--- old/src/share/vm/opto/library_call.cpp	2014-10-21 16:47:08.000000000 -0700
+++ new/src/share/vm/opto/library_call.cpp	2014-10-21 16:47:08.000000000 -0700
@@ -268,6 +268,7 @@
   bool inline_fp_conversions(vmIntrinsics::ID id);
   bool inline_number_methods(vmIntrinsics::ID id);
   bool inline_reference_get();
+  bool inline_Class_cast();
   bool inline_aescrypt_Block(vmIntrinsics::ID id);
   bool inline_cipherBlockChaining_AESCrypt(vmIntrinsics::ID id);
   Node* inline_cipherBlockChaining_AESCrypt_predicate(bool decrypting);
@@ -869,6 +870,8 @@
 
   case vmIntrinsics::_Reference_get:            return inline_reference_get();
 
+  case vmIntrinsics::_class_cast:               return inline_Class_cast();
+
   case vmIntrinsics::_aescrypt_encryptBlock:
   case vmIntrinsics::_aescrypt_decryptBlock:    return inline_aescrypt_Block(intrinsic_id());
 
@@ -3546,6 +3549,49 @@
   return true;
 }
 
+//-------------------------inline_Class_cast-------------------
+bool LibraryCallKit::inline_Class_cast() {
+  // See if we can statically collapse isInstance() check in Class.cast();
+  Node* mirror = argument(0); // Class
+  Node* obj    = argument(1);
+
+  const TypeInstPtr* mirror_con = _gvn.type(mirror)->isa_instptr();
+  if (mirror_con == NULL) {
+    return false;  // cannot happen?
+  }
+  const TypeOopPtr* obj_type = _gvn.type(obj)->isa_oopptr();
+  if (obj_type == NULL) {
+    return false;  // skip NULL_PTR and TOP
+  }
+
+  assert(mirror_con->klass()->as_instance_klass() == C->env()->Class_klass(), "sanity");
+  // We are loading a special hidden field from a Class mirror object,
+  // the field which points to the VM's Klass metaobject.
+
+  // java_mirror_type returns non-null for compile-time Class constants.
+  ciType* t = mirror_con->java_mirror_type();
+  if (t == NULL || !t->is_klass()) {
+    return false; // non-constant or primitive Class
+  }
+  // constant oop => constant klass
+  const TypeKlassPtr* superklass = TypeKlassPtr::make(t->as_klass());
+
+  if (superklass->singleton()) {
+    ciKlass* superk = superklass->klass();
+    ciKlass* subk = obj_type->klass();
+    if (subk != NULL && subk->is_loaded()) {
+      int static_res = C->static_subtype_check(superk, subk);
+      if (static_res == Compile::SSC_always_true) {
+        // isInstance() is true
+        set_result(obj);
+        return true;
+      }
+    }
+  }
+
+  return false;
+}
+
 //--------------------------inline_native_subtype_check------------------------
 // This intrinsic takes the JNI calls out of the heart of
 // UnsafeFieldAccessorImpl.set, which improves Field.set, readObject, etc.