* builtins.c (c_strlen): Use TREE_STRING_LENGTH - 1 for max.
	(c_getstr): New function.
	(expand_builtin_strstr): Do nothing if -fcheck-memory-usage.
	If both arguments are constant string, optimize out.
	(expand_builtin_strchr, expand_builtin_strrchr): New functions.
	(expand_builtin_strpbrk): Use c_getstr, do nothing if
	-fcheck-memory-usage.
	(expand_builtin_fputs): Likewise.
	(expand_builtin_strcmp): Add MODE argument.
	Use even if !HAVE_cmpstrsi.
	Optimize the case when both arguments are constant strings.
	(expand_builtin): Adjust expand_builtin_strcmp caller.
	Call expand_builtin_strchr and expand_builtin_strrchr.
	* c-common.c (c_common_nodes_and_builtins): Add strchr and strrchr
	builtins.
	* builtins.def (BUILT_IN_STRRCHR): Add.

	* gcc.c-torture/execute/string-opt-1.c: Add test for strstr
	with both arguments constant strings.
	* gcc.c-torture/execute/string-opt-3.c: New test.
	* gcc.c-torture/execute/string-opt-4.c: New test.
	* gcc.c-torture/execute/string-opt-5.c: New test.

From-SVN: r37338