Bruno Raoult
7bba3c559b
- int types definitions moved to br.h - bits_implementation() -> print_bitops_impl() - 64 bitops use ...ll builtins instead of ...l - add lsb and msb macros - bit_for_each -> bit_for_each_1 (count from 1) - bit_for_each_2 -> bit_for_each (count from 0)
472 lines
12 KiB
C
472 lines
12 KiB
C
/* bits.h - bits functions.
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*
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* Copyright (C) 2021-2022 Bruno Raoult ("br")
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* Licensed under the GNU General Public License v3.0 or later.
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* Some rights reserved. See COPYING.
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*
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* You should have received a copy of the GNU General Public License along with this
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* program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
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*
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* SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
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*
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*/
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#ifndef _BITS_H
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#define _BITS_H
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#include "br.h"
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/**
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* print_bitops_impl() - print bitops implementation.
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*
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* For basic bitops (popcount, ctz, etc...), print the implementation
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* (builtin, emulated, ...).
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*/
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void print_bitops_impl(void);
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#ifndef __has_builtin
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#define __has_builtin(x) 0
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#endif
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/* no plan to support 32bits for now...
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* #if __WORDSIZE != 64
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* #error "Only 64 bits word size supported."
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* #endif
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*/
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/* lsb, msb: least/most significant bit: 10101000
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* msb = 7 ^ ^ lsb = 3
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*/
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#define lsb64(x) (ctz64(x))
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#define lsb32(x) (ctz32(x))
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#define msb64(x) (63 ^ clz64(x))
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#define msb32(x) (31 ^ clz32(x))
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/* count set bits: 10101000 -> 3
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* ^ ^ ^
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*/
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static __always_inline int popcount64(u64 n)
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{
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# if __has_builtin(__builtin_popcountll)
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return __builtin_popcountll(n);
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# else
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int count = 0;
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while (n) {
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count++;
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n &= (n - 1);
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}
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return count;
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# endif
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}
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static __always_inline int popcount32(u32 n)
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{
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# if __has_builtin(__builtin_popcount)
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return __builtin_popcount(n);
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# else
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int count = 0;
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while (n) {
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count++;
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n &= (n - 1);
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}
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return count;
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# endif
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}
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/* count trailing zeroes : 00101000 -> 3
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* ^^^
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*/
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static __always_inline int ctz64(u64 n)
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{
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# if __has_builtin(__builtin_ctzll)
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return __builtin_ctzll(n);
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# elif __has_builtin(__builtin_clzll)
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return __WORDSIZE - (__builtin_clzll(n & -n) + 1);
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# else
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return popcount64((n & -n) - 1);
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# endif
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}
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static __always_inline int ctz32(u32 n)
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{
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# if __has_builtin(__builtin_ctz)
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return __builtin_ctz(n);
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# elif __has_builtin(__builtin_clz)
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return __WORDSIZE - (__builtin_clz(n & -n) + 1);
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# else
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return popcount32((n & -n) - 1);
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# endif
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}
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/* clz - count leading zeroes : 00101000 -> 2
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* ^^
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*/
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static __always_inline int clz64(u64 n)
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{
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# if __has_builtin(__builtin_clzll)
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return __builtin_clzll(n);
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# else
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u64 r, q;
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r = (n > 0xFFFFFFFF) << 5; n >>= r;
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q = (n > 0xFFFF) << 4; n >>= q; r |= q;
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q = (n > 0xFF ) << 3; n >>= q; r |= q;
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q = (n > 0xF ) << 2; n >>= q; r |= q;
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q = (n > 0x3 ) << 1; n >>= q; r |= q;
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r |= (n >> 1);
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return 64 - r - 1;
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# endif
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}
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static __always_inline int clz32(u32 n)
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{
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# if __has_builtin(__builtin_clz)
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return __builtin_clz(n);
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# else
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u32 r, q;
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r = (n > 0xFFFF) << 4; n >>= r;
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q = (n > 0xFF ) << 3; n >>= q; r |= q;
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q = (n > 0xF ) << 2; n >>= q; r |= q;
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q = (n > 0x3 ) << 1; n >>= q; r |= q;
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r |= (n >> 1);
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return 32 - r - 1;
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# endif
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}
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/* fls - return one plus msb : 00101000 -> 6
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* ^
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*/
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static __always_inline int fls64(u64 n)
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{
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if (!n)
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return 0;
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return 64 - clz64(n);
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}
