[llvm] [Coroutines] Create C++ noop coroutine with default function attributes (PR #134878)

[Chuanqi Xu via llvm-commits]

ChuanqiXu9 wrote:

> Really, why aren't we generating this in the frontend? I don't see the benefit to having a special "no-op coroutine", as opposed to just generating a coroutine that's a no-op.

I am not sure. This is historic. The people who implemented it is not active now. The only reason I can see may be the possible optimization. e.g., if we know we're going to resume/destroy a noop coroutine, we can save one memory access.

https://github.com/llvm/llvm-project/pull/134878