1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (C) 1991-2015 Free Software Foundation, Inc.
3 @c UPDATE!! On future updates--
4 @c (1) check for new machine-dep cmdline options in
5 @c md_parse_option definitions in config/tc-*.c
6 @c (2) for platform-specific directives, examine md_pseudo_op
8 @c (3) for object-format specific directives, examine obj_pseudo_op
10 @c (4) portable directives in potable[] in read.c
14 @macro gcctabopt{body}
17 @c defaults, config file may override:
22 @include asconfig.texi
27 @c common OR combinations of conditions
53 @set abnormal-separator
57 @settitle Using @value{AS}
60 @settitle Using @value{AS} (@value{TARGET})
62 @setchapternewpage odd
67 @c WARE! Some of the machine-dependent sections contain tables of machine
68 @c instructions. Except in multi-column format, these tables look silly.
69 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
70 @c the multi-col format is faked within @example sections.
72 @c Again unfortunately, the natural size that fits on a page, for these tables,
73 @c is different depending on whether or not smallbook is turned on.
74 @c This matters, because of order: text flow switches columns at each page
77 @c The format faked in this source works reasonably well for smallbook,
78 @c not well for the default large-page format. This manual expects that if you
79 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
80 @c tables in question. You can turn on one without the other at your
81 @c discretion, of course.
84 @c the insn tables look just as silly in info files regardless of smallbook,
85 @c might as well show 'em anyways.
89 @dircategory Software development
91 * As: (as). The GNU assembler.
92 * Gas: (as). The GNU assembler.
100 This file documents the GNU Assembler "@value{AS}".
102 @c man begin COPYRIGHT
103 Copyright @copyright{} 1991-2015 Free Software Foundation, Inc.
105 Permission is granted to copy, distribute and/or modify this document
106 under the terms of the GNU Free Documentation License, Version 1.3
107 or any later version published by the Free Software Foundation;
108 with no Invariant Sections, with no Front-Cover Texts, and with no
109 Back-Cover Texts. A copy of the license is included in the
110 section entitled ``GNU Free Documentation License''.
116 @title Using @value{AS}
117 @subtitle The @sc{gnu} Assembler
119 @subtitle for the @value{TARGET} family
121 @ifset VERSION_PACKAGE
123 @subtitle @value{VERSION_PACKAGE}
126 @subtitle Version @value{VERSION}
129 The Free Software Foundation Inc.@: thanks The Nice Computer
130 Company of Australia for loaning Dean Elsner to write the
131 first (Vax) version of @command{as} for Project @sc{gnu}.
132 The proprietors, management and staff of TNCCA thank FSF for
133 distracting the boss while they got some work
136 @author Dean Elsner, Jay Fenlason & friends
140 \hfill {\it Using {\tt @value{AS}}}\par
141 \hfill Edited by Cygnus Support\par
143 %"boxit" macro for figures:
144 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
145 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
146 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
147 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
148 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
151 @vskip 0pt plus 1filll
152 Copyright @copyright{} 1991-2015 Free Software Foundation, Inc.
154 Permission is granted to copy, distribute and/or modify this document
155 under the terms of the GNU Free Documentation License, Version 1.3
156 or any later version published by the Free Software Foundation;
157 with no Invariant Sections, with no Front-Cover Texts, and with no
158 Back-Cover Texts. A copy of the license is included in the
159 section entitled ``GNU Free Documentation License''.
166 @top Using @value{AS}
168 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
169 @ifset VERSION_PACKAGE
170 @value{VERSION_PACKAGE}
172 version @value{VERSION}.
174 This version of the file describes @command{@value{AS}} configured to generate
175 code for @value{TARGET} architectures.
178 This document is distributed under the terms of the GNU Free
179 Documentation License. A copy of the license is included in the
180 section entitled ``GNU Free Documentation License''.
183 * Overview:: Overview
184 * Invoking:: Command-Line Options
186 * Sections:: Sections and Relocation
188 * Expressions:: Expressions
189 * Pseudo Ops:: Assembler Directives
191 * Object Attributes:: Object Attributes
193 * Machine Dependencies:: Machine Dependent Features
194 * Reporting Bugs:: Reporting Bugs
195 * Acknowledgements:: Who Did What
196 * GNU Free Documentation License:: GNU Free Documentation License
197 * AS Index:: AS Index
204 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
206 This version of the manual describes @command{@value{AS}} configured to generate
207 code for @value{TARGET} architectures.
211 @cindex invocation summary
212 @cindex option summary
213 @cindex summary of options
214 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
215 see @ref{Invoking,,Command-Line Options}.
217 @c man title AS the portable GNU assembler.
221 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
225 @c We don't use deffn and friends for the following because they seem
226 @c to be limited to one line for the header.
228 @c man begin SYNOPSIS
229 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
230 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
231 [@b{--debug-prefix-map} @var{old}=@var{new}]
232 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
233 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--gdwarf-sections}]
234 [@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}]
238 [@b{-o} @var{objfile}] [@b{-R}]
239 [@b{--hash-size}=@var{NUM}] [@b{--reduce-memory-overheads}]
241 [@b{-v}] [@b{-version}] [@b{--version}]
242 [@b{-W}] [@b{--warn}] [@b{--fatal-warnings}] [@b{-w}] [@b{-x}]
243 [@b{-Z}] [@b{@@@var{FILE}}]
244 [@b{--sectname-subst}] [@b{--size-check=[error|warning]}]
245 [@b{--target-help}] [@var{target-options}]
246 [@b{--}|@var{files} @dots{}]
248 @c Target dependent options are listed below. Keep the list sorted.
249 @c Add an empty line for separation.
252 @emph{Target AArch64 options:}
254 [@b{-mabi}=@var{ABI}]
258 @emph{Target Alpha options:}
260 [@b{-mdebug} | @b{-no-mdebug}]
261 [@b{-replace} | @b{-noreplace}]
262 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
263 [@b{-F}] [@b{-32addr}]
267 @emph{Target ARC options:}
273 @emph{Target ARM options:}
274 @c Don't document the deprecated options
275 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
276 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
277 [@b{-mfpu}=@var{floating-point-format}]
278 [@b{-mfloat-abi}=@var{abi}]
279 [@b{-meabi}=@var{ver}]
282 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
283 @b{-mapcs-reentrant}]
284 [@b{-mthumb-interwork}] [@b{-k}]
288 @emph{Target Blackfin options:}
289 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
296 @emph{Target CRIS options:}
297 [@b{--underscore} | @b{--no-underscore}]
299 [@b{--emulation=criself} | @b{--emulation=crisaout}]
300 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
301 @c Deprecated -- deliberately not documented.
306 @emph{Target D10V options:}
311 @emph{Target D30V options:}
312 [@b{-O}|@b{-n}|@b{-N}]
316 @emph{Target EPIPHANY options:}
317 [@b{-mepiphany}|@b{-mepiphany16}]
321 @emph{Target H8/300 options:}
325 @c HPPA has no machine-dependent assembler options (yet).
329 @emph{Target i386 options:}
330 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
331 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
335 @emph{Target i960 options:}
336 @c see md_parse_option in tc-i960.c
337 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
339 [@b{-b}] [@b{-no-relax}]
343 @emph{Target IA-64 options:}
344 [@b{-mconstant-gp}|@b{-mauto-pic}]
345 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
347 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
348 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
349 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
350 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
354 @emph{Target IP2K options:}
355 [@b{-mip2022}|@b{-mip2022ext}]
359 @emph{Target M32C options:}
360 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
364 @emph{Target M32R options:}
365 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
370 @emph{Target M680X0 options:}
371 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
375 @emph{Target M68HC11 options:}
376 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
377 [@b{-mshort}|@b{-mlong}]
378 [@b{-mshort-double}|@b{-mlong-double}]
379 [@b{--force-long-branches}] [@b{--short-branches}]
380 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
381 [@b{--print-opcodes}] [@b{--generate-example}]
385 @emph{Target MCORE options:}
386 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
387 [@b{-mcpu=[210|340]}]
391 @emph{Target Meta options:}
392 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
395 @emph{Target MICROBLAZE options:}
396 @c MicroBlaze has no machine-dependent assembler options.
400 @emph{Target MIPS options:}
401 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
402 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
403 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
404 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
405 [@b{-mfp64}] [@b{-mgp64}] [@b{-mfpxx}]
406 [@b{-modd-spreg}] [@b{-mno-odd-spreg}]
407 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
408 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
409 [@b{-mips32r3}] [@b{-mips32r5}] [@b{-mips32r6}] [@b{-mips64}] [@b{-mips64r2}]
410 [@b{-mips64r3}] [@b{-mips64r5}] [@b{-mips64r6}]
411 [@b{-construct-floats}] [@b{-no-construct-floats}]
412 [@b{-mnan=@var{encoding}}]
413 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
414 [@b{-mips16}] [@b{-no-mips16}]
415 [@b{-mmicromips}] [@b{-mno-micromips}]
416 [@b{-msmartmips}] [@b{-mno-smartmips}]
417 [@b{-mips3d}] [@b{-no-mips3d}]
418 [@b{-mdmx}] [@b{-no-mdmx}]
419 [@b{-mdsp}] [@b{-mno-dsp}]
420 [@b{-mdspr2}] [@b{-mno-dspr2}]
421 [@b{-mmsa}] [@b{-mno-msa}]
422 [@b{-mxpa}] [@b{-mno-xpa}]
423 [@b{-mmt}] [@b{-mno-mt}]
424 [@b{-mmcu}] [@b{-mno-mcu}]
425 [@b{-minsn32}] [@b{-mno-insn32}]
426 [@b{-mfix7000}] [@b{-mno-fix7000}]
427 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
428 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
429 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
430 [@b{-mdebug}] [@b{-no-mdebug}]
431 [@b{-mpdr}] [@b{-mno-pdr}]
435 @emph{Target MMIX options:}
436 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
437 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
438 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
439 [@b{--linker-allocated-gregs}]
443 @emph{Target Nios II options:}
444 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
449 @emph{Target NDS32 options:}
450 [@b{-EL}] [@b{-EB}] [@b{-O}] [@b{-Os}] [@b{-mcpu=@var{cpu}}]
451 [@b{-misa=@var{isa}}] [@b{-mabi=@var{abi}}] [@b{-mall-ext}]
452 [@b{-m[no-]16-bit}] [@b{-m[no-]perf-ext}] [@b{-m[no-]perf2-ext}]
453 [@b{-m[no-]string-ext}] [@b{-m[no-]dsp-ext}] [@b{-m[no-]mac}] [@b{-m[no-]div}]
454 [@b{-m[no-]audio-isa-ext}] [@b{-m[no-]fpu-sp-ext}] [@b{-m[no-]fpu-dp-ext}]
455 [@b{-m[no-]fpu-fma}] [@b{-mfpu-freg=@var{FREG}}] [@b{-mreduced-regs}]
456 [@b{-mfull-regs}] [@b{-m[no-]dx-regs}] [@b{-mpic}] [@b{-mno-relax}]
461 @emph{Target PDP11 options:}
462 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
463 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
464 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
468 @emph{Target picoJava options:}
473 @emph{Target PowerPC options:}
475 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
476 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
477 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
478 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
479 @b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-ma2}|@b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
480 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
481 [@b{-mregnames}|@b{-mno-regnames}]
482 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
483 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
484 [@b{-msolaris}|@b{-mno-solaris}]
485 [@b{-nops=@var{count}}]
489 @emph{Target RL78 options:}
491 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
495 @emph{Target RX options:}
496 [@b{-mlittle-endian}|@b{-mbig-endian}]
497 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
498 [@b{-muse-conventional-section-names}]
499 [@b{-msmall-data-limit}]
502 [@b{-mint-register=@var{number}}]
503 [@b{-mgcc-abi}|@b{-mrx-abi}]
507 @emph{Target s390 options:}
508 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
509 [@b{-mregnames}|@b{-mno-regnames}]
510 [@b{-mwarn-areg-zero}]
514 @emph{Target SCORE options:}
515 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
516 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
517 [@b{-march=score7}][@b{-march=score3}]
518 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
522 @emph{Target SPARC options:}
523 @c The order here is important. See c-sparc.texi.
524 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
525 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
526 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
531 @emph{Target TIC54X options:}
532 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
533 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
537 @emph{Target TIC6X options:}
538 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
539 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
540 [@b{-mpic}|@b{-mno-pic}]
544 @emph{Target TILE-Gx options:}
545 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
548 @c TILEPro has no machine-dependent assembler options
552 @emph{Target Visium options:}
553 [@b{-mtune=@var{arch}}]
557 @emph{Target Xtensa options:}
558 [@b{--[no-]text-section-literals}] [@b{--[no-]auto-litpools}]
559 [@b{--[no-]absolute-literals}]
560 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
561 [@b{--[no-]transform}]
562 [@b{--rename-section} @var{oldname}=@var{newname}]
563 [@b{--[no-]trampolines}]
567 @emph{Target Z80 options:}
568 [@b{-z80}] [@b{-r800}]
569 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
570 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
571 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
572 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
573 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
574 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
578 @c Z8000 has no machine-dependent assembler options
587 @include at-file.texi
590 Turn on listings, in any of a variety of ways:
594 omit false conditionals
597 omit debugging directives
600 include general information, like @value{AS} version and options passed
603 include high-level source
609 include macro expansions
612 omit forms processing
618 set the name of the listing file
621 You may combine these options; for example, use @samp{-aln} for assembly
622 listing without forms processing. The @samp{=file} option, if used, must be
623 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
626 Begin in alternate macro mode.
628 @xref{Altmacro,,@code{.altmacro}}.
631 @item --compress-debug-sections
632 Compress DWARF debug sections using zlib with SHF_COMPRESSED from the
633 ELF ABI. The resulting object file may not be compatible with older
634 linkers and object file utilities. Note if compression would make a
635 given section @emph{larger} then it is not compressed.
638 @cindex @samp{--compress-debug-sections=} option
639 @item --compress-debug-sections=none
640 @itemx --compress-debug-sections=zlib
641 @itemx --compress-debug-sections=zlib-gnu
642 @itemx --compress-debug-sections=zlib-gabi
643 These options control how DWARF debug sections are compressed.
644 @option{--compress-debug-sections=none} is equivalent to
645 @option{--nocompress-debug-sections}.
646 @option{--compress-debug-sections=zlib} and
647 @option{--compress-debug-sections=zlib-gabi} are equivalent to
648 @option{--compress-debug-sections}.
649 @option{--compress-debug-sections=zlib-gnu} compresses DWARF debug
650 sections using zlib. The debug sections are renamed to begin with
651 @samp{.zdebug}. Note if compression would make a given section
652 @emph{larger} then it is not compressed nor renamed.
656 @item --nocompress-debug-sections
657 Do not compress DWARF debug sections. This is the default.
660 Ignored. This option is accepted for script compatibility with calls to
663 @item --debug-prefix-map @var{old}=@var{new}
664 When assembling files in directory @file{@var{old}}, record debugging
665 information describing them as in @file{@var{new}} instead.
667 @item --defsym @var{sym}=@var{value}
668 Define the symbol @var{sym} to be @var{value} before assembling the input file.
669 @var{value} must be an integer constant. As in C, a leading @samp{0x}
670 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
671 value. The value of the symbol can be overridden inside a source file via the
672 use of a @code{.set} pseudo-op.
675 ``fast''---skip whitespace and comment preprocessing (assume source is
680 Generate debugging information for each assembler source line using whichever
681 debug format is preferred by the target. This currently means either STABS,
685 Generate stabs debugging information for each assembler line. This
686 may help debugging assembler code, if the debugger can handle it.
689 Generate stabs debugging information for each assembler line, with GNU
690 extensions that probably only gdb can handle, and that could make other
691 debuggers crash or refuse to read your program. This
692 may help debugging assembler code. Currently the only GNU extension is
693 the location of the current working directory at assembling time.
696 Generate DWARF2 debugging information for each assembler line. This
697 may help debugging assembler code, if the debugger can handle it. Note---this
698 option is only supported by some targets, not all of them.
700 @item --gdwarf-sections
701 Instead of creating a .debug_line section, create a series of
702 .debug_line.@var{foo} sections where @var{foo} is the name of the
703 corresponding code section. For example a code section called @var{.text.func}
704 will have its dwarf line number information placed into a section called
705 @var{.debug_line.text.func}. If the code section is just called @var{.text}
706 then debug line section will still be called just @var{.debug_line} without any
709 @item --size-check=error
710 @itemx --size-check=warning
711 Issue an error or warning for invalid ELF .size directive.
714 Print a summary of the command line options and exit.
717 Print a summary of all target specific options and exit.
720 Add directory @var{dir} to the search list for @code{.include} directives.
723 Don't warn about signed overflow.
726 @ifclear DIFF-TBL-KLUGE
727 This option is accepted but has no effect on the @value{TARGET} family.
729 @ifset DIFF-TBL-KLUGE
730 Issue warnings when difference tables altered for long displacements.
735 Keep (in the symbol table) local symbols. These symbols start with
736 system-specific local label prefixes, typically @samp{.L} for ELF systems
737 or @samp{L} for traditional a.out systems.
742 @item --listing-lhs-width=@var{number}
743 Set the maximum width, in words, of the output data column for an assembler
744 listing to @var{number}.
746 @item --listing-lhs-width2=@var{number}
747 Set the maximum width, in words, of the output data column for continuation
748 lines in an assembler listing to @var{number}.
750 @item --listing-rhs-width=@var{number}
751 Set the maximum width of an input source line, as displayed in a listing, to
754 @item --listing-cont-lines=@var{number}
755 Set the maximum number of lines printed in a listing for a single line of input
758 @item -o @var{objfile}
759 Name the object-file output from @command{@value{AS}} @var{objfile}.
762 Fold the data section into the text section.
764 @item --hash-size=@var{number}
765 Set the default size of GAS's hash tables to a prime number close to
766 @var{number}. Increasing this value can reduce the length of time it takes the
767 assembler to perform its tasks, at the expense of increasing the assembler's
768 memory requirements. Similarly reducing this value can reduce the memory
769 requirements at the expense of speed.
771 @item --reduce-memory-overheads
772 This option reduces GAS's memory requirements, at the expense of making the
773 assembly processes slower. Currently this switch is a synonym for
774 @samp{--hash-size=4051}, but in the future it may have other effects as well.
777 @item --sectname-subst
778 Honor substitution sequences in section names.
780 @xref{Section Name Substitutions,,@code{.section @var{name}}}.
785 Print the maximum space (in bytes) and total time (in seconds) used by
788 @item --strip-local-absolute
789 Remove local absolute symbols from the outgoing symbol table.
793 Print the @command{as} version.
796 Print the @command{as} version and exit.
800 Suppress warning messages.
802 @item --fatal-warnings
803 Treat warnings as errors.
806 Don't suppress warning messages or treat them as errors.
815 Generate an object file even after errors.
817 @item -- | @var{files} @dots{}
818 Standard input, or source files to assemble.
826 @xref{AArch64 Options}, for the options available when @value{AS} is configured
827 for the 64-bit mode of the ARM Architecture (AArch64).
832 The following options are available when @value{AS} is configured for the
833 64-bit mode of the ARM Architecture (AArch64).
836 @include c-aarch64.texi
837 @c ended inside the included file
845 @xref{Alpha Options}, for the options available when @value{AS} is configured
846 for an Alpha processor.
851 The following options are available when @value{AS} is configured for an Alpha
855 @include c-alpha.texi
856 @c ended inside the included file
863 The following options are available when @value{AS} is configured for
868 This option selects the core processor variant.
870 Select either big-endian (-EB) or little-endian (-EL) output.
875 The following options are available when @value{AS} is configured for the ARM
879 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
880 Specify which ARM processor variant is the target.
881 @item -march=@var{architecture}[+@var{extension}@dots{}]
882 Specify which ARM architecture variant is used by the target.
883 @item -mfpu=@var{floating-point-format}
884 Select which Floating Point architecture is the target.
885 @item -mfloat-abi=@var{abi}
886 Select which floating point ABI is in use.
888 Enable Thumb only instruction decoding.
889 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
890 Select which procedure calling convention is in use.
892 Select either big-endian (-EB) or little-endian (-EL) output.
893 @item -mthumb-interwork
894 Specify that the code has been generated with interworking between Thumb and
897 Turns on CodeComposer Studio assembly syntax compatibility mode.
899 Specify that PIC code has been generated.
907 @xref{Blackfin Options}, for the options available when @value{AS} is
908 configured for the Blackfin processor family.
913 The following options are available when @value{AS} is configured for
914 the Blackfin processor family.
918 @c ended inside the included file
925 See the info pages for documentation of the CRIS-specific options.
929 The following options are available when @value{AS} is configured for
932 @cindex D10V optimization
933 @cindex optimization, D10V
935 Optimize output by parallelizing instructions.
940 The following options are available when @value{AS} is configured for a D30V
943 @cindex D30V optimization
944 @cindex optimization, D30V
946 Optimize output by parallelizing instructions.
950 Warn when nops are generated.
952 @cindex D30V nops after 32-bit multiply
954 Warn when a nop after a 32-bit multiply instruction is generated.
960 The following options are available when @value{AS} is configured for the
961 Adapteva EPIPHANY series.
964 @xref{Epiphany Options}, for the options available when @value{AS} is
965 configured for an Epiphany processor.
970 The following options are available when @value{AS} is configured for
971 an Epiphany processor.
974 @include c-epiphany.texi
975 @c ended inside the included file
983 @xref{H8/300 Options}, for the options available when @value{AS} is configured
984 for an H8/300 processor.
989 The following options are available when @value{AS} is configured for an H8/300
993 @include c-h8300.texi
994 @c ended inside the included file
1002 @xref{i386-Options}, for the options available when @value{AS} is
1003 configured for an i386 processor.
1007 @c man begin OPTIONS
1008 The following options are available when @value{AS} is configured for
1011 @c man begin INCLUDE
1012 @include c-i386.texi
1013 @c ended inside the included file
1018 @c man begin OPTIONS
1020 The following options are available when @value{AS} is configured for the
1021 Intel 80960 processor.
1024 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
1025 Specify which variant of the 960 architecture is the target.
1028 Add code to collect statistics about branches taken.
1031 Do not alter compare-and-branch instructions for long displacements;
1038 The following options are available when @value{AS} is configured for the
1044 Specifies that the extended IP2022 instructions are allowed.
1047 Restores the default behaviour, which restricts the permitted instructions to
1048 just the basic IP2022 ones.
1054 The following options are available when @value{AS} is configured for the
1055 Renesas M32C and M16C processors.
1060 Assemble M32C instructions.
1063 Assemble M16C instructions (the default).
1066 Enable support for link-time relaxations.
1069 Support H'00 style hex constants in addition to 0x00 style.
1075 The following options are available when @value{AS} is configured for the
1076 Renesas M32R (formerly Mitsubishi M32R) series.
1081 Specify which processor in the M32R family is the target. The default
1082 is normally the M32R, but this option changes it to the M32RX.
1084 @item --warn-explicit-parallel-conflicts or --Wp
1085 Produce warning messages when questionable parallel constructs are
1088 @item --no-warn-explicit-parallel-conflicts or --Wnp
1089 Do not produce warning messages when questionable parallel constructs are
1096 The following options are available when @value{AS} is configured for the
1097 Motorola 68000 series.
1102 Shorten references to undefined symbols, to one word instead of two.
1104 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1105 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1106 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1107 Specify what processor in the 68000 family is the target. The default
1108 is normally the 68020, but this can be changed at configuration time.
1110 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1111 The target machine does (or does not) have a floating-point coprocessor.
1112 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1113 the basic 68000 is not compatible with the 68881, a combination of the
1114 two can be specified, since it's possible to do emulation of the
1115 coprocessor instructions with the main processor.
1117 @item -m68851 | -mno-68851
1118 The target machine does (or does not) have a memory-management
1119 unit coprocessor. The default is to assume an MMU for 68020 and up.
1127 @xref{Nios II Options}, for the options available when @value{AS} is configured
1128 for an Altera Nios II processor.
1132 @c man begin OPTIONS
1133 The following options are available when @value{AS} is configured for an
1134 Altera Nios II processor.
1136 @c man begin INCLUDE
1137 @include c-nios2.texi
1138 @c ended inside the included file
1144 For details about the PDP-11 machine dependent features options,
1145 see @ref{PDP-11-Options}.
1148 @item -mpic | -mno-pic
1149 Generate position-independent (or position-dependent) code. The
1150 default is @option{-mpic}.
1153 @itemx -mall-extensions
1154 Enable all instruction set extensions. This is the default.
1156 @item -mno-extensions
1157 Disable all instruction set extensions.
1159 @item -m@var{extension} | -mno-@var{extension}
1160 Enable (or disable) a particular instruction set extension.
1163 Enable the instruction set extensions supported by a particular CPU, and
1164 disable all other extensions.
1166 @item -m@var{machine}
1167 Enable the instruction set extensions supported by a particular machine
1168 model, and disable all other extensions.
