Re: [FFmpeg-devel] [PATCH 1/2] aarch64: Simplify the linux runtime cpu detection code

[Sean McGovern <gseanmcg@gmail.com>]

On Thu, Oct 26, 2023 at 5:40 PM Sean McGovern <gseanmcg@gmail.com> wrote:
>
> On Tue, Oct 24, 2023 at 8:40 AM Sean McGovern <gseanmcg@gmail.com> wrote:
> >
> >
> >
> > On Tue, Oct 24, 2023, 08:23 Martin Storsjö <martin@martin.st> wrote:
> >>
> >> Skip doing the whole getauxval(AT_HWCAP) if HWCAP_CPUID isn't
> >> defined.
> >> ---
> >>  libavutil/aarch64/cpu.c | 6 +-----
> >>  1 file changed, 1 insertion(+), 5 deletions(-)
> >>
> >> diff --git a/libavutil/aarch64/cpu.c b/libavutil/aarch64/cpu.c
> >> index bd780e8591..2b50c426bc 100644
> >> --- a/libavutil/aarch64/cpu.c
> >> +++ b/libavutil/aarch64/cpu.c
> >> @@ -30,11 +30,9 @@
> >>  static int detect_flags(void)
> >>  {
> >>      int flags = 0;
> >> -    unsigned long hwcap;
> >> -
> >> -    hwcap = getauxval(AT_HWCAP);
> >>
> >>  #if defined(HWCAP_CPUID)
> >> +    unsigned long hwcap = getauxval(AT_HWCAP);
> >>      // We can check for DOTPROD and I8MM using HWCAP_ASIMDDP and
> >>      // HWCAP2_I8MM too, avoiding to read the CPUID registers (which triggers
> >>      // a trap, handled by the kernel). However the HWCAP_* defines for these
> >> @@ -53,8 +51,6 @@ static int detect_flags(void)
> >>          if (((tmp >> 52) & 0xf) == 0x1)
> >>              flags |= AV_CPU_FLAG_I8MM;
> >>      }
> >> -#else
> >> -    (void)hwcap;
> >>  #endif
> >>
> >>      return flags;
> >> --
> >> 2.34.1
> >>
> >> _______________________________________________
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> >> ffmpeg-devel@ffmpeg.org
> >> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >>
> >> To unsubscribe, visit link above, or email
> >> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
> >
> >
> > Good call, and LGTM.
> >
> > -- Sean McGovern
>
> Ooops! I don't have c= so maybe someone who does could push this --
> and the 2nd patch in this set needs a pair of eyes more familiar with
> compiler bugs.
>
> -- Sean McG

Looks like I missed the push notification on patch #2.

-- Sean McG.
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