I think that from this commit

https://github.com/imasahiro/rujit/commit/eb2e6cc5da47c212e8...

To this one

https://github.com/imasahiro/rujit/commit/c0e131bad4f0551425...

resides the JIT implementation; it was better if it was a real fork of Ruby Git, so one could compare Ruby master to RuJIT in order to look at the changes.