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

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  25. <title>RTL (GNU Compiler Collection (GCC) Internals)</title>

  26. 

  27. <meta name="description" content="RTL (GNU Compiler Collection (GCC) Internals)">

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  35. <link href="index.html#Top" rel="up" title="Top">

  36. <link href="RTL-Objects.html#RTL-Objects" rel="next" title="RTL Objects">

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  69. <body lang="en">

  70. <a name="RTL"></a>

  71. <div class="header">

  72. <p>

  73. Next: <a href="Control-Flow.html#Control-Flow" accesskey="n" rel="next">Control Flow</a>, Previous: <a href="Tree-SSA.html#Tree-SSA" accesskey="p" rel="prev">Tree SSA</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>

  74. </div>

  75. <hr>

  76. <a name="RTL-Representation"></a>

  77. <h2 class="chapter">14 RTL Representation</h2>

  78. <a name="index-RTL-representation"></a>

  79. <a name="index-representation-of-RTL"></a>

  80. <a name="index-Register-Transfer-Language-_0028RTL_0029"></a>

  81. 

  82. <p>The last part of the compiler work is done on a low-level intermediate

  83. representation called Register Transfer Language.  In this language, the

  84. instructions to be output are described, pretty much one by one, in an

  85. algebraic form that describes what the instruction does.

  86. </p>

  87. <p>RTL is inspired by Lisp lists.  It has both an internal form, made up of

  88. structures that point at other structures, and a textual form that is used

  89. in the machine description and in printed debugging dumps.  The textual

  90. form uses nested parentheses to indicate the pointers in the internal form.

  91. </p>

  92. <table class="menu" border="0" cellspacing="0">

  93. <tr><td align="left" valign="top">&bull; <a href="RTL-Objects.html#RTL-Objects" accesskey="1">RTL Objects</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Expressions vs vectors vs strings vs integers.

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  95. <tr><td align="left" valign="top">&bull; <a href="RTL-Classes.html#RTL-Classes" accesskey="2">RTL Classes</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Categories of RTL expression objects, and their structure.

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  97. <tr><td align="left" valign="top">&bull; <a href="Accessors.html#Accessors" accesskey="3">Accessors</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Macros to access expression operands or vector elts.

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  101. <tr><td align="left" valign="top">&bull; <a href="Flags.html#Flags" accesskey="5">Flags</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Other flags in an RTL expression.

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  103. <tr><td align="left" valign="top">&bull; <a href="Machine-Modes.html#Machine-Modes" accesskey="6">Machine Modes</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Describing the size and format of a datum.

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  107. <tr><td align="left" valign="top">&bull; <a href="Regs-and-Memory.html#Regs-and-Memory" accesskey="8">Regs and Memory</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Expressions representing register contents or memory.

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  109. <tr><td align="left" valign="top">&bull; <a href="Arithmetic.html#Arithmetic" accesskey="9">Arithmetic</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Expressions representing arithmetic on other expressions.

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  115. <tr><td align="left" valign="top">&bull; <a href="Vector-Operations.html#Vector-Operations">Vector Operations</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Expressions involving vector datatypes.

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  121. <tr><td align="left" valign="top">&bull; <a href="Side-Effects.html#Side-Effects">Side Effects</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Expressions for storing in registers, etc.

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  123. <tr><td align="left" valign="top">&bull; <a href="Incdec.html#Incdec">Incdec</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Embedded side-effects for autoincrement addressing.

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  125. <tr><td align="left" valign="top">&bull; <a href="Assembler.html#Assembler">Assembler</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Representing <code>asm</code> with operands.

  126. </td></tr>

  127. <tr><td align="left" valign="top">&bull; <a href="Debug-Information.html#Debug-Information">Debug Information</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Expressions representing debugging information.

  128. </td></tr>

  129. <tr><td align="left" valign="top">&bull; <a href="Insns.html#Insns">Insns</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Expression types for entire insns.

  130. </td></tr>

  131. <tr><td align="left" valign="top">&bull; <a href="Calls.html#Calls">Calls</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">RTL representation of function call insns.

  132. </td></tr>

  133. <tr><td align="left" valign="top">&bull; <a href="Sharing.html#Sharing">Sharing</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Some expressions are unique; others *must* be copied.

  134. </td></tr>

  135. <tr><td align="left" valign="top">&bull; <a href="Reading-RTL.html#Reading-RTL">Reading RTL</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Reading textual RTL from a file.

  136. </td></tr>

  137. </table>

  138. 

  139. <hr>

  140. <div class="header">

  141. <p>

  142. Next: <a href="Control-Flow.html#Control-Flow" accesskey="n" rel="next">Control Flow</a>, Previous: <a href="Tree-SSA.html#Tree-SSA" accesskey="p" rel="prev">Tree SSA</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>

  143. </div>

  144. 

  145. 

  146. 

  147. </body>

  148. </html>