[FFmpeg-devel] Don't use _tzcnt instrinics with clang for windows w/o BMI.
michael at niedermayer.cc
Wed Oct 25 20:53:27 EEST 2017
On Thu, Oct 26, 2017 at 03:39:57AM +1100, Matt Oliver wrote:
> On 25 October 2017 at 07:15, Dale Curtis <dalecurtis at chromium.org> wrote:
> > Technically _tzcnt* intrinsics are only available when the BMI
> > instruction set is present. However the instruction encoding
> > degrades to "rep bsf" on older processors.
> > Clang for Windows debatably restricts the _tzcnt* instrinics behind
> > the __BMI__ architecture define, so check for its presence or
> > exclude the usage of these intrinics when clang is present.
> > See also:
> > https://ffmpeg.org/pipermail/ffmpeg-devel/2015-November/183404.html
> > https://bugs.llvm.org/show_bug.cgi?id=30506
> > http://lists.llvm.org/pipermail/cfe-dev/2016-October/051034.html
> > Signed-off-by: Dale Curtis <dalecurtis at chromium.org
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
When you are offended at any man's fault, turn to yourself and study your
own failings. Then you will forget your anger. -- Epictetus
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