PR tree-optimization/59597
	* tree-ssa-threadupdate.c (dump_jump_thread_path): Move to earlier
	in file.  Accept new argument REGISTERING and use it to modify
	dump output appropriately.
	(register_jump_thread): Corresponding changes.
	(mark_threaded_blocks): Reinstate code to cancel unprofitable
	thread paths involving joiner blocks.  Add code to dump cancelled
	jump threading paths.

	PR tree-optimization/59597
	* gcc.dg/tree-ssa/pr59597.c: New test.

From-SVN: r206941