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include: update log2 header from the Linux kernel

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Without the patch gcc 8 produces:
warning: ignoring attribute ‘noreturn’ because it conflicts with
attribute ‘const’ [-Wattributes]
 int ____ilog2_NaN(void);

So let's update the include from Linux kernel v4.16.

This removes static checks of ilog2() arguments.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
This commit is contained in:
Heinrich Schuchardt 2018-05-07 22:18:27 +02:00 committed by Tom Rini
parent 23c648982b
commit 4a8e72954e
1 changed files with 37 additions and 26 deletions
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63
include/linux/log2.h
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@ -3,6 +3,11 @@
*
* Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* 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.
*/
#ifndef _LINUX_LOG2_H
@ -11,12 +16,6 @@
#include <linux/types.h>
#include <linux/bitops.h>
/*
* deal with unrepresentable constant logarithms
*/
extern __attribute__((const, noreturn))
int ____ilog2_NaN(void);
/*
* non-constant log of base 2 calculators
* - the arch may override these in asm/bitops.h if they can be implemented
@ -39,19 +38,23 @@ int __ilog2_u64(u64 n)
}
#endif
/*
* Determine whether some value is a power of two, where zero is
/**
* is_power_of_2() - check if a value is a power of two
* @n: the value to check
*
* Determine whether some value is a power of two, where zero is
* *not* considered a power of two.
* Return: true if @n is a power of 2, otherwise false.
*/
static inline __attribute__((const))
bool is_power_of_2(unsigned long n)
{
return (n != 0 && ((n & (n - 1)) == 0));
}
/*
* round up to nearest power of two
/**
* __roundup_pow_of_two() - round up to nearest power of two
* @n: value to round up
*/
static inline __attribute__((const))
unsigned long __roundup_pow_of_two(unsigned long n)
@ -59,8 +62,9 @@ unsigned long __roundup_pow_of_two(unsigned long n)
return 1UL << fls_long(n - 1);
}
/*
* round down to nearest power of two
/**
* __rounddown_pow_of_two() - round down to nearest power of two
* @n: value to round down
*/
static inline __attribute__((const))
unsigned long __rounddown_pow_of_two(unsigned long n)
@ -69,19 +73,19 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
}
/**
* ilog2 - log of base 2 of 32-bit or a 64-bit unsigned value
* @n - parameter
* ilog2 - log base 2 of 32-bit or a 64-bit unsigned value
* @n: parameter
*
* constant-capable log of base 2 calculation
* - this can be used to initialise global variables from constant data, hence
* the massive ternary operator construction
* the massive ternary operator construction
*
* selects the appropriately-sized optimised version depending on sizeof(n)
*/
#define ilog2(n) \
( \
__builtin_constant_p(n) ? ( \
(n) < 1 ? ____ilog2_NaN() : \
(n) < 2 ? 0 : \
(n) & (1ULL << 63) ? 63 : \
(n) & (1ULL << 62) ? 62 : \
(n) & (1ULL << 61) ? 61 : \
@ -144,10 +148,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
(n) & (1ULL << 4) ? 4 : \
(n) & (1ULL << 3) ? 3 : \
(n) & (1ULL << 2) ? 2 : \
(n) & (1ULL << 1) ? 1 : \
(n) & (1ULL << 0) ? 0 : \
____ilog2_NaN() \
) : \
1) : \
(sizeof(n) <= 4) ? \
__ilog2_u32(n) : \
__ilog2_u64(n) \
@ -155,7 +156,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
/**
* roundup_pow_of_two - round the given value up to nearest power of two
* @n - parameter
* @n: parameter
*
* round the given value up to the nearest power of two
* - the result is undefined when n == 0
@ -172,7 +173,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
/**
* rounddown_pow_of_two - round the given value down to nearest power of two
* @n - parameter
* @n: parameter
*
* round the given value down to the nearest power of two
* - the result is undefined when n == 0
@ -185,6 +186,12 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
__rounddown_pow_of_two(n) \
)
static inline __attribute_const__
int __order_base_2(unsigned long n)
{
return n > 1 ? ilog2(n - 1) + 1 : 0;
}
/**
* order_base_2 - calculate the (rounded up) base 2 order of the argument
* @n: parameter
@ -198,7 +205,11 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
* ob2(5) = 3
* ... and so on.
*/
#define order_base_2(n) ilog2(roundup_pow_of_two(n))
#define order_base_2(n) \
( \
__builtin_constant_p(n) ? ( \
((n) == 0 || (n) == 1) ? 0 : \
ilog2((n) - 1) + 1) : \
__order_base_2(n) \
)
#endif /* _LINUX_LOG2_H */