[clang] [llvm] AMDGPU: Add llvm.amdgcn.s.wait.event intrinsic (PR #180170)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

We have things like `__builtin_readcyclecounter` that lowers to something different every time the HW team changes the clock interface, was wondering if we could just do something similar but I don't know the full context here.

https://github.com/llvm/llvm-project/pull/180170