On Mon, Oct 14, 2013 at 2:50 PM, Jan Hubicka <hubi...@ucw.cz> wrote: >> 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.
Oh, actually in AutoFDO, only functions with samples will be marked as PROFILE_READ. Others will all be marked as PROFILE_GUESSED. Dehao > > 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
