On Fri, Oct 14, 2016 at 11:31 AM, Michael Niedermayer <mich...@niedermayer.cc> wrote: > On Fri, Oct 14, 2016 at 08:29:37PM +0200, Michael Niedermayer wrote: >> On Fri, Oct 14, 2016 at 11:09:30AM -0700, James Zern wrote: >> > Ronald, >> > >> > On Fri, Oct 14, 2016 at 10:01 AM, Ronald S. Bultje <rsbul...@gmail.com> >> > wrote: >> > > This is intended to workaround bug "665 Integer Divide Instruction May >> > > Cause Unpredictable Behavior" on some early AMD CPUs, which causes a >> > > div-by-zero in this codepath, such as reported in Mozilla bug #1293996. >> > > >> > > Note that this isn't guaranteed to fix the bug, since a compiler is free >> > > to reorder instructions that don't depend on each other. However, it >> > > appears to fix the bug in Firefox, and a similar patch was applied to >> > > libvpx also (see Chrome bug #599899). >> > > >> > >> > I recently made a few additional changes as this regressed in chrome >> > [1][2], but just like this change there's no guarantee it won't occur >> > again. >> >> maybe you can use empty "asm volatile(:::"memory")" statments to >> prevent unwanted instruction reordering by the compiler >> never tried something like this so dunno, also it would be specific >> to gcc compatible compilers but should not be architecture specific > > thinking again, why dont you write the function in asm for x86 ? > this would take the compiler out of the equation >
That could work, I started with a portion in assembly before making the C changes, but didn't follow through with it. > [...] > > -- > Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB > > The educated differ from the uneducated as much as the living from the > dead. -- Aristotle > > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel > _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel