PR tree-optimization/18601
	* tree-cfg.c (thread_jumps, thread_jumps_from_bb): Removed.
	(tree_forwarder_block_p): Do not consider blocks that are its own
	successors forwarders.
	(cleanup_forwarder_blocks, remove_forwarder_block): New functions.
	(cleanup_tree_cfg): Use cleanup_forwarder_blocks instead of
	thread_jumps.
	* tree-flow.h (bb_ann_d): Remove forwardable.

Co-Authored-By: Kazu Hirata <kazu@cs.umass.edu>

From-SVN: r91787