[Bug tree-optimization/66558] Missed vectorization of loop with control flow

[alalaw01 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66558

--- Comment #2 from alalaw01 at gcc dot gnu.org ---
This generalizes https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65947, but
vectorizing the predicate as a reduction is not sufficient here.