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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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"GNU Free Documentation License".
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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): MIPS Function Attributes</title>
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<meta name="description" content="Using the GNU Compiler Collection (GCC): MIPS Function Attributes">
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<meta name="keywords" content="Using the GNU Compiler Collection (GCC): MIPS Function Attributes">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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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="MSP430-Function-Attributes.html#MSP430-Function-Attributes" rel="next" title="MSP430 Function Attributes">
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<link href="Microsoft-Windows-Function-Attributes.html#Microsoft-Windows-Function-Attributes" rel="prev" title="Microsoft Windows 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="MIPS-Function-Attributes"></a>
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<div class="header">
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<p>
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Next: <a href="MSP430-Function-Attributes.html#MSP430-Function-Attributes" accesskey="n" rel="next">MSP430 Function Attributes</a>, Previous: <a href="Microsoft-Windows-Function-Attributes.html#Microsoft-Windows-Function-Attributes" accesskey="p" rel="prev">Microsoft Windows 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="MIPS-Function-Attributes-1"></a>
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<h4 class="subsection">6.31.18 MIPS Function Attributes</h4>
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<p>These function attributes are supported by the MIPS back end:
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</p>
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<dl compact="compact">
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<dt><code>interrupt</code></dt>
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<dd><a name="index-interrupt-function-attribute_002c-MIPS"></a>
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<p>Use this attribute to indicate that the specified function is an interrupt
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handler. The compiler generates function entry and exit sequences suitable
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for use in an interrupt handler when this attribute is present.
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An optional argument is supported for the interrupt attribute which allows
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the interrupt mode to be described. By default GCC assumes the external
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interrupt controller (EIC) mode is in use, this can be explicitly set using
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<code>eic</code>. When interrupts are non-masked then the requested Interrupt
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Priority Level (IPL) is copied to the current IPL which has the effect of only
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enabling higher priority interrupts. To use vectored interrupt mode use
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the argument <code>vector=[sw0|sw1|hw0|hw1|hw2|hw3|hw4|hw5]</code>, this will change
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the behavior of the non-masked interrupt support and GCC will arrange to mask
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all interrupts from sw0 up to and including the specified interrupt vector.
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</p>
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<p>You can use the following attributes to modify the behavior
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of an interrupt handler:
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</p><dl compact="compact">
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<dt><code>use_shadow_register_set</code></dt>
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<dd><a name="index-use_005fshadow_005fregister_005fset-function-attribute_002c-MIPS"></a>
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<p>Assume that the handler uses a shadow register set, instead of
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the main general-purpose registers. An optional argument <code>intstack</code> is
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supported to indicate that the shadow register set contains a valid stack
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pointer.
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</p>
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</dd>
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<dt><code>keep_interrupts_masked</code></dt>
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<dd><a name="index-keep_005finterrupts_005fmasked-function-attribute_002c-MIPS"></a>
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<p>Keep interrupts masked for the whole function. Without this attribute,
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GCC tries to reenable interrupts for as much of the function as it can.
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</p>
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</dd>
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<dt><code>use_debug_exception_return</code></dt>
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<dd><a name="index-use_005fdebug_005fexception_005freturn-function-attribute_002c-MIPS"></a>
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<p>Return using the <code>deret</code> instruction. Interrupt handlers that don’t
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have this attribute return using <code>eret</code> instead.
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</p></dd>
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</dl>
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<p>You can use any combination of these attributes, as shown below:
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</p><div class="smallexample">
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<pre class="smallexample">void __attribute__ ((interrupt)) v0 ();
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void __attribute__ ((interrupt, use_shadow_register_set)) v1 ();
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void __attribute__ ((interrupt, keep_interrupts_masked)) v2 ();
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void __attribute__ ((interrupt, use_debug_exception_return)) v3 ();
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void __attribute__ ((interrupt, use_shadow_register_set,
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keep_interrupts_masked)) v4 ();
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void __attribute__ ((interrupt, use_shadow_register_set,
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use_debug_exception_return)) v5 ();
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void __attribute__ ((interrupt, keep_interrupts_masked,
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use_debug_exception_return)) v6 ();
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void __attribute__ ((interrupt, use_shadow_register_set,
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keep_interrupts_masked,
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use_debug_exception_return)) v7 ();
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void __attribute__ ((interrupt("eic"))) v8 ();
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void __attribute__ ((interrupt("vector=hw3"))) v9 ();
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</pre></div>
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</dd>
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<dt><code>long_call</code></dt>
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<dt><code>near</code></dt>
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<dt><code>far</code></dt>
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<dd><a name="index-indirect-calls_002c-MIPS"></a>
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<a name="index-long_005fcall-function-attribute_002c-MIPS"></a>
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<a name="index-near-function-attribute_002c-MIPS"></a>
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<a name="index-far-function-attribute_002c-MIPS"></a>
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<p>These attributes specify how a particular function is called on MIPS.
