8332243: Value classes implementing Cloneable

Reviewed-by: dsimms

src/hotspot/share/classfile/classFileParser.cpp

@@ -4310,25 +4310,6 @@ void OopMapBlocksBuilder::print_value_on(outputStream* st) const {
   print_on(st);
 }
 
-void ClassFileParser::throwInlineTypeLimitation(THREAD_AND_LOCATION_DECL,
-                                                const char* msg,
-                                                const Symbol* name,
-                                                const Symbol* sig) const {
-
-  ResourceMark rm(THREAD);
-  if (name == nullptr || sig == nullptr) {
-    Exceptions::fthrow(THREAD_AND_LOCATION_ARGS,
-        vmSymbols::java_lang_ClassFormatError(),
-        "class: %s - %s", _class_name->as_C_string(), msg);
-  }
-  else {
-    Exceptions::fthrow(THREAD_AND_LOCATION_ARGS,
-        vmSymbols::java_lang_ClassFormatError(),
-        "\"%s\" sig: \"%s\" class: %s - %s", name->as_C_string(), sig->as_C_string(),
-        _class_name->as_C_string(), msg);
-  }
-}
-
 void ClassFileParser::set_precomputed_flags(InstanceKlass* ik) {
   assert(ik != nullptr, "invariant");
 
@@ -4363,11 +4344,6 @@ void ClassFileParser::set_precomputed_flags(InstanceKlass* ik) {
   // Check if this klass supports the java.lang.Cloneable interface
   if (vmClasses::Cloneable_klass_loaded()) {
     if (ik->is_subtype_of(vmClasses::Cloneable_klass())) {
-      if (ik->is_inline_klass()) {
-        JavaThread *THREAD = JavaThread::current();
-        throwInlineTypeLimitation(THREAD_AND_LOCATION, "Inline Types do not support Cloneable");
-        return;
-      }
       ik->set_is_cloneable();
     }
   }

src/hotspot/share/classfile/classFileParser.hpp

@@ -478,11 +478,6 @@ class ClassFileParser {
                              const Symbol* sig,
                              TRAPS) const;
 
-  void throwInlineTypeLimitation(THREAD_AND_LOCATION_DECL,
-                                 const char* msg,
-                                 const Symbol* name = nullptr,
-                                 const Symbol* sig  = nullptr) const;
-
   void verify_constantvalue(const ConstantPool* const cp,
                             int constantvalue_index,
                             int signature_index,

src/hotspot/share/prims/jvm.cpp

@@ -720,13 +720,18 @@ JVM_ENTRY(jobject, JVM_Clone(JNIEnv* env, jobject handle))
   // All arrays are considered to be cloneable (See JLS 20.1.5).
   // All j.l.r.Reference classes are considered non-cloneable.
   if (!klass->is_cloneable() ||
-       klass->is_inline_klass() ||
       (klass->is_instance_klass() &&
        InstanceKlass::cast(klass)->reference_type() != REF_NONE)) {
     ResourceMark rm(THREAD);
     THROW_MSG_0(vmSymbols::java_lang_CloneNotSupportedException(), klass->external_name());
   }
 
+  if (klass->is_inline_klass()) {
+    // Value instances have no identity, so return the current instance instead of allocating a new one
+    // Value classes cannot have finalizers, so the method can return immediately
+    return JNIHandles::make_local(THREAD, obj());
+  }
+
   // Make shallow object copy
   const size_t size = obj->size();
   oop new_obj_oop = nullptr;

test/hotspot/jtreg/runtime/valhalla/inlinetypes/TestCloneableValue.java

@@ -0,0 +1,91 @@
+/*
+ * Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * @test TestCloneableValue
+ * @library /test/lib
+ * @enablePreview
+ * @compile TestCloneableValue.java
+ * @run main/othervm runtime.valhalla.inlinetypes.TestCloneableValue
+ */
+
+ package runtime.valhalla.inlinetypes;
+
+ import jdk.test.lib.Asserts;
+
+ import java.util.ArrayList;
+
+ public class TestCloneableValue  {
+
+    static value class SimpleValue implements Cloneable {
+      int i;
+      double j;
+
+      public SimpleValue() {
+        i = 42;
+        j = Math.E;
+      }
+
+      @Override
+      public Object clone() throws CloneNotSupportedException {
+        return super.clone(); // delegate to Object's method performing a shallow copy
+      }
+     }
+
+    static value class NotSoSimpleValue implements Cloneable {
+      ArrayList list;
+
+      public NotSoSimpleValue() {
+        list = new ArrayList<>();
+      }
+
+      private NotSoSimpleValue(ArrayList l) {
+        list = l;
+      }
+
+      @Override
+      public Object clone() throws CloneNotSupportedException {
+        return new NotSoSimpleValue((ArrayList)list.clone());
+      }
+    }
+
+     public static void main(String[] args) {
+      var sv = new SimpleValue();
+      try {
+        var c1 = sv.clone();
+        Asserts.assertEQ(sv, c1);
+        Asserts.assertEQ(sv.hashCode(), c1.hashCode());
+      } catch(CloneNotSupportedException e) {
+        Asserts.fail("Unexpected exception", e);
+      }
+
+      var nssv = new NotSoSimpleValue();
+      try {
+        var c2 = nssv.clone();
+        Asserts.assertNE(nssv, c2);
+        Asserts.assertEQ(nssv.hashCode(), c2.hashCode());
+      } catch(CloneNotSupportedException e) {
+        Asserts.fail("Unexpected exception", e);
+      }
+     }
+ }