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148 lines
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<title>RISC-V Function Attributes (Using the GNU Compiler Collection (GCC))</title>
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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="RL78-Function-Attributes.html#RL78-Function-Attributes" rel="next" title="RL78 Function Attributes">
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<a name="RISC_002dV-Function-Attributes"></a>
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<div class="header">
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<p>
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Next: <a href="RL78-Function-Attributes.html#RL78-Function-Attributes" accesskey="n" rel="next">RL78 Function Attributes</a>, Previous: <a href="PowerPC-Function-Attributes.html#PowerPC-Function-Attributes" accesskey="p" rel="prev">PowerPC 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="RISC_002dV-Function-Attributes-1"></a>
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<h4 class="subsection">6.31.24 RISC-V Function Attributes</h4>
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<p>These function attributes are supported by the RISC-V back end:
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</p>
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<dl compact="compact">
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<dt><code>naked</code></dt>
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<dd><a name="index-naked-function-attribute_002c-RISC_002dV"></a>
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<p>This attribute allows the compiler to construct the
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requisite function declaration, while allowing the body of the
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function to be assembly code. The specified function will not have
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prologue/epilogue sequences generated by the compiler. Only basic
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<code>asm</code> statements can safely be included in naked functions
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(see <a href="Basic-Asm.html#Basic-Asm">Basic Asm</a>). While using extended <code>asm</code> or a mixture of
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basic <code>asm</code> and C code may appear to work, they cannot be
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depended upon to work reliably and are not supported.
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</p>
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</dd>
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<dt><code>interrupt</code></dt>
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<dd><a name="index-interrupt-function-attribute_002c-RISC_002dV"></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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</p>
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<p>You can specify the kind of interrupt to be handled by adding an optional
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parameter to the interrupt attribute like this:
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</p>
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<div class="smallexample">
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<pre class="smallexample">void f (void) __attribute__ ((interrupt ("user")));
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</pre></div>
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<p>Permissible values for this parameter are <code>user</code>, <code>supervisor</code>,
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and <code>machine</code>. If there is no parameter, then it defaults to
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<code>machine</code>.
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</p>
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<p>You can specify an SiFive CLIC preemptible interrupt handler by adding an
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optional parameter to the interrupt attribute like this:
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</p>
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<div class="smallexample">
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<pre class="smallexample">void f (void) __attribute__ ((interrupt ("SiFive-CLIC-preemptible")));
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</pre></div>
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<p>In this type of interrupt handler, in the prologue, the mepc and
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mcause registers are saved, and interrupts are enabled. In the epilogue,
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interrupts are disabled, and the mepc and mcause registers are restored.
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This type of interrupt handler must be <code>machine</code> mode, and must
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not use the frame pointer.
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</p>
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<p>You can specify an SiFive CLIC stack swapping interrupt handler by adding an
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optional parameter to the interrupt attribute like this:
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</p>
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<div class="smallexample">
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<pre class="smallexample">void f (void) __attribute__ ((interrupt ("SiFive-CLIC-stack-swap")));
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</pre></div>
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<p>In this type of interrupt handler, the stack pointer will be swapped with
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the <code>mscratch</code> register in the prologue before the first use of the stack
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pointer, and in the epilogue after the last use of the stack pointer. This
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type of interrupt handler must be <code>machine</code> mode.
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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="RL78-Function-Attributes.html#RL78-Function-Attributes" accesskey="n" rel="next">RL78 Function Attributes</a>, Previous: <a href="PowerPC-Function-Attributes.html#PowerPC-Function-Attributes" accesskey="p" rel="prev">PowerPC 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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