bug fix
[IRC.git] / Robust / src / Analysis / SSJava / DefinitelyWrittenCheck.java
index 8033efd4cac3b815566e803eb3b53cf994c047b9..2536171de0ec1049f11cba86a0988f63991ca57f 100644 (file)
@@ -8,6 +8,7 @@ import java.util.Set;
 import java.util.Stack;
 
 import Analysis.CallGraph.CallGraph;
+import Analysis.Loops.LoopFinder;
 import IR.Descriptor;
 import IR.FieldDescriptor;
 import IR.MethodDescriptor;
@@ -16,13 +17,17 @@ import IR.State;
 import IR.TypeDescriptor;
 import IR.Flat.FKind;
 import IR.Flat.FlatCall;
+import IR.Flat.FlatElementNode;
 import IR.Flat.FlatFieldNode;
 import IR.Flat.FlatLiteralNode;
 import IR.Flat.FlatMethod;
 import IR.Flat.FlatNode;
 import IR.Flat.FlatOpNode;
+import IR.Flat.FlatSetElementNode;
 import IR.Flat.FlatSetFieldNode;
 import IR.Flat.TempDescriptor;
+import IR.Tree.Modifiers;
+import Util.Pair;
 
 public class DefinitelyWrittenCheck {
 
@@ -58,6 +63,44 @@ public class DefinitelyWrittenCheck {
   // maps a flatnode to definitely written analysis mapping M
   private Hashtable<FlatNode, Hashtable<NTuple<Descriptor>, Hashtable<FlatNode, Boolean>>> definitelyWrittenResults;
 
+  // maps a method descriptor to its current summary during the analysis
+  // then analysis reaches fixed-point, this mapping will have the final summary
+  // for each method descriptor
+  private Hashtable<MethodDescriptor, ClearingSummary> mapMethodDescriptorToCompleteClearingSummary;
+
+  // maps a method descriptor to the merged incoming caller's current
+  // overwritten status
+  private Hashtable<MethodDescriptor, ClearingSummary> mapMethodDescriptorToInitialClearingSummary;
+
+  // maps a flat node to current partial results
+  private Hashtable<FlatNode, ClearingSummary> mapFlatNodeToClearingSummary;
+
+  // maps shared location to the set of descriptors which belong to the shared
+  // location
+  private Hashtable<Location, Set<Descriptor>> mapSharedLocation2DescriptorSet;
+
+  // keep current descriptors to visit in fixed-point interprocedural analysis,
+  private Stack<MethodDescriptor> methodDescriptorsToVisitStack;
+
+  // when analyzing flatcall, need to re-schedule set of callee
+  private Set<MethodDescriptor> calleesToEnqueue;
+
+  public static final String arrayElementFieldName = "___element_";
+  static protected Hashtable<TypeDescriptor, FieldDescriptor> mapTypeToArrayField;
+
+  private Set<ClearingSummary> possibleCalleeCompleteSummarySetToCaller;
+
+  private LinkedList<MethodDescriptor> sortedDescriptors;
+
+  private FlatNode ssjavaLoopEntrance;
+  private LoopFinder ssjavaLoop;
+  private Set<FlatNode> loopIncElements;
+
+  private Set<NTuple<Descriptor>> calleeUnionBoundReadSet;
+  private Set<NTuple<Descriptor>> calleeIntersectBoundOverWriteSet;
+
+  private TempDescriptor LOCAL;
+
   public DefinitelyWrittenCheck(SSJavaAnalysis ssjava, State state) {
     this.state = state;
     this.ssjava = ssjava;
@@ -69,15 +112,645 @@ public class DefinitelyWrittenCheck {
     this.mapFlatMethodToOverWrite = new Hashtable<FlatMethod, Set<NTuple<Descriptor>>>();
     this.definitelyWrittenResults =
         new Hashtable<FlatNode, Hashtable<NTuple<Descriptor>, Hashtable<FlatNode, Boolean>>>();
+    this.calleeUnionBoundReadSet = new HashSet<NTuple<Descriptor>>();
+    this.calleeIntersectBoundOverWriteSet = new HashSet<NTuple<Descriptor>>();
+
+    this.mapMethodDescriptorToCompleteClearingSummary =
+        new Hashtable<MethodDescriptor, ClearingSummary>();
+    this.mapMethodDescriptorToInitialClearingSummary =
+        new Hashtable<MethodDescriptor, ClearingSummary>();
+    this.mapSharedLocation2DescriptorSet = new Hashtable<Location, Set<Descriptor>>();
+    this.methodDescriptorsToVisitStack = new Stack<MethodDescriptor>();
+    this.calleesToEnqueue = new HashSet<MethodDescriptor>();
+    this.possibleCalleeCompleteSummarySetToCaller = new HashSet<ClearingSummary>();
+    this.mapTypeToArrayField = new Hashtable<TypeDescriptor, FieldDescriptor>();
+    this.LOCAL = new TempDescriptor("LOCAL");
   }
 
