[Truffle] Store object_id as a dynamic object field so it doesn't take up any space unless it's set.

Author: chrisseaton

core/src/main/java/org/jruby/truffle/runtime/InternalName.java

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2014 Oracle and/or its affiliates. All rights reserved. This
+ * code is released under a tri EPL/GPL/LGPL license. You can use it,
+ * redistribute it and/or modify it under the terms of the:
+ *
+ * Eclipse Public License version 1.0
+ * GNU General Public License version 2
+ * GNU Lesser General Public License version 2.1
+ */
+package org.jruby.truffle.runtime;
+
+public class InternalName {
+
+    private final String name;
+
+    public InternalName(String name) {
+        this.name = name;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("internal(%s)", name);
+    }
+
+}

core/src/main/java/org/jruby/truffle/runtime/RubyOperations.java

@@ -55,7 +55,9 @@ public Map<String,Object> getInstanceVariables(RubyBasicObject receiver) {
         Map<String, Object> vars = new LinkedHashMap<>();
         List<Property> properties = shape.getPropertyList();
         for (Property property : properties) {
-            vars.put((String) property.getKey(), property.get(receiver.getDynamicObject(), false));
+            if (property.getKey() != RubyBasicObject.OBJECT_ID_IDENTIFIER) {
+                vars.put((String) property.getKey(), property.get(receiver.getDynamicObject(), false));
+            }
         }
         return vars;
     }

core/src/main/java/org/jruby/truffle/runtime/core/RubyBasicObject.java

@@ -15,8 +15,10 @@
 import com.oracle.truffle.api.nodes.Node;
 import com.oracle.truffle.api.object.DynamicObject;
 import com.oracle.truffle.api.object.Layout;
+import com.oracle.truffle.api.object.Property;
 import com.oracle.truffle.api.object.Shape;
 import org.jruby.truffle.nodes.RubyNode;
+import org.jruby.truffle.runtime.InternalName;
 import org.jruby.truffle.runtime.ModuleOperations;
 import org.jruby.truffle.runtime.RubyContext;
 import org.jruby.truffle.runtime.RubyOperations;
@@ -30,6 +32,8 @@
  */
 public class RubyBasicObject {
 
+    public static final InternalName OBJECT_ID_IDENTIFIER = new InternalName("object_id");
+
     public static Layout LAYOUT = Layout.createLayout(Layout.INT_TO_LONG);
 
     private final DynamicObject dynamicObject;
@@ -39,8 +43,6 @@ public class RubyBasicObject {
     /** Either the singleton class if it exists or the logicalClass. */
     @CompilationFinal protected RubyClass metaClass;
 
-    protected long objectID = -1;
-
     private boolean frozen = false;
 
     public RubyBasicObject(RubyClass rubyClass) {
@@ -112,10 +114,15 @@ public void setInstanceVariable(String name, Object value) {
 
     @CompilerDirectives.TruffleBoundary
     public long getObjectID() {
-        if (objectID == -1) {
-            objectID = getContext().getNextObjectID();
+        // TODO(CS): we should specialise on reading this in the #object_id method and anywhere else it's used
+        Property property = dynamicObject.getShape().getProperty(OBJECT_ID_IDENTIFIER);
+
+        if (property != null) {
+            return (long) property.get(dynamicObject, false);
         }
 
+        final long objectID = getContext().getNextObjectID();
+        dynamicObject.define(OBJECT_ID_IDENTIFIER, objectID, 0);
         return objectID;
     }