[RFC PATCH v5] RISC-V: Add support for the Zfa extension

[Nelson Chu]

On Thu, Jun 29, 2023 at 11:52 PM Palmer Dabbelt <palmer@dabbelt.com> wrote:

> On Thu, 29 Jun 2023 08:49:16 PDT (-0700), jeffreyalaw@gmail.com wrote:
> >
> >
> > On 6/29/23 09:37, Palmer Dabbelt wrote:
> >
> >>>> > So my understanding is that this needs to wait for ratification and
> is
> >>>> > not blocked by the mentioned PR.
> >>>> Is there something special about Zfa that makes it desirable to wait
> for
> >>>> ratification as opposed to standard practice of gating things as the
> >>>> specs get to a Frozen state?
> >>>
> >>> Not to my knowledge.
> >>
> >> Waiting for ratification is probably a bad idea, there's really no way
> >> to schedule around it.  That's a big part of the reason we've just
> >> waited for frozen.
> > Exactly.  ISTM that frozen is the right point to trigger.
>

Okay, I never figured out the difference between ratified and frozen, since
both of them have examples that change the behaviors and syntaxes, even
encodings.  But anyway, thanks for clarifying the current rule that we
should commit when extension is frozen, not ratified.


> > And I think enough of it is settled that we can move forward. If RVI
> > changes the set of forms allowed, then we can adjust.
>

Does that mean we don't need to care about compatibility before the
ratified extensions?  That means we can simply change anything and don't
need to maintain the code even if it is frozen.  If that is so, then Jim,
Kito and I had agreed a very long time ago that we should accept the
experiment extension, which hasn't been frozen yet, with the
-experiment-extension option that is the same as LLVM.


> Presumably someone's actually looked at the code?  If not I can look
> over it...
>

I have looked and replied, Kito and Jan should also have looked.  The
special zfa syntax should be the same as LLVM when I looked.  But since
that is almost two month ago, it's good if someone helps to review it again
to make sure everything is on the line.

> I've looked at it earlier.  But I'll go over it again.

Thanks, Jeff, it would be great to get your approval as well.

Thanks
Nelson