Need help about LLVM build coroutine

[Richard (Rikki) Andrew Cattermole]

 From what I'm reading of the documentation, it looks like you have to 
work at the IR level to declare a coroutine.

This isn't something you can do with only intrinsics in library code.

https://llvm.org/docs/Coroutines.html#introduction

Take note of the function attribute ``presplitcoroutine`` under 
coroutine representation.

https://llvm.org/docs/Coroutines.html#coroutine-representation