text: /* SPDX-License-Identifier: GPL-2.0 */
  #ifndef _ASM_WORD_AT_A_TIME_H
  #define _ASM_WORD_AT_A_TIME_H
  
  #include <linux/kernel.h>
  
  /*
   * This is largely generic for little-endian machines, but the
   * optimal byte mask counting is probably going to be something
   * that is architecture-specific. If you have a reliably fast
   * bit count instruction, that might be better than the multiply
   * and shift, for example.
   */
  struct word_at_a_time {
  	const unsigned long one_bits, high_bits;
  };
  
  #define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) }
  
  #ifdef CONFIG_64BIT
  
  /*
   * Jan Achrenius on G+: microoptimized version of
   * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
   * that works for the bytemasks without having to
   * mask them first.
   */
  static inline long count_masked_bytes(unsigned long mask)
  {
  	return mask*0x0001020304050608ul >> 56;
  }
  
  #else	/* 32-bit case */
  
  /* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
  static inline long count_masked_bytes(long mask)
  {
  	/* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
  	long a = (0x0ff0001+mask) >> 23;
  	/* Fix the 1 for 00 case */
  	return a & mask;
  }
  
  #endif
  
  /* Return nonzero if it has a zero */
  static inline unsigned long has_zero(unsigned long a, unsigned long *bits, const struct word_at_a_time *c)
  {
  	unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;
  	*bits = mask;
  	return mask;
  }
  
  static inline unsigned long prep_zero_mask(unsigned long a, unsigned long bits, const struct word_at_a_time *c)
  {
  	return bits;
  }
  
  static inline unsigned long create_zero_mask(unsigned long bits)
  {
  	bits = (bits - 1) & ~bits;
  	return bits >> 7;
  }
  
  /* The mask we created is directly usable as a bytemask */
  #define zero_bytemask(mask) (mask)
  
  static inline unsigned long find_zero(unsigned long mask)
  {
  	return count_masked_bytes(mask);
  }
  
  /*
   * Load an unaligned word from kernel space.
   *
   * In the (very unlikely) case of the word being a page-crosser
   * and the next page not being mapped, take the exception and
   * return zeroes in the non-existing part.
   */
  static inline unsigned long load_unaligned_zeropad(const void *addr)
  {
  	unsigned long ret, dummy;
  
  	asm(
  		"1:\tmov %2,%0\n"
  		"2:\n"
  		".section .fixup,\"ax\"\n"
  		"3:\t"
  		"lea %2,%1\n\t"
  		"and %3,%1\n\t"
  		"mov (%1),%0\n\t"
  		"leal %2,%%ecx\n\t"
  		"andl %4,%%ecx\n\t"
  		"shll $3,%%ecx\n\t"
  		"shr %%cl,%0\n\t"
  		"jmp 2b\n"
  		".previous\n"
  		_ASM_EXTABLE(1b, 3b)
  		:"=&r" (ret),"=&c" (dummy)
  		:"m" (*(unsigned long *)addr),
  		 "i" (-sizeof(unsigned long)),
  		 "i" (sizeof(unsigned long)-1));
  	return ret;
  }
  
  #endif /* _ASM_WORD_AT_A_TIME_H */
  