Apply loop-rotate to several vectorizer tests.

Such loops shouldn't be vectorized due to the loops form.
After applying loop-rotate (+simplifycfg) the tests again start to check
what they are intended to check.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223170 91177308-0d34-0410-b5e6-96231b3b80d8
PR21302. Vectorize only bottom-tested loops.

rdar://problem/18886083

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223171 91177308-0d34-0410-b5e6-96231b3b80d8