Re: [FFmpeg-devel] [PATCH 2/2] lavc/aarch64: Add pix_abs16_x2 neon implementation

[Hubert Mazur <hum@semihalf.com>]

Hi, do you have any feedback regarding the patch?

Regards,
Hubert

On Wed, Jun 29, 2022 at 10:25 AM Hubert Mazur <hum@semihalf.com> wrote:

> Provide neon implementation for pix_abs16_x2 function.
>
> Performance tests of implementation are below.
>  - pix_abs_0_1_c: 291.9
>  - pix_abs_0_1_neon: 73.7
>
> Benchmarks and tests run with checkasm tool on AWS Graviton 3.
>
> Signed-off-by: Hubert Mazur <hum@semihalf.com>
> ---
>  libavcodec/aarch64/me_cmp_init_aarch64.c |   3 +
>  libavcodec/aarch64/me_cmp_neon.S         | 134 +++++++++++++++++++++++
>  2 files changed, 137 insertions(+)
>
> diff --git a/libavcodec/aarch64/me_cmp_init_aarch64.c
> b/libavcodec/aarch64/me_cmp_init_aarch64.c
> index bec9148a1a..136b008eb7 100644
> --- a/libavcodec/aarch64/me_cmp_init_aarch64.c
> +++ b/libavcodec/aarch64/me_cmp_init_aarch64.c
> @@ -27,6 +27,8 @@ int ff_pix_abs16_neon(MpegEncContext *s, uint8_t *blk1,
> uint8_t *blk2,
>                        ptrdiff_t stride, int h);
>  int ff_pix_abs16_xy2_neon(MpegEncContext *s, uint8_t *blk1, uint8_t *blk2,
>                        ptrdiff_t stride, int h);
> +int ff_pix_abs16_x2_neon(MpegEncContext *v, uint8_t *pix1, uint8_t *pix2,
> +                      ptrdiff_t stride, int h);
>
>  av_cold void ff_me_cmp_init_aarch64(MECmpContext *c, AVCodecContext
> *avctx)
>  {
> @@ -34,6 +36,7 @@ av_cold void ff_me_cmp_init_aarch64(MECmpContext *c,
> AVCodecContext *avctx)
>
>      if (have_neon(cpu_flags)) {
>          c->pix_abs[0][0] = ff_pix_abs16_neon;
> +        c->pix_abs[0][1] = ff_pix_abs16_x2_neon;
>          c->pix_abs[0][3] = ff_pix_abs16_xy2_neon;
>
>          c->sad[0] = ff_pix_abs16_neon;
> diff --git a/libavcodec/aarch64/me_cmp_neon.S
> b/libavcodec/aarch64/me_cmp_neon.S
> index a7937bd8be..c2fd94f4b3 100644
> --- a/libavcodec/aarch64/me_cmp_neon.S
> +++ b/libavcodec/aarch64/me_cmp_neon.S
> @@ -203,3 +203,137 @@ function ff_pix_abs16_xy2_neon, export=1
>          fmov            w0, s0                      // copy result to
> general purpose register
>          ret
>  endfunc
> +
> +function ff_pix_abs16_x2_neon, export=1
> +        // x0           unused
> +        // x1           uint8_t *pix1
> +        // x2           uint8_t *pix2
> +        // x3           ptrdiff_t stride
> +        // x4           int h
> +
> +        // preserve value of v8-v12 registers
> +        stp             d10, d11, [sp, #-0x10]!
> +        stp             d8, d9, [sp, #-0x10]!
> +
> +        // initialize buffers
> +        movi            d18, #0
> +        movi            v20.8h, #1
> +        add             x5, x2, #1 // pix2 + 1
> +        cmp             w4, #4
> +        b.lt            2f
> +
> +// make 4 iterations at once
> +1:
> +        // v0 - pix1
> +        // v1 - pix2
> +        // v2 - pix2 + 1
> +        ld1             {v0.16b}, [x1], x3
> +        ld1             {v1.16b}, [x2], x3
> +        ld1             {v2.16b}, [x5], x3
> +
> +        ld1             {v3.16b}, [x1], x3
> +        ld1             {v4.16b}, [x2], x3
> +        ld1             {v5.16b}, [x5], x3
> +
> +        ld1             {v6.16b}, [x1], x3
> +        ld1             {v7.16b}, [x2], x3
> +        ld1             {v8.16b}, [x5], x3
> +
> +        ld1             {v9.16b}, [x1], x3
