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
  10 unsigned 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
  19 unsigned 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 }