   public void definitelyWrittenCheck() {
-    methodReadOverWriteAnalysis();
-    writtenAnalyis();
+    if (!ssjava.getAnnotationRequireSet().isEmpty()) {
+      methodReadOverWriteAnalysis();
+      writtenAnalyis();
+      sharedLocationAnalysis();
+      checkSharedLocationResult();
+    }
+  }
+
+  private void checkSharedLocationResult() {
+
+    // mapping of method containing ssjava loop has the final result of
+    // shared location analysis
+    ClearingSummary result =
+        mapMethodDescriptorToCompleteClearingSummary.get(sortedDescriptors.peekFirst());
+
+
+    Set<NTuple<Descriptor>> hpKeySet = result.keySet();
+    for (Iterator iterator = hpKeySet.iterator(); iterator.hasNext();) {
+      NTuple<Descriptor> hpKey = (NTuple<Descriptor>) iterator.next();
+      SharedStatus state = result.get(hpKey);
+      Set<Location> locKeySet = state.getLocationSet();
+      for (Iterator iterator2 = locKeySet.iterator(); iterator2.hasNext();) {
+        Location locKey = (Location) iterator2.next();
+        if (!state.getFlag(locKey)) {
+          throw new Error(
+              "Some concrete locations of the shared abstract location are not cleared at the same time.");
+        }
+      }
+    }
+
+  }
+
+  private void sharedLocationAnalysis() {
+    // verify that all concrete locations of shared location are cleared out at
+    // the same time once per the out-most loop
+
+    computeReadSharedDescriptorSet();
+
+    methodDescriptorsToVisitStack.clear();
+
+    methodDescriptorsToVisitStack.add(sortedDescriptors.peekFirst());
+
+    // analyze scheduled methods until there are no more to visit
+    while (!methodDescriptorsToVisitStack.isEmpty()) {
+      MethodDescriptor md = methodDescriptorsToVisitStack.pop();
+
+      ClearingSummary completeSummary =
+          sharedLocation_analyzeMethod(md, (md.equals(methodContainingSSJavaLoop)));
+
+      ClearingSummary prevCompleteSummary = mapMethodDescriptorToCompleteClearingSummary.get(md);
+
+      if (!completeSummary.equals(prevCompleteSummary)) {
+
+        mapMethodDescriptorToCompleteClearingSummary.put(md, completeSummary);
+
+        // results for callee changed, so enqueue dependents caller for
+        // further analysis
+        Iterator<MethodDescriptor> depsItr = getDependents(md).iterator();
+        while (depsItr.hasNext()) {
+          MethodDescriptor methodNext = depsItr.next();
+          if (!methodDescriptorsToVisitStack.contains(methodNext)) {
+            methodDescriptorsToVisitStack.add(methodNext);
+          }
+        }
+
+        // if there is set of callee to be analyzed,
+        // add this set into the top of stack
+        Iterator<MethodDescriptor> calleeIter = calleesToEnqueue.iterator();
+        while (calleeIter.hasNext()) {
+          MethodDescriptor mdNext = calleeIter.next();
+          if (!methodDescriptorsToVisitStack.contains(mdNext)) {
+            methodDescriptorsToVisitStack.add(mdNext);
+          }
+        }
+        calleesToEnqueue.clear();
+
+      }
+
+    }
+
+  }
+
+  private ClearingSummary sharedLocation_analyzeMethod(MethodDescriptor md,
+      boolean onlyVisitSSJavaLoop) {
+
+    if (state.SSJAVADEBUG) {
+      System.out.println("Definitely written for shared locations Analyzing: " + md + " "
+          + onlyVisitSSJavaLoop);
+    }
+
+    FlatMethod fm = state.getMethodFlat(md);
+
+    // intraprocedural analysis
+    Set<FlatNode> flatNodesToVisit = new HashSet<FlatNode>();
+
+    // start a new mapping of partial results for each flat node
+    mapFlatNodeToClearingSummary = new Hashtable<FlatNode, ClearingSummary>();
+
+    if (onlyVisitSSJavaLoop) {
+      flatNodesToVisit.add(ssjavaLoopEntrance);
+    } else {
+      flatNodesToVisit.add(fm);
+    }
+
+    Set<FlatNode> returnNodeSet = new HashSet<FlatNode>();
+
+    while (!flatNodesToVisit.isEmpty()) {
+      FlatNode fn = flatNodesToVisit.iterator().next();
+      flatNodesToVisit.remove(fn);
+
+      ClearingSummary curr = new ClearingSummary();
+
+      Set<ClearingSummary> prevSet = new HashSet<ClearingSummary>();
+      for (int i = 0; i < fn.numPrev(); i++) {
+        FlatNode prevFn = fn.getPrev(i);
+        ClearingSummary in = mapFlatNodeToClearingSummary.get(prevFn);
+        if (in != null) {
+          prevSet.add(in);
+        }
+      }
+      mergeSharedLocationAnaylsis(curr, prevSet);
+
+      sharedLocation_nodeActions(md, fn, curr, returnNodeSet, onlyVisitSSJavaLoop);
+      ClearingSummary clearingPrev = mapFlatNodeToClearingSummary.get(fn);
+
+      if (!curr.equals(clearingPrev)) {
+        mapFlatNodeToClearingSummary.put(fn, curr);
+
+        for (int i = 0; i < fn.numNext(); i++) {
+          FlatNode nn = fn.getNext(i);
+
+          if (!onlyVisitSSJavaLoop || (onlyVisitSSJavaLoop && loopIncElements.contains(nn))) {
+            flatNodesToVisit.add(nn);
+          }
+
+        }
+      }
+
+    }
+
+    ClearingSummary completeSummary = new ClearingSummary();
+    Set<ClearingSummary> summarySet = new HashSet<ClearingSummary>();
+
+    if (onlyVisitSSJavaLoop) {
+      // when analyzing ssjava loop,
+      // complete summary is merging of all previous nodes of ssjava loop
+      // entrance
+      for (int i = 0; i < ssjavaLoopEntrance.numPrev(); i++) {
+        ClearingSummary frnSummary =
+            mapFlatNodeToClearingSummary.get(ssjavaLoopEntrance.getPrev(i));
+        if (frnSummary != null) {
+          summarySet.add(frnSummary);
+        }
+      }
+    } else {
+      // merging all exit node summary into the complete summary
+      if (!returnNodeSet.isEmpty()) {
+        for (Iterator iterator = returnNodeSet.iterator(); iterator.hasNext();) {
+          FlatNode frn = (FlatNode) iterator.next();
+          ClearingSummary frnSummary = mapFlatNodeToClearingSummary.get(frn);
+          summarySet.add(frnSummary);
+        }
+      }
+    }
+    mergeSharedLocationAnaylsis(completeSummary, summarySet);
+    return completeSummary;
+  }
+
+  private void sharedLocation_nodeActions(MethodDescriptor caller, FlatNode fn,
+      ClearingSummary curr, Set<FlatNode> returnNodeSet, boolean isSSJavaLoop) {
+
+    TempDescriptor lhs;
+    TempDescriptor rhs;
+    FieldDescriptor fld;
+    switch (fn.kind()) {
+
+    case FKind.FlatMethod: {
+      FlatMethod fm = (FlatMethod) fn;
+
+      ClearingSummary summaryFromCaller =
+          mapMethodDescriptorToInitialClearingSummary.get(fm.getMethod());
+
+      Set<ClearingSummary> inSet = new HashSet<ClearingSummary>();
+      inSet.add(summaryFromCaller);
+      mergeSharedLocationAnaylsis(curr, inSet);
+
+    }
+      break;
+
+    case FKind.FlatOpNode: {
+      FlatOpNode fon = (FlatOpNode) fn;
+      lhs = fon.getDest();
+      rhs = fon.getLeft();
+
+      if (fon.getOp().getOp() == Operation.ASSIGN) {
+        if (rhs.getType().isImmutable() && isSSJavaLoop) {
+          // in ssjavaloop, we need to take care about reading local variables!
+          NTuple<Descriptor> rhsHeapPath = new NTuple<Descriptor>();
+          NTuple<Descriptor> lhsHeapPath = new NTuple<Descriptor>();
+          rhsHeapPath.add(LOCAL);
+          lhsHeapPath.add(LOCAL);
+          if (!lhs.getSymbol().startsWith("neverused")) {
+            readLocation(curr, rhsHeapPath, rhs);
+            writeLocation(curr, lhsHeapPath, lhs);
+          }
+        }
+      }
+
+    }
+      break;
+
+    case FKind.FlatFieldNode:
+    case FKind.FlatElementNode: {
+
+      FlatFieldNode ffn = (FlatFieldNode) fn;
+      lhs = ffn.getDst();
+      rhs = ffn.getSrc();
+      fld = ffn.getField();
+
+      // read field
+      NTuple<Descriptor> srcHeapPath = mapHeapPath.get(rhs);
+      NTuple<Descriptor> fldHeapPath = new NTuple<Descriptor>(srcHeapPath.getList());
+
+      if (fld.getType().isImmutable()) {
+        readLocation(curr, fldHeapPath, fld);
+      }
+
+    }
+      break;
+
+    case FKind.FlatSetFieldNode:
+    case FKind.FlatSetElementNode: {
+
+      FlatSetFieldNode fsfn = (FlatSetFieldNode) fn;
+      lhs = fsfn.getDst();
+      fld = fsfn.getField();
+
+      // write(field)
+      NTuple<Descriptor> lhsHeapPath = computePath(lhs);
+      NTuple<Descriptor> fldHeapPath = new NTuple<Descriptor>(lhsHeapPath.getList());
+      if (fld.getType().isImmutable()) {
+        writeLocation(curr, fldHeapPath, fld);
+      } else {
+        // updates reference field case:
+        // 2. if there exists a tuple t in sharing summary that starts with
+        // hp(x) then, set flag of tuple t to 'true'
+        fldHeapPath.add(fld);
+        Set<NTuple<Descriptor>> hpKeySet = curr.keySet();
+        for (Iterator iterator = hpKeySet.iterator(); iterator.hasNext();) {
+          NTuple<Descriptor> hpKey = (NTuple<Descriptor>) iterator.next();
+          if (hpKey.startsWith(fldHeapPath)) {
+            curr.get(hpKey).updateFlag(true);
+          }
+        }
+      }
+
+    }
+      break;
+
+    case FKind.FlatCall: {
+
+      FlatCall fc = (FlatCall) fn;
+
+      // find out the set of callees
+      MethodDescriptor mdCallee = fc.getMethod();
+      FlatMethod fmCallee = state.getMethodFlat(mdCallee);
+      Set<MethodDescriptor> setPossibleCallees = new HashSet<MethodDescriptor>();
+      TypeDescriptor typeDesc = fc.getThis().getType();
+      setPossibleCallees.addAll(callGraph.getMethods(mdCallee, typeDesc));
+
+      possibleCalleeCompleteSummarySetToCaller.clear();
+
+      for (Iterator iterator = setPossibleCallees.iterator(); iterator.hasNext();) {
+        MethodDescriptor mdPossibleCallee = (MethodDescriptor) iterator.next();
+        FlatMethod calleeFlatMethod = state.getMethodFlat(mdPossibleCallee);
+
+        addDependent(mdPossibleCallee, // callee
+            caller); // caller
+
+        calleesToEnqueue.add(mdPossibleCallee);
+
+        // updates possible callee's initial summary using caller's current
+        // writing status
+        ClearingSummary prevCalleeInitSummary =
+            mapMethodDescriptorToInitialClearingSummary.get(mdPossibleCallee);
+
+        ClearingSummary calleeInitSummary =
+            bindHeapPathOfCalleeCallerEffects(fc, calleeFlatMethod, curr);
+
+        // if changes, update the init summary
+        // and reschedule the callee for analysis
+        if (!calleeInitSummary.equals(prevCalleeInitSummary)) {
+
+          if (!methodDescriptorsToVisitStack.contains(mdPossibleCallee)) {
+            methodDescriptorsToVisitStack.add(mdPossibleCallee);
+          }
+          mapMethodDescriptorToInitialClearingSummary.put(mdPossibleCallee, calleeInitSummary);
+        }
+
+      }
+
+      // contribute callee's writing effects to the caller
+      mergeSharedLocationAnaylsis(curr, possibleCalleeCompleteSummarySetToCaller);
