[llvm] [AMDGPU] Make readonly noilas kernel arguments constant memory (PR #139629)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> Yes, const only guaranties it is not modified in this function. Arguably one should use atomics for cross-thread communication though.

Yes, you need to use atomics. But that doesn't change the readonlyness of the pointer. Atomic load is still just a load 


https://github.com/llvm/llvm-project/pull/139629