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

[Philip Reames via llvm-commits]

preames wrote:

Thank you for doing this.  This API has become quite complicated over time.  I'd played with trying something like this a couple times, and kept getting stuck.  Thank you for pushing it through.  

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