[llvm] [AMDGPU] Automatic conversion from wave32 to wave64 (PR #137376)

[via llvm-commits]

alex-t wrote:

A few questions to discuss right now:
1. May we assume that for the targets which have a wave32 as default correct attribute will be set by the FE?
2. Non-convergent intrinsic calls are left in the IR as a calls. I guess we should change the callee version (.i32/i64) if we set wave64 on the caller.

https://github.com/llvm/llvm-project/pull/137376