[clang] [llvm] Introduce -defer-thinlto-prelink-coro-split that skips Coro passes in ThinLTO pre-link pipeline (PR #107153)

[Adrian Vogelsgesang via cfe-commits]

vogelsgesang wrote:

> Unfortunately, it seems we have an "either-or" decision here

Although... Is this even an either-or decision?

Could we add coro-split to the llc unconditionally, also for non-thin-lto pipelines? Afaict, coro-split is a no-op pass if coroutines were already split previously. Hence, codegen would simply work, even if a thin-lto-prelink pipeline is combined with a non-thin-lto post-link step.

Doing so, I think we wouldn't need to introduce a flag at all?

https://github.com/llvm/llvm-project/pull/107153