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The attributes override the <samp>-mlong-calls</samp> (see <a href="MIPS-Options.html#MIPS-Options">MIPS Options</a>)
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command-line switch. The <code>long_call</code> and <code>far</code> attributes are
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synonyms, and cause the compiler to always call
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the function by first loading its address into a register, and then using
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the contents of that register. The <code>near</code> attribute has the opposite
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effect; it specifies that non-PIC calls should be made using the more
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efficient <code>jal</code> instruction.
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</p>
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</dd>
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<dt><code>mips16</code></dt>
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<dt><code>nomips16</code></dt>
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<dd><a name="index-mips16-function-attribute_002c-MIPS"></a>
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<a name="index-nomips16-function-attribute_002c-MIPS"></a>
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<p>On MIPS targets, you can use the <code>mips16</code> and <code>nomips16</code>
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function attributes to locally select or turn off MIPS16 code generation.
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A function with the <code>mips16</code> attribute is emitted as MIPS16 code,
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while MIPS16 code generation is disabled for functions with the
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<code>nomips16</code> attribute. These attributes override the
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<samp>-mips16</samp> and <samp>-mno-mips16</samp> options on the command line
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(see <a href="MIPS-Options.html#MIPS-Options">MIPS Options</a>).
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</p>
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<p>When compiling files containing mixed MIPS16 and non-MIPS16 code, the
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preprocessor symbol <code>__mips16</code> reflects the setting on the command line,
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not that within individual functions. Mixed MIPS16 and non-MIPS16 code
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may interact badly with some GCC extensions such as <code>__builtin_apply</code>
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(see <a href="Constructing-Calls.html#Constructing-Calls">Constructing Calls</a>).
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</p>
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</dd>
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<dt><code>micromips, MIPS</code></dt>
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<dt><code>nomicromips, MIPS</code></dt>
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<dd><a name="index-micromips-function-attribute"></a>
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<a name="index-nomicromips-function-attribute"></a>
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<p>On MIPS targets, you can use the <code>micromips</code> and <code>nomicromips</code>
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function attributes to locally select or turn off microMIPS code generation.
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A function with the <code>micromips</code> attribute is emitted as microMIPS code,
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while microMIPS code generation is disabled for functions with the
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<code>nomicromips</code> attribute. These attributes override the
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<samp>-mmicromips</samp> and <samp>-mno-micromips</samp> options on the command line
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(see <a href="MIPS-Options.html#MIPS-Options">MIPS Options</a>).
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</p>
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<p>When compiling files containing mixed microMIPS and non-microMIPS code, the
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preprocessor symbol <code>__mips_micromips</code> reflects the setting on the
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command line,
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not that within individual functions. Mixed microMIPS and non-microMIPS code
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may interact badly with some GCC extensions such as <code>__builtin_apply</code>
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(see <a href="Constructing-Calls.html#Constructing-Calls">Constructing Calls</a>).
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</p>
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</dd>
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<dt><code>nocompression</code></dt>
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<dd><a name="index-nocompression-function-attribute_002c-MIPS"></a>
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<p>On MIPS targets, you can use the <code>nocompression</code> function attribute
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to locally turn off MIPS16 and microMIPS code generation. This attribute
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overrides the <samp>-mips16</samp> and <samp>-mmicromips</samp> options on the
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command line (see <a href="MIPS-Options.html#MIPS-Options">MIPS Options</a>).
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</p></dd>
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</dl>
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<hr>
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<div class="header">
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<p>
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Next: <a href="MSP430-Function-Attributes.html#MSP430-Function-Attributes" accesskey="n" rel="next">MSP430 Function Attributes</a>, Previous: <a href="Microsoft-Windows-Function-Attributes.html#Microsoft-Windows-Function-Attributes" accesskey="p" rel="prev">Microsoft Windows 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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