src/share/vm/opto/parse2.cpp

rev 5464 : 8024070: C2 needs some form of type speculation
Summary: record unused type profile information with type system, propagate and use it.
Reviewed-by:
rev 5465 : imported patch speculative-cleanup

*** 2237,2246 ****
--- 2237,2271 ----
      // If this is a backwards branch in the bytecodes, add Safepoint
      maybe_add_safepoint(iter().get_dest());
      a = pop();
      b = pop();
      c = _gvn.transform( new (C) CmpPNode(b, a) );
+     // If this is transformed by the _gvn to a comparison with the low
+     // level klass then we may be able to use speculation
+     if (c->Opcode() == Op_CmpP &&
+         (c->in(1)->Opcode() == Op_LoadKlass || c->in(1)->Opcode() == Op_DecodeNKlass ) &&
+         c->in(2)->is_Con()) {
+       Node* load_klass = NULL;
+       if (c->in(1)->Opcode() == Op_DecodeNKlass) {
+         load_klass = c->in(1)->in(1);
+       } else {
+         load_klass = c->in(1);
+       }
+       if (load_klass->in(2)->is_AddP()) {
+         Node* obj = load_klass->in(2)->in(AddPNode::Address);
+         const TypeOopPtr* obj_type = _gvn.type(obj)->is_oopptr();
+         if (obj_type->speculative_type() != NULL) {
+           ciKlass* k = obj_type->speculative_type();
+           inc_sp(2);
+           obj = maybe_cast_profiled_obj(obj, k);
+           dec_sp(2);
+           // now redo the CmpP which should always fail or succeed and
+           // be optimized out
+           c = _gvn.transform( new (C) CmpPNode(b, a) );
+         }
+       }
+     }
      do_if(btest, c);
      break;
  
    case Bytecodes::_ifeq: btest = BoolTest::eq; goto handle_ifxx;
    case Bytecodes::_ifne: btest = BoolTest::ne; goto handle_ifxx;