1174 The following options are available when @value{AS} is configured for
1175 a picoJava processor.
1179 @cindex PJ endianness
1180 @cindex endianness, PJ
1181 @cindex big endian output, PJ
1183 Generate ``big endian'' format output.
1185 @cindex little endian output, PJ
1187 Generate ``little endian'' format output.
1193 The following options are available when @value{AS} is configured for the
1194 Motorola 68HC11 or 68HC12 series.
1198 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1199 Specify what processor is the target. The default is
1200 defined by the configuration option when building the assembler.
1202 @item --xgate-ramoffset
1203 Instruct the linker to offset RAM addresses from S12X address space into
1204 XGATE address space.
1207 Specify to use the 16-bit integer ABI.
1210 Specify to use the 32-bit integer ABI.
1212 @item -mshort-double
1213 Specify to use the 32-bit double ABI.
1216 Specify to use the 64-bit double ABI.
1218 @item --force-long-branches
1219 Relative branches are turned into absolute ones. This concerns
1220 conditional branches, unconditional branches and branches to a
1223 @item -S | --short-branches
1224 Do not turn relative branches into absolute ones
1225 when the offset is out of range.
1227 @item --strict-direct-mode
1228 Do not turn the direct addressing mode into extended addressing mode
1229 when the instruction does not support direct addressing mode.
1231 @item --print-insn-syntax
1232 Print the syntax of instruction in case of error.
1234 @item --print-opcodes
1235 Print the list of instructions with syntax and then exit.
1237 @item --generate-example
1238 Print an example of instruction for each possible instruction and then exit.
1239 This option is only useful for testing @command{@value{AS}}.
1245 The following options are available when @command{@value{AS}} is configured
1246 for the SPARC architecture:
1249 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1250 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1251 Explicitly select a variant of the SPARC architecture.
1253 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1254 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1256 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1257 UltraSPARC extensions.
1259 @item -xarch=v8plus | -xarch=v8plusa
1260 For compatibility with the Solaris v9 assembler. These options are
1261 equivalent to -Av8plus and -Av8plusa, respectively.
1264 Warn when the assembler switches to another architecture.
1269 The following options are available when @value{AS} is configured for the 'c54x
1274 Enable extended addressing mode. All addresses and relocations will assume
1275 extended addressing (usually 23 bits).
1276 @item -mcpu=@var{CPU_VERSION}
1277 Sets the CPU version being compiled for.
1278 @item -merrors-to-file @var{FILENAME}
1279 Redirect error output to a file, for broken systems which don't support such
1280 behaviour in the shell.
1285 The following options are available when @value{AS} is configured for
1290 This option sets the largest size of an object that can be referenced
1291 implicitly with the @code{gp} register. It is only accepted for targets that
1292 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1294 @cindex MIPS endianness
1295 @cindex endianness, MIPS
1296 @cindex big endian output, MIPS
1298 Generate ``big endian'' format output.
1300 @cindex little endian output, MIPS
1302 Generate ``little endian'' format output.
1320 Generate code for a particular MIPS Instruction Set Architecture level.
1321 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1322 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1323 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1324 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1325 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1326 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1327 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1328 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1329 MIPS64 Release 6 ISA processors, respectively.
1331 @item -march=@var{cpu}
1332 Generate code for a particular MIPS CPU.
1334 @item -mtune=@var{cpu}
1335 Schedule and tune for a particular MIPS CPU.
1339 Cause nops to be inserted if the read of the destination register
1340 of an mfhi or mflo instruction occurs in the following two instructions.
1343 @itemx -mno-fix-rm7000
1344 Cause nops to be inserted if a dmult or dmultu instruction is
1345 followed by a load instruction.
1349 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1350 section instead of the standard ELF .stabs sections.
1354 Control generation of @code{.pdr} sections.
1358 The register sizes are normally inferred from the ISA and ABI, but these
1359 flags force a certain group of registers to be treated as 32 bits wide at
1360 all times. @samp{-mgp32} controls the size of general-purpose registers
1361 and @samp{-mfp32} controls the size of floating-point registers.
1365 The register sizes are normally inferred from the ISA and ABI, but these
1366 flags force a certain group of registers to be treated as 64 bits wide at
1367 all times. @samp{-mgp64} controls the size of general-purpose registers
1368 and @samp{-mfp64} controls the size of floating-point registers.
1371 The register sizes are normally inferred from the ISA and ABI, but using
1372 this flag in combination with @samp{-mabi=32} enables an ABI variant
1373 which will operate correctly with floating-point registers which are
1377 @itemx -mno-odd-spreg
1378 Enable use of floating-point operations on odd-numbered single-precision
1379 registers when supported by the ISA. @samp{-mfpxx} implies
1380 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1384 Generate code for the MIPS 16 processor. This is equivalent to putting
1385 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1386 turns off this option.
1389 @itemx -mno-micromips
1390 Generate code for the microMIPS processor. This is equivalent to putting
1391 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1392 turns off this option. This is equivalent to putting @code{.set nomicromips}
1393 at the start of the assembly file.
1396 @itemx -mno-smartmips
1397 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1398 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1399 @samp{-mno-smartmips} turns off this option.
1403 Generate code for the MIPS-3D Application Specific Extension.
1404 This tells the assembler to accept MIPS-3D instructions.
1405 @samp{-no-mips3d} turns off this option.
1409 Generate code for the MDMX Application Specific Extension.
1410 This tells the assembler to accept MDMX instructions.
1411 @samp{-no-mdmx} turns off this option.
1415 Generate code for the DSP Release 1 Application Specific Extension.
1416 This tells the assembler to accept DSP Release 1 instructions.
1417 @samp{-mno-dsp} turns off this option.
1421 Generate code for the DSP Release 2 Application Specific Extension.
1422 This option implies -mdsp.
1423 This tells the assembler to accept DSP Release 2 instructions.
1424 @samp{-mno-dspr2} turns off this option.
1428 Generate code for the MIPS SIMD Architecture Extension.
1429 This tells the assembler to accept MSA instructions.
1430 @samp{-mno-msa} turns off this option.
1434 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1435 This tells the assembler to accept XPA instructions.
1436 @samp{-mno-xpa} turns off this option.
1440 Generate code for the MT Application Specific Extension.
1441 This tells the assembler to accept MT instructions.
1442 @samp{-mno-mt} turns off this option.
1446 Generate code for the MCU Application Specific Extension.
1447 This tells the assembler to accept MCU instructions.
1448 @samp{-mno-mcu} turns off this option.
1452 Only use 32-bit instruction encodings when generating code for the
1453 microMIPS processor. This option inhibits the use of any 16-bit
1454 instructions. This is equivalent to putting @code{.set insn32} at
1455 the start of the assembly file. @samp{-mno-insn32} turns off this
1456 option. This is equivalent to putting @code{.set noinsn32} at the
1457 start of the assembly file. By default @samp{-mno-insn32} is
1458 selected, allowing all instructions to be used.
1460 @item --construct-floats
1461 @itemx --no-construct-floats
1462 The @samp{--no-construct-floats} option disables the construction of
1463 double width floating point constants by loading the two halves of the
1464 value into the two single width floating point registers that make up
1465 the double width register. By default @samp{--construct-floats} is
1466 selected, allowing construction of these floating point constants.
1468 @item --relax-branch
1469 @itemx --no-relax-branch
1470 The @samp{--relax-branch} option enables the relaxation of out-of-range
1471 branches. By default @samp{--no-relax-branch} is selected, causing any
1472 out-of-range branches to produce an error.
1474 @item -mnan=@var{encoding}
1475 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1476 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1479 @item --emulation=@var{name}
1480 This option was formerly used to switch between ELF and ECOFF output
1481 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1482 removed in GAS 2.24, so the option now serves little purpose.
1483 It is retained for backwards compatibility.
1485 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1486 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1487 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1488 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1489 preferred options instead.
1492 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1499 Control how to deal with multiplication overflow and division by zero.
1500 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1501 (and only work for Instruction Set Architecture level 2 and higher);
1502 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1506 When this option is used, @command{@value{AS}} will issue a warning every
1507 time it generates a nop instruction from a macro.
1512 The following options are available when @value{AS} is configured for
1518 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1519 The command line option @samp{-nojsri2bsr} can be used to disable it.
1523 Enable or disable the silicon filter behaviour. By default this is disabled.
1524 The default can be overridden by the @samp{-sifilter} command line option.
1527 Alter jump instructions for long displacements.
1529 @item -mcpu=[210|340]
1530 Select the cpu type on the target hardware. This controls which instructions
1534 Assemble for a big endian target.
1537 Assemble for a little endian target.
1546 @xref{Meta Options}, for the options available when @value{AS} is configured
1547 for a Meta processor.
1551 @c man begin OPTIONS
1552 The following options are available when @value{AS} is configured for a
1555 @c man begin INCLUDE
1556 @include c-metag.texi
1557 @c ended inside the included file
1562 @c man begin OPTIONS
1564 See the info pages for documentation of the MMIX-specific options.
1570 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1571 for a NDS32 processor.
1573 @c ended inside the included file
1577 @c man begin OPTIONS
1578 The following options are available when @value{AS} is configured for a
1581 @c man begin INCLUDE
1582 @include c-nds32.texi
1583 @c ended inside the included file
1590 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1591 for a PowerPC processor.
1595 @c man begin OPTIONS
1596 The following options are available when @value{AS} is configured for a
1599 @c man begin INCLUDE
1601 @c ended inside the included file
1606 @c man begin OPTIONS
1608 See the info pages for documentation of the RX-specific options.
1612 The following options are available when @value{AS} is configured for the s390
1618 Select the word size, either 31/32 bits or 64 bits.
1621 Select the architecture mode, either the Enterprise System
1622 Architecture (esa) or the z/Architecture mode (zarch).
1623 @item -march=@var{processor}
1624 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1625 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, @samp{z10},
1626 @samp{z196}, @samp{zEC12}, or @samp{z13}.
1628 @itemx -mno-regnames
1629 Allow or disallow symbolic names for registers.
1630 @item -mwarn-areg-zero
1631 Warn whenever the operand for a base or index register has been specified
1632 but evaluates to zero.
1640 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1641 for a TMS320C6000 processor.
1645 @c man begin OPTIONS
1646 The following options are available when @value{AS} is configured for a
1647 TMS320C6000 processor.
1649 @c man begin INCLUDE
1650 @include c-tic6x.texi
1651 @c ended inside the included file
1659 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1660 for a TILE-Gx processor.
1664 @c man begin OPTIONS
1665 The following options are available when @value{AS} is configured for a TILE-Gx
1668 @c man begin INCLUDE
1669 @include c-tilegx.texi
1670 @c ended inside the included file
1678 @xref{Visium Options}, for the options available when @value{AS} is configured
1679 for a Visium processor.
1683 @c man begin OPTIONS
1684 The following option is available when @value{AS} is configured for a Visium
1687 @c man begin INCLUDE
1688 @include c-visium.texi
1689 @c ended inside the included file
1697 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1698 for an Xtensa processor.
1702 @c man begin OPTIONS
1703 The following options are available when @value{AS} is configured for an
1706 @c man begin INCLUDE
1707 @include c-xtensa.texi
1708 @c ended inside the included file
1713 @c man begin OPTIONS
1716 The following options are available when @value{AS} is configured for
1717 a Z80 family processor.
1720 Assemble for Z80 processor.
1722 Assemble for R800 processor.
1723 @item -ignore-undocumented-instructions
1725 Assemble undocumented Z80 instructions that also work on R800 without warning.
1726 @item -ignore-unportable-instructions
1728 Assemble all undocumented Z80 instructions without warning.
1729 @item -warn-undocumented-instructions
1731 Issue a warning for undocumented Z80 instructions that also work on R800.
1732 @item -warn-unportable-instructions
1734 Issue a warning for undocumented Z80 instructions that do not work on R800.
1735 @item -forbid-undocumented-instructions
1737 Treat all undocumented instructions as errors.
1738 @item -forbid-unportable-instructions
1740 Treat undocumented Z80 instructions that do not work on R800 as errors.
1747 * Manual:: Structure of this Manual
1748 * GNU Assembler:: The GNU Assembler
1749 * Object Formats:: Object File Formats
1750 * Command Line:: Command Line
1751 * Input Files:: Input Files
1752 * Object:: Output (Object) File
1753 * Errors:: Error and Warning Messages
1757 @section Structure of this Manual
1759 @cindex manual, structure and purpose
1760 This manual is intended to describe what you need to know to use
1761 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1762 notation for symbols, constants, and expressions; the directives that
1763 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1766 We also cover special features in the @value{TARGET}
1767 configuration of @command{@value{AS}}, including assembler directives.
1770 This manual also describes some of the machine-dependent features of
1771 various flavors of the assembler.
1774 @cindex machine instructions (not covered)
1775 On the other hand, this manual is @emph{not} intended as an introduction
1776 to programming in assembly language---let alone programming in general!
1777 In a similar vein, we make no attempt to introduce the machine
1778 architecture; we do @emph{not} describe the instruction set, standard
1779 mnemonics, registers or addressing modes that are standard to a
1780 particular architecture.
1782 You may want to consult the manufacturer's
1783 machine architecture manual for this information.
1787 For information on the H8/300 machine instruction set, see @cite{H8/300
1788 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1789 Programming Manual} (Renesas).
1792 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1793 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1794 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1795 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1798 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1802 @c I think this is premature---doc@cygnus.com, 17jan1991
1804 Throughout this manual, we assume that you are running @dfn{GNU},
1805 the portable operating system from the @dfn{Free Software
1806 Foundation, Inc.}. This restricts our attention to certain kinds of
1807 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1808 once this assumption is granted examples and definitions need less
1811 @command{@value{AS}} is part of a team of programs that turn a high-level
1812 human-readable series of instructions into a low-level
1813 computer-readable series of instructions. Different versions of
1814 @command{@value{AS}} are used for different kinds of computer.
1817 @c There used to be a section "Terminology" here, which defined
1818 @c "contents", "byte", "word", and "long". Defining "word" to any
1819 @c particular size is confusing when the .word directive may generate 16
1820 @c bits on one machine and 32 bits on another; in general, for the user
1821 @c version of this manual, none of these terms seem essential to define.
1822 @c They were used very little even in the former draft of the manual;
1823 @c this draft makes an effort to avoid them (except in names of
1827 @section The GNU Assembler
1829 @c man begin DESCRIPTION
1831 @sc{gnu} @command{as} is really a family of assemblers.
1833 This manual describes @command{@value{AS}}, a member of that family which is
1834 configured for the @value{TARGET} architectures.
1836 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1837 should find a fairly similar environment when you use it on another
1838 architecture. Each version has much in common with the others,
1839 including object file formats, most assembler directives (often called
1840 @dfn{pseudo-ops}) and assembler syntax.@refill
1842 @cindex purpose of @sc{gnu} assembler
1843 @command{@value{AS}} is primarily intended to assemble the output of the
1844 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1845 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1846 assemble correctly everything that other assemblers for the same
1847 machine would assemble.
1849 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1852 @c This remark should appear in generic version of manual; assumption
1853 @c here is that generic version sets M680x0.
1854 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1855 assembler for the same architecture; for example, we know of several
1856 incompatible versions of 680x0 assembly language syntax.
1861 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1862 program in one pass of the source file. This has a subtle impact on the
1863 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1865 @node Object Formats
1866 @section Object File Formats
1868 @cindex object file format
1869 The @sc{gnu} assembler can be configured to produce several alternative
1870 object file formats. For the most part, this does not affect how you
1871 write assembly language programs; but directives for debugging symbols
1872 are typically different in different file formats. @xref{Symbol
1873 Attributes,,Symbol Attributes}.
1876 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1877 @value{OBJ-NAME} format object files.
1879 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1881 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1882 @code{b.out} or COFF format object files.
1885 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1886 SOM or ELF format object files.
1891 @section Command Line
1893 @cindex command line conventions
1895 After the program name @command{@value{AS}}, the command line may contain
1896 options and file names. Options may appear in any order, and may be
1897 before, after, or between file names. The order of file names is
1900 @cindex standard input, as input file
1902 @file{--} (two hyphens) by itself names the standard input file
1903 explicitly, as one of the files for @command{@value{AS}} to assemble.
1905 @cindex options, command line
1906 Except for @samp{--} any command line argument that begins with a
1907 hyphen (@samp{-}) is an option. Each option changes the behavior of
1908 @command{@value{AS}}. No option changes the way another option works. An
1909 option is a @samp{-} followed by one or more letters; the case of
1910 the letter is important. All options are optional.
1912 Some options expect exactly one file name to follow them. The file
1913 name may either immediately follow the option's letter (compatible
1914 with older assemblers) or it may be the next command argument (@sc{gnu}
1915 standard). These two command lines are equivalent:
1918 @value{AS} -o my-object-file.o mumble.s
1919 @value{AS} -omy-object-file.o mumble.s
1923 @section Input Files
1926 @cindex source program
1927 @cindex files, input
1928 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1929 describe the program input to one run of @command{@value{AS}}. The program may
1930 be in one or more files; how the source is partitioned into files
1931 doesn't change the meaning of the source.
1933 @c I added "con" prefix to "catenation" just to prove I can overcome my
1934 @c APL training... doc@cygnus.com
1935 The source program is a concatenation of the text in all the files, in the
1938 @c man begin DESCRIPTION
1939 Each time you run @command{@value{AS}} it assembles exactly one source
1940 program. The source program is made up of one or more files.
1941 (The standard input is also a file.)
1943 You give @command{@value{AS}} a command line that has zero or more input file
1944 names. The input files are read (from left file name to right). A
1945 command line argument (in any position) that has no special meaning
1946 is taken to be an input file name.
1948 If you give @command{@value{AS}} no file names it attempts to read one input file
1949 from the @command{@value{AS}} standard input, which is normally your terminal. You
1950 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1953 Use @samp{--} if you need to explicitly name the standard input file
1954 in your command line.
1956 If the source is empty, @command{@value{AS}} produces a small, empty object
1961 @subheading Filenames and Line-numbers
1963 @cindex input file linenumbers
1964 @cindex line numbers, in input files
1965 There are two ways of locating a line in the input file (or files) and
1966 either may be used in reporting error messages. One way refers to a line
1967 number in a physical file; the other refers to a line number in a
1968 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1970 @dfn{Physical files} are those files named in the command line given
1971 to @command{@value{AS}}.
1973 @dfn{Logical files} are simply names declared explicitly by assembler
1974 directives; they bear no relation to physical files. Logical file names help
1975 error messages reflect the original source file, when @command{@value{AS}} source
1976 is itself synthesized from other files. @command{@value{AS}} understands the
1977 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1978 @ref{File,,@code{.file}}.
1981 @section Output (Object) File
1987 Every time you run @command{@value{AS}} it produces an output file, which is
1988 your assembly language program translated into numbers. This file
1989 is the object file. Its default name is
1997 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1999 You can give it another name by using the @option{-o} option. Conventionally,
2000 object file names end with @file{.o}. The default name is used for historical
2001 reasons: older assemblers were capable of assembling self-contained programs
2002 directly into a runnable program. (For some formats, this isn't currently
2003 possible, but it can be done for the @code{a.out} format.)
2007 The object file is meant for input to the linker @code{@value{LD}}. It contains
2008 assembled program code, information to help @code{@value{LD}} integrate
2009 the assembled program into a runnable file, and (optionally) symbolic
2010 information for the debugger.
2012 @c link above to some info file(s) like the description of a.out.
2013 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2016 @section Error and Warning Messages
2018 @c man begin DESCRIPTION
2020 @cindex error messages
2021 @cindex warning messages
2022 @cindex messages from assembler
2023 @command{@value{AS}} may write warnings and error messages to the standard error
2024 file (usually your terminal). This should not happen when a compiler
2025 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2026 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2027 grave problem that stops the assembly.
2031 @cindex format of warning messages
2032 Warning messages have the format
2035 file_name:@b{NNN}:Warning Message Text
2039 @cindex line numbers, in warnings/errors
2040 (where @b{NNN} is a line number). If a logical file name has been given
2041 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
2042 the current input file is used. If a logical line number was given
2044 (@pxref{Line,,@code{.line}})
2046 then it is used to calculate the number printed,
2047 otherwise the actual line in the current source file is printed. The
2048 message text is intended to be self explanatory (in the grand Unix
2051 @cindex format of error messages
2052 Error messages have the format
2054 file_name:@b{NNN}:FATAL:Error Message Text
2056 The file name and line number are derived as for warning
2057 messages. The actual message text may be rather less explanatory
2058 because many of them aren't supposed to happen.
2061 @chapter Command-Line Options
2063 @cindex options, all versions of assembler
2064 This chapter describes command-line options available in @emph{all}
2065 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2066 for options specific
2068 to the @value{TARGET} target.
2071 to particular machine architectures.
2074 @c man begin DESCRIPTION
2076 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2077 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2078 The assembler arguments must be separated from each other (and the @samp{-Wa})
2079 by commas. For example:
2082 gcc -c -g -O -Wa,-alh,-L file.c
2086 This passes two options to the assembler: @samp{-alh} (emit a listing to
2087 standard output with high-level and assembly source) and @samp{-L} (retain
2088 local symbols in the symbol table).
2090 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2091 command-line options are automatically passed to the assembler by the compiler.
2092 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2093 precisely what options it passes to each compilation pass, including the
2099 * a:: -a[cdghlns] enable listings
2100 * alternate:: --alternate enable alternate macro syntax
2101 * D:: -D for compatibility
2102 * f:: -f to work faster
2103 * I:: -I for .include search path
2104 @ifclear DIFF-TBL-KLUGE
2105 * K:: -K for compatibility
2107 @ifset DIFF-TBL-KLUGE
2108 * K:: -K for difference tables
2111 * L:: -L to retain local symbols
2112 * listing:: --listing-XXX to configure listing output
2113 * M:: -M or --mri to assemble in MRI compatibility mode
2114 * MD:: --MD for dependency tracking
2115 * o:: -o to name the object file
2116 * R:: -R to join data and text sections
2117 * statistics:: --statistics to see statistics about assembly
2118 * traditional-format:: --traditional-format for compatible output
2119 * v:: -v to announce version
2120 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2121 * Z:: -Z to make object file even after errors
2125 @section Enable Listings: @option{-a[cdghlns]}
2135 @cindex listings, enabling
2136 @cindex assembly listings, enabling
2138 These options enable listing output from the assembler. By itself,
2139 @samp{-a} requests high-level, assembly, and symbols listing.
2140 You can use other letters to select specific options for the list:
2141 @samp{-ah} requests a high-level language listing,
2142 @samp{-al} requests an output-program assembly listing, and
2143 @samp{-as} requests a symbol table listing.
2144 High-level listings require that a compiler debugging option like
2145 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2148 Use the @samp{-ag} option to print a first section with general assembly
2149 information, like @value{AS} version, switches passed, or time stamp.
2151 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2152 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2153 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2154 omitted from the listing.
2156 Use the @samp{-ad} option to omit debugging directives from the
2159 Once you have specified one of these options, you can further control
2160 listing output and its appearance using the directives @code{.list},
2161 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2163 The @samp{-an} option turns off all forms processing.
2164 If you do not request listing output with one of the @samp{-a} options, the
2165 listing-control directives have no effect.
2167 The letters after @samp{-a} may be combined into one option,
2168 @emph{e.g.}, @samp{-aln}.
2170 Note if the assembler source is coming from the standard input (e.g.,
2172 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2173 is being used) then the listing will not contain any comments or preprocessor
2174 directives. This is because the listing code buffers input source lines from
2175 stdin only after they have been preprocessed by the assembler. This reduces
2176 memory usage and makes the code more efficient.
2179 @section @option{--alternate}
2182 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2185 @section @option{-D}
2188 This option has no effect whatsoever, but it is accepted to make it more
2189 likely that scripts written for other assemblers also work with
2190 @command{@value{AS}}.
2193 @section Work Faster: @option{-f}
2196 @cindex trusted compiler
2197 @cindex faster processing (@option{-f})
2198 @samp{-f} should only be used when assembling programs written by a
2199 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2200 and comment preprocessing on
2201 the input file(s) before assembling them. @xref{Preprocessing,
2205 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2206 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2211 @section @code{.include} Search Path: @option{-I} @var{path}
2213 @kindex -I @var{path}
2214 @cindex paths for @code{.include}
2215 @cindex search path for @code{.include}
2216 @cindex @code{include} directive search path
2217 Use this option to add a @var{path} to the list of directories
2218 @command{@value{AS}} searches for files specified in @code{.include}
2219 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2220 many times as necessary to include a variety of paths. The current
2221 working directory is always searched first; after that, @command{@value{AS}}
2222 searches any @samp{-I} directories in the same order as they were
2223 specified (left to right) on the command line.
