Reverting Ref to the original implementation which did not pass an additional

"Scriptable target" argument to Ref.(get|set|has|delete) methods. The idea was
to optimize away in many cases creation of Ref instances, but given that modern
JVM can GC short-lived objects efficiently it does not sound right to have code
complexity now in the hope of slightly more efficient implementation later.

js/rhino/src/org/mozilla/javascript/Context.java

@@ -2561,7 +2561,4 @@ public class Context
 
     // It can be used to return the second Scriptable result from function
     Scriptable scratchScriptable;
-
-    // It is used to return the target component for Ref instance
-    Scriptable scratchRefTarget;
 }

js/rhino/src/org/mozilla/javascript/Interpreter.java

@@ -857,7 +857,6 @@ public class Interpreter
         int type = node.getType();
         Node child = node.getFirstChild();
         int savedStackDepth = itsStackDepth;
-        int expectedStackDelta = 1;
         switch (type) {
 
           case Token.FUNCTION:
@@ -902,9 +901,6 @@ public class Interpreter
             break;
 
           case Token.REF_CALL:
-            // account for the reference represented as pair (ref, target)
-            expectedStackDelta = 2;
-            // fallthrough
           case Token.CALL:
           case Token.NEW:
             {
@@ -1043,7 +1039,6 @@ public class Interpreter
           case Token.DEL_REF:
             visitExpression(child, 0);
             addToken(type);
-            stackChange(-1);
             break;
 
           case Token.SETPROP:
@@ -1090,16 +1085,15 @@ public class Interpreter
             visitExpression(child, 0);
             child = child.getNext();
             if (type == Token.SET_REF_OP) {
-                addIcode(Icode_DUP2);
-                stackChange(2);
+                addIcode(Icode_DUP);
+                stackChange(1);
                 addToken(Token.GET_REF);
-                stackChange(-1);
                 // Compensate for the following USE_STACK
                 stackChange(-1);
             }
             visitExpression(child, 0);
             addToken(Token.SET_REF);
-            stackChange(-2);
+            stackChange(-1);
             break;
 
           case Token.SETNAME:
@@ -1225,8 +1219,6 @@ public class Interpreter
           case Token.REF_SPECIAL:
             visitExpression(child, 0);
             addStringOp(type, (String)node.getProp(Node.NAME_PROP));
-            stackChange(1);
-            expectedStackDelta = 2;
             break;
 
           case Token.REF_MEMBER:
@@ -1243,8 +1235,7 @@ public class Interpreter
                     child = child.getNext();
                 } while (child != null);
                 addIndexOp(type, memberTypeFlags);
-                stackChange(2 - childCount);
-                expectedStackDelta = 2;
+                stackChange(1 - childCount);
             }
             break;
 
