Check lines for some of these tests were regenerated. The difference
is that with opaque pointers SCEVExpander always emits i8 GEPs,
making the address calculation explicit. This is a known problem
that will be solved long term by making all address calculations
explicit.
The vectorizer will choose at times to "vectorize" loops with a scalar
factor (VF=1) with interleaving (IC > 1). This can occasionally produce
better code than the unroller (notable for reductions where it can
produce independent reduction chains that are combined after the loop).
At times this is not very beneficial though, for example when runtime
checks are needed or when the scalar code requires predication.
This addresses the second point, preventing the vectorizer from
interleaving when the scalar loop will require predication. This
prevents it from making a bit of a mess, that is worse than the original
and better left for the unroller to unroll if beneficial. It helps
reverse some of the regressions from D118090.
Differential Revision: https://reviews.llvm.org/D118566