2226 @section Difference Tables: @option{-K}
2229 @ifclear DIFF-TBL-KLUGE
2230 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2231 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2232 where it can be used to warn when the assembler alters the machine code
2233 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2234 family does not have the addressing limitations that sometimes lead to this
2235 alteration on other platforms.
2238 @ifset DIFF-TBL-KLUGE
2239 @cindex difference tables, warning
2240 @cindex warning for altered difference tables
2241 @command{@value{AS}} sometimes alters the code emitted for directives of the
2242 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2243 You can use the @samp{-K} option if you want a warning issued when this
2248 @section Include Local Symbols: @option{-L}
2251 @cindex local symbols, retaining in output
2252 Symbols beginning with system-specific local label prefixes, typically
2253 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2254 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2255 such symbols when debugging, because they are intended for the use of
2256 programs (like compilers) that compose assembler programs, not for your
2257 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2258 such symbols, so you do not normally debug with them.
2260 This option tells @command{@value{AS}} to retain those local symbols
2261 in the object file. Usually if you do this you also tell the linker
2262 @code{@value{LD}} to preserve those symbols.
2265 @section Configuring listing output: @option{--listing}
2267 The listing feature of the assembler can be enabled via the command line switch
2268 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2269 hex dump of the corresponding locations in the output object file, and displays
2270 them as a listing file. The format of this listing can be controlled by
2271 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2272 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2273 @code{.psize} (@pxref{Psize}), and
2274 @code{.eject} (@pxref{Eject}) and also by the following switches:
2277 @item --listing-lhs-width=@samp{number}
2278 @kindex --listing-lhs-width
2279 @cindex Width of first line disassembly output
2280 Sets the maximum width, in words, of the first line of the hex byte dump. This
2281 dump appears on the left hand side of the listing output.
2283 @item --listing-lhs-width2=@samp{number}
2284 @kindex --listing-lhs-width2
2285 @cindex Width of continuation lines of disassembly output
2286 Sets the maximum width, in words, of any further lines of the hex byte dump for
2287 a given input source line. If this value is not specified, it defaults to being
2288 the same as the value specified for @samp{--listing-lhs-width}. If neither
2289 switch is used the default is to one.
2291 @item --listing-rhs-width=@samp{number}
2292 @kindex --listing-rhs-width
2293 @cindex Width of source line output
2294 Sets the maximum width, in characters, of the source line that is displayed
2295 alongside the hex dump. The default value for this parameter is 100. The
2296 source line is displayed on the right hand side of the listing output.
2298 @item --listing-cont-lines=@samp{number}
2299 @kindex --listing-cont-lines
2300 @cindex Maximum number of continuation lines
2301 Sets the maximum number of continuation lines of hex dump that will be
2302 displayed for a given single line of source input. The default value is 4.
2306 @section Assemble in MRI Compatibility Mode: @option{-M}
2309 @cindex MRI compatibility mode
2310 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2311 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2312 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2313 configured target) assembler from Microtec Research. The exact nature of the
2314 MRI syntax will not be documented here; see the MRI manuals for more
2315 information. Note in particular that the handling of macros and macro
2316 arguments is somewhat different. The purpose of this option is to permit
2317 assembling existing MRI assembler code using @command{@value{AS}}.
2319 The MRI compatibility is not complete. Certain operations of the MRI assembler
2320 depend upon its object file format, and can not be supported using other object
2321 file formats. Supporting these would require enhancing each object file format
2322 individually. These are:
2325 @item global symbols in common section
2327 The m68k MRI assembler supports common sections which are merged by the linker.
2328 Other object file formats do not support this. @command{@value{AS}} handles
2329 common sections by treating them as a single common symbol. It permits local
2330 symbols to be defined within a common section, but it can not support global
2331 symbols, since it has no way to describe them.
2333 @item complex relocations
2335 The MRI assemblers support relocations against a negated section address, and
2336 relocations which combine the start addresses of two or more sections. These
2337 are not support by other object file formats.
2339 @item @code{END} pseudo-op specifying start address
2341 The MRI @code{END} pseudo-op permits the specification of a start address.
2342 This is not supported by other object file formats. The start address may
2343 instead be specified using the @option{-e} option to the linker, or in a linker
2346 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2348 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2349 name to the output file. This is not supported by other object file formats.
2351 @item @code{ORG} pseudo-op
2353 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2354 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2355 which changes the location within the current section. Absolute sections are
2356 not supported by other object file formats. The address of a section may be
2357 assigned within a linker script.
2360 There are some other features of the MRI assembler which are not supported by
2361 @command{@value{AS}}, typically either because they are difficult or because they
2362 seem of little consequence. Some of these may be supported in future releases.
2366 @item EBCDIC strings
2368 EBCDIC strings are not supported.
2370 @item packed binary coded decimal
2372 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2373 and @code{DCB.P} pseudo-ops are not supported.
2375 @item @code{FEQU} pseudo-op
2377 The m68k @code{FEQU} pseudo-op is not supported.
2379 @item @code{NOOBJ} pseudo-op
2381 The m68k @code{NOOBJ} pseudo-op is not supported.
2383 @item @code{OPT} branch control options
2385 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2386 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2387 relaxes all branches, whether forward or backward, to an appropriate size, so
2388 these options serve no purpose.
2390 @item @code{OPT} list control options
2392 The following m68k @code{OPT} list control options are ignored: @code{C},
2393 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2394 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2396 @item other @code{OPT} options
2398 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2399 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2401 @item @code{OPT} @code{D} option is default
2403 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2404 @code{OPT NOD} may be used to turn it off.
2406 @item @code{XREF} pseudo-op.
2408 The m68k @code{XREF} pseudo-op is ignored.
2410 @item @code{.debug} pseudo-op
2412 The i960 @code{.debug} pseudo-op is not supported.
2414 @item @code{.extended} pseudo-op
2416 The i960 @code{.extended} pseudo-op is not supported.
2418 @item @code{.list} pseudo-op.
2420 The various options of the i960 @code{.list} pseudo-op are not supported.
2422 @item @code{.optimize} pseudo-op
2424 The i960 @code{.optimize} pseudo-op is not supported.
2426 @item @code{.output} pseudo-op
2428 The i960 @code{.output} pseudo-op is not supported.
2430 @item @code{.setreal} pseudo-op
2432 The i960 @code{.setreal} pseudo-op is not supported.
2437 @section Dependency Tracking: @option{--MD}
2440 @cindex dependency tracking
2443 @command{@value{AS}} can generate a dependency file for the file it creates. This
2444 file consists of a single rule suitable for @code{make} describing the
2445 dependencies of the main source file.
2447 The rule is written to the file named in its argument.
2449 This feature is used in the automatic updating of makefiles.
2452 @section Name the Object File: @option{-o}
2455 @cindex naming object file
2456 @cindex object file name
2457 There is always one object file output when you run @command{@value{AS}}. By
2458 default it has the name
2461 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2475 You use this option (which takes exactly one filename) to give the
2476 object file a different name.
2478 Whatever the object file is called, @command{@value{AS}} overwrites any
2479 existing file of the same name.
2482 @section Join Data and Text Sections: @option{-R}
2485 @cindex data and text sections, joining
2486 @cindex text and data sections, joining
2487 @cindex joining text and data sections
2488 @cindex merging text and data sections
2489 @option{-R} tells @command{@value{AS}} to write the object file as if all
2490 data-section data lives in the text section. This is only done at
2491 the very last moment: your binary data are the same, but data
2492 section parts are relocated differently. The data section part of
2493 your object file is zero bytes long because all its bytes are
2494 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2496 When you specify @option{-R} it would be possible to generate shorter
2497 address displacements (because we do not have to cross between text and
2498 data section). We refrain from doing this simply for compatibility with
2499 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2502 When @command{@value{AS}} is configured for COFF or ELF output,
2503 this option is only useful if you use sections named @samp{.text} and
2508 @option{-R} is not supported for any of the HPPA targets. Using
2509 @option{-R} generates a warning from @command{@value{AS}}.
2513 @section Display Assembly Statistics: @option{--statistics}
2515 @kindex --statistics
2516 @cindex statistics, about assembly
2517 @cindex time, total for assembly
2518 @cindex space used, maximum for assembly
2519 Use @samp{--statistics} to display two statistics about the resources used by
2520 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2521 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2524 @node traditional-format
2525 @section Compatible Output: @option{--traditional-format}
2527 @kindex --traditional-format
2528 For some targets, the output of @command{@value{AS}} is different in some ways
2529 from the output of some existing assembler. This switch requests
2530 @command{@value{AS}} to use the traditional format instead.
2532 For example, it disables the exception frame optimizations which
2533 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2536 @section Announce Version: @option{-v}
2540 @cindex assembler version
2541 @cindex version of assembler
2542 You can find out what version of as is running by including the
2543 option @samp{-v} (which you can also spell as @samp{-version}) on the
2547 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2549 @command{@value{AS}} should never give a warning or error message when
2550 assembling compiler output. But programs written by people often
2551 cause @command{@value{AS}} to give a warning that a particular assumption was
2552 made. All such warnings are directed to the standard error file.
2556 @cindex suppressing warnings
2557 @cindex warnings, suppressing
2558 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2559 This only affects the warning messages: it does not change any particular of
2560 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2563 @kindex --fatal-warnings
2564 @cindex errors, caused by warnings
2565 @cindex warnings, causing error
2566 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2567 files that generate warnings to be in error.
2570 @cindex warnings, switching on
2571 You can switch these options off again by specifying @option{--warn}, which
2572 causes warnings to be output as usual.
2575 @section Generate Object File in Spite of Errors: @option{-Z}
2576 @cindex object file, after errors
2577 @cindex errors, continuing after
2578 After an error message, @command{@value{AS}} normally produces no output. If for
2579 some reason you are interested in object file output even after
2580 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2581 option. If there are any errors, @command{@value{AS}} continues anyways, and
2582 writes an object file after a final warning message of the form @samp{@var{n}
2583 errors, @var{m} warnings, generating bad object file.}
2588 @cindex machine-independent syntax
2589 @cindex syntax, machine-independent
2590 This chapter describes the machine-independent syntax allowed in a
2591 source file. @command{@value{AS}} syntax is similar to what many other
2592 assemblers use; it is inspired by the BSD 4.2
2597 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2601 * Preprocessing:: Preprocessing
2602 * Whitespace:: Whitespace
2603 * Comments:: Comments
2604 * Symbol Intro:: Symbols
2605 * Statements:: Statements
2606 * Constants:: Constants
2610 @section Preprocessing
2612 @cindex preprocessing
2613 The @command{@value{AS}} internal preprocessor:
2615 @cindex whitespace, removed by preprocessor
2617 adjusts and removes extra whitespace. It leaves one space or tab before
2618 the keywords on a line, and turns any other whitespace on the line into
2621 @cindex comments, removed by preprocessor
2623 removes all comments, replacing them with a single space, or an
2624 appropriate number of newlines.
2626 @cindex constants, converted by preprocessor
2628 converts character constants into the appropriate numeric values.
2631 It does not do macro processing, include file handling, or
2632 anything else you may get from your C compiler's preprocessor. You can
2633 do include file processing with the @code{.include} directive
2634 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2635 to get other ``CPP'' style preprocessing by giving the input file a
2636 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2637 Output, gcc.info, Using GNU CC}.
2639 Excess whitespace, comments, and character constants
2640 cannot be used in the portions of the input text that are not
2643 @cindex turning preprocessing on and off
2644 @cindex preprocessing, turning on and off
2647 If the first line of an input file is @code{#NO_APP} or if you use the
2648 @samp{-f} option, whitespace and comments are not removed from the input file.
2649 Within an input file, you can ask for whitespace and comment removal in
2650 specific portions of the by putting a line that says @code{#APP} before the
2651 text that may contain whitespace or comments, and putting a line that says
2652 @code{#NO_APP} after this text. This feature is mainly intend to support
2653 @code{asm} statements in compilers whose output is otherwise free of comments
2660 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2661 Whitespace is used to separate symbols, and to make programs neater for
2662 people to read. Unless within character constants
2663 (@pxref{Characters,,Character Constants}), any whitespace means the same
2664 as exactly one space.
2670 There are two ways of rendering comments to @command{@value{AS}}. In both
2671 cases the comment is equivalent to one space.
2673 Anything from @samp{/*} through the next @samp{*/} is a comment.
2674 This means you may not nest these comments.
2678 The only way to include a newline ('\n') in a comment
2679 is to use this sort of comment.
2682 /* This sort of comment does not nest. */
2685 @cindex line comment character
2686 Anything from a @dfn{line comment} character up to the next newline is
2687 considered a comment and is ignored. The line comment character is target
2688 specific, and some targets multiple comment characters. Some targets also have
2689 line comment characters that only work if they are the first character on a
2690 line. Some targets use a sequence of two characters to introduce a line
2691 comment. Some targets can also change their line comment characters depending
2692 upon command line options that have been used. For more details see the
2693 @emph{Syntax} section in the documentation for individual targets.
2695 If the line comment character is the hash sign (@samp{#}) then it still has the
2696 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2697 to specify logical line numbers:
2700 @cindex lines starting with @code{#}
2701 @cindex logical line numbers
2702 To be compatible with past assemblers, lines that begin with @samp{#} have a
2703 special interpretation. Following the @samp{#} should be an absolute
2704 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2705 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2706 new logical file name. The rest of the line, if any, should be whitespace.
2708 If the first non-whitespace characters on the line are not numeric,
2709 the line is ignored. (Just like a comment.)
2712 # This is an ordinary comment.
2713 # 42-6 "new_file_name" # New logical file name
2714 # This is logical line # 36.
2716 This feature is deprecated, and may disappear from future versions
2717 of @command{@value{AS}}.
2722 @cindex characters used in symbols
2723 @ifclear SPECIAL-SYMS
2724 A @dfn{symbol} is one or more characters chosen from the set of all
2725 letters (both upper and lower case), digits and the three characters
2731 A @dfn{symbol} is one or more characters chosen from the set of all
2732 letters (both upper and lower case), digits and the three characters
2733 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2739 On most machines, you can also use @code{$} in symbol names; exceptions
2740 are noted in @ref{Machine Dependencies}.
2742 No symbol may begin with a digit. Case is significant.
2743 There is no length limit; all characters are significant. Multibyte characters
2744 are supported. Symbols are delimited by characters not in that set, or by the
2745 beginning of a file (since the source program must end with a newline, the end
2746 of a file is not a possible symbol delimiter). @xref{Symbols}.
2748 Symbol names may also be enclosed in double quote @code{"} characters. In such
2749 cases any characters are allowed, except for the NUL character. If a double
2750 quote character is to be included in the symbol name it must be preceeded by a
2751 backslash @code{\} character.
2752 @cindex length of symbols
2757 @cindex statements, structure of
2758 @cindex line separator character
2759 @cindex statement separator character
2761 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2762 @dfn{line separator character}. The line separator character is target
2763 specific and described in the @emph{Syntax} section of each
2764 target's documentation. Not all targets support a line separator character.
2765 The newline or line separator character is considered to be part of the
2766 preceding statement. Newlines and separators within character constants are an
2767 exception: they do not end statements.
2769 @cindex newline, required at file end
2770 @cindex EOF, newline must precede
2771 It is an error to end any statement with end-of-file: the last
2772 character of any input file should be a newline.@refill
2774 An empty statement is allowed, and may include whitespace. It is ignored.
2776 @cindex instructions and directives
2777 @cindex directives and instructions
2778 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2779 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2781 A statement begins with zero or more labels, optionally followed by a
2782 key symbol which determines what kind of statement it is. The key
2783 symbol determines the syntax of the rest of the statement. If the
2784 symbol begins with a dot @samp{.} then the statement is an assembler
2785 directive: typically valid for any computer. If the symbol begins with
2786 a letter the statement is an assembly language @dfn{instruction}: it
2787 assembles into a machine language instruction.
2789 Different versions of @command{@value{AS}} for different computers
2790 recognize different instructions. In fact, the same symbol may
2791 represent a different instruction in a different computer's assembly
2795 @cindex @code{:} (label)
2796 @cindex label (@code{:})
2797 A label is a symbol immediately followed by a colon (@code{:}).
2798 Whitespace before a label or after a colon is permitted, but you may not
2799 have whitespace between a label's symbol and its colon. @xref{Labels}.
2802 For HPPA targets, labels need not be immediately followed by a colon, but
2803 the definition of a label must begin in column zero. This also implies that
2804 only one label may be defined on each line.
2808 label: .directive followed by something
2809 another_label: # This is an empty statement.
2810 instruction operand_1, operand_2, @dots{}
2817 A constant is a number, written so that its value is known by
2818 inspection, without knowing any context. Like this:
2821 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2822 .ascii "Ring the bell\7" # A string constant.
2823 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2824 .float 0f-314159265358979323846264338327\
2825 95028841971.693993751E-40 # - pi, a flonum.
2830 * Characters:: Character Constants
2831 * Numbers:: Number Constants
2835 @subsection Character Constants
2837 @cindex character constants
2838 @cindex constants, character
2839 There are two kinds of character constants. A @dfn{character} stands
2840 for one character in one byte and its value may be used in
2841 numeric expressions. String constants (properly called string
2842 @emph{literals}) are potentially many bytes and their values may not be
2843 used in arithmetic expressions.
2847 * Chars:: Characters
2851 @subsubsection Strings
2853 @cindex string constants
2854 @cindex constants, string
2855 A @dfn{string} is written between double-quotes. It may contain
2856 double-quotes or null characters. The way to get special characters
2857 into a string is to @dfn{escape} these characters: precede them with
2858 a backslash @samp{\} character. For example @samp{\\} represents
2859 one backslash: the first @code{\} is an escape which tells
2860 @command{@value{AS}} to interpret the second character literally as a backslash
2861 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2862 escape character). The complete list of escapes follows.
2864 @cindex escape codes, character
2865 @cindex character escape codes
2868 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2870 @cindex @code{\b} (backspace character)
2871 @cindex backspace (@code{\b})
2873 Mnemonic for backspace; for ASCII this is octal code 010.
2876 @c Mnemonic for EOText; for ASCII this is octal code 004.
2878 @cindex @code{\f} (formfeed character)
2879 @cindex formfeed (@code{\f})
2881 Mnemonic for FormFeed; for ASCII this is octal code 014.
2883 @cindex @code{\n} (newline character)
2884 @cindex newline (@code{\n})
2886 Mnemonic for newline; for ASCII this is octal code 012.
2889 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2891 @cindex @code{\r} (carriage return character)
2892 @cindex carriage return (@code{\r})
2894 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2897 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2898 @c other assemblers.
2900 @cindex @code{\t} (tab)
2901 @cindex tab (@code{\t})
2903 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2906 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2907 @c @item \x @var{digit} @var{digit} @var{digit}
2908 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2910 @cindex @code{\@var{ddd}} (octal character code)
2911 @cindex octal character code (@code{\@var{ddd}})
2912 @item \ @var{digit} @var{digit} @var{digit}
2913 An octal character code. The numeric code is 3 octal digits.
2914 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2915 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2917 @cindex @code{\@var{xd...}} (hex character code)
2918 @cindex hex character code (@code{\@var{xd...}})
2919 @item \@code{x} @var{hex-digits...}
2920 A hex character code. All trailing hex digits are combined. Either upper or
2921 lower case @code{x} works.
2923 @cindex @code{\\} (@samp{\} character)
2924 @cindex backslash (@code{\\})
2926 Represents one @samp{\} character.
2929 @c Represents one @samp{'} (accent acute) character.
2930 @c This is needed in single character literals
2931 @c (@xref{Characters,,Character Constants}.) to represent
2934 @cindex @code{\"} (doublequote character)
2935 @cindex doublequote (@code{\"})
2937 Represents one @samp{"} character. Needed in strings to represent
2938 this character, because an unescaped @samp{"} would end the string.
2940 @item \ @var{anything-else}
2941 Any other character when escaped by @kbd{\} gives a warning, but
2942 assembles as if the @samp{\} was not present. The idea is that if
2943 you used an escape sequence you clearly didn't want the literal
2944 interpretation of the following character. However @command{@value{AS}} has no
2945 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2946 code and warns you of the fact.
2949 Which characters are escapable, and what those escapes represent,
2950 varies widely among assemblers. The current set is what we think
2951 the BSD 4.2 assembler recognizes, and is a subset of what most C
2952 compilers recognize. If you are in doubt, do not use an escape
2956 @subsubsection Characters
2958 @cindex single character constant
2959 @cindex character, single
2960 @cindex constant, single character
2961 A single character may be written as a single quote immediately
2962 followed by that character. The same escapes apply to characters as
2963 to strings. So if you want to write the character backslash, you
2964 must write @kbd{'\\} where the first @code{\} escapes the second
2965 @code{\}. As you can see, the quote is an acute accent, not a
2966 grave accent. A newline
2968 @ifclear abnormal-separator
2969 (or semicolon @samp{;})
2971 @ifset abnormal-separator
2973 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2978 immediately following an acute accent is taken as a literal character
2979 and does not count as the end of a statement. The value of a character
2980 constant in a numeric expression is the machine's byte-wide code for
2981 that character. @command{@value{AS}} assumes your character code is ASCII:
2982 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2985 @subsection Number Constants
2987 @cindex constants, number
2988 @cindex number constants
2989 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2990 are stored in the target machine. @emph{Integers} are numbers that
2991 would fit into an @code{int} in the C language. @emph{Bignums} are
2992 integers, but they are stored in more than 32 bits. @emph{Flonums}
2993 are floating point numbers, described below.
2996 * Integers:: Integers
3001 * Bit Fields:: Bit Fields
3007 @subsubsection Integers
3009 @cindex constants, integer
3011 @cindex binary integers
3012 @cindex integers, binary
3013 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3014 the binary digits @samp{01}.
3016 @cindex octal integers
3017 @cindex integers, octal
3018 An octal integer is @samp{0} followed by zero or more of the octal
3019 digits (@samp{01234567}).
3021 @cindex decimal integers
3022 @cindex integers, decimal
3023 A decimal integer starts with a non-zero digit followed by zero or
3024 more digits (@samp{0123456789}).
3026 @cindex hexadecimal integers
3027 @cindex integers, hexadecimal
3028 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3029 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3031 Integers have the usual values. To denote a negative integer, use
3032 the prefix operator @samp{-} discussed under expressions
3033 (@pxref{Prefix Ops,,Prefix Operators}).
3036 @subsubsection Bignums
3039 @cindex constants, bignum
3040 A @dfn{bignum} has the same syntax and semantics as an integer
3041 except that the number (or its negative) takes more than 32 bits to
3042 represent in binary. The distinction is made because in some places
3043 integers are permitted while bignums are not.
3046 @subsubsection Flonums
3048 @cindex floating point numbers
3049 @cindex constants, floating point
3051 @cindex precision, floating point
3052 A @dfn{flonum} represents a floating point number. The translation is
3053 indirect: a decimal floating point number from the text is converted by
3054 @command{@value{AS}} to a generic binary floating point number of more than
3055 sufficient precision. This generic floating point number is converted
3056 to a particular computer's floating point format (or formats) by a
3057 portion of @command{@value{AS}} specialized to that computer.
3059 A flonum is written by writing (in order)
3064 (@samp{0} is optional on the HPPA.)
3068 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3070 @kbd{e} is recommended. Case is not important.
3072 @c FIXME: verify if flonum syntax really this vague for most cases
3073 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3074 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3077 On the H8/300, Renesas / SuperH SH,
3078 and AMD 29K architectures, the letter must be
3079 one of the letters @samp{DFPRSX} (in upper or lower case).
3081 On the ARC, the letter must be one of the letters @samp{DFRS}
3082 (in upper or lower case).
3084 On the Intel 960 architecture, the letter must be
3085 one of the letters @samp{DFT} (in upper or lower case).
3087 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3091 One of the letters @samp{DFRS} (in upper or lower case).
3094 One of the letters @samp{DFPRSX} (in upper or lower case).
3097 The letter @samp{E} (upper case only).
3100 One of the letters @samp{DFT} (in upper or lower case).
3105 An optional sign: either @samp{+} or @samp{-}.
3108 An optional @dfn{integer part}: zero or more decimal digits.
3111 An optional @dfn{fractional part}: @samp{.} followed by zero
3112 or more decimal digits.
3115 An optional exponent, consisting of:
3119 An @samp{E} or @samp{e}.
3120 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3121 @c principle this can perfectly well be different on different targets.
3123 Optional sign: either @samp{+} or @samp{-}.
3125 One or more decimal digits.
3130 At least one of the integer part or the fractional part must be
3131 present. The floating point number has the usual base-10 value.
3133 @command{@value{AS}} does all processing using integers. Flonums are computed
3134 independently of any floating point hardware in the computer running
3135 @command{@value{AS}}.
3139 @c Bit fields are written as a general facility but are also controlled
3140 @c by a conditional-compilation flag---which is as of now (21mar91)
3141 @c turned on only by the i960 config of GAS.
