tree-ssa-pre.c (eliminate_dom_walker::before_dom_children): Eliminate edges marked as not executable by SCCVN.

2015-08-12  Richard Biener  <rguenther@suse.de>

	* tree-ssa-pre.c (eliminate_dom_walker::before_dom_children):
	Eliminate edges marked as not executable by SCCVN.
	* tree-ssa-sccvn.c: Include gimple-iterator.h.
	(cond_dom_walker): Rename to sccvn_dom_walker.
	(sccvn_dom_walker::before_dom_children): Value-number defs
	of all stmts.
	(run_scc_vn): Remove loop value-numbering all SSA names.
	Drop not visited SSA names to varying.

	* gcc.dg/tree-ssa/ssa-fre-43.c: Adjust.

From-SVN: r226801