re PR tree-optimization/83887 ([graphite] ICE in verify_dominators, at dominance...

re PR tree-optimization/83887 ([graphite] ICE in verify_dominators, at dominance.c:1184 (error: dominator of 3 should be 21, not 18))

2018-01-18  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/83887
	* graphite-scop-detection.c
	(scop_detection::get_nearest_dom_with_single_entry): Remove.
	(scop_detection::get_nearest_pdom_with_single_exit): Likewise.
	(scop_detection::merge_sese): Re-implement with a flood-fill
	algorithm that properly finds a SESE region if it exists.

	* gcc.dg/graphite/pr83887.c: New testcase.
	* gfortran.dg/graphite/pr83887.f90: Likewise.
	* gfortran.dg/graphite/pr83887.f: Likewise.

From-SVN: r256841