[Mesa-dev] [PATCH 10/12] i965/fs: Make compact_virtual_grfs an optimization pass

[Jason Ekstrand]

On Fri, Sep 19, 2014 at 5:41 PM, Matt Turner <mattst88 at gmail.com> wrote:

> On Fri, Sep 19, 2014 at 1:10 PM, Jason Ekstrand <jason at jlekstrand.net>
> wrote:
> > Previously we disabled compact_virtual_grfs when dumping optimizations.
> > The idea here was to make it easier to diff the dumped shader because you
> > didn't have a sudden renaming.  However, sometimes a bug is affected by
> > compact_virtual_grfs and, when this happens, you want to keep dumping
> > instructions with compact_virtual_grfs enabled.  By turning it into an
> > optimization pass and dumping it along with the others, we retain the
> > ability to diff because you can just diff against the compact_virtual_grf
> > output.
>
> I'd like to understand the bug you encountered.
>

I really don't think you'd like that.  Those bugs are a real pain.  But
yes, I've hit this more times than I can count while working on this stuff.


>
> I'm kind of concerned that we're going to just run the optimization
> loop an extra time for every shader now, since compact_virtual_grfs is
> going to set progress = true after the last actual optimization pass
> made progress. I guess we could remove that problem by calling
> compact_virtual_grfs at the end of the loop, rather than at the
> beginning.
>

Sure, we can do something to make it not run an extra time.  I'm mostly
concerned about not just shutting it off.
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