[intel-linux-intel-lts:5.4/yocto 1/2] arch/x86/kernel/tsc.c:1263:6: warning: variable 'rem' is used uninitialized whenever 'if' condition is false

[kernel test robot <lkp@intel.com>]

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tree:   https://github.com/intel/linux-intel-lts.git 5.4/yocto
head:   53cbd8c20c3f8e8afcc3482e6dd4c9400fc77dcd
commit: 056abbf6314ea7d95396062560c605f172e7535e [1/2] ptp: PSE TGPIO IOCTLs fix
config: x86_64-randconfig-r013-20210625 (attached as .config)
compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 9ca0171a9ffdef5fdb1511d197a3fd72490362de)
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
        # install x86_64 cross compiling tool for clang build
        # apt-get install binutils-x86-64-linux-gnu
        # https://github.com/intel/linux-intel-lts/commit/056abbf6314ea7d95396062560c605f172e7535e
        git remote add intel-linux-intel-lts https://github.com/intel/linux-intel-lts.git
        git fetch --no-tags intel-linux-intel-lts 5.4/yocto
        git checkout 056abbf6314ea7d95396062560c605f172e7535e
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 

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

All warnings (new ones prefixed by >>):

>> arch/x86/kernel/tsc.c:1263:6: warning: variable 'rem' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
           if (art_to_tsc_numerator)
               ^~~~~~~~~~~~~~~~~~~~
   arch/x86/kernel/tsc.c:1267:8: note: uninitialized use occurs here
           tmp = rem * art_to_tsc_denominator;
                 ^~~
   arch/x86/kernel/tsc.c:1263:2: note: remove the 'if' if its condition is always true
           if (art_to_tsc_numerator)
           ^~~~~~~~~~~~~~~~~~~~~~~~~
   arch/x86/kernel/tsc.c:1257:19: note: initialize the variable 'rem' to silence this warning
           u64 tmp, res, rem;
                            ^
                             = 0
   1 warning generated.


vim +1263 arch/x86/kernel/tsc.c

  1244	
  1245	/**
  1246	 * convert_tsc_to_art() - Returns ART value associated with system counter
  1247	 *
  1248	 * Converts input TSC to the corresponding ART value using conversion
  1249	 * factors discovered by detect_art()
  1250	 *
  1251	 * Return:
  1252	 * u64 ART value
  1253	 */
  1254	int convert_tsc_to_art(const struct system_counterval_t *system_counter,
  1255			       u64 *art)
  1256	{
  1257		u64 tmp, res, rem;
  1258	
  1259		if (system_counter->cs != art_related_clocksource)
  1260			return -EINVAL;
  1261	
  1262		res = system_counter->cycles - art_to_tsc_offset;
> 1263		if (art_to_tsc_numerator)
  1264			rem = do_div(res, art_to_tsc_numerator);
  1265	
  1266		*art = res * art_to_tsc_denominator;
  1267		tmp = rem * art_to_tsc_denominator;
  1268	
  1269		if (art_to_tsc_numerator)
  1270			do_div(tmp, art_to_tsc_numerator);
  1271		*art += tmp;
  1272	
  1273		return 0;
  1274	}
  1275	EXPORT_SYMBOL(convert_tsc_to_art);
  1276	

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

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