coroutines and yielding are a pretty high-level concept that I wouldn't expect to see in a backend, but there's a really great explanation of how to map them to low-level concepts here: http://llvm.lyngvig.org/Articles/Mapping-High-Level-Construc...

the same author actually has a tutorial on how to write green threads yourself http://c9x.me/art/gthreads/intro.html