2017-09-07  Richard Biener  <rguenther@suse.de>

	* passes.def (pass_split_crit_edges): Remove instance before PRE.
	* tree-ssa-pre.c (pass_pre::execute): Instead manually split
	critical edges here, after loop init.
	(pass_data_pre): Remove PROP_no_crit_edges flags.
	* tree-ssa-sccvn.c (vn_reference_lookup_3): Use vn_valueize
	for valueization of call args to avoid leaking VN_TOP.
	(visit_use): Assert we do not visit default defs.
	(init_scc_vn): Use build_decl for VN_TOP to make name nicer.
	Use error_mark_node to more easily detect leaking VN_TOP.
	All default-defs are varying, not VN_TOP.  Mark them visited.
	(run_scc_vn): Make code match comment.

	* gcc.dg/tree-ssa/ssa-thread-12.c: XFAIL third FSM threading
	opportunity.

From-SVN: r251833