64 lines · c
1// SPDX-License-Identifier: GPL-2.02#include <linux/bitops.h>3#include <asm/types.h>4 5/**6 * hweightN - returns the hamming weight of a N-bit word7 * @x: the word to weigh8 *9 * The Hamming Weight of a number is the total number of bits set in it.10 */11 12unsigned int __sw_hweight32(unsigned int w)13{14#ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER15 w -= (w >> 1) & 0x55555555;16 w = (w & 0x33333333) + ((w >> 2) & 0x33333333);17 w = (w + (w >> 4)) & 0x0f0f0f0f;18 return (w * 0x01010101) >> 24;19#else20 unsigned int res = w - ((w >> 1) & 0x55555555);21 res = (res & 0x33333333) + ((res >> 2) & 0x33333333);22 res = (res + (res >> 4)) & 0x0F0F0F0F;23 res = res + (res >> 8);24 return (res + (res >> 16)) & 0x000000FF;25#endif26}27 28unsigned int __sw_hweight16(unsigned int w)29{30 unsigned int res = w - ((w >> 1) & 0x5555);31 res = (res & 0x3333) + ((res >> 2) & 0x3333);32 res = (res + (res >> 4)) & 0x0F0F;33 return (res + (res >> 8)) & 0x00FF;34}35 36unsigned int __sw_hweight8(unsigned int w)37{38 unsigned int res = w - ((w >> 1) & 0x55);39 res = (res & 0x33) + ((res >> 2) & 0x33);40 return (res + (res >> 4)) & 0x0F;41}42 43unsigned long __sw_hweight64(__u64 w)44{45#if BITS_PER_LONG == 3246 return __sw_hweight32((unsigned int)(w >> 32)) +47 __sw_hweight32((unsigned int)w);48#elif BITS_PER_LONG == 6449#ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER50 w -= (w >> 1) & 0x5555555555555555ul;51 w = (w & 0x3333333333333333ul) + ((w >> 2) & 0x3333333333333333ul);52 w = (w + (w >> 4)) & 0x0f0f0f0f0f0f0f0ful;53 return (w * 0x0101010101010101ul) >> 56;54#else55 __u64 res = w - ((w >> 1) & 0x5555555555555555ul);56 res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul);57 res = (res + (res >> 4)) & 0x0F0F0F0F0F0F0F0Ful;58 res = res + (res >> 8);59 res = res + (res >> 16);60 return (res + (res >> 32)) & 0x00000000000000FFul;61#endif62#endif63}64