Add STORE_STORE barrier after Object.clone().

(cherry picked from commit 7eab68b6200d6f4995c30dc26d6c3570760baccf)

Author: christianhaeubl

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/graal/jdk/SubstrateObjectCloneSnippets.java

@@ -41,6 +41,7 @@
 import org.graalvm.compiler.nodes.ValueNode;
 import org.graalvm.compiler.nodes.extended.BranchProbabilityNode;
 import org.graalvm.compiler.nodes.extended.ForeignCallNode;
+import org.graalvm.compiler.nodes.extended.MembarNode;
 import org.graalvm.compiler.nodes.java.ArrayLengthNode;
 import org.graalvm.compiler.nodes.spi.LoweringTool;
 import org.graalvm.compiler.nodes.spi.VirtualizerTool;
@@ -170,6 +171,12 @@ private static Object doClone(Object original) throws CloneNotSupportedException
             BarrieredAccess.writeObject(result, monitorOffset, null);
         }
 
+        /*
+         * Emit a STORE_STORE barrier to ensure that other threads see consistent values for final
+         * fields and VM internal fields.
+         */
+        MembarNode.memoryBarrier(MembarNode.FenceKind.STORE_STORE);
+
         return result;
     }