Cosmin,

You may find this code interesting as well, and it would be a third
potential candidate for your project:
http://webkit.org/blog/189/announcing-squirrelfish/

Paul

PS:
If the observations on that page are correct, than FB would benefit
from refactoring 'looper' (essentially a parse tree walker coroutine)
into a byte-code engine. Not sure if it would benefit from "direct
threading" (unrelated to execution threads), as the instructions would
be much higher level than those in Squirrelfish, Lua or a JVM.