diff options
| author | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
|---|---|---|
| committer | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
| commit | abdaadbcae30fe0c9a66c7516798279fdfd97750 (patch) | |
| tree | 00a54a6e25601e43876d03c1a4a12a749d4a914c /share/doc/gcc/Size-of-an-asm.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
Change-Id: I7303388733328cd98ab9aa3c30236db67f2e9e9c
Diffstat (limited to 'share/doc/gcc/Size-of-an-asm.html')
| -rw-r--r-- | share/doc/gcc/Size-of-an-asm.html | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/share/doc/gcc/Size-of-an-asm.html b/share/doc/gcc/Size-of-an-asm.html new file mode 100644 index 0000000..9b93bc1 --- /dev/null +++ b/share/doc/gcc/Size-of-an-asm.html @@ -0,0 +1,110 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- This file documents the use of the GNU compilers. + +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>Using the GNU Compiler Collection (GCC): Size of an asm</title> + +<meta name="description" content="Using the GNU Compiler Collection (GCC): Size of an asm"> +<meta name="keywords" content="Using the GNU Compiler Collection (GCC): Size of an asm"> +<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="Indices.html#Indices" rel="index" title="Indices"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Using-Assembly-Language-with-C.html#Using-Assembly-Language-with-C" rel="up" title="Using Assembly Language with C"> +<link href="Alternate-Keywords.html#Alternate-Keywords" rel="next" title="Alternate Keywords"> +<link href="Local-Register-Variables.html#Local-Register-Variables" rel="previous" title="Local Register Variables"> +<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_US" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Size-of-an-asm"></a> +<div class="header"> +<p> +Previous: <a href="Explicit-Register-Variables.html#Explicit-Register-Variables" accesskey="p" rel="previous">Explicit Register Variables</a>, Up: <a href="Using-Assembly-Language-with-C.html#Using-Assembly-Language-with-C" accesskey="u" rel="up">Using Assembly Language with C</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="Size-of-an-asm-1"></a> +<h4 class="subsection">6.47.6 Size of an <code>asm</code></h4> + +<p>Some targets require that GCC track the size of each instruction used +in order to generate correct code. Because the final length of the +code produced by an <code>asm</code> statement is only known by the +assembler, GCC must make an estimate as to how big it will be. It +does this by counting the number of instructions in the pattern of the +<code>asm</code> and multiplying that by the length of the longest +instruction supported by that processor. (When working out the number +of instructions, it assumes that any occurrence of a newline or of +whatever statement separator character is supported by the assembler — +typically ‘<samp>;</samp>’ — indicates the end of an instruction.) +</p> +<p>Normally, GCC’s estimate is adequate to ensure that correct +code is generated, but it is possible to confuse the compiler if you use +pseudo instructions or assembler macros that expand into multiple real +instructions, or if you use assembler directives that expand to more +space in the object file than is needed for a single instruction. +If this happens then the assembler may produce a diagnostic saying that +a label is unreachable. +</p> +<a name="index-asm-inline"></a> +<p>This size is also used for inlining decisions. If you use <code>asm inline</code> +instead of just <code>asm</code>, then for inlining purposes the size of the asm +is taken as the minimum size, ignoring how many instructions GCC thinks it is. +</p> + + + +</body> +</html> |