[llvm] [NVPTX] Auto-Upgrade some nvvm.annotations to attributes (PR #119261)

[Alex MacLean via llvm-commits]

AlexMaclean wrote:

> Hi, we run into a failure in downstream project (i.e., IREE) with the change. I'm not an expert of this area, but I'd like to see how to fix our problem properly. Without the test, we are generating something like:

Hi @hanhanW, my guess here is that your downstream project contains a front-end that is still generating IR that designates kernels via the `nvvm.annotations` metadata, If this IR is directly lowered via the backend (without getting serialized or otherwise going though a path where auto-upgrade runs), then this metadata will no longer be recognized. 

If my assumption is correct, to fix this you should update your frontend to mark kernels via the calling convention. (Similar to this change for clang: https://github.com/llvm/llvm-project/pull/120806/files#diff-148cd424d4a2056106448d04727450e281ca1bf03ac68d5db2e8dff59d397090R261)

https://github.com/llvm/llvm-project/blob/34929853bc39d28943373b8a96371a7e81e98917/clang/lib/CodeGen/Targets/NVPTX.cpp#L288

https://github.com/llvm/llvm-project/pull/119261