1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (C) 1991-2019 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{} 1991-2019 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{} 1991-2019 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{--no-pad-sections}]
239 [@b{-o} @var{objfile}] [@b{-R}]
240 [@b{--hash-size}=@var{NUM}] [@b{--reduce-memory-overheads}]
242 [@b{-v}] [@b{-version}] [@b{--version}]
243 [@b{-W}] [@b{--warn}] [@b{--fatal-warnings}] [@b{-w}] [@b{-x}]
244 [@b{-Z}] [@b{@@@var{FILE}}]
245 [@b{--sectname-subst}] [@b{--size-check=[error|warning]}]
246 [@b{--elf-stt-common=[no|yes]}]
247 [@b{--generate-missing-build-notes=[no|yes]}]
248 [@b{--target-help}] [@var{target-options}]
249 [@b{--}|@var{files} @dots{}]
252 @c Target dependent options are listed below. Keep the list sorted.
253 @c Add an empty line for separation.
257 @emph{Target AArch64 options:}
259 [@b{-mabi}=@var{ABI}]
263 @emph{Target Alpha options:}
265 [@b{-mdebug} | @b{-no-mdebug}]
266 [@b{-replace} | @b{-noreplace}]
267 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
268 [@b{-F}] [@b{-32addr}]
272 @emph{Target ARC options:}
273 [@b{-mcpu=@var{cpu}}]
274 [@b{-mA6}|@b{-mARC600}|@b{-mARC601}|@b{-mA7}|@b{-mARC700}|@b{-mEM}|@b{-mHS}]
281 @emph{Target ARM options:}
282 @c Don't document the deprecated options
283 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
284 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
285 [@b{-mfpu}=@var{floating-point-format}]
286 [@b{-mfloat-abi}=@var{abi}]
287 [@b{-meabi}=@var{ver}]
290 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
291 @b{-mapcs-reentrant}]
292 [@b{-mthumb-interwork}] [@b{-k}]
296 @emph{Target Blackfin options:}
297 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
304 @emph{Target BPF options:}
309 @emph{Target CRIS options:}
310 [@b{--underscore} | @b{--no-underscore}]
312 [@b{--emulation=criself} | @b{--emulation=crisaout}]
313 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
314 @c Deprecated -- deliberately not documented.
319 @emph{Target C-SKY options:}
320 [@b{-march=@var{arch}}] [@b{-mcpu=@var{cpu}}]
321 [@b{-EL}] [@b{-mlittle-endian}] [@b{-EB}] [@b{-mbig-endian}]
322 [@b{-fpic}] [@b{-pic}]
323 [@b{-mljump}] [@b{-mno-ljump}]
324 [@b{-force2bsr}] [@b{-mforce2bsr}] [@b{-no-force2bsr}] [@b{-mno-force2bsr}]
325 [@b{-jsri2bsr}] [@b{-mjsri2bsr}] [@b{-no-jsri2bsr }] [@b{-mno-jsri2bsr}]
326 [@b{-mnolrw }] [@b{-mno-lrw}]
327 [@b{-melrw}] [@b{-mno-elrw}]
328 [@b{-mlaf }] [@b{-mliterals-after-func}]
329 [@b{-mno-laf}] [@b{-mno-literals-after-func}]
330 [@b{-mlabr}] [@b{-mliterals-after-br}]
331 [@b{-mno-labr}] [@b{-mnoliterals-after-br}]
332 [@b{-mistack}] [@b{-mno-istack}]
333 [@b{-mhard-float}] [@b{-mmp}] [@b{-mcp}] [@b{-mcache}]
334 [@b{-msecurity}] [@b{-mtrust}]
335 [@b{-mdsp}] [@b{-medsp}] [@b{-mvdsp}]
339 @emph{Target D10V options:}
344 @emph{Target D30V options:}
345 [@b{-O}|@b{-n}|@b{-N}]
349 @emph{Target EPIPHANY options:}
350 [@b{-mepiphany}|@b{-mepiphany16}]
354 @emph{Target H8/300 options:}
358 @c HPPA has no machine-dependent assembler options (yet).
362 @emph{Target i386 options:}
363 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
364 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
368 @emph{Target IA-64 options:}
369 [@b{-mconstant-gp}|@b{-mauto-pic}]
370 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
372 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
373 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
374 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
375 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
379 @emph{Target IP2K options:}
380 [@b{-mip2022}|@b{-mip2022ext}]
384 @emph{Target M32C options:}
385 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
389 @emph{Target M32R options:}
390 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
395 @emph{Target M680X0 options:}
396 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
400 @emph{Target M68HC11 options:}
401 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
402 [@b{-mshort}|@b{-mlong}]
403 [@b{-mshort-double}|@b{-mlong-double}]
404 [@b{--force-long-branches}] [@b{--short-branches}]
405 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
406 [@b{--print-opcodes}] [@b{--generate-example}]
410 @emph{Target MCORE options:}
411 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
412 [@b{-mcpu=[210|340]}]
416 @emph{Target Meta options:}
417 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
420 @emph{Target MICROBLAZE options:}
421 @c MicroBlaze has no machine-dependent assembler options.
425 @emph{Target MIPS options:}
426 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
427 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
428 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
429 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
430 [@b{-mfp64}] [@b{-mgp64}] [@b{-mfpxx}]
431 [@b{-modd-spreg}] [@b{-mno-odd-spreg}]
432 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
433 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
434 [@b{-mips32r3}] [@b{-mips32r5}] [@b{-mips32r6}] [@b{-mips64}] [@b{-mips64r2}]
435 [@b{-mips64r3}] [@b{-mips64r5}] [@b{-mips64r6}]
436 [@b{-construct-floats}] [@b{-no-construct-floats}]
437 [@b{-mignore-branch-isa}] [@b{-mno-ignore-branch-isa}]
438 [@b{-mnan=@var{encoding}}]
439 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
440 [@b{-mips16}] [@b{-no-mips16}]
441 [@b{-mmips16e2}] [@b{-mno-mips16e2}]
442 [@b{-mmicromips}] [@b{-mno-micromips}]
443 [@b{-msmartmips}] [@b{-mno-smartmips}]
444 [@b{-mips3d}] [@b{-no-mips3d}]
445 [@b{-mdmx}] [@b{-no-mdmx}]
446 [@b{-mdsp}] [@b{-mno-dsp}]
447 [@b{-mdspr2}] [@b{-mno-dspr2}]
448 [@b{-mdspr3}] [@b{-mno-dspr3}]
449 [@b{-mmsa}] [@b{-mno-msa}]
450 [@b{-mxpa}] [@b{-mno-xpa}]
451 [@b{-mmt}] [@b{-mno-mt}]
452 [@b{-mmcu}] [@b{-mno-mcu}]
453 [@b{-mcrc}] [@b{-mno-crc}]
454 [@b{-mginv}] [@b{-mno-ginv}]
455 [@b{-mloongson-mmi}] [@b{-mno-loongson-mmi}]
456 [@b{-mloongson-cam}] [@b{-mno-loongson-cam}]
457 [@b{-mloongson-ext}] [@b{-mno-loongson-ext}]
458 [@b{-mloongson-ext2}] [@b{-mno-loongson-ext2}]
459 [@b{-minsn32}] [@b{-mno-insn32}]
460 [@b{-mfix7000}] [@b{-mno-fix7000}]
461 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
462 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
463 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
464 [@b{-mfix-r5900}] [@b{-mno-fix-r5900}]
465 [@b{-mdebug}] [@b{-no-mdebug}]
466 [@b{-mpdr}] [@b{-mno-pdr}]
470 @emph{Target MMIX options:}
471 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
472 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
473 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
474 [@b{--linker-allocated-gregs}]
478 @emph{Target Nios II options:}
479 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
484 @emph{Target NDS32 options:}
485 [@b{-EL}] [@b{-EB}] [@b{-O}] [@b{-Os}] [@b{-mcpu=@var{cpu}}]
486 [@b{-misa=@var{isa}}] [@b{-mabi=@var{abi}}] [@b{-mall-ext}]
487 [@b{-m[no-]16-bit}] [@b{-m[no-]perf-ext}] [@b{-m[no-]perf2-ext}]
488 [@b{-m[no-]string-ext}] [@b{-m[no-]dsp-ext}] [@b{-m[no-]mac}] [@b{-m[no-]div}]
489 [@b{-m[no-]audio-isa-ext}] [@b{-m[no-]fpu-sp-ext}] [@b{-m[no-]fpu-dp-ext}]
490 [@b{-m[no-]fpu-fma}] [@b{-mfpu-freg=@var{FREG}}] [@b{-mreduced-regs}]
491 [@b{-mfull-regs}] [@b{-m[no-]dx-regs}] [@b{-mpic}] [@b{-mno-relax}]
495 @c OpenRISC has no machine-dependent assembler options.
499 @emph{Target PDP11 options:}
500 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
501 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
502 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
506 @emph{Target picoJava options:}
511 @emph{Target PowerPC options:}
513 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
514 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mgekko}|
515 @b{-mbroadway}|@b{-mppc64}|@b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|
516 @b{-me6500}|@b{-mppc64bridge}|@b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|
517 @b{-mpower6}|@b{-mpwr6}|@b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-mpower9}|@b{-mpwr9}@b{-ma2}|
518 @b{-mcell}|@b{-mspe}|@b{-mspe2}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
519 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
520 [@b{-mregnames}|@b{-mno-regnames}]
521 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
522 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
523 [@b{-msolaris}|@b{-mno-solaris}]
524 [@b{-nops=@var{count}}]
528 @emph{Target PRU options:}
531 [@b{-mno-warn-regname-label}]
535 @emph{Target RISC-V options:}
536 [@b{-fpic}|@b{-fPIC}|@b{-fno-pic}]
537 [@b{-march}=@var{ISA}]
538 [@b{-mabi}=@var{ABI}]
542 @emph{Target RL78 options:}
544 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
548 @emph{Target RX options:}
549 [@b{-mlittle-endian}|@b{-mbig-endian}]
550 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
551 [@b{-muse-conventional-section-names}]
552 [@b{-msmall-data-limit}]
555 [@b{-mint-register=@var{number}}]
556 [@b{-mgcc-abi}|@b{-mrx-abi}]
560 @emph{Target s390 options:}
561 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
562 [@b{-mregnames}|@b{-mno-regnames}]
563 [@b{-mwarn-areg-zero}]
567 @emph{Target SCORE options:}
568 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
569 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
570 [@b{-march=score7}][@b{-march=score3}]
571 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
575 @emph{Target SPARC options:}
576 @c The order here is important. See c-sparc.texi.
577 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Aleon}|@b{-Asparclet}|@b{-Asparclite}
578 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av8plusb}|@b{-Av8plusc}|@b{-Av8plusd}
579 @b{-Av8plusv}|@b{-Av8plusm}|@b{-Av9}|@b{-Av9a}|@b{-Av9b}|@b{-Av9c}
580 @b{-Av9d}|@b{-Av9e}|@b{-Av9v}|@b{-Av9m}|@b{-Asparc}|@b{-Asparcvis}
581 @b{-Asparcvis2}|@b{-Asparcfmaf}|@b{-Asparcima}|@b{-Asparcvis3}
582 @b{-Asparcvisr}|@b{-Asparc5}]
583 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}]|@b{-xarch=v8plusb}|@b{-xarch=v8plusc}
584 @b{-xarch=v8plusd}|@b{-xarch=v8plusv}|@b{-xarch=v8plusm}|@b{-xarch=v9}
585 @b{-xarch=v9a}|@b{-xarch=v9b}|@b{-xarch=v9c}|@b{-xarch=v9d}|@b{-xarch=v9e}
586 @b{-xarch=v9v}|@b{-xarch=v9m}|@b{-xarch=sparc}|@b{-xarch=sparcvis}
587 @b{-xarch=sparcvis2}|@b{-xarch=sparcfmaf}|@b{-xarch=sparcima}
588 @b{-xarch=sparcvis3}|@b{-xarch=sparcvisr}|@b{-xarch=sparc5}
591 [@b{--enforce-aligned-data}][@b{--dcti-couples-detect}]
595 @emph{Target TIC54X options:}
596 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
597 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
601 @emph{Target TIC6X options:}
602 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
603 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
604 [@b{-mpic}|@b{-mno-pic}]
608 @emph{Target TILE-Gx options:}
609 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
612 @c TILEPro has no machine-dependent assembler options
616 @emph{Target Visium options:}
617 [@b{-mtune=@var{arch}}]
621 @emph{Target Xtensa options:}
622 [@b{--[no-]text-section-literals}] [@b{--[no-]auto-litpools}]
623 [@b{--[no-]absolute-literals}]
624 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
625 [@b{--[no-]transform}]
626 [@b{--rename-section} @var{oldname}=@var{newname}]
627 [@b{--[no-]trampolines}]
631 @emph{Target Z80 options:}
632 [@b{-z80}] [@b{-r800}]
633 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
634 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
635 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
636 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
637 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
638 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
642 @c Z8000 has no machine-dependent assembler options
651 @include at-file.texi
654 Turn on listings, in any of a variety of ways:
658 omit false conditionals
661 omit debugging directives
664 include general information, like @value{AS} version and options passed
667 include high-level source
673 include macro expansions
676 omit forms processing
682 set the name of the listing file
685 You may combine these options; for example, use @samp{-aln} for assembly
686 listing without forms processing. The @samp{=file} option, if used, must be
687 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
690 Begin in alternate macro mode.
692 @xref{Altmacro,,@code{.altmacro}}.
695 @item --compress-debug-sections
696 Compress DWARF debug sections using zlib with SHF_COMPRESSED from the
697 ELF ABI. The resulting object file may not be compatible with older
698 linkers and object file utilities. Note if compression would make a
699 given section @emph{larger} then it is not compressed.
702 @cindex @samp{--compress-debug-sections=} option
703 @item --compress-debug-sections=none
704 @itemx --compress-debug-sections=zlib
705 @itemx --compress-debug-sections=zlib-gnu
706 @itemx --compress-debug-sections=zlib-gabi
707 These options control how DWARF debug sections are compressed.
708 @option{--compress-debug-sections=none} is equivalent to
709 @option{--nocompress-debug-sections}.
710 @option{--compress-debug-sections=zlib} and
711 @option{--compress-debug-sections=zlib-gabi} are equivalent to
712 @option{--compress-debug-sections}.
713 @option{--compress-debug-sections=zlib-gnu} compresses DWARF debug
714 sections using zlib. The debug sections are renamed to begin with
715 @samp{.zdebug}. Note if compression would make a given section
716 @emph{larger} then it is not compressed nor renamed.
720 @item --nocompress-debug-sections
721 Do not compress DWARF debug sections. This is usually the default for all
722 targets except the x86/x86_64, but a configure time option can be used to
726 Ignored. This option is accepted for script compatibility with calls to
729 @item --debug-prefix-map @var{old}=@var{new}
730 When assembling files in directory @file{@var{old}}, record debugging
731 information describing them as in @file{@var{new}} instead.
733 @item --defsym @var{sym}=@var{value}
734 Define the symbol @var{sym} to be @var{value} before assembling the input file.
735 @var{value} must be an integer constant. As in C, a leading @samp{0x}
736 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
737 value. The value of the symbol can be overridden inside a source file via the
738 use of a @code{.set} pseudo-op.
741 ``fast''---skip whitespace and comment preprocessing (assume source is
746 Generate debugging information for each assembler source line using whichever
747 debug format is preferred by the target. This currently means either STABS,
751 Generate stabs debugging information for each assembler line. This
752 may help debugging assembler code, if the debugger can handle it.
755 Generate stabs debugging information for each assembler line, with GNU
756 extensions that probably only gdb can handle, and that could make other
757 debuggers crash or refuse to read your program. This
758 may help debugging assembler code. Currently the only GNU extension is
759 the location of the current working directory at assembling time.
762 Generate DWARF2 debugging information for each assembler line. This
763 may help debugging assembler code, if the debugger can handle it. Note---this
764 option is only supported by some targets, not all of them.
766 @item --gdwarf-sections
767 Instead of creating a .debug_line section, create a series of
768 .debug_line.@var{foo} sections where @var{foo} is the name of the
769 corresponding code section. For example a code section called @var{.text.func}
770 will have its dwarf line number information placed into a section called
771 @var{.debug_line.text.func}. If the code section is just called @var{.text}
772 then debug line section will still be called just @var{.debug_line} without any
776 @item --size-check=error
777 @itemx --size-check=warning
778 Issue an error or warning for invalid ELF .size directive.
780 @item --elf-stt-common=no
781 @itemx --elf-stt-common=yes
782 These options control whether the ELF assembler should generate common
783 symbols with the @code{STT_COMMON} type. The default can be controlled
784 by a configure option @option{--enable-elf-stt-common}.
786 @item --generate-missing-build-notes=yes
787 @itemx --generate-missing-build-notes=no
788 These options control whether the ELF assembler should generate GNU Build
789 attribute notes if none are present in the input sources.
790 The default can be controlled by the @option{--enable-generate-build-notes}
796 Print a summary of the command-line options and exit.
799 Print a summary of all target specific options and exit.
802 Add directory @var{dir} to the search list for @code{.include} directives.
805 Don't warn about signed overflow.
808 @ifclear DIFF-TBL-KLUGE
809 This option is accepted but has no effect on the @value{TARGET} family.
811 @ifset DIFF-TBL-KLUGE
812 Issue warnings when difference tables altered for long displacements.
817 Keep (in the symbol table) local symbols. These symbols start with
818 system-specific local label prefixes, typically @samp{.L} for ELF systems
819 or @samp{L} for traditional a.out systems.
824 @item --listing-lhs-width=@var{number}
825 Set the maximum width, in words, of the output data column for an assembler
826 listing to @var{number}.
828 @item --listing-lhs-width2=@var{number}
829 Set the maximum width, in words, of the output data column for continuation
830 lines in an assembler listing to @var{number}.
832 @item --listing-rhs-width=@var{number}
833 Set the maximum width of an input source line, as displayed in a listing, to
836 @item --listing-cont-lines=@var{number}
837 Set the maximum number of lines printed in a listing for a single line of input
840 @item --no-pad-sections
841 Stop the assembler for padding the ends of output sections to the alignment
842 of that section. The default is to pad the sections, but this can waste space
843 which might be needed on targets which have tight memory constraints.
845 @item -o @var{objfile}
846 Name the object-file output from @command{@value{AS}} @var{objfile}.
849 Fold the data section into the text section.
851 @item --hash-size=@var{number}
852 Set the default size of GAS's hash tables to a prime number close to
853 @var{number}. Increasing this value can reduce the length of time it takes the
854 assembler to perform its tasks, at the expense of increasing the assembler's
855 memory requirements. Similarly reducing this value can reduce the memory
856 requirements at the expense of speed.
858 @item --reduce-memory-overheads
859 This option reduces GAS's memory requirements, at the expense of making the
860 assembly processes slower. Currently this switch is a synonym for
861 @samp{--hash-size=4051}, but in the future it may have other effects as well.
864 @item --sectname-subst
865 Honor substitution sequences in section names.
867 @xref{Section Name Substitutions,,@code{.section @var{name}}}.
872 Print the maximum space (in bytes) and total time (in seconds) used by
875 @item --strip-local-absolute
876 Remove local absolute symbols from the outgoing symbol table.
880 Print the @command{as} version.
883 Print the @command{as} version and exit.
887 Suppress warning messages.
889 @item --fatal-warnings
890 Treat warnings as errors.
893 Don't suppress warning messages or treat them as errors.
902 Generate an object file even after errors.
904 @item -- | @var{files} @dots{}
905 Standard input, or source files to assemble.
913 @xref{AArch64 Options}, for the options available when @value{AS} is configured
914 for the 64-bit mode of the ARM Architecture (AArch64).
919 The following options are available when @value{AS} is configured for the
920 64-bit mode of the ARM Architecture (AArch64).
923 @include c-aarch64.texi
924 @c ended inside the included file
932 @xref{Alpha Options}, for the options available when @value{AS} is configured
933 for an Alpha processor.
938 The following options are available when @value{AS} is configured for an Alpha
942 @include c-alpha.texi
943 @c ended inside the included file
950 The following options are available when @value{AS} is configured for an ARC
954 @item -mcpu=@var{cpu}
955 This option selects the core processor variant.
957 Select either big-endian (-EB) or little-endian (-EL) output.
959 Enable Code Density extenssion instructions.
964 The following options are available when @value{AS} is configured for the ARM
968 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
969 Specify which ARM processor variant is the target.
970 @item -march=@var{architecture}[+@var{extension}@dots{}]
971 Specify which ARM architecture variant is used by the target.
972 @item -mfpu=@var{floating-point-format}
973 Select which Floating Point architecture is the target.
974 @item -mfloat-abi=@var{abi}
975 Select which floating point ABI is in use.
977 Enable Thumb only instruction decoding.
978 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
979 Select which procedure calling convention is in use.
981 Select either big-endian (-EB) or little-endian (-EL) output.
982 @item -mthumb-interwork
983 Specify that the code has been generated with interworking between Thumb and
986 Turns on CodeComposer Studio assembly syntax compatibility mode.
988 Specify that PIC code has been generated.
996 @xref{Blackfin Options}, for the options available when @value{AS} is
997 configured for the Blackfin processor family.
1001 @c man begin OPTIONS
1002 The following options are available when @value{AS} is configured for
1003 the Blackfin processor family.
1005 @c man begin INCLUDE
1006 @include c-bfin.texi
1007 @c ended inside the included file
1015 @xref{BPF Options}, for the options available when @value{AS} is
1016 configured for the Linux kernel BPF processor family.
1020 @c man begin OPTIONS
1021 The following options are available when @value{AS} is configured for
1022 the Linux kernel BPF processor family.
1024 @c man begin INCLUDE
1026 @c ended inside the included file
1031 @c man begin OPTIONS
1033 See the info pages for documentation of the CRIS-specific options.
1039 @xref{C-SKY Options}, for the options available when @value{AS} is
1040 configured for the C-SKY processor family.
1044 @c man begin OPTIONS
1045 The following options are available when @value{AS} is configured for
1046 the C-SKY processor family.
1048 @c man begin INCLUDE
1049 @include c-csky.texi
1050 @c ended inside the included file
1056 The following options are available when @value{AS} is configured for
1059 @cindex D10V optimization
1060 @cindex optimization, D10V
1062 Optimize output by parallelizing instructions.
1067 The following options are available when @value{AS} is configured for a D30V
1070 @cindex D30V optimization
1071 @cindex optimization, D30V
1073 Optimize output by parallelizing instructions.
1077 Warn when nops are generated.
1079 @cindex D30V nops after 32-bit multiply
1081 Warn when a nop after a 32-bit multiply instruction is generated.
1087 The following options are available when @value{AS} is configured for the
1088 Adapteva EPIPHANY series.
1091 @xref{Epiphany Options}, for the options available when @value{AS} is
1092 configured for an Epiphany processor.
1096 @c man begin OPTIONS
1097 The following options are available when @value{AS} is configured for
1098 an Epiphany processor.
1100 @c man begin INCLUDE
1101 @include c-epiphany.texi
1102 @c ended inside the included file
1110 @xref{H8/300 Options}, for the options available when @value{AS} is configured
1111 for an H8/300 processor.
1115 @c man begin OPTIONS
1116 The following options are available when @value{AS} is configured for an H8/300
1119 @c man begin INCLUDE
1120 @include c-h8300.texi
1121 @c ended inside the included file
1129 @xref{i386-Options}, for the options available when @value{AS} is
1130 configured for an i386 processor.
1134 @c man begin OPTIONS
1135 The following options are available when @value{AS} is configured for
1138 @c man begin INCLUDE
1139 @include c-i386.texi
1140 @c ended inside the included file
1145 @c man begin OPTIONS
1147 The following options are available when @value{AS} is configured for the
1153 Specifies that the extended IP2022 instructions are allowed.
1156 Restores the default behaviour, which restricts the permitted instructions to
1157 just the basic IP2022 ones.
1163 The following options are available when @value{AS} is configured for the
1164 Renesas M32C and M16C processors.
1169 Assemble M32C instructions.
1172 Assemble M16C instructions (the default).
1175 Enable support for link-time relaxations.
1178 Support H'00 style hex constants in addition to 0x00 style.
1184 The following options are available when @value{AS} is configured for the
1185 Renesas M32R (formerly Mitsubishi M32R) series.
1190 Specify which processor in the M32R family is the target. The default
1191 is normally the M32R, but this option changes it to the M32RX.
1193 @item --warn-explicit-parallel-conflicts or --Wp
1194 Produce warning messages when questionable parallel constructs are
1197 @item --no-warn-explicit-parallel-conflicts or --Wnp
1198 Do not produce warning messages when questionable parallel constructs are
1205 The following options are available when @value{AS} is configured for the
1206 Motorola 68000 series.
1211 Shorten references to undefined symbols, to one word instead of two.
1213 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1214 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1215 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1216 Specify what processor in the 68000 family is the target. The default
1217 is normally the 68020, but this can be changed at configuration time.
1219 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1220 The target machine does (or does not) have a floating-point coprocessor.
1221 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1222 the basic 68000 is not compatible with the 68881, a combination of the
1223 two can be specified, since it's possible to do emulation of the
1224 coprocessor instructions with the main processor.
1226 @item -m68851 | -mno-68851
1227 The target machine does (or does not) have a memory-management
1228 unit coprocessor. The default is to assume an MMU for 68020 and up.
1236 @xref{Nios II Options}, for the options available when @value{AS} is configured
1237 for an Altera Nios II processor.
1241 @c man begin OPTIONS
1242 The following options are available when @value{AS} is configured for an
1243 Altera Nios II processor.
1245 @c man begin INCLUDE
1246 @include c-nios2.texi
1247 @c ended inside the included file
1253 For details about the PDP-11 machine dependent features options,
1254 see @ref{PDP-11-Options}.
1257 @item -mpic | -mno-pic
1258 Generate position-independent (or position-dependent) code. The
1259 default is @option{-mpic}.
1262 @itemx -mall-extensions
1263 Enable all instruction set extensions. This is the default.
1265 @item -mno-extensions
1266 Disable all instruction set extensions.
1268 @item -m@var{extension} | -mno-@var{extension}
1269 Enable (or disable) a particular instruction set extension.
1272 Enable the instruction set extensions supported by a particular CPU, and
1273 disable all other extensions.
1275 @item -m@var{machine}
1276 Enable the instruction set extensions supported by a particular machine
1277 model, and disable all other extensions.
1283 The following options are available when @value{AS} is configured for
1284 a picoJava processor.
1288 @cindex PJ endianness
1289 @cindex endianness, PJ
1290 @cindex big endian output, PJ
1292 Generate ``big endian'' format output.
1294 @cindex little endian output, PJ
1296 Generate ``little endian'' format output.
1304 @xref{PRU Options}, for the options available when @value{AS} is configured
1305 for a PRU processor.
1309 @c man begin OPTIONS
1310 The following options are available when @value{AS} is configured for a
1313 @c man begin INCLUDE
1315 @c ended inside the included file
1320 The following options are available when @value{AS} is configured for the
1321 Motorola 68HC11 or 68HC12 series.
1325 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1326 Specify what processor is the target. The default is
1327 defined by the configuration option when building the assembler.
1329 @item --xgate-ramoffset
1330 Instruct the linker to offset RAM addresses from S12X address space into
1331 XGATE address space.
1334 Specify to use the 16-bit integer ABI.
1337 Specify to use the 32-bit integer ABI.
1339 @item -mshort-double
1340 Specify to use the 32-bit double ABI.
1343 Specify to use the 64-bit double ABI.
1345 @item --force-long-branches
1346 Relative branches are turned into absolute ones. This concerns
1347 conditional branches, unconditional branches and branches to a
1350 @item -S | --short-branches
1351 Do not turn relative branches into absolute ones
1352 when the offset is out of range.
1354 @item --strict-direct-mode
1355 Do not turn the direct addressing mode into extended addressing mode
1356 when the instruction does not support direct addressing mode.
1358 @item --print-insn-syntax
1359 Print the syntax of instruction in case of error.
1361 @item --print-opcodes
1362 Print the list of instructions with syntax and then exit.
1364 @item --generate-example
1365 Print an example of instruction for each possible instruction and then exit.
1366 This option is only useful for testing @command{@value{AS}}.
1372 The following options are available when @command{@value{AS}} is configured
1373 for the SPARC architecture:
1376 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1377 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1378 Explicitly select a variant of the SPARC architecture.
1380 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1381 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1383 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1384 UltraSPARC extensions.
1386 @item -xarch=v8plus | -xarch=v8plusa
1387 For compatibility with the Solaris v9 assembler. These options are
1388 equivalent to -Av8plus and -Av8plusa, respectively.
1391 Warn when the assembler switches to another architecture.
1396 The following options are available when @value{AS} is configured for the 'c54x
1401 Enable extended addressing mode. All addresses and relocations will assume
1402 extended addressing (usually 23 bits).
1403 @item -mcpu=@var{CPU_VERSION}
1404 Sets the CPU version being compiled for.
1405 @item -merrors-to-file @var{FILENAME}
1406 Redirect error output to a file, for broken systems which don't support such
1407 behaviour in the shell.
1412 @c man begin OPTIONS
1413 The following options are available when @value{AS} is configured for
1418 This option sets the largest size of an object that can be referenced
1419 implicitly with the @code{gp} register. It is only accepted for targets that
1420 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1422 @cindex MIPS endianness
1423 @cindex endianness, MIPS
1424 @cindex big endian output, MIPS
1426 Generate ``big endian'' format output.
1428 @cindex little endian output, MIPS
1430 Generate ``little endian'' format output.
1448 Generate code for a particular MIPS Instruction Set Architecture level.
1449 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1450 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1451 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1452 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1453 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1454 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1455 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1456 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1457 MIPS64 Release 6 ISA processors, respectively.
1459 @item -march=@var{cpu}
1460 Generate code for a particular MIPS CPU.
1462 @item -mtune=@var{cpu}
1463 Schedule and tune for a particular MIPS CPU.
1467 Cause nops to be inserted if the read of the destination register
1468 of an mfhi or mflo instruction occurs in the following two instructions.
1471 @itemx -mno-fix-rm7000
1472 Cause nops to be inserted if a dmult or dmultu instruction is
1473 followed by a load instruction.
1476 @itemx -mno-fix-r5900
1477 Do not attempt to schedule the preceding instruction into the delay slot
1478 of a branch instruction placed at the end of a short loop of six
1479 instructions or fewer and always schedule a @code{nop} instruction there
1480 instead. The short loop bug under certain conditions causes loops to
1481 execute only once or twice, due to a hardware bug in the R5900 chip.
1485 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1486 section instead of the standard ELF .stabs sections.
1490 Control generation of @code{.pdr} sections.
1494 The register sizes are normally inferred from the ISA and ABI, but these
1495 flags force a certain group of registers to be treated as 32 bits wide at
1496 all times. @samp{-mgp32} controls the size of general-purpose registers
1497 and @samp{-mfp32} controls the size of floating-point registers.
1501 The register sizes are normally inferred from the ISA and ABI, but these
1502 flags force a certain group of registers to be treated as 64 bits wide at
1503 all times. @samp{-mgp64} controls the size of general-purpose registers
1504 and @samp{-mfp64} controls the size of floating-point registers.
1507 The register sizes are normally inferred from the ISA and ABI, but using
1508 this flag in combination with @samp{-mabi=32} enables an ABI variant
1509 which will operate correctly with floating-point registers which are
1513 @itemx -mno-odd-spreg
1514 Enable use of floating-point operations on odd-numbered single-precision
1515 registers when supported by the ISA. @samp{-mfpxx} implies
1516 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1520 Generate code for the MIPS 16 processor. This is equivalent to putting
1521 @code{.module mips16} at the start of the assembly file. @samp{-no-mips16}
1522 turns off this option.
1525 @itemx -mno-mips16e2
1526 Enable the use of MIPS16e2 instructions in MIPS16 mode. This is equivalent
1527 to putting @code{.module mips16e2} at the start of the assembly file.
1528 @samp{-mno-mips16e2} turns off this option.
1531 @itemx -mno-micromips
1532 Generate code for the microMIPS processor. This is equivalent to putting
1533 @code{.module micromips} at the start of the assembly file.
1534 @samp{-mno-micromips} turns off this option. This is equivalent to putting
1535 @code{.module nomicromips} at the start of the assembly file.
1538 @itemx -mno-smartmips
1539 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1540 equivalent to putting @code{.module smartmips} at the start of the assembly
1541 file. @samp{-mno-smartmips} turns off this option.
1545 Generate code for the MIPS-3D Application Specific Extension.
1546 This tells the assembler to accept MIPS-3D instructions.
1547 @samp{-no-mips3d} turns off this option.
1551 Generate code for the MDMX Application Specific Extension.
1552 This tells the assembler to accept MDMX instructions.
1553 @samp{-no-mdmx} turns off this option.
1557 Generate code for the DSP Release 1 Application Specific Extension.
1558 This tells the assembler to accept DSP Release 1 instructions.
1559 @samp{-mno-dsp} turns off this option.
1563 Generate code for the DSP Release 2 Application Specific Extension.
1564 This option implies @samp{-mdsp}.
1565 This tells the assembler to accept DSP Release 2 instructions.
1566 @samp{-mno-dspr2} turns off this option.
1570 Generate code for the DSP Release 3 Application Specific Extension.
1571 This option implies @samp{-mdsp} and @samp{-mdspr2}.
1572 This tells the assembler to accept DSP Release 3 instructions.
1573 @samp{-mno-dspr3} turns off this option.
1577 Generate code for the MIPS SIMD Architecture Extension.
1578 This tells the assembler to accept MSA instructions.
1579 @samp{-mno-msa} turns off this option.
1583 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1584 This tells the assembler to accept XPA instructions.
1585 @samp{-mno-xpa} turns off this option.
1589 Generate code for the MT Application Specific Extension.
1590 This tells the assembler to accept MT instructions.
1591 @samp{-mno-mt} turns off this option.
1595 Generate code for the MCU Application Specific Extension.
1596 This tells the assembler to accept MCU instructions.
1597 @samp{-mno-mcu} turns off this option.
1601 Generate code for the MIPS cyclic redundancy check (CRC) Application
1602 Specific Extension. This tells the assembler to accept CRC instructions.
1603 @samp{-mno-crc} turns off this option.
1607 Generate code for the Global INValidate (GINV) Application Specific
1608 Extension. This tells the assembler to accept GINV instructions.
1609 @samp{-mno-ginv} turns off this option.
1611 @item -mloongson-mmi
1612 @itemx -mno-loongson-mmi
1613 Generate code for the Loongson MultiMedia extensions Instructions (MMI)
1614 Application Specific Extension. This tells the assembler to accept MMI
1616 @samp{-mno-loongson-mmi} turns off this option.
1618 @item -mloongson-cam
1619 @itemx -mno-loongson-cam
1620 Generate code for the Loongson Content Address Memory (CAM) instructions.
1621 This tells the assembler to accept Loongson CAM instructions.
1622 @samp{-mno-loongson-cam} turns off this option.
1624 @item -mloongson-ext
1625 @itemx -mno-loongson-ext
1626 Generate code for the Loongson EXTensions (EXT) instructions.
1627 This tells the assembler to accept Loongson EXT instructions.
1628 @samp{-mno-loongson-ext} turns off this option.
1630 @item -mloongson-ext2
1631 @itemx -mno-loongson-ext2
1632 Generate code for the Loongson EXTensions R2 (EXT2) instructions.
1633 This option implies @samp{-mloongson-ext}.
1634 This tells the assembler to accept Loongson EXT2 instructions.
1635 @samp{-mno-loongson-ext2} turns off this option.
1639 Only use 32-bit instruction encodings when generating code for the
1640 microMIPS processor. This option inhibits the use of any 16-bit
1641 instructions. This is equivalent to putting @code{.set insn32} at
1642 the start of the assembly file. @samp{-mno-insn32} turns off this
1643 option. This is equivalent to putting @code{.set noinsn32} at the
1644 start of the assembly file. By default @samp{-mno-insn32} is
1645 selected, allowing all instructions to be used.
1647 @item --construct-floats
1648 @itemx --no-construct-floats
1649 The @samp{--no-construct-floats} option disables the construction of
1650 double width floating point constants by loading the two halves of the
1651 value into the two single width floating point registers that make up
1652 the double width register. By default @samp{--construct-floats} is
1653 selected, allowing construction of these floating point constants.
1655 @item --relax-branch
1656 @itemx --no-relax-branch
1657 The @samp{--relax-branch} option enables the relaxation of out-of-range
1658 branches. By default @samp{--no-relax-branch} is selected, causing any
1659 out-of-range branches to produce an error.
1661 @item -mignore-branch-isa
1662 @itemx -mno-ignore-branch-isa
1663 Ignore branch checks for invalid transitions between ISA modes. The
1664 semantics of branches does not provide for an ISA mode switch, so in
1665 most cases the ISA mode a branch has been encoded for has to be the
1666 same as the ISA mode of the branch's target label. Therefore GAS has
1667 checks implemented that verify in branch assembly that the two ISA
1668 modes match. @samp{-mignore-branch-isa} disables these checks. By
1669 default @samp{-mno-ignore-branch-isa} is selected, causing any invalid
1670 branch requiring a transition between ISA modes to produce an error.
1672 @item -mnan=@var{encoding}
1673 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1674 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1677 @item --emulation=@var{name}
1678 This option was formerly used to switch between ELF and ECOFF output
1679 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1680 removed in GAS 2.24, so the option now serves little purpose.
1681 It is retained for backwards compatibility.
1683 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1684 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1685 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1686 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1687 preferred options instead.
1690 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1697 Control how to deal with multiplication overflow and division by zero.
1698 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1699 (and only work for Instruction Set Architecture level 2 and higher);
1700 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1704 When this option is used, @command{@value{AS}} will issue a warning every
1705 time it generates a nop instruction from a macro.
1711 The following options are available when @value{AS} is configured for
1717 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1718 The command-line option @samp{-nojsri2bsr} can be used to disable it.
1722 Enable or disable the silicon filter behaviour. By default this is disabled.
1723 The default can be overridden by the @samp{-sifilter} command-line option.
1726 Alter jump instructions for long displacements.
1728 @item -mcpu=[210|340]
1729 Select the cpu type on the target hardware. This controls which instructions
1733 Assemble for a big endian target.
1736 Assemble for a little endian target.
1745 @xref{Meta Options}, for the options available when @value{AS} is configured
1746 for a Meta processor.
1750 @c man begin OPTIONS
1751 The following options are available when @value{AS} is configured for a
1754 @c man begin INCLUDE
1755 @include c-metag.texi
1756 @c ended inside the included file
1761 @c man begin OPTIONS
1763 See the info pages for documentation of the MMIX-specific options.
1769 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1770 for a NDS32 processor.
1772 @c ended inside the included file
1776 @c man begin OPTIONS
1777 The following options are available when @value{AS} is configured for a
1780 @c man begin INCLUDE
1781 @include c-nds32.texi
1782 @c ended inside the included file
1789 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1790 for a PowerPC processor.
1794 @c man begin OPTIONS
1795 The following options are available when @value{AS} is configured for a
1798 @c man begin INCLUDE
1800 @c ended inside the included file
1808 @xref{RISC-V-Options}, for the options available when @value{AS} is configured
1809 for a RISC-V processor.
1813 @c man begin OPTIONS
1814 The following options are available when @value{AS} is configured for a
1817 @c man begin INCLUDE
1818 @include c-riscv.texi
1819 @c ended inside the included file
1824 @c man begin OPTIONS
1826 See the info pages for documentation of the RX-specific options.
1830 The following options are available when @value{AS} is configured for the s390
1836 Select the word size, either 31/32 bits or 64 bits.
1839 Select the architecture mode, either the Enterprise System
1840 Architecture (esa) or the z/Architecture mode (zarch).
1841 @item -march=@var{processor}
1842 Specify which s390 processor variant is the target, @samp{g5} (or
1843 @samp{arch3}), @samp{g6}, @samp{z900} (or @samp{arch5}), @samp{z990} (or
1844 @samp{arch6}), @samp{z9-109}, @samp{z9-ec} (or @samp{arch7}), @samp{z10} (or
1845 @samp{arch8}), @samp{z196} (or @samp{arch9}), @samp{zEC12} (or @samp{arch10}),
1846 @samp{z13} (or @samp{arch11}), @samp{z14} (or @samp{arch12}), or @samp{z15}
1849 @itemx -mno-regnames
1850 Allow or disallow symbolic names for registers.
1851 @item -mwarn-areg-zero
1852 Warn whenever the operand for a base or index register has been specified
1853 but evaluates to zero.
1861 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1862 for a TMS320C6000 processor.
1866 @c man begin OPTIONS
1867 The following options are available when @value{AS} is configured for a
1868 TMS320C6000 processor.
1870 @c man begin INCLUDE
1871 @include c-tic6x.texi
1872 @c ended inside the included file
1880 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1881 for a TILE-Gx processor.
1885 @c man begin OPTIONS
1886 The following options are available when @value{AS} is configured for a TILE-Gx
1889 @c man begin INCLUDE
1890 @include c-tilegx.texi
1891 @c ended inside the included file
1899 @xref{Visium Options}, for the options available when @value{AS} is configured
1900 for a Visium processor.
1904 @c man begin OPTIONS
1905 The following option is available when @value{AS} is configured for a Visium
1908 @c man begin INCLUDE
1909 @include c-visium.texi
1910 @c ended inside the included file
1918 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1919 for an Xtensa processor.
1923 @c man begin OPTIONS
1924 The following options are available when @value{AS} is configured for an
1927 @c man begin INCLUDE
1928 @include c-xtensa.texi
1929 @c ended inside the included file
1934 @c man begin OPTIONS
1937 The following options are available when @value{AS} is configured for
1938 a Z80 family processor.
1941 Assemble for Z80 processor.
1943 Assemble for R800 processor.
1944 @item -ignore-undocumented-instructions
1946 Assemble undocumented Z80 instructions that also work on R800 without warning.
1947 @item -ignore-unportable-instructions
1949 Assemble all undocumented Z80 instructions without warning.
1950 @item -warn-undocumented-instructions
1952 Issue a warning for undocumented Z80 instructions that also work on R800.
1953 @item -warn-unportable-instructions
1955 Issue a warning for undocumented Z80 instructions that do not work on R800.
1956 @item -forbid-undocumented-instructions
1958 Treat all undocumented instructions as errors.
1959 @item -forbid-unportable-instructions
1961 Treat undocumented Z80 instructions that do not work on R800 as errors.
1968 * Manual:: Structure of this Manual
1969 * GNU Assembler:: The GNU Assembler
1970 * Object Formats:: Object File Formats
1971 * Command Line:: Command Line
1972 * Input Files:: Input Files
1973 * Object:: Output (Object) File
1974 * Errors:: Error and Warning Messages
1978 @section Structure of this Manual
1980 @cindex manual, structure and purpose
1981 This manual is intended to describe what you need to know to use
1982 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1983 notation for symbols, constants, and expressions; the directives that
1984 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1987 We also cover special features in the @value{TARGET}
1988 configuration of @command{@value{AS}}, including assembler directives.
1991 This manual also describes some of the machine-dependent features of
1992 various flavors of the assembler.
1995 @cindex machine instructions (not covered)
1996 On the other hand, this manual is @emph{not} intended as an introduction
1997 to programming in assembly language---let alone programming in general!
1998 In a similar vein, we make no attempt to introduce the machine
1999 architecture; we do @emph{not} describe the instruction set, standard
2000 mnemonics, registers or addressing modes that are standard to a
2001 particular architecture.
2003 You may want to consult the manufacturer's
2004 machine architecture manual for this information.
2008 For information on the H8/300 machine instruction set, see @cite{H8/300
2009 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
2010 Programming Manual} (Renesas).
2013 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
2014 see @cite{SH-Microcomputer User's Manual} (Renesas) or
2015 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
2016 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
2019 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
2023 @c I think this is premature---doc@cygnus.com, 17jan1991
2025 Throughout this manual, we assume that you are running @dfn{GNU},
2026 the portable operating system from the @dfn{Free Software
2027 Foundation, Inc.}. This restricts our attention to certain kinds of
2028 computer (in particular, the kinds of computers that @sc{gnu} can run on);
2029 once this assumption is granted examples and definitions need less
2032 @command{@value{AS}} is part of a team of programs that turn a high-level
2033 human-readable series of instructions into a low-level
2034 computer-readable series of instructions. Different versions of
2035 @command{@value{AS}} are used for different kinds of computer.
2038 @c There used to be a section "Terminology" here, which defined
2039 @c "contents", "byte", "word", and "long". Defining "word" to any
2040 @c particular size is confusing when the .word directive may generate 16
2041 @c bits on one machine and 32 bits on another; in general, for the user
2042 @c version of this manual, none of these terms seem essential to define.
2043 @c They were used very little even in the former draft of the manual;
2044 @c this draft makes an effort to avoid them (except in names of
2048 @section The GNU Assembler
2050 @c man begin DESCRIPTION
2052 @sc{gnu} @command{as} is really a family of assemblers.
2054 This manual describes @command{@value{AS}}, a member of that family which is
2055 configured for the @value{TARGET} architectures.
2057 If you use (or have used) the @sc{gnu} assembler on one architecture, you
2058 should find a fairly similar environment when you use it on another
2059 architecture. Each version has much in common with the others,
2060 including object file formats, most assembler directives (often called
2061 @dfn{pseudo-ops}) and assembler syntax.@refill
2063 @cindex purpose of @sc{gnu} assembler
2064 @command{@value{AS}} is primarily intended to assemble the output of the
2065 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
2066 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
2067 assemble correctly everything that other assemblers for the same
2068 machine would assemble.
2070 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
2073 @c This remark should appear in generic version of manual; assumption
2074 @c here is that generic version sets M680x0.
2075 This doesn't mean @command{@value{AS}} always uses the same syntax as another
2076 assembler for the same architecture; for example, we know of several
2077 incompatible versions of 680x0 assembly language syntax.
2082 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
2083 program in one pass of the source file. This has a subtle impact on the
2084 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
2086 @node Object Formats
2087 @section Object File Formats
2089 @cindex object file format
2090 The @sc{gnu} assembler can be configured to produce several alternative
2091 object file formats. For the most part, this does not affect how you
2092 write assembly language programs; but directives for debugging symbols
2093 are typically different in different file formats. @xref{Symbol
2094 Attributes,,Symbol Attributes}.
2097 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
2098 @value{OBJ-NAME} format object files.
2100 @c The following should exhaust all configs that set MULTI-OBJ, ideally
2102 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
2103 SOM or ELF format object files.
2108 @section Command Line
2110 @cindex command line conventions
2112 After the program name @command{@value{AS}}, the command line may contain
2113 options and file names. Options may appear in any order, and may be
2114 before, after, or between file names. The order of file names is
2117 @cindex standard input, as input file
2119 @file{--} (two hyphens) by itself names the standard input file
2120 explicitly, as one of the files for @command{@value{AS}} to assemble.
2122 @cindex options, command line
2123 Except for @samp{--} any command-line argument that begins with a
2124 hyphen (@samp{-}) is an option. Each option changes the behavior of
2125 @command{@value{AS}}. No option changes the way another option works. An
2126 option is a @samp{-} followed by one or more letters; the case of
2127 the letter is important. All options are optional.
2129 Some options expect exactly one file name to follow them. The file
2130 name may either immediately follow the option's letter (compatible
2131 with older assemblers) or it may be the next command argument (@sc{gnu}
2132 standard). These two command lines are equivalent:
2135 @value{AS} -o my-object-file.o mumble.s
2136 @value{AS} -omy-object-file.o mumble.s
2140 @section Input Files
2143 @cindex source program
2144 @cindex files, input
2145 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
2146 describe the program input to one run of @command{@value{AS}}. The program may
2147 be in one or more files; how the source is partitioned into files
2148 doesn't change the meaning of the source.
2150 @c I added "con" prefix to "catenation" just to prove I can overcome my
2151 @c APL training... doc@cygnus.com
2152 The source program is a concatenation of the text in all the files, in the
2155 @c man begin DESCRIPTION
2156 Each time you run @command{@value{AS}} it assembles exactly one source
2157 program. The source program is made up of one or more files.
2158 (The standard input is also a file.)
2160 You give @command{@value{AS}} a command line that has zero or more input file
2161 names. The input files are read (from left file name to right). A
2162 command-line argument (in any position) that has no special meaning
2163 is taken to be an input file name.
2165 If you give @command{@value{AS}} no file names it attempts to read one input file
2166 from the @command{@value{AS}} standard input, which is normally your terminal. You
2167 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
2170 Use @samp{--} if you need to explicitly name the standard input file
2171 in your command line.
2173 If the source is empty, @command{@value{AS}} produces a small, empty object
2178 @subheading Filenames and Line-numbers
2180 @cindex input file linenumbers
2181 @cindex line numbers, in input files
2182 There are two ways of locating a line in the input file (or files) and
2183 either may be used in reporting error messages. One way refers to a line
2184 number in a physical file; the other refers to a line number in a
2185 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
2187 @dfn{Physical files} are those files named in the command line given
2188 to @command{@value{AS}}.
2190 @dfn{Logical files} are simply names declared explicitly by assembler
2191 directives; they bear no relation to physical files. Logical file names help
2192 error messages reflect the original source file, when @command{@value{AS}} source
2193 is itself synthesized from other files. @command{@value{AS}} understands the
2194 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
2195 @ref{File,,@code{.file}}.
2198 @section Output (Object) File
2204 Every time you run @command{@value{AS}} it produces an output file, which is
2205 your assembly language program translated into numbers. This file
2206 is the object file. Its default name is @code{a.out}.
2207 You can give it another name by using the @option{-o} option. Conventionally,
2208 object file names end with @file{.o}. The default name is used for historical
2209 reasons: older assemblers were capable of assembling self-contained programs
2210 directly into a runnable program. (For some formats, this isn't currently
2211 possible, but it can be done for the @code{a.out} format.)
2215 The object file is meant for input to the linker @code{@value{LD}}. It contains
2216 assembled program code, information to help @code{@value{LD}} integrate
2217 the assembled program into a runnable file, and (optionally) symbolic
2218 information for the debugger.
2220 @c link above to some info file(s) like the description of a.out.
2221 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2224 @section Error and Warning Messages
2226 @c man begin DESCRIPTION
2228 @cindex error messages
2229 @cindex warning messages
2230 @cindex messages from assembler
2231 @command{@value{AS}} may write warnings and error messages to the standard error
2232 file (usually your terminal). This should not happen when a compiler
2233 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2234 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2235 grave problem that stops the assembly.
2239 @cindex format of warning messages
2240 Warning messages have the format
2243 file_name:@b{NNN}:Warning Message Text
2247 @cindex file names and line numbers, in warnings/errors
2248 (where @b{NNN} is a line number). If both a logical file name
2249 (@pxref{File,,@code{.file}}) and a logical line number
2251 (@pxref{Line,,@code{.line}})
2253 have been given then they will be used, otherwise the file name and line number
2254 in the current assembler source file will be used. The message text is
2255 intended to be self explanatory (in the grand Unix tradition).
2257 Note the file name must be set via the logical version of the @code{.file}
2258 directive, not the DWARF2 version of the @code{.file} directive. For example:
2262 error_assembler_source
2268 produces this output:
2272 asm.s:2: Error: no such instruction: `error_assembler_source'
2273 foo.c:31: Error: no such instruction: `error_c_source'
2276 @cindex format of error messages
2277 Error messages have the format
2280 file_name:@b{NNN}:FATAL:Error Message Text
2283 The file name and line number are derived as for warning
2284 messages. The actual message text may be rather less explanatory
2285 because many of them aren't supposed to happen.
2288 @chapter Command-Line Options
2290 @cindex options, all versions of assembler
2291 This chapter describes command-line options available in @emph{all}
2292 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2293 for options specific
2295 to the @value{TARGET} target.
2298 to particular machine architectures.
2301 @c man begin DESCRIPTION
2303 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2304 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2305 The assembler arguments must be separated from each other (and the @samp{-Wa})
2306 by commas. For example:
2309 gcc -c -g -O -Wa,-alh,-L file.c
2313 This passes two options to the assembler: @samp{-alh} (emit a listing to
2314 standard output with high-level and assembly source) and @samp{-L} (retain
2315 local symbols in the symbol table).
2317 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2318 command-line options are automatically passed to the assembler by the compiler.
2319 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2320 precisely what options it passes to each compilation pass, including the
2326 * a:: -a[cdghlns] enable listings
2327 * alternate:: --alternate enable alternate macro syntax
2328 * D:: -D for compatibility
2329 * f:: -f to work faster
2330 * I:: -I for .include search path
2331 @ifclear DIFF-TBL-KLUGE
2332 * K:: -K for compatibility
2334 @ifset DIFF-TBL-KLUGE
2335 * K:: -K for difference tables
2338 * L:: -L to retain local symbols
2339 * listing:: --listing-XXX to configure listing output
2340 * M:: -M or --mri to assemble in MRI compatibility mode
2341 * MD:: --MD for dependency tracking
2342 * no-pad-sections:: --no-pad-sections to stop section padding
2343 * o:: -o to name the object file
2344 * R:: -R to join data and text sections
2345 * statistics:: --statistics to see statistics about assembly
2346 * traditional-format:: --traditional-format for compatible output
2347 * v:: -v to announce version
2348 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2349 * Z:: -Z to make object file even after errors
2353 @section Enable Listings: @option{-a[cdghlns]}
2363 @cindex listings, enabling
2364 @cindex assembly listings, enabling
2366 These options enable listing output from the assembler. By itself,
2367 @samp{-a} requests high-level, assembly, and symbols listing.
