arch/mips/boot/compressed/../../../../lib/ashldi3.c:9:19: warning: no previous prototype for '__ashldi3'

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   1f2cfdd349b7647f438c1e552dc1b983da86d830
commit: 31b2f3dc851c65fee288612432c4fc956f1a264e MIPS: enable both vmlinux.gz.itb and vmlinuz for generic
date:   5 weeks ago
config: mips-ci20_defconfig (https://download.01.org/0day-ci/archive/20220204/202202041004.sFUBmVAX-lkp@xxxxxxxxx/config)
compiler: mipsel-linux-gcc (GCC) 11.2.0
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=31b2f3dc851c65fee288612432c4fc956f1a264e
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout 31b2f3dc851c65fee288612432c4fc956f1a264e
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=mips SHELL=/bin/bash

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>

All warnings (new ones prefixed by >>):

   In file included from arch/mips/boot/compressed/ashldi3.c:2:
>> arch/mips/boot/compressed/../../../../lib/ashldi3.c:9:19: warning: no previous prototype for '__ashldi3' [-Wmissing-prototypes]
       9 | long long notrace __ashldi3(long long u, word_type b)
         |                   ^~~~~~~~~


vim +/__ashldi3 +9 arch/mips/boot/compressed/../../../../lib/ashldi3.c

b35cd9884fa5d8 Palmer Dabbelt 2017-05-23  8  
b35cd9884fa5d8 Palmer Dabbelt 2017-05-23 @9  long long notrace __ashldi3(long long u, word_type b)

:::::: The code at line 9 was first introduced by commit
:::::: b35cd9884fa5d81c9d5e7f57c9d03264ae2bd835 lib: Add shared copies of some GCC library routines

:::::: TO: Palmer Dabbelt <palmer@xxxxxxxxxxx>
:::::: CC: Palmer Dabbelt <palmer@xxxxxxxxxxx>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx