On Thu, 3 Nov 2016, Diego Biurrun wrote:
On Thu, Nov 03, 2016 at 09:42:44PM +0100, Janne Grunau wrote:
On 2016-11-03 20:38:11 +0100, Diego Biurrun wrote:
> On Wed, Nov 02, 2016 at 07:24:03PM +0100, Janne Grunau wrote:
> > On 2016-11-02 15:29:34 +0100, Diego Biurrun wrote:
> > > On Wed, Nov 02, 2016 at 04:00:38PM +0200, Martin Storsjö wrote:
> > > > On Wed, 2 Nov 2016, Diego Biurrun wrote:
> > > > >On Wed, Nov 02, 2016 at 03:23:14PM +0200, Martin Storsjö wrote:
> > > > >>On Wed, 2 Nov 2016, Martin Storsjö wrote:
> > > > >>Technically, having a _neon prefix for them is wrong, but anything
else
> > > > >>(omitting these two while hooking up avg32/avg64 separately) is more
> > > > >>complication - although I'm open for suggestions on how to handle it
best.
> > > > >
> > > > >Where exactly is the complication? In the way you assign the function
> > > > >pointers in the init file?
> > > >
> > > > Yes, it'd require splitting up those macros a bit; either for assigning the
> > > > same function pointers, but with a different simd instruction set
suffix, or
> > > > for only assigning the avg function pointer for those sizes.
> > >
> > > Try something like
> > >
> > > #define ff_vp9_copy32_neon ff_vp9_copy32_aarch64
> > > #define ff_vp9_copy64_neon ff_vp9_copy64_aarch64
> > >
> > > before the assignment macros. You don't have to somehow drop some of the
> > > assignments in the macros then. There's precedent for this in some of the
> > > x86 init files.
> >
> > That only fixes the function names but not the cpu_flag based assignment
> > if I understand it correctly. And it is a little bit silly since neon is
> > not really optional on aarch64. At least in the Application profile.
>
> I forgot to say that ff_vp9_copy32_aarch64 and ff_vp9_copy64_aarch64
> should be assigned to the function pointer unconditionally before
> checking for neon support.
unconditionally is not nice since we want to compare them to C in
checkasm. That's the reason why we have the otherwise pointless
AV_CPU_FLAG_ARMV8
Unconditional in the aarch64 init function is not unconditional:
libavcodec/foodsp.c:
if (ARCH_AARCH64)
init_aarch64(..);
libavcodec/aarch64/foodsp_init.c:
init_aarch64(..)
{
function.pointer = ff_vp9_copy32_aarch64;
if (have_neon())
something.else = ff_whatever;
Anyway, you get the idea. Quite possibly I'm overlooking something
and it does not work as I envision...
Yes, because as Janne said, in that case, you can't via cpuflags choose
not to use this function, and you can't benchmark against the C version in
checkasm, since the C version always gets overridden by this function,
regardless of cpuflags.
That's why we've introduced the flag AV_CPU_FLAG_ARMV8, and one should
wrap such functions within have_armv8(cpuflags) instead of
have_neon(cpuflags).
// Martin
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