@@ -1271,7 +1262,7 @@ public class Interpreter
           default:
             throw badTree(node);
         }
-        if (savedStackDepth + expectedStackDelta != itsStackDepth) {
+        if (savedStackDepth + 1 != itsStackDepth) {
             Kit.codeBug();
         }
     }
@@ -1359,7 +1350,6 @@ public class Interpreter
             visitExpression(ref, 0);
             addIcode(Icode_REF_INC_DEC);
             addUint8(incrDecrMask);
-            stackChange(-1);
             break;
           }
           default : {
@@ -2763,35 +2753,26 @@ switch (op) {
         continue Loop;
     }
     case Token.GET_REF : {
-        Scriptable target = (Scriptable)stack[stackTop];
-        --stackTop;
         Ref ref = (Ref)stack[stackTop];
-        stack[stackTop] = ScriptRuntime.refGet(ref, target, cx);
+        stack[stackTop] = ScriptRuntime.refGet(ref, cx);
         continue Loop;
     }
     case Token.SET_REF : {
         Object value = stack[stackTop];
         if (value == DBL_MRK) value = ScriptRuntime.wrapNumber(sDbl[stackTop]);
         --stackTop;
-        Scriptable target = (Scriptable)stack[stackTop];
-        --stackTop;
         Ref ref = (Ref)stack[stackTop];
-        stack[stackTop] = ScriptRuntime.refSet(ref, target, value, cx);
+        stack[stackTop] = ScriptRuntime.refSet(ref, value, cx);
         continue Loop;
     }
     case Token.DEL_REF : {
-        Scriptable target = (Scriptable)stack[stackTop];
-        --stackTop;
         Ref ref = (Ref)stack[stackTop];
-        stack[stackTop] = ScriptRuntime.refDel(ref, target, cx);
+        stack[stackTop] = ScriptRuntime.refDel(ref, cx);
         continue Loop;
     }
     case Icode_REF_INC_DEC : {
-        Scriptable target = (Scriptable)stack[stackTop];
-        --stackTop;
         Ref ref = (Ref)stack[stackTop];
-        stack[stackTop] = ScriptRuntime.refIncrDecr(ref, target, cx,
-                                                    iCode[frame.pc]);
+        stack[stackTop] = ScriptRuntime.refIncrDecr(ref, cx, iCode[frame.pc]);
         ++frame.pc;
         continue Loop;
     }
@@ -2902,8 +2883,6 @@ switch (op) {
                                             indexReg);
             stack[stackTop] = ScriptRuntime.callRef(fun, funThisObj, outArgs,
                                                     cx, calleeScope);
-            ++stackTop;
-            stack[stackTop] = Ref.popTarget(cx);
             continue Loop;
         }
 
@@ -3195,8 +3174,6 @@ switch (op) {
         Object obj = stack[stackTop];
         if (obj == DBL_MRK) obj = ScriptRuntime.wrapNumber(sDbl[stackTop]);
         stack[stackTop] = ScriptRuntime.specialRef(obj, stringReg, cx);
-        ++stackTop;
-        stack[stackTop] = Ref.popTarget(cx);
         continue Loop;
     }
     case Token.REF_MEMBER: {
@@ -3207,8 +3184,6 @@ switch (op) {
         Object obj = stack[stackTop];
         if (obj == DBL_MRK) obj = ScriptRuntime.wrapNumber(sDbl[stackTop]);
         stack[stackTop] = ScriptRuntime.memberRef(obj, elem, cx, indexReg);
-        ++stackTop;
-        stack[stackTop] = Ref.popTarget(cx);
         continue Loop;
     }
     case Token.REF_NS_MEMBER: {
@@ -3222,8 +3197,6 @@ switch (op) {
         Object obj = stack[stackTop];
         if (obj == DBL_MRK) obj = ScriptRuntime.wrapNumber(sDbl[stackTop]);
         stack[stackTop] = ScriptRuntime.memberRef(obj, ns, elem, cx, indexReg);
-        ++stackTop;
-        stack[stackTop] = Ref.popTarget(cx);
         continue Loop;
     }
     case Token.REF_NAME: {
@@ -3232,8 +3205,6 @@ switch (op) {
         if (name == DBL_MRK) name = ScriptRuntime.wrapNumber(sDbl[stackTop]);
         stack[stackTop] = ScriptRuntime.nameRef(name, cx, frame.scope,
                                                 indexReg);
-        ++stackTop;
-        stack[stackTop] = Ref.popTarget(cx);
         continue Loop;
     }
     case Token.REF_NS_NAME: {
@@ -3245,8 +3216,6 @@ switch (op) {
         if (ns == DBL_MRK) ns = ScriptRuntime.wrapNumber(sDbl[stackTop]);
         stack[stackTop] = ScriptRuntime.nameRef(ns, name, cx, frame.scope,
                                                 indexReg);
-        ++stackTop;
-        stack[stackTop] = Ref.popTarget(cx);
         continue Loop;
     }
     case Icode_SCOPE_LOAD :

js/rhino/src/org/mozilla/javascript/Ref.java

@@ -43,30 +43,16 @@ import java.io.Serializable;
  */
 public abstract class Ref implements Serializable
 {
-    public static Ref pushTarget(Context cx, Ref ref, Scriptable target)
-    {
-        if (cx.scratchRefTarget != null) throw new IllegalStateException();
-        cx.scratchRefTarget = target;
-        return ref;
-    }
-
-    public static Scriptable popTarget(Context cx)
-    {
-        Scriptable target = cx.scratchRefTarget;
-        cx.scratchRefTarget = null;
-        return target;
-    }
-
-    public boolean has(Context cx, Scriptable target)
+    public boolean has(Context cx)
     {
         return true;
     }
 
