xref: /openbmc/linux/lib/hweight.c (revision 22d55f02)
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  unsigned 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  }
28  EXPORT_SYMBOL(__sw_hweight32);
29  
30  unsigned 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  }
37  EXPORT_SYMBOL(__sw_hweight16);
38  
39  unsigned 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  }
45  EXPORT_SYMBOL(__sw_hweight8);
46  
47  unsigned long __sw_hweight64(__u64 w)
48  {
49  #if BITS_PER_LONG == 32
50  	return __sw_hweight32((unsigned int)(w >> 32)) +
51  	       __sw_hweight32((unsigned int)w);
52  #elif BITS_PER_LONG == 64
53  #ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER
54  	w -= (w >> 1) & 0x5555555555555555ul;
55  	w =  (w & 0x3333333333333333ul) + ((w >> 2) & 0x3333333333333333ul);
56  	w =  (w + (w >> 4)) & 0x0f0f0f0f0f0f0f0ful;
57  	return (w * 0x0101010101010101ul) >> 56;
58  #else
59  	__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  #endif
66  #endif
67  }
68  EXPORT_SYMBOL(__sw_hweight64);
69