+
+    }
+      break;
+
+    case FKind.FlatReturnNode: {
+      returnNodeSet.add(fn);
+    }
+      break;
+
+    }
+
+  }
+
+  private ClearingSummary bindHeapPathOfCalleeCallerEffects(FlatCall fc,
+      FlatMethod calleeFlatMethod, ClearingSummary curr) {
+
+    ClearingSummary boundSet = new ClearingSummary();
+
+    // create mapping from arg idx to its heap paths
+    Hashtable<Integer, NTuple<Descriptor>> mapArgIdx2CallerArgHeapPath =
+        new Hashtable<Integer, NTuple<Descriptor>>();
+
+    // arg idx is starting from 'this' arg
+    NTuple<Descriptor> thisHeapPath = mapHeapPath.get(fc.getThis());
+    if (thisHeapPath == null) {
+      // method is called without creating new flat node representing 'this'
+      thisHeapPath = new NTuple<Descriptor>();
+      thisHeapPath.add(fc.getThis());
+    }
+
+    mapArgIdx2CallerArgHeapPath.put(Integer.valueOf(0), thisHeapPath);
+
+    for (int i = 0; i < fc.numArgs(); i++) {
+      TempDescriptor arg = fc.getArg(i);
+      NTuple<Descriptor> argHeapPath = computePath(arg);
+      mapArgIdx2CallerArgHeapPath.put(Integer.valueOf(i + 1), argHeapPath);
+    }
+
+    Hashtable<Integer, TempDescriptor> mapParamIdx2ParamTempDesc =
+        new Hashtable<Integer, TempDescriptor>();
+    for (int i = 0; i < calleeFlatMethod.numParameters(); i++) {
+      TempDescriptor param = calleeFlatMethod.getParameter(i);
+      mapParamIdx2ParamTempDesc.put(Integer.valueOf(i), param);
+    }
+
+    // binding caller's writing effects to callee's params
+    for (int i = 0; i < calleeFlatMethod.numParameters(); i++) {
+      NTuple<Descriptor> argHeapPath = mapArgIdx2CallerArgHeapPath.get(Integer.valueOf(i));
+      TempDescriptor calleeParamHeapPath = mapParamIdx2ParamTempDesc.get(Integer.valueOf(i));
+
+      // iterate over caller's writing effect set
+      Set<NTuple<Descriptor>> hpKeySet = curr.keySet();
+      for (Iterator iterator = hpKeySet.iterator(); iterator.hasNext();) {
+        NTuple<Descriptor> hpKey = (NTuple<Descriptor>) iterator.next();
+        // current element is reachable caller's arg
+        // so need to bind it to the caller's side and add it to the callee's
+        // init summary
+        if (hpKey.startsWith(argHeapPath)) {
+          NTuple<Descriptor> boundHeapPath = replace(hpKey, argHeapPath, calleeParamHeapPath);
+          boundSet.put(boundHeapPath, curr.get(hpKey).clone());
+        }
+
+      }
+
+    }
+
+    // contribute callee's complete summary into the caller's current summary
+    ClearingSummary calleeCompleteSummary =
+        mapMethodDescriptorToCompleteClearingSummary.get(calleeFlatMethod.getMethod());
+
+    if (calleeCompleteSummary != null) {
+      ClearingSummary boundCalleeEfffects = new ClearingSummary();
+      for (int i = 0; i < calleeFlatMethod.numParameters(); i++) {
+        NTuple<Descriptor> argHeapPath = mapArgIdx2CallerArgHeapPath.get(Integer.valueOf(i));
+        TempDescriptor calleeParamHeapPath = mapParamIdx2ParamTempDesc.get(Integer.valueOf(i));
+
+        // iterate over callee's writing effect set
+        Set<NTuple<Descriptor>> hpKeySet = calleeCompleteSummary.keySet();
+        for (Iterator iterator = hpKeySet.iterator(); iterator.hasNext();) {
+          NTuple<Descriptor> hpKey = (NTuple<Descriptor>) iterator.next();
+          // current element is reachable caller's arg
+          // so need to bind it to the caller's side and add it to the callee's
+          // init summary
+          if (hpKey.startsWith(calleeParamHeapPath)) {
+
+            NTuple<Descriptor> boundHeapPathForCaller = replace(hpKey, argHeapPath);
+
+            boundCalleeEfffects.put(boundHeapPathForCaller, calleeCompleteSummary.get(hpKey)
+                .clone());
+
+          }
+        }
+      }
+      possibleCalleeCompleteSummarySetToCaller.add(boundCalleeEfffects);
+    }
+
+    return boundSet;
+  }
+
+  private NTuple<Descriptor> replace(NTuple<Descriptor> hpKey, NTuple<Descriptor> argHeapPath) {
+
+    // replace the head of heap path with caller's arg path
+    // for example, heap path 'param.a.b' in callee's side will be replaced with
+    // (corresponding arg heap path).a.b for caller's side
+
+    NTuple<Descriptor> bound = new NTuple<Descriptor>();
+
+    for (int i = 0; i < argHeapPath.size(); i++) {
+      bound.add(argHeapPath.get(i));
+    }
+
+    for (int i = 1; i < hpKey.size(); i++) {
+      bound.add(hpKey.get(i));
+    }
+
+    return bound;
+  }
+
+  private NTuple<Descriptor> replace(NTuple<Descriptor> effectHeapPath,
+      NTuple<Descriptor> argHeapPath, TempDescriptor calleeParamHeapPath) {
+    // replace the head of caller's heap path with callee's param heap path
+
+    NTuple<Descriptor> boundHeapPath = new NTuple<Descriptor>();
+    boundHeapPath.add(calleeParamHeapPath);
+
+    for (int i = argHeapPath.size(); i < effectHeapPath.size(); i++) {
+      boundHeapPath.add(effectHeapPath.get(i));
+    }
+
+    return boundHeapPath;
+  }
+
+  private void computeReadSharedDescriptorSet() {
+    Set<MethodDescriptor> methodDescriptorsToAnalyze = new HashSet<MethodDescriptor>();
+    methodDescriptorsToAnalyze.addAll(ssjava.getAnnotationRequireSet());
+
+    for (Iterator iterator = methodDescriptorsToAnalyze.iterator(); iterator.hasNext();) {
+      MethodDescriptor md = (MethodDescriptor) iterator.next();
+      FlatMethod fm = state.getMethodFlat(md);
+      computeReadSharedDescriptorSet_analyzeMethod(fm, md.equals(methodContainingSSJavaLoop));
+    }
+
+  }
+
+  private void computeReadSharedDescriptorSet_analyzeMethod(FlatMethod fm,
+      boolean onlyVisitSSJavaLoop) {
+
+    Set<FlatNode> flatNodesToVisit = new HashSet<FlatNode>();
+    Set<FlatNode> visited = new HashSet<FlatNode>();
+
+    if (onlyVisitSSJavaLoop) {
+      flatNodesToVisit.add(ssjavaLoopEntrance);
+    } else {
+      flatNodesToVisit.add(fm);
+    }
+
+    while (!flatNodesToVisit.isEmpty()) {
+      FlatNode fn = flatNodesToVisit.iterator().next();
+      flatNodesToVisit.remove(fn);
+      visited.add(fn);
+
+      computeReadSharedDescriptorSet_nodeActions(fn, onlyVisitSSJavaLoop);
+
+      for (int i = 0; i < fn.numNext(); i++) {
+        FlatNode nn = fn.getNext(i);
+        if (!visited.contains(nn)) {
+          if (!onlyVisitSSJavaLoop || (onlyVisitSSJavaLoop && loopIncElements.contains(nn))) {
+            flatNodesToVisit.add(nn);
+          }
+        }
+      }
+
+    }
+
+  }
+
+  private void computeReadSharedDescriptorSet_nodeActions(FlatNode fn, boolean isSSJavaLoop) {
+
+    TempDescriptor lhs;
+    TempDescriptor rhs;
+    FieldDescriptor fld;
+
+    switch (fn.kind()) {
+    case FKind.FlatOpNode: {
+      FlatOpNode fon = (FlatOpNode) fn;
+      lhs = fon.getDest();
+      rhs = fon.getLeft();
+
+      if (fon.getOp().getOp() == Operation.ASSIGN) {
+        if (rhs.getType().isImmutable() && isSSJavaLoop && (!rhs.getSymbol().startsWith("srctmp"))) {
+          // in ssjavaloop, we need to take care about reading local variables!
+          NTuple<Descriptor> rhsHeapPath = new NTuple<Descriptor>();
+          NTuple<Descriptor> lhsHeapPath = new NTuple<Descriptor>();
+          rhsHeapPath.add(LOCAL);
+          addReadDescriptor(rhsHeapPath, rhs);
+        }
+      }
+
+    }
+      break;
+
+    case FKind.FlatFieldNode:
+    case FKind.FlatElementNode: {
+
+      FlatFieldNode ffn = (FlatFieldNode) fn;
+      lhs = ffn.getDst();
+      rhs = ffn.getSrc();
+      fld = ffn.getField();
+
+      // read field
+      NTuple<Descriptor> srcHeapPath = mapHeapPath.get(rhs);
+      NTuple<Descriptor> fldHeapPath = new NTuple<Descriptor>(srcHeapPath.getList());
+      // fldHeapPath.add(fld);
+
+      if (fld.getType().isImmutable()) {
+        addReadDescriptor(fldHeapPath, fld);
+      }
+
+      // propagate rhs's heap path to the lhs
+      mapHeapPath.put(lhs, fldHeapPath);
+
+    }
+      break;
+
+    case FKind.FlatSetFieldNode:
+    case FKind.FlatSetElementNode: {
+
+      FlatSetFieldNode fsfn = (FlatSetFieldNode) fn;
+      lhs = fsfn.getDst();
+      fld = fsfn.getField();
+
+      // write(field)
+      NTuple<Descriptor> lhsHeapPath = computePath(lhs);
+      NTuple<Descriptor> fldHeapPath = new NTuple<Descriptor>(lhsHeapPath.getList());
+      // writeLocation(curr, fldHeapPath, fld, getLocation(fld));
+
+    }
+      break;
+
+    }
+  }
+
+  private boolean hasReadingEffectOnSharedLocation(NTuple<Descriptor> hp, Location loc, Descriptor d) {
+    if (!mapSharedLocation2DescriptorSet.containsKey(loc)) {
+      return false;
+    } else {
+      return mapSharedLocation2DescriptorSet.get(loc).contains(d);
+    }
+  }
+
+  private void addReadDescriptor(NTuple<Descriptor> hp, Descriptor d) {
+
+    Location loc = getLocation(d);
+
+    if (loc != null && ssjava.isSharedLocation(loc)) {
+
+      Set<Descriptor> set = mapSharedLocation2DescriptorSet.get(loc);
+      if (set == null) {
+        set = new HashSet<Descriptor>();
+        mapSharedLocation2DescriptorSet.put(loc, set);
+      }
+      set.add(d);
+    }
+
+  }
+
+  private Location getLocation(Descriptor d) {
+
+    if (d instanceof FieldDescriptor) {
+      return (Location) ((FieldDescriptor) d).getType().getExtension();
+    } else {
+      assert d instanceof TempDescriptor;
+      CompositeLocation comp = (CompositeLocation) ((TempDescriptor) d).getType().getExtension();
+      if (comp == null) {
+        return null;
+      } else {
+        return comp.get(comp.getSize() - 1);
+      }
+    }
+
+  }
+
+  private void writeLocation(ClearingSummary curr, NTuple<Descriptor> hp, Descriptor d) {
+    Location loc = getLocation(d);
+    if (loc != null && hasReadingEffectOnSharedLocation(hp, loc, d)) {
+
+      // 1. add field x to the clearing set
+      SharedStatus state = getState(curr, hp);
+      state.addVar(loc, d);
+
+      // 3. if the set v contains all of variables belonging to the shared
+      // location, set flag to true
+      Set<Descriptor> sharedVarSet = mapSharedLocation2DescriptorSet.get(loc);
+      if (state.getVarSet(loc).containsAll(sharedVarSet)) {
+        state.updateFlag(loc, true);
+      }
+    }
+  }
+
+  private void readLocation(ClearingSummary curr, NTuple<Descriptor> hp, Descriptor d) {
+    // remove reading var x from written set
+    Location loc = getLocation(d);
+    if (loc != null && hasReadingEffectOnSharedLocation(hp, loc, d)) {
+      SharedStatus state = getState(curr, hp);
+      state.removeVar(loc, d);
+    }
+  }
+
+  private SharedStatus getState(ClearingSummary curr, NTuple<Descriptor> hp) {
+    SharedStatus state = curr.get(hp);
+    if (state == null) {
+      state = new SharedStatus();
+      curr.put(hp, state);
+    }
+    return state;
   }
 
