LXR linux/include/asm-generic/bitops/fls.h

   1#ifndef _ASM_GENERIC_BITOPS_FLS_H_
   2#define _ASM_GENERIC_BITOPS_FLS_H_
   3
   4/**
   5 * fls - find last (most-significant) bit set
   6 * @x: the word to search
   7 *
   8 * This is defined the same way as ffs.
   9 * Note fls(0) = 0, fls(1) = 1, fls(0x80000000) = 32.
  10 */
  11
  12static __always_inline int fls(int x)
  13{
  14        int r = 32;
  15
  16        if (!x)
  17                return 0;
  18        if (!(x & 0xffff0000u)) {
  19                x <<= 16;
  20                r -= 16;
  21        }
  22        if (!(x & 0xff000000u)) {
  23                x <<= 8;
  24                r -= 8;
  25        }
  26        if (!(x & 0xf0000000u)) {
  27                x <<= 4;
  28                r -= 4;
  29        }
  30        if (!(x & 0xc0000000u)) {
  31                x <<= 2;
  32                r -= 2;
  33        }
  34        if (!(x & 0x80000000u)) {
  35                x <<= 1;
  36                r -= 1;
  37        }
  38        return r;
  39}
  40
  41#endif /* _ASM_GENERIC_BITOPS_FLS_H_ */
  42