3143 @subsubsection Bit Fields
3146 @cindex constants, bit field
3147 You can also define numeric constants as @dfn{bit fields}.
3148 Specify two numbers separated by a colon---
3150 @var{mask}:@var{value}
3153 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3156 The resulting number is then packed
3158 @c this conditional paren in case bit fields turned on elsewhere than 960
3159 (in host-dependent byte order)
3161 into a field whose width depends on which assembler directive has the
3162 bit-field as its argument. Overflow (a result from the bitwise and
3163 requiring more binary digits to represent) is not an error; instead,
3164 more constants are generated, of the specified width, beginning with the
3165 least significant digits.@refill
3167 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3168 @code{.short}, and @code{.word} accept bit-field arguments.
3173 @chapter Sections and Relocation
3178 * Secs Background:: Background
3179 * Ld Sections:: Linker Sections
3180 * As Sections:: Assembler Internal Sections
3181 * Sub-Sections:: Sub-Sections
3185 @node Secs Background
3188 Roughly, a section is a range of addresses, with no gaps; all data
3189 ``in'' those addresses is treated the same for some particular purpose.
3190 For example there may be a ``read only'' section.
3192 @cindex linker, and assembler
3193 @cindex assembler, and linker
3194 The linker @code{@value{LD}} reads many object files (partial programs) and
3195 combines their contents to form a runnable program. When @command{@value{AS}}
3196 emits an object file, the partial program is assumed to start at address 0.
3197 @code{@value{LD}} assigns the final addresses for the partial program, so that
3198 different partial programs do not overlap. This is actually an
3199 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3202 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3203 addresses. These blocks slide to their run-time addresses as rigid
3204 units; their length does not change and neither does the order of bytes
3205 within them. Such a rigid unit is called a @emph{section}. Assigning
3206 run-time addresses to sections is called @dfn{relocation}. It includes
3207 the task of adjusting mentions of object-file addresses so they refer to
3208 the proper run-time addresses.
3210 For the H8/300, and for the Renesas / SuperH SH,
3211 @command{@value{AS}} pads sections if needed to
3212 ensure they end on a word (sixteen bit) boundary.
3215 @cindex standard assembler sections
3216 An object file written by @command{@value{AS}} has at least three sections, any
3217 of which may be empty. These are named @dfn{text}, @dfn{data} and
3222 When it generates COFF or ELF output,
3224 @command{@value{AS}} can also generate whatever other named sections you specify
3225 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3226 If you do not use any directives that place output in the @samp{.text}
3227 or @samp{.data} sections, these sections still exist, but are empty.
3232 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3234 @command{@value{AS}} can also generate whatever other named sections you
3235 specify using the @samp{.space} and @samp{.subspace} directives. See
3236 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3237 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3238 assembler directives.
3241 Additionally, @command{@value{AS}} uses different names for the standard
3242 text, data, and bss sections when generating SOM output. Program text
3243 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3244 BSS into @samp{$BSS$}.
3248 Within the object file, the text section starts at address @code{0}, the
3249 data section follows, and the bss section follows the data section.
3252 When generating either SOM or ELF output files on the HPPA, the text
3253 section starts at address @code{0}, the data section at address
3254 @code{0x4000000}, and the bss section follows the data section.
3257 To let @code{@value{LD}} know which data changes when the sections are
3258 relocated, and how to change that data, @command{@value{AS}} also writes to the
3259 object file details of the relocation needed. To perform relocation
3260 @code{@value{LD}} must know, each time an address in the object
3264 Where in the object file is the beginning of this reference to
3267 How long (in bytes) is this reference?
3269 Which section does the address refer to? What is the numeric value of
3271 (@var{address}) @minus{} (@var{start-address of section})?
3274 Is the reference to an address ``Program-Counter relative''?
3277 @cindex addresses, format of
3278 @cindex section-relative addressing
3279 In fact, every address @command{@value{AS}} ever uses is expressed as
3281 (@var{section}) + (@var{offset into section})
3284 Further, most expressions @command{@value{AS}} computes have this section-relative
3287 (For some object formats, such as SOM for the HPPA, some expressions are
3288 symbol-relative instead.)
3291 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3292 @var{N} into section @var{secname}.''
3294 Apart from text, data and bss sections you need to know about the
3295 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3296 addresses in the absolute section remain unchanged. For example, address
3297 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3298 @code{@value{LD}}. Although the linker never arranges two partial programs'
3299 data sections with overlapping addresses after linking, @emph{by definition}
3300 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3301 part of a program is always the same address when the program is running as
3302 address @code{@{absolute@ 239@}} in any other part of the program.
3304 The idea of sections is extended to the @dfn{undefined} section. Any
3305 address whose section is unknown at assembly time is by definition
3306 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3307 Since numbers are always defined, the only way to generate an undefined
3308 address is to mention an undefined symbol. A reference to a named
3309 common block would be such a symbol: its value is unknown at assembly
3310 time so it has section @emph{undefined}.
3312 By analogy the word @emph{section} is used to describe groups of sections in
3313 the linked program. @code{@value{LD}} puts all partial programs' text
3314 sections in contiguous addresses in the linked program. It is
3315 customary to refer to the @emph{text section} of a program, meaning all
3316 the addresses of all partial programs' text sections. Likewise for
3317 data and bss sections.
3319 Some sections are manipulated by @code{@value{LD}}; others are invented for
3320 use of @command{@value{AS}} and have no meaning except during assembly.
3323 @section Linker Sections
3324 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3329 @cindex named sections
3330 @cindex sections, named
3331 @item named sections
3334 @cindex text section
3335 @cindex data section
3339 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3340 separate but equal sections. Anything you can say of one section is
3343 When the program is running, however, it is
3344 customary for the text section to be unalterable. The
3345 text section is often shared among processes: it contains
3346 instructions, constants and the like. The data section of a running
3347 program is usually alterable: for example, C variables would be stored
3348 in the data section.
3353 This section contains zeroed bytes when your program begins running. It
3354 is used to hold uninitialized variables or common storage. The length of
3355 each partial program's bss section is important, but because it starts
3356 out containing zeroed bytes there is no need to store explicit zero
3357 bytes in the object file. The bss section was invented to eliminate
3358 those explicit zeros from object files.
3360 @cindex absolute section
3361 @item absolute section
3362 Address 0 of this section is always ``relocated'' to runtime address 0.
3363 This is useful if you want to refer to an address that @code{@value{LD}} must
3364 not change when relocating. In this sense we speak of absolute
3365 addresses being ``unrelocatable'': they do not change during relocation.
3367 @cindex undefined section
3368 @item undefined section
3369 This ``section'' is a catch-all for address references to objects not in
3370 the preceding sections.
3371 @c FIXME: ref to some other doc on obj-file formats could go here.
3374 @cindex relocation example
3375 An idealized example of three relocatable sections follows.
3377 The example uses the traditional section names @samp{.text} and @samp{.data}.
3379 Memory addresses are on the horizontal axis.
3383 @c END TEXI2ROFF-KILL
3386 partial program # 1: |ttttt|dddd|00|
3393 partial program # 2: |TTT|DDD|000|
3396 +--+---+-----+--+----+---+-----+~~
3397 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3398 +--+---+-----+--+----+---+-----+~~
3400 addresses: 0 @dots{}
3407 \line{\it Partial program \#1: \hfil}
3408 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3409 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3411 \line{\it Partial program \#2: \hfil}
3412 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3413 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3415 \line{\it linked program: \hfil}
3416 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3417 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3418 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3419 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3421 \line{\it addresses: \hfil}
3425 @c END TEXI2ROFF-KILL
3428 @section Assembler Internal Sections
3430 @cindex internal assembler sections
3431 @cindex sections in messages, internal
3432 These sections are meant only for the internal use of @command{@value{AS}}. They
3433 have no meaning at run-time. You do not really need to know about these
3434 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3435 warning messages, so it might be helpful to have an idea of their
3436 meanings to @command{@value{AS}}. These sections are used to permit the
3437 value of every expression in your assembly language program to be a
3438 section-relative address.
3441 @cindex assembler internal logic error
3442 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3443 An internal assembler logic error has been found. This means there is a
3444 bug in the assembler.
3446 @cindex expr (internal section)
3448 The assembler stores complex expression internally as combinations of
3449 symbols. When it needs to represent an expression as a symbol, it puts
3450 it in the expr section.
3452 @c FIXME item transfer[t] vector preload
3453 @c FIXME item transfer[t] vector postload
3454 @c FIXME item register
3458 @section Sub-Sections
3460 @cindex numbered subsections
3461 @cindex grouping data
3467 fall into two sections: text and data.
3469 You may have separate groups of
3471 data in named sections
3475 data in named sections
3481 that you want to end up near to each other in the object file, even though they
3482 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3483 use @dfn{subsections} for this purpose. Within each section, there can be
3484 numbered subsections with values from 0 to 8192. Objects assembled into the
3485 same subsection go into the object file together with other objects in the same
3486 subsection. For example, a compiler might want to store constants in the text
3487 section, but might not want to have them interspersed with the program being
3488 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3489 section of code being output, and a @samp{.text 1} before each group of
3490 constants being output.
3492 Subsections are optional. If you do not use subsections, everything
3493 goes in subsection number zero.
3496 Each subsection is zero-padded up to a multiple of four bytes.
3497 (Subsections may be padded a different amount on different flavors
3498 of @command{@value{AS}}.)
3502 On the H8/300 platform, each subsection is zero-padded to a word
3503 boundary (two bytes).
3504 The same is true on the Renesas SH.
3507 @c FIXME section padding (alignment)?
3508 @c Rich Pixley says padding here depends on target obj code format; that
3509 @c doesn't seem particularly useful to say without further elaboration,
3510 @c so for now I say nothing about it. If this is a generic BFD issue,
3511 @c these paragraphs might need to vanish from this manual, and be
3512 @c discussed in BFD chapter of binutils (or some such).
3516 Subsections appear in your object file in numeric order, lowest numbered
3517 to highest. (All this to be compatible with other people's assemblers.)
3518 The object file contains no representation of subsections; @code{@value{LD}} and
3519 other programs that manipulate object files see no trace of them.
3520 They just see all your text subsections as a text section, and all your
3521 data subsections as a data section.
3523 To specify which subsection you want subsequent statements assembled
3524 into, use a numeric argument to specify it, in a @samp{.text
3525 @var{expression}} or a @samp{.data @var{expression}} statement.
3528 When generating COFF output, you
3533 can also use an extra subsection
3534 argument with arbitrary named sections: @samp{.section @var{name},
3539 When generating ELF output, you
3544 can also use the @code{.subsection} directive (@pxref{SubSection})
3545 to specify a subsection: @samp{.subsection @var{expression}}.
3547 @var{Expression} should be an absolute expression
3548 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3549 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3550 begins in @code{text 0}. For instance:
3552 .text 0 # The default subsection is text 0 anyway.
3553 .ascii "This lives in the first text subsection. *"
3555 .ascii "But this lives in the second text subsection."
3557 .ascii "This lives in the data section,"
3558 .ascii "in the first data subsection."
3560 .ascii "This lives in the first text section,"
3561 .ascii "immediately following the asterisk (*)."
3564 Each section has a @dfn{location counter} incremented by one for every byte
3565 assembled into that section. Because subsections are merely a convenience
3566 restricted to @command{@value{AS}} there is no concept of a subsection location
3567 counter. There is no way to directly manipulate a location counter---but the
3568 @code{.align} directive changes it, and any label definition captures its
3569 current value. The location counter of the section where statements are being
3570 assembled is said to be the @dfn{active} location counter.
3573 @section bss Section
3576 @cindex common variable storage
3577 The bss section is used for local common variable storage.
3578 You may allocate address space in the bss section, but you may
3579 not dictate data to load into it before your program executes. When
3580 your program starts running, all the contents of the bss
3581 section are zeroed bytes.
3583 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3584 @ref{Lcomm,,@code{.lcomm}}.
3586 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3587 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3590 When assembling for a target which supports multiple sections, such as ELF or
3591 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3592 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3593 section. Typically the section will only contain symbol definitions and
3594 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3601 Symbols are a central concept: the programmer uses symbols to name
3602 things, the linker uses symbols to link, and the debugger uses symbols
3606 @cindex debuggers, and symbol order
3607 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3608 the same order they were declared. This may break some debuggers.
3613 * Setting Symbols:: Giving Symbols Other Values
3614 * Symbol Names:: Symbol Names
3615 * Dot:: The Special Dot Symbol
3616 * Symbol Attributes:: Symbol Attributes
3623 A @dfn{label} is written as a symbol immediately followed by a colon
3624 @samp{:}. The symbol then represents the current value of the
3625 active location counter, and is, for example, a suitable instruction
3626 operand. You are warned if you use the same symbol to represent two
3627 different locations: the first definition overrides any other
3631 On the HPPA, the usual form for a label need not be immediately followed by a
3632 colon, but instead must start in column zero. Only one label may be defined on
3633 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3634 provides a special directive @code{.label} for defining labels more flexibly.
3637 @node Setting Symbols
3638 @section Giving Symbols Other Values
3640 @cindex assigning values to symbols
3641 @cindex symbol values, assigning
3642 A symbol can be given an arbitrary value by writing a symbol, followed
3643 by an equals sign @samp{=}, followed by an expression
3644 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3645 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3646 equals sign @samp{=}@samp{=} here represents an equivalent of the
3647 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3650 Blackfin does not support symbol assignment with @samp{=}.
3654 @section Symbol Names
3656 @cindex symbol names
3657 @cindex names, symbol
3658 @ifclear SPECIAL-SYMS
3659 Symbol names begin with a letter or with one of @samp{._}. On most
3660 machines, you can also use @code{$} in symbol names; exceptions are
3661 noted in @ref{Machine Dependencies}. That character may be followed by any
3662 string of digits, letters, dollar signs (unless otherwise noted for a
3663 particular target machine), and underscores.
3667 Symbol names begin with a letter or with one of @samp{._}. On the
3668 Renesas SH you can also use @code{$} in symbol names. That
3669 character may be followed by any string of digits, letters, dollar signs (save
3670 on the H8/300), and underscores.
3674 Case of letters is significant: @code{foo} is a different symbol name
3677 Symbol names do not start with a digit. An exception to this rule is made for
3678 Local Labels. See below.
3680 Multibyte characters are supported. To generate a symbol name containing
3681 multibyte characters enclose it within double quotes and use escape codes. cf
3682 @xref{Strings}. Generating a multibyte symbol name from a label is not
3683 currently supported.
3685 Each symbol has exactly one name. Each name in an assembly language program
3686 refers to exactly one symbol. You may use that symbol name any number of times
3689 @subheading Local Symbol Names
3691 @cindex local symbol names
3692 @cindex symbol names, local
3693 A local symbol is any symbol beginning with certain local label prefixes.
3694 By default, the local label prefix is @samp{.L} for ELF systems or
3695 @samp{L} for traditional a.out systems, but each target may have its own
3696 set of local label prefixes.
3698 On the HPPA local symbols begin with @samp{L$}.
3701 Local symbols are defined and used within the assembler, but they are
3702 normally not saved in object files. Thus, they are not visible when debugging.
3703 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3704 to retain the local symbols in the object files.
3706 @subheading Local Labels
3708 @cindex local labels
3709 @cindex temporary symbol names
3710 @cindex symbol names, temporary
3711 Local labels are different from local symbols. Local labels help compilers and
3712 programmers use names temporarily. They create symbols which are guaranteed to
3713 be unique over the entire scope of the input source code and which can be
3714 referred to by a simple notation. To define a local label, write a label of
3715 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3716 To refer to the most recent previous definition of that label write
3717 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3718 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3719 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3721 There is no restriction on how you can use these labels, and you can reuse them
3722 too. So that it is possible to repeatedly define the same local label (using
3723 the same number @samp{@b{N}}), although you can only refer to the most recently
3724 defined local label of that number (for a backwards reference) or the next
3725 definition of a specific local label for a forward reference. It is also worth
3726 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3727 implemented in a slightly more efficient manner than the others.
3738 Which is the equivalent of:
3741 label_1: branch label_3
3742 label_2: branch label_1
3743 label_3: branch label_4
3744 label_4: branch label_3
3747 Local label names are only a notational device. They are immediately
3748 transformed into more conventional symbol names before the assembler uses them.
3749 The symbol names are stored in the symbol table, appear in error messages, and
3750 are optionally emitted to the object file. The names are constructed using
3754 @item @emph{local label prefix}
3755 All local symbols begin with the system-specific local label prefix.
3756 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3757 that start with the local label prefix. These labels are
3758 used for symbols you are never intended to see. If you use the
3759 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3760 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3761 you may use them in debugging.
3764 This is the number that was used in the local label definition. So if the
3765 label is written @samp{55:} then the number is @samp{55}.
3768 This unusual character is included so you do not accidentally invent a symbol
3769 of the same name. The character has ASCII value of @samp{\002} (control-B).
3771 @item @emph{ordinal number}
3772 This is a serial number to keep the labels distinct. The first definition of
3773 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3774 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3775 the number @samp{1} and its 15th definition gets @samp{15} as well.
3778 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3779 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3781 @subheading Dollar Local Labels
3782 @cindex dollar local symbols
3784 On some targets @code{@value{AS}} also supports an even more local form of
3785 local labels called dollar labels. These labels go out of scope (i.e., they
3786 become undefined) as soon as a non-local label is defined. Thus they remain
3787 valid for only a small region of the input source code. Normal local labels,
3788 by contrast, remain in scope for the entire file, or until they are redefined
3789 by another occurrence of the same local label.
3791 Dollar labels are defined in exactly the same way as ordinary local labels,
3792 except that they have a dollar sign suffix to their numeric value, e.g.,
3795 They can also be distinguished from ordinary local labels by their transformed
3796 names which use ASCII character @samp{\001} (control-A) as the magic character
3797 to distinguish them from ordinary labels. For example, the fifth definition of
3798 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3801 @section The Special Dot Symbol
3803 @cindex dot (symbol)
3804 @cindex @code{.} (symbol)
3805 @cindex current address
3806 @cindex location counter
3807 The special symbol @samp{.} refers to the current address that
3808 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3809 .long .} defines @code{melvin} to contain its own address.
3810 Assigning a value to @code{.} is treated the same as a @code{.org}
3812 @ifclear no-space-dir
3813 Thus, the expression @samp{.=.+4} is the same as saying
3817 @node Symbol Attributes
3818 @section Symbol Attributes
3820 @cindex symbol attributes
3821 @cindex attributes, symbol
3822 Every symbol has, as well as its name, the attributes ``Value'' and
3823 ``Type''. Depending on output format, symbols can also have auxiliary
3826 The detailed definitions are in @file{a.out.h}.
3829 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3830 all these attributes, and probably won't warn you. This makes the
3831 symbol an externally defined symbol, which is generally what you
3835 * Symbol Value:: Value
3836 * Symbol Type:: Type
3839 * a.out Symbols:: Symbol Attributes: @code{a.out}
3843 * a.out Symbols:: Symbol Attributes: @code{a.out}
3846 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3851 * COFF Symbols:: Symbol Attributes for COFF
3854 * SOM Symbols:: Symbol Attributes for SOM
3861 @cindex value of a symbol
3862 @cindex symbol value
3863 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3864 location in the text, data, bss or absolute sections the value is the
3865 number of addresses from the start of that section to the label.
3866 Naturally for text, data and bss sections the value of a symbol changes
3867 as @code{@value{LD}} changes section base addresses during linking. Absolute
3868 symbols' values do not change during linking: that is why they are
3871 The value of an undefined symbol is treated in a special way. If it is
3872 0 then the symbol is not defined in this assembler source file, and
3873 @code{@value{LD}} tries to determine its value from other files linked into the
3874 same program. You make this kind of symbol simply by mentioning a symbol
3875 name without defining it. A non-zero value represents a @code{.comm}
3876 common declaration. The value is how much common storage to reserve, in
3877 bytes (addresses). The symbol refers to the first address of the
3883 @cindex type of a symbol
3885 The type attribute of a symbol contains relocation (section)
3886 information, any flag settings indicating that a symbol is external, and
3887 (optionally), other information for linkers and debuggers. The exact
3888 format depends on the object-code output format in use.
3893 @c The following avoids a "widow" subsection title. @group would be
3894 @c better if it were available outside examples.
3897 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3899 @cindex @code{b.out} symbol attributes
3900 @cindex symbol attributes, @code{b.out}
3901 These symbol attributes appear only when @command{@value{AS}} is configured for
3902 one of the Berkeley-descended object output formats---@code{a.out} or
3908 @subsection Symbol Attributes: @code{a.out}
3910 @cindex @code{a.out} symbol attributes
3911 @cindex symbol attributes, @code{a.out}
3917 @subsection Symbol Attributes: @code{a.out}
3919 @cindex @code{a.out} symbol attributes
3920 @cindex symbol attributes, @code{a.out}
3924 * Symbol Desc:: Descriptor
3925 * Symbol Other:: Other
3929 @subsubsection Descriptor
3931 @cindex descriptor, of @code{a.out} symbol
3932 This is an arbitrary 16-bit value. You may establish a symbol's
3933 descriptor value by using a @code{.desc} statement
3934 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3935 @command{@value{AS}}.
3938 @subsubsection Other
3940 @cindex other attribute, of @code{a.out} symbol
3941 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3946 @subsection Symbol Attributes for COFF
3948 @cindex COFF symbol attributes
3949 @cindex symbol attributes, COFF
3951 The COFF format supports a multitude of auxiliary symbol attributes;
3952 like the primary symbol attributes, they are set between @code{.def} and
3953 @code{.endef} directives.
3955 @subsubsection Primary Attributes
3957 @cindex primary attributes, COFF symbols
3958 The symbol name is set with @code{.def}; the value and type,
3959 respectively, with @code{.val} and @code{.type}.
3961 @subsubsection Auxiliary Attributes
3963 @cindex auxiliary attributes, COFF symbols
3964 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3965 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3966 table information for COFF.
3971 @subsection Symbol Attributes for SOM
3973 @cindex SOM symbol attributes
3974 @cindex symbol attributes, SOM
3976 The SOM format for the HPPA supports a multitude of symbol attributes set with
3977 the @code{.EXPORT} and @code{.IMPORT} directives.
3979 The attributes are described in @cite{HP9000 Series 800 Assembly
3980 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3981 @code{EXPORT} assembler directive documentation.
3985 @chapter Expressions
3989 @cindex numeric values
3990 An @dfn{expression} specifies an address or numeric value.
3991 Whitespace may precede and/or follow an expression.
3993 The result of an expression must be an absolute number, or else an offset into
3994 a particular section. If an expression is not absolute, and there is not
3995 enough information when @command{@value{AS}} sees the expression to know its
3996 section, a second pass over the source program might be necessary to interpret
3997 the expression---but the second pass is currently not implemented.
3998 @command{@value{AS}} aborts with an error message in this situation.
4001 * Empty Exprs:: Empty Expressions
4002 * Integer Exprs:: Integer Expressions
4006 @section Empty Expressions
4008 @cindex empty expressions
4009 @cindex expressions, empty
4010 An empty expression has no value: it is just whitespace or null.
4011 Wherever an absolute expression is required, you may omit the
4012 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4013 is compatible with other assemblers.
4016 @section Integer Expressions
4018 @cindex integer expressions
4019 @cindex expressions, integer
4020 An @dfn{integer expression} is one or more @emph{arguments} delimited
4021 by @emph{operators}.
4024 * Arguments:: Arguments
4025 * Operators:: Operators
4026 * Prefix Ops:: Prefix Operators
4027 * Infix Ops:: Infix Operators
4031 @subsection Arguments
4033 @cindex expression arguments
4034 @cindex arguments in expressions
4035 @cindex operands in expressions
4036 @cindex arithmetic operands
4037 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4038 contexts arguments are sometimes called ``arithmetic operands''. In
4039 this manual, to avoid confusing them with the ``instruction operands'' of
4040 the machine language, we use the term ``argument'' to refer to parts of
4041 expressions only, reserving the word ``operand'' to refer only to machine
4042 instruction operands.
4044 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4045 @var{section} is one of text, data, bss, absolute,
4046 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4049 Numbers are usually integers.
4051 A number can be a flonum or bignum. In this case, you are warned
4052 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4053 these 32 bits are an integer. You may write integer-manipulating
4054 instructions that act on exotic constants, compatible with other
4057 @cindex subexpressions
4058 Subexpressions are a left parenthesis @samp{(} followed by an integer
4059 expression, followed by a right parenthesis @samp{)}; or a prefix
4060 operator followed by an argument.
4063 @subsection Operators
4065 @cindex operators, in expressions
4066 @cindex arithmetic functions
4067 @cindex functions, in expressions
4068 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4069 operators are followed by an argument. Infix operators appear
4070 between their arguments. Operators may be preceded and/or followed by
4074 @subsection Prefix Operator
4076 @cindex prefix operators
4077 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4078 one argument, which must be absolute.
