* builtins.c (expand_builtin_strcmp): Use const*_rtx when

	* builtins.c (expand_builtin_strcmp): Use const*_rtx when
	expanding strcmp at compile-time.  Add another transformation.
	(expand_builtin_strncmp): Add more transformations.  Call
	expand_builtin_memcmp, not expand_builtin_strcmp, under
	appropriate conditions if HAVE_cmpstrsi.

testsuite:
	gcc.c-torture/execute/string-opt-3.c: Add more strcmp checks.
	gcc.c-torture/execute/string-opt-8.c: Add more strncmp checks.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@37963 138bc75d-0d04-0410-961f-82ee72b054a4