On Sat, Jun 2, 2012 at 9:17 PM, Jan Hubicka <hubi...@ucw.cz> wrote: >> > Well, perhaps the feature would be more useful with command line option >> > allowing >> > to add an attribute instead of having special case command line options >> > for individual >> > cases. >> >> Hi, Honza, I'm not sure what you mean by "command line option allowing >> to add an attribution". But this seems what this patch does: it adds >> attributes to functions with specified name patterns. > > I mean that if we want to go this route, we may want to allow this interface > to i.e. add > always_inline attrbute or noinline or such. I can imagine this to be useful > especially for > languages that has no attributes.
This annotation is mainly for static branch prediction. Some functions may be very cold, but it may still be good to inline it. > >> >> > I guess the problem would be also solvable with header included after >> > the library adding the attributes to the declarations >> > >> > typeof (printf) printf __attribute__ ((cold)); >> >> Do you mean that for each specific application, we extract a common >> header file to include all function annotations, and all source files >> will include this header file? > > Yes, something like that... > Where do you use the likely_hot/likely_cold logic? For really cold functions, we predict the branch to be 0.04% taken. However, some callee functions are not that extremely cold, and predicting them as 0.04% is too aggressive. Likely_cold is for such functions, and we predict them as 25% taken (at least we can predict the direction right). Vise versa for likely_hot annotation. Thanks, Dehao > > Honza >> >> Thanks, >> Dehao >> >> > >> > Honza >> >> >> >> thanks, >> >> >> >> David >> >> > Honza
