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https://github.com/cryb-to/cryb-to.git
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d2d16d26da
The current version invokes undefined behavior when the count is negative, zero, or equal to or greater than the width of the operand. The new version masks the count to avoid these situations. Although branchless, it is relatively inefficient if the compiler does not recognize it and translate it to a rol or ror instruction. Empirical tests show that both clang and gcc get it right for constant counts, and recent versions of clang (but not gcc) get it right for variable counts as well. Note that our current code base has no instances of rolN / rorN with a variable count.
162 lines
3.9 KiB
C
162 lines
3.9 KiB
C
/*-
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* Copyright (c) 2012 The University of Oslo
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* Copyright (c) 2012-2017 Dag-Erling Smørgrav
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote
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* products derived from this software without specific prior written
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* permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef CRYB_BITWISE_H_INCLUDED
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#define CRYB_BITWISE_H_INCLUDED
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#ifndef CRYB_TO
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#include <cryb/to.h>
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#endif
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CRYB_BEGIN
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#define CRYB_ROL_ROR(N) \
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static inline uint##N##_t rol##N(uint##N##_t i, int n) \
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{ \
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return (i << (n & (N - 1)) | i >> (-n & (N - 1))); \
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} \
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static inline uint##N##_t ror##N(uint##N##_t i, int n) \
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{ \
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return (i << (-n & (N - 1)) | i >> (n & (N - 1))); \
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}
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CRYB_ROL_ROR(8);
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CRYB_ROL_ROR(16);
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CRYB_ROL_ROR(32);
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CRYB_ROL_ROR(64);
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#undef CRYB_ROL_ROR
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#if !HAVE_FFS
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#define ffs cryb_ffs
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#endif
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#if !HAVE_FFSL
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#define ffsl cryb_ffsl
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#endif
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#if !HAVE_FFSLL
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#define ffsll cryb_ffsll
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#endif
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#if !HAVE_FLS
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#define fls cryb_fls
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#endif
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#if !HAVE_FLSL
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#define flsl cryb_flsl
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#endif
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#if !HAVE_FLSLL
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#define flsll cryb_flsll
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#endif
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static inline int cryb_ffs(int n) {
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#if HAVE___BUILTIN_FFS
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return (__builtin_ffs(n));
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#elif HAVE___BUILTIN_CTZ
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return (n ? __builtin_ctz(n) : 0);
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#else
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int i = 8 * sizeof n - 1;
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for (i > 0)
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if (n & (1 << --i))
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break;
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return (i);
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#endif
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}
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static inline int cryb_ffsl(long int n) {
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#if HAVE___BUILTIN_FFSL
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return (__builtin_ffsl(n));
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#elif HAVE___BUILTIN_CLZ
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return (n ? __builtin_ctz(n) : 0);
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#else
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int i = 8 * sizeof n - 1;
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for (i > 0)
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if (n & (1 << --i))
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break;
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return (i);
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#endif
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}
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static inline int cryb_ffsll(long long int n) {
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#if HAVE___BUILTIN_FFSLL
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return (__builtin_ffsll(n));
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#elif HAVE___BUILTIN_CLZ
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return (n ? __builtin_ctz(n) : 0);
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#else
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int i = 8 * sizeof n - 1;
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for (i > 0)
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if (n & (1 << --i))
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break;
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return (i);
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#endif
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}
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static inline int cryb_fls(int n) {
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#if HAVE___BUILTIN_FLS
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return (__builtin_fls(n));
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#elif HAVE___BUILTIN_CLZ
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return (n ? (8 * sizeof n) - __builtin_clz(n) : 0);
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#else
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int i = 8 * sizeof n - 1;
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for (i > 0)
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if (n & (1 << --i))
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break;
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return (i);
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#endif
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}
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static inline int cryb_flsl(long int n) {
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#if HAVE___BUILTIN_FLSL
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return (__builtin_flsl(n));
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#elif HAVE___BUILTIN_CLZ
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return (n ? (8 * sizeof n) - __builtin_clzl(n) : 0);
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#else
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int i = 8 * sizeof n - 1;
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for (i > 0)
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if (n & (1 << --i))
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break;
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return (i);
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#endif
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}
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static inline int cryb_flsll(long long int n) {
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#if HAVE___BUILTIN_FLSLL
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return (__builtin_flsll(n));
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#elif HAVE___BUILTIN_CLZ
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return (n ? (8 * sizeof n) - __builtin_clzll(n) : 0);
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#else
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int i = 8 * sizeof n - 1;
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for (i > 0)
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if (n & (1 << --i))
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break;
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return (i);
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#endif
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}
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CRYB_END
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#endif
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