5458 lines
184 KiB
Plaintext
5458 lines
184 KiB
Plaintext
\input texinfo @c -*-Texinfo-*-
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@c Copyright (c) 1991, 92, 93, 94, 95, 96, 97, 98, 2000
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@c Free Software Foundation, Inc.
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@c UPDATE!! On future updates--
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@c (1) check for new machine-dep cmdline options in
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@c md_parse_option definitions in config/tc-*.c
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@c (2) for platform-specific directives, examine md_pseudo_op
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@c in config/tc-*.c
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@c (3) for object-format specific directives, examine obj_pseudo_op
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@c in config/obj-*.c
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@c (4) portable directives in potable[] in read.c
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@c %**start of header
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@setfilename as.info
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@c ---config---
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@c defaults, config file may override:
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@set have-stabs
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@c ---
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@include asconfig.texi
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@include gasver.texi
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@c ---
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@c common OR combinations of conditions
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@ifset AOUT
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@set aout-bout
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@end ifset
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@ifset ARM/Thumb
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@set ARM
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@end ifset
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@ifset BOUT
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@set aout-bout
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@end ifset
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@ifset H8/300
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@set H8
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@end ifset
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@ifset H8/500
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@set H8
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@end ifset
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@ifset SH
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@set H8
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@end ifset
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@ifset HPPA
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@set abnormal-separator
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@end ifset
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@c ------------
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@ifset GENERIC
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@settitle Using @value{AS}
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@end ifset
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@ifclear GENERIC
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@settitle Using @value{AS} (@value{TARGET})
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@end ifclear
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@setchapternewpage odd
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@c %**end of header
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@c @smallbook
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@c @set SMALL
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@c WARE! Some of the machine-dependent sections contain tables of machine
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@c instructions. Except in multi-column format, these tables look silly.
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@c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
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@c the multi-col format is faked within @example sections.
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@c
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@c Again unfortunately, the natural size that fits on a page, for these tables,
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@c is different depending on whether or not smallbook is turned on.
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@c This matters, because of order: text flow switches columns at each page
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@c break.
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@c
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@c The format faked in this source works reasonably well for smallbook,
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@c not well for the default large-page format. This manual expects that if you
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@c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
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@c tables in question. You can turn on one without the other at your
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@c discretion, of course.
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@ifinfo
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@set SMALL
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@c the insn tables look just as silly in info files regardless of smallbook,
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@c might as well show 'em anyways.
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@end ifinfo
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@ifinfo
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@format
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START-INFO-DIR-ENTRY
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* As: (as). The GNU assembler.
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END-INFO-DIR-ENTRY
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@end format
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@end ifinfo
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@finalout
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@syncodeindex ky cp
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@ifinfo
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This file documents the GNU Assembler "@value{AS}".
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Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 1998 Free Software Foundation, Inc.
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Permission is granted to make and distribute verbatim copies of
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this manual provided the copyright notice and this permission notice
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are preserved on all copies.
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@ignore
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Permission is granted to process this file through Tex and print the
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results, provided the printed document carries copying permission
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notice identical to this one except for the removal of this paragraph
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(this paragraph not being relevant to the printed manual).
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@end ignore
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Permission is granted to copy and distribute modified versions of this manual
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under the conditions for verbatim copying, provided that the entire resulting
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derived work is distributed under the terms of a permission notice identical to
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this one.
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Permission is granted to copy and distribute translations of this manual
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into another language, under the above conditions for modified versions.
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@end ifinfo
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@titlepage
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@title Using @value{AS}
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@subtitle The @sc{gnu} Assembler
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@ifclear GENERIC
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@subtitle for the @value{TARGET} family
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@end ifclear
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@sp 1
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@subtitle Version @value{VERSION}
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@sp 1
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@sp 13
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The Free Software Foundation Inc. thanks The Nice Computer
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Company of Australia for loaning Dean Elsner to write the
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first (Vax) version of @code{as} for Project @sc{gnu}.
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The proprietors, management and staff of TNCCA thank FSF for
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distracting the boss while they got some work
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done.
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@sp 3
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@author Dean Elsner, Jay Fenlason & friends
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@page
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@tex
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{\parskip=0pt
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\hfill {\it Using {\tt @value{AS}}}\par
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\hfill Edited by Cygnus Support\par
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}
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%"boxit" macro for figures:
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%Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
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\gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
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\vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
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#2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
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\gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
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@end tex
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@vskip 0pt plus 1filll
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Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 1998 Free Software Foundation, Inc.
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Permission is granted to make and distribute verbatim copies of
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this manual provided the copyright notice and this permission notice
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are preserved on all copies.
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Permission is granted to copy and distribute modified versions of this manual
|
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under the conditions for verbatim copying, provided that the entire resulting
|
|
derived work is distributed under the terms of a permission notice identical to
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this one.
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Permission is granted to copy and distribute translations of this manual
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into another language, under the above conditions for modified versions.
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@end titlepage
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@ifinfo
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@node Top
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@top Using @value{AS}
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This file is a user guide to the @sc{gnu} assembler @code{@value{AS}} version
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@value{VERSION}.
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@ifclear GENERIC
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This version of the file describes @code{@value{AS}} configured to generate
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code for @value{TARGET} architectures.
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@end ifclear
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@menu
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* Overview:: Overview
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* Invoking:: Command-Line Options
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* Syntax:: Syntax
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* Sections:: Sections and Relocation
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* Symbols:: Symbols
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* Expressions:: Expressions
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* Pseudo Ops:: Assembler Directives
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* Machine Dependencies:: Machine Dependent Features
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* Reporting Bugs:: Reporting Bugs
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* Acknowledgements:: Who Did What
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* Index:: Index
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@end menu
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@end ifinfo
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@node Overview
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@chapter Overview
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@iftex
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This manual is a user guide to the @sc{gnu} assembler @code{@value{AS}}.
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@ifclear GENERIC
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This version of the manual describes @code{@value{AS}} configured to generate
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code for @value{TARGET} architectures.
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@end ifclear
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@end iftex
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@cindex invocation summary
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@cindex option summary
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@cindex summary of options
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Here is a brief summary of how to invoke @code{@value{AS}}. For details,
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@pxref{Invoking,,Comand-Line Options}.
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@c We don't use deffn and friends for the following because they seem
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@c to be limited to one line for the header.
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@smallexample
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@value{AS} [ -a[cdhlns][=file] ] [ -D ] [ --defsym @var{sym}=@var{val} ]
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[ -f ] [ --gstabs ] [ --gdwarf2 ] [ --help ] [ -I @var{dir} ] [ -J ] [ -K ] [ -L ]
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[ --keep-locals ] [ -o @var{objfile} ] [ -R ] [ --statistics ] [ -v ]
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[ -version ] [ --version ] [ -W ] [ --warn ] [ --fatal-warnings ]
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[ -w ] [ -x ] [ -Z ]
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@ifset A29K
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@c am29k has no machine-dependent assembler options
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@end ifset
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@ifset ARC
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[ -mbig-endian | -mlittle-endian ]
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@end ifset
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@ifset ARM
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[ -m[arm]1 | -m[arm]2 | -m[arm]250 | -m[arm]3 | -m[arm]6 | -m[arm]60 |
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-m[arm]600 | -m[arm]610 | -m[arm]620 | -m[arm]7[t][[d]m[i]][fe] | -m[arm]70 |
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-m[arm]700 | -m[arm]710[c] | -m[arm]7100 | -m[arm]7500 | -m[arm]8 |
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-m[arm]810 | -m[arm]9 | -m[arm]920 | -m[arm]920t | -m[arm]9tdmi |
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-mstrongarm | -mstrongarm110 | -mstrongarm1100 ]
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[ -m[arm]v2 | -m[arm]v2a | -m[arm]v3 | -m[arm]v3m | -m[arm]v4 | -m[arm]v4t |
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-m[arm]v5 | -[arm]v5t ]
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[ -mthumb | -mall ]
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[ -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu ]
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[ -EB | -EL ]
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[ -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant ]
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[ -mthumb-interwork ]
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[ -moabi ]
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[ -k ]
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@end ifset
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@ifset D10V
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[ -O ]
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@end ifset
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@ifset D30V
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[ -O | -n | -N ]
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@end ifset
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@ifset H8
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@c Hitachi family chips have no machine-dependent assembler options
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@end ifset
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@ifset HPPA
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@c HPPA has no machine-dependent assembler options (yet).
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@end ifset
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@ifset PJ
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[ -mb | -me ]
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@end ifset
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@ifset SPARC
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@c The order here is important. See c-sparc.texi.
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[ -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
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-Av8plus | -Av8plusa | -Av9 | -Av9a ]
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[ -xarch=v8plus | -xarch=v8plusa ] [ -bump ] [ -32 | -64 ]
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@end ifset
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@ifset Z8000
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@c Z8000 has no machine-dependent assembler options
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@end ifset
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@ifset I960
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@c see md_parse_option in tc-i960.c
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[ -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC ]
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[ -b ] [ -no-relax ]
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@end ifset
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@ifset M680X0
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[ -l ] [ -m68000 | -m68010 | -m68020 | ... ]
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@end ifset
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@ifset MCORE
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[ -jsri2bsr ] [ -sifilter ] [ -relax ]
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@end ifset
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@ifset MIPS
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[ -nocpp ] [ -EL ] [ -EB ] [ -G @var{num} ] [ -mcpu=@var{CPU} ]
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[ -mips1 ] [ -mips2 ] [ -mips3 ] [ -m4650 ] [ -no-m4650 ]
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[ --trap ] [ --break ]
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[ --emulation=@var{name} ]
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@end ifset
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[ -- | @var{files} @dots{} ]
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@end smallexample
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@table @code
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@item -a[cdhlmns]
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Turn on listings, in any of a variety of ways:
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@table @code
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@item -ac
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omit false conditionals
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@item -ad
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omit debugging directives
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@item -ah
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include high-level source
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@item -al
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include assembly
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@item -am
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include macro expansions
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@item -an
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omit forms processing
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@item -as
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include symbols
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@item =file
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set the name of the listing file
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@end table
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You may combine these options; for example, use @samp{-aln} for assembly
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listing without forms processing. The @samp{=file} option, if used, must be
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the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
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@item -D
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Ignored. This option is accepted for script compatibility with calls to
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other assemblers.
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@item --defsym @var{sym}=@var{value}
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Define the symbol @var{sym} to be @var{value} before assembling the input file.
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@var{value} must be an integer constant. As in C, a leading @samp{0x}
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indicates a hexadecimal value, and a leading @samp{0} indicates an octal value.
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@item -f
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``fast''---skip whitespace and comment preprocessing (assume source is
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compiler output).
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@item --gstabs
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Generate stabs debugging information for each assembler line. This
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may help debugging assembler code, if the debugger can handle it.
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@item --gdwarf2
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Generate DWARF2 debugging information for each assembler line. This
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may help debugging assembler code, if the debugger can handle it.
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@item --help
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Print a summary of the command line options and exit.
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@item -I @var{dir}
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Add directory @var{dir} to the search list for @code{.include} directives.
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@item -J
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Don't warn about signed overflow.
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@item -K
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@ifclear DIFF-TBL-KLUGE
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This option is accepted but has no effect on the @value{TARGET} family.
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@end ifclear
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@ifset DIFF-TBL-KLUGE
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Issue warnings when difference tables altered for long displacements.
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@end ifset
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@item -L
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@itemx --keep-locals
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Keep (in the symbol table) local symbols. On traditional a.out systems
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these start with @samp{L}, but different systems have different local
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label prefixes.
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@item -o @var{objfile}
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Name the object-file output from @code{@value{AS}} @var{objfile}.
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@item -R
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Fold the data section into the text section.
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@item --statistics
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Print the maximum space (in bytes) and total time (in seconds) used by
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assembly.
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@item --strip-local-absolute
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Remove local absolute symbols from the outgoing symbol table.
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@item -v
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@itemx -version
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Print the @code{as} version.
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@item --version
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Print the @code{as} version and exit.
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@item -W
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@itemx --no-warn
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Suppress warning messages.
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@item --fatal-warnings
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Treat warnings as errors.
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@item --warn
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Don't suppress warning messages or treat them as errors.
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@item -w
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Ignored.
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@item -x
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Ignored.
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@item -Z
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Generate an object file even after errors.
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@item -- | @var{files} @dots{}
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Standard input, or source files to assemble.
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@end table
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@ifset ARC
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The following options are available when @value{AS} is configured for
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an ARC processor.
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|
@table @code
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|
@cindex ARC endianness
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|
@cindex endianness, ARC
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|
@cindex big endian output, ARC
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|
@item -mbig-endian
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|
Generate ``big endian'' format output.
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|
@cindex little endian output, ARC
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|
@item -mlittle-endian
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|
Generate ``little endian'' format output.
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|
@end table
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|
@end ifset
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|
@ifset ARM
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|
The following options are available when @value{AS} is configured for the ARM
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|
processor family.
|
|
|
|
@table @code
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|
@item -m[arm][1|2|3|6|7|8|9][...]
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|
Specify which ARM processor variant is the target.
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|
@item -m[arm]v[2|2a|3|3m|4|4t|5|5t]
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|
Specify which ARM architecture variant is used by the target.
|
|
@item -mthumb | -mall
|
|
Enable or disable Thumb only instruction decoding.
|
|
@item -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu
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|
Select which Floating Point architcture is the target.
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|
@item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant | -moabi
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|
Select which procedure calling convention is in use.
|
|
@item -EB | -EL
|
|
Select either big-endian (-EB) or little-endian (-EL) output.
|
|
@item -mthumb-interwork
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|
Specify that the code has been generated with interworking between Thumb and
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|
ARM code in mind.
|
|
@item -k
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|
Specify that PIC code has been generated.
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|
@end table
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|
@end ifset
|
|
|
|
@ifset D10V
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|
The following options are available when @value{AS} is configured for
|
|
a D10V processor.
|
|
@table @code
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|
@cindex D10V optimization
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|
@cindex optimization, D10V
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|
@item -O
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|
Optimize output by parallelizing instructions.
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|
@end table
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|
@end ifset
|
|
|
|
@ifset D30V
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|
The following options are available when @value{AS} is configured for a D30V
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|
processor.
|
|
@table @code
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|
@cindex D30V optimization
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|
@cindex optimization, D30V
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|
@item -O
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|
Optimize output by parallelizing instructions.
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|
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|
@cindex D30V nops
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|
@item -n
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|
Warn when nops are generated.
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|
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|
@cindex D30V nops after 32-bit multiply
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|
@item -N
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|
Warn when a nop after a 32-bit multiply instruction is generated.
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|
@end table
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|
@end ifset
|
|
|
|
@ifset I960
|
|
The following options are available when @value{AS} is configured for the
|
|
Intel 80960 processor.
|
|
|
|
@table @code
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|
@item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
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|
Specify which variant of the 960 architecture is the target.
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|
@item -b
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|
Add code to collect statistics about branches taken.
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|
|
|
@item -no-relax
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|
Do not alter compare-and-branch instructions for long displacements;
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|
error if necessary.
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|
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|
@end table
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|
@end ifset
|
|
|
|
|
|
@ifset M680X0
|
|
The following options are available when @value{AS} is configured for the
|
|
Motorola 68000 series.
|
|
|
|
@table @code
|
|
|
|
@item -l
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|
Shorten references to undefined symbols, to one word instead of two.
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|
|
|
@item -m68000 | -m68008 | -m68010 | -m68020 | -m68030 | -m68040 | -m68060
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|
@itemx | -m68302 | -m68331 | -m68332 | -m68333 | -m68340 | -mcpu32 | -m5200
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|
Specify what processor in the 68000 family is the target. The default
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|
is normally the 68020, but this can be changed at configuration time.
|
|
|
|
@item -m68881 | -m68882 | -mno-68881 | -mno-68882
|
|
The target machine does (or does not) have a floating-point coprocessor.
|
|
The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
|
|
the basic 68000 is not compatible with the 68881, a combination of the
|
|
two can be specified, since it's possible to do emulation of the
|
|
coprocessor instructions with the main processor.
|
|
|
|
@item -m68851 | -mno-68851
|
|
The target machine does (or does not) have a memory-management
|
|
unit coprocessor. The default is to assume an MMU for 68020 and up.
|
|
|
|
@end table
|
|
@end ifset
|
|
|
|
@ifset PJ
|
|
The following options are available when @value{AS} is configured for
|
|
a picoJava processor.
|
|
|
|
@table @code
|
|
|
|
@cindex PJ endianness
|
|
@cindex endianness, PJ
|
|
@cindex big endian output, PJ
|
|
@item -mb
|
|
Generate ``big endian'' format output.
|
|
|
|
@cindex little endian output, PJ
|
|
@item -ml
|
|
Generate ``little endian'' format output.
|
|
|
|
@end table
|
|
@end ifset
|
|
|
|
|
|
@ifset SPARC
|
|
The following options are available when @code{@value{AS}} is configured
|
|
for the SPARC architecture:
|
|
|
|
@table @code
|
|
@item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
|
|
@itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
|
|
Explicitly select a variant of the SPARC architecture.
|
|
|
|
@samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
|
|
@samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
|
|
|
|
@samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
|
|
UltraSPARC extensions.
|
|
|
|
@item -xarch=v8plus | -xarch=v8plusa
|
|
For compatibility with the Solaris v9 assembler. These options are
|
|
equivalent to -Av8plus and -Av8plusa, respectively.
|
|
|
|
@item -bump
|
|
Warn when the assembler switches to another architecture.
|
|
@end table
|
|
@end ifset
|
|
|
|
@ifset MIPS
|
|
The following options are available when @value{AS} is configured for
|
|
a MIPS processor.
|
|
|
|
@table @code
|
|
@item -G @var{num}
|
|
This option sets the largest size of an object that can be referenced
|
|
implicitly with the @code{gp} register. It is only accepted for targets that
|
|
use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
|
|
|
|
@cindex MIPS endianness
|
|
@cindex endianness, MIPS
|
|
@cindex big endian output, MIPS
|
|
@item -EB
|
|
Generate ``big endian'' format output.
|
|
|
|
@cindex little endian output, MIPS
|
|
@item -EL
|
|
Generate ``little endian'' format output.
|
|
|
|
@cindex MIPS ISA
|
|
@item -mips1
|
|
@itemx -mips2
|
|
@itemx -mips3
|
|
Generate code for a particular MIPS Instruction Set Architecture level.
|
|
@samp{-mips1} corresponds to the @sc{r2000} and @sc{r3000} processors,
|
|
@samp{-mips2} to the @sc{r6000} processor, and @samp{-mips3} to the @sc{r4000}
|
|
processor.
|
|
|
|
@item -m4650
|
|
@itemx -no-m4650
|
|
Generate code for the MIPS @sc{r4650} chip. This tells the assembler to accept
|
|
the @samp{mad} and @samp{madu} instruction, and to not schedule @samp{nop}
|
|
instructions around accesses to the @samp{HI} and @samp{LO} registers.
|
|
@samp{-no-m4650} turns off this option.
|
|
|
|
@item -mcpu=@var{CPU}
|
|
Generate code for a particular MIPS cpu. This has little effect on the
|
|
assembler, but it is passed by @code{@value{GCC}}.
|
|
|
|
@cindex emulation
|
|
@item --emulation=@var{name}
|
|
This option causes @code{@value{AS}} to emulate @code{@value{AS}} configured
|
|
for some other target, in all respects, including output format (choosing
|
|
between ELF and ECOFF only), handling of pseudo-opcodes which may generate
|
|
debugging information or store symbol table information, and default
|
|
endianness. The available configuration names are: @samp{mipsecoff},
|
|
@samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
|
|
@samp{mipsbelf}. The first two do not alter the default endianness from that
|
|
of the primary target for which the assembler was configured; the others change
|
|
the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
|
|
in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
|
|
selection in any case.
|
|
|
|
This option is currently supported only when the primary target
|
|
@code{@value{AS}} is configured for is a MIPS ELF or ECOFF target.
|
|
Furthermore, the primary target or others specified with
|
|
@samp{--enable-targets=@dots{}} at configuration time must include support for
|
|
the other format, if both are to be available. For example, the Irix 5
|
|
configuration includes support for both.
|
|
|
|
Eventually, this option will support more configurations, with more
|
|
fine-grained control over the assembler's behavior, and will be supported for
|
|
more processors.
|
|
|
|
@item -nocpp
|
|
@code{@value{AS}} ignores this option. It is accepted for compatibility with
|
|
the native tools.
|
|
|
|
@need 900
|
|
@item --trap
|
|
@itemx --no-trap
|
|
@itemx --break
|
|
@itemx --no-break
|
|
Control how to deal with multiplication overflow and division by zero.
|
|
@samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
|
|
(and only work for Instruction Set Architecture level 2 and higher);
|
|
@samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
|
|
break exception.
|
|
@end table
|
|
@end ifset
|
|
|
|
@ifset MCORE
|
|
The following options are available when @value{AS} is configured for
|
|
an MCore processor.
|
|
|
|
@table @code
|
|
@item -jsri2bsr
|
|
@itemx -nojsri2bsr
|
|
Enable or disable the JSRI to BSR transformation. By default this is enabled.
|
|
The command line option @samp{-nojsri2bsr} can be used to disable it.
|
|
|
|
@item -sifilter
|
|
@itemx -nosifilter
|
|
Enable or disable the silicon filter behaviour. By default this is disabled.
|
|
The default can be overidden by the @samp{-sifilter} command line option.
|
|
|
|
@item -relax
|
|
Alter jump instructions for long displacements.
|
|
|
|
|
|
@end table
|
|
@end ifset
|
|
|
|
@menu
|
|
* Manual:: Structure of this Manual
|
|
* GNU Assembler:: The GNU Assembler
|
|
* Object Formats:: Object File Formats
|
|
* Command Line:: Command Line
|
|
* Input Files:: Input Files
|
|
* Object:: Output (Object) File
|
|
* Errors:: Error and Warning Messages
|
|
@end menu
|
|
|
|
@node Manual
|
|
@section Structure of this Manual
|
|
|
|
@cindex manual, structure and purpose
|
|
This manual is intended to describe what you need to know to use
|
|
@sc{gnu} @code{@value{AS}}. We cover the syntax expected in source files, including
|
|
notation for symbols, constants, and expressions; the directives that
|
|
@code{@value{AS}} understands; and of course how to invoke @code{@value{AS}}.
|
|
|
|
@ifclear GENERIC
|
|
We also cover special features in the @value{TARGET}
|
|
configuration of @code{@value{AS}}, including assembler directives.
|
|
@end ifclear
|
|
@ifset GENERIC
|
|
This manual also describes some of the machine-dependent features of
|
|
various flavors of the assembler.
|
|
@end ifset
|
|
|
|
@cindex machine instructions (not covered)
|
|
On the other hand, this manual is @emph{not} intended as an introduction
|
|
to programming in assembly language---let alone programming in general!
|
|
In a similar vein, we make no attempt to introduce the machine
|
|
architecture; we do @emph{not} describe the instruction set, standard
|
|
mnemonics, registers or addressing modes that are standard to a
|
|
particular architecture.
|
|
@ifset GENERIC
|
|
You may want to consult the manufacturer's
|
|
machine architecture manual for this information.
|
|
@end ifset
|
|
@ifclear GENERIC
|
|
@ifset H8/300
|
|
For information on the H8/300 machine instruction set, see @cite{H8/300
|
|
Series Programming Manual} (Hitachi ADE--602--025). For the H8/300H,
|
|
see @cite{H8/300H Series Programming Manual} (Hitachi).
|
|
@end ifset
|
|
@ifset H8/500
|
|
For information on the H8/500 machine instruction set, see @cite{H8/500
|
|
Series Programming Manual} (Hitachi M21T001).
|
|
@end ifset
|
|
@ifset SH
|
|
For information on the Hitachi SH machine instruction set, see
|
|
@cite{SH-Microcomputer User's Manual} (Hitachi Micro Systems, Inc.).
|
|
@end ifset
|
|
@ifset Z8000
|
|
For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
|
|
@end ifset
|
|
@end ifclear
|
|
|
|
@c I think this is premature---doc@cygnus.com, 17jan1991
|
|
@ignore
|
|
Throughout this manual, we assume that you are running @dfn{GNU},
|
|
the portable operating system from the @dfn{Free Software
|
|
Foundation, Inc.}. This restricts our attention to certain kinds of
|
|
computer (in particular, the kinds of computers that @sc{gnu} can run on);
|
|
once this assumption is granted examples and definitions need less
|
|
qualification.
|
|
|
|
@code{@value{AS}} is part of a team of programs that turn a high-level
|
|
human-readable series of instructions into a low-level
|
|
computer-readable series of instructions. Different versions of
|
|
@code{@value{AS}} are used for different kinds of computer.
|
|
@end ignore
|
|
|
|
@c There used to be a section "Terminology" here, which defined
|
|
@c "contents", "byte", "word", and "long". Defining "word" to any
|
|
@c particular size is confusing when the .word directive may generate 16
|
|
@c bits on one machine and 32 bits on another; in general, for the user
|
|
@c version of this manual, none of these terms seem essential to define.
|
|
@c They were used very little even in the former draft of the manual;
|
|
@c this draft makes an effort to avoid them (except in names of
|
|
@c directives).
|
|
|
|
@node GNU Assembler
|
|
@section The GNU Assembler
|
|
|
|
@sc{gnu} @code{as} is really a family of assemblers.
|
|
@ifclear GENERIC
|
|
This manual describes @code{@value{AS}}, a member of that family which is
|
|
configured for the @value{TARGET} architectures.
|
|
@end ifclear
|
|
If you use (or have used) the @sc{gnu} assembler on one architecture, you
|
|
should find a fairly similar environment when you use it on another
|
|
architecture. Each version has much in common with the others,
|
|
including object file formats, most assembler directives (often called
|
|
@dfn{pseudo-ops}) and assembler syntax.@refill
|
|
|
|
@cindex purpose of @sc{gnu} assembler
|
|
@code{@value{AS}} is primarily intended to assemble the output of the
|
|
@sc{gnu} C compiler @code{@value{GCC}} for use by the linker
|
|
@code{@value{LD}}. Nevertheless, we've tried to make @code{@value{AS}}
|
|
assemble correctly everything that other assemblers for the same
|
|
machine would assemble.
