Re: Indirect memory addresses vs. lra

[Vladimir Makarov <vmakarov at redhat dot com>]

On 2019-08-08 12:43 p.m., Paul Koning wrote:
> > On Aug 8, 2019, at 12:25 PM, Vladimir Makarov <vmakarov@redhat.com> wrote:
> >
> >
> > On 2019-08-04 3:18 p.m., John Darrington wrote:
> > > I'm trying to write a back-end for an architecture (s12z - the ISA you can
> > > download from [1]).  This arch accepts indirect memory addresses.   That is to
> > > say, those of the form (mem (mem (...)))  and although my TARGET_LEGITIMATE_ADDRESS
> > > function returns true for such addresses, LRA insists on reloading them out of
> > > existence.
> > > ...
> > The old reload (reload[1].c) supports such addressing.  As modern mainstream architectures have no this kind of addressing, it was not implemented in LRA.
> Is LRA only intended for "modern mainstream architectures"?


No.  As I wrote patches implementing indirect addressing is welcomed.  
It is hard to implement everything at once and by one person.


> If yes, why is the old reload being deprecated?
>    You can't have it both ways.  Unless you want to obsolete all "not modern mainstream architectures" in GCC, it doesn't make sense to get rid of core functionality used by those architectures.
>
> Indirect addressing is a key feature in size-optimized code.
>
>