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Re: GNU Fortran 90?


On Thu, Nov 16, 2000 at 09:24:52PM +0100, Toon Moene wrote:
> Zack Weinberg wrote:
> 
> > I hope you are not still intending to keep g77 around after g95 is
> > complete.
> 
> No, but the operative word here is "complete".  g95 is *not* "complete
> as a replacement for g77* IMHO, until it implements all language
> features that g77 now offers.
...

> So from my point of view it could well be that automatic vectorisation
> is added to GCC before g77 is removed.  In that case g77 would benefit
> from this as well - although not as much as I would want, because RTH
> recently discovered that John Carr's alias analysis just doesn't work
> perfectly for g77 (expletives elided).

The thing is, I got to listen to a discussion on how we could
implement autovectorization, not so long ago, and the consensus was we
don't want to do it in RTL.  Instead, we want to reimplement general
loop optimization - including unrolling and vectorization - at the
tree level.  That of course requires we have function-at-a-time mode
in every front end that uses the new optimizer.  And I don't think
anyone wants to implement function-at-a-time mode in g77; the effort
would be far better spent finishing g95 sooner.

We've got good or at least decent low level optimizers, I think the
trend is toward more high level stuff, and RTL is too close to the
bare iron to do that with.

I flipped through some of the documentation for SGI's compilers.
WHIRL looks quite nifty.  Alas, right now what little time I have for
gcc needs to be spent on the garbage collector.

zw

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