[llvm] [VectorCombine] Add support for zext/sext/trunc to shuffleToIdentity (PR #92696)

[David Green via llvm-commits]

davemgreen wrote:

> I did a partial review of the existing code, and my suggestions are along the lines of the following diff. I think it would be nice if you could improve the existing code as an NFC patch before landing this patch.

Do you want to put together a patch for them? It is hard to see why the cast<Instruction> is always correct but some of the other changes look decent.

https://github.com/llvm/llvm-project/pull/92696