c-family: Add __builtin_assoc_barrier

New builtin to enable explicit use of PAREN_EXPR in C & C++ code.

Signed-off-by: Matthias Kretz <m.kretz@gsi.de>

gcc/testsuite/ChangeLog:

	* c-c++-common/builtin-assoc-barrier-1.c: New test.

gcc/cp/ChangeLog:

	* constexpr.c (cxx_eval_constant_expression): Handle PAREN_EXPR
	via cxx_eval_constant_expression.
	* cp-objcp-common.c (names_builtin_p): Handle
	RID_BUILTIN_ASSOC_BARRIER.
	* cp-tree.h: Adjust TREE_LANG_FLAG documentation to include
	PAREN_EXPR in REF_PARENTHESIZED_P.
	(REF_PARENTHESIZED_P): Add PAREN_EXPR.
	* parser.c (cp_parser_postfix_expression): Handle
	RID_BUILTIN_ASSOC_BARRIER.
	* pt.c (tsubst_copy_and_build): If the PAREN_EXPR is not a
	parenthesized initializer, build a new PAREN_EXPR.
	* semantics.c (force_paren_expr): Simplify conditionals. Set
	REF_PARENTHESIZED_P on PAREN_EXPR.
	(maybe_undo_parenthesized_ref): Test PAREN_EXPR for
	REF_PARENTHESIZED_P.

gcc/c-family/ChangeLog:

	* c-common.c (c_common_reswords): Add __builtin_assoc_barrier.
	* c-common.h (enum rid): Add RID_BUILTIN_ASSOC_BARRIER.

gcc/c/ChangeLog:

	* c-decl.c (names_builtin_p): Handle RID_BUILTIN_ASSOC_BARRIER.
	* c-parser.c (c_parser_postfix_expression): Likewise.

gcc/ChangeLog:

	* doc/extend.texi: Document __builtin_assoc_barrier.

2 files changed, 21 insertions, 0 deletions

diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 63d806a..3e28a03 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -10621,6 +10621,7 @@ names_builtin_p (const char *name)
     case RID_BUILTIN_HAS_ATTRIBUTE:
     case RID_BUILTIN_SHUFFLE:
     case RID_BUILTIN_SHUFFLEVECTOR:
+    case RID_BUILTIN_ASSOC_BARRIER:
     case RID_CHOOSE_EXPR:
     case RID_OFFSETOF:
     case RID_TYPES_COMPATIBLE_P:
diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index 40c46ec..81eea18 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -8962,6 +8962,7 @@ c_parser_predefined_identifier (c_parser *parser)
 			 assignment-expression ,
 			 assignment-expression, )
      __builtin_convertvector ( assignment-expression , type-name )
+     __builtin_assoc_barrier ( assignment-expression )
 
    offsetof-member-designator:
      identifier
@@ -10107,6 +10108,25 @@ c_parser_postfix_expression (c_parser *parser)
 	      }
 	  }
 	  break;
+	case RID_BUILTIN_ASSOC_BARRIER:
+	  {
+	    location_t start_loc = loc;
+	    c_parser_consume_token (parser);
+	    matching_parens parens;
+	    if (!parens.require_open (parser))
+	      {
+		expr.set_error ();
+		break;
+	      }
+	    e1 = c_parser_expr_no_commas (parser, NULL);
+	    mark_exp_read (e1.value);
+	    location_t end_loc = c_parser_peek_token (parser)->get_finish ();
+	    parens.skip_until_found_close (parser);
+	    expr.value = build1_loc (loc, PAREN_EXPR, TREE_TYPE (e1.value),
+				     e1.value);
+	    set_c_expr_source_range (&expr, start_loc, end_loc);
+	  }
+	  break;
 	case RID_AT_SELECTOR:
 	  {
 	    gcc_assert (c_dialect_objc ());