That reminds me--a friend was telling me earlier today about a piece of software he was working on that only allowed forward jumps. (It ensures that the program halts.)

It does slightly more than that - it provides a cheap computation of the upper bound of how long it will take.

Yeah, that too. Come to think of it, that was probably more his concern than just halting.

Going out on a limb here, but I don't suppose it was for a superoptimizer?