re PR tree-optimization/92751 (VN partial def support confused about clobbers)

2019-12-03  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/92751
	* tree-ssa-sccvn.c (vn_walk_cb_data::push_partial_def): Fail
	when a clobber ends up in the partial-def vector.
	(vn_reference_lookup_3): Let clobbers be handled by the
	assignment from CTOR handling.

	* g++.dg/tree-ssa/pr92751.C: New testcase.

From-SVN: r278931