SIMD vs no SIMD on i686 (was: [Bug 3975] executable stack flag prevents use of libx264.so.148 with selinux in enforcing mode)

[Dominik 'Rathann' Mierzejewski]

On Tuesday, 19 July 2016 at 09:35, Nicolas Chauvet wrote:
> 2016-07-19 2:55 GMT+02:00  <dominik at greysector.net>:
> > Hello, Sérgio.
> >
> > On Tuesday, 19 July 2016 at 02:35, RPM Fusion Bugzilla wrote:
> >> https://bugzilla.rpmfusion.org/show_bug.cgi?id=3975
> >>
> >> --- Comment #4 from Sérgio Basto <sergio at serjux.com> 2016-07-19 02:35:19 CEST ---
> >> (In reply to comment #3)
> >> > I'll take a look at this. Could you try running execstack -c on the installed
> >> > library in the meantime?
> >>
> >> Be my guest , in  meantime I read your thread on packaging Mailing list about
> >> sse3 , I'd like understand if we need 2 builds for i686 ... one with sse2 other
> >> without it, can you give us your opinion ?
> >
> > The only real concern here are applications linked against libx264,
> > which someone might want to run on low-end hardware, because I don't
> > think anyone would want to encode anything to H.264 on non-SSE2 capable
> > CPU (i.e. Pentium 3 or Athlon XP and older). Considering last non-SSE2
> > CPUs went out of production about 8 years ago, I think it's fairly safe
> > to assume that the impact of doing SSE2-only builds would be negligible,
> > if any.
> 
> I'm okay to have a SSE2 only build for single binaries such as pcsx2
> for the following reasons:
> - pcsx2 requires more CPU resources than barely capable sse2 CPU anyway.
> - Using sse2 will allow older but sse2 capable CPU to run.
> - Runtime test has to be made to avoid crash and notify user if the
> CPU don't have sse2.
> 
> But for libraries it's not possible to assume a given usage and ensure
> users notification.
> I expect you can have webcam app to encode to h264 low profile just
> fine using x264 even on non-sse2 capable cpu.
> It's expected not to crash here.
> 
> So I don't understand why this discussion raised up again, but I'd
> like not to more anything in i686 that will made some corner case
> users to crash.

In principle, I agree, even though I doubt it's a real world issue.
There's no reason not to build both with and without sse2 enabled,
though.

Regards,
-- 
Fedora http://fedoraproject.org/wiki/User:Rathann
RPMFusion http://rpmfusion.org
"Faith manages."
        -- Delenn to Lennier in Babylon 5:"Confessions and Lamentations"