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102 lines
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HTML
102 lines
4.1 KiB
HTML
<!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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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>ARM-Instruction-Set (Using as)</title>
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<meta name="description" content="ARM-Instruction-Set (Using as)">
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<meta name="keywords" content="ARM-Instruction-Set (Using as)">
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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="ARM-Syntax.html#ARM-Syntax" rel="up" title="ARM Syntax">
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<link href="ARM_002dChars.html#ARM_002dChars" rel="next" title="ARM-Chars">
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<link href="ARM-Syntax.html#ARM-Syntax" rel="prev" title="ARM Syntax">
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</head>
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<body lang="en">
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<a name="ARM_002dInstruction_002dSet"></a>
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<div class="header">
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<p>
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Next: <a href="ARM_002dChars.html#ARM_002dChars" accesskey="n" rel="next">ARM-Chars</a>, Up: <a href="ARM-Syntax.html#ARM-Syntax" accesskey="u" rel="up">ARM Syntax</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="Instruction-Set-Syntax"></a>
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<h4 class="subsubsection">9.4.2.1 Instruction Set Syntax</h4>
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<p>Two slightly different syntaxes are support for ARM and THUMB
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instructions. The default, <code>divided</code>, uses the old style where
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ARM and THUMB instructions had their own, separate syntaxes. The new,
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<code>unified</code> syntax, which can be selected via the <code>.syntax</code>
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directive, and has the following main features:
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</p>
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<ul>
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<li> Immediate operands do not require a <code>#</code> prefix.
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</li><li> The <code>IT</code> instruction may appear, and if it does it is validated
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against subsequent conditional affixes. In ARM mode it does not
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generate machine code, in THUMB mode it does.
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</li><li> For ARM instructions the conditional affixes always appear at the end
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of the instruction. For THUMB instructions conditional affixes can be
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used, but only inside the scope of an <code>IT</code> instruction.
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</li><li> All of the instructions new to the V6T2 architecture (and later) are
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available. (Only a few such instructions can be written in the
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<code>divided</code> syntax).
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</li><li> The <code>.N</code> and <code>.W</code> suffixes are recognized and honored.
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</li><li> All instructions set the flags if and only if they have an <code>s</code>
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affix.
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</li></ul>
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</body>
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</html>
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