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<h4 class="subsection">6.58.24 SH Built-in Functions</h4>
<p>The following built-in functions are supported on the SH1, SH2, SH3 and SH4
families of processors:
<div class="defun">
— Built-in Function: void <b>__builtin_set_thread_pointer</b> (<var>void *ptr</var>)<var><a name="index-g_t_005f_005fbuiltin_005fset_005fthread_005fpointer-4142"></a></var><br>
<blockquote><p>Sets the ‘<samp><span class="samp">GBR</span></samp>’ register to the specified value <var>ptr</var>. This is usually
used by system code that manages threads and execution contexts. The compiler
normally does not generate code that modifies the contents of ‘<samp><span class="samp">GBR</span></samp>’ and
thus the value is preserved across function calls. Changing the ‘<samp><span class="samp">GBR</span></samp>’
value in user code must be done with caution, since the compiler might use
‘<samp><span class="samp">GBR</span></samp>’ in order to access thread local variables.
</blockquote></div>
<div class="defun">
— Built-in Function: void * <b>__builtin_thread_pointer</b> (<var>void</var>)<var><a name="index-g_t_005f_005fbuiltin_005fthread_005fpointer-4143"></a></var><br>
<blockquote><p>Returns the value that is currently set in the ‘<samp><span class="samp">GBR</span></samp>’ register.
Memory loads and stores that use the thread pointer as a base address are
turned into ‘<samp><span class="samp">GBR</span></samp>’ based displacement loads and stores, if possible.
For example:
<pre class="smallexample"> struct my_tcb
{
int a, b, c, d, e;
};
int get_tcb_value (void)
{
// Generate ‘<samp><span class="samp">mov.l @(8,gbr),r0</span></samp>’ instruction
return ((my_tcb*)__builtin_thread_pointer ())->c;
}
</pre>
</blockquote></div>
<div class="defun">
— Built-in Function: unsigned int <b>__builtin_sh_get_fpscr</b> (<var>void</var>)<var><a name="index-g_t_005f_005fbuiltin_005fsh_005fget_005ffpscr-4144"></a></var><br>
<blockquote><p>Returns the value that is currently set in the ‘<samp><span class="samp">FPSCR</span></samp>’ register.
</p></blockquote></div>
<div class="defun">
— Built-in Function: void <b>__builtin_sh_set_fpscr</b> (<var>unsigned int val</var>)<var><a name="index-g_t_005f_005fbuiltin_005fsh_005fset_005ffpscr-4145"></a></var><br>
<blockquote><p>Sets the ‘<samp><span class="samp">FPSCR</span></samp>’ register to the specified value <var>val</var>, while
preserving the current values of the FR, SZ and PR bits.
</p></blockquote></div>
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