1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (C) 1991-2020 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{} 1991-2020 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{} 1991-2020 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-<N>}] [@b{--gdwarf-sections}]
234 [@b{--gdwarf-cie-version}=@var{VERSION}]
235 [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
236 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
237 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
238 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}]
239 [@b{--no-pad-sections}]
240 [@b{-o} @var{objfile}] [@b{-R}]
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}]
628 [@b{--abi-windowed}|@b{--abi-call0}]
632 @emph{Target Z80 options:}
633 [@b{-march=@var{CPU}@var{[-EXT]}@var{[+EXT]}}]
634 [@b{-local-prefix=}@var{PREFIX}]
637 [@b{-fp-s=}@var{FORMAT}]
638 [@b{-fp-d=}@var{FORMAT}]
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,
748 ECOFF or DWARF2. When the debug format is DWARF then a @code{.debug_info} and
749 @code{.debug_line} section is only emitted when the assembly file doesn't
753 Generate stabs debugging information for each assembler line. This
754 may help debugging assembler code, if the debugger can handle it.
757 Generate stabs debugging information for each assembler line, with GNU
758 extensions that probably only gdb can handle, and that could make other
759 debuggers crash or refuse to read your program. This
760 may help debugging assembler code. Currently the only GNU extension is
761 the location of the current working directory at assembling time.
764 Generate DWARF2 debugging information for each assembler line. This
765 may help debugging assembler code, if the debugger can handle it. Note---this
766 option is only supported by some targets, not all of them.
769 This option is the same as the @option{--gdwarf-2} option, except that it
770 allows for the possibility of the generation of extra debug information as per
771 version 3 of the DWARF specification. Note - enabling this option does not
772 guarantee the generation of any extra information, the choice to do so is on a
776 This option is the same as the @option{--gdwarf-2} option, except that it
777 allows for the possibility of the generation of extra debug information as per
778 version 4 of the DWARF specification. Note - enabling this option does not
779 guarantee the generation of any extra information, the choice to do so is on a
783 This option is the same as the @option{--gdwarf-2} option, except that it
784 allows for the possibility of the generation of extra debug information as per
785 version 5 of the DWARF specification. Note - enabling this option does not
786 guarantee the generation of any extra information, the choice to do so is on a
789 @item --gdwarf-sections
790 Instead of creating a .debug_line section, create a series of
791 .debug_line.@var{foo} sections where @var{foo} is the name of the
792 corresponding code section. For example a code section called @var{.text.func}
793 will have its dwarf line number information placed into a section called
794 @var{.debug_line.text.func}. If the code section is just called @var{.text}
795 then debug line section will still be called just @var{.debug_line} without any
798 @item --gdwarf-cie-version=@var{version}
799 Control which version of DWARF Common Information Entries (CIEs) are produced.
800 When this flag is not specificed the default is version 1, though some targets
801 can modify this default. Other possible values for @var{version} are 3 or 4.
804 @item --size-check=error
805 @itemx --size-check=warning
806 Issue an error or warning for invalid ELF .size directive.
808 @item --elf-stt-common=no
809 @itemx --elf-stt-common=yes
810 These options control whether the ELF assembler should generate common
811 symbols with the @code{STT_COMMON} type. The default can be controlled
812 by a configure option @option{--enable-elf-stt-common}.
814 @item --generate-missing-build-notes=yes
815 @itemx --generate-missing-build-notes=no
816 These options control whether the ELF assembler should generate GNU Build
817 attribute notes if none are present in the input sources.
818 The default can be controlled by the @option{--enable-generate-build-notes}
824 Print a summary of the command-line options and exit.
827 Print a summary of all target specific options and exit.
830 Add directory @var{dir} to the search list for @code{.include} directives.
833 Don't warn about signed overflow.
836 @ifclear DIFF-TBL-KLUGE
837 This option is accepted but has no effect on the @value{TARGET} family.
839 @ifset DIFF-TBL-KLUGE
840 Issue warnings when difference tables altered for long displacements.
845 Keep (in the symbol table) local symbols. These symbols start with
846 system-specific local label prefixes, typically @samp{.L} for ELF systems
847 or @samp{L} for traditional a.out systems.
852 @item --listing-lhs-width=@var{number}
853 Set the maximum width, in words, of the output data column for an assembler
854 listing to @var{number}.
856 @item --listing-lhs-width2=@var{number}
857 Set the maximum width, in words, of the output data column for continuation
858 lines in an assembler listing to @var{number}.
860 @item --listing-rhs-width=@var{number}
861 Set the maximum width of an input source line, as displayed in a listing, to
864 @item --listing-cont-lines=@var{number}
865 Set the maximum number of lines printed in a listing for a single line of input
868 @item --no-pad-sections
869 Stop the assembler for padding the ends of output sections to the alignment
870 of that section. The default is to pad the sections, but this can waste space
871 which might be needed on targets which have tight memory constraints.
873 @item -o @var{objfile}
874 Name the object-file output from @command{@value{AS}} @var{objfile}.
877 Fold the data section into the text section.
880 @item --sectname-subst
881 Honor substitution sequences in section names.
883 @xref{Section Name Substitutions,,@code{.section @var{name}}}.
888 Print the maximum space (in bytes) and total time (in seconds) used by
891 @item --strip-local-absolute
892 Remove local absolute symbols from the outgoing symbol table.
896 Print the @command{as} version.
899 Print the @command{as} version and exit.
903 Suppress warning messages.
905 @item --fatal-warnings
906 Treat warnings as errors.
909 Don't suppress warning messages or treat them as errors.
918 Generate an object file even after errors.
920 @item -- | @var{files} @dots{}
921 Standard input, or source files to assemble.
929 @xref{AArch64 Options}, for the options available when @value{AS} is configured
930 for the 64-bit mode of the ARM Architecture (AArch64).
935 The following options are available when @value{AS} is configured for the
936 64-bit mode of the ARM Architecture (AArch64).
939 @include c-aarch64.texi
940 @c ended inside the included file
948 @xref{Alpha Options}, for the options available when @value{AS} is configured
949 for an Alpha processor.
954 The following options are available when @value{AS} is configured for an Alpha
958 @include c-alpha.texi
959 @c ended inside the included file
966 The following options are available when @value{AS} is configured for an ARC
970 @item -mcpu=@var{cpu}
971 This option selects the core processor variant.
973 Select either big-endian (-EB) or little-endian (-EL) output.
975 Enable Code Density extension instructions.
980 The following options are available when @value{AS} is configured for the ARM
984 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
985 Specify which ARM processor variant is the target.
986 @item -march=@var{architecture}[+@var{extension}@dots{}]
987 Specify which ARM architecture variant is used by the target.
988 @item -mfpu=@var{floating-point-format}
989 Select which Floating Point architecture is the target.
990 @item -mfloat-abi=@var{abi}
991 Select which floating point ABI is in use.
993 Enable Thumb only instruction decoding.
994 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
995 Select which procedure calling convention is in use.
997 Select either big-endian (-EB) or little-endian (-EL) output.
998 @item -mthumb-interwork
999 Specify that the code has been generated with interworking between Thumb and
1002 Turns on CodeComposer Studio assembly syntax compatibility mode.
1004 Specify that PIC code has been generated.
1012 @xref{Blackfin Options}, for the options available when @value{AS} is
1013 configured for the Blackfin processor family.
1017 @c man begin OPTIONS
1018 The following options are available when @value{AS} is configured for
1019 the Blackfin processor family.
1021 @c man begin INCLUDE
1022 @include c-bfin.texi
1023 @c ended inside the included file
1031 @xref{BPF Options}, for the options available when @value{AS} is
1032 configured for the Linux kernel BPF processor family.
1036 @c man begin OPTIONS
1037 The following options are available when @value{AS} is configured for
1038 the Linux kernel BPF processor family.
1040 @c man begin INCLUDE
1042 @c ended inside the included file
1047 @c man begin OPTIONS
1049 See the info pages for documentation of the CRIS-specific options.
1055 @xref{C-SKY Options}, for the options available when @value{AS} is
1056 configured for the C-SKY processor family.
1060 @c man begin OPTIONS
1061 The following options are available when @value{AS} is configured for
1062 the C-SKY processor family.
1064 @c man begin INCLUDE
1065 @include c-csky.texi
1066 @c ended inside the included file
1072 The following options are available when @value{AS} is configured for
1075 @cindex D10V optimization
1076 @cindex optimization, D10V
1078 Optimize output by parallelizing instructions.
1083 The following options are available when @value{AS} is configured for a D30V
1086 @cindex D30V optimization
1087 @cindex optimization, D30V
1089 Optimize output by parallelizing instructions.
1093 Warn when nops are generated.
1095 @cindex D30V nops after 32-bit multiply
1097 Warn when a nop after a 32-bit multiply instruction is generated.
1103 The following options are available when @value{AS} is configured for the
1104 Adapteva EPIPHANY series.
1107 @xref{Epiphany Options}, for the options available when @value{AS} is
1108 configured for an Epiphany processor.
1112 @c man begin OPTIONS
1113 The following options are available when @value{AS} is configured for
1114 an Epiphany processor.
1116 @c man begin INCLUDE
1117 @include c-epiphany.texi
1118 @c ended inside the included file
1126 @xref{H8/300 Options}, for the options available when @value{AS} is configured
1127 for an H8/300 processor.
1131 @c man begin OPTIONS
1132 The following options are available when @value{AS} is configured for an H8/300
1135 @c man begin INCLUDE
1136 @include c-h8300.texi
1137 @c ended inside the included file
1145 @xref{i386-Options}, for the options available when @value{AS} is
1146 configured for an i386 processor.
1150 @c man begin OPTIONS
1151 The following options are available when @value{AS} is configured for
1154 @c man begin INCLUDE
1155 @include c-i386.texi
1156 @c ended inside the included file
1161 @c man begin OPTIONS
1163 The following options are available when @value{AS} is configured for the
1169 Specifies that the extended IP2022 instructions are allowed.
1172 Restores the default behaviour, which restricts the permitted instructions to
1173 just the basic IP2022 ones.
1179 The following options are available when @value{AS} is configured for the
1180 Renesas M32C and M16C processors.
1185 Assemble M32C instructions.
1188 Assemble M16C instructions (the default).
1191 Enable support for link-time relaxations.
1194 Support H'00 style hex constants in addition to 0x00 style.
1200 The following options are available when @value{AS} is configured for the
1201 Renesas M32R (formerly Mitsubishi M32R) series.
1206 Specify which processor in the M32R family is the target. The default
1207 is normally the M32R, but this option changes it to the M32RX.
1209 @item --warn-explicit-parallel-conflicts or --Wp
1210 Produce warning messages when questionable parallel constructs are
1213 @item --no-warn-explicit-parallel-conflicts or --Wnp
1214 Do not produce warning messages when questionable parallel constructs are
1221 The following options are available when @value{AS} is configured for the
1222 Motorola 68000 series.
1227 Shorten references to undefined symbols, to one word instead of two.
1229 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1230 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1231 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1232 Specify what processor in the 68000 family is the target. The default
1233 is normally the 68020, but this can be changed at configuration time.
1235 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1236 The target machine does (or does not) have a floating-point coprocessor.
1237 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1238 the basic 68000 is not compatible with the 68881, a combination of the
1239 two can be specified, since it's possible to do emulation of the
1240 coprocessor instructions with the main processor.
1242 @item -m68851 | -mno-68851
1243 The target machine does (or does not) have a memory-management
1244 unit coprocessor. The default is to assume an MMU for 68020 and up.
1252 @xref{Nios II Options}, for the options available when @value{AS} is configured
1253 for an Altera Nios II processor.
1257 @c man begin OPTIONS
1258 The following options are available when @value{AS} is configured for an
1259 Altera Nios II processor.
1261 @c man begin INCLUDE
1262 @include c-nios2.texi
1263 @c ended inside the included file
1269 For details about the PDP-11 machine dependent features options,
1270 see @ref{PDP-11-Options}.
1273 @item -mpic | -mno-pic
1274 Generate position-independent (or position-dependent) code. The
1275 default is @option{-mpic}.
1278 @itemx -mall-extensions
1279 Enable all instruction set extensions. This is the default.
1281 @item -mno-extensions
1282 Disable all instruction set extensions.
1284 @item -m@var{extension} | -mno-@var{extension}
1285 Enable (or disable) a particular instruction set extension.
1288 Enable the instruction set extensions supported by a particular CPU, and
1289 disable all other extensions.
1291 @item -m@var{machine}
1292 Enable the instruction set extensions supported by a particular machine
1293 model, and disable all other extensions.
1299 The following options are available when @value{AS} is configured for
1300 a picoJava processor.
1304 @cindex PJ endianness
1305 @cindex endianness, PJ
1306 @cindex big endian output, PJ
1308 Generate ``big endian'' format output.
1310 @cindex little endian output, PJ
1312 Generate ``little endian'' format output.
1320 @xref{PRU Options}, for the options available when @value{AS} is configured
1321 for a PRU processor.
1325 @c man begin OPTIONS
1326 The following options are available when @value{AS} is configured for a
1329 @c man begin INCLUDE
1331 @c ended inside the included file
1336 The following options are available when @value{AS} is configured for the
1337 Motorola 68HC11 or 68HC12 series.
1341 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1342 Specify what processor is the target. The default is
1343 defined by the configuration option when building the assembler.
1345 @item --xgate-ramoffset
1346 Instruct the linker to offset RAM addresses from S12X address space into
1347 XGATE address space.
1350 Specify to use the 16-bit integer ABI.
1353 Specify to use the 32-bit integer ABI.
1355 @item -mshort-double
1356 Specify to use the 32-bit double ABI.
1359 Specify to use the 64-bit double ABI.
1361 @item --force-long-branches
1362 Relative branches are turned into absolute ones. This concerns
1363 conditional branches, unconditional branches and branches to a
1366 @item -S | --short-branches
1367 Do not turn relative branches into absolute ones
1368 when the offset is out of range.
1370 @item --strict-direct-mode
1371 Do not turn the direct addressing mode into extended addressing mode
1372 when the instruction does not support direct addressing mode.
1374 @item --print-insn-syntax
1375 Print the syntax of instruction in case of error.
1377 @item --print-opcodes
1378 Print the list of instructions with syntax and then exit.
1380 @item --generate-example
1381 Print an example of instruction for each possible instruction and then exit.
1382 This option is only useful for testing @command{@value{AS}}.
1388 The following options are available when @command{@value{AS}} is configured
1389 for the SPARC architecture:
1392 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1393 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1394 Explicitly select a variant of the SPARC architecture.
1396 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1397 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1399 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1400 UltraSPARC extensions.
1402 @item -xarch=v8plus | -xarch=v8plusa
1403 For compatibility with the Solaris v9 assembler. These options are
1404 equivalent to -Av8plus and -Av8plusa, respectively.
1407 Warn when the assembler switches to another architecture.
1412 The following options are available when @value{AS} is configured for the 'c54x
1417 Enable extended addressing mode. All addresses and relocations will assume
1418 extended addressing (usually 23 bits).
1419 @item -mcpu=@var{CPU_VERSION}
1420 Sets the CPU version being compiled for.
1421 @item -merrors-to-file @var{FILENAME}
1422 Redirect error output to a file, for broken systems which don't support such
1423 behaviour in the shell.
1428 @c man begin OPTIONS
1429 The following options are available when @value{AS} is configured for
1434 This option sets the largest size of an object that can be referenced
1435 implicitly with the @code{gp} register. It is only accepted for targets that
1436 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1438 @cindex MIPS endianness
1439 @cindex endianness, MIPS
1440 @cindex big endian output, MIPS
1442 Generate ``big endian'' format output.
1444 @cindex little endian output, MIPS
1446 Generate ``little endian'' format output.
1464 Generate code for a particular MIPS Instruction Set Architecture level.
1465 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1466 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1467 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1468 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1469 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1470 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1471 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1472 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1473 MIPS64 Release 6 ISA processors, respectively.
1475 @item -march=@var{cpu}
1476 Generate code for a particular MIPS CPU.
1478 @item -mtune=@var{cpu}
1479 Schedule and tune for a particular MIPS CPU.
1483 Cause nops to be inserted if the read of the destination register
1484 of an mfhi or mflo instruction occurs in the following two instructions.
1487 @itemx -mno-fix-rm7000
1488 Cause nops to be inserted if a dmult or dmultu instruction is
1489 followed by a load instruction.
1492 @itemx -mno-fix-r5900
1493 Do not attempt to schedule the preceding instruction into the delay slot
1494 of a branch instruction placed at the end of a short loop of six
1495 instructions or fewer and always schedule a @code{nop} instruction there
1496 instead. The short loop bug under certain conditions causes loops to
1497 execute only once or twice, due to a hardware bug in the R5900 chip.
1501 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1502 section instead of the standard ELF .stabs sections.
1506 Control generation of @code{.pdr} sections.
1510 The register sizes are normally inferred from the ISA and ABI, but these
1511 flags force a certain group of registers to be treated as 32 bits wide at
1512 all times. @samp{-mgp32} controls the size of general-purpose registers
1513 and @samp{-mfp32} controls the size of floating-point registers.
1517 The register sizes are normally inferred from the ISA and ABI, but these
1518 flags force a certain group of registers to be treated as 64 bits wide at
1519 all times. @samp{-mgp64} controls the size of general-purpose registers
1520 and @samp{-mfp64} controls the size of floating-point registers.
1523 The register sizes are normally inferred from the ISA and ABI, but using
1524 this flag in combination with @samp{-mabi=32} enables an ABI variant
1525 which will operate correctly with floating-point registers which are
1529 @itemx -mno-odd-spreg
1530 Enable use of floating-point operations on odd-numbered single-precision
1531 registers when supported by the ISA. @samp{-mfpxx} implies
1532 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1536 Generate code for the MIPS 16 processor. This is equivalent to putting
1537 @code{.module mips16} at the start of the assembly file. @samp{-no-mips16}
1538 turns off this option.
1541 @itemx -mno-mips16e2
1542 Enable the use of MIPS16e2 instructions in MIPS16 mode. This is equivalent
1543 to putting @code{.module mips16e2} at the start of the assembly file.
1544 @samp{-mno-mips16e2} turns off this option.
1547 @itemx -mno-micromips
1548 Generate code for the microMIPS processor. This is equivalent to putting
1549 @code{.module micromips} at the start of the assembly file.
1550 @samp{-mno-micromips} turns off this option. This is equivalent to putting
1551 @code{.module nomicromips} at the start of the assembly file.
1554 @itemx -mno-smartmips
1555 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1556 equivalent to putting @code{.module smartmips} at the start of the assembly
1557 file. @samp{-mno-smartmips} turns off this option.
1561 Generate code for the MIPS-3D Application Specific Extension.
1562 This tells the assembler to accept MIPS-3D instructions.
1563 @samp{-no-mips3d} turns off this option.
1567 Generate code for the MDMX Application Specific Extension.
1568 This tells the assembler to accept MDMX instructions.
1569 @samp{-no-mdmx} turns off this option.
1573 Generate code for the DSP Release 1 Application Specific Extension.
1574 This tells the assembler to accept DSP Release 1 instructions.
1575 @samp{-mno-dsp} turns off this option.
1579 Generate code for the DSP Release 2 Application Specific Extension.
1580 This option implies @samp{-mdsp}.
1581 This tells the assembler to accept DSP Release 2 instructions.
1582 @samp{-mno-dspr2} turns off this option.
1586 Generate code for the DSP Release 3 Application Specific Extension.
1587 This option implies @samp{-mdsp} and @samp{-mdspr2}.
1588 This tells the assembler to accept DSP Release 3 instructions.
1589 @samp{-mno-dspr3} turns off this option.
1593 Generate code for the MIPS SIMD Architecture Extension.
1594 This tells the assembler to accept MSA instructions.
1595 @samp{-mno-msa} turns off this option.
1599 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1600 This tells the assembler to accept XPA instructions.
1601 @samp{-mno-xpa} turns off this option.
1605 Generate code for the MT Application Specific Extension.
1606 This tells the assembler to accept MT instructions.
1607 @samp{-mno-mt} turns off this option.
1611 Generate code for the MCU Application Specific Extension.
1612 This tells the assembler to accept MCU instructions.
1613 @samp{-mno-mcu} turns off this option.
1617 Generate code for the MIPS cyclic redundancy check (CRC) Application
1618 Specific Extension. This tells the assembler to accept CRC instructions.
1619 @samp{-mno-crc} turns off this option.
1623 Generate code for the Global INValidate (GINV) Application Specific
1624 Extension. This tells the assembler to accept GINV instructions.
1625 @samp{-mno-ginv} turns off this option.
1627 @item -mloongson-mmi
1628 @itemx -mno-loongson-mmi
1629 Generate code for the Loongson MultiMedia extensions Instructions (MMI)
1630 Application Specific Extension. This tells the assembler to accept MMI
1632 @samp{-mno-loongson-mmi} turns off this option.
1634 @item -mloongson-cam
1635 @itemx -mno-loongson-cam
1636 Generate code for the Loongson Content Address Memory (CAM) instructions.
1637 This tells the assembler to accept Loongson CAM instructions.
1638 @samp{-mno-loongson-cam} turns off this option.
1640 @item -mloongson-ext
1641 @itemx -mno-loongson-ext
1642 Generate code for the Loongson EXTensions (EXT) instructions.
1643 This tells the assembler to accept Loongson EXT instructions.
1644 @samp{-mno-loongson-ext} turns off this option.
1646 @item -mloongson-ext2
1647 @itemx -mno-loongson-ext2
1648 Generate code for the Loongson EXTensions R2 (EXT2) instructions.
1649 This option implies @samp{-mloongson-ext}.
1650 This tells the assembler to accept Loongson EXT2 instructions.
1651 @samp{-mno-loongson-ext2} turns off this option.
1655 Only use 32-bit instruction encodings when generating code for the
1656 microMIPS processor. This option inhibits the use of any 16-bit
1657 instructions. This is equivalent to putting @code{.set insn32} at
1658 the start of the assembly file. @samp{-mno-insn32} turns off this
1659 option. This is equivalent to putting @code{.set noinsn32} at the
1660 start of the assembly file. By default @samp{-mno-insn32} is
1661 selected, allowing all instructions to be used.
1663 @item --construct-floats
1664 @itemx --no-construct-floats
1665 The @samp{--no-construct-floats} option disables the construction of
1666 double width floating point constants by loading the two halves of the
1667 value into the two single width floating point registers that make up
1668 the double width register. By default @samp{--construct-floats} is
1669 selected, allowing construction of these floating point constants.
1671 @item --relax-branch
1672 @itemx --no-relax-branch
1673 The @samp{--relax-branch} option enables the relaxation of out-of-range
1674 branches. By default @samp{--no-relax-branch} is selected, causing any
1675 out-of-range branches to produce an error.
1677 @item -mignore-branch-isa
1678 @itemx -mno-ignore-branch-isa
1679 Ignore branch checks for invalid transitions between ISA modes. The
1680 semantics of branches does not provide for an ISA mode switch, so in
1681 most cases the ISA mode a branch has been encoded for has to be the
1682 same as the ISA mode of the branch's target label. Therefore GAS has
1683 checks implemented that verify in branch assembly that the two ISA
1684 modes match. @samp{-mignore-branch-isa} disables these checks. By
1685 default @samp{-mno-ignore-branch-isa} is selected, causing any invalid
1686 branch requiring a transition between ISA modes to produce an error.
1688 @item -mnan=@var{encoding}
1689 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1690 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1693 @item --emulation=@var{name}
1694 This option was formerly used to switch between ELF and ECOFF output
1695 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1696 removed in GAS 2.24, so the option now serves little purpose.
1697 It is retained for backwards compatibility.
1699 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1700 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1701 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1702 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1703 preferred options instead.
1706 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1713 Control how to deal with multiplication overflow and division by zero.
1714 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1715 (and only work for Instruction Set Architecture level 2 and higher);
1716 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1720 When this option is used, @command{@value{AS}} will issue a warning every
1721 time it generates a nop instruction from a macro.
1727 The following options are available when @value{AS} is configured for
1733 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1734 The command-line option @samp{-nojsri2bsr} can be used to disable it.
1738 Enable or disable the silicon filter behaviour. By default this is disabled.
1739 The default can be overridden by the @samp{-sifilter} command-line option.
1742 Alter jump instructions for long displacements.
1744 @item -mcpu=[210|340]
1745 Select the cpu type on the target hardware. This controls which instructions
1749 Assemble for a big endian target.
1752 Assemble for a little endian target.
1761 @xref{Meta Options}, for the options available when @value{AS} is configured
1762 for a Meta processor.
1766 @c man begin OPTIONS
1767 The following options are available when @value{AS} is configured for a
1770 @c man begin INCLUDE
1771 @include c-metag.texi
1772 @c ended inside the included file
1777 @c man begin OPTIONS
1779 See the info pages for documentation of the MMIX-specific options.
1785 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1786 for a NDS32 processor.
1788 @c ended inside the included file
1792 @c man begin OPTIONS
1793 The following options are available when @value{AS} is configured for a
1796 @c man begin INCLUDE
1797 @include c-nds32.texi
1798 @c ended inside the included file
1805 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1806 for a PowerPC processor.
1810 @c man begin OPTIONS
1811 The following options are available when @value{AS} is configured for a
1814 @c man begin INCLUDE
1816 @c ended inside the included file
1824 @xref{RISC-V-Options}, for the options available when @value{AS} is configured
1825 for a RISC-V processor.
