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<title>GNU Compiler Collection (GCC) Internals: Cilk Plus Transformation</title>
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<a name="Cilk-Plus-Transformation"></a>
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<p>
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Next: <a href="Gimplification-pass.html#Gimplification-pass" accesskey="n" rel="next">Gimplification pass</a>, Previous: <a href="Parsing-pass.html#Parsing-pass" accesskey="p" rel="prev">Parsing pass</a>, Up: <a href="Passes.html#Passes" accesskey="u" rel="up">Passes</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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<hr>
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<a name="Cilk-Plus-Transformation-1"></a>
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<h3 class="section">9.2 Cilk Plus Transformation</h3>
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<a name="index-CILK_005fPLUS"></a>
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<p>If Cilk Plus generation (flag <samp>-fcilkplus</samp>) is enabled, all the Cilk
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Plus code is transformed into equivalent C and C++ functions. Majority of this
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transformation occurs toward the end of the parsing and right before the
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gimplification pass.
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</p>
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<p>These are the major components to the Cilk Plus language extension:
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</p><ul>
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<li> Array Notations:
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During parsing phase, all the array notation specific information is stored in
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<code>ARRAY_NOTATION_REF</code> tree using the function
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<code>c_parser_array_notation</code>. During the end of parsing, we check the entire
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function to see if there are any array notation specific code (using the
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function <code>contains_array_notation_expr</code>). If this function returns
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true, then we expand them using either <code>expand_array_notation_exprs</code> or
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<code>build_array_notation_expr</code>. For the cases where array notations are
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inside conditions, they are transformed using the function
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<code>fix_conditional_array_notations</code>. The C language-specific routines are
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located in <samp>c/c-array-notation.c</samp> and the equivalent C++ routines are in
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the file <samp>cp/cp-array-notation.c</samp>. Common routines such as functions to
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initialize built-in functions are stored in <samp>array-notation-common.c</samp>.
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</li><li> Cilk keywords:
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<ul>
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<li> <code>_Cilk_spawn</code>:
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The <code>_Cilk_spawn</code> keyword is parsed and the function it contains is marked
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as a spawning function. The spawning function is called the spawner. At
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the end of the parsing phase, appropriate built-in functions are
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added to the spawner that are defined in the Cilk runtime. The appropriate
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locations of these functions, and the internal structures are detailed in
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<code>cilk_init_builtins</code> in the file <samp>cilk-common.c</samp>. The pointers to
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Cilk functions and fields of internal structures are described
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in <samp>cilk.h</samp>. The built-in functions are described in
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<samp>cilk-builtins.def</samp>.
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<p>During gimplification, a new "spawn-helper" function is created.
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The spawned function is replaced with a spawn helper function in the spawner.
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The spawned function-call is moved into the spawn helper. The main function
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that does these transformations is <code>gimplify_cilk_spawn</code> in
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<samp>c-family/cilk.c</samp>. In the spawn-helper, the gimplification function
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<code>gimplify_call_expr</code>, inserts a function call <code>__cilkrts_detach</code>.
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This function is expanded by <code>builtin_expand_cilk_detach</code> located in
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<samp>c-family/cilk.c</samp>.
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</p>
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</li><li> <code>_Cilk_sync</code>:
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<code>_Cilk_sync</code> is parsed like a keyword. During gimplification,
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the function <code>gimplify_cilk_sync</code> in <samp>c-family/cilk.c</samp>, will replace
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this keyword with a set of functions that are stored in the Cilk runtime.
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One of the internal functions inserted during gimplification,
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<code>__cilkrts_pop_frame</code> must be expanded by the compiler and is
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done by <code>builtin_expand_cilk_pop_frame</code> in <samp>cilk-common.c</samp>.
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</li></ul>
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</li></ul>
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<p>Documentation about Cilk Plus and language specification is provided under the
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"Learn" section in <a href="https://www.cilkplus.org">https://www.cilkplus.org</a><!-- /@w -->. It is worth mentioning
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that the current implementation follows ABI 1.1.
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</p>
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<div class="header">
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<p>
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Next: <a href="Gimplification-pass.html#Gimplification-pass" accesskey="n" rel="next">Gimplification pass</a>, Previous: <a href="Parsing-pass.html#Parsing-pass" accesskey="p" rel="prev">Parsing pass</a>, Up: <a href="Passes.html#Passes" accesskey="u" rel="up">Passes</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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