This changes the vectorizer to explicitly use the loopsimplify and lcssa utils,
instead of "requiring" the transformations as if they were analyses.
This is not NFC, since it changes the LCSSA behavior - we no longer run LCSSA
for all loops, but rather only for the loops we expect to modify.
Differential Revision: https://reviews.llvm.org/D28868
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@292456 91177308-0d34-0410-b5e6-96231b3b80d8
