Dear Fortranners,

we should be able to simplify the length of a substring with known
constant bounds.  The attached patch adds this.

Regtested on x86_64-pc-linux-gnu.

OK for mainline?  Since this should be rather safe, to at least 11-branch?

Thanks,
Harald


Fortran - simplify length of substring with constant bounds

gcc/fortran/ChangeLog:

	PR fortran/100950
	* simplify.c (substring_has_constant_len): New.
	(gfc_simplify_len): Handle case of substrings with constant
	bounds.

gcc/testsuite/ChangeLog:

	PR fortran/100950
	* gfortran.dg/pr100950.f90: New test.