> For my test case, the entire inline instance is optimized away, so > there is no info about it in the profile. I can do some fixup in the > rebuild_cgraph_edge though.
Yep, I understand that. In this case we should turn PROFILE_READ to PROFILE_GUESSED and guess the profile when we detect this (i.e. we have edges with non-0 counts into functions with 0 profile). That should prvent these from getting UNLIKELY_EXECUTED and they will be inlined normal way. Honza > > Dehao > > On Mon, Oct 14, 2013 at 2:27 PM, Xinliang David Li <davi...@google.com> wrote: > > Is it possible to update the callee node summary after profile > > annotate (using information from inline instances which are not > > inlined in early inline)? > > > > David > > > > On Mon, Oct 14, 2013 at 2:18 PM, Dehao Chen <de...@google.com> wrote: > >> On Mon, Oct 14, 2013 at 12:49 PM, Jan Hubicka <hubi...@ucw.cz> wrote: > >>>> Not for instrumented FDO (not as I know of). But for AutoFDO, this > >>>> could be a potential risk because some callee is marked unlikely > >>>> executed simply because they are inlined and eliminated in the O2 > >>>> binary. But in ipa-inline it will not get inlined because the edge is > >>>> not hot from cgraph_maybe_hot_edge_p (because callee is > >>>> UNLIKELY_EXECUTED), while the edge->count is actually hot. > >>> > >>> Can't you prevent setting calle to UNLIKELY_EXECUTED in these cases > >>> instead? > >>> It seems that having profile set incorrectly will lead to other problems > >>> later, too. > >>> We discussed similar problem with Teresa about the missing profiles for > >>> comdat, > >>> basically one should detect these cases as profile being lost and go with > >>> guessed > >>> profile. (I believe patch for that was posted, too, and so far it seems > >>> best approach > >>> to this issue) > >> > >> The current AutoFDO implementation will take all functions that do not > >> have have profile as normally executed, thus use guessed profile for > >> it. This is like using profile for truly hot functions, and using O2 > >> for other functions. This works fine. However, it leads to larger code > >> size (approximately 10%~20% larger than FDO). > >> > >> I'd like to introduce another mode for users who care about both > >> performance and code size, and can be sure that profile is > >> representative. In this mode, we will mark all functions without > >> sample as "unlikely executed". However, because AutoFDO use debug info > >> (of optimized code) to represent profile, it's possible that some hot > >> functions (say foo) are inlined and fully eliminated into another hot > >> function (say bar). So in the profile, bar is cold, and because the > >> profile for foo::bar is eliminated, bar will not be inlined into foo > >> before the profile annotation. However, after profile annotate, we can > >> infer from the bb count that foo->bar is hot, thus it should be > >> inlined in ipa-inline phase. However, because bar itself is marked > >> UNLIKELY_EXECUTED, it will not be inlined. > >> > >> One possible workaround would be that during rebuild_cgraph_edges, if > >> we find an edge's callee is unlikely executed, add the edge count to > >> the callee's count and recalculate callee's frequency. > >> > >> Dehao > >> > >>> > >>> Honza