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142 lines
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142 lines
6.7 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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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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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Xtensa Syntax (Using as)</title>
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<meta name="description" content="Xtensa Syntax (Using as)">
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<meta name="keywords" content="Xtensa Syntax (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="Xtensa_002dDependent.html#Xtensa_002dDependent" rel="up" title="Xtensa-Dependent">
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<link href="Xtensa-Opcodes.html#Xtensa-Opcodes" rel="next" title="Xtensa Opcodes">
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<link href="Xtensa-Options.html#Xtensa-Options" rel="prev" title="Xtensa Options">
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</head>
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<body lang="en">
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<a name="Xtensa-Syntax"></a>
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<div class="header">
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<p>
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Next: <a href="Xtensa-Optimizations.html#Xtensa-Optimizations" accesskey="n" rel="next">Xtensa Optimizations</a>, Previous: <a href="Xtensa-Options.html#Xtensa-Options" accesskey="p" rel="prev">Xtensa Options</a>, Up: <a href="Xtensa_002dDependent.html#Xtensa_002dDependent" accesskey="u" rel="up">Xtensa-Dependent</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="Assembler-Syntax"></a>
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<h4 class="subsection">9.54.2 Assembler Syntax</h4>
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<a name="index-syntax_002c-Xtensa-assembler"></a>
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<a name="index-Xtensa-assembler-syntax"></a>
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<a name="index-FLIX-syntax"></a>
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<p>Block comments are delimited by ‘<samp>/*</samp>’ and ‘<samp>*/</samp>’. End of line
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comments may be introduced with either ‘<samp>#</samp>’ or ‘<samp>//</samp>’.
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</p>
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<p>If a ‘<samp>#</samp>’ appears as the first character of a line then the whole
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line is treated as a comment, but in this case the line could also be
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a logical line number directive (see <a href="Comments.html#Comments">Comments</a>) or a preprocessor
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control command (see <a href="Preprocessing.html#Preprocessing">Preprocessing</a>).
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</p>
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<p>Instructions consist of a leading opcode or macro name followed by
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whitespace and an optional comma-separated list of operands:
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</p>
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<div class="smallexample">
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<pre class="smallexample"><var>opcode</var> [<var>operand</var>, …]
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</pre></div>
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<p>Instructions must be separated by a newline or semicolon (‘<samp>;</samp>’).
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</p>
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<p>FLIX instructions, which bundle multiple opcodes together in a single
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instruction, are specified by enclosing the bundled opcodes inside
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braces:
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</p>
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<div class="smallexample">
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<pre class="smallexample">{
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[<var>format</var>]
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<var>opcode0</var> [<var>operands</var>]
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</pre><pre class="smallexample"><var>opcode1</var> [<var>operands</var>]
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</pre><pre class="smallexample"><var>opcode2</var> [<var>operands</var>]
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…
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}
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</pre></div>
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<p>The opcodes in a FLIX instruction are listed in the same order as the
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corresponding instruction slots in the TIE format declaration.
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Directives and labels are not allowed inside the braces of a FLIX
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instruction. A particular TIE format name can optionally be specified
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immediately after the opening brace, but this is usually unnecessary.
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The assembler will automatically search for a format that can encode the
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specified opcodes, so the format name need only be specified in rare
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cases where there is more than one applicable format and where it
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matters which of those formats is used. A FLIX instruction can also be
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specified on a single line by separating the opcodes with semicolons:
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</p>
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<div class="smallexample">
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<pre class="smallexample">{ [<var>format</var>;] <var>opcode0</var> [<var>operands</var>]; <var>opcode1</var> [<var>operands</var>]; <var>opcode2</var> [<var>operands</var>]; … }
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</pre></div>
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<p>If an opcode can only be encoded in a FLIX instruction but is not
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specified as part of a FLIX bundle, the assembler will choose the
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smallest format where the opcode can be encoded and
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will fill unused instruction slots with no-ops.
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</p>
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<table class="menu" border="0" cellspacing="0">
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<tr><td align="left" valign="top">• <a href="Xtensa-Opcodes.html#Xtensa-Opcodes" accesskey="1">Xtensa Opcodes</a>:</td><td> </td><td align="left" valign="top">Opcode Naming Conventions.
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Xtensa-Registers.html#Xtensa-Registers" accesskey="2">Xtensa Registers</a>:</td><td> </td><td align="left" valign="top">Register Naming.
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</td></tr>
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</table>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Xtensa-Optimizations.html#Xtensa-Optimizations" accesskey="n" rel="next">Xtensa Optimizations</a>, Previous: <a href="Xtensa-Options.html#Xtensa-Options" accesskey="p" rel="prev">Xtensa Options</a>, Up: <a href="Xtensa_002dDependent.html#Xtensa_002dDependent" accesskey="u" rel="up">Xtensa-Dependent</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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