[llvm] [DirectX] Scalarize `extractelement` and `insertelement` with dynamic indices (PR #141676)

[Deric C. via llvm-commits]

================

----------------
Icohedron wrote:

I didn't think 2D vectors were a valid type.

You do make a good point about extra allocas when there are successive insert/extractelement instructions on the same vector. Is there an existing pass that could clean it up?

https://github.com/llvm/llvm-project/pull/141676