Messages in this thread | | | Subject | Re: kernel + gcc 4.1 = several problems | From | Arjan van de Ven <> | Date | Wed, 03 Jan 2007 05:32:16 -0800 |
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On Wed, 2007-01-03 at 12:44 +0000, Alan wrote: > > > fixed. At that point an i686 kernel would contain i686 instructions and > > > actually run on all i686 processors ending all the i586 pain for most > > > users and distributions. > > > > Could you explain why CMOV is pointless now? Are there any benchmarks > > proving that? > > Take a look at the recent ffmpeg bits on the mplayer list for one example > I have to hand - P4 cmov is pretty slow. The crypto folks find the same > things.
cmov is effectively the same cost as a compare and jump, in both cases the cpu needs to do a prediction, and on a mispredict, restart.
the reason cmov can make sense is because it's smaller code...
-- if you want to mail me at work (you don't), use arjan (at) linux.intel.com Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org
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