-funsafe-loop-optimizations

[Zdenek Dvorak]

Hello,

> > > 	While we discuss whether this should be the default or enabled at
> > > any optimization level, can we agree that users should be able to assert
> > > with a commandline option that they want less strict induction variable
> > > semantics?
> > 
> > And/or a -W option that warns for these sorts of loops so that
> > (a) we can see how often this happens, really, (b) so that users
> > can fix the presumed mistake.
> 
> If you could detect them and warn for them, you could not optimize
> them in the first place (and that's what happens when the boundaries
> are constants).  They're detectable only at runtime and even en not
> necessarily easily.

I think Richard means issuing warning in case where
-funsafe-loop-optimizations causes us to ignore some conditions
for optimizations we were not able to prove.  Which definitely is
a good idea.

Zdenek