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diff --git a/share/doc/gcc/ARM-Function-Attributes.html b/share/doc/gcc/ARM-Function-Attributes.html new file mode 100644 index 0000000..0d7e1aa --- /dev/null +++ b/share/doc/gcc/ARM-Function-Attributes.html @@ -0,0 +1,252 @@ +<!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): ARM Function Attributes</title> + +<meta name="description" content="Using the GNU Compiler Collection (GCC): ARM Function Attributes"> +<meta name="keywords" content="Using the GNU Compiler Collection (GCC): ARM Function Attributes"> +<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="Function-Attributes.html#Function-Attributes" rel="up" title="Function Attributes"> +<link href="AVR-Function-Attributes.html#AVR-Function-Attributes" rel="next" title="AVR Function Attributes"> +<link href="ARC-Function-Attributes.html#ARC-Function-Attributes" rel="previous" title="ARC Function 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_US" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="ARM-Function-Attributes"></a> +<div class="header"> +<p> +Next: <a href="AVR-Function-Attributes.html#AVR-Function-Attributes" accesskey="n" rel="next">AVR Function Attributes</a>, Previous: <a href="ARC-Function-Attributes.html#ARC-Function-Attributes" accesskey="p" rel="previous">ARC Function Attributes</a>, Up: <a href="Function-Attributes.html#Function-Attributes" accesskey="u" rel="up">Function Attributes</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="ARM-Function-Attributes-1"></a> +<h4 class="subsection">6.33.5 ARM Function Attributes</h4> + +<p>These function attributes are supported for ARM targets: +</p> +<dl compact="compact"> +<dd> +<a name="index-general_002dregs_002donly-function-attribute_002c-ARM"></a> +</dd> +<dt><code>general-regs-only</code></dt> +<dd><p>Indicates that no floating-point or Advanced SIMD registers should be +used when generating code for this function. If the function explicitly +uses floating-point code, then the compiler gives an error. This is +the same behavior as that of the command-line option +<samp>-mgeneral-regs-only</samp>. +</p> +<a name="index-interrupt-function-attribute_002c-ARM"></a> +</dd> +<dt><code>interrupt</code></dt> +<dd><p>Use this attribute to indicate +that the specified function is an interrupt handler. The compiler generates +function entry and exit sequences suitable for use in an interrupt handler +when this attribute is present. +</p> +<p>You can specify the kind of interrupt to be handled by +adding an optional parameter to the interrupt attribute like this: +</p> +<div class="smallexample"> +<pre class="smallexample">void f () __attribute__ ((interrupt ("IRQ"))); +</pre></div> + +<p>Permissible values for this parameter are: <code>IRQ</code>, <code>FIQ</code>, +<code>SWI</code>, <code>ABORT</code> and <code>UNDEF</code>. +</p> +<p>On ARMv7-M the interrupt type is ignored, and the attribute means the function +may be called with a word-aligned stack pointer. +</p> +<a name="index-isr-function-attribute_002c-ARM"></a> +</dd> +<dt><code>isr</code></dt> +<dd><p>Use this attribute on ARM to write Interrupt Service Routines. This is an +alias to the <code>interrupt</code> attribute above. +</p> +<a name="index-long_005fcall-function-attribute_002c-ARM"></a> +<a name="index-short_005fcall-function-attribute_002c-ARM"></a> +<a name="index-indirect-calls_002c-ARM"></a> +</dd> +<dt><code>long_call</code></dt> +<dt><code>short_call</code></dt> +<dd><p>These attributes specify how a particular function is called. +These attributes override the +<samp>-mlong-calls</samp> (see <a href="ARM-Options.html#ARM-Options">ARM Options</a>) +command-line switch and <code>#pragma long_calls</code> settings. For ARM, the +<code>long_call</code> attribute indicates that the function might be far +away from the call site and require a different (more expensive) +calling sequence. The <code>short_call</code> attribute always places +the offset to the function from the call site into the ‘<samp>BL</samp>’ +instruction directly. +</p> +<a name="index-naked-function-attribute_002c-ARM"></a> +</dd> +<dt><code>naked</code></dt> +<dd><p>This attribute allows the compiler to construct the +requisite function declaration, while allowing the body of the +function to be assembly