Re: [FFmpeg-devel] [PATCH v2 12/15] avfilter/vf_bwdif: Add a filter_line3 method for optimisation

[Thomas Mundt <tmundt75@gmail.com>]

Am So., 2. Juli 2023 um 14:34 Uhr schrieb John Cox <jc@kynesim.co.uk>:

> Add an optional filter_line3 to the available optimisations.
>
> filter_line3 is equivalent to filter_line, memcpy, filter_line
>
> filter_line shares quite a number of loads and some calculations in
> common with its next iteration and testing shows that using aarch64
> neon filter_line3s performance is 30% better than two filter_lines
> and a memcpy.
>
> Signed-off-by: John Cox <jc@kynesim.co.uk>
> ---
>  libavfilter/bwdif.h    |  7 +++++++
>  libavfilter/vf_bwdif.c | 31 +++++++++++++++++++++++++++++++
>  2 files changed, 38 insertions(+)
>
> diff --git a/libavfilter/bwdif.h b/libavfilter/bwdif.h
> index cce99953f3..496cec72ef 100644
> --- a/libavfilter/bwdif.h
> +++ b/libavfilter/bwdif.h
> @@ -35,6 +35,9 @@ typedef struct BWDIFContext {
>      void (*filter_edge)(void *dst, void *prev, void *cur, void *next,
>                          int w, int prefs, int mrefs, int prefs2, int
> mrefs2,
>                          int parity, int clip_max, int spat);
> +    void (*filter_line3)(void *dst, int dstride,
> +                         const void *prev, const void *cur, const void
> *next, int prefs,
> +                         int w, int parity, int clip_max);
>  } BWDIFContext;
>
>  void ff_bwdif_init_filter_line(BWDIFContext *bwdif, int bit_depth);
> @@ -53,4 +56,8 @@ void ff_bwdif_filter_line_c(void *dst1, void *prev1,
> void *cur1, void *next1,
>                              int prefs3, int mrefs3, int prefs4, int
> mrefs4,
>                              int parity, int clip_max);
>
> +void ff_bwdif_filter_line3_c(void * dst1, int d_stride,
> +                             const void * prev1, const void * cur1, const
> void * next1, int s_stride,
> +                             int w, int parity, int clip_max);
> +
>  #endif /* AVFILTER_BWDIF_H */
> diff --git a/libavfilter/vf_bwdif.c b/libavfilter/vf_bwdif.c
> index 26349da1fd..52bc676cf8 100644
> --- a/libavfilter/vf_bwdif.c
> +++ b/libavfilter/vf_bwdif.c
> @@ -150,6 +150,31 @@ void ff_bwdif_filter_line_c(void *dst1, void *prev1,
> void *cur1, void *next1,
>      FILTER2()
>  }
>
> +#define NEXT_LINE()\
> +    dst += d_stride; \
> +    prev += prefs; \
> +    cur  += prefs; \
> +    next += prefs;
> +
> +void ff_bwdif_filter_line3_c(void * dst1, int d_stride,
> +                             const void * prev1, const void * cur1, const
> void * next1, int s_stride,
> +                             int w, int parity, int clip_max)
> +{
> +    const int prefs = s_stride;
> +    uint8_t * dst  = dst1;
> +    const uint8_t * prev = prev1;
> +    const uint8_t * cur  = cur1;
> +    const uint8_t * next = next1;
> +
> +    ff_bwdif_filter_line_c(dst, (void*)prev, (void*)cur, (void*)next, w,
> +                           prefs, -prefs, prefs * 2, - prefs * 2, prefs *
> 3, -prefs * 3, prefs * 4, -prefs * 4, parity, clip_max);
> +    NEXT_LINE();
> +    memcpy(dst, cur, w);
> +    NEXT_LINE();
> +    ff_bwdif_filter_line_c(dst, (void*)prev, (void*)cur, (void*)next, w,
> +                           prefs, -prefs, prefs * 2, - prefs * 2, prefs *
> 3, -prefs * 3, prefs * 4, -prefs * 4, parity, clip_max);
> +}
> +
>  void ff_bwdif_filter_edge_c(void *dst1, void *prev1, void *cur1, void
> *next1,
>                              int w, int prefs, int mrefs, int prefs2, int
> mrefs2,
>                              int parity, int clip_max, int spat)
> @@ -244,6 +269,11 @@ static int filter_slice(AVFilterContext *ctx, void
> *arg, int jobnr, int nb_jobs)
>                                 refs << 1, -(refs << 1),
>                                 td->parity ^ td->tff, clip_max,
>                                 (y < 2) || ((y + 3) > td->h) ? 0 : 1);
> +            } else if (s->filter_line3 && y + 2 < slice_end && y + 6 <
> td->h) {
> +                s->filter_line3(dst, td->frame->linesize[td->plane],
> +                                prev, cur, next, linesize, td->w,
> +                                td->parity ^ td->tff, clip_max);
> +                y += 2;
>              } else {
>                  s->filter_line(dst, prev, cur, next, td->w,
>                                 refs, -refs, refs << 1, -(refs << 1),
>

Maybe I'm missing something, but doesn't this kick out most of the x86 SIMD
optimization because there is no filter_line3?
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