LXR linux/lib/hweight.c

   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
  13unsigned 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}
  28EXPORT_SYMBOL(__sw_hweight32);
  29
  30unsigned 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}
  37EXPORT_SYMBOL(__sw_hweight16);
  38
  39unsigned 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}
  45EXPORT_SYMBOL(__sw_hweight8);
  46
  47unsigned 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}
  68EXPORT_SYMBOL(__sw_hweight64);
  69