1829 @c man begin OPTIONS
1830 The following options are available when @value{AS} is configured for a
1833 @c man begin INCLUDE
1834 @include c-riscv.texi
1835 @c ended inside the included file
1840 @c man begin OPTIONS
1842 See the info pages for documentation of the RX-specific options.
1846 The following options are available when @value{AS} is configured for the s390
1852 Select the word size, either 31/32 bits or 64 bits.
1855 Select the architecture mode, either the Enterprise System
1856 Architecture (esa) or the z/Architecture mode (zarch).
1857 @item -march=@var{processor}
1858 Specify which s390 processor variant is the target, @samp{g5} (or
1859 @samp{arch3}), @samp{g6}, @samp{z900} (or @samp{arch5}), @samp{z990} (or
1860 @samp{arch6}), @samp{z9-109}, @samp{z9-ec} (or @samp{arch7}), @samp{z10} (or
1861 @samp{arch8}), @samp{z196} (or @samp{arch9}), @samp{zEC12} (or @samp{arch10}),
1862 @samp{z13} (or @samp{arch11}), @samp{z14} (or @samp{arch12}), or @samp{z15}
1865 @itemx -mno-regnames
1866 Allow or disallow symbolic names for registers.
1867 @item -mwarn-areg-zero
1868 Warn whenever the operand for a base or index register has been specified
1869 but evaluates to zero.
1877 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1878 for a TMS320C6000 processor.
1882 @c man begin OPTIONS
1883 The following options are available when @value{AS} is configured for a
1884 TMS320C6000 processor.
1886 @c man begin INCLUDE
1887 @include c-tic6x.texi
1888 @c ended inside the included file
1896 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1897 for a TILE-Gx processor.
1901 @c man begin OPTIONS
1902 The following options are available when @value{AS} is configured for a TILE-Gx
1905 @c man begin INCLUDE
1906 @include c-tilegx.texi
1907 @c ended inside the included file
1915 @xref{Visium Options}, for the options available when @value{AS} is configured
1916 for a Visium processor.
1920 @c man begin OPTIONS
1921 The following option is available when @value{AS} is configured for a Visium
1924 @c man begin INCLUDE
1925 @include c-visium.texi
1926 @c ended inside the included file
1934 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1935 for an Xtensa processor.
1939 @c man begin OPTIONS
1940 The following options are available when @value{AS} is configured for an
1943 @c man begin INCLUDE
1944 @include c-xtensa.texi
1945 @c ended inside the included file
1953 @xref{Z80 Options}, for the options available when @value{AS} is configured
1954 for an Z80 processor.
1958 @c man begin OPTIONS
1959 The following options are available when @value{AS} is configured for an
1962 @c man begin INCLUDE
1964 @c ended inside the included file
1970 * Manual:: Structure of this Manual
1971 * GNU Assembler:: The GNU Assembler
1972 * Object Formats:: Object File Formats
1973 * Command Line:: Command Line
1974 * Input Files:: Input Files
1975 * Object:: Output (Object) File
1976 * Errors:: Error and Warning Messages
1980 @section Structure of this Manual
1982 @cindex manual, structure and purpose
1983 This manual is intended to describe what you need to know to use
1984 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1985 notation for symbols, constants, and expressions; the directives that
1986 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1989 We also cover special features in the @value{TARGET}
1990 configuration of @command{@value{AS}}, including assembler directives.
1993 This manual also describes some of the machine-dependent features of
1994 various flavors of the assembler.
1997 @cindex machine instructions (not covered)
1998 On the other hand, this manual is @emph{not} intended as an introduction
1999 to programming in assembly language---let alone programming in general!
2000 In a similar vein, we make no attempt to introduce the machine
2001 architecture; we do @emph{not} describe the instruction set, standard
2002 mnemonics, registers or addressing modes that are standard to a
2003 particular architecture.
2005 You may want to consult the manufacturer's
2006 machine architecture manual for this information.
2010 For information on the H8/300 machine instruction set, see @cite{H8/300
2011 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
2012 Programming Manual} (Renesas).
2015 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
2016 see @cite{SH-Microcomputer User's Manual} (Renesas) or
2017 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
2018 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
2021 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
2025 @c I think this is premature---doc@cygnus.com, 17jan1991
2027 Throughout this manual, we assume that you are running @dfn{GNU},
2028 the portable operating system from the @dfn{Free Software
2029 Foundation, Inc.}. This restricts our attention to certain kinds of
2030 computer (in particular, the kinds of computers that @sc{gnu} can run on);
2031 once this assumption is granted examples and definitions need less
2034 @command{@value{AS}} is part of a team of programs that turn a high-level
2035 human-readable series of instructions into a low-level
2036 computer-readable series of instructions. Different versions of
2037 @command{@value{AS}} are used for different kinds of computer.
2040 @c There used to be a section "Terminology" here, which defined
2041 @c "contents", "byte", "word", and "long". Defining "word" to any
2042 @c particular size is confusing when the .word directive may generate 16
2043 @c bits on one machine and 32 bits on another; in general, for the user
2044 @c version of this manual, none of these terms seem essential to define.
2045 @c They were used very little even in the former draft of the manual;
2046 @c this draft makes an effort to avoid them (except in names of
2050 @section The GNU Assembler
2052 @c man begin DESCRIPTION
2054 @sc{gnu} @command{as} is really a family of assemblers.
2056 This manual describes @command{@value{AS}}, a member of that family which is
2057 configured for the @value{TARGET} architectures.
2059 If you use (or have used) the @sc{gnu} assembler on one architecture, you
2060 should find a fairly similar environment when you use it on another
2061 architecture. Each version has much in common with the others,
2062 including object file formats, most assembler directives (often called
2063 @dfn{pseudo-ops}) and assembler syntax.@refill
2065 @cindex purpose of @sc{gnu} assembler
2066 @command{@value{AS}} is primarily intended to assemble the output of the
2067 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
2068 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
2069 assemble correctly everything that other assemblers for the same
2070 machine would assemble.
2072 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
2075 @c This remark should appear in generic version of manual; assumption
2076 @c here is that generic version sets M680x0.
2077 This doesn't mean @command{@value{AS}} always uses the same syntax as another
2078 assembler for the same architecture; for example, we know of several
2079 incompatible versions of 680x0 assembly language syntax.
2084 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
2085 program in one pass of the source file. This has a subtle impact on the
2086 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
2088 @node Object Formats
2089 @section Object File Formats
2091 @cindex object file format
2092 The @sc{gnu} assembler can be configured to produce several alternative
2093 object file formats. For the most part, this does not affect how you
2094 write assembly language programs; but directives for debugging symbols
2095 are typically different in different file formats. @xref{Symbol
2096 Attributes,,Symbol Attributes}.
2099 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
2100 @value{OBJ-NAME} format object files.
2102 @c The following should exhaust all configs that set MULTI-OBJ, ideally
2104 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
2105 SOM or ELF format object files.
2110 @section Command Line
2112 @cindex command line conventions
2114 After the program name @command{@value{AS}}, the command line may contain
2115 options and file names. Options may appear in any order, and may be
2116 before, after, or between file names. The order of file names is
2119 @cindex standard input, as input file
2121 @file{--} (two hyphens) by itself names the standard input file
2122 explicitly, as one of the files for @command{@value{AS}} to assemble.
2124 @cindex options, command line
2125 Except for @samp{--} any command-line argument that begins with a
2126 hyphen (@samp{-}) is an option. Each option changes the behavior of
2127 @command{@value{AS}}. No option changes the way another option works. An
2128 option is a @samp{-} followed by one or more letters; the case of
2129 the letter is important. All options are optional.
2131 Some options expect exactly one file name to follow them. The file
2132 name may either immediately follow the option's letter (compatible
2133 with older assemblers) or it may be the next command argument (@sc{gnu}
2134 standard). These two command lines are equivalent:
2137 @value{AS} -o my-object-file.o mumble.s
2138 @value{AS} -omy-object-file.o mumble.s
2142 @section Input Files
2145 @cindex source program
2146 @cindex files, input
2147 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
2148 describe the program input to one run of @command{@value{AS}}. The program may
2149 be in one or more files; how the source is partitioned into files
2150 doesn't change the meaning of the source.
2152 @c I added "con" prefix to "catenation" just to prove I can overcome my
2153 @c APL training... doc@cygnus.com
2154 The source program is a concatenation of the text in all the files, in the
2157 @c man begin DESCRIPTION
2158 Each time you run @command{@value{AS}} it assembles exactly one source
2159 program. The source program is made up of one or more files.
2160 (The standard input is also a file.)
2162 You give @command{@value{AS}} a command line that has zero or more input file
2163 names. The input files are read (from left file name to right). A
2164 command-line argument (in any position) that has no special meaning
2165 is taken to be an input file name.
2167 If you give @command{@value{AS}} no file names it attempts to read one input file
2168 from the @command{@value{AS}} standard input, which is normally your terminal. You
2169 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
2172 Use @samp{--} if you need to explicitly name the standard input file
2173 in your command line.
2175 If the source is empty, @command{@value{AS}} produces a small, empty object
2180 @subheading Filenames and Line-numbers
2182 @cindex input file linenumbers
2183 @cindex line numbers, in input files
2184 There are two ways of locating a line in the input file (or files) and
2185 either may be used in reporting error messages. One way refers to a line
2186 number in a physical file; the other refers to a line number in a
2187 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
2189 @dfn{Physical files} are those files named in the command line given
2190 to @command{@value{AS}}.
2192 @dfn{Logical files} are simply names declared explicitly by assembler
2193 directives; they bear no relation to physical files. Logical file names help
2194 error messages reflect the original source file, when @command{@value{AS}} source
2195 is itself synthesized from other files. @command{@value{AS}} understands the
2196 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
2197 @ref{File,,@code{.file}}.
2200 @section Output (Object) File
2206 Every time you run @command{@value{AS}} it produces an output file, which is
2207 your assembly language program translated into numbers. This file
2208 is the object file. Its default name is @code{a.out}.
2209 You can give it another name by using the @option{-o} option. Conventionally,
2210 object file names end with @file{.o}. The default name is used for historical
2211 reasons: older assemblers were capable of assembling self-contained programs
2212 directly into a runnable program. (For some formats, this isn't currently
2213 possible, but it can be done for the @code{a.out} format.)
2217 The object file is meant for input to the linker @code{@value{LD}}. It contains
2218 assembled program code, information to help @code{@value{LD}} integrate
2219 the assembled program into a runnable file, and (optionally) symbolic
2220 information for the debugger.
2222 @c link above to some info file(s) like the description of a.out.
2223 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2226 @section Error and Warning Messages
2228 @c man begin DESCRIPTION
2230 @cindex error messages
2231 @cindex warning messages
2232 @cindex messages from assembler
2233 @command{@value{AS}} may write warnings and error messages to the standard error
2234 file (usually your terminal). This should not happen when a compiler
2235 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2236 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2237 grave problem that stops the assembly.
2241 @cindex format of warning messages
2242 Warning messages have the format
2245 file_name:@b{NNN}:Warning Message Text
2249 @cindex file names and line numbers, in warnings/errors
2250 (where @b{NNN} is a line number). If both a logical file name
2251 (@pxref{File,,@code{.file}}) and a logical line number
2253 (@pxref{Line,,@code{.line}})
2255 have been given then they will be used, otherwise the file name and line number
2256 in the current assembler source file will be used. The message text is
2257 intended to be self explanatory (in the grand Unix tradition).
2259 Note the file name must be set via the logical version of the @code{.file}
2260 directive, not the DWARF2 version of the @code{.file} directive. For example:
2264 error_assembler_source
2270 produces this output:
2274 asm.s:2: Error: no such instruction: `error_assembler_source'
2275 foo.c:31: Error: no such instruction: `error_c_source'
2278 @cindex format of error messages
2279 Error messages have the format
2282 file_name:@b{NNN}:FATAL:Error Message Text
2285 The file name and line number are derived as for warning
2286 messages. The actual message text may be rather less explanatory
2287 because many of them aren't supposed to happen.
2290 @chapter Command-Line Options
2292 @cindex options, all versions of assembler
2293 This chapter describes command-line options available in @emph{all}
2294 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2295 for options specific
2297 to the @value{TARGET} target.
2300 to particular machine architectures.
2303 @c man begin DESCRIPTION
2305 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2306 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2307 The assembler arguments must be separated from each other (and the @samp{-Wa})
2308 by commas. For example:
2311 gcc -c -g -O -Wa,-alh,-L file.c
2315 This passes two options to the assembler: @samp{-alh} (emit a listing to
2316 standard output with high-level and assembly source) and @samp{-L} (retain
2317 local symbols in the symbol table).
2319 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2320 command-line options are automatically passed to the assembler by the compiler.
2321 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2322 precisely what options it passes to each compilation pass, including the
2328 * a:: -a[cdghlns] enable listings
2329 * alternate:: --alternate enable alternate macro syntax
2330 * D:: -D for compatibility
2331 * f:: -f to work faster
2332 * I:: -I for .include search path
2333 @ifclear DIFF-TBL-KLUGE
2334 * K:: -K for compatibility
2336 @ifset DIFF-TBL-KLUGE
2337 * K:: -K for difference tables
2340 * L:: -L to retain local symbols
2341 * listing:: --listing-XXX to configure listing output
2342 * M:: -M or --mri to assemble in MRI compatibility mode
2343 * MD:: --MD for dependency tracking
2344 * no-pad-sections:: --no-pad-sections to stop section padding
2345 * o:: -o to name the object file
2346 * R:: -R to join data and text sections
2347 * statistics:: --statistics to see statistics about assembly
2348 * traditional-format:: --traditional-format for compatible output
2349 * v:: -v to announce version
2350 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2351 * Z:: -Z to make object file even after errors
2355 @section Enable Listings: @option{-a[cdghlns]}
2365 @cindex listings, enabling
2366 @cindex assembly listings, enabling
2368 These options enable listing output from the assembler. By itself,
2369 @samp{-a} requests high-level, assembly, and symbols listing.
2370 You can use other letters to select specific options for the list:
2371 @samp{-ah} requests a high-level language listing,
2372 @samp{-al} requests an output-program assembly listing, and
2373 @samp{-as} requests a symbol table listing.
2374 High-level listings require that a compiler debugging option like
2375 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2378 Use the @samp{-ag} option to print a first section with general assembly
2379 information, like @value{AS} version, switches passed, or time stamp.
2381 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2382 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2383 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2384 omitted from the listing.
2386 Use the @samp{-ad} option to omit debugging directives from the
2389 Once you have specified one of these options, you can further control
2390 listing output and its appearance using the directives @code{.list},
2391 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2393 The @samp{-an} option turns off all forms processing.
2394 If you do not request listing output with one of the @samp{-a} options, the
2395 listing-control directives have no effect.
2397 The letters after @samp{-a} may be combined into one option,
2398 @emph{e.g.}, @samp{-aln}.
2400 Note if the assembler source is coming from the standard input (e.g.,
2402 is being created by @code{@value{GCC}} and the @samp{-pipe} command-line switch
2403 is being used) then the listing will not contain any comments or preprocessor
2404 directives. This is because the listing code buffers input source lines from
2405 stdin only after they have been preprocessed by the assembler. This reduces
2406 memory usage and makes the code more efficient.
2409 @section @option{--alternate}
2412 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2415 @section @option{-D}
2418 This option has no effect whatsoever, but it is accepted to make it more
2419 likely that scripts written for other assemblers also work with
2420 @command{@value{AS}}.
2423 @section Work Faster: @option{-f}
2426 @cindex trusted compiler
2427 @cindex faster processing (@option{-f})
2428 @samp{-f} should only be used when assembling programs written by a
2429 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2430 and comment preprocessing on
2431 the input file(s) before assembling them. @xref{Preprocessing,
2435 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2436 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2441 @section @code{.include} Search Path: @option{-I} @var{path}
2443 @kindex -I @var{path}
2444 @cindex paths for @code{.include}
2445 @cindex search path for @code{.include}
2446 @cindex @code{include} directive search path
2447 Use this option to add a @var{path} to the list of directories
2448 @command{@value{AS}} searches for files specified in @code{.include}
2449 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2450 many times as necessary to include a variety of paths. The current
2451 working directory is always searched first; after that, @command{@value{AS}}
2452 searches any @samp{-I} directories in the same order as they were
2453 specified (left to right) on the command line.
2456 @section Difference Tables: @option{-K}
2459 @ifclear DIFF-TBL-KLUGE
2460 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2461 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2462 where it can be used to warn when the assembler alters the machine code
2463 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2464 family does not have the addressing limitations that sometimes lead to this
2465 alteration on other platforms.
2468 @ifset DIFF-TBL-KLUGE
2469 @cindex difference tables, warning
2470 @cindex warning for altered difference tables
2471 @command{@value{AS}} sometimes alters the code emitted for directives of the
2472 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2473 You can use the @samp{-K} option if you want a warning issued when this
2478 @section Include Local Symbols: @option{-L}
2481 @cindex local symbols, retaining in output
2482 Symbols beginning with system-specific local label prefixes, typically
2483 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2484 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2485 such symbols when debugging, because they are intended for the use of
2486 programs (like compilers) that compose assembler programs, not for your
2487 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2488 such symbols, so you do not normally debug with them.
2490 This option tells @command{@value{AS}} to retain those local symbols
2491 in the object file. Usually if you do this you also tell the linker
2492 @code{@value{LD}} to preserve those symbols.
2495 @section Configuring listing output: @option{--listing}
2497 The listing feature of the assembler can be enabled via the command-line switch
2498 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2499 hex dump of the corresponding locations in the output object file, and displays
2500 them as a listing file. The format of this listing can be controlled by
2501 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2502 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2503 @code{.psize} (@pxref{Psize}), and
2504 @code{.eject} (@pxref{Eject}) and also by the following switches:
2507 @item --listing-lhs-width=@samp{number}
2508 @kindex --listing-lhs-width
2509 @cindex Width of first line disassembly output
2510 Sets the maximum width, in words, of the first line of the hex byte dump. This
2511 dump appears on the left hand side of the listing output.
2513 @item --listing-lhs-width2=@samp{number}
2514 @kindex --listing-lhs-width2
2515 @cindex Width of continuation lines of disassembly output
2516 Sets the maximum width, in words, of any further lines of the hex byte dump for
2517 a given input source line. If this value is not specified, it defaults to being
2518 the same as the value specified for @samp{--listing-lhs-width}. If neither
2519 switch is used the default is to one.
2521 @item --listing-rhs-width=@samp{number}
2522 @kindex --listing-rhs-width
2523 @cindex Width of source line output
2524 Sets the maximum width, in characters, of the source line that is displayed
2525 alongside the hex dump. The default value for this parameter is 100. The
2526 source line is displayed on the right hand side of the listing output.
2528 @item --listing-cont-lines=@samp{number}
2529 @kindex --listing-cont-lines
2530 @cindex Maximum number of continuation lines
2531 Sets the maximum number of continuation lines of hex dump that will be
2532 displayed for a given single line of source input. The default value is 4.
2536 @section Assemble in MRI Compatibility Mode: @option{-M}
2539 @cindex MRI compatibility mode
2540 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2541 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2542 compatible with the @code{ASM68K} assembler from Microtec Research.
2543 The exact nature of the
2544 MRI syntax will not be documented here; see the MRI manuals for more
2545 information. Note in particular that the handling of macros and macro
2546 arguments is somewhat different. The purpose of this option is to permit
2547 assembling existing MRI assembler code using @command{@value{AS}}.
2549 The MRI compatibility is not complete. Certain operations of the MRI assembler
2550 depend upon its object file format, and can not be supported using other object
2551 file formats. Supporting these would require enhancing each object file format
2552 individually. These are:
2555 @item global symbols in common section
2557 The m68k MRI assembler supports common sections which are merged by the linker.
2558 Other object file formats do not support this. @command{@value{AS}} handles
2559 common sections by treating them as a single common symbol. It permits local
2560 symbols to be defined within a common section, but it can not support global
2561 symbols, since it has no way to describe them.
2563 @item complex relocations
2565 The MRI assemblers support relocations against a negated section address, and
2566 relocations which combine the start addresses of two or more sections. These
2567 are not support by other object file formats.
2569 @item @code{END} pseudo-op specifying start address
2571 The MRI @code{END} pseudo-op permits the specification of a start address.
2572 This is not supported by other object file formats. The start address may
2573 instead be specified using the @option{-e} option to the linker, or in a linker
2576 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2578 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2579 name to the output file. This is not supported by other object file formats.
2581 @item @code{ORG} pseudo-op
2583 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2584 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2585 which changes the location within the current section. Absolute sections are
2586 not supported by other object file formats. The address of a section may be
2587 assigned within a linker script.
2590 There are some other features of the MRI assembler which are not supported by
2591 @command{@value{AS}}, typically either because they are difficult or because they
2592 seem of little consequence. Some of these may be supported in future releases.
2596 @item EBCDIC strings
2598 EBCDIC strings are not supported.
2600 @item packed binary coded decimal
2602 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2603 and @code{DCB.P} pseudo-ops are not supported.
2605 @item @code{FEQU} pseudo-op
2607 The m68k @code{FEQU} pseudo-op is not supported.
2609 @item @code{NOOBJ} pseudo-op
2611 The m68k @code{NOOBJ} pseudo-op is not supported.
2613 @item @code{OPT} branch control options
2615 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2616 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2617 relaxes all branches, whether forward or backward, to an appropriate size, so
2618 these options serve no purpose.
2620 @item @code{OPT} list control options
2622 The following m68k @code{OPT} list control options are ignored: @code{C},
2623 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2624 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2626 @item other @code{OPT} options
2628 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2629 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2631 @item @code{OPT} @code{D} option is default
2633 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2634 @code{OPT NOD} may be used to turn it off.
2636 @item @code{XREF} pseudo-op.
2638 The m68k @code{XREF} pseudo-op is ignored.
2643 @section Dependency Tracking: @option{--MD}
2646 @cindex dependency tracking
2649 @command{@value{AS}} can generate a dependency file for the file it creates. This
2650 file consists of a single rule suitable for @code{make} describing the
2651 dependencies of the main source file.
2653 The rule is written to the file named in its argument.
2655 This feature is used in the automatic updating of makefiles.
2657 @node no-pad-sections
2658 @section Output Section Padding
2659 @kindex --no-pad-sections
2660 @cindex output section padding
2661 Normally the assembler will pad the end of each output section up to its
2662 alignment boundary. But this can waste space, which can be significant on
2663 memory constrained targets. So the @option{--no-pad-sections} option will
2664 disable this behaviour.
2667 @section Name the Object File: @option{-o}
2670 @cindex naming object file
2671 @cindex object file name
2672 There is always one object file output when you run @command{@value{AS}}. By
2673 default it has the name @file{a.out}.
2674 You use this option (which takes exactly one filename) to give the
2675 object file a different name.
2677 Whatever the object file is called, @command{@value{AS}} overwrites any
2678 existing file of the same name.
2681 @section Join Data and Text Sections: @option{-R}
2684 @cindex data and text sections, joining
2685 @cindex text and data sections, joining
2686 @cindex joining text and data sections
2687 @cindex merging text and data sections
2688 @option{-R} tells @command{@value{AS}} to write the object file as if all
2689 data-section data lives in the text section. This is only done at
2690 the very last moment: your binary data are the same, but data
2691 section parts are relocated differently. The data section part of
2692 your object file is zero bytes long because all its bytes are
2693 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2695 When you specify @option{-R} it would be possible to generate shorter
2696 address displacements (because we do not have to cross between text and
2697 data section). We refrain from doing this simply for compatibility with
2698 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2701 When @command{@value{AS}} is configured for COFF or ELF output,
2702 this option is only useful if you use sections named @samp{.text} and
2707 @option{-R} is not supported for any of the HPPA targets. Using
2708 @option{-R} generates a warning from @command{@value{AS}}.
2712 @section Display Assembly Statistics: @option{--statistics}
2714 @kindex --statistics
2715 @cindex statistics, about assembly
2716 @cindex time, total for assembly
2717 @cindex space used, maximum for assembly
2718 Use @samp{--statistics} to display two statistics about the resources used by
2719 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2720 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2723 @node traditional-format
2724 @section Compatible Output: @option{--traditional-format}
2726 @kindex --traditional-format
2727 For some targets, the output of @command{@value{AS}} is different in some ways
2728 from the output of some existing assembler. This switch requests
2729 @command{@value{AS}} to use the traditional format instead.
2731 For example, it disables the exception frame optimizations which
2732 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2735 @section Announce Version: @option{-v}
2739 @cindex assembler version
2740 @cindex version of assembler
2741 You can find out what version of as is running by including the
2742 option @samp{-v} (which you can also spell as @samp{-version}) on the
2746 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2748 @command{@value{AS}} should never give a warning or error message when
2749 assembling compiler output. But programs written by people often
2750 cause @command{@value{AS}} to give a warning that a particular assumption was
2751 made. All such warnings are directed to the standard error file.
2755 @cindex suppressing warnings
2756 @cindex warnings, suppressing
2757 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2758 This only affects the warning messages: it does not change any particular of
2759 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2762 @kindex --fatal-warnings
2763 @cindex errors, caused by warnings
2764 @cindex warnings, causing error
2765 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2766 files that generate warnings to be in error.
2769 @cindex warnings, switching on
2770 You can switch these options off again by specifying @option{--warn}, which
2771 causes warnings to be output as usual.
2774 @section Generate Object File in Spite of Errors: @option{-Z}
2775 @cindex object file, after errors
2776 @cindex errors, continuing after
2777 After an error message, @command{@value{AS}} normally produces no output. If for
2778 some reason you are interested in object file output even after
2779 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2780 option. If there are any errors, @command{@value{AS}} continues anyways, and
2781 writes an object file after a final warning message of the form @samp{@var{n}
2782 errors, @var{m} warnings, generating bad object file.}
2787 @cindex machine-independent syntax
2788 @cindex syntax, machine-independent
2789 This chapter describes the machine-independent syntax allowed in a
2790 source file. @command{@value{AS}} syntax is similar to what many other
2791 assemblers use; it is inspired by the BSD 4.2
2796 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2800 * Preprocessing:: Preprocessing
2801 * Whitespace:: Whitespace
2802 * Comments:: Comments
2803 * Symbol Intro:: Symbols
2804 * Statements:: Statements
2805 * Constants:: Constants
2809 @section Preprocessing
2811 @cindex preprocessing
2812 The @command{@value{AS}} internal preprocessor:
2814 @cindex whitespace, removed by preprocessor
2816 adjusts and removes extra whitespace. It leaves one space or tab before
2817 the keywords on a line, and turns any other whitespace on the line into
2820 @cindex comments, removed by preprocessor
2822 removes all comments, replacing them with a single space, or an
2823 appropriate number of newlines.
