Some remarks:

- I don't think doing a bulk backport of ceval.c is the right approach.
Instead, each functionality should be considered and backported
independently, if desired.

- Guido already said that 3.0 should be mostly clean from
compatibility-related code, so forward-porting 2.x opcodes is out of the
question. There's a reason they removed in the first place :-)

- Some functionalities shouldn't be backported, e.g. introducing
SETUP_EXCEPT was motivated by the different semantics of exception
cleanup in py3k, backporting it would probably break some 2.x code.

- Compatibility between the two eval loops (2.x and py3k) is probably
the tip of the iceberg.