include/asm-generic/bitops/__fls.h

   1 #ifndef _ASM_GENERIC_BITOPS___FLS_H_
   2 #define _ASM_GENERIC_BITOPS___FLS_H_
   3
   4 #include <asm/types.h>
   5
   6 /**
   7  * __fls - find last (most-significant) set bit in a long word
   8  * @word: the word to search
   9  *
  10  * Undefined if no set bit exists, so code should check against 0 first.
  11  */
  12 static __always_inline unsigned long __fls(unsigned long word)
  13 {
  14         int num = BITS_PER_LONG - 1;
  15
  16 #if BITS_PER_LONG == 64
  17         if (!(word & (~0ul << 32))) {
  18                 num -= 32;
  19                 word <<= 32;
  20         }
  21 #endif
  22         if (!(word & (~0ul << (BITS_PER_LONG-16)))) {
  23                 num -= 16;
  24                 word <<= 16;
  25         }
  26         if (!(word & (~0ul << (BITS_PER_LONG-8)))) {
  27                 num -= 8;
  28                 word <<= 8;
  29         }
  30         if (!(word & (~0ul << (BITS_PER_LONG-4)))) {
  31                 num -= 4;
  32                 word <<= 4;
  33         }
  34         if (!(word & (~0ul << (BITS_PER_LONG-2)))) {
  35                 num -= 2;
  36                 word <<= 2;
  37         }
  38         if (!(word & (~0ul << (BITS_PER_LONG-1))))
  39                 num -= 1;
  40         return num;
  41 }
  42
  43 #endif /* _ASM_GENERIC_BITOPS___FLS_H_ */