tree-optimization/104960 - unsplit edges after late sinking

tree-optimization/104960 - unsplit edges after late sinking

Something went wrong when testing the earlier patch to move the
late sinking to before the late phiopt for PR102008.  The following
makes sure to unsplit edges after the late sinking since the split
edges confuse the following phiopt leading to missed optimizations.

I've went for a new pass parameter for this to avoid changing the
CFG after the early sinking pass at this point.

2022-03-17  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/104960
	* passes.def: Add pass parameter to pass_sink_code, mark
	last one to unsplit edges.
	* tree-ssa-sink.cc (pass_sink_code::set_pass_param): New.
	(pass_sink_code::execute): Always execute TODO_cleanup_cfg
	when we need to unsplit edges.

	* gcc.dg/gimplefe-37.c: Adjust to allow either the true
	or false edge to have a forwarder.