Initialize extension arrays with empty array constant instead of null.

Author: woess

truffle/src/com.oracle.truffle.api.object/src/com/oracle/truffle/api/object/DynamicObject.java

@@ -173,6 +173,9 @@
 @SuppressWarnings("deprecation")
 public abstract class DynamicObject implements TruffleObject {
 
+    static final Object[] EMPTY_OBJECT_ARRAY = {};
+    static final int[] EMPTY_INT_ARRAY = {};
+
     private static final MethodHandles.Lookup LOOKUP = internalLookup();
 
     /**
@@ -192,9 +195,9 @@ public abstract class DynamicObject implements TruffleObject {
     private Shape shape;
 
     /** Object extension array. */
-    @DynamicField private Object[] extRef;
+    @DynamicField private Object[] extRef = EMPTY_OBJECT_ARRAY;
     /** Primitive extension array. */
-    @DynamicField private int[] extVal;
+    @DynamicField private int[] extVal = EMPTY_INT_ARRAY;
 
     /**
      * Constructor for {@link DynamicObject} subclasses. Initializes the object with the provided

truffle/src/com.oracle.truffle.api.object/src/com/oracle/truffle/api/object/DynamicObjectSupport.java

@@ -77,6 +77,7 @@ static void grow(DynamicObject object, Shape thisShape, Shape otherShape) {
     }
 
     private static void growObjectStore(DynamicObject object, Shape thisShape, int sourceCapacity, int targetCapacity) {
+        assert targetCapacity != 0;
         Object[] newObjectStore = new Object[targetCapacity];
         if (sourceCapacity != 0) {
             int sourceSize = thisShape.getObjectArraySize();
@@ -87,6 +88,7 @@ private static void growObjectStore(DynamicObject object, Shape thisShape, int s
     }
 
     private static void growPrimitiveStore(DynamicObject object, Shape thisShape, int sourceCapacity, int targetCapacity) {
+        assert targetCapacity != 0;
         int[] newPrimitiveArray = new int[targetCapacity];
         if (sourceCapacity != 0) {
             int sourceSize = thisShape.getPrimitiveArraySize();
@@ -108,81 +110,83 @@ static void trimToSize(DynamicObject object, Shape thisShape, Shape otherShape)
 
     private static void resizeObjectStore(DynamicObject object, Shape oldShape, Shape newShape) {
         int destinationCapacity = newShape.getObjectArrayCapacity();
+        int sourceCapacity = oldShape.getObjectArrayCapacity();
+        if (sourceCapacity == destinationCapacity) {
+            return;
+        }
+        Object[] newObjectStore;
         if (destinationCapacity == 0) {
-            object.setObjectStore(null);
+            newObjectStore = DynamicObject.EMPTY_OBJECT_ARRAY;
         } else {
-            int sourceCapacity = oldShape.getObjectArrayCapacity();
-            if (sourceCapacity != destinationCapacity) {
-                int sourceSize = oldShape.getObjectArraySize();
-                Object[] newObjectStore = new Object[destinationCapacity];
-                if (sourceSize != 0) {
-                    Object[] oldObjectStore = object.getObjectStore();
-                    int destinationSize = newShape.getObjectArraySize();
-                    int length = Math.min(sourceSize, destinationSize);
-                    UnsafeAccess.arrayCopy(oldObjectStore, newObjectStore, length);
-                }
-                object.setObjectStore(newObjectStore);
+            int sourceSize = oldShape.getObjectArraySize();
+            newObjectStore = new Object[destinationCapacity];
+            if (sourceSize != 0) {
+                Object[] oldObjectStore = object.getObjectStore();
+                int destinationSize = newShape.getObjectArraySize();
+                int length = Math.min(sourceSize, destinationSize);
+                UnsafeAccess.arrayCopy(oldObjectStore, newObjectStore, length);
             }
         }
+        object.setObjectStore(newObjectStore);
     }
 
