gen_jmp_64
u8 gen_jmp_64(u8 *buf, u8 rd, u8 rs, u8 cond, u32 c_off, u32 t_off);
*len += gen_jmp_64(BUF(buf, *len), rd, rs, cond,
*len = gen_jmp_64(buf, 0, 0, ARC_CC_AL, curr_off, epi_off);