-    public abstract Object get(Context cx, Scriptable target);
+    public abstract Object get(Context cx);
 
-    public abstract Object set(Context cx, Scriptable target, Object value);
+    public abstract Object set(Context cx, Object value);
 
-    public boolean delete(Context cx, Scriptable target)
+    public boolean delete(Context cx)
     {
         return false;
     }

js/rhino/src/org/mozilla/javascript/ScriptRuntime.java

@@ -1505,20 +1505,19 @@ public class ScriptRuntime {
         return result;
     }
 
-    public static Object refGet(Ref ref, Scriptable target, Context cx)
+    public static Object refGet(Ref ref, Context cx)
     {
-        return ref.get(cx, target);
+        return ref.get(cx);
     }
 
-    public static Object refSet(Ref ref, Scriptable target,
-                                Object value, Context cx)
+    public static Object refSet(Ref ref, Object value, Context cx)
     {
-        return ref.set(cx, target, value);
+        return ref.set(cx, value);
     }
 
-    public static Object refDel(Ref ref, Scriptable target, Context cx)
+    public static Object refDel(Ref ref, Context cx)
     {
-        return wrapBoolean(ref.delete(cx, target));
+        return wrapBoolean(ref.delete(cx));
     }
 
     static boolean isSpecialProperty(String s)
@@ -2035,7 +2034,6 @@ public class ScriptRuntime {
             BaseFunction bf = (BaseFunction)function;
             Ref ref = bf.callRef(cx, scope, thisObj, args);
             if (ref != null) {
-                storeScriptable(cx, thisObj);
                 return ref;
             }
         }
@@ -2405,10 +2403,9 @@ public class ScriptRuntime {
         }
     }
 
-    public static Object refIncrDecr(Ref ref, Scriptable target,
-                                     Context cx, int incrDecrMask)
+    public static Object refIncrDecr(Ref ref, Context cx, int incrDecrMask)
     {
-        Object value = ref.get(cx, target);
+        Object value = ref.get(cx);
         boolean post = ((incrDecrMask & Node.POST_FLAG) != 0);
         double number;
         if (value instanceof Number) {
@@ -2426,7 +2423,7 @@ public class ScriptRuntime {
             --number;
         }
         Number result = wrapNumber(number);
-        ref.set(cx, target, result);
+        ref.set(cx, result);
         if (post) {
             return value;
         } else {

js/rhino/src/org/mozilla/javascript/SpecialRef.java

@@ -41,11 +41,13 @@ class SpecialRef extends Ref
     private static final int SPECIAL_PROTO = 1;
     private static final int SPECIAL_PARENT = 2;
 
+    private Scriptable target;
     private int type;
     private String name;
 
-    private SpecialRef(int type, String name)
+    private SpecialRef(Scriptable target, int type, String name)
     {
+        this.target = target;
         this.type = type;
         this.name = name;
     }
@@ -71,10 +73,10 @@ class SpecialRef extends Ref
             type = SPECIAL_NONE;
         }
 
-        return Ref.pushTarget(cx, new SpecialRef(type, name), target);
+        return new SpecialRef(target, type, name);
     }
 
-    public Object get(Context cx, Scriptable target)
+    public Object get(Context cx)
     {
         switch (type) {
           case SPECIAL_NONE:
@@ -88,7 +90,7 @@ class SpecialRef extends Ref
         }
     }
 
-    public Object set(Context cx, Scriptable target, Object value)
+    public Object set(Context cx, Object value)
     {
         switch (type) {
           case SPECIAL_NONE:
@@ -125,7 +127,7 @@ class SpecialRef extends Ref
         }
     }
 
