[Libre-soc-dev] pysvp64asm: opcode setvli not supported

[Lauri Kasanen]

On Tue, 15 Jun 2021 16:23:29 +0100
Luke Kenneth Casson Leighton <lkcl at lkcl.net> wrote:

> ---
> crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68
>
>
> On Tue, Jun 15, 2021 at 4:18 PM Lauri Kasanen <cand at gmx.com> wrote:
>
> >
> > Nice that it works, but I think that there's something going wrong here.
> >
> > That last op is MLSS:
> > for i in range(8)
> >     sum -= fv0[i] * fv1[i]
> >
> > Subtraction, not add. So the neg after a mul-add loop should be there,
> > no?
> >
>
> i looked again at the c code:
>     SUM8(MLSS, sum, w + 32, p);
>     *samples = round_sample(&sum);
>     *dither_state= sum;
>
> all i know is, it produces the right answer :)

With just the first data, or all of them? That line only affects one
result float, so only testing with one dataset is not enough.

Hm, that difference was in a zero. So -0, which is possible in floats,
but should not happen in this case - there should be a test for zero,
and fneg only done for nonzero sum.

This is another case where the optimized ver will want the fpr-to-gpr
move, though I need to check if the ppc comparison works for floats
(the period after an instr).

- Lauri