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<h3 class="section">9.2 Cilk Plus Transformation</h3>
<p><a name="index-CILK_005fPLUS-1683"></a>
If Cilk Plus generation (flag <samp><span class="option">-fcilkplus</span></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>These are the major components to the Cilk Plus language extension:
<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><span class="file">c/c-array-notation.c</span></samp> and the equivalent C++ routines are in
the file <samp><span class="file">cp/cp-array-notation.c</span></samp>. Common routines such as functions to
initialize built-in functions are stored in <samp><span class="file">array-notation-common.c</span></samp>.
<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><span class="file">cilk-common.c</span></samp>. The pointers to
Cilk functions and fields of internal structures are described
in <samp><span class="file">cilk.h</span></samp>. The built-in functions are described in
<samp><span class="file">cilk-builtins.def</span></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><span class="file">c-family/cilk.c</span></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><span class="file">c-family/cilk.c</span></samp>.
<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><span class="file">c-family/cilk.c</span></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><span class="file">cilk-common.c</span></samp>.
</ul>
</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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