On Mon, Oct 14, 2013 at 3:26 PM, Dehao Chen <de...@google.com> wrote: > 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.
Here is Honza's patch that he was referring to: Index: tree-profile.c =================================================================== --- tree-profile.c (revision 201838) +++ tree-profile.c (working copy) @@ -604,6 +604,34 @@ pop_cfun (); } + /* See if 0 count function has non-0 count callers. In this case we + lost some profile. Drop its function profile to PROFILE_GUESSED. */ + FOR_EACH_DEFINED_FUNCTION (node) + { + struct cgraph_edge *e; + bool called = false; + if (node->count) + continue; + for (e = node->callers; e; e = e->next_caller) + { + if (e->count) + called = true; + if (cgraph_maybe_hot_edge_p (e)) + break; + } + if (e || called + && profile_status_for_function + (DECL_STRUCT_FUNCTION (node->symbol.decl)) == PROFILE_READ) + { + if (dump_file) + fprintf (stderr, "Dropping 0 profile for %s/%i.%s based on calls.\n", + cgraph_node_name (node), node->symbol.order, + e ? "function is hot" : "function is normal"); + profile_status_for_function (DECL_STRUCT_FUNCTION (node->symbol.decl)) + = (flag_guess_branch_prob ? PROFILE_GUESSED : PROFILE_ABSENT); + node->frequency = e ? NODE_FREQUENCY_HOT : NODE_FREQUENCY_NORMAL; + } + } del_node_map(); return 0; Index: predict.c =================================================================== --- predict.c (revision 201838) +++ predict.c (working copy) @@ -2715,6 +2715,9 @@ gcov_type count_max, true_count_max = 0; basic_block bb; + if (!ENTRY_BLOCK_PTR->count) + return 0; + FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb) true_count_max = MAX (bb->count, true_count_max); Which is discussed in this email: http://gcc.gnu.org/ml/gcc-patches/2013-08/msg01185.html For COMDATs I need to extend this to do it a little later to do it recursively to catch the case of COMDATs feeding other COMDATs and I need to do some other handling to compute counts from the frequencies when inlining. I have been meaning to work on this for awhile but finally am getting to it this week. (Here's the last message from a later thread that forked off the above one: http://gcc.gnu.org/ml/gcc-patches/2013-08/msg01907.html) In the meantime, perhaps Honza's patch will suffice? Teresa > > 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 -- Teresa Johnson | Software Engineer | tejohn...@google.com | 408-460-2413