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299 lines
11 KiB
HTML
299 lines
11 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1988-2018 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Funding Free Software", the Front-Cover
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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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(see below). A copy of the license is included in the section entitled
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"GNU Free Documentation License".
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development. -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>RTL Classes (GNU Compiler Collection (GCC) Internals)</title>
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<meta name="description" content="RTL Classes (GNU Compiler Collection (GCC) Internals)">
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<meta name="keywords" content="RTL Classes (GNU Compiler Collection (GCC) Internals)">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="RTL.html#RTL" rel="up" title="RTL">
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<link href="Accessors.html#Accessors" rel="next" title="Accessors">
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<link href="RTL-Objects.html#RTL-Objects" rel="prev" title="RTL Objects">
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</style>
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</head>
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<body lang="en">
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<a name="RTL-Classes"></a>
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<div class="header">
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<p>
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Next: <a href="Accessors.html#Accessors" accesskey="n" rel="next">Accessors</a>, Previous: <a href="RTL-Objects.html#RTL-Objects" accesskey="p" rel="prev">RTL Objects</a>, Up: <a href="RTL.html#RTL" accesskey="u" rel="up">RTL</a> [<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>
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</div>
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<hr>
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<a name="RTL-Classes-and-Formats"></a>
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<h3 class="section">14.2 RTL Classes and Formats</h3>
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<a name="index-RTL-classes"></a>
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<a name="index-classes-of-RTX-codes"></a>
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<a name="index-RTX-codes_002c-classes-of"></a>
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<a name="index-GET_005fRTX_005fCLASS"></a>
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<p>The various expression codes are divided into several <em>classes</em>,
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which are represented by single characters. You can determine the class
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of an RTX code with the macro <code>GET_RTX_CLASS (<var>code</var>)</code>.
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Currently, <samp>rtl.def</samp> defines these classes:
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</p>
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<dl compact="compact">
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<dt><code>RTX_OBJ</code></dt>
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<dd><p>An RTX code that represents an actual object, such as a register
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(<code>REG</code>) or a memory location (<code>MEM</code>, <code>SYMBOL_REF</code>).
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<code>LO_SUM</code>) is also included; instead, <code>SUBREG</code> and
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<code>STRICT_LOW_PART</code> are not in this class, but in class <code>x</code>.
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</p>
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</dd>
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<dt><code>RTX_CONST_OBJ</code></dt>
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<dd><p>An RTX code that represents a constant object. <code>HIGH</code> is also
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included in this class.
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</p>
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</dd>
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<dt><code>RTX_COMPARE</code></dt>
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<dd><p>An RTX code for a non-symmetric comparison, such as <code>GEU</code> or
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<code>LT</code>.
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</p>
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</dd>
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<dt><code>RTX_COMM_COMPARE</code></dt>
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<dd><p>An RTX code for a symmetric (commutative) comparison, such as <code>EQ</code>
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or <code>ORDERED</code>.
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</p>
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</dd>
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<dt><code>RTX_UNARY</code></dt>
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<dd><p>An RTX code for a unary arithmetic operation, such as <code>NEG</code>,
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<code>NOT</code>, or <code>ABS</code>. This category also includes value extension
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(sign or zero) and conversions between integer and floating point.
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</p>
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</dd>
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<dt><code>RTX_COMM_ARITH</code></dt>
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<dd><p>An RTX code for a commutative binary operation, such as <code>PLUS</code> or
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<code>AND</code>. <code>NE</code> and <code>EQ</code> are comparisons, so they have class
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<code><</code>.
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</p>
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</dd>
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<dt><code>RTX_BIN_ARITH</code></dt>
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<dd><p>An RTX code for a non-commutative binary operation, such as <code>MINUS</code>,
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<code>DIV</code>, or <code>ASHIFTRT</code>.
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</p>
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</dd>
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<dt><code>RTX_BITFIELD_OPS</code></dt>
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<dd><p>An RTX code for a bit-field operation. Currently only
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<code>ZERO_EXTRACT</code> and <code>SIGN_EXTRACT</code>. These have three inputs
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and are lvalues (so they can be used for insertion as well).
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See <a href="Bit_002dFields.html#Bit_002dFields">Bit-Fields</a>.
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</p>
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</dd>
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<dt><code>RTX_TERNARY</code></dt>
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<dd><p>An RTX code for other three input operations. Currently only
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<code>IF_THEN_ELSE</code>, <code>VEC_MERGE</code>, <code>SIGN_EXTRACT</code>,
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<code>ZERO_EXTRACT</code>, and <code>FMA</code>.
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</p>
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</dd>
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<dt><code>RTX_INSN</code></dt>
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<dd><p>An RTX code for an entire instruction: <code>INSN</code>, <code>JUMP_INSN</code>, and
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<code>CALL_INSN</code>. See <a href="Insns.html#Insns">Insns</a>.
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</p>
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</dd>
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<dt><code>RTX_MATCH</code></dt>
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<dd><p>An RTX code for something that matches in insns, such as
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<code>MATCH_DUP</code>. These only occur in machine descriptions.
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</p>
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</dd>
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<dt><code>RTX_AUTOINC</code></dt>
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<dd><p>An RTX code for an auto-increment addressing mode, such as
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<code>POST_INC</code>. ‘<samp>XEXP (<var>x</var>, 0)</samp>’ gives the auto-modified
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register.
