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| <h4 class="subsection">6.57.26 SH Built-in Functions</h4> |
| <p>The following built-in functions are supported on the SH1, SH2, SH3 and SH4 |
| families of processors: |
| </p> |
| <dl> |
| <dt><a name="index-_005f_005fbuiltin_005fset_005fthread_005fpointer"></a>Built-in Function: <em>void</em> <strong>__builtin_set_thread_pointer</strong> <em>(void *<var>ptr</var>)</em></dt> |
| <dd><p>Sets the ‘<samp>GBR</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>GBR</samp>’ and |
| thus the value is preserved across function calls. Changing the ‘<samp>GBR</samp>’ |
| value in user code must be done with caution, since the compiler might use |
| ‘<samp>GBR</samp>’ in order to access thread local variables. |
| </p> |
| </dd></dl> |
| |
| <dl> |
| <dt><a name="index-_005f_005fbuiltin_005fthread_005fpointer"></a>Built-in Function: <em>void *</em> <strong>__builtin_thread_pointer</strong> <em>(void)</em></dt> |
| <dd><p>Returns the value that is currently set in the ‘<samp>GBR</samp>’ register. |
| Memory loads and stores that use the thread pointer as a base address are |
| turned into ‘<samp>GBR</samp>’ based displacement loads and stores, if possible. |
| For example: |
| </p><div class="smallexample"> |
| <pre class="smallexample">struct my_tcb |
| { |
| int a, b, c, d, e; |
| }; |
| |
| int get_tcb_value (void) |
| { |
| // Generate ‘<samp>mov.l @(8,gbr),r0</samp>’ instruction |
| return ((my_tcb*)__builtin_thread_pointer ())->c; |
| } |
| |
| </pre></div> |
| </dd></dl> |
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