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| <a name="RTL-Representation"></a> |
| <h2 class="chapter">13 RTL Representation</h2> |
| <a name="index-RTL-representation"></a> |
| <a name="index-representation-of-RTL"></a> |
| <a name="index-Register-Transfer-Language-_0028RTL_0029"></a> |
| |
| <p>The last part of the compiler work is done on a low-level intermediate |
| representation called Register Transfer Language. In this language, the |
| instructions to be output are described, pretty much one by one, in an |
| algebraic form that describes what the instruction does. |
| </p> |
| <p>RTL is inspired by Lisp lists. It has both an internal form, made up of |
| structures that point at other structures, and a textual form that is used |
| in the machine description and in printed debugging dumps. The textual |
| form uses nested parentheses to indicate the pointers in the internal form. |
| </p> |
| <table class="menu" border="0" cellspacing="0"> |
| <tr><td align="left" valign="top">• <a href="RTL-Objects.html#RTL-Objects" accesskey="1">RTL Objects</a>:</td><td> </td><td align="left" valign="top">Expressions vs vectors vs strings vs integers. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="RTL-Classes.html#RTL-Classes" accesskey="2">RTL Classes</a>:</td><td> </td><td align="left" valign="top">Categories of RTL expression objects, and their structure. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Accessors.html#Accessors" accesskey="3">Accessors</a>:</td><td> </td><td align="left" valign="top">Macros to access expression operands or vector elts. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Special-Accessors.html#Special-Accessors" accesskey="4">Special Accessors</a>:</td><td> </td><td align="left" valign="top">Macros to access specific annotations on RTL. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Flags.html#Flags" accesskey="5">Flags</a>:</td><td> </td><td align="left" valign="top">Other flags in an RTL expression. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Machine-Modes.html#Machine-Modes" accesskey="6">Machine Modes</a>:</td><td> </td><td align="left" valign="top">Describing the size and format of a datum. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Constants.html#Constants" accesskey="7">Constants</a>:</td><td> </td><td align="left" valign="top">Expressions with constant values. |
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| <tr><td align="left" valign="top">• <a href="Regs-and-Memory.html#Regs-and-Memory" accesskey="8">Regs and Memory</a>:</td><td> </td><td align="left" valign="top">Expressions representing register contents or memory. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Arithmetic.html#Arithmetic" accesskey="9">Arithmetic</a>:</td><td> </td><td align="left" valign="top">Expressions representing arithmetic on other expressions. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Comparisons.html#Comparisons">Comparisons</a>:</td><td> </td><td align="left" valign="top">Expressions representing comparison of expressions. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Bit_002dFields.html#Bit_002dFields">Bit-Fields</a>:</td><td> </td><td align="left" valign="top">Expressions representing bit-fields in memory or reg. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Vector-Operations.html#Vector-Operations">Vector Operations</a>:</td><td> </td><td align="left" valign="top">Expressions involving vector datatypes. |
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| <tr><td align="left" valign="top">• <a href="Conversions.html#Conversions">Conversions</a>:</td><td> </td><td align="left" valign="top">Extending, truncating, floating or fixing. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="RTL-Declarations.html#RTL-Declarations">RTL Declarations</a>:</td><td> </td><td align="left" valign="top">Declaring volatility, constancy, etc. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Side-Effects.html#Side-Effects">Side Effects</a>:</td><td> </td><td align="left" valign="top">Expressions for storing in registers, etc. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Incdec.html#Incdec">Incdec</a>:</td><td> </td><td align="left" valign="top">Embedded side-effects for autoincrement addressing. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Assembler.html#Assembler">Assembler</a>:</td><td> </td><td align="left" valign="top">Representing <code>asm</code> with operands. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Debug-Information.html#Debug-Information">Debug Information</a>:</td><td> </td><td align="left" valign="top">Expressions representing debugging information. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Insns.html#Insns">Insns</a>:</td><td> </td><td align="left" valign="top">Expression types for entire insns. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Calls.html#Calls">Calls</a>:</td><td> </td><td align="left" valign="top">RTL representation of function call insns. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Sharing.html#Sharing">Sharing</a>:</td><td> </td><td align="left" valign="top">Some expressions are unique; others *must* be copied. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Reading-RTL.html#Reading-RTL">Reading RTL</a>:</td><td> </td><td align="left" valign="top">Reading textual RTL from a file. |
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