Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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kernel
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linux
1#include <linux/export.h>
2#include <linux/bitops.h>
3#include <asm/types.h>
4
5/**
6 * hweightN - returns the hamming weight of a N-bit word
7 * @x: the word to weigh
8 *
9 * The Hamming Weight of a number is the total number of bits set in it.
10 */
11
12#ifndef __HAVE_ARCH_SW_HWEIGHT
13unsigned int __sw_hweight32(unsigned int w)
14{
15#ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER
16 w -= (w >> 1) & 0x55555555;
17 w = (w & 0x33333333) + ((w >> 2) & 0x33333333);
18 w = (w + (w >> 4)) & 0x0f0f0f0f;
19 return (w * 0x01010101) >> 24;
20#else
21 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#endif
27}
28EXPORT_SYMBOL(__sw_hweight32);
29#endif
30
31unsigned int __sw_hweight16(unsigned int w)
32{
33 unsigned int res = w - ((w >> 1) & 0x5555);
34 res = (res & 0x3333) + ((res >> 2) & 0x3333);
35 res = (res + (res >> 4)) & 0x0F0F;
36 return (res + (res >> 8)) & 0x00FF;
37}
38EXPORT_SYMBOL(__sw_hweight16);
39
40unsigned int __sw_hweight8(unsigned int w)
41{
42 unsigned int res = w - ((w >> 1) & 0x55);
43 res = (res & 0x33) + ((res >> 2) & 0x33);
44 return (res + (res >> 4)) & 0x0F;
45}
46EXPORT_SYMBOL(__sw_hweight8);
47
48#ifndef __HAVE_ARCH_SW_HWEIGHT
49unsigned long __sw_hweight64(__u64 w)
50{
51#if BITS_PER_LONG == 32
52 return __sw_hweight32((unsigned int)(w >> 32)) +
53 __sw_hweight32((unsigned int)w);
54#elif BITS_PER_LONG == 64
55#ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER
56 w -= (w >> 1) & 0x5555555555555555ul;
57 w = (w & 0x3333333333333333ul) + ((w >> 2) & 0x3333333333333333ul);
58 w = (w + (w >> 4)) & 0x0f0f0f0f0f0f0f0ful;
59 return (w * 0x0101010101010101ul) >> 56;
60#else
61 __u64 res = w - ((w >> 1) & 0x5555555555555555ul);
62 res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul);
63 res = (res + (res >> 4)) & 0x0F0F0F0F0F0F0F0Ful;
64 res = res + (res >> 8);
65 res = res + (res >> 16);
66 return (res + (res >> 32)) & 0x00000000000000FFul;
67#endif
68#endif
69}
70EXPORT_SYMBOL(__sw_hweight64);
71#endif