2368 You can use other letters to select specific options for the list:
2369 @samp{-ah} requests a high-level language listing,
2370 @samp{-al} requests an output-program assembly listing, and
2371 @samp{-as} requests a symbol table listing.
2372 High-level listings require that a compiler debugging option like
2373 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2376 Use the @samp{-ag} option to print a first section with general assembly
2377 information, like @value{AS} version, switches passed, or time stamp.
2379 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2380 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2381 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2382 omitted from the listing.
2384 Use the @samp{-ad} option to omit debugging directives from the
2387 Once you have specified one of these options, you can further control
2388 listing output and its appearance using the directives @code{.list},
2389 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2391 The @samp{-an} option turns off all forms processing.
2392 If you do not request listing output with one of the @samp{-a} options, the
2393 listing-control directives have no effect.
2395 The letters after @samp{-a} may be combined into one option,
2396 @emph{e.g.}, @samp{-aln}.
2398 Note if the assembler source is coming from the standard input (e.g.,
2400 is being created by @code{@value{GCC}} and the @samp{-pipe} command-line switch
2401 is being used) then the listing will not contain any comments or preprocessor
2402 directives. This is because the listing code buffers input source lines from
2403 stdin only after they have been preprocessed by the assembler. This reduces
2404 memory usage and makes the code more efficient.
2407 @section @option{--alternate}
2410 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2413 @section @option{-D}
2416 This option has no effect whatsoever, but it is accepted to make it more
2417 likely that scripts written for other assemblers also work with
2418 @command{@value{AS}}.
2421 @section Work Faster: @option{-f}
2424 @cindex trusted compiler
2425 @cindex faster processing (@option{-f})
2426 @samp{-f} should only be used when assembling programs written by a
2427 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2428 and comment preprocessing on
2429 the input file(s) before assembling them. @xref{Preprocessing,
2433 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2434 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2439 @section @code{.include} Search Path: @option{-I} @var{path}
2441 @kindex -I @var{path}
2442 @cindex paths for @code{.include}
2443 @cindex search path for @code{.include}
2444 @cindex @code{include} directive search path
2445 Use this option to add a @var{path} to the list of directories
2446 @command{@value{AS}} searches for files specified in @code{.include}
2447 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2448 many times as necessary to include a variety of paths. The current
2449 working directory is always searched first; after that, @command{@value{AS}}
2450 searches any @samp{-I} directories in the same order as they were
2451 specified (left to right) on the command line.
2454 @section Difference Tables: @option{-K}
2457 @ifclear DIFF-TBL-KLUGE
2458 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2459 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2460 where it can be used to warn when the assembler alters the machine code
2461 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2462 family does not have the addressing limitations that sometimes lead to this
2463 alteration on other platforms.
2466 @ifset DIFF-TBL-KLUGE
2467 @cindex difference tables, warning
2468 @cindex warning for altered difference tables
2469 @command{@value{AS}} sometimes alters the code emitted for directives of the
2470 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2471 You can use the @samp{-K} option if you want a warning issued when this
2476 @section Include Local Symbols: @option{-L}
2479 @cindex local symbols, retaining in output
2480 Symbols beginning with system-specific local label prefixes, typically
2481 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2482 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2483 such symbols when debugging, because they are intended for the use of
2484 programs (like compilers) that compose assembler programs, not for your
2485 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2486 such symbols, so you do not normally debug with them.
2488 This option tells @command{@value{AS}} to retain those local symbols
2489 in the object file. Usually if you do this you also tell the linker
2490 @code{@value{LD}} to preserve those symbols.
2493 @section Configuring listing output: @option{--listing}
2495 The listing feature of the assembler can be enabled via the command-line switch
2496 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2497 hex dump of the corresponding locations in the output object file, and displays
2498 them as a listing file. The format of this listing can be controlled by
2499 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2500 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2501 @code{.psize} (@pxref{Psize}), and
2502 @code{.eject} (@pxref{Eject}) and also by the following switches:
2505 @item --listing-lhs-width=@samp{number}
2506 @kindex --listing-lhs-width
2507 @cindex Width of first line disassembly output
2508 Sets the maximum width, in words, of the first line of the hex byte dump. This
2509 dump appears on the left hand side of the listing output.
2511 @item --listing-lhs-width2=@samp{number}
2512 @kindex --listing-lhs-width2
2513 @cindex Width of continuation lines of disassembly output
2514 Sets the maximum width, in words, of any further lines of the hex byte dump for
2515 a given input source line. If this value is not specified, it defaults to being
2516 the same as the value specified for @samp{--listing-lhs-width}. If neither
2517 switch is used the default is to one.
2519 @item --listing-rhs-width=@samp{number}
2520 @kindex --listing-rhs-width
2521 @cindex Width of source line output
2522 Sets the maximum width, in characters, of the source line that is displayed
2523 alongside the hex dump. The default value for this parameter is 100. The
2524 source line is displayed on the right hand side of the listing output.
2526 @item --listing-cont-lines=@samp{number}
2527 @kindex --listing-cont-lines
2528 @cindex Maximum number of continuation lines
2529 Sets the maximum number of continuation lines of hex dump that will be
2530 displayed for a given single line of source input. The default value is 4.
2534 @section Assemble in MRI Compatibility Mode: @option{-M}
2537 @cindex MRI compatibility mode
2538 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2539 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2540 compatible with the @code{ASM68K} assembler from Microtec Research.
2541 The exact nature of the
2542 MRI syntax will not be documented here; see the MRI manuals for more
2543 information. Note in particular that the handling of macros and macro
2544 arguments is somewhat different. The purpose of this option is to permit
2545 assembling existing MRI assembler code using @command{@value{AS}}.
2547 The MRI compatibility is not complete. Certain operations of the MRI assembler
2548 depend upon its object file format, and can not be supported using other object
2549 file formats. Supporting these would require enhancing each object file format
2550 individually. These are:
2553 @item global symbols in common section
2555 The m68k MRI assembler supports common sections which are merged by the linker.
2556 Other object file formats do not support this. @command{@value{AS}} handles
2557 common sections by treating them as a single common symbol. It permits local
2558 symbols to be defined within a common section, but it can not support global
2559 symbols, since it has no way to describe them.
2561 @item complex relocations
2563 The MRI assemblers support relocations against a negated section address, and
2564 relocations which combine the start addresses of two or more sections. These
2565 are not support by other object file formats.
2567 @item @code{END} pseudo-op specifying start address
2569 The MRI @code{END} pseudo-op permits the specification of a start address.
2570 This is not supported by other object file formats. The start address may
2571 instead be specified using the @option{-e} option to the linker, or in a linker
2574 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2576 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2577 name to the output file. This is not supported by other object file formats.
2579 @item @code{ORG} pseudo-op
2581 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2582 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2583 which changes the location within the current section. Absolute sections are
2584 not supported by other object file formats. The address of a section may be
2585 assigned within a linker script.
2588 There are some other features of the MRI assembler which are not supported by
2589 @command{@value{AS}}, typically either because they are difficult or because they
2590 seem of little consequence. Some of these may be supported in future releases.
2594 @item EBCDIC strings
2596 EBCDIC strings are not supported.
2598 @item packed binary coded decimal
2600 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2601 and @code{DCB.P} pseudo-ops are not supported.
2603 @item @code{FEQU} pseudo-op
2605 The m68k @code{FEQU} pseudo-op is not supported.
2607 @item @code{NOOBJ} pseudo-op
2609 The m68k @code{NOOBJ} pseudo-op is not supported.
2611 @item @code{OPT} branch control options
2613 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2614 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2615 relaxes all branches, whether forward or backward, to an appropriate size, so
2616 these options serve no purpose.
2618 @item @code{OPT} list control options
2620 The following m68k @code{OPT} list control options are ignored: @code{C},
2621 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2622 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2624 @item other @code{OPT} options
2626 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2627 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2629 @item @code{OPT} @code{D} option is default
2631 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2632 @code{OPT NOD} may be used to turn it off.
2634 @item @code{XREF} pseudo-op.
2636 The m68k @code{XREF} pseudo-op is ignored.
2641 @section Dependency Tracking: @option{--MD}
2644 @cindex dependency tracking
2647 @command{@value{AS}} can generate a dependency file for the file it creates. This
2648 file consists of a single rule suitable for @code{make} describing the
2649 dependencies of the main source file.
2651 The rule is written to the file named in its argument.
2653 This feature is used in the automatic updating of makefiles.
2655 @node no-pad-sections
2656 @section Output Section Padding
2657 @kindex --no-pad-sections
2658 @cindex output section padding
2659 Normally the assembler will pad the end of each output section up to its
2660 alignment boundary. But this can waste space, which can be significant on
2661 memory constrained targets. So the @option{--no-pad-sections} option will
2662 disable this behaviour.
2665 @section Name the Object File: @option{-o}
2668 @cindex naming object file
2669 @cindex object file name
2670 There is always one object file output when you run @command{@value{AS}}. By
2671 default it has the name @file{a.out}.
2672 You use this option (which takes exactly one filename) to give the
2673 object file a different name.
2675 Whatever the object file is called, @command{@value{AS}} overwrites any
2676 existing file of the same name.
2679 @section Join Data and Text Sections: @option{-R}
2682 @cindex data and text sections, joining
2683 @cindex text and data sections, joining
2684 @cindex joining text and data sections
2685 @cindex merging text and data sections
2686 @option{-R} tells @command{@value{AS}} to write the object file as if all
2687 data-section data lives in the text section. This is only done at
2688 the very last moment: your binary data are the same, but data
2689 section parts are relocated differently. The data section part of
2690 your object file is zero bytes long because all its bytes are
2691 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2693 When you specify @option{-R} it would be possible to generate shorter
2694 address displacements (because we do not have to cross between text and
2695 data section). We refrain from doing this simply for compatibility with
2696 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2699 When @command{@value{AS}} is configured for COFF or ELF output,
2700 this option is only useful if you use sections named @samp{.text} and
2705 @option{-R} is not supported for any of the HPPA targets. Using
2706 @option{-R} generates a warning from @command{@value{AS}}.
2710 @section Display Assembly Statistics: @option{--statistics}
2712 @kindex --statistics
2713 @cindex statistics, about assembly
2714 @cindex time, total for assembly
2715 @cindex space used, maximum for assembly
2716 Use @samp{--statistics} to display two statistics about the resources used by
2717 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2718 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2721 @node traditional-format
2722 @section Compatible Output: @option{--traditional-format}
2724 @kindex --traditional-format
2725 For some targets, the output of @command{@value{AS}} is different in some ways
2726 from the output of some existing assembler. This switch requests
2727 @command{@value{AS}} to use the traditional format instead.
2729 For example, it disables the exception frame optimizations which
2730 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2733 @section Announce Version: @option{-v}
2737 @cindex assembler version
2738 @cindex version of assembler
2739 You can find out what version of as is running by including the
2740 option @samp{-v} (which you can also spell as @samp{-version}) on the
2744 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2746 @command{@value{AS}} should never give a warning or error message when
2747 assembling compiler output. But programs written by people often
2748 cause @command{@value{AS}} to give a warning that a particular assumption was
2749 made. All such warnings are directed to the standard error file.
2753 @cindex suppressing warnings
2754 @cindex warnings, suppressing
2755 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2756 This only affects the warning messages: it does not change any particular of
2757 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2760 @kindex --fatal-warnings
2761 @cindex errors, caused by warnings
2762 @cindex warnings, causing error
2763 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2764 files that generate warnings to be in error.
2767 @cindex warnings, switching on
2768 You can switch these options off again by specifying @option{--warn}, which
2769 causes warnings to be output as usual.
2772 @section Generate Object File in Spite of Errors: @option{-Z}
2773 @cindex object file, after errors
2774 @cindex errors, continuing after
2775 After an error message, @command{@value{AS}} normally produces no output. If for
2776 some reason you are interested in object file output even after
2777 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2778 option. If there are any errors, @command{@value{AS}} continues anyways, and
2779 writes an object file after a final warning message of the form @samp{@var{n}
2780 errors, @var{m} warnings, generating bad object file.}
2785 @cindex machine-independent syntax
2786 @cindex syntax, machine-independent
2787 This chapter describes the machine-independent syntax allowed in a
2788 source file. @command{@value{AS}} syntax is similar to what many other
2789 assemblers use; it is inspired by the BSD 4.2
2794 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2798 * Preprocessing:: Preprocessing
2799 * Whitespace:: Whitespace
2800 * Comments:: Comments
2801 * Symbol Intro:: Symbols
2802 * Statements:: Statements
2803 * Constants:: Constants
2807 @section Preprocessing
2809 @cindex preprocessing
2810 The @command{@value{AS}} internal preprocessor:
2812 @cindex whitespace, removed by preprocessor
2814 adjusts and removes extra whitespace. It leaves one space or tab before
2815 the keywords on a line, and turns any other whitespace on the line into
2818 @cindex comments, removed by preprocessor
2820 removes all comments, replacing them with a single space, or an
2821 appropriate number of newlines.
2823 @cindex constants, converted by preprocessor
2825 converts character constants into the appropriate numeric values.
2828 It does not do macro processing, include file handling, or
2829 anything else you may get from your C compiler's preprocessor. You can
2830 do include file processing with the @code{.include} directive
2831 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2832 to get other ``CPP'' style preprocessing by giving the input file a
2833 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2834 Output, gcc info, Using GNU CC}.
2836 Excess whitespace, comments, and character constants
2837 cannot be used in the portions of the input text that are not
2840 @cindex turning preprocessing on and off
2841 @cindex preprocessing, turning on and off
2844 If the first line of an input file is @code{#NO_APP} or if you use the
2845 @samp{-f} option, whitespace and comments are not removed from the input file.
2846 Within an input file, you can ask for whitespace and comment removal in
2847 specific portions of the by putting a line that says @code{#APP} before the
2848 text that may contain whitespace or comments, and putting a line that says
2849 @code{#NO_APP} after this text. This feature is mainly intend to support
2850 @code{asm} statements in compilers whose output is otherwise free of comments
2857 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2858 Whitespace is used to separate symbols, and to make programs neater for
2859 people to read. Unless within character constants
2860 (@pxref{Characters,,Character Constants}), any whitespace means the same
2861 as exactly one space.
2867 There are two ways of rendering comments to @command{@value{AS}}. In both
2868 cases the comment is equivalent to one space.
2870 Anything from @samp{/*} through the next @samp{*/} is a comment.
2871 This means you may not nest these comments.
2875 The only way to include a newline ('\n') in a comment
2876 is to use this sort of comment.
2879 /* This sort of comment does not nest. */
2882 @cindex line comment character
2883 Anything from a @dfn{line comment} character up to the next newline is
2884 considered a comment and is ignored. The line comment character is target
2885 specific, and some targets multiple comment characters. Some targets also have
2886 line comment characters that only work if they are the first character on a
2887 line. Some targets use a sequence of two characters to introduce a line
2888 comment. Some targets can also change their line comment characters depending
2889 upon command-line options that have been used. For more details see the
2890 @emph{Syntax} section in the documentation for individual targets.
2892 If the line comment character is the hash sign (@samp{#}) then it still has the
2893 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2894 to specify logical line numbers:
2897 @cindex lines starting with @code{#}
2898 @cindex logical line numbers
2899 To be compatible with past assemblers, lines that begin with @samp{#} have a
2900 special interpretation. Following the @samp{#} should be an absolute
2901 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2902 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2903 new logical file name. The rest of the line, if any, should be whitespace.
2905 If the first non-whitespace characters on the line are not numeric,
2906 the line is ignored. (Just like a comment.)
2909 # This is an ordinary comment.
2910 # 42-6 "new_file_name" # New logical file name
2911 # This is logical line # 36.
2913 This feature is deprecated, and may disappear from future versions
2914 of @command{@value{AS}}.
2919 @cindex characters used in symbols
2920 @ifclear SPECIAL-SYMS
2921 A @dfn{symbol} is one or more characters chosen from the set of all
2922 letters (both upper and lower case), digits and the three characters
2928 A @dfn{symbol} is one or more characters chosen from the set of all
2929 letters (both upper and lower case), digits and the three characters
2930 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2936 On most machines, you can also use @code{$} in symbol names; exceptions
2937 are noted in @ref{Machine Dependencies}.
2939 No symbol may begin with a digit. Case is significant.
2940 There is no length limit; all characters are significant. Multibyte characters
2941 are supported. Symbols are delimited by characters not in that set, or by the
2942 beginning of a file (since the source program must end with a newline, the end
2943 of a file is not a possible symbol delimiter). @xref{Symbols}.
2945 Symbol names may also be enclosed in double quote @code{"} characters. In such
2946 cases any characters are allowed, except for the NUL character. If a double
2947 quote character is to be included in the symbol name it must be preceeded by a
2948 backslash @code{\} character.
2949 @cindex length of symbols
2954 @cindex statements, structure of
2955 @cindex line separator character
2956 @cindex statement separator character
2958 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2959 @dfn{line separator character}. The line separator character is target
2960 specific and described in the @emph{Syntax} section of each
2961 target's documentation. Not all targets support a line separator character.
2962 The newline or line separator character is considered to be part of the
2963 preceding statement. Newlines and separators within character constants are an
2964 exception: they do not end statements.
2966 @cindex newline, required at file end
2967 @cindex EOF, newline must precede
2968 It is an error to end any statement with end-of-file: the last
2969 character of any input file should be a newline.@refill
2971 An empty statement is allowed, and may include whitespace. It is ignored.
2973 @cindex instructions and directives
2974 @cindex directives and instructions
2975 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2976 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2978 A statement begins with zero or more labels, optionally followed by a
2979 key symbol which determines what kind of statement it is. The key
2980 symbol determines the syntax of the rest of the statement. If the
2981 symbol begins with a dot @samp{.} then the statement is an assembler
2982 directive: typically valid for any computer. If the symbol begins with
2983 a letter the statement is an assembly language @dfn{instruction}: it
2984 assembles into a machine language instruction.
2986 Different versions of @command{@value{AS}} for different computers
2987 recognize different instructions. In fact, the same symbol may
2988 represent a different instruction in a different computer's assembly
2992 @cindex @code{:} (label)
2993 @cindex label (@code{:})
2994 A label is a symbol immediately followed by a colon (@code{:}).
2995 Whitespace before a label or after a colon is permitted, but you may not
2996 have whitespace between a label's symbol and its colon. @xref{Labels}.
2999 For HPPA targets, labels need not be immediately followed by a colon, but
3000 the definition of a label must begin in column zero. This also implies that
3001 only one label may be defined on each line.
3005 label: .directive followed by something
3006 another_label: # This is an empty statement.
3007 instruction operand_1, operand_2, @dots{}
3014 A constant is a number, written so that its value is known by
3015 inspection, without knowing any context. Like this:
3018 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
3019 .ascii "Ring the bell\7" # A string constant.
3020 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
3021 .float 0f-314159265358979323846264338327\
3022 95028841971.693993751E-40 # - pi, a flonum.
3027 * Characters:: Character Constants
3028 * Numbers:: Number Constants
3032 @subsection Character Constants
3034 @cindex character constants
3035 @cindex constants, character
3036 There are two kinds of character constants. A @dfn{character} stands
3037 for one character in one byte and its value may be used in
3038 numeric expressions. String constants (properly called string
3039 @emph{literals}) are potentially many bytes and their values may not be
3040 used in arithmetic expressions.
3044 * Chars:: Characters
3048 @subsubsection Strings
3050 @cindex string constants
3051 @cindex constants, string
3052 A @dfn{string} is written between double-quotes. It may contain
3053 double-quotes or null characters. The way to get special characters
3054 into a string is to @dfn{escape} these characters: precede them with
3055 a backslash @samp{\} character. For example @samp{\\} represents
3056 one backslash: the first @code{\} is an escape which tells
3057 @command{@value{AS}} to interpret the second character literally as a backslash
3058 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
3059 escape character). The complete list of escapes follows.
3061 @cindex escape codes, character
3062 @cindex character escape codes
3063 @c NOTE: Cindex entries must not start with a backlash character.
3064 @c NOTE: This confuses the pdf2texi script when it is creating the
3065 @c NOTE: index based upon the first character and so it generates:
3066 @c NOTE: \initial {\\}
3067 @c NOTE: which then results in the error message:
3068 @c NOTE: Argument of \\ has an extra }.
3069 @c NOTE: So in the index entries below a space character has been
3070 @c NOTE: prepended to avoid this problem.
3073 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
3075 @cindex @code{ \b} (backspace character)
3076 @cindex backspace (@code{\b})
3078 Mnemonic for backspace; for ASCII this is octal code 010.
3081 @c Mnemonic for EOText; for ASCII this is octal code 004.
3083 @cindex @code{ \f} (formfeed character)
3084 @cindex formfeed (@code{\f})
3086 Mnemonic for FormFeed; for ASCII this is octal code 014.
3088 @cindex @code{ \n} (newline character)
3089 @cindex newline (@code{\n})
3091 Mnemonic for newline; for ASCII this is octal code 012.
3094 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
3096 @cindex @code{ \r} (carriage return character)
3097 @cindex carriage return (@code{backslash-r})
3099 Mnemonic for carriage-Return; for ASCII this is octal code 015.
3102 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
3103 @c other assemblers.
3105 @cindex @code{ \t} (tab)
3106 @cindex tab (@code{\t})
3108 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
3111 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
3112 @c @item \x @var{digit} @var{digit} @var{digit}
3113 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
3115 @cindex @code{ \@var{ddd}} (octal character code)
3116 @cindex octal character code (@code{\@var{ddd}})
3117 @item \ @var{digit} @var{digit} @var{digit}
3118 An octal character code. The numeric code is 3 octal digits.
3119 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
3120 for example, @code{\008} has the value 010, and @code{\009} the value 011.
3122 @cindex @code{ \@var{xd...}} (hex character code)
3123 @cindex hex character code (@code{\@var{xd...}})
3124 @item \@code{x} @var{hex-digits...}
3125 A hex character code. All trailing hex digits are combined. Either upper or
3126 lower case @code{x} works.
3128 @cindex @code{ \\} (@samp{\} character)
3129 @cindex backslash (@code{\\})
3131 Represents one @samp{\} character.
3134 @c Represents one @samp{'} (accent acute) character.
3135 @c This is needed in single character literals
3136 @c (@xref{Characters,,Character Constants}.) to represent
3139 @cindex @code{ \"} (doublequote character)
3140 @cindex doublequote (@code{\"})
3142 Represents one @samp{"} character. Needed in strings to represent
3143 this character, because an unescaped @samp{"} would end the string.
3145 @item \ @var{anything-else}
3146 Any other character when escaped by @kbd{\} gives a warning, but
3147 assembles as if the @samp{\} was not present. The idea is that if
3148 you used an escape sequence you clearly didn't want the literal
3149 interpretation of the following character. However @command{@value{AS}} has no
3150 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
3151 code and warns you of the fact.
3154 Which characters are escapable, and what those escapes represent,
3155 varies widely among assemblers. The current set is what we think
3156 the BSD 4.2 assembler recognizes, and is a subset of what most C
3157 compilers recognize. If you are in doubt, do not use an escape
3161 @subsubsection Characters
3163 @cindex single character constant
3164 @cindex character, single
3165 @cindex constant, single character
3166 A single character may be written as a single quote immediately followed by
3167 that character. Some backslash escapes apply to characters, @code{\b},
3168 @code{\f}, @code{\n}, @code{\r}, @code{\t}, and @code{\"} with the same meaning
3169 as for strings, plus @code{\'} for a single quote. So if you want to write the
3170 character backslash, you must write @kbd{'\\} where the first @code{\} escapes
3171 the second @code{\}. As you can see, the quote is an acute accent, not a grave
3174 @ifclear abnormal-separator
3175 (or semicolon @samp{;})
3177 @ifset abnormal-separator
3179 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
3184 immediately following an acute accent is taken as a literal character
3185 and does not count as the end of a statement. The value of a character
3186 constant in a numeric expression is the machine's byte-wide code for
3187 that character. @command{@value{AS}} assumes your character code is ASCII:
3188 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
3191 @subsection Number Constants
3193 @cindex constants, number
3194 @cindex number constants
3195 @command{@value{AS}} distinguishes three kinds of numbers according to how they
3196 are stored in the target machine. @emph{Integers} are numbers that
3197 would fit into an @code{int} in the C language. @emph{Bignums} are
3198 integers, but they are stored in more than 32 bits. @emph{Flonums}
3199 are floating point numbers, described below.
3202 * Integers:: Integers
3210 @subsubsection Integers
3212 @cindex constants, integer
3214 @cindex binary integers
3215 @cindex integers, binary
3216 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3217 the binary digits @samp{01}.
3219 @cindex octal integers
3220 @cindex integers, octal
3221 An octal integer is @samp{0} followed by zero or more of the octal
3222 digits (@samp{01234567}).
3224 @cindex decimal integers
3225 @cindex integers, decimal
3226 A decimal integer starts with a non-zero digit followed by zero or
3227 more digits (@samp{0123456789}).
3229 @cindex hexadecimal integers
3230 @cindex integers, hexadecimal
3231 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3232 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3234 Integers have the usual values. To denote a negative integer, use
3235 the prefix operator @samp{-} discussed under expressions
3236 (@pxref{Prefix Ops,,Prefix Operators}).
3239 @subsubsection Bignums
3242 @cindex constants, bignum
3243 A @dfn{bignum} has the same syntax and semantics as an integer
3244 except that the number (or its negative) takes more than 32 bits to
3245 represent in binary. The distinction is made because in some places
3246 integers are permitted while bignums are not.
3249 @subsubsection Flonums
3251 @cindex floating point numbers
3252 @cindex constants, floating point
3254 @cindex precision, floating point
3255 A @dfn{flonum} represents a floating point number. The translation is
3256 indirect: a decimal floating point number from the text is converted by
3257 @command{@value{AS}} to a generic binary floating point number of more than
3258 sufficient precision. This generic floating point number is converted
3259 to a particular computer's floating point format (or formats) by a
3260 portion of @command{@value{AS}} specialized to that computer.
3262 A flonum is written by writing (in order)
3267 (@samp{0} is optional on the HPPA.)
3271 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3273 @kbd{e} is recommended. Case is not important.
3275 @c FIXME: verify if flonum syntax really this vague for most cases
3276 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3277 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3280 On the H8/300 and Renesas / SuperH SH architectures, the letter must be
3281 one of the letters @samp{DFPRSX} (in upper or lower case).
3283 On the ARC, the letter must be one of the letters @samp{DFRS}
3284 (in upper or lower case).
3286 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3290 One of the letters @samp{DFRS} (in upper or lower case).
