Efficient lowering of vector sdiv when the divisor is a splatted power of two constant.
PR 14848. The lowered sequence is based on the existing sequence the target-independent
DAG Combiner creates for the scalar case.

Patch by Zvi Rackover.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171953 91177308-0d34-0410-b5e6-96231b3b80d8