2013-04-18  Richard Biener  <rguenther@suse.de>

	* tree-vect-data-refs.c (vect_analyze_group_access): Properly
	handle negative step.  Remove redundant checks.
	(vect_create_data_ref_ptr): Avoid ICEs with non-constant steps.
	* tree-vect-stmts.c (vectorizable_load): Instead of asserting
	for negative step and grouped loads fail to vectorize.

From-SVN: r198054