code. The specified function will not have +prologue/epilogue sequences generated by the compiler. Only basic +<code>asm</code> statements can safely be included in naked functions +(see <a href="Basic-Asm.html#Basic-Asm">Basic Asm</a>). While using extended <code>asm</code> or a mixture of +basic <code>asm</code> and C code may appear to work, they cannot be +depended upon to work reliably and are not supported. +</p> +<a name="index-pcs-function-attribute_002c-ARM"></a> +</dd> +<dt><code>pcs</code></dt> +<dd> +<p>The <code>pcs</code> attribute can be used to control the calling convention +used for a function on ARM. The attribute takes an argument that specifies +the calling convention to use. +</p> +<p>When compiling using the AAPCS ABI (or a variant of it) then valid +values for the argument are <code>"aapcs"</code> and <code>"aapcs-vfp"</code>. In +order to use a variant other than <code>"aapcs"</code> then the compiler must +be permitted to use the appropriate co-processor registers (i.e., the +VFP registers must be available in order to use <code>"aapcs-vfp"</code>). +For example, +</p> +<div class="smallexample"> +<pre class="smallexample">/* Argument passed in r0, and result returned in r0+r1. */ +double f2d (float) __attribute__((pcs("aapcs"))); +</pre></div> + +<p>Variadic functions always use the <code>"aapcs"</code> calling convention and +the compiler rejects attempts to specify an alternative. +</p> +<a name="index-target-function-attribute-1"></a> +</dd> +<dt><code>target (<var>options</var>)</code></dt> +<dd><p>As discussed in <a href="Common-Function-Attributes.html#Common-Function-Attributes">Common Function Attributes</a>, this attribute +allows specification of target-specific compilation options. +</p> +<p>On ARM, the following options are allowed: +</p> +<dl compact="compact"> +<dd><a name="index-target_0028_0022thumb_0022_0029-function-attribute_002c-ARM"></a> +</dd> +<dt>‘<samp>thumb</samp>’</dt> +<dd><p>Force code generation in the Thumb (T16/T32) ISA, depending on the +architecture level. +</p> +<a name="index-target_0028_0022arm_0022_0029-function-attribute_002c-ARM"></a> +</dd> +<dt>‘<samp>arm</samp>’</dt> +<dd><p>Force code generation in the ARM (A32) ISA. +</p> +<p>Functions from different modes can be inlined in the caller’s mode. +</p> +<a name="index-target_0028_0022fpu_003d_0022_0029-function-attribute_002c-ARM"></a> +</dd> +<dt>‘<samp>fpu=</samp>’</dt> +<dd><p>Specifies the fpu for which to tune the performance of this function. +The behavior and permissible arguments are the same as for the <samp>-mfpu=</samp> +command-line option. +</p> +<a name="index-arch_003d-function-attribute_002c-ARM"></a> +</dd> +<dt>‘<samp>arch=</samp>’</dt> +<dd><p>Specifies the architecture version and architectural extensions to use +for this function. The behavior and permissible arguments are the same as +for the <samp>-march=</samp> command-line option. +</p> +<p>The above target attributes can be specified as follows: +</p> +<div class="smallexample"> +<pre class="smallexample">__attribute__((target("arch=armv8-a+crc"))) +int +f (int a) +{ + return a + 5; +} +</pre></div> + +<p>Additionally, the architectural extension string may be specified on its +own. This can be used to turn on and off particular architectural extensions +without having to specify a particular architecture version or core. Example: +</p> +<div class="smallexample"> +<pre class="smallexample">__attribute__((target("+crc+nocrypto"))) +int +foo (int a) +{ + return a + 5; +} +</pre></div> + +<p>In this example <code>target("+crc+nocrypto")</code> enables the <code>crc</code> +extension and disables the <code>crypto</code> extension for the function <code>foo</code> +without modifying an existing <samp>-march=</samp> or <samp>-mcpu</samp> option. +</p> +</dd> +</dl> + +</dd> +</dl> + +<hr> +<div class="header"> +<p> +Next: <a href="AVR-Function-Attributes.html#AVR-Function-Attributes" accesskey="n" rel="next">AVR Function Attributes</a>, Previous: <a href="ARC-Function-Attributes.html#ARC-Function-Attributes" accesskey="p" rel="previous">ARC Function Attributes</a>, Up: <a href="Function-Attributes.html#Function-Attributes" accesskey="u" rel="up">Function Attributes</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> + + + +</body> +</html> |