[PATCH] Optimize is_power_of_2().
- From: Vegard Nossum <vegard.nossum@xxxxxxxxx>
- Date: Fri, 15 Jun 2007 18:56:42 +0200
From: Vegard Nossum <vegard@xxxxxxxxxxxx>
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@xxxxxxxxxxxx>
---
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
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