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Fedora 33 Moving Closer To LTO-Optimizing Packages

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  • Fedora 33 Moving Closer To LTO-Optimizing Packages

    Phoronix: Fedora 33 Moving Closer To LTO-Optimizing Packages

    Going back to last year Fedora has been working to enable link-time optimizations by default for their packages. That goal wasn't achieved for Fedora 32 but for Fedora 33 this autumn they still have chances of marking that feature off their TODO list...

    http://www.phoronix.com/scan.php?pag...3-LTO-Progress

  • #2
    I've inspected a dozen of build failures and none of them are related to GCC LTO - all the failures are related to bad spec files/build system (CMake/Makefile/etc) errors, e.g. this

    Undertakings like these are great for GCC as it allows to fix rare compiler errors.

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    • #3
      It would be a shame if this was missed again, I hope it makes it into F33.

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      • #4
        and then several library(ahem, mesa) builds for newer than base amd64 architectures for fedora 34?
        Last edited by pal666; 08-09-2020, 11:23 AM.

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        • #5
          Perhaps the article could mention that OpenSUSE tumbleweed builds with LTO since switch to gcc 9 (thanks to effort of Martin Liska). This really helped a lot to hammer out LTO issues from various places.

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          • #6
            Originally posted by birdie View Post
            I've inspected a dozen of build failures and none of them are related to GCC LTO
            There are a few LTO related failures in the list, and some are apparently due to exceeding memory limits on 32-bit platforms during the compile phase.

            ... all the failures are related to bad spec files/build system (CMake/Makefile/etc) errors ...
            The CMake change(s) resulted in something in the order of magnitude of an initial thousand failures during the mass rebuild. Those, too, are being dealt with, but are, possibly, the single largest remaining identified contributor of failures (the cmake changes can show up in multiple different ways, depending on how people were using cmake in their builds).

            And, as always, there are also a set of packages that are failing to build due to other changes in other packages/libraries that now require updating that package to the newer upstream(s).

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            • #7
              Originally posted by hubicka View Post
              Perhaps the article could mention that OpenSUSE tumbleweed builds with LTO since switch to gcc 9 (thanks to effort of Martin Liska). This really helped a lot to hammer out LTO issues from various places.
              Tumbleweed was an excellent step, and the Fedora change owner depended on that experience to give them added confidence about the expected results. It also turns out that tumbleweed did end up having to punt some of the work down the line, as will Fedora, due to specific package issues. Some (as previously mentioned) are due to things like gcc needing more memory to complete the build with LTO, and there are some packages which at the source level are not compliant with LTO builds (and while the fixes are typically trivial for someone familiar with the code base, they do usually require upstream to do the work), and then there are the packages with interesting (that is putting it kindly) build processes that also need changes to properly support LTO (sometimes that build process is an issue for the packagers to fix, sometimes upstream itself). It is expected that it will take some time to address all the exceptions that will be used for this cycle.
              Last edited by CommunityMember; 08-09-2020, 03:08 PM.

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              • #8
                Anyone knows what the status of such an effort is on Debian land?

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                • #9
                  i wouldnt be surprised if this Feature doesnt makes it along with some others that have been mentioned, IMO Fedora try to add to many Features into a release an some just dont get done.
                  Last edited by Anvil; 08-10-2020, 12:32 AM.

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                  • #10
                    https://bugzilla.redhat.com/show_bug.cgi?id=1803234
                    https://kojipkgs.fedoraproject.org/m...d-rebuild.html

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