|
|
@ifset VAX
|
|
Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
|
|
@end ifset
|
|
@ifset M680X0
|
|
@c This remark should appear in generic version of manual; assumption
|
|
@c here is that generic version sets M680x0.
|
|
This doesn't mean @code{@value{AS}} always uses the same syntax as another
|
|
assembler for the same architecture; for example, we know of several
|
|
incompatible versions of 680x0 assembly language syntax.
|
|
@end ifset
|
|
|
|
Unlike older assemblers, @code{@value{AS}} is designed to assemble a source
|
|
program in one pass of the source file. This has a subtle impact on the
|
|
@kbd{.org} directive (@pxref{Org,,@code{.org}}).
|
|
|
|
@node Object Formats
|
|
@section Object File Formats
|
|
|
|
@cindex object file format
|
|
The @sc{gnu} assembler can be configured to produce several alternative
|
|
object file formats. For the most part, this does not affect how you
|
|
write assembly language programs; but directives for debugging symbols
|
|
are typically different in different file formats. @xref{Symbol
|
|
Attributes,,Symbol Attributes}.
|
|
@ifclear GENERIC
|
|
@ifclear MULTI-OBJ
|
|
On the @value{TARGET}, @code{@value{AS}} is configured to produce
|
|
@value{OBJ-NAME} format object files.
|
|
@end ifclear
|
|
@c The following should exhaust all configs that set MULTI-OBJ, ideally
|
|
@ifset A29K
|
|
On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
|
|
@code{a.out} or COFF format object files.
|
|
@end ifset
|
|
@ifset I960
|
|
On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
|
|
@code{b.out} or COFF format object files.
|
|
@end ifset
|
|
@ifset HPPA
|
|
On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
|
|
SOM or ELF format object files.
|
|
@end ifset
|
|
@end ifclear
|
|
|
|
@node Command Line
|
|
@section Command Line
|
|
|
|
@cindex command line conventions
|
|
After the program name @code{@value{AS}}, the command line may contain
|
|
options and file names. Options may appear in any order, and may be
|
|
before, after, or between file names. The order of file names is
|
|
significant.
|
|
|
|
@cindex standard input, as input file
|
|
@kindex --
|
|
@file{--} (two hyphens) by itself names the standard input file
|
|
explicitly, as one of the files for @code{@value{AS}} to assemble.
|
|
|
|
@cindex options, command line
|
|
Except for @samp{--} any command line argument that begins with a
|
|
hyphen (@samp{-}) is an option. Each option changes the behavior of
|
|
@code{@value{AS}}. No option changes the way another option works. An
|
|
option is a @samp{-} followed by one or more letters; the case of
|
|
the letter is important. All options are optional.
|
|
|
|
Some options expect exactly one file name to follow them. The file
|
|
name may either immediately follow the option's letter (compatible
|
|
with older assemblers) or it may be the next command argument (@sc{gnu}
|
|
standard). These two command lines are equivalent:
|
|
|
|
@smallexample
|
|
@value{AS} -o my-object-file.o mumble.s
|
|
@value{AS} -omy-object-file.o mumble.s
|
|
@end smallexample
|
|
|
|
@node Input Files
|
|
@section Input Files
|
|
|
|
@cindex input
|
|
@cindex source program
|
|
@cindex files, input
|
|
We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
|
|
describe the program input to one run of @code{@value{AS}}. The program may
|
|
be in one or more files; how the source is partitioned into files
|
|
doesn't change the meaning of the source.
|
|
|
|
@c I added "con" prefix to "catenation" just to prove I can overcome my
|
|
@c APL training... doc@cygnus.com
|
|
The source program is a concatenation of the text in all the files, in the
|
|
order specified.
|
|
|
|
Each time you run @code{@value{AS}} it assembles exactly one source
|
|
program. The source program is made up of one or more files.
|
|
(The standard input is also a file.)
|
|
|
|
You give @code{@value{AS}} a command line that has zero or more input file
|
|
names. The input files are read (from left file name to right). A
|
|
command line argument (in any position) that has no special meaning
|
|
is taken to be an input file name.
|
|
|
|
If you give @code{@value{AS}} no file names it attempts to read one input file
|
|
from the @code{@value{AS}} standard input, which is normally your terminal. You
|
|
may have to type @key{ctl-D} to tell @code{@value{AS}} there is no more program
|
|
to assemble.
|
|
|
|
Use @samp{--} if you need to explicitly name the standard input file
|
|
in your command line.
|
|
|
|
If the source is empty, @code{@value{AS}} produces a small, empty object
|
|
file.
|
|
|
|
@subheading Filenames and Line-numbers
|
|
|
|
@cindex input file linenumbers
|
|
@cindex line numbers, in input files
|
|
There are two ways of locating a line in the input file (or files) and
|
|
either may be used in reporting error messages. One way refers to a line
|
|
number in a physical file; the other refers to a line number in a
|
|
``logical'' file. @xref{Errors, ,Error and Warning Messages}.
|
|
|
|
@dfn{Physical files} are those files named in the command line given
|
|
to @code{@value{AS}}.
|
|
|
|
@dfn{Logical files} are simply names declared explicitly by assembler
|
|
directives; they bear no relation to physical files. Logical file names help
|
|
error messages reflect the original source file, when @code{@value{AS}} source
|
|
is itself synthesized from other files. @code{@value{AS}} understands the
|
|
@samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
|
|
@ref{File,,@code{.file}}.
|
|
|
|
@node Object
|
|
@section Output (Object) File
|
|
|
|
@cindex object file
|
|
@cindex output file
|
|
@kindex a.out
|
|
@kindex .o
|
|
Every time you run @code{@value{AS}} it produces an output file, which is
|
|
your assembly language program translated into numbers. This file
|
|
is the object file. Its default name is
|
|
@ifclear BOUT
|
|
@code{a.out}.
|
|
@end ifclear
|
|
@ifset BOUT
|
|
@ifset GENERIC
|
|
@code{a.out}, or
|
|
@end ifset
|
|
@code{b.out} when @code{@value{AS}} is configured for the Intel 80960.
|
|
@end ifset
|
|
You can give it another name by using the @code{-o} option. Conventionally,
|
|
object file names end with @file{.o}. The default name is used for historical
|
|
reasons: older assemblers were capable of assembling self-contained programs
|
|
directly into a runnable program. (For some formats, this isn't currently
|
|
possible, but it can be done for the @code{a.out} format.)
|
|
|
|
@cindex linker
|
|
@kindex ld
|
|
The object file is meant for input to the linker @code{@value{LD}}. It contains
|
|
assembled program code, information to help @code{@value{LD}} integrate
|
|
the assembled program into a runnable file, and (optionally) symbolic
|
|
information for the debugger.
|
|
|
|
@c link above to some info file(s) like the description of a.out.
|
|
@c don't forget to describe @sc{gnu} info as well as Unix lossage.
|
|
|
|
@node Errors
|
|
@section Error and Warning Messages
|
|
|
|
@cindex error messsages
|
|
@cindex warning messages
|
|
@cindex messages from assembler
|
|
@code{@value{AS}} may write warnings and error messages to the standard error
|
|
file (usually your terminal). This should not happen when a compiler
|
|
runs @code{@value{AS}} automatically. Warnings report an assumption made so
|
|
that @code{@value{AS}} could keep assembling a flawed program; errors report a
|
|
grave problem that stops the assembly.
|
|
|
|
@cindex format of warning messages
|
|
Warning messages have the format
|
|
|
|
@smallexample
|
|
file_name:@b{NNN}:Warning Message Text
|
|
@end smallexample
|
|
|
|
@noindent
|
|
@cindex line numbers, in warnings/errors
|
|
(where @b{NNN} is a line number). If a logical file name has been given
|
|
(@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
|
|
the current input file is used. If a logical line number was given
|
|
@ifset GENERIC
|
|
(@pxref{Line,,@code{.line}})
|
|
@end ifset
|
|
@ifclear GENERIC
|
|
@ifclear A29K
|
|
(@pxref{Line,,@code{.line}})
|
|
@end ifclear
|
|
@ifset A29K
|
|
(@pxref{Ln,,@code{.ln}})
|
|
@end ifset
|
|
@end ifclear
|
|
then it is used to calculate the number printed,
|
|
otherwise the actual line in the current source file is printed. The
|
|
message text is intended to be self explanatory (in the grand Unix
|
|
tradition).
|
|
|
|
@cindex format of error messages
|
|
Error messages have the format
|
|
@smallexample
|
|
file_name:@b{NNN}:FATAL:Error Message Text
|
|
@end smallexample
|
|
The file name and line number are derived as for warning
|
|
messages. The actual message text may be rather less explanatory
|
|
because many of them aren't supposed to happen.
|
|
|
|
@node Invoking
|
|
@chapter Command-Line Options
|
|
|
|
@cindex options, all versions of assembler
|
|
This chapter describes command-line options available in @emph{all}
|
|
versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
|
|
@ifclear GENERIC
|
|
to the @value{TARGET}.
|
|
@end ifclear
|
|
@ifset GENERIC
|
|
to particular machine architectures.
|
|
@end ifset
|
|
|
|
If you are invoking @code{@value{AS}} via the @sc{gnu} C compiler (version 2),
|
|
you can use the @samp{-Wa} option to pass arguments through to the assembler.
|
|
The assembler arguments must be separated from each other (and the @samp{-Wa})
|
|
by commas. For example:
|
|
|
|
@smallexample
|
|
gcc -c -g -O -Wa,-alh,-L file.c
|
|
@end smallexample
|
|
|
|
@noindent
|
|
This passes two options to the assembler: @samp{-alh} (emit a listing to
|
|
standard output with with high-level and assembly source) and @samp{-L} (retain
|
|
local symbols in the symbol table).
|
|
|
|
Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
|
|
command-line options are automatically passed to the assembler by the compiler.
|
|
(You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
|
|
precisely what options it passes to each compilation pass, including the
|
|
assembler.)
|
|
|
|
@menu
|
|
* a:: -a[cdhlns] enable listings
|
|
* D:: -D for compatibility
|
|
* f:: -f to work faster
|
|
* I:: -I for .include search path
|
|
@ifclear DIFF-TBL-KLUGE
|
|
* K:: -K for compatibility
|
|
@end ifclear
|
|
@ifset DIFF-TBL-KLUGE
|
|
* K:: -K for difference tables
|
|
@end ifset
|
|
|
|
* L:: -L to retain local labels
|
|
* M:: -M or --mri to assemble in MRI compatibility mode
|
|
* MD:: --MD for dependency tracking
|
|
* o:: -o to name the object file
|
|
* R:: -R to join data and text sections
|
|
* statistics:: --statistics to see statistics about assembly
|
|
* traditional-format:: --traditional-format for compatible output
|
|
* v:: -v to announce version
|
|
* W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
|
|
* Z:: -Z to make object file even after errors
|
|
@end menu
|
|
|
|
@node a
|
|
@section Enable Listings: @code{-a[cdhlns]}
|
|
|
|
@kindex -a
|
|
@kindex -ac
|
|
@kindex -ad
|
|
@kindex -ah
|
|
@kindex -al
|
|
@kindex -an
|
|
@kindex -as
|
|
@cindex listings, enabling
|
|
@cindex assembly listings, enabling
|
|
|
|
These options enable listing output from the assembler. By itself,
|
|
@samp{-a} requests high-level, assembly, and symbols listing.
|
|
You can use other letters to select specific options for the list:
|
|
@samp{-ah} requests a high-level language listing,
|
|
@samp{-al} requests an output-program assembly listing, and
|
|
@samp{-as} requests a symbol table listing.
|
|
High-level listings require that a compiler debugging option like
|
|
@samp{-g} be used, and that assembly listings (@samp{-al}) be requested
|
|
also.
|
|
|
|
Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
|
|
which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
|
|
other conditional), or a true @code{.if} followed by an @code{.else}, will be
|
|
omitted from the listing.
|
|
|
|
Use the @samp{-ad} option to omit debugging directives from the
|
|
listing.
|
|
|
|
Once you have specified one of these options, you can further control
|
|
listing output and its appearance using the directives @code{.list},
|
|
@code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
|
|
@code{.sbttl}.
|
|
The @samp{-an} option turns off all forms processing.
|
|
If you do not request listing output with one of the @samp{-a} options, the
|
|
listing-control directives have no effect.
|
|
|
|
The letters after @samp{-a} may be combined into one option,
|
|
@emph{e.g.}, @samp{-aln}.
|
|
|
|
@node D
|
|
@section @code{-D}
|
|
|
|
@kindex -D
|
|
This option has no effect whatsoever, but it is accepted to make it more
|
|
likely that scripts written for other assemblers also work with
|
|
@code{@value{AS}}.
|
|
|
|
@node f
|
|
@section Work Faster: @code{-f}
|
|
|
|
@kindex -f
|
|
@cindex trusted compiler
|
|
@cindex faster processing (@code{-f})
|
|
@samp{-f} should only be used when assembling programs written by a
|
|
(trusted) compiler. @samp{-f} stops the assembler from doing whitespace
|
|
and comment preprocessing on
|
|
the input file(s) before assembling them. @xref{Preprocessing,
|
|
,Preprocessing}.
|
|
|
|
@quotation
|
|
@emph{Warning:} if you use @samp{-f} when the files actually need to be
|
|
preprocessed (if they contain comments, for example), @code{@value{AS}} does
|
|
not work correctly.
|
|
@end quotation
|
|
|
|
@node I
|
|
@section @code{.include} search path: @code{-I} @var{path}
|
|
|
|
@kindex -I @var{path}
|
|
@cindex paths for @code{.include}
|
|
@cindex search path for @code{.include}
|
|
@cindex @code{include} directive search path
|
|
Use this option to add a @var{path} to the list of directories
|
|
@code{@value{AS}} searches for files specified in @code{.include}
|
|
directives (@pxref{Include,,@code{.include}}). You may use @code{-I} as
|
|
many times as necessary to include a variety of paths. The current
|
|
working directory is always searched first; after that, @code{@value{AS}}
|
|
searches any @samp{-I} directories in the same order as they were
|
|
specified (left to right) on the command line.
|
|
|
|
@node K
|
|
@section Difference Tables: @code{-K}
|
|
|
|
@kindex -K
|
|
@ifclear DIFF-TBL-KLUGE
|
|
On the @value{TARGET} family, this option is allowed, but has no effect. It is
|
|
permitted for compatibility with the @sc{gnu} assembler on other platforms,
|
|
where it can be used to warn when the assembler alters the machine code
|
|
generated for @samp{.word} directives in difference tables. The @value{TARGET}
|
|
family does not have the addressing limitations that sometimes lead to this
|
|
alteration on other platforms.
|
|
@end ifclear
|
|
|
|
@ifset DIFF-TBL-KLUGE
|
|
@cindex difference tables, warning
|
|
@cindex warning for altered difference tables
|
|
@code{@value{AS}} sometimes alters the code emitted for directives of the form
|
|
@samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
|
|
You can use the @samp{-K} option if you want a warning issued when this
|
|
is done.
|
|
@end ifset
|
|
|
|
@node L
|
|
@section Include Local Labels: @code{-L}
|
|
|
|
@kindex -L
|
|
@cindex local labels, retaining in output
|
|
Labels beginning with @samp{L} (upper case only) are called @dfn{local
|
|
labels}. @xref{Symbol Names}. Normally you do not see such labels when
|
|
debugging, because they are intended for the use of programs (like
|
|
compilers) that compose assembler programs, not for your notice.
|
|
Normally both @code{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
|
|
normally debug with them.
|
|
|
|
This option tells @code{@value{AS}} to retain those @samp{L@dots{}} symbols
|
|
in the object file. Usually if you do this you also tell the linker
|
|
@code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
|
|
|
|
By default, a local label is any label beginning with @samp{L}, but each
|
|
target is allowed to redefine the local label prefix.
|
|
@ifset HPPA
|
|
On the HPPA local labels begin with @samp{L$}.
|
|
@end ifset
|
|
@ifset ARM
|
|
@samp{;} for the ARM family;
|
|
@end ifset
|
|
|
|
@node M
|
|
@section Assemble in MRI Compatibility Mode: @code{-M}
|
|
|
|
@kindex -M
|
|
@cindex MRI compatibility mode
|
|
The @code{-M} or @code{--mri} option selects MRI compatibility mode. This
|
|
changes the syntax and pseudo-op handling of @code{@value{AS}} to make it
|
|
compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
|
|
configured target) assembler from Microtec Research. The exact nature of the
|
|
MRI syntax will not be documented here; see the MRI manuals for more
|
|
information. Note in particular that the handling of macros and macro
|
|
arguments is somewhat different. The purpose of this option is to permit
|
|
assembling existing MRI assembler code using @code{@value{AS}}.
|
|
|
|
The MRI compatibility is not complete. Certain operations of the MRI assembler
|
|
depend upon its object file format, and can not be supported using other object
|
|
file formats. Supporting these would require enhancing each object file format
|
|
individually. These are:
|
|
|
|
@itemize @bullet
|
|
@item global symbols in common section
|
|
|
|
The m68k MRI assembler supports common sections which are merged by the linker.
|
|
Other object file formats do not support this. @code{@value{AS}} handles
|
|
common sections by treating them as a single common symbol. It permits local
|
|
symbols to be defined within a common section, but it can not support global
|
|
symbols, since it has no way to describe them.
|
|
|
|
@item complex relocations
|
|
|
|
The MRI assemblers support relocations against a negated section address, and
|
|
relocations which combine the start addresses of two or more sections. These
|
|
are not support by other object file formats.
|
|
|
|
@item @code{END} pseudo-op specifying start address
|
|
|
|
The MRI @code{END} pseudo-op permits the specification of a start address.
|
|
This is not supported by other object file formats. The start address may
|
|
instead be specified using the @code{-e} option to the linker, or in a linker
|
|
script.
|
|
|
|
@item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
|
|
|
|
The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
|
|
name to the output file. This is not supported by other object file formats.
|
|
|
|
@item @code{ORG} pseudo-op
|
|
|
|
The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
|
|
address. This differs from the usual @code{@value{AS}} @code{.org} pseudo-op,
|
|
which changes the location within the current section. Absolute sections are
|
|
not supported by other object file formats. The address of a section may be
|
|
assigned within a linker script.
|
|
@end itemize
|
|
|
|
There are some other features of the MRI assembler which are not supported by
|
|
@code{@value{AS}}, typically either because they are difficult or because they
|
|
seem of little consequence. Some of these may be supported in future releases.
|
|
|
|
@itemize @bullet
|
|
|
|
@item EBCDIC strings
|
|
|
|
EBCDIC strings are not supported.
|
|
|
|
@item packed binary coded decimal
|
|
|
|
Packed binary coded decimal is not supported. This means that the @code{DC.P}
|
|
and @code{DCB.P} pseudo-ops are not supported.
|
|
|
|
@item @code{FEQU} pseudo-op
|
|
|
|
The m68k @code{FEQU} pseudo-op is not supported.
|
|
|
|
@item @code{NOOBJ} pseudo-op
|
|
|
|
The m68k @code{NOOBJ} pseudo-op is not supported.
|
|
|
|
@item @code{OPT} branch control options
|
|
|
|
The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
|
|
@code{BRL}, and @code{BRW}---are ignored. @code{@value{AS}} automatically
|
|
relaxes all branches, whether forward or backward, to an appropriate size, so
|
|
these options serve no purpose.
|
|
|
|
@item @code{OPT} list control options
|
|
|
|
The following m68k @code{OPT} list control options are ignored: @code{C},
|
|
@code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
|
|
@code{MEX}, @code{MC}, @code{MD}, @code{X}.
|
|
|
|
@item other @code{OPT} options
|
|
|
|
The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
|
|
@code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
|
|
|
|
@item @code{OPT} @code{D} option is default
|
|
|
|
The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
|
|
@code{OPT NOD} may be used to turn it off.
|
|
|
|
@item @code{XREF} pseudo-op.
|
|
|
|
The m68k @code{XREF} pseudo-op is ignored.
|
|
|
|
@item @code{.debug} pseudo-op
|
|
|
|
The i960 @code{.debug} pseudo-op is not supported.
|
|
|
|
@item @code{.extended} pseudo-op
|
|
|
|
The i960 @code{.extended} pseudo-op is not supported.
|
|
|
|
@item @code{.list} pseudo-op.
|
|
|
|
The various options of the i960 @code{.list} pseudo-op are not supported.
|
|
|
|
@item @code{.optimize} pseudo-op
|
|
|
|
The i960 @code{.optimize} pseudo-op is not supported.
|
|
|
|
@item @code{.output} pseudo-op
|
|
|
|
The i960 @code{.output} pseudo-op is not supported.
|
|
|
|
@item @code{.setreal} pseudo-op
|
|
|
|
The i960 @code{.setreal} pseudo-op is not supported.
|
|
|
|
@end itemize
|
|
|
|
@node MD
|
|
@section Dependency tracking: @code{--MD}
|
|
|
|
@kindex --MD
|
|
@cindex dependency tracking
|
|
@cindex make rules
|
|
|
|
@code{@value{AS}} can generate a dependency file for the file it creates. This
|
|
file consists of a single rule suitable for @code{make} describing the
|
|
dependencies of the main source file.
|
|
|
|
The rule is written to the file named in its argument.
|
|
|
|
This feature is used in the automatic updating of makefiles.
|
|
|
|
@node o
|
|
@section Name the Object File: @code{-o}
|
|
|
|
@kindex -o
|
|
@cindex naming object file
|
|
@cindex object file name
|
|
There is always one object file output when you run @code{@value{AS}}. By
|
|
default it has the name
|
|
@ifset GENERIC
|
|
@ifset I960
|
|
@file{a.out} (or @file{b.out}, for Intel 960 targets only).
|
|
@end ifset
|
|
@ifclear I960
|
|
@file{a.out}.
|
|
@end ifclear
|
|
@end ifset
|
|
@ifclear GENERIC
|
|
@ifset I960
|
|
@file{b.out}.
|
|
@end ifset
|
|
@ifclear I960
|
|
@file{a.out}.
|
|
@end ifclear
|
|
@end ifclear
|
|
You use this option (which takes exactly one filename) to give the
|
|
object file a different name.
|
|
|
|
Whatever the object file is called, @code{@value{AS}} overwrites any
|
|
existing file of the same name.
|
|
|
|
@node R
|
|
@section Join Data and Text Sections: @code{-R}
|
|
|
|
@kindex -R
|
|
@cindex data and text sections, joining
|
|
@cindex text and data sections, joining
|
|
@cindex joining text and data sections
|
|
@cindex merging text and data sections
|
|
@code{-R} tells @code{@value{AS}} to write the object file as if all
|
|
data-section data lives in the text section. This is only done at
|
|
the very last moment: your binary data are the same, but data
|
|
section parts are relocated differently. The data section part of
|
|
your object file is zero bytes long because all its bytes are
|
|
appended to the text section. (@xref{Sections,,Sections and Relocation}.)
|
|
|
|
When you specify @code{-R} it would be possible to generate shorter
|
|
address displacements (because we do not have to cross between text and
|
|
data section). We refrain from doing this simply for compatibility with
|
|
older versions of @code{@value{AS}}. In future, @code{-R} may work this way.
|
|
|
|
@ifset COFF
|
|
When @code{@value{AS}} is configured for COFF output,
|
|
this option is only useful if you use sections named @samp{.text} and
|
|
@samp{.data}.
|
|
@end ifset
|
|
|
|
@ifset HPPA
|
|
@code{-R} is not supported for any of the HPPA targets. Using
|
|
@code{-R} generates a warning from @code{@value{AS}}.
|
|
@end ifset
|
|
|
|
@node statistics
|
|
@section Display Assembly Statistics: @code{--statistics}
|
|
|
|
@kindex --statistics
|
|
@cindex statistics, about assembly
|
|
@cindex time, total for assembly
|
|
@cindex space used, maximum for assembly
|
|
Use @samp{--statistics} to display two statistics about the resources used by
|
|
@code{@value{AS}}: the maximum amount of space allocated during the assembly
|
|
(in bytes), and the total execution time taken for the assembly (in @sc{cpu}
|
|
seconds).
|
|
|
|
@node traditional-format
|
|
@section Compatible output: @code{--traditional-format}
|
|
|
|
@kindex --traditional-format
|
|
For some targets, the output of @code{@value{AS}} is different in some ways
|
|
from the output of some existing assembler. This switch requests
|
|
@code{@value{AS}} to use the traditional format instead.
|
|
|
|
For example, it disables the exception frame optimizations which
|
|
@code{@value{AS}} normally does by default on @code{@value{GCC}} output.
|
|
|
|
@node v
|
|
@section Announce Version: @code{-v}
|
|
|
|
@kindex -v
|
|
@kindex -version
|
|
@cindex assembler version
|
|
@cindex version of assembler
|
|
You can find out what version of as is running by including the
|
|
option @samp{-v} (which you can also spell as @samp{-version}) on the
|
|
command line.
|
|
|
|
@node W
|
|
@section Control Warnings: @code{-W}, @code{--warn}, @code{--no-warn}, @code{--fatal-warnings}
|
|
|
|
@code{@value{AS}} should never give a warning or error message when
|
|
assembling compiler output. But programs written by people often
|
|
cause @code{@value{AS}} to give a warning that a particular assumption was
|
|
made. All such warnings are directed to the standard error file.
|
|
|
|
@kindex @samp{-W}
|
|
@kindex @samp{--no-warn}
|
|
@cindex suppressing warnings
|
|
@cindex warnings, suppressing
|
|
If you use the @code{-W} and @code{--no-warn} options, no warnings are issued.
|
|
This only affects the warning messages: it does not change any particular of
|
|
how @code{@value{AS}} assembles your file. Errors, which stop the assembly,
|
|
are still reported.
|
|
|
|
@kindex @samp{--fatal-warnings}
|
|
@cindex errors, caused by warnings
|
|
@cindex warnings, causing error
|
|
If you use the @code{--fatal-warnings} option, @code{@value{AS}} considers
|
|
files that generate warnings to be in error.
|
|
|
|
@kindex @samp{--warn}
|
|
@cindex warnings, switching on
|
|
You can switch these options off again by specifying @code{--warn}, which
|
|
causes warnings to be output as usual.
|
|
|
|
@node Z
|
|
@section Generate Object File in Spite of Errors: @code{-Z}
|
|
@cindex object file, after errors
|
|
@cindex errors, continuing after
|
|
After an error message, @code{@value{AS}} normally produces no output. If for
|
|
some reason you are interested in object file output even after
|
|
@code{@value{AS}} gives an error message on your program, use the @samp{-Z}
|
|
option. If there are any errors, @code{@value{AS}} continues anyways, and
|
|
writes an object file after a final warning message of the form @samp{@var{n}
|
|
errors, @var{m} warnings, generating bad object file.}
|
|
|
|
@node Syntax
|
|
@chapter Syntax
|
|
|
|
@cindex machine-independent syntax
|
|
@cindex syntax, machine-independent
|
|
This chapter describes the machine-independent syntax allowed in a
|
|
source file. @code{@value{AS}} syntax is similar to what many other
|
|
assemblers use; it is inspired by the BSD 4.2
|
|
@ifclear VAX
|
|
assembler.
|
|
@end ifclear
|
|
@ifset VAX
|
|
assembler, except that @code{@value{AS}} does not assemble Vax bit-fields.
|
|
@end ifset
|
|
|
|
@menu
|
|
* Preprocessing:: Preprocessing
|
|
* Whitespace:: Whitespace
|
|
* Comments:: Comments
|
|
* Symbol Intro:: Symbols
|
|
* Statements:: Statements
|
|
* Constants:: Constants
|
|
@end menu
|
|
|
|
@node Preprocessing
|
|
@section Preprocessing
|
|
|
|
@cindex preprocessing
|
|
The @code{@value{AS}} internal preprocessor:
|
|
@itemize @bullet
|
|
@cindex whitespace, removed by preprocessor
|
|
@item
|
|
adjusts and removes extra whitespace. It leaves one space or tab before
|
|
the keywords on a line, and turns any other whitespace on the line into
|
|
a single space.
|
|
|
|
@cindex comments, removed by preprocessor
|
|
@item
|
|
removes all comments, replacing them with a single space, or an
|
|
appropriate number of newlines.
|
|
|
|
@cindex constants, converted by preprocessor
|
|
@item
|
|
converts character constants into the appropriate numeric values.
|
|
@end itemize
|
|
|
|
It does not do macro processing, include file handling, or
|
|
anything else you may get from your C compiler's preprocessor. You can
|
|
do include file processing with the @code{.include} directive
|
|
(@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
|
|
to get other ``CPP'' style preprocessing, by giving the input file a
|
|
@samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
|
|
Output, gcc.info, Using GNU CC}.
|
|
|
|
Excess whitespace, comments, and character constants
|
|
cannot be used in the portions of the input text that are not
|
|
preprocessed.
|
|
|
|
@cindex turning preprocessing on and off
|
|
@cindex preprocessing, turning on and off
|
|
@kindex #NO_APP
|
|
@kindex #APP
|
|
If the first line of an input file is @code{#NO_APP} or if you use the
|
|
@samp{-f} option, whitespace and comments are not removed from the input file.
|
|
Within an input file, you can ask for whitespace and comment removal in
|
|
specific portions of the by putting a line that says @code{#APP} before the
|
|
text that may contain whitespace or comments, and putting a line that says
|
|
@code{#NO_APP} after this text. This feature is mainly intend to support
|
|
@code{asm} statements in compilers whose output is otherwise free of comments
|
|
and whitespace.
|
|
|
|
@node Whitespace
|
|
@section Whitespace
|
|
|
|
@cindex whitespace
|
|
@dfn{Whitespace} is one or more blanks or tabs, in any order.
|
|
Whitespace is used to separate symbols, and to make programs neater for
|
|
people to read. Unless within character constants
|
|
(@pxref{Characters,,Character Constants}), any whitespace means the same
|
|
as exactly one space.
|
|
|
|
@node Comments
|
|
@section Comments
|
|
|
|
@cindex comments
|
|
There are two ways of rendering comments to @code{@value{AS}}. In both
|
|
cases the comment is equivalent to one space.
|
|
|
|
Anything from @samp{/*} through the next @samp{*/} is a comment.
|
|
This means you may not nest these comments.
|
|
|
|
@smallexample
|
|
/*
|
|
The only way to include a newline ('\n') in a comment
|
|
is to use this sort of comment.
|
|
*/
|
|
|
|
/* This sort of comment does not nest. */
|
|
@end smallexample
|
|
|
|
@cindex line comment character
|
|
Anything from the @dfn{line comment} character to the next newline
|
|
is considered a comment and is ignored. The line comment character is
|
|
@ifset A29K
|
|
@samp{;} for the AMD 29K family;
|
|
@end ifset
|
|
@ifset ARC
|
|
@samp{;} on the ARC;
|
|
@end ifset
|
|
@ifset ARM
|
|
@samp{@@} on the ARM;
|
|
@end ifset
|
|
@ifset H8/300
|
|
@samp{;} for the H8/300 family;
|
|
@end ifset
|
|
@ifset H8/500
|
|
@samp{!} for the H8/500 family;
|
|
@end ifset
|
|
@ifset HPPA
|
|
@samp{;} for the HPPA;
|
|
@end ifset
|
|
@ifset I960
|
|
@samp{#} on the i960;
|
|
@end ifset
|
|
@ifset PJ
|
|
@samp{;} for picoJava;
|
|
@end ifset
|
|
@ifset SH
|
|
@samp{!} for the Hitachi SH;
|
|
@end ifset
|
|
@ifset SPARC
|
|
@samp{!} on the SPARC;
|
|
@end ifset
|
|
@ifset M32R
|
|
@samp{#} on the m32r;
|
|
@end ifset
|
|
@ifset M680X0
|
|
@samp{|} on the 680x0;
|
|
@end ifset
|
|
@ifset VAX
|
|
@samp{#} on the Vax;
|
|
@end ifset
|
|
@ifset Z8000
|
|
@samp{!} for the Z8000;
|
|
@end ifset
|
|
@ifset V850
|
|
@samp{#} on the V850;
|
|
@end ifset
|
|
see @ref{Machine Dependencies}. @refill
|
|
@c FIXME What about i386, m88k, i860?
|
|
|
|
@ifset GENERIC
|
|
On some machines there are two different line comment characters. One
|
|
character only begins a comment if it is the first non-whitespace character on
|
|
a line, while the other always begins a comment.
|
|
@end ifset
|
|
|
|
@ifset V850
|
|
The V850 assembler also supports a double dash as starting a comment that
|
|
extends to the end of the line.
|
|
|
|
@samp{--};
|
|
@end ifset
|
|
|
|
@kindex #
|
|
@cindex lines starting with @code{#}
|
|
@cindex logical line numbers
|
|
To be compatible with past assemblers, lines that begin with @samp{#} have a
|
|
special interpretation. Following the @samp{#} should be an absolute
|
|
expression (@pxref{Expressions}): the logical line number of the @emph{next}
|
|
line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
|
|
new logical file name. The rest of the line, if any, should be whitespace.
|
|
|
|
If the first non-whitespace characters on the line are not numeric,
|
|
the line is ignored. (Just like a comment.)
|
|
|
|
@smallexample
|
|
# This is an ordinary comment.
|
|
# 42-6 "new_file_name" # New logical file name
|
|
# This is logical line # 36.
|
|
@end smallexample
|
|
This feature is deprecated, and may disappear from future versions
|
|
of @code{@value{AS}}.
|
|
|
|
@node Symbol Intro
|
|
@section Symbols
|
|
|
|
@cindex characters used in symbols
|
|
@ifclear SPECIAL-SYMS
|
|
A @dfn{symbol} is one or more characters chosen from the set of all
|
|
letters (both upper and lower case), digits and the three characters
|
|
@samp{_.$}.
|
|
@end ifclear
|
|
@ifset SPECIAL-SYMS
|
|
@ifclear GENERIC
|
|
@ifset H8
|
|
A @dfn{symbol} is one or more characters chosen from the set of all
|
|
letters (both upper and lower case), digits and the three characters
|
|
@samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
|
|
symbol names.)
|
|
@end ifset
|
|
@end ifclear
|
|
@end ifset
|
|
@ifset GENERIC
|
|
On most machines, you can also use @code{$} in symbol names; exceptions
|
|
are noted in @ref{Machine Dependencies}.
|
|
@end ifset
|
|
No symbol may begin with a digit. Case is significant.
|
|
There is no length limit: all characters are significant. Symbols are
|
|
delimited by characters not in that set, or by the beginning of a file
|
|
(since the source program must end with a newline, the end of a file is
|
|
not a possible symbol delimiter). @xref{Symbols}.
|
|
@cindex length of symbols
|
|
|
|
@node Statements
|
|
@section Statements
|
|
|
|
@cindex statements, structure of
|
|
@cindex line separator character
|
|
@cindex statement separator character
|
|
@ifclear GENERIC
|
|
@ifclear abnormal-separator
|
|
A @dfn{statement} ends at a newline character (@samp{\n}) or at a
|
|
semicolon (@samp{;}). The newline or semicolon is considered part of
|
|
the preceding statement. Newlines and semicolons within character
|
|
constants are an exception: they do not end statements.
|
|
@end ifclear
|
|
@ifset abnormal-separator
|
|
@ifset A29K
|
|
A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at''
|
|
sign (@samp{@@}). The newline or at sign is considered part of the
|
|
preceding statement. Newlines and at signs within character constants
|
|
are an exception: they do not end statements.
|
|
@end ifset
|
|
@ifset HPPA
|
|
A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
|
|
point (@samp{!}). The newline or exclamation point is considered part of the
|
|
preceding statement. Newlines and exclamation points within character
|
|
constants are an exception: they do not end statements.
|
|
@end ifset
|
|
@ifset H8
|
|
A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
|
|
H8/300) a dollar sign (@samp{$}); or (for the
|
|
Hitachi-SH or the
|
|
H8/500) a semicolon
|
|
(@samp{;}). The newline or separator character is considered part of
|
|
the preceding statement. Newlines and separators within character
|
|
constants are an exception: they do not end statements.
|
|
@end ifset
|
|
@end ifset
|
|
@end ifclear
|
|
@ifset GENERIC
|
|
A @dfn{statement} ends at a newline character (@samp{\n}) or line
|
|
separator character. (The line separator is usually @samp{;}, unless
|
|
this conflicts with the comment character; @pxref{Machine Dependencies}.) The
|
|
newline or separator character is considered part of the preceding
|
|
statement. Newlines and separators within character constants are an
|
|
exception: they do not end statements.
|
|
@end ifset
|
|
|
|
@cindex newline, required at file end
|
|
@cindex EOF, newline must precede
|
|
It is an error to end any statement with end-of-file: the last
|
|
character of any input file should be a newline.@refill
|
|
|
|
An empty statement is allowed, and may include whitespace. It is ignored.
|
|
|
|
@cindex instructions and directives
|
|
@cindex directives and instructions
|
|
@c "key symbol" is not used elsewhere in the document; seems pedantic to
|
|
@c @defn{} it in that case, as was done previously... doc@cygnus.com,
|
|
@c 13feb91.
|
|
A statement begins with zero or more labels, optionally followed by a
|
|
key symbol which determines what kind of statement it is. The key
|
|
symbol determines the syntax of the rest of the statement. If the
|
|
symbol begins with a dot @samp{.} then the statement is an assembler
|
|
directive: typically valid for any computer. If the symbol begins with
|
|
a letter the statement is an assembly language @dfn{instruction}: it
|
|
assembles into a machine language instruction.
|
|
@ifset GENERIC
|
|
Different versions of @code{@value{AS}} for different computers
|
|
recognize different instructions. In fact, the same symbol may
|
|
represent a different instruction in a different computer's assembly
|
|
language.@refill
|
|
@end ifset
|
|
|
|
@cindex @code{:} (label)
|
|
@cindex label (@code{:})
|
|
A label is a symbol immediately followed by a colon (@code{:}).
|
|
Whitespace before a label or after a colon is permitted, but you may not
|
|
have whitespace between a label's symbol and its colon. @xref{Labels}.
|
|
|
|
@ifset HPPA
|
|
For HPPA targets, labels need not be immediately followed by a colon, but
|
|
the definition of a label must begin in column zero. This also implies that
|
|
only one label may be defined on each line.
|
|
@end ifset
|
|
|
|
@smallexample
|
|
label: .directive followed by something
|
|
another_label: # This is an empty statement.
|
|
instruction operand_1, operand_2, @dots{}
|
|
@end smallexample
|
|
|
|
@node Constants
|
|
@section Constants
|
|
|
|
@cindex constants
|
|
A constant is a number, written so that its value is known by
|
|
inspection, without knowing any context. Like this:
|
|
@smallexample
|
|
@group
|
|
.byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
|
|
.ascii "Ring the bell\7" # A string constant.
|
|
.octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
|
|
.float 0f-314159265358979323846264338327\
|
|
95028841971.693993751E-40 # - pi, a flonum.
|
|
@end group
|
|
@end smallexample
|
|
|
|
@menu
|
|
* Characters:: Character Constants
|
|
* Numbers:: Number Constants
|
|
@end menu
|
|
|
|
@node Characters
|
|
@subsection Character Constants
|
|
|
|
@cindex character constants
|
|
@cindex constants, character
|
|
There are two kinds of character constants. A @dfn{character} stands
|
|
for one character in one byte and its value may be used in
|
|
numeric expressions. String constants (properly called string
|
|
@emph{literals}) are potentially many bytes and their values may not be
|
|
used in arithmetic expressions.
|
|
|
|
@menu
|
|
* Strings:: Strings
|
|
* Chars:: Characters
|
|
@end menu
|
|
|
|
@node Strings
|
|
@subsubsection Strings
|
|
|
|
@cindex string constants
|
|
@cindex constants, string
|
|
A @dfn{string} is written between double-quotes. It may contain
|
|
double-quotes or null characters. The way to get special characters
|
|
into a string is to @dfn{escape} these characters: precede them with
|
|
a backslash @samp{\} character. For example @samp{\\} represents
|
|
one backslash: the first @code{\} is an escape which tells
|
|
@code{@value{AS}} to interpret the second character literally as a backslash
|
|
(which prevents @code{@value{AS}} from recognizing the second @code{\} as an
|
|
escape character). The complete list of escapes follows.
|
|
|
|
@cindex escape codes, character
|
|
@cindex character escape codes
|
|
@table @kbd
|
|
@c @item \a
|
|
@c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
|
|
@c
|
|
@cindex @code{\b} (backspace character)
|
|
@cindex backspace (@code{\b})
|
|
@item \b
|
|
Mnemonic for backspace; for ASCII this is octal code 010.
|
|
|
|
@c @item \e
|
|
@c Mnemonic for EOText; for ASCII this is octal code 004.
|
|
@c
|
|
@cindex @code{\f} (formfeed character)
|
|
@cindex formfeed (@code{\f})
|
|
@item \f
|
|
Mnemonic for FormFeed; for ASCII this is octal code 014.
|
|
|
|
@cindex @code{\n} (newline character)
|
|
@cindex newline (@code{\n})
|
|
@item \n
|
|
Mnemonic for newline; for ASCII this is octal code 012.
|
|
|
|
@c @item \p
|
|
@c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
|
|
@c
|
|
@cindex @code{\r} (carriage return character)
|
|
@cindex carriage return (@code{\r})
|
|
@item \r
|
|
Mnemonic for carriage-Return; for ASCII this is octal code 015.
|
|
|
|
@c @item \s
|
|
@c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
|
|
@c other assemblers.
|
|
@c
|
|
@cindex @code{\t} (tab)
|
|
@cindex tab (@code{\t})
|
|
@item \t
|
|
Mnemonic for horizontal Tab; for ASCII this is octal code 011.
|
|
|
|
@c @item \v
|
|
@c Mnemonic for Vertical tab; for ASCII this is octal code 013.
|
|
@c @item \x @var{digit} @var{digit} @var{digit}
|
|
@c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
|
|
@c
|
|
@cindex @code{\@var{ddd}} (octal character code)
|
|
@cindex octal character code (@code{\@var{ddd}})
|
|
@item \ @var{digit} @var{digit} @var{digit}
|
|
An octal character code. The numeric code is 3 octal digits.
|
|
For compatibility with other Unix systems, 8 and 9 are accepted as digits:
|
|
for example, @code{\008} has the value 010, and @code{\009} the value 011.
|
|
|
|
@cindex @code{\@var{xd...}} (hex character code)
|
|
@cindex hex character code (@code{\@var{xd...}})
|
|
@item \@code{x} @var{hex-digits...}
|
|
A hex character code. All trailing hex digits are combined. Either upper or
|
|
lower case @code{x} works.
|
|
|
|
@cindex @code{\\} (@samp{\} character)
|
|
@cindex backslash (@code{\\})
|
|
@item \\
|
|
Represents one @samp{\} character.
|
|
|
|
@c @item \'
|
|
@c Represents one @samp{'} (accent acute) character.
|
|
@c This is needed in single character literals
|
|
@c (@xref{Characters,,Character Constants}.) to represent
|
|
@c a @samp{'}.
|
|
@c
|
|
@cindex @code{\"} (doublequote character)
|
|
@cindex doublequote (@code{\"})
|
|
@item \"
|
|
Represents one @samp{"} character. Needed in strings to represent
|
|
this character, because an unescaped @samp{"} would end the string.
|
|
|
|
@item \ @var{anything-else}
|
|
Any other character when escaped by @kbd{\} gives a warning, but
|
|
assembles as if the @samp{\} was not present. The idea is that if
|
|
you used an escape sequence you clearly didn't want the literal
|
|
interpretation of the following character. However @code{@value{AS}} has no
|
|
other interpretation, so @code{@value{AS}} knows it is giving you the wrong
|
|
code and warns you of the fact.
|
|
@end table
|
|
|
|
Which characters are escapable, and what those escapes represent,
|
|
varies widely among assemblers. The current set is what we think
|
|
the BSD 4.2 assembler recognizes, and is a subset of what most C
|
|
compilers recognize. If you are in doubt, do not use an escape
|
|
sequence.
|
|
|
|
@node Chars
|
|
@subsubsection Characters
|
|
|
|
@cindex single character constant
|
|
@cindex character, single
|
|
@cindex constant, single character
|
|
A single character may be written as a single quote immediately
|
|
followed by that character. The same escapes apply to characters as
|
|
to strings. So if you want to write the character backslash, you
|
|
must write @kbd{'\\} where the first @code{\} escapes the second
|
|
@code{\}. As you can see, the quote is an acute accent, not a
|
|
grave accent. A newline
|
|
@ifclear GENERIC
|
|
@ifclear abnormal-separator
|
|
(or semicolon @samp{;})
|
|
@end ifclear
|
|
@ifset abnormal-separator
|
|
@ifset A29K
|
|
(or at sign @samp{@@})
|
|
@end ifset
|
|
@ifset H8
|
|
(or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
|
|
Hitachi SH or
|
|
H8/500)
|
|
@end ifset
|
|
@end ifset
|
|
@end ifclear
|
|
immediately following an acute accent is taken as a literal character
|
|
and does not count as the end of a statement. The value of a character
|
|
constant in a numeric expression is the machine's byte-wide code for
|
|
that character. @code{@value{AS}} assumes your character code is ASCII:
|
|
@kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
|
|
|
|
@node Numbers
|
|
@subsection Number Constants
|
|
|
|
@cindex constants, number
|
|
@cindex number constants
|
|
@code{@value{AS}} distinguishes three kinds of numbers according to how they
|
|
are stored in the target machine. @emph{Integers} are numbers that
|
|
would fit into an @code{int} in the C language. @emph{Bignums} are
|
|
integers, but they are stored in more than 32 bits. @emph{Flonums}
|
|
are floating point numbers, described below.
|
|
|
|
@menu
|
|
* Integers:: Integers
|
|
* Bignums:: Bignums
|
|
* Flonums:: Flonums
|
|
@ifclear GENERIC
|
|
@ifset I960
|
|
* Bit Fields:: Bit Fields
|
|
@end ifset
|
|
@end ifclear
|
|
@end menu
|
|
|
|
@node Integers
|
|
@subsubsection Integers
|
|
@cindex integers
|
|
@cindex constants, integer
|
|
|
|
@cindex binary integers
|
|
@cindex integers, binary
|
|
A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
|
|
the binary digits @samp{01}.
|
|
|
|
@cindex octal integers
|
|
@cindex integers, octal
|
|
An octal integer is @samp{0} followed by zero or more of the octal
|
|
digits (@samp{01234567}).
|
|
|
|
@cindex decimal integers
|
|
@cindex integers, decimal
|
|
A decimal integer starts with a non-zero digit followed by zero or
|
|
more digits (@samp{0123456789}).
|
|
|
|
@cindex hexadecimal integers
|
|
@cindex integers, hexadecimal
|
|
A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
|
|
more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
|
|
|
|
Integers have the usual values. To denote a negative integer, use
|
|
the prefix operator @samp{-} discussed under expressions
|
|
(@pxref{Prefix Ops,,Prefix Operators}).
|
|
|
|
@node Bignums
|
|
@subsubsection Bignums
|
|
|
|
@cindex bignums
|
|
@cindex constants, bignum
|
|
A @dfn{bignum} has the same syntax and semantics as an integer
|
|
except that the number (or its negative) takes more than 32 bits to
|
|
represent in binary. The distinction is made because in some places
|
|
integers are permitted while bignums are not.
|
|
|
|
@node Flonums
|
|
@subsubsection Flonums
|
|
@cindex flonums
|
|
@cindex floating point numbers
|
|
@cindex constants, floating point
|
|
|
|
@cindex precision, floating point
|
|
A @dfn{flonum} represents a floating point number. The translation is
|
|
indirect: a decimal floating point number from the text is converted by
|
|
@code{@value{AS}} to a generic binary floating point number of more than
|
|
sufficient precision. This generic floating point number is converted
|
|
to a particular computer's floating point format (or formats) by a
|
|
portion of @code{@value{AS}} specialized to that computer.
|
|
|
|
A flonum is written by writing (in order)
|
|
@itemize @bullet
|
|
@item
|
|
The digit @samp{0}.
|
|
@ifset HPPA
|
|
(@samp{0} is optional on the HPPA.)
|
|
@end ifset
|
|
|
|
@item
|
|
A letter, to tell @code{@value{AS}} the rest of the number is a flonum.
|
|
@ifset GENERIC
|
|
@kbd{e} is recommended. Case is not important.
|
|
@ignore
|
|
@c FIXME: verify if flonum syntax really this vague for most cases
|
|
(Any otherwise illegal letter works here, but that might be changed. Vax BSD
|
|
4.2 assembler seems to allow any of @samp{defghDEFGH}.)
|
|
@end ignore
|
|
|
|
On the H8/300, H8/500,
|
|
Hitachi SH,
|
|
and AMD 29K architectures, the letter must be
|
|
one of the letters @samp{DFPRSX} (in upper or lower case).
|
|
|
|
On the ARC, the letter must be one of the letters @samp{DFRS}
|
|
(in upper or lower case).
|
|
|
|
On the Intel 960 architecture, the letter must be
|
|
one of the letters @samp{DFT} (in upper or lower case).
|
|
|
|
On the HPPA architecture, the letter must be @samp{E} (upper case only).
|
|
@end ifset
|
|
@ifclear GENERIC
|
|
@ifset A29K
|
|
One of the letters @samp{DFPRSX} (in upper or lower case).
|
|
@end ifset
|
|
@ifset ARC
|
|
One of the letters @samp{DFRS} (in upper or lower case).
|
|
@end ifset
|
|
@ifset H8
|
|
One of the letters @samp{DFPRSX} (in upper or lower case).
|
|
@end ifset
|
|
@ifset HPPA
|
|
The letter @samp{E} (upper case only).
|
|
@end ifset
|
|
@ifset I960
|
|
One of the letters @samp{DFT} (in upper or lower case).
|
|
@end ifset
|
|
@end ifclear
|
|
|
|
@item
|
|
An optional sign: either @samp{+} or @samp{-}.
|
|
|
|
@item
|
|
An optional @dfn{integer part}: zero or more decimal digits.
|
|
|
|
@item
|
|
An optional @dfn{fractional part}: @samp{.} followed by zero
|
|
or more decimal digits.
|
|
|
|
@item
|
|
An optional exponent, consisting of:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
An @samp{E} or @samp{e}.
|
|
@c I can't find a config where "EXP_CHARS" is other than 'eE', but in
|
|
@c principle this can perfectly well be different on different targets.
|
|
@item
|
|
Optional sign: either @samp{+} or @samp{-}.
|
|
@item
|
|
One or more decimal digits.
|
|
@end itemize
|
|
|
|
@end itemize
|
|
|
|
At least one of the integer part or the fractional part must be
|
|
present. The floating point number has the usual base-10 value.
|
|
|
|
@code{@value{AS}} does all processing using integers. Flonums are computed
|
|
independently of any floating point hardware in the computer running
|
|
@code{@value{AS}}.
|
|
|
|
@ifclear GENERIC
|
|
@ifset I960
|
|
@c Bit fields are written as a general facility but are also controlled
|
|
@c by a conditional-compilation flag---which is as of now (21mar91)
|
|
@c turned on only by the i960 config of GAS.
|
|
@node Bit Fields
|
|
@subsubsection Bit Fields
|
|
|
|
@cindex bit fields
|
|
@cindex constants, bit field
|
|
You can also define numeric constants as @dfn{bit fields}.
|
|
specify two numbers separated by a colon---
|
|
@example
|
|
@var{mask}:@var{value}
|
|
@end example
|
|
@noindent
|
|
@code{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
|
|
@var{value}.
|
|
|
|
The resulting number is then packed
|
|
@ifset GENERIC
|
|
@c this conditional paren in case bit fields turned on elsewhere than 960
|
|
(in host-dependent byte order)
|
|
@end ifset
|
|
into a field whose width depends on which assembler directive has the
|
|
bit-field as its argument. Overflow (a result from the bitwise and
|
|
requiring more binary digits to represent) is not an error; instead,
|
|
more constants are generated, of the specified width, beginning with the
|
|
least significant digits.@refill
|
|
|
|
The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
|
|
@code{.short}, and @code{.word} accept bit-field arguments.
|
|
@end ifset
|
|
@end ifclear
|
|
|
|
@node Sections
|
|
@chapter Sections and Relocation
|
|
@cindex sections
|
|
@cindex relocation
|
|
|
|
@menu
|
|
* Secs Background:: Background
|
|
* Ld Sections:: Linker Sections
|
|
* As Sections:: Assembler Internal Sections
|
|
* Sub-Sections:: Sub-Sections
|
|
* bss:: bss Section
|
|
@end menu
|
|
|
|
@node Secs Background
|
|
@section Background
|
|
|
|
Roughly, a section is a range of addresses, with no gaps; all data
|
|
``in'' those addresses is treated the same for some particular purpose.
|
|
For example there may be a ``read only'' section.
|
|
|
|
@cindex linker, and assembler
|
|
@cindex assembler, and linker
|
|
The linker @code{@value{LD}} reads many object files (partial programs) and
|
|
combines their contents to form a runnable program. When @code{@value{AS}}
|
|
emits an object file, the partial program is assumed to start at address 0.
|
|
@code{@value{LD}} assigns the final addresses for the partial program, so that
|
|
different partial programs do not overlap. This is actually an
|
|
oversimplification, but it suffices to explain how @code{@value{AS}} uses
|
|
sections.
|
|
|
|
@code{@value{LD}} moves blocks of bytes of your program to their run-time
|
|
addresses. These blocks slide to their run-time addresses as rigid
|
|
units; their length does not change and neither does the order of bytes
|
|
within them. Such a rigid unit is called a @emph{section}. Assigning
|
|
run-time addresses to sections is called @dfn{relocation}. It includes
|
|
the task of adjusting mentions of object-file addresses so they refer to
|
|
the proper run-time addresses.
|
|
@ifset H8
|
|
For the H8/300 and H8/500,
|
|
and for the Hitachi SH,
|
|
@code{@value{AS}} pads sections if needed to
|
|
ensure they end on a word (sixteen bit) boundary.
|
|
@end ifset
|
|
|
|
@cindex standard assembler sections
|
|
An object file written by @code{@value{AS}} has at least three sections, any
|
|
of which may be empty. These are named @dfn{text}, @dfn{data} and
|
|
@dfn{bss} sections.
|
|
|
|
@ifset COFF
|
|
@ifset GENERIC
|
|
When it generates COFF output,
|
|
@end ifset
|
|
@code{@value{AS}} can also generate whatever other named sections you specify
|
|
using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
|
|
If you do not use any directives that place output in the @samp{.text}
|
|
or @samp{.data} sections, these sections still exist, but are empty.
|
|
@end ifset
|
|
|
|
@ifset HPPA
|
|
@ifset GENERIC
|
|
When @code{@value{AS}} generates SOM or ELF output for the HPPA,
|
|
@end ifset
|
|
@code{@value{AS}} can also generate whatever other named sections you
|
|
specify using the @samp{.space} and @samp{.subspace} directives. See
|
|
@cite{HP9000 Series 800 Assembly Language Reference Manual}
|
|
(HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
|
|
assembler directives.
|
|
|
|
@ifset SOM
|
|
Additionally, @code{@value{AS}} uses different names for the standard
|
|
text, data, and bss sections when generating SOM output. Program text
|
|
is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
|
|
BSS into @samp{$BSS$}.
|
|
@end ifset
|
|
@end ifset
|
|
|
|
Within the object file, the text section starts at address @code{0}, the
|
|
data section follows, and the bss section follows the data section.
|
|
|
|
@ifset HPPA
|
|
When generating either SOM or ELF output files on the HPPA, the text
|
|
section starts at address @code{0}, the data section at address
|
|
@code{0x4000000}, and the bss section follows the data section.
|
|
@end ifset
|
|
|
|
To let @code{@value{LD}} know which data changes when the sections are
|
|
relocated, and how to change that data, @code{@value{AS}} also writes to the
|
|
object file details of the relocation needed. To perform relocation
|
|
@code{@value{LD}} must know, each time an address in the object
|
|
file is mentioned:
|
|
@itemize @bullet
|
|
@item
|
|
Where in the object file is the beginning of this reference to
|
|
an address?
|
|
@item
|
|
How long (in bytes) is this reference?
|
|
@item
|
|
Which section does the address refer to? What is the numeric value of
|
|
@display
|
|
(@var{address}) @minus{} (@var{start-address of section})?
|
|
@end display
|
|
@item
|
|
Is the reference to an address ``Program-Counter relative''?
|
|
@end itemize
|
|
|
|
@cindex addresses, format of
|
|
@cindex section-relative addressing
|
|
In fact, every address @code{@value{AS}} ever uses is expressed as
|
|
@display
|
|
(@var{section}) + (@var{offset into section})
|
|
@end display
|
|
@noindent
|
|
Further, most expressions @code{@value{AS}} computes have this section-relative
|
|
nature.
|
|
@ifset SOM
|
|
(For some object formats, such as SOM for the HPPA, some expressions are
|
|
symbol-relative instead.)
|
|
@end ifset
|
|
|
|
In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
|
|
@var{N} into section @var{secname}.''
|
|
|
|
Apart from text, data and bss sections you need to know about the
|
|
@dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
|
|
addresses in the absolute section remain unchanged. For example, address
|
|
@code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
|
|
@code{@value{LD}}. Although the linker never arranges two partial programs'
|
|
data sections with overlapping addresses after linking, @emph{by definition}
|
|
their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
|
|
part of a program is always the same address when the program is running as
|
|
address @code{@{absolute@ 239@}} in any other part of the program.
|
|
|
|
The idea of sections is extended to the @dfn{undefined} section. Any
|
|
address whose section is unknown at assembly time is by definition
|
|
rendered @{undefined @var{U}@}---where @var{U} is filled in later.
|
|
Since numbers are always defined, the only way to generate an undefined
|
|
address is to mention an undefined symbol. A reference to a named
|
|
common block would be such a symbol: its value is unknown at assembly
|
|
time so it has section @emph{undefined}.
|
|
|
|
By analogy the word @emph{section} is used to describe groups of sections in
|
|
the linked program. @code{@value{LD}} puts all partial programs' text
|
|
sections in contiguous addresses in the linked program. It is
|
|
customary to refer to the @emph{text section} of a program, meaning all
|
|
the addresses of all partial programs' text sections. Likewise for
|
|
data and bss sections.
|
|
|
|
Some sections are manipulated by @code{@value{LD}}; others are invented for
|
|
use of @code{@value{AS}} and have no meaning except during assembly.
|
|
|
|
@node Ld Sections
|
|
@section Linker Sections
|
|
@code{@value{LD}} deals with just four kinds of sections, summarized below.
|
|
|
|
@table @strong
|
|
|
|
@ifset COFF
|
|
@cindex named sections
|
|
@cindex sections, named
|
|
@item named sections
|
|
@end ifset
|
|
@ifset aout-bout
|
|
@cindex text section
|
|
@cindex data section
|
|
@itemx text section
|
|
@itemx data section
|
|
@end ifset
|
|
These sections hold your program. @code{@value{AS}} and @code{@value{LD}} treat them as
|
|
separate but equal sections. Anything you can say of one section is
|
|
true another.
|
|
@ifset aout-bout
|
|
When the program is running, however, it is
|
|
customary for the text section to be unalterable. The
|
|
text section is often shared among processes: it contains
|
|
instructions, constants and the like. The data section of a running
|
|
program is usually alterable: for example, C variables would be stored
|
|
in the data section.
|
|
@end ifset
|
|
|
|
@cindex bss section
|
|
@item bss section
|
|
This section contains zeroed bytes when your program begins running. It
|
|
is used to hold unitialized variables or common storage. The length of
|
|
each partial program's bss section is important, but because it starts
|
|
out containing zeroed bytes there is no need to store explicit zero
|
|
bytes in the object file. The bss section was invented to eliminate
|
|
those explicit zeros from object files.
|
|
|
|
@cindex absolute section
|
|
@item absolute section
|
|
Address 0 of this section is always ``relocated'' to runtime address 0.
|
|
This is useful if you want to refer to an address that @code{@value{LD}} must
|
|
not change when relocating. In this sense we speak of absolute
|
|
addresses being ``unrelocatable'': they do not change during relocation.
|
|
|
|
@cindex undefined section
|
|
@item undefined section
|
|
This ``section'' is a catch-all for address references to objects not in
|
|
the preceding sections.
|
|
@c FIXME: ref to some other doc on obj-file formats could go here.
|
|
@end table
|
|
|
|
@cindex relocation example
|
|
An idealized example of three relocatable sections follows.
|
|
@ifset COFF
|
|
The example uses the traditional section names @samp{.text} and @samp{.data}.
|
|
@end ifset
|
|
Memory addresses are on the horizontal axis.
|
|
|
|
@c TEXI2ROFF-KILL
|
|
@ifinfo
|
|
@c END TEXI2ROFF-KILL
|
|
@smallexample
|
|
+-----+----+--+
|
|
partial program # 1: |ttttt|dddd|00|
|
|
+-----+----+--+
|
|
|
|
text data bss
|
|
seg. seg. seg.
|
|
|
|
+---+---+---+
|
|
partial program # 2: |TTT|DDD|000|
|
|
+---+---+---+
|
|
|
|
+--+---+-----+--+----+---+-----+~~
|
|
linked program: | |TTT|ttttt| |dddd|DDD|00000|
|
|
+--+---+-----+--+----+---+-----+~~
|
|
|
|
addresses: 0 @dots{}
|
|
@end smallexample
|
|
@c TEXI2ROFF-KILL
|
|
@end ifinfo
|
|
@need 5000
|
|
@tex
|
|
|
|
\line{\it Partial program \#1: \hfil}
|
|
\line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
|
|
\line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
|
|
|
|
\line{\it Partial program \#2: \hfil}
|
|
\line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
|
|
\line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
|
|
|
|
\line{\it linked program: \hfil}
|
|
\line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
|
|
\line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
|
|
ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
|
|
DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
|
|
|
|
\line{\it addresses: \hfil}
|
|
\line{0\dots\hfil}
|
|
|
|
@end tex
|
|
@c END TEXI2ROFF-KILL
|
|
|
|
@node As Sections
|
|
@section Assembler Internal Sections
|
|
|
|
@cindex internal assembler sections
|
|
@cindex sections in messages, internal
|
|
These sections are meant only for the internal use of @code{@value{AS}}. They
|
|
have no meaning at run-time. You do not really need to know about these
|
|
sections for most purposes; but they can be mentioned in @code{@value{AS}}
|
|
warning messages, so it might be helpful to have an idea of their
|
|
meanings to @code{@value{AS}}. These sections are used to permit the
|
|
value of every expression in your assembly language program to be a
|
|
section-relative address.
|
|
|
|
@table @b
|
|
@cindex assembler internal logic error
|
|
@item ASSEMBLER-INTERNAL-LOGIC-ERROR!
|
|
An internal assembler logic error has been found. This means there is a
|
|
bug in the assembler.
|
|
|
|
@cindex expr (internal section)
|
|
@item expr section
|
|
The assembler stores complex expression internally as combinations of
|
|
symbols. When it needs to represent an expression as a symbol, it puts
|
|
it in the expr section.
|
|
@c FIXME item debug
|
|
@c FIXME item transfer[t] vector preload
|
|
@c FIXME item transfer[t] vector postload
|
|
@c FIXME item register
|
|
@end table
|
|
|
|
@node Sub-Sections
|
|
@section Sub-Sections
|
|
|
|
@cindex numbered subsections
|
|
@cindex grouping data
|
|
@ifset aout-bout
|
|
Assembled bytes
|
|
@ifset COFF
|
|
conventionally
|
|
@end ifset
|
|
fall into two sections: text and data.
|
|
@end ifset
|
|
You may have separate groups of
|
|
@ifset GENERIC
|
|
data in named sections
|
|
@end ifset
|
|
@ifclear GENERIC
|
|
@ifclear aout-bout
|
|
data in named sections
|
|
@end ifclear
|
|
@ifset aout-bout
|
|
text or data
|
|
@end ifset
|
|
@end ifclear
|
|
that you want to end up near to each other in the object file, even though they
|
|
are not contiguous in the assembler source. @code{@value{AS}} allows you to
|
|
use @dfn{subsections} for this purpose. Within each section, there can be
|
|
numbered subsections with values from 0 to 8192. Objects assembled into the
|
|
same subsection go into the object file together with other objects in the same
|
|
subsection. For example, a compiler might want to store constants in the text
|
|
section, but might not want to have them interspersed with the program being
|
|
assembled. In this case, the compiler could issue a @samp{.text 0} before each
|
|
section of code being output, and a @samp{.text 1} before each group of
|
|
constants being output.
|
|
|
|
Subsections are optional. If you do not use subsections, everything
|
|
goes in subsection number zero.
|
|
|
|
@ifset GENERIC
|
|
Each subsection is zero-padded up to a multiple of four bytes.
|
|
(Subsections may be padded a different amount on different flavors
|
|
of @code{@value{AS}}.)
|
|
@end ifset
|
|
@ifclear GENERIC
|
|
@ifset H8
|
|
On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word
|
|
boundary (two bytes).
|
|
The same is true on the Hitachi SH.
|
|
@end ifset
|
|
@ifset I960
|
|
@c FIXME section padding (alignment)?
|
|
@c Rich Pixley says padding here depends on target obj code format; that
|
|
@c doesn't seem particularly useful to say without further elaboration,
|
|
@c so for now I say nothing about it. If this is a generic BFD issue,
|
|
@c these paragraphs might need to vanish from this manual, and be
|
|
@c discussed in BFD chapter of binutils (or some such).
|
|
@end ifset
|
|
@ifset A29K
|
|
On the AMD 29K family, no particular padding is added to section or
|
|
subsection sizes; @value{AS} forces no alignment on this platform.
|
|
@end ifset
|
|
@end ifclear
|
|
|
|
Subsections appear in your object file in numeric order, lowest numbered
|
|
to highest. (All this to be compatible with other people's assemblers.)
|
|
The object file contains no representation of subsections; @code{@value{LD}} and
|
|
other programs that manipulate object files see no trace of them.
|
|
They just see all your text subsections as a text section, and all your
|
|
data subsections as a data section.
|
|
|
|
To specify which subsection you want subsequent statements assembled
|
|
into, use a numeric argument to specify it, in a @samp{.text
|
|
@var{expression}} or a @samp{.data @var{expression}} statement.
|
|
@ifset COFF
|
|
@ifset GENERIC
|
|
When generating COFF output, you
|
|
@end ifset
|
|
@ifclear GENERIC
|
|
You
|
|
@end ifclear
|
|
can also use an extra subsection
|
|
argument with arbitrary named sections: @samp{.section @var{name},
|
|
@var{expression}}.
|
|
@end ifset
|
|
@var{Expression} should be an absolute expression.
|
|
(@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
|
|
is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
|
|
begins in @code{text 0}. For instance:
|
|
@smallexample
|
|
.text 0 # The default subsection is text 0 anyway.
|
|
.ascii "This lives in the first text subsection. *"
|
|
.text 1
|
|
.ascii "But this lives in the second text subsection."
|
|
.data 0
|
|
.ascii "This lives in the data section,"
|
|
.ascii "in the first data subsection."
|
|
.text 0
|
|
.ascii "This lives in the first text section,"
|
|
.ascii "immediately following the asterisk (*)."
|
|
@end smallexample
|
|
|
|
Each section has a @dfn{location counter} incremented by one for every byte
|
|
assembled into that section. Because subsections are merely a convenience
|
|
restricted to @code{@value{AS}} there is no concept of a subsection location
|
|
counter. There is no way to directly manipulate a location counter---but the
|
|
@code{.align} directive changes it, and any label definition captures its
|
|
current value. The location counter of the section where statements are being
|
|
assembled is said to be the @dfn{active} location counter.
|
|
|
|
@node bss
|
|
@section bss Section
|
|
|
|
@cindex bss section
|
|
@cindex common variable storage
|
|
The bss section is used for local common variable storage.
|
|
You may allocate address space in the bss section, but you may
|
|
not dictate data to load into it before your program executes. When
|
|
your program starts running, all the contents of the bss
|
|
section are zeroed bytes.
|
|
|
|
The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
|
|
@ref{Lcomm,,@code{.lcomm}}.
|
|
|
|
The @code{.comm} pseudo-op may be used to declare a common symbol, which is
|
|
another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}.
|
|
|
|
@ifset GENERIC
|
|
When assembling for a target which supports multiple sections, such as ELF or
|
|
COFF, you may switch into the @code{.bss} section and define symbols as usual;
|
|
see @ref{Section,,@code{.section}}. You may only assemble zero values into the
|
|
section. Typically the section will only contain symbol definitions and
|
|
@code{.skip} directives (@pxref{Skip,,@code{.skip}}).
|
|
@end ifset
|
|
|
|
@node Symbols
|
|
@chapter Symbols
|
|
|
|
@cindex symbols
|
|
Symbols are a central concept: the programmer uses symbols to name
|
|
things, the linker uses symbols to link, and the debugger uses symbols
|
|
to debug.
|
|
|
|
@quotation
|
|
@cindex debuggers, and symbol order
|
|
@emph{Warning:} @code{@value{AS}} does not place symbols in the object file in
|
|
the same order they were declared. This may break some debuggers.
|
|
@end quotation
|
|
|
|
@menu
|
|
* Labels:: Labels
|
|
* Setting Symbols:: Giving Symbols Other Values
|
|
* Symbol Names:: Symbol Names
|
|
* Dot:: The Special Dot Symbol
|
|
* Symbol Attributes:: Symbol Attributes
|
|
@end menu
|
|
|
|
@node Labels
|
|
@section Labels
|
|
|
|
@cindex labels
|
|
A @dfn{label} is written as a symbol immediately followed by a colon
|
|
@samp{:}. The symbol then represents the current value of the
|
|
active location counter, and is, for example, a suitable instruction
|
|
operand. You are warned if you use the same symbol to represent two
|
|
different locations: the first definition overrides any other
|
|
definitions.
|
|
|
|
@ifset HPPA
|
|
On the HPPA, the usual form for a label need not be immediately followed by a
|
|
colon, but instead must start in column zero. Only one label may be defined on
|
|
a single line. To work around this, the HPPA version of @code{@value{AS}} also
|
|
provides a special directive @code{.label} for defining labels more flexibly.
|
|
@end ifset
|
|
|
|
@node Setting Symbols
|
|
@section Giving Symbols Other Values
|
|
|
|
@cindex assigning values to symbols
|
|
@cindex symbol values, assigning
|
|
A symbol can be given an arbitrary value by writing a symbol, followed
|
|
by an equals sign @samp{=}, followed by an expression
|
|
(@pxref{Expressions}). This is equivalent to using the @code{.set}
|
|
directive. @xref{Set,,@code{.set}}.
|
|
|
|
@node Symbol Names
|
|
@section Symbol Names
|
|
|
|
@cindex symbol names
|
|
@cindex names, symbol
|
|
@ifclear SPECIAL-SYMS
|
|
Symbol names begin with a letter or with one of @samp{._}. On most
|
|
machines, you can also use @code{$} in symbol names; exceptions are
|
|
noted in @ref{Machine Dependencies}. That character may be followed by any
|
|
string of digits, letters, dollar signs (unless otherwise noted in
|
|
@ref{Machine Dependencies}), and underscores.
|
|
@end ifclear
|
|
@ifset A29K
|
|
For the AMD 29K family, @samp{?} is also allowed in the
|
|
body of a symbol name, though not at its beginning.
|
|
@end ifset
|
|
|
|
@ifset SPECIAL-SYMS
|
|
@ifset H8
|
|
Symbol names begin with a letter or with one of @samp{._}. On the
|
|
Hitachi SH or the
|
|
H8/500, you can also use @code{$} in symbol names. That character may
|
|
be followed by any string of digits, letters, dollar signs (save on the
|
|
H8/300), and underscores.
|
|
@end ifset
|
|
@end ifset
|
|
|
|
Case of letters is significant: @code{foo} is a different symbol name
|
|
than @code{Foo}.
|
|
|
|
Each symbol has exactly one name. Each name in an assembly language program
|
|
refers to exactly one symbol. You may use that symbol name any number of times
|
|
in a program.
|
|
|
|
@subheading Local Symbol Names
|
|
|
|
@cindex local symbol names
|
|
@cindex symbol names, local
|
|
@cindex temporary symbol names
|
|
@cindex symbol names, temporary
|
|
Local symbols help compilers and programmers use names temporarily.
|
|
There are ten local symbol names, which are re-used throughout the
|
|
program. You may refer to them using the names @samp{0} @samp{1}
|
|
@dots{} @samp{9}. To define a local symbol, write a label of the form
|
|
@samp{@b{N}:} (where @b{N} represents any digit). To refer to the most
|
|
recent previous definition of that symbol write @samp{@b{N}b}, using the
|
|
same digit as when you defined the label. To refer to the next
|
|
definition of a local label, write @samp{@b{N}f}---where @b{N} gives you
|
|
a choice of 10 forward references. The @samp{b} stands for
|
|
``backwards'' and the @samp{f} stands for ``forwards''.
|
|
|
|
Local symbols are not emitted by the current @sc{gnu} C compiler.
|
|
|
|
There is no restriction on how you can use these labels, but
|
|
remember that at any point in the assembly you can refer to at most
|
|
10 prior local labels and to at most 10 forward local labels.
|
|
|
|
Local symbol names are only a notation device. They are immediately
|
|
transformed into more conventional symbol names before the assembler
|
|
uses them. The symbol names stored in the symbol table, appearing in
|
|
error messages and optionally emitted to the object file have these
|
|
parts:
|
|
|
|
@table @code
|
|
@item L
|
|
All local labels begin with @samp{L}. Normally both @code{@value{AS}} and
|
|
@code{@value{LD}} forget symbols that start with @samp{L}. These labels are
|
|
used for symbols you are never intended to see. If you use the
|
|
@samp{-L} option then @code{@value{AS}} retains these symbols in the
|
|
object file. If you also instruct @code{@value{LD}} to retain these symbols,
|
|
you may use them in debugging.
|
|
|
|
@item @var{digit}
|
|
If the label is written @samp{0:} then the digit is @samp{0}.
|
|
If the label is written @samp{1:} then the digit is @samp{1}.
|
|
And so on up through @samp{9:}.
|
|
|
|
@item @kbd{C-A}
|
|
This unusual character is included so you do not accidentally invent
|
|
a symbol of the same name. The character has ASCII value
|
|
@samp{\001}.
|
|
|
|
@item @emph{ordinal number}
|
|
This is a serial number to keep the labels distinct. The first
|
|
@samp{0:} gets the number @samp{1}; The 15th @samp{0:} gets the
|
|
number @samp{15}; @emph{etc.}. Likewise for the other labels @samp{1:}
|
|
through @samp{9:}.
|
|
@end table
|
|
|
|
For instance, the first @code{1:} is named @code{L1@kbd{C-A}1}, the 44th
|
|
@code{3:} is named @code{L3@kbd{C-A}44}.
|
|
|
|
@node Dot
|
|
@section The Special Dot Symbol
|
|
|
|
@cindex dot (symbol)
|
|
@cindex @code{.} (symbol)
|
|
@cindex current address
|
|
@cindex location counter
|
|
The special symbol @samp{.} refers to the current address that
|
|
@code{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
|
|
.long .} defines @code{melvin} to contain its own address.
|
|
Assigning a value to @code{.} is treated the same as a @code{.org}
|
|
directive. Thus, the expression @samp{.=.+4} is the same as saying
|
|
@ifclear no-space-dir
|
|
@samp{.space 4}.
|
|
@end ifclear
|
|
@ifset no-space-dir
|
|
@ifset A29K
|
|
@samp{.block 4}.
|
|
@end ifset
|
|
@end ifset
|
|
|
|
@node Symbol Attributes
|
|
@section Symbol Attributes
|
|
|
|
@cindex symbol attributes
|
|
@cindex attributes, symbol
|
|
Every symbol has, as well as its name, the attributes ``Value'' and
|
|
``Type''. Depending on output format, symbols can also have auxiliary
|
|
attributes.
|
|
@ifset INTERNALS
|
|
The detailed definitions are in @file{a.out.h}.
|
|
@end ifset
|
|
|
|
If you use a symbol without defining it, @code{@value{AS}} assumes zero for
|
|
all these attributes, and probably won't warn you. This makes the
|
|
symbol an externally defined symbol, which is generally what you
|
|
would want.
|
|
|
|
@menu
|
|
* Symbol Value:: Value
|
|
* Symbol Type:: Type
|
|
@ifset aout-bout
|
|
@ifset GENERIC
|
|
* a.out Symbols:: Symbol Attributes: @code{a.out}
|
|
@end ifset
|
|
@ifclear GENERIC
|
|
@ifclear BOUT
|
|
* a.out Symbols:: Symbol Attributes: @code{a.out}
|
|
@end ifclear
|
|
@ifset BOUT
|
|
* a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
|
|
@end ifset
|
|
@end ifclear
|
|
@end ifset
|
|
@ifset COFF
|
|
* COFF Symbols:: Symbol Attributes for COFF
|
|
@end ifset
|
|
@ifset SOM
|
|
* SOM Symbols:: Symbol Attributes for SOM
|
|
@end ifset
|
|
@end menu
|
|
|
|
@node Symbol Value
|
|
@subsection Value
|
|
|
|
@cindex value of a symbol
|
|
@cindex symbol value
|
|
The value of a symbol is (usually) 32 bits. For a symbol which labels a
|
|
location in the text, data, bss or absolute sections the value is the
|
|
number of addresses from the start of that section to the label.
|
|
Naturally for text, data and bss sections the value of a symbol changes
|
|
as @code{@value{LD}} changes section base addresses during linking. Absolute
|
|
symbols' values do not change during linking: that is why they are
|
|
called absolute.
