2012-05-11  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/52537
	* frontend-passes.c (optimize_op):  Change
	old-style comparison operators to new-style, simplify
	switch as a result.
	(empty_string):  New function.
	(get_len_trim_call):  New function.
	(optimize_comparison):  If comparing to an empty string,
	use comparison of len_trim to zero.
	Use new-style comparison operators only.
	(optimize_trim):  Use get_len_trim_call.

2012-05-11  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/52537
	* gfortran.dg/string_compare_4.f90:  New test.

From-SVN: r187406