tree-ssa-dom.c (dom_opt_dom_walker::optimize_stmt): Pass down the vr_values instance to cprop_into_stmt.

	* tree-ssa-dom.c (dom_opt_dom_walker::optimize_stmt): Pass down
	the vr_values instance to cprop_into_stmt.
	(cprop_into_stmt): Pass vr_values instance down to cprop_operand.
	(cprop_operand): Also query EVRP to determine if OP is a constant.

From-SVN: r263342