In SuperWord::output we create a CountedLoopReserveKit, so that we can reverse edits to the loop, in case something goes wrong. As far as I understand all of these conditions should never occur. We should at least add asserts so that we can catch such failures and fix them. We can later decide if it makes sense to clone the whole loop via CountedLoopReserveKit (the loops can be large!), or if we should just have a regular compilation bailout instead (could simplify the code and reduce overhead of loop cloning).

Plus: it seems the checks and bailouts are very selectively applied. I don't see why we would nullptr check some "vector_opd" but not all of them.