[FFmpeg-devel] [PATCH] swscale: aarch64: Optimize the final summation in the hscale routine

Swinney, Jonathan jswinney at amazon.com
Fri Apr 22 00:43:53 EEST 2022


Thanks for making this improvement. I will rebase my patches on your change. I also measured the performance on AWS Graviton 2 and 3. I added the numbers to your table.

Before:                     Cortex A53      A72      A73  Graviton 2  Graviton 3
hscale_8_to_15_width8_neon:     8273.0   4602.5   4289.5      2429.7      1629.1
hscale_8_to_15_width16_neon:   12405.7   6803.0   6359.0      3549.0      2378.4
hscale_8_to_15_width32_neon:   21258.7  11491.7  11469.2      5797.2      3919.6
hscale_8_to_15_width40_neon:   25652.0  14173.7  12488.2      6893.5      4810.4

After:
hscale_8_to_15_width8_neon:     7633.0   3981.5   3350.2      1980.7      1261.1
hscale_8_to_15_width16_neon:   11666.7   5951.0   5512.0      3080.7      2131.4
hscale_8_to_15_width32_neon:   20900.7  10733.2   9481.7      5275.2      3862.1
hscale_8_to_15_width40_neon:   24826.0  13536.2  11502.0      6397.2      4731.9

-- 

Jonathan Swinney

On 4/20/22, 3:58 AM, "ffmpeg-devel on behalf of Martin Storsjö" <ffmpeg-devel-bounces at ffmpeg.org on behalf of martin at martin.st> wrote:

    CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.



    Before:                     Cortex A53      A72      A73
    hscale_8_to_15_width8_neon:     8273.0   4602.5   4289.5
    hscale_8_to_15_width16_neon:   12405.7   6803.0   6359.0
    hscale_8_to_15_width32_neon:   21258.7  11491.7  11469.2
    hscale_8_to_15_width40_neon:   25652.0  14173.7  12488.2

    After:
    hscale_8_to_15_width8_neon:     7633.0   3981.5   3350.2
    hscale_8_to_15_width16_neon:   11666.7   5951.0   5512.0
    hscale_8_to_15_width32_neon:   20900.7  10733.2   9481.7
    hscale_8_to_15_width40_neon:   24826.0  13536.2  11502.0

    Thus, this gives overall a 8-28% speedup for the smaller filter
    sizes, around 3-8% for the smaller filter sizes.

    Inspired by a patch by Jonathan Swinney <jswinney at amazon.com>.

    Signed-off-by: Martin Storsjö <martin at martin.st>
    ---
    I'll go ahead and apply this patch within a few days if there's no
    opposition, as it should be a fairly uncontroversial change.
    ---
     libswscale/aarch64/hscale.S | 14 +++-----------
     1 file changed, 3 insertions(+), 11 deletions(-)

    diff --git a/libswscale/aarch64/hscale.S b/libswscale/aarch64/hscale.S
    index af55ffe2b7..da34f1cb8d 100644
    --- a/libswscale/aarch64/hscale.S
    +++ b/libswscale/aarch64/hscale.S
    @@ -61,17 +61,9 @@ function ff_hscale_8_to_15_neon, export=1
             smlal               v3.4S, v18.4H, v19.4H       // v3 accumulates srcp[filterPos[3] + {0..3}] * filter[{0..3}]
             smlal2              v3.4S, v18.8H, v19.8H       // v3 accumulates srcp[filterPos[3] + {4..7}] * filter[{4..7}]
             b.gt                2b                          // inner loop if filterSize not consumed completely
    -        addp                v0.4S, v0.4S, v0.4S         // part0 horizontal pair adding
    -        addp                v1.4S, v1.4S, v1.4S         // part1 horizontal pair adding
    -        addp                v2.4S, v2.4S, v2.4S         // part2 horizontal pair adding
    -        addp                v3.4S, v3.4S, v3.4S         // part3 horizontal pair adding
    -        addp                v0.4S, v0.4S, v0.4S         // part0 horizontal pair adding
    -        addp                v1.4S, v1.4S, v1.4S         // part1 horizontal pair adding
    -        addp                v2.4S, v2.4S, v2.4S         // part2 horizontal pair adding
    -        addp                v3.4S, v3.4S, v3.4S         // part3 horizontal pair adding
    -        zip1                v0.4S, v0.4S, v1.4S         // part01 = zip values from part0 and part1
    -        zip1                v2.4S, v2.4S, v3.4S         // part23 = zip values from part2 and part3
    -        mov                 v0.d[1], v2.d[0]            // part0123 = zip values from part01 and part23
    +        addp                v0.4S, v0.4S, v1.4S         // part01 horizontal pair adding
    +        addp                v2.4S, v2.4S, v3.4S         // part23 horizontal pair adding
    +        addp                v0.4S, v0.4S, v2.4S         // part0123 horizontal pair adding
             subs                w2, w2, #4                  // dstW -= 4
             sqshrn              v0.4H, v0.4S, #7            // shift and clip the 2x16-bit final values
             st1                 {v0.4H}, [x1], #8           // write to destination part0123
    --
    2.25.1

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