Barcelona optimization guide

By: Michael S (already5chosen.delete@this.yahoo.com), May 13, 2007 9:03 am
Room: Moderated Discussions
Vincent Diepeveen (diep@xs4all.nl) on 5/13/07 wrote:
---------------------------
>
>No need to have a history to predict next branch:
>
>for( i = 0 ; i < 4 ; i++ ) {
>for( j = 0 ; j < 4 ; j++ ) {
>...
>}
>}
>
>If K8-barcelona can't perfectly predict that, then AMD has some work to do.
>

Hammer core (at least, relatively new revision of K8 that I played with) seem to have short loop predictor that could correctly predict loops with eight or nine iterations or less. It's fair to assume that Greyhound core keeps that ability or may be even extend it to 16 iterations. I don't understand why AMD prefers to not document this feature.

See also at Agner Fog:
http://www.agner.org/optimize/microarchitecture.pdf
p.24
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            Barcelona optimization guideMichael S2007/05/17 04:26 AM
              Barcelona optimization guideanonymous2007/05/17 05:23 PM
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