Vector peeling cost model 1/6

Vector peeling cost model 1/6

gcc/ChangeLog:

2017-05-30  Robin Dapp  <rdapp@linux.vnet.ibm.com>

	* tree-vect-data-refs.c (vect_compute_data_ref_alignment): Create
	DR_HAS_NEGATIVE_STEP.
	(vect_update_misalignment_for_peel): Define DR_MISALIGNMENT.
	(vect_enhance_data_refs_alignment): Use.
	(vect_duplicate_ssa_name_ptr_info): Use.
	* tree-vectorizer.h (dr_misalignment): Use.
	(known_alignment_for_access_p): Use.

From-SVN: r248675