Re: Indirect memory addresses vs. lra

[Segher Boessenkool <segher@kernel.crashing.org>]

On Thu, Aug 08, 2019 at 01:30:41PM -0400, Paul Koning wrote:
> 
> 
> > On Aug 8, 2019, at 1:21 PM, Segher Boessenkool <segher@kernel.crashing.org> wrote:
> > 
> > On Thu, Aug 08, 2019 at 12:43:52PM -0400, Paul Koning wrote:
> >>> On Aug 8, 2019, at 12:25 PM, Vladimir Makarov <vmakarov@redhat.com> wrote:
> >>> 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"?
> > 
> > I sure hope not!  But it has only been *used* and *tested* much on such,
> > so far. 
> 
> That's not entirely accurate.  At the prodding of people pushing for
> the removal of CC0 and reload, I've added LRA support to pdp11 in the
> V9 cycle.

I said "much" :-)

Pretty much all design input so far has been from "modern mainstream
architectures", as far as I can make out.  Now one of those has the
most "interesting" (for RA) features that many less mainstream archs
have (a not-so-very-flat register file), so it should still work pretty
well hopefully.

> And it works pretty well, in the sense of passing the
> compile tests.  But I haven't yet examined the code quality vs. the
> old one in any detail.

That would be quite interesting to see, also for the other ports that
still need conversion: how much (if any) degradation should you expect
from a straight-up conversion of a port to LRA, without any retuning?


Segher