In this patch we are trying to do two things:
1) If the width of vectorization list candidate is bigger than vector reg width, we will break it down to fit the vector reg.
2) We do not vectorize the width which is not power of two.

The performance result shows it will help some spec benchmarks. mesa improved 6.97% and ammp improved 1.54%. 

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189830 91177308-0d34-0410-b5e6-96231b3b80d8