re PR tree-optimization/83238 ([graphite] ICE in graphite_can_represent_scev, at graphite-scop-detection.c:971)

2017-12-04  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/83238
	* graphite-scop-detection.c (scop_detection::merge_sese): Make
	code match comment, rejecting invalid SESE regions.

	* gcc.dg/graphite/pr83238.c: New testcase.

From-SVN: r255375