2016-02-15  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/69776
	* tree-ssa-sccvn.h (vn_reference_lookup): Adjust prototype.
	* tree-ssa-sccvn.c (vn_reference_lookup): Add parameter to
	indicate whether we can use TBAA to disambiguate against stores.
	Use alias-set zero if not.
	(visit_reference_op_store): Do not use TBAA when looking up
	redundant stores.
	* tree-ssa-pre.c (compute_avail): Use TBAA here.
	(eliminate_dom_walker::before_dom_children): But not when looking
	up redundant stores.

	* gcc.dg/torture/pr69776.c: New testcase.

From-SVN: r233418