Messages in this thread | | | Subject | Re: gettimeofday order of magnitude slower with pmtimer, which is default | From | Arjan van de Ven <> | Date | Tue, 21 Mar 2006 13:04:44 +0100 |
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On Tue, 2006-03-21 at 22:58 +1100, Con Kolivas wrote: > On Tuesday 21 March 2006 19:53, Andreas Mohr wrote: > > (and the fact that invoking a function pointer should be similarly > > expensive to a conditional) I don't think it's useful. > > Is > > *blah(); > > as expensive as > > if (conditional) > blah(); > > I don't know the answer. I just know cmp is expensive. Comments?
function pointer is usually MORE expensive. for if() the processor has a change to predict the branch right, while call <register> (which is what function pointer calls end up being) are basically always mispredicted unless you have a really really fancy branch predictor...
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