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, 8 insertions, 2 deletions

diff --git a/gcc/c/c-parser.cc b/gcc/c/c-parser.cc
index 00f8bf4..2d9e9c0 100644
--- a/gcc/c/c-parser.cc
+++ b/gcc/c/c-parser.cc
@@ -10848,9 +10848,12 @@ c_parser_postfix_expression (c_parser *parser)
 	    if (c_parser_next_token_is (parser, CPP_NAME))
 	      {
 		c_token *comp_tok = c_parser_peek_token (parser);
+		/* Ignore the counted_by attribute for reference inside
+		   offsetof since the information is not useful at all.  */
 		offsetof_ref
 		  = build_component_ref (loc, offsetof_ref, comp_tok->value,
-					 comp_tok->location, UNKNOWN_LOCATION);
+					 comp_tok->location, UNKNOWN_LOCATION,
+					 false);
 		c_parser_consume_token (parser);
 		while (c_parser_next_token_is (parser, CPP_DOT)
 		       || c_parser_next_token_is (parser,
@@ -10877,11 +10880,14 @@ c_parser_postfix_expression (c_parser *parser)
 			    break;
 			  }
 			c_token *comp_tok = c_parser_peek_token (parser);
+			/* Ignore the counted_by attribute for reference inside
+			   offsetof since the information is not useful.  */
 			offsetof_ref
 			  = build_component_ref (loc, offsetof_ref,
 						 comp_tok->value,
 						 comp_tok->location,
-						 UNKNOWN_LOCATION);
+						 UNKNOWN_LOCATION,
+						 false);
 			c_parser_consume_token (parser);
 		      }
 		    else