include/asm-generic/bitops/fls64.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_GENERIC_BITOPS_FLS64_H_
   3 #define _ASM_GENERIC_BITOPS_FLS64_H_
   4
   5 #include <asm/types.h>
   6
   7 /**
   8  * fls64 - find last set bit in a 64-bit word
   9  * @x: the word to search
  10  *
  11  * This is defined in a similar way as the libc and compiler builtin
  12  * ffsll, but returns the position of the most significant set bit.
  13  *
  14  * fls64(value) returns 0 if value is 0 or the position of the last
  15  * set bit if value is nonzero. The last (most significant) bit is
  16  * at position 64.
  17  */
  18 #if BITS_PER_LONG == 32
  19 static __always_inline int fls64(__u64 x)
  20 {
  21         __u32 h = x >> 32;
  22         if (h)
  23                 return fls(h) + 32;
  24         return fls(x);
  25 }
  26 #elif BITS_PER_LONG == 64
  27 static __always_inline int fls64(__u64 x)
  28 {
  29         if (x == 0)
  30                 return 0;
  31         return __fls(x) + 1;
  32 }
  33 #else
  34 #error BITS_PER_LONG not 32 or 64
  35 #endif
  36
  37 #endif /* _ASM_GENERIC_BITOPS_FLS64_H_ */