tools/include/asm-generic/bitops/__ffs.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _TOOLS_LINUX_ASM_GENERIC_BITOPS___FFS_H_
   3 #define _TOOLS_LINUX_ASM_GENERIC_BITOPS___FFS_H_
   4
   5 #include <asm/types.h>
   6 #include <asm/bitsperlong.h>
   7
   8 /**
   9  * __ffs - find first bit in word.
  10  * @word: The word to search
  11  *
  12  * Undefined if no bit exists, so code should check against 0 first.
  13  */
  14 static __always_inline unsigned long __ffs(unsigned long word)
  15 {
  16         int num = 0;
  17
  18 #if __BITS_PER_LONG == 64
  19         if ((word & 0xffffffff) == 0) {
  20                 num += 32;
  21                 word >>= 32;
  22         }
  23 #endif
  24         if ((word & 0xffff) == 0) {
  25                 num += 16;
  26                 word >>= 16;
  27         }
  28         if ((word & 0xff) == 0) {
  29                 num += 8;
  30                 word >>= 8;
  31         }
  32         if ((word & 0xf) == 0) {
  33                 num += 4;
  34                 word >>= 4;
  35         }
  36         if ((word & 0x3) == 0) {
  37                 num += 2;
  38                 word >>= 2;
  39         }
  40         if ((word & 0x1) == 0)
  41                 num += 1;
  42         return num;
  43 }
  44
  45 #endif /* _TOOLS_LINUX_ASM_GENERIC_BITOPS___FFS_H_ */