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static __always_inline int fls32(u32 n)
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{
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if (!n)
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return 0;
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return 32 - clz32(n);
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}
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/* ffs - return one plus lsb index: 00101000 -> 4
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* ^
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*/
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static __always_inline uint ffs64(u64 n)
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{
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# if __has_builtin(__builtin_ffsll)
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return __builtin_ffsll(n);
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# elif __has_builtin(__builtin_ctzll)
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if (n == 0)
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return (0);
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return __builtin_ctzll(n) + 1;
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# else
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return popcount64(n ^ ~-n);
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# endif
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}
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static __always_inline uint ffs32(u32 n)
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{
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# if __has_builtin(__builtin_ffs)
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return __builtin_ffs(n);
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# elif __has_builtin(__builtin_ctz)
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if (n == 0)
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return (0);
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return __builtin_ctz(n) + 1;
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# else
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return popcount32(n ^ ~-n);
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# endif
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}
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/* rolXX/rorXX are taken from kernel's <linux/bitops.h> are are:
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* SPDX-License-Identifier: GPL-2.0
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*/
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/**
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* rol64 - rotate a 64-bit value left
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* @word: value to rotate
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* @shift: bits to roll
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*/
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static inline u64 rol64(u64 word, unsigned int shift)
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{
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return (word << (shift & 63)) | (word >> ((-shift) & 63));
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}
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/**
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* ror64 - rotate a 64-bit value right
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* @word: value to rotate
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* @shift: bits to roll
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*/
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static inline u64 ror64(u64 word, unsigned int shift)
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{
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return (word >> (shift & 63)) | (word << ((-shift) & 63));
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}
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/**
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* rol32 - rotate a 32-bit value left
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* @word: value to rotate
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* @shift: bits to roll
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*/
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static inline u32 rol32(u32 word, unsigned int shift)
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{
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return (word << (shift & 31)) | (word >> ((-shift) & 31));
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}
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/**
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* ror32 - rotate a 32-bit value right
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* @word: value to rotate
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* @shift: bits to roll
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*/
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static inline u32 ror32(u32 word, unsigned int shift)
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{
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return (word >> (shift & 31)) | (word << ((-shift) & 31));
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}
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/**
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* rol16 - rotate a 16-bit value left
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* @word: value to rotate
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* @shift: bits to roll
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*/
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static inline u16 rol16(u16 word, unsigned int shift)
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{
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return (word << (shift & 15)) | (word >> ((-shift) & 15));
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}
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/**
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* ror16 - rotate a 16-bit value right
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* @word: value to rotate
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* @shift: bits to roll
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*/
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static inline u16 ror16(u16 word, unsigned int shift)
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{
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return (word >> (shift & 15)) | (word << ((-shift) & 15));
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}
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/**
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* rol8 - rotate an 8-bit value left
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* @word: value to rotate
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* @shift: bits to roll
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*/
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static inline u8 rol8(u8 word, unsigned int shift)
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{
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return (word << (shift & 7)) | (word >> ((-shift) & 7));
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}
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/**
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* ror8 - rotate an 8-bit value right
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* @word: value to rotate
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* @shift: bits to roll
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*/
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static inline u8 ror8(u8 word, unsigned int shift)
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{
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return (word >> (shift & 7)) | (word << ((-shift) & 7));
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}
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/**
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* __ilog2 - non-constant log of base 2 calculators
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* - the arch may override these in asm/bitops.h if they can be implemented
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* more efficiently than using fls() and fls64()
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* - the arch is not required to handle n==0 if implementing the fallback
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*/
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static __always_inline __attribute__((const))
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int __ilog2_u64(u64 n)
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{
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return fls64(n) - 1;
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}
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static __always_inline __attribute__((const))
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int __ilog2_u32(u32 n)
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{
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return fls32(n) - 1;
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}
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/**
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* is_power_of_2() - check if a value is a power of two
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* @n: the value to check
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*
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* Determine whether some value is a power of two, where zero is
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* *not* considered a power of two.
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* Return: true if @n is a power of 2, otherwise false.
