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
  13#ifndef __HAVE_ARCH_SW_HWEIGHT
  14unsigned int __sw_hweight32(unsigned int w)
  15{
  16#ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER
  17        w -= (w >> 1) & 0x55555555;
  18        w =  (w & 0x33333333) + ((w >> 2) & 0x33333333);
  19        w =  (w + (w >> 4)) & 0x0f0f0f0f;
  20        return (w * 0x01010101) >> 24;
  21#else
  22        unsigned int res = w - ((w >> 1) & 0x55555555);
  23        res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
  24        res = (res + (res >> 4)) & 0x0F0F0F0F;
  25        res = res + (res >> 8);
  26        return (res + (res >> 16)) & 0x000000FF;
  27#endif
  28}
  29EXPORT_SYMBOL(__sw_hweight32);
  30#endif
  31
  32unsigned int __sw_hweight16(unsigned int w)
  33{
  34        unsigned int res = w - ((w >> 1) & 0x5555);
  35        res = (res & 0x3333) + ((res >> 2) & 0x3333);
  36        res = (res + (res >> 4)) & 0x0F0F;
  37        return (res + (res >> 8)) & 0x00FF;
  38}
  39EXPORT_SYMBOL(__sw_hweight16);
  40
  41unsigned int __sw_hweight8(unsigned int w)
  42{
  43        unsigned int res = w - ((w >> 1) & 0x55);
  44        res = (res & 0x33) + ((res >> 2) & 0x33);
  45        return (res + (res >> 4)) & 0x0F;
  46}
  47EXPORT_SYMBOL(__sw_hweight8);
  48
  49#ifndef __HAVE_ARCH_SW_HWEIGHT
  50unsigned long __sw_hweight64(__u64 w)
  51{
  52#if BITS_PER_LONG == 32
  53        return __sw_hweight32((unsigned int)(w >> 32)) +
  54               __sw_hweight32((unsigned int)w);
  55#elif BITS_PER_LONG == 64
  56#ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER
  57        w -= (w >> 1) & 0x5555555555555555ul;
  58        w =  (w & 0x3333333333333333ul) + ((w >> 2) & 0x3333333333333333ul);
  59        w =  (w + (w >> 4)) & 0x0f0f0f0f0f0f0f0ful;
  60        return (w * 0x0101010101010101ul) >> 56;
  61#else
  62        __u64 res = w - ((w >> 1) & 0x5555555555555555ul);
  63        res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul);
  64        res = (res + (res >> 4)) & 0x0F0F0F0F0F0F0F0Ful;
  65        res = res + (res >> 8);
  66        res = res + (res >> 16);
  67        return (res + (res >> 32)) & 0x00000000000000FFul;
  68#endif
  69#endif
  70}
  71EXPORT_SYMBOL(__sw_hweight64);
  72#endif
  73