4080 @c the tex/end tex stuff surrounding this small table is meant to make
4081 @c it align, on the printed page, with the similar table in the next
4082 @c section (which is inside an enumerate).
4084 \global\advance\leftskip by \itemindent
4089 @dfn{Negation}. Two's complement negation.
4091 @dfn{Complementation}. Bitwise not.
4095 \global\advance\leftskip by -\itemindent
4099 @subsection Infix Operators
4101 @cindex infix operators
4102 @cindex operators, permitted arguments
4103 @dfn{Infix operators} take two arguments, one on either side. Operators
4104 have precedence, but operations with equal precedence are performed left
4105 to right. Apart from @code{+} or @option{-}, both arguments must be
4106 absolute, and the result is absolute.
4109 @cindex operator precedence
4110 @cindex precedence of operators
4117 @dfn{Multiplication}.
4120 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4126 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4129 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4133 Intermediate precedence
4138 @dfn{Bitwise Inclusive Or}.
4144 @dfn{Bitwise Exclusive Or}.
4147 @dfn{Bitwise Or Not}.
4154 @cindex addition, permitted arguments
4155 @cindex plus, permitted arguments
4156 @cindex arguments for addition
4158 @dfn{Addition}. If either argument is absolute, the result has the section of
4159 the other argument. You may not add together arguments from different
4162 @cindex subtraction, permitted arguments
4163 @cindex minus, permitted arguments
4164 @cindex arguments for subtraction
4166 @dfn{Subtraction}. If the right argument is absolute, the
4167 result has the section of the left argument.
4168 If both arguments are in the same section, the result is absolute.
4169 You may not subtract arguments from different sections.
4170 @c FIXME is there still something useful to say about undefined - undefined ?
4172 @cindex comparison expressions
4173 @cindex expressions, comparison
4178 @dfn{Is Not Equal To}
4182 @dfn{Is Greater Than}
4184 @dfn{Is Greater Than Or Equal To}
4186 @dfn{Is Less Than Or Equal To}
4188 The comparison operators can be used as infix operators. A true results has a
4189 value of -1 whereas a false result has a value of 0. Note, these operators
4190 perform signed comparisons.
4193 @item Lowest Precedence
4202 These two logical operations can be used to combine the results of sub
4203 expressions. Note, unlike the comparison operators a true result returns a
4204 value of 1 but a false results does still return 0. Also note that the logical
4205 or operator has a slightly lower precedence than logical and.
4210 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4211 address; you can only have a defined section in one of the two arguments.
4214 @chapter Assembler Directives
4216 @cindex directives, machine independent
4217 @cindex pseudo-ops, machine independent
4218 @cindex machine independent directives
4219 All assembler directives have names that begin with a period (@samp{.}).
4220 The names are case insensitive for most targets, and usually written
4223 This chapter discusses directives that are available regardless of the
4224 target machine configuration for the @sc{gnu} assembler.
4226 Some machine configurations provide additional directives.
4227 @xref{Machine Dependencies}.
4230 @ifset machine-directives
4231 @xref{Machine Dependencies}, for additional directives.
4236 * Abort:: @code{.abort}
4238 * ABORT (COFF):: @code{.ABORT}
4241 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4242 * Altmacro:: @code{.altmacro}
4243 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4244 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4245 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4246 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4247 * Byte:: @code{.byte @var{expressions}}
4248 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4249 * Comm:: @code{.comm @var{symbol} , @var{length} }
4250 * Data:: @code{.data @var{subsection}}
4252 * Def:: @code{.def @var{name}}
4255 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4261 * Double:: @code{.double @var{flonums}}
4262 * Eject:: @code{.eject}
4263 * Else:: @code{.else}
4264 * Elseif:: @code{.elseif}
4267 * Endef:: @code{.endef}
4270 * Endfunc:: @code{.endfunc}
4271 * Endif:: @code{.endif}
4272 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4273 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4274 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4276 * Error:: @code{.error @var{string}}
4277 * Exitm:: @code{.exitm}
4278 * Extern:: @code{.extern}
4279 * Fail:: @code{.fail}
4280 * File:: @code{.file}
4281 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4282 * Float:: @code{.float @var{flonums}}
4283 * Func:: @code{.func}
4284 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4286 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4287 * Hidden:: @code{.hidden @var{names}}
4290 * hword:: @code{.hword @var{expressions}}
4291 * Ident:: @code{.ident}
4292 * If:: @code{.if @var{absolute expression}}
4293 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4294 * Include:: @code{.include "@var{file}"}
4295 * Int:: @code{.int @var{expressions}}
4297 * Internal:: @code{.internal @var{names}}
4300 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4301 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4302 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4303 * Lflags:: @code{.lflags}
4304 @ifclear no-line-dir
4305 * Line:: @code{.line @var{line-number}}
4308 * Linkonce:: @code{.linkonce [@var{type}]}
4309 * List:: @code{.list}
4310 * Ln:: @code{.ln @var{line-number}}
4311 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4312 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4314 * Local:: @code{.local @var{names}}
4317 * Long:: @code{.long @var{expressions}}
4319 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4322 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4323 * MRI:: @code{.mri @var{val}}
4324 * Noaltmacro:: @code{.noaltmacro}
4325 * Nolist:: @code{.nolist}
4326 * Octa:: @code{.octa @var{bignums}}
4327 * Offset:: @code{.offset @var{loc}}
4328 * Org:: @code{.org @var{new-lc}, @var{fill}}
4329 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4331 * PopSection:: @code{.popsection}
4332 * Previous:: @code{.previous}
4335 * Print:: @code{.print @var{string}}
4337 * Protected:: @code{.protected @var{names}}
4340 * Psize:: @code{.psize @var{lines}, @var{columns}}
4341 * Purgem:: @code{.purgem @var{name}}
4343 * PushSection:: @code{.pushsection @var{name}}
4346 * Quad:: @code{.quad @var{bignums}}
4347 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4348 * Rept:: @code{.rept @var{count}}
4349 * Sbttl:: @code{.sbttl "@var{subheading}"}
4351 * Scl:: @code{.scl @var{class}}
4354 * Section:: @code{.section @var{name}[, @var{flags}]}
4357 * Set:: @code{.set @var{symbol}, @var{expression}}
4358 * Short:: @code{.short @var{expressions}}
4359 * Single:: @code{.single @var{flonums}}
4361 * Size:: @code{.size [@var{name} , @var{expression}]}
4363 @ifclear no-space-dir
4364 * Skip:: @code{.skip @var{size} , @var{fill}}
4367 * Sleb128:: @code{.sleb128 @var{expressions}}
4368 @ifclear no-space-dir
4369 * Space:: @code{.space @var{size} , @var{fill}}
4372 * Stab:: @code{.stabd, .stabn, .stabs}
4375 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4376 * Struct:: @code{.struct @var{expression}}
4378 * SubSection:: @code{.subsection}
4379 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4383 * Tag:: @code{.tag @var{structname}}
4386 * Text:: @code{.text @var{subsection}}
4387 * Title:: @code{.title "@var{heading}"}
4389 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4392 * Uleb128:: @code{.uleb128 @var{expressions}}
4394 * Val:: @code{.val @var{addr}}
4398 * Version:: @code{.version "@var{string}"}
4399 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4400 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4403 * Warning:: @code{.warning @var{string}}
4404 * Weak:: @code{.weak @var{names}}
4405 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4406 * Word:: @code{.word @var{expressions}}
4407 @ifclear no-space-dir
4408 * Zero:: @code{.zero @var{size}}
4410 * Deprecated:: Deprecated Directives
4414 @section @code{.abort}
4416 @cindex @code{abort} directive
4417 @cindex stopping the assembly
4418 This directive stops the assembly immediately. It is for
4419 compatibility with other assemblers. The original idea was that the
4420 assembly language source would be piped into the assembler. If the sender
4421 of the source quit, it could use this directive tells @command{@value{AS}} to
4422 quit also. One day @code{.abort} will not be supported.
4426 @section @code{.ABORT} (COFF)
4428 @cindex @code{ABORT} directive
4429 When producing COFF output, @command{@value{AS}} accepts this directive as a
4430 synonym for @samp{.abort}.
4433 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4439 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4441 @cindex padding the location counter
4442 @cindex @code{align} directive
4443 Pad the location counter (in the current subsection) to a particular storage
4444 boundary. The first expression (which must be absolute) is the alignment
4445 required, as described below.
4447 The second expression (also absolute) gives the fill value to be stored in the
4448 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4449 padding bytes are normally zero. However, on some systems, if the section is
4450 marked as containing code and the fill value is omitted, the space is filled
4451 with no-op instructions.
4453 The third expression is also absolute, and is also optional. If it is present,
4454 it is the maximum number of bytes that should be skipped by this alignment
4455 directive. If doing the alignment would require skipping more bytes than the
4456 specified maximum, then the alignment is not done at all. You can omit the
4457 fill value (the second argument) entirely by simply using two commas after the
4458 required alignment; this can be useful if you want the alignment to be filled
4459 with no-op instructions when appropriate.
4461 The way the required alignment is specified varies from system to system.
4462 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or1k,
4463 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4464 alignment request in bytes. For example @samp{.align 8} advances
4465 the location counter until it is a multiple of 8. If the location counter
4466 is already a multiple of 8, no change is needed. For the tic54x, the
4467 first expression is the alignment request in words.
4469 For other systems, including ppc, i386 using a.out format, arm and
4470 strongarm, it is the
4471 number of low-order zero bits the location counter must have after
4472 advancement. For example @samp{.align 3} advances the location
4473 counter until it a multiple of 8. If the location counter is already a
4474 multiple of 8, no change is needed.
4476 This inconsistency is due to the different behaviors of the various
4477 native assemblers for these systems which GAS must emulate.
4478 GAS also provides @code{.balign} and @code{.p2align} directives,
4479 described later, which have a consistent behavior across all
4480 architectures (but are specific to GAS).
4483 @section @code{.altmacro}
4484 Enable alternate macro mode, enabling:
4487 @item LOCAL @var{name} [ , @dots{} ]
4488 One additional directive, @code{LOCAL}, is available. It is used to
4489 generate a string replacement for each of the @var{name} arguments, and
4490 replace any instances of @var{name} in each macro expansion. The
4491 replacement string is unique in the assembly, and different for each
4492 separate macro expansion. @code{LOCAL} allows you to write macros that
4493 define symbols, without fear of conflict between separate macro expansions.
4495 @item String delimiters
4496 You can write strings delimited in these other ways besides
4497 @code{"@var{string}"}:
4500 @item '@var{string}'
4501 You can delimit strings with single-quote characters.
4503 @item <@var{string}>
4504 You can delimit strings with matching angle brackets.
4507 @item single-character string escape
4508 To include any single character literally in a string (even if the
4509 character would otherwise have some special meaning), you can prefix the
4510 character with @samp{!} (an exclamation mark). For example, you can
4511 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4513 @item Expression results as strings
4514 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4515 and use the result as a string.
4519 @section @code{.ascii "@var{string}"}@dots{}
4521 @cindex @code{ascii} directive
4522 @cindex string literals
4523 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4524 separated by commas. It assembles each string (with no automatic
4525 trailing zero byte) into consecutive addresses.
4528 @section @code{.asciz "@var{string}"}@dots{}
4530 @cindex @code{asciz} directive
4531 @cindex zero-terminated strings
4532 @cindex null-terminated strings
4533 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4534 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4537 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4539 @cindex padding the location counter given number of bytes
4540 @cindex @code{balign} directive
4541 Pad the location counter (in the current subsection) to a particular
4542 storage boundary. The first expression (which must be absolute) is the
4543 alignment request in bytes. For example @samp{.balign 8} advances
4544 the location counter until it is a multiple of 8. If the location counter
4545 is already a multiple of 8, no change is needed.
4547 The second expression (also absolute) gives the fill value to be stored in the
4548 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4549 padding bytes are normally zero. However, on some systems, if the section is
4550 marked as containing code and the fill value is omitted, the space is filled
4551 with no-op instructions.
4553 The third expression is also absolute, and is also optional. If it is present,
4554 it is the maximum number of bytes that should be skipped by this alignment
4555 directive. If doing the alignment would require skipping more bytes than the
4556 specified maximum, then the alignment is not done at all. You can omit the
4557 fill value (the second argument) entirely by simply using two commas after the
4558 required alignment; this can be useful if you want the alignment to be filled
4559 with no-op instructions when appropriate.
4561 @cindex @code{balignw} directive
4562 @cindex @code{balignl} directive
4563 The @code{.balignw} and @code{.balignl} directives are variants of the
4564 @code{.balign} directive. The @code{.balignw} directive treats the fill
4565 pattern as a two byte word value. The @code{.balignl} directives treats the
4566 fill pattern as a four byte longword value. For example, @code{.balignw
4567 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4568 filled in with the value 0x368d (the exact placement of the bytes depends upon
4569 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4572 @node Bundle directives
4573 @section Bundle directives
4574 @subsection @code{.bundle_align_mode @var{abs-expr}}
4575 @cindex @code{bundle_align_mode} directive
4577 @cindex instruction bundle
4578 @cindex aligned instruction bundle
4579 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4580 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4581 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4582 disabled (which is the default state). If the argument it not zero, it
4583 gives the size of an instruction bundle as a power of two (as for the
4584 @code{.p2align} directive, @pxref{P2align}).
4586 For some targets, it's an ABI requirement that no instruction may span a
4587 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4588 instructions that starts on an aligned boundary. For example, if
4589 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4590 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4591 effect, no single instruction may span a boundary between bundles. If an
4592 instruction would start too close to the end of a bundle for the length of
4593 that particular instruction to fit within the bundle, then the space at the
4594 end of that bundle is filled with no-op instructions so the instruction
4595 starts in the next bundle. As a corollary, it's an error if any single
4596 instruction's encoding is longer than the bundle size.
4598 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4599 @cindex @code{bundle_lock} directive
4600 @cindex @code{bundle_unlock} directive
4601 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4602 allow explicit control over instruction bundle padding. These directives
4603 are only valid when @code{.bundle_align_mode} has been used to enable
4604 aligned instruction bundle mode. It's an error if they appear when
4605 @code{.bundle_align_mode} has not been used at all, or when the last
4606 directive was @w{@code{.bundle_align_mode 0}}.
4608 @cindex bundle-locked
4609 For some targets, it's an ABI requirement that certain instructions may
4610 appear only as part of specified permissible sequences of multiple
4611 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4612 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4613 instruction sequence. For purposes of aligned instruction bundle mode, a
4614 sequence starting with @code{.bundle_lock} and ending with
4615 @code{.bundle_unlock} is treated as a single instruction. That is, the
4616 entire sequence must fit into a single bundle and may not span a bundle
4617 boundary. If necessary, no-op instructions will be inserted before the
4618 first instruction of the sequence so that the whole sequence starts on an
4619 aligned bundle boundary. It's an error if the sequence is longer than the
4622 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4623 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4624 nested. That is, a second @code{.bundle_lock} directive before the next
4625 @code{.bundle_unlock} directive has no effect except that it must be
4626 matched by another closing @code{.bundle_unlock} so that there is the
4627 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4630 @section @code{.byte @var{expressions}}
4632 @cindex @code{byte} directive
4633 @cindex integers, one byte
4634 @code{.byte} expects zero or more expressions, separated by commas.
4635 Each expression is assembled into the next byte.
4637 @node CFI directives
4638 @section CFI directives
4639 @subsection @code{.cfi_sections @var{section_list}}
4640 @cindex @code{cfi_sections} directive
4641 @code{.cfi_sections} may be used to specify whether CFI directives
4642 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4643 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4644 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4645 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4646 directive is not used is @code{.cfi_sections .eh_frame}.
4648 On targets that support compact unwinding tables these can be generated
4649 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4651 @subsection @code{.cfi_startproc [simple]}
4652 @cindex @code{cfi_startproc} directive
4653 @code{.cfi_startproc} is used at the beginning of each function that
4654 should have an entry in @code{.eh_frame}. It initializes some internal
4655 data structures. Don't forget to close the function by
4656 @code{.cfi_endproc}.
4658 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4659 it also emits some architecture dependent initial CFI instructions.
4661 @subsection @code{.cfi_endproc}
4662 @cindex @code{cfi_endproc} directive
4663 @code{.cfi_endproc} is used at the end of a function where it closes its
4664 unwind entry previously opened by
4665 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4667 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4668 @cindex @code{cfi_personality} directive
4669 @code{.cfi_personality} defines personality routine and its encoding.
4670 @var{encoding} must be a constant determining how the personality
4671 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4672 argument is not present, otherwise second argument should be
4673 a constant or a symbol name. When using indirect encodings,
4674 the symbol provided should be the location where personality
4675 can be loaded from, not the personality routine itself.
4676 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4677 no personality routine.
4679 @subsection @code{.cfi_personality_id @var{id}}
4680 @cindex @code{cfi_personality_id} directive
4681 @code{cfi_personality_id} defines a personality routine by its index as
4682 defined in a compact unwinding format.
4683 Only valid when generating compact EH frames (i.e.
4684 with @code{.cfi_sections eh_frame_entry}.
4686 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4687 @cindex @code{cfi_fde_data} directive
4688 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4689 used for the current function. These are emitted inline in the
4690 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4691 in the @code{.gnu.extab} section otherwise.
4692 Only valid when generating compact EH frames (i.e.
4693 with @code{.cfi_sections eh_frame_entry}.
4695 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4696 @code{.cfi_lsda} defines LSDA and its encoding.
4697 @var{encoding} must be a constant determining how the LSDA
4698 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4699 argument is not present, otherwise the second argument should be a constant
4700 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4701 meaning that no LSDA is present.
4703 @subsection @code{.cfi_inline_lsda} [@var{align}]
4704 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4705 switches to the corresponding @code{.gnu.extab} section.
4706 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4707 Only valid when generating compact EH frames (i.e.
4708 with @code{.cfi_sections eh_frame_entry}.
4710 The table header and unwinding opcodes will be generated at this point,
4711 so that they are immediately followed by the LSDA data. The symbol
4712 referenced by the @code{.cfi_lsda} directive should still be defined
4713 in case a fallback FDE based encoding is used. The LSDA data is terminated
4714 by a section directive.
4716 The optional @var{align} argument specifies the alignment required.
4717 The alignment is specified as a power of two, as with the
4718 @code{.p2align} directive.
4720 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4721 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4722 address from @var{register} and add @var{offset} to it}.
4724 @subsection @code{.cfi_def_cfa_register @var{register}}
4725 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4726 now on @var{register} will be used instead of the old one. Offset
4729 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4730 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4731 remains the same, but @var{offset} is new. Note that it is the
4732 absolute offset that will be added to a defined register to compute
4735 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4736 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4737 value that is added/substracted from the previous offset.
4739 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4740 Previous value of @var{register} is saved at offset @var{offset} from
4743 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4744 Previous value of @var{register} is saved at offset @var{offset} from
4745 the current CFA register. This is transformed to @code{.cfi_offset}
4746 using the known displacement of the CFA register from the CFA.
4747 This is often easier to use, because the number will match the
4748 code it's annotating.
4750 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4751 Previous value of @var{register1} is saved in register @var{register2}.
4753 @subsection @code{.cfi_restore @var{register}}
4754 @code{.cfi_restore} says that the rule for @var{register} is now the
4755 same as it was at the beginning of the function, after all initial
4756 instruction added by @code{.cfi_startproc} were executed.
4758 @subsection @code{.cfi_undefined @var{register}}
4759 From now on the previous value of @var{register} can't be restored anymore.
4761 @subsection @code{.cfi_same_value @var{register}}
4762 Current value of @var{register} is the same like in the previous frame,
4763 i.e. no restoration needed.
4765 @subsection @code{.cfi_remember_state},
4766 First save all current rules for all registers by @code{.cfi_remember_state},
4767 then totally screw them up by subsequent @code{.cfi_*} directives and when
4768 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4769 the previous saved state.
4771 @subsection @code{.cfi_return_column @var{register}}
4772 Change return column @var{register}, i.e. the return address is either
4773 directly in @var{register} or can be accessed by rules for @var{register}.
4775 @subsection @code{.cfi_signal_frame}
4776 Mark current function as signal trampoline.
4778 @subsection @code{.cfi_window_save}
4779 SPARC register window has been saved.
4781 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
4782 Allows the user to add arbitrary bytes to the unwind info. One
4783 might use this to add OS-specific CFI opcodes, or generic CFI
4784 opcodes that GAS does not yet support.
4786 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4787 The current value of @var{register} is @var{label}. The value of @var{label}
4788 will be encoded in the output file according to @var{encoding}; see the
4789 description of @code{.cfi_personality} for details on this encoding.
4791 The usefulness of equating a register to a fixed label is probably
4792 limited to the return address register. Here, it can be useful to
4793 mark a code segment that has only one return address which is reached
4794 by a direct branch and no copy of the return address exists in memory
4795 or another register.
4798 @section @code{.comm @var{symbol} , @var{length} }
4800 @cindex @code{comm} directive
4801 @cindex symbol, common
4802 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4803 common symbol in one object file may be merged with a defined or common symbol
4804 of the same name in another object file. If @code{@value{LD}} does not see a
4805 definition for the symbol--just one or more common symbols--then it will
4806 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4807 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4808 the same name, and they do not all have the same size, it will allocate space
4809 using the largest size.
4812 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4813 an optional third argument. This is the desired alignment of the symbol,
4814 specified for ELF as a byte boundary (for example, an alignment of 16 means
4815 that the least significant 4 bits of the address should be zero), and for PE
4816 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4817 boundary). The alignment must be an absolute expression, and it must be a
4818 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4819 common symbol, it will use the alignment when placing the symbol. If no
4820 alignment is specified, @command{@value{AS}} will set the alignment to the
4821 largest power of two less than or equal to the size of the symbol, up to a
4822 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4823 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4824 @samp{--section-alignment} option; image file sections in PE are aligned to
4825 multiples of 4096, which is far too large an alignment for ordinary variables.
4826 It is rather the default alignment for (non-debug) sections within object
4827 (@samp{*.o}) files, which are less strictly aligned.}.
4831 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4832 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4836 @section @code{.data @var{subsection}}
4838 @cindex @code{data} directive
4839 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4840 end of the data subsection numbered @var{subsection} (which is an
4841 absolute expression). If @var{subsection} is omitted, it defaults
4846 @section @code{.def @var{name}}
4848 @cindex @code{def} directive
4849 @cindex COFF symbols, debugging
4850 @cindex debugging COFF symbols
4851 Begin defining debugging information for a symbol @var{name}; the
4852 definition extends until the @code{.endef} directive is encountered.
4855 This directive is only observed when @command{@value{AS}} is configured for COFF
4856 format output; when producing @code{b.out}, @samp{.def} is recognized,
4863 @section @code{.desc @var{symbol}, @var{abs-expression}}
4865 @cindex @code{desc} directive
4866 @cindex COFF symbol descriptor
4867 @cindex symbol descriptor, COFF
4868 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4869 to the low 16 bits of an absolute expression.
4872 The @samp{.desc} directive is not available when @command{@value{AS}} is
4873 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4874 object format. For the sake of compatibility, @command{@value{AS}} accepts
4875 it, but produces no output, when configured for COFF.
4881 @section @code{.dim}
4883 @cindex @code{dim} directive
4884 @cindex COFF auxiliary symbol information
4885 @cindex auxiliary symbol information, COFF
4886 This directive is generated by compilers to include auxiliary debugging
4887 information in the symbol table. It is only permitted inside
4888 @code{.def}/@code{.endef} pairs.
4891 @samp{.dim} is only meaningful when generating COFF format output; when
4892 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4898 @section @code{.double @var{flonums}}
4900 @cindex @code{double} directive
4901 @cindex floating point numbers (double)
4902 @code{.double} expects zero or more flonums, separated by commas. It
4903 assembles floating point numbers.
4905 The exact kind of floating point numbers emitted depends on how
4906 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4910 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4911 in @sc{ieee} format.
4916 @section @code{.eject}
4918 @cindex @code{eject} directive
4919 @cindex new page, in listings
4920 @cindex page, in listings
4921 @cindex listing control: new page
4922 Force a page break at this point, when generating assembly listings.
4925 @section @code{.else}
4927 @cindex @code{else} directive
4928 @code{.else} is part of the @command{@value{AS}} support for conditional
4929 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4930 of code to be assembled if the condition for the preceding @code{.if}
4934 @section @code{.elseif}
4936 @cindex @code{elseif} directive
4937 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4938 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4939 @code{.if} block that would otherwise fill the entire @code{.else} section.
4942 @section @code{.end}
4944 @cindex @code{end} directive
4945 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4946 process anything in the file past the @code{.end} directive.
4950 @section @code{.endef}
4952 @cindex @code{endef} directive
4953 This directive flags the end of a symbol definition begun with
4957 @samp{.endef} is only meaningful when generating COFF format output; if
4958 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4959 directive but ignores it.
4964 @section @code{.endfunc}
4965 @cindex @code{endfunc} directive
4966 @code{.endfunc} marks the end of a function specified with @code{.func}.
