[PATCH] Don't combine across likely spilled hard reg setters (PR rtl-optimization/59477)

Vladimir Makarov vmakarov@redhat.com
Mon Jan 20 15:28:00 GMT 2014


On 1/20/2014, 4:12 AM, Eric Botcazou wrote:
>> I think the problem is still either a missed feature in LRA/reload
>> (split live-ranges), a problem in how we represent calls & argument
>> setup (magic hard-reg uses), or a backend problem (should spill
>> itself if necessary, via a post-reload splitter or always spill
>> and undo via a peephole2).
>>
>> Of course papering over in combine might be the best at this
>> stage.  So the above was just observations from the less experienced
>> people in this area.
>
> Yes, this is ultimately a RA issue, but an ancient and hard one as far as I
> understand so papering over it makes sense I think.  That being said, while
> Joern's machinery was IMO acceptable because relatively simple and localized,
> Jakub's looks more complicated and far-reaching (that's why I suggested to try
> to extend the existing machinery if possible) so I think that we ought to try
> something simpler first.
>

I've just started to work on fixing this in LRA.  But I am not going to 
work on fixing this in reload.  It would be just wasting enormous amount 
of time.



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