On Sun, Apr 25, 2021 at 12:07 PM Jan Hubicka <hubi...@ucw.cz> wrote: > David, > > > > The text format is documented here: > > https://clang.llvm.org/docs/UsersManual.html > > The binary format is not documented. The binary format is not guaranteed > to > > be backward compatible, so sharing the same format may not be the best > way > > as changes for clang may break GCC. > > > > Since linux perf format does not change, the tool should be relatively > > stable with low maintenance cost. Changes are needed only when some new > > AutoFDO features are added to the compiler side. > > I was under impression that it is indeed problem with the tool requiring > old format of linux perf. At least with opensuse distro the shipped tool > fails for me: > jan@skylake:~> create_llvm_prof --binary=./code --out=code.prof > E0425 21:01:55.038128 17977 perf_reader.cc:996] Unsupported event type > 79 > F0425 21:01:55.038295 17977 perf_parser.cc:240] Check failed: > reader_.ReadPerfSampleInfo(*parsed_event.raw_event, &sample_info) > *** Check failure stack trace: *** > @ 0x55e6deb6058e (unknown) > @ 0x55e6deb94a49 (unknown) > .. > Aborted (core dumped) > > I collect data as intstructed here: > https://clang.llvm.org/docs/UsersManual.html > > It is from package autofdo-0.18-4.4.x86_64 and perf 5.11.15. > > Is there a way to get this working w/o using older perf? > Honza > >
Interesting. That means we will also see the same error when using the latest perf. Wei, are you aware of the issue? David > > > Does LLVM's auto-FDO support non-Intel CPUs these days? > > > > > > > It supports LBR like events, so it is CPU vendor dependent. For ARM, > using > > ETM can achieve the goal, but I don't have detailed knowledge of it. > > > > David > > > > > > > > Honza > > > > > > > > David > > > > > > > > > > > > > > >> Honza > > > > >> > > > > > >> > David > > > > >> > > > > > >> > > > > > >> > > Honza > > > > >> > > > > > > > >> > > > David > > > > >> > > > > > > > >> > > > > > > > > >> > > > > Thoughts? > > > > >> > > > > Martin > > > > >> > > > > > > > > >> > > > > > > > > > >> > > > > > Having the tool third-party makes keeping the whole > chain > > > > >> working > > > > >> > > more > > > > >> > > > > > difficult. > > > > >> > > > > > > > > > >> > > > > > Richard. > > > > >> > > > > > > > > > >> > > > > >> Thanks, > > > > >> > > > > >> > > > > >> > > > > >> David > > > > >> > > > > >> > > > > >> > > > > >> On Thu, Apr 22, 2021 at 3:29 PM Jan Hubicka < > > > hubi...@ucw.cz> > > > > >> wrote: > > > > >> > > > > >> > > > > >> > > > > >>>> On 4/22/21 9:58 PM, Eugene Rozenfeld via Gcc wrote: > > > > >> > > > > >>>>> GCC documentation for AutoFDO points to create_gcov > tool > > > > >> that > > > > >> > > > > converts > > > > >> > > > > >>> perf.data file into gcov format that can be consumed > by > > > gcc > > > > >> with > > > > >> > > > > >>> -fauto-profile ( > > > > >> > > > > https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html, > > > > >> > > > > >>> https://gcc.gnu.org/wiki/AutoFDO/Tutorial). > > > > >> > > > > >>>>> > > > > >> > > > > >>>>> I noticed that the source code for create_gcov has > been > > > > >> deleted > > > > >> > > from > > > > >> > > > > >>> https://github.com/google/autofdo on April 7. I asked > > > about > > > > >> that > > > > >> > > > > change > > > > >> > > > > >>> in that repo and got the following reply: > > > > >> > > > > >>>>> > > > > >> > > > > >>>>> > > > > >> > > > https://github.com/google/autofdo/pull/107#issuecomment-819108738 > > > > >> > > > > >>>>> > > > > >> > > > > >>>>> "Actually we didn't use create_gcov and havn't > updated > > > > >> > > create_gcov > > > > >> > > > > for > > > > >> > > > > >>> years, and we also didn't have enough tests to > guarantee > > > it > > > > >> works > > > > >> > > (It > > > > >> > > > > was > > > > >> > > > > >>> gcc-4.8 when we used and verified create_gcov). If you > > > need > > > > >> it, it > > > > >> > > is > > > > >> > > > > >>> welcomed to update create_gcov and add it to the > > > respository." > > > > >> > > > > >>>>> > > > > >> > > > > >>>>> Does this mean that AutoFDO is currently dead in > gcc? > > > > >> > > > > >>>> > > > > >> > > > > >>>> Hello. > > > > >> > > > > >>>> > > > > >> > > > > >>>> Yes. I know that even basic test cases have been > broken > > > for > > > > >> years > > > > >> > > in > > > > >> > > > > the > > > > >> > > > > >>> GCC. > > > > >> > > > > >>>> It's new to me that create_gcov was removed. > > > > >> > > > > >>>> > > > > >> > > > > >>>> I tend to send patch to GCC that will remove AutoFDO > from > > > > >> GCC. > > > > >> > > > > >>>> I known Bin spent some time working on AutoFDO, has > he > > > came > > > > >> up to > > > > >> > > > > >>> something? > > > > >> > > > > >>> > > > > >> > > > > >>> The GCC side of auto-FDO is not that hard. We have > most > > > of > > > > >> > > > > >>> infrastructure in place, but stopping point for me was > > > always > > > > >> > > > > difficulty > > > > >> > > > > >>> to get gcov-tool working. If some maintainer steps > up, I > > > > >> think I > > > > >> > > can > > > > >> > > > > >>> fix GCC side. > > > > >> > > > > >>> > > > > >> > > > > >>> I am bit unsure how important feature it is - we have > FDO > > > that > > > > >> > > works > > > > >> > > > > >>> quite well for most users but I know there are some > users > > > of > > > > >> the > > > > >> > > LLVM > > > > >> > > > > >>> implementation and there is potential to tie this with > > > other > > > > >> > > hardware > > > > >> > > > > >>> events to asist i.e. if conversion (where one wants to > > > know > > > > >> how > > > > >> > > well > > > > >> > > > > CPU > > > > >> > > > > >>> predicts the jump rather than just the jump > probability) > > > > >> which I > > > > >> > > always > > > > >> > > > > >>> found potentially interesting. > > > > >> > > > > >>> > > > > >> > > > > >>> Honza > > > > >> > > > > >>>> > > > > >> > > > > >>>> Martin > > > > >> > > > > >>>> > > > > >> > > > > >>>>> > > > > >> > > > > >>>>> Thanks, > > > > >> > > > > >>>>> > > > > >> > > > > >>>>> Eugene > > > > >> > > > > >>>>> > > > > >> > > > > >>>> > > > > >> > > > > >>> > > > > >> > > > > > > > > >> > > > > > > > > >> > > > > > > >> > > > > > > > > >
