Use simple_dce_from_worklist with match_simplify_replacement.

Use simple_dce_from_worklist with match_simplify_replacement.

This is a simple patch to do some DCE after a successful
match and simplify replacement in PHI-OPT. match and simplify
likes to generate some extra statements which should be cleaned
up.

OK? Bootstrapped and tested on x86_64-linux with no regressions.

Thanks,
Andrew Pinski

gcc/ChangeLog:

	* tree-ssa-phiopt.cc: Include tree-ssa-dce.h
	(replace_phi_edge_with_variable):
	New argument, dce_ssa_names. Call simple_dce_from_worklist.
	(match_simplify_replacement): If we inserted a sequence,
	mark the lhs of the new sequence to be possible dce.
	Always move the statement and mark the lhs (if it is a name)
	as possible to remove.