[llvm] [CostModel] Add a DstTy to getShuffleCost (PR #141634)

[David Green via llvm-commits]

davemgreen wrote:

Thanks. I have rebased this and given it some more testing on various test suites and architectures. It is intended to roughly be an NFC, but there is a chance some of the new asserts will trigger in some cases, with mismatching dst types and masks. 

https://github.com/llvm/llvm-project/pull/141634