Parallel Suffix cleanup

[jamierpond]

Not totally sure how this can be turned into AI right now... i think this function might be too simple for associative iteration?

template<typename S>
constexpr auto parallelSuffix(S input) {
    auto
        log2Count = log2_of_power_of_two(S::NBits),
        power = 1;
    auto
        result = input,
        shiftMask = S{~S::MostSignificantBit};

    for (;;) {
        result = result ^ result.shiftIntraLaneLeft(power, shiftMask);
        if (!--log2Count) { break; }
        shiftMask = shiftMask & S{shiftMask.value() >> power};
        power <<= 1;
    }

    return S{result};
}