4969 @section @code{.endif}
4971 @cindex @code{endif} directive
4972 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4973 it marks the end of a block of code that is only assembled
4974 conditionally. @xref{If,,@code{.if}}.
4977 @section @code{.equ @var{symbol}, @var{expression}}
4979 @cindex @code{equ} directive
4980 @cindex assigning values to symbols
4981 @cindex symbols, assigning values to
4982 This directive sets the value of @var{symbol} to @var{expression}.
4983 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4986 The syntax for @code{equ} on the HPPA is
4987 @samp{@var{symbol} .equ @var{expression}}.
4991 The syntax for @code{equ} on the Z80 is
4992 @samp{@var{symbol} equ @var{expression}}.
4993 On the Z80 it is an eror if @var{symbol} is already defined,
4994 but the symbol is not protected from later redefinition.
4995 Compare @ref{Equiv}.
4999 @section @code{.equiv @var{symbol}, @var{expression}}
5000 @cindex @code{equiv} directive
5001 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5002 the assembler will signal an error if @var{symbol} is already defined. Note a
5003 symbol which has been referenced but not actually defined is considered to be
5006 Except for the contents of the error message, this is roughly equivalent to
5013 plus it protects the symbol from later redefinition.
5016 @section @code{.eqv @var{symbol}, @var{expression}}
5017 @cindex @code{eqv} directive
5018 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5019 evaluate the expression or any part of it immediately. Instead each time
5020 the resulting symbol is used in an expression, a snapshot of its current
5024 @section @code{.err}
5025 @cindex @code{err} directive
5026 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5027 message and, unless the @option{-Z} option was used, it will not generate an
5028 object file. This can be used to signal an error in conditionally compiled code.
5031 @section @code{.error "@var{string}"}
5032 @cindex error directive
5034 Similarly to @code{.err}, this directive emits an error, but you can specify a
5035 string that will be emitted as the error message. If you don't specify the
5036 message, it defaults to @code{".error directive invoked in source file"}.
5037 @xref{Errors, ,Error and Warning Messages}.
5040 .error "This code has not been assembled and tested."
5044 @section @code{.exitm}
5045 Exit early from the current macro definition. @xref{Macro}.
5048 @section @code{.extern}
5050 @cindex @code{extern} directive
5051 @code{.extern} is accepted in the source program---for compatibility
5052 with other assemblers---but it is ignored. @command{@value{AS}} treats
5053 all undefined symbols as external.
5056 @section @code{.fail @var{expression}}
5058 @cindex @code{fail} directive
5059 Generates an error or a warning. If the value of the @var{expression} is 500
5060 or more, @command{@value{AS}} will print a warning message. If the value is less
5061 than 500, @command{@value{AS}} will print an error message. The message will
5062 include the value of @var{expression}. This can occasionally be useful inside
5063 complex nested macros or conditional assembly.
5066 @section @code{.file}
5067 @cindex @code{file} directive
5069 @ifclear no-file-dir
5070 There are two different versions of the @code{.file} directive. Targets
5071 that support DWARF2 line number information use the DWARF2 version of
5072 @code{.file}. Other targets use the default version.
5074 @subheading Default Version
5076 @cindex logical file name
5077 @cindex file name, logical
5078 This version of the @code{.file} directive tells @command{@value{AS}} that we
5079 are about to start a new logical file. The syntax is:
5085 @var{string} is the new file name. In general, the filename is
5086 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5087 to specify an empty file name, you must give the quotes--@code{""}. This
5088 statement may go away in future: it is only recognized to be compatible with
5089 old @command{@value{AS}} programs.
5091 @subheading DWARF2 Version
5094 When emitting DWARF2 line number information, @code{.file} assigns filenames
5095 to the @code{.debug_line} file name table. The syntax is:
5098 .file @var{fileno} @var{filename}
5101 The @var{fileno} operand should be a unique positive integer to use as the
5102 index of the entry in the table. The @var{filename} operand is a C string
5105 The detail of filename indices is exposed to the user because the filename
5106 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5107 information, and thus the user must know the exact indices that table
5111 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5113 @cindex @code{fill} directive
5114 @cindex writing patterns in memory
5115 @cindex patterns, writing in memory
5116 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5117 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5118 may be zero or more. @var{Size} may be zero or more, but if it is
5119 more than 8, then it is deemed to have the value 8, compatible with
5120 other people's assemblers. The contents of each @var{repeat} bytes
5121 is taken from an 8-byte number. The highest order 4 bytes are
5122 zero. The lowest order 4 bytes are @var{value} rendered in the
5123 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5124 Each @var{size} bytes in a repetition is taken from the lowest order
5125 @var{size} bytes of this number. Again, this bizarre behavior is
5126 compatible with other people's assemblers.
5128 @var{size} and @var{value} are optional.
5129 If the second comma and @var{value} are absent, @var{value} is
5130 assumed zero. If the first comma and following tokens are absent,
5131 @var{size} is assumed to be 1.
5134 @section @code{.float @var{flonums}}
5136 @cindex floating point numbers (single)
5137 @cindex @code{float} directive
5138 This directive assembles zero or more flonums, separated by commas. It
5139 has the same effect as @code{.single}.
5141 The exact kind of floating point numbers emitted depends on how
5142 @command{@value{AS}} is configured.
5143 @xref{Machine Dependencies}.
5147 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5148 in @sc{ieee} format.
5153 @section @code{.func @var{name}[,@var{label}]}
5154 @cindex @code{func} directive
5155 @code{.func} emits debugging information to denote function @var{name}, and
5156 is ignored unless the file is assembled with debugging enabled.
5157 Only @samp{--gstabs[+]} is currently supported.
5158 @var{label} is the entry point of the function and if omitted @var{name}
5159 prepended with the @samp{leading char} is used.
5160 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5161 All functions are currently defined to have @code{void} return type.
5162 The function must be terminated with @code{.endfunc}.
5165 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5167 @cindex @code{global} directive
5168 @cindex symbol, making visible to linker
5169 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5170 @var{symbol} in your partial program, its value is made available to
5171 other partial programs that are linked with it. Otherwise,
5172 @var{symbol} takes its attributes from a symbol of the same name
5173 from another file linked into the same program.
5175 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5176 compatibility with other assemblers.
5179 On the HPPA, @code{.global} is not always enough to make it accessible to other
5180 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5181 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5186 @section @code{.gnu_attribute @var{tag},@var{value}}
5187 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5190 @section @code{.hidden @var{names}}
5192 @cindex @code{hidden} directive
5194 This is one of the ELF visibility directives. The other two are
5195 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5196 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5198 This directive overrides the named symbols default visibility (which is set by
5199 their binding: local, global or weak). The directive sets the visibility to
5200 @code{hidden} which means that the symbols are not visible to other components.
5201 Such symbols are always considered to be @code{protected} as well.
5205 @section @code{.hword @var{expressions}}
5207 @cindex @code{hword} directive
5208 @cindex integers, 16-bit
5209 @cindex numbers, 16-bit
5210 @cindex sixteen bit integers
5211 This expects zero or more @var{expressions}, and emits
5212 a 16 bit number for each.
5215 This directive is a synonym for @samp{.short}; depending on the target
5216 architecture, it may also be a synonym for @samp{.word}.
5220 This directive is a synonym for @samp{.short}.
5223 This directive is a synonym for both @samp{.short} and @samp{.word}.
5228 @section @code{.ident}
5230 @cindex @code{ident} directive
5232 This directive is used by some assemblers to place tags in object files. The
5233 behavior of this directive varies depending on the target. When using the
5234 a.out object file format, @command{@value{AS}} simply accepts the directive for
5235 source-file compatibility with existing assemblers, but does not emit anything
5236 for it. When using COFF, comments are emitted to the @code{.comment} or
5237 @code{.rdata} section, depending on the target. When using ELF, comments are
5238 emitted to the @code{.comment} section.
5241 @section @code{.if @var{absolute expression}}
5243 @cindex conditional assembly
5244 @cindex @code{if} directive
5245 @code{.if} marks the beginning of a section of code which is only
5246 considered part of the source program being assembled if the argument
5247 (which must be an @var{absolute expression}) is non-zero. The end of
5248 the conditional section of code must be marked by @code{.endif}
5249 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5250 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5251 If you have several conditions to check, @code{.elseif} may be used to avoid
5252 nesting blocks if/else within each subsequent @code{.else} block.
5254 The following variants of @code{.if} are also supported:
5256 @cindex @code{ifdef} directive
5257 @item .ifdef @var{symbol}
5258 Assembles the following section of code if the specified @var{symbol}
5259 has been defined. Note a symbol which has been referenced but not yet defined
5260 is considered to be undefined.
5262 @cindex @code{ifb} directive
5263 @item .ifb @var{text}
5264 Assembles the following section of code if the operand is blank (empty).
5266 @cindex @code{ifc} directive
5267 @item .ifc @var{string1},@var{string2}
5268 Assembles the following section of code if the two strings are the same. The
5269 strings may be optionally quoted with single quotes. If they are not quoted,
5270 the first string stops at the first comma, and the second string stops at the
5271 end of the line. Strings which contain whitespace should be quoted. The
5272 string comparison is case sensitive.
5274 @cindex @code{ifeq} directive
5275 @item .ifeq @var{absolute expression}
5276 Assembles the following section of code if the argument is zero.
5278 @cindex @code{ifeqs} directive
5279 @item .ifeqs @var{string1},@var{string2}
5280 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5282 @cindex @code{ifge} directive
5283 @item .ifge @var{absolute expression}
5284 Assembles the following section of code if the argument is greater than or
5287 @cindex @code{ifgt} directive
5288 @item .ifgt @var{absolute expression}
5289 Assembles the following section of code if the argument is greater than zero.
5291 @cindex @code{ifle} directive
5292 @item .ifle @var{absolute expression}
5293 Assembles the following section of code if the argument is less than or equal
5296 @cindex @code{iflt} directive
5297 @item .iflt @var{absolute expression}
5298 Assembles the following section of code if the argument is less than zero.
5300 @cindex @code{ifnb} directive
5301 @item .ifnb @var{text}
5302 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5303 following section of code if the operand is non-blank (non-empty).
5305 @cindex @code{ifnc} directive
5306 @item .ifnc @var{string1},@var{string2}.
5307 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5308 following section of code if the two strings are not the same.
5310 @cindex @code{ifndef} directive
5311 @cindex @code{ifnotdef} directive
5312 @item .ifndef @var{symbol}
5313 @itemx .ifnotdef @var{symbol}
5314 Assembles the following section of code if the specified @var{symbol}
5315 has not been defined. Both spelling variants are equivalent. Note a symbol
5316 which has been referenced but not yet defined is considered to be undefined.
5318 @cindex @code{ifne} directive
5319 @item .ifne @var{absolute expression}
5320 Assembles the following section of code if the argument is not equal to zero
5321 (in other words, this is equivalent to @code{.if}).
5323 @cindex @code{ifnes} directive
5324 @item .ifnes @var{string1},@var{string2}
5325 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5326 following section of code if the two strings are not the same.
5330 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5332 @cindex @code{incbin} directive
5333 @cindex binary files, including
5334 The @code{incbin} directive includes @var{file} verbatim at the current
5335 location. You can control the search paths used with the @samp{-I} command-line
5336 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5339 The @var{skip} argument skips a number of bytes from the start of the
5340 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5341 read. Note that the data is not aligned in any way, so it is the user's
5342 responsibility to make sure that proper alignment is provided both before and
5343 after the @code{incbin} directive.
5346 @section @code{.include "@var{file}"}
5348 @cindex @code{include} directive
5349 @cindex supporting files, including
5350 @cindex files, including
5351 This directive provides a way to include supporting files at specified
5352 points in your source program. The code from @var{file} is assembled as
5353 if it followed the point of the @code{.include}; when the end of the
5354 included file is reached, assembly of the original file continues. You
5355 can control the search paths used with the @samp{-I} command-line option
5356 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5360 @section @code{.int @var{expressions}}
5362 @cindex @code{int} directive
5363 @cindex integers, 32-bit
5364 Expect zero or more @var{expressions}, of any section, separated by commas.
5365 For each expression, emit a number that, at run time, is the value of that
5366 expression. The byte order and bit size of the number depends on what kind
5367 of target the assembly is for.
5371 On most forms of the H8/300, @code{.int} emits 16-bit
5372 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5379 @section @code{.internal @var{names}}
5381 @cindex @code{internal} directive
5383 This is one of the ELF visibility directives. The other two are
5384 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5385 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5387 This directive overrides the named symbols default visibility (which is set by
5388 their binding: local, global or weak). The directive sets the visibility to
5389 @code{internal} which means that the symbols are considered to be @code{hidden}
5390 (i.e., not visible to other components), and that some extra, processor specific
5391 processing must also be performed upon the symbols as well.
5395 @section @code{.irp @var{symbol},@var{values}}@dots{}
5397 @cindex @code{irp} directive
5398 Evaluate a sequence of statements assigning different values to @var{symbol}.
5399 The sequence of statements starts at the @code{.irp} directive, and is
5400 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5401 set to @var{value}, and the sequence of statements is assembled. If no
5402 @var{value} is listed, the sequence of statements is assembled once, with
5403 @var{symbol} set to the null string. To refer to @var{symbol} within the
5404 sequence of statements, use @var{\symbol}.
5406 For example, assembling
5414 is equivalent to assembling
5422 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5425 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5427 @cindex @code{irpc} directive
5428 Evaluate a sequence of statements assigning different values to @var{symbol}.
5429 The sequence of statements starts at the @code{.irpc} directive, and is
5430 terminated by an @code{.endr} directive. For each character in @var{value},
5431 @var{symbol} is set to the character, and the sequence of statements is
5432 assembled. If no @var{value} is listed, the sequence of statements is
5433 assembled once, with @var{symbol} set to the null string. To refer to
5434 @var{symbol} within the sequence of statements, use @var{\symbol}.
5436 For example, assembling
5444 is equivalent to assembling
5452 For some caveats with the spelling of @var{symbol}, see also the discussion
5456 @section @code{.lcomm @var{symbol} , @var{length}}
5458 @cindex @code{lcomm} directive
5459 @cindex local common symbols
5460 @cindex symbols, local common
5461 Reserve @var{length} (an absolute expression) bytes for a local common
5462 denoted by @var{symbol}. The section and value of @var{symbol} are
5463 those of the new local common. The addresses are allocated in the bss
5464 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5465 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5466 not visible to @code{@value{LD}}.
5469 Some targets permit a third argument to be used with @code{.lcomm}. This
5470 argument specifies the desired alignment of the symbol in the bss section.
5474 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5475 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5479 @section @code{.lflags}
5481 @cindex @code{lflags} directive (ignored)
5482 @command{@value{AS}} accepts this directive, for compatibility with other
5483 assemblers, but ignores it.
5485 @ifclear no-line-dir
5487 @section @code{.line @var{line-number}}
5489 @cindex @code{line} directive
5490 @cindex logical line number
5492 Change the logical line number. @var{line-number} must be an absolute
5493 expression. The next line has that logical line number. Therefore any other
5494 statements on the current line (after a statement separator character) are
5495 reported as on logical line number @var{line-number} @minus{} 1. One day
5496 @command{@value{AS}} will no longer support this directive: it is recognized only
5497 for compatibility with existing assembler programs.
5500 Even though this is a directive associated with the @code{a.out} or
5501 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5502 when producing COFF output, and treats @samp{.line} as though it
5503 were the COFF @samp{.ln} @emph{if} it is found outside a
5504 @code{.def}/@code{.endef} pair.
5506 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5507 used by compilers to generate auxiliary symbol information for
5512 @section @code{.linkonce [@var{type}]}
5514 @cindex @code{linkonce} directive
5515 @cindex common sections
5516 Mark the current section so that the linker only includes a single copy of it.
5517 This may be used to include the same section in several different object files,
5518 but ensure that the linker will only include it once in the final output file.
5519 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5520 Duplicate sections are detected based on the section name, so it should be
5523 This directive is only supported by a few object file formats; as of this
5524 writing, the only object file format which supports it is the Portable
5525 Executable format used on Windows NT.
5527 The @var{type} argument is optional. If specified, it must be one of the
5528 following strings. For example:
5532 Not all types may be supported on all object file formats.
5536 Silently discard duplicate sections. This is the default.
5539 Warn if there are duplicate sections, but still keep only one copy.
5542 Warn if any of the duplicates have different sizes.
5545 Warn if any of the duplicates do not have exactly the same contents.
5549 @section @code{.list}
5551 @cindex @code{list} directive
5552 @cindex listing control, turning on
5553 Control (in conjunction with the @code{.nolist} directive) whether or
5554 not assembly listings are generated. These two directives maintain an
5555 internal counter (which is zero initially). @code{.list} increments the
5556 counter, and @code{.nolist} decrements it. Assembly listings are
5557 generated whenever the counter is greater than zero.
5559 By default, listings are disabled. When you enable them (with the
5560 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5561 the initial value of the listing counter is one.
5564 @section @code{.ln @var{line-number}}
5566 @cindex @code{ln} directive
5567 @ifclear no-line-dir
5568 @samp{.ln} is a synonym for @samp{.line}.
5571 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5572 must be an absolute expression. The next line has that logical
5573 line number, so any other statements on the current line (after a
5574 statement separator character @code{;}) are reported as on logical
5575 line number @var{line-number} @minus{} 1.
5578 This directive is accepted, but ignored, when @command{@value{AS}} is
5579 configured for @code{b.out}; its effect is only associated with COFF
5585 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5586 @cindex @code{loc} directive
5587 When emitting DWARF2 line number information,
5588 the @code{.loc} directive will add a row to the @code{.debug_line} line
5589 number matrix corresponding to the immediately following assembly
5590 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5591 arguments will be applied to the @code{.debug_line} state machine before
5594 The @var{options} are a sequence of the following tokens in any order:
5598 This option will set the @code{basic_block} register in the
5599 @code{.debug_line} state machine to @code{true}.
5602 This option will set the @code{prologue_end} register in the
5603 @code{.debug_line} state machine to @code{true}.
5605 @item epilogue_begin
5606 This option will set the @code{epilogue_begin} register in the
5607 @code{.debug_line} state machine to @code{true}.
5609 @item is_stmt @var{value}
5610 This option will set the @code{is_stmt} register in the
5611 @code{.debug_line} state machine to @code{value}, which must be
5614 @item isa @var{value}
5615 This directive will set the @code{isa} register in the @code{.debug_line}
5616 state machine to @var{value}, which must be an unsigned integer.
5618 @item discriminator @var{value}
5619 This directive will set the @code{discriminator} register in the @code{.debug_line}
5620 state machine to @var{value}, which must be an unsigned integer.
5624 @node Loc_mark_labels
5625 @section @code{.loc_mark_labels @var{enable}}
5626 @cindex @code{loc_mark_labels} directive
5627 When emitting DWARF2 line number information,
5628 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5629 to the @code{.debug_line} line number matrix with the @code{basic_block}
5630 register in the state machine set whenever a code label is seen.
5631 The @var{enable} argument should be either 1 or 0, to enable or disable
5632 this function respectively.
5636 @section @code{.local @var{names}}
5638 @cindex @code{local} directive
5639 This directive, which is available for ELF targets, marks each symbol in
5640 the comma-separated list of @code{names} as a local symbol so that it
5641 will not be externally visible. If the symbols do not already exist,
5642 they will be created.
5644 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5645 accept an alignment argument, which is the case for most ELF targets,
5646 the @code{.local} directive can be used in combination with @code{.comm}
5647 (@pxref{Comm}) to define aligned local common data.
5651 @section @code{.long @var{expressions}}
5653 @cindex @code{long} directive
5654 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5657 @c no one seems to know what this is for or whether this description is
5658 @c what it really ought to do
5660 @section @code{.lsym @var{symbol}, @var{expression}}
5662 @cindex @code{lsym} directive
5663 @cindex symbol, not referenced in assembly
5664 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5665 the hash table, ensuring it cannot be referenced by name during the
5666 rest of the assembly. This sets the attributes of the symbol to be
5667 the same as the expression value:
5669 @var{other} = @var{descriptor} = 0
5670 @var{type} = @r{(section of @var{expression})}
5671 @var{value} = @var{expression}
5674 The new symbol is not flagged as external.
5678 @section @code{.macro}
5681 The commands @code{.macro} and @code{.endm} allow you to define macros that
5682 generate assembly output. For example, this definition specifies a macro
5683 @code{sum} that puts a sequence of numbers into memory:
5686 .macro sum from=0, to=5
5695 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5707 @item .macro @var{macname}
5708 @itemx .macro @var{macname} @var{macargs} @dots{}
5709 @cindex @code{macro} directive
5710 Begin the definition of a macro called @var{macname}. If your macro
5711 definition requires arguments, specify their names after the macro name,
5712 separated by commas or spaces. You can qualify the macro argument to
5713 indicate whether all invocations must specify a non-blank value (through
5714 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5715 (through @samp{:@code{vararg}}). You can supply a default value for any
5716 macro argument by following the name with @samp{=@var{deflt}}. You
5717 cannot define two macros with the same @var{macname} unless it has been
5718 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5719 definitions. For example, these are all valid @code{.macro} statements:
5723 Begin the definition of a macro called @code{comm}, which takes no
5726 @item .macro plus1 p, p1
5727 @itemx .macro plus1 p p1
5728 Either statement begins the definition of a macro called @code{plus1},
5729 which takes two arguments; within the macro definition, write
5730 @samp{\p} or @samp{\p1} to evaluate the arguments.
5732 @item .macro reserve_str p1=0 p2
5733 Begin the definition of a macro called @code{reserve_str}, with two
5734 arguments. The first argument has a default value, but not the second.
5735 After the definition is complete, you can call the macro either as
5736 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5737 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5738 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5739 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5741 @item .macro m p1:req, p2=0, p3:vararg
5742 Begin the definition of a macro called @code{m}, with at least three
5743 arguments. The first argument must always have a value specified, but
5744 not the second, which instead has a default value. The third formal
5745 will get assigned all remaining arguments specified at invocation time.
5747 When you call a macro, you can specify the argument values either by
5748 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5749 @samp{sum to=17, from=9}.
5753 Note that since each of the @var{macargs} can be an identifier exactly
5754 as any other one permitted by the target architecture, there may be
5755 occasional problems if the target hand-crafts special meanings to certain
5756 characters when they occur in a special position. For example, if the colon
5757 (@code{:}) is generally permitted to be part of a symbol name, but the
5758 architecture specific code special-cases it when occurring as the final
5759 character of a symbol (to denote a label), then the macro parameter
5760 replacement code will have no way of knowing that and consider the whole
5761 construct (including the colon) an identifier, and check only this
5762 identifier for being the subject to parameter substitution. So for example
5763 this macro definition:
5771 might not work as expected. Invoking @samp{label foo} might not create a label
5772 called @samp{foo} but instead just insert the text @samp{\l:} into the
5773 assembler source, probably generating an error about an unrecognised
5776 Similarly problems might occur with the period character (@samp{.})
5777 which is often allowed inside opcode names (and hence identifier names). So
5778 for example constructing a macro to build an opcode from a base name and a
5779 length specifier like this:
5782 .macro opcode base length
5787 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5788 instruction but instead generate some kind of error as the assembler tries to
5789 interpret the text @samp{\base.\length}.
5791 There are several possible ways around this problem:
5794 @item Insert white space
5795 If it is possible to use white space characters then this is the simplest
5804 @item Use @samp{\()}
5805 The string @samp{\()} can be used to separate the end of a macro argument from
5806 the following text. eg:
5809 .macro opcode base length
5814 @item Use the alternate macro syntax mode
5815 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5816 used as a separator. eg:
5826 Note: this problem of correctly identifying string parameters to pseudo ops
5827 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5828 and @code{.irpc} (@pxref{Irpc}) as well.
5831 @cindex @code{endm} directive
5832 Mark the end of a macro definition.
5835 @cindex @code{exitm} directive
5836 Exit early from the current macro definition.
5838 @cindex number of macros executed
5839 @cindex macros, count executed
5841 @command{@value{AS}} maintains a counter of how many macros it has
5842 executed in this pseudo-variable; you can copy that number to your
5843 output with @samp{\@@}, but @emph{only within a macro definition}.
5845 @item LOCAL @var{name} [ , @dots{} ]
5846 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5847 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5848 @xref{Altmacro,,@code{.altmacro}}.
5852 @section @code{.mri @var{val}}
5854 @cindex @code{mri} directive
5855 @cindex MRI mode, temporarily
5856 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5857 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5858 affects code assembled until the next @code{.mri} directive, or until the end
5859 of the file. @xref{M, MRI mode, MRI mode}.
