6894807: No ClassCastException for HashAttributeSet constructors if run with -Xcomp

Summary: Return interface klass type if it is exact.
Reviewed-by: never

src/share/vm/opto/cfgnode.cpp

@@ -956,6 +956,7 @@ const Type *PhiNode::Value( PhaseTransform *phase ) const {
     }
     if( jtkp && ttkp ) {
       if( jtkp->is_loaded() &&  jtkp->klass()->is_interface() &&
+          !jtkp->klass_is_exact() && // Keep exact interface klass (6894807)
           ttkp->is_loaded() && !ttkp->klass()->is_interface() ) {
         assert(ft == ttkp->cast_to_ptr_type(jtkp->ptr()) ||
                ft->isa_narrowoop() && ft->make_ptr() == ttkp->cast_to_ptr_type(jtkp->ptr()), "");

src/share/vm/opto/type.cpp

@@ -2545,12 +2545,15 @@ const Type *TypeOopPtr::filter( const Type *kills ) const {
       ftip->is_loaded() &&  ftip->klass()->is_interface() &&
       ktip->is_loaded() && !ktip->klass()->is_interface()) {
     // Happens in a CTW of rt.jar, 320-341, no extra flags
+    assert(!ftip->klass_is_exact(), "interface could not be exact");
     return ktip->cast_to_ptr_type(ftip->ptr());
   }
+  // Interface klass type could be exact in opposite to interface type,
+  // return it here instead of incorrect Constant ptr J/L/Object (6894807).
   if (ftkp != NULL && ktkp != NULL &&
       ftkp->is_loaded() &&  ftkp->klass()->is_interface() &&
+      !ftkp->klass_is_exact() && // Keep exact interface klass
       ktkp->is_loaded() && !ktkp->klass()->is_interface()) {
-    // Happens in a CTW of rt.jar, 320-341, no extra flags
     return ktkp->cast_to_ptr_type(ftkp->ptr());
   }