clz

    pub fn clz(a: Const, bits: Limb) Limb {
        // Limbs are stored in little-endian order but we need to iterate big-endian.
        if (!a.positive and !a.eqlZero()) return 0;
        var total_limb_lz: Limb = 0;
        var i: usize = a.limbs.len;
        const bits_per_limb = @bitSizeOf(Limb);
        while (i != 0) {
            i -= 1;
            const this_limb_lz = @clz(a.limbs[i]);
            total_limb_lz += this_limb_lz;
            if (this_limb_lz != bits_per_limb) break;
        }
        const total_limb_bits = a.limbs.len * bits_per_limb;
        return total_limb_lz + bits - total_limb_bits;
    }