include/asm-generic/bitops/__fls.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_GENERIC_BITOPS___FLS_H_
   3 #define _ASM_GENERIC_BITOPS___FLS_H_
   4
   5 #include <asm/types.h>
   6
   7 /**
   8  * __fls - find last (most-significant) set bit in a long word
   9  * @word: the word to search
  10  *
  11  * Undefined if no set bit exists, so code should check against 0 first.
  12  */
  13 static __always_inline unsigned long __fls(unsigned long word)
  14 {
  15         int num = BITS_PER_LONG - 1;
  16
  17 #if BITS_PER_LONG == 64
  18         if (!(word & (~0ul << 32))) {
  19                 num -= 32;
  20                 word <<= 32;
  21         }
  22 #endif
  23         if (!(word & (~0ul << (BITS_PER_LONG-16)))) {
  24                 num -= 16;
  25                 word <<= 16;
  26         }
  27         if (!(word & (~0ul << (BITS_PER_LONG-8)))) {
  28                 num -= 8;
  29                 word <<= 8;
  30         }
  31         if (!(word & (~0ul << (BITS_PER_LONG-4)))) {
  32                 num -= 4;
  33                 word <<= 4;
  34         }
  35         if (!(word & (~0ul << (BITS_PER_LONG-2)))) {
  36                 num -= 2;
  37                 word <<= 2;
  38         }
  39         if (!(word & (~0ul << (BITS_PER_LONG-1))))
  40                 num -= 1;
  41         return num;
  42 }
  43
  44 #endif /* _ASM_GENERIC_BITOPS___FLS_H_ */