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<title>Using as: Density Instructions</title>

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Next: <a href="Xtensa-Automatic-Alignment.html#Xtensa-Automatic-Alignment" accesskey="n" rel="next">Xtensa Automatic Alignment</a>, Up: <a href="Xtensa-Optimizations.html#Xtensa-Optimizations" accesskey="u" rel="up">Xtensa Optimizations</a> &nbsp; [<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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<a name="Using-Density-Instructions"></a>
<h4 class="subsubsection">9.53.3.1 Using Density Instructions</h4>
<a name="index-density-instructions"></a>

<p>The Xtensa instruction set has a code density option that provides
16-bit versions of some of the most commonly used opcodes.  Use of these
opcodes can significantly reduce code size.  When possible, the
assembler automatically translates instructions from the core
Xtensa instruction set into equivalent instructions from the Xtensa code
density option.  This translation can be disabled by using underscore
prefixes (see <a href="Xtensa-Opcodes.html#Xtensa-Opcodes">Opcode Names</a>), by using the
&lsquo;<samp>--no-transform</samp>&rsquo; command-line option (see <a href="Xtensa-Options.html#Xtensa-Options">Command
Line Options</a>), or by using the <code>no-transform</code> directive
(see <a href="Transform-Directive.html#Transform-Directive">transform</a>).
</p>
<p>It is a good idea <em>not</em> to use the density instructions directly.
The assembler will automatically select dense instructions where
possible.  If you later need to use an Xtensa processor without the code
density option, the same assembly code will then work without modification.
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