Re: [FFmpeg-devel] [PATCH 3/5] lavc/aarch64: new optimization for 8-bit hevc_epel_uni_w_v

["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    | 504 ++++++++++++++++++++++
> libavcodec/aarch64/hevcdsp_init_aarch64.c |   6 +
> 2 files changed, 510 insertions(+)
>
> diff --git a/libavcodec/aarch64/hevcdsp_epel_neon.S b/libavcodec/aarch64/hevcdsp_epel_neon.S
> index fe494dd843..4841f49dab 100644
> --- a/libavcodec/aarch64/hevcdsp_epel_neon.S
> +++ b/libavcodec/aarch64/hevcdsp_epel_neon.S


> +function ff_hevc_put_hevc_epel_uni_w_v48_8_neon, export=1
> +        stp             q8, q9, [sp, #-32]
> +        stp             q10, q11, [sp, #-64]

This backs up values on the stack without decrementing the stack pointer, 
i.e. storing it in the red zone. Whether this is supported depends on the 
platform ABI. Linux and macOS have a 128 byte red zone on aarch64, while 
Windows only has 16 bytes. So for portability, don't rely on a red zone at 
all.

I.e., here please decrement the stack pointer like in a previous patch:

     stp q8,  q9,  [sp, #-64]!
     stp q10, q11, [sp, #32]

And inversely when restoring it.

> +        EPEL_UNI_W_V_HEADER
> +
> +        ld1             {v16.16b, v17.16b, v18.16b}, [x2], x3
> +        ld1             {v19.16b, v20.16b, v21.16b}, [x2], x3
> +        ld1             {v22.16b, v23.16b, v24.16b}, [x2], x3
> +1:
> +        ld1             {v25.16b, v26.16b, v27.16b}, [x2], x3
> +
> +        EPEL_UNI_W_V16_CALC v4, v6, v16, v19, v22, v25, v8, v9, v10, v11
> +        EPEL_UNI_W_V16_CALC v5, v7, v17, v20, v23, v26, v8, v9, v10, v11
> +        EPEL_UNI_W_V16_CALC v6, v7, v18, v21, v24, v27, v8, v9, v10, v11
> +        st1             {v4.16b, v5.16b, v6.16b}, [x0], x1
> +        subs            w4, w4, #1
> +        b.eq            2f
> +        ld1             {v16.16b, v17.16b, v18.16b}, [x2], x3
> +        EPEL_UNI_W_V16_CALC v4, v6, v19, v22, v25, v16, v8, v9, v10, v11
> +        EPEL_UNI_W_V16_CALC v5, v7, v20, v23, v26, v17, v8, v9, v10, v11
> +        EPEL_UNI_W_V16_CALC v6, v7, v21, v24, v27, v18, v8, v9, v10, v11
> +        st1             {v4.16b, v5.16b, v6.16b}, [x0], x1
> +        subs            w4, w4, #1
> +        b.eq            2f
> +        ld1             {v19.16b, v20.16b, v21.16b}, [x2], x3
> +        EPEL_UNI_W_V16_CALC v4, v6,  v22, v25, v16, v19, v8, v9, v10, v11
> +        EPEL_UNI_W_V16_CALC v5, v7,  v23, v26, v17, v20, v8, v9, v10, v11
> +        EPEL_UNI_W_V16_CALC v6, v7,  v24, v27, v18, v21, v8, v9, v10, v11
> +        st1             {v4.16b, v5.16b, v6.16b}, [x0], x1
> +        subs            w4, w4, #1
> +        b.eq            2f
> +        ld1             {v22.16b, v23.16b, v24.16b}, [x2], x3
> +        EPEL_UNI_W_V16_CALC v4, v6,  v25, v16, v19, v22, v8, v9, v10, v11
> +        EPEL_UNI_W_V16_CALC v5, v7,  v26, v17, v20, v23, v8, v9, v10, v11
> +        EPEL_UNI_W_V16_CALC v6, v7,  v27, v18, v21, v24, v8, v9, v10, v11
> +        st1             {v4.16b, v5.16b, v6.16b}, [x0], x1
> +        subs            w4, w4, #1
> +        b.hi            1b
> +2:
> +        ldp             q8, q9, [sp, #-32]
> +        ldp             q10, q11, [sp, #-64]
> +        ret
> +endfunc
> +
> +function ff_hevc_put_hevc_epel_uni_w_v64_8_neon, export=1
> +        stp             q8, q9, [sp, #-32]
> +        stp             q10, q11, [sp, #-64]
> +        stp             q12, q13, [sp, #-96]
> +        stp             q14, q15, [sp, #-128]

Same thing here.

// Martin

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