LXR linux/tools/lib/hweight.c

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