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| <h3 class="section">9.2 Cilk Plus Transformation</h3> |
| <a name="index-CILK_005fPLUS"></a> |
| |
| <p>If Cilk Plus generation (flag <samp>-fcilkplus</samp>) is enabled, all the Cilk |
| Plus code is transformed into equivalent C and C++ functions. Majority of this |
| transformation occurs toward the end of the parsing and right before the |
| gimplification pass. |
| </p> |
| <p>These are the major components to the Cilk Plus language extension: |
| </p><ul> |
| <li> Array Notations: |
| During parsing phase, all the array notation specific information is stored in |
| <code>ARRAY_NOTATION_REF</code> tree using the function |
| <code>c_parser_array_notation</code>. During the end of parsing, we check the entire |
| function to see if there are any array notation specific code (using the |
| function <code>contains_array_notation_expr</code>). If this function returns |
| true, then we expand them using either <code>expand_array_notation_exprs</code> or |
| <code>build_array_notation_expr</code>. For the cases where array notations are |
| inside conditions, they are transformed using the function |
| <code>fix_conditional_array_notations</code>. The C language-specific routines are |
| located in <samp>c/c-array-notation.c</samp> and the equivalent C++ routines are in |
| the file <samp>cp/cp-array-notation.c</samp>. Common routines such as functions to |
| initialize built-in functions are stored in <samp>array-notation-common.c</samp>. |
| |
| </li><li> Cilk keywords: |
| <ul> |
| <li> <code>_Cilk_spawn</code>: |
| The <code>_Cilk_spawn</code> keyword is parsed and the function it contains is marked |
| as a spawning function. The spawning function is called the spawner. At |
| the end of the parsing phase, appropriate built-in functions are |
| added to the spawner that are defined in the Cilk runtime. The appropriate |
| locations of these functions, and the internal structures are detailed in |
| <code>cilk_init_builtins</code> in the file <samp>cilk-common.c</samp>. The pointers to |
| Cilk functions and fields of internal structures are described |
| in <samp>cilk.h</samp>. The built-in functions are described in |
| <samp>cilk-builtins.def</samp>. |
| |
| <p>During gimplification, a new "spawn-helper" function is created. |
| The spawned function is replaced with a spawn helper function in the spawner. |
| The spawned function-call is moved into the spawn helper. The main function |
| that does these transformations is <code>gimplify_cilk_spawn</code> in |
| <samp>c-family/cilk.c</samp>. In the spawn-helper, the gimplification function |
| <code>gimplify_call_expr</code>, inserts a function call <code>__cilkrts_detach</code>. |
| This function is expanded by <code>builtin_expand_cilk_detach</code> located in |
| <samp>c-family/cilk.c</samp>. |
| </p> |
| </li><li> <code>_Cilk_sync</code>: |
| <code>_Cilk_sync</code> is parsed like a keyword. During gimplification, |
| the function <code>gimplify_cilk_sync</code> in <samp>c-family/cilk.c</samp>, will replace |
| this keyword with a set of functions that are stored in the Cilk runtime. |
| One of the internal functions inserted during gimplification, |
| <code>__cilkrts_pop_frame</code> must be expanded by the compiler and is |
| done by <code>builtin_expand_cilk_pop_frame</code> in <samp>cilk-common.c</samp>. |
| |
| </li></ul> |
| </li></ul> |
| |
| <p>Documentation about Cilk Plus and language specification is provided under the |
| "Learn" section in <a href="http://www.cilkplus.org/">http://www.cilkplus.org/</a><!-- /@w -->. It is worth mentioning |
| that the current implementation follows ABI 1.1. |
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