2016-09-23  Richard Biener  <rguenther@suse.de>

	* tree-ssa-sccvn.c (visit_reference_op_call): Value number
	virtual definition to virtual use if the call devirtualizes
	to a const or pure function.
	(visit_use): Also visit calls we can devirtualize to a
	const or pure function.

	* gcc.dg/tree-ssa/ssa-fre-56.c: New testcase.

From-SVN: r240431