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<title>Using the GNU Compiler Collection (GCC): MIPS Function Attributes</title>

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<a name="MIPS-Function-Attributes"></a>
<div class="header">
<p>
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> &nbsp; [<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="MIPS-Function-Attributes-1"></a>
<h4 class="subsection">6.31.18 MIPS Function Attributes</h4>

<p>These function attributes are supported by the MIPS back end:
</p>
<dl compact="compact">
<dt><code>interrupt</code></dt>
<dd><a name="index-interrupt-function-attribute_002c-MIPS"></a>
<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.
An optional argument is supported for the interrupt attribute which allows
the interrupt mode to be described.  By default GCC assumes the external
interrupt controller (EIC) mode is in use, this can be explicitly set using
<code>eic</code>.  When interrupts are non-masked then the requested Interrupt
Priority Level (IPL) is copied to the current IPL which has the effect of only
enabling higher priority interrupts.  To use vectored interrupt mode use
the argument <code>vector=[sw0|sw1|hw0|hw1|hw2|hw3|hw4|hw5]</code>, this will change
the behavior of the non-masked interrupt support and GCC will arrange to mask
all interrupts from sw0 up to and including the specified interrupt vector.
</p>
<p>You can use the following attributes to modify the behavior
of an interrupt handler:
</p><dl compact="compact">
<dt><code>use_shadow_register_set</code></dt>
<dd><a name="index-use_005fshadow_005fregister_005fset-function-attribute_002c-MIPS"></a>
<p>Assume that the handler uses a shadow register set, instead of
the main general-purpose registers.  An optional argument <code>intstack</code> is
supported to indicate that the shadow register set contains a valid stack
pointer.
</p>
</dd>
<dt><code>keep_interrupts_masked</code></dt>
<dd><a name="index-keep_005finterrupts_005fmasked-function-attribute_002c-MIPS"></a>
<p>Keep interrupts masked for the whole function.  Without this attribute,
GCC tries to reenable interrupts for as much of the function as it can.
</p>
</dd>
<dt><code>use_debug_exception_return</code></dt>
<dd><a name="index-use_005fdebug_005fexception_005freturn-function-attribute_002c-MIPS"></a>
<p>Return using the <code>deret</code> instruction.  Interrupt handlers that don&rsquo;t
have this attribute return using <code>eret</code> instead.
</p></dd>
</dl>

<p>You can use any combination of these attributes, as shown below:
</p><div class="smallexample">
<pre class="smallexample">void __attribute__ ((interrupt)) v0 ();
void __attribute__ ((interrupt, use_shadow_register_set)) v1 ();
void __attribute__ ((interrupt, keep_interrupts_masked)) v2 ();
void __attribute__ ((interrupt, use_debug_exception_return)) v3 ();
void __attribute__ ((interrupt, use_shadow_register_set,
                     keep_interrupts_masked)) v4 ();
void __attribute__ ((interrupt, use_shadow_register_set,
                     use_debug_exception_return)) v5 ();
void __attribute__ ((interrupt, keep_interrupts_masked,
                     use_debug_exception_return)) v6 ();
void __attribute__ ((interrupt, use_shadow_register_set,
                     keep_interrupts_masked,
                     use_debug_exception_return)) v7 ();
void __attribute__ ((interrupt(&quot;eic&quot;))) v8 ();
void __attribute__ ((interrupt(&quot;vector=hw3&quot;))) v9 ();
</pre></div>

</dd>
<dt><code>long_call</code></dt>
<dt><code>near</code></dt>
<dt><code>far</code></dt>
<dd><a name="index-indirect-calls_002c-MIPS"></a>
<a name="index-long_005fcall-function-attribute_002c-MIPS"></a>
<a name="index-near-function-attribute_002c-MIPS"></a>
<a name="index-far-function-attribute_002c-MIPS"></a>
<p>These attributes specify how a particular function is called on MIPS.
The attributes override the <samp>-mlong-calls</samp> (see <a href="MIPS-Options.html#MIPS-Options">MIPS Options</a>)
command-line switch.  The <code>long_call</code> and <code>far</code> attributes are
synonyms, and cause the compiler to always call
the function by first loading its address into a register, and then using
the contents of that register.  The <code>near</code> attribute has the opposite
effect; it specifies that non-PIC calls should be made using the more
efficient <code>jal</code> instruction.
</p>
</dd>
<dt><code>mips16</code></dt>
<dt><code>nomips16</code></dt>
<dd><a name="index-mips16-function-attribute_002c-MIPS"></a>
<a name="index-nomips16-function-attribute_002c-MIPS"></a>

<p>On MIPS targets, you can use the <code>mips16</code> and <code>nomips16</code>
function attributes to locally select or turn off MIPS16 code generation.
A function with the <code>mips16</code> attribute is emitted as MIPS16 code,
while MIPS16 code generation is disabled for functions with the
<code>nomips16</code> attribute.  These attributes override the
<samp>-mips16</samp> and <samp>-mno-mips16</samp> options on the command line
(see <a href="MIPS-Options.html#MIPS-Options">MIPS Options</a>).
</p>
<p>When compiling files containing mixed MIPS16 and non-MIPS16 code, the
preprocessor symbol <code>__mips16</code> reflects the setting on the command line,
not that within individual functions.  Mixed MIPS16 and non-MIPS16 code
may interact badly with some GCC extensions such as <code>__builtin_apply</code>
(see <a href="Constructing-Calls.html#Constructing-Calls">Constructing Calls</a>).
</p>
</dd>
<dt><code>micromips, MIPS</code></dt>
<dt><code>nomicromips, MIPS</code></dt>
<dd><a name="index-micromips-function-attribute"></a>
<a name="index-nomicromips-function-attribute"></a>

<p>On MIPS targets, you can use the <code>micromips</code> and <code>nomicromips</code>
function attributes to locally select or turn off microMIPS code generation.
A function with the <code>micromips</code> attribute is emitted as microMIPS code,
while microMIPS code generation is disabled for functions with the
<code>nomicromips</code> attribute.  These attributes override the
<samp>-mmicromips</samp> and <samp>-mno-micromips</samp> options on the command line
(see <a href="MIPS-Options.html#MIPS-Options">MIPS Options</a>).
</p>
<p>When compiling files containing mixed microMIPS and non-microMIPS code, the
preprocessor symbol <code>__mips_micromips</code> reflects the setting on the
command line,
not that within individual functions.  Mixed microMIPS and non-microMIPS code
may interact badly with some GCC extensions such as <code>__builtin_apply</code>
(see <a href="Constructing-Calls.html#Constructing-Calls">Constructing Calls</a>).
</p>
</dd>
<dt><code>nocompression</code></dt>
<dd><a name="index-nocompression-function-attribute_002c-MIPS"></a>
<p>On MIPS targets, you can use the <code>nocompression</code> function attribute
to locally turn off MIPS16 and microMIPS code generation.  This attribute
overrides the <samp>-mips16</samp> and <samp>-mmicromips</samp> options on the
command line (see <a href="MIPS-Options.html#MIPS-Options">MIPS Options</a>).
</p></dd>
</dl>

<hr>
<div class="header">
<p>
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> &nbsp; [<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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