[Bug tree-optimization/38984] New: [4.2/4.3/4.4 Regression] NULL pointers always considered distinct by PTA, even with -fno-delete-null-pointer-checks

["bonzini at gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

This testcase fails:

/* { dg-do compile } */
/* { dg-options "-O2 -fno-delete-null-pointer-checks -fdump-tree-optimized" }
*/

int f(int *p)
{
  int a = *p;
  int *null = 0;
  *null = 5;
  return *p == a;
}

/* { dg-final { scan-tree-dump-times " = \\\*p" 2 "optimized" } } */
/* { dg-final { scan-tree-dump-not "return 1" "optimized" } } */
/* { dg-final { cleanup-tree-dump "optimized" } } */

This testcase is important because targets that are always MMU-less (like AVR)
will always have -fdelete-null-pointer-checks disabled, so the wrong code bug
will happen with -O2.  IMO it is a P2.


-- 
           Summary: [4.2/4.3/4.4 Regression] NULL pointers always considered
                    distinct by PTA, even with -fno-delete-null-pointer-
                    checks
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bonzini at gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38984