   private void writtenAnalyis() {
-    // perform second stage analysis: intraprocedural analysis ensure that all
+    // perform second stage analysis: intraprocedural analysis ensure that
+    // all
     // variables are definitely written in-between the same read
 
     // First, identify ssjava loop entrace
@@ -85,7 +758,7 @@ public class DefinitelyWrittenCheck {
     Set<FlatNode> flatNodesToVisit = new HashSet<FlatNode>();
     flatNodesToVisit.add(fm);
 
-    FlatNode entrance = null;
+    LoopFinder loopFinder = new LoopFinder(fm);
 
     while (!flatNodesToVisit.isEmpty()) {
       FlatNode fn = flatNodesToVisit.iterator().next();
@@ -95,7 +768,7 @@ public class DefinitelyWrittenCheck {
       if (label != null) {
 
         if (label.equals(ssjava.SSJAVA)) {
-          entrance = fn;
+          ssjavaLoopEntrance = fn;
           break;
         }
       }
@@ -106,16 +779,29 @@ public class DefinitelyWrittenCheck {
       }
     }
 
-    assert entrance != null;
+    assert ssjavaLoopEntrance != null;
+
+    // assume that ssjava loop is top-level loop in method, not nested loop
+    Set nestedLoop = loopFinder.nestedLoops();
+    for (Iterator loopIter = nestedLoop.iterator(); loopIter.hasNext();) {
+      LoopFinder lf = (LoopFinder) loopIter.next();
+      if (lf.loopEntrances().iterator().next().equals(ssjavaLoopEntrance)) {
+        ssjavaLoop = lf;
+      }
+    }
+
+    assert ssjavaLoop != null;
 
-    writtenAnalysis_analyzeLoop(entrance);
+    writtenAnalysis_analyzeLoop();
 
   }
 
-  private void writtenAnalysis_analyzeLoop(FlatNode entrance) {
+  private void writtenAnalysis_analyzeLoop() {
 
     Set<FlatNode> flatNodesToVisit = new HashSet<FlatNode>();
-    flatNodesToVisit.add(entrance);
+    flatNodesToVisit.add(ssjavaLoopEntrance);
+
+    loopIncElements = (Set<FlatNode>) ssjavaLoop.loopIncElements();
 
     while (!flatNodesToVisit.isEmpty()) {
       FlatNode fn = (FlatNode) flatNodesToVisit.iterator().next();
@@ -135,8 +821,7 @@ public class DefinitelyWrittenCheck {
         }
       }
 
-      writtenAnalysis_nodeAction(fn, curr, entrance);
-      // definitelyWritten_nodeActions(fn, curr, entrance);
+      writtenAnalysis_nodeAction(fn, curr, ssjavaLoopEntrance);
 
       // if a new result, schedule forward nodes for analysis
       if (!curr.equals(prev)) {
@@ -144,7 +829,10 @@ public class DefinitelyWrittenCheck {
 
         for (int i = 0; i < fn.numNext(); i++) {
           FlatNode nn = fn.getNext(i);
-          flatNodesToVisit.add(nn);
+          if (loopIncElements.contains(nn)) {
+            flatNodesToVisit.add(nn);
+          }
+
         }
       }
     }
@@ -152,6 +840,7 @@ public class DefinitelyWrittenCheck {
 
   private void writtenAnalysis_nodeAction(FlatNode fn,
       Hashtable<NTuple<Descriptor>, Hashtable<FlatNode, Boolean>> curr, FlatNode loopEntrance) {
+
     if (fn.equals(loopEntrance)) {
       // it reaches loop entrance: changes all flag to true
       Set<NTuple<Descriptor>> keySet = curr.keySet();
@@ -177,33 +866,18 @@ public class DefinitelyWrittenCheck {
         lhs = fon.getDest();
         rhs = fon.getLeft();
 
