2017-06-09  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/66623
	* tree-vect-loop.c (vect_is_simple_reduction): Cleanup,
	refactor check_reduction into two parts, properly computing
	whether we have to check reduction validity for outer loop
	vectorization.

	* gcc.dg/vect/pr66623.c: New testcase.

From-SVN: r249053