Hi, The binary gotten via clang's `-O1` runs much slower (3x) than that gotten via GCC's `-O1`. Reproducible with: https://github.com/m-chaturvedi/test_valgrind_slowdown We are seeing this difference between gcc and clang at other places as well. The `-O0` and `-O2` times are comparable, however. Are there some compile time flags one could add to make the `-O1` times comparable? Apologies if this has been discussed somewhere already. Thank you, Mmanu -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20180531/8f4d02f1/attachment.html>
What are you trying to achieve? If faster runs is the goal, why not compile with -O2? Michael 2018-05-31 16:27 GMT-05:00 M. Chaturvedi via llvm-dev <llvm-dev at lists.llvm.org>:> Hi, > > The binary gotten via clang's `-O1` runs much slower (3x) than that gotten > via GCC's `-O1`. > > Reproducible with: > > https://github.com/m-chaturvedi/test_valgrind_slowdown > > We are seeing this difference between gcc and clang at other places as well. > > The `-O0` and `-O2` times are comparable, however. Are there some compile > time flags one could add to make the `-O1` times comparable? > > Apologies if this has been discussed somewhere already. > > Thank you, > Mmanu > > _______________________________________________ > LLVM Developers mailing list > llvm-dev at lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >
Thanks for the quick reply. `-O0` is too slow with Valgrind and `-O2` is not recommended. We use `-O1` in Valgrind runs.> Use of -O2 and above is not recommended as Memcheck occasionally reportsuninitialised-value errors which don't really exist. http://valgrind.org/docs/manual/quick-start.html On Thu, May 31, 2018 at 5:34 PM, Michael Kruse <llvmdev at meinersbur.de> wrote:> What are you trying to achieve? If faster runs is the goal, why not > compile with -O2? > > Michael > > > 2018-05-31 16:27 GMT-05:00 M. Chaturvedi via llvm-dev < > llvm-dev at lists.llvm.org>: > > Hi, > > > > The binary gotten via clang's `-O1` runs much slower (3x) than that > gotten > > via GCC's `-O1`. > > > > Reproducible with: > > > > https://github.com/m-chaturvedi/test_valgrind_slowdown > > > > We are seeing this difference between gcc and clang at other places as > well. > > > > The `-O0` and `-O2` times are comparable, however. Are there some > compile > > time flags one could add to make the `-O1` times comparable? > > > > Apologies if this has been discussed somewhere already. > > > > Thank you, > > Mmanu > > > > _______________________________________________ > > LLVM Developers mailing list > > llvm-dev at lists.llvm.org > > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev > > >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20180531/8d8c0341/attachment.html>