[FFmpeg-devel] [PATCH 2/5] lavc/aarch64: new optimization for 8-bit hevc_epel_uni_w_h

[Martin Storsjö]

On Sun, 4 Jun 2023, Logan.Lyu at myais.com.cn wrote:

> From: Logan Lyu <Logan.Lyu at myais.com.cn>
>
> Signed-off-by: Logan Lyu <Logan.Lyu at myais.com.cn>
> ---
> libavcodec/aarch64/Makefile               |   1 +
> libavcodec/aarch64/hevcdsp_epel_neon.S    | 378 ++++++++++++++++++++++
> libavcodec/aarch64/hevcdsp_init_aarch64.c |   7 +-
> 3 files changed, 385 insertions(+), 1 deletion(-)
> create mode 100644 libavcodec/aarch64/hevcdsp_epel_neon.S
>
> diff --git a/libavcodec/aarch64/Makefile b/libavcodec/aarch64/Makefile
> index 216191640c..cb428b49e0 100644
> --- a/libavcodec/aarch64/Makefile
> +++ b/libavcodec/aarch64/Makefile
> @@ -69,4 +69,5 @@ NEON-OBJS-$(CONFIG_HEVC_DECODER)        += aarch64/hevcdsp_deblock_neon.o      \
>                                            aarch64/hevcdsp_idct_neon.o         \
>                                            aarch64/hevcdsp_init_aarch64.o      \
>                                            aarch64/hevcdsp_qpel_neon.o         \
> +                                           aarch64/hevcdsp_epel_neon.o         \
>                                            aarch64/hevcdsp_sao_neon.o
> diff --git a/libavcodec/aarch64/hevcdsp_epel_neon.S b/libavcodec/aarch64/hevcdsp_epel_neon.S
> new file mode 100644
> index 0000000000..fe494dd843
> --- /dev/null
> +++ b/libavcodec/aarch64/hevcdsp_epel_neon.S
> @@ -0,0 +1,378 @@
> +/* -*-arm64-*-
> + * vim: syntax=arm64asm
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +#include "libavutil/aarch64/asm.S"
> +#define MAX_PB_SIZE 64
> +
> +const epel_filters, align=4
> +        .byte  0,  0,  0,  0
> +        .byte -2, 58, 10, -2
> +        .byte -4, 54, 16, -2
> +        .byte -6, 46, 28, -4
> +        .byte -4, 36, 36, -4
> +        .byte -4, 28, 46, -6
> +        .byte -2, 16, 54, -4
> +        .byte -2, 10, 58, -2
> +endconst
> +
> +#if HAVE_I8MM
> +.macro EPEL_UNI_W_H_HEADER
> +        ldr             x12, [sp]
> +        sub             x2, x2, #1
> +        movrel          x9, epel_filters
> +        add             x9, x9, x12, lsl #2
> +        ldr             w11, [x9]
> +        dup             v28.4s, w11

Why not just do "ld1r {v28.4s}, [x9]" here instead, avoiding the 
indirection via GPRs?

Other than that, I think this mostly looks reasonable.

Btw, for any assembly patches like these, it would be appreciated if you 
can provide benchmarks from checkasm, e.g. "checkasm --test=hevc_pel 
--bench=put_hevc" (or maybe just "--bench") and extract the relevant lines 
for the functions that you've added/modified, and mention what system 
you've benchmarked it on. You get the most useful benchmarks for 
micro-tuning if you can enable userspace access to the timing registers 
and configure with --disable-linux-perf.

// Martin