LXR linux/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/**
   6 * fls - find last (most-significant) bit set
   7 * @x: the word to search
   8 *
   9 * This is defined the same way as ffs.
  10 * Note fls(0) = 0, fls(1) = 1, fls(0x80000000) = 32.
  11 */
  12
  13static __always_inline int fls(unsigned int x)
  14{
  15        int r = 32;
  16
  17        if (!x)
  18                return 0;
  19        if (!(x & 0xffff0000u)) {
  20                x <<= 16;
  21                r -= 16;
  22        }
  23        if (!(x & 0xff000000u)) {
  24                x <<= 8;
  25                r -= 8;
  26        }
  27        if (!(x & 0xf0000000u)) {
  28                x <<= 4;
  29                r -= 4;
  30        }
  31        if (!(x & 0xc0000000u)) {
  32                x <<= 2;
  33                r -= 2;
  34        }
  35        if (!(x & 0x80000000u)) {
  36                x <<= 1;
  37                r -= 1;
  38        }
  39        return r;
  40}
  41
  42#endif /* _ASM_GENERIC_BITOPS_FLS_H_ */
  43