[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
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
environmnent.
> , 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