[clang] [Coroutines] Mark parameter allocas with coro.outside.frame metadata (PR #127653)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

I'm not really happy with that... but if the semantics were never properly defined in the first place, I guess this isn't making things worse.

Not sure if marking the allocas themselves is actually the right approach long-term.  It seems like there's a distinction between code that's "inside" the coroutine (between the begin/end) and "outside" the coroutine, and there are a bunch of restrictions on code that's "outside" the coroutine.  I'm not sure I really understand the mechanics of that, though.

https://github.com/llvm/llvm-project/pull/127653