tree-optimization/106186 - propagate out virtual LC PHI nodes properly

The code to remove LC PHI nodes in clean_up_loop_closed_phi does not handle
virtual operands because may_propagate_copy generally returns false
for them.  The following copies the merge_blocks variant for
dealing with them.

This fixes a missed jump threading in gcc.dg/auto-init-uninit-4.c
which manifests in bogus uninit diagnostics.

	PR tree-optimization/106186
	* (clean_up_loop_closed_phi):
	Properly handle virtual PHI nodes.
1 file changed