[Bug tree-optimization/45791] Missed devirtualization

[hubicka at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45791

--- Comment #9 from Jan Hubicka <hubicka at gcc dot gnu.org> 2010-12-14 
23:15:16 UTC ---
OK, main() code seems to optimize out that is an imrovement. Is it optimized
away with your patch pre-IPA too? 

Derived() is also devirtualizable:

Derived::Derived() (struct Derived * const this)
{
  int (*__vtbl_ptr_type) (void) * D.2237;
  int (*__vtbl_ptr_type) (void) D.2236;
  struct Base * D.2215;

<bb 2>:
  D.2215_2 = &this_1(D)->D.2115;
  D.2215_2->_vptr.Base = &_ZTV4Base[2];
  this_1(D)->D.2115._vptr.Base = &_ZTV7Derived[2];
  D.2215_3 = &this_1(D)->D.2115;
  D.2237_9 = D.2215_3->_vptr.Base;
  D.2236_10 = MEM[(int (*__vtbl_ptr_type) (void) *)D.2237_9 + 16B];
  OBJ_TYPE_REF(D.2236_10;D.2215_3->2) (D.2215_3);

We fail to devirtualize pre-IPA.  After IPA we compile into:

<bb 2>:
  MEM[(struct Base *)this_1(D)]._vptr.Base = &_ZTV4Base[2];
  this_1(D)->D.2115._vptr.Base = &_ZTV7Derived[2];
  D.2215_3 = &this_1(D)->D.2115;
  D.2236_10 = (int (*__vtbl_ptr_type) (void)) f;

a type mismatch?