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184 lines
7.7 KiB
HTML
184 lines
7.7 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- This file documents the GNU Assembler "as".
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Copyright (C) 1991-2019 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, with no Front-Cover Texts, and with no
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Back-Cover Texts. A copy of the license is included in the
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section entitled "GNU Free Documentation License".
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-->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>M (Using as)</title>
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<meta name="description" content="M (Using as)">
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<meta name="keywords" content="M (Using as)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="AS-Index.html#AS-Index" rel="index" title="AS Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Invoking.html#Invoking" rel="up" title="Invoking">
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<link href="MD.html#MD" rel="next" title="MD">
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<link href="listing.html#listing" rel="prev" title="listing">
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<style type="text/css">
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<!--
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a.summary-letter {text-decoration: none}
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blockquote.indentedblock {margin-right: 0em}
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blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
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blockquote.smallquotation {font-size: smaller}
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div.display {margin-left: 3.2em}
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div.example {margin-left: 3.2em}
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div.lisp {margin-left: 3.2em}
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div.smalldisplay {margin-left: 3.2em}
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div.smallexample {margin-left: 3.2em}
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div.smalllisp {margin-left: 3.2em}
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kbd {font-style: oblique}
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pre.display {font-family: inherit}
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pre.format {font-family: inherit}
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pre.menu-comment {font-family: serif}
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pre.menu-preformatted {font-family: serif}
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pre.smalldisplay {font-family: inherit; font-size: smaller}
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pre.smallexample {font-size: smaller}
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pre.smallformat {font-family: inherit; font-size: smaller}
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pre.smalllisp {font-size: smaller}
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span.nolinebreak {white-space: nowrap}
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span.roman {font-family: initial; font-weight: normal}
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span.sansserif {font-family: sans-serif; font-weight: normal}
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ul.no-bullet {list-style: none}
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-->
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</style>
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</head>
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<body lang="en">
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<a name="M"></a>
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<div class="header">
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<p>
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Next: <a href="MD.html#MD" accesskey="n" rel="next">MD</a>, Previous: <a href="listing.html#listing" accesskey="p" rel="prev">listing</a>, Up: <a href="Invoking.html#Invoking" accesskey="u" rel="up">Invoking</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Assemble-in-MRI-Compatibility-Mode_003a-_002dM"></a>
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<h3 class="section">2.9 Assemble in MRI Compatibility Mode: <samp>-M</samp></h3>
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<a name="index-_002dM"></a>
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<a name="index-MRI-compatibility-mode"></a>
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<p>The <samp>-M</samp> or <samp>--mri</samp> option selects MRI compatibility mode. This
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changes the syntax and pseudo-op handling of <code>as</code> to make it
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compatible with the <code>ASM68K</code> assembler from Microtec Research.
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The exact nature of the
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MRI syntax will not be documented here; see the MRI manuals for more
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information. Note in particular that the handling of macros and macro
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arguments is somewhat different. The purpose of this option is to permit
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assembling existing MRI assembler code using <code>as</code>.
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</p>
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<p>The MRI compatibility is not complete. Certain operations of the MRI assembler
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depend upon its object file format, and can not be supported using other object
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file formats. Supporting these would require enhancing each object file format
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individually. These are:
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</p>
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<ul>
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<li> global symbols in common section
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<p>The m68k MRI assembler supports common sections which are merged by the linker.
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Other object file formats do not support this. <code>as</code> handles
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common sections by treating them as a single common symbol. It permits local
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symbols to be defined within a common section, but it can not support global
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symbols, since it has no way to describe them.
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</p>
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</li><li> complex relocations
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<p>The MRI assemblers support relocations against a negated section address, and
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relocations which combine the start addresses of two or more sections. These
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are not support by other object file formats.
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</p>
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</li><li> <code>END</code> pseudo-op specifying start address
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<p>The MRI <code>END</code> pseudo-op permits the specification of a start address.
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This is not supported by other object file formats. The start address may
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instead be specified using the <samp>-e</samp> option to the linker, or in a linker
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script.
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</p>
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</li><li> <code>IDNT</code>, <code>.ident</code> and <code>NAME</code> pseudo-ops
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<p>The MRI <code>IDNT</code>, <code>.ident</code> and <code>NAME</code> pseudo-ops assign a module
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name to the output file. This is not supported by other object file formats.
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</p>
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</li><li> <code>ORG</code> pseudo-op
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<p>The m68k MRI <code>ORG</code> pseudo-op begins an absolute section at a given
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address. This differs from the usual <code>as</code> <code>.org</code> pseudo-op,
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which changes the location within the current section. Absolute sections are
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not supported by other object file formats. The address of a section may be
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assigned within a linker script.
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</p></li></ul>
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<p>There are some other features of the MRI assembler which are not supported by
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<code>as</code>, typically either because they are difficult or because they
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seem of little consequence. Some of these may be supported in future releases.
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</p>
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<ul>
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<li> EBCDIC strings
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<p>EBCDIC strings are not supported.
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</p>
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</li><li> packed binary coded decimal
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<p>Packed binary coded decimal is not supported. This means that the <code>DC.P</code>
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and <code>DCB.P</code> pseudo-ops are not supported.
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</p>
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</li><li> <code>FEQU</code> pseudo-op
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<p>The m68k <code>FEQU</code> pseudo-op is not supported.
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</p>
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</li><li> <code>NOOBJ</code> pseudo-op
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<p>The m68k <code>NOOBJ</code> pseudo-op is not supported.
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</p>
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</li><li> <code>OPT</code> branch control options
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<p>The m68k <code>OPT</code> branch control options—<code>B</code>, <code>BRS</code>, <code>BRB</code>,
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<code>BRL</code>, and <code>BRW</code>—are ignored. <code>as</code> automatically
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relaxes all branches, whether forward or backward, to an appropriate size, so
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these options serve no purpose.
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</p>
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</li><li> <code>OPT</code> list control options
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<p>The following m68k <code>OPT</code> list control options are ignored: <code>C</code>,
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<code>CEX</code>, <code>CL</code>, <code>CRE</code>, <code>E</code>, <code>G</code>, <code>I</code>, <code>M</code>,
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<code>MEX</code>, <code>MC</code>, <code>MD</code>, <code>X</code>.
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</p>
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</li><li> other <code>OPT</code> options
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<p>The following m68k <code>OPT</code> options are ignored: <code>NEST</code>, <code>O</code>,
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<code>OLD</code>, <code>OP</code>, <code>P</code>, <code>PCO</code>, <code>PCR</code>, <code>PCS</code>, <code>R</code>.
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</p>
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</li><li> <code>OPT</code> <code>D</code> option is default
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<p>The m68k <code>OPT</code> <code>D</code> option is the default, unlike the MRI assembler.
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<code>OPT NOD</code> may be used to turn it off.
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</p>
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</li><li> <code>XREF</code> pseudo-op.
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<p>The m68k <code>XREF</code> pseudo-op is ignored.
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</p>
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</li></ul>
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<hr>
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<div class="header">
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<p>
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Next: <a href="MD.html#MD" accesskey="n" rel="next">MD</a>, Previous: <a href="listing.html#listing" accesskey="p" rel="prev">listing</a>, Up: <a href="Invoking.html#Invoking" accesskey="u" rel="up">Invoking</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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</html>
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