|
|
|
|
The value of an undefined symbol is treated in a special way. If it is
|
|
0 then the symbol is not defined in this assembler source file, and
|
|
@code{@value{LD}} tries to determine its value from other files linked into the
|
|
same program. You make this kind of symbol simply by mentioning a symbol
|
|
name without defining it. A non-zero value represents a @code{.comm}
|
|
common declaration. The value is how much common storage to reserve, in
|
|
bytes (addresses). The symbol refers to the first address of the
|
|
allocated storage.
|
|
|
|
@node Symbol Type
|
|
@subsection Type
|
|
|
|
@cindex type of a symbol
|
|
@cindex symbol type
|
|
The type attribute of a symbol contains relocation (section)
|
|
information, any flag settings indicating that a symbol is external, and
|
|
(optionally), other information for linkers and debuggers. The exact
|
|
format depends on the object-code output format in use.
|
|
|
|
@ifset aout-bout
|
|
@ifclear GENERIC
|
|
@ifset BOUT
|
|
@c The following avoids a "widow" subsection title. @group would be
|
|
@c better if it were available outside examples.
|
|
@need 1000
|
|
@node a.out Symbols
|
|
@subsection Symbol Attributes: @code{a.out}, @code{b.out}
|
|
|
|
@cindex @code{b.out} symbol attributes
|
|
@cindex symbol attributes, @code{b.out}
|
|
These symbol attributes appear only when @code{@value{AS}} is configured for
|
|
one of the Berkeley-descended object output formats---@code{a.out} or
|
|
@code{b.out}.
|
|
|
|
@end ifset
|
|
@ifclear BOUT
|
|
@node a.out Symbols
|
|
@subsection Symbol Attributes: @code{a.out}
|
|
|
|
@cindex @code{a.out} symbol attributes
|
|
@cindex symbol attributes, @code{a.out}
|
|
|
|
@end ifclear
|
|
@end ifclear
|
|
@ifset GENERIC
|
|
@node a.out Symbols
|
|
@subsection Symbol Attributes: @code{a.out}
|
|
|
|
@cindex @code{a.out} symbol attributes
|
|
@cindex symbol attributes, @code{a.out}
|
|
|
|
@end ifset
|
|
@menu
|
|
* Symbol Desc:: Descriptor
|
|
* Symbol Other:: Other
|
|
@end menu
|
|
|
|
@node Symbol Desc
|
|
@subsubsection Descriptor
|
|
|
|
@cindex descriptor, of @code{a.out} symbol
|
|
This is an arbitrary 16-bit value. You may establish a symbol's
|
|
descriptor value by using a @code{.desc} statement
|
|
(@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
|
|
@code{@value{AS}}.
|
|
|
|
@node Symbol Other
|
|
@subsubsection Other
|
|
|
|
@cindex other attribute, of @code{a.out} symbol
|
|
This is an arbitrary 8-bit value. It means nothing to @code{@value{AS}}.
|
|
@end ifset
|
|
|
|
@ifset COFF
|
|
@node COFF Symbols
|
|
@subsection Symbol Attributes for COFF
|
|
|
|
@cindex COFF symbol attributes
|
|
@cindex symbol attributes, COFF
|
|
|
|
The COFF format supports a multitude of auxiliary symbol attributes;
|
|
like the primary symbol attributes, they are set between @code{.def} and
|
|
@code{.endef} directives.
|
|
|
|
@subsubsection Primary Attributes
|
|
|
|
@cindex primary attributes, COFF symbols
|
|
The symbol name is set with @code{.def}; the value and type,
|
|
respectively, with @code{.val} and @code{.type}.
|
|
|
|
@subsubsection Auxiliary Attributes
|
|
|
|
@cindex auxiliary attributes, COFF symbols
|
|
The @code{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
|
|
@code{.size}, and @code{.tag} can generate auxiliary symbol table
|
|
information for COFF.
|
|
@end ifset
|
|
|
|
@ifset SOM
|
|
@node SOM Symbols
|
|
@subsection Symbol Attributes for SOM
|
|
|
|
@cindex SOM symbol attributes
|
|
@cindex symbol attributes, SOM
|
|
|
|
The SOM format for the HPPA supports a multitude of symbol attributes set with
|
|
the @code{.EXPORT} and @code{.IMPORT} directives.
|
|
|
|
The attributes are described in @cite{HP9000 Series 800 Assembly
|
|
Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
|
|
@code{EXPORT} assembler directive documentation.
|
|
@end ifset
|
|
|
|
@node Expressions
|
|
@chapter Expressions
|
|
|
|
@cindex expressions
|
|
@cindex addresses
|
|
@cindex numeric values
|
|
An @dfn{expression} specifies an address or numeric value.
|
|
Whitespace may precede and/or follow an expression.
|
|
|
|
The result of an expression must be an absolute number, or else an offset into
|
|
a particular section. If an expression is not absolute, and there is not
|
|
enough information when @code{@value{AS}} sees the expression to know its
|
|
section, a second pass over the source program might be necessary to interpret
|
|
the expression---but the second pass is currently not implemented.
|
|
@code{@value{AS}} aborts with an error message in this situation.
|
|
|
|
@menu
|
|
* Empty Exprs:: Empty Expressions
|
|
* Integer Exprs:: Integer Expressions
|
|
@end menu
|
|
|
|
@node Empty Exprs
|
|
@section Empty Expressions
|
|
|
|
@cindex empty expressions
|
|
@cindex expressions, empty
|
|
An empty expression has no value: it is just whitespace or null.
|
|
Wherever an absolute expression is required, you may omit the
|
|
expression, and @code{@value{AS}} assumes a value of (absolute) 0. This
|
|
is compatible with other assemblers.
|
|
|
|
@node Integer Exprs
|
|
@section Integer Expressions
|
|
|
|
@cindex integer expressions
|
|
@cindex expressions, integer
|
|
An @dfn{integer expression} is one or more @emph{arguments} delimited
|
|
by @emph{operators}.
|
|
|
|
@menu
|
|
* Arguments:: Arguments
|
|
* Operators:: Operators
|
|
* Prefix Ops:: Prefix Operators
|
|
* Infix Ops:: Infix Operators
|
|
@end menu
|
|
|
|
@node Arguments
|
|
@subsection Arguments
|
|
|
|
@cindex expression arguments
|
|
@cindex arguments in expressions
|
|
@cindex operands in expressions
|
|
@cindex arithmetic operands
|
|
@dfn{Arguments} are symbols, numbers or subexpressions. In other
|
|
contexts arguments are sometimes called ``arithmetic operands''. In
|
|
this manual, to avoid confusing them with the ``instruction operands'' of
|
|
the machine language, we use the term ``argument'' to refer to parts of
|
|
expressions only, reserving the word ``operand'' to refer only to machine
|
|
instruction operands.
|
|
|
|
Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
|
|
@var{section} is one of text, data, bss, absolute,
|
|
or undefined. @var{NNN} is a signed, 2's complement 32 bit
|
|
integer.
|
|
|
|
Numbers are usually integers.
|
|
|
|
A number can be a flonum or bignum. In this case, you are warned
|
|
that only the low order 32 bits are used, and @code{@value{AS}} pretends
|
|
these 32 bits are an integer. You may write integer-manipulating
|
|
instructions that act on exotic constants, compatible with other
|
|
assemblers.
|
|
|
|
@cindex subexpressions
|
|
Subexpressions are a left parenthesis @samp{(} followed by an integer
|
|
expression, followed by a right parenthesis @samp{)}; or a prefix
|
|
operator followed by an argument.
|
|
|
|
@node Operators
|
|
@subsection Operators
|
|
|
|
@cindex operators, in expressions
|
|
@cindex arithmetic functions
|
|
@cindex functions, in expressions
|
|
@dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
|
|
operators are followed by an argument. Infix operators appear
|
|
between their arguments. Operators may be preceded and/or followed by
|
|
whitespace.
|
|
|
|
@node Prefix Ops
|
|
@subsection Prefix Operator
|
|
|
|
@cindex prefix operators
|
|
@code{@value{AS}} has the following @dfn{prefix operators}. They each take
|
|
one argument, which must be absolute.
|
|
|
|
@c the tex/end tex stuff surrounding this small table is meant to make
|
|
@c it align, on the printed page, with the similar table in the next
|
|
@c section (which is inside an enumerate).
|
|
@tex
|
|
\global\advance\leftskip by \itemindent
|
|
@end tex
|
|
|
|
@table @code
|
|
@item -
|
|
@dfn{Negation}. Two's complement negation.
|
|
@item ~
|
|
@dfn{Complementation}. Bitwise not.
|
|
@end table
|
|
|
|
@tex
|
|
\global\advance\leftskip by -\itemindent
|
|
@end tex
|
|
|
|
@node Infix Ops
|
|
@subsection Infix Operators
|
|
|
|
@cindex infix operators
|
|
@cindex operators, permitted arguments
|
|
@dfn{Infix operators} take two arguments, one on either side. Operators
|
|
have precedence, but operations with equal precedence are performed left
|
|
to right. Apart from @code{+} or @code{-}, both arguments must be
|
|
absolute, and the result is absolute.
|
|
|
|
@enumerate
|
|
@cindex operator precedence
|
|
@cindex precedence of operators
|
|
|
|
@item
|
|
Highest Precedence
|
|
|
|
@table @code
|
|
@item *
|
|
@dfn{Multiplication}.
|
|
|
|
@item /
|
|
@dfn{Division}. Truncation is the same as the C operator @samp{/}
|
|
|
|
@item %
|
|
@dfn{Remainder}.
|
|
|
|
@item <
|
|
@itemx <<
|
|
@dfn{Shift Left}. Same as the C operator @samp{<<}.
|
|
|
|
@item >
|
|
@itemx >>
|
|
@dfn{Shift Right}. Same as the C operator @samp{>>}.
|
|
@end table
|
|
|
|
@item
|
|
Intermediate precedence
|
|
|
|
@table @code
|
|
@item |
|
|
|
|
@dfn{Bitwise Inclusive Or}.
|
|
|
|
@item &
|
|
@dfn{Bitwise And}.
|
|
|
|
@item ^
|
|
@dfn{Bitwise Exclusive Or}.
|
|
|
|
@item !
|
|
@dfn{Bitwise Or Not}.
|
|
@end table
|
|
|
|
@item
|
|
Lowest Precedence
|
|
|
|
@table @code
|
|
@cindex addition, permitted arguments
|
|
@cindex plus, permitted arguments
|
|
@cindex arguments for addition
|
|
@item +
|
|
@dfn{Addition}. If either argument is absolute, the result has the section of
|
|
the other argument. You may not add together arguments from different
|
|
sections.
|
|
|
|
@cindex subtraction, permitted arguments
|
|
@cindex minus, permitted arguments
|
|
@cindex arguments for subtraction
|
|
@item -
|
|
@dfn{Subtraction}. If the right argument is absolute, the
|
|
result has the section of the left argument.
|
|
If both arguments are in the same section, the result is absolute.
|
|
You may not subtract arguments from different sections.
|
|
@c FIXME is there still something useful to say about undefined - undefined ?
|
|
@end table
|
|
@end enumerate
|
|
|
|
In short, it's only meaningful to add or subtract the @emph{offsets} in an
|
|
address; you can only have a defined section in one of the two arguments.
|
|
|
|
@node Pseudo Ops
|
|
@chapter Assembler Directives
|
|
|
|
@cindex directives, machine independent
|
|
@cindex pseudo-ops, machine independent
|
|
@cindex machine independent directives
|
|
All assembler directives have names that begin with a period (@samp{.}).
|
|
The rest of the name is letters, usually in lower case.
|
|
|
|
This chapter discusses directives that are available regardless of the
|
|
target machine configuration for the @sc{gnu} assembler.
|
|
@ifset GENERIC
|
|
Some machine configurations provide additional directives.
|
|
@xref{Machine Dependencies}.
|
|
@end ifset
|
|
@ifclear GENERIC
|
|
@ifset machine-directives
|
|
@xref{Machine Dependencies} for additional directives.
|
|
@end ifset
|
|
@end ifclear
|
|
|
|
@menu
|
|
* Abort:: @code{.abort}
|
|
@ifset COFF
|
|
* ABORT:: @code{.ABORT}
|
|
@end ifset
|
|
|
|
* Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
|
|
* Ascii:: @code{.ascii "@var{string}"}@dots{}
|
|
* Asciz:: @code{.asciz "@var{string}"}@dots{}
|
|
* Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
|
|
* Byte:: @code{.byte @var{expressions}}
|
|
* Comm:: @code{.comm @var{symbol} , @var{length} }
|
|
* Data:: @code{.data @var{subsection}}
|
|
@ifset COFF
|
|
* Def:: @code{.def @var{name}}
|
|
@end ifset
|
|
@ifset aout-bout
|
|
* Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
|
|
@end ifset
|
|
@ifset COFF
|
|
* Dim:: @code{.dim}
|
|
@end ifset
|
|
|
|
* Double:: @code{.double @var{flonums}}
|
|
* Eject:: @code{.eject}
|
|
* Else:: @code{.else}
|
|
* Elseif:: @code{.elseif}
|
|
* End:: @code{.end}
|
|
@ifset COFF
|
|
* Endef:: @code{.endef}
|
|
@end ifset
|
|
|
|
* Endfunc:: @code{.endfunc}
|
|
* Endif:: @code{.endif}
|
|
* Equ:: @code{.equ @var{symbol}, @var{expression}}
|
|
* Equiv:: @code{.equiv @var{symbol}, @var{expression}}
|
|
* Err:: @code{.err}
|
|
* Exitm:: @code{.exitm}
|
|
* Extern:: @code{.extern}
|
|
* Fail:: @code{.fail}
|
|
@ifclear no-file-dir
|
|
* File:: @code{.file @var{string}}
|
|
@end ifclear
|
|
|
|
* Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
|
|
* Float:: @code{.float @var{flonums}}
|
|
* Func:: @code{.func}
|
|
* Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
|
|
* hword:: @code{.hword @var{expressions}}
|
|
* Ident:: @code{.ident}
|
|
* If:: @code{.if @var{absolute expression}}
|
|
* Include:: @code{.include "@var{file}"}
|
|
* Int:: @code{.int @var{expressions}}
|
|
* Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
|
|
* Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
|
|
* Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
|
|
* Lflags:: @code{.lflags}
|
|
@ifclear no-line-dir
|
|
* Line:: @code{.line @var{line-number}}
|
|
@end ifclear
|
|
|
|
* Ln:: @code{.ln @var{line-number}}
|
|
* Linkonce:: @code{.linkonce [@var{type}]}
|
|
* List:: @code{.list}
|
|
* Long:: @code{.long @var{expressions}}
|
|
@ignore
|
|
* Lsym:: @code{.lsym @var{symbol}, @var{expression}}
|
|
@end ignore
|
|
|
|
* Macro:: @code{.macro @var{name} @var{args}}@dots{}
|
|
* MRI:: @code{.mri @var{val}}
|
|
|
|
* Nolist:: @code{.nolist}
|
|
* Octa:: @code{.octa @var{bignums}}
|
|
* Org:: @code{.org @var{new-lc} , @var{fill}}
|
|
* P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
|
|
* Print:: @code{.print @var{string}}
|
|
* Psize:: @code{.psize @var{lines}, @var{columns}}
|
|
* Purgem:: @code{.purgem @var{name}}
|
|
* Quad:: @code{.quad @var{bignums}}
|
|
* Rept:: @code{.rept @var{count}}
|
|
* Sbttl:: @code{.sbttl "@var{subheading}"}
|
|
@ifset COFF
|
|
* Scl:: @code{.scl @var{class}}
|
|
* Section:: @code{.section @var{name}, @var{subsection}}
|
|
@end ifset
|
|
|
|
* Set:: @code{.set @var{symbol}, @var{expression}}
|
|
* Short:: @code{.short @var{expressions}}
|
|
* Single:: @code{.single @var{flonums}}
|
|
@ifset COFF
|
|
* Size:: @code{.size}
|
|
@end ifset
|
|
|
|
* Skip:: @code{.skip @var{size} , @var{fill}}
|
|
* Sleb128:: @code{.sleb128 @var{expressions}}
|
|
* Space:: @code{.space @var{size} , @var{fill}}
|
|
@ifset have-stabs
|
|
* Stab:: @code{.stabd, .stabn, .stabs}
|
|
@end ifset
|
|
|
|
* String:: @code{.string "@var{str}"}
|
|
* Struct:: @code{.struct @var{expression}}
|
|
@ifset ELF
|
|
* Symver:: @code{.symver @var{name},@var{name2@@nodename}}
|
|
@end ifset
|
|
@ifset COFF
|
|
* Tag:: @code{.tag @var{structname}}
|
|
@end ifset
|
|
|
|
* Text:: @code{.text @var{subsection}}
|
|
* Title:: @code{.title "@var{heading}"}
|
|
@ifset COFF
|
|
* Type:: @code{.type @var{int}}
|
|
* Val:: @code{.val @var{addr}}
|
|
@end ifset
|
|
@ifset ELF
|
|
* Visibility:: @code{.internal @var{name}, .hidden @var{name}, .protected @var{name}}
|
|
@end ifset
|
|
|
|
* Uleb128:: @code{.uleb128 @var{expressions}}
|
|
* Word:: @code{.word @var{expressions}}
|
|
* Deprecated:: Deprecated Directives
|
|
@end menu
|
|
|
|
@node Abort
|
|
@section @code{.abort}
|
|
|
|
@cindex @code{abort} directive
|
|
@cindex stopping the assembly
|
|
This directive stops the assembly immediately. It is for
|
|
compatibility with other assemblers. The original idea was that the
|
|
assembly language source would be piped into the assembler. If the sender
|
|
of the source quit, it could use this directive tells @code{@value{AS}} to
|
|
quit also. One day @code{.abort} will not be supported.
|
|
|
|
@ifset COFF
|
|
@node ABORT
|
|
@section @code{.ABORT}
|
|
|
|
@cindex @code{ABORT} directive
|
|
When producing COFF output, @code{@value{AS}} accepts this directive as a
|
|
synonym for @samp{.abort}.
|
|
|
|
@ifset BOUT
|
|
When producing @code{b.out} output, @code{@value{AS}} accepts this directive,
|
|
but ignores it.
|
|
@end ifset
|
|
@end ifset
|
|
|
|
@node Align
|
|
@section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
|
|
|
|
@cindex padding the location counter
|
|
@cindex @code{align} directive
|
|
Pad the location counter (in the current subsection) to a particular storage
|
|
boundary. The first expression (which must be absolute) is the alignment
|
|
required, as described below.
|
|
|
|
The second expression (also absolute) gives the fill value to be stored in the
|
|
padding bytes. It (and the comma) may be omitted. If it is omitted, the
|
|
padding bytes are normally zero. However, on some systems, if the section is
|
|
marked as containing code and the fill value is omitted, the space is filled
|
|
with no-op instructions.
|
|
|
|
The third expression is also absolute, and is also optional. If it is present,
|
|
it is the maximum number of bytes that should be skipped by this alignment
|
|
directive. If doing the alignment would require skipping more bytes than the
|
|
specified maximum, then the alignment is not done at all. You can omit the
|
|
fill value (the second argument) entirely by simply using two commas after the
|
|
required alignment; this can be useful if you want the alignment to be filled
|
|
with no-op instructions when appropriate.
|
|
|
|
The way the required alignment is specified varies from system to system.
|
|
For the a29k, hppa, m68k, m88k, w65, sparc, and Hitachi SH, and i386 using ELF
|
|
format,
|
|
the first expression is the
|
|
alignment request in bytes. For example @samp{.align 8} advances
|
|
the location counter until it is a multiple of 8. If the location counter
|
|
is already a multiple of 8, no change is needed.
|
|
|
|
For other systems, including the i386 using a.out format, it is the
|
|
number of low-order zero bits the location counter must have after
|
|
advancement. For example @samp{.align 3} advances the location
|
|
counter until it a multiple of 8. If the location counter is already a
|
|
multiple of 8, no change is needed.
|
|
|
|
This inconsistency is due to the different behaviors of the various
|
|
native assemblers for these systems which GAS must emulate.
|
|
GAS also provides @code{.balign} and @code{.p2align} directives,
|
|
described later, which have a consistent behavior across all
|
|
architectures (but are specific to GAS).
|
|
|
|
@node Ascii
|
|
@section @code{.ascii "@var{string}"}@dots{}
|
|
|
|
@cindex @code{ascii} directive
|
|
@cindex string literals
|
|
@code{.ascii} expects zero or more string literals (@pxref{Strings})
|
|
separated by commas. It assembles each string (with no automatic
|
|
trailing zero byte) into consecutive addresses.
|
|
|
|
@node Asciz
|
|
@section @code{.asciz "@var{string}"}@dots{}
|
|
|
|
@cindex @code{asciz} directive
|
|
@cindex zero-terminated strings
|
|
@cindex null-terminated strings
|
|
@code{.asciz} is just like @code{.ascii}, but each string is followed by
|
|
a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
|
|
|
|
@node Balign
|
|
@section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
|
|
|
|
@cindex padding the location counter given number of bytes
|
|
@cindex @code{balign} directive
|
|
Pad the location counter (in the current subsection) to a particular
|
|
storage boundary. The first expression (which must be absolute) is the
|
|
alignment request in bytes. For example @samp{.balign 8} advances
|
|
the location counter until it is a multiple of 8. If the location counter
|
|
is already a multiple of 8, no change is needed.
|
|
|
|
The second expression (also absolute) gives the fill value to be stored in the
|
|
padding bytes. It (and the comma) may be omitted. If it is omitted, the
|
|
padding bytes are normally zero. However, on some systems, if the section is
|
|
marked as containing code and the fill value is omitted, the space is filled
|
|
with no-op instructions.
|
|
|
|
The third expression is also absolute, and is also optional. If it is present,
|
|
it is the maximum number of bytes that should be skipped by this alignment
|
|
directive. If doing the alignment would require skipping more bytes than the
|
|
specified maximum, then the alignment is not done at all. You can omit the
|
|
fill value (the second argument) entirely by simply using two commas after the
|
|
required alignment; this can be useful if you want the alignment to be filled
|
|
with no-op instructions when appropriate.
|
|
|
|
@cindex @code{balignw} directive
|
|
@cindex @code{balignl} directive
|
|
The @code{.balignw} and @code{.balignl} directives are variants of the
|
|
@code{.balign} directive. The @code{.balignw} directive treats the fill
|
|
pattern as a two byte word value. The @code{.balignl} directives treats the
|
|
fill pattern as a four byte longword value. For example, @code{.balignw
|
|
4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
|
|
filled in with the value 0x368d (the exact placement of the bytes depends upon
|
|
the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
|
|
undefined.
|
|
|
|
@node Byte
|
|
@section @code{.byte @var{expressions}}
|
|
|
|
@cindex @code{byte} directive
|
|
@cindex integers, one byte
|
|
@code{.byte} expects zero or more expressions, separated by commas.
|
|
Each expression is assembled into the next byte.
|
|
|
|
@node Comm
|
|
@section @code{.comm @var{symbol} , @var{length} }
|
|
|
|
@cindex @code{comm} directive
|
|
@cindex symbol, common
|
|
@code{.comm} declares a common symbol named @var{symbol}. When linking, a
|
|
common symbol in one object file may be merged with a defined or common symbol
|
|
of the same name in another object file. If @code{@value{LD}} does not see a
|
|
definition for the symbol--just one or more common symbols--then it will
|
|
allocate @var{length} bytes of uninitialized memory. @var{length} must be an
|
|
absolute expression. If @code{@value{LD}} sees multiple common symbols with
|
|
the same name, and they do not all have the same size, it will allocate space
|
|
using the largest size.
|
|
|
|
@ifset ELF
|
|
When using ELF, the @code{.comm} directive takes an optional third argument.
|
|
This is the desired alignment of the symbol, specified as a byte boundary (for
|
|
example, an alignment of 16 means that the least significant 4 bits of the
|
|
address should be zero). The alignment must be an absolute expression, and it
|
|
must be a power of two. If @code{@value{LD}} allocates uninitialized memory
|
|
for the common symbol, it will use the alignment when placing the symbol. If
|
|
no alignment is specified, @code{@value{AS}} will set the alignment to the
|
|
largest power of two less than or equal to the size of the symbol, up to a
|
|
maximum of 16.
|
|
@end ifset
|
|
|
|
@ifset HPPA
|
|
The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
|
|
@samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
|
|
@end ifset
|
|
|
|
@node Data
|
|
@section @code{.data @var{subsection}}
|
|
|
|
@cindex @code{data} directive
|
|
@code{.data} tells @code{@value{AS}} to assemble the following statements onto the
|
|
end of the data subsection numbered @var{subsection} (which is an
|
|
absolute expression). If @var{subsection} is omitted, it defaults
|
|
to zero.
|
|
|
|
@ifset COFF
|
|
@node Def
|
|
@section @code{.def @var{name}}
|
|
|
|
@cindex @code{def} directive
|
|
@cindex COFF symbols, debugging
|
|
@cindex debugging COFF symbols
|
|
Begin defining debugging information for a symbol @var{name}; the
|
|
definition extends until the @code{.endef} directive is encountered.
|
|
@ifset BOUT
|
|
|
|
This directive is only observed when @code{@value{AS}} is configured for COFF
|
|
format output; when producing @code{b.out}, @samp{.def} is recognized,
|
|
but ignored.
|
|
@end ifset
|
|
@end ifset
|
|
|
|
@ifset aout-bout
|
|
@node Desc
|
|
@section @code{.desc @var{symbol}, @var{abs-expression}}
|
|
|
|
@cindex @code{desc} directive
|
|
@cindex COFF symbol descriptor
|
|
@cindex symbol descriptor, COFF
|
|
This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
|
|
to the low 16 bits of an absolute expression.
|
|
|
|
@ifset COFF
|
|
The @samp{.desc} directive is not available when @code{@value{AS}} is
|
|
configured for COFF output; it is only for @code{a.out} or @code{b.out}
|
|
object format. For the sake of compatibility, @code{@value{AS}} accepts
|
|
it, but produces no output, when configured for COFF.