3293 One of the letters @samp{DFPRSX} (in upper or lower case).
3296 The letter @samp{E} (upper case only).
3301 An optional sign: either @samp{+} or @samp{-}.
3304 An optional @dfn{integer part}: zero or more decimal digits.
3307 An optional @dfn{fractional part}: @samp{.} followed by zero
3308 or more decimal digits.
3311 An optional exponent, consisting of:
3315 An @samp{E} or @samp{e}.
3316 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3317 @c principle this can perfectly well be different on different targets.
3319 Optional sign: either @samp{+} or @samp{-}.
3321 One or more decimal digits.
3326 At least one of the integer part or the fractional part must be
3327 present. The floating point number has the usual base-10 value.
3329 @command{@value{AS}} does all processing using integers. Flonums are computed
3330 independently of any floating point hardware in the computer running
3331 @command{@value{AS}}.
3334 @chapter Sections and Relocation
3339 * Secs Background:: Background
3340 * Ld Sections:: Linker Sections
3341 * As Sections:: Assembler Internal Sections
3342 * Sub-Sections:: Sub-Sections
3346 @node Secs Background
3349 Roughly, a section is a range of addresses, with no gaps; all data
3350 ``in'' those addresses is treated the same for some particular purpose.
3351 For example there may be a ``read only'' section.
3353 @cindex linker, and assembler
3354 @cindex assembler, and linker
3355 The linker @code{@value{LD}} reads many object files (partial programs) and
3356 combines their contents to form a runnable program. When @command{@value{AS}}
3357 emits an object file, the partial program is assumed to start at address 0.
3358 @code{@value{LD}} assigns the final addresses for the partial program, so that
3359 different partial programs do not overlap. This is actually an
3360 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3363 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3364 addresses. These blocks slide to their run-time addresses as rigid
3365 units; their length does not change and neither does the order of bytes
3366 within them. Such a rigid unit is called a @emph{section}. Assigning
3367 run-time addresses to sections is called @dfn{relocation}. It includes
3368 the task of adjusting mentions of object-file addresses so they refer to
3369 the proper run-time addresses.
3371 For the H8/300, and for the Renesas / SuperH SH,
3372 @command{@value{AS}} pads sections if needed to
3373 ensure they end on a word (sixteen bit) boundary.
3376 @cindex standard assembler sections
3377 An object file written by @command{@value{AS}} has at least three sections, any
3378 of which may be empty. These are named @dfn{text}, @dfn{data} and
3383 When it generates COFF or ELF output,
3385 @command{@value{AS}} can also generate whatever other named sections you specify
3386 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3387 If you do not use any directives that place output in the @samp{.text}
3388 or @samp{.data} sections, these sections still exist, but are empty.
3393 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3395 @command{@value{AS}} can also generate whatever other named sections you
3396 specify using the @samp{.space} and @samp{.subspace} directives. See
3397 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3398 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3399 assembler directives.
3402 Additionally, @command{@value{AS}} uses different names for the standard
3403 text, data, and bss sections when generating SOM output. Program text
3404 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3405 BSS into @samp{$BSS$}.
3409 Within the object file, the text section starts at address @code{0}, the
3410 data section follows, and the bss section follows the data section.
3413 When generating either SOM or ELF output files on the HPPA, the text
3414 section starts at address @code{0}, the data section at address
3415 @code{0x4000000}, and the bss section follows the data section.
3418 To let @code{@value{LD}} know which data changes when the sections are
3419 relocated, and how to change that data, @command{@value{AS}} also writes to the
3420 object file details of the relocation needed. To perform relocation
3421 @code{@value{LD}} must know, each time an address in the object
3425 Where in the object file is the beginning of this reference to
3428 How long (in bytes) is this reference?
3430 Which section does the address refer to? What is the numeric value of
3432 (@var{address}) @minus{} (@var{start-address of section})?
3435 Is the reference to an address ``Program-Counter relative''?
3438 @cindex addresses, format of
3439 @cindex section-relative addressing
3440 In fact, every address @command{@value{AS}} ever uses is expressed as
3442 (@var{section}) + (@var{offset into section})
3445 Further, most expressions @command{@value{AS}} computes have this section-relative
3448 (For some object formats, such as SOM for the HPPA, some expressions are
3449 symbol-relative instead.)
3452 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3453 @var{N} into section @var{secname}.''
3455 Apart from text, data and bss sections you need to know about the
3456 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3457 addresses in the absolute section remain unchanged. For example, address
3458 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3459 @code{@value{LD}}. Although the linker never arranges two partial programs'
3460 data sections with overlapping addresses after linking, @emph{by definition}
3461 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3462 part of a program is always the same address when the program is running as
3463 address @code{@{absolute@ 239@}} in any other part of the program.
3465 The idea of sections is extended to the @dfn{undefined} section. Any
3466 address whose section is unknown at assembly time is by definition
3467 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3468 Since numbers are always defined, the only way to generate an undefined
3469 address is to mention an undefined symbol. A reference to a named
3470 common block would be such a symbol: its value is unknown at assembly
3471 time so it has section @emph{undefined}.
3473 By analogy the word @emph{section} is used to describe groups of sections in
3474 the linked program. @code{@value{LD}} puts all partial programs' text
3475 sections in contiguous addresses in the linked program. It is
3476 customary to refer to the @emph{text section} of a program, meaning all
3477 the addresses of all partial programs' text sections. Likewise for
3478 data and bss sections.
3480 Some sections are manipulated by @code{@value{LD}}; others are invented for
3481 use of @command{@value{AS}} and have no meaning except during assembly.
3484 @section Linker Sections
3485 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3490 @cindex named sections
3491 @cindex sections, named
3492 @item named sections
3495 @cindex text section
3496 @cindex data section
3500 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3501 separate but equal sections. Anything you can say of one section is
3504 When the program is running, however, it is
3505 customary for the text section to be unalterable. The
3506 text section is often shared among processes: it contains
3507 instructions, constants and the like. The data section of a running
3508 program is usually alterable: for example, C variables would be stored
3509 in the data section.
3514 This section contains zeroed bytes when your program begins running. It
3515 is used to hold uninitialized variables or common storage. The length of
3516 each partial program's bss section is important, but because it starts
3517 out containing zeroed bytes there is no need to store explicit zero
3518 bytes in the object file. The bss section was invented to eliminate
3519 those explicit zeros from object files.
3521 @cindex absolute section
3522 @item absolute section
3523 Address 0 of this section is always ``relocated'' to runtime address 0.
3524 This is useful if you want to refer to an address that @code{@value{LD}} must
3525 not change when relocating. In this sense we speak of absolute
3526 addresses being ``unrelocatable'': they do not change during relocation.
3528 @cindex undefined section
3529 @item undefined section
3530 This ``section'' is a catch-all for address references to objects not in
3531 the preceding sections.
3532 @c FIXME: ref to some other doc on obj-file formats could go here.
3535 @cindex relocation example
3536 An idealized example of three relocatable sections follows.
3538 The example uses the traditional section names @samp{.text} and @samp{.data}.
3540 Memory addresses are on the horizontal axis.
3544 @c END TEXI2ROFF-KILL
3547 partial program # 1: |ttttt|dddd|00|
3554 partial program # 2: |TTT|DDD|000|
3557 +--+---+-----+--+----+---+-----+~~
3558 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3559 +--+---+-----+--+----+---+-----+~~
3561 addresses: 0 @dots{}
3568 \line{\it Partial program \#1: \hfil}
3569 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3570 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3572 \line{\it Partial program \#2: \hfil}
3573 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3574 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3576 \line{\it linked program: \hfil}
3577 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3578 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3579 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3580 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3582 \line{\it addresses: \hfil}
3586 @c END TEXI2ROFF-KILL
3589 @section Assembler Internal Sections
3591 @cindex internal assembler sections
3592 @cindex sections in messages, internal
3593 These sections are meant only for the internal use of @command{@value{AS}}. They
3594 have no meaning at run-time. You do not really need to know about these
3595 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3596 warning messages, so it might be helpful to have an idea of their
3597 meanings to @command{@value{AS}}. These sections are used to permit the
3598 value of every expression in your assembly language program to be a
3599 section-relative address.
3602 @cindex assembler internal logic error
3603 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3604 An internal assembler logic error has been found. This means there is a
3605 bug in the assembler.
3607 @cindex expr (internal section)
3609 The assembler stores complex expression internally as combinations of
3610 symbols. When it needs to represent an expression as a symbol, it puts
3611 it in the expr section.
3613 @c FIXME item transfer[t] vector preload
3614 @c FIXME item transfer[t] vector postload
3615 @c FIXME item register
3619 @section Sub-Sections
3621 @cindex numbered subsections
3622 @cindex grouping data
3628 fall into two sections: text and data.
3630 You may have separate groups of
3632 data in named sections
3636 data in named sections
3642 that you want to end up near to each other in the object file, even though they
3643 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3644 use @dfn{subsections} for this purpose. Within each section, there can be
3645 numbered subsections with values from 0 to 8192. Objects assembled into the
3646 same subsection go into the object file together with other objects in the same
3647 subsection. For example, a compiler might want to store constants in the text
3648 section, but might not want to have them interspersed with the program being
3649 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3650 section of code being output, and a @samp{.text 1} before each group of
3651 constants being output.
3653 Subsections are optional. If you do not use subsections, everything
3654 goes in subsection number zero.
3657 Each subsection is zero-padded up to a multiple of four bytes.
3658 (Subsections may be padded a different amount on different flavors
3659 of @command{@value{AS}}.)
3663 On the H8/300 platform, each subsection is zero-padded to a word
3664 boundary (two bytes).
3665 The same is true on the Renesas SH.
3669 Subsections appear in your object file in numeric order, lowest numbered
3670 to highest. (All this to be compatible with other people's assemblers.)
3671 The object file contains no representation of subsections; @code{@value{LD}} and
3672 other programs that manipulate object files see no trace of them.
3673 They just see all your text subsections as a text section, and all your
3674 data subsections as a data section.
3676 To specify which subsection you want subsequent statements assembled
3677 into, use a numeric argument to specify it, in a @samp{.text
3678 @var{expression}} or a @samp{.data @var{expression}} statement.
3681 When generating COFF output, you
3686 can also use an extra subsection
3687 argument with arbitrary named sections: @samp{.section @var{name},
3692 When generating ELF output, you
3697 can also use the @code{.subsection} directive (@pxref{SubSection})
3698 to specify a subsection: @samp{.subsection @var{expression}}.
3700 @var{Expression} should be an absolute expression
3701 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3702 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3703 begins in @code{text 0}. For instance:
3705 .text 0 # The default subsection is text 0 anyway.
3706 .ascii "This lives in the first text subsection. *"
3708 .ascii "But this lives in the second text subsection."
3710 .ascii "This lives in the data section,"
3711 .ascii "in the first data subsection."
3713 .ascii "This lives in the first text section,"
3714 .ascii "immediately following the asterisk (*)."
3717 Each section has a @dfn{location counter} incremented by one for every byte
3718 assembled into that section. Because subsections are merely a convenience
3719 restricted to @command{@value{AS}} there is no concept of a subsection location
3720 counter. There is no way to directly manipulate a location counter---but the
3721 @code{.align} directive changes it, and any label definition captures its
3722 current value. The location counter of the section where statements are being
3723 assembled is said to be the @dfn{active} location counter.
3726 @section bss Section
3729 @cindex common variable storage
3730 The bss section is used for local common variable storage.
3731 You may allocate address space in the bss section, but you may
3732 not dictate data to load into it before your program executes. When
3733 your program starts running, all the contents of the bss
3734 section are zeroed bytes.
3736 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3737 @ref{Lcomm,,@code{.lcomm}}.
3739 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3740 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3743 When assembling for a target which supports multiple sections, such as ELF or
3744 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3745 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3746 section. Typically the section will only contain symbol definitions and
3747 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3754 Symbols are a central concept: the programmer uses symbols to name
3755 things, the linker uses symbols to link, and the debugger uses symbols
3759 @cindex debuggers, and symbol order
3760 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3761 the same order they were declared. This may break some debuggers.
3766 * Setting Symbols:: Giving Symbols Other Values
3767 * Symbol Names:: Symbol Names
3768 * Dot:: The Special Dot Symbol
3769 * Symbol Attributes:: Symbol Attributes
3776 A @dfn{label} is written as a symbol immediately followed by a colon
3777 @samp{:}. The symbol then represents the current value of the
3778 active location counter, and is, for example, a suitable instruction
3779 operand. You are warned if you use the same symbol to represent two
3780 different locations: the first definition overrides any other
3784 On the HPPA, the usual form for a label need not be immediately followed by a
3785 colon, but instead must start in column zero. Only one label may be defined on
3786 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3787 provides a special directive @code{.label} for defining labels more flexibly.
3790 @node Setting Symbols
3791 @section Giving Symbols Other Values
3793 @cindex assigning values to symbols
3794 @cindex symbol values, assigning
3795 A symbol can be given an arbitrary value by writing a symbol, followed
3796 by an equals sign @samp{=}, followed by an expression
3797 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3798 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3799 equals sign @samp{=}@samp{=} here represents an equivalent of the
3800 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3803 Blackfin does not support symbol assignment with @samp{=}.
3807 @section Symbol Names
3809 @cindex symbol names
3810 @cindex names, symbol
3811 @ifclear SPECIAL-SYMS
3812 Symbol names begin with a letter or with one of @samp{._}. On most
3813 machines, you can also use @code{$} in symbol names; exceptions are
3814 noted in @ref{Machine Dependencies}. That character may be followed by any
3815 string of digits, letters, dollar signs (unless otherwise noted for a
3816 particular target machine), and underscores.
3820 Symbol names begin with a letter or with one of @samp{._}. On the
3821 Renesas SH you can also use @code{$} in symbol names. That
3822 character may be followed by any string of digits, letters, dollar signs (save
3823 on the H8/300), and underscores.
3827 Case of letters is significant: @code{foo} is a different symbol name
3830 Symbol names do not start with a digit. An exception to this rule is made for
3831 Local Labels. See below.
3833 Multibyte characters are supported. To generate a symbol name containing
3834 multibyte characters enclose it within double quotes and use escape codes. cf
3835 @xref{Strings}. Generating a multibyte symbol name from a label is not
3836 currently supported.
3838 Each symbol has exactly one name. Each name in an assembly language program
3839 refers to exactly one symbol. You may use that symbol name any number of times
3842 @subheading Local Symbol Names
3844 @cindex local symbol names
3845 @cindex symbol names, local
3846 A local symbol is any symbol beginning with certain local label prefixes.
3847 By default, the local label prefix is @samp{.L} for ELF systems or
3848 @samp{L} for traditional a.out systems, but each target may have its own
3849 set of local label prefixes.
3851 On the HPPA local symbols begin with @samp{L$}.
3854 Local symbols are defined and used within the assembler, but they are
3855 normally not saved in object files. Thus, they are not visible when debugging.
3856 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3857 to retain the local symbols in the object files.
3859 @subheading Local Labels
3861 @cindex local labels
3862 @cindex temporary symbol names
3863 @cindex symbol names, temporary
3864 Local labels are different from local symbols. Local labels help compilers and
3865 programmers use names temporarily. They create symbols which are guaranteed to
3866 be unique over the entire scope of the input source code and which can be
3867 referred to by a simple notation. To define a local label, write a label of
3868 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3869 To refer to the most recent previous definition of that label write
3870 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3871 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3872 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3874 There is no restriction on how you can use these labels, and you can reuse them
3875 too. So that it is possible to repeatedly define the same local label (using
3876 the same number @samp{@b{N}}), although you can only refer to the most recently
3877 defined local label of that number (for a backwards reference) or the next
3878 definition of a specific local label for a forward reference. It is also worth
3879 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3880 implemented in a slightly more efficient manner than the others.
3891 Which is the equivalent of:
3894 label_1: branch label_3
3895 label_2: branch label_1
3896 label_3: branch label_4
3897 label_4: branch label_3
3900 Local label names are only a notational device. They are immediately
3901 transformed into more conventional symbol names before the assembler uses them.
3902 The symbol names are stored in the symbol table, appear in error messages, and
3903 are optionally emitted to the object file. The names are constructed using
3907 @item @emph{local label prefix}
3908 All local symbols begin with the system-specific local label prefix.
3909 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3910 that start with the local label prefix. These labels are
3911 used for symbols you are never intended to see. If you use the
3912 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3913 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3914 you may use them in debugging.
3917 This is the number that was used in the local label definition. So if the
3918 label is written @samp{55:} then the number is @samp{55}.
3921 This unusual character is included so you do not accidentally invent a symbol
3922 of the same name. The character has ASCII value of @samp{\002} (control-B).
3924 @item @emph{ordinal number}
3925 This is a serial number to keep the labels distinct. The first definition of
3926 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3927 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3928 the number @samp{1} and its 15th definition gets @samp{15} as well.
3931 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3932 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3934 @subheading Dollar Local Labels
3935 @cindex dollar local symbols
3937 On some targets @code{@value{AS}} also supports an even more local form of
3938 local labels called dollar labels. These labels go out of scope (i.e., they
3939 become undefined) as soon as a non-local label is defined. Thus they remain
3940 valid for only a small region of the input source code. Normal local labels,
3941 by contrast, remain in scope for the entire file, or until they are redefined
3942 by another occurrence of the same local label.
3944 Dollar labels are defined in exactly the same way as ordinary local labels,
3945 except that they have a dollar sign suffix to their numeric value, e.g.,
3948 They can also be distinguished from ordinary local labels by their transformed
3949 names which use ASCII character @samp{\001} (control-A) as the magic character
3950 to distinguish them from ordinary labels. For example, the fifth definition of
3951 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3954 @section The Special Dot Symbol
3956 @cindex dot (symbol)
3957 @cindex @code{.} (symbol)
3958 @cindex current address
3959 @cindex location counter
3960 The special symbol @samp{.} refers to the current address that
3961 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3962 .long .} defines @code{melvin} to contain its own address.
3963 Assigning a value to @code{.} is treated the same as a @code{.org}
3965 @ifclear no-space-dir
3966 Thus, the expression @samp{.=.+4} is the same as saying
3970 @node Symbol Attributes
3971 @section Symbol Attributes
3973 @cindex symbol attributes
3974 @cindex attributes, symbol
3975 Every symbol has, as well as its name, the attributes ``Value'' and
3976 ``Type''. Depending on output format, symbols can also have auxiliary
3979 The detailed definitions are in @file{a.out.h}.
3982 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3983 all these attributes, and probably won't warn you. This makes the
3984 symbol an externally defined symbol, which is generally what you
3988 * Symbol Value:: Value
3989 * Symbol Type:: Type
3991 * a.out Symbols:: Symbol Attributes: @code{a.out}
3994 * COFF Symbols:: Symbol Attributes for COFF
3997 * SOM Symbols:: Symbol Attributes for SOM
4004 @cindex value of a symbol
4005 @cindex symbol value
4006 The value of a symbol is (usually) 32 bits. For a symbol which labels a
4007 location in the text, data, bss or absolute sections the value is the
4008 number of addresses from the start of that section to the label.
4009 Naturally for text, data and bss sections the value of a symbol changes
4010 as @code{@value{LD}} changes section base addresses during linking. Absolute
4011 symbols' values do not change during linking: that is why they are
4014 The value of an undefined symbol is treated in a special way. If it is
4015 0 then the symbol is not defined in this assembler source file, and
4016 @code{@value{LD}} tries to determine its value from other files linked into the
4017 same program. You make this kind of symbol simply by mentioning a symbol
4018 name without defining it. A non-zero value represents a @code{.comm}
4019 common declaration. The value is how much common storage to reserve, in
4020 bytes (addresses). The symbol refers to the first address of the
4026 @cindex type of a symbol
4028 The type attribute of a symbol contains relocation (section)
4029 information, any flag settings indicating that a symbol is external, and
4030 (optionally), other information for linkers and debuggers. The exact
4031 format depends on the object-code output format in use.
4035 @subsection Symbol Attributes: @code{a.out}
4037 @cindex @code{a.out} symbol attributes
4038 @cindex symbol attributes, @code{a.out}
4041 * Symbol Desc:: Descriptor
4042 * Symbol Other:: Other
4046 @subsubsection Descriptor
4048 @cindex descriptor, of @code{a.out} symbol
4049 This is an arbitrary 16-bit value. You may establish a symbol's
4050 descriptor value by using a @code{.desc} statement
4051 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
4052 @command{@value{AS}}.
4055 @subsubsection Other
4057 @cindex other attribute, of @code{a.out} symbol
4058 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
4063 @subsection Symbol Attributes for COFF
4065 @cindex COFF symbol attributes
4066 @cindex symbol attributes, COFF
4068 The COFF format supports a multitude of auxiliary symbol attributes;
4069 like the primary symbol attributes, they are set between @code{.def} and
4070 @code{.endef} directives.
4072 @subsubsection Primary Attributes
4074 @cindex primary attributes, COFF symbols
4075 The symbol name is set with @code{.def}; the value and type,
4076 respectively, with @code{.val} and @code{.type}.
4078 @subsubsection Auxiliary Attributes
4080 @cindex auxiliary attributes, COFF symbols
4081 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
4082 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
4083 table information for COFF.
4088 @subsection Symbol Attributes for SOM
4090 @cindex SOM symbol attributes
4091 @cindex symbol attributes, SOM
4093 The SOM format for the HPPA supports a multitude of symbol attributes set with
4094 the @code{.EXPORT} and @code{.IMPORT} directives.
4096 The attributes are described in @cite{HP9000 Series 800 Assembly
4097 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
4098 @code{EXPORT} assembler directive documentation.
4102 @chapter Expressions
4106 @cindex numeric values
4107 An @dfn{expression} specifies an address or numeric value.
4108 Whitespace may precede and/or follow an expression.
4110 The result of an expression must be an absolute number, or else an offset into
4111 a particular section. If an expression is not absolute, and there is not
4112 enough information when @command{@value{AS}} sees the expression to know its
4113 section, a second pass over the source program might be necessary to interpret
4114 the expression---but the second pass is currently not implemented.
4115 @command{@value{AS}} aborts with an error message in this situation.
4118 * Empty Exprs:: Empty Expressions
4119 * Integer Exprs:: Integer Expressions
4123 @section Empty Expressions
4125 @cindex empty expressions
4126 @cindex expressions, empty
4127 An empty expression has no value: it is just whitespace or null.
4128 Wherever an absolute expression is required, you may omit the
4129 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4130 is compatible with other assemblers.
4133 @section Integer Expressions
4135 @cindex integer expressions
4136 @cindex expressions, integer
4137 An @dfn{integer expression} is one or more @emph{arguments} delimited
4138 by @emph{operators}.
4141 * Arguments:: Arguments
4142 * Operators:: Operators
4143 * Prefix Ops:: Prefix Operators
4144 * Infix Ops:: Infix Operators
4148 @subsection Arguments
4150 @cindex expression arguments
4151 @cindex arguments in expressions
4152 @cindex operands in expressions
4153 @cindex arithmetic operands
4154 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4155 contexts arguments are sometimes called ``arithmetic operands''. In
4156 this manual, to avoid confusing them with the ``instruction operands'' of
4157 the machine language, we use the term ``argument'' to refer to parts of
4158 expressions only, reserving the word ``operand'' to refer only to machine
4159 instruction operands.
4161 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4162 @var{section} is one of text, data, bss, absolute,
4163 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4166 Numbers are usually integers.
4168 A number can be a flonum or bignum. In this case, you are warned
4169 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4170 these 32 bits are an integer. You may write integer-manipulating
4171 instructions that act on exotic constants, compatible with other
4174 @cindex subexpressions
4175 Subexpressions are a left parenthesis @samp{(} followed by an integer
4176 expression, followed by a right parenthesis @samp{)}; or a prefix
4177 operator followed by an argument.
4180 @subsection Operators
4182 @cindex operators, in expressions
4183 @cindex arithmetic functions
4184 @cindex functions, in expressions
4185 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4186 operators are followed by an argument. Infix operators appear
4187 between their arguments. Operators may be preceded and/or followed by
4191 @subsection Prefix Operator
4193 @cindex prefix operators
4194 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4195 one argument, which must be absolute.
4197 @c the tex/end tex stuff surrounding this small table is meant to make
4198 @c it align, on the printed page, with the similar table in the next
4199 @c section (which is inside an enumerate).
4201 \global\advance\leftskip by \itemindent
4206 @dfn{Negation}. Two's complement negation.
4208 @dfn{Complementation}. Bitwise not.
4212 \global\advance\leftskip by -\itemindent
4216 @subsection Infix Operators
4218 @cindex infix operators
4219 @cindex operators, permitted arguments
4220 @dfn{Infix operators} take two arguments, one on either side. Operators
4221 have precedence, but operations with equal precedence are performed left
4222 to right. Apart from @code{+} or @option{-}, both arguments must be
4223 absolute, and the result is absolute.
4226 @cindex operator precedence
4227 @cindex precedence of operators
4234 @dfn{Multiplication}.
4237 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4243 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4246 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4250 Intermediate precedence
4255 @dfn{Bitwise Inclusive Or}.
4261 @dfn{Bitwise Exclusive Or}.
4264 @dfn{Bitwise Or Not}.
4271 @cindex addition, permitted arguments
4272 @cindex plus, permitted arguments
4273 @cindex arguments for addition
4275 @dfn{Addition}. If either argument is absolute, the result has the section of
4276 the other argument. You may not add together arguments from different
4279 @cindex subtraction, permitted arguments
4280 @cindex minus, permitted arguments
4281 @cindex arguments for subtraction
4283 @dfn{Subtraction}. If the right argument is absolute, the
4284 result has the section of the left argument.
4285 If both arguments are in the same section, the result is absolute.
4286 You may not subtract arguments from different sections.
4287 @c FIXME is there still something useful to say about undefined - undefined ?
4289 @cindex comparison expressions
4290 @cindex expressions, comparison
4295 @dfn{Is Not Equal To}
4299 @dfn{Is Greater Than}
4301 @dfn{Is Greater Than Or Equal To}
4303 @dfn{Is Less Than Or Equal To}
4305 The comparison operators can be used as infix operators. A true results has a
4306 value of -1 whereas a false result has a value of 0. Note, these operators
4307 perform signed comparisons.
4310 @item Lowest Precedence
4319 These two logical operations can be used to combine the results of sub
4320 expressions. Note, unlike the comparison operators a true result returns a
4321 value of 1 but a false results does still return 0. Also note that the logical
4322 or operator has a slightly lower precedence than logical and.
4327 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4328 address; you can only have a defined section in one of the two arguments.
4331 @chapter Assembler Directives
4333 @cindex directives, machine independent
4334 @cindex pseudo-ops, machine independent
4335 @cindex machine independent directives
4336 All assembler directives have names that begin with a period (@samp{.}).
4337 The names are case insensitive for most targets, and usually written
4340 This chapter discusses directives that are available regardless of the
4341 target machine configuration for the @sc{gnu} assembler.
