Le torstaina 15. kesäkuuta 2023, 16.57.18 EEST Lynne a écrit :
> Jun 15, 2023, 12:37 by shenpeit...@eswincomputing.com:
> > From: Shen Peiting
> >
> > 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,
Well... I accept hardware donations (with regular USB-C power supply and
passive cooling) to back what would be the third generation of RISC-V FATE
instances.
Until R-V-V 1.0 hardware production substitutes unobtainium for silicium, I
also accept Lichee Pi4A or equivalent hardware bundles, which would be able to
run most (but definitely not all) of FFmpeg's RVV functions with a sizable
amount of kludging.
> 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?
It could also be that Spike counts everything as one cycle, regardless of the
group multipler, not (just) the vector size.
--
Rémi Denis-Courmont
http://www.remlab.net/
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