MD5_SHIFT_24
GG(b, c, d, a, x_0, MD5_SHIFT_24, MD5_CONST_o(19)); /* 20 */
GG(b, c, d, a, x_4, MD5_SHIFT_24, MD5_CONST_o(23)); /* 24 */
GG(b, c, d, a, x_8, MD5_SHIFT_24, MD5_CONST_o(27)); /* 28 */
GG(b, c, d, a, x_12, MD5_SHIFT_24, MD5_CONST_o(31)); /* 32 */