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</p>
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</dd>
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<dt><code>RTX_EXTRA</code></dt>
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<dd><p>All other RTX codes. This category includes the remaining codes used
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only in machine descriptions (<code>DEFINE_*</code>, etc.). It also includes
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all the codes describing side effects (<code>SET</code>, <code>USE</code>,
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<code>CLOBBER</code>, etc.) and the non-insns that may appear on an insn
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chain, such as <code>NOTE</code>, <code>BARRIER</code>, and <code>CODE_LABEL</code>.
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<code>SUBREG</code> is also part of this class.
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</p></dd>
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</dl>
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<a name="index-RTL-format"></a>
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<p>For each expression code, <samp>rtl.def</samp> specifies the number of
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contained objects and their kinds using a sequence of characters
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called the <em>format</em> of the expression code. For example,
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the format of <code>subreg</code> is ‘<samp>ep</samp>’.
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</p>
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<a name="index-RTL-format-characters"></a>
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<p>These are the most commonly used format characters:
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</p>
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<dl compact="compact">
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<dt><code>e</code></dt>
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<dd><p>An expression (actually a pointer to an expression).
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</p>
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</dd>
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<dt><code>i</code></dt>
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<dd><p>An integer.
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</p>
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</dd>
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<dt><code>w</code></dt>
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<dd><p>A wide integer.
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</p>
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</dd>
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<dt><code>s</code></dt>
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<dd><p>A string.
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</p>
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</dd>
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<dt><code>E</code></dt>
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<dd><p>A vector of expressions.
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</p></dd>
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</dl>
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<p>A few other format characters are used occasionally:
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</p>
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<dl compact="compact">
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<dt><code>u</code></dt>
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<dd><p>‘<samp>u</samp>’ is equivalent to ‘<samp>e</samp>’ except that it is printed differently
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in debugging dumps. It is used for pointers to insns.
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</p>
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</dd>
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<dt><code>n</code></dt>
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<dd><p>‘<samp>n</samp>’ is equivalent to ‘<samp>i</samp>’ except that it is printed differently
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in debugging dumps. It is used for the line number or code number of a
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<code>note</code> insn.
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</p>
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</dd>
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<dt><code>S</code></dt>
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<dd><p>‘<samp>S</samp>’ indicates a string which is optional. In the RTL objects in
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core, ‘<samp>S</samp>’ is equivalent to ‘<samp>s</samp>’, but when the object is read,
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from an ‘<samp>md</samp>’ file, the string value of this operand may be omitted.
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An omitted string is taken to be the null string.
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</p>
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</dd>
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<dt><code>V</code></dt>
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<dd><p>‘<samp>V</samp>’ indicates a vector which is optional. In the RTL objects in
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core, ‘<samp>V</samp>’ is equivalent to ‘<samp>E</samp>’, but when the object is read
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from an ‘<samp>md</samp>’ file, the vector value of this operand may be omitted.
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An omitted vector is effectively the same as a vector of no elements.
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</p>
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</dd>
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<dt><code>B</code></dt>
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<dd><p>‘<samp>B</samp>’ indicates a pointer to basic block structure.
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</p>
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</dd>
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<dt><code>p</code></dt>
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<dd><p>A polynomial integer. At present this is used only for <code>SUBREG_BYTE</code>.
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</p>
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</dd>
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<dt><code>0</code></dt>
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<dd><p>‘<samp>0</samp>’ means a slot whose contents do not fit any normal category.
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‘<samp>0</samp>’ slots are not printed at all in dumps, and are often used in
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special ways by small parts of the compiler.
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</p></dd>
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</dl>
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<p>There are macros to get the number of operands and the format
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of an expression code:
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</p>
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<dl compact="compact">
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<dd><a name="index-GET_005fRTX_005fLENGTH"></a>
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</dd>
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<dt><code>GET_RTX_LENGTH (<var>code</var>)</code></dt>
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<dd><p>Number of operands of an RTX of code <var>code</var>.
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</p>
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<a name="index-GET_005fRTX_005fFORMAT"></a>
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</dd>
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<dt><code>GET_RTX_FORMAT (<var>code</var>)</code></dt>
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<dd><p>The format of an RTX of code <var>code</var>, as a C string.
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</p></dd>
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</dl>
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<p>Some classes of RTX codes always have the same format. For example, it
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is safe to assume that all comparison operations have format <code>ee</code>.
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</p>
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<dl compact="compact">
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<dt><code>1</code></dt>
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<dd><p>All codes of this class have format <code>e</code>.
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</p>
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</dd>
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<dt><code><</code></dt>
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<dt><code>c</code></dt>
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<dt><code>2</code></dt>
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<dd><p>All codes of these classes have format <code>ee</code>.
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</p>
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</dd>
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<dt><code>b</code></dt>
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<dt><code>3</code></dt>
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<dd><p>All codes of these classes have format <code>eee</code>.
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</p>
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</dd>
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<dt><code>i</code></dt>
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<dd><p>All codes of this class have formats that begin with <code>iuueiee</code>.
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See <a href="Insns.html#Insns">Insns</a>. Note that not all RTL objects linked onto an insn chain
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are of class <code>i</code>.
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</p>
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</dd>
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<dt><code>o</code></dt>
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<dt><code>m</code></dt>
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<dt><code>x</code></dt>
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<dd><p>You can make no assumptions about the format of these codes.
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</p></dd>
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</dl>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Accessors.html#Accessors" accesskey="n" rel="next">Accessors</a>, Previous: <a href="RTL-Objects.html#RTL-Objects" accesskey="p" rel="prev">RTL Objects</a>, Up: <a href="RTL.html#RTL" accesskey="u" rel="up">RTL</a> [<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>
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</div>
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</body>
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</html>
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