re PR c/19449 (__builtin_constant_p cannot resolve to const when optimizing)

re PR c/19449 (__builtin_constant_p cannot resolve to const when optimizing)

	PR c/19449
	* tree.h (force_folding_builtin_constant_p): New decl.
	* builtins.c (force_folding_builtin_constant_p): New variable.
	(fold_builtin_constant_p): Fold immediately also if
	force_folding_builtin_constant_p.

	* c-parser.c (c_parser_get_builtin_args): Add choose_expr_p
	argument.  If set, or it temporarily for parsing of the first
	argument into force_folding_builtin_constant_p.
	(c_parser_postfix_expression): Adjust callers.

	* gcc.c-torture/execute/pr19449.c: New test.

From-SVN: r197393