On 2016-11-03 23:36:08 +0200, Martin Storsjö wrote:
> On Thu, 3 Nov 2016, Diego Biurrun wrote:
>
> >On Thu, Nov 03, 2016 at 11:02:17PM +0200, Martin Storsjö wrote:
> >>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).
> >
> >OK, last try then :)
> >
> > #define ff_vp9_copy32_neon ff_vp9_copy32_aarch64
> >
> > init_aarch64(..)
> > {
> > if (have_armv8())
> > function.pointer = ff_vp9_copy32_aarch64;
> >
> > if (have_neon())
> > [neon macro trickery
> > function.pointer = ff_vp9_copy32_neon;
> > neon macro trickery]
>
> Sure, something like that would work. Except if we go this way, I wouldn't
> assign it at all within the neon section, since it already is hooked up
> within have_armv8.
No the basic idea was to assign the same functions twice. Once under if
(have_armv8()) with their real name and once under if (have_neon()) with
the current macros. The missing _neon functions are provided by '#define
ff_vp9_copy32_neon ff_vp9_copy32_aarch64'. That's not too messy and the
functions have the correct debug symbols.
I can live with the current misleading function names but this solution
is not too messy.
Janne
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