Messages in this thread Patch in this message | | | From | David Howells <> | Subject | [PATCH 6/6] Alter roundup_pow_of_two() so that it can make use of long_log2() on a constant | Date | Wed, 13 Sep 2006 14:03:04 +0100 |
| |
From: David Howells <dhowells@redhat.com>
Alter roundup_pow_of_two() so that it can make use of long_log2() 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 | 23 +++++++++++++++++++++++ 2 files changed, 23 insertions(+), 6 deletions(-)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h index e8c6c66..e5947fb 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -155,12 +155,6 @@ #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 a2f6858..2b55af0 100644 --- a/include/linux/log2.h +++ b/include/linux/log2.h @@ -74,6 +74,15 @@ #endif #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); +} + +/* * constant-capable 32-bit log of base 2 calculation * - this can be used to initialise global variables from constant data, hence * the massive ternary operator construction @@ -218,4 +227,18 @@ ( \ __get_order(n, PAGE_SHIFT) \ ) +/* + * round up to 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 << (long_log2((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/
| |