-
         NTuple<Descriptor> rhsHeapPath = computePath(rhs);
         if (!rhs.getType().isImmutable()) {
           mapHeapPath.put(lhs, rhsHeapPath);
-        }
-
-        if (fon.getOp().getOp() == Operation.ASSIGN) {
-          // read(rhs)
-          Hashtable<FlatNode, Boolean> gen = curr.get(rhsHeapPath);
-
-          if (gen == null) {
-            gen = new Hashtable<FlatNode, Boolean>();
-            curr.put(rhsHeapPath, gen);
-          }
-          Boolean currentStatus = gen.get(fn);
-          if (currentStatus == null) {
-            gen.put(fn, Boolean.FALSE);
-          } else {
-            if (!rhs.getType().isClass()) {
-              checkFlag(currentStatus.booleanValue(), fn);
-            }
+        } else {
+          if (fon.getOp().getOp() == Operation.ASSIGN) {
+            // read(rhs)
+            readValue(fn, rhsHeapPath, curr);
           }
-
+          // write(lhs)
+          NTuple<Descriptor> lhsHeapPath = computePath(lhs);
+          removeHeapPath(curr, lhsHeapPath);
         }
-        // write(lhs)
-        NTuple<Descriptor> lhsHeapPath = computePath(lhs);
-        curr.put(lhsHeapPath, new Hashtable<FlatNode, Boolean>());
       }
         break;
 
@@ -213,8 +887,7 @@ public class DefinitelyWrittenCheck {
 
         // write(lhs)
         NTuple<Descriptor> lhsHeapPath = computePath(lhs);
-        curr.put(lhsHeapPath, new Hashtable<FlatNode, Boolean>());
-
+        removeHeapPath(curr, lhsHeapPath);
 
       }
         break;
@@ -222,28 +895,35 @@ public class DefinitelyWrittenCheck {
       case FKind.FlatFieldNode:
       case FKind.FlatElementNode: {
 
-        FlatFieldNode ffn = (FlatFieldNode) fn;
-        lhs = ffn.getSrc();
-        fld = ffn.getField();
+        if (fn.kind() == FKind.FlatFieldNode) {
+          FlatFieldNode ffn = (FlatFieldNode) fn;
+          lhs = ffn.getDst();
+          rhs = ffn.getSrc();
+          fld = ffn.getField();
+        } else {
+          FlatElementNode fen = (FlatElementNode) fn;
+          lhs = fen.getDst();
+          rhs = fen.getSrc();
+          TypeDescriptor td = rhs.getType().dereference();
+          fld = getArrayField(td);
+        }
+
+        if (fld.isFinal() /* && fld.isStatic() */) {
+          // if field is final and static, no need to check
+          break;
+        }
 
         // read field
-        NTuple<Descriptor> srcHeapPath = mapHeapPath.get(lhs);
+        NTuple<Descriptor> srcHeapPath = mapHeapPath.get(rhs);
         NTuple<Descriptor> fldHeapPath = new NTuple<Descriptor>(srcHeapPath.getList());
         fldHeapPath.add(fld);
-        Hashtable<FlatNode, Boolean> gen = curr.get(fldHeapPath);
 
-        if (gen == null) {
-          gen = new Hashtable<FlatNode, Boolean>();
-          curr.put(fldHeapPath, gen);
-        }
-
-        Boolean currentStatus = gen.get(fn);
-        if (currentStatus == null) {
-          gen.put(fn, Boolean.FALSE);
-        } else {
-          checkFlag(currentStatus.booleanValue(), fn);
+        if (fld.getType().isImmutable()) {
+          readValue(fn, fldHeapPath, curr);
         }
 
+        // propagate rhs's heap path to the lhs
+        mapHeapPath.put(lhs, fldHeapPath);
 
       }
         break;
@@ -251,92 +931,37 @@ public class DefinitelyWrittenCheck {
       case FKind.FlatSetFieldNode:
       case FKind.FlatSetElementNode: {
 
-        FlatSetFieldNode fsfn = (FlatSetFieldNode) fn;
-        lhs = fsfn.getDst();
-        fld = fsfn.getField();
+        if (fn.kind() == FKind.FlatSetFieldNode) {
+          FlatSetFieldNode fsfn = (FlatSetFieldNode) fn;
+          lhs = fsfn.getDst();
+          fld = fsfn.getField();
+        } else {
+          FlatSetElementNode fsen = (FlatSetElementNode) fn;
+          lhs = fsen.getDst();
+          rhs = fsen.getSrc();
+          TypeDescriptor td = lhs.getType().dereference();
+          fld = getArrayField(td);
+        }
 
         // write(field)
-        NTuple<Descriptor> lhsHeapPath = mapHeapPath.get(lhs);
+        NTuple<Descriptor> lhsHeapPath = computePath(lhs);
         NTuple<Descriptor> fldHeapPath = new NTuple<Descriptor>(lhsHeapPath.getList());
         fldHeapPath.add(fld);
-        curr.put(fldHeapPath, new Hashtable<FlatNode, Boolean>());
-
+        removeHeapPath(curr, fldHeapPath);
 
       }
         break;
 
       case FKind.FlatCall: {
-
         FlatCall fc = (FlatCall) fn;
-
-        // compute all possible callee set
-        // transform all READ/OVERWRITE set from the any possible callees to the
-        // caller
-        MethodDescriptor mdCallee = fc.getMethod();
-        FlatMethod fmCallee = state.getMethodFlat(mdCallee);
-        Set<MethodDescriptor> setPossibleCallees = new HashSet<MethodDescriptor>();
-        TypeDescriptor typeDesc = fc.getThis().getType();
-        setPossibleCallees.addAll(callGraph.getMethods(mdCallee, typeDesc));
-
-        // create mapping from arg idx to its heap paths
-        Hashtable<Integer, NTuple<Descriptor>> mapArgIdx2CallerArgHeapPath =
-            new Hashtable<Integer, NTuple<Descriptor>>();
-
-        // arg idx is starting from 'this' arg
-        NTuple<Descriptor> thisHeapPath = new NTuple<Descriptor>();
-        thisHeapPath.add(fc.getThis());
-        mapArgIdx2CallerArgHeapPath.put(Integer.valueOf(0), thisHeapPath);
-
-        for (int i = 0; i < fc.numArgs(); i++) {
-          TempDescriptor arg = fc.getArg(i);
-          NTuple<Descriptor> argHeapPath = computePath(arg);
-          mapArgIdx2CallerArgHeapPath.put(Integer.valueOf(i + 1), argHeapPath);
-        }
-
-        Set<NTuple<Descriptor>> calleeUnionBoundReadSet = new HashSet<NTuple<Descriptor>>();
-        Set<NTuple<Descriptor>> calleeIntersectBoundOverWriteSet =
-            new HashSet<NTuple<Descriptor>>();
-
-        for (Iterator iterator = setPossibleCallees.iterator(); iterator.hasNext();) {
-          MethodDescriptor callee = (MethodDescriptor) iterator.next();
-          FlatMethod calleeFlatMethod = state.getMethodFlat(callee);
-
-          // binding caller's args and callee's params
-          Set<NTuple<Descriptor>> calleeReadSet = mapFlatMethodToRead.get(calleeFlatMethod);
-          if (calleeReadSet == null) {
-            calleeReadSet = new HashSet<NTuple<Descriptor>>();
-            mapFlatMethodToRead.put(calleeFlatMethod, calleeReadSet);
-          }
-          Set<NTuple<Descriptor>> calleeOverWriteSet =
-              mapFlatMethodToOverWrite.get(calleeFlatMethod);
-          if (calleeOverWriteSet == null) {
-            calleeOverWriteSet = new HashSet<NTuple<Descriptor>>();
-            mapFlatMethodToOverWrite.put(calleeFlatMethod, calleeOverWriteSet);
-          }
-
-          Hashtable<Integer, TempDescriptor> mapParamIdx2ParamTempDesc =
-              new Hashtable<Integer, TempDescriptor>();
-          for (int i = 0; i < calleeFlatMethod.numParameters(); i++) {
-            TempDescriptor param = calleeFlatMethod.getParameter(i);
-            mapParamIdx2ParamTempDesc.put(Integer.valueOf(i), param);
-          }
-
-          Set<NTuple<Descriptor>> calleeBoundReadSet =
-              bindSet(calleeReadSet, mapParamIdx2ParamTempDesc, mapArgIdx2CallerArgHeapPath);
-          // union of the current read set and the current callee's read set
-          calleeUnionBoundReadSet.addAll(calleeBoundReadSet);
-          Set<NTuple<Descriptor>> calleeBoundWriteSet =
-              bindSet(calleeOverWriteSet, mapParamIdx2ParamTempDesc, mapArgIdx2CallerArgHeapPath);
-          // intersection of the current overwrite set and the current callee's
-          // overwrite set
-          merge(calleeIntersectBoundOverWriteSet, calleeBoundWriteSet);
-        }
-
-        // add <hp,statement,false> in which hp is an element of READ_bound set
+        bindHeapPathCallerArgWithCaleeParam(fc);
+        // add <hp,statement,false> in which hp is an element of
+        // READ_bound set
         // of callee: callee has 'read' requirement!
+
+        
         for (Iterator iterator = calleeUnionBoundReadSet.iterator(); iterator.hasNext();) {
           NTuple<Descriptor> read = (NTuple<Descriptor>) iterator.next();
-
           Hashtable<FlatNode, Boolean> gen = curr.get(read);
           if (gen == null) {
             gen = new Hashtable<FlatNode, Boolean>();
@@ -346,29 +971,137 @@ public class DefinitelyWrittenCheck {
           if (currentStatus == null) {
             gen.put(fn, Boolean.FALSE);
           } else {
-            checkFlag(currentStatus.booleanValue(), fn);
+            checkFlag(currentStatus.booleanValue(), fn, read);
           }
         }
 
