even to odd for tempering

 y ^= (y << 7) & 0x9d2c5680UL;
 y = spu_xor(spu_and(spu_sl(y, 7), 0x9d2c5680UL), y);
 y = spu_xor(spu_and(spu_slqw(y, 7), 0x9d2c5680UL), y);