[llvm] [AMDGPU] Introduce "amdgpu-sw-lower-lds" pass to lower LDS accesses. (PR #87265)

[Jon Chesterfield via llvm-commits]

https://github.com/JonChesterfield commented:

Large blocks of this will be correct. I know that because they're exact copy and pastes from the LDS lowering pass I wrote, complete with my esoteric naming convention choices.

Heuristically, I think this will be broken. It's very large, heavily copy&paste themed from another pass, and has very large amounts of generated lit tests. It also runs unconditionally which means it'll change code which doesn't use the sanitizer which is extra wrong.

However I really don't want this to land in rocm as it will then stay in the current state forever, and if it lands in trunk there's a better chance of fixing it post commit.

So overall, landing this might be the lesser of two evils.

https://github.com/llvm/llvm-project/pull/87265