Zbigniew Jędrzejewski-Szmek
a12bc99ef0
__builtin_popcount() is a bit of a mouthful, so let's provide a helper. Using _Generic has the advantage that if a type other then the ones on the list is given, compilation will fail. This is nice, because if by any change we pass a wider type, it is rejected immediately instead of being truncated. log.h is also needed. It is included transitively, but let's include it directly. macro.h is *not* needed.
60 lines
1.9 KiB
C
60 lines
1.9 KiB
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#pragma once
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#include <stdint.h>
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/* Note: log2(0) == log2(1) == 0 here and below. */
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#define CONST_LOG2ULL(x) ((x) > 1 ? (unsigned) __builtin_clzll(x) ^ 63U : 0)
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#define NONCONST_LOG2ULL(x) ({ \
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unsigned long long _x = (x); \
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_x > 1 ? (unsigned) __builtin_clzll(_x) ^ 63U : 0; \
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})
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#define LOG2ULL(x) __builtin_choose_expr(__builtin_constant_p(x), CONST_LOG2ULL(x), NONCONST_LOG2ULL(x))
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static inline unsigned log2u64(uint64_t x) {
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#if __SIZEOF_LONG_LONG__ == 8
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return LOG2ULL(x);
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#else
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# error "Wut?"
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#endif
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}
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static inline unsigned u32ctz(uint32_t n) {
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#if __SIZEOF_INT__ == 4
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return n != 0 ? __builtin_ctz(n) : 32;
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#else
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# error "Wut?"
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#endif
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}
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#define popcount(n) \
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_Generic((n), \
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unsigned char: __builtin_popcount(n), \
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unsigned short: __builtin_popcount(n), \
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unsigned: __builtin_popcount(n), \
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unsigned long: __builtin_popcountl(n), \
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unsigned long long: __builtin_popcountll(n))
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#define CONST_LOG2U(x) ((x) > 1 ? __SIZEOF_INT__ * 8 - __builtin_clz(x) - 1 : 0)
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#define NONCONST_LOG2U(x) ({ \
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unsigned _x = (x); \
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_x > 1 ? __SIZEOF_INT__ * 8 - __builtin_clz(_x) - 1 : 0; \
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})
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#define LOG2U(x) __builtin_choose_expr(__builtin_constant_p(x), CONST_LOG2U(x), NONCONST_LOG2U(x))
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static inline unsigned log2i(int x) {
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return LOG2U(x);
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}
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static inline unsigned log2u(unsigned x) {
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return LOG2U(x);
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}
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static inline unsigned log2u_round_up(unsigned x) {
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if (x <= 1)
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return 0;
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return log2u(x - 1) + 1;
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}
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