|
|
@end ifset
|
|
@end ifset
|
|
|
|
@ifset COFF
|
|
@node Dim
|
|
@section @code{.dim}
|
|
|
|
@cindex @code{dim} directive
|
|
@cindex COFF auxiliary symbol information
|
|
@cindex auxiliary symbol information, COFF
|
|
This directive is generated by compilers to include auxiliary debugging
|
|
information in the symbol table. It is only permitted inside
|
|
@code{.def}/@code{.endef} pairs.
|
|
@ifset BOUT
|
|
|
|
@samp{.dim} is only meaningful when generating COFF format output; when
|
|
@code{@value{AS}} is generating @code{b.out}, it accepts this directive but
|
|
ignores it.
|
|
@end ifset
|
|
@end ifset
|
|
|
|
@node Double
|
|
@section @code{.double @var{flonums}}
|
|
|
|
@cindex @code{double} directive
|
|
@cindex floating point numbers (double)
|
|
@code{.double} expects zero or more flonums, separated by commas. It
|
|
assembles floating point numbers.
|
|
@ifset GENERIC
|
|
The exact kind of floating point numbers emitted depends on how
|
|
@code{@value{AS}} is configured. @xref{Machine Dependencies}.
|
|
@end ifset
|
|
@ifclear GENERIC
|
|
@ifset IEEEFLOAT
|
|
On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
|
|
in @sc{ieee} format.
|
|
@end ifset
|
|
@end ifclear
|
|
|
|
@node Eject
|
|
@section @code{.eject}
|
|
|
|
@cindex @code{eject} directive
|
|
@cindex new page, in listings
|
|
@cindex page, in listings
|
|
@cindex listing control: new page
|
|
Force a page break at this point, when generating assembly listings.
|
|
|
|
@node Else
|
|
@section @code{.else}
|
|
|
|
@cindex @code{else} directive
|
|
@code{.else} is part of the @code{@value{AS}} support for conditional
|
|
assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
|
|
of code to be assembled if the condition for the preceding @code{.if}
|
|
was false.
|
|
|
|
@node Elseif
|
|
@section @code{.elseif}
|
|
|
|
@cindex @code{elseif} directive
|
|
@code{.elseif} is part of the @code{@value{AS}} support for conditional
|
|
assembly; @pxref{If,,@code{.if}}. It is shorthand for beginning a new
|
|
@code{.if} block that would otherwise fill the entire @code{.else} section.
|
|
|
|
@node End
|
|
@section @code{.end}
|
|
|
|
@cindex @code{end} directive
|
|
@code{.end} marks the end of the assembly file. @code{@value{AS}} does not
|
|
process anything in the file past the @code{.end} directive.
|
|
|
|
@ifset COFF
|
|
@node Endef
|
|
@section @code{.endef}
|
|
|
|
@cindex @code{endef} directive
|
|
This directive flags the end of a symbol definition begun with
|
|
@code{.def}.
|
|
@ifset BOUT
|
|
|
|
@samp{.endef} is only meaningful when generating COFF format output; if
|
|
@code{@value{AS}} is configured to generate @code{b.out}, it accepts this
|
|
directive but ignores it.
|
|
@end ifset
|
|
@end ifset
|
|
|
|
@node Endfunc
|
|
@section @code{.endfunc}
|
|
@cindex @code{endfunc} directive
|
|
@code{.endfunc} marks the end of a function specified with @code{.func}.
|
|
|
|
@node Endif
|
|
@section @code{.endif}
|
|
|
|
@cindex @code{endif} directive
|
|
@code{.endif} is part of the @code{@value{AS}} support for conditional assembly;
|
|
it marks the end of a block of code that is only assembled
|
|
conditionally. @xref{If,,@code{.if}}.
|
|
|
|
@node Equ
|
|
@section @code{.equ @var{symbol}, @var{expression}}
|
|
|
|
@cindex @code{equ} directive
|
|
@cindex assigning values to symbols
|
|
@cindex symbols, assigning values to
|
|
This directive sets the value of @var{symbol} to @var{expression}.
|
|
It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
|
|
|
|
@ifset HPPA
|
|
The syntax for @code{equ} on the HPPA is
|
|
@samp{@var{symbol} .equ @var{expression}}.
|
|
@end ifset
|
|
|
|
@node Equiv
|
|
@section @code{.equiv @var{symbol}, @var{expression}}
|
|
@cindex @code{equiv} directive
|
|
The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
|
|
the assembler will signal an error if @var{symbol} is already defined.
|
|
|
|
Except for the contents of the error message, this is roughly equivalent to
|
|
@smallexample
|
|
.ifdef SYM
|
|
.err
|
|
.endif
|
|
.equ SYM,VAL
|
|
@end smallexample
|
|
|
|
@node Err
|
|
@section @code{.err}
|
|
@cindex @code{err} directive
|
|
If @code{@value{AS}} assembles a @code{.err} directive, it will print an error
|
|
message and, unless the @code{-Z} option was used, it will not generate an
|
|
object file. This can be used to signal error an conditionally compiled code.
|
|
|
|
@node Exitm
|
|
@section @code{.exitm}
|
|
Exit early from the current macro definition. @xref{Macro}.
|
|
|
|
@node Extern
|
|
@section @code{.extern}
|
|
|
|
@cindex @code{extern} directive
|
|
@code{.extern} is accepted in the source program---for compatibility
|
|
with other assemblers---but it is ignored. @code{@value{AS}} treats
|
|
all undefined symbols as external.
|
|
|
|
@node Fail
|
|
@section @code{.fail @var{expression}}
|
|
|
|
@cindex @code{fail} directive
|
|
Generates an error or a warning. If the value of the @var{expression} is 500
|
|
or more, @code{@value{AS}} will print a warning message. If the value is less
|
|
than 500, @code{@value{AS}} will print an error message. The message will
|
|
include the value of @var{expression}. This can occasionally be useful inside
|
|
complex nested macros or conditional assembly.
|
|
|
|
@ifclear no-file-dir
|
|
@node File
|
|
@section @code{.file @var{string}}
|
|
|
|
@cindex @code{file} directive
|
|
@cindex logical file name
|
|
@cindex file name, logical
|
|
@code{.file} tells @code{@value{AS}} that we are about to start a new logical
|
|
file. @var{string} is the new file name. In general, the filename is
|
|
recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
|
|
to specify an empty file name, you must give the quotes--@code{""}. This
|
|
statement may go away in future: it is only recognized to be compatible with
|
|
old @code{@value{AS}} programs.
|
|
@ifset A29K
|
|
In some configurations of @code{@value{AS}}, @code{.file} has already been
|
|
removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}.
|
|
@end ifset
|
|
@end ifclear
|
|
|
|
@node Fill
|
|
@section @code{.fill @var{repeat} , @var{size} , @var{value}}
|
|
|
|
@cindex @code{fill} directive
|
|
@cindex writing patterns in memory
|
|
@cindex patterns, writing in memory
|
|
@var{result}, @var{size} and @var{value} are absolute expressions.
|
|
This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
|
|
may be zero or more. @var{Size} may be zero or more, but if it is
|
|
more than 8, then it is deemed to have the value 8, compatible with
|
|
other people's assemblers. The contents of each @var{repeat} bytes
|
|
is taken from an 8-byte number. The highest order 4 bytes are
|
|
zero. The lowest order 4 bytes are @var{value} rendered in the
|
|
byte-order of an integer on the computer @code{@value{AS}} is assembling for.
|
|
Each @var{size} bytes in a repetition is taken from the lowest order
|
|
@var{size} bytes of this number. Again, this bizarre behavior is
|
|
compatible with other people's assemblers.
|
|
|
|
@var{size} and @var{value} are optional.
|
|
If the second comma and @var{value} are absent, @var{value} is
|
|
assumed zero. If the first comma and following tokens are absent,
|
|
@var{size} is assumed to be 1.
|
|
|
|
@node Float
|
|
@section @code{.float @var{flonums}}
|
|
|
|
@cindex floating point numbers (single)
|
|
@cindex @code{float} directive
|
|
This directive assembles zero or more flonums, separated by commas. It
|
|
has the same effect as @code{.single}.
|
|
@ifset GENERIC
|
|
The exact kind of floating point numbers emitted depends on how
|
|
@code{@value{AS}} is configured.
|
|
@xref{Machine Dependencies}.
|
|
@end ifset
|
|
@ifclear GENERIC
|
|
@ifset IEEEFLOAT
|
|
On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
|
|
in @sc{ieee} format.
|
|
@end ifset
|
|
@end ifclear
|
|
|
|
@node Func
|
|
@section @code{.func @var{name}[,@var{label}]}
|
|
@cindex @code{func} directive
|
|
@code{.func} emits debugging information to denote function @var{name}, and
|
|
is ignored unless the file is assembled with debugging enabled.
|
|
Only @samp{--gstabs} is currently supported.
|
|
@var{label} is the entry point of the function and if omitted @var{name}
|
|
prepended with the @samp{leading char} is used.
|
|
@samp{leading char} is usually @code{_} or nothing, depending on the target.
|
|
All functions are currently defined to have @code{void} return type.
|
|
The function must be terminated with @code{.endfunc}.
|
|
|
|
@node Global
|
|
@section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
|
|
|
|
@cindex @code{global} directive
|
|
@cindex symbol, making visible to linker
|
|
@code{.global} makes the symbol visible to @code{@value{LD}}. If you define
|
|
@var{symbol} in your partial program, its value is made available to
|
|
other partial programs that are linked with it. Otherwise,
|
|
@var{symbol} takes its attributes from a symbol of the same name
|
|
from another file linked into the same program.
|
|
|
|
Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
|
|
compatibility with other assemblers.
|
|
|
|
@ifset HPPA
|
|
On the HPPA, @code{.global} is not always enough to make it accessible to other
|
|
partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
|
|
@xref{HPPA Directives,, HPPA Assembler Directives}.
|
|
@end ifset
|
|
|
|
@node hword
|
|
@section @code{.hword @var{expressions}}
|
|
|
|
@cindex @code{hword} directive
|
|
@cindex integers, 16-bit
|
|
@cindex numbers, 16-bit
|
|
@cindex sixteen bit integers
|
|
This expects zero or more @var{expressions}, and emits
|
|
a 16 bit number for each.
|
|
|
|
@ifset GENERIC
|
|
This directive is a synonym for @samp{.short}; depending on the target
|
|
architecture, it may also be a synonym for @samp{.word}.
|
|
@end ifset
|
|
@ifclear GENERIC
|
|
@ifset W32
|
|
This directive is a synonym for @samp{.short}.
|
|
@end ifset
|
|
@ifset W16
|
|
This directive is a synonym for both @samp{.short} and @samp{.word}.
|
|
@end ifset
|
|
@end ifclear
|
|
|
|
@node Ident
|
|
@section @code{.ident}
|
|
|
|
@cindex @code{ident} directive
|
|
This directive is used by some assemblers to place tags in object files.
|
|
@code{@value{AS}} simply accepts the directive for source-file
|
|
compatibility with such assemblers, but does not actually emit anything
|
|
for it.
|
|
|
|
@node If
|
|
@section @code{.if @var{absolute expression}}
|
|
|
|
@cindex conditional assembly
|
|
@cindex @code{if} directive
|
|
@code{.if} marks the beginning of a section of code which is only
|
|
considered part of the source program being assembled if the argument
|
|
(which must be an @var{absolute expression}) is non-zero. The end of
|
|
the conditional section of code must be marked by @code{.endif}
|
|
(@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
|
|
alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
|
|
If you have several conditions to check, @code{.elseif} may be used to avoid
|
|
nesting blocks if/else within each subsequent @code{.else} block.
|
|
|
|
The following variants of @code{.if} are also supported:
|
|
@table @code
|
|
@cindex @code{ifdef} directive
|
|
@item .ifdef @var{symbol}
|
|
Assembles the following section of code if the specified @var{symbol}
|
|
has been defined.
|
|
|
|
@cindex @code{ifc} directive
|
|
@item .ifc @var{string1},@var{string2}
|
|
Assembles the following section of code if the two strings are the same. The
|
|
strings may be optionally quoted with single quotes. If they are not quoted,
|
|
the first string stops at the first comma, and the second string stops at the
|
|
end of the line. Strings which contain whitespace should be quoted. The
|
|
string comparison is case sensitive.
|
|
|
|
@cindex @code{ifeq} directive
|
|
@item .ifeq @var{absolute expression}
|
|
Assembles the following section of code if the argument is zero.
|
|
|
|
@cindex @code{ifeqs} directive
|
|
@item .ifeqs @var{string1},@var{string2}
|
|
Another form of @code{.ifc}. The strings must be quoted using double quotes.
|
|
|
|
@cindex @code{ifge} directive
|
|
@item .ifge @var{absolute expression}
|
|
Assembles the following section of code if the argument is greater than or
|
|
equal to zero.
|
|
|
|
@cindex @code{ifgt} directive
|
|
@item .ifgt @var{absolute expression}
|
|
Assembles the following section of code if the argument is greater than zero.
|
|
|
|
@cindex @code{ifle} directive
|
|
@item .ifle @var{absolute expression}
|
|
Assembles the following section of code if the argument is less than or equal
|
|
to zero.
|
|
|
|
@cindex @code{iflt} directive
|
|
@item .iflt @var{absolute expression}
|
|
Assembles the following section of code if the argument is less than zero.
|
|
|
|
@cindex @code{ifnc} directive
|
|
@item .ifnc @var{string1},@var{string2}.
|
|
Like @code{.ifc}, but the sense of the test is reversed: this assembles the
|
|
following section of code if the two strings are not the same.
|
|
|
|
@cindex @code{ifndef} directive
|
|
@cindex @code{ifnotdef} directive
|
|
@item .ifndef @var{symbol}
|
|
@itemx .ifnotdef @var{symbol}
|
|
Assembles the following section of code if the specified @var{symbol}
|
|
has not been defined. Both spelling variants are equivalent.
|
|
|
|
@cindex @code{ifne} directive
|
|
@item .ifne @var{absolute expression}
|
|
Assembles the following section of code if the argument is not equal to zero
|
|
(in other words, this is equivalent to @code{.if}).
|
|
|
|
@cindex @code{ifnes} directive
|
|
@item .ifnes @var{string1},@var{string2}
|
|
Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
|
|
following section of code if the two strings are not the same.
|
|
@end table
|
|
|
|
@node Include
|
|
@section @code{.include "@var{file}"}
|
|
|
|
@cindex @code{include} directive
|
|
@cindex supporting files, including
|
|
@cindex files, including
|
|
This directive provides a way to include supporting files at specified
|
|
points in your source program. The code from @var{file} is assembled as
|
|
if it followed the point of the @code{.include}; when the end of the
|
|
included file is reached, assembly of the original file continues. You
|
|
can control the search paths used with the @samp{-I} command-line option
|
|
(@pxref{Invoking,,Command-Line Options}). Quotation marks are required
|
|
around @var{file}.
|
|
|
|
@node Int
|
|
@section @code{.int @var{expressions}}
|
|
|
|
@cindex @code{int} directive
|
|
@cindex integers, 32-bit
|
|
Expect zero or more @var{expressions}, of any section, separated by commas.
|
|
For each expression, emit a number that, at run time, is the value of that
|
|
expression. The byte order and bit size of the number depends on what kind
|
|
of target the assembly is for.
|
|
|
|
@ifclear GENERIC
|
|
@ifset H8
|
|
On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit
|
|
integers. On the H8/300H and the Hitachi SH, however, @code{.int} emits
|
|
32-bit integers.
|
|
@end ifset
|
|
@end ifclear
|
|
|
|
@node Irp
|
|
@section @code{.irp @var{symbol},@var{values}}@dots{}
|
|
|
|
@cindex @code{irp} directive
|
|
Evaluate a sequence of statements assigning different values to @var{symbol}.
|
|
The sequence of statements starts at the @code{.irp} directive, and is
|
|
terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
|
|
set to @var{value}, and the sequence of statements is assembled. If no
|
|
@var{value} is listed, the sequence of statements is assembled once, with
|
|
@var{symbol} set to the null string. To refer to @var{symbol} within the
|
|
sequence of statements, use @var{\symbol}.
|
|
|
|
For example, assembling
|
|
|
|
@example
|
|
.irp param,1,2,3
|
|
move d\param,sp@@-
|
|
.endr
|
|
@end example
|
|
|
|
is equivalent to assembling
|
|
|
|
@example
|
|
move d1,sp@@-
|
|
move d2,sp@@-
|
|
move d3,sp@@-
|
|
@end example
|
|
|
|
@node Irpc
|
|
@section @code{.irpc @var{symbol},@var{values}}@dots{}
|
|
|
|
@cindex @code{irpc} directive
|
|
Evaluate a sequence of statements assigning different values to @var{symbol}.
|
|
The sequence of statements starts at the @code{.irpc} directive, and is
|
|
terminated by an @code{.endr} directive. For each character in @var{value},
|
|
@var{symbol} is set to the character, and the sequence of statements is
|
|
assembled. If no @var{value} is listed, the sequence of statements is
|
|
assembled once, with @var{symbol} set to the null string. To refer to
|
|
@var{symbol} within the sequence of statements, use @var{\symbol}.
|
|
|
|
For example, assembling
|
|
|
|
@example
|
|
.irpc param,123
|
|
move d\param,sp@@-
|
|
.endr
|
|
@end example
|
|
|
|
is equivalent to assembling
|
|
|
|
@example
|
|
move d1,sp@@-
|
|
move d2,sp@@-
|
|
move d3,sp@@-
|
|
@end example
|
|
|
|
@node Lcomm
|
|
@section @code{.lcomm @var{symbol} , @var{length}}
|
|
|
|
@cindex @code{lcomm} directive
|
|
@cindex local common symbols
|
|
@cindex symbols, local common
|
|
Reserve @var{length} (an absolute expression) bytes for a local common
|
|
denoted by @var{symbol}. The section and value of @var{symbol} are
|
|
those of the new local common. The addresses are allocated in the bss
|
|
section, so that at run-time the bytes start off zeroed. @var{Symbol}
|
|
is not declared global (@pxref{Global,,@code{.global}}), so is normally
|
|
not visible to @code{@value{LD}}.
|
|
|
|
@ifset GENERIC
|
|
Some targets permit a third argument to be used with @code{.lcomm}. This
|
|
argument specifies the desired alignment of the symbol in the bss section.
|
|
@end ifset
|
|
|
|
@ifset HPPA
|
|
The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
|
|
@samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
|
|
@end ifset
|
|
|
|
@node Lflags
|
|
@section @code{.lflags}
|
|
|
|
@cindex @code{lflags} directive (ignored)
|
|
@code{@value{AS}} accepts this directive, for compatibility with other
|
|
assemblers, but ignores it.
|
|
|
|
@ifclear no-line-dir
|
|
@node Line
|
|
@section @code{.line @var{line-number}}
|
|
|
|
@cindex @code{line} directive
|
|
@end ifclear
|
|
@ifset no-line-dir
|
|
@node Ln
|
|
@section @code{.ln @var{line-number}}
|
|
|
|
@cindex @code{ln} directive
|
|
@end ifset
|
|
@cindex logical line number
|
|
@ifset aout-bout
|
|
Change the logical line number. @var{line-number} must be an absolute
|
|
expression. The next line has that logical line number. Therefore any other
|
|
statements on the current line (after a statement separator character) are
|
|
reported as on logical line number @var{line-number} @minus{} 1. One day
|
|
@code{@value{AS}} will no longer support this directive: it is recognized only
|
|
for compatibility with existing assembler programs.
|
|
|
|
@ifset GENERIC
|
|
@ifset A29K
|
|
@emph{Warning:} In the AMD29K configuration of @value{AS}, this command is
|
|
not available; use the synonym @code{.ln} in that context.
|
|
@end ifset
|
|
@end ifset
|
|
@end ifset
|
|
|
|
@ifclear no-line-dir
|
|
Even though this is a directive associated with the @code{a.out} or
|
|
@code{b.out} object-code formats, @code{@value{AS}} still recognizes it
|
|
when producing COFF output, and treats @samp{.line} as though it
|
|
were the COFF @samp{.ln} @emph{if} it is found outside a
|
|
@code{.def}/@code{.endef} pair.
|
|
|
|
Inside a @code{.def}, @samp{.line} is, instead, one of the directives
|
|
used by compilers to generate auxiliary symbol information for
|
|
debugging.
|
|
@end ifclear
|
|
|
|
@node Linkonce
|
|
@section @code{.linkonce [@var{type}]}
|
|
@cindex COMDAT
|
|
@cindex @code{linkonce} directive
|
|
@cindex common sections
|
|
Mark the current section so that the linker only includes a single copy of it.
|
|
This may be used to include the same section in several different object files,
|
|
but ensure that the linker will only include it once in the final output file.
|
|
The @code{.linkonce} pseudo-op must be used for each instance of the section.
|
|
Duplicate sections are detected based on the section name, so it should be
|
|
unique.
|
|
|
|
This directive is only supported by a few object file formats; as of this
|
|
writing, the only object file format which supports it is the Portable
|
|
Executable format used on Windows NT.
|
|
|
|
The @var{type} argument is optional. If specified, it must be one of the
|
|
following strings. For example:
|
|
@smallexample
|
|
.linkonce same_size
|
|
@end smallexample
|
|
Not all types may be supported on all object file formats.
|
|
|
|
@table @code
|
|
@item discard
|
|
Silently discard duplicate sections. This is the default.
|
|
|
|
@item one_only
|
|
Warn if there are duplicate sections, but still keep only one copy.
|
|
|
|
@item same_size
|
|
Warn if any of the duplicates have different sizes.
|
|
|
|
@item same_contents
|
|
Warn if any of the duplicates do not have exactly the same contents.
|
|
@end table
|
|
|
|
@node Ln
|
|
@section @code{.ln @var{line-number}}
|
|
|
|
@cindex @code{ln} directive
|
|
@ifclear no-line-dir
|
|
@samp{.ln} is a synonym for @samp{.line}.
|
|
@end ifclear
|
|
@ifset no-line-dir
|
|
Tell @code{@value{AS}} to change the logical line number. @var{line-number}
|
|
must be an absolute expression. The next line has that logical
|
|
line number, so any other statements on the current line (after a
|
|
statement separator character @code{;}) are reported as on logical
|
|
line number @var{line-number} @minus{} 1.
|
|
@ifset BOUT
|
|
|
|
This directive is accepted, but ignored, when @code{@value{AS}} is
|
|
configured for @code{b.out}; its effect is only associated with COFF
|
|
output format.
|
|
@end ifset
|
|
@end ifset
|
|
|
|
@node MRI
|
|
@section @code{.mri @var{val}}
|
|
|
|
@cindex @code{mri} directive
|
|
@cindex MRI mode, temporarily
|
|
If @var{val} is non-zero, this tells @code{@value{AS}} to enter MRI mode. If
|
|
@var{val} is zero, this tells @code{@value{AS}} to exit MRI mode. This change
|
|
affects code assembled until the next @code{.mri} directive, or until the end
|
|
of the file. @xref{M, MRI mode, MRI mode}.
|
|
|
|
@node List
|
|
@section @code{.list}
|
|
|
|
@cindex @code{list} directive
|
|
@cindex listing control, turning on
|
|
Control (in conjunction with the @code{.nolist} directive) whether or
|
|
not assembly listings are generated. These two directives maintain an
|
|
internal counter (which is zero initially). @code{.list} increments the
|
|
counter, and @code{.nolist} decrements it. Assembly listings are
|
|
generated whenever the counter is greater than zero.
|
|
|
|
By default, listings are disabled. When you enable them (with the
|
|
@samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
|
|
the initial value of the listing counter is one.
|
|
|
|
@node Long
|
|
@section @code{.long @var{expressions}}
|
|
|
|
@cindex @code{long} directive
|
|
@code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
|
|
|
|
@ignore
|
|
@c no one seems to know what this is for or whether this description is
|
|
@c what it really ought to do
|
|
@node Lsym
|
|
@section @code{.lsym @var{symbol}, @var{expression}}
|
|
|
|
@cindex @code{lsym} directive
|
|
@cindex symbol, not referenced in assembly
|
|
@code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
|
|
the hash table, ensuring it cannot be referenced by name during the
|
|
rest of the assembly. This sets the attributes of the symbol to be
|
|
the same as the expression value:
|
|
@smallexample
|
|
@var{other} = @var{descriptor} = 0
|
|
@var{type} = @r{(section of @var{expression})}
|
|
@var{value} = @var{expression}
|
|
@end smallexample
|
|
@noindent
|
|
The new symbol is not flagged as external.
|
|
@end ignore
|
|
|
|
@node Macro
|
|
@section @code{.macro}
|
|
|
|
@cindex macros
|
|
The commands @code{.macro} and @code{.endm} allow you to define macros that
|
|
generate assembly output. For example, this definition specifies a macro
|
|
@code{sum} that puts a sequence of numbers into memory:
|
|
|
|
@example
|
|
.macro sum from=0, to=5
|
|
.long \from
|
|
.if \to-\from
|
|
sum "(\from+1)",\to
|
|
.endif
|
|
.endm
|
|
@end example
|
|
|
|
@noindent
|
|
With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
|
|
|
|
@example
|
|
.long 0
|
|
.long 1
|
|
.long 2
|
|
.long 3
|
|
.long 4
|
|
.long 5
|
|
@end example
|
|
|
|
@ftable @code
|
|
@item .macro @var{macname}
|
|
@itemx .macro @var{macname} @var{macargs} @dots{}
|
|
@cindex @code{macro} directive
|
|
Begin the definition of a macro called @var{macname}. If your macro
|
|
definition requires arguments, specify their names after the macro name,
|
|
separated by commas or spaces. You can supply a default value for any
|
|
macro argument by following the name with @samp{=@var{deflt}}. For
|
|
example, these are all valid @code{.macro} statements:
|
|
|
|
@table @code
|
|
@item .macro comm
|
|
Begin the definition of a macro called @code{comm}, which takes no
|
|
arguments.
|
|
|
|
@item .macro plus1 p, p1
|
|
@itemx .macro plus1 p p1
|
|
Either statement begins the definition of a macro called @code{plus1},
|
|
which takes two arguments; within the macro definition, write
|
|
@samp{\p} or @samp{\p1} to evaluate the arguments.
