Gregory's Server@neauoire iirc gur pendulum cpu's paper actually describes a "garbage stack" which is pushed to for otherwise dustructive operations and has data pulled back off of it when its being reversed. there's also sets of exchanging operations instead of moving ones, if you have loads and stores happen in pairs so that they balence out you might be able to get a similar benefit
@bx yeah, and uxn has the advantage of the keep mode which is non destructive. More more than that, I can probably unliteralize directly from the graveyard if I know the exact value, but in the case of itteration loops, the iterator and boundary are the same value, so that's an enthropy-free operation if I release it after the loop.