[llvm] [AMDGPU] Support lowering of cluster related instrinsics (PR #157978)

[Shilei Tian via llvm-commits]

shiltian wrote:

This is a big PR but there is no obvious way that I can see to split it, since everything is just connected. There are still some changes to be upstreamed, such as the kernel descriptor related changes, which will be in a separate PR.

https://github.com/llvm/llvm-project/pull/157978