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*/
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static inline __attribute__((const))
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bool is_power_of_2(unsigned long n)
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{
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return (n != 0 && ((n & (n - 1)) == 0));
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}
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/**
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* __roundup_pow_of_two() - round up to nearest power of two
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* @n: value to round up
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*/
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static inline __attribute__((const))
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u64 __roundup_pow_of_two(u64 n)
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{
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return 1UL << fls64(n - 1);
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}
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/**
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* __rounddown_pow_of_two() - round down to nearest power of two
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* @n: value to round down
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*/
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static inline __attribute__((const)) u64 __rounddown_pow_of_two(u64 n)
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{
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return 1UL << (fls64(n) - 1);
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}
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/**
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* ilog2 - log base 2 of 32-bit or a 64-bit unsigned value
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* @n: parameter
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*
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* constant-capable log of base 2 calculation
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* - this can be used to initialise global variables from constant data, hence
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* the massive ternary operator construction
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*
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* selects the appropriately-sized optimised version depending on sizeof(n)
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*/
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#define ilog2(n) \
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( \
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__builtin_constant_p(n) ? \
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((n) < 2 ? 0 : \
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63 - __builtin_clzll(n)) : \
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(sizeof(n) <= 4) ? \
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__ilog2_u32(n) : \
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__ilog2_u64(n) \
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)
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/**
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* roundup_pow_of_two - round the given value up to nearest power of two
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* @n: parameter
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*
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* round the given value up to the nearest power of two
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* - the result is undefined when n == 0
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* - this can be used to initialise global variables from constant data
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*/
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#define roundup_pow_of_two(n) \
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( \
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__builtin_constant_p(n) ? ( \
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((n) == 1) ? 1 : \
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(1UL << (ilog2((n) - 1) + 1)) \
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) : \
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__roundup_pow_of_two(n) \
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)
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/**
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* rounddown_pow_of_two - round the given value down to nearest power of two
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* @n: parameter
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*
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* round the given value down to the nearest power of two
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* - the result is undefined when n == 0
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* - this can be used to initialise global variables from constant data
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*/
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#define rounddown_pow_of_two(n) \
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( \
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__builtin_constant_p(n) ? ( \
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(1UL << ilog2(n))) : \
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__rounddown_pow_of_two(n) \
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)
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static inline __attribute_const__ int __order_base_2(unsigned long n)
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{
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return n > 1 ? ilog2(n - 1) + 1 : 0;
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}
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/**
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* order_base_2 - calculate the (rounded up) base 2 order of the argument
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* @n: parameter
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*
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* The first few values calculated by this routine:
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* ob2(0) = 0
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* ob2(1) = 0
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* ob2(2) = 1
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* ob2(3) = 2
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* ob2(4) = 2
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* ob2(5) = 3
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* ... and so on.
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*/
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#define order_base_2(n) \
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( \
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__builtin_constant_p(n) ? ( \
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((n) == 0 || (n) == 1) ? \
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0 : \
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ilog2((n) - 1) + 1) : \
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__order_base_2(n) \
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)
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static inline __attribute__((const)) int __bits_per(unsigned long n)
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{
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if (n < 2)
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return 1;
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if (is_power_of_2(n))
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return order_base_2(n) + 1;
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return order_base_2(n);
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}
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/**
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* bits_per - calculate the number of bits required for the argument
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* @n: parameter
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*
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* This is constant-capable and can be used for compile time
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* initializations, e.g bitfields.
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*
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* The first few values calculated by this routine:
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* bf(0) = 1
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* bf(1) = 1
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* bf(2) = 2
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* bf(3) = 2
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* bf(4) = 3
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* ... and so on.
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*/
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#define bits_per(n) \
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( \
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__builtin_constant_p(n) ? ( \
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((n) == 0 || (n) == 1) ? \
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1 : \
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ilog2(n) + 1 : \
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__bits_per(n) \
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)
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/**
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* bit_for_each - iterate over an u64/u32 bits
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* @pos: an int used as current bit
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* @tmp: a temp u64/u32 used as temporary storage
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* @ul: the u64/u32 to loop over
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*
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* Usage:
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* u64 u=139, _t; // u=b10001011
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* int cur;
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* bit_for_each64(cur, _t, u) {
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* printf("%d\n", cur);
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* }
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* This will display the position of each bit set in ul: 1, 2, 4, 8
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*
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* I should probably re-think the implementation...
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*/
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#define bit_for_each64(pos, tmp, ul) \
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for (tmp = ul, pos = ctz64(tmp); tmp; tmp ^= 1UL << pos, pos = ctz64(tmp))
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#define bit_for_each32(pos, tmp, ul) \
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for (tmp = ul, pos = ctz32(tmp); tmp; tmp ^= 1U << pos, pos = ctz32(tmp))
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/** or would it be more useful (counting bits from zero instead of 1) ?
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*/
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#define bit_for_each64_1(pos, tmp, ul) \
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for (tmp = ul, pos = ffs64(tmp); tmp; tmp &= (tmp - 1), pos = ffs64(tmp))
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#define bit_for_each32_1(pos, tmp, ul) \
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for (tmp = ul, pos = ffs32(tmp); tmp; tmp &= (tmp - 1), pos = ffs32(tmp))
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#endif /* _BITS_H */
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