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<!-- Copyright (C) 1988-2016 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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(see below). A copy of the license is included in the section entitled
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Using the GNU Compiler Collection (GCC): x86 Function Attributes</title>
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<meta name="description" content="Using the GNU Compiler Collection (GCC): x86 Function Attributes">
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<meta name="keywords" content="Using the GNU Compiler Collection (GCC): x86 Function Attributes">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Function-Attributes.html#Function-Attributes" rel="up" title="Function Attributes">
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<link href="Xstormy16-Function-Attributes.html#Xstormy16-Function-Attributes" rel="next" title="Xstormy16 Function Attributes">
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<link href="Visium-Function-Attributes.html#Visium-Function-Attributes" rel="prev" title="Visium Function Attributes">
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="x86-Function-Attributes"></a>
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<div class="header">
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<p>
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Next: <a href="Xstormy16-Function-Attributes.html#Xstormy16-Function-Attributes" accesskey="n" rel="next">Xstormy16 Function Attributes</a>, Previous: <a href="Visium-Function-Attributes.html#Visium-Function-Attributes" accesskey="p" rel="prev">Visium 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="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="x86-Function-Attributes-1"></a>
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<h4 class="subsection">6.31.32 x86 Function Attributes</h4>
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<p>These function attributes are supported by the x86 back end:
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</p>
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<dl compact="compact">
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<dt><code>cdecl</code></dt>
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<dd><a name="index-cdecl-function-attribute_002c-x86_002d32"></a>
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<a name="index-functions-that-pop-the-argument-stack-on-x86_002d32"></a>
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<a name="index-mrtd-2"></a>
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<p>On the x86-32 targets, the <code>cdecl</code> attribute causes the compiler to
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assume that the calling function pops off the stack space used to
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pass arguments. This is
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useful to override the effects of the <samp>-mrtd</samp> switch.
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</p>
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</dd>
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<dt><code>fastcall</code></dt>
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<dd><a name="index-fastcall-function-attribute_002c-x86_002d32"></a>
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<a name="index-functions-that-pop-the-argument-stack-on-x86_002d32-1"></a>
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<p>On x86-32 targets, the <code>fastcall</code> attribute causes the compiler to
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pass the first argument (if of integral type) in the register ECX and
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the second argument (if of integral type) in the register EDX. Subsequent
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and other typed arguments are passed on the stack. The called function
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pops the arguments off the stack. If the number of arguments is variable all
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arguments are pushed on the stack.
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</p>
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</dd>
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<dt><code>thiscall</code></dt>
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<dd><a name="index-thiscall-function-attribute_002c-x86_002d32"></a>
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<a name="index-functions-that-pop-the-argument-stack-on-x86_002d32-2"></a>
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<p>On x86-32 targets, the <code>thiscall</code> attribute causes the compiler to
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pass the first argument (if of integral type) in the register ECX.
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Subsequent and other typed arguments are passed on the stack. The called
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function pops the arguments off the stack.
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If the number of arguments is variable all arguments are pushed on the
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stack.
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The <code>thiscall</code> attribute is intended for C++ non-static member functions.
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As a GCC extension, this calling convention can be used for C functions
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and for static member methods.
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</p>
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</dd>
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<dt><code>ms_abi</code></dt>
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<dt><code>sysv_abi</code></dt>
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<dd><a name="index-ms_005fabi-function-attribute_002c-x86"></a>
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<a name="index-sysv_005fabi-function-attribute_002c-x86"></a>
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<p>On 32-bit and 64-bit x86 targets, you can use an ABI attribute
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to indicate which calling convention should be used for a function. The
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<code>ms_abi</code> attribute tells the compiler to use the Microsoft ABI,
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while the <code>sysv_abi</code> attribute tells the compiler to use the ABI
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used on GNU/Linux and other systems. The default is to use the Microsoft ABI
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when targeting Windows. On all other systems, the default is the x86/AMD ABI.
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</p>
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<p>Note, the <code>ms_abi</code> attribute for Microsoft Windows 64-bit targets currently
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requires the <samp>-maccumulate-outgoing-args</samp> option.
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</p>
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</dd>
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<dt><code>callee_pop_aggregate_return (<var>number</var>)</code></dt>
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<dd><a name="index-callee_005fpop_005faggregate_005freturn-function-attribute_002c-x86"></a>
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<p>On x86-32 targets, you can use this attribute to control how
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aggregates are returned in memory. If the caller is responsible for
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popping the hidden pointer together with the rest of the arguments, specify
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<var>number</var> equal to zero. If callee is responsible for popping the
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hidden pointer, specify <var>number</var> equal to one.
