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<h5 class="subsubsection">9.42.2.2 Register Names</h5>

<p><a name="index-Xtensa-register-names-2015"></a><a name="index-register-names_002c-Xtensa-2016"></a><a name="index-sp-register-2017"></a>
The assembly syntax for a register file entry is the &ldquo;short&rdquo; name for
a TIE register file followed by the index into that register file.  For
example, the general-purpose <code>AR</code> register file has a short name of
<code>a</code>, so these registers are named <code>a0</code><small class="dots">...</small><code>a15</code>. 
As a special feature, <code>sp</code> is also supported as a synonym for
<code>a1</code>.  Additional registers may be added by processor configuration
options and by designer-defined TIE extensions.  An initial &lsquo;<samp><span class="samp">$</span></samp>&rsquo;
character is optional in all register names.

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