Linux kernel mirror (for testing)
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linux
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