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

[via llvm-commits]

b-sumner wrote:

> Introducing more LDS while also lowering it also introduces a range of possible pass order binding problems. You could just as well put the pointer in a regular addrspace(1) global

Each workgroup needs a different pointer, and a grid can have a lot of work groups.   I don't think a global would work.

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