1 // SPDX-License-Identifier: GPL-2.0
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 unsigned int __sw_hweight32(unsigned int w)
13 {
14 #ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER
15 w -= (w >> 1) & 0x55555555;
16 w = (w & 0x33333333) + ((w >> 2) & 0x33333333);
17 w = (w + (w >> 4)) & 0x0f0f0f0f;
18 return (w * 0x01010101) >> 24;
19 #else
20 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 #endif
26 }
27
28 unsigned 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
36 unsigned 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
43 unsigned long __sw_hweight64(__u64 w)
44 {
45 #if BITS_PER_LONG == 32
46 return __sw_hweight32((unsigned int)(w >> 32)) +
47 __sw_hweight32((unsigned int)w);
48 #elif BITS_PER_LONG == 64
49 #ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER
50 w -= (w >> 1) & 0x5555555555555555ul;
51 w = (w & 0x3333333333333333ul) + ((w >> 2) & 0x3333333333333333ul);
52 w = (w + (w >> 4)) & 0x0f0f0f0f0f0f0f0ful;
53 return (w * 0x0101010101010101ul) >> 56;
54 #else
55 __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 #endif
62 #endif
63 }
64
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.