LXR linux/tools/perf/util/hweight.c

   1#include <linux/bitops.h>
   2
   3/**
   4 * hweightN - returns the hamming weight of a N-bit word
   5 * @x: the word to weigh
   6 *
   7 * The Hamming Weight of a number is the total number of bits set in it.
   8 */
   9
  10unsigned int hweight32(unsigned int w)
  11{
  12        unsigned int res = w - ((w >> 1) & 0x55555555);
  13        res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
  14        res = (res + (res >> 4)) & 0x0F0F0F0F;
  15        res = res + (res >> 8);
  16        return (res + (res >> 16)) & 0x000000FF;
  17}
  18
  19unsigned long hweight64(__u64 w)
  20{
  21#if BITS_PER_LONG == 32
  22        return hweight32((unsigned int)(w >> 32)) + hweight32((unsigned int)w);
  23#elif BITS_PER_LONG == 64
  24        __u64 res = w - ((w >> 1) & 0x5555555555555555ul);
  25        res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul);
  26        res = (res + (res >> 4)) & 0x0F0F0F0F0F0F0F0Ful;
  27        res = res + (res >> 8);
  28        res = res + (res >> 16);
  29        return (res + (res >> 32)) & 0x00000000000000FFul;
  30#endif
  31}
  32