[llvm] [DXIL] Implement pow lowering (PR #86733)

[Paul Kirth via llvm-commits]

ilovepi wrote:

@farzonl I'm sorry to say that I think you can ignore my issue. I found an error in my bisect script, and discovered that the toolchain I'd pointed the script at was pointed to a clang that wasn't getting updated w/ the clang build. Because of that, when I ran the reproducer script it still pointed to a broken (but not updated version of clang) and I assumed your commit was still bad. So I'm very sorry for wasting your time.

https://github.com/llvm/llvm-project/pull/86733