[PATCH] Merging Cilk Plus into Trunk (Patch 1 of approximately 22)

["Iyer, Balaji V" <balaji dot v dot iyer at intel dot com>]

Hello Everyone,
	Attached, please find the 1st of ~22 patches that implements Cilk Plus. This patch will implement Elemental Functions into the C compiler.  Please check it in to the trunk if it looks OK.

	Below, I will give you a small example about what elemental function is and how it can be useful. Details about elemental function can be found in the following link (http://software.intel.com/en-us/articles/elemental-functions-writing-data-parallel-code-in-cc-using-intel-cilk-plus)

Let's say we have two for loops like this:

int my_func (int x, int y);

For (ii = 0; ii < 10000; ii++)
	X[ii] = my_func (Y[ii], Z[ii]);

For (jj = 1; jj < 10000; jj++) {
 	A[jj] =  my_func (B[ii], A[jj-1]) + A[jj-1];


Assume that my_func's body is not visible during this compilation (e.g it is in some library). 

If a vectorized version for my_func is available, then the first for loop can be vectorized. However, even if such a version of my_func is available, the 2nd for loop cannot be vectorized. It would be beneficial if there is a vectorized version and a scalar version of my_func. This is where an elemental function comes to play. If we annotate *both* the function declaration and the function with the following attribute, the compiler will create a vector and scalar version of the function. 

__attribute__((vector)) my_func (int x, int y);

__attribute__((vector)) my_func (int x, int y) 
    {
      ... /* Body of the function.  */
    }

If the architecture allows, the vector version will accept the parameters through vector registers and return the result through a vector register. There are several clauses that can be used to convey information about function parameters. The vector version of the function follows a mangling format that is based on the clauses provided and the vectorlength. All these changes are transparent to the user. A great application for elemental functions is writing libraries and reusable functions. Detailed explanations and syntax about these can be found in the Cilk Plus language specification document: http://software.intel.com/sites/default/files/m/6/3/1/cilk_plus_language_specification.pdf

Here are the Changelog Entries:

============================================================================================
gcc/Changelog
2012-09-05  Balaji V. Iyer  <balaji.v.iyer@intel.com>

        * attribs.c (is_elem_fn_attribute_p): New function.
        (decl_attributes): Added a check for Elemental function attribute when
        Cilk Plus is enabled.
        * cgraphunit.c (cgraph_decide_is_function_needed): Added a check for
        cloned elemental function when Cilk Plus is enabled.
        (cgraph_add_new_function): When Cilk Plus is enabled we call
        cgraph_get_create_node.
        (cgraph_analyze_functions): Added a check if the function call is a
        cloned elemental function when Cilk Plus is enabled.
        * elem-function-common.c (find_processor_code): New function.
        (find_vlength_code): Likewise.
        (rename_elem_fn): Likewise.
        (find_suffix): Likewise.
        (find_elem_fn_parm_type_1): Likewise.
        (find_elem_fn_parm_type): Likewise.
        (find_elem_fn_name): Likewise.
        (extract_elem_fn_values): Likewise.
        (is_elem_fn): Likewise.
        * expr.c (expand_expr_real_1): Added a check if Cilk Plus is enabled.
        * function.h (struct function): Added elem_fn_already_cloned field.
        * gimplify.c (gimplify_function_tree): Added a check if Cilk Plus is
        enabled and if the function is an elemental function.  If so, then call
        the function to clone elemental function.
        * langhooks.c (lhd_elem_fn_create_fn): New function.
        * langhooks-def.h (LANG_HOOKS_CILKPLUS): New define.
        (LANG_HOOK_DECLS): Added LANG_HOOKS_CILKPLUS field.
        * langhooks.h (struct lang_hooks_for_cilkplus): New struct.
        (struct lang_hooks): Added a field called cilkplus.
        * tree.h (tree_function_decl): Added a new field called
        elem_fn_already_cloned.
        (DECL_ELEM_FN_ALREADY_CLONED): New define.
        * tree-data-ref.c (find_data_references_in_stmt): Added a check for
        an elemental function call when Cilk Plus is enabled.
        * tree-inline.c (elem_fn_copy_arguments_for_versioning): New function.
        (initialize_elem_fn_cfun): Likewise.
        (tree_elem_fn_versioning): Likewise.
        * tree-vect-stmts.c (vect_get_vec_def_for_operand): Check parm type for
        an elemental function when Cilk Plus is enabled and set data definition
        accordingly.
        (elem_fn_vect_get_vec_def_for_operand): New function.
        (vect_finish_stmt_generation): Added a check for elemental function.
        (vectorizable_function): Check if the function call is a Cilk Plus
        elemental function.  If so, then insert the appopriate mangled name.
        (vectorizable_call): Eliminate the argument requirement when Cilk Plus
        is enabled for vectorization.  Also, set thee appropriate data def. for
        an elemental function call.
        (elem_fn_linear_init_vector): New function.
        * tree.c (build_elem_fn_linear_vector): Likewise.

gcc/c-family/ChangeLog
2012-09-05  Balaji V. Iyer  <balaji.v.iyer@intel.com>

        * c-common.c (struct c_common_attribute_table): Added vector
        attribute for Cilk Plus elemental function.
        (handle_vector_atribute): New function.
        * c-cpp-elem-function.c (create_processor_attribute): Likewise.
        (create_optimize_attribute): Likewise.
        (replace_return_with_new_var): Likewise.
        (elem_fn_build_array): Likewise.
        (replace_array_ref_for_vec): Likewise.
        (fix_elem_fn_return_value): Likewise.
        (add_elem_fn_loop): Likewise.
        (add_elem_fn_mask): Likewise.
        (call_graph_add_fn): Likewise.
        (elem_fn_create_fn): Likewise.
        * c.opt (-fcilkplus): Added new flag.

gcc/c/ChangeLog
2012-09-05  Balaji V. Iyer  <balaji.v.iyer@intel.com>

        * c-decl.c (bind): Added a check for non NULL scope.
        * c-parser.c (c_parser_declaration_or_fndef): Added a check if Cilk
        Plus defined.  If so, then we save the arguments for a function
        declaration.
        (c_parser_attributes): Added a check if Cilk Plus is enabled and if
        elemental function vector attribute is given.  If so, then call the
        function c_parser_elem_fn_expr_list ().
        (c_parser_elem_fn_processor_clause): New function.
        (c_parser_elem_fn_uniform_clause): Likewise.
        (c_parser_elem_fn_linear_clause): Likewise.
        (c_parser_elem_fn_vlength_clause): Likewise.
        (c_parser_elem_fn_expr_list): Likewise.

===========================================================================================

Thanking You,

Yours Sincerely,

Balaji V. Iyer.

Attachment: elem_fn_c_patch.txt
Description: elem_fn_c_patch.txt