Re: [FFmpeg-devel] [PATCH 11/15] avfilter/vf_bwdif: Add neon for filter_line

["Martin Storsjö" <martin@martin.st>]

On Sun, 2 Jul 2023, John Cox wrote:

> On Sun, 2 Jul 2023 00:44:10 +0300 (EEST), you wrote:
>
>> On Thu, 29 Jun 2023, John Cox wrote:
>>
>>> Signed-off-by: John Cox <jc@kynesim.co.uk>
>>> ---
>>> libavfilter/aarch64/vf_bwdif_init_aarch64.c |  21 ++
>>> libavfilter/aarch64/vf_bwdif_neon.S         | 215 ++++++++++++++++++++
>>> 2 files changed, 236 insertions(+)
>>>
>>> diff --git a/libavfilter/aarch64/vf_bwdif_init_aarch64.c b/libavfilter/aarch64/vf_bwdif_init_aarch64.c
>>> index e75cf2f204..21e67884ab 100644
>>> --- a/libavfilter/aarch64/vf_bwdif_init_aarch64.c
>>> +++ b/libavfilter/aarch64/vf_bwdif_init_aarch64.c
>>> @@ -31,6 +31,26 @@ void ff_bwdif_filter_edge_neon(void *dst1, void *prev1, void *cur1, void *next1,
>>> void ff_bwdif_filter_intra_neon(void *dst1, void *cur1, int w, int prefs, int mrefs,
>>>                                 int prefs3, int mrefs3, int parity, int clip_max);
>>>
>>> +void ff_bwdif_filter_line_neon(void *dst1, void *prev1, void *cur1, void *next1,
>>> +                               int w, int prefs, int mrefs, int prefs2, int mrefs2,
>>> +                               int prefs3, int mrefs3, int prefs4, int mrefs4,
>>> +                               int parity, int clip_max);
>>> +
>>> +
>>> +static void filter_line_helper(void *dst1, void *prev1, void *cur1, void *next1,
>>> +                               int w, int prefs, int mrefs, int prefs2, int mrefs2,
>>> +                               int prefs3, int mrefs3, int prefs4, int mrefs4,
>>> +                               int parity, int clip_max)
>>> +{
>>> +    const int w0 = clip_max != 255 ? 0 : w & ~15;
>>> +
>>> +    ff_bwdif_filter_line_neon(dst1, prev1, cur1, next1,
>>> +                              w0, prefs, mrefs, prefs2, mrefs2, prefs3, mrefs3, prefs4, mrefs4, parity, clip_max);
>>> +
>>> +    if (w0 < w)
>>> +        ff_bwdif_filter_line_c((char *)dst1 + w0, (char *)prev1 + w0, (char *)cur1 + w0, (char *)next1 + w0,
>>> +                               w - w0, prefs, mrefs, prefs2, mrefs2, prefs3, mrefs3, prefs4, mrefs4, parity, clip_max);
>>> +}
>>>
>>> static void filter_edge_helper(void *dst1, void *prev1, void *cur1, void *next1,
>>>                                int w, int prefs, int mrefs, int prefs2, int mrefs2,
>>> @@ -71,6 +91,7 @@ ff_bwdif_init_aarch64(BWDIFContext *s, int bit_depth)
>>>         return;
>>>
>>>     s->filter_intra = filter_intra_helper;
>>> +    s->filter_line  = filter_line_helper;
>>>     s->filter_edge  = filter_edge_helper;
>>> }
>>>
>>> diff --git a/libavfilter/aarch64/vf_bwdif_neon.S b/libavfilter/aarch64/vf_bwdif_neon.S
>>> index a33b235882..675e97d966 100644
>>> --- a/libavfilter/aarch64/vf_bwdif_neon.S
>>> +++ b/libavfilter/aarch64/vf_bwdif_neon.S
>>> @@ -128,6 +128,221 @@ coeffs:
>>>         .hword          5570, 3801, 1016, -3801         // hf[0] = v0.h[2], -hf[1] = v0.h[5]
>>>         .hword          5077, 981                       // sp[0] = v0.h[6]
>>>
>>> +// ===========================================================================
>>> +//
>>> +// void filter_line(
>>> +//      void *dst1,     // x0
>>> +//      void *prev1,    // x1
>>> +//      void *cur1,     // x2
>>> +//      void *next1,    // x3
>>> +//      int w,          // w4
>>> +//      int prefs,      // w5
>>> +//      int mrefs,      // w6
>>> +//      int prefs2,     // w7
>>> +//      int mrefs2,     // [sp, #0]
>>> +//      int prefs3,     // [sp, #8]
>>> +//      int mrefs3,     // [sp, #16]
>>> +//      int prefs4,     // [sp, #24]
>>> +//      int mrefs4,     // [sp, #32]
>>> +//      int parity,     // [sp, #40]
>>> +//      int clip_max)   // [sp, #48]
>>> +
>>> +function ff_bwdif_filter_line_neon, export=1
>>> +        // Sanity check w
>>> +        cmp             w4, #0
>>> +        ble             99f
>>> +
>>> +        // Rearrange regs to be the same as line3 for ease of debug!
>>> +        mov             w10, w4                         // w10 = loop count
>>> +        mov             w9,  w6                         // w9  = mref
>>> +        mov             w12, w7                         // w12 = pref2
>>> +        mov             w11, w5                         // w11 = pref
>>> +        ldr             w8,  [sp, #0]                   // w8 =  mref2
>>> +        ldr             w7,  [sp, #16]                  // w7  = mref3
>>> +        ldr             w6,  [sp, #32]                  // w6  = mref4
>>> +        ldr             w13, [sp, #8]                   // w13 = pref3
>>> +        ldr             w14, [sp, #24]                  // w14 = pref4
>>
>> Btw, remember that you can load two arguments from the stack at once with
>> ldp, e.g. "ldp x8, x13, [sp, #0]". If they're made intptr_t/ptrdiff_t, you
>> won't have an issue with garbage in the upper 32 bits either.
>
> Fair point - I was indeed worrying about garbage in the upper half (and
> this is not performance or size critical code).

Well as long as you actually do refer to the register in the form of w8 
instead of x8, it shouldn't matter. Checkasm does try to make sure that 
you actually should get garbage in such areas, so if it passes checkasm, 
it should be fine.

// Martin

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