2825 @cindex constants, converted by preprocessor
2827 converts character constants into the appropriate numeric values.
2830 It does not do macro processing, include file handling, or
2831 anything else you may get from your C compiler's preprocessor. You can
2832 do include file processing with the @code{.include} directive
2833 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2834 to get other ``CPP'' style preprocessing by giving the input file a
2835 @samp{.S} suffix. @url{https://gcc.gnu.org/onlinedocs/gcc/Overall-Options.html#Overall-Options,
2836 See the 'Options Controlling the Kind of Output' section of the GCC manual for
2839 Excess whitespace, comments, and character constants
2840 cannot be used in the portions of the input text that are not
2843 @cindex turning preprocessing on and off
2844 @cindex preprocessing, turning on and off
2847 If the first line of an input file is @code{#NO_APP} or if you use the
2848 @samp{-f} option, whitespace and comments are not removed from the input file.
2849 Within an input file, you can ask for whitespace and comment removal in
2850 specific portions of the by putting a line that says @code{#APP} before the
2851 text that may contain whitespace or comments, and putting a line that says
2852 @code{#NO_APP} after this text. This feature is mainly intend to support
2853 @code{asm} statements in compilers whose output is otherwise free of comments
2860 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2861 Whitespace is used to separate symbols, and to make programs neater for
2862 people to read. Unless within character constants
2863 (@pxref{Characters,,Character Constants}), any whitespace means the same
2864 as exactly one space.
2870 There are two ways of rendering comments to @command{@value{AS}}. In both
2871 cases the comment is equivalent to one space.
2873 Anything from @samp{/*} through the next @samp{*/} is a comment.
2874 This means you may not nest these comments.
2878 The only way to include a newline ('\n') in a comment
2879 is to use this sort of comment.
2882 /* This sort of comment does not nest. */
2885 @cindex line comment character
2886 Anything from a @dfn{line comment} character up to the next newline is
2887 considered a comment and is ignored. The line comment character is target
2888 specific, and some targets multiple comment characters. Some targets also have
2889 line comment characters that only work if they are the first character on a
2890 line. Some targets use a sequence of two characters to introduce a line
2891 comment. Some targets can also change their line comment characters depending
2892 upon command-line options that have been used. For more details see the
2893 @emph{Syntax} section in the documentation for individual targets.
2895 If the line comment character is the hash sign (@samp{#}) then it still has the
2896 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2897 to specify logical line numbers:
2900 @cindex lines starting with @code{#}
2901 @cindex logical line numbers
2902 To be compatible with past assemblers, lines that begin with @samp{#} have a
2903 special interpretation. Following the @samp{#} should be an absolute
2904 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2905 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2906 new logical file name. The rest of the line, if any, should be whitespace.
2908 If the first non-whitespace characters on the line are not numeric,
2909 the line is ignored. (Just like a comment.)
2912 # This is an ordinary comment.
2913 # 42-6 "new_file_name" # New logical file name
2914 # This is logical line # 36.
2916 This feature is deprecated, and may disappear from future versions
2917 of @command{@value{AS}}.
2922 @cindex characters used in symbols
2923 @ifclear SPECIAL-SYMS
2924 A @dfn{symbol} is one or more characters chosen from the set of all
2925 letters (both upper and lower case), digits and the three characters
2931 A @dfn{symbol} is one or more characters chosen from the set of all
2932 letters (both upper and lower case), digits and the three characters
2933 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2939 On most machines, you can also use @code{$} in symbol names; exceptions
2940 are noted in @ref{Machine Dependencies}.
2942 No symbol may begin with a digit. Case is significant.
2943 There is no length limit; all characters are significant. Multibyte characters
2944 are supported. Symbols are delimited by characters not in that set, or by the
2945 beginning of a file (since the source program must end with a newline, the end
2946 of a file is not a possible symbol delimiter). @xref{Symbols}.
2948 Symbol names may also be enclosed in double quote @code{"} characters. In such
2949 cases any characters are allowed, except for the NUL character. If a double
2950 quote character is to be included in the symbol name it must be preceded by a
2951 backslash @code{\} character.
2952 @cindex length of symbols
2957 @cindex statements, structure of
2958 @cindex line separator character
2959 @cindex statement separator character
2961 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2962 @dfn{line separator character}. The line separator character is target
2963 specific and described in the @emph{Syntax} section of each
2964 target's documentation. Not all targets support a line separator character.
2965 The newline or line separator character is considered to be part of the
2966 preceding statement. Newlines and separators within character constants are an
2967 exception: they do not end statements.
2969 @cindex newline, required at file end
2970 @cindex EOF, newline must precede
2971 It is an error to end any statement with end-of-file: the last
2972 character of any input file should be a newline.@refill
2974 An empty statement is allowed, and may include whitespace. It is ignored.
2976 @cindex instructions and directives
2977 @cindex directives and instructions
2978 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2979 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2981 A statement begins with zero or more labels, optionally followed by a
2982 key symbol which determines what kind of statement it is. The key
2983 symbol determines the syntax of the rest of the statement. If the
2984 symbol begins with a dot @samp{.} then the statement is an assembler
2985 directive: typically valid for any computer. If the symbol begins with
2986 a letter the statement is an assembly language @dfn{instruction}: it
2987 assembles into a machine language instruction.
2989 Different versions of @command{@value{AS}} for different computers
2990 recognize different instructions. In fact, the same symbol may
2991 represent a different instruction in a different computer's assembly
2995 @cindex @code{:} (label)
2996 @cindex label (@code{:})
2997 A label is a symbol immediately followed by a colon (@code{:}).
2998 Whitespace before a label or after a colon is permitted, but you may not
2999 have whitespace between a label's symbol and its colon. @xref{Labels}.
3002 For HPPA targets, labels need not be immediately followed by a colon, but
3003 the definition of a label must begin in column zero. This also implies that
3004 only one label may be defined on each line.
3008 label: .directive followed by something
3009 another_label: # This is an empty statement.
3010 instruction operand_1, operand_2, @dots{}
3017 A constant is a number, written so that its value is known by
3018 inspection, without knowing any context. Like this:
3021 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
3022 .ascii "Ring the bell\7" # A string constant.
3023 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
3024 .float 0f-314159265358979323846264338327\
3025 95028841971.693993751E-40 # - pi, a flonum.
3030 * Characters:: Character Constants
3031 * Numbers:: Number Constants
3035 @subsection Character Constants
3037 @cindex character constants
3038 @cindex constants, character
3039 There are two kinds of character constants. A @dfn{character} stands
3040 for one character in one byte and its value may be used in
3041 numeric expressions. String constants (properly called string
3042 @emph{literals}) are potentially many bytes and their values may not be
3043 used in arithmetic expressions.
3047 * Chars:: Characters
3051 @subsubsection Strings
3053 @cindex string constants
3054 @cindex constants, string
3055 A @dfn{string} is written between double-quotes. It may contain
3056 double-quotes or null characters. The way to get special characters
3057 into a string is to @dfn{escape} these characters: precede them with
3058 a backslash @samp{\} character. For example @samp{\\} represents
3059 one backslash: the first @code{\} is an escape which tells
3060 @command{@value{AS}} to interpret the second character literally as a backslash
3061 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
3062 escape character). The complete list of escapes follows.
3064 @cindex escape codes, character
3065 @cindex character escape codes
3066 @c NOTE: Cindex entries must not start with a backlash character.
3067 @c NOTE: This confuses the pdf2texi script when it is creating the
3068 @c NOTE: index based upon the first character and so it generates:
3069 @c NOTE: \initial {\\}
3070 @c NOTE: which then results in the error message:
3071 @c NOTE: Argument of \\ has an extra }.
3072 @c NOTE: So in the index entries below a space character has been
3073 @c NOTE: prepended to avoid this problem.
3076 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
3078 @cindex @code{ \b} (backspace character)
3079 @cindex backspace (@code{\b})
3081 Mnemonic for backspace; for ASCII this is octal code 010.
3084 @c Mnemonic for EOText; for ASCII this is octal code 004.
3086 @cindex @code{ \f} (formfeed character)
3087 @cindex formfeed (@code{\f})
3089 Mnemonic for FormFeed; for ASCII this is octal code 014.
3091 @cindex @code{ \n} (newline character)
3092 @cindex newline (@code{\n})
3094 Mnemonic for newline; for ASCII this is octal code 012.
3097 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
3099 @cindex @code{ \r} (carriage return character)
3100 @cindex carriage return (@code{backslash-r})
3102 Mnemonic for carriage-Return; for ASCII this is octal code 015.
3105 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
3106 @c other assemblers.
3108 @cindex @code{ \t} (tab)
3109 @cindex tab (@code{\t})
3111 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
3114 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
3115 @c @item \x @var{digit} @var{digit} @var{digit}
3116 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
3118 @cindex @code{ \@var{ddd}} (octal character code)
3119 @cindex octal character code (@code{\@var{ddd}})
3120 @item \ @var{digit} @var{digit} @var{digit}
3121 An octal character code. The numeric code is 3 octal digits.
3122 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
3123 for example, @code{\008} has the value 010, and @code{\009} the value 011.
3125 @cindex @code{ \@var{xd...}} (hex character code)
3126 @cindex hex character code (@code{\@var{xd...}})
3127 @item \@code{x} @var{hex-digits...}
3128 A hex character code. All trailing hex digits are combined. Either upper or
3129 lower case @code{x} works.
3131 @cindex @code{ \\} (@samp{\} character)
3132 @cindex backslash (@code{\\})
3134 Represents one @samp{\} character.
3137 @c Represents one @samp{'} (accent acute) character.
3138 @c This is needed in single character literals
3139 @c (@xref{Characters,,Character Constants}.) to represent
3142 @cindex @code{ \"} (doublequote character)
3143 @cindex doublequote (@code{\"})
3145 Represents one @samp{"} character. Needed in strings to represent
3146 this character, because an unescaped @samp{"} would end the string.
3148 @item \ @var{anything-else}
3149 Any other character when escaped by @kbd{\} gives a warning, but
3150 assembles as if the @samp{\} was not present. The idea is that if
3151 you used an escape sequence you clearly didn't want the literal
3152 interpretation of the following character. However @command{@value{AS}} has no
3153 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
3154 code and warns you of the fact.
3157 Which characters are escapable, and what those escapes represent,
3158 varies widely among assemblers. The current set is what we think
3159 the BSD 4.2 assembler recognizes, and is a subset of what most C
3160 compilers recognize. If you are in doubt, do not use an escape
3164 @subsubsection Characters
3166 @cindex single character constant
3167 @cindex character, single
3168 @cindex constant, single character
3169 A single character may be written as a single quote immediately followed by
3170 that character. Some backslash escapes apply to characters, @code{\b},
3171 @code{\f}, @code{\n}, @code{\r}, @code{\t}, and @code{\"} with the same meaning
3172 as for strings, plus @code{\'} for a single quote. So if you want to write the
3173 character backslash, you must write @kbd{'\\} where the first @code{\} escapes
3174 the second @code{\}. As you can see, the quote is an acute accent, not a grave
3177 @ifclear abnormal-separator
3178 (or semicolon @samp{;})
3180 @ifset abnormal-separator
3182 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
3187 immediately following an acute accent is taken as a literal character
3188 and does not count as the end of a statement. The value of a character
3189 constant in a numeric expression is the machine's byte-wide code for
3190 that character. @command{@value{AS}} assumes your character code is ASCII:
3191 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
3194 @subsection Number Constants
3196 @cindex constants, number
3197 @cindex number constants
3198 @command{@value{AS}} distinguishes three kinds of numbers according to how they
3199 are stored in the target machine. @emph{Integers} are numbers that
3200 would fit into an @code{int} in the C language. @emph{Bignums} are
3201 integers, but they are stored in more than 32 bits. @emph{Flonums}
3202 are floating point numbers, described below.
3205 * Integers:: Integers
3213 @subsubsection Integers
3215 @cindex constants, integer
3217 @cindex binary integers
3218 @cindex integers, binary
3219 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3220 the binary digits @samp{01}.
3222 @cindex octal integers
3223 @cindex integers, octal
3224 An octal integer is @samp{0} followed by zero or more of the octal
3225 digits (@samp{01234567}).
3227 @cindex decimal integers
3228 @cindex integers, decimal
3229 A decimal integer starts with a non-zero digit followed by zero or
3230 more digits (@samp{0123456789}).
3232 @cindex hexadecimal integers
3233 @cindex integers, hexadecimal
3234 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3235 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3237 Integers have the usual values. To denote a negative integer, use
3238 the prefix operator @samp{-} discussed under expressions
3239 (@pxref{Prefix Ops,,Prefix Operators}).
3242 @subsubsection Bignums
3245 @cindex constants, bignum
3246 A @dfn{bignum} has the same syntax and semantics as an integer
3247 except that the number (or its negative) takes more than 32 bits to
3248 represent in binary. The distinction is made because in some places
3249 integers are permitted while bignums are not.
3252 @subsubsection Flonums
3254 @cindex floating point numbers
3255 @cindex constants, floating point
3257 @cindex precision, floating point
3258 A @dfn{flonum} represents a floating point number. The translation is
3259 indirect: a decimal floating point number from the text is converted by
3260 @command{@value{AS}} to a generic binary floating point number of more than
3261 sufficient precision. This generic floating point number is converted
3262 to a particular computer's floating point format (or formats) by a
3263 portion of @command{@value{AS}} specialized to that computer.
3265 A flonum is written by writing (in order)
3270 (@samp{0} is optional on the HPPA.)
3274 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3276 @kbd{e} is recommended. Case is not important.
3278 @c FIXME: verify if flonum syntax really this vague for most cases
3279 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3280 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3283 On the H8/300 and Renesas / SuperH SH architectures, the letter must be
3284 one of the letters @samp{DFPRSX} (in upper or lower case).
3286 On the ARC, the letter must be one of the letters @samp{DFRS}
3287 (in upper or lower case).
3289 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3293 One of the letters @samp{DFRS} (in upper or lower case).
3296 One of the letters @samp{DFPRSX} (in upper or lower case).
3299 The letter @samp{E} (upper case only).
3304 An optional sign: either @samp{+} or @samp{-}.
3307 An optional @dfn{integer part}: zero or more decimal digits.
3310 An optional @dfn{fractional part}: @samp{.} followed by zero
3311 or more decimal digits.
3314 An optional exponent, consisting of:
3318 An @samp{E} or @samp{e}.
3319 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3320 @c principle this can perfectly well be different on different targets.
3322 Optional sign: either @samp{+} or @samp{-}.
3324 One or more decimal digits.
3329 At least one of the integer part or the fractional part must be
3330 present. The floating point number has the usual base-10 value.
3332 @command{@value{AS}} does all processing using integers. Flonums are computed
3333 independently of any floating point hardware in the computer running
3334 @command{@value{AS}}.
3337 @chapter Sections and Relocation
3342 * Secs Background:: Background
3343 * Ld Sections:: Linker Sections
3344 * As Sections:: Assembler Internal Sections
3345 * Sub-Sections:: Sub-Sections
3349 @node Secs Background
3352 Roughly, a section is a range of addresses, with no gaps; all data
3353 ``in'' those addresses is treated the same for some particular purpose.
3354 For example there may be a ``read only'' section.
3356 @cindex linker, and assembler
3357 @cindex assembler, and linker
3358 The linker @code{@value{LD}} reads many object files (partial programs) and
3359 combines their contents to form a runnable program. When @command{@value{AS}}
3360 emits an object file, the partial program is assumed to start at address 0.
3361 @code{@value{LD}} assigns the final addresses for the partial program, so that
3362 different partial programs do not overlap. This is actually an
3363 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3366 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3367 addresses. These blocks slide to their run-time addresses as rigid
3368 units; their length does not change and neither does the order of bytes
3369 within them. Such a rigid unit is called a @emph{section}. Assigning
3370 run-time addresses to sections is called @dfn{relocation}. It includes
3371 the task of adjusting mentions of object-file addresses so they refer to
3372 the proper run-time addresses.
3374 For the H8/300, and for the Renesas / SuperH SH,
3375 @command{@value{AS}} pads sections if needed to
3376 ensure they end on a word (sixteen bit) boundary.
3379 @cindex standard assembler sections
3380 An object file written by @command{@value{AS}} has at least three sections, any
3381 of which may be empty. These are named @dfn{text}, @dfn{data} and
3386 When it generates COFF or ELF output,
3388 @command{@value{AS}} can also generate whatever other named sections you specify
3389 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3390 If you do not use any directives that place output in the @samp{.text}
3391 or @samp{.data} sections, these sections still exist, but are empty.
3396 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3398 @command{@value{AS}} can also generate whatever other named sections you
3399 specify using the @samp{.space} and @samp{.subspace} directives. See
3400 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3401 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3402 assembler directives.
3405 Additionally, @command{@value{AS}} uses different names for the standard
3406 text, data, and bss sections when generating SOM output. Program text
3407 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3408 BSS into @samp{$BSS$}.
3412 Within the object file, the text section starts at address @code{0}, the
3413 data section follows, and the bss section follows the data section.
3416 When generating either SOM or ELF output files on the HPPA, the text
3417 section starts at address @code{0}, the data section at address
3418 @code{0x4000000}, and the bss section follows the data section.
3421 To let @code{@value{LD}} know which data changes when the sections are
3422 relocated, and how to change that data, @command{@value{AS}} also writes to the
3423 object file details of the relocation needed. To perform relocation
3424 @code{@value{LD}} must know, each time an address in the object
3428 Where in the object file is the beginning of this reference to
3431 How long (in bytes) is this reference?
3433 Which section does the address refer to? What is the numeric value of
3435 (@var{address}) @minus{} (@var{start-address of section})?
3438 Is the reference to an address ``Program-Counter relative''?
3441 @cindex addresses, format of
3442 @cindex section-relative addressing
3443 In fact, every address @command{@value{AS}} ever uses is expressed as
3445 (@var{section}) + (@var{offset into section})
3448 Further, most expressions @command{@value{AS}} computes have this section-relative
3451 (For some object formats, such as SOM for the HPPA, some expressions are
3452 symbol-relative instead.)
3455 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3456 @var{N} into section @var{secname}.''
3458 Apart from text, data and bss sections you need to know about the
3459 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3460 addresses in the absolute section remain unchanged. For example, address
3461 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3462 @code{@value{LD}}. Although the linker never arranges two partial programs'
3463 data sections with overlapping addresses after linking, @emph{by definition}
3464 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3465 part of a program is always the same address when the program is running as
3466 address @code{@{absolute@ 239@}} in any other part of the program.
3468 The idea of sections is extended to the @dfn{undefined} section. Any
3469 address whose section is unknown at assembly time is by definition
3470 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3471 Since numbers are always defined, the only way to generate an undefined
3472 address is to mention an undefined symbol. A reference to a named
3473 common block would be such a symbol: its value is unknown at assembly
3474 time so it has section @emph{undefined}.
3476 By analogy the word @emph{section} is used to describe groups of sections in
3477 the linked program. @code{@value{LD}} puts all partial programs' text
3478 sections in contiguous addresses in the linked program. It is
3479 customary to refer to the @emph{text section} of a program, meaning all
3480 the addresses of all partial programs' text sections. Likewise for
3481 data and bss sections.
3483 Some sections are manipulated by @code{@value{LD}}; others are invented for
3484 use of @command{@value{AS}} and have no meaning except during assembly.
3487 @section Linker Sections
3488 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3493 @cindex named sections
3494 @cindex sections, named
3495 @item named sections
3498 @cindex text section
3499 @cindex data section
3503 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3504 separate but equal sections. Anything you can say of one section is
3507 When the program is running, however, it is
3508 customary for the text section to be unalterable. The
3509 text section is often shared among processes: it contains
3510 instructions, constants and the like. The data section of a running
3511 program is usually alterable: for example, C variables would be stored
3512 in the data section.
3517 This section contains zeroed bytes when your program begins running. It
3518 is used to hold uninitialized variables or common storage. The length of
3519 each partial program's bss section is important, but because it starts
3520 out containing zeroed bytes there is no need to store explicit zero
3521 bytes in the object file. The bss section was invented to eliminate
3522 those explicit zeros from object files.
3524 @cindex absolute section
3525 @item absolute section
3526 Address 0 of this section is always ``relocated'' to runtime address 0.
3527 This is useful if you want to refer to an address that @code{@value{LD}} must
3528 not change when relocating. In this sense we speak of absolute
3529 addresses being ``unrelocatable'': they do not change during relocation.
3531 @cindex undefined section
3532 @item undefined section
3533 This ``section'' is a catch-all for address references to objects not in
3534 the preceding sections.
3535 @c FIXME: ref to some other doc on obj-file formats could go here.
3538 @cindex relocation example
3539 An idealized example of three relocatable sections follows.
3541 The example uses the traditional section names @samp{.text} and @samp{.data}.
3543 Memory addresses are on the horizontal axis.
3547 @c END TEXI2ROFF-KILL
3550 partial program # 1: |ttttt|dddd|00|
3557 partial program # 2: |TTT|DDD|000|
3560 +--+---+-----+--+----+---+-----+~~
3561 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3562 +--+---+-----+--+----+---+-----+~~
3564 addresses: 0 @dots{}
3571 \line{\it Partial program \#1: \hfil}
3572 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3573 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3575 \line{\it Partial program \#2: \hfil}
3576 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3577 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3579 \line{\it linked program: \hfil}
3580 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3581 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3582 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3583 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3585 \line{\it addresses: \hfil}
3589 @c END TEXI2ROFF-KILL
3592 @section Assembler Internal Sections
3594 @cindex internal assembler sections
3595 @cindex sections in messages, internal
3596 These sections are meant only for the internal use of @command{@value{AS}}. They
3597 have no meaning at run-time. You do not really need to know about these
3598 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3599 warning messages, so it might be helpful to have an idea of their
3600 meanings to @command{@value{AS}}. These sections are used to permit the
3601 value of every expression in your assembly language program to be a
3602 section-relative address.
3605 @cindex assembler internal logic error
3606 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3607 An internal assembler logic error has been found. This means there is a
3608 bug in the assembler.
3610 @cindex expr (internal section)
3612 The assembler stores complex expression internally as combinations of
3613 symbols. When it needs to represent an expression as a symbol, it puts
3614 it in the expr section.
3616 @c FIXME item transfer[t] vector preload
3617 @c FIXME item transfer[t] vector postload
3618 @c FIXME item register
3622 @section Sub-Sections
3624 @cindex numbered subsections
3625 @cindex grouping data
3631 fall into two sections: text and data.
3633 You may have separate groups of
3635 data in named sections
3639 data in named sections
3645 that you want to end up near to each other in the object file, even though they
3646 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3647 use @dfn{subsections} for this purpose. Within each section, there can be
3648 numbered subsections with values from 0 to 8192. Objects assembled into the
3649 same subsection go into the object file together with other objects in the same
3650 subsection. For example, a compiler might want to store constants in the text
3651 section, but might not want to have them interspersed with the program being
3652 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3653 section of code being output, and a @samp{.text 1} before each group of
3654 constants being output.
3656 Subsections are optional. If you do not use subsections, everything
3657 goes in subsection number zero.
3660 Each subsection is zero-padded up to a multiple of four bytes.
3661 (Subsections may be padded a different amount on different flavors
3662 of @command{@value{AS}}.)
3666 On the H8/300 platform, each subsection is zero-padded to a word
3667 boundary (two bytes).
3668 The same is true on the Renesas SH.
3672 Subsections appear in your object file in numeric order, lowest numbered
3673 to highest. (All this to be compatible with other people's assemblers.)
3674 The object file contains no representation of subsections; @code{@value{LD}} and
3675 other programs that manipulate object files see no trace of them.
3676 They just see all your text subsections as a text section, and all your
3677 data subsections as a data section.
3679 To specify which subsection you want subsequent statements assembled
3680 into, use a numeric argument to specify it, in a @samp{.text
3681 @var{expression}} or a @samp{.data @var{expression}} statement.
3684 When generating COFF output, you
3689 can also use an extra subsection
3690 argument with arbitrary named sections: @samp{.section @var{name},
3695 When generating ELF output, you
3700 can also use the @code{.subsection} directive (@pxref{SubSection})
3701 to specify a subsection: @samp{.subsection @var{expression}}.
3703 @var{Expression} should be an absolute expression
3704 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3705 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3706 begins in @code{text 0}. For instance:
3708 .text 0 # The default subsection is text 0 anyway.
3709 .ascii "This lives in the first text subsection. *"
3711 .ascii "But this lives in the second text subsection."
3713 .ascii "This lives in the data section,"
3714 .ascii "in the first data subsection."
3716 .ascii "This lives in the first text section,"
3717 .ascii "immediately following the asterisk (*)."
3720 Each section has a @dfn{location counter} incremented by one for every byte
3721 assembled into that section. Because subsections are merely a convenience
3722 restricted to @command{@value{AS}} there is no concept of a subsection location
3723 counter. There is no way to directly manipulate a location counter---but the
3724 @code{.align} directive changes it, and any label definition captures its
3725 current value. The location counter of the section where statements are being
3726 assembled is said to be the @dfn{active} location counter.
3729 @section bss Section
3732 @cindex common variable storage
3733 The bss section is used for local common variable storage.
3734 You may allocate address space in the bss section, but you may
3735 not dictate data to load into it before your program executes. When
3736 your program starts running, all the contents of the bss
3737 section are zeroed bytes.
