[pypy-dev] PPC backend design questions

[David Edelsohn]

On Wed, Aug 10, 2011 at 4:26 AM, Michael Hudson-Doyle <micahel at gmail.com> wrote:

> There are already fields that behave in unusual ways -- see
>
> https://bitbucket.org/pypy/pypy/src/f8c92c646275/pypy/jit/backend/ppc/ppcgen/ppc_field.py#cl-55
>
> I think you should be able to add your fields in this fashion -- in
> fact, the IField looks a teensy bit like how the displacement field
> should be already.  The split encodings should be fairly easy too,
> although there might be some paranoid code checking that fields don't
> overlap that you need to change.

Yes and no.  The ds displacement field for 64 bit loads is similar to
the LI field of branches.  But the shift fields are not like the spr
field -- the value is split between multiple fields with different bit
ranges, not just permuted within the field.

Thanks, David