On Mon, Jan 26, 2015 at 04:18:32PM +0100, Richard Biener wrote:
> > > Ok for trunk? Or should I delay this to GCC 6?
> >
> > Does this work even without the other patch?
>
> Yes, I've actually developed 2/2 first. The other patch only ever
> emits more warnings...
Then it probably should be ok. I'm really afraid of emitting more warnings
with such high false positive rate now.
> > What do you think about Ilya's patch to set TREE_NO_WARNING in the unrolled
> > iterations where we had to keep the exit check?
>
> I don't like it too much - it papers over the real issue and prevents
> valid warnings from being emitted. Maybe we can set TREE_NO_WARNING on
> the last iteration (that is the only one we usually end up warning
> on - like after this patch). There are also many dups - regressions
> in 4.8 I belive where we warn for the last iteration in an unrolled loop.
Do we check only the last iteration? Won't we warn about other iterations
too? -Warray-bounds have plenty of warnings in dead jump threaded code that
the compiler can't prove is dead etc.
IMHO the warning should be done in VRP1 only.
Jakub
