middle-end/96453 - relax gimple_expand_vec_cond_expr

middle-end/96453 - relax gimple_expand_vec_cond_expr

This relaxes the condition under which we also try NE_EXPR
for a fake generated compare in addition to LT_EXPR given
the fact the verification ICEd when it failed but obviously
was only implemented for constants.  Thus the patch removes
the verification and the restriction to constant operands.

2020-09-23  Richard Biener  <rguenther@suse.de>

	PR middle-end/96453
	* gimple-isel.cc (gimple_expand_vec_cond_expr): Remove
	LT_EXPR -> NE_EXPR verification and also apply it for
	non-constant masks.

	* gcc.dg/pr96453.c: New testcase.