[FFmpeg-devel] [PATCH 3/4] lavc/aarch64: Provide optimized implementation of vsse8 for arm64.
Martin Storsjö
martin at martin.st
Wed Sep 28 12:09:34 EEST 2022
On Mon, 26 Sep 2022, Grzegorz Bernacki wrote:
> Provide optimized implementation of vsse8 for arm64.
>
> Performance comparison tests are shown below.
> - vsse_1_c: 141.5
> - vsse_1_neon: 32.5
>
> Benchmarks and tests are run with checkasm tool on AWS Graviton 3.
>
> Signed-off-by: Grzegorz Bernacki <gjb at semihalf.com>
> ---
> libavcodec/aarch64/me_cmp_init_aarch64.c | 5 ++
> libavcodec/aarch64/me_cmp_neon.S | 70 ++++++++++++++++++++++++
> 2 files changed, 75 insertions(+)
>
> diff --git a/libavcodec/aarch64/me_cmp_init_aarch64.c b/libavcodec/aarch64/me_cmp_init_aarch64.c
> index 2c61cfcf63..f247372c94 100644
> --- a/libavcodec/aarch64/me_cmp_init_aarch64.c
> +++ b/libavcodec/aarch64/me_cmp_init_aarch64.c
> @@ -71,6 +71,9 @@ int nsse8_neon(int multiplier, const uint8_t *s, const uint8_t *s2,
> int nsse8_neon_wrapper(MpegEncContext *c, const uint8_t *s1, const uint8_t *s2,
> ptrdiff_t stride, int h);
>
> +int vsse8_neon(MpegEncContext *c, const uint8_t *s1, const uint8_t *s2,
> + ptrdiff_t stride, int h);
> +
> av_cold void ff_me_cmp_init_aarch64(MECmpContext *c, AVCodecContext *avctx)
> {
> int cpu_flags = av_get_cpu_flags();
> @@ -96,6 +99,8 @@ av_cold void ff_me_cmp_init_aarch64(MECmpContext *c, AVCodecContext *avctx)
> c->vsad[5] = vsad_intra8_neon;
>
> c->vsse[0] = vsse16_neon;
> + c->vsse[1] = vsse8_neon;
> +
> c->vsse[4] = vsse_intra16_neon;
>
> c->nsse[0] = nsse16_neon_wrapper;
> diff --git a/libavcodec/aarch64/me_cmp_neon.S b/libavcodec/aarch64/me_cmp_neon.S
> index 6f7c7c1690..386d2de0c5 100644
> --- a/libavcodec/aarch64/me_cmp_neon.S
> +++ b/libavcodec/aarch64/me_cmp_neon.S
> @@ -843,6 +843,76 @@ function vsad16_neon, export=1
> ret
> endfunc
>
> +function vsse8_neon, export=1
> + // x0 unused
> + // x1 uint8_t *pix1
> + // x2 uint8_t *pix2
> + // x3 ptrdiff_t stride
> + // w4 int h
> +
> + ld1 {v0.8b}, [x1], x3 // Load pix1[0], first iteration
> + ld1 {v1.8b}, [x2], x3 // Load pix2[0], first iteration
> +
> + sub w4, w4, #1 // we need to make h-1 iterations
> + movi v16.4s, #0
> + movi v17.4s, #0
> +
> + cmp w4, #3 // check if we can make 3 iterations at once
> + usubl v31.8h, v0.8b, v1.8b // Signed difference of pix1[0] - pix2[0], first iteration
> + b.le 2f
Why the b.le here, shouldn't it be enough with b.lt? If we're run with
h=<unroll amount>, it should be enough to run one round in the unrolled
loop.
I see that we've got the same issue in a couple preexisting functions;
I'll send a patch to fix that.
Other than that, this looks reasonable to me.
// Martin
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