Fixed up another canonical misuse, changed wording of alias reporting to see the...
[IRC.git] / Robust / src / Analysis / OwnershipAnalysis / OwnershipAnalysis.java
index 4e7be31b37d06af9c53dbe3503a59e85dda3fe0f..b0dcfb47a193e390bb8ed8bf04889e7f65433564 100644 (file)
@@ -3,144 +3,142 @@ package Analysis.OwnershipAnalysis;
 import Analysis.CallGraph.*;
 import IR.*;
 import IR.Flat.*;
+import IR.Tree.Modifiers;
 import java.util.*;
 import java.io.*;
 
 
 public class OwnershipAnalysis {
 
+
   ///////////////////////////////////////////
   //
   //  Public interface to discover possible
   //  aliases in the program under analysis
   //
   ///////////////////////////////////////////
-  /*
-     public HashSet<AllocationSite>
-      getFlaggedAllocationSitesReachableFromTask( TaskDescriptor td ) {
 
-      return getFlaggedAllocationSitesReachableFromTaskPRIVATE( td );
-     }
+  public HashSet<AllocationSite>
+  getFlaggedAllocationSitesReachableFromTask(TaskDescriptor td) {
+    return getFlaggedAllocationSitesReachableFromTaskPRIVATE(td);
+  }
 
-     public AllocationSite getAllocationSiteFromFlatNew( FlatNew fn ) {
-      return getAllocationSiteFromFlatNewPRIVATE( fn );
-     }
+  public AllocationSite getAllocationSiteFromFlatNew(FlatNew fn) {
+    return getAllocationSiteFromFlatNewPRIVATE(fn);
+  }
 
-     public boolean createsPotentialAliases( Descriptor     taskOrMethod,
-                                          int            paramIndex1,
-                                          int            paramIndex2 ) {
+  public boolean createsPotentialAliases(Descriptor taskOrMethod,
+                                         int paramIndex1,
+                                         int paramIndex2) {
 
-      OwnershipGraph og = mapDescriptorToCompleteOwnershipGraph.get( taskOrMethod );
-      assert( og != null );
+    OwnershipGraph og = mapDescriptorToCompleteOwnershipGraph.get(taskOrMethod);
+    assert(og != null);
+    return og.hasPotentialAlias(paramIndex1, paramIndex2);
+  }
 
-      return createsPotentialAliases( og,
-                                      getHeapRegionIDset( og, paramIndex1 ),
-                                      getHeapRegionIDset( og, paramIndex2 ) );
-     }
+  public boolean createsPotentialAliases(Descriptor taskOrMethod,
+                                         int paramIndex,
+                                         AllocationSite alloc) {
 
-     public boolean createsPotentialAliases( Descriptor     taskOrMethod,
-                                          int            paramIndex,
-                                          AllocationSite alloc ) {
+    OwnershipGraph og = mapDescriptorToCompleteOwnershipGraph.get(taskOrMethod);
+    assert(og != null);
+    return og.hasPotentialAlias(paramIndex, alloc);
+  }
 
-      OwnershipGraph og = mapDescriptorToCompleteOwnershipGraph.get( taskOrMethod );
-      assert( og != null );
+  public boolean createsPotentialAliases(Descriptor taskOrMethod,
+                                         AllocationSite alloc,
+                                         int paramIndex) {
 
-      return createsPotentialAliases( og,
-                                      getHeapRegionIDset( og, paramIndex ),
-                                      getHeapRegionIDset( alloc ) );
-     }
+    OwnershipGraph og = mapDescriptorToCompleteOwnershipGraph.get(taskOrMethod);
+    assert(og != null);
+    return og.hasPotentialAlias(paramIndex, alloc);
+  }
 
-     public boolean createsPotentialAliases( Descriptor     taskOrMethod,
-                                          AllocationSite alloc,
-                                          int            paramIndex ) {
+  public boolean createsPotentialAliases(Descriptor taskOrMethod,
+                                         AllocationSite alloc1,
+                                         AllocationSite alloc2) {
 
-      OwnershipGraph og = mapDescriptorToCompleteOwnershipGraph.get( taskOrMethod );
-      assert( og != null );
+    OwnershipGraph og = mapDescriptorToCompleteOwnershipGraph.get(taskOrMethod);
+    assert(og != null);
+    return og.hasPotentialAlias(alloc1, alloc2);
+  }
 
-      return createsPotentialAliases( og,
-                                      getHeapRegionIDset( og, paramIndex ),
-                                      getHeapRegionIDset( alloc ) );
-     }
+  // use the methods given above to check every possible alias
+  // between task parameters and flagged allocation sites reachable
+  // from the task
+  public void writeAllAliases(String outputFile) throws java.io.IOException {
 
-     public boolean createsPotentialAliases( Descriptor     taskOrMethod,
-                                          AllocationSite alloc1,
-                                          AllocationSite alloc2 ) {
+    BufferedWriter bw = new BufferedWriter(new FileWriter(outputFile) );
 
-      OwnershipGraph og = mapDescriptorToCompleteOwnershipGraph.get( taskOrMethod );
-      assert( og != null );
+    bw.write("Conducting ownership analysis with allocation depth = "+allocationDepth);
 
-      return createsPotentialAliases( og,
-                                      getHeapRegionIDset( alloc1 ),
-                                      getHeapRegionIDset( alloc2 ) );
-     }
+    // look through every task for potential aliases
+    Iterator taskItr = state.getTaskSymbolTable().getDescriptorsIterator();
+    while( taskItr.hasNext() ) {
+      TaskDescriptor td = (TaskDescriptor) taskItr.next();
 
-     public boolean createsPotentialAliases( Descriptor              taskOrMethod,
-                                          AllocationSite          alloc,
-                                          HashSet<AllocationSite> allocSet ) {
+      bw.write("\n---------"+td+"--------\n");
 
-      OwnershipGraph og = mapDescriptorToCompleteOwnershipGraph.get( taskOrMethod );
-      assert( og != null );
+      HashSet<AllocationSite> allocSites = getFlaggedAllocationSitesReachableFromTask(td);
 
-      return createsPotentialAliases( og,
-                                      getHeapRegionIDset( alloc ),
-                                      getHeapRegionIDset( allocSet ) );
-     }
-   */
+      // for each task parameter, check for aliases with
+      // other task parameters and every allocation site
+      // reachable from this task
+      boolean foundSomeAlias = false;
 
-  // use the methods given above to check every possible alias
-  // between task parameters and flagged allocation sites reachable
-  // from the task
-  public void writeAllAliases(String outputFile) throws java.io.IOException {
+      FlatMethod fm = state.getMethodFlat(td);
+      for( int i = 0; i < fm.numParameters(); ++i ) {
 
-    BufferedWriter bw = new BufferedWriter(new FileWriter(outputFile) );
-    /*
-       // look through every task for potential aliases
-       Iterator taskItr = state.getTaskSymbolTable().getDescriptorsIterator();
-       while( taskItr.hasNext() ) {
-        TaskDescriptor td = (TaskDescriptor) taskItr.next();
-
-        HashSet<AllocationSite> allocSites = getFlaggedAllocationSitesReachableFromTask( td );
-
-        // for each task parameter, check for aliases with
-        // other task parameters and every allocation site
-        // reachable from this task
-        FlatMethod fm = state.getMethodFlat( td );
-        for( int i = 0; i < fm.numParameters(); ++i ) {
-
-            // for the ith parameter check for aliases to all
-            // higher numbered parameters
-            for( int j = i + 1; j < fm.numParameters(); ++j ) {
-                if( createsPotentialAliases( td, i, j ) ) {
-                    bw.write( "Task "+td+" potentially aliases parameters "+i+" and "+j+".\n" );
-                }
-            }
-
-            // for the ith parameter, check for aliases against
-            // the set of allocation sites reachable from this
-            // task context
-            Iterator allocItr = allocSites.iterator();
-            while( allocItr.hasNext() ) {
-                AllocationSite as = (AllocationSite) allocItr.next();
-                if( createsPotentialAliases( td, i, as ) ) {
-                    bw.write( "Task "+td+" potentially aliases parameter "+i+" and "+as+".\n" );
-                }
-            }
-        }
-
-        // for each allocation site check for aliases with
-        // other allocation sites in the context of execution
-        // of this task
-        Iterator allocItr = allocSites.iterator();
-        while( allocItr.hasNext() ) {
-            AllocationSite as = (AllocationSite) allocItr.next();
-            if( createsPotentialAliases( td, as, allocSites ) ) {
-                bw.write( "Task "+td+" potentially aliases "+as+" and the rest of the set.\n" );
-            }
-        }
-       }
-
-       bw.close();
-     */
+       // for the ith parameter check for aliases to all
+       // higher numbered parameters
+       for( int j = i + 1; j < fm.numParameters(); ++j ) {
+         if( createsPotentialAliases(td, i, j) ) {
+           foundSomeAlias = true;
+           bw.write("Potential alias between parameters "+i+" and "+j+".\n");
+         }
+       }
+
+       // for the ith parameter, check for aliases against
+       // the set of allocation sites reachable from this
+       // task context
+       Iterator allocItr = allocSites.iterator();
+       while( allocItr.hasNext() ) {
+         AllocationSite as = (AllocationSite) allocItr.next();
+         if( createsPotentialAliases(td, i, as) ) {
+           foundSomeAlias = true;
+           bw.write("Potential alias between parameter "+i+" and "+as.getFlatNew()+".\n");
+         }
+       }
+      }
+
+      // for each allocation site check for aliases with
+      // other allocation sites in the context of execution
+      // of this task
+      HashSet<AllocationSite> outerChecked = new HashSet<AllocationSite>();
+      Iterator allocItr1 = allocSites.iterator();
+      while( allocItr1.hasNext() ) {
+       AllocationSite as1 = (AllocationSite) allocItr1.next();
+
+       Iterator allocItr2 = allocSites.iterator();
+       while( allocItr2.hasNext() ) {
+         AllocationSite as2 = (AllocationSite) allocItr2.next();
+
+         if( !outerChecked.contains(as2) &&
+             createsPotentialAliases(td, as1, as2) ) {
+           foundSomeAlias = true;
+           bw.write("Potential alias between "+as1.getFlatNew()+" and "+as2.getFlatNew()+".\n");
+         }
+       }
+
+       outerChecked.add(as1);
+      }
+
+      if( !foundSomeAlias ) {
+       bw.write("No aliases between flagged objects in Task "+td+".\n");
+      }
+    }
+
+    bw.close();
   }
 
