limb = mpz_getlimbn(d_val_gmp, i);
      if (mp_bits_per_limb == 64)
      {
        uint64_t lo = limb;
        uint64_t hi = (limb >> 32);
        x           = lo ^ res;
        x           = ((x >> 16) ^ x) * p0;
        x           = ((x >> 16) ^ x) * p1;
        x           = ((x >> 16) ^ x);
        p0          = s_hash_primes[j++];
        if (j == s_n_primes) j = 0;
        p1 = s_hash_primes[j++];
        if (j == s_n_primes) j = 0;
        x = x ^ hi;
      }
      else
      {
        assert(mp_bits_per_limb == 32);
        x = res ^ limb;
      }