-        // removes <hp,statement,flag> if hp is an element of OVERWRITE_bound
+        // removes <hp,statement,flag> if hp is an element of
+        // OVERWRITE_bound
         // set of callee. it means that callee will overwrite it
         for (Iterator iterator = calleeIntersectBoundOverWriteSet.iterator(); iterator.hasNext();) {
           NTuple<Descriptor> write = (NTuple<Descriptor>) iterator.next();
-          curr.put(write, new Hashtable<FlatNode, Boolean>());
+          removeHeapPath(curr, write);
         }
       }
         break;
 
       }
+    }
+
+  }
+
+  private void readValue(FlatNode fn, NTuple<Descriptor> hp,
+      Hashtable<NTuple<Descriptor>, Hashtable<FlatNode, Boolean>> curr) {
+    Hashtable<FlatNode, Boolean> gen = curr.get(hp);
+    if (gen == null) {
+      gen = new Hashtable<FlatNode, Boolean>();
+      curr.put(hp, gen);
+    }
+    Boolean currentStatus = gen.get(fn);
+    if (currentStatus == null) {
+      gen.put(fn, Boolean.FALSE);
+    } else {
+      checkFlag(currentStatus.booleanValue(), fn, hp);
+    }
+
+  }
+
+  private void removeHeapPath(Hashtable<NTuple<Descriptor>, Hashtable<FlatNode, Boolean>> curr,
+      NTuple<Descriptor> hp) {
 
+    // removes all of heap path that starts with prefix 'hp'
+    // since any reference overwrite along heap path gives overwriting side
+    // effects on the value
+
+    Set<NTuple<Descriptor>> keySet = curr.keySet();
+    for (Iterator<NTuple<Descriptor>> iter = keySet.iterator(); iter.hasNext();) {
+      NTuple<Descriptor> key = iter.next();
+      if (key.startsWith(hp)) {
+        curr.put(key, new Hashtable<FlatNode, Boolean>());
+      }
     }
 
   }
 
-  private void checkFlag(boolean booleanValue, FlatNode fn) {
+  private void bindHeapPathCallerArgWithCaleeParam(FlatCall fc) {
+    // compute all possible callee set
+    // transform all READ/OVERWRITE set from the any possible
+    // callees to the
+    // caller
+    calleeUnionBoundReadSet.clear();
+    calleeIntersectBoundOverWriteSet.clear();
+
+    MethodDescriptor mdCallee = fc.getMethod();
+    FlatMethod fmCallee = state.getMethodFlat(mdCallee);
+    Set<MethodDescriptor> setPossibleCallees = new HashSet<MethodDescriptor>();
+    TypeDescriptor typeDesc = fc.getThis().getType();
+    setPossibleCallees.addAll(callGraph.getMethods(mdCallee, typeDesc));
+
+    // create mapping from arg idx to its heap paths
+    Hashtable<Integer, NTuple<Descriptor>> mapArgIdx2CallerArgHeapPath =
+        new Hashtable<Integer, NTuple<Descriptor>>();
+
+    // arg idx is starting from 'this' arg
+    NTuple<Descriptor> thisHeapPath = mapHeapPath.get(fc.getThis());
+    if (thisHeapPath == null) {
+      // method is called without creating new flat node representing 'this'
+      thisHeapPath = new NTuple<Descriptor>();
+      thisHeapPath.add(fc.getThis());
+    }
+
+    mapArgIdx2CallerArgHeapPath.put(Integer.valueOf(0), thisHeapPath);
+
+    for (int i = 0; i < fc.numArgs(); i++) {
+      TempDescriptor arg = fc.getArg(i);
+      NTuple<Descriptor> argHeapPath = computePath(arg);
+      mapArgIdx2CallerArgHeapPath.put(Integer.valueOf(i + 1), argHeapPath);
+    }
+
+    for (Iterator iterator = setPossibleCallees.iterator(); iterator.hasNext();) {
+      MethodDescriptor callee = (MethodDescriptor) iterator.next();
+      FlatMethod calleeFlatMethod = state.getMethodFlat(callee);
+
+      // binding caller's args and callee's params
+
+      Set<NTuple<Descriptor>> calleeReadSet = mapFlatMethodToRead.get(calleeFlatMethod);
+      if (calleeReadSet == null) {
+        calleeReadSet = new HashSet<NTuple<Descriptor>>();
+        mapFlatMethodToRead.put(calleeFlatMethod, calleeReadSet);
+      }
+      Set<NTuple<Descriptor>> calleeOverWriteSet = mapFlatMethodToOverWrite.get(calleeFlatMethod);
+      if (calleeOverWriteSet == null) {
+        calleeOverWriteSet = new HashSet<NTuple<Descriptor>>();
+        mapFlatMethodToOverWrite.put(calleeFlatMethod, calleeOverWriteSet);
+      }
+
+      Hashtable<Integer, TempDescriptor> mapParamIdx2ParamTempDesc =
+          new Hashtable<Integer, TempDescriptor>();
+      for (int i = 0; i < calleeFlatMethod.numParameters(); i++) {
+        TempDescriptor param = calleeFlatMethod.getParameter(i);
+        mapParamIdx2ParamTempDesc.put(Integer.valueOf(i), param);
+      }
+
+      Set<NTuple<Descriptor>> calleeBoundReadSet =
+          bindSet(calleeReadSet, mapParamIdx2ParamTempDesc, mapArgIdx2CallerArgHeapPath);
+      // union of the current read set and the current callee's
+      // read set
+      calleeUnionBoundReadSet.addAll(calleeBoundReadSet);
+      Set<NTuple<Descriptor>> calleeBoundWriteSet =
+          bindSet(calleeOverWriteSet, mapParamIdx2ParamTempDesc, mapArgIdx2CallerArgHeapPath);
+      // intersection of the current overwrite set and the current
+      // callee's
+      // overwrite set
+      merge(calleeIntersectBoundOverWriteSet, calleeBoundWriteSet);
+    }
+
+  }
+
+  private void checkFlag(boolean booleanValue, FlatNode fn, NTuple<Descriptor> hp) {
     if (booleanValue) {
       throw new Error(
-          "There is a variable who comes back to the same read statement at the out-most iteration at "
+          "There is a variable, which is reachable through references "
+              + hp
+              + ", who comes back to the same read statement without being overwritten at the out-most iteration at "
               + methodContainingSSJavaLoop.getClassDesc().getSourceFileName() + "::"
               + fn.getNumLine());
     }
@@ -411,21 +1144,25 @@ public class DefinitelyWrittenCheck {
     Set<MethodDescriptor> methodDescriptorsToAnalyze = new HashSet<MethodDescriptor>();
     methodDescriptorsToAnalyze.addAll(ssjava.getAnnotationRequireSet());
 
-    LinkedList<MethodDescriptor> sortedDescriptors = topologicalSort(methodDescriptorsToAnalyze);
+    sortedDescriptors = topologicalSort(methodDescriptorsToAnalyze);
+
+    LinkedList<MethodDescriptor> descriptorListToAnalyze =
+        (LinkedList<MethodDescriptor>) sortedDescriptors.clone();
 
     // no need to analyze method having ssjava loop
-    methodContainingSSJavaLoop = sortedDescriptors.removeFirst();
+    // methodContainingSSJavaLoop = descriptorListToAnalyze.removeFirst();
+    methodContainingSSJavaLoop = ssjava.getMethodContainingSSJavaLoop();
 
