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<title>MIPS Symbol Sizes (Using as)</title>

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<a name="MIPS-Symbol-Sizes"></a>
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Next: <a href="MIPS-Small-Data.html#MIPS-Small-Data" accesskey="n" rel="next">MIPS Small Data</a>, Previous: <a href="MIPS-Macros.html#MIPS-Macros" accesskey="p" rel="prev">MIPS Macros</a>, Up: <a href="MIPS_002dDependent.html#MIPS_002dDependent" accesskey="u" rel="up">MIPS-Dependent</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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<hr>
<a name="Directives-to-override-the-size-of-symbols"></a>
<h4 class="subsection">9.27.3 Directives to override the size of symbols</h4>

<a name="index-_002eset-sym32"></a>
<a name="index-_002eset-nosym32"></a>
<p>The n64 ABI allows symbols to have any 64-bit value.  Although this
provides a great deal of flexibility, it means that some macros have
much longer expansions than their 32-bit counterparts.  For example,
the non-PIC expansion of &lsquo;<samp>dla $4,sym</samp>&rsquo; is usually:
</p>
<div class="smallexample">
<pre class="smallexample">lui     $4,%highest(sym)
lui     $1,%hi(sym)
daddiu  $4,$4,%higher(sym)
daddiu  $1,$1,%lo(sym)
dsll32  $4,$4,0
daddu   $4,$4,$1
</pre></div>

<p>whereas the 32-bit expansion is simply:
</p>
<div class="smallexample">
<pre class="smallexample">lui     $4,%hi(sym)
daddiu  $4,$4,%lo(sym)
</pre></div>

<p>n64 code is sometimes constructed in such a way that all symbolic
constants are known to have 32-bit values, and in such cases, it&rsquo;s
preferable to use the 32-bit expansion instead of the 64-bit
expansion.
</p>
<p>You can use the <code>.set sym32</code> directive to tell the assembler
that, from this point on, all expressions of the form
&lsquo;<samp><var>symbol</var></samp>&rsquo; or &lsquo;<samp><var>symbol</var> + <var>offset</var></samp>&rsquo;
have 32-bit values.  For example:
</p>
<div class="smallexample">
<pre class="smallexample">.set sym32
dla     $4,sym
lw      $4,sym+16
sw      $4,sym+0x8000($4)
</pre></div>

<p>will cause the assembler to treat &lsquo;<samp>sym</samp>&rsquo;, <code>sym+16</code> and
<code>sym+0x8000</code> as 32-bit values.  The handling of non-symbolic
addresses is not affected.
</p>
<p>The directive <code>.set nosym32</code> ends a <code>.set sym32</code> block and
reverts to the normal behavior.  It is also possible to change the
symbol size using the command-line options <samp>-msym32</samp> and
<samp>-mno-sym32</samp>.
</p>
<p>These options and directives are always accepted, but at present,
they have no effect for anything other than n64.
</p>


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