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| author | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
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| committer | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
| commit | abdaadbcae30fe0c9a66c7516798279fdfd97750 (patch) | |
| tree | 00a54a6e25601e43876d03c1a4a12a749d4a914c /share/doc/gccint/Expressions.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
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diff --git a/share/doc/gccint/Expressions.html b/share/doc/gccint/Expressions.html new file mode 100644 index 0000000..b23cda6 --- /dev/null +++ b/share/doc/gccint/Expressions.html @@ -0,0 +1,323 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1988-2023 Free Software Foundation, Inc. + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with the +Invariant Sections being "Funding Free Software", the Front-Cover +Texts being (a) (see below), and with the Back-Cover Texts being (b) +(see below). A copy of the license is included in the section entitled +"GNU Free Documentation License". + +(a) The FSF's Front-Cover Text is: + +A GNU Manual + +(b) The FSF's Back-Cover Text is: + +You have freedom to copy and modify this GNU Manual, like GNU + software. Copies published by the Free Software Foundation raise + funds for GNU development. --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>GNU Compiler Collection (GCC) Internals: Expressions</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: Expressions"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Expressions"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<link href="index.html#Top" rel="start" title="Top"> +<link href="Option-Index.html#Option-Index" rel="index" title="Option Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Insn-Attributes.html#Insn-Attributes" rel="up" title="Insn Attributes"> +<link href="Tagging-Insns.html#Tagging-Insns" rel="next" title="Tagging Insns"> +<link href="Defining-Attributes.html#Defining-Attributes" rel="previous" title="Defining Attributes"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +div.smalllisp {margin-left: 3.2em} +kbd {font-style:oblique} +pre.display {font-family: inherit} +pre.format {font-family: inherit} +pre.menu-comment {font-family: serif} +pre.menu-preformatted {font-family: serif} +pre.smalldisplay {font-family: inherit; font-size: smaller} +pre.smallexample {font-size: smaller} +pre.smallformat {font-family: inherit; font-size: smaller} +pre.smalllisp {font-size: smaller} +span.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Expressions"></a> +<div class="header"> +<p> +Next: <a href="Tagging-Insns.html#Tagging-Insns" accesskey="n" rel="next">Tagging Insns</a>, Previous: <a href="Defining-Attributes.html#Defining-Attributes" accesskey="p" rel="previous">Defining Attributes</a>, Up: <a href="Insn-Attributes.html#Insn-Attributes" accesskey="u" rel="up">Insn Attributes</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> +</div> +<hr> +<a name="Attribute-Expressions"></a> +<h4 class="subsection">17.19.2 Attribute Expressions</h4> +<a name="index-attribute-expressions"></a> + +<p>RTL expressions used to define attributes use the codes described above +plus a few specific to attribute definitions, to be discussed below. +Attribute value expressions must have one of the following forms: +</p> +<dl compact="compact"> +<dd><a name="index-const_005fint-and-attributes"></a> +</dd> +<dt><code>(const_int <var>i</var>)</code></dt> +<dd><p>The integer <var>i</var> specifies the value of a numeric attribute. <var>i</var> +must be non-negative. +</p> +<p>The value of a numeric attribute can be specified either with a +<code>const_int</code>, or as an integer represented as a string in +<code>const_string</code>, <code>eq_attr</code> (see below), <code>attr</code>, +<code>symbol_ref</code>, simple arithmetic expressions, and <code>set_attr</code> +overrides on specific instructions (see <a href="Tagging-Insns.html#Tagging-Insns">Tagging Insns</a>). +</p> +<a name="index-const_005fstring-and-attributes"></a> +</dd> +<dt><code>(const_string <var>value</var>)</code></dt> +<dd><p>The string <var>value</var> specifies a constant attribute value. +If <var>value</var> is specified as ‘<samp>"*"</samp>’, it means that the default value of +the attribute is to be used for the insn containing this expression. +‘<samp>"*"</samp>’ obviously cannot be used in the <var>default</var> expression +of a <code>define_attr</code>. +</p> +<p>If the attribute whose value is being specified is numeric, <var>value</var> +must be a string containing a non-negative integer (normally +<code>const_int</code> would be used in this case). Otherwise, it must +contain one of the