3739 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3740 @ref{Lcomm,,@code{.lcomm}}.
3742 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3743 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3746 When assembling for a target which supports multiple sections, such as ELF or
3747 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3748 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3749 section. Typically the section will only contain symbol definitions and
3750 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3757 Symbols are a central concept: the programmer uses symbols to name
3758 things, the linker uses symbols to link, and the debugger uses symbols
3762 @cindex debuggers, and symbol order
3763 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3764 the same order they were declared. This may break some debuggers.
3769 * Setting Symbols:: Giving Symbols Other Values
3770 * Symbol Names:: Symbol Names
3771 * Dot:: The Special Dot Symbol
3772 * Symbol Attributes:: Symbol Attributes
3779 A @dfn{label} is written as a symbol immediately followed by a colon
3780 @samp{:}. The symbol then represents the current value of the
3781 active location counter, and is, for example, a suitable instruction
3782 operand. You are warned if you use the same symbol to represent two
3783 different locations: the first definition overrides any other
3787 On the HPPA, the usual form for a label need not be immediately followed by a
3788 colon, but instead must start in column zero. Only one label may be defined on
3789 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3790 provides a special directive @code{.label} for defining labels more flexibly.
3793 @node Setting Symbols
3794 @section Giving Symbols Other Values
3796 @cindex assigning values to symbols
3797 @cindex symbol values, assigning
3798 A symbol can be given an arbitrary value by writing a symbol, followed
3799 by an equals sign @samp{=}, followed by an expression
3800 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3801 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3802 equals sign @samp{=}@samp{=} here represents an equivalent of the
3803 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3806 Blackfin does not support symbol assignment with @samp{=}.
3810 @section Symbol Names
3812 @cindex symbol names
3813 @cindex names, symbol
3814 @ifclear SPECIAL-SYMS
3815 Symbol names begin with a letter or with one of @samp{._}. On most
3816 machines, you can also use @code{$} in symbol names; exceptions are
3817 noted in @ref{Machine Dependencies}. That character may be followed by any
3818 string of digits, letters, dollar signs (unless otherwise noted for a
3819 particular target machine), and underscores.
3823 Symbol names begin with a letter or with one of @samp{._}. On the
3824 Renesas SH you can also use @code{$} in symbol names. That
3825 character may be followed by any string of digits, letters, dollar signs (save
3826 on the H8/300), and underscores.
3830 Case of letters is significant: @code{foo} is a different symbol name
3833 Symbol names do not start with a digit. An exception to this rule is made for
3834 Local Labels. See below.
3836 Multibyte characters are supported. To generate a symbol name containing
3837 multibyte characters enclose it within double quotes and use escape codes. cf
3838 @xref{Strings}. Generating a multibyte symbol name from a label is not
3839 currently supported.
3841 Each symbol has exactly one name. Each name in an assembly language program
3842 refers to exactly one symbol. You may use that symbol name any number of times
3845 @subheading Local Symbol Names
3847 @cindex local symbol names
3848 @cindex symbol names, local
3849 A local symbol is any symbol beginning with certain local label prefixes.
3850 By default, the local label prefix is @samp{.L} for ELF systems or
3851 @samp{L} for traditional a.out systems, but each target may have its own
3852 set of local label prefixes.
3854 On the HPPA local symbols begin with @samp{L$}.
3857 Local symbols are defined and used within the assembler, but they are
3858 normally not saved in object files. Thus, they are not visible when debugging.
3859 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3860 to retain the local symbols in the object files.
3862 @subheading Local Labels
3864 @cindex local labels
3865 @cindex temporary symbol names
3866 @cindex symbol names, temporary
3867 Local labels are different from local symbols. Local labels help compilers and
3868 programmers use names temporarily. They create symbols which are guaranteed to
3869 be unique over the entire scope of the input source code and which can be
3870 referred to by a simple notation. To define a local label, write a label of
3871 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3872 To refer to the most recent previous definition of that label write
3873 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3874 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3875 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3877 There is no restriction on how you can use these labels, and you can reuse them
3878 too. So that it is possible to repeatedly define the same local label (using
3879 the same number @samp{@b{N}}), although you can only refer to the most recently
3880 defined local label of that number (for a backwards reference) or the next
3881 definition of a specific local label for a forward reference. It is also worth
3882 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3883 implemented in a slightly more efficient manner than the others.
3894 Which is the equivalent of:
3897 label_1: branch label_3
3898 label_2: branch label_1
3899 label_3: branch label_4
3900 label_4: branch label_3
3903 Local label names are only a notational device. They are immediately
3904 transformed into more conventional symbol names before the assembler uses them.
3905 The symbol names are stored in the symbol table, appear in error messages, and
3906 are optionally emitted to the object file. The names are constructed using
3910 @item @emph{local label prefix}
3911 All local symbols begin with the system-specific local label prefix.
3912 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3913 that start with the local label prefix. These labels are
3914 used for symbols you are never intended to see. If you use the
3915 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3916 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3917 you may use them in debugging.
3920 This is the number that was used in the local label definition. So if the
3921 label is written @samp{55:} then the number is @samp{55}.
3924 This unusual character is included so you do not accidentally invent a symbol
3925 of the same name. The character has ASCII value of @samp{\002} (control-B).
3927 @item @emph{ordinal number}
3928 This is a serial number to keep the labels distinct. The first definition of
3929 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3930 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3931 the number @samp{1} and its 15th definition gets @samp{15} as well.
3934 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3935 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3937 @subheading Dollar Local Labels
3938 @cindex dollar local symbols
3940 On some targets @code{@value{AS}} also supports an even more local form of
3941 local labels called dollar labels. These labels go out of scope (i.e., they
3942 become undefined) as soon as a non-local label is defined. Thus they remain
3943 valid for only a small region of the input source code. Normal local labels,
3944 by contrast, remain in scope for the entire file, or until they are redefined
3945 by another occurrence of the same local label.
3947 Dollar labels are defined in exactly the same way as ordinary local labels,
3948 except that they have a dollar sign suffix to their numeric value, e.g.,
3951 They can also be distinguished from ordinary local labels by their transformed
3952 names which use ASCII character @samp{\001} (control-A) as the magic character
3953 to distinguish them from ordinary labels. For example, the fifth definition of
3954 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3957 @section The Special Dot Symbol
3959 @cindex dot (symbol)
3960 @cindex @code{.} (symbol)
3961 @cindex current address
3962 @cindex location counter
3963 The special symbol @samp{.} refers to the current address that
3964 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3965 .long .} defines @code{melvin} to contain its own address.
3966 Assigning a value to @code{.} is treated the same as a @code{.org}
3968 @ifclear no-space-dir
3969 Thus, the expression @samp{.=.+4} is the same as saying
3973 @node Symbol Attributes
3974 @section Symbol Attributes
3976 @cindex symbol attributes
3977 @cindex attributes, symbol
3978 Every symbol has, as well as its name, the attributes ``Value'' and
3979 ``Type''. Depending on output format, symbols can also have auxiliary
3982 The detailed definitions are in @file{a.out.h}.
3985 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3986 all these attributes, and probably won't warn you. This makes the
3987 symbol an externally defined symbol, which is generally what you
3991 * Symbol Value:: Value
3992 * Symbol Type:: Type
3994 * a.out Symbols:: Symbol Attributes: @code{a.out}
3997 * COFF Symbols:: Symbol Attributes for COFF
4000 * SOM Symbols:: Symbol Attributes for SOM
4007 @cindex value of a symbol
4008 @cindex symbol value
4009 The value of a symbol is (usually) 32 bits. For a symbol which labels a
4010 location in the text, data, bss or absolute sections the value is the
4011 number of addresses from the start of that section to the label.
4012 Naturally for text, data and bss sections the value of a symbol changes
4013 as @code{@value{LD}} changes section base addresses during linking. Absolute
4014 symbols' values do not change during linking: that is why they are
4017 The value of an undefined symbol is treated in a special way. If it is
4018 0 then the symbol is not defined in this assembler source file, and
4019 @code{@value{LD}} tries to determine its value from other files linked into the
4020 same program. You make this kind of symbol simply by mentioning a symbol
4021 name without defining it. A non-zero value represents a @code{.comm}
4022 common declaration. The value is how much common storage to reserve, in
4023 bytes (addresses). The symbol refers to the first address of the
4029 @cindex type of a symbol
4031 The type attribute of a symbol contains relocation (section)
4032 information, any flag settings indicating that a symbol is external, and
4033 (optionally), other information for linkers and debuggers. The exact
4034 format depends on the object-code output format in use.
4038 @subsection Symbol Attributes: @code{a.out}
4040 @cindex @code{a.out} symbol attributes
4041 @cindex symbol attributes, @code{a.out}
4044 * Symbol Desc:: Descriptor
4045 * Symbol Other:: Other
4049 @subsubsection Descriptor
4051 @cindex descriptor, of @code{a.out} symbol
4052 This is an arbitrary 16-bit value. You may establish a symbol's
4053 descriptor value by using a @code{.desc} statement
4054 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
4055 @command{@value{AS}}.
4058 @subsubsection Other
4060 @cindex other attribute, of @code{a.out} symbol
4061 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
4066 @subsection Symbol Attributes for COFF
4068 @cindex COFF symbol attributes
4069 @cindex symbol attributes, COFF
4071 The COFF format supports a multitude of auxiliary symbol attributes;
4072 like the primary symbol attributes, they are set between @code{.def} and
4073 @code{.endef} directives.
4075 @subsubsection Primary Attributes
4077 @cindex primary attributes, COFF symbols
4078 The symbol name is set with @code{.def}; the value and type,
4079 respectively, with @code{.val} and @code{.type}.
4081 @subsubsection Auxiliary Attributes
4083 @cindex auxiliary attributes, COFF symbols
4084 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
4085 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
4086 table information for COFF.
4091 @subsection Symbol Attributes for SOM
4093 @cindex SOM symbol attributes
4094 @cindex symbol attributes, SOM
4096 The SOM format for the HPPA supports a multitude of symbol attributes set with
4097 the @code{.EXPORT} and @code{.IMPORT} directives.
4099 The attributes are described in @cite{HP9000 Series 800 Assembly
4100 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
4101 @code{EXPORT} assembler directive documentation.
4105 @chapter Expressions
4109 @cindex numeric values
4110 An @dfn{expression} specifies an address or numeric value.
4111 Whitespace may precede and/or follow an expression.
4113 The result of an expression must be an absolute number, or else an offset into
4114 a particular section. If an expression is not absolute, and there is not
4115 enough information when @command{@value{AS}} sees the expression to know its
4116 section, a second pass over the source program might be necessary to interpret
4117 the expression---but the second pass is currently not implemented.
4118 @command{@value{AS}} aborts with an error message in this situation.
4121 * Empty Exprs:: Empty Expressions
4122 * Integer Exprs:: Integer Expressions
4126 @section Empty Expressions
4128 @cindex empty expressions
4129 @cindex expressions, empty
4130 An empty expression has no value: it is just whitespace or null.
4131 Wherever an absolute expression is required, you may omit the
4132 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4133 is compatible with other assemblers.
4136 @section Integer Expressions
4138 @cindex integer expressions
4139 @cindex expressions, integer
4140 An @dfn{integer expression} is one or more @emph{arguments} delimited
4141 by @emph{operators}.
4144 * Arguments:: Arguments
4145 * Operators:: Operators
4146 * Prefix Ops:: Prefix Operators
4147 * Infix Ops:: Infix Operators
4151 @subsection Arguments
4153 @cindex expression arguments
4154 @cindex arguments in expressions
4155 @cindex operands in expressions
4156 @cindex arithmetic operands
4157 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4158 contexts arguments are sometimes called ``arithmetic operands''. In
4159 this manual, to avoid confusing them with the ``instruction operands'' of
4160 the machine language, we use the term ``argument'' to refer to parts of
4161 expressions only, reserving the word ``operand'' to refer only to machine
4162 instruction operands.
4164 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4165 @var{section} is one of text, data, bss, absolute,
4166 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4169 Numbers are usually integers.
4171 A number can be a flonum or bignum. In this case, you are warned
4172 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4173 these 32 bits are an integer. You may write integer-manipulating
4174 instructions that act on exotic constants, compatible with other
4177 @cindex subexpressions
4178 Subexpressions are a left parenthesis @samp{(} followed by an integer
4179 expression, followed by a right parenthesis @samp{)}; or a prefix
4180 operator followed by an argument.
4183 @subsection Operators
4185 @cindex operators, in expressions
4186 @cindex arithmetic functions
4187 @cindex functions, in expressions
4188 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4189 operators are followed by an argument. Infix operators appear
4190 between their arguments. Operators may be preceded and/or followed by
4194 @subsection Prefix Operator
4196 @cindex prefix operators
4197 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4198 one argument, which must be absolute.
4200 @c the tex/end tex stuff surrounding this small table is meant to make
4201 @c it align, on the printed page, with the similar table in the next
4202 @c section (which is inside an enumerate).
4204 \global\advance\leftskip by \itemindent
4209 @dfn{Negation}. Two's complement negation.
4211 @dfn{Complementation}. Bitwise not.
4215 \global\advance\leftskip by -\itemindent
4219 @subsection Infix Operators
4221 @cindex infix operators
4222 @cindex operators, permitted arguments
4223 @dfn{Infix operators} take two arguments, one on either side. Operators
4224 have precedence, but operations with equal precedence are performed left
4225 to right. Apart from @code{+} or @option{-}, both arguments must be
4226 absolute, and the result is absolute.
4229 @cindex operator precedence
4230 @cindex precedence of operators
4237 @dfn{Multiplication}.
4240 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4246 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4249 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4253 Intermediate precedence
4258 @dfn{Bitwise Inclusive Or}.
4264 @dfn{Bitwise Exclusive Or}.
4267 @dfn{Bitwise Or Not}.
4274 @cindex addition, permitted arguments
4275 @cindex plus, permitted arguments
4276 @cindex arguments for addition
4278 @dfn{Addition}. If either argument is absolute, the result has the section of
4279 the other argument. You may not add together arguments from different
4282 @cindex subtraction, permitted arguments
4283 @cindex minus, permitted arguments
4284 @cindex arguments for subtraction
4286 @dfn{Subtraction}. If the right argument is absolute, the
4287 result has the section of the left argument.
4288 If both arguments are in the same section, the result is absolute.
4289 You may not subtract arguments from different sections.
4290 @c FIXME is there still something useful to say about undefined - undefined ?
4292 @cindex comparison expressions
4293 @cindex expressions, comparison
4298 @dfn{Is Not Equal To}
4302 @dfn{Is Greater Than}
4304 @dfn{Is Greater Than Or Equal To}
4306 @dfn{Is Less Than Or Equal To}
4308 The comparison operators can be used as infix operators. A true results has a
4309 value of -1 whereas a false result has a value of 0. Note, these operators
4310 perform signed comparisons.
4313 @item Lowest Precedence
4322 These two logical operations can be used to combine the results of sub
4323 expressions. Note, unlike the comparison operators a true result returns a
4324 value of 1 but a false results does still return 0. Also note that the logical
4325 or operator has a slightly lower precedence than logical and.
4330 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4331 address; you can only have a defined section in one of the two arguments.
4334 @chapter Assembler Directives
4336 @cindex directives, machine independent
4337 @cindex pseudo-ops, machine independent
4338 @cindex machine independent directives
4339 All assembler directives have names that begin with a period (@samp{.}).
4340 The names are case insensitive for most targets, and usually written
4343 This chapter discusses directives that are available regardless of the
4344 target machine configuration for the @sc{gnu} assembler.
4346 Some machine configurations provide additional directives.
4347 @xref{Machine Dependencies}.
4350 @ifset machine-directives
4351 @xref{Machine Dependencies}, for additional directives.
4356 * Abort:: @code{.abort}
4358 * ABORT (COFF):: @code{.ABORT}
4361 * Align:: @code{.align [@var{abs-expr}[, @var{abs-expr}[, @var{abs-expr}]]]}
4362 * Altmacro:: @code{.altmacro}
4363 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4364 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4365 * Attach_to_group:: @code{.attach_to_group @var{name}}
4366 * Balign:: @code{.balign [@var{abs-expr}[, @var{abs-expr}]]}
4367 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4368 * Byte:: @code{.byte @var{expressions}}
4369 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4370 * Comm:: @code{.comm @var{symbol} , @var{length} }
4371 * Data:: @code{.data @var{subsection}}
4372 * Dc:: @code{.dc[@var{size}] @var{expressions}}
4373 * Dcb:: @code{.dcb[@var{size}] @var{number} [,@var{fill}]}
4374 * Ds:: @code{.ds[@var{size}] @var{number} [,@var{fill}]}
4376 * Def:: @code{.def @var{name}}
4379 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4385 * Double:: @code{.double @var{flonums}}
4386 * Eject:: @code{.eject}
4387 * Else:: @code{.else}
4388 * Elseif:: @code{.elseif}
4391 * Endef:: @code{.endef}
4394 * Endfunc:: @code{.endfunc}
4395 * Endif:: @code{.endif}
4396 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4397 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4398 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4400 * Error:: @code{.error @var{string}}
4401 * Exitm:: @code{.exitm}
4402 * Extern:: @code{.extern}
4403 * Fail:: @code{.fail}
4404 * File:: @code{.file}
4405 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4406 * Float:: @code{.float @var{flonums}}
4407 * Func:: @code{.func}
4408 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4410 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4411 * Hidden:: @code{.hidden @var{names}}
4414 * hword:: @code{.hword @var{expressions}}
4415 * Ident:: @code{.ident}
4416 * If:: @code{.if @var{absolute expression}}
4417 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4418 * Include:: @code{.include "@var{file}"}
4419 * Int:: @code{.int @var{expressions}}
4421 * Internal:: @code{.internal @var{names}}
4424 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4425 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4426 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4427 * Lflags:: @code{.lflags}
4428 @ifclear no-line-dir
4429 * Line:: @code{.line @var{line-number}}
4432 * Linkonce:: @code{.linkonce [@var{type}]}
4433 * List:: @code{.list}
4434 * Ln:: @code{.ln @var{line-number}}
4435 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4436 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4438 * Local:: @code{.local @var{names}}
4441 * Long:: @code{.long @var{expressions}}
4443 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4446 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4447 * MRI:: @code{.mri @var{val}}
4448 * Noaltmacro:: @code{.noaltmacro}
4449 * Nolist:: @code{.nolist}
4451 * Nops:: @code{.nops @var{size}[, @var{control}]}
4452 * Octa:: @code{.octa @var{bignums}}
4453 * Offset:: @code{.offset @var{loc}}
4454 * Org:: @code{.org @var{new-lc}, @var{fill}}
4455 * P2align:: @code{.p2align [@var{abs-expr}[, @var{abs-expr}[, @var{abs-expr}]]]}
4457 * PopSection:: @code{.popsection}
4458 * Previous:: @code{.previous}
4461 * Print:: @code{.print @var{string}}
4463 * Protected:: @code{.protected @var{names}}
4466 * Psize:: @code{.psize @var{lines}, @var{columns}}
4467 * Purgem:: @code{.purgem @var{name}}
4469 * PushSection:: @code{.pushsection @var{name}}
4472 * Quad:: @code{.quad @var{bignums}}
4473 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4474 * Rept:: @code{.rept @var{count}}
4475 * Sbttl:: @code{.sbttl "@var{subheading}"}
4477 * Scl:: @code{.scl @var{class}}
4480 * Section:: @code{.section @var{name}[, @var{flags}]}
4483 * Set:: @code{.set @var{symbol}, @var{expression}}
4484 * Short:: @code{.short @var{expressions}}
4485 * Single:: @code{.single @var{flonums}}
4487 * Size:: @code{.size [@var{name} , @var{expression}]}
4489 @ifclear no-space-dir
4490 * Skip:: @code{.skip @var{size} [,@var{fill}]}
4493 * Sleb128:: @code{.sleb128 @var{expressions}}
4494 @ifclear no-space-dir
4495 * Space:: @code{.space @var{size} [,@var{fill}]}
4498 * Stab:: @code{.stabd, .stabn, .stabs}
4501 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4502 * Struct:: @code{.struct @var{expression}}
4504 * SubSection:: @code{.subsection}
4505 * Symver:: @code{.symver @var{name},@var{name2@@nodename}[,@var{visibility}]}
4509 * Tag:: @code{.tag @var{structname}}
4512 * Text:: @code{.text @var{subsection}}
4513 * Title:: @code{.title "@var{heading}"}
4515 * Tls_common:: @code{.tls_common @var{symbol}, @var{length}[, @var{alignment}]}
4518 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4521 * Uleb128:: @code{.uleb128 @var{expressions}}
4523 * Val:: @code{.val @var{addr}}
4527 * Version:: @code{.version "@var{string}"}
4528 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4529 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4532 * Warning:: @code{.warning @var{string}}
4533 * Weak:: @code{.weak @var{names}}
4534 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4535 * Word:: @code{.word @var{expressions}}
4536 @ifclear no-space-dir
4537 * Zero:: @code{.zero @var{size}}
4540 * 2byte:: @code{.2byte @var{expressions}}
4541 * 4byte:: @code{.4byte @var{expressions}}
4542 * 8byte:: @code{.8byte @var{bignums}}
4544 * Deprecated:: Deprecated Directives
4548 @section @code{.abort}
4550 @cindex @code{abort} directive
4551 @cindex stopping the assembly
4552 This directive stops the assembly immediately. It is for
4553 compatibility with other assemblers. The original idea was that the
4554 assembly language source would be piped into the assembler. If the sender
4555 of the source quit, it could use this directive tells @command{@value{AS}} to
4556 quit also. One day @code{.abort} will not be supported.
4560 @section @code{.ABORT} (COFF)
4562 @cindex @code{ABORT} directive
4563 When producing COFF output, @command{@value{AS}} accepts this directive as a
4564 synonym for @samp{.abort}.
4569 @section @code{.align [@var{abs-expr}[, @var{abs-expr}[, @var{abs-expr}]]]}
4571 @cindex padding the location counter
4572 @cindex @code{align} directive
4573 Pad the location counter (in the current subsection) to a particular storage
4574 boundary. The first expression (which must be absolute) is the alignment
4575 required, as described below. If this expression is omitted then a default
4576 value of 0 is used, effectively disabling alignment requirements.
4578 The second expression (also absolute) gives the fill value to be stored in the
4579 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4580 padding bytes are normally zero. However, on most systems, if the section is
4581 marked as containing code and the fill value is omitted, the space is filled
4582 with no-op instructions.
4584 The third expression is also absolute, and is also optional. If it is present,
4585 it is the maximum number of bytes that should be skipped by this alignment
4586 directive. If doing the alignment would require skipping more bytes than the
4587 specified maximum, then the alignment is not done at all. You can omit the
4588 fill value (the second argument) entirely by simply using two commas after the
4589 required alignment; this can be useful if you want the alignment to be filled
4590 with no-op instructions when appropriate.
4592 The way the required alignment is specified varies from system to system.
4593 For the arc, hppa, i386 using ELF, iq2000, m68k, or1k,
4594 s390, sparc, tic4x and xtensa, the first expression is the
4595 alignment request in bytes. For example @samp{.align 8} advances
4596 the location counter until it is a multiple of 8. If the location counter
4597 is already a multiple of 8, no change is needed. For the tic54x, the
4598 first expression is the alignment request in words.
4600 For other systems, including ppc, i386 using a.out format, arm and
4601 strongarm, it is the
4602 number of low-order zero bits the location counter must have after
4603 advancement. For example @samp{.align 3} advances the location
4604 counter until it is a multiple of 8. If the location counter is already a
4605 multiple of 8, no change is needed.
4607 This inconsistency is due to the different behaviors of the various
4608 native assemblers for these systems which GAS must emulate.
4609 GAS also provides @code{.balign} and @code{.p2align} directives,
4610 described later, which have a consistent behavior across all
4611 architectures (but are specific to GAS).
4614 @section @code{.altmacro}
4615 Enable alternate macro mode, enabling:
4618 @item LOCAL @var{name} [ , @dots{} ]
4619 One additional directive, @code{LOCAL}, is available. It is used to
4620 generate a string replacement for each of the @var{name} arguments, and
4621 replace any instances of @var{name} in each macro expansion. The
4622 replacement string is unique in the assembly, and different for each
4623 separate macro expansion. @code{LOCAL} allows you to write macros that
4624 define symbols, without fear of conflict between separate macro expansions.
4626 @item String delimiters
4627 You can write strings delimited in these other ways besides
4628 @code{"@var{string}"}:
4631 @item '@var{string}'
4632 You can delimit strings with single-quote characters.
4634 @item <@var{string}>
4635 You can delimit strings with matching angle brackets.
4638 @item single-character string escape
4639 To include any single character literally in a string (even if the
4640 character would otherwise have some special meaning), you can prefix the
4641 character with @samp{!} (an exclamation mark). For example, you can
4642 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4644 @item Expression results as strings
4645 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4646 and use the result as a string.
4650 @section @code{.ascii "@var{string}"}@dots{}
4652 @cindex @code{ascii} directive
4653 @cindex string literals
4654 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4655 separated by commas. It assembles each string (with no automatic
4656 trailing zero byte) into consecutive addresses.
4659 @section @code{.asciz "@var{string}"}@dots{}
4661 @cindex @code{asciz} directive
4662 @cindex zero-terminated strings
4663 @cindex null-terminated strings
4664 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4665 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''. Note that
4666 multiple string arguments not separated by commas will be concatenated
4667 together and only one final zero byte will be stored.
4669 @node Attach_to_group
4670 @section @code{.attach_to_group @var{name}}
4671 Attaches the current section to the named group. This is like declaring
4672 the section with the @code{G} attribute, but can be done after the section
4673 has been created. Note if the group section does not exist at the point that
4674 this directive is used then it will be created.
