tree-vect-stmts.c (get_group_load_store_type): Avoid peeling for gaps by loading only lower halves of vectors if possible.

2019-05-03  Richard Biener  <rguenther@suse.de>

	* tree-vect-stmts.c (get_group_load_store_type): Avoid
	peeling for gaps by loading only lower halves of vectors
	if possible.
	(vectorizable_load): Likewise.

	* gcc.dg/vect/slp-reduc-sad-2.c: New testcase.

From-SVN: r270847