[Bug tree-optimization/27090] New: FRE does not value number effective types

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

Extracted from tramp3d:

template <class T>
struct Bar
{
        int get() { return static_cast<T*>(this)->get2(); }
};
struct Foo : public Bar<Foo>
{
        int get2() { return x; }
        int x;
};

int foo(Foo& f)
{
        return f.get();
}

We end up with

int foo(Foo&) (f)
{
  struct Foo * this.1;
  int D.2027;
  struct Bar<Foo> * f.0;

<bb 2>:
  f.0_2 = (struct Bar<Foo> *) f_1;
  this.1_4 = (struct Foo *) f.0_2;
  D.2027_6 = this.1_4->x;
  return D.2027_6;

}

while we can load x directly from f_1.  This looks like something FRE
should be able to do - tell that f_1 has the same VN as this.1_4 and
(struct Foo *) f.0_2.  Danny - does the new value-numbering catch this
case?  It can even strip const qualifiers for loads from the pointer.


-- 
           Summary: FRE does not value number effective types
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org
OtherBugsDependingO 22501
             nThis:


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27090