On Mon, Oct 14, 2013 at 2:34 PM, Dehao Chen <de...@google.com> wrote: > For my test case, the entire inline instance is optimized away,
do you mean there is no out of line instance for the target function in the profile binary? David > so > there is no info about it in the profile. I can do some fixup in the > rebuild_cgraph_edge though. > > 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