[PATCH] Remove backedge handling support in tree-ssa-threadupdate.c

[PATCH] Remove backedge handling support in tree-ssa-threadupdate.c

	* tree-ssa-threadupdate.c (register_jump_thraed): Assert that a
	non-FSM path has no edges marked with EDGE_DFS_BACK.
	(ssa_redirect_edges): No longer call mark_loop_for_removal.
	(thread_single_edge, def_split_header_continue_p): Remove.
	(bb_ends_with_multiway_branch): Likewise.
	(thread_through_loop_header): Remove cases of threading from
	latch through the header.  Simplify knowing we won't thread
	the latch.
	(thread_through_all_blocks): Simplify knowing that only the FSM
	threader needs to handle backedges.

From-SVN: r229982