[llvm] [RFC] IR: Define noalias.addrspace metadata (PR #102461)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> Is the MD a promise to the backend that the attached memory operation is not in a specific address space?

Yes, for the underlying object definition.

> 
> Who will attach the MD to the IR? FE or some LLVM passes? FE may not be able to figure out the real address space of some memory operations.

The main user is the frontend since OpenCL/CUDA give the guarantee. We can also infer this in many cases in backend passes.

https://github.com/llvm/llvm-project/pull/102461