> On May 4, 2023, at 4:30 AM, Martin Liška <mli...@suse.cz> wrote: > > On 5/3/23 21:10, Qing Zhao via Gcc-patches wrote: >> Hi, Jan, >> >> You added the following patch into gcc10: >> >> From 34fbe3f0946f88828765184ed6581bda62cdf49f Mon Sep 17 00:00:00 2001 >> From: Jan Hubicka <hubi...@ucw.cz> >> Date: Thu, 5 Dec 2019 19:12:51 +0100 >> Subject: [PATCH] cgraphclones.c (localize_profile): New function. >> >> * cgraphclones.c (localize_profile): New function. >> (cgraph_node::create_clone): Use it for partial profiles. >> * common.opt (fprofile-partial-training): New flag. >> * doc/invoke.texi (-fprofile-partial-training): Document. >> * ipa-cp.c (update_profiling_info): For partial profiles do not >> set function profile to zero. >> * profile.c (compute_branch_probabilities): With partial profile >> watch if edge count is zero and turn all probabilities to guessed. >> (compute_branch_probabilities): For partial profiles do not apply >> profile when entry count is zero. >> * tree-profile.c (tree_profiling): Only do >> value_profile_transformations >> when profile is read. >> >> My question is: > > Hello. > > Why would anybody backport such change to unsupported code-stream of GCC 8? > Generally speaking, I discourage from doing that.
Yes, I agree. However, many users still use GCC8 right now, and some of them are asking for more performance from PGO recently. That’s the reason I am studying this right now. From my understanding, -fprofile-partial-training is one important option for PGO performance. I’d like to see any big technique difficult to prevent it from being back ported to GCC8. Thanks. Qing > > Martin > >> >> Can this patch be back ported to GCC8 easily? I am wondering any significant >> Change between GCC8 and GCC10 that might make the backporting very hard> >> Thanks a lot for your help. >> >> Qing
