root/lib/hweight.c

DEFINITIONS

1. __sw_hweight32
2. __sw_hweight16
3. __sw_hweight8
4. __sw_hweight64

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/export.h>
   3 #include <linux/bitops.h>
   4 #include <asm/types.h>
   5 
   6 /**
   7  * hweightN - returns the hamming weight of a N-bit word
   8  * @x: the word to weigh
   9  *
  10  * The Hamming Weight of a number is the total number of bits set in it.
  11  */
  12 
  13 unsigned int __sw_hweight32(unsigned int w)
  14 {
  15 #ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER
  16         w -= (w >> 1) & 0x55555555;
  17         w =  (w & 0x33333333) + ((w >> 2) & 0x33333333);
  18         w =  (w + (w >> 4)) & 0x0f0f0f0f;
  19         return (w * 0x01010101) >> 24;
  20 #else
  21         unsigned int res = w - ((w >> 1) & 0x55555555);
  22         res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
  23         res = (res + (res >> 4)) & 0x0F0F0F0F;
  24         res = res + (res >> 8);
  25         return (res + (res >> 16)) & 0x000000FF;
  26 #endif
  27 }
  28 EXPORT_SYMBOL(__sw_hweight32);
  29 
  30 unsigned int __sw_hweight16(unsigned int w)
  31 {
  32         unsigned int res = w - ((w >> 1) & 0x5555);
  33         res = (res & 0x3333) + ((res >> 2) & 0x3333);
  34         res = (res + (res >> 4)) & 0x0F0F;
  35         return (res + (res >> 8)) & 0x00FF;
  36 }
  37 EXPORT_SYMBOL(__sw_hweight16);
  38 
  39 unsigned int __sw_hweight8(unsigned int w)
  40 {
  41         unsigned int res = w - ((w >> 1) & 0x55);
  42         res = (res & 0x33) + ((res >> 2) & 0x33);
  43         return (res + (res >> 4)) & 0x0F;
  44 }
  45 EXPORT_SYMBOL(__sw_hweight8);
  46 
  47 unsigned long __sw_hweight64(__u64 w)
  48 {
  49 #if BITS_PER_LONG == 32
  50         return __sw_hweight32((unsigned int)(w >> 32)) +
  51                __sw_hweight32((unsigned int)w);
  52 #elif BITS_PER_LONG == 64
  53 #ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER
  54         w -= (w >> 1) & 0x5555555555555555ul;
  55         w =  (w & 0x3333333333333333ul) + ((w >> 2) & 0x3333333333333333ul);
  56         w =  (w + (w >> 4)) & 0x0f0f0f0f0f0f0f0ful;
  57         return (w * 0x0101010101010101ul) >> 56;
  58 #else
  59         __u64 res = w - ((w >> 1) & 0x5555555555555555ul);
  60         res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul);
  61         res = (res + (res >> 4)) & 0x0F0F0F0F0F0F0F0Ful;
  62         res = res + (res >> 8);
  63         res = res + (res >> 16);
  64         return (res + (res >> 32)) & 0x00000000000000FFul;
  65 #endif
  66 #endif
  67 }
  68 EXPORT_SYMBOL(__sw_hweight64);