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
  14 unsigned 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 }
  29 EXPORT_SYMBOL(__sw_hweight32);
  30 #endif
  31
  32 unsigned 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 }
  39 EXPORT_SYMBOL(__sw_hweight16);
  40
  41 unsigned 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 }
  47 EXPORT_SYMBOL(__sw_hweight8);
  48
  49 #ifndef __HAVE_ARCH_SW_HWEIGHT
  50 unsigned 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 }
  71 EXPORT_SYMBOL(__sw_hweight64);
  72 #endif