4677 @section @code{.balign[wl] [@var{abs-expr}[, @var{abs-expr}[, @var{abs-expr}]]]}
4679 @cindex padding the location counter given number of bytes
4680 @cindex @code{balign} directive
4681 Pad the location counter (in the current subsection) to a particular
4682 storage boundary. The first expression (which must be absolute) is the
4683 alignment request in bytes. For example @samp{.balign 8} advances
4684 the location counter until it is a multiple of 8. If the location counter
4685 is already a multiple of 8, no change is needed. If the expression is omitted
4686 then a default value of 0 is used, effectively disabling alignment requirements.
4688 The second expression (also absolute) gives the fill value to be stored in the
4689 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4690 padding bytes are normally zero. However, on most systems, if the section is
4691 marked as containing code and the fill value is omitted, the space is filled
4692 with no-op instructions.
4694 The third expression is also absolute, and is also optional. If it is present,
4695 it is the maximum number of bytes that should be skipped by this alignment
4696 directive. If doing the alignment would require skipping more bytes than the
4697 specified maximum, then the alignment is not done at all. You can omit the
4698 fill value (the second argument) entirely by simply using two commas after the
4699 required alignment; this can be useful if you want the alignment to be filled
4700 with no-op instructions when appropriate.
4702 @cindex @code{balignw} directive
4703 @cindex @code{balignl} directive
4704 The @code{.balignw} and @code{.balignl} directives are variants of the
4705 @code{.balign} directive. The @code{.balignw} directive treats the fill
4706 pattern as a two byte word value. The @code{.balignl} directives treats the
4707 fill pattern as a four byte longword value. For example, @code{.balignw
4708 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4709 filled in with the value 0x368d (the exact placement of the bytes depends upon
4710 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4713 @node Bundle directives
4714 @section Bundle directives
4715 @subsection @code{.bundle_align_mode @var{abs-expr}}
4716 @cindex @code{bundle_align_mode} directive
4718 @cindex instruction bundle
4719 @cindex aligned instruction bundle
4720 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4721 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4722 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4723 disabled (which is the default state). If the argument it not zero, it
4724 gives the size of an instruction bundle as a power of two (as for the
4725 @code{.p2align} directive, @pxref{P2align}).
4727 For some targets, it's an ABI requirement that no instruction may span a
4728 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4729 instructions that starts on an aligned boundary. For example, if
4730 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4731 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4732 effect, no single instruction may span a boundary between bundles. If an
4733 instruction would start too close to the end of a bundle for the length of
4734 that particular instruction to fit within the bundle, then the space at the
4735 end of that bundle is filled with no-op instructions so the instruction
4736 starts in the next bundle. As a corollary, it's an error if any single
4737 instruction's encoding is longer than the bundle size.
4739 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4740 @cindex @code{bundle_lock} directive
4741 @cindex @code{bundle_unlock} directive
4742 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4743 allow explicit control over instruction bundle padding. These directives
4744 are only valid when @code{.bundle_align_mode} has been used to enable
4745 aligned instruction bundle mode. It's an error if they appear when
4746 @code{.bundle_align_mode} has not been used at all, or when the last
4747 directive was @w{@code{.bundle_align_mode 0}}.
4749 @cindex bundle-locked
4750 For some targets, it's an ABI requirement that certain instructions may
4751 appear only as part of specified permissible sequences of multiple
4752 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4753 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4754 instruction sequence. For purposes of aligned instruction bundle mode, a
4755 sequence starting with @code{.bundle_lock} and ending with
4756 @code{.bundle_unlock} is treated as a single instruction. That is, the
4757 entire sequence must fit into a single bundle and may not span a bundle
4758 boundary. If necessary, no-op instructions will be inserted before the
4759 first instruction of the sequence so that the whole sequence starts on an
4760 aligned bundle boundary. It's an error if the sequence is longer than the
4763 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4764 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4765 nested. That is, a second @code{.bundle_lock} directive before the next
4766 @code{.bundle_unlock} directive has no effect except that it must be
4767 matched by another closing @code{.bundle_unlock} so that there is the
4768 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4771 @section @code{.byte @var{expressions}}
4773 @cindex @code{byte} directive
4774 @cindex integers, one byte
4775 @code{.byte} expects zero or more expressions, separated by commas.
4776 Each expression is assembled into the next byte.
4778 @node CFI directives
4779 @section CFI directives
4780 @subsection @code{.cfi_sections @var{section_list}}
4781 @cindex @code{cfi_sections} directive
4782 @code{.cfi_sections} may be used to specify whether CFI directives
4783 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4784 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4785 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4786 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4787 directive is not used is @code{.cfi_sections .eh_frame}.
4789 On targets that support compact unwinding tables these can be generated
4790 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4792 Some targets may support an additional name, such as @code{.c6xabi.exidx}
4793 which is used by the @value{TIC6X} target.
4795 The @code{.cfi_sections} directive can be repeated, with the same or different
4796 arguments, provided that CFI generation has not yet started. Once CFI
4797 generation has started however the section list is fixed and any attempts to
4798 redefine it will result in an error.
4800 @subsection @code{.cfi_startproc [simple]}
4801 @cindex @code{cfi_startproc} directive
4802 @code{.cfi_startproc} is used at the beginning of each function that
4803 should have an entry in @code{.eh_frame}. It initializes some internal
4804 data structures. Don't forget to close the function by
4805 @code{.cfi_endproc}.
4807 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4808 it also emits some architecture dependent initial CFI instructions.
4810 @subsection @code{.cfi_endproc}
4811 @cindex @code{cfi_endproc} directive
4812 @code{.cfi_endproc} is used at the end of a function where it closes its
4813 unwind entry previously opened by
4814 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4816 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4817 @cindex @code{cfi_personality} directive
4818 @code{.cfi_personality} defines personality routine and its encoding.
4819 @var{encoding} must be a constant determining how the personality
4820 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4821 argument is not present, otherwise second argument should be
4822 a constant or a symbol name. When using indirect encodings,
4823 the symbol provided should be the location where personality
4824 can be loaded from, not the personality routine itself.
4825 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4826 no personality routine.
4828 @subsection @code{.cfi_personality_id @var{id}}
4829 @cindex @code{cfi_personality_id} directive
4830 @code{cfi_personality_id} defines a personality routine by its index as
4831 defined in a compact unwinding format.
4832 Only valid when generating compact EH frames (i.e.
4833 with @code{.cfi_sections eh_frame_entry}.
4835 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4836 @cindex @code{cfi_fde_data} directive
4837 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4838 used for the current function. These are emitted inline in the
4839 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4840 in the @code{.gnu.extab} section otherwise.
4841 Only valid when generating compact EH frames (i.e.
4842 with @code{.cfi_sections eh_frame_entry}.
4844 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4845 @code{.cfi_lsda} defines LSDA and its encoding.
4846 @var{encoding} must be a constant determining how the LSDA
4847 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4848 argument is not present, otherwise the second argument should be a constant
4849 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4850 meaning that no LSDA is present.
4852 @subsection @code{.cfi_inline_lsda} [@var{align}]
4853 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4854 switches to the corresponding @code{.gnu.extab} section.
4855 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4856 Only valid when generating compact EH frames (i.e.
4857 with @code{.cfi_sections eh_frame_entry}.
4859 The table header and unwinding opcodes will be generated at this point,
4860 so that they are immediately followed by the LSDA data. The symbol
4861 referenced by the @code{.cfi_lsda} directive should still be defined
4862 in case a fallback FDE based encoding is used. The LSDA data is terminated
4863 by a section directive.
4865 The optional @var{align} argument specifies the alignment required.
4866 The alignment is specified as a power of two, as with the
4867 @code{.p2align} directive.
4869 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4870 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4871 address from @var{register} and add @var{offset} to it}.
4873 @subsection @code{.cfi_def_cfa_register @var{register}}
4874 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4875 now on @var{register} will be used instead of the old one. Offset
4878 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4879 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4880 remains the same, but @var{offset} is new. Note that it is the
4881 absolute offset that will be added to a defined register to compute
4884 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4885 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4886 value that is added/subtracted from the previous offset.
4888 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4889 Previous value of @var{register} is saved at offset @var{offset} from
4892 @subsection @code{.cfi_val_offset @var{register}, @var{offset}}
4893 Previous value of @var{register} is CFA + @var{offset}.
4895 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4896 Previous value of @var{register} is saved at offset @var{offset} from
4897 the current CFA register. This is transformed to @code{.cfi_offset}
4898 using the known displacement of the CFA register from the CFA.
4899 This is often easier to use, because the number will match the
4900 code it's annotating.
4902 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4903 Previous value of @var{register1} is saved in register @var{register2}.
4905 @subsection @code{.cfi_restore @var{register}}
4906 @code{.cfi_restore} says that the rule for @var{register} is now the
4907 same as it was at the beginning of the function, after all initial
4908 instruction added by @code{.cfi_startproc} were executed.
4910 @subsection @code{.cfi_undefined @var{register}}
4911 From now on the previous value of @var{register} can't be restored anymore.
4913 @subsection @code{.cfi_same_value @var{register}}
4914 Current value of @var{register} is the same like in the previous frame,
4915 i.e. no restoration needed.
4917 @subsection @code{.cfi_remember_state} and @code{.cfi_restore_state}
4918 @code{.cfi_remember_state} pushes the set of rules for every register onto an
4919 implicit stack, while @code{.cfi_restore_state} pops them off the stack and
4920 places them in the current row. This is useful for situations where you have
4921 multiple @code{.cfi_*} directives that need to be undone due to the control
4922 flow of the program. For example, we could have something like this (assuming
4923 the CFA is the value of @code{rbp}):
4933 .cfi_def_cfa %rsp, 8
4936 /* Do something else */
4939 Here, we want the @code{.cfi} directives to affect only the rows corresponding
4940 to the instructions before @code{label}. This means we'd have to add multiple
4941 @code{.cfi} directives after @code{label} to recreate the original save
4942 locations of the registers, as well as setting the CFA back to the value of
4943 @code{rbp}. This would be clumsy, and result in a larger binary size. Instead,
4955 .cfi_def_cfa %rsp, 8
4959 /* Do something else */
4962 That way, the rules for the instructions after @code{label} will be the same
4963 as before the first @code{.cfi_restore} without having to use multiple
4964 @code{.cfi} directives.
4966 @subsection @code{.cfi_return_column @var{register}}
4967 Change return column @var{register}, i.e. the return address is either
4968 directly in @var{register} or can be accessed by rules for @var{register}.
4970 @subsection @code{.cfi_signal_frame}
4971 Mark current function as signal trampoline.
4973 @subsection @code{.cfi_window_save}
4974 SPARC register window has been saved.
4976 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
4977 Allows the user to add arbitrary bytes to the unwind info. One
4978 might use this to add OS-specific CFI opcodes, or generic CFI
4979 opcodes that GAS does not yet support.
4981 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4982 The current value of @var{register} is @var{label}. The value of @var{label}
4983 will be encoded in the output file according to @var{encoding}; see the
4984 description of @code{.cfi_personality} for details on this encoding.
4986 The usefulness of equating a register to a fixed label is probably
4987 limited to the return address register. Here, it can be useful to
4988 mark a code segment that has only one return address which is reached
4989 by a direct branch and no copy of the return address exists in memory
4990 or another register.
4993 @section @code{.comm @var{symbol} , @var{length} }
4995 @cindex @code{comm} directive
4996 @cindex symbol, common
4997 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4998 common symbol in one object file may be merged with a defined or common symbol
4999 of the same name in another object file. If @code{@value{LD}} does not see a
5000 definition for the symbol--just one or more common symbols--then it will
5001 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
5002 absolute expression. If @code{@value{LD}} sees multiple common symbols with
5003 the same name, and they do not all have the same size, it will allocate space
5004 using the largest size.
5007 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
5008 an optional third argument. This is the desired alignment of the symbol,
5009 specified for ELF as a byte boundary (for example, an alignment of 16 means
5010 that the least significant 4 bits of the address should be zero), and for PE
5011 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
5012 boundary). The alignment must be an absolute expression, and it must be a
5013 power of two. If @code{@value{LD}} allocates uninitialized memory for the
5014 common symbol, it will use the alignment when placing the symbol. If no
5015 alignment is specified, @command{@value{AS}} will set the alignment to the
5016 largest power of two less than or equal to the size of the symbol, up to a
5017 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
5018 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
5019 @samp{--section-alignment} option; image file sections in PE are aligned to
5020 multiples of 4096, which is far too large an alignment for ordinary variables.
5021 It is rather the default alignment for (non-debug) sections within object
5022 (@samp{*.o}) files, which are less strictly aligned.}.
5026 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
5027 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
5031 @section @code{.data @var{subsection}}
5032 @cindex @code{data} directive
5034 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
5035 end of the data subsection numbered @var{subsection} (which is an
5036 absolute expression). If @var{subsection} is omitted, it defaults
5040 @section @code{.dc[@var{size}] @var{expressions}}
5041 @cindex @code{dc} directive
5043 The @code{.dc} directive expects zero or more @var{expressions} separated by
5044 commas. These expressions are evaluated and their values inserted into the
5045 current section. The size of the emitted value depends upon the suffix to the
5046 @code{.dc} directive:
5050 Emits N-bit values, where N is the size of an address on the target system.
5054 Emits double precision floating-point values.
5056 Emits 32-bit values.
5058 Emits single precision floating-point values.
5060 Emits 16-bit values.
5061 Note - this is true even on targets where the @code{.word} directive would emit
5064 Emits long double precision floating-point values.
5067 If no suffix is used then @samp{.w} is assumed.
5069 The byte ordering is target dependent, as is the size and format of floating
5073 @section @code{.dcb[@var{size}] @var{number} [,@var{fill}]}
5074 @cindex @code{dcb} directive
5075 This directive emits @var{number} copies of @var{fill}, each of @var{size}
5076 bytes. Both @var{number} and @var{fill} are absolute expressions. If the
5077 comma and @var{fill} are omitted, @var{fill} is assumed to be zero. The
5078 @var{size} suffix, if present, must be one of:
5082 Emits single byte values.
5084 Emits double-precision floating point values.
5086 Emits 4-byte values.
5088 Emits single-precision floating point values.
5090 Emits 2-byte values.
5092 Emits long double-precision floating point values.
5095 If the @var{size} suffix is omitted then @samp{.w} is assumed.
5097 The byte ordering is target dependent, as is the size and format of floating
5101 @section @code{.ds[@var{size}] @var{number} [,@var{fill}]}
5102 @cindex @code{ds} directive
5103 This directive emits @var{number} copies of @var{fill}, each of @var{size}
5104 bytes. Both @var{number} and @var{fill} are absolute expressions. If the
5105 comma and @var{fill} are omitted, @var{fill} is assumed to be zero. The
5106 @var{size} suffix, if present, must be one of:
5110 Emits single byte values.
5112 Emits 8-byte values.
5114 Emits 4-byte values.
5116 Emits 12-byte values.
5118 Emits 4-byte values.
5120 Emits 2-byte values.
5122 Emits 12-byte values.
5125 Note - unlike the @code{.dcb} directive the @samp{.d}, @samp{.s} and @samp{.x}
5126 suffixes do not indicate that floating-point values are to be inserted.
5128 If the @var{size} suffix is omitted then @samp{.w} is assumed.
5130 The byte ordering is target dependent.
5135 @section @code{.def @var{name}}
5137 @cindex @code{def} directive
5138 @cindex COFF symbols, debugging
5139 @cindex debugging COFF symbols
5140 Begin defining debugging information for a symbol @var{name}; the
5141 definition extends until the @code{.endef} directive is encountered.
5146 @section @code{.desc @var{symbol}, @var{abs-expression}}
5148 @cindex @code{desc} directive
5149 @cindex COFF symbol descriptor
5150 @cindex symbol descriptor, COFF
5151 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
5152 to the low 16 bits of an absolute expression.
5155 The @samp{.desc} directive is not available when @command{@value{AS}} is
5156 configured for COFF output; it is only for @code{a.out} or @code{b.out}
5157 object format. For the sake of compatibility, @command{@value{AS}} accepts
5158 it, but produces no output, when configured for COFF.
5164 @section @code{.dim}
5166 @cindex @code{dim} directive
5167 @cindex COFF auxiliary symbol information
5168 @cindex auxiliary symbol information, COFF
5169 This directive is generated by compilers to include auxiliary debugging
5170 information in the symbol table. It is only permitted inside
5171 @code{.def}/@code{.endef} pairs.
5175 @section @code{.double @var{flonums}}
5177 @cindex @code{double} directive
5178 @cindex floating point numbers (double)
5179 @code{.double} expects zero or more flonums, separated by commas. It
5180 assembles floating point numbers.
5182 The exact kind of floating point numbers emitted depends on how
5183 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5187 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
5188 in @sc{ieee} format.
5193 @section @code{.eject}
5195 @cindex @code{eject} directive
5196 @cindex new page, in listings
5197 @cindex page, in listings
5198 @cindex listing control: new page
5199 Force a page break at this point, when generating assembly listings.
5202 @section @code{.else}
5204 @cindex @code{else} directive
5205 @code{.else} is part of the @command{@value{AS}} support for conditional
5206 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
5207 of code to be assembled if the condition for the preceding @code{.if}
5211 @section @code{.elseif}
5213 @cindex @code{elseif} directive
5214 @code{.elseif} is part of the @command{@value{AS}} support for conditional
5215 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
5216 @code{.if} block that would otherwise fill the entire @code{.else} section.
5219 @section @code{.end}
5221 @cindex @code{end} directive
5222 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
5223 process anything in the file past the @code{.end} directive.
5227 @section @code{.endef}
5229 @cindex @code{endef} directive
5230 This directive flags the end of a symbol definition begun with
5235 @section @code{.endfunc}
5236 @cindex @code{endfunc} directive
5237 @code{.endfunc} marks the end of a function specified with @code{.func}.
5240 @section @code{.endif}
5242 @cindex @code{endif} directive
5243 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
5244 it marks the end of a block of code that is only assembled
5245 conditionally. @xref{If,,@code{.if}}.
5248 @section @code{.equ @var{symbol}, @var{expression}}
5250 @cindex @code{equ} directive
5251 @cindex assigning values to symbols
5252 @cindex symbols, assigning values to
5253 This directive sets the value of @var{symbol} to @var{expression}.
5254 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
5257 The syntax for @code{equ} on the HPPA is
5258 @samp{@var{symbol} .equ @var{expression}}.
5262 The syntax for @code{equ} on the Z80 is
5263 @samp{@var{symbol} equ @var{expression}}.
5264 On the Z80 it is an error if @var{symbol} is already defined,
5265 but the symbol is not protected from later redefinition.
5266 Compare @ref{Equiv}.
5270 @section @code{.equiv @var{symbol}, @var{expression}}
5271 @cindex @code{equiv} directive
5272 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5273 the assembler will signal an error if @var{symbol} is already defined. Note a
5274 symbol which has been referenced but not actually defined is considered to be
5277 Except for the contents of the error message, this is roughly equivalent to
5284 plus it protects the symbol from later redefinition.
5287 @section @code{.eqv @var{symbol}, @var{expression}}
5288 @cindex @code{eqv} directive
5289 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5290 evaluate the expression or any part of it immediately. Instead each time
5291 the resulting symbol is used in an expression, a snapshot of its current
5295 @section @code{.err}
5296 @cindex @code{err} directive
5297 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5298 message and, unless the @option{-Z} option was used, it will not generate an
5299 object file. This can be used to signal an error in conditionally compiled code.
5302 @section @code{.error "@var{string}"}
5303 @cindex error directive
5305 Similarly to @code{.err}, this directive emits an error, but you can specify a
5306 string that will be emitted as the error message. If you don't specify the
5307 message, it defaults to @code{".error directive invoked in source file"}.
5308 @xref{Errors, ,Error and Warning Messages}.
5311 .error "This code has not been assembled and tested."
5315 @section @code{.exitm}
5316 Exit early from the current macro definition. @xref{Macro}.
5319 @section @code{.extern}
5321 @cindex @code{extern} directive
5322 @code{.extern} is accepted in the source program---for compatibility
5323 with other assemblers---but it is ignored. @command{@value{AS}} treats
5324 all undefined symbols as external.
5327 @section @code{.fail @var{expression}}
5329 @cindex @code{fail} directive
5330 Generates an error or a warning. If the value of the @var{expression} is 500
5331 or more, @command{@value{AS}} will print a warning message. If the value is less
5332 than 500, @command{@value{AS}} will print an error message. The message will
5333 include the value of @var{expression}. This can occasionally be useful inside
5334 complex nested macros or conditional assembly.
5337 @section @code{.file}
5338 @cindex @code{file} directive
5340 @ifclear no-file-dir
5341 There are two different versions of the @code{.file} directive. Targets
5342 that support DWARF2 line number information use the DWARF2 version of
5343 @code{.file}. Other targets use the default version.
5345 @subheading Default Version
5347 @cindex logical file name
5348 @cindex file name, logical
5349 This version of the @code{.file} directive tells @command{@value{AS}} that we
5350 are about to start a new logical file. The syntax is:
5356 @var{string} is the new file name. In general, the filename is
5357 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5358 to specify an empty file name, you must give the quotes--@code{""}. This
5359 statement may go away in future: it is only recognized to be compatible with
5360 old @command{@value{AS}} programs.
5362 @subheading DWARF2 Version
5365 When emitting DWARF2 line number information, @code{.file} assigns filenames
5366 to the @code{.debug_line} file name table. The syntax is:
5369 .file @var{fileno} @var{filename}
5372 The @var{fileno} operand should be a unique positive integer to use as the
5373 index of the entry in the table. The @var{filename} operand is a C string
5374 literal enclosed in double quotes. The @var{filename} can include directory
5375 elements. If it does, then the directory will be added to the directory table
5376 and the basename will be added to the file table.
5378 The detail of filename indices is exposed to the user because the filename
5379 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5380 information, and thus the user must know the exact indices that table
5383 If DWARF-5 support has been enabled via the @option{-gdwarf-5} option then
5384 an extended version of the @code{file} is also allowed:
5387 .file @var{fileno} [@var{dirname}] @var{filename} [md5 @var{value}]
5390 With this version a separate directory name is allowed, although if this is
5391 used then @var{filename} should not contain any directory components. In
5392 addtion an md5 hash value of the contents of @var{filename} can be provided.
5393 This will be stored in the the file table as well, and can be used by tools
5394 reading the debug information to verify that the contents of the source file
5395 match the contents of the compiled file.
5398 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5400 @cindex @code{fill} directive
5401 @cindex writing patterns in memory
5402 @cindex patterns, writing in memory
5403 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5404 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5405 may be zero or more. @var{Size} may be zero or more, but if it is
5406 more than 8, then it is deemed to have the value 8, compatible with
5407 other people's assemblers. The contents of each @var{repeat} bytes
5408 is taken from an 8-byte number. The highest order 4 bytes are
5409 zero. The lowest order 4 bytes are @var{value} rendered in the
5410 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5411 Each @var{size} bytes in a repetition is taken from the lowest order
5412 @var{size} bytes of this number. Again, this bizarre behavior is
5413 compatible with other people's assemblers.
5415 @var{size} and @var{value} are optional.
5416 If the second comma and @var{value} are absent, @var{value} is
5417 assumed zero. If the first comma and following tokens are absent,
5418 @var{size} is assumed to be 1.
5421 @section @code{.float @var{flonums}}
5423 @cindex floating point numbers (single)
5424 @cindex @code{float} directive
5425 This directive assembles zero or more flonums, separated by commas. It
5426 has the same effect as @code{.single}.
5428 The exact kind of floating point numbers emitted depends on how
5429 @command{@value{AS}} is configured.
5430 @xref{Machine Dependencies}.
5434 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5435 in @sc{ieee} format.
5440 @section @code{.func @var{name}[,@var{label}]}
5441 @cindex @code{func} directive
5442 @code{.func} emits debugging information to denote function @var{name}, and
5443 is ignored unless the file is assembled with debugging enabled.
5444 Only @samp{--gstabs[+]} is currently supported.
5445 @var{label} is the entry point of the function and if omitted @var{name}
5446 prepended with the @samp{leading char} is used.
5447 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5448 All functions are currently defined to have @code{void} return type.
5449 The function must be terminated with @code{.endfunc}.
5452 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5454 @cindex @code{global} directive
5455 @cindex symbol, making visible to linker
5456 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5457 @var{symbol} in your partial program, its value is made available to
5458 other partial programs that are linked with it. Otherwise,
5459 @var{symbol} takes its attributes from a symbol of the same name
5460 from another file linked into the same program.
5462 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5463 compatibility with other assemblers.
5466 On the HPPA, @code{.global} is not always enough to make it accessible to other
5467 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5468 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5473 @section @code{.gnu_attribute @var{tag},@var{value}}
5474 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5477 @section @code{.hidden @var{names}}
5479 @cindex @code{hidden} directive
5481 This is one of the ELF visibility directives. The other two are
5482 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5483 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5485 This directive overrides the named symbols default visibility (which is set by
5486 their binding: local, global or weak). The directive sets the visibility to
5487 @code{hidden} which means that the symbols are not visible to other components.
5488 Such symbols are always considered to be @code{protected} as well.
5492 @section @code{.hword @var{expressions}}
5494 @cindex @code{hword} directive
5495 @cindex integers, 16-bit
5496 @cindex numbers, 16-bit
5497 @cindex sixteen bit integers
5498 This expects zero or more @var{expressions}, and emits
5499 a 16 bit number for each.
5502 This directive is a synonym for @samp{.short}; depending on the target
5503 architecture, it may also be a synonym for @samp{.word}.
