Author: Gerd Isenberg
Date: 05:41:07 12/21/02
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On December 21, 2002 at 02:40:42, Matt Taylor wrote: >OK, after a bit of work cleaning up an undergrad project (the buggy source >highlighter that I used to convert the code -> html), I've got the code up. > >Timings: >http://65.186.75.165/~mtaylor/bitscan_athlon.html > >Code: >http://65.186.75.165/~mtaylor/ipcbench.c.html >http://65.186.75.165/~mtaylor/bitscan.c.html > >I'll run results for an original K6 tomorrow just as a matter of curiousity. I >don't have access to -ANY- Intel machines right now, so I can't get Intel data. >If anyone wants to help out, I can toss the binary up on FTP. Offhand I don't >think it will run terribly well on a P4 and possibly not very well on previous >Intel processors. > >-Matt Hi Matt, thanks for sharing the results and sources. A few remarks. I missed the last pi2fd/mmx-version i posted recently. The one you reported was a bit outdated ;-) Anyway, i made my conclusions already. The implementation of the while-conditions favours the lower half a bit. So i would prefere Walter's methode, looking for carry after substaction, or this one: mov edx, [bb] or edx, [bb+4] jnz ScanAgain instead of two cmp,jne statements. What about mispredicted branches here? Gerd
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