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Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 3029 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Allison Randal <allison@lohutok.net> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
175 lines
4.5 KiB
C
175 lines
4.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/* Integer base 2 logarithm calculation
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*
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* Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#ifndef _TOOLS_LINUX_LOG2_H
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#define _TOOLS_LINUX_LOG2_H
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#include <linux/bitops.h>
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#include <linux/types.h>
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/*
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* 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 inline __attribute__((const))
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int __ilog2_u32(u32 n)
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{
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return fls(n) - 1;
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}
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static 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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/*
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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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*/
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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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* round up to nearest power of two
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*/
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static inline __attribute__((const))
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unsigned long __roundup_pow_of_two(unsigned long n)
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{
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return 1UL << fls_long(n - 1);
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}
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/*
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* round down to nearest power of two
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*/
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static inline __attribute__((const))
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unsigned long __rounddown_pow_of_two(unsigned long n)
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{
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return 1UL << (fls_long(n) - 1);
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}
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/**
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* ilog2 - log of 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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(n) & (1ULL << 63) ? 63 : \
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(n) & (1ULL << 62) ? 62 : \
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(n) & (1ULL << 61) ? 61 : \
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(n) & (1ULL << 60) ? 60 : \
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(n) & (1ULL << 59) ? 59 : \
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(n) & (1ULL << 58) ? 58 : \
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(n) & (1ULL << 57) ? 57 : \
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(n) & (1ULL << 56) ? 56 : \
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(n) & (1ULL << 55) ? 55 : \
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(n) & (1ULL << 54) ? 54 : \
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(n) & (1ULL << 53) ? 53 : \
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(n) & (1ULL << 52) ? 52 : \
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(n) & (1ULL << 51) ? 51 : \
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(n) & (1ULL << 50) ? 50 : \
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(n) & (1ULL << 49) ? 49 : \
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(n) & (1ULL << 48) ? 48 : \
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(n) & (1ULL << 47) ? 47 : \
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(n) & (1ULL << 46) ? 46 : \
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(n) & (1ULL << 45) ? 45 : \
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(n) & (1ULL << 44) ? 44 : \
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(n) & (1ULL << 43) ? 43 : \
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(n) & (1ULL << 42) ? 42 : \
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(n) & (1ULL << 41) ? 41 : \
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(n) & (1ULL << 40) ? 40 : \
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(n) & (1ULL << 39) ? 39 : \
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(n) & (1ULL << 38) ? 38 : \
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(n) & (1ULL << 37) ? 37 : \
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(n) & (1ULL << 36) ? 36 : \
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(n) & (1ULL << 35) ? 35 : \
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(n) & (1ULL << 34) ? 34 : \
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(n) & (1ULL << 33) ? 33 : \
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(n) & (1ULL << 32) ? 32 : \
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(n) & (1ULL << 31) ? 31 : \
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(n) & (1ULL << 30) ? 30 : \
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(n) & (1ULL << 29) ? 29 : \
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(n) & (1ULL << 28) ? 28 : \
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(n) & (1ULL << 27) ? 27 : \
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(n) & (1ULL << 26) ? 26 : \
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(n) & (1ULL << 25) ? 25 : \
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(n) & (1ULL << 24) ? 24 : \
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(n) & (1ULL << 23) ? 23 : \
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(n) & (1ULL << 22) ? 22 : \
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(n) & (1ULL << 21) ? 21 : \
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(n) & (1ULL << 20) ? 20 : \
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(n) & (1ULL << 19) ? 19 : \
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(n) & (1ULL << 18) ? 18 : \
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(n) & (1ULL << 17) ? 17 : \
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(n) & (1ULL << 16) ? 16 : \
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(n) & (1ULL << 15) ? 15 : \
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(n) & (1ULL << 14) ? 14 : \
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(n) & (1ULL << 13) ? 13 : \
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(n) & (1ULL << 12) ? 12 : \
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(n) & (1ULL << 11) ? 11 : \
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(n) & (1ULL << 10) ? 10 : \
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(n) & (1ULL << 9) ? 9 : \
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(n) & (1ULL << 8) ? 8 : \
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(n) & (1ULL << 7) ? 7 : \
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(n) & (1ULL << 6) ? 6 : \
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(n) & (1ULL << 5) ? 5 : \
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(n) & (1ULL << 4) ? 4 : \
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(n) & (1ULL << 3) ? 3 : \
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(n) & (1ULL << 2) ? 2 : \
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1 ) : \
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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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#endif /* _TOOLS_LINUX_LOG2_H */
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