5507 This directive is a synonym for @samp{.short}.
5510 This directive is a synonym for both @samp{.short} and @samp{.word}.
5515 @section @code{.ident}
5517 @cindex @code{ident} directive
5519 This directive is used by some assemblers to place tags in object files. The
5520 behavior of this directive varies depending on the target. When using the
5521 a.out object file format, @command{@value{AS}} simply accepts the directive for
5522 source-file compatibility with existing assemblers, but does not emit anything
5523 for it. When using COFF, comments are emitted to the @code{.comment} or
5524 @code{.rdata} section, depending on the target. When using ELF, comments are
5525 emitted to the @code{.comment} section.
5528 @section @code{.if @var{absolute expression}}
5530 @cindex conditional assembly
5531 @cindex @code{if} directive
5532 @code{.if} marks the beginning of a section of code which is only
5533 considered part of the source program being assembled if the argument
5534 (which must be an @var{absolute expression}) is non-zero. The end of
5535 the conditional section of code must be marked by @code{.endif}
5536 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5537 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5538 If you have several conditions to check, @code{.elseif} may be used to avoid
5539 nesting blocks if/else within each subsequent @code{.else} block.
5541 The following variants of @code{.if} are also supported:
5543 @cindex @code{ifdef} directive
5544 @item .ifdef @var{symbol}
5545 Assembles the following section of code if the specified @var{symbol}
5546 has been defined. Note a symbol which has been referenced but not yet defined
5547 is considered to be undefined.
5549 @cindex @code{ifb} directive
5550 @item .ifb @var{text}
5551 Assembles the following section of code if the operand is blank (empty).
5553 @cindex @code{ifc} directive
5554 @item .ifc @var{string1},@var{string2}
5555 Assembles the following section of code if the two strings are the same. The
5556 strings may be optionally quoted with single quotes. If they are not quoted,
5557 the first string stops at the first comma, and the second string stops at the
5558 end of the line. Strings which contain whitespace should be quoted. The
5559 string comparison is case sensitive.
5561 @cindex @code{ifeq} directive
5562 @item .ifeq @var{absolute expression}
5563 Assembles the following section of code if the argument is zero.
5565 @cindex @code{ifeqs} directive
5566 @item .ifeqs @var{string1},@var{string2}
5567 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5569 @cindex @code{ifge} directive
5570 @item .ifge @var{absolute expression}
5571 Assembles the following section of code if the argument is greater than or
5574 @cindex @code{ifgt} directive
5575 @item .ifgt @var{absolute expression}
5576 Assembles the following section of code if the argument is greater than zero.
5578 @cindex @code{ifle} directive
5579 @item .ifle @var{absolute expression}
5580 Assembles the following section of code if the argument is less than or equal
5583 @cindex @code{iflt} directive
5584 @item .iflt @var{absolute expression}
5585 Assembles the following section of code if the argument is less than zero.
5587 @cindex @code{ifnb} directive
5588 @item .ifnb @var{text}
5589 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5590 following section of code if the operand is non-blank (non-empty).
5592 @cindex @code{ifnc} directive
5593 @item .ifnc @var{string1},@var{string2}.
5594 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5595 following section of code if the two strings are not the same.
5597 @cindex @code{ifndef} directive
5598 @cindex @code{ifnotdef} directive
5599 @item .ifndef @var{symbol}
5600 @itemx .ifnotdef @var{symbol}
5601 Assembles the following section of code if the specified @var{symbol}
5602 has not been defined. Both spelling variants are equivalent. Note a symbol
5603 which has been referenced but not yet defined is considered to be undefined.
5605 @cindex @code{ifne} directive
5606 @item .ifne @var{absolute expression}
5607 Assembles the following section of code if the argument is not equal to zero
5608 (in other words, this is equivalent to @code{.if}).
5610 @cindex @code{ifnes} directive
5611 @item .ifnes @var{string1},@var{string2}
5612 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5613 following section of code if the two strings are not the same.
5617 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5619 @cindex @code{incbin} directive
5620 @cindex binary files, including
5621 The @code{incbin} directive includes @var{file} verbatim at the current
5622 location. You can control the search paths used with the @samp{-I} command-line
5623 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5626 The @var{skip} argument skips a number of bytes from the start of the
5627 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5628 read. Note that the data is not aligned in any way, so it is the user's
5629 responsibility to make sure that proper alignment is provided both before and
5630 after the @code{incbin} directive.
5633 @section @code{.include "@var{file}"}
5635 @cindex @code{include} directive
5636 @cindex supporting files, including
5637 @cindex files, including
5638 This directive provides a way to include supporting files at specified
5639 points in your source program. The code from @var{file} is assembled as
5640 if it followed the point of the @code{.include}; when the end of the
5641 included file is reached, assembly of the original file continues. You
5642 can control the search paths used with the @samp{-I} command-line option
5643 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5647 @section @code{.int @var{expressions}}
5649 @cindex @code{int} directive
5650 @cindex integers, 32-bit
5651 Expect zero or more @var{expressions}, of any section, separated by commas.
5652 For each expression, emit a number that, at run time, is the value of that
5653 expression. The byte order and bit size of the number depends on what kind
5654 of target the assembly is for.
5658 On most forms of the H8/300, @code{.int} emits 16-bit
5659 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5666 @section @code{.internal @var{names}}
5668 @cindex @code{internal} directive
5670 This is one of the ELF visibility directives. The other two are
5671 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5672 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5674 This directive overrides the named symbols default visibility (which is set by
5675 their binding: local, global or weak). The directive sets the visibility to
5676 @code{internal} which means that the symbols are considered to be @code{hidden}
5677 (i.e., not visible to other components), and that some extra, processor specific
5678 processing must also be performed upon the symbols as well.
5682 @section @code{.irp @var{symbol},@var{values}}@dots{}
5684 @cindex @code{irp} directive
5685 Evaluate a sequence of statements assigning different values to @var{symbol}.
5686 The sequence of statements starts at the @code{.irp} directive, and is
5687 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5688 set to @var{value}, and the sequence of statements is assembled. If no
5689 @var{value} is listed, the sequence of statements is assembled once, with
5690 @var{symbol} set to the null string. To refer to @var{symbol} within the
5691 sequence of statements, use @var{\symbol}.
5693 For example, assembling
5701 is equivalent to assembling
5709 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5712 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5714 @cindex @code{irpc} directive
5715 Evaluate a sequence of statements assigning different values to @var{symbol}.
5716 The sequence of statements starts at the @code{.irpc} directive, and is
5717 terminated by an @code{.endr} directive. For each character in @var{value},
5718 @var{symbol} is set to the character, and the sequence of statements is
5719 assembled. If no @var{value} is listed, the sequence of statements is
5720 assembled once, with @var{symbol} set to the null string. To refer to
5721 @var{symbol} within the sequence of statements, use @var{\symbol}.
5723 For example, assembling
5731 is equivalent to assembling
5739 For some caveats with the spelling of @var{symbol}, see also the discussion
5743 @section @code{.lcomm @var{symbol} , @var{length}}
5745 @cindex @code{lcomm} directive
5746 @cindex local common symbols
5747 @cindex symbols, local common
5748 Reserve @var{length} (an absolute expression) bytes for a local common
5749 denoted by @var{symbol}. The section and value of @var{symbol} are
5750 those of the new local common. The addresses are allocated in the bss
5751 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5752 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5753 not visible to @code{@value{LD}}.
5756 Some targets permit a third argument to be used with @code{.lcomm}. This
5757 argument specifies the desired alignment of the symbol in the bss section.
5761 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5762 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5766 @section @code{.lflags}
5768 @cindex @code{lflags} directive (ignored)
5769 @command{@value{AS}} accepts this directive, for compatibility with other
5770 assemblers, but ignores it.
5772 @ifclear no-line-dir
5774 @section @code{.line @var{line-number}}
5776 @cindex @code{line} directive
5777 @cindex logical line number
5779 Change the logical line number. @var{line-number} must be an absolute
5780 expression. The next line has that logical line number. Therefore any other
5781 statements on the current line (after a statement separator character) are
5782 reported as on logical line number @var{line-number} @minus{} 1. One day
5783 @command{@value{AS}} will no longer support this directive: it is recognized only
5784 for compatibility with existing assembler programs.
5787 Even though this is a directive associated with the @code{a.out} or
5788 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5789 when producing COFF output, and treats @samp{.line} as though it
5790 were the COFF @samp{.ln} @emph{if} it is found outside a
5791 @code{.def}/@code{.endef} pair.
5793 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5794 used by compilers to generate auxiliary symbol information for
5799 @section @code{.linkonce [@var{type}]}
5801 @cindex @code{linkonce} directive
5802 @cindex common sections
5803 Mark the current section so that the linker only includes a single copy of it.
5804 This may be used to include the same section in several different object files,
5805 but ensure that the linker will only include it once in the final output file.
5806 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5807 Duplicate sections are detected based on the section name, so it should be
5810 This directive is only supported by a few object file formats; as of this
5811 writing, the only object file format which supports it is the Portable
5812 Executable format used on Windows NT.
5814 The @var{type} argument is optional. If specified, it must be one of the
5815 following strings. For example:
5819 Not all types may be supported on all object file formats.
5823 Silently discard duplicate sections. This is the default.
5826 Warn if there are duplicate sections, but still keep only one copy.
5829 Warn if any of the duplicates have different sizes.
5832 Warn if any of the duplicates do not have exactly the same contents.
5836 @section @code{.list}
5838 @cindex @code{list} directive
5839 @cindex listing control, turning on
5840 Control (in conjunction with the @code{.nolist} directive) whether or
5841 not assembly listings are generated. These two directives maintain an
5842 internal counter (which is zero initially). @code{.list} increments the
5843 counter, and @code{.nolist} decrements it. Assembly listings are
5844 generated whenever the counter is greater than zero.
5846 By default, listings are disabled. When you enable them (with the
5847 @samp{-a} command-line option; @pxref{Invoking,,Command-Line Options}),
5848 the initial value of the listing counter is one.
5851 @section @code{.ln @var{line-number}}
5853 @cindex @code{ln} directive
5854 @ifclear no-line-dir
5855 @samp{.ln} is a synonym for @samp{.line}.
5858 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5859 must be an absolute expression. The next line has that logical
5860 line number, so any other statements on the current line (after a
5861 statement separator character @code{;}) are reported as on logical
5862 line number @var{line-number} @minus{} 1.
5866 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5867 @cindex @code{loc} directive
5868 When emitting DWARF2 line number information,
5869 the @code{.loc} directive will add a row to the @code{.debug_line} line
5870 number matrix corresponding to the immediately following assembly
5871 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5872 arguments will be applied to the @code{.debug_line} state machine before
5873 the row is added. It is an error for the input assembly file to generate
5874 a non-empty @code{.debug_line} and also use @code{loc} directives.
5876 The @var{options} are a sequence of the following tokens in any order:
5880 This option will set the @code{basic_block} register in the
5881 @code{.debug_line} state machine to @code{true}.
5884 This option will set the @code{prologue_end} register in the
5885 @code{.debug_line} state machine to @code{true}.
5887 @item epilogue_begin
5888 This option will set the @code{epilogue_begin} register in the
5889 @code{.debug_line} state machine to @code{true}.
5891 @item is_stmt @var{value}
5892 This option will set the @code{is_stmt} register in the
5893 @code{.debug_line} state machine to @code{value}, which must be
5896 @item isa @var{value}
5897 This directive will set the @code{isa} register in the @code{.debug_line}
5898 state machine to @var{value}, which must be an unsigned integer.
5900 @item discriminator @var{value}
5901 This directive will set the @code{discriminator} register in the @code{.debug_line}
5902 state machine to @var{value}, which must be an unsigned integer.
5904 @item view @var{value}
5905 This option causes a row to be added to @code{.debug_line} in reference to the
5906 current address (which might not be the same as that of the following assembly
5907 instruction), and to associate @var{value} with the @code{view} register in the
5908 @code{.debug_line} state machine. If @var{value} is a label, both the
5909 @code{view} register and the label are set to the number of prior @code{.loc}
5910 directives at the same program location. If @var{value} is the literal
5911 @code{0}, the @code{view} register is set to zero, and the assembler asserts
5912 that there aren't any prior @code{.loc} directives at the same program
5913 location. If @var{value} is the literal @code{-0}, the assembler arrange for
5914 the @code{view} register to be reset in this row, even if there are prior
5915 @code{.loc} directives at the same program location.
5919 @node Loc_mark_labels
5920 @section @code{.loc_mark_labels @var{enable}}
5921 @cindex @code{loc_mark_labels} directive
5922 When emitting DWARF2 line number information,
5923 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5924 to the @code{.debug_line} line number matrix with the @code{basic_block}
5925 register in the state machine set whenever a code label is seen.
5926 The @var{enable} argument should be either 1 or 0, to enable or disable
5927 this function respectively.
5931 @section @code{.local @var{names}}
5933 @cindex @code{local} directive
5934 This directive, which is available for ELF targets, marks each symbol in
5935 the comma-separated list of @code{names} as a local symbol so that it
5936 will not be externally visible. If the symbols do not already exist,
5937 they will be created.
5939 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5940 accept an alignment argument, which is the case for most ELF targets,
5941 the @code{.local} directive can be used in combination with @code{.comm}
5942 (@pxref{Comm}) to define aligned local common data.
5946 @section @code{.long @var{expressions}}
5948 @cindex @code{long} directive
5949 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5952 @c no one seems to know what this is for or whether this description is
5953 @c what it really ought to do
5955 @section @code{.lsym @var{symbol}, @var{expression}}
5957 @cindex @code{lsym} directive
5958 @cindex symbol, not referenced in assembly
5959 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5960 the hash table, ensuring it cannot be referenced by name during the
5961 rest of the assembly. This sets the attributes of the symbol to be
5962 the same as the expression value:
5964 @var{other} = @var{descriptor} = 0
5965 @var{type} = @r{(section of @var{expression})}
5966 @var{value} = @var{expression}
5969 The new symbol is not flagged as external.
5973 @section @code{.macro}
5976 The commands @code{.macro} and @code{.endm} allow you to define macros that
5977 generate assembly output. For example, this definition specifies a macro
5978 @code{sum} that puts a sequence of numbers into memory:
5981 .macro sum from=0, to=5
5990 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
6002 @item .macro @var{macname}
6003 @itemx .macro @var{macname} @var{macargs} @dots{}
6004 @cindex @code{macro} directive
6005 Begin the definition of a macro called @var{macname}. If your macro
6006 definition requires arguments, specify their names after the macro name,
6007 separated by commas or spaces. You can qualify the macro argument to
6008 indicate whether all invocations must specify a non-blank value (through
6009 @samp{:@code{req}}), or whether it takes all of the remaining arguments
6010 (through @samp{:@code{vararg}}). You can supply a default value for any
6011 macro argument by following the name with @samp{=@var{deflt}}. You
6012 cannot define two macros with the same @var{macname} unless it has been
6013 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
6014 definitions. For example, these are all valid @code{.macro} statements:
6018 Begin the definition of a macro called @code{comm}, which takes no
6021 @item .macro plus1 p, p1
6022 @itemx .macro plus1 p p1
6023 Either statement begins the definition of a macro called @code{plus1},
6024 which takes two arguments; within the macro definition, write
6025 @samp{\p} or @samp{\p1} to evaluate the arguments.
6027 @item .macro reserve_str p1=0 p2
6028 Begin the definition of a macro called @code{reserve_str}, with two
6029 arguments. The first argument has a default value, but not the second.
6030 After the definition is complete, you can call the macro either as
6031 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
6032 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
6033 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
6034 @samp{0}, and @samp{\p2} evaluating to @var{b}).
6036 @item .macro m p1:req, p2=0, p3:vararg
6037 Begin the definition of a macro called @code{m}, with at least three
6038 arguments. The first argument must always have a value specified, but
6039 not the second, which instead has a default value. The third formal
6040 will get assigned all remaining arguments specified at invocation time.
6042 When you call a macro, you can specify the argument values either by
6043 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
6044 @samp{sum to=17, from=9}.
6048 Note that since each of the @var{macargs} can be an identifier exactly
6049 as any other one permitted by the target architecture, there may be
6050 occasional problems if the target hand-crafts special meanings to certain
6051 characters when they occur in a special position. For example, if the colon
6052 (@code{:}) is generally permitted to be part of a symbol name, but the
6053 architecture specific code special-cases it when occurring as the final
6054 character of a symbol (to denote a label), then the macro parameter
6055 replacement code will have no way of knowing that and consider the whole
6056 construct (including the colon) an identifier, and check only this
6057 identifier for being the subject to parameter substitution. So for example
6058 this macro definition:
6066 might not work as expected. Invoking @samp{label foo} might not create a label
6067 called @samp{foo} but instead just insert the text @samp{\l:} into the
6068 assembler source, probably generating an error about an unrecognised
6071 Similarly problems might occur with the period character (@samp{.})
6072 which is often allowed inside opcode names (and hence identifier names). So
6073 for example constructing a macro to build an opcode from a base name and a
6074 length specifier like this:
6077 .macro opcode base length
6082 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
6083 instruction but instead generate some kind of error as the assembler tries to
6084 interpret the text @samp{\base.\length}.
6086 There are several possible ways around this problem:
6089 @item Insert white space
6090 If it is possible to use white space characters then this is the simplest
6099 @item Use @samp{\()}
6100 The string @samp{\()} can be used to separate the end of a macro argument from
6101 the following text. eg:
6104 .macro opcode base length
6109 @item Use the alternate macro syntax mode
6110 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
6111 used as a separator. eg:
6121 Note: this problem of correctly identifying string parameters to pseudo ops
6122 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
6123 and @code{.irpc} (@pxref{Irpc}) as well.
6126 @cindex @code{endm} directive
6127 Mark the end of a macro definition.
6130 @cindex @code{exitm} directive
6131 Exit early from the current macro definition.
6133 @cindex number of macros executed
6134 @cindex macros, count executed
6136 @command{@value{AS}} maintains a counter of how many macros it has
6137 executed in this pseudo-variable; you can copy that number to your
6138 output with @samp{\@@}, but @emph{only within a macro definition}.
6140 @item LOCAL @var{name} [ , @dots{} ]
6141 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
6142 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
6143 @xref{Altmacro,,@code{.altmacro}}.
6147 @section @code{.mri @var{val}}
6149 @cindex @code{mri} directive
6150 @cindex MRI mode, temporarily
6151 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
6152 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
6153 affects code assembled until the next @code{.mri} directive, or until the end
6154 of the file. @xref{M, MRI mode, MRI mode}.
6157 @section @code{.noaltmacro}
6158 Disable alternate macro mode. @xref{Altmacro}.
6161 @section @code{.nolist}
6163 @cindex @code{nolist} directive
6164 @cindex listing control, turning off
6165 Control (in conjunction with the @code{.list} directive) whether or
6166 not assembly listings are generated. These two directives maintain an
6167 internal counter (which is zero initially). @code{.list} increments the
6168 counter, and @code{.nolist} decrements it. Assembly listings are
6169 generated whenever the counter is greater than zero.
6172 @section @code{.nop}
6174 @cindex @code{nop} directive
6175 @cindex filling memory with no-op instructions
6176 This directive emits a single no-op instruction. It is provided on all
6177 architectures, allowing the creation of architecture neutral tests involving
6178 actual code. The size of the generated instruction is target specific. The
6179 instruction does affect the generation of DWARF debug line information.
6182 @section @code{.nops @var{size}[, @var{control}]}
6184 @cindex @code{nops} directive
6185 @cindex filling memory with no-op instructions
6186 This directive emits no-op instructions. It is specific to the Intel 80386 and
6187 AMD x86-64 targets. It takes a @var{size} argument and generates @var{size}
6188 bytes of no-op instructions. @var{size} must be absolute and positive. These
6189 bytes do not affect the generation of DWARF debug line information.
6191 The optional @var{control} argument specifies a size limit for a single no-op
6192 instruction. If not provided then a value of 0 is assumed. The valid values
6193 of @var{control} are between 0 and 4 in 16-bit mode, between 0 and 7 when
6194 tuning for older processors in 32-bit mode, between 0 and 11 in 64-bit mode or
6195 when tuning for newer processors in 32-bit mode. When 0 is used, the no-op
6196 instruction size limit is set to the maximum supported size.
6199 @section @code{.octa @var{bignums}}
6201 @c FIXME: double size emitted for "octa" on some? Or warn?
6202 @cindex @code{octa} directive
6203 @cindex integer, 16-byte
6204 @cindex sixteen byte integer
6205 This directive expects zero or more bignums, separated by commas. For each
6206 bignum, it emits a 16-byte integer.
6208 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
6209 hence @emph{octa}-word for 16 bytes.
6212 @section @code{.offset @var{loc}}
6214 @cindex @code{offset} directive
6215 Set the location counter to @var{loc} in the absolute section. @var{loc} must
6216 be an absolute expression. This directive may be useful for defining
6217 symbols with absolute values. Do not confuse it with the @code{.org}
6221 @section @code{.org @var{new-lc} , @var{fill}}
6223 @cindex @code{org} directive
6224 @cindex location counter, advancing
6225 @cindex advancing location counter
6226 @cindex current address, advancing
6227 Advance the location counter of the current section to
6228 @var{new-lc}. @var{new-lc} is either an absolute expression or an
6229 expression with the same section as the current subsection. That is,
6230 you can't use @code{.org} to cross sections: if @var{new-lc} has the
6231 wrong section, the @code{.org} directive is ignored. To be compatible
6232 with former assemblers, if the section of @var{new-lc} is absolute,
6233 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
6234 is the same as the current subsection.
6236 @code{.org} may only increase the location counter, or leave it
6237 unchanged; you cannot use @code{.org} to move the location counter
6240 @c double negative used below "not undefined" because this is a specific
6241 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
6242 @c section. doc@cygnus.com 18feb91
6243 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
6244 may not be undefined. If you really detest this restriction we eagerly await
6245 a chance to share your improved assembler.
6247 Beware that the origin is relative to the start of the section, not
6248 to the start of the subsection. This is compatible with other
6249 people's assemblers.
6251 When the location counter (of the current subsection) is advanced, the
6252 intervening bytes are filled with @var{fill} which should be an
6253 absolute expression. If the comma and @var{fill} are omitted,
6254 @var{fill} defaults to zero.
6257 @section @code{.p2align[wl] [@var{abs-expr}[, @var{abs-expr}[, @var{abs-expr}]]]}
6259 @cindex padding the location counter given a power of two
6260 @cindex @code{p2align} directive
6261 Pad the location counter (in the current subsection) to a particular
6262 storage boundary. The first expression (which must be absolute) is the
6263 number of low-order zero bits the location counter must have after
6264 advancement. For example @samp{.p2align 3} advances the location
6265 counter until it is a multiple of 8. If the location counter is already a
6266 multiple of 8, no change is needed. If the expression is omitted then a
6267 default value of 0 is used, effectively disabling alignment requirements.
6269 The second expression (also absolute) gives the fill value to be stored in the
6270 padding bytes. It (and the comma) may be omitted. If it is omitted, the
6271 padding bytes are normally zero. However, on most systems, if the section is
6272 marked as containing code and the fill value is omitted, the space is filled
6273 with no-op instructions.
6275 The third expression is also absolute, and is also optional. If it is present,
6276 it is the maximum number of bytes that should be skipped by this alignment
6277 directive. If doing the alignment would require skipping more bytes than the
6278 specified maximum, then the alignment is not done at all. You can omit the
6279 fill value (the second argument) entirely by simply using two commas after the
6280 required alignment; this can be useful if you want the alignment to be filled
6281 with no-op instructions when appropriate.
6283 @cindex @code{p2alignw} directive
6284 @cindex @code{p2alignl} directive
6285 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
6286 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
6287 pattern as a two byte word value. The @code{.p2alignl} directives treats the
6288 fill pattern as a four byte longword value. For example, @code{.p2alignw
6289 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
6290 filled in with the value 0x368d (the exact placement of the bytes depends upon
6291 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
6296 @section @code{.popsection}
6298 @cindex @code{popsection} directive
6299 @cindex Section Stack
6300 This is one of the ELF section stack manipulation directives. The others are
6301 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6302 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
6305 This directive replaces the current section (and subsection) with the top
6306 section (and subsection) on the section stack. This section is popped off the
6312 @section @code{.previous}
6314 @cindex @code{previous} directive
6315 @cindex Section Stack
6316 This is one of the ELF section stack manipulation directives. The others are
6317 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6318 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6319 (@pxref{PopSection}).
6321 This directive swaps the current section (and subsection) with most recently
6322 referenced section/subsection pair prior to this one. Multiple
6323 @code{.previous} directives in a row will flip between two sections (and their
6324 subsections). For example:
6336 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6342 # Now in section A subsection 1
6346 # Now in section B subsection 0
6349 # Now in section B subsection 1
6352 # Now in section B subsection 0
6356 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6357 section B and 0x9abc into subsection 1 of section B.
6359 In terms of the section stack, this directive swaps the current section with
6360 the top section on the section stack.
6364 @section @code{.print @var{string}}
6366 @cindex @code{print} directive
6367 @command{@value{AS}} will print @var{string} on the standard output during
6368 assembly. You must put @var{string} in double quotes.
6372 @section @code{.protected @var{names}}
6374 @cindex @code{protected} directive
6376 This is one of the ELF visibility directives. The other two are
6377 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6379 This directive overrides the named symbols default visibility (which is set by
6380 their binding: local, global or weak). The directive sets the visibility to
6381 @code{protected} which means that any references to the symbols from within the
6382 components that defines them must be resolved to the definition in that
6383 component, even if a definition in another component would normally preempt
6388 @section @code{.psize @var{lines} , @var{columns}}
6390 @cindex @code{psize} directive
6391 @cindex listing control: paper size
6392 @cindex paper size, for listings
6393 Use this directive to declare the number of lines---and, optionally, the
6394 number of columns---to use for each page, when generating listings.
6396 If you do not use @code{.psize}, listings use a default line-count
6397 of 60. You may omit the comma and @var{columns} specification; the
6398 default width is 200 columns.
