[PATCH v5 3/3] xtensa: Emulate two-byte cmpxchg

[kernel test robot]

Hi Bradley,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]
[also build test ERROR on vgupta-arc/for-curr jcmvbkbc-xtensa/xtensa-for-next linus/master v7.3-rc6 next-20261005]
[cannot apply to vgupta-arc/for-next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Bradley-Morgan/ARC-Emulate-two-byte-cmpxchg/20261005-120658
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20261005120700.383058-4-brads%40mainlining.org
patch subject: [PATCH v5 3/3] xtensa: Emulate two-byte cmpxchg
config: xtensa-allyesconfig (https://download.01.org/0day-ci/archive/20261006/202610061704.rvbolgPy-lkp@intel.com/config)
compiler: xtensa-linux-gcc (GCC) 16.1.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20261006/202610061704.rvbolgPy-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp at intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202610061704.rvbolgPy-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from arch/xtensa/include/asm/atomic.h:19,
                    from include/linux/atomic.h:7,
                    from include/asm-generic/bitops/atomic.h:5,
                    from arch/xtensa/include/asm/bitops.h:192,
                    from include/linux/bitops.h:67,
                    from include/linux/log2.h:12,
                    from kernel/bounds.c:14:
   arch/xtensa/include/asm/cmpxchg.h: In function '__cmpxchg':
>> arch/xtensa/include/asm/cmpxchg.h:79:25: error: implicit declaration of function 'cmpxchg_emu_u16'; did you mean 'cmpxchg_emu_u8'? [-Wimplicit-function-declaration]
      79 |         case 2:  return cmpxchg_emu_u16(ptr, old, new);
         |                         ^~~~~~~~~~~~~~~
         |                         cmpxchg_emu_u8
   make[3]: *** [scripts/Makefile.build:185: kernel/bounds.s] Error 1
   make[3]: Target 'prepare' not remade because of errors.
   make[2]: *** [Makefile:1405: prepare0] Error 2
   make[2]: Target 'prepare' not remade because of errors.
   make[1]: *** [Makefile:248: __sub-make] Error 2
   make[1]: Target 'prepare' not remade because of errors.
   make: *** [Makefile:248: __sub-make] Error 2
   make: Target 'prepare' not remade because of errors.


vim +79 arch/xtensa/include/asm/cmpxchg.h

    73	
    74	static __inline__ unsigned long
    75	__cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size)
    76	{
    77		switch (size) {
    78		case 1:  return cmpxchg_emu_u8(ptr, old, new);
  > 79		case 2:  return cmpxchg_emu_u16(ptr, old, new);
    80		case 4:  return __cmpxchg_u32(ptr, old, new);
    81		default: __cmpxchg_called_with_bad_pointer();
    82			 return old;
    83		}
    84	}
    85	

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