tree-optimization/96349 - avoid abnormal coalescing issues in loop split

tree-optimization/96349 - avoid abnormal coalescing issues in loop split

This avoids splitting a loop when the entry value of a loop PHI is
involved with abnormal coalescing.

2020-07-28  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/96349
	* tree-ssa-loop-split.c (stmt_semi_invariant_p_1): When the
	condition runs into a loop PHI with an abnormal entry value give up.

	* gcc.dg/torture/pr96349.c: New testcase.