fix invalid bounds on array refs

fix invalid bounds on array refs

While enabling graphite in -O3 we found a Fortran testcase that fails
because the max of the type domain is -1.  We used to add that as a constraint
to the elements accessed by the array, leading to a unfeasible constraint:
0 <= i <= -1.  Having that constraint, drops the data reference as that says
that there are no elements accessed in the array.

	* graphite-dependences.c (scop_get_reads): Add extra dumps.
	(scop_get_must_writes): Same.
	(scop_get_may_writes): Same.
	(compute_deps): Same.
	* graphite-sese-to-poly.c (bounds_are_valid): New.
	(pdr_add_data_dimensions): Call bounds_are_valid.

	* gfortran.dg/graphite/run-id-3.f90: New.

Co-Authored-By: Sebastian Pop <s.pop@samsung.com>
From-SVN: r231191