @file{.s}, and also show you exactly how
7092 @command{@value{AS}} is being run.
7095 A description of what behavior you observe that you believe is
7096 incorrect. For example, ``It gets a fatal signal.''
7098 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7099 will certainly notice it. But if the bug is incorrect output, we might not
7100 notice unless it is glaringly wrong. You might as well not give us a chance to
7103 Even if the problem you experience is a fatal signal, you should still say so
7104 explicitly. Suppose something strange is going on, such as, your copy of
7105 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7106 library on your system. (This has happened!) Your copy might crash and ours
7107 would not. If you told us to expect a crash, then when ours fails to crash, we
7108 would know that the bug was not happening for us. If you had not told us to
7109 expect a crash, then we would not be able to draw any conclusion from our
7113 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7114 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7115 option. Always send diffs from the old file to the new file. If you even
7116 discuss something in the @command{@value{AS}} source, refer to it by context, not
7119 The line numbers in our development sources will not match those in your
7120 sources. Your line numbers would convey no useful information to us.
7123 Here are some things that are not necessary:
7127 A description of the envelope of the bug.
7129 Often people who encounter a bug spend a lot of time investigating
7130 which changes to the input file will make the bug go away and which
7131 changes will not affect it.
7133 This is often time consuming and not very useful, because the way we
7134 will find the bug is by running a single example under the debugger
7135 with breakpoints, not by pure deduction from a series of examples.
7136 We recommend that you save your time for something else.
7138 Of course, if you can find a simpler example to report @emph{instead}
7139 of the original one, that is a convenience for us. Errors in the
7140 output will be easier to spot, running under the debugger will take
7141 less time, and so on.
7143 However, simplification is not vital; if you do not want to do this,
7144 report the bug anyway and send us the entire test case you used.
7147 A patch for the bug.
7149 A patch for the bug does help us if it is a good one. But do not omit
7150 the necessary information, such as the test case, on the assumption that
7151 a patch is all we need. We might see problems with your patch and decide
7152 to fix the problem another way, or we might not understand it at all.
7154 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7155 construct an example that will make the program follow a certain path through
7156 the code. If you do not send us the example, we will not be able to construct
7157 one, so we will not be able to verify that the bug is fixed.
7159 And if we cannot understand what bug you are trying to fix, or why your
7160 patch should be an improvement, we will not install it. A test case will
7161 help us to understand.
7164 A guess about what the bug is or what it depends on.
7166 Such guesses are usually wrong. Even we cannot guess right about such
7167 things without first using the debugger to find the facts.
7170 @node Acknowledgements
7171 @chapter Acknowledgements
7173 If you have contributed to GAS and your name isn't listed here,
7174 it is not meant as a slight. We just don't know about it. Send mail to the
7175 maintainer, and we'll correct the situation. Currently
7177 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
7179 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7182 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7183 information and the 68k series machines, most of the preprocessing pass, and
7184 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7186 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7187 many bug fixes, including merging support for several processors, breaking GAS
7188 up to handle multiple object file format back ends (including heavy rewrite,
7189 testing, an integration of the coff and b.out back ends), adding configuration
7190 including heavy testing and verification of cross assemblers and file splits
7191 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7192 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7193 port (including considerable amounts of reverse engineering), a SPARC opcode
7194 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7195 assertions and made them work, much other reorganization, cleanup, and lint.
7197 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7198 in format-specific I/O modules.
7200 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7201 has done much work with it since.
7203 The Intel 80386 machine description was written by Eliot Dresselhaus.
7205 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7207 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7208 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7210 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7211 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7212 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7213 support a.out format.
7215 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7216 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7217 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7218 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7221 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7222 simplified the configuration of which versions accept which directives. He
7223 updated the 68k machine description so that Motorola's opcodes always produced
7224 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7225 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7226 cross-compilation support, and one bug in relaxation that took a week and
7227 required the proverbial one-bit fix.
7229 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7230 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7231 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7232 PowerPC assembler, and made a few other minor patches.
7234 Steve Chamberlain made GAS able to generate listings.
7236 Hewlett-Packard contributed support for the HP9000/300.
7238 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7239 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7240 formats). This work was supported by both the Center for Software Science at
7241 the University of Utah and Cygnus Support.
7243 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7244 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7245 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7246 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7247 and some initial 64-bit support).
7249 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7251 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7252 support for openVMS/Alpha.
7254 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7257 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7258 Inc.@: added support for Xtensa processors.
7260 Several engineers at Cygnus Support have also provided many small bug fixes and
7261 configuration enhancements.
7263 Jon Beniston added support for the Lattice Mico32 architecture.
7265 Many others have contributed large or small bugfixes and enhancements. If
7266 you have contributed significant work and are not mentioned on this list, and
7267 want to be, let us know. Some of the history has been lost; we are not
7268 intentionally leaving anyone out.
7270 @node GNU Free Documentation License
7271 @appendix GNU Free Documentation License
7275 @unnumbered AS Index