>
> Antonio Cuni made some experiments on PyPy about this, If you ask at
> the pypy-dev mailing list or on irc (#pypy on freenode.net) he or
> others can explain what happened.
The biggest complication I can think of with a register-based VM is that you
have to decref objects as soon as they aren't used anymore, which means you have
to track the actual lifetime of registers (while it's done automatically with a
stack-based design).