[llvm] [AMDGPU] Handle amdgpu.last.use metadata (PR #83816)

[Jay Foad via llvm-commits]

https://github.com/jayfoad commented:

Looks good overall. I think we should document `amdgpu.last.use` in AMDGPUUsage, in a new "LLVM IR Metadata" section like the existing "LLVM IR Intrinsics" documentation.

https://github.com/llvm/llvm-project/pull/83816