include: update log2 header from the Linux kernel
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>
diff --git a/include/linux/log2.h b/include/linux/log2.h
index 4ded5ee..d4e32ec 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
@@ -12,12 +17,6 @@
#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
* more efficiently than using fls() and fls64()
@@ -39,19 +38,23 @@
}
#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 @@
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 @@
}
/**
- * 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 @@
(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 @@
/**
* 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 @@
/**
* 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 @@
__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 @@
* 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 */