     // current descriptors to visit in fixed-point interprocedural analysis,
     // prioritized by
     // dependency in the call graph
-    Stack<MethodDescriptor> methodDescriptorsToVisitStack = new Stack<MethodDescriptor>();
+    methodDescriptorsToVisitStack.clear();
 
     Set<MethodDescriptor> methodDescriptorToVistSet = new HashSet<MethodDescriptor>();
-    methodDescriptorToVistSet.addAll(sortedDescriptors);
+    methodDescriptorToVistSet.addAll(descriptorListToAnalyze);
 
-    while (!sortedDescriptors.isEmpty()) {
-      MethodDescriptor md = sortedDescriptors.removeFirst();
+    while (!descriptorListToAnalyze.isEmpty()) {
+      MethodDescriptor md = descriptorListToAnalyze.removeFirst();
       methodDescriptorsToVisitStack.add(md);
     }
 
@@ -447,7 +1184,8 @@ public class DefinitelyWrittenCheck {
         mapFlatMethodToRead.put(fm, readSet);
         mapFlatMethodToOverWrite.put(fm, overWriteSet);
 
-        // results for callee changed, so enqueue dependents caller for further
+        // results for callee changed, so enqueue dependents caller for
+        // further
         // analysis
         Iterator<MethodDescriptor> depsItr = getDependents(md).iterator();
         while (depsItr.hasNext()) {
@@ -491,11 +1229,13 @@ public class DefinitelyWrittenCheck {
 
       methodReadOverWrite_nodeActions(fn, curr, readSet, overWriteSet);
 
-      mapFlatNodeToWrittenSet.put(fn, curr);
-
-      for (int i = 0; i < fn.numNext(); i++) {
-        FlatNode nn = fn.getNext(i);
-        flatNodesToVisit.add(nn);
+      Set<NTuple<Descriptor>> writtenSetPrev = mapFlatNodeToWrittenSet.get(fn);
+      if (!curr.equals(writtenSetPrev)) {
+        mapFlatNodeToWrittenSet.put(fn, curr);
+        for (int i = 0; i < fn.numNext(); i++) {
+          FlatNode nn = fn.getNext(i);
+          flatNodesToVisit.add(nn);
+        }
       }
 
     }
@@ -524,7 +1264,8 @@ public class DefinitelyWrittenCheck {
 
     case FKind.FlatOpNode: {
       FlatOpNode fon = (FlatOpNode) fn;
-      // for a normal assign node, need to propagate lhs's heap path to rhs
+      // for a normal assign node, need to propagate lhs's heap path to
+      // rhs
       if (fon.getOp().getOp() == Operation.ASSIGN) {
         rhs = fon.getLeft();
         lhs = fon.getDest();
@@ -538,31 +1279,50 @@ public class DefinitelyWrittenCheck {
     }
       break;
 
-    case FKind.FlatFieldNode:
-    case FKind.FlatElementNode: {
+    case FKind.FlatElementNode:
+    case FKind.FlatFieldNode: {
 
       // y=x.f;
 
-      FlatFieldNode ffn = (FlatFieldNode) fn;
-      lhs = ffn.getDst();
-      rhs = ffn.getSrc();
-      fld = ffn.getField();
+      if (fn.kind() == FKind.FlatFieldNode) {
+        FlatFieldNode ffn = (FlatFieldNode) fn;
+        lhs = ffn.getDst();
+        rhs = ffn.getSrc();
+        fld = ffn.getField();
+      } else {
+        FlatElementNode fen = (FlatElementNode) fn;
+        lhs = fen.getDst();
+        rhs = fen.getSrc();
+        TypeDescriptor td = rhs.getType().dereference();
+        fld = getArrayField(td);
+      }
+
+      if (fld.isFinal() /* && fld.isStatic() */) {
+        // if field is final and static, no need to check
+        break;
+      }
 
       // set up heap path
       NTuple<Descriptor> srcHeapPath = mapHeapPath.get(rhs);
-      NTuple<Descriptor> readingHeapPath = new NTuple<Descriptor>(srcHeapPath.getList());
-      readingHeapPath.add(fld);
-      mapHeapPath.put(lhs, readingHeapPath);
+      if (srcHeapPath != null) {
+        // if lhs srcHeapPath is null, it means that it is not reachable from
+        // callee's parameters. so just ignore it
+
+        NTuple<Descriptor> readingHeapPath = new NTuple<Descriptor>(srcHeapPath.getList());
+        readingHeapPath.add(fld);
+        mapHeapPath.put(lhs, readingHeapPath);
+
+        // read (x.f)
+        if (fld.getType().isImmutable()) {
+          // if WT doesnot have hp(x.f), add hp(x.f) to READ
+          if (!writtenSet.contains(readingHeapPath)) {
+            readSet.add(readingHeapPath);
+          }
+        }
 
-      // read (x.f)
-      // if WT doesnot have hp(x.f), add hp(x.f) to READ
-      if (!writtenSet.contains(readingHeapPath)) {
-        readSet.add(readingHeapPath);
+        //no need to kill hp(x.f) from WT
       }
 
-      // need to kill hp(x.f) from WT
-      writtenSet.remove(readingHeapPath);
-
     }
       break;
 
@@ -570,20 +1330,33 @@ public class DefinitelyWrittenCheck {
     case FKind.FlatSetElementNode: {
 
       // x.f=y;
-      FlatSetFieldNode fsfn = (FlatSetFieldNode) fn;
-      lhs = fsfn.getDst();
-      fld = fsfn.getField();
-      rhs = fsfn.getSrc();
+
+      if (fn.kind() == FKind.FlatSetFieldNode) {
+        FlatSetFieldNode fsfn = (FlatSetFieldNode) fn;
+        lhs = fsfn.getDst();
+        fld = fsfn.getField();
+        rhs = fsfn.getSrc();
+      } else {
+        FlatSetElementNode fsen = (FlatSetElementNode) fn;
+        lhs = fsen.getDst();
+        rhs = fsen.getSrc();
+        TypeDescriptor td = lhs.getType().dereference();
+        fld = getArrayField(td);
+      }
 
       // set up heap path
       NTuple<Descriptor> lhsHeapPath = mapHeapPath.get(lhs);
-      NTuple<Descriptor> newHeapPath = new NTuple<Descriptor>(lhsHeapPath.getList());
-      newHeapPath.add(fld);
-      mapHeapPath.put(fld, newHeapPath);
-
-      // write(x.f)
-      // need to add hp(y) to WT
-      writtenSet.add(newHeapPath);
+      if (lhsHeapPath != null) {
+        // if lhs heap path is null, it means that it is not reachable from
+        // callee's parameters. so just ignore it
+        NTuple<Descriptor> newHeapPath = new NTuple<Descriptor>(lhsHeapPath.getList());
+        newHeapPath.add(fld);
+        mapHeapPath.put(fld, newHeapPath);
+
+        // write(x.f)
+        // need to add hp(y) to WT
+        writtenSet.add(newHeapPath);
+      }
 
     }
       break;
@@ -592,100 +1365,120 @@ public class DefinitelyWrittenCheck {
 
       FlatCall fc = (FlatCall) fn;
 
-      // compute all possible callee set
-      // transform all READ/OVERWRITE set from the any possible callees to the
-      // caller
-      MethodDescriptor mdCallee = fc.getMethod();
-      FlatMethod fmCallee = state.getMethodFlat(mdCallee);
-      Set<MethodDescriptor> setPossibleCallees = new HashSet<MethodDescriptor>();
-      TypeDescriptor typeDesc = fc.getThis().getType();
-      setPossibleCallees.addAll(callGraph.getMethods(mdCallee, typeDesc));
+      if (fc.getThis() != null) {
+        bindHeapPathCallerArgWithCaleeParam(fc);
+        
+        // add heap path, which is an element of READ_bound set and is not
+        // an
+        // element of WT set, to the caller's READ set
+        for (Iterator iterator = calleeUnionBoundReadSet.iterator(); iterator.hasNext();) {
+          NTuple<Descriptor> read = (NTuple<Descriptor>) iterator.next();
+          if (!writtenSet.contains(read)) {
+            readSet.add(read);
+          }
+        }
 
-      // create mapping from arg idx to its heap paths
-      Hashtable<Integer, NTuple<Descriptor>> mapArgIdx2CallerArgHeapPath =
-          new Hashtable<Integer, NTuple<Descriptor>>();
+        // add heap path, which is an element of OVERWRITE_bound set, to the
+        // caller's WT set
+        for (Iterator iterator = calleeIntersectBoundOverWriteSet.iterator(); iterator.hasNext();) {
+          NTuple<Descriptor> write = (NTuple<Descriptor>) iterator.next();
+          writtenSet.add(write);
+        }
+      } 
 
