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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/Accessors.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
Change-Id: I7303388733328cd98ab9aa3c30236db67f2e9e9c
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diff --git a/share/doc/gccint/Accessors.html b/share/doc/gccint/Accessors.html new file mode 100644 index 0000000..4e32b12 --- /dev/null +++ b/share/doc/gccint/Accessors.html @@ -0,0 +1,161 @@ +<!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: Accessors</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: Accessors"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Accessors"> +<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="RTL.html#RTL" rel="up" title="RTL"> +<link href="Special-Accessors.html#Special-Accessors" rel="next" title="Special Accessors"> +<link href="RTL-Classes.html#RTL-Classes" rel="previous" title="RTL Classes"> +<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="Accessors"></a> +<div class="header"> +<p> +Next: <a href="Special-Accessors.html#Special-Accessors" accesskey="n" rel="next">Special Accessors</a>, Previous: <a href="RTL-Classes.html#RTL-Classes" accesskey="p" rel="previous">RTL Classes</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> +</div> +<hr> +<a name="Access-to-Operands"></a> +<h3 class="section">14.3 Access to Operands</h3> +<a name="index-accessors"></a> +<a name="index-access-to-operands"></a> +<a name="index-operand-access"></a> + +<a name="index-XEXP"></a> +<a name="index-XINT"></a> +<a name="index-XWINT"></a> +<a name="index-XSTR"></a> +<p>Operands of expressions are accessed using the macros <code>XEXP</code>, +<code>XINT</code>, <code>XWINT</code> and <code>XSTR</code>. Each of these macros takes +two arguments: an expression-pointer (RTX) and an operand number +(counting from zero). Thus, +</p> +<div class="smallexample"> +<pre class="smallexample">XEXP (<var>x</var>, 2) +</pre></div> + +<p>accesses operand 2 of expression <var>x</var>, as an expression. +</p> +<div class="smallexample"> +<pre class="smallexample">XINT (<var>x</var>, 2) +</pre></div> + +<p>accesses the same operand as an integer. <code>XSTR</code>, used in the same +fashion, would access it as a string. +</p> +<p>Any operand can be accessed as an integer, as an expression or as a string. +You must choose the correct method of access for the kind of value actually +stored in the operand. You would do this based on the expression code of +the containing expression. That is also how you would know how many +operands there are. +</p> +<p>For example, if <var>x</var> is an <code>int_list</code> expression, you know that it has +two operands which can be correctly accessed as <code>XINT (<var>x</var>, 0)</code> +and <code>XEXP (<var>x</var>, 1)</code>. Incorrect accesses like +<code>XEXP (<var>x</var>, 0)</code> and <code>XINT (<var>x</var>, 1)</code> would compile, +but would trigger an internal compiler error when rtl checking is enabled. +Nothing stops you from writing <code>XEXP (<var>x</var>, 28)</code> either, but +this will access memory past the end of the expression with +unpredictable results. +</p> +<p>Access to operands which are vectors is more complicated. You can use the +macro <code>XVEC</code> to get the vector-pointer itself, or the macros +<code>XVECEXP</code> and <code>XVECLEN</code> to access the elements and length of a +vector. +</p> +<dl compact="compact"> +<dd><a name="index-XVEC"></a> +</dd> +<dt><code>XVEC (<var>exp</var>, <var>idx</var>)</code></dt> +<dd><p>Access the vector-pointer which is operand number <var>idx</var> in <var>exp</var>. +</p> +<a name="index-XVECLEN"></a> +</dd> +<dt><code>XVECLEN (<var>exp</var>, <var>idx</var>)</code></dt> +<dd><p>Access the length (number of elements) in the vector which is +in operand number <var>idx</var> in <var>exp</var>. This value is an <code>int</code>. +</p> +<a name="index-XVECEXP"></a> +</dd> +<dt><code>XVECEXP (<var>exp</var>, <var>idx</var>, <var>eltnum</var>)</code></dt> +<dd><p>Access element number <var>eltnum</var> in the vector which is +in operand number <var>idx</var> in <var>exp</var>. This value is an RTX. +</p> +<p>It is up to you to make sure that <var>eltnum</var> is not negative +and is less than <code>XVECLEN (<var>exp</var>, <var>idx</var>)</code>. +</p></dd> +</dl> + +<p>All the macros defined in this section expand into lvalues and therefore +can be used to assign the operands, lengths and vector elements as well as +to access them. +</p> +<hr> +<div class="header"> +<p> +Next: <a href="Special-Accessors.html#Special-Accessors" accesskey="n" rel="next">Special Accessors</a>, Previous: <a href="RTL-Classes.html#RTL-Classes" accesskey="p" rel="previous">RTL Classes</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> +</div> + + + +</body> +</html> |