[Bug tree-optimization/36917] [4.3 regression] miscompilation with -O2 and r136501

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

------- Comment #9 from rguenth at gcc dot gnu dot org  2008-07-24 09:52 -------
The difference comes from the second VRP pass which concludes that c_76 is
[1, +INF] from which it changes

# c_173 = PHI <0(7), c_76(12)>

to

# c_173 = PHI <0(7), 1(12)>

which it concludes from

c_76 = (Cell) D.156138_4;

where Cell is

  enum Cell {
    Cell_0
  };

so the only valid values for c_76 are 0 and 1.  The problem is probably here
(c is of type Cell):

  D.156112_62 = c_173 * 4;

(D.156112 is unsigned int), where we obviously miss a cast in the IL.

This is from inlining ciTypeFlow::StateVector::type_at which looks like

ciType* ciTypeFlow::StateVector::type_at(ciTypeFlow::Cell) const (this, c)
{
  struct ciType * D.144073;
  struct ciType * * D.144074;
  unsigned int D.144075;
  struct ciType * * D.144076;

  D.144074 = this->_types;
  D.144075 = c * 4;
  D.144076 = D.144074 + D.144075;
  D.144073 = *D.144076;
  return D.144073;
}

gimplified from

return <retval> = *((struct ciType * *) ((const struct StateVector *)
this)->_types + (unsigned int) ((unsigned int) c * 4));

which hints at that c probably has the same precision and signedness as
unsigned int.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36917