2010-10-22  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/45720
	* tree-vect-data-refs.c (vect_update_misalignment_for_peel):
	Handle negative step.
	(vect_enhance_data_refs_alignment): Likewise.
	* tree-vect-loop-manip.c (vect_gen_niters_for_prolog_loop): Likewise.
	(vect_create_cond_for_align_checks): Likewise.
	(vect_create_cond_for_alias_checks): Likewise.

	* gcc.dg/torture/pr45720.c: New testcase.

From-SVN: r165832