gimple-match-head.c (do_valueize): Return OP if valueize returns NULL_TREE.

gimple-match-head.c (do_valueize): Return OP if valueize returns NULL_TREE.

2017-07-26  Richard Biener  <rguenther@suse.de>

	* gimple-match-head.c (do_valueize): Return OP if valueize
	returns NULL_TREE.
	(get_def): New helper to get at the def stmt of a SSA name
	if valueize allows.
	* genmatch.c (dt_node::gen_kids_1): Use get_def instead of
	do_valueize to get at the def stmt.
	(dt_operand::gen_gimple_expr): Simplify do_valueize calls.

	* gcc/testsuite/gcc.dg/pr70920-2.c: Adjust for transform already
	happening in ccp1.
	* gcc/testsuite/gcc.dg/pr70920-4.c: Likewise.

From-SVN: r250565