4343 Some machine configurations provide additional directives.
4344 @xref{Machine Dependencies}.
4347 @ifset machine-directives
4348 @xref{Machine Dependencies}, for additional directives.
4353 * Abort:: @code{.abort}
4355 * ABORT (COFF):: @code{.ABORT}
4358 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4359 * Altmacro:: @code{.altmacro}
4360 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4361 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4362 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4363 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4364 * Byte:: @code{.byte @var{expressions}}
4365 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4366 * Comm:: @code{.comm @var{symbol} , @var{length} }
4367 * Data:: @code{.data @var{subsection}}
4368 * Dc:: @code{.dc[@var{size}] @var{expressions}}
4369 * Dcb:: @code{.dcb[@var{size}] @var{number} [,@var{fill}]}
4370 * Ds:: @code{.ds[@var{size}] @var{number} [,@var{fill}]}
4372 * Def:: @code{.def @var{name}}
4375 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4381 * Double:: @code{.double @var{flonums}}
4382 * Eject:: @code{.eject}
4383 * Else:: @code{.else}
4384 * Elseif:: @code{.elseif}
4387 * Endef:: @code{.endef}
4390 * Endfunc:: @code{.endfunc}
4391 * Endif:: @code{.endif}
4392 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4393 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4394 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4396 * Error:: @code{.error @var{string}}
4397 * Exitm:: @code{.exitm}
4398 * Extern:: @code{.extern}
4399 * Fail:: @code{.fail}
4400 * File:: @code{.file}
4401 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4402 * Float:: @code{.float @var{flonums}}
4403 * Func:: @code{.func}
4404 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4406 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4407 * Hidden:: @code{.hidden @var{names}}
4410 * hword:: @code{.hword @var{expressions}}
4411 * Ident:: @code{.ident}
4412 * If:: @code{.if @var{absolute expression}}
4413 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4414 * Include:: @code{.include "@var{file}"}
4415 * Int:: @code{.int @var{expressions}}
4417 * Internal:: @code{.internal @var{names}}
4420 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4421 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4422 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4423 * Lflags:: @code{.lflags}
4424 @ifclear no-line-dir
4425 * Line:: @code{.line @var{line-number}}
4428 * Linkonce:: @code{.linkonce [@var{type}]}
4429 * List:: @code{.list}
4430 * Ln:: @code{.ln @var{line-number}}
4431 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4432 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4434 * Local:: @code{.local @var{names}}
4437 * Long:: @code{.long @var{expressions}}
4439 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4442 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4443 * MRI:: @code{.mri @var{val}}
4444 * Noaltmacro:: @code{.noaltmacro}
4445 * Nolist:: @code{.nolist}
4446 * Nops:: @code{.nops @var{size}[, @var{control}]}
4447 * Octa:: @code{.octa @var{bignums}}
4448 * Offset:: @code{.offset @var{loc}}
4449 * Org:: @code{.org @var{new-lc}, @var{fill}}
4450 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4452 * PopSection:: @code{.popsection}
4453 * Previous:: @code{.previous}
4456 * Print:: @code{.print @var{string}}
4458 * Protected:: @code{.protected @var{names}}
4461 * Psize:: @code{.psize @var{lines}, @var{columns}}
4462 * Purgem:: @code{.purgem @var{name}}
4464 * PushSection:: @code{.pushsection @var{name}}
4467 * Quad:: @code{.quad @var{bignums}}
4468 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4469 * Rept:: @code{.rept @var{count}}
4470 * Sbttl:: @code{.sbttl "@var{subheading}"}
4472 * Scl:: @code{.scl @var{class}}
4475 * Section:: @code{.section @var{name}[, @var{flags}]}
4478 * Set:: @code{.set @var{symbol}, @var{expression}}
4479 * Short:: @code{.short @var{expressions}}
4480 * Single:: @code{.single @var{flonums}}
4482 * Size:: @code{.size [@var{name} , @var{expression}]}
4484 @ifclear no-space-dir
4485 * Skip:: @code{.skip @var{size} [,@var{fill}]}
4488 * Sleb128:: @code{.sleb128 @var{expressions}}
4489 @ifclear no-space-dir
4490 * Space:: @code{.space @var{size} [,@var{fill}]}
4493 * Stab:: @code{.stabd, .stabn, .stabs}
4496 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4497 * Struct:: @code{.struct @var{expression}}
4499 * SubSection:: @code{.subsection}
4500 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4504 * Tag:: @code{.tag @var{structname}}
4507 * Text:: @code{.text @var{subsection}}
4508 * Title:: @code{.title "@var{heading}"}
4510 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4513 * Uleb128:: @code{.uleb128 @var{expressions}}
4515 * Val:: @code{.val @var{addr}}
4519 * Version:: @code{.version "@var{string}"}
4520 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4521 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4524 * Warning:: @code{.warning @var{string}}
4525 * Weak:: @code{.weak @var{names}}
4526 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4527 * Word:: @code{.word @var{expressions}}
4528 @ifclear no-space-dir
4529 * Zero:: @code{.zero @var{size}}
4532 * 2byte:: @code{.2byte @var{expressions}}
4533 * 4byte:: @code{.4byte @var{expressions}}
4534 * 8byte:: @code{.8byte @var{bignums}}
4536 * Deprecated:: Deprecated Directives
4540 @section @code{.abort}
4542 @cindex @code{abort} directive
4543 @cindex stopping the assembly
4544 This directive stops the assembly immediately. It is for
4545 compatibility with other assemblers. The original idea was that the
4546 assembly language source would be piped into the assembler. If the sender
4547 of the source quit, it could use this directive tells @command{@value{AS}} to
4548 quit also. One day @code{.abort} will not be supported.
4552 @section @code{.ABORT} (COFF)
4554 @cindex @code{ABORT} directive
4555 When producing COFF output, @command{@value{AS}} accepts this directive as a
4556 synonym for @samp{.abort}.
4561 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4563 @cindex padding the location counter
4564 @cindex @code{align} directive
4565 Pad the location counter (in the current subsection) to a particular storage
4566 boundary. The first expression (which must be absolute) is the alignment
4567 required, as described below.
4569 The second expression (also absolute) gives the fill value to be stored in the
4570 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4571 padding bytes are normally zero. However, on most systems, if the section is
4572 marked as containing code and the fill value is omitted, the space is filled
4573 with no-op instructions.
4575 The third expression is also absolute, and is also optional. If it is present,
4576 it is the maximum number of bytes that should be skipped by this alignment
4577 directive. If doing the alignment would require skipping more bytes than the
4578 specified maximum, then the alignment is not done at all. You can omit the
4579 fill value (the second argument) entirely by simply using two commas after the
4580 required alignment; this can be useful if you want the alignment to be filled
4581 with no-op instructions when appropriate.
4583 The way the required alignment is specified varies from system to system.
4584 For the arc, hppa, i386 using ELF, iq2000, m68k, or1k,
4585 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4586 alignment request in bytes. For example @samp{.align 8} advances
4587 the location counter until it is a multiple of 8. If the location counter
4588 is already a multiple of 8, no change is needed. For the tic54x, the
4589 first expression is the alignment request in words.
4591 For other systems, including ppc, i386 using a.out format, arm and
4592 strongarm, it is the
4593 number of low-order zero bits the location counter must have after
4594 advancement. For example @samp{.align 3} advances the location
4595 counter until it is a multiple of 8. If the location counter is already a
4596 multiple of 8, no change is needed.
4598 This inconsistency is due to the different behaviors of the various
4599 native assemblers for these systems which GAS must emulate.
4600 GAS also provides @code{.balign} and @code{.p2align} directives,
4601 described later, which have a consistent behavior across all
4602 architectures (but are specific to GAS).
4605 @section @code{.altmacro}
4606 Enable alternate macro mode, enabling:
4609 @item LOCAL @var{name} [ , @dots{} ]
4610 One additional directive, @code{LOCAL}, is available. It is used to
4611 generate a string replacement for each of the @var{name} arguments, and
4612 replace any instances of @var{name} in each macro expansion. The
4613 replacement string is unique in the assembly, and different for each
4614 separate macro expansion. @code{LOCAL} allows you to write macros that
4615 define symbols, without fear of conflict between separate macro expansions.
4617 @item String delimiters
4618 You can write strings delimited in these other ways besides
4619 @code{"@var{string}"}:
4622 @item '@var{string}'
4623 You can delimit strings with single-quote characters.
4625 @item <@var{string}>
4626 You can delimit strings with matching angle brackets.
4629 @item single-character string escape
4630 To include any single character literally in a string (even if the
4631 character would otherwise have some special meaning), you can prefix the
4632 character with @samp{!} (an exclamation mark). For example, you can
4633 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4635 @item Expression results as strings
4636 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4637 and use the result as a string.
4641 @section @code{.ascii "@var{string}"}@dots{}
4643 @cindex @code{ascii} directive
4644 @cindex string literals
4645 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4646 separated by commas. It assembles each string (with no automatic
4647 trailing zero byte) into consecutive addresses.
4650 @section @code{.asciz "@var{string}"}@dots{}
4652 @cindex @code{asciz} directive
4653 @cindex zero-terminated strings
4654 @cindex null-terminated strings
4655 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4656 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4659 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4661 @cindex padding the location counter given number of bytes
4662 @cindex @code{balign} directive
4663 Pad the location counter (in the current subsection) to a particular
4664 storage boundary. The first expression (which must be absolute) is the
4665 alignment request in bytes. For example @samp{.balign 8} advances
4666 the location counter until it is a multiple of 8. If the location counter
4667 is already a multiple of 8, no change is needed.
4669 The second expression (also absolute) gives the fill value to be stored in the
4670 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4671 padding bytes are normally zero. However, on most systems, if the section is
4672 marked as containing code and the fill value is omitted, the space is filled
4673 with no-op instructions.
4675 The third expression is also absolute, and is also optional. If it is present,
4676 it is the maximum number of bytes that should be skipped by this alignment
4677 directive. If doing the alignment would require skipping more bytes than the
4678 specified maximum, then the alignment is not done at all. You can omit the
4679 fill value (the second argument) entirely by simply using two commas after the
4680 required alignment; this can be useful if you want the alignment to be filled
4681 with no-op instructions when appropriate.
4683 @cindex @code{balignw} directive
4684 @cindex @code{balignl} directive
4685 The @code{.balignw} and @code{.balignl} directives are variants of the
4686 @code{.balign} directive. The @code{.balignw} directive treats the fill
4687 pattern as a two byte word value. The @code{.balignl} directives treats the
4688 fill pattern as a four byte longword value. For example, @code{.balignw
4689 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4690 filled in with the value 0x368d (the exact placement of the bytes depends upon
4691 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4694 @node Bundle directives
4695 @section Bundle directives
4696 @subsection @code{.bundle_align_mode @var{abs-expr}}
4697 @cindex @code{bundle_align_mode} directive
4699 @cindex instruction bundle
4700 @cindex aligned instruction bundle
4701 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4702 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4703 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4704 disabled (which is the default state). If the argument it not zero, it
4705 gives the size of an instruction bundle as a power of two (as for the
4706 @code{.p2align} directive, @pxref{P2align}).
4708 For some targets, it's an ABI requirement that no instruction may span a
4709 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4710 instructions that starts on an aligned boundary. For example, if
4711 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4712 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4713 effect, no single instruction may span a boundary between bundles. If an
4714 instruction would start too close to the end of a bundle for the length of
4715 that particular instruction to fit within the bundle, then the space at the
4716 end of that bundle is filled with no-op instructions so the instruction
4717 starts in the next bundle. As a corollary, it's an error if any single
4718 instruction's encoding is longer than the bundle size.
4720 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4721 @cindex @code{bundle_lock} directive
4722 @cindex @code{bundle_unlock} directive
4723 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4724 allow explicit control over instruction bundle padding. These directives
4725 are only valid when @code{.bundle_align_mode} has been used to enable
4726 aligned instruction bundle mode. It's an error if they appear when
4727 @code{.bundle_align_mode} has not been used at all, or when the last
4728 directive was @w{@code{.bundle_align_mode 0}}.
4730 @cindex bundle-locked
4731 For some targets, it's an ABI requirement that certain instructions may
4732 appear only as part of specified permissible sequences of multiple
4733 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4734 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4735 instruction sequence. For purposes of aligned instruction bundle mode, a
4736 sequence starting with @code{.bundle_lock} and ending with
4737 @code{.bundle_unlock} is treated as a single instruction. That is, the
4738 entire sequence must fit into a single bundle and may not span a bundle
4739 boundary. If necessary, no-op instructions will be inserted before the
4740 first instruction of the sequence so that the whole sequence starts on an
4741 aligned bundle boundary. It's an error if the sequence is longer than the
4744 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4745 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4746 nested. That is, a second @code{.bundle_lock} directive before the next
4747 @code{.bundle_unlock} directive has no effect except that it must be
4748 matched by another closing @code{.bundle_unlock} so that there is the
4749 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4752 @section @code{.byte @var{expressions}}
4754 @cindex @code{byte} directive
4755 @cindex integers, one byte
4756 @code{.byte} expects zero or more expressions, separated by commas.
4757 Each expression is assembled into the next byte.
4759 @node CFI directives
4760 @section CFI directives
4761 @subsection @code{.cfi_sections @var{section_list}}
4762 @cindex @code{cfi_sections} directive
4763 @code{.cfi_sections} may be used to specify whether CFI directives
4764 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4765 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4766 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4767 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4768 directive is not used is @code{.cfi_sections .eh_frame}.
4770 On targets that support compact unwinding tables these can be generated
4771 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4773 Some targets may support an additional name, such as @code{.c6xabi.exidx}
4774 which is used by the @value{TIC6X} target.
4776 The @code{.cfi_sections} directive can be repeated, with the same or different
4777 arguments, provided that CFI generation has not yet started. Once CFI
4778 generation has started however the section list is fixed and any attempts to
4779 redefine it will result in an error.
4781 @subsection @code{.cfi_startproc [simple]}
4782 @cindex @code{cfi_startproc} directive
4783 @code{.cfi_startproc} is used at the beginning of each function that
4784 should have an entry in @code{.eh_frame}. It initializes some internal
4785 data structures. Don't forget to close the function by
4786 @code{.cfi_endproc}.
4788 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4789 it also emits some architecture dependent initial CFI instructions.
4791 @subsection @code{.cfi_endproc}
4792 @cindex @code{cfi_endproc} directive
4793 @code{.cfi_endproc} is used at the end of a function where it closes its
4794 unwind entry previously opened by
4795 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4797 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4798 @cindex @code{cfi_personality} directive
4799 @code{.cfi_personality} defines personality routine and its encoding.
4800 @var{encoding} must be a constant determining how the personality
4801 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4802 argument is not present, otherwise second argument should be
4803 a constant or a symbol name. When using indirect encodings,
4804 the symbol provided should be the location where personality
4805 can be loaded from, not the personality routine itself.
4806 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4807 no personality routine.
4809 @subsection @code{.cfi_personality_id @var{id}}
4810 @cindex @code{cfi_personality_id} directive
4811 @code{cfi_personality_id} defines a personality routine by its index as
4812 defined in a compact unwinding format.
4813 Only valid when generating compact EH frames (i.e.
4814 with @code{.cfi_sections eh_frame_entry}.
4816 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4817 @cindex @code{cfi_fde_data} directive
4818 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4819 used for the current function. These are emitted inline in the
4820 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4821 in the @code{.gnu.extab} section otherwise.
4822 Only valid when generating compact EH frames (i.e.
4823 with @code{.cfi_sections eh_frame_entry}.
4825 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4826 @code{.cfi_lsda} defines LSDA and its encoding.
4827 @var{encoding} must be a constant determining how the LSDA
4828 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4829 argument is not present, otherwise the second argument should be a constant
4830 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4831 meaning that no LSDA is present.
4833 @subsection @code{.cfi_inline_lsda} [@var{align}]
4834 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4835 switches to the corresponding @code{.gnu.extab} section.
4836 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4837 Only valid when generating compact EH frames (i.e.
4838 with @code{.cfi_sections eh_frame_entry}.
4840 The table header and unwinding opcodes will be generated at this point,
4841 so that they are immediately followed by the LSDA data. The symbol
4842 referenced by the @code{.cfi_lsda} directive should still be defined
4843 in case a fallback FDE based encoding is used. The LSDA data is terminated
4844 by a section directive.
4846 The optional @var{align} argument specifies the alignment required.
4847 The alignment is specified as a power of two, as with the
4848 @code{.p2align} directive.
4850 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4851 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4852 address from @var{register} and add @var{offset} to it}.
4854 @subsection @code{.cfi_def_cfa_register @var{register}}
4855 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4856 now on @var{register} will be used instead of the old one. Offset
4859 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4860 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4861 remains the same, but @var{offset} is new. Note that it is the
4862 absolute offset that will be added to a defined register to compute
4865 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4866 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4867 value that is added/subtracted from the previous offset.
4869 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4870 Previous value of @var{register} is saved at offset @var{offset} from
4873 @subsection @code{.cfi_val_offset @var{register}, @var{offset}}
4874 Previous value of @var{register} is CFA + @var{offset}.
4876 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4877 Previous value of @var{register} is saved at offset @var{offset} from
4878 the current CFA register. This is transformed to @code{.cfi_offset}
4879 using the known displacement of the CFA register from the CFA.
4880 This is often easier to use, because the number will match the
4881 code it's annotating.
4883 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4884 Previous value of @var{register1} is saved in register @var{register2}.
4886 @subsection @code{.cfi_restore @var{register}}
4887 @code{.cfi_restore} says that the rule for @var{register} is now the
4888 same as it was at the beginning of the function, after all initial
4889 instruction added by @code{.cfi_startproc} were executed.
4891 @subsection @code{.cfi_undefined @var{register}}
4892 From now on the previous value of @var{register} can't be restored anymore.
4894 @subsection @code{.cfi_same_value @var{register}}
4895 Current value of @var{register} is the same like in the previous frame,
4896 i.e. no restoration needed.
4898 @subsection @code{.cfi_remember_state} and @code{.cfi_restore_state}
4899 @code{.cfi_remember_state} pushes the set of rules for every register onto an
4900 implicit stack, while @code{.cfi_restore_state} pops them off the stack and
4901 places them in the current row. This is useful for situations where you have
4902 multiple @code{.cfi_*} directives that need to be undone due to the control
4903 flow of the program. For example, we could have something like this (assuming
4904 the CFA is the value of @code{rbp}):
4914 .cfi_def_cfa %rsp, 8
4917 /* Do something else */
4920 Here, we want the @code{.cfi} directives to affect only the rows corresponding
4921 to the instructions before @code{label}. This means we'd have to add multiple
4922 @code{.cfi} directives after @code{label} to recreate the original save
4923 locations of the registers, as well as setting the CFA back to the value of
4924 @code{rbp}. This would be clumsy, and result in a larger binary size. Instead,
4936 .cfi_def_cfa %rsp, 8
4940 /* Do something else */
4943 That way, the rules for the instructions after @code{label} will be the same
4944 as before the first @code{.cfi_restore} without having to use multiple
4945 @code{.cfi} directives.
4947 @subsection @code{.cfi_return_column @var{register}}
4948 Change return column @var{register}, i.e. the return address is either
4949 directly in @var{register} or can be accessed by rules for @var{register}.
4951 @subsection @code{.cfi_signal_frame}
4952 Mark current function as signal trampoline.
4954 @subsection @code{.cfi_window_save}
4955 SPARC register window has been saved.
4957 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
4958 Allows the user to add arbitrary bytes to the unwind info. One
4959 might use this to add OS-specific CFI opcodes, or generic CFI
4960 opcodes that GAS does not yet support.
4962 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4963 The current value of @var{register} is @var{label}. The value of @var{label}
4964 will be encoded in the output file according to @var{encoding}; see the
4965 description of @code{.cfi_personality} for details on this encoding.
4967 The usefulness of equating a register to a fixed label is probably
4968 limited to the return address register. Here, it can be useful to
4969 mark a code segment that has only one return address which is reached
4970 by a direct branch and no copy of the return address exists in memory
4971 or another register.
4974 @section @code{.comm @var{symbol} , @var{length} }
4976 @cindex @code{comm} directive
4977 @cindex symbol, common
4978 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4979 common symbol in one object file may be merged with a defined or common symbol
4980 of the same name in another object file. If @code{@value{LD}} does not see a
4981 definition for the symbol--just one or more common symbols--then it will
4982 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4983 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4984 the same name, and they do not all have the same size, it will allocate space
4985 using the largest size.
4988 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4989 an optional third argument. This is the desired alignment of the symbol,
4990 specified for ELF as a byte boundary (for example, an alignment of 16 means
4991 that the least significant 4 bits of the address should be zero), and for PE
4992 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4993 boundary). The alignment must be an absolute expression, and it must be a
4994 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4995 common symbol, it will use the alignment when placing the symbol. If no
4996 alignment is specified, @command{@value{AS}} will set the alignment to the
4997 largest power of two less than or equal to the size of the symbol, up to a
4998 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4999 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
5000 @samp{--section-alignment} option; image file sections in PE are aligned to
5001 multiples of 4096, which is far too large an alignment for ordinary variables.
5002 It is rather the default alignment for (non-debug) sections within object
5003 (@samp{*.o}) files, which are less strictly aligned.}.
5007 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
5008 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
5012 @section @code{.data @var{subsection}}
5013 @cindex @code{data} directive
5015 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
5016 end of the data subsection numbered @var{subsection} (which is an
5017 absolute expression). If @var{subsection} is omitted, it defaults
5021 @section @code{.dc[@var{size}] @var{expressions}}
5022 @cindex @code{dc} directive
5024 The @code{.dc} directive expects zero or more @var{expressions} separated by
5025 commas. These expressions are evaluated and their values inserted into the
5026 current section. The size of the emitted value depends upon the suffix to the
5027 @code{.dc} directive:
5031 Emits N-bit values, where N is the size of an address on the target system.
5035 Emits double precision floating-point values.
5037 Emits 32-bit values.
5039 Emits single precision floating-point values.
5041 Emits 16-bit values.
5042 Note - this is true even on targets where the @code{.word} directive would emit
5045 Emits long double precision floating-point values.
5048 If no suffix is used then @samp{.w} is assumed.
5050 The byte ordering is target dependent, as is the size and format of floating
5054 @section @code{.dcb[@var{size}] @var{number} [,@var{fill}]}
5055 @cindex @code{dcb} directive
5056 This directive emits @var{number} copies of @var{fill}, each of @var{size}
5057 bytes. Both @var{number} and @var{fill} are absolute expressions. If the
5058 comma and @var{fill} are omitted, @var{fill} is assumed to be zero. The
5059 @var{size} suffix, if present, must be one of:
5063 Emits single byte values.
5065 Emits double-precision floating point values.
5067 Emits 4-byte values.
5069 Emits single-precision floating point values.
5071 Emits 2-byte values.
5073 Emits long double-precision floating point values.
5076 If the @var{size} suffix is omitted then @samp{.w} is assumed.
5078 The byte ordering is target dependent, as is the size and format of floating
5082 @section @code{.ds[@var{size}] @var{number} [,@var{fill}]}
5083 @cindex @code{ds} directive
5084 This directive emits @var{number} copies of @var{fill}, each of @var{size}
5085 bytes. Both @var{number} and @var{fill} are absolute expressions. If the
5086 comma and @var{fill} are omitted, @var{fill} is assumed to be zero. The
5087 @var{size} suffix, if present, must be one of:
5091 Emits single byte values.
5093 Emits 8-byte values.
5095 Emits 4-byte values.
5097 Emits 12-byte values.
5099 Emits 4-byte values.
5101 Emits 2-byte values.
5103 Emits 12-byte values.
5106 Note - unlike the @code{.dcb} directive the @samp{.d}, @samp{.s} and @samp{.x}
5107 suffixes do not indicate that floating-point values are to be inserted.
5109 If the @var{size} suffix is omitted then @samp{.w} is assumed.
5111 The byte ordering is target dependent.
5116 @section @code{.def @var{name}}
5118 @cindex @code{def} directive
5119 @cindex COFF symbols, debugging
5120 @cindex debugging COFF symbols
5121 Begin defining debugging information for a symbol @var{name}; the
5122 definition extends until the @code{.endef} directive is encountered.
5127 @section @code{.desc @var{symbol}, @var{abs-expression}}
5129 @cindex @code{desc} directive
5130 @cindex COFF symbol descriptor
5131 @cindex symbol descriptor, COFF
5132 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
5133 to the low 16 bits of an absolute expression.
5136 The @samp{.desc} directive is not available when @command{@value{AS}} is
5137 configured for COFF output; it is only for @code{a.out} or @code{b.out}
5138 object format. For the sake of compatibility, @command{@value{AS}} accepts
5139 it, but produces no output, when configured for COFF.
5145 @section @code{.dim}
5147 @cindex @code{dim} directive
5148 @cindex COFF auxiliary symbol information
5149 @cindex auxiliary symbol information, COFF
5150 This directive is generated by compilers to include auxiliary debugging
5151 information in the symbol table. It is only permitted inside
5152 @code{.def}/@code{.endef} pairs.
5156 @section @code{.double @var{flonums}}
5158 @cindex @code{double} directive
5159 @cindex floating point numbers (double)
5160 @code{.double} expects zero or more flonums, separated by commas. It
5161 assembles floating point numbers.
5163 The exact kind of floating point numbers emitted depends on how
5164 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5168 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
5169 in @sc{ieee} format.
5174 @section @code{.eject}
5176 @cindex @code{eject} directive
5177 @cindex new page, in listings
5178 @cindex page, in listings
5179 @cindex listing control: new page
5180 Force a page break at this point, when generating assembly listings.
5183 @section @code{.else}
5185 @cindex @code{else} directive
5186 @code{.else} is part of the @command{@value{AS}} support for conditional
5187 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
5188 of code to be assembled if the condition for the preceding @code{.if}
5192 @section @code{.elseif}
5194 @cindex @code{elseif} directive
5195 @code{.elseif} is part of the @command{@value{AS}} support for conditional
5196 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
5197 @code{.if} block that would otherwise fill the entire @code{.else} section.
5200 @section @code{.end}
5202 @cindex @code{end} directive
5203 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
5204 process anything in the file past the @code{.end} directive.
5208 @section @code{.endef}
5210 @cindex @code{endef} directive
5211 This directive flags the end of a symbol definition begun with
5216 @section @code{.endfunc}
5217 @cindex @code{endfunc} directive
5218 @code{.endfunc} marks the end of a function specified with @code{.func}.
5221 @section @code{.endif}
5223 @cindex @code{endif} directive
5224 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
5225 it marks the end of a block of code that is only assembled
5226 conditionally. @xref{If,,@code{.if}}.
