[Bug tree-optimization/22117] New: VRP thinks <ptr type> + <ptr type> is always nonnull.

["kazu at cs dot umass dot edu" <gcc-bugzilla at gcc dot gnu dot org>]

Consider:

void
foo (int *p, int q)
{
  if (p == 0)
    {
      if (q == 0)
	{
	  int *r = &p[q];
	  if (r != 0)
	    link_error ();
	}
    }
}

Note that the innermost "if" condition should be folded to false,
but VRP folds that to true.

Under "if (q == 0)", both p and q are known to be zero,
but VRP thinks that regardless of their values, p + q is always nonnull.

-- 
           Summary: VRP thinks <ptr type> + <ptr type> is always nonnull.
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: kazu at cs dot umass dot edu
                CC: dnovillo at redhat dot com,gcc-bugs at gcc dot gnu dot
                    org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22117