I’ve been searching for a while now, but I could not find any engine that emits LLVM bytecode.
But somehow I cannot belief there is no such engine 🙂
You can get more info on JXcore here.
This part of the answer is in a response to Albert’s answer:
According to ktrzeciaknubisa’s post they will publish the source as soon as they are out of the beta stages and have clean code…this might take some time.
There doesn’t seem to be any.
It appears Webkit now includes this functionality as of May 2014:
The code for this seems to be here:
JXCore (a fork of Nodejs) claims to have implemented that. Since Feb 2015, it is open source, the code is here on GitHub.