PR tree-optimization/21513
	* builtins.c (build_builtin_expect_predicate): New function.
	(fold_builtin_expect): Add argument for expected value.
	Distribute __builtin_expect over short-circuiting operations.
	Fold nested builtin_expects.
	(fold_builtin_2): Adjust call to fold_builtin_expect.

From-SVN: r128147