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<h4 class="subsection">9.24.4 Directives to override the size of symbols</h4>

<p><a name="index-g_t_0040code_007b_002eset-sym32_007d-1271"></a><a name="index-g_t_0040code_007b_002eset-nosym32_007d-1272"></a>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><span class="samp">dla $4,sym</span></samp>&rsquo; is usually:

<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>
   <p>whereas the 32-bit expansion is simply:

<pre class="smallexample">     lui     $4,%hi(sym)
     daddiu  $4,$4,%lo(sym)
</pre>
   <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's
preferable to use the 32-bit expansion instead of the 64-bit
expansion.

   <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><span class="samp"> + </span><var>offset</var></samp>&rsquo;
have 32-bit values.  For example:

<pre class="smallexample">     .set sym32
     dla     $4,sym
     lw      $4,sym+16
     sw      $4,sym+0x8000($4)
</pre>
   <p>will cause the assembler to treat &lsquo;<samp><span class="samp">sym</span></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>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><span class="option">-msym32</span></samp> and
<samp><span class="option">-mno-sym32</span></samp>.

   <p>These options and directives are always accepted, but at present,
they have no effect for anything other than n64.

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