[llvm] [Coroutines] fix coroutines + std::unique_ptr with async exceptions validation errors (PR #149691)

[Chuanqi Xu via llvm-commits]

https://github.com/ChuanqiXu9 commented:

I had a impression that this patch tries to fix problematic patterns after the conversion. This is generally unwanted.  We prefer to make the checks before the conversion. e.g., in certain cases, let's avoid adding something as the spills or vice versa.

It will be helpful to me to understand the problem if you can give more description to the issue with IR examples.

https://github.com/llvm/llvm-project/pull/149691