Re: [FFmpeg-devel] [PATCH 4/5] lavc/aarch64: new optimization for 8-bit hevc_epel_h

["Martin Storsjö" <martin@martin.st>]

On Sun, 4 Jun 2023, Logan.Lyu@myais.com.cn wrote:

> From: Logan Lyu <Logan.Lyu@myais.com.cn>
>
> Signed-off-by: Logan Lyu <Logan.Lyu@myais.com.cn>
> ---
> libavcodec/aarch64/hevcdsp_epel_neon.S    | 343 ++++++++++++++++++++++
> libavcodec/aarch64/hevcdsp_init_aarch64.c |   7 +-
> 2 files changed, 349 insertions(+), 1 deletion(-)


> +        st2             {v20.8h, v21.8h}, [x7]
> +        subs            w3, w3, #1   // height
> +        b.ne            1b
> +        ret

In general, place the loop counter decrement somewhere else than exactly 
before the branch that depends on the result. E.g. after the initial loads 
is usually a good place, or between the st1/2 instructions and the 
instructions that calculate the final output values.

The same goes probably for all places in all these patches.

> @@ -283,13 +287,14 @@ av_cold void ff_hevc_dsp_init_aarch64(HEVCDSPContext *c, const int bit_depth)
>         NEON8_FNASSIGN_PARTIAL_4(c->put_hevc_qpel_uni_w, 1, 0, qpel_uni_w_v,);
>
>         if (have_i8mm(cpu_flags)) {
> +            NEON8_FNASSIGN(c->put_hevc_epel, 0, 1, epel_h, _i8mm);
>             NEON8_FNASSIGN(c->put_hevc_epel_uni_w, 0, 1, epel_uni_w_h ,_i8mm);
>             NEON8_FNASSIGN(c->put_hevc_qpel, 0, 1, qpel_h, _i8mm);
>             NEON8_FNASSIGN(c->put_hevc_qpel_uni_w, 0, 1, qpel_uni_w_h, _i8mm);
>             NEON8_FNASSIGN_PARTIAL_5(c->put_hevc_qpel_uni_w, 1, 1, qpel_uni_w_hv, _i8mm);
>         }
> -
>     }
> +
>     if (bit_depth == 10) {

Here are some stray unrelated whitespace changes.

Other than that, this patch looks mostly reasonable.

// Martin

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