6400 @command{@value{AS}} generates formfeeds whenever the specified number of
6401 lines is exceeded (or whenever you explicitly request one, using
6404 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6405 those explicitly specified with @code{.eject}.
6408 @section @code{.purgem @var{name}}
6410 @cindex @code{purgem} directive
6411 Undefine the macro @var{name}, so that later uses of the string will not be
6412 expanded. @xref{Macro}.
6416 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6418 @cindex @code{pushsection} directive
6419 @cindex Section Stack
6420 This is one of the ELF section stack manipulation directives. The others are
6421 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6422 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6425 This directive pushes the current section (and subsection) onto the
6426 top of the section stack, and then replaces the current section and
6427 subsection with @code{name} and @code{subsection}. The optional
6428 @code{flags}, @code{type} and @code{arguments} are treated the same
6429 as in the @code{.section} (@pxref{Section}) directive.
6433 @section @code{.quad @var{bignums}}
6435 @cindex @code{quad} directive
6436 @code{.quad} expects zero or more bignums, separated by commas. For
6437 each bignum, it emits
6439 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6440 warning message; and just takes the lowest order 8 bytes of the bignum.
6441 @cindex eight-byte integer
6442 @cindex integer, 8-byte
6444 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6445 hence @emph{quad}-word for 8 bytes.
6448 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6449 warning message; and just takes the lowest order 16 bytes of the bignum.
6450 @cindex sixteen-byte integer
6451 @cindex integer, 16-byte
6455 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6457 @cindex @code{reloc} directive
6458 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6459 @var{expression}. If @var{offset} is a number, the relocation is generated in
6460 the current section. If @var{offset} is an expression that resolves to a
6461 symbol plus offset, the relocation is generated in the given symbol's section.
6462 @var{expression}, if present, must resolve to a symbol plus addend or to an
6463 absolute value, but note that not all targets support an addend. e.g. ELF REL
6464 targets such as i386 store an addend in the section contents rather than in the
6465 relocation. This low level interface does not support addends stored in the
6469 @section @code{.rept @var{count}}
6471 @cindex @code{rept} directive
6472 Repeat the sequence of lines between the @code{.rept} directive and the next
6473 @code{.endr} directive @var{count} times.
6475 For example, assembling
6483 is equivalent to assembling
6491 A count of zero is allowed, but nothing is generated. Negative counts are not
6492 allowed and if encountered will be treated as if they were zero.
6495 @section @code{.sbttl "@var{subheading}"}
6497 @cindex @code{sbttl} directive
6498 @cindex subtitles for listings
6499 @cindex listing control: subtitle
6500 Use @var{subheading} as the title (third line, immediately after the
6501 title line) when generating assembly listings.
6503 This directive affects subsequent pages, as well as the current page if
6504 it appears within ten lines of the top of a page.
6508 @section @code{.scl @var{class}}
6510 @cindex @code{scl} directive
6511 @cindex symbol storage class (COFF)
6512 @cindex COFF symbol storage class
6513 Set the storage-class value for a symbol. This directive may only be
6514 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6515 whether a symbol is static or external, or it may record further
6516 symbolic debugging information.
6521 @section @code{.section @var{name}}
6523 @cindex named section
6524 Use the @code{.section} directive to assemble the following code into a section
6527 This directive is only supported for targets that actually support arbitrarily
6528 named sections; on @code{a.out} targets, for example, it is not accepted, even
6529 with a standard @code{a.out} section name.
6533 @c only print the extra heading if both COFF and ELF are set
6534 @subheading COFF Version
6537 @cindex @code{section} directive (COFF version)
6538 For COFF targets, the @code{.section} directive is used in one of the following
6542 .section @var{name}[, "@var{flags}"]
6543 .section @var{name}[, @var{subsection}]
6546 If the optional argument is quoted, it is taken as flags to use for the
6547 section. Each flag is a single character. The following flags are recognized:
6551 bss section (uninitialized data)
6553 section is not loaded
6559 exclude section from linking
6565 shared section (meaningful for PE targets)
6567 ignored. (For compatibility with the ELF version)
6569 section is not readable (meaningful for PE targets)
6571 single-digit power-of-two section alignment (GNU extension)
6574 If no flags are specified, the default flags depend upon the section name. If
6575 the section name is not recognized, the default will be for the section to be
6576 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6577 from the section, rather than adding them, so if they are used on their own it
6578 will be as if no flags had been specified at all.
6580 If the optional argument to the @code{.section} directive is not quoted, it is
6581 taken as a subsection number (@pxref{Sub-Sections}).
6586 @c only print the extra heading if both COFF and ELF are set
6587 @subheading ELF Version
6590 @cindex Section Stack
6591 This is one of the ELF section stack manipulation directives. The others are
6592 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6593 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6594 @code{.previous} (@pxref{Previous}).
6596 @cindex @code{section} directive (ELF version)
6597 For ELF targets, the @code{.section} directive is used like this:
6600 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6603 @anchor{Section Name Substitutions}
6604 @kindex --sectname-subst
6605 @cindex section name substitution
6606 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6607 argument may contain a substitution sequence. Only @code{%S} is supported
6608 at the moment, and substitutes the current section name. For example:
6611 .macro exception_code
6612 .section %S.exception
6613 [exception code here]
6628 The two @code{exception_code} invocations above would create the
6629 @code{.text.exception} and @code{.init.exception} sections respectively.
6630 This is useful e.g. to discriminate between ancillary sections that are
6631 tied to setup code to be discarded after use from ancillary sections that
6632 need to stay resident without having to define multiple @code{exception_code}
6633 macros just for that purpose.
6635 The optional @var{flags} argument is a quoted string which may contain any
6636 combination of the following characters:
6640 section is allocatable
6642 section is a GNU_MBIND section
6644 section is excluded from executable and shared library.
6646 section references a symbol defined in another section (the linked-to
6647 section) in the same file.
6651 section is executable
6653 section is mergeable
6655 section contains zero terminated strings
6657 section is a member of a section group
6659 section is used for thread-local-storage
6661 section is a member of the previously-current section's group, if any
6662 @item @code{<number>}
6663 a numeric value indicating the bits to be set in the ELF section header's flags
6664 field. Note - if one or more of the alphabetic characters described above is
6665 also included in the flags field, their bit values will be ORed into the
6667 @item @code{<target specific>}
6668 some targets extend this list with their own flag characters
6671 Note - once a section's flags have been set they cannot be changed. There are
6672 a few exceptions to this rule however. Processor and application specific
6673 flags can be added to an already defined section. The @code{.interp},
6674 @code{.strtab} and @code{.symtab} sections can have the allocate flag
6675 (@code{a}) set after they are initially defined, and the @code{.note-GNU-stack}
6676 section may have the executable (@code{x}) flag added. Also note that the
6677 @code{.attach_to_group} directive can be used to add a section to a group even
6678 if the section was not originally declared to be part of that group.
6680 The optional @var{type} argument may contain one of the following constants:
6684 section contains data
6686 section does not contain data (i.e., section only occupies space)
6688 section contains data which is used by things other than the program
6690 section contains an array of pointers to init functions
6692 section contains an array of pointers to finish functions
6693 @item @@preinit_array
6694 section contains an array of pointers to pre-init functions
6695 @item @@@code{<number>}
6696 a numeric value to be set as the ELF section header's type field.
6697 @item @@@code{<target specific>}
6698 some targets extend this list with their own types
6701 Many targets only support the first three section types. The type may be
6702 enclosed in double quotes if necessary.
6704 Note on targets where the @code{@@} character is the start of a comment (eg
6705 ARM) then another character is used instead. For example the ARM port uses the
6708 Note - some sections, eg @code{.text} and @code{.data} are considered to be
6709 special and have fixed types. Any attempt to declare them with a different
6710 type will generate an error from the assembler.
6712 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6713 be specified as well as an extra argument---@var{entsize}---like this:
6716 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6719 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6720 constants, each @var{entsize} octets long. Sections with both @code{M} and
6721 @code{S} must contain zero terminated strings where each character is
6722 @var{entsize} bytes long. The linker may remove duplicates within sections with
6723 the same name, same entity size and same flags. @var{entsize} must be an
6724 absolute expression. For sections with both @code{M} and @code{S}, a string
6725 which is a suffix of a larger string is considered a duplicate. Thus
6726 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6727 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6729 If @var{flags} contains the @code{o} flag, then the @var{type} argument
6730 must be present along with an additional field like this:
6733 .section @var{name},"@var{flags}"o,@@@var{type},@var{SymbolName}|@var{SectionIndex}
6736 The @var{SymbolName} field specifies the symbol name which the section
6737 references. Alternatively a numeric @var{SectionIndex} can be provided. This
6738 is not generally a good idea as section indicies are rarely known at assembly
6739 time, but the facility is provided for testing purposes. An index of zero is
6740 allowed. It indicates that the linked-to section has already been discarded.
6742 Note: If both the @var{M} and @var{o} flags are present, then the fields
6743 for the Merge flag should come first, like this:
6746 .section @var{name},"@var{flags}"Mo,@@@var{type},@var{entsize},@var{SymbolName}
6749 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6750 be present along with an additional field like this:
6753 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6756 The @var{GroupName} field specifies the name of the section group to which this
6757 particular section belongs. The optional linkage field can contain:
6761 indicates that only one copy of this section should be retained
6766 Note: if both the @var{M} and @var{G} flags are present then the fields for
6767 the Merge flag should come first, like this:
6770 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6773 If both @code{o} flag and @code{G} flag are present, then the
6774 @var{SymbolName} field for @code{o} comes first, like this:
6777 .section @var{name},"@var{flags}"oG,@@@var{type},@var{SymbolName},@var{GroupName}[,@var{linkage}]
6780 If @var{flags} contains the @code{?} symbol then it may not also contain the
6781 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6782 present. Instead, @code{?} says to consider the section that's current before
6783 this directive. If that section used @code{G}, then the new section will use
6784 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6785 If not, then the @code{?} symbol has no effect.
6787 The optional @var{unique,@code{<number>}} argument must come last. It
6788 assigns @var{@code{<number>}} as a unique section ID to distinguish
6789 different sections with the same section name like these:
6792 .section @var{name},"@var{flags}",@@@var{type},@var{unique,@code{<number>}}
6793 .section @var{name},"@var{flags}"G,@@@var{type},@var{GroupName},[@var{linkage}],@var{unique,@code{<number>}}
6794 .section @var{name},"@var{flags}"MG,@@@var{type},@var{entsize},@var{GroupName}[,@var{linkage}],@var{unique,@code{<number>}}
6797 The valid values of @var{@code{<number>}} are between 0 and 4294967295.
6799 If no flags are specified, the default flags depend upon the section name. If
6800 the section name is not recognized, the default will be for the section to have
6801 none of the above flags: it will not be allocated in memory, nor writable, nor
6802 executable. The section will contain data.
6804 For ELF targets, the assembler supports another type of @code{.section}
6805 directive for compatibility with the Solaris assembler:
6808 .section "@var{name}"[, @var{flags}...]
6811 Note that the section name is quoted. There may be a sequence of comma
6816 section is allocatable
6820 section is executable
6822 section is excluded from executable and shared library.
6824 section is used for thread local storage
6827 This directive replaces the current section and subsection. See the
6828 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6829 some examples of how this directive and the other section stack directives
6835 @section @code{.set @var{symbol}, @var{expression}}
6837 @cindex @code{set} directive
6838 @cindex symbol value, setting
6839 Set the value of @var{symbol} to @var{expression}. This
6840 changes @var{symbol}'s value and type to conform to
6841 @var{expression}. If @var{symbol} was flagged as external, it remains
6842 flagged (@pxref{Symbol Attributes}).
6844 You may @code{.set} a symbol many times in the same assembly provided that the
6845 values given to the symbol are constants. Values that are based on expressions
6846 involving other symbols are allowed, but some targets may restrict this to only
6847 being done once per assembly. This is because those targets do not set the
6848 addresses of symbols at assembly time, but rather delay the assignment until a
6849 final link is performed. This allows the linker a chance to change the code in
6850 the files, changing the location of, and the relative distance between, various
6853 If you @code{.set} a global symbol, the value stored in the object
6854 file is the last value stored into it.
6857 On Z80 @code{set} is a real instruction, use @code{.set} or
6858 @samp{@var{symbol} defl @var{expression}} instead.
6862 @section @code{.short @var{expressions}}
6864 @cindex @code{short} directive
6866 @code{.short} is normally the same as @samp{.word}.
6867 @xref{Word,,@code{.word}}.
6869 In some configurations, however, @code{.short} and @code{.word} generate
6870 numbers of different lengths. @xref{Machine Dependencies}.
6874 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6877 This expects zero or more @var{expressions}, and emits
6878 a 16 bit number for each.
6883 @section @code{.single @var{flonums}}
6885 @cindex @code{single} directive
6886 @cindex floating point numbers (single)
6887 This directive assembles zero or more flonums, separated by commas. It
6888 has the same effect as @code{.float}.
6890 The exact kind of floating point numbers emitted depends on how
6891 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6895 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6896 numbers in @sc{ieee} format.
6902 @section @code{.size}
6904 This directive is used to set the size associated with a symbol.
6908 @c only print the extra heading if both COFF and ELF are set
6909 @subheading COFF Version
6912 @cindex @code{size} directive (COFF version)
6913 For COFF targets, the @code{.size} directive is only permitted inside
6914 @code{.def}/@code{.endef} pairs. It is used like this:
6917 .size @var{expression}
6924 @c only print the extra heading if both COFF and ELF are set
6925 @subheading ELF Version
6928 @cindex @code{size} directive (ELF version)
6929 For ELF targets, the @code{.size} directive is used like this:
6932 .size @var{name} , @var{expression}
6935 This directive sets the size associated with a symbol @var{name}.
6936 The size in bytes is computed from @var{expression} which can make use of label
6937 arithmetic. This directive is typically used to set the size of function
6942 @ifclear no-space-dir
6944 @section @code{.skip @var{size} [,@var{fill}]}
6946 @cindex @code{skip} directive
6947 @cindex filling memory
6948 This directive emits @var{size} bytes, each of value @var{fill}. Both
6949 @var{size} and @var{fill} are absolute expressions. If the comma and
6950 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6955 @section @code{.sleb128 @var{expressions}}
6957 @cindex @code{sleb128} directive
6958 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6959 compact, variable length representation of numbers used by the DWARF
6960 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6962 @ifclear no-space-dir
6964 @section @code{.space @var{size} [,@var{fill}]}
6966 @cindex @code{space} directive
6967 @cindex filling memory
6968 This directive emits @var{size} bytes, each of value @var{fill}. Both
6969 @var{size} and @var{fill} are absolute expressions. If the comma
6970 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6975 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6976 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6977 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6978 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6986 @section @code{.stabd, .stabn, .stabs}
6988 @cindex symbolic debuggers, information for
6989 @cindex @code{stab@var{x}} directives
6990 There are three directives that begin @samp{.stab}.
6991 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6992 The symbols are not entered in the @command{@value{AS}} hash table: they
6993 cannot be referenced elsewhere in the source file.
6994 Up to five fields are required:
6998 This is the symbol's name. It may contain any character except
6999 @samp{\000}, so is more general than ordinary symbol names. Some
7000 debuggers used to code arbitrarily complex structures into symbol names
7004 An absolute expression. The symbol's type is set to the low 8 bits of
7005 this expression. Any bit pattern is permitted, but @code{@value{LD}}
7006 and debuggers choke on silly bit patterns.
7009 An absolute expression. The symbol's ``other'' attribute is set to the
7010 low 8 bits of this expression.
7013 An absolute expression. The symbol's descriptor is set to the low 16
7014 bits of this expression.
7017 An absolute expression which becomes the symbol's value.
7020 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
7021 or @code{.stabs} statement, the symbol has probably already been created;
7022 you get a half-formed symbol in your object file. This is
7023 compatible with earlier assemblers!
7026 @cindex @code{stabd} directive
7027 @item .stabd @var{type} , @var{other} , @var{desc}
7029 The ``name'' of the symbol generated is not even an empty string.
7030 It is a null pointer, for compatibility. Older assemblers used a
7031 null pointer so they didn't waste space in object files with empty
7034 The symbol's value is set to the location counter,
7035 relocatably. When your program is linked, the value of this symbol
7036 is the address of the location counter when the @code{.stabd} was
7039 @cindex @code{stabn} directive
7040 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
7041 The name of the symbol is set to the empty string @code{""}.
7043 @cindex @code{stabs} directive
7044 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
7045 All five fields are specified.
7051 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
7052 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
7054 @cindex string, copying to object file
7055 @cindex string8, copying to object file
7056 @cindex string16, copying to object file
7057 @cindex string32, copying to object file
7058 @cindex string64, copying to object file
7059 @cindex @code{string} directive
7060 @cindex @code{string8} directive
7061 @cindex @code{string16} directive
7062 @cindex @code{string32} directive
7063 @cindex @code{string64} directive
7065 Copy the characters in @var{str} to the object file. You may specify more than
7066 one string to copy, separated by commas. Unless otherwise specified for a
7067 particular machine, the assembler marks the end of each string with a 0 byte.
7068 You can use any of the escape sequences described in @ref{Strings,,Strings}.
7070 The variants @code{string16}, @code{string32} and @code{string64} differ from
7071 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
7072 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
7073 are stored in target endianness byte order.
7079 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
7080 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
7085 @section @code{.struct @var{expression}}
7087 @cindex @code{struct} directive
7088 Switch to the absolute section, and set the section offset to @var{expression},
7089 which must be an absolute expression. You might use this as follows:
7098 This would define the symbol @code{field1} to have the value 0, the symbol
7099 @code{field2} to have the value 4, and the symbol @code{field3} to have the
7100 value 8. Assembly would be left in the absolute section, and you would need to
7101 use a @code{.section} directive of some sort to change to some other section
7102 before further assembly.
7106 @section @code{.subsection @var{name}}
7108 @cindex @code{subsection} directive
7109 @cindex Section Stack
7110 This is one of the ELF section stack manipulation directives. The others are
7111 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
7112 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
7115 This directive replaces the current subsection with @code{name}. The current
7116 section is not changed. The replaced subsection is put onto the section stack
7117 in place of the then current top of stack subsection.
7122 @section @code{.symver}
7123 @cindex @code{symver} directive
7124 @cindex symbol versioning
7125 @cindex versions of symbols
7126 Use the @code{.symver} directive to bind symbols to specific version nodes
7127 within a source file. This is only supported on ELF platforms, and is
7128 typically used when assembling files to be linked into a shared library.
7129 There are cases where it may make sense to use this in objects to be bound
7130 into an application itself so as to override a versioned symbol from a
7133 For ELF targets, the @code{.symver} directive can be used like this:
7135 .symver @var{name}, @var{name2@@nodename}[ ,@var{visibility}]
7137 If the original symbol @var{name} is defined within the file
7138 being assembled, the @code{.symver} directive effectively creates a symbol
7139 alias with the name @var{name2@@nodename}, and in fact the main reason that we
7140 just don't try and create a regular alias is that the @var{@@} character isn't
7141 permitted in symbol names. The @var{name2} part of the name is the actual name
7142 of the symbol by which it will be externally referenced. The name @var{name}
7143 itself is merely a name of convenience that is used so that it is possible to
7144 have definitions for multiple versions of a function within a single source
7145 file, and so that the compiler can unambiguously know which version of a
7146 function is being mentioned. The @var{nodename} portion of the alias should be
7147 the name of a node specified in the version script supplied to the linker when
7148 building a shared library. If you are attempting to override a versioned
7149 symbol from a shared library, then @var{nodename} should correspond to the
7150 nodename of the symbol you are trying to override. The optional argument
7151 @var{visibility} updates the visibility of the original symbol. The valid
7152 visibilities are @code{local}, @code{hidden}, and @code{remove}. The
7153 @code{local} visibility makes the original symbol a local symbol
7154 (@pxref{Local}). The @code{hidden} visibility sets the visibility of the
7155 original symbol to @code{hidden} (@pxref{Hidden}). The @code{remove}
7156 visibility removes the original symbol from the symbol table. If visibility
7157 isn't specified, the original symbol is unchanged.
7159 If the symbol @var{name} is not defined within the file being assembled, all
7160 references to @var{name} will be changed to @var{name2@@nodename}. If no
7161 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
7164 Another usage of the @code{.symver} directive is:
7166 .symver @var{name}, @var{name2@@@@nodename}
7168 In this case, the symbol @var{name} must exist and be defined within
7169 the file being assembled. It is similar to @var{name2@@nodename}. The
7170 difference is @var{name2@@@@nodename} will also be used to resolve
7171 references to @var{name2} by the linker.
7173 The third usage of the @code{.symver} directive is:
7175 .symver @var{name}, @var{name2@@@@@@nodename}
7177 When @var{name} is not defined within the
7178 file being assembled, it is treated as @var{name2@@nodename}. When
7179 @var{name} is defined within the file being assembled, the symbol
7180 name, @var{name}, will be changed to @var{name2@@@@nodename}.
7185 @section @code{.tag @var{structname}}
7187 @cindex COFF structure debugging
7188 @cindex structure debugging, COFF
7189 @cindex @code{tag} directive
7190 This directive is generated by compilers to include auxiliary debugging
7191 information in the symbol table. It is only permitted inside
7192 @code{.def}/@code{.endef} pairs. Tags are used to link structure
7193 definitions in the symbol table with instances of those structures.
7197 @section @code{.text @var{subsection}}
7199 @cindex @code{text} directive
7200 Tells @command{@value{AS}} to assemble the following statements onto the end of
7201 the text subsection numbered @var{subsection}, which is an absolute
7202 expression. If @var{subsection} is omitted, subsection number zero
7206 @section @code{.title "@var{heading}"}
7208 @cindex @code{title} directive
7209 @cindex listing control: title line
7210 Use @var{heading} as the title (second line, immediately after the
7211 source file name and pagenumber) when generating assembly listings.
7213 This directive affects subsequent pages, as well as the current page if
7214 it appears within ten lines of the top of a page.
7218 @section @code{.tls_common @var{symbol}, @var{length}[, @var{alignment}]}
7220 @cindex @code{tls_common} directive
7221 This directive behaves in the same way as the @code{.comm} directive
7222 (@pxref{Comm}) except that @var{symbol} has type of STT_TLS instead of
7228 @section @code{.type}
7230 This directive is used to set the type of a symbol.
7234 @c only print the extra heading if both COFF and ELF are set
7235 @subheading COFF Version
7238 @cindex COFF symbol type
7239 @cindex symbol type, COFF
7240 @cindex @code{type} directive (COFF version)
7241 For COFF targets, this directive is permitted only within
7242 @code{.def}/@code{.endef} pairs. It is used like this:
7248 This records the integer @var{int} as the type attribute of a symbol table
7255 @c only print the extra heading if both COFF and ELF are set
7256 @subheading ELF Version
7259 @cindex ELF symbol type
7260 @cindex symbol type, ELF
7261 @cindex @code{type} directive (ELF version)
7262 For ELF targets, the @code{.type} directive is used like this:
7265 .type @var{name} , @var{type description}
7268 This sets the type of symbol @var{name} to be either a
7269 function symbol or an object symbol. There are five different syntaxes
7270 supported for the @var{type description} field, in order to provide
7271 compatibility with various other assemblers.
7273 Because some of the characters used in these syntaxes (such as @samp{@@} and
7274 @samp{#}) are comment characters for some architectures, some of the syntaxes
7275 below do not work on all architectures. The first variant will be accepted by
7276 the GNU assembler on all architectures so that variant should be used for
7277 maximum portability, if you do not need to assemble your code with other
7280 The syntaxes supported are:
7283 .type <name> STT_<TYPE_IN_UPPER_CASE>
7284 .type <name>,#<type>
7285 .type <name>,@@<type>
7286 .type <name>,%<type>
7287 .type <name>,"<type>"
7290 The types supported are:
7295 Mark the symbol as being a function name.
7298 @itemx gnu_indirect_function
7299 Mark the symbol as an indirect function when evaluated during reloc
7300 processing. (This is only supported on assemblers targeting GNU systems).
7304 Mark the symbol as being a data object.
7308 Mark the symbol as being a thread-local data object.
7312 Mark the symbol as being a common data object.
7316 Does not mark the symbol in any way. It is supported just for completeness.
7318 @item gnu_unique_object
7319 Marks the symbol as being a globally unique data object. The dynamic linker
7320 will make sure that in the entire process there is just one symbol with this
7321 name and type in use. (This is only supported on assemblers targeting GNU
7326 Changing between incompatible types other than from/to STT_NOTYPE will
7327 result in a diagnostic. An intermediate change to STT_NOTYPE will silence
7330 Note: Some targets support extra types in addition to those listed above.
7336 @section @code{.uleb128 @var{expressions}}
7338 @cindex @code{uleb128} directive
7339 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
7340 compact, variable length representation of numbers used by the DWARF
7341 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
7345 @section @code{.val @var{addr}}
7347 @cindex @code{val} directive
7348 @cindex COFF value attribute
7349 @cindex value attribute, COFF
7350 This directive, permitted only within @code{.def}/@code{.endef} pairs,
7351 records the address @var{addr} as the value attribute of a symbol table
7357 @section @code{.version "@var{string}"}
7359 @cindex @code{version} directive
7360 This directive creates a @code{.note} section and places into it an ELF
7361 formatted note of type NT_VERSION. The note's name is set to @code{string}.
7366 @section @code{.vtable_entry @var{table}, @var{offset}}
7368 @cindex @code{vtable_entry} directive
7369 This directive finds or creates a symbol @code{table} and creates a
7370 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
7373 @section @code{.vtable_inherit @var{child}, @var{parent}}
7375 @cindex @code{vtable_inherit} directive
7376 This directive finds the symbol @code{child} and finds or creates the symbol
7377 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
7378 parent whose addend is the value of the child symbol. As a special case the
7379 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
7383 @section @code{.warning "@var{string}"}
7384 @cindex warning directive
7385 Similar to the directive @code{.error}
7386 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7389 @section @code{.weak @var{names}}
7391 @cindex @code{weak} directive
7392 This directive sets the weak attribute on the comma separated list of symbol
7393 @code{names}. If the symbols do not already exist, they will be created.
