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Next: <a href="Code-Iterators.html#Code-Iterators" accesskey="n" rel="next">Code Iterators</a>, Up: <a href="Iterators.html#Iterators" accesskey="u" rel="up">Iterators</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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<a name="Mode-Iterators-1"></a>
<h4 class="subsection">17.23.1 Mode Iterators</h4>
<a name="index-mode-iterators-in-_002emd-files"></a>

<p>Ports often need to define similar patterns for two or more different modes.
For example:
</p>
<ul>
<li> If a processor has hardware support for both single and double
floating-point arithmetic, the <code>SFmode</code> patterns tend to be
very similar to the <code>DFmode</code> ones.

</li><li> If a port uses <code>SImode</code> pointers in one configuration and
<code>DImode</code> pointers in another, it will usually have very similar
<code>SImode</code> and <code>DImode</code> patterns for manipulating pointers.
</li></ul>

<p>Mode iterators allow several patterns to be instantiated from one
<samp>.md</samp> file template.  They can be used with any type of
rtx-based construct, such as a <code>define_insn</code>,
<code>define_split</code>, or <code>define_peephole2</code>.
</p>
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<tr><td align="left" valign="top">&bull; <a href="Defining-Mode-Iterators.html#Defining-Mode-Iterators" accesskey="1">Defining Mode Iterators</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Defining a new mode iterator.
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<tr><td align="left" valign="top">&bull; <a href="Substitutions.html#Substitutions" accesskey="2">Substitutions</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Combining mode iterators with substitutions
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<tr><td align="left" valign="top">&bull; <a href="Examples.html#Examples" accesskey="3">Examples</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Examples
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