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- <a name="SH-Function-Attributes"></a>
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- Next: <a href="Symbian-OS-Function-Attributes.html#Symbian-OS-Function-Attributes" accesskey="n" rel="next">Symbian OS Function Attributes</a>, Previous: <a href="S_002f390-Function-Attributes.html#S_002f390-Function-Attributes" accesskey="p" rel="prev">S/390 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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- <a name="SH-Function-Attributes-1"></a>
- <h4 class="subsection">6.33.31 SH Function Attributes</h4>
-
- <p>These function attributes are supported on the SH family of processors:
- </p>
- <dl compact="compact">
- <dt><code>function_vector</code></dt>
- <dd><a name="index-function_005fvector-function-attribute_002c-SH"></a>
- <a name="index-calling-functions-through-the-function-vector-on-SH2A"></a>
- <p>On SH2A targets, this attribute declares a function to be called using the
- TBR relative addressing mode. The argument to this attribute is the entry
- number of the same function in a vector table containing all the TBR
- relative addressable functions. For correct operation the TBR must be setup
- accordingly to point to the start of the vector table before any functions with
- this attribute are invoked. Usually a good place to do the initialization is
- the startup routine. The TBR relative vector table can have at max 256 function
- entries. The jumps to these functions are generated using a SH2A specific,
- non delayed branch instruction JSR/N @(disp8,TBR). You must use GAS and GLD
- from GNU binutils version 2.7 or later for this attribute to work correctly.
- </p>
- <p>In an application, for a function being called once, this attribute
- saves at least 8 bytes of code; and if other successive calls are being
- made to the same function, it saves 2 bytes of code per each of these
- calls.
- </p>
- </dd>
- <dt><code>interrupt_handler</code></dt>
- <dd><a name="index-interrupt_005fhandler-function-attribute_002c-SH"></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.
- </p>
- </dd>
- <dt><code>nosave_low_regs</code></dt>
- <dd><a name="index-nosave_005flow_005fregs-function-attribute_002c-SH"></a>
- <p>Use this attribute on SH targets to indicate that an <code>interrupt_handler</code>
- function should not save and restore registers R0..R7. This can be used on SH3*
- and SH4* targets that have a second R0..R7 register bank for non-reentrant
- interrupt handlers.
- </p>
- </dd>
- <dt><code>renesas</code></dt>
- <dd><a name="index-renesas-function-attribute_002c-SH"></a>
- <p>On SH targets this attribute specifies that the function or struct follows the
- Renesas ABI.
- </p>
- </dd>
- <dt><code>resbank</code></dt>
- <dd><a name="index-resbank-function-attribute_002c-SH"></a>
- <p>On the SH2A target, this attribute enables the high-speed register
- saving and restoration using a register bank for <code>interrupt_handler</code>
- routines. Saving to the bank is performed automatically after the CPU
- accepts an interrupt that uses a register bank.
- </p>
- <p>The nineteen 32-bit registers comprising general register R0 to R14,
- control register GBR, and system registers MACH, MACL, and PR and the
- vector table address offset are saved into a register bank. Register
- banks are stacked in first-in last-out (FILO) sequence. Restoration
- from the bank is executed by issuing a RESBANK instruction.
- </p>
- </dd>
- <dt><code>sp_switch</code></dt>
- <dd><a name="index-sp_005fswitch-function-attribute_002c-SH"></a>
- <p>Use this attribute on the SH to indicate an <code>interrupt_handler</code>
- function should switch to an alternate stack. It expects a string
- argument that names a global variable holding the address of the
- alternate stack.
- </p>
- <div class="smallexample">
- <pre class="smallexample">void *alt_stack;
- void f () __attribute__ ((interrupt_handler,
- sp_switch ("alt_stack")));
- </pre></div>
-
- </dd>
- <dt><code>trap_exit</code></dt>
- <dd><a name="index-trap_005fexit-function-attribute_002c-SH"></a>
- <p>Use this attribute on the SH for an <code>interrupt_handler</code> to return using
- <code>trapa</code> instead of <code>rte</code>. This attribute expects an integer
- argument specifying the trap number to be used.
- </p>
- </dd>
- <dt><code>trapa_handler</code></dt>
- <dd><a name="index-trapa_005fhandler-function-attribute_002c-SH"></a>
- <p>On SH targets this function attribute is similar to <code>interrupt_handler</code>
- but it does not save and restore all registers.
- </p></dd>
- </dl>
-
- <hr>
- <div class="header">
- <p>
- Next: <a href="Symbian-OS-Function-Attributes.html#Symbian-OS-Function-Attributes" accesskey="n" rel="next">Symbian OS Function Attributes</a>, Previous: <a href="S_002f390-Function-Attributes.html#S_002f390-Function-Attributes" accesskey="p" rel="prev">S/390 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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