tree-optimization/100089 - BB vectorization of if-converted loop bodies

tree-optimization/100089 - BB vectorization of if-converted loop bodies

The PR complains that when we only partially BB vectorize an
if-converted loop body that this can leave unvectorized code
unconditionally executed and thus effectively slow down code.
For -O2 we already mitigated the issue by not doing BB vectorization
when not all if-converted stmts were covered but the issue is
present with -O3 as well.  Thus the following simply extends the
fix to cover all but the unlimited cost models.  It is after all
very likely that we vectorize some stmts, if only a single
paired store.

2022-01-21  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/100089
	* tree-vect-slp.cc (vect_slp_region): Reject BB vectorization
	of if-converted loops with unvectorized COND_EXPRs for
	all but the unlimited cost models.