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Re: [Qemu-devel] Mips 64 emulation not compiling

From: J. Mayer
Subject: Re: [Qemu-devel] Mips 64 emulation not compiling
Date: Sat, 27 Oct 2007 16:12:50 +0200

On Sat, 2007-10-27 at 15:27 +0200, Christian "Eddie" Dost wrote:
> The sparc64 popc works in O(lg(n))

No, it has a fix cost, whatever the operand is.
It has another advantage: it does not need any intermediate variable,
which is great when running on CISC host in the Qemu execution

> , the "optimized" code below work in 
> O(n).

Yes. But it's false.... It shoudl be val &= val - 1
instead of val  ^= val - 1...


I did tests on my PC, which will imho close the debate: the Sparc
implementation is at least 50 % faster. I did generate 2 ^ 29 random
numbers to achieve this test (and checked that the repartition was OK).

J. Mayer <address@hidden>
Never organized

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