5862 @section @code{.noaltmacro}
5863 Disable alternate macro mode. @xref{Altmacro}.
5866 @section @code{.nolist}
5868 @cindex @code{nolist} directive
5869 @cindex listing control, turning off
5870 Control (in conjunction with the @code{.list} directive) whether or
5871 not assembly listings are generated. These two directives maintain an
5872 internal counter (which is zero initially). @code{.list} increments the
5873 counter, and @code{.nolist} decrements it. Assembly listings are
5874 generated whenever the counter is greater than zero.
5877 @section @code{.octa @var{bignums}}
5879 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5880 @cindex @code{octa} directive
5881 @cindex integer, 16-byte
5882 @cindex sixteen byte integer
5883 This directive expects zero or more bignums, separated by commas. For each
5884 bignum, it emits a 16-byte integer.
5886 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5887 hence @emph{octa}-word for 16 bytes.
5890 @section @code{.offset @var{loc}}
5892 @cindex @code{offset} directive
5893 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5894 be an absolute expression. This directive may be useful for defining
5895 symbols with absolute values. Do not confuse it with the @code{.org}
5899 @section @code{.org @var{new-lc} , @var{fill}}
5901 @cindex @code{org} directive
5902 @cindex location counter, advancing
5903 @cindex advancing location counter
5904 @cindex current address, advancing
5905 Advance the location counter of the current section to
5906 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5907 expression with the same section as the current subsection. That is,
5908 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5909 wrong section, the @code{.org} directive is ignored. To be compatible
5910 with former assemblers, if the section of @var{new-lc} is absolute,
5911 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5912 is the same as the current subsection.
5914 @code{.org} may only increase the location counter, or leave it
5915 unchanged; you cannot use @code{.org} to move the location counter
5918 @c double negative used below "not undefined" because this is a specific
5919 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5920 @c section. doc@cygnus.com 18feb91
5921 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5922 may not be undefined. If you really detest this restriction we eagerly await
5923 a chance to share your improved assembler.
5925 Beware that the origin is relative to the start of the section, not
5926 to the start of the subsection. This is compatible with other
5927 people's assemblers.
5929 When the location counter (of the current subsection) is advanced, the
5930 intervening bytes are filled with @var{fill} which should be an
5931 absolute expression. If the comma and @var{fill} are omitted,
5932 @var{fill} defaults to zero.
5935 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5937 @cindex padding the location counter given a power of two
5938 @cindex @code{p2align} directive
5939 Pad the location counter (in the current subsection) to a particular
5940 storage boundary. The first expression (which must be absolute) is the
5941 number of low-order zero bits the location counter must have after
5942 advancement. For example @samp{.p2align 3} advances the location
5943 counter until it a multiple of 8. If the location counter is already a
5944 multiple of 8, no change is needed.
5946 The second expression (also absolute) gives the fill value to be stored in the
5947 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5948 padding bytes are normally zero. However, on some systems, if the section is
5949 marked as containing code and the fill value is omitted, the space is filled
5950 with no-op instructions.
5952 The third expression is also absolute, and is also optional. If it is present,
5953 it is the maximum number of bytes that should be skipped by this alignment
5954 directive. If doing the alignment would require skipping more bytes than the
5955 specified maximum, then the alignment is not done at all. You can omit the
5956 fill value (the second argument) entirely by simply using two commas after the
5957 required alignment; this can be useful if you want the alignment to be filled
5958 with no-op instructions when appropriate.
5960 @cindex @code{p2alignw} directive
5961 @cindex @code{p2alignl} directive
5962 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5963 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5964 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5965 fill pattern as a four byte longword value. For example, @code{.p2alignw
5966 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5967 filled in with the value 0x368d (the exact placement of the bytes depends upon
5968 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5973 @section @code{.popsection}
5975 @cindex @code{popsection} directive
5976 @cindex Section Stack
5977 This is one of the ELF section stack manipulation directives. The others are
5978 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5979 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5982 This directive replaces the current section (and subsection) with the top
5983 section (and subsection) on the section stack. This section is popped off the
5989 @section @code{.previous}
5991 @cindex @code{previous} directive
5992 @cindex Section Stack
5993 This is one of the ELF section stack manipulation directives. The others are
5994 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5995 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5996 (@pxref{PopSection}).
5998 This directive swaps the current section (and subsection) with most recently
5999 referenced section/subsection pair prior to this one. Multiple
6000 @code{.previous} directives in a row will flip between two sections (and their
6001 subsections). For example:
6013 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6019 # Now in section A subsection 1
6023 # Now in section B subsection 0
6026 # Now in section B subsection 1
6029 # Now in section B subsection 0
6033 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6034 section B and 0x9abc into subsection 1 of section B.
6036 In terms of the section stack, this directive swaps the current section with
6037 the top section on the section stack.
6041 @section @code{.print @var{string}}
6043 @cindex @code{print} directive
6044 @command{@value{AS}} will print @var{string} on the standard output during
6045 assembly. You must put @var{string} in double quotes.
6049 @section @code{.protected @var{names}}
6051 @cindex @code{protected} directive
6053 This is one of the ELF visibility directives. The other two are
6054 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6056 This directive overrides the named symbols default visibility (which is set by
6057 their binding: local, global or weak). The directive sets the visibility to
6058 @code{protected} which means that any references to the symbols from within the
6059 components that defines them must be resolved to the definition in that
6060 component, even if a definition in another component would normally preempt
6065 @section @code{.psize @var{lines} , @var{columns}}
6067 @cindex @code{psize} directive
6068 @cindex listing control: paper size
6069 @cindex paper size, for listings
6070 Use this directive to declare the number of lines---and, optionally, the
6071 number of columns---to use for each page, when generating listings.
6073 If you do not use @code{.psize}, listings use a default line-count
6074 of 60. You may omit the comma and @var{columns} specification; the
6075 default width is 200 columns.
6077 @command{@value{AS}} generates formfeeds whenever the specified number of
6078 lines is exceeded (or whenever you explicitly request one, using
6081 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6082 those explicitly specified with @code{.eject}.
6085 @section @code{.purgem @var{name}}
6087 @cindex @code{purgem} directive
6088 Undefine the macro @var{name}, so that later uses of the string will not be
6089 expanded. @xref{Macro}.
6093 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6095 @cindex @code{pushsection} directive
6096 @cindex Section Stack
6097 This is one of the ELF section stack manipulation directives. The others are
6098 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6099 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6102 This directive pushes the current section (and subsection) onto the
6103 top of the section stack, and then replaces the current section and
6104 subsection with @code{name} and @code{subsection}. The optional
6105 @code{flags}, @code{type} and @code{arguments} are treated the same
6106 as in the @code{.section} (@pxref{Section}) directive.
6110 @section @code{.quad @var{bignums}}
6112 @cindex @code{quad} directive
6113 @code{.quad} expects zero or more bignums, separated by commas. For
6114 each bignum, it emits
6116 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6117 warning message; and just takes the lowest order 8 bytes of the bignum.
6118 @cindex eight-byte integer
6119 @cindex integer, 8-byte
6121 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6122 hence @emph{quad}-word for 8 bytes.
6125 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6126 warning message; and just takes the lowest order 16 bytes of the bignum.
6127 @cindex sixteen-byte integer
6128 @cindex integer, 16-byte
6132 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6134 @cindex @code{reloc} directive
6135 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6136 @var{expression}. If @var{offset} is a number, the relocation is generated in
6137 the current section. If @var{offset} is an expression that resolves to a
6138 symbol plus offset, the relocation is generated in the given symbol's section.
6139 @var{expression}, if present, must resolve to a symbol plus addend or to an
6140 absolute value, but note that not all targets support an addend. e.g. ELF REL
6141 targets such as i386 store an addend in the section contents rather than in the
6142 relocation. This low level interface does not support addends stored in the
6146 @section @code{.rept @var{count}}
6148 @cindex @code{rept} directive
6149 Repeat the sequence of lines between the @code{.rept} directive and the next
6150 @code{.endr} directive @var{count} times.
6152 For example, assembling
6160 is equivalent to assembling
6169 @section @code{.sbttl "@var{subheading}"}
6171 @cindex @code{sbttl} directive
6172 @cindex subtitles for listings
6173 @cindex listing control: subtitle
6174 Use @var{subheading} as the title (third line, immediately after the
6175 title line) when generating assembly listings.
6177 This directive affects subsequent pages, as well as the current page if
6178 it appears within ten lines of the top of a page.
6182 @section @code{.scl @var{class}}
6184 @cindex @code{scl} directive
6185 @cindex symbol storage class (COFF)
6186 @cindex COFF symbol storage class
6187 Set the storage-class value for a symbol. This directive may only be
6188 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6189 whether a symbol is static or external, or it may record further
6190 symbolic debugging information.
6193 The @samp{.scl} directive is primarily associated with COFF output; when
6194 configured to generate @code{b.out} output format, @command{@value{AS}}
6195 accepts this directive but ignores it.
6201 @section @code{.section @var{name}}
6203 @cindex named section
6204 Use the @code{.section} directive to assemble the following code into a section
6207 This directive is only supported for targets that actually support arbitrarily
6208 named sections; on @code{a.out} targets, for example, it is not accepted, even
6209 with a standard @code{a.out} section name.
6213 @c only print the extra heading if both COFF and ELF are set
6214 @subheading COFF Version
6217 @cindex @code{section} directive (COFF version)
6218 For COFF targets, the @code{.section} directive is used in one of the following
6222 .section @var{name}[, "@var{flags}"]
6223 .section @var{name}[, @var{subsection}]
6226 If the optional argument is quoted, it is taken as flags to use for the
6227 section. Each flag is a single character. The following flags are recognized:
6230 bss section (uninitialized data)
6232 section is not loaded
6238 exclude section from linking
6244 shared section (meaningful for PE targets)
6246 ignored. (For compatibility with the ELF version)
6248 section is not readable (meaningful for PE targets)
6250 single-digit power-of-two section alignment (GNU extension)
6253 If no flags are specified, the default flags depend upon the section name. If
6254 the section name is not recognized, the default will be for the section to be
6255 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6256 from the section, rather than adding them, so if they are used on their own it
6257 will be as if no flags had been specified at all.
6259 If the optional argument to the @code{.section} directive is not quoted, it is
6260 taken as a subsection number (@pxref{Sub-Sections}).
6265 @c only print the extra heading if both COFF and ELF are set
6266 @subheading ELF Version
6269 @cindex Section Stack
6270 This is one of the ELF section stack manipulation directives. The others are
6271 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6272 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6273 @code{.previous} (@pxref{Previous}).
6275 @cindex @code{section} directive (ELF version)
6276 For ELF targets, the @code{.section} directive is used like this:
6279 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6282 @anchor{Section Name Substitutions}
6283 @kindex --sectname-subst
6284 @cindex section name substitution
6285 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6286 argument may contain a substitution sequence. Only @code{%S} is supported
6287 at the moment, and substitutes the current section name. For example:
6290 .macro exception_code
6291 .section %S.exception
6292 [exception code here]
6307 The two @code{exception_code} invocations above would create the
6308 @code{.text.exception} and @code{.init.exception} sections respectively.
6309 This is useful e.g. to discriminate between anciliary sections that are
6310 tied to setup code to be discarded after use from anciliary sections that
6311 need to stay resident without having to define multiple @code{exception_code}
6312 macros just for that purpose.
6314 The optional @var{flags} argument is a quoted string which may contain any
6315 combination of the following characters:
6318 section is allocatable
6320 section is excluded from executable and shared library.
6324 section is executable
6326 section is mergeable
6328 section contains zero terminated strings
6330 section is a member of a section group
6332 section is used for thread-local-storage
6334 section is a member of the previously-current section's group, if any
6337 The optional @var{type} argument may contain one of the following constants:
6340 section contains data
6342 section does not contain data (i.e., section only occupies space)
6344 section contains data which is used by things other than the program
6346 section contains an array of pointers to init functions
6348 section contains an array of pointers to finish functions
6349 @item @@preinit_array
6350 section contains an array of pointers to pre-init functions
6353 Many targets only support the first three section types.
6355 Note on targets where the @code{@@} character is the start of a comment (eg
6356 ARM) then another character is used instead. For example the ARM port uses the
6359 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6360 be specified as well as an extra argument---@var{entsize}---like this:
6363 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6366 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6367 constants, each @var{entsize} octets long. Sections with both @code{M} and
6368 @code{S} must contain zero terminated strings where each character is
6369 @var{entsize} bytes long. The linker may remove duplicates within sections with
6370 the same name, same entity size and same flags. @var{entsize} must be an
6371 absolute expression. For sections with both @code{M} and @code{S}, a string
6372 which is a suffix of a larger string is considered a duplicate. Thus
6373 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6374 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6376 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6377 be present along with an additional field like this:
6380 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6383 The @var{GroupName} field specifies the name of the section group to which this
6384 particular section belongs. The optional linkage field can contain:
6387 indicates that only one copy of this section should be retained
6392 Note: if both the @var{M} and @var{G} flags are present then the fields for
6393 the Merge flag should come first, like this:
6396 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6399 If @var{flags} contains the @code{?} symbol then it may not also contain the
6400 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6401 present. Instead, @code{?} says to consider the section that's current before
6402 this directive. If that section used @code{G}, then the new section will use
6403 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6404 If not, then the @code{?} symbol has no effect.
6406 If no flags are specified, the default flags depend upon the section name. If
6407 the section name is not recognized, the default will be for the section to have
6408 none of the above flags: it will not be allocated in memory, nor writable, nor
6409 executable. The section will contain data.
6411 For ELF targets, the assembler supports another type of @code{.section}
6412 directive for compatibility with the Solaris assembler:
6415 .section "@var{name}"[, @var{flags}...]
6418 Note that the section name is quoted. There may be a sequence of comma
6422 section is allocatable
6426 section is executable
6428 section is excluded from executable and shared library.
6430 section is used for thread local storage
6433 This directive replaces the current section and subsection. See the
6434 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6435 some examples of how this directive and the other section stack directives
6441 @section @code{.set @var{symbol}, @var{expression}}
6443 @cindex @code{set} directive
6444 @cindex symbol value, setting
6445 Set the value of @var{symbol} to @var{expression}. This
6446 changes @var{symbol}'s value and type to conform to
6447 @var{expression}. If @var{symbol} was flagged as external, it remains
6448 flagged (@pxref{Symbol Attributes}).
6450 You may @code{.set} a symbol many times in the same assembly provided that the
6451 values given to the symbol are constants. Values that are based on expressions
6452 involving other symbols are allowed, but some targets may restrict this to only
6453 being done once per assembly. This is because those targets do not set the
6454 addresses of symbols at assembly time, but rather delay the assignment until a
6455 final link is performed. This allows the linker a chance to change the code in
6456 the files, changing the location of, and the relative distance between, various
6459 If you @code{.set} a global symbol, the value stored in the object
6460 file is the last value stored into it.
6463 On Z80 @code{set} is a real instruction, use
6464 @samp{@var{symbol} defl @var{expression}} instead.
6468 @section @code{.short @var{expressions}}
6470 @cindex @code{short} directive
6472 @code{.short} is normally the same as @samp{.word}.
6473 @xref{Word,,@code{.word}}.
6475 In some configurations, however, @code{.short} and @code{.word} generate
6476 numbers of different lengths. @xref{Machine Dependencies}.
6480 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6483 This expects zero or more @var{expressions}, and emits
6484 a 16 bit number for each.
6489 @section @code{.single @var{flonums}}
6491 @cindex @code{single} directive
6492 @cindex floating point numbers (single)
6493 This directive assembles zero or more flonums, separated by commas. It
6494 has the same effect as @code{.float}.
6496 The exact kind of floating point numbers emitted depends on how
6497 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6501 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6502 numbers in @sc{ieee} format.
6508 @section @code{.size}
6510 This directive is used to set the size associated with a symbol.
6514 @c only print the extra heading if both COFF and ELF are set
6515 @subheading COFF Version
6518 @cindex @code{size} directive (COFF version)
6519 For COFF targets, the @code{.size} directive is only permitted inside
6520 @code{.def}/@code{.endef} pairs. It is used like this:
6523 .size @var{expression}
6527 @samp{.size} is only meaningful when generating COFF format output; when
6528 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6535 @c only print the extra heading if both COFF and ELF are set
6536 @subheading ELF Version
6539 @cindex @code{size} directive (ELF version)
6540 For ELF targets, the @code{.size} directive is used like this:
6543 .size @var{name} , @var{expression}
6546 This directive sets the size associated with a symbol @var{name}.
6547 The size in bytes is computed from @var{expression} which can make use of label
6548 arithmetic. This directive is typically used to set the size of function
6553 @ifclear no-space-dir
6555 @section @code{.skip @var{size} , @var{fill}}
6557 @cindex @code{skip} directive
6558 @cindex filling memory
6559 This directive emits @var{size} bytes, each of value @var{fill}. Both
6560 @var{size} and @var{fill} are absolute expressions. If the comma and
6561 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6566 @section @code{.sleb128 @var{expressions}}
6568 @cindex @code{sleb128} directive
6569 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6570 compact, variable length representation of numbers used by the DWARF
6571 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6573 @ifclear no-space-dir
6575 @section @code{.space @var{size} , @var{fill}}
6577 @cindex @code{space} directive
6578 @cindex filling memory
6579 This directive emits @var{size} bytes, each of value @var{fill}. Both
6580 @var{size} and @var{fill} are absolute expressions. If the comma
6581 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6586 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6587 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6588 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6589 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6597 @section @code{.stabd, .stabn, .stabs}
6599 @cindex symbolic debuggers, information for
6600 @cindex @code{stab@var{x}} directives
6601 There are three directives that begin @samp{.stab}.
6602 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6603 The symbols are not entered in the @command{@value{AS}} hash table: they
6604 cannot be referenced elsewhere in the source file.
6605 Up to five fields are required:
6609 This is the symbol's name. It may contain any character except
6610 @samp{\000}, so is more general than ordinary symbol names. Some
6611 debuggers used to code arbitrarily complex structures into symbol names
6615 An absolute expression. The symbol's type is set to the low 8 bits of
6616 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6617 and debuggers choke on silly bit patterns.
6620 An absolute expression. The symbol's ``other'' attribute is set to the
6621 low 8 bits of this expression.
6624 An absolute expression. The symbol's descriptor is set to the low 16
6625 bits of this expression.
6628 An absolute expression which becomes the symbol's value.
6631 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6632 or @code{.stabs} statement, the symbol has probably already been created;
6633 you get a half-formed symbol in your object file. This is
6634 compatible with earlier assemblers!
6637 @cindex @code{stabd} directive
6638 @item .stabd @var{type} , @var{other} , @var{desc}
6640 The ``name'' of the symbol generated is not even an empty string.
6641 It is a null pointer, for compatibility. Older assemblers used a
6642 null pointer so they didn't waste space in object files with empty
6645 The symbol's value is set to the location counter,
6646 relocatably. When your program is linked, the value of this symbol
6647 is the address of the location counter when the @code{.stabd} was
6650 @cindex @code{stabn} directive
6651 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6652 The name of the symbol is set to the empty string @code{""}.
6654 @cindex @code{stabs} directive
6655 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6656 All five fields are specified.
6662 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6663 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6665 @cindex string, copying to object file
6666 @cindex string8, copying to object file
6667 @cindex string16, copying to object file
6668 @cindex string32, copying to object file
6669 @cindex string64, copying to object file
6670 @cindex @code{string} directive
6671 @cindex @code{string8} directive
6672 @cindex @code{string16} directive
6673 @cindex @code{string32} directive
6674 @cindex @code{string64} directive
6676 Copy the characters in @var{str} to the object file. You may specify more than
6677 one string to copy, separated by commas. Unless otherwise specified for a
6678 particular machine, the assembler marks the end of each string with a 0 byte.
6679 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6681 The variants @code{string16}, @code{string32} and @code{string64} differ from
6682 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6683 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6684 are stored in target endianness byte order.
6690 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6691 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6696 @section @code{.struct @var{expression}}
6698 @cindex @code{struct} directive
6699 Switch to the absolute section, and set the section offset to @var{expression},
6700 which must be an absolute expression. You might use this as follows:
6709 This would define the symbol @code{field1} to have the value 0, the symbol
6710 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6711 value 8. Assembly would be left in the absolute section, and you would need to
6712 use a @code{.section} directive of some sort to change to some other section
6713 before further assembly.
6717 @section @code{.subsection @var{name}}
6719 @cindex @code{subsection} directive
6720 @cindex Section Stack
6721 This is one of the ELF section stack manipulation directives. The others are
6722 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6723 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6726 This directive replaces the current subsection with @code{name}. The current
6727 section is not changed. The replaced subsection is put onto the section stack
6728 in place of the then current top of stack subsection.
6733 @section @code{.symver}
6734 @cindex @code{symver} directive
6735 @cindex symbol versioning
6736 @cindex versions of symbols
6737 Use the @code{.symver} directive to bind symbols to specific version nodes
6738 within a source file. This is only supported on ELF platforms, and is
6739 typically used when assembling files to be linked into a shared library.
6740 There are cases where it may make sense to use this in objects to be bound
6741 into an application itself so as to override a versioned symbol from a
6744 For ELF targets, the @code{.symver} directive can be used like this:
6746 .symver @var{name}, @var{name2@@nodename}
6748 If the symbol @var{name} is defined within the file
6749 being assembled, the @code{.symver} directive effectively creates a symbol
6750 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6751 just don't try and create a regular alias is that the @var{@@} character isn't
6752 permitted in symbol names. The @var{name2} part of the name is the actual name
6753 of the symbol by which it will be externally referenced. The name @var{name}
6754 itself is merely a name of convenience that is used so that it is possible to
6755 have definitions for multiple versions of a function within a single source
6756 file, and so that the compiler can unambiguously know which version of a
6757 function is being mentioned. The @var{nodename} portion of the alias should be
6758 the name of a node specified in the version script supplied to the linker when
6759 building a shared library. If you are attempting to override a versioned
6760 symbol from a shared library, then @var{nodename} should correspond to the
6761 nodename of the symbol you are trying to override.
6763 If the symbol @var{name} is not defined within the file being assembled, all
6764 references to @var{name} will be changed to @var{name2@@nodename}. If no
6765 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6768 Another usage of the @code{.symver} directive is:
6770 .symver @var{name}, @var{name2@@@@nodename}
6772 In this case, the symbol @var{name} must exist and be defined within
6773 the file being assembled. It is similar to @var{name2@@nodename}. The
6774 difference is @var{name2@@@@nodename} will also be used to resolve
6775 references to @var{name2} by the linker.
6777 The third usage of the @code{.symver} directive is:
6779 .symver @var{name}, @var{name2@@@@@@nodename}
6781 When @var{name} is not defined within the
6782 file being assembled, it is treated as @var{name2@@nodename}. When
6783 @var{name} is defined within the file being assembled, the symbol
6784 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6789 @section @code{.tag @var{structname}}
6791 @cindex COFF structure debugging
6792 @cindex structure debugging, COFF
6793 @cindex @code{tag} directive
6794 This directive is generated by compilers to include auxiliary debugging
6795 information in the symbol table. It is only permitted inside
6796 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6797 definitions in the symbol table with instances of those structures.
6800 @samp{.tag} is only used when generating COFF format output; when
6801 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6807 @section @code{.text @var{subsection}}
6809 @cindex @code{text} directive
6810 Tells @command{@value{AS}} to assemble the following statements onto the end of
6811 the text subsection numbered @var{subsection}, which is an absolute
6812 expression. If @var{subsection} is omitted, subsection number zero
6816 @section @code{.title "@var{heading}"}
6818 @cindex @code{title} directive
6819 @cindex listing control: title line
6820 Use @var{heading} as the title (second line, immediately after the
6821 source file name and pagenumber) when generating assembly listings.
6823 This directive affects subsequent pages, as well as the current page if
6824 it appears within ten lines of the top of a page.
6828 @section @code{.type}
6830 This directive is used to set the type of a symbol.
6834 @c only print the extra heading if both COFF and ELF are set
6835 @subheading COFF Version
6838 @cindex COFF symbol type
6839 @cindex symbol type, COFF
6840 @cindex @code{type} directive (COFF version)
6841 For COFF targets, this directive is permitted only within
6842 @code{.def}/@code{.endef} pairs. It is used like this:
6848 This records the integer @var{int} as the type attribute of a symbol table
6852 @samp{.type} is associated only with COFF format output; when
6853 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6854 directive but ignores it.
6860 @c only print the extra heading if both COFF and ELF are set
6861 @subheading ELF Version
6864 @cindex ELF symbol type
6865 @cindex symbol type, ELF
6866 @cindex @code{type} directive (ELF version)
6867 For ELF targets, the @code{.type} directive is used like this:
6870 .type @var{name} , @var{type description}
6873 This sets the type of symbol @var{name} to be either a
6874 function symbol or an object symbol. There are five different syntaxes
6875 supported for the @var{type description} field, in order to provide
6876 compatibility with various other assemblers.
