Convert references with "counted_by" attributes to/from .ACCESS_WITH_SIZE.

Including the following changes:
* The definition of the new internal function .ACCESS_WITH_SIZE
  in internal-fn.def.
* C FE converts every reference to a FAM with a "counted_by" attribute
  to a call to the internal function .ACCESS_WITH_SIZE.
  (build_component_ref in c_typeck.cc)

  This includes the case when the object is statically allocated and
  initialized.
  In order to make this working, the routine digest_init in c-typeck.cc
  is updated to fold calls to .ACCESS_WITH_SIZE to its first argument
  when require_constant is TRUE.

  However, for the reference inside "offsetof", the "counted_by" attribute is
  ignored since it's not useful at all.
  (c_parser_postfix_expression in c/c-parser.cc)

  In addtion to "offsetof", for the reference inside operator "typeof" and
  "alignof", we ignore counted_by attribute too.

  When building ADDR_EXPR for the .ACCESS_WITH_SIZE in C FE,
  replace the call with its first argument.

* Convert every call to .ACCESS_WITH_SIZE to its first argument.
  (expand_ACCESS_WITH_SIZE in internal-fn.cc)
* Provide the utility routines to check the call is .ACCESS_WITH_SIZE and
  get the reference from the call to .ACCESS_WITH_SIZE.
  (is_access_with_size_p and get_ref_from_access_with_size in tree.cc)

gcc/c/ChangeLog:

	* c-parser.cc (c_parser_postfix_expression): Ignore the counted-by
	attribute when build_component_ref inside offsetof operator.
	* c-tree.h (build_component_ref): Add one more parameter.
	* c-typeck.cc (build_counted_by_ref): New function.
	(build_access_with_size_for_counted_by): New function.
	(build_component_ref): Check the counted-by attribute and build
	call to .ACCESS_WITH_SIZE.
	(build_unary_op): When building ADDR_EXPR for
	.ACCESS_WITH_SIZE, use its first argument.
	(lvalue_p): Accept call to .ACCESS_WITH_SIZE.
	(digest_init): Fold call to .ACCESS_WITH_SIZE to its first
	argument when require_constant is TRUE.

gcc/ChangeLog:

	* internal-fn.cc (expand_ACCESS_WITH_SIZE): New function.
	* internal-fn.def (ACCESS_WITH_SIZE): New internal function.
	* tree.cc (is_access_with_size_p): New function.
	(get_ref_from_access_with_size): New function.
	* tree.h (is_access_with_size_p): New prototype.
	(get_ref_from_access_with_size): New prototype.

gcc/testsuite/ChangeLog:

	* gcc.dg/flex-array-counted-by-2.c: New test.

1 files changed, 1 insertions, 1 deletions

diff --git a/gcc/c/c-tree.h b/gcc/c/c-tree.h
index 531a7e8..56a33b8 100644
--- a/gcc/c/c-tree.h
+++ b/gcc/c/c-tree.h
@@ -779,7 +779,7 @@ extern void mark_exp_read (tree);
 extern tree composite_type (tree, tree);
 extern tree lookup_field (const_tree, tree);
 extern tree build_component_ref (location_t, tree, tree, location_t,
-				 location_t);
+				 location_t, bool = true);
 extern tree build_array_ref (location_t, tree, tree);
 extern tree build_omp_array_section (location_t, tree, tree, tree);
 extern tree build_external_ref (location_t, tree, bool, tree *);