domwalk.h (dom_walker::dom_walker): Add additional constructor for specifying RPO order and allow NULL for that.

2018-02-01  Richard Biener  <rguenther@suse.de>

	* domwalk.h (dom_walker::dom_walker): Add additional constructor
	for specifying RPO order and allow NULL for that.
	* domwalk.c (dom_walker::dom_walker): Likewise.
	(dom_walker::walk): Handle NULL RPO order.
	* tree-into-ssa.c (rewrite_dom_walker): Do not walk dom children
	in RPO order.
	(rewrite_update_dom_walker): Likewise.
	(mark_def_dom_walker): Likewise.

	* gcc.dg/graphite/pr35356-1.c: Adjust.

From-SVN: r257293