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
  11 unsigned 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
  27 unsigned 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
  35 unsigned 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
  42 unsigned 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 }