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kernel/linux-rt-4.4.41/include/asm-generic/bitops/__fls.h 881 Bytes
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  #ifndef _ASM_GENERIC_BITOPS___FLS_H_
  #define _ASM_GENERIC_BITOPS___FLS_H_
  
  #include <asm/types.h>
  
  /**
   * __fls - find last (most-significant) set bit in a long word
   * @word: the word to search
   *
   * Undefined if no set bit exists, so code should check against 0 first.
   */
  static __always_inline unsigned long __fls(unsigned long word)
  {
  	int num = BITS_PER_LONG - 1;
  
  #if BITS_PER_LONG == 64
  	if (!(word & (~0ul << 32))) {
  		num -= 32;
  		word <<= 32;
  	}
  #endif
  	if (!(word & (~0ul << (BITS_PER_LONG-16)))) {
  		num -= 16;
  		word <<= 16;
  	}
  	if (!(word & (~0ul << (BITS_PER_LONG-8)))) {
  		num -= 8;
  		word <<= 8;
  	}
  	if (!(word & (~0ul << (BITS_PER_LONG-4)))) {
  		num -= 4;
  		word <<= 4;
  	}
  	if (!(word & (~0ul << (BITS_PER_LONG-2)))) {
  		num -= 2;
  		word <<= 2;
  	}
  	if (!(word & (~0ul << (BITS_PER_LONG-1))))
  		num -= 1;
  	return num;
  }
  
  #endif /* _ASM_GENERIC_BITOPS___FLS_H_ */