[Bug tree-optimization/47538] [4.6 Regression] GNU Scientific Library miscompiled by gcc 4.6

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47538

--- Comment #11 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-01-31 10:44:08 UTC ---
(In reply to comment #9)
> > Why do we need something so ill-designed as sizetype?  Just for Ada?
> 
> Yes, they are useful for Ada, but the _original_ design; the POINTER_PLUS_EXPR
> mistake is orthogonal to it and shouldn't be an excuse to eliminate them.

I agree with that POINTER_PLUS_EXPR shouldn't have used sizetype.

But - the problem with sizetype is not that they exist (and have that
special overflow behavior), but - that sizetypes are considered
always sign-extended despite TYPE_UNSIGNED saying "yes!".  That's a
very very very bad design mistake.  I tried to "fix" that mistake
at least two times IIRC but failed.

At the end -> no-undefined-overflow branch (no more sizetype).