[llvm] [Coroutines] Split buildCoroutineFrame into normalization and frame building (PR #108076)

[Chuanqi Xu via llvm-commits]

ChuanqiXu9 wrote:

I think the concept `normalization` is pretty narrow in CoroFrame itself (or even buildCoroutineFrame itself). It is simply some transformations to make it easier to construct and use the frame. So I didn't take it as a formal concept. 

https://github.com/llvm/llvm-project/pull/108076