code: function ADD64AC(v, a, b0, b1) {
      var o0 = v[a] + b0;
      if (b0 < 0) {
          o0 += 0x100000000;
      }
      var o1 = v[a + 1] + b1;
      if (o0 >= 0x100000000) {
          o1++;
      }
      v[a] = o0;
      v[a + 1] = o1;
  }
docs: 64-bit unsigned addition Sets v[a,a+1] += b b0 is the low 32 bits of b, b1 represents the high 32 bits