[Bug middle-end/96564] [11/12/13/14 Regression] New maybe use of uninitialized variable warning since r11-959

["law at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96564

Jeffrey A. Law <law at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |law at gcc dot gnu.org,
                   |                            |rguenth at gcc dot gnu.org

--- Comment #12 from Jeffrey A. Law <law at gcc dot gnu.org> ---
So I think we could solve this with a bit of help from the alias oracle.  We
have  the routine ptrs_compare_unequal, but points-to-null is going to get in
the way.

I think VRP and DOM have enough information to rule out NULL for both objects
in question.  So if we could query the points-to information, ignoring NULL
then we could likely solve this particular bug.

Essentially VRP or DOM would prove NULL isn't in the set of possible values at
the comparison point.  Then we query the alias information ignoring NULL. 
Voila we compute a static result for the comparison of the two pointers and the
problematical block becomes unreachable and the bogus warning goes away.

Richi, any thoughts in viability of such an API?