tree-ssa-sccvn.c (sccvn_dom_walker): Add unreachable_dom member and initialize it.

tree-ssa-sccvn.c (sccvn_dom_walker): Add unreachable_dom member and initialize it.

2015-12-04  Richard Biener  <rguenther@suse.de>

	* tree-ssa-sccvn.c (sccvn_dom_walker): Add unreachable_dom
	member and initialize it.
	(sccvn_dom_walker::after_dom_children): Reset unreachable_dom
	if necessary.
	(sccvn_dom_walker::before_dom_children): If unreachable_dom
	is set BB is not reachable either.  Set unreachable_dom
	if not set and BB is unreachable.

From-SVN: r231262