6878 Because some of the characters used in these syntaxes (such as @samp{@@} and
6879 @samp{#}) are comment characters for some architectures, some of the syntaxes
6880 below do not work on all architectures. The first variant will be accepted by
6881 the GNU assembler on all architectures so that variant should be used for
6882 maximum portability, if you do not need to assemble your code with other
6885 The syntaxes supported are:
6888 .type <name> STT_<TYPE_IN_UPPER_CASE>
6889 .type <name>,#<type>
6890 .type <name>,@@<type>
6891 .type <name>,%<type>
6892 .type <name>,"<type>"
6895 The types supported are:
6900 Mark the symbol as being a function name.
6903 @itemx gnu_indirect_function
6904 Mark the symbol as an indirect function when evaluated during reloc
6905 processing. (This is only supported on assemblers targeting GNU systems).
6909 Mark the symbol as being a data object.
6913 Mark the symbol as being a thead-local data object.
6917 Mark the symbol as being a common data object.
6921 Does not mark the symbol in any way. It is supported just for completeness.
6923 @item gnu_unique_object
6924 Marks the symbol as being a globally unique data object. The dynamic linker
6925 will make sure that in the entire process there is just one symbol with this
6926 name and type in use. (This is only supported on assemblers targeting GNU
6931 Note: Some targets support extra types in addition to those listed above.
6937 @section @code{.uleb128 @var{expressions}}
6939 @cindex @code{uleb128} directive
6940 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6941 compact, variable length representation of numbers used by the DWARF
6942 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6946 @section @code{.val @var{addr}}
6948 @cindex @code{val} directive
6949 @cindex COFF value attribute
6950 @cindex value attribute, COFF
6951 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6952 records the address @var{addr} as the value attribute of a symbol table
6956 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6957 configured for @code{b.out}, it accepts this directive but ignores it.
6963 @section @code{.version "@var{string}"}
6965 @cindex @code{version} directive
6966 This directive creates a @code{.note} section and places into it an ELF
6967 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6972 @section @code{.vtable_entry @var{table}, @var{offset}}
6974 @cindex @code{vtable_entry} directive
6975 This directive finds or creates a symbol @code{table} and creates a
6976 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6979 @section @code{.vtable_inherit @var{child}, @var{parent}}
6981 @cindex @code{vtable_inherit} directive
6982 This directive finds the symbol @code{child} and finds or creates the symbol
6983 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6984 parent whose addend is the value of the child symbol. As a special case the
6985 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6989 @section @code{.warning "@var{string}"}
6990 @cindex warning directive
6991 Similar to the directive @code{.error}
6992 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6995 @section @code{.weak @var{names}}
6997 @cindex @code{weak} directive
6998 This directive sets the weak attribute on the comma separated list of symbol
6999 @code{names}. If the symbols do not already exist, they will be created.
7001 On COFF targets other than PE, weak symbols are a GNU extension. This
7002 directive sets the weak attribute on the comma separated list of symbol
7003 @code{names}. If the symbols do not already exist, they will be created.
7005 On the PE target, weak symbols are supported natively as weak aliases.
7006 When a weak symbol is created that is not an alias, GAS creates an
7007 alternate symbol to hold the default value.
7010 @section @code{.weakref @var{alias}, @var{target}}
7012 @cindex @code{weakref} directive
7013 This directive creates an alias to the target symbol that enables the symbol to
7014 be referenced with weak-symbol semantics, but without actually making it weak.
7015 If direct references or definitions of the symbol are present, then the symbol
7016 will not be weak, but if all references to it are through weak references, the
7017 symbol will be marked as weak in the symbol table.
7019 The effect is equivalent to moving all references to the alias to a separate
7020 assembly source file, renaming the alias to the symbol in it, declaring the
7021 symbol as weak there, and running a reloadable link to merge the object files
7022 resulting from the assembly of the new source file and the old source file that
7023 had the references to the alias removed.
7025 The alias itself never makes to the symbol table, and is entirely handled
7026 within the assembler.
7029 @section @code{.word @var{expressions}}
7031 @cindex @code{word} directive
7032 This directive expects zero or more @var{expressions}, of any section,
7033 separated by commas.
7036 For each expression, @command{@value{AS}} emits a 32-bit number.
7039 For each expression, @command{@value{AS}} emits a 16-bit number.
7044 The size of the number emitted, and its byte order,
7045 depend on what target computer the assembly is for.
7048 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
7049 @c happen---32-bit addressability, period; no long/short jumps.
7050 @ifset DIFF-TBL-KLUGE
7051 @cindex difference tables altered
7052 @cindex altered difference tables
7054 @emph{Warning: Special Treatment to support Compilers}
7058 Machines with a 32-bit address space, but that do less than 32-bit
7059 addressing, require the following special treatment. If the machine of
7060 interest to you does 32-bit addressing (or doesn't require it;
7061 @pxref{Machine Dependencies}), you can ignore this issue.
7064 In order to assemble compiler output into something that works,
7065 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7066 Directives of the form @samp{.word sym1-sym2} are often emitted by
7067 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7068 directive of the form @samp{.word sym1-sym2}, and the difference between
7069 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7070 creates a @dfn{secondary jump table}, immediately before the next label.
7071 This secondary jump table is preceded by a short-jump to the
7072 first byte after the secondary table. This short-jump prevents the flow
7073 of control from accidentally falling into the new table. Inside the
7074 table is a long-jump to @code{sym2}. The original @samp{.word}
7075 contains @code{sym1} minus the address of the long-jump to
7078 If there were several occurrences of @samp{.word sym1-sym2} before the
7079 secondary jump table, all of them are adjusted. If there was a
7080 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7081 long-jump to @code{sym4} is included in the secondary jump table,
7082 and the @code{.word} directives are adjusted to contain @code{sym3}
7083 minus the address of the long-jump to @code{sym4}; and so on, for as many
7084 entries in the original jump table as necessary.
7087 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7088 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7089 assembly language programmers.
7092 @c end DIFF-TBL-KLUGE
7094 @ifclear no-space-dir
7096 @section @code{.zero @var{size}}
7098 @cindex @code{zero} directive
7099 @cindex filling memory with zero bytes
7100 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7101 expression. This directive is actually an alias for the @samp{.skip} directive
7102 so in can take an optional second argument of the value to store in the bytes
7103 instead of zero. Using @samp{.zero} in this way would be confusing however.
7107 @section Deprecated Directives
7109 @cindex deprecated directives
7110 @cindex obsolescent directives
7111 One day these directives won't work.
7112 They are included for compatibility with older assemblers.
7119 @node Object Attributes
7120 @chapter Object Attributes
7121 @cindex object attributes
7123 @command{@value{AS}} assembles source files written for a specific architecture
7124 into object files for that architecture. But not all object files are alike.
7125 Many architectures support incompatible variations. For instance, floating
7126 point arguments might be passed in floating point registers if the object file
7127 requires hardware floating point support---or floating point arguments might be
7128 passed in integer registers if the object file supports processors with no
7129 hardware floating point unit. Or, if two objects are built for different
7130 generations of the same architecture, the combination may require the
7131 newer generation at run-time.
7133 This information is useful during and after linking. At link time,
7134 @command{@value{LD}} can warn about incompatible object files. After link
7135 time, tools like @command{gdb} can use it to process the linked file
7138 Compatibility information is recorded as a series of object attributes. Each
7139 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7140 string, and indicates who sets the meaning of the tag. The tag is an integer,
7141 and indicates what property the attribute describes. The value may be a string
7142 or an integer, and indicates how the property affects this object. Missing
7143 attributes are the same as attributes with a zero value or empty string value.
7145 Object attributes were developed as part of the ABI for the ARM Architecture.
7146 The file format is documented in @cite{ELF for the ARM Architecture}.
7149 * GNU Object Attributes:: @sc{gnu} Object Attributes
7150 * Defining New Object Attributes:: Defining New Object Attributes
7153 @node GNU Object Attributes
7154 @section @sc{gnu} Object Attributes
7156 The @code{.gnu_attribute} directive records an object attribute
7157 with vendor @samp{gnu}.
7159 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7160 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7161 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7162 2} is set for architecture-independent attributes and clear for
7163 architecture-dependent ones.
7165 @subsection Common @sc{gnu} attributes
7167 These attributes are valid on all architectures.
7170 @item Tag_compatibility (32)
7171 The compatibility attribute takes an integer flag value and a vendor name. If
7172 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7173 then the file is only compatible with the named toolchain. If it is greater
7174 than 1, the file can only be processed by other toolchains under some private
7175 arrangement indicated by the flag value and the vendor name.
7178 @subsection MIPS Attributes
7181 @item Tag_GNU_MIPS_ABI_FP (4)
7182 The floating-point ABI used by this object file. The value will be:
7186 0 for files not affected by the floating-point ABI.
7188 1 for files using the hardware floating-point ABI with a standard
7189 double-precision FPU.
7191 2 for files using the hardware floating-point ABI with a single-precision FPU.
7193 3 for files using the software floating-point ABI.
7195 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7196 floating-point registers, 32-bit general-purpose registers and increased the
7197 number of callee-saved floating-point registers.
7199 5 for files using the hardware floating-point ABI with a double-precision FPU
7200 with either 32-bit or 64-bit floating-point registers and 32-bit
7201 general-purpose registers.
7203 6 for files using the hardware floating-point ABI with 64-bit floating-point
7204 registers and 32-bit general-purpose registers.
7206 7 for files using the hardware floating-point ABI with 64-bit floating-point
7207 registers, 32-bit general-purpose registers and a rule that forbids the
7208 direct use of odd-numbered single-precision floating-point registers.
7212 @subsection PowerPC Attributes
7215 @item Tag_GNU_Power_ABI_FP (4)
7216 The floating-point ABI used by this object file. The value will be:
7220 0 for files not affected by the floating-point ABI.
7222 1 for files using double-precision hardware floating-point ABI.
7224 2 for files using the software floating-point ABI.
7226 3 for files using single-precision hardware floating-point ABI.
7229 @item Tag_GNU_Power_ABI_Vector (8)
7230 The vector ABI used by this object file. The value will be:
7234 0 for files not affected by the vector ABI.
7236 1 for files using general purpose registers to pass vectors.
7238 2 for files using AltiVec registers to pass vectors.
7240 3 for files using SPE registers to pass vectors.
7244 @subsection IBM z Systems Attributes
7247 @item Tag_GNU_S390_ABI_Vector (8)
7248 The vector ABI used by this object file. The value will be:
7252 0 for files not affected by the vector ABI.
7254 1 for files using software vector ABI.
7256 2 for files using hardware vector ABI.
7260 @node Defining New Object Attributes
7261 @section Defining New Object Attributes
7263 If you want to define a new @sc{gnu} object attribute, here are the places you
7264 will need to modify. New attributes should be discussed on the @samp{binutils}
7269 This manual, which is the official register of attributes.
7271 The header for your architecture @file{include/elf}, to define the tag.
7273 The @file{bfd} support file for your architecture, to merge the attribute
7274 and issue any appropriate link warnings.
7276 Test cases in @file{ld/testsuite} for merging and link warnings.
7278 @file{binutils/readelf.c} to display your attribute.
7280 GCC, if you want the compiler to mark the attribute automatically.
7286 @node Machine Dependencies
7287 @chapter Machine Dependent Features
7289 @cindex machine dependencies
7290 The machine instruction sets are (almost by definition) different on
7291 each machine where @command{@value{AS}} runs. Floating point representations
7292 vary as well, and @command{@value{AS}} often supports a few additional
7293 directives or command-line options for compatibility with other
7294 assemblers on a particular platform. Finally, some versions of
7295 @command{@value{AS}} support special pseudo-instructions for branch
7298 This chapter discusses most of these differences, though it does not
7299 include details on any machine's instruction set. For details on that
7300 subject, see the hardware manufacturer's manual.
7304 * AArch64-Dependent:: AArch64 Dependent Features
7307 * Alpha-Dependent:: Alpha Dependent Features
7310 * ARC-Dependent:: ARC Dependent Features
7313 * ARM-Dependent:: ARM Dependent Features
7316 * AVR-Dependent:: AVR Dependent Features
7319 * Blackfin-Dependent:: Blackfin Dependent Features
7322 * CR16-Dependent:: CR16 Dependent Features
7325 * CRIS-Dependent:: CRIS Dependent Features
7328 * D10V-Dependent:: D10V Dependent Features
7331 * D30V-Dependent:: D30V Dependent Features
7334 * Epiphany-Dependent:: EPIPHANY Dependent Features
7337 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7340 * HPPA-Dependent:: HPPA Dependent Features
7343 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7346 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7349 * i860-Dependent:: Intel 80860 Dependent Features
7352 * i960-Dependent:: Intel 80960 Dependent Features
7355 * IA-64-Dependent:: Intel IA-64 Dependent Features
7358 * IP2K-Dependent:: IP2K Dependent Features
7361 * LM32-Dependent:: LM32 Dependent Features
7364 * M32C-Dependent:: M32C Dependent Features
7367 * M32R-Dependent:: M32R Dependent Features
7370 * M68K-Dependent:: M680x0 Dependent Features
7373 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7376 * Meta-Dependent :: Meta Dependent Features
7379 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7382 * MIPS-Dependent:: MIPS Dependent Features
7385 * MMIX-Dependent:: MMIX Dependent Features
7388 * MSP430-Dependent:: MSP430 Dependent Features
7391 * NDS32-Dependent:: Andes NDS32 Dependent Features
7394 * NiosII-Dependent:: Altera Nios II Dependent Features
7397 * NS32K-Dependent:: NS32K Dependent Features
7400 * PDP-11-Dependent:: PDP-11 Dependent Features
7403 * PJ-Dependent:: picoJava Dependent Features
7406 * PPC-Dependent:: PowerPC Dependent Features
7409 * RL78-Dependent:: RL78 Dependent Features
7412 * RX-Dependent:: RX Dependent Features
7415 * S/390-Dependent:: IBM S/390 Dependent Features
7418 * SCORE-Dependent:: SCORE Dependent Features
7421 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7422 * SH64-Dependent:: SuperH SH64 Dependent Features
7425 * Sparc-Dependent:: SPARC Dependent Features
7428 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7431 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7434 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7437 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7440 * V850-Dependent:: V850 Dependent Features
7443 * Vax-Dependent:: VAX Dependent Features
7446 * Visium-Dependent:: Visium Dependent Features
7449 * XGATE-Dependent:: XGATE Features
7452 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7455 * Xtensa-Dependent:: Xtensa Dependent Features
7458 * Z80-Dependent:: Z80 Dependent Features
7461 * Z8000-Dependent:: Z8000 Dependent Features
7468 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7469 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7470 @c peculiarity: to preserve cross-references, there must be a node called
7471 @c "Machine Dependencies". Hence the conditional nodenames in each
7472 @c major node below. Node defaulting in makeinfo requires adjacency of
7473 @c node and sectioning commands; hence the repetition of @chapter BLAH
7474 @c in both conditional blocks.
7477 @include c-aarch64.texi
7481 @include c-alpha.texi
7497 @include c-bfin.texi
7501 @include c-cr16.texi
7505 @include c-cris.texi
7510 @node Machine Dependencies
7511 @chapter Machine Dependent Features
7513 The machine instruction sets are different on each Renesas chip family,
7514 and there are also some syntax differences among the families. This
7515 chapter describes the specific @command{@value{AS}} features for each
7519 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7520 * SH-Dependent:: Renesas SH Dependent Features
7527 @include c-d10v.texi
7531 @include c-d30v.texi
7535 @include c-epiphany.texi
7539 @include c-h8300.texi
7543 @include c-hppa.texi
7547 @include c-i370.texi
7551 @include c-i386.texi
7555 @include c-i860.texi
7559 @include c-i960.texi
7563 @include c-ia64.texi
7567 @include c-ip2k.texi
7571 @include c-lm32.texi
7575 @include c-m32c.texi
7579 @include c-m32r.texi
7583 @include c-m68k.texi
7587 @include c-m68hc11.texi
7591 @include c-metag.texi
7595 @include c-microblaze.texi
7599 @include c-mips.texi
7603 @include c-mmix.texi
7607 @include c-msp430.texi
7611 @include c-nds32.texi
7615 @include c-nios2.texi
7619 @include c-ns32k.texi
7623 @include c-pdp11.texi
7635 @include c-rl78.texi
7643 @include c-s390.texi
7647 @include c-score.texi
7652 @include c-sh64.texi
7656 @include c-sparc.texi
7660 @include c-tic54x.texi
7664 @include c-tic6x.texi
7668 @include c-tilegx.texi
7672 @include c-tilepro.texi
7676 @include c-v850.texi
7684 @include c-visium.texi
7688 @include c-xgate.texi
7692 @include c-xstormy16.texi
7696 @include c-xtensa.texi
7708 @c reverse effect of @down at top of generic Machine-Dep chapter
7712 @node Reporting Bugs
7713 @chapter Reporting Bugs
7714 @cindex bugs in assembler
7715 @cindex reporting bugs in assembler
7717 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7719 Reporting a bug may help you by bringing a solution to your problem, or it may
7720 not. But in any case the principal function of a bug report is to help the
7721 entire community by making the next version of @command{@value{AS}} work better.
7722 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7724 In order for a bug report to serve its purpose, you must include the
7725 information that enables us to fix the bug.
7728 * Bug Criteria:: Have you found a bug?
7729 * Bug Reporting:: How to report bugs
7733 @section Have You Found a Bug?
7734 @cindex bug criteria
7736 If you are not sure whether you have found a bug, here are some guidelines:
7739 @cindex fatal signal
7740 @cindex assembler crash
7741 @cindex crash of assembler
7743 If the assembler gets a fatal signal, for any input whatever, that is a
7744 @command{@value{AS}} bug. Reliable assemblers never crash.
7746 @cindex error on valid input
7748 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7750 @cindex invalid input
7752 If @command{@value{AS}} does not produce an error message for invalid input, that
7753 is a bug. However, you should note that your idea of ``invalid input'' might
7754 be our idea of ``an extension'' or ``support for traditional practice''.
7757 If you are an experienced user of assemblers, your suggestions for improvement
7758 of @command{@value{AS}} are welcome in any case.
7762 @section How to Report Bugs
7764 @cindex assembler bugs, reporting
7766 A number of companies and individuals offer support for @sc{gnu} products. If
7767 you obtained @command{@value{AS}} from a support organization, we recommend you
7768 contact that organization first.
7770 You can find contact information for many support companies and
7771 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7775 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7779 The fundamental principle of reporting bugs usefully is this:
7780 @strong{report all the facts}. If you are not sure whether to state a
7781 fact or leave it out, state it!
7783 Often people omit facts because they think they know what causes the problem
7784 and assume that some details do not matter. Thus, you might assume that the
7785 name of a symbol you use in an example does not matter. Well, probably it does
7786 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7787 happens to fetch from the location where that name is stored in memory;
7788 perhaps, if the name were different, the contents of that location would fool
7789 the assembler into doing the right thing despite the bug. Play it safe and
7790 give a specific, complete example. That is the easiest thing for you to do,
7791 and the most helpful.
7793 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7794 it is new to us. Therefore, always write your bug reports on the assumption
7795 that the bug has not been reported previously.
7797 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7798 bell?'' This cannot help us fix a bug, so it is basically useless. We
7799 respond by asking for enough details to enable us to investigate.
7800 You might as well expedite matters by sending them to begin with.
7802 To enable us to fix the bug, you should include all these things:
7806 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7807 it with the @samp{--version} argument.
7809 Without this, we will not know whether there is any point in looking for
7810 the bug in the current version of @command{@value{AS}}.
7813 Any patches you may have applied to the @command{@value{AS}} source.
7816 The type of machine you are using, and the operating system name and
7820 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7824 The command arguments you gave the assembler to assemble your example and
7825 observe the bug. To guarantee you will not omit something important, list them
7826 all. A copy of the Makefile (or the output from make) is sufficient.
7828 If we were to try to guess the arguments, we would probably guess wrong
7829 and then we might not encounter the bug.
7832 A complete input file that will reproduce the bug. If the bug is observed when
7833 the assembler is invoked via a compiler, send the assembler source, not the
7834 high level language source. Most compilers will produce the assembler source
7835 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7836 the options @samp{-v --save-temps}; this will save the assembler source in a
7837 file with an extension of @file{.s}, and also show you exactly how
7838 @command{@value{AS}} is being run.
7841 A description of what behavior you observe that you believe is
7842 incorrect. For example, ``It gets a fatal signal.''
7844 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7845 will certainly notice it. But if the bug is incorrect output, we might not
7846 notice unless it is glaringly wrong. You might as well not give us a chance to
7849 Even if the problem you experience is a fatal signal, you should still say so
7850 explicitly. Suppose something strange is going on, such as, your copy of
7851 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7852 library on your system. (This has happened!) Your copy might crash and ours
7853 would not. If you told us to expect a crash, then when ours fails to crash, we
7854 would know that the bug was not happening for us. If you had not told us to
7855 expect a crash, then we would not be able to draw any conclusion from our
7859 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7860 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7861 option. Always send diffs from the old file to the new file. If you even
7862 discuss something in the @command{@value{AS}} source, refer to it by context, not
7865 The line numbers in our development sources will not match those in your
7866 sources. Your line numbers would convey no useful information to us.
7869 Here are some things that are not necessary:
7873 A description of the envelope of the bug.
7875 Often people who encounter a bug spend a lot of time investigating
7876 which changes to the input file will make the bug go away and which
7877 changes will not affect it.
7879 This is often time consuming and not very useful, because the way we
7880 will find the bug is by running a single example under the debugger
7881 with breakpoints, not by pure deduction from a series of examples.
7882 We recommend that you save your time for something else.
7884 Of course, if you can find a simpler example to report @emph{instead}
7885 of the original one, that is a convenience for us. Errors in the
7886 output will be easier to spot, running under the debugger will take
7887 less time, and so on.
7889 However, simplification is not vital; if you do not want to do this,
7890 report the bug anyway and send us the entire test case you used.
7893 A patch for the bug.
7895 A patch for the bug does help us if it is a good one. But do not omit
7896 the necessary information, such as the test case, on the assumption that
7897 a patch is all we need. We might see problems with your patch and decide
7898 to fix the problem another way, or we might not understand it at all.
7900 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7901 construct an example that will make the program follow a certain path through
7902 the code. If you do not send us the example, we will not be able to construct
7903 one, so we will not be able to verify that the bug is fixed.
7905 And if we cannot understand what bug you are trying to fix, or why your
7906 patch should be an improvement, we will not install it. A test case will
7907 help us to understand.
7910 A guess about what the bug is or what it depends on.
7912 Such guesses are usually wrong. Even we cannot guess right about such
7913 things without first using the debugger to find the facts.
7916 @node Acknowledgements
7917 @chapter Acknowledgements
7919 If you have contributed to GAS and your name isn't listed here,
7920 it is not meant as a slight. We just don't know about it. Send mail to the
7921 maintainer, and we'll correct the situation. Currently
7923 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
7925 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7928 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7929 information and the 68k series machines, most of the preprocessing pass, and
7930 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7932 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7933 many bug fixes, including merging support for several processors, breaking GAS
7934 up to handle multiple object file format back ends (including heavy rewrite,
7935 testing, an integration of the coff and b.out back ends), adding configuration
7936 including heavy testing and verification of cross assemblers and file splits
7937 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7938 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7939 port (including considerable amounts of reverse engineering), a SPARC opcode
7940 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7941 assertions and made them work, much other reorganization, cleanup, and lint.
7943 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7944 in format-specific I/O modules.
7946 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7947 has done much work with it since.
7949 The Intel 80386 machine description was written by Eliot Dresselhaus.
7951 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7953 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7954 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7956 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7957 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7958 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7959 support a.out format.
7961 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7962 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7963 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7964 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7967 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7968 simplified the configuration of which versions accept which directives. He
7969 updated the 68k machine description so that Motorola's opcodes always produced
7970 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7971 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7972 cross-compilation support, and one bug in relaxation that took a week and
7973 required the proverbial one-bit fix.
7975 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7976 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7977 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7978 PowerPC assembler, and made a few other minor patches.
7980 Steve Chamberlain made GAS able to generate listings.
7982 Hewlett-Packard contributed support for the HP9000/300.
7984 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7985 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7986 formats). This work was supported by both the Center for Software Science at
7987 the University of Utah and Cygnus Support.
7989 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7990 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7991 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7992 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7993 and some initial 64-bit support).
7995 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7997 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7998 support for openVMS/Alpha.
8000 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8003 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8004 Inc.@: added support for Xtensa processors.
8006 Several engineers at Cygnus Support have also provided many small bug fixes and
8007 configuration enhancements.
8009 Jon Beniston added support for the Lattice Mico32 architecture.
8011 Many others have contributed large or small bugfixes and enhancements. If
8012 you have contributed significant work and are not mentioned on this list, and
8013 want to be, let us know. Some of the history has been lost; we are not
8014 intentionally leaving anyone out.
8016 @node GNU Free Documentation License
8017 @appendix GNU Free Documentation License
8021 @unnumbered AS Index