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Linux/tools/lib/hweight.c

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  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 

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