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191 lines
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191 lines
9.8 KiB
HTML
4 years ago
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<html lang="en">
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<head>
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<title>RTL Classes - GNU Compiler Collection (GCC) Internals</title>
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<meta http-equiv="Content-Type" content="text/html">
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<meta name="description" content="GNU Compiler Collection (GCC) Internals">
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<meta name="generator" content="makeinfo 4.13">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="RTL.html#RTL" title="RTL">
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<link rel="prev" href="RTL-Objects.html#RTL-Objects" title="RTL Objects">
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<link rel="next" href="Accessors.html#Accessors" title="Accessors">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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Copyright (C) 1988-2015 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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funds for GNU development.-->
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--></style>
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</head>
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<body>
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<div class="node">
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<a name="RTL-Classes"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Accessors.html#Accessors">Accessors</a>,
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Previous: <a rel="previous" accesskey="p" href="RTL-Objects.html#RTL-Objects">RTL Objects</a>,
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Up: <a rel="up" accesskey="u" href="RTL.html#RTL">RTL</a>
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<hr>
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</div>
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<h3 class="section">13.2 RTL Classes and Formats</h3>
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<p><a name="index-RTL-classes-2549"></a><a name="index-classes-of-RTX-codes-2550"></a><a name="index-RTX-codes_002c-classes-of-2551"></a><a name="index-GET_005fRTX_005fCLASS-2552"></a>
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The various expression codes are divided into several <dfn>classes</dfn>,
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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 (</code><var>code</var><code>)</code>.
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Currently, <samp><span class="file">rtl.def</span></samp> defines these classes:
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<dl>
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<dt><code>RTX_OBJ</code><dd>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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<br><dt><code>RTX_CONST_OBJ</code><dd>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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<br><dt><code>RTX_COMPARE</code><dd>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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<br><dt><code>RTX_COMM_COMPARE</code><dd>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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<br><dt><code>RTX_UNARY</code><dd>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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<br><dt><code>RTX_COMM_ARITH</code><dd>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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<br><dt><code>RTX_BIN_ARITH</code><dd>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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<br><dt><code>RTX_BITFIELD_OPS</code><dd>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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<br><dt><code>RTX_TERNARY</code><dd>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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<br><dt><code>RTX_INSN</code><dd>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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<br><dt><code>RTX_MATCH</code><dd>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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<br><dt><code>RTX_AUTOINC</code><dd>An RTX code for an auto-increment addressing mode, such as
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<code>POST_INC</code>. ‘<samp><span class="samp">XEXP (</span><var>x</var><span class="samp">, 0)</span></samp>’ gives the auto-modified
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register.
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<br><dt><code>RTX_EXTRA</code><dd>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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</dl>
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<p><a name="index-RTL-format-2553"></a>For each expression code, <samp><span class="file">rtl.def</span></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 <dfn>format</dfn> of the expression code. For example,
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the format of <code>subreg</code> is ‘<samp><span class="samp">ei</span></samp>’.
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<p><a name="index-RTL-format-characters-2554"></a>These are the most commonly used format characters:
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<dl>
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<dt><code>e</code><dd>An expression (actually a pointer to an expression).
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<br><dt><code>i</code><dd>An integer.
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<br><dt><code>w</code><dd>A wide integer.
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<br><dt><code>s</code><dd>A string.
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<br><dt><code>E</code><dd>A vector of expressions.
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</dl>
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<p>A few other format characters are used occasionally:
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<dl>
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<dt><code>u</code><dd>‘<samp><span class="samp">u</span></samp>’ is equivalent to ‘<samp><span class="samp">e</span></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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<br><dt><code>n</code><dd>‘<samp><span class="samp">n</span></samp>’ is equivalent to ‘<samp><span class="samp">i</span></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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<br><dt><code>S</code><dd>‘<samp><span class="samp">S</span></samp>’ indicates a string which is optional. In the RTL objects in
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core, ‘<samp><span class="samp">S</span></samp>’ is equivalent to ‘<samp><span class="samp">s</span></samp>’, but when the object is read,
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from an ‘<samp><span class="samp">md</span></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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<br><dt><code>V</code><dd>‘<samp><span class="samp">V</span></samp>’ indicates a vector which is optional. In the RTL objects in
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core, ‘<samp><span class="samp">V</span></samp>’ is equivalent to ‘<samp><span class="samp">E</span></samp>’, but when the object is read
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from an ‘<samp><span class="samp">md</span></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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<br><dt><code>B</code><dd>‘<samp><span class="samp">B</span></samp>’ indicates a pointer to basic block structure.
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<br><dt><code>0</code><dd>‘<samp><span class="samp">0</span></samp>’ means a slot whose contents do not fit any normal category.
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‘<samp><span class="samp">0</span></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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</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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<a name="index-GET_005fRTX_005fLENGTH-2555"></a>
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<dl><dt><code>GET_RTX_LENGTH (</code><var>code</var><code>)</code><dd>Number of operands of an RTX of code <var>code</var>.
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<p><a name="index-GET_005fRTX_005fFORMAT-2556"></a><br><dt><code>GET_RTX_FORMAT (</code><var>code</var><code>)</code><dd>The format of an RTX of code <var>code</var>, as a C string.
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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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<dl>
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<dt><code>1</code><dd>All codes of this class have format <code>e</code>.
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<br><dt><code><</code><dt><code>c</code><dt><code>2</code><dd>All codes of these classes have format <code>ee</code>.
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<br><dt><code>b</code><dt><code>3</code><dd>All codes of these classes have format <code>eee</code>.
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<br><dt><code>i</code><dd>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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<br><dt><code>o</code><dt><code>m</code><dt><code>x</code><dd>You can make no assumptions about the format of these codes.
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</dl>
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</body></html>
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