Re: [FFmpeg-devel] [PATCH 0/6] RISC-V initial ac3dsp

[Lynne <dev@lynne.ee>]

Jun 15, 2023, 12:37 by shenpeiting@eswincomputing.com:

> From: Shen Peiting <shenpeiting@eswincomputing.com>
>
> We optimized the six interfaces of AC3 init by RVV, the optimized 
> performance was tested on the RISC-V ISA simulator--Spike, and the 
> results were attached to each commit.
>
> shenpeiting (6):
>  lavc/ac3dsp: RISC-V V ac3_exponent_min
>  lavc/ac3dsp: RISC-V V float_to_fixed24
>  lavc/ac3dsp: RISC-V V ac3_sum_square_butterfly_int32
>  lavc/ac3dsp: RISC-V V ac3_sum_square_butterfly_float
>  lavc/ac3dsp: RISC-V V ac3_compute_mantissa_size
>  lavc/ac3dsp: RISC-V B ac3_extract_exponents
>
>  libavcodec/ac3dsp.c            |   2 +
>  libavcodec/ac3dsp.h            |   1 +
>  libavcodec/riscv/Makefile      |   3 +
>  libavcodec/riscv/ac3dsp_init.c |  60 +++++++++
>  libavcodec/riscv/ac3dsp_rvb.S  |  42 ++++++
>  libavcodec/riscv/ac3dsp_rvv.S  | 225 +++++++++++++++++++++++++++++++++
>  6 files changed, 333 insertions(+)
>  create mode 100644 libavcodec/riscv/ac3dsp_init.c
>  create mode 100644 libavcodec/riscv/ac3dsp_rvb.S
>  create mode 100644 libavcodec/riscv/ac3dsp_rvv.S
>

Could you implement checkasm for this? It shouldn't
be more than a hundred lines, and there are examples,
tests/checkasm/aacpsdsp.c being the most similar.
Since CPUs with the needed extensions aren't released,
we're not doing any FATE runs, and so if the results don't
match the C version, we'll end up with broken code once
they do exist. And no one wants to debug someone else's
assembly.

Those results look far too optimistic, and I'm guessing
it's because they're using a theoretical huge vector size
limit. Could you re-test with something more realistic,
like 256-bit vectors, using checkasm --bench?
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