A prototype loop reverser for the scalarizer

[Steven Bosscher]

On 10/15/06, Toon Moene <toon@moene.indiv.nluug.nl> wrote:
> Paul Thomas wrote:
>
> > Daniel and Steven,
> >
> > Once again, thanks for the illuminating correspondence; you can put the
> > daggers away now!
>
> Might it be useful to discuss front end versus back end optimizations at
> the next GCC Summit.  I'm willing to write a paper about it.

Go for it!

I don't know if Paul will be at the summit, but I don't expect to be.
But it would still be a good idea to collect and summarize the ideas
people have about this, if it  really alsi is a relevant issue for
languages other than Fortran.

> My pet peeve (front end doesn't give necessary info to middle end):
>
>        DIMENSION A(100)
>        READ, A
>        PRINT*, SUM(A)
>        END
>
> This won't get vectorized, because, by the time the vectorizer sees this
> code, it already has been scalarized into a loop with a definite order
> of summation, contrary to the coder's intent ;-)

Not even on the autovect branch?  Or are reductions on the trunk already, too?

Gr.
Steven