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  1. <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

  2. <html>

  3. <!-- This file documents the GNU Assembler "as".

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  15. <head>

  16. <meta http-equiv="Content-Type" content="text/html; charset=utf-8">

  17. <title>i386-Float (Using as)</title>

  18. 

  19. <meta name="description" content="i386-Float (Using as)">

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  25. <link href="AS-Index.html#AS-Index" rel="index" title="AS Index">

  26. <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">

  27. <link href="i386_002dDependent.html#i386_002dDependent" rel="up" title="i386-Dependent">

  28. <link href="i386_002dSIMD.html#i386_002dSIMD" rel="next" title="i386-SIMD">

  29. <link href="i386_002dJumps.html#i386_002dJumps" rel="prev" title="i386-Jumps">

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  60. 

  61. <body lang="en">

  62. <a name="i386_002dFloat"></a>

  63. <div class="header">

  64. <p>

  65. 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>

  66. </div>

  67. <hr>

  68. <a name="Floating-Point-7"></a>

  69. <h4 class="subsection">9.16.9 Floating Point</h4>

  70. 

  71. <a name="index-i386-floating-point"></a>

  72. <a name="index-floating-point_002c-i386"></a>

  73. <a name="index-x86_002d64-floating-point"></a>

  74. <a name="index-floating-point_002c-x86_002d64"></a>

  75. <p>All 80387 floating point types except packed BCD are supported.

  76. (BCD support may be added without much difficulty).  These data

  77. types are 16-, 32-, and 64- bit integers, and single (32-bit),

  78. double (64-bit), and extended (80-bit) precision floating point.

  79. Each supported type has an instruction mnemonic suffix and a constructor

  80. associated with it.  Instruction mnemonic suffixes specify the operand&rsquo;s

  81. data type.  Constructors build these data types into memory.

  82. </p>

  83. <a name="index-float-directive_002c-i386"></a>

  84. <a name="index-single-directive_002c-i386"></a>

  85. <a name="index-double-directive_002c-i386"></a>

  86. <a name="index-tfloat-directive_002c-i386"></a>

  87. <a name="index-float-directive_002c-x86_002d64"></a>

  88. <a name="index-single-directive_002c-x86_002d64"></a>

  89. <a name="index-double-directive_002c-x86_002d64"></a>

  90. <a name="index-tfloat-directive_002c-x86_002d64"></a>

  91. <ul>

  92. <li> Floating point constructors are &lsquo;<samp>.float</samp>&rsquo; or &lsquo;<samp>.single</samp>&rsquo;,

  93. &lsquo;<samp>.double</samp>&rsquo;, and &lsquo;<samp>.tfloat</samp>&rsquo; for 32-, 64-, and 80-bit formats.

  94. These correspond to instruction mnemonic suffixes &lsquo;<samp>s</samp>&rsquo;, &lsquo;<samp>l</samp>&rsquo;,

  95. and &lsquo;<samp>t</samp>&rsquo;. &lsquo;<samp>t</samp>&rsquo; stands for 80-bit (ten byte) real.  The 80387

  96. only supports this format via the &lsquo;<samp>fldt</samp>&rsquo; (load 80-bit real to stack

  97. top) and &lsquo;<samp>fstpt</samp>&rsquo; (store 80-bit real and pop stack) instructions.

  98. 

  99. </li><li> <a name="index-word-directive_002c-i386"></a>

  100. <a name="index-long-directive_002c-i386"></a>

  101. <a name="index-int-directive_002c-i386"></a>

  102. <a name="index-quad-directive_002c-i386"></a>

  103. <a name="index-word-directive_002c-x86_002d64"></a>

  104. <a name="index-long-directive_002c-x86_002d64"></a>

  105. <a name="index-int-directive_002c-x86_002d64"></a>

  106. <a name="index-quad-directive_002c-x86_002d64"></a>

  107. Integer constructors are &lsquo;<samp>.word</samp>&rsquo;, &lsquo;<samp>.long</samp>&rsquo; or &lsquo;<samp>.int</samp>&rsquo;, and

  108. &lsquo;<samp>.quad</samp>&rsquo; for the 16-, 32-, and 64-bit integer formats.  The

  109. corresponding instruction mnemonic suffixes are &lsquo;<samp>s</samp>&rsquo; (single),

  110. &lsquo;<samp>l</samp>&rsquo; (long), and &lsquo;<samp>q</samp>&rsquo; (quad).  As with the 80-bit real format,

  111. the 64-bit &lsquo;<samp>q</samp>&rsquo; format is only present in the &lsquo;<samp>fildq</samp>&rsquo; (load

  112. quad integer to stack top) and &lsquo;<samp>fistpq</samp>&rsquo; (store quad integer and pop

  113. stack) instructions.

  114. </li></ul>

  115. 

  116. <p>Register to register operations should not use instruction mnemonic suffixes.

  117. &lsquo;<samp>fstl %st, %st(1)</samp>&rsquo; will give a warning, and be assembled as if you

  118. wrote &lsquo;<samp>fst %st, %st(1)</samp>&rsquo;, since all register to register operations

  119. use 80-bit floating point operands. (Contrast this with &lsquo;<samp>fstl %st, mem</samp>&rsquo;,

  120. which converts &lsquo;<samp>%st</samp>&rsquo; from 80-bit to 64-bit floating point format,

  121. then stores the result in the 4 byte location &lsquo;<samp>mem</samp>&rsquo;)

  122. </p>

  123. <hr>

  124. <div class="header">

  125. <p>

  126. 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>

  127. </div>

  128. 

  129. 

  130. 

  131. </body>

  132. </html>