re PR tree-optimization/91756 (g++.dg/lto/alias-3 FAILs)

re PR tree-optimization/91756 (g++.dg/lto/alias-3 FAILs)

2019-09-16  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/91756
	PR tree-optimization/87132
	* tree-ssa-alias.h (enum translate_flags): New.
	(get_continuation_for_phi): Use it instead of simple bool flag.
	(walk_non_aliased_vuses): Likewise.
	* tree-ssa-alias.c (maybe_skip_until): Adjust.
	(get_continuation_for_phi): When looking across backedges only
	disallow valueization.
	(walk_non_aliased_vuses): Adjust.
	* tree-ssa-sccvn.c (vn_reference_lookup_3): Avoid valueization
	if requested.

	* gcc.dg/tree-ssa/ssa-fre-81.c: New testcase.

From-SVN: r275747