PR middle-end/35509

	* builtins.c (mathfn_built_in_1): Renamed from mathfn_built_in.
	Add `implicit' parameter.  Handle BUILT_IN_SIGNBIT.
	(mathfn_built_in): Rewrite in terms of mathfn_built_in_1.
	(fold_builtin_classify): Handle BUILT_IN_ISINF_SIGN.
	(fold_builtin_1): Likewise.
	* builtins.def (BUILT_IN_ISINF_SIGN): New.
	c-common.c (check_builtin_function_arguments): Handle
	BUILT_IN_ISINF_SIGN.
	* doc/extend.texi: Document __builtin_isinf_sign.
	* fold-const.c (operand_equal_p): Handle COND_EXPR.

testsuite:
	* gcc.dg/builtins-error.c: Test __builtin_isinf_sign.
	* gcc.dg/tg-tests.h: Likewise.  Mark variables volatile.
	* gcc.dg/torture/builtin-isinf_sign-1.c: New test.

From-SVN: r135517