Messages in this thread Patch in this message | | | Subject | [PATCH] Optimize is_power_of_2(). | From | Vegard Nossum <> | Date | Fri, 15 Jun 2007 18:56:42 +0200 |
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From: Vegard Nossum <vegard@peltkore.net> Date: Fri, 15 Jun 2007 18:35:49 +0200 Subject: [PATCH] Optimize is_power_of_2().
Rationale: Removes one conditional branch and reduces icache footprint. Proof: If n is false, the product of n and any value is false. If n is true, the truth of (n * x) is the truth of x.
Signed-off-by: Vegard Nossum <vegard@peltkore.net> --- include/linux/log2.h | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/include/linux/log2.h b/include/linux/log2.h index 1b8a2c1..56196b1 100644 --- a/include/linux/log2.h +++ b/include/linux/log2.h @@ -51,7 +51,7 @@ int __ilog2_u64(u64 n) static inline __attribute__((const)) bool is_power_of_2(unsigned long n) { - return (n != 0 && ((n & (n - 1)) == 0)); + return n * !(n & (n - 1)); } /* -- 1.5.0.6 - 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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