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 --- v2 rebased --- include/linux/log2.h | 63 ++++++++++++++++++++++++++------------------ 1 file changed, 37 insertions(+), 26 deletions(-)
diff --git a/include/linux/log2.h b/include/linux/log2.h index 4ded5ee68a9..d4e32ecfc64 100644 --- a/include/linux/log2.h +++ b/include/linux/log2.h @@ -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 */