69 lines · c
1// SPDX-License-Identifier: GPL-2.02#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 word8 * @x: the word to weigh9 *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_MULTIPLIER16 w -= (w >> 1) & 0x55555555;17 w = (w & 0x33333333) + ((w >> 2) & 0x33333333);18 w = (w + (w >> 4)) & 0x0f0f0f0f;19 return (w * 0x01010101) >> 24;20#else21 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#endif27}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 == 3250 return __sw_hweight32((unsigned int)(w >> 32)) +51 __sw_hweight32((unsigned int)w);52#elif BITS_PER_LONG == 6453#ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER54 w -= (w >> 1) & 0x5555555555555555ul;55 w = (w & 0x3333333333333333ul) + ((w >> 2) & 0x3333333333333333ul);56 w = (w + (w >> 4)) & 0x0f0f0f0f0f0f0f0ful;57 return (w * 0x0101010101010101ul) >> 56;58#else59 __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#endif66#endif67}68EXPORT_SYMBOL(__sw_hweight64);69