Based on Honza's feedback, I think it is bettre to add command line interface such as this:
-ffunction-attribute-list=<attribute_name>:<function_pattern_list> or -ffunction-attribute-filelist=<attribute_name>:<function_pattern_list_filename> e.g, -ffunction-attribute-list=code:foo1,foo2,bar_*,blah It probably needs to be processed as deferred option to allow other option to be translated into this form -- for instance extracted from some global profile data. thanks, David On Sat, Jun 2, 2012 at 7:16 AM, Dehao Chen <de...@google.com> wrote: > 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
