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| Next: <a href="Substitutions.html#Substitutions" accesskey="n" rel="next">Substitutions</a>, Up: <a href="Mode-Iterators.html#Mode-Iterators" accesskey="u" rel="up">Mode Iterators</a> [<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="Defining-Mode-Iterators-1"></a> |
| <h4 class="subsubsection">16.23.1.1 Defining Mode Iterators</h4> |
| <a name="index-define_005fmode_005fiterator"></a> |
| |
| <p>The syntax for defining a mode iterator is: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">(define_mode_iterator <var>name</var> [(<var>mode1</var> "<var>cond1</var>") … (<var>moden</var> "<var>condn</var>")]) |
| </pre></div> |
| |
| <p>This allows subsequent <samp>.md</samp> file constructs to use the mode suffix |
| <code>:<var>name</var></code>. Every construct that does so will be expanded |
| <var>n</var> times, once with every use of <code>:<var>name</var></code> replaced by |
| <code>:<var>mode1</var></code>, once with every use replaced by <code>:<var>mode2</var></code>, |
| and so on. In the expansion for a particular <var>modei</var>, every |
| C condition will also require that <var>condi</var> be true. |
| </p> |
| <p>For example: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">(define_mode_iterator P [(SI "Pmode == SImode") (DI "Pmode == DImode")]) |
| </pre></div> |
| |
| <p>defines a new mode suffix <code>:P</code>. Every construct that uses |
| <code>:P</code> will be expanded twice, once with every <code>:P</code> replaced |
| by <code>:SI</code> and once with every <code>:P</code> replaced by <code>:DI</code>. |
| The <code>:SI</code> version will only apply if <code>Pmode == SImode</code> and |
| the <code>:DI</code> version will only apply if <code>Pmode == DImode</code>. |
| </p> |
| <p>As with other <samp>.md</samp> conditions, an empty string is treated |
| as “always true”. <code>(<var>mode</var> "")</code> can also be abbreviated |
| to <code><var>mode</var></code>. For example: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">(define_mode_iterator GPR [SI (DI "TARGET_64BIT")]) |
| </pre></div> |
| |
| <p>means that the <code>:DI</code> expansion only applies if <code>TARGET_64BIT</code> |
| but that the <code>:SI</code> expansion has no such constraint. |
| </p> |
| <p>Iterators are applied in the order they are defined. This can be |
| significant if two iterators are used in a construct that requires |
| substitutions. See <a href="Substitutions.html#Substitutions">Substitutions</a>. |
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