7395 On COFF targets other than PE, weak symbols are a GNU extension. This
7396 directive sets the weak attribute on the comma separated list of symbol
7397 @code{names}. If the symbols do not already exist, they will be created.
7399 On the PE target, weak symbols are supported natively as weak aliases.
7400 When a weak symbol is created that is not an alias, GAS creates an
7401 alternate symbol to hold the default value.
7404 @section @code{.weakref @var{alias}, @var{target}}
7406 @cindex @code{weakref} directive
7407 This directive creates an alias to the target symbol that enables the symbol to
7408 be referenced with weak-symbol semantics, but without actually making it weak.
7409 If direct references or definitions of the symbol are present, then the symbol
7410 will not be weak, but if all references to it are through weak references, the
7411 symbol will be marked as weak in the symbol table.
7413 The effect is equivalent to moving all references to the alias to a separate
7414 assembly source file, renaming the alias to the symbol in it, declaring the
7415 symbol as weak there, and running a reloadable link to merge the object files
7416 resulting from the assembly of the new source file and the old source file that
7417 had the references to the alias removed.
7419 The alias itself never makes to the symbol table, and is entirely handled
7420 within the assembler.
7423 @section @code{.word @var{expressions}}
7425 @cindex @code{word} directive
7426 This directive expects zero or more @var{expressions}, of any section,
7427 separated by commas.
7430 For each expression, @command{@value{AS}} emits a 32-bit number.
7433 For each expression, @command{@value{AS}} emits a 16-bit number.
7438 The size of the number emitted, and its byte order,
7439 depend on what target computer the assembly is for.
7442 @c on sparc the "special treatment to support compilers" doesn't
7443 @c happen---32-bit addressability, period; no long/short jumps.
7444 @ifset DIFF-TBL-KLUGE
7445 @cindex difference tables altered
7446 @cindex altered difference tables
7448 @emph{Warning: Special Treatment to support Compilers}
7452 Machines with a 32-bit address space, but that do less than 32-bit
7453 addressing, require the following special treatment. If the machine of
7454 interest to you does 32-bit addressing (or doesn't require it;
7455 @pxref{Machine Dependencies}), you can ignore this issue.
7458 In order to assemble compiler output into something that works,
7459 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7460 Directives of the form @samp{.word sym1-sym2} are often emitted by
7461 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7462 directive of the form @samp{.word sym1-sym2}, and the difference between
7463 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7464 creates a @dfn{secondary jump table}, immediately before the next label.
7465 This secondary jump table is preceded by a short-jump to the
7466 first byte after the secondary table. This short-jump prevents the flow
7467 of control from accidentally falling into the new table. Inside the
7468 table is a long-jump to @code{sym2}. The original @samp{.word}
7469 contains @code{sym1} minus the address of the long-jump to
7472 If there were several occurrences of @samp{.word sym1-sym2} before the
7473 secondary jump table, all of them are adjusted. If there was a
7474 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7475 long-jump to @code{sym4} is included in the secondary jump table,
7476 and the @code{.word} directives are adjusted to contain @code{sym3}
7477 minus the address of the long-jump to @code{sym4}; and so on, for as many
7478 entries in the original jump table as necessary.
7481 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7482 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7483 assembly language programmers.
7486 @c end DIFF-TBL-KLUGE
7488 @ifclear no-space-dir
7490 @section @code{.zero @var{size}}
7492 @cindex @code{zero} directive
7493 @cindex filling memory with zero bytes
7494 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7495 expression. This directive is actually an alias for the @samp{.skip} directive
7496 so it can take an optional second argument of the value to store in the bytes
7497 instead of zero. Using @samp{.zero} in this way would be confusing however.
7502 @section @code{.2byte @var{expression} [, @var{expression}]*}
7503 @cindex @code{2byte} directive
7504 @cindex two-byte integer
7505 @cindex integer, 2-byte
7507 This directive expects zero or more expressions, separated by commas. If there
7508 are no expressions then the directive does nothing. Otherwise each expression
7509 is evaluated in turn and placed in the next two bytes of the current output
7510 section, using the endian model of the target. If an expression will not fit
7511 in two bytes, a warning message is displayed and the least significant two
7512 bytes of the expression's value are used. If an expression cannot be evaluated
7513 at assembly time then relocations will be generated in order to compute the
7516 This directive does not apply any alignment before or after inserting the
7517 values. As a result of this, if relocations are generated, they may be
7518 different from those used for inserting values with a guaranteed alignment.
7520 This directive is only available for ELF targets,
7523 @section @code{.4byte @var{expression} [, @var{expression}]*}
7524 @cindex @code{4byte} directive
7525 @cindex four-byte integer
7526 @cindex integer, 4-byte
7528 Like the @option{.2byte} directive, except that it inserts unaligned, four byte
7529 long values into the output.
7532 @section @code{.8byte @var{expression} [, @var{expression}]*}
7533 @cindex @code{8byte} directive
7534 @cindex eight-byte integer
7535 @cindex integer, 8-byte
7537 Like the @option{.2byte} directive, except that it inserts unaligned, eight
7538 byte long bignum values into the output.
7543 @section Deprecated Directives
7545 @cindex deprecated directives
7546 @cindex obsolescent directives
7547 One day these directives won't work.
7548 They are included for compatibility with older assemblers.
7555 @node Object Attributes
7556 @chapter Object Attributes
7557 @cindex object attributes
7559 @command{@value{AS}} assembles source files written for a specific architecture
7560 into object files for that architecture. But not all object files are alike.
7561 Many architectures support incompatible variations. For instance, floating
7562 point arguments might be passed in floating point registers if the object file
7563 requires hardware floating point support---or floating point arguments might be
7564 passed in integer registers if the object file supports processors with no
7565 hardware floating point unit. Or, if two objects are built for different
7566 generations of the same architecture, the combination may require the
7567 newer generation at run-time.
7569 This information is useful during and after linking. At link time,
7570 @command{@value{LD}} can warn about incompatible object files. After link
7571 time, tools like @command{gdb} can use it to process the linked file
7574 Compatibility information is recorded as a series of object attributes. Each
7575 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7576 string, and indicates who sets the meaning of the tag. The tag is an integer,
7577 and indicates what property the attribute describes. The value may be a string
7578 or an integer, and indicates how the property affects this object. Missing
7579 attributes are the same as attributes with a zero value or empty string value.
7581 Object attributes were developed as part of the ABI for the ARM Architecture.
7582 The file format is documented in @cite{ELF for the ARM Architecture}.
7585 * GNU Object Attributes:: @sc{gnu} Object Attributes
7586 * Defining New Object Attributes:: Defining New Object Attributes
7589 @node GNU Object Attributes
7590 @section @sc{gnu} Object Attributes
7592 The @code{.gnu_attribute} directive records an object attribute
7593 with vendor @samp{gnu}.
7595 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7596 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7597 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7598 2} is set for architecture-independent attributes and clear for
7599 architecture-dependent ones.
7601 @subsection Common @sc{gnu} attributes
7603 These attributes are valid on all architectures.
7606 @item Tag_compatibility (32)
7607 The compatibility attribute takes an integer flag value and a vendor name. If
7608 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7609 then the file is only compatible with the named toolchain. If it is greater
7610 than 1, the file can only be processed by other toolchains under some private
7611 arrangement indicated by the flag value and the vendor name.
7614 @subsection M680x0 Attributes
7617 @item Tag_GNU_M68K_ABI_FP (4)
7618 The floating-point ABI used by this object file. The value will be:
7622 0 for files not affected by the floating-point ABI.
7624 1 for files using double-precision hardware floating-point ABI.
7626 2 for files using the software floating-point ABI.
7630 @subsection MIPS Attributes
7633 @item Tag_GNU_MIPS_ABI_FP (4)
7634 The floating-point ABI used by this object file. The value will be:
7638 0 for files not affected by the floating-point ABI.
7640 1 for files using the hardware floating-point ABI with a standard
7641 double-precision FPU.
7643 2 for files using the hardware floating-point ABI with a single-precision FPU.
7645 3 for files using the software floating-point ABI.
7647 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7648 floating-point registers, 32-bit general-purpose registers and increased the
7649 number of callee-saved floating-point registers.
7651 5 for files using the hardware floating-point ABI with a double-precision FPU
7652 with either 32-bit or 64-bit floating-point registers and 32-bit
7653 general-purpose registers.
7655 6 for files using the hardware floating-point ABI with 64-bit floating-point
7656 registers and 32-bit general-purpose registers.
7658 7 for files using the hardware floating-point ABI with 64-bit floating-point
7659 registers, 32-bit general-purpose registers and a rule that forbids the
7660 direct use of odd-numbered single-precision floating-point registers.
7664 @subsection PowerPC Attributes
7667 @item Tag_GNU_Power_ABI_FP (4)
7668 The floating-point ABI used by this object file. The value will be:
7672 0 for files not affected by the floating-point ABI.
7674 1 for files using double-precision hardware floating-point ABI.
7676 2 for files using the software floating-point ABI.
7678 3 for files using single-precision hardware floating-point ABI.
7681 @item Tag_GNU_Power_ABI_Vector (8)
7682 The vector ABI used by this object file. The value will be:
7686 0 for files not affected by the vector ABI.
7688 1 for files using general purpose registers to pass vectors.
7690 2 for files using AltiVec registers to pass vectors.
7692 3 for files using SPE registers to pass vectors.
7696 @subsection IBM z Systems Attributes
7699 @item Tag_GNU_S390_ABI_Vector (8)
7700 The vector ABI used by this object file. The value will be:
7704 0 for files not affected by the vector ABI.
7706 1 for files using software vector ABI.
7708 2 for files using hardware vector ABI.
7712 @subsection MSP430 Attributes
7715 @item Tag_GNU_MSP430_Data_Region (4)
7716 The data region used by this object file. The value will be:
7720 0 for files not using the large memory model.
7722 1 for files which have been compiled with the condition that all
7723 data is in the lower memory region, i.e. below address 0x10000.
7725 2 for files which allow data to be placed in the full 20-bit memory range.
7729 @node Defining New Object Attributes
7730 @section Defining New Object Attributes
7732 If you want to define a new @sc{gnu} object attribute, here are the places you
7733 will need to modify. New attributes should be discussed on the @samp{binutils}
7738 This manual, which is the official register of attributes.
7740 The header for your architecture @file{include/elf}, to define the tag.
7742 The @file{bfd} support file for your architecture, to merge the attribute
7743 and issue any appropriate link warnings.
7745 Test cases in @file{ld/testsuite} for merging and link warnings.
7747 @file{binutils/readelf.c} to display your attribute.
7749 GCC, if you want the compiler to mark the attribute automatically.
7755 @node Machine Dependencies
7756 @chapter Machine Dependent Features
7758 @cindex machine dependencies
7759 The machine instruction sets are (almost by definition) different on
7760 each machine where @command{@value{AS}} runs. Floating point representations
7761 vary as well, and @command{@value{AS}} often supports a few additional
7762 directives or command-line options for compatibility with other
7763 assemblers on a particular platform. Finally, some versions of
7764 @command{@value{AS}} support special pseudo-instructions for branch
7767 This chapter discusses most of these differences, though it does not
7768 include details on any machine's instruction set. For details on that
7769 subject, see the hardware manufacturer's manual.
7773 * AArch64-Dependent:: AArch64 Dependent Features
7776 * Alpha-Dependent:: Alpha Dependent Features
7779 * ARC-Dependent:: ARC Dependent Features
7782 * ARM-Dependent:: ARM Dependent Features
7785 * AVR-Dependent:: AVR Dependent Features
7788 * Blackfin-Dependent:: Blackfin Dependent Features
7791 * BPF-Dependent:: BPF Dependent Features
7794 * CR16-Dependent:: CR16 Dependent Features
7797 * CRIS-Dependent:: CRIS Dependent Features
7800 * C-SKY-Dependent:: C-SKY Dependent Features
7803 * D10V-Dependent:: D10V Dependent Features
7806 * D30V-Dependent:: D30V Dependent Features
7809 * Epiphany-Dependent:: EPIPHANY Dependent Features
7812 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7815 * HPPA-Dependent:: HPPA Dependent Features
7818 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7821 * IA-64-Dependent:: Intel IA-64 Dependent Features
7824 * IP2K-Dependent:: IP2K Dependent Features
7827 * LM32-Dependent:: LM32 Dependent Features
7830 * M32C-Dependent:: M32C Dependent Features
7833 * M32R-Dependent:: M32R Dependent Features
7836 * M68K-Dependent:: M680x0 Dependent Features
7839 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7842 * S12Z-Dependent:: S12Z Dependent Features
7845 * Meta-Dependent :: Meta Dependent Features
7848 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7851 * MIPS-Dependent:: MIPS Dependent Features
7854 * MMIX-Dependent:: MMIX Dependent Features
7857 * MSP430-Dependent:: MSP430 Dependent Features
7860 * NDS32-Dependent:: Andes NDS32 Dependent Features
7863 * NiosII-Dependent:: Altera Nios II Dependent Features
7866 * NS32K-Dependent:: NS32K Dependent Features
7869 * OpenRISC-Dependent:: OpenRISC 1000 Features
7872 * PDP-11-Dependent:: PDP-11 Dependent Features
7875 * PJ-Dependent:: picoJava Dependent Features
7878 * PPC-Dependent:: PowerPC Dependent Features
7881 * PRU-Dependent:: PRU Dependent Features
7884 * RISC-V-Dependent:: RISC-V Dependent Features
7887 * RL78-Dependent:: RL78 Dependent Features
7890 * RX-Dependent:: RX Dependent Features
7893 * S/390-Dependent:: IBM S/390 Dependent Features
7896 * SCORE-Dependent:: SCORE Dependent Features
7899 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7902 * Sparc-Dependent:: SPARC Dependent Features
7905 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7908 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7911 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7914 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7917 * V850-Dependent:: V850 Dependent Features
7920 * Vax-Dependent:: VAX Dependent Features
7923 * Visium-Dependent:: Visium Dependent Features
7926 * WebAssembly-Dependent:: WebAssembly Dependent Features
7929 * XGATE-Dependent:: XGATE Dependent Features
7932 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7935 * Xtensa-Dependent:: Xtensa Dependent Features
7938 * Z80-Dependent:: Z80 Dependent Features
7941 * Z8000-Dependent:: Z8000 Dependent Features
7948 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7949 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7950 @c peculiarity: to preserve cross-references, there must be a node called
7951 @c "Machine Dependencies". Hence the conditional nodenames in each
7952 @c major node below. Node defaulting in makeinfo requires adjacency of
7953 @c node and sectioning commands; hence the repetition of @chapter BLAH
7954 @c in both conditional blocks.
7957 @include c-aarch64.texi
7961 @include c-alpha.texi
7977 @include c-bfin.texi
7985 @include c-cr16.texi
7989 @include c-cris.texi
7993 @include c-csky.texi
7998 @node Machine Dependencies
7999 @chapter Machine Dependent Features
8001 The machine instruction sets are different on each Renesas chip family,
8002 and there are also some syntax differences among the families. This
8003 chapter describes the specific @command{@value{AS}} features for each
8007 * H8/300-Dependent:: Renesas H8/300 Dependent Features
8008 * SH-Dependent:: Renesas SH Dependent Features
8015 @include c-d10v.texi
8019 @include c-d30v.texi
8023 @include c-epiphany.texi
8027 @include c-h8300.texi
8031 @include c-hppa.texi
8035 @include c-i386.texi
8039 @include c-ia64.texi
8043 @include c-ip2k.texi
8047 @include c-lm32.texi
8051 @include c-m32c.texi
8055 @include c-m32r.texi
8059 @include c-m68k.texi
8063 @include c-m68hc11.texi
8067 @include c-s12z.texi
8071 @include c-metag.texi
8075 @include c-microblaze.texi
8079 @include c-mips.texi
8083 @include c-mmix.texi
8087 @include c-msp430.texi
8091 @include c-nds32.texi
8095 @include c-nios2.texi
8099 @include c-ns32k.texi
8103 @include c-or1k.texi
8107 @include c-pdp11.texi
8123 @include c-riscv.texi
8127 @include c-rl78.texi
8135 @include c-s390.texi
8139 @include c-score.texi
8147 @include c-sparc.texi
8151 @include c-tic54x.texi
8155 @include c-tic6x.texi
8159 @include c-tilegx.texi
8163 @include c-tilepro.texi
8167 @include c-v850.texi
8175 @include c-visium.texi
8179 @include c-wasm32.texi
8183 @include c-xgate.texi
8187 @include c-xstormy16.texi
8191 @include c-xtensa.texi
8203 @c reverse effect of @down at top of generic Machine-Dep chapter
8207 @node Reporting Bugs
8208 @chapter Reporting Bugs
8209 @cindex bugs in assembler
8210 @cindex reporting bugs in assembler
8212 Your bug reports play an essential role in making @command{@value{AS}} reliable.
8214 Reporting a bug may help you by bringing a solution to your problem, or it may
8215 not. But in any case the principal function of a bug report is to help the
8216 entire community by making the next version of @command{@value{AS}} work better.
8217 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
8219 In order for a bug report to serve its purpose, you must include the
8220 information that enables us to fix the bug.
8223 * Bug Criteria:: Have you found a bug?
8224 * Bug Reporting:: How to report bugs
8228 @section Have You Found a Bug?
8229 @cindex bug criteria
8231 If you are not sure whether you have found a bug, here are some guidelines:
8234 @cindex fatal signal
8235 @cindex assembler crash
8236 @cindex crash of assembler
8238 If the assembler gets a fatal signal, for any input whatever, that is a
8239 @command{@value{AS}} bug. Reliable assemblers never crash.
8241 @cindex error on valid input
8243 If @command{@value{AS}} produces an error message for valid input, that is a bug.
8245 @cindex invalid input
8247 If @command{@value{AS}} does not produce an error message for invalid input, that
8248 is a bug. However, you should note that your idea of ``invalid input'' might
8249 be our idea of ``an extension'' or ``support for traditional practice''.
8252 If you are an experienced user of assemblers, your suggestions for improvement
8253 of @command{@value{AS}} are welcome in any case.
8257 @section How to Report Bugs
8259 @cindex assembler bugs, reporting
8261 A number of companies and individuals offer support for @sc{gnu} products. If
8262 you obtained @command{@value{AS}} from a support organization, we recommend you
8263 contact that organization first.
8265 You can find contact information for many support companies and
8266 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
8270 In any event, we also recommend that you send bug reports for @command{@value{AS}}
8274 The fundamental principle of reporting bugs usefully is this:
8275 @strong{report all the facts}. If you are not sure whether to state a
8276 fact or leave it out, state it!
8278 Often people omit facts because they think they know what causes the problem
8279 and assume that some details do not matter. Thus, you might assume that the
8280 name of a symbol you use in an example does not matter. Well, probably it does
8281 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
8282 happens to fetch from the location where that name is stored in memory;
8283 perhaps, if the name were different, the contents of that location would fool
8284 the assembler into doing the right thing despite the bug. Play it safe and
8285 give a specific, complete example. That is the easiest thing for you to do,
8286 and the most helpful.
8288 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
8289 it is new to us. Therefore, always write your bug reports on the assumption
8290 that the bug has not been reported previously.
8292 Sometimes people give a few sketchy facts and ask, ``Does this ring a
8293 bell?'' This cannot help us fix a bug, so it is basically useless. We
8294 respond by asking for enough details to enable us to investigate.
8295 You might as well expedite matters by sending them to begin with.
8297 To enable us to fix the bug, you should include all these things:
8301 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
8302 it with the @samp{--version} argument.
8304 Without this, we will not know whether there is any point in looking for
8305 the bug in the current version of @command{@value{AS}}.
8308 Any patches you may have applied to the @command{@value{AS}} source.
8311 The type of machine you are using, and the operating system name and
8315 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
8319 The command arguments you gave the assembler to assemble your example and
8320 observe the bug. To guarantee you will not omit something important, list them
8321 all. A copy of the Makefile (or the output from make) is sufficient.
8323 If we were to try to guess the arguments, we would probably guess wrong
8324 and then we might not encounter the bug.
8327 A complete input file that will reproduce the bug. If the bug is observed when
8328 the assembler is invoked via a compiler, send the assembler source, not the
8329 high level language source. Most compilers will produce the assembler source
8330 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
8331 the options @samp{-v --save-temps}; this will save the assembler source in a
8332 file with an extension of @file{.s}, and also show you exactly how
8333 @command{@value{AS}} is being run.
8336 A description of what behavior you observe that you believe is
8337 incorrect. For example, ``It gets a fatal signal.''
8339 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
8340 will certainly notice it. But if the bug is incorrect output, we might not
8341 notice unless it is glaringly wrong. You might as well not give us a chance to
8344 Even if the problem you experience is a fatal signal, you should still say so
8345 explicitly. Suppose something strange is going on, such as, your copy of
8346 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
8347 library on your system. (This has happened!) Your copy might crash and ours
8348 would not. If you told us to expect a crash, then when ours fails to crash, we
8349 would know that the bug was not happening for us. If you had not told us to
8350 expect a crash, then we would not be able to draw any conclusion from our
8354 If you wish to suggest changes to the @command{@value{AS}} source, send us context
8355 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
8356 option. Always send diffs from the old file to the new file. If you even
8357 discuss something in the @command{@value{AS}} source, refer to it by context, not
8360 The line numbers in our development sources will not match those in your
8361 sources. Your line numbers would convey no useful information to us.
8364 Here are some things that are not necessary:
8368 A description of the envelope of the bug.
8370 Often people who encounter a bug spend a lot of time investigating
8371 which changes to the input file will make the bug go away and which
8372 changes will not affect it.
8374 This is often time consuming and not very useful, because the way we
8375 will find the bug is by running a single example under the debugger
8376 with breakpoints, not by pure deduction from a series of examples.
8377 We recommend that you save your time for something else.
8379 Of course, if you can find a simpler example to report @emph{instead}
8380 of the original one, that is a convenience for us. Errors in the
8381 output will be easier to spot, running under the debugger will take
8382 less time, and so on.
8384 However, simplification is not vital; if you do not want to do this,
8385 report the bug anyway and send us the entire test case you used.
8388 A patch for the bug.
8390 A patch for the bug does help us if it is a good one. But do not omit
8391 the necessary information, such as the test case, on the assumption that
8392 a patch is all we need. We might see problems with your patch and decide
8393 to fix the problem another way, or we might not understand it at all.
8395 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
8396 construct an example that will make the program follow a certain path through
8397 the code. If you do not send us the example, we will not be able to construct
8398 one, so we will not be able to verify that the bug is fixed.
8400 And if we cannot understand what bug you are trying to fix, or why your
8401 patch should be an improvement, we will not install it. A test case will
8402 help us to understand.
8405 A guess about what the bug is or what it depends on.
8407 Such guesses are usually wrong. Even we cannot guess right about such
8408 things without first using the debugger to find the facts.
8411 @node Acknowledgements
8412 @chapter Acknowledgements
8414 If you have contributed to GAS and your name isn't listed here,
8415 it is not meant as a slight. We just don't know about it. Send mail to the
8416 maintainer, and we'll correct the situation. Currently
8418 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
8420 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
8423 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
8424 information and the 68k series machines, most of the preprocessing pass, and
8425 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
8427 K. Richard Pixley maintained GAS for a while, adding various enhancements and
8428 many bug fixes, including merging support for several processors, breaking GAS
8429 up to handle multiple object file format back ends (including heavy rewrite,
8430 testing, an integration of the coff and b.out back ends), adding configuration
8431 including heavy testing and verification of cross assemblers and file splits
8432 and renaming, converted GAS to strictly ANSI C including full prototypes, added
8433 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
8434 port (including considerable amounts of reverse engineering), a SPARC opcode
8435 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
8436 assertions and made them work, much other reorganization, cleanup, and lint.
8438 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
8439 in format-specific I/O modules.
8441 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
8442 has done much work with it since.
8444 The Intel 80386 machine description was written by Eliot Dresselhaus.
8446 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
8448 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
8449 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
8451 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
8452 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
8453 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
8454 support a.out format.
8456 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
8457 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
8458 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
8459 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
8462 John Gilmore built the AMD 29000 support, added @code{.include} support, and
8463 simplified the configuration of which versions accept which directives. He
8464 updated the 68k machine description so that Motorola's opcodes always produced
8465 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
8466 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
8467 cross-compilation support, and one bug in relaxation that took a week and
8468 required the proverbial one-bit fix.
8470 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
8471 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
8472 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
8473 PowerPC assembler, and made a few other minor patches.
8475 Steve Chamberlain made GAS able to generate listings.
8477 Hewlett-Packard contributed support for the HP9000/300.
8479 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
8480 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
8481 formats). This work was supported by both the Center for Software Science at
8482 the University of Utah and Cygnus Support.
8484 Support for ELF format files has been worked on by Mark Eichin of Cygnus
8485 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
8486 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
8487 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
8488 and some initial 64-bit support).
8490 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8492 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8493 support for openVMS/Alpha.
8495 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8498 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8499 Inc.@: added support for Xtensa processors.
8501 Several engineers at Cygnus Support have also provided many small bug fixes and
8502 configuration enhancements.
8504 Jon Beniston added support for the Lattice Mico32 architecture.
8506 Many others have contributed large or small bugfixes and enhancements. If
8507 you have contributed significant work and are not mentioned on this list, and
8508 want to be, let us know. Some of the history has been lost; we are not
8509 intentionally leaving anyone out.
8511 @node GNU Free Documentation License
8512 @appendix GNU Free Documentation License
8516 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob