One of the cool new features in LLVM 4.0 is intermediate-language support for coroutines http://llvm.org/docs/Coroutines.html.

Gor Nishanov from Microsoft gave a very informative presentation last year on the topic: "LLVM Coroutines: Bringing resumable functions to LLVM"
https://www.youtube.com/watch?v=Ztr8QvMhqmQ