Messages in this thread | | | Date | Wed, 16 Jan 2002 17:00:14 +1100 | From | Anton Blanchard <> | Subject | Re: likely/unlikely |
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> likely/unlikely set the branch prediction values to 99% or 1% > respectively. If this causes the code generated to perform less > optimally than without, I'm sure the gcc guys would be -very- interested > to hear that...
On some ppc64 the branch prediction is quite good and static prediction will override the dynamic prediction. I think we avoid predicting a branch unless we are quite sure (95%/5%).
So if likely/unlikely is overused (on more marginal conditionals) then it could be a performance loss.
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