   ///////////////////////////////////////////
@@ -158,6 +156,7 @@ public class OwnershipAnalysis {
 
   // data from the compiler
   private State state;
+  private TypeUtil typeUtil;
   private CallGraph callGraph;
   private int allocationDepth;
 
@@ -166,17 +165,20 @@ public class OwnershipAnalysis {
   // ownership graph with an object in another
   // graph that logically represents the same
   // heap region
-  static private int uniqueIDcount = 0;
+  // start at 10 and incerement to leave some
+  // reserved IDs for special purposes
+  static private int uniqueIDcount = 10;
 
 
   // Use these data structures to track progress of
   // processing all methods in the program, and by methods
   // TaskDescriptor and MethodDescriptor are combined
   // together, with a common parent class Descriptor
-  private HashSet  <Descriptor>                           descriptorsToVisit;
+  private Hashtable<FlatMethod, OwnershipGraph>           mapFlatMethodToInitialParamAllocGraph;
   private Hashtable<Descriptor, OwnershipGraph>           mapDescriptorToCompleteOwnershipGraph;
   private Hashtable<FlatNew,    AllocationSite>           mapFlatNewToAllocationSite;
   private Hashtable<Descriptor, HashSet<AllocationSite> > mapDescriptorToAllocationSiteSet;
+  private Hashtable<Descriptor, Integer>                  mapDescriptorToNumUpdates;
 
   // Use these data structures to track progress of one pass of
   // processing the FlatNodes of a particular method
@@ -184,20 +186,50 @@ public class OwnershipAnalysis {
   private Hashtable<FlatNode, OwnershipGraph> mapFlatNodeToOwnershipGraph;
   private HashSet  <FlatReturnNode>           returnNodesToCombineForCompleteOwnershipGraph;
 
+  // descriptorsToAnalyze identifies the set of tasks and methods
+  // that are reachable from the program tasks, this set is initialized
+  // and then remains static
+  private HashSet<Descriptor> descriptorsToAnalyze;
+
+  // descriptorsToVisit is initialized to descriptorsToAnalyze and is
+  // reduced by visiting a descriptor during analysis.  When dependents
+  // must be scheduled, only those contained in descriptorsToAnalyze
+  // should be re-added to this set
+  private HashSet<Descriptor> descriptorsToVisit;
+
+  // a special field descriptor for all array elements
+  private static FieldDescriptor fdElement = new FieldDescriptor(new Modifiers(Modifiers.PUBLIC),
+                                                                 new TypeDescriptor("Array[]"),
+                                                                 "elements",
+                                                                 null,
+                                                                 false);
+  // for controlling DOT file output
+  private boolean writeDOTs;
+  private boolean writeAllDOTs;
+
+
 
   // this analysis generates an ownership graph for every task
   // in the program
   public OwnershipAnalysis(State state,
+                           TypeUtil tu,
                            CallGraph callGraph,
-                           int allocationDepth) throws java.io.IOException {
+                           int allocationDepth,
+                           boolean writeDOTs,
+                           boolean writeAllDOTs,
+                           String aliasFile) throws java.io.IOException {
+
     this.state           = state;
+    this.typeUtil        = tu;
     this.callGraph       = callGraph;
     this.allocationDepth = allocationDepth;
+    this.writeDOTs       = writeDOTs;
+    this.writeAllDOTs    = writeAllDOTs;
 
-    // temporary for debugging
-    this.allocationDepth = 1;
+    descriptorsToAnalyze = new HashSet<Descriptor>();
 