> +        ld1             {v10.16b}, [x2], x3
> +        ld1             {v11.16b}, [x5], x3
> +
> +        // abs(pix1[0] - avg2(pix2[0], pix2[1]))
> +        // avg2(a,b) = (((a) + (b) + 1) >> 1)
> +        // abs(x) = (x < 0 ? -x : x)
> +
> +        // pix2[0] + pix2[1]
> +        uaddl           v30.8h, v1.8b, v2.8b
> +        uaddl2          v29.8h, v1.16b, v2.16b
> +        // add one to each element
> +        add             v30.8h, v30.8h, v20.8h
> +        add             v29.8h, v29.8h, v20.8h
> +        // divide by 2, narrow width and store in v30
> +        uqshrn          v30.8b, v30.8h, #1
> +        uqshrn2         v30.16b, v29.8h, #1
> +
> +        // abs(pix1[0] - avg2(pix2[0], pix2[1]))
> +        uabd            v16.16b, v0.16b, v30.16b
> +        uaddlv          h16, v16.16b
> +
> +        // 2nd iteration
> +        uaddl           v28.8h, v4.8b, v5.8b
> +        uaddl2          v27.8h, v4.16b, v5.16b
> +        add             v28.8h, v28.8h, v20.8h
> +        add             v27.8h, v27.8h, v20.8h
> +
> +        uqshrn          v28.8b, v28.8h, #1
> +        uqshrn2         v28.16b, v27.8h, #1
> +
> +        uabd            v17.16b, v3.16b, v28.16b
> +        uaddlv          h17, v17.16b
> +
> +        // 3rd iteration
> +        uaddl           v26.8h, v7.8b, v8.8b
> +        uaddl2          v25.8h, v7.16b, v8.16b
> +        add             v26.8h, v26.8h, v20.8h
> +        add             v25.8h, v25.8h, v20.8h
> +
> +        uqshrn          v26.8b, v26.8h, #1
> +        uqshrn2         v26.16b, v25.8h, #1
> +
> +        uabd            v19.16b, v6.16b, v26.16b
> +        uaddlv          h19, v19.16b
> +
> +        // 4th iteration
> +        uaddl           v24.8h, v10.8b, v11.8b
> +        uaddl2          v23.8h, v10.16b, v11.16b
> +        add             v24.8h, v24.8h, v20.8h
> +        add             v23.8h, v23.8h, v20.8h
> +
> +        uqshrn          v24.8b, v24.8h, #1
> +        uqshrn2         v24.16b, v23.8h, #1
> +
> +        uabd            v21.16b, v9.16b, v24.16b
> +        uaddlv          h21, v21.16b
> +
> +        sub             w4, w4, #4
> +
> +        // accumulate the result in d18
> +        add             d18, d18, d16
> +        add             d18, d18, d17
> +        add             d18, d18, d19
> +        add             d18, d18, d21
> +
> +        cmp             w4, #4
> +        b.ge            1b
> +        cbz             w4, 3f
> +
> +// iterate by one
> +2:
> +        ld1             {v0.16b}, [x1], x3
> +        ld1             {v1.16b}, [x2], x3
> +        ld1             {v2.16b}, [x5], x3
> +
> +        uaddl           v30.8h, v1.8b, v2.8b
> +        uaddl2          v29.8h, v1.16b, v2.16b
> +        add             v30.8h, v30.8h, v20.8h
> +        add             v29.8h, v29.8h, v20.8h
> +
> +        uqshrn          v30.8b, v30.8h, #1
> +        uqshrn2         v30.16b, v20.8h, #1
> +
> +        uabd            v28.16b, v0.16b, v30.16b
> +        uaddlv          h28, v28.16b
> +
> +        add             d18, d18, d28
> +        subs            w4, w4, #1
> +        b.ne            2b
> +
> +3:
> +        fmov            w0, s18
> +        ldp             d8, d9, [sp], 0x10
> +        ldp             d10, d11, [sp], 0x10
> +
> +        ret
> +endfunc
> --
> 2.34.1
>
>
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