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96 lines
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HTML
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<title>Xtensa Syntax - Using as</title>
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<!--
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This file documents the GNU Assembler "as".
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Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002,
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2006, 2007 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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<div class="node">
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<p>
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<a name="Xtensa-Syntax"></a>Next: <a rel="next" accesskey="n" href="Xtensa-Optimizations.html#Xtensa-Optimizations">Xtensa Optimizations</a>,
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Previous: <a rel="previous" accesskey="p" href="Xtensa-Options.html#Xtensa-Options">Xtensa Options</a>,
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Up: <a rel="up" accesskey="u" href="Xtensa_002dDependent.html#Xtensa_002dDependent">Xtensa-Dependent</a>
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<hr><br>
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<h4 class="subsection">9.36.2 Assembler Syntax</h4>
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<p><a name="index-syntax_002c-Xtensa-assembler-1848"></a><a name="index-Xtensa-assembler-syntax-1849"></a><a name="index-FLIX-syntax-1850"></a>
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Block comments are delimited by <span class="samp">/*</span> and <span class="samp">*/</span>. End of line
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comments may be introduced with either <span class="samp">#</span> or <span class="samp">//</span>.
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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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<pre class="smallexample"> <var>opcode</var> [<var>operand</var>, ...]
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</pre>
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<p>Instructions must be separated by a newline or semicolon.
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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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<pre class="smallexample"> {
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[<var>format</var>]
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<var>opcode0</var> [<var>operands</var>]
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<var>opcode1</var> [<var>operands</var>]
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<var>opcode2</var> [<var>operands</var>]
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...
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}
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</pre>
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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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<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>
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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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<ul class="menu">
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<li><a accesskey="1" href="Xtensa-Opcodes.html#Xtensa-Opcodes">Xtensa Opcodes</a>: Opcode Naming Conventions.
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<li><a accesskey="2" href="Xtensa-Registers.html#Xtensa-Registers">Xtensa Registers</a>: Register Naming.
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</ul>
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