[Bug c++/54770] sibling call optimization is not applied where it ought to be

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54770



Steven Bosscher <steven at gcc dot gnu.org> changed:



           What    |Removed                     |Added

----------------------------------------------------------------------------

             Status|WAITING                     |NEW



--- Comment #2 from Steven Bosscher <steven at gcc dot gnu.org> 2012-10-02 
11:44:41 UTC ---

Confirmed, complete test case:



---------------------- 8< ----------------------

typedef long unsigned int size_t;



namespace std

{

    using ::size_t;



  class exception

    {

  public:

    exception() throw() { }

    virtual ~exception() throw();

    };



  class bad_alloc : public exception

    {

  public:

    bad_alloc() throw() { }

    virtual ~bad_alloc() throw();

    };



  struct nothrow_t { };

  extern const nothrow_t nothrow;

}



inline void* operator new(std::size_t, void* __p) throw() { return __p; }

inline void operator delete (void*, void*) throw() { }



template<typename T> struct Intrusive

{

  Intrusive(T * p = 0) : px(p) { if(px) incref(px); }

  ~Intrusive() { if(px) decref(px); }

  T * operator->() const { return px; }

  T * px;

};

struct Node;

typedef Intrusive<Node> NodePtr;

struct Node

{

  Node() : refcnt(0) {}

  virtual ~Node() {}

  virtual void H() {}

  unsigned short refcnt;

  friend void incref(Node * node) { ++node->refcnt; }

  friend void decref(Node * node) { if(--node->refcnt == 0) delete node; }

};

struct MainNode : Node

{

  MainNode(NodePtr const & arg_) : Node(), arg(arg_) {}

  virtual ~MainNode() {}

  NodePtr arg;

  virtual void H()

    {

        {

          NodePtr tmp(arg);

          this->~Node();

          new(this) MainNode(tmp);

        }

      this->H();

    }

};

int main()

{

  NodePtr arg = NodePtr();

  NodePtr root(new MainNode(arg));

  root->H();

  return 0;

}

---------------------- 8< ----------------------



At trunk r191835, compiling with:

"./xgcc -B. -S -O3 -fdump-tree-optimized-lineno t.C"



Gives the call at line 58:



<L6>:

  tmp ={v} {CLOBBER};

  [t.C : 58:15] _13 = MEM[(int (*__vtbl_ptr_type) () *)prephitmp_29+16B];

  [t.C : 58:16] OBJ_TYPE_REF(_13;this_3(D)->2) (this_3(D));

  [t.C : 59:5] return;