Re: syncing the GCC vax port

[coypu%sdf.org@localhost]

On Sun, Mar 31, 2019 at 01:25:50PM -0400, Paul Koning wrote:
> 
> 
> > On Mar 30, 2019, at 5:03 AM, coypu%sdf.org@localhost wrote:
> > 
> > hi folks,
> > 
> > i was interesting in tackling some problems gcc netbsd/vax has.
> > it has some ICEs which are in reload phase. searching around, the answer
> > to that is "switch to LRA first". Now, I don't quite know what that is
> > yet, but I know I need to try to do it.
> 
> That's not quite the whole story.
> 
> The answer is (1) switch from CC0 to CCmode condition code handling, which enables (2) switch from Reload to LRA.
> 
> (1) requires actual work, not terribly hard but not entirely trivial.  (2) may take as little as switching the "use LRA" flag to "yes".
> 
> I did (1) as well as a tentative (2) for pdp11 last year.  It was reasonably straightforward thanks to a pile of help from Eric Botcazou and his gcc wiki articles on the subject.  You might find the pdp11 deltas for CCmode helpful as a source of ideas, since the two machines have a fair amount in common as far as condition codes goes.  At least for the integer ops (pdp11 has separate floating point conditions, vax doesn't).
> 
> 	paul
> 

Hi paul!

I have been reading on this, so now I have a draft that compiles the
world's simplest C code (and nothing more, it will crash), but using
CCmode (I think).

I am being inspired by your port (which is a good thing since I know I
can ask questions about it :))

https://github.com/coypoop/gcc/commit/df135c019de33950c9997fdea3ce07c5c920384d

(I know that it's wrong!)