From 0136611c62e8650e354b95c76dff6d2ce6030eff Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Tue, 26 Sep 2006 10:52:38 +0200 Subject: [PATCH] optimize hweight64 for x86_64 Based on patch from David Rientjes , but changed by AK. Optimizes the 64-bit hamming weight for x86_64 processors assuming they have fast multiplication. Uses five fewer bitops than the generic hweight64. Benchmark on one EMT64 showed ~25% speedup with 2^24 consecutive calls. Define a new ARCH_HAS_FAST_MULTIPLIER that can be set by other architectures that can also multiply fast. Signed-off-by: Andi Kleen --- include/asm-x86_64/bitops.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include') diff --git a/include/asm-x86_64/bitops.h b/include/asm-x86_64/bitops.h index f7ba57b1cc0..5b535eaf530 100644 --- a/include/asm-x86_64/bitops.h +++ b/include/asm-x86_64/bitops.h @@ -399,6 +399,8 @@ static __inline__ int fls(int x) return r+1; } +#define ARCH_HAS_FAST_MULTIPLIER 1 + #include #endif /* __KERNEL__ */ -- cgit v1.2.3