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</p>
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<p>The default x86-32 ABI assumes that the callee pops the
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stack for hidden pointer. However, on x86-32 Microsoft Windows targets,
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the compiler assumes that the
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caller pops the stack for hidden pointer.
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</p>
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</dd>
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<dt><code>ms_hook_prologue</code></dt>
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<dd><a name="index-ms_005fhook_005fprologue-function-attribute_002c-x86"></a>
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<p>On 32-bit and 64-bit x86 targets, you can use
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this function attribute to make GCC generate the “hot-patching” function
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prologue used in Win32 API functions in Microsoft Windows XP Service Pack 2
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and newer.
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</p>
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</dd>
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<dt><code>regparm (<var>number</var>)</code></dt>
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<dd><a name="index-regparm-function-attribute_002c-x86"></a>
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<a name="index-functions-that-are-passed-arguments-in-registers-on-x86_002d32"></a>
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<p>On x86-32 targets, the <code>regparm</code> attribute causes the compiler to
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pass arguments number one to <var>number</var> if they are of integral type
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in registers EAX, EDX, and ECX instead of on the stack. Functions that
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take a variable number of arguments continue to be passed all of their
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arguments on the stack.
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</p>
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<p>Beware that on some ELF systems this attribute is unsuitable for
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global functions in shared libraries with lazy binding (which is the
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default). Lazy binding sends the first call via resolving code in
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the loader, which might assume EAX, EDX and ECX can be clobbered, as
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per the standard calling conventions. Solaris 8 is affected by this.
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Systems with the GNU C Library version 2.1 or higher
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and FreeBSD are believed to be
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safe since the loaders there save EAX, EDX and ECX. (Lazy binding can be
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disabled with the linker or the loader if desired, to avoid the
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problem.)
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</p>
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</dd>
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<dt><code>sseregparm</code></dt>
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<dd><a name="index-sseregparm-function-attribute_002c-x86"></a>
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<p>On x86-32 targets with SSE support, the <code>sseregparm</code> attribute
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causes the compiler to pass up to 3 floating-point arguments in
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SSE registers instead of on the stack. Functions that take a
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variable number of arguments continue to pass all of their
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floating-point arguments on the stack.
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</p>
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</dd>
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<dt><code>force_align_arg_pointer</code></dt>
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<dd><a name="index-force_005falign_005farg_005fpointer-function-attribute_002c-x86"></a>
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<p>On x86 targets, the <code>force_align_arg_pointer</code> attribute may be
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applied to individual function definitions, generating an alternate
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prologue and epilogue that realigns the run-time stack if necessary.
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This supports mixing legacy codes that run with a 4-byte aligned stack
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with modern codes that keep a 16-byte stack for SSE compatibility.
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</p>
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</dd>
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<dt><code>stdcall</code></dt>
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<dd><a name="index-stdcall-function-attribute_002c-x86_002d32"></a>
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<a name="index-functions-that-pop-the-argument-stack-on-x86_002d32-3"></a>
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<p>On x86-32 targets, the <code>stdcall</code> attribute causes the compiler to
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assume that the called function pops off the stack space used to
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pass arguments, unless it takes a variable number of arguments.
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</p>
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</dd>
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<dt><code>target (<var>options</var>)</code></dt>
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<dd><a name="index-target-function-attribute-5"></a>
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<p>As discussed in <a href="Common-Function-Attributes.html#Common-Function-Attributes">Common Function Attributes</a>, this attribute
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allows specification of target-specific compilation options.
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</p>
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<p>On the x86, the following options are allowed:
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</p><dl compact="compact">
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<dt>‘<samp>abm</samp>’</dt>
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<dt>‘<samp>no-abm</samp>’</dt>
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<dd><a name="index-target_0028_0022abm_0022_0029-function-attribute_002c-x86"></a>
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<p>Enable/disable the generation of the advanced bit instructions.
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</p>
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</dd>
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<dt>‘<samp>aes</samp>’</dt>
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<dt>‘<samp>no-aes</samp>’</dt>
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<dd><a name="index-target_0028_0022aes_0022_0029-function-attribute_002c-x86"></a>
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<p>Enable/disable the generation of the AES instructions.
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</p>
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</dd>
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<dt>‘<samp>default</samp>’</dt>
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<dd><a name="index-target_0028_0022default_0022_0029-function-attribute_002c-x86"></a>
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<p>See <a href="Function-Multiversioning.html#Function-Multiversioning">Function Multiversioning</a>, where it is used to specify the
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default function version.
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</p>
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</dd>
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<dt>‘<samp>mmx</samp>’</dt>
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<dt>‘<samp>no-mmx</samp>’</dt>
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<dd><a name="index-target_0028_0022mmx_0022_0029-function-attribute_002c-x86"></a>
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<p>Enable/disable the generation of the MMX instructions.
