[FFmpeg-devel] [PATCH] ac3dsp: RISC-V V float_to_fixed24

[flow gg]

Thank you for your guidance, I finally understand..  How about choosing
manual zero-extension for rv64? I modified the patch.

#if (__riscv_xlen == 64)
        slli a2, a2, 32
        srli a2, a2, 32
#endif

Rémi Denis-Courmont <remi at remlab.net> 于2023年11月22日周三 22:51写道：

>
>
> Le 22 novembre 2023 16:30:44 GMT+02:00, flow gg <hlefthleft at gmail.com> a
> écrit :
> >> How did you test it?
> >
> >I wrote a test, but it was a bit rough, so I want to modify it before
> >submitting. I've added it to this reply.
> >
> >> This does not seem according to the C ABI. AFAIK `unsigned` is
> >sign-extended.
> >
> >I'm a bit confused... because this passed in the tests I wrote in qemu.
> >Maybe there's a problem with my test？
>
> You probably didn't test sizes between 2^31 and 2^32-1. This might not
> even be feasible in QEMU.
>
> Ideally the prototype would use size_t, then the problem wouldn't exist.
>
> >
> >> ALU right before dependent conditional branch should be avoided.
> >
> >Should the sub be moved forward? I've modified it.
> >
> >> SHxADD can be used advantageously.
> >
> >Okay, I've made the modification
> >
> >Rémi Denis-Courmont <remi at remlab.net> 于2023年11月22日周三 21:41写道：
> >
> >> Hi,
> >>
> >> How did you test it? As per
> >> http://ffmpeg.org/pipermail/ffmpeg-devel/2023-June/310720.html we still
> >> don't have a FATE instance set up with the RISC-V Vector extension. The
> >> only testing consists of my manual runs of checkasm on a K230 board. (We
> >> *do* have Zba and Zbb now though, hence the existing
> extract_exponents()).
> >>
> >> Also:
> >> - This does not seem according to the C ABI. AFAIK `unsigned` is
> >> sign-extended.
> >> - ALU right before dependent conditional branch should be avoided.
> >> - SHxADD can be used advantageously.
> >>
> >>
> >> Le 22 novembre 2023 14:00:07 GMT+02:00, flow gg <hlefthleft at gmail.com>
> a
> >> écrit :
> >> >c910
> >> >    float_to_fixed24_c: 208.2
> >> >    float_to_fixed24_rvv_f32: 71.5
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> >>
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> >>
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