PR tree-optimization/77820

	PR tree-optimization/77820
	* tree-ssa-threadedge.c
	(edge_forwards_cmp_to_conditional_jump_through_empty_bb_p): New
	function.
	(thread_across_edge): Add call to
	edge_forwards_cmp_to_conditional_jump_through_empty_bb_p.

	PR tree-optimization/77820
	* gcc.dg/tree-ssa/phi_on_compare-1.c: New testcase.
	* gcc.dg/tree-ssa/phi_on_compare-2.c: New testcase.
	* gcc.dg/tree-ssa/phi_on_compare-3.c: New testcase.
	* gcc.dg/tree-ssa/phi_on_compare-4.c: New testcase.
	* gcc.dg/tree-ssa/split-path-6.c: Update testcase.
	* gcc.target/sh/pr51244-20.c: Update testcase.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@272261 138bc75d-0d04-0410-961f-82ee72b054a4