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lib/hweight.c
1.92 KB
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// SPDX-License-Identifier: GPL-2.0 |
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#include <linux/export.h> |
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#include <linux/bitops.h> |
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#include <asm/types.h> /** * hweightN - returns the hamming weight of a N-bit word * @x: the word to weigh * * The Hamming Weight of a number is the total number of bits set in it. */ |
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unsigned int __sw_hweight32(unsigned int w) |
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{ |
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#ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER |
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w -= (w >> 1) & 0x55555555; w = (w & 0x33333333) + ((w >> 2) & 0x33333333); w = (w + (w >> 4)) & 0x0f0f0f0f; return (w * 0x01010101) >> 24; #else |
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unsigned int res = w - ((w >> 1) & 0x55555555); |
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res = (res & 0x33333333) + ((res >> 2) & 0x33333333); |
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res = (res + (res >> 4)) & 0x0F0F0F0F; res = res + (res >> 8); return (res + (res >> 16)) & 0x000000FF; |
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#endif |
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} |
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EXPORT_SYMBOL(__sw_hweight32); |
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unsigned int __sw_hweight16(unsigned int w) |
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{ |
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unsigned int res = w - ((w >> 1) & 0x5555); |
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res = (res & 0x3333) + ((res >> 2) & 0x3333); |
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res = (res + (res >> 4)) & 0x0F0F; return (res + (res >> 8)) & 0x00FF; |
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} |
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EXPORT_SYMBOL(__sw_hweight16); |
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unsigned int __sw_hweight8(unsigned int w) |
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{ |
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unsigned int res = w - ((w >> 1) & 0x55); |
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res = (res & 0x33) + ((res >> 2) & 0x33); |
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return (res + (res >> 4)) & 0x0F; |
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} |
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EXPORT_SYMBOL(__sw_hweight8); |
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unsigned long __sw_hweight64(__u64 w) |
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{ #if BITS_PER_LONG == 32 |
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return __sw_hweight32((unsigned int)(w >> 32)) + __sw_hweight32((unsigned int)w); |
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#elif BITS_PER_LONG == 64 |
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#ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER |
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w -= (w >> 1) & 0x5555555555555555ul; w = (w & 0x3333333333333333ul) + ((w >> 2) & 0x3333333333333333ul); w = (w + (w >> 4)) & 0x0f0f0f0f0f0f0f0ful; return (w * 0x0101010101010101ul) >> 56; #else |
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__u64 res = w - ((w >> 1) & 0x5555555555555555ul); |
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res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul); |
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res = (res + (res >> 4)) & 0x0F0F0F0F0F0F0F0Ful; res = res + (res >> 8); res = res + (res >> 16); return (res + (res >> 32)) & 0x00000000000000FFul; |
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#endif |
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#endif } |
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EXPORT_SYMBOL(__sw_hweight64); |