tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 
master
head:   06a4ec1d9dc652e17ee3ac2ceb6c7cf6c2b75cdd
commit: c9b0299034665d594e56ee343f28033d1b24de6d MIPS: Use fallthrough for 
arch/mips
date:   3 months ago
config: mips-randconfig-m031-20200818 (attached as .config)
compiler: mips-linux-gcc (GCC) 9.3.0

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

New smatch warnings:
arch/mips/include/asm/fpu.h:79 __enable_fpu() warn: ignoring unreachable code.
arch/mips/include/asm/fpu.h:79 __enable_fpu() warn: ignoring unreachable code.

Old smatch warnings:
arch/mips/kernel/traps.c:1914 nmi_exception_handler() warn: ignoring 
unreachable code.

# 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c9b0299034665d594e56ee343f28033d1b24de6d
git remote add linus 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
git fetch --no-tags linus master
git checkout c9b0299034665d594e56ee343f28033d1b24de6d
vim +79 arch/mips/include/asm/fpu.h

    53  
    54  static inline int __enable_fpu(enum fpu_mode mode)
    55  {
    56          int fr;
    57  
    58          switch (mode) {
    59          case FPU_AS_IS:
    60                  /* just enable the FPU in its current mode */
    61                  set_c0_status(ST0_CU1);
    62                  enable_fpu_hazard();
    63                  return 0;
    64  
    65          case FPU_HYBRID:
    66                  if (!cpu_has_fre)
    67                          return SIGFPE;
    68  
    69                  /* set FRE */
    70                  set_c0_config5(MIPS_CONF5_FRE);
    71                  goto fr_common;
    72  
    73          case FPU_64BIT:
    74  #if !(defined(CONFIG_CPU_MIPSR2) || defined(CONFIG_CPU_MIPSR6) \
    75        || defined(CONFIG_64BIT))
    76                  /* we only have a 32-bit FPU */
    77                  return SIGFPE;
    78  #endif
  > 79                  fallthrough;
    80          case FPU_32BIT:
    81                  if (cpu_has_fre) {
    82                          /* clear FRE */
    83                          clear_c0_config5(MIPS_CONF5_FRE);
    84                  }
    85  fr_common:
    86                  /* set CU1 & change FR appropriately */
    87                  fr = (int)mode & FPU_FR_MASK;
    88                  change_c0_status(ST0_CU1 | ST0_FR, ST0_CU1 | (fr ? 
ST0_FR : 0));
    89                  enable_fpu_hazard();
    90  
    91                  /* check FR has the desired value */
    92                  if (!!(read_c0_status() & ST0_FR) == !!fr)
    93                          return 0;
    94  
    95                  /* unsupported FR value */
    96                  __disable_fpu();
    97                  return SIGFPE;
    98  
    99          default:
   100                  BUG();
   101          }
   102  
   103          return SIGFPE;
   104  }
   105  

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

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