Use EDGE_EXECUTABLE in ranger and return UNDEFINED for those edges.

Use EDGE_EXECUTABLE in ranger and return UNDEFINED for those edges.

If an incoming edge is UNDEFINED, don't process it.  Track if other edges
equate to a single value, and add an equivalence if appropriate.

	gcc/
	* gimple-range-fold.cc (fold_using_range::range_of_phi): Ignore
	undefined edges, apply an equivalence if appropriate.
	* gimple-range-gori.cc (gori_compute::outgoing_edge_range_p): Return
	UNDEFINED if EDGE_EXECUTABLE is not set.
	* gimple-range.cc (gimple_ranger::gimple_ranger): Set all edges
	as EXECUTABLE upon startup.
	(gimple_ranger::range_on_edge): Return UNDEFINED for edges without
	EDGE_EXECUTABLE set.
	* vr-values.c (set_and_propagate_unexecutable): New.
	(simplify_using_ranges::fold_cond): Call set_and_propagate.
	(simplify_using_ranges::simplify_switch_using_ranges): Ditto.
	* vr-values.h: Add prototype.

	gcc/testsuite/
	* gcc.dg/tree-ssa/evrp-ignore.c: New.