[llvm] [NVPTX] Add syncscope support for cmpxchg (PR #140812)

[via llvm-commits]

gonzalobg wrote:

@akshayrdeodhar when looking at the tests, e.g., here: https://github.com/llvm/llvm-project/blob/026e94ab2832d1e207439c8f52f2482206b848f5/llvm/test/CodeGen/NVPTX/cmpxchg-sm90.ll#L28 

I observe that a non-atomic load is being generated to read the initial CAS value.
Do you agree?

If so, that load needs to be an atomic load of the appropriate scope.

https://github.com/llvm/llvm-project/pull/140812