|
|
|
|
@item .macro reserve_str p1=0 p2
|
|
Begin the definition of a macro called @code{reserve_str}, with two
|
|
arguments. The first argument has a default value, but not the second.
|
|
After the definition is complete, you can call the macro either as
|
|
@samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
|
|
@var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
|
|
,@var{b}} (with @samp{\p1} evaluating as the default, in this case
|
|
@samp{0}, and @samp{\p2} evaluating to @var{b}).
|
|
@end table
|
|
|
|
When you call a macro, you can specify the argument values either by
|
|
position, or by keyword. For example, @samp{sum 9,17} is equivalent to
|
|
@samp{sum to=17, from=9}.
|
|
|
|
@item .endm
|
|
@cindex @code{endm} directive
|
|
Mark the end of a macro definition.
|
|
|
|
@item .exitm
|
|
@cindex @code{exitm} directive
|
|
Exit early from the current macro definition.
|
|
|
|
@cindex number of macros executed
|
|
@cindex macros, count executed
|
|
@item \@@
|
|
@code{@value{AS}} maintains a counter of how many macros it has
|
|
executed in this pseudo-variable; you can copy that number to your
|
|
output with @samp{\@@}, but @emph{only within a macro definition}.
|
|
|
|
@ignore
|
|
@item LOCAL @var{name} [ , @dots{} ]
|
|
@emph{Warning: @code{LOCAL} is only available if you select ``alternate
|
|
macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,,
|
|
Alternate macro syntax}.
|
|
|
|
Generate a string replacement for each of the @var{name} arguments, and
|
|
replace any instances of @var{name} in each macro expansion. The
|
|
replacement string is unique in the assembly, and different for each
|
|
separate macro expansion. @code{LOCAL} allows you to write macros that
|
|
define symbols, without fear of conflict between separate macro expansions.
|
|
@end ignore
|
|
@end ftable
|
|
|
|
@node Nolist
|
|
@section @code{.nolist}
|
|
|
|
@cindex @code{nolist} directive
|
|
@cindex listing control, turning off
|
|
Control (in conjunction with the @code{.list} directive) whether or
|
|
not assembly listings are generated. These two directives maintain an
|
|
internal counter (which is zero initially). @code{.list} increments the
|
|
counter, and @code{.nolist} decrements it. Assembly listings are
|
|
generated whenever the counter is greater than zero.
|
|
|
|
@node Octa
|
|
@section @code{.octa @var{bignums}}
|
|
|
|
@c FIXME: double size emitted for "octa" on i960, others? Or warn?
|
|
@cindex @code{octa} directive
|
|
@cindex integer, 16-byte
|
|
@cindex sixteen byte integer
|
|
This directive expects zero or more bignums, separated by commas. For each
|
|
bignum, it emits a 16-byte integer.
|
|
|
|
The term ``octa'' comes from contexts in which a ``word'' is two bytes;
|
|
hence @emph{octa}-word for 16 bytes.
|
|
|
|
@node Org
|
|
@section @code{.org @var{new-lc} , @var{fill}}
|
|
|
|
@cindex @code{org} directive
|
|
@cindex location counter, advancing
|
|
@cindex advancing location counter
|
|
@cindex current address, advancing
|
|
Advance the location counter of the current section to
|
|
@var{new-lc}. @var{new-lc} is either an absolute expression or an
|
|
expression with the same section as the current subsection. That is,
|
|
you can't use @code{.org} to cross sections: if @var{new-lc} has the
|
|
wrong section, the @code{.org} directive is ignored. To be compatible
|
|
with former assemblers, if the section of @var{new-lc} is absolute,
|
|
@code{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
|
|
is the same as the current subsection.
|
|
|
|
@code{.org} may only increase the location counter, or leave it
|
|
unchanged; you cannot use @code{.org} to move the location counter
|
|
backwards.
|
|
|
|
@c double negative used below "not undefined" because this is a specific
|
|
@c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
|
|
@c section. doc@cygnus.com 18feb91
|
|
Because @code{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
|
|
may not be undefined. If you really detest this restriction we eagerly await
|
|
a chance to share your improved assembler.
|
|
|
|
Beware that the origin is relative to the start of the section, not
|
|
to the start of the subsection. This is compatible with other
|
|
people's assemblers.
|
|
|
|
When the location counter (of the current subsection) is advanced, the
|
|
intervening bytes are filled with @var{fill} which should be an
|
|
absolute expression. If the comma and @var{fill} are omitted,
|
|
@var{fill} defaults to zero.
|
|
|
|
@node P2align
|
|
@section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
|
|
|
|
@cindex padding the location counter given a power of two
|
|
@cindex @code{p2align} directive
|
|
Pad the location counter (in the current subsection) to a particular
|
|
storage boundary. The first expression (which must be absolute) is the
|
|
number of low-order zero bits the location counter must have after
|
|
advancement. For example @samp{.p2align 3} advances the location
|
|
counter until it a multiple of 8. If the location counter is already a
|
|
multiple of 8, no change is needed.
|
|
|
|
The second expression (also absolute) gives the fill value to be stored in the
|
|
padding bytes. It (and the comma) may be omitted. If it is omitted, the
|
|
padding bytes are normally zero. However, on some systems, if the section is
|
|
marked as containing code and the fill value is omitted, the space is filled
|
|
with no-op instructions.
|
|
|
|
The third expression is also absolute, and is also optional. If it is present,
|
|
it is the maximum number of bytes that should be skipped by this alignment
|
|
directive. If doing the alignment would require skipping more bytes than the
|
|
specified maximum, then the alignment is not done at all. You can omit the
|
|
fill value (the second argument) entirely by simply using two commas after the
|
|
required alignment; this can be useful if you want the alignment to be filled
|
|
with no-op instructions when appropriate.
|
|
|
|
@cindex @code{p2alignw} directive
|
|
@cindex @code{p2alignl} directive
|
|
The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
|
|
@code{.p2align} directive. The @code{.p2alignw} directive treats the fill
|
|
pattern as a two byte word value. The @code{.p2alignl} directives treats the
|
|
fill pattern as a four byte longword value. For example, @code{.p2alignw
|
|
2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
|
|
filled in with the value 0x368d (the exact placement of the bytes depends upon
|
|
the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
|
|
undefined.
|
|
|
|
@node Print
|
|
@section @code{.print @var{string}}
|
|
|
|
@cindex @code{print} directive
|
|
@code{@value{AS}} will print @var{string} on the standard output during
|
|
assembly. You must put @var{string} in double quotes.
|
|
|
|
@node Psize
|
|
@section @code{.psize @var{lines} , @var{columns}}
|
|
|
|
@cindex @code{psize} directive
|
|
@cindex listing control: paper size
|
|
@cindex paper size, for listings
|
|
Use this directive to declare the number of lines---and, optionally, the
|
|
number of columns---to use for each page, when generating listings.
|
|
|
|
If you do not use @code{.psize}, listings use a default line-count
|
|
of 60. You may omit the comma and @var{columns} specification; the
|
|
default width is 200 columns.
|
|
|
|
@code{@value{AS}} generates formfeeds whenever the specified number of
|
|
lines is exceeded (or whenever you explicitly request one, using
|
|
@code{.eject}).
|
|
|
|
If you specify @var{lines} as @code{0}, no formfeeds are generated save
|
|
those explicitly specified with @code{.eject}.
|
|
|
|
@node Purgem
|
|
@section @code{.purgem @var{name}}
|
|
|
|
@cindex @code{purgem} directive
|
|
Undefine the macro @var{name}, so that later uses of the string will not be
|
|
expanded. @xref{Macro}.
|
|
|
|
@node Quad
|
|
@section @code{.quad @var{bignums}}
|
|
|
|
@cindex @code{quad} directive
|
|
@code{.quad} expects zero or more bignums, separated by commas. For
|
|
each bignum, it emits
|
|
@ifclear bignum-16
|
|
an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
|
|
warning message; and just takes the lowest order 8 bytes of the bignum.
|
|
@cindex eight-byte integer
|
|
@cindex integer, 8-byte
|
|
|
|
The term ``quad'' comes from contexts in which a ``word'' is two bytes;
|
|
hence @emph{quad}-word for 8 bytes.
|
|
@end ifclear
|
|
@ifset bignum-16
|
|
a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
|
|
warning message; and just takes the lowest order 16 bytes of the bignum.
|
|
@cindex sixteen-byte integer
|
|
@cindex integer, 16-byte
|
|
@end ifset
|
|
|
|
@node Rept
|
|
@section @code{.rept @var{count}}
|
|
|
|
@cindex @code{rept} directive
|
|
Repeat the sequence of lines between the @code{.rept} directive and the next
|
|
@code{.endr} directive @var{count} times.
|
|
|
|
For example, assembling
|
|
|
|
@example
|
|
.rept 3
|
|
.long 0
|
|
.endr
|
|
@end example
|
|
|
|
is equivalent to assembling
|
|
|
|
@example
|
|
.long 0
|
|
.long 0
|
|
.long 0
|
|
@end example
|
|
|
|
@node Sbttl
|
|
@section @code{.sbttl "@var{subheading}"}
|
|
|
|
@cindex @code{sbttl} directive
|
|
@cindex subtitles for listings
|
|
@cindex listing control: subtitle
|
|
Use @var{subheading} as the title (third line, immediately after the
|
|
title line) when generating assembly listings.
|
|
|
|
This directive affects subsequent pages, as well as the current page if
|
|
it appears within ten lines of the top of a page.
|
|
|
|
@ifset COFF
|
|
@node Scl
|
|
@section @code{.scl @var{class}}
|
|
|
|
@cindex @code{scl} directive
|
|
@cindex symbol storage class (COFF)
|
|
@cindex COFF symbol storage class
|
|
Set the storage-class value for a symbol. This directive may only be
|
|
used inside a @code{.def}/@code{.endef} pair. Storage class may flag
|
|
whether a symbol is static or external, or it may record further
|
|
symbolic debugging information.
|
|
@ifset BOUT
|
|
|
|
The @samp{.scl} directive is primarily associated with COFF output; when
|
|
configured to generate @code{b.out} output format, @code{@value{AS}}
|
|
accepts this directive but ignores it.
|
|
@end ifset
|
|
@end ifset
|
|
|
|
@node Section
|
|
@section @code{.section @var{name}}
|
|
|
|
@cindex @code{section} directive
|
|
@cindex named section
|
|
Use the @code{.section} directive to assemble the following code into a section
|
|
named @var{name}.
|
|
|
|
This directive is only supported for targets that actually support arbitrarily
|
|
named sections; on @code{a.out} targets, for example, it is not accepted, even
|
|
with a standard @code{a.out} section name.
|
|
|
|
@ifset COFF
|
|
For COFF targets, the @code{.section} directive is used in one of the following
|
|
ways:
|
|
@smallexample
|
|
.section @var{name}[, "@var{flags}"]
|
|
.section @var{name}[, @var{subsegment}]
|
|
@end smallexample
|
|
|
|
If the optional argument is quoted, it is taken as flags to use for the
|
|
section. Each flag is a single character. The following flags are recognized:
|
|
@table @code
|
|
@item b
|
|
bss section (uninitialized data)
|
|
@item n
|
|
section is not loaded
|
|
@item w
|
|
writable section
|
|
@item d
|
|
data section
|
|
@item r
|
|
read-only section
|
|
@item x
|
|
executable section
|
|
@item s
|
|
shared section (meaningful for PE targets)
|
|
@end table
|
|
|
|
If no flags are specified, the default flags depend upon the section name. If
|
|
the section name is not recognized, the default will be for the section to be
|
|
loaded and writable.
|
|
|
|
If the optional argument to the @code{.section} directive is not quoted, it is
|
|
taken as a subsegment number (@pxref{Sub-Sections}).
|
|
@end ifset
|
|
|
|
@ifset ELF
|
|
For ELF targets, the @code{.section} directive is used like this:
|
|
@smallexample
|
|
.section @var{name}[, "@var{flags}"[, @@@var{type}]]
|
|
@end smallexample
|
|
The optional @var{flags} argument is a quoted string which may contain any
|
|
combintion of the following characters:
|
|
@table @code
|
|
@item a
|
|
section is allocatable
|
|
@item w
|
|
section is writable
|
|
@item x
|
|
section is executable
|
|
@end table
|
|
|
|
The optional @var{type} argument may contain one of the following constants:
|
|
@table @code
|
|
@item @@progbits
|
|
section contains data
|
|
@item @@nobits
|
|
section does not contain data (i.e., section only occupies space)
|
|
@end table
|
|
|
|
If no flags are specified, the default flags depend upon the section name. If
|
|
the section name is not recognized, the default will be for the section to have
|
|
none of the above flags: it will not be allocated in memory, nor writable, nor
|
|
executable. The section will contain data.
|
|
|
|
For ELF targets, the assembler supports another type of @code{.section}
|
|
directive for compatibility with the Solaris assembler:
|
|
@smallexample
|
|
.section "@var{name}"[, @var{flags}...]
|
|
@end smallexample
|
|
Note that the section name is quoted. There may be a sequence of comma
|
|
separated flags:
|
|
@table @code
|
|
@item #alloc
|
|
section is allocatable
|
|
@item #write
|
|
section is writable
|
|
@item #execinstr
|
|
section is executable
|
|
@end table
|
|
@end ifset
|
|
|
|
@node Set
|
|
@section @code{.set @var{symbol}, @var{expression}}
|
|
|
|
@cindex @code{set} directive
|
|
@cindex symbol value, setting
|
|
Set the value of @var{symbol} to @var{expression}. This
|
|
changes @var{symbol}'s value and type to conform to
|
|
@var{expression}. If @var{symbol} was flagged as external, it remains
|
|
flagged (@pxref{Symbol Attributes}).
|
|
|
|
You may @code{.set} a symbol many times in the same assembly.
|
|
|
|
If you @code{.set} a global symbol, the value stored in the object
|
|
file is the last value stored into it.
|
|
|
|
@ifset HPPA
|
|
The syntax for @code{set} on the HPPA is
|
|
@samp{@var{symbol} .set @var{expression}}.
|
|
@end ifset
|
|
|
|
@node Short
|
|
@section @code{.short @var{expressions}}
|
|
|
|
@cindex @code{short} directive
|
|
@ifset GENERIC
|
|
@code{.short} is normally the same as @samp{.word}.
|
|
@xref{Word,,@code{.word}}.
|
|
|
|
In some configurations, however, @code{.short} and @code{.word} generate
|
|
numbers of different lengths; @pxref{Machine Dependencies}.
|
|
@end ifset
|
|
@ifclear GENERIC
|
|
@ifset W16
|
|
@code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
|
|
@end ifset
|
|
@ifset W32
|
|
This expects zero or more @var{expressions}, and emits
|
|
a 16 bit number for each.
|
|
@end ifset
|
|
@end ifclear
|
|
|
|
@node Single
|
|
@section @code{.single @var{flonums}}
|
|
|
|
@cindex @code{single} directive
|
|
@cindex floating point numbers (single)
|
|
This directive assembles zero or more flonums, separated by commas. It
|
|
has the same effect as @code{.float}.
|
|
@ifset GENERIC
|
|
The exact kind of floating point numbers emitted depends on how
|
|
@code{@value{AS}} is configured. @xref{Machine Dependencies}.
|
|
@end ifset
|
|
@ifclear GENERIC
|
|
@ifset IEEEFLOAT
|
|
On the @value{TARGET} family, @code{.single} emits 32-bit floating point
|
|
numbers in @sc{ieee} format.
|
|
@end ifset
|
|
@end ifclear
|
|
|
|
@ifset COFF
|
|
@node Size
|
|
@section @code{.size}
|
|
|
|
@cindex @code{size} directive
|
|
This directive is generated by compilers to include auxiliary debugging
|
|
information in the symbol table. It is only permitted inside
|
|
@code{.def}/@code{.endef} pairs.
|
|
@ifset BOUT
|
|
|
|
@samp{.size} is only meaningful when generating COFF format output; when
|
|
@code{@value{AS}} is generating @code{b.out}, it accepts this directive but
|
|
ignores it.
|
|
@end ifset
|
|
@end ifset
|
|
|
|
@node Sleb128
|
|
@section @code{.sleb128 @var{expressions}}
|
|
|
|
@cindex @code{sleb128} directive
|
|
@var{sleb128} stands for ``signed little endian base 128.'' This is a
|
|
compact, variable length representation of numbers used by the DWARF
|
|
symbolic debugging format. @xref{Uleb128,@code{.uleb128}}.
|
|
|
|
@ifclear no-space-dir
|
|
@node Skip
|
|
@section @code{.skip @var{size} , @var{fill}}
|
|
|
|
@cindex @code{skip} directive
|
|
@cindex filling memory
|
|
This directive emits @var{size} bytes, each of value @var{fill}. Both
|
|
@var{size} and @var{fill} are absolute expressions. If the comma and
|
|
@var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
|
|
@samp{.space}.
|
|
|
|
@node Space
|
|
@section @code{.space @var{size} , @var{fill}}
|
|
|
|
@cindex @code{space} directive
|
|
@cindex filling memory
|
|
This directive emits @var{size} bytes, each of value @var{fill}. Both
|
|
@var{size} and @var{fill} are absolute expressions. If the comma
|
|
and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
|
|
as @samp{.skip}.
|
|
|
|
@ifset HPPA
|
|
@quotation
|
|
@emph{Warning:} @code{.space} has a completely different meaning for HPPA
|
|
targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
|
|
Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
|
|
@code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
|
|
for a summary.
|
|
@end quotation
|
|
@end ifset
|
|
@end ifclear
|
|
|
|
@ifset A29K
|
|
@ifclear GENERIC
|
|
@node Space
|
|
@section @code{.space}
|
|
@cindex @code{space} directive
|
|
@end ifclear
|
|
On the AMD 29K, this directive is ignored; it is accepted for
|
|
compatibility with other AMD 29K assemblers.
|
|
|
|
@quotation
|
|
@emph{Warning:} In most versions of the @sc{gnu} assembler, the directive
|
|
@code{.space} has the effect of @code{.block} @xref{Machine Dependencies}.
|
|
@end quotation
|
|
@end ifset
|
|
|
|
@ifset have-stabs
|
|
@node Stab
|
|
@section @code{.stabd, .stabn, .stabs}
|
|
|
|
@cindex symbolic debuggers, information for
|
|
@cindex @code{stab@var{x}} directives
|
|
There are three directives that begin @samp{.stab}.
|
|
All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
|
|
The symbols are not entered in the @code{@value{AS}} hash table: they
|
|
cannot be referenced elsewhere in the source file.
|
|
Up to five fields are required:
|
|
|
|
@table @var
|
|
@item string
|
|
This is the symbol's name. It may contain any character except
|
|
@samp{\000}, so is more general than ordinary symbol names. Some
|
|
debuggers used to code arbitrarily complex structures into symbol names
|
|
using this field.
|
|
|
|
@item type
|
|
An absolute expression. The symbol's type is set to the low 8 bits of
|
|
this expression. Any bit pattern is permitted, but @code{@value{LD}}
|
|
and debuggers choke on silly bit patterns.
|
|
|
|
@item other
|
|
An absolute expression. The symbol's ``other'' attribute is set to the
|
|
low 8 bits of this expression.
|
|
|
|
@item desc
|
|
An absolute expression. The symbol's descriptor is set to the low 16
|
|
bits of this expression.
|
|
|
|
@item value
|
|
An absolute expression which becomes the symbol's value.
|
|
@end table
|
|
|
|
If a warning is detected while reading a @code{.stabd}, @code{.stabn},
|
|
or @code{.stabs} statement, the symbol has probably already been created;
|
|
you get a half-formed symbol in your object file. This is
|
|
compatible with earlier assemblers!
|
|
|
|
@table @code
|
|
@cindex @code{stabd} directive
|
|
@item .stabd @var{type} , @var{other} , @var{desc}
|
|
|
|
The ``name'' of the symbol generated is not even an empty string.
|
|
It is a null pointer, for compatibility. Older assemblers used a
|
|
null pointer so they didn't waste space in object files with empty
|
|
strings.
|
|
|
|
The symbol's value is set to the location counter,
|
|
relocatably. When your program is linked, the value of this symbol
|
|
is the address of the location counter when the @code{.stabd} was
|
|
assembled.
|
|
|
|
@cindex @code{stabn} directive
|
|
@item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
|
|
The name of the symbol is set to the empty string @code{""}.
|
|
|
|
@cindex @code{stabs} directive
|
|
@item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
|
|
All five fields are specified.
|
|
@end table
|
|
@end ifset
|
|
@c end have-stabs
|
|
|
|
@node String
|
|
@section @code{.string} "@var{str}"
|
|
|
|
@cindex string, copying to object file
|
|
@cindex @code{string} directive
|
|
|
|
Copy the characters in @var{str} to the object file. You may specify more than
|
|
one string to copy, separated by commas. Unless otherwise specified for a
|
|
particular machine, the assembler marks the end of each string with a 0 byte.
|
|
You can use any of the escape sequences described in @ref{Strings,,Strings}.
|
|
|
|
@node Struct
|
|
@section @code{.struct @var{expression}}
|
|
|
|
@cindex @code{struct} directive
|
|
Switch to the absolute section, and set the section offset to @var{expression},
|
|
which must be an absolute expression. You might use this as follows:
|
|
@smallexample
|
|
.struct 0
|
|
field1:
|
|
.struct field1 + 4
|
|
field2:
|
|
.struct field2 + 4
|
|
field3:
|
|
@end smallexample
|
|
This would define the symbol @code{field1} to have the value 0, the symbol
|
|
@code{field2} to have the value 4, and the symbol @code{field3} to have the
|
|
value 8. Assembly would be left in the absolute section, and you would need to
|
|
use a @code{.section} directive of some sort to change to some other section
|
|
before further assembly.
|
|
|
|
@ifset ELF
|
|
@node Symver
|
|
@section @code{.symver}
|
|
@cindex @code{symver} directive
|
|
@cindex symbol versioning
|
|
@cindex versions of symbols
|
|
Use the @code{.symver} directive to bind symbols to specific version nodes
|
|
within a source file. This is only supported on ELF platforms, and is
|
|
typically used when assembling files to be linked into a shared library.
|
|
There are cases where it may make sense to use this in objects to be bound
|
|
into an application itself so as to override a versioned symbol from a
|
|
shared library.
|
|
|
|
For ELF targets, the @code{.symver} directive is used like this:
|
|
@smallexample
|
|
.symver @var{name}, @var{name2@@nodename}
|
|
@end smallexample
|
|
In this case, the symbol @var{name} must exist and be defined within the file
|
|
being assembled. The @code{.versym} directive effectively creates a symbol
|
|
alias with the name @var{name2@@nodename}, and in fact the main reason that we
|
|
just don't try and create a regular alias is that the @var{@@} character isn't
|
|
permitted in symbol names. The @var{name2} part of the name is the actual name
|
|
of the symbol by which it will be externally referenced. The name @var{name}
|
|
itself is merely a name of convenience that is used so that it is possible to
|
|
have definitions for multiple versions of a function within a single source
|
|
file, and so that the compiler can unambiguously know which version of a
|
|
function is being mentioned. The @var{nodename} portion of the alias should be
|
|
the name of a node specified in the version script supplied to the linker when
|
|
building a shared library. If you are attempting to override a versioned
|
|
symbol from a shared library, then @var{nodename} should correspond to the
|
|
nodename of the symbol you are trying to override.
|
|
@end ifset
|
|
|
|
@ifset COFF
|
|
@node Tag
|
|
@section @code{.tag @var{structname}}
|
|
|
|
@cindex COFF structure debugging
|
|
@cindex structure debugging, COFF
|
|
@cindex @code{tag} directive
|
|
This directive is generated by compilers to include auxiliary debugging
|
|
information in the symbol table. It is only permitted inside
|
|
@code{.def}/@code{.endef} pairs. Tags are used to link structure
|
|
definitions in the symbol table with instances of those structures.
|
|
@ifset BOUT
|
|
|
|
@samp{.tag} is only used when generating COFF format output; when
|
|
@code{@value{AS}} is generating @code{b.out}, it accepts this directive but
|
|
ignores it.
|
|
@end ifset
|
|
@end ifset
|
|
|
|
@node Text
|
|
@section @code{.text @var{subsection}}
|
|
|
|
@cindex @code{text} directive
|
|
Tells @code{@value{AS}} to assemble the following statements onto the end of
|
|
the text subsection numbered @var{subsection}, which is an absolute
|
|
expression. If @var{subsection} is omitted, subsection number zero
|
|
is used.
|
|
|
|
@node Title
|
|
@section @code{.title "@var{heading}"}
|
|
|
|
@cindex @code{title} directive
|
|
@cindex listing control: title line
|
|
Use @var{heading} as the title (second line, immediately after the
|
|
source file name and pagenumber) when generating assembly listings.
|
|
|
|
This directive affects subsequent pages, as well as the current page if
|
|
it appears within ten lines of the top of a page.
|
|
|
|
@ifset COFF
|
|
@node Type
|
|
@section @code{.type @var{int}}
|
|
|
|
@cindex COFF symbol type
|
|
@cindex symbol type, COFF
|
|
@cindex @code{type} directive
|
|
This directive, permitted only within @code{.def}/@code{.endef} pairs,
|
|
records the integer @var{int} as the type attribute of a symbol table entry.
|
|
@ifset BOUT
|
|
|
|
@samp{.type} is associated only with COFF format output; when
|
|
@code{@value{AS}} is configured for @code{b.out} output, it accepts this
|
|
directive but ignores it.
|
|
@end ifset
|
|
@end ifset
|
|
|
|
@ifset COFF
|
|
@node Val
|
|
@section @code{.val @var{addr}}
|
|
|
|
@cindex @code{val} directive
|
|
@cindex COFF value attribute
|
|
@cindex value attribute, COFF
|
|
This directive, permitted only within @code{.def}/@code{.endef} pairs,
|
|
records the address @var{addr} as the value attribute of a symbol table
|
|
entry.
|
|
@ifset BOUT
|
|
|
|
@samp{.val} is used only for COFF output; when @code{@value{AS}} is
|
|
configured for @code{b.out}, it accepts this directive but ignores it.