valid values for the attribute. +</p> +<a name="index-if_005fthen_005felse-and-attributes"></a> +</dd> +<dt><code>(if_then_else <var>test</var> <var>true-value</var> <var>false-value</var>)</code></dt> +<dd><p><var>test</var> specifies an attribute test, whose format is defined below. +The value of this expression is <var>true-value</var> if <var>test</var> is true, +otherwise it is <var>false-value</var>. +</p> +<a name="index-cond-and-attributes"></a> +</dd> +<dt><code>(cond [<var>test1</var> <var>value1</var> …] <var>default</var>)</code></dt> +<dd><p>The first operand of this expression is a vector containing an even +number of expressions and consisting of pairs of <var>test</var> and <var>value</var> +expressions. The value of the <code>cond</code> expression is that of the +<var>value</var> corresponding to the first true <var>test</var> expression. If +none of the <var>test</var> expressions are true, the value of the <code>cond</code> +expression is that of the <var>default</var> expression. +</p></dd> +</dl> + +<p><var>test</var> expressions can have one of the following forms: +</p> +<dl compact="compact"> +<dd><a name="index-const_005fint-and-attribute-tests"></a> +</dd> +<dt><code>(const_int <var>i</var>)</code></dt> +<dd><p>This test is true if <var>i</var> is nonzero and false otherwise. +</p> +<a name="index-not-and-attributes"></a> +<a name="index-ior-and-attributes"></a> +<a name="index-and-and-attributes"></a> +</dd> +<dt><code>(not <var>test</var>)</code></dt> +<dt><code>(ior <var>test1</var> <var>test2</var>)</code></dt> +<dt><code>(and <var>test1</var> <var>test2</var>)</code></dt> +<dd><p>These tests are true if the indicated logical function is true. +</p> +<a name="index-match_005foperand-and-attributes"></a> +</dd> +<dt><code>(match_operand:<var>m</var> <var>n</var> <var>pred</var> <var>constraints</var>)</code></dt> +<dd><p>This test is true if operand <var>n</var> of the insn whose attribute value +is being determined has mode <var>m</var> (this part of the test is ignored +if <var>m</var> is <code>VOIDmode</code>) and the function specified by the string +<var>pred</var> returns a nonzero value when passed operand <var>n</var> and mode +<var>m</var> (this part of the test is ignored if <var>pred</var> is the null +string). +</p> +<p>The <var>constraints</var> operand is ignored and should be the null string. +</p> +<a name="index-match_005ftest-and-attributes"></a> +</dd> +<dt><code>(match_test <var>c-expr</var>)</code></dt> +<dd><p>The test is true if C expression <var>c-expr</var> is true. In non-constant +attributes, <var>c-expr</var> has access to the following variables: +</p> +<dl compact="compact"> +<dt><var>insn</var></dt> +<dd><p>The rtl instruction under test. +</p></dd> +<dt><var>which_alternative</var></dt> +<dd><p>The <code>define_insn</code> alternative that <var>insn</var> matches. +See <a href="Output-Statement.html#Output-Statement">Output Statement</a>. +</p></dd> +<dt><var>operands</var></dt> +<dd><p>An array of <var>insn</var>’s rtl operands. +</p></dd> +</dl> + +<p><var>c-expr</var> behaves like the condition in a C <code>if</code> statement, +so there is no need to explicitly convert the expression into a boolean +0 or 1 value. For example, the following two tests are equivalent: +</p> +<div class="smallexample"> +<pre class="smallexample">(match_test "x & 2") +(match_test "(x & 2) != 0") +</pre></div> + +<a name="index-le-and-attributes"></a> +<a name="index-leu-and-attributes"></a> +<a name="index-lt-and-attributes"></a> +<a name="index-gt-and-attributes"></a> +<a name="index-gtu-and-attributes"></a> +<a name="index-ge-and-attributes"></a> +<a name="index-geu-and-attributes"></a> +<a name="index-ne-and-attributes"></a> +<a name="index-eq-and-attributes"></a> +<a name="index-plus-and-attributes"></a> +<a name="index-minus-and-attributes"></a> +<a name="index-mult-and-attributes"></a> +<a name="index-div-and-attributes"></a> +<a name="index-mod-and-attributes"></a> +<a name="index-abs-and-attributes"></a> +<a name="index-neg-and-attributes"></a> +<a name="index-ashift-and-attributes"></a> +<a name="index-lshiftrt-and-attributes"></a> +<a name="index-ashiftrt-and-attributes"></a> +</dd> +<dt><code>(le <var>arith1</var> <var>arith2</var>)</code></dt> +<dt><code>(leu <var>arith1</var> <var>arith2</var>)</code></dt> +<dt><code>(lt <var>arith1</var> <var>arith2</var>)</code></dt> +<dt><code>(ltu <var>arith1</var> <var>arith2</var>)</code></dt> +<dt><code>(gt <var>arith1</var> <var>arith2</var>)</code></dt> +<dt><code>(gtu <var>arith1</var> <var>arith2</var>)</code></dt> +<dt><code>(ge <var>arith1</var> <var>arith2</var>)</code></dt> +<dt><code>(geu <var>arith1</var> <var>arith2</var>)</code></dt> +<dt><code>(ne <var>arith1</var> <var>arith2</var>)</code></dt> +<dt><code>(eq <var>arith1</var> <var>arith2</var>)</code></dt> +<dd><p>These tests are true if the indicated comparison of the two arithmetic +expressions is true. Arithmetic expressions are formed with +<code>plus</code>, <code>minus</code>, <code>mult</code>, <code>div</code>, <code>mod</code>, +<code>abs</code>, <code>neg</code>, <code>and</code>, <code>ior</code>, <code>xor</code>, <code>not</code>, +<code>ashift</code>, <code>lshiftrt</code>, and <code>ashiftrt</code> expressions. +</p> +<a name="index-get_005fattr"></a> +<p><code>const_int</code> and <code>symbol_ref</code> are always valid terms (see <a href="Insn-Lengths.html#Insn-Lengths">Insn Lengths</a>,for additional forms). <code>symbol_ref</code> is a string +denoting a C expression that yields an <code>int</code> when evaluated by the +‘<samp>get_attr_…</samp>’ routine. It should normally be a global +variable. +</p> +<a name="index-eq_005fattr"></a> +</dd> +<dt><code>(eq_attr <var>name</var> <var>value</var>)</code></dt> +<dd><p><var>name</var> is a string specifying the name of an attribute. +</p> +<p><var>value</var> is a string that is either a valid value for attribute +<var>name</var>, a comma-separated list of values, or ‘<samp>!</samp>’ followed by a +value or list. If <var>value</var> does not begin with a ‘<samp>!</samp>’, this +test is true if the value of the <var>name</var> attribute of the current +insn is in the list specified by <var>value</var>. If <var>value</var> begins +with a ‘<samp>!</samp>’, this test is true if the attribute’s value is +<em>not</em> in the specified list. +</p> +<p>For example, +</p> +<div class="smallexample"> +<pre class="smallexample">(eq_attr "type" "load,store") +</pre></div> + +<p>is equivalent to +</p> +<div class="smallexample"> +<pre class="smallexample">(ior (eq_attr "type" "load") (eq_attr "type" "store")) +</pre></div> + +<p>If <var>name</var> specifies an attribute of ‘<samp>alternative</samp>’, it refers to the +value of the compiler variable <code>which_alternative</code> +(see <a href="Output-Statement.html#Output-Statement">Output Statement</a>) and the values must be small integers. For +example, +</p> +<div class="smallexample"> +<pre class="smallexample">(eq_attr "alternative" "2,3") +</pre></div> + +<p>is equivalent to +</p> +<div class="smallexample"> +<pre class="smallexample">(ior (eq (symbol_ref "which_alternative") (const_int 2)) + (eq (symbol_ref "which_alternative") (const_int 3))) +</pre></div> + +<p>Note that, for most attributes, an <code>eq_attr</code> test is simplified in cases +where the value of the attribute being tested is known for all insns matching +a particular pattern. This is by far the most common case. +</p> +<a name="index-attr_005fflag"></a> +</dd> +<dt><code>(attr_flag <var>name</var>)</code></dt> +<dd><p>The value of an <code>attr_flag</code> expression is true if the flag +specified by <var>name</var> is true for the <code>insn</code> currently being +scheduled. +</p> +<p><var>name</var> is a string specifying one of a fixed set of flags to test. +Test the flags <code>forward</code> and <code>backward</code> to determine the +direction of a conditional branch. +</p> +<p>This example describes a conditional branch delay slot which +can be nullified for forward branches that are taken (annul-true) or +for backward branches which are not taken (annul-false). +</p> +<div class="smallexample"> +<pre class="smallexample">(define_delay (eq_attr "type" "cbranch") + [(eq_attr "in_branch_delay" "true") + (and (eq_attr "in_branch_delay" "true") + (attr_flag "forward")) + (and (eq_attr "in_branch_delay" "true") + (attr_flag "backward"))]) +</pre></div> + +<p>The <code>forward</code> and <code>backward</code> flags are false if the current +<code>insn</code> being scheduled is not a conditional branch. +</p> +<p><code>attr_flag</code> is only used during delay slot scheduling and has no +meaning to other passes of the compiler. +</p> +<a name="index-attr"></a> +</dd> +<dt><code>(attr <var>name</var>)</code></dt> +<dd><p>The value of another attribute is returned. This is most useful +for numeric attributes, as <code>eq_attr</code> and <code>attr_flag</code> +produce more efficient code for non-numeric attributes. +</p></dd> +</dl> + +<hr> +<div class="header"> +<p> +Next: <a href="Tagging-Insns.html#Tagging-Insns" accesskey="n" rel="next">Tagging Insns</a>, Previous: <a href="Defining-Attributes.html#Defining-Attributes" accesskey="p" rel="previous">Defining Attributes</a>, Up: <a href="Insn-Attributes.html#Insn-Attributes" accesskey="u" rel="up">Insn Attributes</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> +</div> + + + +</body> +</html> |