[Bug tree-optimization/56273] [4.8 regression] Bogus -Warray-bounds warning

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56273

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic,
                   |                            |missed-optimization
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-02-10
          Component|other                       |tree-optimization
     Ever Confirmed|0                           |1

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> 2013-02-10 07:34:54 UTC ---
The problem is a missing VRP.  Basically ivopts changes:
  if (j_10 != 9)

Which works into:

  j_10 = ivtmp.12_56;
  if (ivtmp.12_56 != 9)
    goto <bb 7>;
  else
    goto <bb 6>;


Which does not work as VRP cannot figure out j_10 will never be 9.
I have some patches to VRP which improves this but I don't remember if it fixes
this case where there is an assignment which is used later on.