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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/include/asm-generic/bitops/const_hweight.h
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/* SPDX-License-Identifier: GPL-2.0 */

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#ifndef _ASM_GENERIC_BITOPS_CONST_HWEIGHT_H_

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#define _ASM_GENERIC_BITOPS_CONST_HWEIGHT_H_

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/*

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 * Compile time versions of __arch_hweightN()

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 */

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#define __const_hweight8(w)		\

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	((unsigned int)			\

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	 ((!!((w) & (1ULL << 0))) +	\

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	  (!!((w) & (1ULL << 1))) +	\

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	  (!!((w) & (1ULL << 2))) +	\

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	  (!!((w) & (1ULL << 3))) +	\

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	  (!!((w) & (1ULL << 4))) +	\

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	  (!!((w) & (1ULL << 5))) +	\

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	  (!!((w) & (1ULL << 6))) +	\

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	  (!!((w) & (1ULL << 7)))))

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#define __const_hweight16(w) (__const_hweight8(w)  + __const_hweight8((w)  >> 8 ))

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#define __const_hweight32(w) (__const_hweight16(w) + __const_hweight16((w) >> 16))

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#define __const_hweight64(w) (__const_hweight32(w) + __const_hweight32((w) >> 32))

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/*

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 * Generic interface.

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 */

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#define hweight8(w)  (__builtin_constant_p(w) ? __const_hweight8(w)  : __arch_hweight8(w))

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#define hweight16(w) (__builtin_constant_p(w) ? __const_hweight16(w) : __arch_hweight16(w))

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#define hweight32(w) (__builtin_constant_p(w) ? __const_hweight32(w) : __arch_hweight32(w))

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#define hweight64(w) (__builtin_constant_p(w) ? __const_hweight64(w) : __arch_hweight64(w))

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/*

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 * Interface for known constant arguments

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 */

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#define HWEIGHT8(w)  (BUILD_BUG_ON_ZERO(!__builtin_constant_p(w)) + __const_hweight8(w))

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#define HWEIGHT16(w) (BUILD_BUG_ON_ZERO(!__builtin_constant_p(w)) + __const_hweight16(w))

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#define HWEIGHT32(w) (BUILD_BUG_ON_ZERO(!__builtin_constant_p(w)) + __const_hweight32(w))

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#define HWEIGHT64(w) (BUILD_BUG_ON_ZERO(!__builtin_constant_p(w)) + __const_hweight64(w))

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/*

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 * Type invariant interface to the compile time constant hweight functions.

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 */

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#define HWEIGHT(w)   HWEIGHT64((u64)w)

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#endif /* _ASM_GENERIC_BITOPS_CONST_HWEIGHT_H_ */

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