5229 @section @code{.equ @var{symbol}, @var{expression}}
5231 @cindex @code{equ} directive
5232 @cindex assigning values to symbols
5233 @cindex symbols, assigning values to
5234 This directive sets the value of @var{symbol} to @var{expression}.
5235 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
5238 The syntax for @code{equ} on the HPPA is
5239 @samp{@var{symbol} .equ @var{expression}}.
5243 The syntax for @code{equ} on the Z80 is
5244 @samp{@var{symbol} equ @var{expression}}.
5245 On the Z80 it is an error if @var{symbol} is already defined,
5246 but the symbol is not protected from later redefinition.
5247 Compare @ref{Equiv}.
5251 @section @code{.equiv @var{symbol}, @var{expression}}
5252 @cindex @code{equiv} directive
5253 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5254 the assembler will signal an error if @var{symbol} is already defined. Note a
5255 symbol which has been referenced but not actually defined is considered to be
5258 Except for the contents of the error message, this is roughly equivalent to
5265 plus it protects the symbol from later redefinition.
5268 @section @code{.eqv @var{symbol}, @var{expression}}
5269 @cindex @code{eqv} directive
5270 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5271 evaluate the expression or any part of it immediately. Instead each time
5272 the resulting symbol is used in an expression, a snapshot of its current
5276 @section @code{.err}
5277 @cindex @code{err} directive
5278 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5279 message and, unless the @option{-Z} option was used, it will not generate an
5280 object file. This can be used to signal an error in conditionally compiled code.
5283 @section @code{.error "@var{string}"}
5284 @cindex error directive
5286 Similarly to @code{.err}, this directive emits an error, but you can specify a
5287 string that will be emitted as the error message. If you don't specify the
5288 message, it defaults to @code{".error directive invoked in source file"}.
5289 @xref{Errors, ,Error and Warning Messages}.
5292 .error "This code has not been assembled and tested."
5296 @section @code{.exitm}
5297 Exit early from the current macro definition. @xref{Macro}.
5300 @section @code{.extern}
5302 @cindex @code{extern} directive
5303 @code{.extern} is accepted in the source program---for compatibility
5304 with other assemblers---but it is ignored. @command{@value{AS}} treats
5305 all undefined symbols as external.
5308 @section @code{.fail @var{expression}}
5310 @cindex @code{fail} directive
5311 Generates an error or a warning. If the value of the @var{expression} is 500
5312 or more, @command{@value{AS}} will print a warning message. If the value is less
5313 than 500, @command{@value{AS}} will print an error message. The message will
5314 include the value of @var{expression}. This can occasionally be useful inside
5315 complex nested macros or conditional assembly.
5318 @section @code{.file}
5319 @cindex @code{file} directive
5321 @ifclear no-file-dir
5322 There are two different versions of the @code{.file} directive. Targets
5323 that support DWARF2 line number information use the DWARF2 version of
5324 @code{.file}. Other targets use the default version.
5326 @subheading Default Version
5328 @cindex logical file name
5329 @cindex file name, logical
5330 This version of the @code{.file} directive tells @command{@value{AS}} that we
5331 are about to start a new logical file. The syntax is:
5337 @var{string} is the new file name. In general, the filename is
5338 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5339 to specify an empty file name, you must give the quotes--@code{""}. This
5340 statement may go away in future: it is only recognized to be compatible with
5341 old @command{@value{AS}} programs.
5343 @subheading DWARF2 Version
5346 When emitting DWARF2 line number information, @code{.file} assigns filenames
5347 to the @code{.debug_line} file name table. The syntax is:
5350 .file @var{fileno} @var{filename}
5353 The @var{fileno} operand should be a unique positive integer to use as the
5354 index of the entry in the table. The @var{filename} operand is a C string
5357 The detail of filename indices is exposed to the user because the filename
5358 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5359 information, and thus the user must know the exact indices that table
5363 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5365 @cindex @code{fill} directive
5366 @cindex writing patterns in memory
5367 @cindex patterns, writing in memory
5368 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5369 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5370 may be zero or more. @var{Size} may be zero or more, but if it is
5371 more than 8, then it is deemed to have the value 8, compatible with
5372 other people's assemblers. The contents of each @var{repeat} bytes
5373 is taken from an 8-byte number. The highest order 4 bytes are
5374 zero. The lowest order 4 bytes are @var{value} rendered in the
5375 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5376 Each @var{size} bytes in a repetition is taken from the lowest order
5377 @var{size} bytes of this number. Again, this bizarre behavior is
5378 compatible with other people's assemblers.
5380 @var{size} and @var{value} are optional.
5381 If the second comma and @var{value} are absent, @var{value} is
5382 assumed zero. If the first comma and following tokens are absent,
5383 @var{size} is assumed to be 1.
5386 @section @code{.float @var{flonums}}
5388 @cindex floating point numbers (single)
5389 @cindex @code{float} directive
5390 This directive assembles zero or more flonums, separated by commas. It
5391 has the same effect as @code{.single}.
5393 The exact kind of floating point numbers emitted depends on how
5394 @command{@value{AS}} is configured.
5395 @xref{Machine Dependencies}.
5399 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5400 in @sc{ieee} format.
5405 @section @code{.func @var{name}[,@var{label}]}
5406 @cindex @code{func} directive
5407 @code{.func} emits debugging information to denote function @var{name}, and
5408 is ignored unless the file is assembled with debugging enabled.
5409 Only @samp{--gstabs[+]} is currently supported.
5410 @var{label} is the entry point of the function and if omitted @var{name}
5411 prepended with the @samp{leading char} is used.
5412 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5413 All functions are currently defined to have @code{void} return type.
5414 The function must be terminated with @code{.endfunc}.
5417 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5419 @cindex @code{global} directive
5420 @cindex symbol, making visible to linker
5421 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5422 @var{symbol} in your partial program, its value is made available to
5423 other partial programs that are linked with it. Otherwise,
5424 @var{symbol} takes its attributes from a symbol of the same name
5425 from another file linked into the same program.
5427 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5428 compatibility with other assemblers.
5431 On the HPPA, @code{.global} is not always enough to make it accessible to other
5432 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5433 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5438 @section @code{.gnu_attribute @var{tag},@var{value}}
5439 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5442 @section @code{.hidden @var{names}}
5444 @cindex @code{hidden} directive
5446 This is one of the ELF visibility directives. The other two are
5447 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5448 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5450 This directive overrides the named symbols default visibility (which is set by
5451 their binding: local, global or weak). The directive sets the visibility to
5452 @code{hidden} which means that the symbols are not visible to other components.
5453 Such symbols are always considered to be @code{protected} as well.
5457 @section @code{.hword @var{expressions}}
5459 @cindex @code{hword} directive
5460 @cindex integers, 16-bit
5461 @cindex numbers, 16-bit
5462 @cindex sixteen bit integers
5463 This expects zero or more @var{expressions}, and emits
5464 a 16 bit number for each.
5467 This directive is a synonym for @samp{.short}; depending on the target
5468 architecture, it may also be a synonym for @samp{.word}.
5472 This directive is a synonym for @samp{.short}.
5475 This directive is a synonym for both @samp{.short} and @samp{.word}.
5480 @section @code{.ident}
5482 @cindex @code{ident} directive
5484 This directive is used by some assemblers to place tags in object files. The
5485 behavior of this directive varies depending on the target. When using the
5486 a.out object file format, @command{@value{AS}} simply accepts the directive for
5487 source-file compatibility with existing assemblers, but does not emit anything
5488 for it. When using COFF, comments are emitted to the @code{.comment} or
5489 @code{.rdata} section, depending on the target. When using ELF, comments are
5490 emitted to the @code{.comment} section.
5493 @section @code{.if @var{absolute expression}}
5495 @cindex conditional assembly
5496 @cindex @code{if} directive
5497 @code{.if} marks the beginning of a section of code which is only
5498 considered part of the source program being assembled if the argument
5499 (which must be an @var{absolute expression}) is non-zero. The end of
5500 the conditional section of code must be marked by @code{.endif}
5501 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5502 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5503 If you have several conditions to check, @code{.elseif} may be used to avoid
5504 nesting blocks if/else within each subsequent @code{.else} block.
5506 The following variants of @code{.if} are also supported:
5508 @cindex @code{ifdef} directive
5509 @item .ifdef @var{symbol}
5510 Assembles the following section of code if the specified @var{symbol}
5511 has been defined. Note a symbol which has been referenced but not yet defined
5512 is considered to be undefined.
5514 @cindex @code{ifb} directive
5515 @item .ifb @var{text}
5516 Assembles the following section of code if the operand is blank (empty).
5518 @cindex @code{ifc} directive
5519 @item .ifc @var{string1},@var{string2}
5520 Assembles the following section of code if the two strings are the same. The
5521 strings may be optionally quoted with single quotes. If they are not quoted,
5522 the first string stops at the first comma, and the second string stops at the
5523 end of the line. Strings which contain whitespace should be quoted. The
5524 string comparison is case sensitive.
5526 @cindex @code{ifeq} directive
5527 @item .ifeq @var{absolute expression}
5528 Assembles the following section of code if the argument is zero.
5530 @cindex @code{ifeqs} directive
5531 @item .ifeqs @var{string1},@var{string2}
5532 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5534 @cindex @code{ifge} directive
5535 @item .ifge @var{absolute expression}
5536 Assembles the following section of code if the argument is greater than or
5539 @cindex @code{ifgt} directive
5540 @item .ifgt @var{absolute expression}
5541 Assembles the following section of code if the argument is greater than zero.
5543 @cindex @code{ifle} directive
5544 @item .ifle @var{absolute expression}
5545 Assembles the following section of code if the argument is less than or equal
5548 @cindex @code{iflt} directive
5549 @item .iflt @var{absolute expression}
5550 Assembles the following section of code if the argument is less than zero.
5552 @cindex @code{ifnb} directive
5553 @item .ifnb @var{text}
5554 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5555 following section of code if the operand is non-blank (non-empty).
5557 @cindex @code{ifnc} directive
5558 @item .ifnc @var{string1},@var{string2}.
5559 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5560 following section of code if the two strings are not the same.
5562 @cindex @code{ifndef} directive
5563 @cindex @code{ifnotdef} directive
5564 @item .ifndef @var{symbol}
5565 @itemx .ifnotdef @var{symbol}
5566 Assembles the following section of code if the specified @var{symbol}
5567 has not been defined. Both spelling variants are equivalent. Note a symbol
5568 which has been referenced but not yet defined is considered to be undefined.
5570 @cindex @code{ifne} directive
5571 @item .ifne @var{absolute expression}
5572 Assembles the following section of code if the argument is not equal to zero
5573 (in other words, this is equivalent to @code{.if}).
5575 @cindex @code{ifnes} directive
5576 @item .ifnes @var{string1},@var{string2}
5577 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5578 following section of code if the two strings are not the same.
5582 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5584 @cindex @code{incbin} directive
5585 @cindex binary files, including
5586 The @code{incbin} directive includes @var{file} verbatim at the current
5587 location. You can control the search paths used with the @samp{-I} command-line
5588 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5591 The @var{skip} argument skips a number of bytes from the start of the
5592 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5593 read. Note that the data is not aligned in any way, so it is the user's
5594 responsibility to make sure that proper alignment is provided both before and
5595 after the @code{incbin} directive.
5598 @section @code{.include "@var{file}"}
5600 @cindex @code{include} directive
5601 @cindex supporting files, including
5602 @cindex files, including
5603 This directive provides a way to include supporting files at specified
5604 points in your source program. The code from @var{file} is assembled as
5605 if it followed the point of the @code{.include}; when the end of the
5606 included file is reached, assembly of the original file continues. You
5607 can control the search paths used with the @samp{-I} command-line option
5608 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5612 @section @code{.int @var{expressions}}
5614 @cindex @code{int} directive
5615 @cindex integers, 32-bit
5616 Expect zero or more @var{expressions}, of any section, separated by commas.
5617 For each expression, emit a number that, at run time, is the value of that
5618 expression. The byte order and bit size of the number depends on what kind
5619 of target the assembly is for.
5623 On most forms of the H8/300, @code{.int} emits 16-bit
5624 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5631 @section @code{.internal @var{names}}
5633 @cindex @code{internal} directive
5635 This is one of the ELF visibility directives. The other two are
5636 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5637 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5639 This directive overrides the named symbols default visibility (which is set by
5640 their binding: local, global or weak). The directive sets the visibility to
5641 @code{internal} which means that the symbols are considered to be @code{hidden}
5642 (i.e., not visible to other components), and that some extra, processor specific
5643 processing must also be performed upon the symbols as well.
5647 @section @code{.irp @var{symbol},@var{values}}@dots{}
5649 @cindex @code{irp} directive
5650 Evaluate a sequence of statements assigning different values to @var{symbol}.
5651 The sequence of statements starts at the @code{.irp} directive, and is
5652 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5653 set to @var{value}, and the sequence of statements is assembled. If no
5654 @var{value} is listed, the sequence of statements is assembled once, with
5655 @var{symbol} set to the null string. To refer to @var{symbol} within the
5656 sequence of statements, use @var{\symbol}.
5658 For example, assembling
5666 is equivalent to assembling
5674 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5677 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5679 @cindex @code{irpc} directive
5680 Evaluate a sequence of statements assigning different values to @var{symbol}.
5681 The sequence of statements starts at the @code{.irpc} directive, and is
5682 terminated by an @code{.endr} directive. For each character in @var{value},
5683 @var{symbol} is set to the character, and the sequence of statements is
5684 assembled. If no @var{value} is listed, the sequence of statements is
5685 assembled once, with @var{symbol} set to the null string. To refer to
5686 @var{symbol} within the sequence of statements, use @var{\symbol}.
5688 For example, assembling
5696 is equivalent to assembling
5704 For some caveats with the spelling of @var{symbol}, see also the discussion
5708 @section @code{.lcomm @var{symbol} , @var{length}}
5710 @cindex @code{lcomm} directive
5711 @cindex local common symbols
5712 @cindex symbols, local common
5713 Reserve @var{length} (an absolute expression) bytes for a local common
5714 denoted by @var{symbol}. The section and value of @var{symbol} are
5715 those of the new local common. The addresses are allocated in the bss
5716 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5717 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5718 not visible to @code{@value{LD}}.
5721 Some targets permit a third argument to be used with @code{.lcomm}. This
5722 argument specifies the desired alignment of the symbol in the bss section.
5726 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5727 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5731 @section @code{.lflags}
5733 @cindex @code{lflags} directive (ignored)
5734 @command{@value{AS}} accepts this directive, for compatibility with other
5735 assemblers, but ignores it.
5737 @ifclear no-line-dir
5739 @section @code{.line @var{line-number}}
5741 @cindex @code{line} directive
5742 @cindex logical line number
5744 Change the logical line number. @var{line-number} must be an absolute
5745 expression. The next line has that logical line number. Therefore any other
5746 statements on the current line (after a statement separator character) are
5747 reported as on logical line number @var{line-number} @minus{} 1. One day
5748 @command{@value{AS}} will no longer support this directive: it is recognized only
5749 for compatibility with existing assembler programs.
5752 Even though this is a directive associated with the @code{a.out} or
5753 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5754 when producing COFF output, and treats @samp{.line} as though it
5755 were the COFF @samp{.ln} @emph{if} it is found outside a
5756 @code{.def}/@code{.endef} pair.
5758 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5759 used by compilers to generate auxiliary symbol information for
5764 @section @code{.linkonce [@var{type}]}
5766 @cindex @code{linkonce} directive
5767 @cindex common sections
5768 Mark the current section so that the linker only includes a single copy of it.
5769 This may be used to include the same section in several different object files,
5770 but ensure that the linker will only include it once in the final output file.
5771 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5772 Duplicate sections are detected based on the section name, so it should be
5775 This directive is only supported by a few object file formats; as of this
5776 writing, the only object file format which supports it is the Portable
5777 Executable format used on Windows NT.
5779 The @var{type} argument is optional. If specified, it must be one of the
5780 following strings. For example:
5784 Not all types may be supported on all object file formats.
5788 Silently discard duplicate sections. This is the default.
5791 Warn if there are duplicate sections, but still keep only one copy.
5794 Warn if any of the duplicates have different sizes.
5797 Warn if any of the duplicates do not have exactly the same contents.
5801 @section @code{.list}
5803 @cindex @code{list} directive
5804 @cindex listing control, turning on
5805 Control (in conjunction with the @code{.nolist} directive) whether or
5806 not assembly listings are generated. These two directives maintain an
5807 internal counter (which is zero initially). @code{.list} increments the
5808 counter, and @code{.nolist} decrements it. Assembly listings are
5809 generated whenever the counter is greater than zero.
5811 By default, listings are disabled. When you enable them (with the
5812 @samp{-a} command-line option; @pxref{Invoking,,Command-Line Options}),
5813 the initial value of the listing counter is one.
5816 @section @code{.ln @var{line-number}}
5818 @cindex @code{ln} directive
5819 @ifclear no-line-dir
5820 @samp{.ln} is a synonym for @samp{.line}.
5823 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5824 must be an absolute expression. The next line has that logical
5825 line number, so any other statements on the current line (after a
5826 statement separator character @code{;}) are reported as on logical
5827 line number @var{line-number} @minus{} 1.
5831 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5832 @cindex @code{loc} directive
5833 When emitting DWARF2 line number information,
5834 the @code{.loc} directive will add a row to the @code{.debug_line} line
5835 number matrix corresponding to the immediately following assembly
5836 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5837 arguments will be applied to the @code{.debug_line} state machine before
5840 The @var{options} are a sequence of the following tokens in any order:
5844 This option will set the @code{basic_block} register in the
5845 @code{.debug_line} state machine to @code{true}.
5848 This option will set the @code{prologue_end} register in the
5849 @code{.debug_line} state machine to @code{true}.
5851 @item epilogue_begin
5852 This option will set the @code{epilogue_begin} register in the
5853 @code{.debug_line} state machine to @code{true}.
5855 @item is_stmt @var{value}
5856 This option will set the @code{is_stmt} register in the
5857 @code{.debug_line} state machine to @code{value}, which must be
5860 @item isa @var{value}
5861 This directive will set the @code{isa} register in the @code{.debug_line}
5862 state machine to @var{value}, which must be an unsigned integer.
5864 @item discriminator @var{value}
5865 This directive will set the @code{discriminator} register in the @code{.debug_line}
5866 state machine to @var{value}, which must be an unsigned integer.
5868 @item view @var{value}
5869 This option causes a row to be added to @code{.debug_line} in reference to the
5870 current address (which might not be the same as that of the following assembly
5871 instruction), and to associate @var{value} with the @code{view} register in the
5872 @code{.debug_line} state machine. If @var{value} is a label, both the
5873 @code{view} register and the label are set to the number of prior @code{.loc}
5874 directives at the same program location. If @var{value} is the literal
5875 @code{0}, the @code{view} register is set to zero, and the assembler asserts
5876 that there aren't any prior @code{.loc} directives at the same program
5877 location. If @var{value} is the literal @code{-0}, the assembler arrange for
5878 the @code{view} register to be reset in this row, even if there are prior
5879 @code{.loc} directives at the same program location.
5883 @node Loc_mark_labels
5884 @section @code{.loc_mark_labels @var{enable}}
5885 @cindex @code{loc_mark_labels} directive
5886 When emitting DWARF2 line number information,
5887 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5888 to the @code{.debug_line} line number matrix with the @code{basic_block}
5889 register in the state machine set whenever a code label is seen.
5890 The @var{enable} argument should be either 1 or 0, to enable or disable
5891 this function respectively.
5895 @section @code{.local @var{names}}
5897 @cindex @code{local} directive
5898 This directive, which is available for ELF targets, marks each symbol in
5899 the comma-separated list of @code{names} as a local symbol so that it
5900 will not be externally visible. If the symbols do not already exist,
5901 they will be created.
5903 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5904 accept an alignment argument, which is the case for most ELF targets,
5905 the @code{.local} directive can be used in combination with @code{.comm}
5906 (@pxref{Comm}) to define aligned local common data.
5910 @section @code{.long @var{expressions}}
5912 @cindex @code{long} directive
5913 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5916 @c no one seems to know what this is for or whether this description is
5917 @c what it really ought to do
5919 @section @code{.lsym @var{symbol}, @var{expression}}
5921 @cindex @code{lsym} directive
5922 @cindex symbol, not referenced in assembly
5923 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5924 the hash table, ensuring it cannot be referenced by name during the
5925 rest of the assembly. This sets the attributes of the symbol to be
5926 the same as the expression value:
5928 @var{other} = @var{descriptor} = 0
5929 @var{type} = @r{(section of @var{expression})}
5930 @var{value} = @var{expression}
5933 The new symbol is not flagged as external.
5937 @section @code{.macro}
5940 The commands @code{.macro} and @code{.endm} allow you to define macros that
5941 generate assembly output. For example, this definition specifies a macro
5942 @code{sum} that puts a sequence of numbers into memory:
5945 .macro sum from=0, to=5
5954 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5966 @item .macro @var{macname}
5967 @itemx .macro @var{macname} @var{macargs} @dots{}
5968 @cindex @code{macro} directive
5969 Begin the definition of a macro called @var{macname}. If your macro
5970 definition requires arguments, specify their names after the macro name,
5971 separated by commas or spaces. You can qualify the macro argument to
5972 indicate whether all invocations must specify a non-blank value (through
5973 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5974 (through @samp{:@code{vararg}}). You can supply a default value for any
5975 macro argument by following the name with @samp{=@var{deflt}}. You
5976 cannot define two macros with the same @var{macname} unless it has been
5977 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5978 definitions. For example, these are all valid @code{.macro} statements:
5982 Begin the definition of a macro called @code{comm}, which takes no
5985 @item .macro plus1 p, p1
5986 @itemx .macro plus1 p p1
5987 Either statement begins the definition of a macro called @code{plus1},
5988 which takes two arguments; within the macro definition, write
5989 @samp{\p} or @samp{\p1} to evaluate the arguments.
5991 @item .macro reserve_str p1=0 p2
5992 Begin the definition of a macro called @code{reserve_str}, with two
5993 arguments. The first argument has a default value, but not the second.
5994 After the definition is complete, you can call the macro either as
5995 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5996 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5997 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5998 @samp{0}, and @samp{\p2} evaluating to @var{b}).
6000 @item .macro m p1:req, p2=0, p3:vararg
6001 Begin the definition of a macro called @code{m}, with at least three
6002 arguments. The first argument must always have a value specified, but
6003 not the second, which instead has a default value. The third formal
6004 will get assigned all remaining arguments specified at invocation time.
6006 When you call a macro, you can specify the argument values either by
6007 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
6008 @samp{sum to=17, from=9}.
6012 Note that since each of the @var{macargs} can be an identifier exactly
6013 as any other one permitted by the target architecture, there may be
6014 occasional problems if the target hand-crafts special meanings to certain
6015 characters when they occur in a special position. For example, if the colon
6016 (@code{:}) is generally permitted to be part of a symbol name, but the
6017 architecture specific code special-cases it when occurring as the final
6018 character of a symbol (to denote a label), then the macro parameter
6019 replacement code will have no way of knowing that and consider the whole
6020 construct (including the colon) an identifier, and check only this
6021 identifier for being the subject to parameter substitution. So for example
6022 this macro definition:
6030 might not work as expected. Invoking @samp{label foo} might not create a label
6031 called @samp{foo} but instead just insert the text @samp{\l:} into the
6032 assembler source, probably generating an error about an unrecognised
6035 Similarly problems might occur with the period character (@samp{.})
6036 which is often allowed inside opcode names (and hence identifier names). So
6037 for example constructing a macro to build an opcode from a base name and a
6038 length specifier like this:
6041 .macro opcode base length
6046 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
6047 instruction but instead generate some kind of error as the assembler tries to
6048 interpret the text @samp{\base.\length}.
6050 There are several possible ways around this problem:
6053 @item Insert white space
6054 If it is possible to use white space characters then this is the simplest
6063 @item Use @samp{\()}
6064 The string @samp{\()} can be used to separate the end of a macro argument from
6065 the following text. eg:
6068 .macro opcode base length
6073 @item Use the alternate macro syntax mode
6074 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
6075 used as a separator. eg:
6085 Note: this problem of correctly identifying string parameters to pseudo ops
6086 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
6087 and @code{.irpc} (@pxref{Irpc}) as well.
6090 @cindex @code{endm} directive
6091 Mark the end of a macro definition.
6094 @cindex @code{exitm} directive
6095 Exit early from the current macro definition.
6097 @cindex number of macros executed
6098 @cindex macros, count executed
6100 @command{@value{AS}} maintains a counter of how many macros it has
6101 executed in this pseudo-variable; you can copy that number to your
6102 output with @samp{\@@}, but @emph{only within a macro definition}.
6104 @item LOCAL @var{name} [ , @dots{} ]
6105 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
6106 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
6107 @xref{Altmacro,,@code{.altmacro}}.
6111 @section @code{.mri @var{val}}
6113 @cindex @code{mri} directive
6114 @cindex MRI mode, temporarily
6115 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
6116 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
6117 affects code assembled until the next @code{.mri} directive, or until the end
6118 of the file. @xref{M, MRI mode, MRI mode}.
6121 @section @code{.noaltmacro}
6122 Disable alternate macro mode. @xref{Altmacro}.
6125 @section @code{.nolist}
6127 @cindex @code{nolist} directive
6128 @cindex listing control, turning off
6129 Control (in conjunction with the @code{.list} directive) whether or
6130 not assembly listings are generated. These two directives maintain an
6131 internal counter (which is zero initially). @code{.list} increments the
6132 counter, and @code{.nolist} decrements it. Assembly listings are
6133 generated whenever the counter is greater than zero.
6136 @section @code{.nops @var{size}[, @var{control}]}
6138 @cindex @code{nops} directive
6139 @cindex filling memory with no-op instructions
6140 This directive emits @var{size} bytes filled with no-op instructions.
6141 @var{size} is absolute expression, which must be a positve value.
6142 @var{control} controls how no-op instructions should be generated. If
6143 the comma and @var{control} are omitted, @var{control} is assumed to be
6146 Note: For Intel 80386 and AMD x86-64 targets, @var{control} specifies
6147 the size limit of a no-op instruction. The valid values of @var{control}
6148 are between 0 and 4 in 16-bit mode, between 0 and 7 when tuning for
6149 older processors in 32-bit mode, between 0 and 11 in 64-bit mode or when
6150 tuning for newer processors in 32-bit mode. When 0 is used, the no-op
6151 instruction size limit is set to the maximum supported size.
6154 @section @code{.octa @var{bignums}}
6156 @c FIXME: double size emitted for "octa" on some? Or warn?
6157 @cindex @code{octa} directive
6158 @cindex integer, 16-byte
6159 @cindex sixteen byte integer
6160 This directive expects zero or more bignums, separated by commas. For each
6161 bignum, it emits a 16-byte integer.
