linux-kernel - arch/alpha/include/asm/xchg.h:234:32: sparse: sparse: cast truncates bits from constant value (5f0ecafe becomes fe)

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Date:   Sat, 25 Jul 2020 15:15:39 +0800
From:   kernel test robot <lkp@...el.com>
To:     Gao Xiang <hsiangkao@....com>
Cc:     kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: arch/alpha/include/asm/xchg.h:234:32: sparse: sparse: cast truncates
 bits from constant value (5f0ecafe becomes fe)

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   23ee3e4e5bd27bdbc0f1785eef7209ce872794c7
commit: 47e4937a4a7ca4184fd282791dfee76c6799966a erofs: move erofs out of staging
date:   11 months ago
config: alpha-randconfig-s031-20200725 (attached as .config)
compiler: alpha-linux-gcc (GCC) 9.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # apt-get install sparse
        # sparse version: v0.6.2-93-g4c6cbe55-dirty
        git checkout 47e4937a4a7ca4184fd282791dfee76c6799966a
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=alpha 

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


sparse warnings: (new ones prefixed by >>)

   fs/erofs/zdata.c: note: in included file (through arch/alpha/include/asm/cmpxchg.h, arch/alpha/include/asm/atomic.h, include/linux/atomic.h, ...):
>> arch/alpha/include/asm/xchg.h:234:32: sparse: sparse: cast truncates bits from constant value (5f0ecafe becomes fe)
>> arch/alpha/include/asm/xchg.h:236:32: sparse: sparse: cast truncates bits from constant value (5f0ecafe becomes cafe)
>> arch/alpha/include/asm/xchg.h:234:32: sparse: sparse: cast truncates bits from constant value (5f0ecafe becomes fe)
>> arch/alpha/include/asm/xchg.h:234:32: sparse: sparse: cast truncates bits from constant value (5f0edead becomes ad)
>> arch/alpha/include/asm/xchg.h:236:32: sparse: sparse: cast truncates bits from constant value (5f0ecafe becomes cafe)
>> arch/alpha/include/asm/xchg.h:236:32: sparse: sparse: cast truncates bits from constant value (5f0edead becomes dead)

vim +234 arch/alpha/include/asm/xchg.h

a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  227  
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  228  static __always_inline unsigned long
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  229  ____cmpxchg(, volatile void *ptr, unsigned long old, unsigned long new,
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  230  	      int size)
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  231  {
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  232  	switch (size) {
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  233  		case 1:
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31 @234  			return ____cmpxchg(_u8, ptr, old, new);
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  235  		case 2:
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31 @236  			return ____cmpxchg(_u16, ptr, old, new);
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  237  		case 4:
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  238  			return ____cmpxchg(_u32, ptr, old, new);
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  239  		case 8:
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  240  			return ____cmpxchg(_u64, ptr, old, new);
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  241  	}
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  242  	__cmpxchg_called_with_bad_pointer();
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  243  	return old;
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  244  }
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  245  

:::::: The code at line 234 was first introduced by commit
:::::: a6209d6d71f2ab8c63cc1587ef65490d83022baf alpha: xchg/cmpxchg cleanup and fixes

:::::: TO: Ivan Kokshaysky <ink@...assic.park.msu.ru>
:::::: CC: Linus Torvalds <torvalds@...ux-foundation.org>

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

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