tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: de5540965853e514a85d3b775e9049deb85a2ff3 commit: cddc40f5617e53f97ef019d5b29c1bd6cbb031ec mips: always link byteswap helpers into decompressor date: 6 days ago config: mips-randconfig-r005-20210711 (attached as .config) compiler: mips64-linux-gcc (GCC) 9.3.0 reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=cddc40f5617e53f97ef019d5b29c1bd6cbb031ec git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git git fetch --no-tags linus master git checkout cddc40f5617e53f97ef019d5b29c1bd6cbb031ec # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=mips If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot All warnings (new ones prefixed by >>): >> arch/mips/boot/compressed/bswapsi.c:5:22: warning: no previous prototype for '__bswapsi2' [-Wmissing-prototypes] 5 | unsigned int notrace __bswapsi2(unsigned int u) | ^~~~~~~~~~ --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org