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</p>
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</dd>
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<dt>‘<samp>pclmul</samp>’</dt>
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<dt>‘<samp>no-pclmul</samp>’</dt>
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<dd><a name="index-target_0028_0022pclmul_0022_0029-function-attribute_002c-x86"></a>
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<p>Enable/disable the generation of the PCLMUL instructions.
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</p>
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</dd>
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<dt>‘<samp>popcnt</samp>’</dt>
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<dt>‘<samp>no-popcnt</samp>’</dt>
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<dd><a name="index-target_0028_0022popcnt_0022_0029-function-attribute_002c-x86"></a>
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<p>Enable/disable the generation of the POPCNT instruction.
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</p>
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</dd>
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<dt>‘<samp>sse</samp>’</dt>
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<dt>‘<samp>no-sse</samp>’</dt>
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<dd><a name="index-target_0028_0022sse_0022_0029-function-attribute_002c-x86"></a>
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<p>Enable/disable the generation of the SSE instructions.
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</p>
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</dd>
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<dt>‘<samp>sse2</samp>’</dt>
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<dt>‘<samp>no-sse2</samp>’</dt>
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<dd><a name="index-target_0028_0022sse2_0022_0029-function-attribute_002c-x86"></a>
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<p>Enable/disable the generation of the SSE2 instructions.
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</p>
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</dd>
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<dt>‘<samp>sse3</samp>’</dt>
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<dt>‘<samp>no-sse3</samp>’</dt>
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<dd><a name="index-target_0028_0022sse3_0022_0029-function-attribute_002c-x86"></a>
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<p>Enable/disable the generation of the SSE3 instructions.
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</p>
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</dd>
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<dt>‘<samp>sse4</samp>’</dt>
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<dt>‘<samp>no-sse4</samp>’</dt>
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<dd><a name="index-target_0028_0022sse4_0022_0029-function-attribute_002c-x86"></a>
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<p>Enable/disable the generation of the SSE4 instructions (both SSE4.1
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and SSE4.2).
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</p>
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</dd>
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<dt>‘<samp>sse4.1</samp>’</dt>
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<dt>‘<samp>no-sse4.1</samp>’</dt>
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<dd><a name="index-target_0028_0022sse4_002e1_0022_0029-function-attribute_002c-x86"></a>
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<p>Enable/disable the generation of the sse4.1 instructions.
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</p>
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</dd>
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<dt>‘<samp>sse4.2</samp>’</dt>
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<dt>‘<samp>no-sse4.2</samp>’</dt>
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<dd><a name="index-target_0028_0022sse4_002e2_0022_0029-function-attribute_002c-x86"></a>
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<p>Enable/disable the generation of the sse4.2 instructions.
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</p>
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</dd>
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<dt>‘<samp>sse4a</samp>’</dt>
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<dt>‘<samp>no-sse4a</samp>’</dt>
|
||
|
|
<dd><a name="index-target_0028_0022sse4a_0022_0029-function-attribute_002c-x86"></a>
|
||
|
|
<p>Enable/disable the generation of the SSE4A instructions.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>fma4</samp>’</dt>
|
||
|
|
<dt>‘<samp>no-fma4</samp>’</dt>
|
||
|
|
<dd><a name="index-target_0028_0022fma4_0022_0029-function-attribute_002c-x86"></a>
|
||
|
|
<p>Enable/disable the generation of the FMA4 instructions.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>xop</samp>’</dt>
|
||
|
|
<dt>‘<samp>no-xop</samp>’</dt>
|
||
|
|
<dd><a name="index-target_0028_0022xop_0022_0029-function-attribute_002c-x86"></a>
|
||
|
|
