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Linux/include/asm-generic/bitops/fls.h

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  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 
 13 static __always_inline int fls(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 

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