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<a name="i386_002dFloat"></a>
<div class="header">
<p>
Next: <a href="i386_002dSIMD.html#i386_002dSIMD" accesskey="n" rel="next">i386-SIMD</a>, Previous: <a href="i386_002dJumps.html#i386_002dJumps" accesskey="p" rel="prev">i386-Jumps</a>, Up: <a href="i386_002dDependent.html#i386_002dDependent" accesskey="u" rel="up">i386-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>
</div>
<hr>
<a name="Floating-Point-7"></a>
<h4 class="subsection">9.16.9 Floating Point</h4>

<a name="index-i386-floating-point"></a>
<a name="index-floating-point_002c-i386"></a>
<a name="index-x86_002d64-floating-point"></a>
<a name="index-floating-point_002c-x86_002d64"></a>
<p>All 80387 floating point types except packed BCD are supported.
(BCD support may be added without much difficulty).  These data
types are 16-, 32-, and 64- bit integers, and single (32-bit),
double (64-bit), and extended (80-bit) precision floating point.
Each supported type has an instruction mnemonic suffix and a constructor
associated with it.  Instruction mnemonic suffixes specify the operand&rsquo;s
data type.  Constructors build these data types into memory.
</p>
<a name="index-float-directive_002c-i386"></a>
<a name="index-single-directive_002c-i386"></a>
<a name="index-double-directive_002c-i386"></a>
<a name="index-tfloat-directive_002c-i386"></a>
<a name="index-float-directive_002c-x86_002d64"></a>
<a name="index-single-directive_002c-x86_002d64"></a>
<a name="index-double-directive_002c-x86_002d64"></a>
<a name="index-tfloat-directive_002c-x86_002d64"></a>
<ul>
<li> Floating point constructors are &lsquo;<samp>.float</samp>&rsquo; or &lsquo;<samp>.single</samp>&rsquo;,
&lsquo;<samp>.double</samp>&rsquo;, and &lsquo;<samp>.tfloat</samp>&rsquo; for 32-, 64-, and 80-bit formats.
These correspond to instruction mnemonic suffixes &lsquo;<samp>s</samp>&rsquo;, &lsquo;<samp>l</samp>&rsquo;,
and &lsquo;<samp>t</samp>&rsquo;. &lsquo;<samp>t</samp>&rsquo; stands for 80-bit (ten byte) real.  The 80387
only supports this format via the &lsquo;<samp>fldt</samp>&rsquo; (load 80-bit real to stack
top) and &lsquo;<samp>fstpt</samp>&rsquo; (store 80-bit real and pop stack) instructions.

</li><li> <a name="index-word-directive_002c-i386"></a>
<a name="index-long-directive_002c-i386"></a>
<a name="index-int-directive_002c-i386"></a>
<a name="index-quad-directive_002c-i386"></a>
<a name="index-word-directive_002c-x86_002d64"></a>
<a name="index-long-directive_002c-x86_002d64"></a>
<a name="index-int-directive_002c-x86_002d64"></a>
<a name="index-quad-directive_002c-x86_002d64"></a>
Integer constructors are &lsquo;<samp>.word</samp>&rsquo;, &lsquo;<samp>.long</samp>&rsquo; or &lsquo;<samp>.int</samp>&rsquo;, and
&lsquo;<samp>.quad</samp>&rsquo; for the 16-, 32-, and 64-bit integer formats.  The
corresponding instruction mnemonic suffixes are &lsquo;<samp>s</samp>&rsquo; (single),
&lsquo;<samp>l</samp>&rsquo; (long), and &lsquo;<samp>q</samp>&rsquo; (quad).  As with the 80-bit real format,
the 64-bit &lsquo;<samp>q</samp>&rsquo; format is only present in the &lsquo;<samp>fildq</samp>&rsquo; (load
quad integer to stack top) and &lsquo;<samp>fistpq</samp>&rsquo; (store quad integer and pop
stack) instructions.
</li></ul>

<p>Register to register operations should not use instruction mnemonic suffixes.
&lsquo;<samp>fstl %st, %st(1)</samp>&rsquo; will give a warning, and be assembled as if you
wrote &lsquo;<samp>fst %st, %st(1)</samp>&rsquo;, since all register to register operations
use 80-bit floating point operands. (Contrast this with &lsquo;<samp>fstl %st, mem</samp>&rsquo;,
which converts &lsquo;<samp>%st</samp>&rsquo; from 80-bit to 64-bit floating point format,
then stores the result in the 4 byte location &lsquo;<samp>mem</samp>&rsquo;)
</p>
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