<p>Enable/disable the generation of the XOP instructions.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>lwp</samp>’</dt>
|
||
|
|
<dt>‘<samp>no-lwp</samp>’</dt>
|
||
|
|
<dd><a name="index-target_0028_0022lwp_0022_0029-function-attribute_002c-x86"></a>
|
||
|
|
<p>Enable/disable the generation of the LWP instructions.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>ssse3</samp>’</dt>
|
||
|
|
<dt>‘<samp>no-ssse3</samp>’</dt>
|
||
|
|
<dd><a name="index-target_0028_0022ssse3_0022_0029-function-attribute_002c-x86"></a>
|
||
|
|
<p>Enable/disable the generation of the SSSE3 instructions.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>cld</samp>’</dt>
|
||
|
|
<dt>‘<samp>no-cld</samp>’</dt>
|
||
|
|
<dd><a name="index-target_0028_0022cld_0022_0029-function-attribute_002c-x86"></a>
|
||
|
|
<p>Enable/disable the generation of the CLD before string moves.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>fancy-math-387</samp>’</dt>
|
||
|
|
<dt>‘<samp>no-fancy-math-387</samp>’</dt>
|
||
|
|
<dd><a name="index-target_0028_0022fancy_002dmath_002d387_0022_0029-function-attribute_002c-x86"></a>
|
||
|
|
<p>Enable/disable the generation of the <code>sin</code>, <code>cos</code>, and
|
||
|
|
<code>sqrt</code> instructions on the 387 floating-point unit.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>fused-madd</samp>’</dt>
|
||
|
|
<dt>‘<samp>no-fused-madd</samp>’</dt>
|
||
|
|
<dd><a name="index-target_0028_0022fused_002dmadd_0022_0029-function-attribute_002c-x86"></a>
|
||
|
|
<p>Enable/disable the generation of the fused multiply/add instructions.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>ieee-fp</samp>’</dt>
|
||
|
|
<dt>‘<samp>no-ieee-fp</samp>’</dt>
|
||
|
|
<dd><a name="index-target_0028_0022ieee_002dfp_0022_0029-function-attribute_002c-x86"></a>
|
||
|
|
<p>Enable/disable the generation of floating point that depends on IEEE arithmetic.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>inline-all-stringops</samp>’</dt>
|
||
|
|
<dt>‘<samp>no-inline-all-stringops</samp>’</dt>
|
||
|
|
<dd><a name="index-target_0028_0022inline_002dall_002dstringops_0022_0029-function-attribute_002c-x86"></a>
|
||
|
|
<p>Enable/disable inlining of string operations.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>inline-stringops-dynamically</samp>’</dt>
|
||
|
|
<dt>‘<samp>no-inline-stringops-dynamically</samp>’</dt>
|
||
|
|
<dd><a name="index-target_0028_0022inline_002dstringops_002ddynamically_0022_0029-function-attribute_002c-x86"></a>
|
||
|
|
<p>Enable/disable the generation of the inline code to do small string
|
||
|
|
operations and calling the library routines for large operations.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>align-stringops</samp>’</dt>
|
||
|
|
<dt>‘<samp>no-align-stringops</samp>’</dt>
|
||
|
|
<dd><a name="index-target_0028_0022align_002dstringops_0022_0029-function-attribute_002c-x86"></a>
|
||
|
|
<p>Do/do not align destination of inlined string operations.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>recip</samp>’</dt>
|
||
|
|
<dt>‘<samp>no-recip</samp>’</dt>
|
||
|
|
<dd><a name="index-target_0028_0022recip_0022_0029-function-attribute_002c-x86"></a>
|
||
|
|
<p>Enable/disable the generation of RCPSS, RCPPS, RSQRTSS and RSQRTPS
|
||
|
|
instructions followed an additional Newton-Raphson step instead of
|
||
|
|
doing a floating-point division.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>arch=<var>ARCH</var></samp>’</dt>
|
||
|
|
<dd><a name="index-target_0028_0022arch_003dARCH_0022_0029-function-attribute_002c-x86"></a>
|
||
|
|
<p>Specify the architecture to generate code for in compiling the function.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>tune=<var>TUNE</var></samp>’</dt>
|
||
|
|
<dd><a name="index-target_0028_0022tune_003dTUNE_0022_0029-function-attribute_002c-x86"></a>
|
||
|
|
<p>Specify the architecture to tune for in compiling the function.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>‘<samp>fpmath=<var>FPMATH</var></samp>’</dt>
|
||
|
|
<dd><a name="index-target_0028_0022fpmath_003dFPMATH_0022_0029-function-attribute_002c-x86"></a>
|
||
|
|
<p>Specify which floating-point unit to use. You must specify the
|
||
|
|
<code>target("fpmath=sse,387")</code> option as
|
||
|
|
<code>target("fpmath=sse+387")</code> because the comma would separate
|
||
|
|
different options.
|
||
|
|
</p></dd>
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
<p>On the x86, the inliner does not inline a
|
||
|
|
function that has different target options than the caller, unless the
|
||
|
|
callee has a subset of the target options of the caller. For example
|
||
|
|
a function declared with <code>target("sse3")</code> can inline a function
|
||
|
|
with <code>target("sse2")</code>, since <code>-msse3</code> implies <code>-msse2</code>.
|
||
|
|
</p></dd>
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
<hr>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Xstormy16-Function-Attributes.html#Xstormy16-Function-Attributes" accesskey="n" rel="next">Xstormy16 Function Attributes</a>, Previous: <a href="Visium-Function-Attributes.html#Visium-Function-Attributes" accesskey="p" rel="prev">Visium 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="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</body>
|
||
|
|
</html>
|