-      // arg idx is starting from 'this' arg
-      NTuple<Descriptor> thisHeapPath = new NTuple<Descriptor>();
-      thisHeapPath.add(fc.getThis());
-      mapArgIdx2CallerArgHeapPath.put(Integer.valueOf(0), thisHeapPath);
+    }
+      break;
 
-      for (int i = 0; i < fc.numArgs(); i++) {
-        TempDescriptor arg = fc.getArg(i);
-        NTuple<Descriptor> argHeapPath = mapHeapPath.get(arg);
-        mapArgIdx2CallerArgHeapPath.put(Integer.valueOf(i + 1), argHeapPath);
-      }
+    case FKind.FlatExit: {
+      // merge the current written set with OVERWRITE set
+      merge(overWriteSet, writtenSet);
+    }
+      break;
 
-      Set<NTuple<Descriptor>> calleeUnionBoundReadSet = new HashSet<NTuple<Descriptor>>();
-      Set<NTuple<Descriptor>> calleeIntersectBoundOverWriteSet = new HashSet<NTuple<Descriptor>>();
+    }
 
-      for (Iterator iterator = setPossibleCallees.iterator(); iterator.hasNext();) {
-        MethodDescriptor callee = (MethodDescriptor) iterator.next();
-        FlatMethod calleeFlatMethod = state.getMethodFlat(callee);
+  }
 
-        // binding caller's args and callee's params
-        Set<NTuple<Descriptor>> calleeReadSet = mapFlatMethodToRead.get(calleeFlatMethod);
-        if (calleeReadSet == null) {
-          calleeReadSet = new HashSet<NTuple<Descriptor>>();
-          mapFlatMethodToRead.put(calleeFlatMethod, calleeReadSet);
-        }
-        Set<NTuple<Descriptor>> calleeOverWriteSet = mapFlatMethodToOverWrite.get(calleeFlatMethod);
-        if (calleeOverWriteSet == null) {
-          calleeOverWriteSet = new HashSet<NTuple<Descriptor>>();
-          mapFlatMethodToOverWrite.put(calleeFlatMethod, calleeOverWriteSet);
-        }
+  static public FieldDescriptor getArrayField(TypeDescriptor td) {
+    FieldDescriptor fd = mapTypeToArrayField.get(td);
+    if (fd == null) {
+      fd =
+          new FieldDescriptor(new Modifiers(Modifiers.PUBLIC), td, arrayElementFieldName, null,
+              false);
+      mapTypeToArrayField.put(td, fd);
+    }
+    return fd;
+  }
 
-        Hashtable<Integer, TempDescriptor> mapParamIdx2ParamTempDesc =
-            new Hashtable<Integer, TempDescriptor>();
-        for (int i = 0; i < calleeFlatMethod.numParameters(); i++) {
-          TempDescriptor param = calleeFlatMethod.getParameter(i);
-          mapParamIdx2ParamTempDesc.put(Integer.valueOf(i), param);
-        }
+  private void mergeSharedLocationAnaylsis(ClearingSummary curr, Set<ClearingSummary> inSet) {
 
-        Set<NTuple<Descriptor>> calleeBoundReadSet =
-            bindSet(calleeReadSet, mapParamIdx2ParamTempDesc, mapArgIdx2CallerArgHeapPath);
-        // union of the current read set and the current callee's read set
-        calleeUnionBoundReadSet.addAll(calleeBoundReadSet);
+    if (inSet.size() == 0) {
+      return;
+    }
 
-        Set<NTuple<Descriptor>> calleeBoundWriteSet =
-            bindSet(calleeOverWriteSet, mapParamIdx2ParamTempDesc, mapArgIdx2CallerArgHeapPath);
-        // intersection of the current overwrite set and the current callee's
-        // overwrite set
-        merge(calleeIntersectBoundOverWriteSet, calleeBoundWriteSet);
-      }
+    Hashtable<Pair<NTuple<Descriptor>, Location>, Boolean> mapHeapPathLoc2Flag =
+        new Hashtable<Pair<NTuple<Descriptor>, Location>, Boolean>();
+
+    for (Iterator inIterator = inSet.iterator(); inIterator.hasNext();) {
+
+      ClearingSummary inTable = (ClearingSummary) inIterator.next();
 
-      // add heap path, which is an element of READ_bound set and is not an
-      // element of WT set, to the caller's READ set
-      for (Iterator iterator = calleeUnionBoundReadSet.iterator(); iterator.hasNext();) {
-        NTuple<Descriptor> read = (NTuple<Descriptor>) iterator.next();
-        if (!writtenSet.contains(read)) {
-          readSet.add(read);
+      Set<NTuple<Descriptor>> keySet = inTable.keySet();
+
+      for (Iterator iterator = keySet.iterator(); iterator.hasNext();) {
+        NTuple<Descriptor> hpKey = (NTuple<Descriptor>) iterator.next();
+        SharedStatus inState = inTable.get(hpKey);
+
+        SharedStatus currState = curr.get(hpKey);
+        if (currState == null) {
+          currState = new SharedStatus();
+          curr.put(hpKey, currState);
+        }
+        currState.merge(inState);
+
+        Set<Location> locSet = inState.getMap().keySet();
+        for (Iterator iterator2 = locSet.iterator(); iterator2.hasNext();) {
+          Location loc = (Location) iterator2.next();
+          Pair<Set<Descriptor>, Boolean> pair = inState.getMap().get(loc);
+          boolean inFlag = pair.getSecond().booleanValue();
+
+          Pair<NTuple<Descriptor>, Location> flagKey =
+              new Pair<NTuple<Descriptor>, Location>(hpKey, loc);
+          Boolean current = mapHeapPathLoc2Flag.get(flagKey);
+          if (current == null) {
+            current = new Boolean(true);
+          }
+          boolean newInFlag = current.booleanValue() & inFlag;
+          mapHeapPathLoc2Flag.put(flagKey, Boolean.valueOf(newInFlag));
         }
-      }
-      writtenSet.removeAll(calleeUnionBoundReadSet);
 
-      // add heap path, which is an element of OVERWRITE_bound set, to the
-      // caller's WT set
-      for (Iterator iterator = calleeIntersectBoundOverWriteSet.iterator(); iterator.hasNext();) {
-        NTuple<Descriptor> write = (NTuple<Descriptor>) iterator.next();
-        writtenSet.add(write);
       }
 
     }
-      break;
-
-    case FKind.FlatExit: {
-      // merge the current written set with OVERWRITE set
-      merge(overWriteSet, writtenSet);
-    }
-      break;
 
+    // merge flag status
+    Set<NTuple<Descriptor>> hpKeySet = curr.keySet();
+    for (Iterator iterator = hpKeySet.iterator(); iterator.hasNext();) {
+      NTuple<Descriptor> hpKey = (NTuple<Descriptor>) iterator.next();
+      SharedStatus currState = curr.get(hpKey);
+      Set<Location> locKeySet = currState.getMap().keySet();
+      for (Iterator iterator2 = locKeySet.iterator(); iterator2.hasNext();) {
+        Location locKey = (Location) iterator2.next();
+        Pair<Set<Descriptor>, Boolean> pair = currState.getMap().get(locKey);
+        boolean currentFlag = pair.getSecond().booleanValue();
+        Boolean inFlag = mapHeapPathLoc2Flag.get(new Pair(hpKey, locKey));
+        if (inFlag != null) {
+          boolean newFlag = currentFlag | inFlag.booleanValue();
+          if (currentFlag != newFlag) {
+            currState.getMap().put(locKey, new Pair(pair.getFirst(), new Boolean(newFlag)));
+          }
+        }
+      }
     }
 
   }
 
   private void merge(Set<NTuple<Descriptor>> curr, Set<NTuple<Descriptor>> in) {
-
     if (curr.isEmpty()) {
       // WrittenSet has a special initial value which covers all possible
       // elements
@@ -774,16 +1567,13 @@ public class DefinitelyWrittenCheck {
 
     discovered.add(md);
 
-    // otherwise call graph guides DFS
     Iterator itr = callGraph.getCallerSet(md).iterator();
     while (itr.hasNext()) {
       MethodDescriptor dCaller = (MethodDescriptor) itr.next();
-
       // only consider callers in the original set to analyze
       if (!toSort.contains(dCaller)) {
         continue;
       }
-
       if (!discovered.contains(dCaller)) {
         addDependent(md, // callee
             dCaller // caller