Re: [PATCH v3 25/51] target/arm: Implement SME MOVA

[Richard Henderson]

On 6/23/22 04:24, Peter Maydell wrote:
> On Mon, 20 Jun 2022 at 19:20, Richard Henderson
> <richard.henderson@linaro.org> wrote:
> > We can reuse the SVE functions for implementing moves to/from
> > horizontal tile slices, but we need new ones for moves to/from
> > vertical tile slices.
> >
> > Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> > ---
> >   target/arm/helper-sme.h    |  11 ++++
> >   target/arm/helper-sve.h    |   2 +
> >   target/arm/translate-a64.h |   9 +++
> >   target/arm/translate.h     |   5 ++
> >   target/arm/sme.decode      |  15 +++++
> >   target/arm/sme_helper.c    | 110 ++++++++++++++++++++++++++++++++++++-
> >   target/arm/sve_helper.c    |  12 ++++
> >   target/arm/translate-a64.c |  19 +++++++
> >   target/arm/translate-sme.c | 105 +++++++++++++++++++++++++++++++++++
> >   9 files changed, 287 insertions(+), 1 deletion(-)
> >
> > diff --git a/target/arm/helper-sme.h b/target/arm/helper-sme.h
> > index c4ee1f09e4..600346e08c 100644
> > --- a/target/arm/helper-sme.h
> > +++ b/target/arm/helper-sme.h
> > @@ -21,3 +21,14 @@ DEF_HELPER_FLAGS_2(set_pstate_sm, TCG_CALL_NO_RWG, void, 
> > env, i32)
> >   DEF_HELPER_FLAGS_2(set_pstate_za, TCG_CALL_NO_RWG, void, env, i32)
> >
> >   DEF_HELPER_FLAGS_3(sme_zero, TCG_CALL_NO_RWG, void, env, i32, i32)
> > +
> > +DEF_HELPER_FLAGS_4(sme_mova_avz_b, TCG_CALL_NO_RWG, void, ptr, ptr, ptr, i32)
> > +DEF_HELPER_FLAGS_4(sme_mova_zav_b, TCG_CALL_NO_RWG, void, ptr, ptr, ptr, i32)
>
> What do the 'avz' and 'zav' stand for here? I thought that
> 'zav' might mean "from the ZA storage to a Vector", but
> then what is 'avz' ?

It was supposed to be z <- av and av <- z.

I've used "z", "p", "w", "x" single letter argument indicators for sve.  I think "av" was 
supposed to indicate "array vertical", but it's definitely non-obvious.  I'll fix this up 
and add some commentary.

> This is too confusing -- I spent half an hour looking at it and
> couldn't figure out if it was correct or not. I can see roughly
> what it's supposed to be doing but I don't really want to try
> to reverse engineer the details from the sequence of operations.

Ok.

> Perhaps (a) more commentary and (b) separating out the
> horizontal and vertical cases would help ?

Ok.


r~