re PR tree-optimization/87931 (ICE in vectorizable_reduction, at tree-vect-loop.c:6193 since r265876)

2018-11-13  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/87931
	* tree-vect-loop.c (vect_is_simple_reduction): Restrict
	nested cycles we support to latch computations vectorizable_reduction
	handles.

	* gcc.dg/graphite/pr87931.c: New testcase.

From-SVN: r266075