Thanks for the response and sorry for taking so long to reply. On Mon, Jun 18, 2018 at 10:05 PM, Kevin Kofler <kevin.kof...@chello.at> wrote:
> Jeff Backus wrote: > > Hmm.. Yes, we've had discussions within the SIG re: window managers that > > support i586/i686, and KDE was on the list of WMs that no longer support > > our target system. Do these patches/hacks only apply to KDE or do they > > apply to Qt in general? > > The absolute worst is QtWebEngine. Chromium dropped support for non-SSE2 > x86 > years ago, so I had to cumulatively revert a whole bunch of commits that > removed runtime SSE2 detection where it was present and added some more > unconditional SSE2 optimizations. And now V8 (the JavaScript engine that > Chromium relies on) dropped the x87 backend (i.e., the one using x87 > rather > than SSE2 for floating-point operations, hence working on non-SSE2 x86 > machines) for their JIT entirely (and there is no interpreter-only > fallback), so I am even stuck trying to port the x87 backend to each new > Qt > branch (which uses a newer Chromium and thus a newer V8). This is a huge > effort, and nobody outside of Fedora cares about non-SSE2 anymore. Even > distros that claim to support non-SSE2 hardware just ship QtWebEngine as > SSE2 only. I haven't seen any other distro even picking up my patch, let > alone working on it. The Fedora Chromium, V8 and Node.js packagers also do > not care. > Wow. Yes, that is a heavy lift. Thank you for your efforts! :) It helps to see how expensive non-SSE2 support is. Thanks. > I think Google sucks for desupporting hardware that way, but I also do not > think maintaining the V8 x87 backend on our own is going to scale in the > long run. My time is limited and I do not currently see anybody else among > the Fedora Qt maintainers who is at the same time both able and willing to > maintain it. (This needs somebody with plenty of free time and with some > experience working on compilers.) > Agreed. Is the only reason to maintain the x87 backend for non-SSE2 support? So the QtWebEngine no-sse2 patch is definitely going to be dropped from > F29+, given the FESCo decision on this issue. For F27 and F28, I will look > into it and see what I can do. > Thank you. Cheers, Jeff -- Jeff Backus jeff.bac...@gmail.com http://github.com/jsbackus
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