2018-09-04  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/87176
	* tree-ssa-sccvn.c (visit_phi): Remove redundant allsame
	variable.  When value-numbering a virtual PHI node make sure
	to not value-number to the backedge value.

	* gcc.dg/torture/pr87176.c: New testcase.
	* gcc.dg/torture/ssa-fre-1.c: Likewise.

From-SVN: r264077