On Fri, Apr 23, 2021 at 10:27 AM Xinliang David Li <davi...@google.com> wrote:
> > > On Fri, Apr 23, 2021 at 10:16 AM Jan Hubicka <hubi...@ucw.cz> wrote: > >> > >> > It uses create_llvm_prof tool which is in the same git repo. The data >> > parsing part is shared with create_gcov, but the writer is obviously >> > different for the two tools. >> >> OK and what are the main differences between llvmand gcc format? >> >> GCC expects GCOV format, I think while LLVM uses a newly designed binary > format. > > Sorry I missed your next reply. I forgot about the details of GCC' format. 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 >> > > > > >>>>> >> > > > > >>>> >> > > > > >>> >> > > > > >> > > > > >> > > >> >
