Re: [FFmpeg-devel] [PATCH 2/5] lavc/aarch64: Add neon implementation for sse4

["Swinney, Jonathan" <jswinney@amazon.com>]

As Martin noted, this patch doesn't build. But other than, that, it would be nice if there were comments on each line at least making some note about which of the 4 iterations each instruction calculates. That would make it a little bit easier to read, in my opinion, since the instructions are manually reordered.

Thanks,
-- 

Jonathan Swinney

On 7/15/22, 3:03 AM, "Hubert Mazur" <hum@semihalf.com> wrote:

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    Provide neon implementation for sse4 function.

    Performance comparison tests are shown below.
    - sse_2_c: 74.0
    - sse_2_neon: 24.0

    Benchmarks and tests are 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         | 65 ++++++++++++++++++++++++
     2 files changed, 68 insertions(+)

    diff --git a/libavcodec/aarch64/me_cmp_init_aarch64.c b/libavcodec/aarch64/me_cmp_init_aarch64.c
    index 3ff5767bd0..72a2062e7e 100644
    --- a/libavcodec/aarch64/me_cmp_init_aarch64.c
    +++ b/libavcodec/aarch64/me_cmp_init_aarch64.c
    @@ -32,6 +32,8 @@ int ff_pix_abs16_x2_neon(MpegEncContext *v, uint8_t *pix1, uint8_t *pix2,

     int sse16_neon(MpegEncContext *v, uint8_t *pix1, uint8_t *pix2,
                       ptrdiff_t stride, int h);
    +int sse4_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)
     {
    @@ -44,5 +46,6 @@ av_cold void ff_me_cmp_init_aarch64(MECmpContext *c, AVCodecContext *avctx)

             c->sad[0] = ff_pix_abs16_neon;
             c->sse[0] = sse16_neon;
    +        c->sse[2] = sse4_neon;
         }
     }
    diff --git a/libavcodec/aarch64/me_cmp_neon.S b/libavcodec/aarch64/me_cmp_neon.S
    index 88cd335443..bacf151314 100644
    --- a/libavcodec/aarch64/me_cmp_neon.S
    +++ b/libavcodec/aarch64/me_cmp_neon.S
    @@ -360,3 +360,68 @@ function sse16_neon, export=1
             ret

     endfunc
    +
    +function sse4_neon, export=1
    +        // x0 - unused
    +        // x1 - pix1
    +        // x2 - pix2
    +        // x3 - stride
    +        // w4 - h
    +
    +        movi            d18, #0
    +        movi            d17, #0
    +        cmp             w4, #4
    +        b.le            2f
    +
    +// make 4 iterations at once
    +1:
    +
    +        // res = abs(pix1[0] - pix2[0])
    +        // res * res
    +
    +        ld1             {v0.4b}, [x1], x3
    +        ld1             {v1.4b}, [x2], x3
    +        uabdl           v30.8h, v0.4b, v1.4b
    +        ld1             {v2.4b}, [x1], x3
    +        ld1             {v3.4b}, [x2], x3
    +        umull           v16.4s, v30.4h, v30.4h
    +        uabdl           v29.8h, v2.4b, v3.4b
    +        ld1             {v4.4b}, [x1], x3
    +        ld1             {v5.4b}, [x2], x3
    +        umlal           v16.4s, v29.4h, v29.4h
    +        uabdl           v28.8h, v4.4b, v5.4b
    +        ld1             {v6.4b}, [x1], x3
    +        ld1             {v7.4b}, [x2], x3
    +        umlal           v16.4s, v28.4h, v28.4h
    +        uabdl           v27.8h, v6.4b, v7.4b
    +        umlal           v16.4s, v27.4h, v27.4h
    +
    +        uaddlv          d17, v16.4s
    +        add             d18, d18, d17
    +
    +        sub             w4, w4, #4
    +        cmp             w4, #4
    +        b.ge            1b
    +
    +        cbnz            w4, 2f
    +        fmov            w0, s18
    +
    +        ret
    +
    +// iterate by one
    +2:
    +        ld1             {v0.4b}, [x1], x3
    +        ld1             {v1.4b}, [x2], x3
    +        uabdl           v30.8h, v0.4b, v1.4b
    +        umull           v16.4s, v30.4h, v30.4h
    +
    +        uaddlv          d17, v16.4s
    +        add             d18, d18, d17
    +
    +        subs            w4, w4, #1
    +        b.ne            2b
    +        fmov            w0, s18
    +
    +        ret
    +
    +endfunc
    --
    2.34.1


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