6163 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
6164 hence @emph{octa}-word for 16 bytes.
6167 @section @code{.offset @var{loc}}
6169 @cindex @code{offset} directive
6170 Set the location counter to @var{loc} in the absolute section. @var{loc} must
6171 be an absolute expression. This directive may be useful for defining
6172 symbols with absolute values. Do not confuse it with the @code{.org}
6176 @section @code{.org @var{new-lc} , @var{fill}}
6178 @cindex @code{org} directive
6179 @cindex location counter, advancing
6180 @cindex advancing location counter
6181 @cindex current address, advancing
6182 Advance the location counter of the current section to
6183 @var{new-lc}. @var{new-lc} is either an absolute expression or an
6184 expression with the same section as the current subsection. That is,
6185 you can't use @code{.org} to cross sections: if @var{new-lc} has the
6186 wrong section, the @code{.org} directive is ignored. To be compatible
6187 with former assemblers, if the section of @var{new-lc} is absolute,
6188 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
6189 is the same as the current subsection.
6191 @code{.org} may only increase the location counter, or leave it
6192 unchanged; you cannot use @code{.org} to move the location counter
6195 @c double negative used below "not undefined" because this is a specific
6196 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
6197 @c section. doc@cygnus.com 18feb91
6198 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
6199 may not be undefined. If you really detest this restriction we eagerly await
6200 a chance to share your improved assembler.
6202 Beware that the origin is relative to the start of the section, not
6203 to the start of the subsection. This is compatible with other
6204 people's assemblers.
6206 When the location counter (of the current subsection) is advanced, the
6207 intervening bytes are filled with @var{fill} which should be an
6208 absolute expression. If the comma and @var{fill} are omitted,
6209 @var{fill} defaults to zero.
6212 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
6214 @cindex padding the location counter given a power of two
6215 @cindex @code{p2align} directive
6216 Pad the location counter (in the current subsection) to a particular
6217 storage boundary. The first expression (which must be absolute) is the
6218 number of low-order zero bits the location counter must have after
6219 advancement. For example @samp{.p2align 3} advances the location
6220 counter until it is a multiple of 8. If the location counter is already a
6221 multiple of 8, no change is needed.
6223 The second expression (also absolute) gives the fill value to be stored in the
6224 padding bytes. It (and the comma) may be omitted. If it is omitted, the
6225 padding bytes are normally zero. However, on most systems, if the section is
6226 marked as containing code and the fill value is omitted, the space is filled
6227 with no-op instructions.
6229 The third expression is also absolute, and is also optional. If it is present,
6230 it is the maximum number of bytes that should be skipped by this alignment
6231 directive. If doing the alignment would require skipping more bytes than the
6232 specified maximum, then the alignment is not done at all. You can omit the
6233 fill value (the second argument) entirely by simply using two commas after the
6234 required alignment; this can be useful if you want the alignment to be filled
6235 with no-op instructions when appropriate.
6237 @cindex @code{p2alignw} directive
6238 @cindex @code{p2alignl} directive
6239 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
6240 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
6241 pattern as a two byte word value. The @code{.p2alignl} directives treats the
6242 fill pattern as a four byte longword value. For example, @code{.p2alignw
6243 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
6244 filled in with the value 0x368d (the exact placement of the bytes depends upon
6245 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
6250 @section @code{.popsection}
6252 @cindex @code{popsection} directive
6253 @cindex Section Stack
6254 This is one of the ELF section stack manipulation directives. The others are
6255 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6256 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
6259 This directive replaces the current section (and subsection) with the top
6260 section (and subsection) on the section stack. This section is popped off the
6266 @section @code{.previous}
6268 @cindex @code{previous} directive
6269 @cindex Section Stack
6270 This is one of the ELF section stack manipulation directives. The others are
6271 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6272 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6273 (@pxref{PopSection}).
6275 This directive swaps the current section (and subsection) with most recently
6276 referenced section/subsection pair prior to this one. Multiple
6277 @code{.previous} directives in a row will flip between two sections (and their
6278 subsections). For example:
6290 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6296 # Now in section A subsection 1
6300 # Now in section B subsection 0
6303 # Now in section B subsection 1
6306 # Now in section B subsection 0
6310 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6311 section B and 0x9abc into subsection 1 of section B.
6313 In terms of the section stack, this directive swaps the current section with
6314 the top section on the section stack.
6318 @section @code{.print @var{string}}
6320 @cindex @code{print} directive
6321 @command{@value{AS}} will print @var{string} on the standard output during
6322 assembly. You must put @var{string} in double quotes.
6326 @section @code{.protected @var{names}}
6328 @cindex @code{protected} directive
6330 This is one of the ELF visibility directives. The other two are
6331 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6333 This directive overrides the named symbols default visibility (which is set by
6334 their binding: local, global or weak). The directive sets the visibility to
6335 @code{protected} which means that any references to the symbols from within the
6336 components that defines them must be resolved to the definition in that
6337 component, even if a definition in another component would normally preempt
6342 @section @code{.psize @var{lines} , @var{columns}}
6344 @cindex @code{psize} directive
6345 @cindex listing control: paper size
6346 @cindex paper size, for listings
6347 Use this directive to declare the number of lines---and, optionally, the
6348 number of columns---to use for each page, when generating listings.
6350 If you do not use @code{.psize}, listings use a default line-count
6351 of 60. You may omit the comma and @var{columns} specification; the
6352 default width is 200 columns.
6354 @command{@value{AS}} generates formfeeds whenever the specified number of
6355 lines is exceeded (or whenever you explicitly request one, using
6358 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6359 those explicitly specified with @code{.eject}.
6362 @section @code{.purgem @var{name}}
6364 @cindex @code{purgem} directive
6365 Undefine the macro @var{name}, so that later uses of the string will not be
6366 expanded. @xref{Macro}.
6370 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6372 @cindex @code{pushsection} directive
6373 @cindex Section Stack
6374 This is one of the ELF section stack manipulation directives. The others are
6375 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6376 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6379 This directive pushes the current section (and subsection) onto the
6380 top of the section stack, and then replaces the current section and
6381 subsection with @code{name} and @code{subsection}. The optional
6382 @code{flags}, @code{type} and @code{arguments} are treated the same
6383 as in the @code{.section} (@pxref{Section}) directive.
6387 @section @code{.quad @var{bignums}}
6389 @cindex @code{quad} directive
6390 @code{.quad} expects zero or more bignums, separated by commas. For
6391 each bignum, it emits
6393 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6394 warning message; and just takes the lowest order 8 bytes of the bignum.
6395 @cindex eight-byte integer
6396 @cindex integer, 8-byte
6398 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6399 hence @emph{quad}-word for 8 bytes.
6402 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6403 warning message; and just takes the lowest order 16 bytes of the bignum.
6404 @cindex sixteen-byte integer
6405 @cindex integer, 16-byte
6409 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6411 @cindex @code{reloc} directive
6412 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6413 @var{expression}. If @var{offset} is a number, the relocation is generated in
6414 the current section. If @var{offset} is an expression that resolves to a
6415 symbol plus offset, the relocation is generated in the given symbol's section.
6416 @var{expression}, if present, must resolve to a symbol plus addend or to an
6417 absolute value, but note that not all targets support an addend. e.g. ELF REL
6418 targets such as i386 store an addend in the section contents rather than in the
6419 relocation. This low level interface does not support addends stored in the
6423 @section @code{.rept @var{count}}
6425 @cindex @code{rept} directive
6426 Repeat the sequence of lines between the @code{.rept} directive and the next
6427 @code{.endr} directive @var{count} times.
6429 For example, assembling
6437 is equivalent to assembling
6445 A count of zero is allowed, but nothing is generated. Negative counts are not
6446 allowed and if encountered will be treated as if they were zero.
6449 @section @code{.sbttl "@var{subheading}"}
6451 @cindex @code{sbttl} directive
6452 @cindex subtitles for listings
6453 @cindex listing control: subtitle
6454 Use @var{subheading} as the title (third line, immediately after the
6455 title line) when generating assembly listings.
6457 This directive affects subsequent pages, as well as the current page if
6458 it appears within ten lines of the top of a page.
6462 @section @code{.scl @var{class}}
6464 @cindex @code{scl} directive
6465 @cindex symbol storage class (COFF)
6466 @cindex COFF symbol storage class
6467 Set the storage-class value for a symbol. This directive may only be
6468 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6469 whether a symbol is static or external, or it may record further
6470 symbolic debugging information.
6475 @section @code{.section @var{name}}
6477 @cindex named section
6478 Use the @code{.section} directive to assemble the following code into a section
6481 This directive is only supported for targets that actually support arbitrarily
6482 named sections; on @code{a.out} targets, for example, it is not accepted, even
6483 with a standard @code{a.out} section name.
6487 @c only print the extra heading if both COFF and ELF are set
6488 @subheading COFF Version
6491 @cindex @code{section} directive (COFF version)
6492 For COFF targets, the @code{.section} directive is used in one of the following
6496 .section @var{name}[, "@var{flags}"]
6497 .section @var{name}[, @var{subsection}]
6500 If the optional argument is quoted, it is taken as flags to use for the
6501 section. Each flag is a single character. The following flags are recognized:
6505 bss section (uninitialized data)
6507 section is not loaded
6513 exclude section from linking
6519 shared section (meaningful for PE targets)
6521 ignored. (For compatibility with the ELF version)
6523 section is not readable (meaningful for PE targets)
6525 single-digit power-of-two section alignment (GNU extension)
6528 If no flags are specified, the default flags depend upon the section name. If
6529 the section name is not recognized, the default will be for the section to be
6530 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6531 from the section, rather than adding them, so if they are used on their own it
6532 will be as if no flags had been specified at all.
6534 If the optional argument to the @code{.section} directive is not quoted, it is
6535 taken as a subsection number (@pxref{Sub-Sections}).
6540 @c only print the extra heading if both COFF and ELF are set
6541 @subheading ELF Version
6544 @cindex Section Stack
6545 This is one of the ELF section stack manipulation directives. The others are
6546 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6547 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6548 @code{.previous} (@pxref{Previous}).
6550 @cindex @code{section} directive (ELF version)
6551 For ELF targets, the @code{.section} directive is used like this:
6554 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6557 @anchor{Section Name Substitutions}
6558 @kindex --sectname-subst
6559 @cindex section name substitution
6560 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6561 argument may contain a substitution sequence. Only @code{%S} is supported
6562 at the moment, and substitutes the current section name. For example:
6565 .macro exception_code
6566 .section %S.exception
6567 [exception code here]
6582 The two @code{exception_code} invocations above would create the
6583 @code{.text.exception} and @code{.init.exception} sections respectively.
6584 This is useful e.g. to discriminate between ancillary sections that are
6585 tied to setup code to be discarded after use from ancillary sections that
6586 need to stay resident without having to define multiple @code{exception_code}
6587 macros just for that purpose.
6589 The optional @var{flags} argument is a quoted string which may contain any
6590 combination of the following characters:
6594 section is allocatable
6596 section is a GNU_MBIND section
6598 section is excluded from executable and shared library.
6602 section is executable
6604 section is mergeable
6606 section contains zero terminated strings
6608 section is a member of a section group
6610 section is used for thread-local-storage
6612 section is a member of the previously-current section's group, if any
6613 @item @code{<number>}
6614 a numeric value indicating the bits to be set in the ELF section header's flags
6615 field. Note - if one or more of the alphabetic characters described above is
6616 also included in the flags field, their bit values will be ORed into the
6618 @item @code{<target specific>}
6619 some targets extend this list with their own flag characters
6622 Note - once a section's flags have been set they cannot be changed. There are
6623 a few exceptions to this rule however. Processor and application specific
6624 flags can be added to an already defined section. The @code{.interp},
6625 @code{.strtab} and @code{.symtab} sections can have the allocate flag
6626 (@code{a}) set after they are initially defined, and the @code{.note-GNU-stack}
6627 section may have the executable (@code{x}) flag added.
6629 The optional @var{type} argument may contain one of the following constants:
6633 section contains data
6635 section does not contain data (i.e., section only occupies space)
6637 section contains data which is used by things other than the program
6639 section contains an array of pointers to init functions
6641 section contains an array of pointers to finish functions
6642 @item @@preinit_array
6643 section contains an array of pointers to pre-init functions
6644 @item @@@code{<number>}
6645 a numeric value to be set as the ELF section header's type field.
6646 @item @@@code{<target specific>}
6647 some targets extend this list with their own types
6650 Many targets only support the first three section types. The type may be
6651 enclosed in double quotes if necessary.
6653 Note on targets where the @code{@@} character is the start of a comment (eg
6654 ARM) then another character is used instead. For example the ARM port uses the
6657 Note - some sections, eg @code{.text} and @code{.data} are considered to be
6658 special and have fixed types. Any attempt to declare them with a different
6659 type will generate an error from the assembler.
6661 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6662 be specified as well as an extra argument---@var{entsize}---like this:
6665 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6668 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6669 constants, each @var{entsize} octets long. Sections with both @code{M} and
6670 @code{S} must contain zero terminated strings where each character is
6671 @var{entsize} bytes long. The linker may remove duplicates within sections with
6672 the same name, same entity size and same flags. @var{entsize} must be an
6673 absolute expression. For sections with both @code{M} and @code{S}, a string
6674 which is a suffix of a larger string is considered a duplicate. Thus
6675 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6676 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6678 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6679 be present along with an additional field like this:
6682 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6685 The @var{GroupName} field specifies the name of the section group to which this
6686 particular section belongs. The optional linkage field can contain:
6690 indicates that only one copy of this section should be retained
6695 Note: if both the @var{M} and @var{G} flags are present then the fields for
6696 the Merge flag should come first, like this:
6699 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6702 If @var{flags} contains the @code{?} symbol then it may not also contain the
6703 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6704 present. Instead, @code{?} says to consider the section that's current before
6705 this directive. If that section used @code{G}, then the new section will use
6706 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6707 If not, then the @code{?} symbol has no effect.
6709 If no flags are specified, the default flags depend upon the section name. If
6710 the section name is not recognized, the default will be for the section to have
6711 none of the above flags: it will not be allocated in memory, nor writable, nor
6712 executable. The section will contain data.
6714 For ELF targets, the assembler supports another type of @code{.section}
6715 directive for compatibility with the Solaris assembler:
6718 .section "@var{name}"[, @var{flags}...]
6721 Note that the section name is quoted. There may be a sequence of comma
6726 section is allocatable
6730 section is executable
6732 section is excluded from executable and shared library.
6734 section is used for thread local storage
6737 This directive replaces the current section and subsection. See the
6738 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6739 some examples of how this directive and the other section stack directives
6745 @section @code{.set @var{symbol}, @var{expression}}
6747 @cindex @code{set} directive
6748 @cindex symbol value, setting
6749 Set the value of @var{symbol} to @var{expression}. This
6750 changes @var{symbol}'s value and type to conform to
6751 @var{expression}. If @var{symbol} was flagged as external, it remains
6752 flagged (@pxref{Symbol Attributes}).
6754 You may @code{.set} a symbol many times in the same assembly provided that the
6755 values given to the symbol are constants. Values that are based on expressions
6756 involving other symbols are allowed, but some targets may restrict this to only
6757 being done once per assembly. This is because those targets do not set the
6758 addresses of symbols at assembly time, but rather delay the assignment until a
6759 final link is performed. This allows the linker a chance to change the code in
6760 the files, changing the location of, and the relative distance between, various
6763 If you @code{.set} a global symbol, the value stored in the object
6764 file is the last value stored into it.
6767 On Z80 @code{set} is a real instruction, use
6768 @samp{@var{symbol} defl @var{expression}} instead.
6772 @section @code{.short @var{expressions}}
6774 @cindex @code{short} directive
6776 @code{.short} is normally the same as @samp{.word}.
6777 @xref{Word,,@code{.word}}.
6779 In some configurations, however, @code{.short} and @code{.word} generate
6780 numbers of different lengths. @xref{Machine Dependencies}.
6784 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6787 This expects zero or more @var{expressions}, and emits
6788 a 16 bit number for each.
6793 @section @code{.single @var{flonums}}
6795 @cindex @code{single} directive
6796 @cindex floating point numbers (single)
6797 This directive assembles zero or more flonums, separated by commas. It
6798 has the same effect as @code{.float}.
6800 The exact kind of floating point numbers emitted depends on how
6801 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6805 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6806 numbers in @sc{ieee} format.
6812 @section @code{.size}
6814 This directive is used to set the size associated with a symbol.
6818 @c only print the extra heading if both COFF and ELF are set
6819 @subheading COFF Version
6822 @cindex @code{size} directive (COFF version)
6823 For COFF targets, the @code{.size} directive is only permitted inside
6824 @code{.def}/@code{.endef} pairs. It is used like this:
6827 .size @var{expression}
6834 @c only print the extra heading if both COFF and ELF are set
6835 @subheading ELF Version
6838 @cindex @code{size} directive (ELF version)
6839 For ELF targets, the @code{.size} directive is used like this:
6842 .size @var{name} , @var{expression}
6845 This directive sets the size associated with a symbol @var{name}.
6846 The size in bytes is computed from @var{expression} which can make use of label
6847 arithmetic. This directive is typically used to set the size of function
6852 @ifclear no-space-dir
6854 @section @code{.skip @var{size} [,@var{fill}]}
6856 @cindex @code{skip} directive
6857 @cindex filling memory
6858 This directive emits @var{size} bytes, each of value @var{fill}. Both
6859 @var{size} and @var{fill} are absolute expressions. If the comma and
6860 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6865 @section @code{.sleb128 @var{expressions}}
6867 @cindex @code{sleb128} directive
6868 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6869 compact, variable length representation of numbers used by the DWARF
6870 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6872 @ifclear no-space-dir
6874 @section @code{.space @var{size} [,@var{fill}]}
6876 @cindex @code{space} directive
6877 @cindex filling memory
6878 This directive emits @var{size} bytes, each of value @var{fill}. Both
6879 @var{size} and @var{fill} are absolute expressions. If the comma
6880 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6885 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6886 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6887 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6888 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6896 @section @code{.stabd, .stabn, .stabs}
6898 @cindex symbolic debuggers, information for
6899 @cindex @code{stab@var{x}} directives
6900 There are three directives that begin @samp{.stab}.
6901 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6902 The symbols are not entered in the @command{@value{AS}} hash table: they
6903 cannot be referenced elsewhere in the source file.
6904 Up to five fields are required:
6908 This is the symbol's name. It may contain any character except
6909 @samp{\000}, so is more general than ordinary symbol names. Some
6910 debuggers used to code arbitrarily complex structures into symbol names
6914 An absolute expression. The symbol's type is set to the low 8 bits of
6915 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6916 and debuggers choke on silly bit patterns.
6919 An absolute expression. The symbol's ``other'' attribute is set to the
6920 low 8 bits of this expression.
6923 An absolute expression. The symbol's descriptor is set to the low 16
6924 bits of this expression.
6927 An absolute expression which becomes the symbol's value.
6930 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6931 or @code{.stabs} statement, the symbol has probably already been created;
6932 you get a half-formed symbol in your object file. This is
6933 compatible with earlier assemblers!
6936 @cindex @code{stabd} directive
6937 @item .stabd @var{type} , @var{other} , @var{desc}
6939 The ``name'' of the symbol generated is not even an empty string.
6940 It is a null pointer, for compatibility. Older assemblers used a
6941 null pointer so they didn't waste space in object files with empty
6944 The symbol's value is set to the location counter,
6945 relocatably. When your program is linked, the value of this symbol
6946 is the address of the location counter when the @code{.stabd} was
6949 @cindex @code{stabn} directive
6950 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6951 The name of the symbol is set to the empty string @code{""}.
6953 @cindex @code{stabs} directive
6954 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6955 All five fields are specified.
6961 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6962 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6964 @cindex string, copying to object file
6965 @cindex string8, copying to object file
6966 @cindex string16, copying to object file
6967 @cindex string32, copying to object file
6968 @cindex string64, copying to object file
6969 @cindex @code{string} directive
6970 @cindex @code{string8} directive
6971 @cindex @code{string16} directive
6972 @cindex @code{string32} directive
6973 @cindex @code{string64} directive
6975 Copy the characters in @var{str} to the object file. You may specify more than
6976 one string to copy, separated by commas. Unless otherwise specified for a
6977 particular machine, the assembler marks the end of each string with a 0 byte.
6978 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6980 The variants @code{string16}, @code{string32} and @code{string64} differ from
6981 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6982 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6983 are stored in target endianness byte order.
6989 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6990 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6995 @section @code{.struct @var{expression}}
6997 @cindex @code{struct} directive
6998 Switch to the absolute section, and set the section offset to @var{expression},
6999 which must be an absolute expression. You might use this as follows:
7008 This would define the symbol @code{field1} to have the value 0, the symbol
7009 @code{field2} to have the value 4, and the symbol @code{field3} to have the
7010 value 8. Assembly would be left in the absolute section, and you would need to
7011 use a @code{.section} directive of some sort to change to some other section
7012 before further assembly.
7016 @section @code{.subsection @var{name}}
7018 @cindex @code{subsection} directive
7019 @cindex Section Stack
7020 This is one of the ELF section stack manipulation directives. The others are
7021 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
7022 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
7025 This directive replaces the current subsection with @code{name}. The current
7026 section is not changed. The replaced subsection is put onto the section stack
7027 in place of the then current top of stack subsection.
7032 @section @code{.symver}
7033 @cindex @code{symver} directive
7034 @cindex symbol versioning
7035 @cindex versions of symbols
7036 Use the @code{.symver} directive to bind symbols to specific version nodes
7037 within a source file. This is only supported on ELF platforms, and is
7038 typically used when assembling files to be linked into a shared library.
7039 There are cases where it may make sense to use this in objects to be bound
7040 into an application itself so as to override a versioned symbol from a
7043 For ELF targets, the @code{.symver} directive can be used like this:
7045 .symver @var{name}, @var{name2@@nodename}
7047 If the symbol @var{name} is defined within the file
7048 being assembled, the @code{.symver} directive effectively creates a symbol
7049 alias with the name @var{name2@@nodename}, and in fact the main reason that we
7050 just don't try and create a regular alias is that the @var{@@} character isn't
7051 permitted in symbol names. The @var{name2} part of the name is the actual name
7052 of the symbol by which it will be externally referenced. The name @var{name}
7053 itself is merely a name of convenience that is used so that it is possible to
7054 have definitions for multiple versions of a function within a single source
7055 file, and so that the compiler can unambiguously know which version of a
7056 function is being mentioned. The @var{nodename} portion of the alias should be
7057 the name of a node specified in the version script supplied to the linker when
7058 building a shared library. If you are attempting to override a versioned
7059 symbol from a shared library, then @var{nodename} should correspond to the
7060 nodename of the symbol you are trying to override.
7062 If the symbol @var{name} is not defined within the file being assembled, all
7063 references to @var{name} will be changed to @var{name2@@nodename}. If no
7064 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
7067 Another usage of the @code{.symver} directive is:
7069 .symver @var{name}, @var{name2@@@@nodename}
7071 In this case, the symbol @var{name} must exist and be defined within
7072 the file being assembled. It is similar to @var{name2@@nodename}. The
7073 difference is @var{name2@@@@nodename} will also be used to resolve
7074 references to @var{name2} by the linker.
7076 The third usage of the @code{.symver} directive is:
7078 .symver @var{name}, @var{name2@@@@@@nodename}
7080 When @var{name} is not defined within the
7081 file being assembled, it is treated as @var{name2@@nodename}. When
7082 @var{name} is defined within the file being assembled, the symbol
7083 name, @var{name}, will be changed to @var{name2@@@@nodename}.
7088 @section @code{.tag @var{structname}}
7090 @cindex COFF structure debugging
7091 @cindex structure debugging, COFF
7092 @cindex @code{tag} directive
7093 This directive is generated by compilers to include auxiliary debugging
7094 information in the symbol table. It is only permitted inside
7095 @code{.def}/@code{.endef} pairs. Tags are used to link structure
7096 definitions in the symbol table with instances of those structures.
7100 @section @code{.text @var{subsection}}
7102 @cindex @code{text} directive
7103 Tells @command{@value{AS}} to assemble the following statements onto the end of
7104 the text subsection numbered @var{subsection}, which is an absolute
7105 expression. If @var{subsection} is omitted, subsection number zero
7109 @section @code{.title "@var{heading}"}
7111 @cindex @code{title} directive
7112 @cindex listing control: title line
7113 Use @var{heading} as the title (second line, immediately after the
7114 source file name and pagenumber) when generating assembly listings.
7116 This directive affects subsequent pages, as well as the current page if
7117 it appears within ten lines of the top of a page.
7121 @section @code{.type}
7123 This directive is used to set the type of a symbol.
7127 @c only print the extra heading if both COFF and ELF are set
7128 @subheading COFF Version
7131 @cindex COFF symbol type
7132 @cindex symbol type, COFF
7133 @cindex @code{type} directive (COFF version)
7134 For COFF targets, this directive is permitted only within
7135 @code{.def}/@code{.endef} pairs. It is used like this:
7141 This records the integer @var{int} as the type attribute of a symbol table
7148 @c only print the extra heading if both COFF and ELF are set
7149 @subheading ELF Version
7152 @cindex ELF symbol type
7153 @cindex symbol type, ELF
7154 @cindex @code{type} directive (ELF version)
7155 For ELF targets, the @code{.type} directive is used like this:
7158 .type @var{name} , @var{type description}
7161 This sets the type of symbol @var{name} to be either a
7162 function symbol or an object symbol. There are five different syntaxes
7163 supported for the @var{type description} field, in order to provide
7164 compatibility with various other assemblers.
7166 Because some of the characters used in these syntaxes (such as @samp{@@} and
7167 @samp{#}) are comment characters for some architectures, some of the syntaxes
7168 below do not work on all architectures. The first variant will be accepted by
7169 the GNU assembler on all architectures so that variant should be used for
7170 maximum portability, if you do not need to assemble your code with other
7173 The syntaxes supported are:
7176 .type <name> STT_<TYPE_IN_UPPER_CASE>
7177 .type <name>,#<type>
7178 .type <name>,@@<type>
7179 .type <name>,%<type>
7180 .type <name>,"<type>"
7183 The types supported are:
7188 Mark the symbol as being a function name.
7191 @itemx gnu_indirect_function
7192 Mark the symbol as an indirect function when evaluated during reloc
7193 processing. (This is only supported on assemblers targeting GNU systems).