-    public boolean has(Context cx, Scriptable target)
+    public boolean has(Context cx)
     {
         if (type == SPECIAL_NONE) {
             return ScriptRuntime.hasObjectElem(target, name, cx);
@@ -133,7 +135,7 @@ class SpecialRef extends Ref
         return true;
     }
 
-    public boolean delete(Context cx, Scriptable target)
+    public boolean delete(Context cx)
     {
         if (type == SPECIAL_NONE) {
             return ScriptRuntime.deleteObjectElem(target, name, cx);

js/rhino/src/org/mozilla/javascript/optimizer/Codegen.java

@@ -1785,8 +1785,6 @@ class BodyCodegen
                     +"Lorg/mozilla/javascript/Context;"
                     +"Lorg/mozilla/javascript/Scriptable;"
                     +")Ljava/lang/Object;");
-                // Load reference target stored in cx by refCal
-                refTargetToStack();
                 break;
 
               case Token.NUMBER:
@@ -2101,12 +2099,11 @@ class BodyCodegen
                 break;
 
               case Token.GET_REF:
-                generateExpression(child, node); // reference and target
+                generateExpression(child, node); // reference
                 cfw.addALoad(contextLocal);
                 addScriptRuntimeInvoke(
                     "refGet",
                     "(Lorg/mozilla/javascript/Ref;"
-                    +"Lorg/mozilla/javascript/Scriptable;"
                     +"Lorg/mozilla/javascript/Context;"
                     +")Ljava/lang/Object;");
                 break;
@@ -2139,12 +2136,11 @@ class BodyCodegen
                     generateExpression(child, node);
                     child = child.getNext();
                     if (type == Token.SET_REF_OP) {
-                        cfw.add(ByteCode.DUP2);
+                        cfw.add(ByteCode.DUP);
                         cfw.addALoad(contextLocal);
                         addScriptRuntimeInvoke(
                             "refGet",
                             "(Lorg/mozilla/javascript/Ref;"
-                            +"Lorg/mozilla/javascript/Scriptable;"
                             +"Lorg/mozilla/javascript/Context;"
                             +")Ljava/lang/Object;");
                     }
@@ -2153,7 +2149,6 @@ class BodyCodegen
                     addScriptRuntimeInvoke(
                         "refSet",
                         "(Lorg/mozilla/javascript/Ref;"
-                        +"Lorg/mozilla/javascript/Scriptable;"
                         +"Ljava/lang/Object;"
                         +"Lorg/mozilla/javascript/Context;"
                         +")Ljava/lang/Object;");
@@ -2165,7 +2160,6 @@ class BodyCodegen
                 cfw.addALoad(contextLocal);
                 addScriptRuntimeInvoke("refDel",
                                        "(Lorg/mozilla/javascript/Ref;"
-                                       +"Lorg/mozilla/javascript/Scriptable;"
                                        +"Lorg/mozilla/javascript/Context;"
                                        +")Ljava/lang/Object;");
                 break;
@@ -2217,8 +2211,6 @@ class BodyCodegen
                         +"Ljava/lang/String;"
                         +"Lorg/mozilla/javascript/Context;"
                         +")Lorg/mozilla/javascript/Ref;");
-                    // Load reference target stored in cx by specialRef
-                    refTargetToStack();
                 }
                 break;
 
@@ -2277,8 +2269,6 @@ class BodyCodegen
                     }
                     cfw.addPush(memberTypeFlags);
                     addScriptRuntimeInvoke(methodName, signature);
-                    // Load reference target stored in cx by methodName
-                    refTargetToStack();
                 }
                 break;
 
@@ -3258,7 +3248,6 @@ Else pass the JS object in the aReg and 0.0 in the dReg.
             addScriptRuntimeInvoke(
                 "refIncrDecr",
                 "(Lorg/mozilla/javascript/Ref;"
-                +"Lorg/mozilla/javascript/Scriptable;"
                 +"Lorg/mozilla/javascript/Context;"
                 +"I)Ljava/lang/Object;");
             break;
@@ -3932,16 +3921,6 @@ Else pass the JS object in the aReg and 0.0 in the dReg.
         }
     }
 
