Variable Expansion Optimization

[Michael Matz]

Hi,

On Mon, 16 Aug 2004, Steven Bosscher wrote:

> > On Sun, 15 Aug 2004, Steven Bosscher wrote:
> > > Hmm, I guess you're going to have carefully analyze what the
> > > effects of such a transformation are on register pressure.
> >
> > Yes.  But note that this transformation mainly helps an autovectorizer.
> 
> Not in this case, it doesn't.  The current proposal is to do this
> transformation on RTL.

Indeed.  I misread the intention.  So it really is just useful for
breaking dependencies over multiple iterations.  That would need even more
careful heuristics to not pessimize code, especially on ooo processors
where a little better scheduling can be more than offset by register
pressure and spills.


Ciao,
Michael.