The cost of splitting a large vector instruction is not being taken into account...

The cost of splitting a large vector instruction is not being taken into account by the getUserCost function. This was leading to some loops being over unrolled. The cost of a vector instruction is now being multiplied by the cost of the type legalization. This will return a more accurate cost.

Committing on behalf on Brad Nemanich (brad.nemanich@ibm.com)

Differential Revision: https://reviews.llvm.org/D38961

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@316174 91177308-0d34-0410-b5e6-96231b3b80d8