On Fri, Mar 16, 2012 at 12:03:08AM +0100, Bernd Schmidt wrote:
> On 03/15/2012 11:12 PM, Zdenek Dvorak wrote:
>
> > the reason unsigned integer types are prefered is that possible overflows
> > during the computation have defined semantics. With pointer types, the
> > intermediate steps of the computations could have undefined behavior,
> > possibly
> > confusing further optimizations. Is the patch with this regard?
>
> It's trying to use sizetype for pointer offset computations. As far as I
> can tell that's supposed to be an unsigned type, so it should be OK. I
> think the final POINTER_PLUS_EXPRs we make can't overflow in valid programs.
In the IL before ivopts it shouldn't for valid programs, but what ivopts
makes out of it often would, that is why it uses unsigned integers instead.
Jakub
