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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/Anchored-Addresses.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
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diff --git a/share/doc/gccint/Anchored-Addresses.html b/share/doc/gccint/Anchored-Addresses.html new file mode 100644 index 0000000..8ec4058 --- /dev/null +++ b/share/doc/gccint/Anchored-Addresses.html @@ -0,0 +1,160 @@ +<!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: Anchored Addresses</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: Anchored Addresses"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Anchored Addresses"> +<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="Target-Macros.html#Target-Macros" rel="up" title="Target Macros"> +<link href="Condition-Code.html#Condition-Code" rel="next" title="Condition Code"> +<link href="Addressing-Modes.html#Addressing-Modes" rel="previous" title="Addressing Modes"> +<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="Anchored-Addresses"></a> +<div class="header"> +<p> +Next: <a href="Condition-Code.html#Condition-Code" accesskey="n" rel="next">Condition Code</a>, Previous: <a href="Addressing-Modes.html#Addressing-Modes" accesskey="p" rel="previous">Addressing Modes</a>, Up: <a href="Target-Macros.html#Target-Macros" accesskey="u" rel="up">Target Macros</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="Anchored-Addresses-1"></a> +<h3 class="section">18.14 Anchored Addresses</h3> +<a name="index-anchored-addresses"></a> +<a name="index-_002dfsection_002danchors-1"></a> + +<p>GCC usually addresses every static object as a separate entity. +For example, if we have: +</p> +<div class="smallexample"> +<pre class="smallexample">static int a, b, c; +int foo (void) { return a + b + c; } +</pre></div> + +<p>the code for <code>foo</code> will usually calculate three separate symbolic +addresses: those of <code>a</code>, <code>b</code> and <code>c</code>. On some targets, +it would be better to calculate just one symbolic address and access +the three variables relative to it. The equivalent pseudocode would +be something like: +</p> +<div class="smallexample"> +<pre class="smallexample">int foo (void) +{ + register int *xr = &x; + return xr[&a - &x] + xr[&b - &x] + xr[&c - &x]; +} +</pre></div> + +<p>(which isn’t valid C). We refer to shared addresses like <code>x</code> as +“section anchors”. Their use is controlled by <samp>-fsection-anchors</samp>. +</p> +<p>The hooks below describe the target properties that GCC needs to know +in order to make effective use of section anchors. It won’t use +section anchors at all unless either <code>TARGET_MIN_ANCHOR_OFFSET</code> +or <code>TARGET_MAX_ANCHOR_OFFSET</code> is set to a nonzero value. +</p> +<dl> +<dt><a name="index-TARGET_005fMIN_005fANCHOR_005fOFFSET"></a>Target Hook: <em>HOST_WIDE_INT</em> <strong>TARGET_MIN_ANCHOR_OFFSET</strong></dt> +<dd><p>The minimum offset that should be applied to a section anchor. +On most targets, it should be the smallest offset that can be +applied to a base register while still giving a legitimate address +for every mode. The default value is 0. +</p></dd></dl> + +<dl> +<dt><a name="index-TARGET_005fMAX_005fANCHOR_005fOFFSET"></a>Target Hook: <em>HOST_WIDE_INT</em> <strong>TARGET_MAX_ANCHOR_OFFSET</strong></dt> +<dd><p>Like <code>TARGET_MIN_ANCHOR_OFFSET</code>, but the maximum (inclusive) +offset that should be applied to section anchors. The default +value is 0. +</p></dd></dl> + +<dl> +<dt><a name="index-TARGET_005fASM_005fOUTPUT_005fANCHOR"></a>Target Hook: <em>void</em> <strong>TARGET_ASM_OUTPUT_ANCHOR</strong> <em>(rtx <var>x</var>)</em></dt> +<dd><p>Write the assembly code to define section anchor <var>x</var>, which is a +<code>SYMBOL_REF</code> for which ‘<samp>SYMBOL_REF_ANCHOR_P (<var>x</var>)</samp>’ is true. +The hook is called with the assembly output position set to the beginning +of <code>SYMBOL_REF_BLOCK (<var>x</var>)</code>. +</p> +<p>If <code>ASM_OUTPUT_DEF</code> is available, the hook’s default definition uses +it to define the symbol as ‘<samp>. + SYMBOL_REF_BLOCK_OFFSET (<var>x</var>)</samp>’. +If <code>ASM_OUTPUT_DEF</code> is not available, the hook’s default definition +is <code>NULL</code>, which disables the use of section anchors altogether. +</p></dd></dl> + +<dl> +<dt><a name="index-TARGET_005fUSE_005fANCHORS_005fFOR_005fSYMBOL_005fP"></a>Target Hook: <em>bool</em> <strong>TARGET_USE_ANCHORS_FOR_SYMBOL_P</strong> <em>(const_rtx <var>x</var>)</em></dt> +<dd><p>Return true if GCC should attempt to use anchors to access <code>SYMBOL_REF</code> +<var>x</var>. You can assume ‘<samp>SYMBOL_REF_HAS_BLOCK_INFO_P (<var>x</var>)</samp>’ and +‘<samp>!SYMBOL_REF_ANCHOR_P (<var>x</var>)</samp>’. +</p> +<p>The default version is correct for most targets, but you might need to +intercept this hook to handle things like target-specific attributes +or target-specific sections. +</p></dd></dl> + +<hr> +<div class="header"> +<p> +Next: <a href="Condition-Code.html#Condition-Code" accesskey="n" rel="next">Condition Code</a>, Previous: <a href="Addressing-Modes.html#Addressing-Modes" accesskey="p" rel="previous">Addressing Modes</a>, Up: <a href="Target-Macros.html#Target-Macros" accesskey="u" rel="up">Target Macros</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> |