PR tree-optimization/68398

	PR tree-optimization/68398
	* params.def (PARAM_FSM_SCALE_PATH_STMTS): New parameter.
	(PARAM_FSM_SCALE_PATH_BLOCKS): Likewise.
	* tree-ssa-threadbackward.c (fsm_find_control_statement_thread_paths):
	Only count PHIs in the last block in the path.  The others will
	const/copy propagate away.  Add heuristic to allow more irreducible
	subloops to be created when it is likely profitable to do so.

	* tree-ssa-threadbackward.c (fsm_find_control_statement_thread_paths):
	Fix typo in comment.  Use gsi_after_labels and remove the GIMPLE_LABEL
	check from within the loop.  Use gsi_next_nondebug rather than gsi_next.

	PR tree-optimization/68398
	* gcc.dg/tree-ssa/pr66752-3.c: Update expected output.
	* gcc.dg/tree-ssa/ssa-dom-thread-2c.c: Add extra statements on thread
	path to avoid new heuristic allowing more irreducible regions
	* gcc.dg/tree-ssa/ssa-dom-thread-2d.c: Likewise.
	* gcc.dg/tree-ssa/vrp46.c: Likewise.
	* gcc.dg/tree-ssa/ssa-dom-thread-7.c: Update expected output.
	* gcc.dg/tree-ssa/ssa-dom-thread-2g.c: New test.
	* gcc.dg/tree-ssa/ssa-dom-thread-2h.c: Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@232897 138bc75d-0d04-0410-961f-82ee72b054a4