143 lines
4.8 KiB
C
143 lines
4.8 KiB
C
/* count-one-bits.h -- counts the number of 1-bits in a word.
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Copyright (C) 2007-2020 Free Software Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Written by Ben Pfaff. */
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#ifndef COUNT_ONE_BITS_H
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#define COUNT_ONE_BITS_H 1
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#include <limits.h>
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#include <stdlib.h>
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#ifndef _GL_INLINE_HEADER_BEGIN
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#error "Please include config.h first."
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#endif
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_GL_INLINE_HEADER_BEGIN
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#ifndef COUNT_ONE_BITS_INLINE
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# define COUNT_ONE_BITS_INLINE _GL_INLINE
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#endif
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* Expand to code that computes the number of 1-bits of the local
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variable 'x' of type TYPE (an unsigned integer type) and return it
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from the current function. */
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#define COUNT_ONE_BITS_GENERIC(TYPE) \
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do \
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{ \
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int count = 0; \
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int bits; \
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for (bits = 0; bits < sizeof (TYPE) * CHAR_BIT; bits += 32) \
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{ \
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count += count_one_bits_32 (x); \
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x = x >> 31 >> 1; \
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} \
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return count; \
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} \
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while (0)
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/* Assuming the GCC builtin is BUILTIN and the MSC builtin is MSC_BUILTIN,
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expand to code that computes the number of 1-bits of the local
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variable 'x' of type TYPE (an unsigned integer type) and return it
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from the current function. */
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#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
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# define COUNT_ONE_BITS(BUILTIN, MSC_BUILTIN, TYPE) return BUILTIN (x)
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#else
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/* Compute and return the number of 1-bits set in the least
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significant 32 bits of X. */
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COUNT_ONE_BITS_INLINE int
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count_one_bits_32 (unsigned int x)
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{
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x = ((x & 0xaaaaaaaaU) >> 1) + (x & 0x55555555U);
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x = ((x & 0xccccccccU) >> 2) + (x & 0x33333333U);
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x = (x >> 16) + (x & 0xffff);
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x = ((x & 0xf0f0) >> 4) + (x & 0x0f0f);
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return (x >> 8) + (x & 0x00ff);
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}
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# if 1500 <= _MSC_VER && (defined _M_IX86 || defined _M_X64)
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/* While gcc falls back to its own generic code if the machine
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on which it's running doesn't support popcount, with Microsoft's
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compiler we need to detect and fallback ourselves. */
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# pragma intrinsic __cpuid
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# pragma intrinsic __popcnt
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# pragma intrinsic __popcnt64
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/* Return nonzero if popcount is supported. */
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/* 1 if supported, 0 if not supported, -1 if unknown. */
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extern int popcount_support;
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COUNT_ONE_BITS_INLINE int
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popcount_supported (void)
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{
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if (popcount_support < 0)
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{
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int cpu_info[4];
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__cpuid (cpu_info, 1);
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popcount_support = (cpu_info[2] >> 23) & 1; /* See MSDN. */
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}
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return popcount_support;
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}
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# define COUNT_ONE_BITS(BUILTIN, MSC_BUILTIN, TYPE) \
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do \
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{ \
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if (popcount_supported ()) \
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return MSC_BUILTIN (x); \
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else \
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COUNT_ONE_BITS_GENERIC (TYPE); \
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} \
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while (0)
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# else
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# define COUNT_ONE_BITS(BUILTIN, MSC_BUILTIN, TYPE) \
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COUNT_ONE_BITS_GENERIC (TYPE)
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# endif
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#endif
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/* Compute and return the number of 1-bits set in X. */
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COUNT_ONE_BITS_INLINE int
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count_one_bits (unsigned int x)
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{
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COUNT_ONE_BITS (__builtin_popcount, __popcnt, unsigned int);
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}
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/* Compute and return the number of 1-bits set in X. */
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COUNT_ONE_BITS_INLINE int
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count_one_bits_l (unsigned long int x)
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{
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COUNT_ONE_BITS (__builtin_popcountl, __popcnt, unsigned long int);
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}
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/* Compute and return the number of 1-bits set in X. */
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COUNT_ONE_BITS_INLINE int
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count_one_bits_ll (unsigned long long int x)
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{
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COUNT_ONE_BITS (__builtin_popcountll, __popcnt64, unsigned long long int);
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}
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#ifdef __cplusplus
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}
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#endif
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_GL_INLINE_HEADER_END
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#endif /* COUNT_ONE_BITS_H */
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