[Bug tree-optimization/43940] New: DOM doesn't propagate constants properly

[rguenth at gcc dot gnu dot org]

For

int main()
{
  void *p = __builtin_malloc (4);
  if (p)
    {
      __builtin_free (p);
      p = 0;
    }
  __builtin_free (p);
  return 0;
}

DOM does not propagate p == 0 on the else path leaving

<bb 2>:
  p_2 = __builtin_malloc (4);
  if (p_2 != 0B)
    goto <bb 3>;
  else
    goto <bb 4>;

<bb 3>:
  __builtin_free (p_2);

<bb 4>:
  # p_1 = PHI <p_2(2), 0B(3)>
  __builtin_free (p_1);


VRP can do this.


-- 
           Summary: DOM doesn't propagate constants properly
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43940