2015-11-18  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/67790
	* tree-vect-loop.c (vect_is_simple_reduction_1): Remove
	IL rewrite for MINUS_EXPR reductions, rename back to ...
	(vect_is_simple_reduction): ... this, removing the wrapper.
	(vect_force_simple_reduction): Adjust.
	(vectorizable_reduction): Adjust reduc_index for MINUS_EXPR
	reductions and make use if reduc_index in all places.  For
	the final reduction of MINUS_EXPR use PLUS_EXPR.

	* gcc.dg/vect/pr67790.c: New testcase.

From-SVN: r230518