7197 Mark the symbol as being a data object.
7201 Mark the symbol as being a thread-local data object.
7205 Mark the symbol as being a common data object.
7209 Does not mark the symbol in any way. It is supported just for completeness.
7211 @item gnu_unique_object
7212 Marks the symbol as being a globally unique data object. The dynamic linker
7213 will make sure that in the entire process there is just one symbol with this
7214 name and type in use. (This is only supported on assemblers targeting GNU
7219 Changing between incompatible types other than from/to STT_NOTYPE will
7220 result in a diagnostic. An intermediate change to STT_NOTYPE will silence
7223 Note: Some targets support extra types in addition to those listed above.
7229 @section @code{.uleb128 @var{expressions}}
7231 @cindex @code{uleb128} directive
7232 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
7233 compact, variable length representation of numbers used by the DWARF
7234 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
7238 @section @code{.val @var{addr}}
7240 @cindex @code{val} directive
7241 @cindex COFF value attribute
7242 @cindex value attribute, COFF
7243 This directive, permitted only within @code{.def}/@code{.endef} pairs,
7244 records the address @var{addr} as the value attribute of a symbol table
7250 @section @code{.version "@var{string}"}
7252 @cindex @code{version} directive
7253 This directive creates a @code{.note} section and places into it an ELF
7254 formatted note of type NT_VERSION. The note's name is set to @code{string}.
7259 @section @code{.vtable_entry @var{table}, @var{offset}}
7261 @cindex @code{vtable_entry} directive
7262 This directive finds or creates a symbol @code{table} and creates a
7263 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
7266 @section @code{.vtable_inherit @var{child}, @var{parent}}
7268 @cindex @code{vtable_inherit} directive
7269 This directive finds the symbol @code{child} and finds or creates the symbol
7270 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
7271 parent whose addend is the value of the child symbol. As a special case the
7272 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
7276 @section @code{.warning "@var{string}"}
7277 @cindex warning directive
7278 Similar to the directive @code{.error}
7279 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7282 @section @code{.weak @var{names}}
7284 @cindex @code{weak} directive
7285 This directive sets the weak attribute on the comma separated list of symbol
7286 @code{names}. If the symbols do not already exist, they will be created.
7288 On COFF targets other than PE, weak symbols are a GNU extension. This
7289 directive sets the weak attribute on the comma separated list of symbol
7290 @code{names}. If the symbols do not already exist, they will be created.
7292 On the PE target, weak symbols are supported natively as weak aliases.
7293 When a weak symbol is created that is not an alias, GAS creates an
7294 alternate symbol to hold the default value.
7297 @section @code{.weakref @var{alias}, @var{target}}
7299 @cindex @code{weakref} directive
7300 This directive creates an alias to the target symbol that enables the symbol to
7301 be referenced with weak-symbol semantics, but without actually making it weak.
7302 If direct references or definitions of the symbol are present, then the symbol
7303 will not be weak, but if all references to it are through weak references, the
7304 symbol will be marked as weak in the symbol table.
7306 The effect is equivalent to moving all references to the alias to a separate
7307 assembly source file, renaming the alias to the symbol in it, declaring the
7308 symbol as weak there, and running a reloadable link to merge the object files
7309 resulting from the assembly of the new source file and the old source file that
7310 had the references to the alias removed.
7312 The alias itself never makes to the symbol table, and is entirely handled
7313 within the assembler.
7316 @section @code{.word @var{expressions}}
7318 @cindex @code{word} directive
7319 This directive expects zero or more @var{expressions}, of any section,
7320 separated by commas.
7323 For each expression, @command{@value{AS}} emits a 32-bit number.
7326 For each expression, @command{@value{AS}} emits a 16-bit number.
7331 The size of the number emitted, and its byte order,
7332 depend on what target computer the assembly is for.
7335 @c on sparc the "special treatment to support compilers" doesn't
7336 @c happen---32-bit addressability, period; no long/short jumps.
7337 @ifset DIFF-TBL-KLUGE
7338 @cindex difference tables altered
7339 @cindex altered difference tables
7341 @emph{Warning: Special Treatment to support Compilers}
7345 Machines with a 32-bit address space, but that do less than 32-bit
7346 addressing, require the following special treatment. If the machine of
7347 interest to you does 32-bit addressing (or doesn't require it;
7348 @pxref{Machine Dependencies}), you can ignore this issue.
7351 In order to assemble compiler output into something that works,
7352 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7353 Directives of the form @samp{.word sym1-sym2} are often emitted by
7354 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7355 directive of the form @samp{.word sym1-sym2}, and the difference between
7356 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7357 creates a @dfn{secondary jump table}, immediately before the next label.
7358 This secondary jump table is preceded by a short-jump to the
7359 first byte after the secondary table. This short-jump prevents the flow
7360 of control from accidentally falling into the new table. Inside the
7361 table is a long-jump to @code{sym2}. The original @samp{.word}
7362 contains @code{sym1} minus the address of the long-jump to
7365 If there were several occurrences of @samp{.word sym1-sym2} before the
7366 secondary jump table, all of them are adjusted. If there was a
7367 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7368 long-jump to @code{sym4} is included in the secondary jump table,
7369 and the @code{.word} directives are adjusted to contain @code{sym3}
7370 minus the address of the long-jump to @code{sym4}; and so on, for as many
7371 entries in the original jump table as necessary.
7374 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7375 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7376 assembly language programmers.
7379 @c end DIFF-TBL-KLUGE
7381 @ifclear no-space-dir
7383 @section @code{.zero @var{size}}
7385 @cindex @code{zero} directive
7386 @cindex filling memory with zero bytes
7387 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7388 expression. This directive is actually an alias for the @samp{.skip} directive
7389 so it can take an optional second argument of the value to store in the bytes
7390 instead of zero. Using @samp{.zero} in this way would be confusing however.
7395 @section @code{.2byte @var{expression} [, @var{expression}]*}
7396 @cindex @code{2byte} directive
7397 @cindex two-byte integer
7398 @cindex integer, 2-byte
7400 This directive expects zero or more expressions, separated by commas. If there
7401 are no expressions then the directive does nothing. Otherwise each expression
7402 is evaluated in turn and placed in the next two bytes of the current output
7403 section, using the endian model of the target. If an expression will not fit
7404 in two bytes, a warning message is displayed and the least significant two
7405 bytes of the expression's value are used. If an expression cannot be evaluated
7406 at assembly time then relocations will be generated in order to compute the
7409 This directive does not apply any alignment before or after inserting the
7410 values. As a result of this, if relocations are generated, they may be
7411 different from those used for inserting values with a guaranteed alignment.
7413 This directive is only available for ELF targets,
7416 @section @code{.4byte @var{expression} [, @var{expression}]*}
7417 @cindex @code{4byte} directive
7418 @cindex four-byte integer
7419 @cindex integer, 4-byte
7421 Like the @option{.2byte} directive, except that it inserts unaligned, four byte
7422 long values into the output.
7425 @section @code{.8byte @var{expression} [, @var{expression}]*}
7426 @cindex @code{8byte} directive
7427 @cindex eight-byte integer
7428 @cindex integer, 8-byte
7430 Like the @option{.2byte} directive, except that it inserts unaligned, eight
7431 byte long bignum values into the output.
7436 @section Deprecated Directives
7438 @cindex deprecated directives
7439 @cindex obsolescent directives
7440 One day these directives won't work.
7441 They are included for compatibility with older assemblers.
7448 @node Object Attributes
7449 @chapter Object Attributes
7450 @cindex object attributes
7452 @command{@value{AS}} assembles source files written for a specific architecture
7453 into object files for that architecture. But not all object files are alike.
7454 Many architectures support incompatible variations. For instance, floating
7455 point arguments might be passed in floating point registers if the object file
7456 requires hardware floating point support---or floating point arguments might be
7457 passed in integer registers if the object file supports processors with no
7458 hardware floating point unit. Or, if two objects are built for different
7459 generations of the same architecture, the combination may require the
7460 newer generation at run-time.
7462 This information is useful during and after linking. At link time,
7463 @command{@value{LD}} can warn about incompatible object files. After link
7464 time, tools like @command{gdb} can use it to process the linked file
7467 Compatibility information is recorded as a series of object attributes. Each
7468 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7469 string, and indicates who sets the meaning of the tag. The tag is an integer,
7470 and indicates what property the attribute describes. The value may be a string
7471 or an integer, and indicates how the property affects this object. Missing
7472 attributes are the same as attributes with a zero value or empty string value.
7474 Object attributes were developed as part of the ABI for the ARM Architecture.
7475 The file format is documented in @cite{ELF for the ARM Architecture}.
7478 * GNU Object Attributes:: @sc{gnu} Object Attributes
7479 * Defining New Object Attributes:: Defining New Object Attributes
7482 @node GNU Object Attributes
7483 @section @sc{gnu} Object Attributes
7485 The @code{.gnu_attribute} directive records an object attribute
7486 with vendor @samp{gnu}.
7488 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7489 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7490 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7491 2} is set for architecture-independent attributes and clear for
7492 architecture-dependent ones.
7494 @subsection Common @sc{gnu} attributes
7496 These attributes are valid on all architectures.
7499 @item Tag_compatibility (32)
7500 The compatibility attribute takes an integer flag value and a vendor name. If
7501 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7502 then the file is only compatible with the named toolchain. If it is greater
7503 than 1, the file can only be processed by other toolchains under some private
7504 arrangement indicated by the flag value and the vendor name.
7507 @subsection MIPS Attributes
7510 @item Tag_GNU_MIPS_ABI_FP (4)
7511 The floating-point ABI used by this object file. The value will be:
7515 0 for files not affected by the floating-point ABI.
7517 1 for files using the hardware floating-point ABI with a standard
7518 double-precision FPU.
7520 2 for files using the hardware floating-point ABI with a single-precision FPU.
7522 3 for files using the software floating-point ABI.
7524 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7525 floating-point registers, 32-bit general-purpose registers and increased the
7526 number of callee-saved floating-point registers.
7528 5 for files using the hardware floating-point ABI with a double-precision FPU
7529 with either 32-bit or 64-bit floating-point registers and 32-bit
7530 general-purpose registers.
7532 6 for files using the hardware floating-point ABI with 64-bit floating-point
7533 registers and 32-bit general-purpose registers.
7535 7 for files using the hardware floating-point ABI with 64-bit floating-point
7536 registers, 32-bit general-purpose registers and a rule that forbids the
7537 direct use of odd-numbered single-precision floating-point registers.
7541 @subsection PowerPC Attributes
7544 @item Tag_GNU_Power_ABI_FP (4)
7545 The floating-point ABI used by this object file. The value will be:
7549 0 for files not affected by the floating-point ABI.
7551 1 for files using double-precision hardware floating-point ABI.
7553 2 for files using the software floating-point ABI.
7555 3 for files using single-precision hardware floating-point ABI.
7558 @item Tag_GNU_Power_ABI_Vector (8)
7559 The vector ABI used by this object file. The value will be:
7563 0 for files not affected by the vector ABI.
7565 1 for files using general purpose registers to pass vectors.
7567 2 for files using AltiVec registers to pass vectors.
7569 3 for files using SPE registers to pass vectors.
7573 @subsection IBM z Systems Attributes
7576 @item Tag_GNU_S390_ABI_Vector (8)
7577 The vector ABI used by this object file. The value will be:
7581 0 for files not affected by the vector ABI.
7583 1 for files using software vector ABI.
7585 2 for files using hardware vector ABI.
7589 @subsection MSP430 Attributes
7592 @item Tag_GNU_MSP430_Data_Region (4)
7593 The data region used by this object file. The value will be:
7597 0 for files not using the large memory model.
7599 1 for files which have been compiled with the condition that all
7600 data is in the lower memory region, i.e. below address 0x10000.
7602 2 for files which allow data to be placed in the full 20-bit memory range.
7606 @node Defining New Object Attributes
7607 @section Defining New Object Attributes
7609 If you want to define a new @sc{gnu} object attribute, here are the places you
7610 will need to modify. New attributes should be discussed on the @samp{binutils}
7615 This manual, which is the official register of attributes.
7617 The header for your architecture @file{include/elf}, to define the tag.
7619 The @file{bfd} support file for your architecture, to merge the attribute
7620 and issue any appropriate link warnings.
7622 Test cases in @file{ld/testsuite} for merging and link warnings.
7624 @file{binutils/readelf.c} to display your attribute.
7626 GCC, if you want the compiler to mark the attribute automatically.
7632 @node Machine Dependencies
7633 @chapter Machine Dependent Features
7635 @cindex machine dependencies
7636 The machine instruction sets are (almost by definition) different on
7637 each machine where @command{@value{AS}} runs. Floating point representations
7638 vary as well, and @command{@value{AS}} often supports a few additional
7639 directives or command-line options for compatibility with other
7640 assemblers on a particular platform. Finally, some versions of
7641 @command{@value{AS}} support special pseudo-instructions for branch
7644 This chapter discusses most of these differences, though it does not
7645 include details on any machine's instruction set. For details on that
7646 subject, see the hardware manufacturer's manual.
7650 * AArch64-Dependent:: AArch64 Dependent Features
7653 * Alpha-Dependent:: Alpha Dependent Features
7656 * ARC-Dependent:: ARC Dependent Features
7659 * ARM-Dependent:: ARM Dependent Features
7662 * AVR-Dependent:: AVR Dependent Features
7665 * Blackfin-Dependent:: Blackfin Dependent Features
7668 * BPF-Dependent:: BPF Dependent Features
7671 * CR16-Dependent:: CR16 Dependent Features
7674 * CRIS-Dependent:: CRIS Dependent Features
7677 * C-SKY-Dependent:: C-SKY Dependent Features
7680 * D10V-Dependent:: D10V Dependent Features
7683 * D30V-Dependent:: D30V Dependent Features
7686 * Epiphany-Dependent:: EPIPHANY Dependent Features
7689 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7692 * HPPA-Dependent:: HPPA Dependent Features
7695 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7698 * IA-64-Dependent:: Intel IA-64 Dependent Features
7701 * IP2K-Dependent:: IP2K Dependent Features
7704 * LM32-Dependent:: LM32 Dependent Features
7707 * M32C-Dependent:: M32C Dependent Features
7710 * M32R-Dependent:: M32R Dependent Features
7713 * M68K-Dependent:: M680x0 Dependent Features
7716 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7719 * S12Z-Dependent:: S12Z Dependent Features
7722 * Meta-Dependent :: Meta Dependent Features
7725 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7728 * MIPS-Dependent:: MIPS Dependent Features
7731 * MMIX-Dependent:: MMIX Dependent Features
7734 * MSP430-Dependent:: MSP430 Dependent Features
7737 * NDS32-Dependent:: Andes NDS32 Dependent Features
7740 * NiosII-Dependent:: Altera Nios II Dependent Features
7743 * NS32K-Dependent:: NS32K Dependent Features
7746 * OpenRISC-Dependent:: OpenRISC 1000 Features
7749 * PDP-11-Dependent:: PDP-11 Dependent Features
7752 * PJ-Dependent:: picoJava Dependent Features
7755 * PPC-Dependent:: PowerPC Dependent Features
7758 * PRU-Dependent:: PRU Dependent Features
7761 * RISC-V-Dependent:: RISC-V Dependent Features
7764 * RL78-Dependent:: RL78 Dependent Features
7767 * RX-Dependent:: RX Dependent Features
7770 * S/390-Dependent:: IBM S/390 Dependent Features
7773 * SCORE-Dependent:: SCORE Dependent Features
7776 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7779 * Sparc-Dependent:: SPARC Dependent Features
7782 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7785 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7788 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7791 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7794 * V850-Dependent:: V850 Dependent Features
7797 * Vax-Dependent:: VAX Dependent Features
7800 * Visium-Dependent:: Visium Dependent Features
7803 * WebAssembly-Dependent:: WebAssembly Dependent Features
7806 * XGATE-Dependent:: XGATE Dependent Features
7809 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7812 * Xtensa-Dependent:: Xtensa Dependent Features
7815 * Z80-Dependent:: Z80 Dependent Features
7818 * Z8000-Dependent:: Z8000 Dependent Features
7825 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7826 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7827 @c peculiarity: to preserve cross-references, there must be a node called
7828 @c "Machine Dependencies". Hence the conditional nodenames in each
7829 @c major node below. Node defaulting in makeinfo requires adjacency of
7830 @c node and sectioning commands; hence the repetition of @chapter BLAH
7831 @c in both conditional blocks.
7834 @include c-aarch64.texi
7838 @include c-alpha.texi
7854 @include c-bfin.texi
7862 @include c-cr16.texi
7866 @include c-cris.texi
7870 @include c-csky.texi
7875 @node Machine Dependencies
7876 @chapter Machine Dependent Features
7878 The machine instruction sets are different on each Renesas chip family,
7879 and there are also some syntax differences among the families. This
7880 chapter describes the specific @command{@value{AS}} features for each
7884 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7885 * SH-Dependent:: Renesas SH Dependent Features
7892 @include c-d10v.texi
7896 @include c-d30v.texi
7900 @include c-epiphany.texi
7904 @include c-h8300.texi
7908 @include c-hppa.texi
7912 @include c-i386.texi
7916 @include c-ia64.texi
7920 @include c-ip2k.texi
7924 @include c-lm32.texi
7928 @include c-m32c.texi
7932 @include c-m32r.texi
7936 @include c-m68k.texi
7940 @include c-m68hc11.texi
7944 @include c-s12z.texi
7948 @include c-metag.texi
7952 @include c-microblaze.texi
7956 @include c-mips.texi
7960 @include c-mmix.texi
7964 @include c-msp430.texi
7968 @include c-nds32.texi
7972 @include c-nios2.texi
7976 @include c-ns32k.texi
7980 @include c-or1k.texi
7984 @include c-pdp11.texi
8000 @include c-riscv.texi
8004 @include c-rl78.texi
8012 @include c-s390.texi
8016 @include c-score.texi
8024 @include c-sparc.texi
8028 @include c-tic54x.texi
8032 @include c-tic6x.texi
8036 @include c-tilegx.texi
8040 @include c-tilepro.texi
8044 @include c-v850.texi
8052 @include c-visium.texi
8056 @include c-wasm32.texi
8060 @include c-xgate.texi
8064 @include c-xstormy16.texi
8068 @include c-xtensa.texi
8080 @c reverse effect of @down at top of generic Machine-Dep chapter
8084 @node Reporting Bugs
8085 @chapter Reporting Bugs
8086 @cindex bugs in assembler
8087 @cindex reporting bugs in assembler
8089 Your bug reports play an essential role in making @command{@value{AS}} reliable.
8091 Reporting a bug may help you by bringing a solution to your problem, or it may
8092 not. But in any case the principal function of a bug report is to help the
8093 entire community by making the next version of @command{@value{AS}} work better.
8094 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
8096 In order for a bug report to serve its purpose, you must include the
8097 information that enables us to fix the bug.
8100 * Bug Criteria:: Have you found a bug?
8101 * Bug Reporting:: How to report bugs
8105 @section Have You Found a Bug?
8106 @cindex bug criteria
8108 If you are not sure whether you have found a bug, here are some guidelines:
8111 @cindex fatal signal
8112 @cindex assembler crash
8113 @cindex crash of assembler
8115 If the assembler gets a fatal signal, for any input whatever, that is a
8116 @command{@value{AS}} bug. Reliable assemblers never crash.
8118 @cindex error on valid input
8120 If @command{@value{AS}} produces an error message for valid input, that is a bug.
8122 @cindex invalid input
8124 If @command{@value{AS}} does not produce an error message for invalid input, that
8125 is a bug. However, you should note that your idea of ``invalid input'' might
8126 be our idea of ``an extension'' or ``support for traditional practice''.
8129 If you are an experienced user of assemblers, your suggestions for improvement
8130 of @command{@value{AS}} are welcome in any case.
8134 @section How to Report Bugs
8136 @cindex assembler bugs, reporting
8138 A number of companies and individuals offer support for @sc{gnu} products. If
8139 you obtained @command{@value{AS}} from a support organization, we recommend you
8140 contact that organization first.
8142 You can find contact information for many support companies and
8143 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
8147 In any event, we also recommend that you send bug reports for @command{@value{AS}}
8151 The fundamental principle of reporting bugs usefully is this:
8152 @strong{report all the facts}. If you are not sure whether to state a
8153 fact or leave it out, state it!
8155 Often people omit facts because they think they know what causes the problem
8156 and assume that some details do not matter. Thus, you might assume that the
8157 name of a symbol you use in an example does not matter. Well, probably it does
8158 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
8159 happens to fetch from the location where that name is stored in memory;
8160 perhaps, if the name were different, the contents of that location would fool
8161 the assembler into doing the right thing despite the bug. Play it safe and
8162 give a specific, complete example. That is the easiest thing for you to do,
8163 and the most helpful.
8165 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
8166 it is new to us. Therefore, always write your bug reports on the assumption
8167 that the bug has not been reported previously.
8169 Sometimes people give a few sketchy facts and ask, ``Does this ring a
8170 bell?'' This cannot help us fix a bug, so it is basically useless. We
8171 respond by asking for enough details to enable us to investigate.
8172 You might as well expedite matters by sending them to begin with.
8174 To enable us to fix the bug, you should include all these things:
8178 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
8179 it with the @samp{--version} argument.
8181 Without this, we will not know whether there is any point in looking for
8182 the bug in the current version of @command{@value{AS}}.
8185 Any patches you may have applied to the @command{@value{AS}} source.
8188 The type of machine you are using, and the operating system name and
8192 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
8196 The command arguments you gave the assembler to assemble your example and
8197 observe the bug. To guarantee you will not omit something important, list them
8198 all. A copy of the Makefile (or the output from make) is sufficient.
8200 If we were to try to guess the arguments, we would probably guess wrong
8201 and then we might not encounter the bug.
8204 A complete input file that will reproduce the bug. If the bug is observed when
8205 the assembler is invoked via a compiler, send the assembler source, not the
8206 high level language source. Most compilers will produce the assembler source
8207 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
8208 the options @samp{-v --save-temps}; this will save the assembler source in a
8209 file with an extension of @file{.s}, and also show you exactly how
8210 @command{@value{AS}} is being run.
8213 A description of what behavior you observe that you believe is
8214 incorrect. For example, ``It gets a fatal signal.''
8216 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
8217 will certainly notice it. But if the bug is incorrect output, we might not
8218 notice unless it is glaringly wrong. You might as well not give us a chance to
8221 Even if the problem you experience is a fatal signal, you should still say so
8222 explicitly. Suppose something strange is going on, such as, your copy of
8223 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
8224 library on your system. (This has happened!) Your copy might crash and ours
8225 would not. If you told us to expect a crash, then when ours fails to crash, we
8226 would know that the bug was not happening for us. If you had not told us to
8227 expect a crash, then we would not be able to draw any conclusion from our
8231 If you wish to suggest changes to the @command{@value{AS}} source, send us context
8232 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
8233 option. Always send diffs from the old file to the new file. If you even
8234 discuss something in the @command{@value{AS}} source, refer to it by context, not
8237 The line numbers in our development sources will not match those in your
8238 sources. Your line numbers would convey no useful information to us.
8241 Here are some things that are not necessary:
8245 A description of the envelope of the bug.
8247 Often people who encounter a bug spend a lot of time investigating
8248 which changes to the input file will make the bug go away and which
8249 changes will not affect it.
8251 This is often time consuming and not very useful, because the way we
8252 will find the bug is by running a single example under the debugger
8253 with breakpoints, not by pure deduction from a series of examples.
8254 We recommend that you save your time for something else.
8256 Of course, if you can find a simpler example to report @emph{instead}
8257 of the original one, that is a convenience for us. Errors in the
8258 output will be easier to spot, running under the debugger will take
8259 less time, and so on.
8261 However, simplification is not vital; if you do not want to do this,
8262 report the bug anyway and send us the entire test case you used.
8265 A patch for the bug.
8267 A patch for the bug does help us if it is a good one. But do not omit
8268 the necessary information, such as the test case, on the assumption that
8269 a patch is all we need. We might see problems with your patch and decide
8270 to fix the problem another way, or we might not understand it at all.
8272 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
8273 construct an example that will make the program follow a certain path through
8274 the code. If you do not send us the example, we will not be able to construct
8275 one, so we will not be able to verify that the bug is fixed.
8277 And if we cannot understand what bug you are trying to fix, or why your
8278 patch should be an improvement, we will not install it. A test case will
8279 help us to understand.
8282 A guess about what the bug is or what it depends on.
8284 Such guesses are usually wrong. Even we cannot guess right about such
8285 things without first using the debugger to find the facts.
8288 @node Acknowledgements
8289 @chapter Acknowledgements
8291 If you have contributed to GAS and your name isn't listed here,
8292 it is not meant as a slight. We just don't know about it. Send mail to the
8293 maintainer, and we'll correct the situation. Currently
8295 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
8297 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
8300 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
8301 information and the 68k series machines, most of the preprocessing pass, and
8302 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
8304 K. Richard Pixley maintained GAS for a while, adding various enhancements and
8305 many bug fixes, including merging support for several processors, breaking GAS
8306 up to handle multiple object file format back ends (including heavy rewrite,
8307 testing, an integration of the coff and b.out back ends), adding configuration
8308 including heavy testing and verification of cross assemblers and file splits
8309 and renaming, converted GAS to strictly ANSI C including full prototypes, added
8310 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
8311 port (including considerable amounts of reverse engineering), a SPARC opcode
8312 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
8313 assertions and made them work, much other reorganization, cleanup, and lint.
8315 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
8316 in format-specific I/O modules.
8318 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
8319 has done much work with it since.
8321 The Intel 80386 machine description was written by Eliot Dresselhaus.
8323 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
8325 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
8326 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
8328 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
8329 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
8330 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
8331 support a.out format.
8333 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
8334 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
8335 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
8336 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
8339 John Gilmore built the AMD 29000 support, added @code{.include} support, and
8340 simplified the configuration of which versions accept which directives. He
8341 updated the 68k machine description so that Motorola's opcodes always produced
8342 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
8343 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
8344 cross-compilation support, and one bug in relaxation that took a week and
8345 required the proverbial one-bit fix.
8347 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
8348 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
8349 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
8350 PowerPC assembler, and made a few other minor patches.
8352 Steve Chamberlain made GAS able to generate listings.
8354 Hewlett-Packard contributed support for the HP9000/300.
8356 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
8357 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
8358 formats). This work was supported by both the Center for Software Science at
8359 the University of Utah and Cygnus Support.
8361 Support for ELF format files has been worked on by Mark Eichin of Cygnus
8362 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
8363 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
8364 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
8365 and some initial 64-bit support).
8367 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8369 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8370 support for openVMS/Alpha.
8372 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8375 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8376 Inc.@: added support for Xtensa processors.
8378 Several engineers at Cygnus Support have also provided many small bug fixes and
8379 configuration enhancements.
8381 Jon Beniston added support for the Lattice Mico32 architecture.
8383 Many others have contributed large or small bugfixes and enhancements. If
8384 you have contributed significant work and are not mentioned on this list, and
8385 want to be, let us know. Some of the history has been lost; we are not
8386 intentionally leaving anyone out.
8388 @node GNU Free Documentation License
8389 @appendix GNU Free Documentation License
8393 @unnumbered AS Index