Re: How to express the fact that arguments don't escape?

[Tobias Schlüter <tobias dot schlueter at physik dot uni-muenchen dot de>]

Richard Guenther wrote:
> 2009/8/16 Tobias Schlüter <tobias.schlueter@physik.uni-muenchen.de>:
> > Richard Guenther wrote:
> > > And this effect will only be positive on optimizations if you have like
> > >
> > >  do i=1,10
> > >     g(i)
> > >     ... = function of i
> > >     f(k)
> > >     ... = function of i
> > >   end do
> > >
> > > where the load from i can be CSEd around the call to f (because it didn't
> > > escape to g).  So I expect this to be a pretty rare case.  Note it doesn't
> > > help
> > > loop optimizations as i is still clobbered in unpredictable ways by g.
> > It's not allowed to be changed inside the loop, so if i is clobbered inside
> > g, the code is undefined.
>
> In that case you can unconditionally omit the copy-back.  For the correct
> variable of course.  Which would then still be profitable (just if you for some
> reason require a copy-back it's likely not always profitable).

Ok, I've already finished the part that identifies the DO loop variable, 
so I should have a patch tonight.

Cheers,
- Tobi