-    private void refTargetToStack()
-    {
-        cfw.addALoad(contextLocal);
-        cfw.addInvoke(ByteCode.INVOKESTATIC,
-                      "org.mozilla.javascript.Ref",
-                      "popTarget",
-                      "(Lorg/mozilla/javascript/Context;"
-                      +")Lorg/mozilla/javascript/Scriptable;");
-    }
-
     private void addScriptRuntimeInvoke(String methodName,
                                         String methodSignature)
     {

js/rhino/xmlimplsrc/org/mozilla/javascript/xmlimpl/XMLLibImpl.java

@@ -678,7 +678,10 @@ public final class XMLLibImpl extends XMLLib
 
         // xmlObj == null corresponds to undefined as the target of
         // the reference
-        return Ref.pushTarget(cx, xmlName, xmlObj);
+        if (xmlObj != null) {
+            xmlName.initXMLObject(xmlObj);
+        }
+        return xmlName;
     }
 
     /**

js/rhino/xmlimplsrc/org/mozilla/javascript/xmlimpl/XMLName.java

@@ -49,6 +49,7 @@ class XMLName extends Ref
     private String localName;
     private boolean isAttributeName;
     private boolean isDescendants;
+    private XMLObjectImpl xmlObject;
 
     private XMLName(String uri, String localName)
     {
@@ -66,6 +67,13 @@ class XMLName extends Ref
         return new XMLName(uri, localName);
     }
     
+    void initXMLObject(XMLObjectImpl xmlObject)
+    {
+        if (xmlObject == null) throw new IllegalArgumentException();
+        if (this.xmlObject != null) throw new IllegalStateException();
+        this.xmlObject = xmlObject;
+    }
+
     String uri()
     {
         return uri;
@@ -98,18 +106,16 @@ class XMLName extends Ref
         isDescendants = true;
     }
 
-    public boolean has(Context cx, Scriptable target)
+    public boolean has(Context cx)
     {
-        XMLObjectImpl xmlObject = (XMLObjectImpl)target;
         if (xmlObject == null) {
             return false;
         }
         return xmlObject.hasXMLProperty(this);
     }
 
-    public Object get(Context cx, Scriptable target)
+    public Object get(Context cx)
     {
-        XMLObjectImpl xmlObject = (XMLObjectImpl)target;
         if (xmlObject == null) {
             throw ScriptRuntime.undefReadError(Undefined.instance,
                                                toString());
@@ -117,9 +123,8 @@ class XMLName extends Ref
         return xmlObject.getXMLProperty(this);
     }
 
-    public Object set(Context cx, Scriptable target, Object value)
+    public Object set(Context cx, Object value)
     {
-        XMLObjectImpl xmlObject = (XMLObjectImpl)target;
         if (xmlObject == null) {
             throw ScriptRuntime.undefWriteError(Undefined.instance,
                                                 toString(),
@@ -132,9 +137,8 @@ class XMLName extends Ref
         return value;
     }
 
-    public boolean delete(Context cx, Scriptable target)
+    public boolean delete(Context cx)
     {
-        XMLObjectImpl xmlObject = (XMLObjectImpl)target;
         if (xmlObject == null) {
             return true;
         }

js/rhino/xmlimplsrc/org/mozilla/javascript/xmlimpl/XMLObjectImpl.java

@@ -267,7 +267,8 @@ abstract class XMLObjectImpl extends XMLObject
         if ((memberTypeFlags & Node.DESCENDANTS_FLAG) != 0) {
             xmlName.setIsDescendants();
         }
-        return Ref.pushTarget(cx, xmlName, this);
+        xmlName.initXMLObject(this);
+        return xmlName;
     }
 
     /**
@@ -285,7 +286,8 @@ abstract class XMLObjectImpl extends XMLObject
         if ((memberTypeFlags & Node.DESCENDANTS_FLAG) != 0) {
             xmlName.setIsDescendants();
         }
-        return Ref.pushTarget(cx, xmlName, this);
+        xmlName.initXMLObject(this);
+        return xmlName;
     }
 
     public NativeWith enterWith(Scriptable scope)