Re: likely/unlikely

[Anton Blanchard]

> 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.

Anton