> Well-defined integer overflow would not preclude loop unrolling in this case. One simple alternative would be for the compiler to emit a guard, skipping unrolling in the case that (offset+16) overflows.

To what end?

        for(i = offset; i < (offset + 16); i++) {
            arr[i] = i + 32;
        }

like most loops in most programs isn't designed to overflow. The program isn't any more correct for emitting two translations of the loop, one unrolled and one which is purely a bugged case anyways.

Changing the way the UB manifests while altering the nature of the optimization hasn't actually fixed anything at all here. All this would seem to accomplish would be to increase pressure on the icache.