[CostModel] Add SK_ExtractSubvector handling to getInstructionThroughput (PR39368)

Add ShuffleVectorInst::isExtractSubvectorMask helper to match shuffle masks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@346510 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed