Barcelona optimization guide

By: Andreas Kaiser (prx99.delete@this.arcor.de), May 12, 2007 8:32 am
Room: Moderated Discussions
Linus Torvalds (torvalds@osdl.org) on 5/10/07 wrote:
---------------------------
>There appears to be something magical about the single-byte
>"ret" form, because the manual states that you can avoid
>the problem with the 3-byte "ret $0" form.

The branch predictor has a 2-byte resolution whan handling nonsequential fetch. It which usually does not matter because all branch instructions are at least 2 byte in size - except for RET which may get lost this way.

Concerning fetch/branch handling, the instruction fetch restart after a mispredicted branch is equivalent to a taken branch. So a branch targetting RET and a conditional branch immediately preceding RET actually are the same case.

This is old news however, because it has been this way since the first K7, the original Athlon.
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TopicPosted ByDate
Barcelona optimization guidemas2007/05/10 06:43 AM
  Barcelona optimization guideLinus Torvalds2007/05/10 09:00 AM
    Barcelona optimization guideRob Thorpe2007/05/10 09:23 AM
      Barcelona optimization guideLinus Torvalds2007/05/10 09:42 AM
        Barcelona optimization guideRob Thorpe2007/05/11 08:22 AM
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          Barcelona vs Core2 Vincent Diepeveen2007/05/16 05:35 AM
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          Barcelona optimization guideanonymous2007/05/16 07:13 PM
            Barcelona optimization guideMichael S2007/05/17 04:26 AM
              Barcelona optimization guideanonymous2007/05/17 05:23 PM
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