re PR tree-optimization/90883 (Generated code is worse if returned struct is unnamed)

re PR tree-optimization/90883 (Generated code is worse if returned struct is unnamed)

2019-10-11  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/90883
	PR tree-optimization/91091
	* tree-ssa-sccvn.c (vn_reference_lookup_3): Use correct
	alias-sets both for recording VN table entries and continuing
	walking after translating through copies.  Handle same-sized
	reads from SSA names by returning the plain SSA name.
	(eliminate_dom_walker::eliminate_stmt): Properly handle
	non-size precision stores in redundant store elimination.

	* gcc.dg/torture/20191011-1.c: New testcase.
	* gcc.dg/tree-ssa/ssa-fre-82.c: Likewise.
	* gcc.dg/tree-ssa/ssa-fre-83.c: Likewise.
	* gcc.dg/tree-ssa/redundant-assign-zero-1.c: Disable FRE.
	* gcc.dg/tree-ssa/redundant-assign-zero-2.c: Likewise.

From-SVN: r276882