Messages in this thread Patch in this message | | | From | David Howells <> | Subject | [PATCH 2/4] LOG2: Alter roundup_pow_of_two() so that it can use a ilog2() on a constant [try #4] | Date | Fri, 06 Oct 2006 14:34:17 +0100 |
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From: David Howells <dhowells@redhat.com>
Alter roundup_pow_of_two() so that it can make use of ilog2() on a constant to produce a constant value, retaining the ability for an arch to override it in the non-const case.
This permits the function to be used to initialise variables.
Signed-Off-By: David Howells <dhowells@redhat.com> ---
include/linux/kernel.h | 6 ------ include/linux/log2.h | 26 ++++++++++++++++++++++++++ 2 files changed, 26 insertions(+), 6 deletions(-)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 473101a..67ca3ad 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -156,12 +156,6 @@ #endif unsigned long int_sqrt(unsigned long); -static inline unsigned long -__attribute_const__ roundup_pow_of_two(unsigned long x) -{ - return 1UL << fls_long(x - 1); -} - extern int printk_ratelimit(void); extern int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst); diff --git a/include/linux/log2.h b/include/linux/log2.h index 3979c60..d02e1a5 100644 --- a/include/linux/log2.h +++ b/include/linux/log2.h @@ -43,6 +43,15 @@ int __ilog2_u64(u64 n) } #endif +/* + * round up to nearest power of two + */ +static inline __attribute__((const)) +unsigned long __roundup_pow_of_two(unsigned long n) +{ + return 1UL << fls_long(n - 1); +} + /** * ilog2 - log of base 2 of 32-bit or a 64-bit unsigned value * @n - parameter @@ -128,4 +137,21 @@ ( \ __ilog2_u64(n) \ ) +/** + * roundup_pow_of_two - round the given value up to nearest power of two + * @n - parameter + * + * round the given balue up to the nearest power of two + * - the result is undefined when n == 0 + * - this can be used to initialise global variables from constant data + */ +#define roundup_pow_of_two(n) \ +( \ + __builtin_constant_p(n) ? ( \ + (n == 1) ? 0 : \ + (1UL << (ilog2((n) - 1) + 1)) \ + ) : \ + __roundup_pow_of_two(n) \ + ) + #endif /* _LINUX_LOG2_H */ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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