     private static void resizePrimitiveStore(DynamicObject object, Shape oldShape, Shape newShape) {
         assert newShape.hasPrimitiveArray();
         int destinationCapacity = newShape.getPrimitiveArrayCapacity();
+        int sourceCapacity = oldShape.getPrimitiveArrayCapacity();
+        if (sourceCapacity == destinationCapacity) {
+            return;
+        }
+        int[] newPrimitiveArray;
         if (destinationCapacity == 0) {
-            object.setPrimitiveStore(null);
+            newPrimitiveArray = DynamicObject.EMPTY_INT_ARRAY;
         } else {
-            int sourceCapacity = oldShape.getPrimitiveArrayCapacity();
-            if (sourceCapacity != destinationCapacity) {
-                int sourceSize = oldShape.getPrimitiveArraySize();
-                int[] newPrimitiveArray = new int[destinationCapacity];
-                if (sourceSize != 0) {
-                    int[] oldPrimitiveArray = object.getPrimitiveStore();
-                    int destinationSize = newShape.getPrimitiveArraySize();
-                    int length = Math.min(sourceSize, destinationSize);
-                    UnsafeAccess.arrayCopy(oldPrimitiveArray, newPrimitiveArray, length);
-                }
-                object.setPrimitiveStore(newPrimitiveArray);
+            int sourceSize = oldShape.getPrimitiveArraySize();
+            newPrimitiveArray = new int[destinationCapacity];
+            if (sourceSize != 0) {
+                int[] oldPrimitiveArray = object.getPrimitiveStore();
+                int destinationSize = newShape.getPrimitiveArraySize();
+                int length = Math.min(sourceSize, destinationSize);
+                UnsafeAccess.arrayCopy(oldPrimitiveArray, newPrimitiveArray, length);
             }
         }
+        object.setPrimitiveStore(newPrimitiveArray);
     }
 
     private static void trimObjectStore(DynamicObject object, Shape thisShape, Shape newShape) {
         Object[] oldObjectStore = object.getObjectStore();
         int destinationCapacity = newShape.getObjectArrayCapacity();
+        int sourceCapacity = thisShape.getObjectArrayCapacity();
+        if (sourceCapacity <= destinationCapacity) {
+            return;
+        }
+        Object[] newObjectStore;
         if (destinationCapacity == 0) {
-            if (oldObjectStore != null) {
-                object.setObjectStore(null);
-            }
-            // else nothing to do
+            newObjectStore = DynamicObject.EMPTY_OBJECT_ARRAY;
         } else {
-            int sourceCapacity = thisShape.getObjectArrayCapacity();
-            if (sourceCapacity > destinationCapacity) {
-                Object[] newObjectStore = new Object[destinationCapacity];
-                int destinationSize = newShape.getObjectArraySize();
-                UnsafeAccess.arrayCopy(oldObjectStore, newObjectStore, destinationSize);
-                object.setObjectStore(newObjectStore);
-            }
+            newObjectStore = new Object[destinationCapacity];
+            int destinationSize = newShape.getObjectArraySize();
+            UnsafeAccess.arrayCopy(oldObjectStore, newObjectStore, destinationSize);
         }
+        object.setObjectStore(newObjectStore);
     }
 
     private static void trimPrimitiveStore(DynamicObject object, Shape thisShape, Shape newShape) {
         int[] oldPrimitiveStore = object.getPrimitiveStore();
         int destinationCapacity = newShape.getPrimitiveArrayCapacity();
+        int sourceCapacity = thisShape.getPrimitiveArrayCapacity();
+        if (sourceCapacity <= destinationCapacity) {
+            return;
+        }
+        int[] newPrimitiveStore;
         if (destinationCapacity == 0) {
-            if (oldPrimitiveStore != null) {
-                object.setPrimitiveStore(null);
-            }
-            // else nothing to do
+            newPrimitiveStore = DynamicObject.EMPTY_INT_ARRAY;
         } else {
-            int sourceCapacity = thisShape.getPrimitiveArrayCapacity();
-            if (sourceCapacity > destinationCapacity) {
-                int[] newPrimitiveStore = new int[destinationCapacity];
-                int destinationSize = newShape.getPrimitiveArraySize();
-                UnsafeAccess.arrayCopy(oldPrimitiveStore, newPrimitiveStore, destinationSize);
-                object.setPrimitiveStore(newPrimitiveStore);
-            }
+            newPrimitiveStore = new int[destinationCapacity];
+            int destinationSize = newShape.getPrimitiveArraySize();
+            UnsafeAccess.arrayCopy(oldPrimitiveStore, newPrimitiveStore, destinationSize);
         }
+        object.setPrimitiveStore(newPrimitiveStore);
     }
 
     @SuppressWarnings("deprecation")