|
|
@end ifset
|
|
@end ifset
|
|
|
|
@node Uleb128
|
|
@section @code{.uleb128 @var{expressions}}
|
|
|
|
@cindex @code{uleb128} directive
|
|
@var{uleb128} stands for ``unsigned little endian base 128.'' This is a
|
|
compact, variable length representation of numbers used by the DWARF
|
|
symbolic debugging format. @xref{Sleb128,@code{.sleb128}}.
|
|
|
|
@ifset ELF
|
|
@node Visibility
|
|
@section @code{.internal}, @code{.hidden}, @code{.protected}
|
|
@cindex @code{internal} directive
|
|
@cindex @code{hidden} directive
|
|
@cindex @code{protected} directive
|
|
@cindex symbol visibility
|
|
|
|
These directives can be used to set the visibility of a specified symbol. By
|
|
default a symbol's visibility is set by its binding (local, global or weak),
|
|
but these directives can be used to override that.
|
|
|
|
A visibility of @code{protected} means that any references to the symbol from
|
|
within the component that defines the symbol must be resolved to the definition
|
|
in that component, even if a definition in another component would normally
|
|
preempt this.
|
|
|
|
A visibility of @code{hidden} means that the symbol is not visible to other
|
|
components. Such a symbol is always considered to be protected as well.
|
|
|
|
A visibility of @code{internal} is the same as a visibility of @code{hidden},
|
|
except that some extra, processor specific processing must also be performed
|
|
upon the symbol.
|
|
|
|
For ELF targets, the directives are used like this:
|
|
|
|
@smallexample
|
|
.internal @var{name}
|
|
.hidden @var{name}
|
|
.protected @var{name}
|
|
@end smallexample
|
|
|
|
@end ifset
|
|
|
|
@node Word
|
|
@section @code{.word @var{expressions}}
|
|
|
|
@cindex @code{word} directive
|
|
This directive expects zero or more @var{expressions}, of any section,
|
|
separated by commas.
|
|
@ifclear GENERIC
|
|
@ifset W32
|
|
For each expression, @code{@value{AS}} emits a 32-bit number.
|
|
@end ifset
|
|
@ifset W16
|
|
For each expression, @code{@value{AS}} emits a 16-bit number.
|
|
@end ifset
|
|
@end ifclear
|
|
@ifset GENERIC
|
|
|
|
The size of the number emitted, and its byte order,
|
|
depend on what target computer the assembly is for.
|
|
@end ifset
|
|
|
|
@c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
|
|
@c happen---32-bit addressability, period; no long/short jumps.
|
|
@ifset DIFF-TBL-KLUGE
|
|
@cindex difference tables altered
|
|
@cindex altered difference tables
|
|
@quotation
|
|
@emph{Warning: Special Treatment to support Compilers}
|
|
@end quotation
|
|
|
|
@ifset GENERIC
|
|
Machines with a 32-bit address space, but that do less than 32-bit
|
|
addressing, require the following special treatment. If the machine of
|
|
interest to you does 32-bit addressing (or doesn't require it;
|
|
@pxref{Machine Dependencies}), you can ignore this issue.
|
|
|
|
@end ifset
|
|
In order to assemble compiler output into something that works,
|
|
@code{@value{AS}} occasionlly does strange things to @samp{.word} directives.
|
|
Directives of the form @samp{.word sym1-sym2} are often emitted by
|
|
compilers as part of jump tables. Therefore, when @code{@value{AS}} assembles a
|
|
directive of the form @samp{.word sym1-sym2}, and the difference between
|
|
@code{sym1} and @code{sym2} does not fit in 16 bits, @code{@value{AS}}
|
|
creates a @dfn{secondary jump table}, immediately before the next label.
|
|
This secondary jump table is preceded by a short-jump to the
|
|
first byte after the secondary table. This short-jump prevents the flow
|
|
of control from accidentally falling into the new table. Inside the
|
|
table is a long-jump to @code{sym2}. The original @samp{.word}
|
|
contains @code{sym1} minus the address of the long-jump to
|
|
@code{sym2}.
|
|
|
|
If there were several occurrences of @samp{.word sym1-sym2} before the
|
|
secondary jump table, all of them are adjusted. If there was a
|
|
@samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
|
|
long-jump to @code{sym4} is included in the secondary jump table,
|
|
and the @code{.word} directives are adjusted to contain @code{sym3}
|
|
minus the address of the long-jump to @code{sym4}; and so on, for as many
|
|
entries in the original jump table as necessary.
|
|
|
|
@ifset INTERNALS
|
|
@emph{This feature may be disabled by compiling @code{@value{AS}} with the
|
|
@samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
|
|
assembly language programmers.
|
|
@end ifset
|
|
@end ifset
|
|
@c end DIFF-TBL-KLUGE
|
|
|
|
@node Deprecated
|
|
@section Deprecated Directives
|
|
|
|
@cindex deprecated directives
|
|
@cindex obsolescent directives
|
|
One day these directives won't work.
|
|
They are included for compatibility with older assemblers.
|
|
@table @t
|
|
@item .abort
|
|
@item .line
|
|
@end table
|
|
|
|
@ifset GENERIC
|
|
@node Machine Dependencies
|
|
@chapter Machine Dependent Features
|
|
|
|
@cindex machine dependencies
|
|
The machine instruction sets are (almost by definition) different on
|
|
each machine where @code{@value{AS}} runs. Floating point representations
|
|
vary as well, and @code{@value{AS}} often supports a few additional
|
|
directives or command-line options for compatibility with other
|
|
assemblers on a particular platform. Finally, some versions of
|
|
@code{@value{AS}} support special pseudo-instructions for branch
|
|
optimization.
|
|
|
|
This chapter discusses most of these differences, though it does not
|
|
include details on any machine's instruction set. For details on that
|
|
subject, see the hardware manufacturer's manual.
|
|
|
|
@menu
|
|
@ifset A29K
|
|
* AMD29K-Dependent:: AMD 29K Dependent Features
|
|
@end ifset
|
|
@ifset ARC
|
|
* ARC-Dependent:: ARC Dependent Features
|
|
@end ifset
|
|
@ifset ARM
|
|
* ARM-Dependent:: ARM Dependent Features
|
|
@end ifset
|
|
@ifset D10V
|
|
* D10V-Dependent:: D10V Dependent Features
|
|
@end ifset
|
|
@ifset D30V
|
|
* D30V-Dependent:: D30V Dependent Features
|
|
@end ifset
|
|
@ifset H8/300
|
|
* H8/300-Dependent:: Hitachi H8/300 Dependent Features
|
|
@end ifset
|
|
@ifset H8/500
|
|
* H8/500-Dependent:: Hitachi H8/500 Dependent Features
|
|
@end ifset
|
|
@ifset HPPA
|
|
* HPPA-Dependent:: HPPA Dependent Features
|
|
@end ifset
|
|
@ifset I370
|
|
* ESA/390-Dependent:: IBM ESA/390 Dependent Features
|
|
@end ifset
|
|
@ifset I80386
|
|
* i386-Dependent:: Intel 80386 Dependent Features
|
|
@end ifset
|
|
@ifset I960
|
|
* i960-Dependent:: Intel 80960 Dependent Features
|
|
@end ifset
|
|
@ifset M680X0
|
|
* M68K-Dependent:: M680x0 Dependent Features
|
|
@end ifset
|
|
@ifset MIPS
|
|
* MIPS-Dependent:: MIPS Dependent Features
|
|
@end ifset
|
|
@ifset SH
|
|
* SH-Dependent:: Hitachi SH Dependent Features
|
|
@end ifset
|
|
@ifset PJ
|
|
* PJ-Dependent:: picoJava Dependent Features
|
|
@end ifset
|
|
@ifset SPARC
|
|
* Sparc-Dependent:: SPARC Dependent Features
|
|
@end ifset
|
|
@ifset V850
|
|
* V850-Dependent:: V850 Dependent Features
|
|
@end ifset
|
|
@ifset Z8000
|
|
* Z8000-Dependent:: Z8000 Dependent Features
|
|
@end ifset
|
|
@ifset VAX
|
|
* Vax-Dependent:: VAX Dependent Features
|
|
@end ifset
|
|
@end menu
|
|
|
|
@lowersections
|
|
@end ifset
|
|
|
|
@c The following major nodes are *sections* in the GENERIC version, *chapters*
|
|
@c in single-cpu versions. This is mainly achieved by @lowersections. There is a
|
|
@c peculiarity: to preserve cross-references, there must be a node called
|
|
@c "Machine Dependencies". Hence the conditional nodenames in each
|
|
@c major node below. Node defaulting in makeinfo requires adjacency of
|
|
@c node and sectioning commands; hence the repetition of @chapter BLAH
|
|
@c in both conditional blocks.
|
|
|
|
@ifset ARC
|
|
@ifset GENERIC
|
|
@page
|
|
@node ARC-Dependent
|
|
@chapter ARC Dependent Features
|
|
@end ifset
|
|
@ifclear GENERIC
|
|
@node Machine Dependencies
|
|
@chapter ARC Dependent Features
|
|
@end ifclear
|
|
|
|
@cindex ARC support
|
|
@menu
|
|
* ARC-Opts:: Options
|
|
* ARC-Float:: Floating Point
|
|
* ARC-Directives:: Sparc Machine Directives
|
|
@end menu
|
|
|
|
@node ARC-Opts
|
|
@section Options
|
|
|
|
@cindex options for ARC
|
|
@cindex ARC options
|
|
@cindex architectures, ARC
|
|
@cindex ARC architectures
|
|
The ARC chip family includes several successive levels (or other
|
|
variants) of chip, using the same core instruction set, but including
|
|
a few additional instructions at each level.
|
|
|
|
By default, @code{@value{AS}} assumes the core instruction set (ARC
|
|
base). The @code{.cpu} pseudo-op is intended to be used to select
|
|
the variant.
|
|
|
|
@table @code
|
|
@cindex @code{-mbig-endian} option (ARC)
|
|
@cindex @code{-mlittle-endian} option (ARC)
|
|
@cindex ARC big-endian output
|
|
@cindex ARC little-endian output
|
|
@cindex big-endian output, ARC
|
|
@cindex little-endian output, ARC
|
|
@item -mbig-endian
|
|
@itemx -mlittle-endian
|
|
Any @sc{arc} configuration of @code{@value{AS}} can select big-endian or
|
|
little-endian output at run time (unlike most other @sc{gnu} development
|
|
tools, which must be configured for one or the other). Use
|
|
@samp{-mbig-endian} to select big-endian output, and @samp{-mlittle-endian}
|
|
for little-endian.
|
|
@end table
|
|
|
|
@node ARC-Float
|
|
@section Floating Point
|
|
|
|
@cindex floating point, ARC (@sc{ieee})
|
|
@cindex ARC floating point (@sc{ieee})
|
|
The ARC cpu family currently does not have hardware floating point
|
|
support. Software floating point support is provided by @code{GCC}
|
|
and uses @sc{ieee} floating-point numbers.
|
|
|
|
@node ARC-Directives
|
|
@section ARC Machine Directives
|
|
|
|
@cindex ARC machine directives
|
|
@cindex machine directives, ARC
|
|
The ARC version of @code{@value{AS}} supports the following additional
|
|
machine directives:
|
|
|
|
@table @code
|
|
@item .cpu
|
|
@cindex @code{cpu} directive, SPARC
|
|
This must be followed by the desired cpu.
|
|
The ARC is intended to be customizable, @code{.cpu} is used to
|
|
select the desired variant [though currently there are none].
|
|
|
|
@end table
|
|
|
|
@end ifset
|
|
|
|
@ifset A29K
|
|
@include c-a29k.texi
|
|
@end ifset
|
|
|
|
@ifset ARM
|
|
@include c-arm.texi
|
|
@end ifset
|
|
|
|
@ifset Hitachi-all
|
|
@ifclear GENERIC
|
|
@node Machine Dependencies
|
|
@chapter Machine Dependent Features
|
|
|
|
The machine instruction sets are different on each Hitachi chip family,
|
|
and there are also some syntax differences among the families. This
|
|
chapter describes the specific @code{@value{AS}} features for each
|
|
family.
|
|
|
|
@menu
|
|
* H8/300-Dependent:: Hitachi H8/300 Dependent Features
|
|
* H8/500-Dependent:: Hitachi H8/500 Dependent Features
|
|
* SH-Dependent:: Hitachi SH Dependent Features
|
|
@end menu
|
|
@lowersections
|
|
@end ifclear
|
|
@end ifset
|
|
|
|
@ifset D10V
|
|
@include c-d10v.texi
|
|
@end ifset
|
|
|
|
@ifset D30V
|
|
@include c-d30v.texi
|
|
@end ifset
|
|
|
|
@ifset H8/300
|
|
@include c-h8300.texi
|
|
@end ifset
|
|
|
|
@ifset H8/500
|
|
@include c-h8500.texi
|
|
@end ifset
|
|
|
|
@ifset HPPA
|
|
@include c-hppa.texi
|
|
@end ifset
|
|
|
|
@ifset I370
|
|
@include c-i370.texi
|
|
@end ifset
|
|
|
|
@ifset I80386
|
|
@include c-i386.texi
|
|
@end ifset
|
|
|
|
@ifset I960
|
|
@include c-i960.texi
|
|
@end ifset
|
|
|
|
|
|
@ifset M680X0
|
|
@include c-m68k.texi
|
|
@end ifset
|
|
|
|
@ifset MIPS
|
|
@include c-mips.texi
|
|
@end ifset
|
|
|
|
@ifset NS32K
|
|
@include c-ns32k.texi
|
|
@end ifset
|
|
|
|
@ifset PJ
|
|
@include c-pj.texi
|
|
@end ifset
|
|
|
|
@ifset SH
|
|
@include c-sh.texi
|
|
@end ifset
|
|
|
|
@ifset SPARC
|
|
@include c-sparc.texi
|
|
@end ifset
|
|
|
|
@ifset Z8000
|
|
@include c-z8k.texi
|
|
@end ifset
|
|
|
|
@ifset VAX
|
|
@include c-vax.texi
|
|
@end ifset
|
|
|
|
@ifset V850
|
|
@include c-v850.texi
|
|
@end ifset
|
|
|
|
@ifset GENERIC
|
|
@c reverse effect of @down at top of generic Machine-Dep chapter
|
|
@raisesections
|
|
@end ifset
|
|
|
|
@node Reporting Bugs
|
|
@chapter Reporting Bugs
|
|
@cindex bugs in assembler
|
|
@cindex reporting bugs in assembler
|
|
|
|
Your bug reports play an essential role in making @code{@value{AS}} reliable.
|
|
|
|
Reporting a bug may help you by bringing a solution to your problem, or it may
|
|
not. But in any case the principal function of a bug report is to help the
|
|
entire community by making the next version of @code{@value{AS}} work better.
|
|
Bug reports are your contribution to the maintenance of @code{@value{AS}}.
|
|
|
|
In order for a bug report to serve its purpose, you must include the
|
|
information that enables us to fix the bug.
|
|
|
|
@menu
|
|
* Bug Criteria:: Have you found a bug?
|
|
* Bug Reporting:: How to report bugs
|
|
@end menu
|
|
|
|
@node Bug Criteria
|
|
@section Have you found a bug?
|
|
@cindex bug criteria
|
|
|
|
If you are not sure whether you have found a bug, here are some guidelines:
|
|
|
|
@itemize @bullet
|
|
@cindex fatal signal
|
|
@cindex assembler crash
|
|
@cindex crash of assembler
|
|
@item
|
|
If the assembler gets a fatal signal, for any input whatever, that is a
|
|
@code{@value{AS}} bug. Reliable assemblers never crash.
|
|
|
|
@cindex error on valid input
|
|
@item
|
|
If @code{@value{AS}} produces an error message for valid input, that is a bug.
|
|
|
|
@cindex invalid input
|
|
@item
|
|
If @code{@value{AS}} does not produce an error message for invalid input, that
|
|
is a bug. However, you should note that your idea of ``invalid input'' might
|
|
be our idea of ``an extension'' or ``support for traditional practice''.
|
|
|
|
@item
|
|
If you are an experienced user of assemblers, your suggestions for improvement
|
|
of @code{@value{AS}} are welcome in any case.
|
|
@end itemize
|
|
|
|
@node Bug Reporting
|
|
@section How to report bugs
|
|
@cindex bug reports
|
|
@cindex assembler bugs, reporting
|
|
|
|
A number of companies and individuals offer support for @sc{gnu} products. If
|
|
you obtained @code{@value{AS}} from a support organization, we recommend you
|
|
contact that organization first.
|
|
|
|
You can find contact information for many support companies and
|
|
individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
|
|
distribution.
|
|
|
|
In any event, we also recommend that you send bug reports for @code{@value{AS}}
|
|
to @samp{bug-gnu-utils@@gnu.org}.
|
|
|
|
The fundamental principle of reporting bugs usefully is this:
|
|
@strong{report all the facts}. If you are not sure whether to state a
|
|
fact or leave it out, state it!
|
|
|
|
Often people omit facts because they think they know what causes the problem
|
|
and assume that some details do not matter. Thus, you might assume that the
|
|
name of a symbol you use in an example does not matter. Well, probably it does
|
|
not, but one cannot be sure. Perhaps the bug is a stray memory reference which
|
|
happens to fetch from the location where that name is stored in memory;
|
|
perhaps, if the name were different, the contents of that location would fool
|
|
the assembler into doing the right thing despite the bug. Play it safe and
|
|
give a specific, complete example. That is the easiest thing for you to do,
|
|
and the most helpful.
|
|
|
|
Keep in mind that the purpose of a bug report is to enable us to fix the bug if
|
|
it is new to us. Therefore, always write your bug reports on the assumption
|
|
that the bug has not been reported previously.
|
|
|
|
Sometimes people give a few sketchy facts and ask, ``Does this ring a
|
|
bell?'' Those bug reports are useless, and we urge everyone to
|
|
@emph{refuse to respond to them} except to chide the sender to report
|
|
bugs properly.
|
|
|
|
To enable us to fix the bug, you should include all these things:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
The version of @code{@value{AS}}. @code{@value{AS}} announces it if you start
|
|
it with the @samp{--version} argument.
|
|
|
|
Without this, we will not know whether there is any point in looking for
|
|
the bug in the current version of @code{@value{AS}}.
|
|
|
|
@item
|
|
Any patches you may have applied to the @code{@value{AS}} source.
|
|
|
|
@item
|
|
The type of machine you are using, and the operating system name and
|
|
version number.
|
|
|
|
@item
|
|
What compiler (and its version) was used to compile @code{@value{AS}}---e.g.
|
|
``@code{gcc-2.7}''.
|
|
|
|
@item
|
|
The command arguments you gave the assembler to assemble your example and
|
|
observe the bug. To guarantee you will not omit something important, list them
|
|
all. A copy of the Makefile (or the output from make) is sufficient.
|
|
|
|
If we were to try to guess the arguments, we would probably guess wrong
|
|
and then we might not encounter the bug.
|
|
|
|
@item
|
|
A complete input file that will reproduce the bug. If the bug is observed when
|
|
the assembler is invoked via a compiler, send the assembler source, not the
|
|
high level language source. Most compilers will produce the assembler source
|
|
when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
|
|
the options @samp{-v --save-temps}; this will save the assembler source in a
|
|
file with an extension of @file{.s}, and also show you exactly how
|
|
@code{@value{AS}} is being run.
|
|
|
|
@item
|
|
A description of what behavior you observe that you believe is
|
|
incorrect. For example, ``It gets a fatal signal.''
|
|
|
|
Of course, if the bug is that @code{@value{AS}} gets a fatal signal, then we
|
|
will certainly notice it. But if the bug is incorrect output, we might not
|
|
notice unless it is glaringly wrong. You might as well not give us a chance to
|
|
make a mistake.
|
|
|
|
Even if the problem you experience is a fatal signal, you should still say so
|
|
explicitly. Suppose something strange is going on, such as, your copy of
|
|
@code{@value{AS}} is out of synch, or you have encountered a bug in the C
|
|
library on your system. (This has happened!) Your copy might crash and ours
|
|
would not. If you told us to expect a crash, then when ours fails to crash, we
|
|
would know that the bug was not happening for us. If you had not told us to
|
|
expect a crash, then we would not be able to draw any conclusion from our
|
|
observations.
|
|
|
|
@item
|
|
If you wish to suggest changes to the @code{@value{AS}} source, send us context
|
|
diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
|
|
option. Always send diffs from the old file to the new file. If you even
|
|
discuss something in the @code{@value{AS}} source, refer to it by context, not
|
|
by line number.
|
|
|
|
The line numbers in our development sources will not match those in your
|
|
sources. Your line numbers would convey no useful information to us.
|
|
@end itemize
|
|
|
|
Here are some things that are not necessary:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
A description of the envelope of the bug.
|
|
|
|
Often people who encounter a bug spend a lot of time investigating
|
|
which changes to the input file will make the bug go away and which
|
|
changes will not affect it.
|
|
|
|
This is often time consuming and not very useful, because the way we
|
|
will find the bug is by running a single example under the debugger
|
|
with breakpoints, not by pure deduction from a series of examples.
|
|
We recommend that you save your time for something else.
|
|
|
|
Of course, if you can find a simpler example to report @emph{instead}
|
|
of the original one, that is a convenience for us. Errors in the
|
|
output will be easier to spot, running under the debugger will take
|
|
less time, and so on.
|
|
|
|
However, simplification is not vital; if you do not want to do this,
|
|
report the bug anyway and send us the entire test case you used.
|
|
|
|
@item
|
|
A patch for the bug.
|
|
|
|
A patch for the bug does help us if it is a good one. But do not omit
|
|
the necessary information, such as the test case, on the assumption that
|
|
a patch is all we need. We might see problems with your patch and decide
|
|
to fix the problem another way, or we might not understand it at all.
|
|
|
|
Sometimes with a program as complicated as @code{@value{AS}} it is very hard to
|
|
construct an example that will make the program follow a certain path through
|
|
the code. If you do not send us the example, we will not be able to construct
|
|
one, so we will not be able to verify that the bug is fixed.
|
|
|
|
And if we cannot understand what bug you are trying to fix, or why your
|
|
patch should be an improvement, we will not install it. A test case will
|
|
help us to understand.
|
|
|
|
@item
|
|
A guess about what the bug is or what it depends on.
|
|
|
|
Such guesses are usually wrong. Even we cannot guess right about such
|
|
things without first using the debugger to find the facts.
|
|
@end itemize
|
|
|
|
@node Acknowledgements
|
|
@chapter Acknowledgements
|
|
|
|
If you have contributed to @code{@value{AS}} and your name isn't listed here,
|
|
it is not meant as a slight. We just don't know about it. Send mail to the
|
|
maintainer, and we'll correct the situation. Currently
|
|
@c (January 1994),
|
|
the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
|
|
|
|
Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
|
|
more details?}
|
|
|
|
Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
|
|
information and the 68k series machines, most of the preprocessing pass, and
|
|
extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
|
|
|
|
K. Richard Pixley maintained GAS for a while, adding various enhancements and
|
|
many bug fixes, including merging support for several processors, breaking GAS
|
|
up to handle multiple object file format back ends (including heavy rewrite,
|
|
testing, an integration of the coff and b.out back ends), adding configuration
|
|
including heavy testing and verification of cross assemblers and file splits
|
|
and renaming, converted GAS to strictly ANSI C including full prototypes, added
|
|
support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
|
|
port (including considerable amounts of reverse engineering), a SPARC opcode
|
|
file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
|
|
assertions and made them work, much other reorganization, cleanup, and lint.
|
|
|
|
Ken Raeburn wrote the high-level BFD interface code to replace most of the code
|
|
in format-specific I/O modules.
|
|
|
|
The original VMS support was contributed by David L. Kashtan. Eric Youngdale
|
|
has done much work with it since.
|
|
|
|
The Intel 80386 machine description was written by Eliot Dresselhaus.
|
|
|
|
Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
|
|
|
|
The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
|
|
University and Torbjorn Granlund of the Swedish Institute of Computer Science.
|
|
|
|
Keith Knowles at the Open Software Foundation wrote the original MIPS back end
|
|
(@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
|
|
(which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
|
|
support a.out format.
|
|
|
|
Support for the Zilog Z8k and Hitachi H8/300 and H8/500 processors (tc-z8k,
|
|
tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by
|
|
Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
|
|
use BFD for some low-level operations, for use with the H8/300 and AMD 29k
|
|
targets.
|
|
|
|
John Gilmore built the AMD 29000 support, added @code{.include} support, and
|
|
simplified the configuration of which versions accept which directives. He
|
|
updated the 68k machine description so that Motorola's opcodes always produced
|
|
fixed-size instructions (e.g. @code{jsr}), while synthetic instructions
|
|
remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
|
|
cross-compilation support, and one bug in relaxation that took a week and
|
|
required the proverbial one-bit fix.
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|
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|
Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
|
|
68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
|
|
added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
|
|
PowerPC assembler, and made a few other minor patches.
|
|
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|
Steve Chamberlain made @code{@value{AS}} able to generate listings.
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|
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|
Hewlett-Packard contributed support for the HP9000/300.
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|
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Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
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|
along with a fairly extensive HPPA testsuite (for both SOM and ELF object
|
|
formats). This work was supported by both the Center for Software Science at
|
|
the University of Utah and Cygnus Support.
|
|
|
|
Support for ELF format files has been worked on by Mark Eichin of Cygnus
|
|
Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
|
|
Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
|
|
Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
|
|
and some initial 64-bit support).
|
|
|
|
Linas Vepstas added GAS support for the ESA/390 "IBM 370" architecture.
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|
|
|
Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
|
|
support for openVMS/Alpha.
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|
|
|
Several engineers at Cygnus Support have also provided many small bug fixes and
|
|
configuration enhancements.
|
|
|
|
Many others have contributed large or small bugfixes and enhancements. If
|
|
you have contributed significant work and are not mentioned on this list, and
|
|
want to be, let us know. Some of the history has been lost; we are not
|
|
intentionally leaving anyone out.
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|
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|
@node Index
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|
@unnumbered Index
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|
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|
@printindex cp
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|
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|
@contents
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|
@bye
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|
@c Local Variables:
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@c fill-column: 79
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@c End:
|