-    descriptorsToVisit = new HashSet<Descriptor>();
+    mapFlatMethodToInitialParamAllocGraph =
+      new Hashtable<FlatMethod, OwnershipGraph>();
 
     mapDescriptorToCompleteOwnershipGraph =
       new Hashtable<Descriptor, OwnershipGraph>();
@@ -208,10 +240,9 @@ public class OwnershipAnalysis {
     mapDescriptorToAllocationSiteSet =
       new Hashtable<Descriptor, HashSet<AllocationSite> >();
 
-    // use this set to prevent infinite recursion when
-    // traversing the call graph
-    HashSet<Descriptor> calleesScheduled = new HashSet<Descriptor>();
-
+    if( writeAllDOTs ) {
+      mapDescriptorToNumUpdates = new Hashtable<Descriptor, Integer>();
+    }
 
     // initialize methods to visit as the set of all tasks in the
     // program and then any method that could be called starting
@@ -219,19 +250,16 @@ public class OwnershipAnalysis {
     Iterator taskItr = state.getTaskSymbolTable().getDescriptorsIterator();
     while( taskItr.hasNext() ) {
       Descriptor d = (Descriptor) taskItr.next();
-      descriptorsToVisit.add(d);
-
-      // recursively find all callees from this task
-      scheduleAllCallees(calleesScheduled, d);
+      scheduleAllCallees(d);
     }
 
     // before beginning analysis, initialize every scheduled method
     // with an ownership graph that has populated parameter index tables
     // by analyzing the first node which is always a FlatMethod node
-    Iterator<Descriptor> dItr = calleesScheduled.iterator();
+    Iterator<Descriptor> dItr = descriptorsToAnalyze.iterator();
     while( dItr.hasNext() ) {
       Descriptor d  = dItr.next();
-      OwnershipGraph og = new OwnershipGraph(allocationDepth);
+      OwnershipGraph og = new OwnershipGraph(allocationDepth, typeUtil);
 
       FlatMethod fm;
       if( d instanceof MethodDescriptor ) {
@@ -241,36 +269,48 @@ public class OwnershipAnalysis {
        fm = state.getMethodFlat( (TaskDescriptor) d);
       }
 
-      analyzeFlatNode(d, fm, null, og);
-      mapDescriptorToCompleteOwnershipGraph.put(d, og);
+      System.out.println("Previsiting " + d);
+
+      og = analyzeFlatNode(d, fm, null, og);
+      setGraphForDescriptor(d, og);
     }
 
+    System.out.println("");
+
     // as mentioned above, analyze methods one-by-one, possibly revisiting
     // a method if the methods that it calls are updated
     analyzeMethods();
+
+    System.out.println("");
+
+    if( aliasFile != null ) {
+      writeAllAliases(aliasFile);
+    }
   }
 
   // called from the constructor to help initialize the set
   // of methods that needs to be analyzed by ownership analysis
-  private void scheduleAllCallees(HashSet<Descriptor> calleesScheduled,
-                                  Descriptor d) {
-    if( calleesScheduled.contains(d) ) {
+  private void scheduleAllCallees(Descriptor d) {
+    if( descriptorsToAnalyze.contains(d) ) {
       return;
     }
-    calleesScheduled.add(d);
+    descriptorsToAnalyze.add(d);
 
-    Set callees = callGraph.getCalleeSet(d);
-    if( callees == null ) {
-      return;
+    // start with all method calls to further schedule
+    Set moreMethodsToCheck = moreMethodsToCheck = callGraph.getMethodCalls(d);
+
+    if( d instanceof MethodDescriptor ) {
+      // see if this method has virtual dispatch
+      Set virtualMethods = callGraph.getMethods( (MethodDescriptor)d);
+      moreMethodsToCheck.addAll(virtualMethods);
     }
 
-    Iterator methItr = callees.iterator();
+    // keep following any further methods identified in
+    // the call chain
+    Iterator methItr = moreMethodsToCheck.iterator();
     while( methItr.hasNext() ) {
-      MethodDescriptor md = (MethodDescriptor) methItr.next();
-      descriptorsToVisit.add(md);
-
-      // recursively find all callees from this task
-      scheduleAllCallees(calleesScheduled, md);
+      Descriptor m = (Descriptor) methItr.next();
+      scheduleAllCallees(m);
     }
   }
 
@@ -280,6 +320,8 @@ public class OwnershipAnalysis {
   // they call are updated
   private void analyzeMethods() throws java.io.IOException {
 
+    descriptorsToVisit = (HashSet<Descriptor>)descriptorsToAnalyze.clone();
+
     while( !descriptorsToVisit.isEmpty() ) {
       Descriptor d = (Descriptor) descriptorsToVisit.iterator().next();
       descriptorsToVisit.remove(d);
@@ -302,18 +344,10 @@ public class OwnershipAnalysis {
        fm = state.getMethodFlat( (TaskDescriptor) d);
       }
 
-      OwnershipGraph og     = analyzeFlatMethod(d, fm);
+      OwnershipGraph og = analyzeFlatMethod(d, fm);
       OwnershipGraph ogPrev = mapDescriptorToCompleteOwnershipGraph.get(d);
       if( !og.equals(ogPrev) ) {
-       mapDescriptorToCompleteOwnershipGraph.put(d, og);
-
-       /*
-          boolean writeLabels,
-          boolean labelSelect,
-          boolean pruneGarbage,
-          boolean writeReferencers
-        */
-       og.writeGraph(d, true, true, true, false);
+       setGraphForDescriptor(d, og);
 
        // only methods have dependents, tasks cannot
        // be invoked by any user program calls
@@ -321,7 +355,13 @@ public class OwnershipAnalysis {
          MethodDescriptor md = (MethodDescriptor) d;
          Set dependents = callGraph.getCallerSet(md);
          if( dependents != null ) {
-           descriptorsToVisit.addAll(dependents);
+           Iterator depItr = dependents.iterator();
+           while( depItr.hasNext() ) {
+             Descriptor dependent = (Descriptor) depItr.next();
+             if( descriptorsToAnalyze.contains(dependent) ) {
+               descriptorsToVisit.add(dependent);
+             }
+           }
          }
        }
       }
@@ -330,9 +370,6 @@ public class OwnershipAnalysis {
   }
 
 
-  int x = 0;
-
-
   // keep passing the Descriptor of the method along for debugging
   // and dot file writing
   private OwnershipGraph
@@ -342,6 +379,7 @@ public class OwnershipAnalysis {
     // initialize flat nodes to visit as the flat method
     // because all other nodes in this flat method are
     // decendents of the flat method itself
+
     flatNodesToVisit = new HashSet<FlatNode>();
     flatNodesToVisit.add(flatm);
 
@@ -353,48 +391,47 @@ public class OwnershipAnalysis {
     // the final ownership graph result to return as an empty set
     returnNodesToCombineForCompleteOwnershipGraph = new HashSet<FlatReturnNode>();
 
+
     while( !flatNodesToVisit.isEmpty() ) {
       FlatNode fn = (FlatNode) flatNodesToVisit.iterator().next();
       flatNodesToVisit.remove(fn);
 
+      //System.out.println( "  "+fn );
+
       // perform this node's contributions to the ownership
       // graph on a new copy, then compare it to the old graph
       // at this node to see if anything was updated.
-      OwnershipGraph og = new OwnershipGraph(allocationDepth);
+      OwnershipGraph og = new OwnershipGraph(allocationDepth, typeUtil);
 
       // start by merging all node's parents' graphs
       for( int i = 0; i < fn.numPrev(); ++i ) {
-       FlatNode pn       = fn.getPrev(i);
-       OwnershipGraph ogParent = getGraphFromFlatNode(pn);
-       og.merge(ogParent);
+       FlatNode pn = fn.getPrev(i);    
+       if( mapFlatNodeToOwnershipGraph.containsKey(pn) ) {
+         OwnershipGraph ogParent = mapFlatNodeToOwnershipGraph.get(pn);
+         og.merge(ogParent);
+       }
       }
 
       // apply the analysis of the flat node to the
       // ownership graph made from the merge of the
       // parent graphs
-      analyzeFlatNode(mDesc,
-                      fn,
-                      returnNodesToCombineForCompleteOwnershipGraph,
-                      og);
+      og = analyzeFlatNode(mDesc,
+                           fn,
+                           returnNodesToCombineForCompleteOwnershipGraph,
+                           og);
+
+
+      //debugSnapshot(og,fn);
+
+
 
       // if the results of the new graph are different from
       // the current graph at this node, replace the graph
       // with the update and enqueue the children for
       // processing
-      OwnershipGraph ogPrev = getGraphFromFlatNode(fn);
-
+      OwnershipGraph ogPrev = mapFlatNodeToOwnershipGraph.get(fn);
       if( !og.equals(ogPrev) ) {
-       setGraphForFlatNode(fn, og);
-
-
-
-       x++;
-       if( x > 0 ) {
-         String s = String.format("debug%04d", x);
-         //og.writeGraph( s, true, true, true, false );
-       }
-
-
+       mapFlatNodeToOwnershipGraph.put(fn, og);
 
        for( int i = 0; i < fn.numNext(); i++ ) {
          FlatNode nn = fn.getNext(i);
@@ -406,25 +443,27 @@ public class OwnershipAnalysis {
     // end by merging all return nodes into a complete
     // ownership graph that represents all possible heap
     // states after the flat method returns
-    OwnershipGraph completeGraph = new OwnershipGraph(allocationDepth);
+    OwnershipGraph completeGraph = new OwnershipGraph(allocationDepth, typeUtil);
     Iterator retItr = returnNodesToCombineForCompleteOwnershipGraph.iterator();
     while( retItr.hasNext() ) {
       FlatReturnNode frn = (FlatReturnNode) retItr.next();
-      OwnershipGraph ogr = getGraphFromFlatNode(frn);
+      assert mapFlatNodeToOwnershipGraph.containsKey(frn);
+      OwnershipGraph ogr = mapFlatNodeToOwnershipGraph.get(frn);
       completeGraph.merge(ogr);
-    }
+    }   
+
     return completeGraph;
   }
 
 
-  private void
+  private OwnershipGraph
   analyzeFlatNode(Descriptor methodDesc,
                   FlatNode fn,
                   HashSet<FlatReturnNode> setRetNodes,
                   OwnershipGraph og) throws java.io.IOException {
 
-    TempDescriptor src;
-    TempDescriptor dst;
+    TempDescriptor lhs;
+    TempDescriptor rhs;
     FieldDescriptor fld;
 
     // use node type to decide what alterations to make
@@ -438,127 +477,172 @@ public class OwnershipAnalysis {
       // parent of all other FlatNode objects, so take
       // the opportunity to construct the initial graph by
       // adding parameters labels to new heap regions
-      for( int i = 0; i < fm.numParameters(); ++i ) {
-       TempDescriptor tdParam = fm.getParameter(i);
-       og.assignParameterAllocationToTemp(methodDesc instanceof TaskDescriptor,
-                                          tdParam,
-                                          new Integer(i) );
-      }
+      // AND this should be done once globally so that the
+      // parameter IDs are consistent between analysis
+      // iterations, so if this step has been done already
+      // just merge in the cached version
+      OwnershipGraph ogInitParamAlloc = mapFlatMethodToInitialParamAllocGraph.get(fm);
+      if( ogInitParamAlloc == null ) {
+
+       // analyze this node one time globally
+       for( int i = 0; i < fm.numParameters(); ++i ) {
+         TempDescriptor tdParam = fm.getParameter(i);
+         og.assignTempEqualToParamAlloc(tdParam,
+                                        methodDesc instanceof TaskDescriptor,
+                                        new Integer(i) );
+       }
+
+       // then remember it
+       OwnershipGraph ogResult = new OwnershipGraph(allocationDepth, typeUtil);
+       ogResult.merge(og);
+       mapFlatMethodToInitialParamAllocGraph.put(fm, ogResult);
 
+      } else {
+       // or just leverage the cached copy
+       og.merge(ogInitParamAlloc);
+      }
       break;
 
     case FKind.FlatOpNode:
       FlatOpNode fon = (FlatOpNode) fn;
       if( fon.getOp().getOp() == Operation.ASSIGN ) {
-       src = fon.getLeft();
-       dst = fon.getDest();
-       og.assignTempYToTempX(src, dst);
+       lhs = fon.getDest();
+       rhs = fon.getLeft();
+       og.assignTempXEqualToTempY(lhs, rhs);
       }
       break;
 
     case FKind.FlatFieldNode:
       FlatFieldNode ffn = (FlatFieldNode) fn;
-      src = ffn.getSrc();
-      dst = ffn.getDst();
+      lhs = ffn.getDst();
+      rhs = ffn.getSrc();
       fld = ffn.getField();
-      if( !fld.getType().isPrimitive() ) {
-       og.assignTempYFieldFToTempX(src, fld, dst);
+      if( !fld.getType().isImmutable() ) {
+       og.assignTempXEqualToTempYFieldF(lhs, rhs, fld);
       }
       break;
 
     case FKind.FlatSetFieldNode:
       FlatSetFieldNode fsfn = (FlatSetFieldNode) fn;
-      src = fsfn.getSrc();
-      dst = fsfn.getDst();
+      lhs = fsfn.getDst();
       fld = fsfn.getField();
-      og.assignTempYToTempXFieldF(src, dst, fld);
+      rhs = fsfn.getSrc();
+      if( !fld.getType().isImmutable() ) {
+       og.assignTempXFieldFEqualToTempY(lhs, fld, rhs);
+      }
+      break;
+
+    case FKind.FlatElementNode:
+      FlatElementNode fen = (FlatElementNode) fn;
+      lhs = fen.getDst();
+      rhs = fen.getSrc();
+      if( !lhs.getType().isImmutable() ) {
+       og.assignTempXEqualToTempYFieldF(lhs, rhs, fdElement);
+      }
+      break;
+
+    case FKind.FlatSetElementNode:
+      FlatSetElementNode fsen = (FlatSetElementNode) fn;
+      lhs = fsen.getDst();
+      rhs = fsen.getSrc();
+      if( !rhs.getType().isImmutable() ) {
+       og.assignTempXFieldFEqualToTempY(lhs, fdElement, rhs);
+      }
       break;
 
     case FKind.FlatNew:
       FlatNew fnn = (FlatNew) fn;
-      dst = fnn.getDst();
-      AllocationSite as = getAllocationSiteFromFlatNewPRIVATE(fnn);
-
-      og.assignNewAllocationToTempX(dst, as);
+      lhs = fnn.getDst();
+      if( !lhs.getType().isImmutable() ) {
+       AllocationSite as = getAllocationSiteFromFlatNewPRIVATE(fnn);
+       og.assignTempEqualToNewAlloc(lhs, as);
+      }
       break;
 
     case FKind.FlatCall:
-      FlatCall fc           = (FlatCall) fn;
-      MethodDescriptor md           = fc.getMethod();
-      FlatMethod flatm        = state.getMethodFlat(md);
-      //HashSet<AllocationSite> allocSiteSet = getAllocationSiteSet( md );
-      OwnershipGraph ogAllPossibleCallees  = new OwnershipGraph(allocationDepth);
+      FlatCall fc = (FlatCall) fn;
+      MethodDescriptor md = fc.getMethod();
+      FlatMethod flatm = state.getMethodFlat(md);
+      OwnershipGraph ogMergeOfAllPossibleCalleeResults = new OwnershipGraph(allocationDepth, typeUtil);
 
       if( md.isStatic() ) {
        // a static method is simply always the same, makes life easy
        OwnershipGraph onlyPossibleCallee = mapDescriptorToCompleteOwnershipGraph.get(md);
-       ogAllPossibleCallees.merge(onlyPossibleCallee);
-
-       /*
-          if( onlyPossibleCallee != null ) {
-           onlyPossibleCallee.writeGraph( "only", false, false );
-           System.out.println( "There was only one possible callee, "+md );
-          }
-        */
-
+       ogMergeOfAllPossibleCalleeResults = og;
+       ogMergeOfAllPossibleCalleeResults.resolveMethodCall(fc, md.isStatic(), flatm, onlyPossibleCallee);
       } else {
        // if the method descriptor is virtual, then there could be a
        // set of possible methods that will actually be invoked, so
-       // find all of them and merge all of their graphs together
-       TypeDescriptor typeDesc        = fc.getThis().getType();
+       // find all of them and merge all of their results together
+       TypeDescriptor typeDesc = fc.getThis().getType();
        Set possibleCallees = callGraph.getMethods(md, typeDesc);
 
-       //int j = 0;
-
        Iterator i = possibleCallees.iterator();
        while( i.hasNext() ) {
          MethodDescriptor possibleMd = (MethodDescriptor) i.next();
-         //allocSiteSet.addAll( getAllocationSiteSet( possibleMd ) );
-         OwnershipGraph ogPotentialCallee = mapDescriptorToCompleteOwnershipGraph.get(possibleMd);
 
-         /*
-            if( ogPotentialCallee != null ) {
-             ogPotentialCallee.writeGraph( "potential"+j, false, false );
-          ++j;
-            }
-          */
+         // don't alter the working graph (og) until we compute a result for every
+         // possible callee, merge them all together, then set og to that
+         OwnershipGraph ogCopy = new OwnershipGraph(allocationDepth, typeUtil);
+         ogCopy.merge(og);
 
-         ogAllPossibleCallees.merge(ogPotentialCallee);
+         OwnershipGraph ogPotentialCallee = mapDescriptorToCompleteOwnershipGraph.get(possibleMd);
+         ogCopy.resolveMethodCall(fc, md.isStatic(), flatm, ogPotentialCallee);
+         ogMergeOfAllPossibleCalleeResults.merge(ogCopy);
        }
-
-       //System.out.println( "There were "+j+" potential callees merged together." );
       }
 
-      //System.out.println( "AllocationSiteSet has "+allocSiteSet.size()+" items." );
-
-      // now we should have the following information to resolve this method call:
-      //
-      // 1. A FlatCall fc to query for the caller's context (argument labels, etc)
-      //
-      // 2. Whether the method is static; if not we need to deal with the "this" pointer
-      //
-      // *******************************************************************************************
-      // 3. The original FlatMethod flatm to query for callee's context (paramter labels)
-      //   NOTE!  I assume FlatMethod before virtual dispatch accurately describes all possible methods!
-      // *******************************************************************************************
-      //
-      // 4. The OwnershipGraph ogAllPossibleCallees is a merge of every ownership graph of all the possible
-      // methods to capture any possible references made.
-      //
-      // 5. The Set of AllocationSite objects, allocSiteSet that is the set of allocation sites from
-      // every possible method we might have chosen
-      //
-      og.resolveMethodCall(fc, md.isStatic(), flatm, ogAllPossibleCallees);
+      og = ogMergeOfAllPossibleCalleeResults;      
       break;
 
     case FKind.FlatReturnNode:
       FlatReturnNode frn = (FlatReturnNode) fn;
+      rhs = frn.getReturnTemp();
+      if( rhs != null && !rhs.getType().isImmutable() ) {
+       og.assignReturnEqualToTemp(rhs);
+      }
       setRetNodes.add(frn);
       break;
     }
+
+    return og;
+  }
+
+
+  // insert a call to debugSnapshot() somewhere in the analysis to get
+  // successive captures of the analysis state
+  int debugCounter        = 0;
+  int numStartCountReport = 0;
+  int freqCountReport     = 1000;
+  int iterStartCapture    = 20000;
+  int numIterToCapture    = 400;
+  void debugSnapshot( OwnershipGraph og, FlatNode fn ) {
+    ++debugCounter;
+    if( debugCounter > numStartCountReport &&
+       debugCounter % freqCountReport == 0 ) {
+      System.out.println( "    @@@ debug counter = "+debugCounter );
+    }
+    if( debugCounter > iterStartCapture ) {
+      System.out.println( "    @@@ capturing debug "+(debugCounter-iterStartCapture)+" @@@" );
+      String graphName = String.format("snap%04d",debugCounter-iterStartCapture);
+      if( fn != null ) {
+       graphName = graphName+fn;
+      }
+      try {
+       og.writeGraph( graphName, true, true, false, false, false );
+      } catch( Exception e ) {
+       System.out.println( "Error writing debug capture." );
+       System.exit( 0 );       
+      }
+    }
+    if( debugCounter == iterStartCapture + numIterToCapture ) {
+      System.out.println( "Stopping analysis after debug captures." );
+      System.exit( 0 );
+    }
   }
 
 
+
   // this method should generate integers strictly greater than zero!
   // special "shadow" regions are made from a heap region by negating
   // the ID
@@ -568,28 +652,40 @@ public class OwnershipAnalysis {
   }
 
 
-  private OwnershipGraph getGraphFromFlatNode(FlatNode fn) {
-    if( !mapFlatNodeToOwnershipGraph.containsKey(fn) ) {
-      mapFlatNodeToOwnershipGraph.put(fn, new OwnershipGraph(allocationDepth) );
-    }
+  private void setGraphForDescriptor(Descriptor d, OwnershipGraph og)
+  throws IOException {
 
-    return mapFlatNodeToOwnershipGraph.get(fn);
-  }
-
-  private void setGraphForFlatNode(FlatNode fn, OwnershipGraph og) {
-    mapFlatNodeToOwnershipGraph.put(fn, og);
-  }
+    mapDescriptorToCompleteOwnershipGraph.put(d, og);
 
+    // arguments to writeGraph are:
+    // boolean writeLabels,
+    // boolean labelSelect,
+    // boolean pruneGarbage,
+    // boolean writeReferencers
+    // boolean writeParamMappings
 
+    if( writeDOTs ) {
 
+      if( !writeAllDOTs ) {
+       og.writeGraph(d, true, true, true, false, false);
 
+      } else {
+       if( !mapDescriptorToNumUpdates.containsKey(d) ) {
+         mapDescriptorToNumUpdates.put(d, new Integer(0) );
+       }
+       Integer n = mapDescriptorToNumUpdates.get(d);
+       og.writeGraph(d, n, true, true, true, false, false);
+       mapDescriptorToNumUpdates.put(d, n + 1);
+      }
+    }
+  }
 
 
   // return just the allocation site associated with one FlatNew node
   private AllocationSite getAllocationSiteFromFlatNewPRIVATE(FlatNew fn) {
 
     if( !mapFlatNewToAllocationSite.containsKey(fn) ) {
-      AllocationSite as = new AllocationSite(allocationDepth, fn.getType() );
+      AllocationSite as = new AllocationSite(allocationDepth, fn );
 
       // the newest nodes are single objects
       for( int i = 0; i < allocationDepth; ++i ) {
@@ -678,8 +774,12 @@ public class OwnershipAnalysis {
       Iterator asItr = asSet.iterator();
       while( asItr.hasNext() ) {
        AllocationSite as = (AllocationSite) asItr.next();
-       if( as.getType().getClassDesc().hasFlags() ) {
-         asSetTotal.add(as);
+       TypeDescriptor typed = as.getType();
+       if( typed != null ) {
+         ClassDescriptor cd = typed.getClassDesc();
+         if( cd != null && cd.hasFlags() ) {
+           asSetTotal.add(as);
+         }
        }
       }
 
@@ -701,78 +801,4 @@ public class OwnershipAnalysis {
 
     return asSetTotal;
   }
-
-
-
-  private HashSet<Integer> getHeapRegionIDset(OwnershipGraph og,
-                                              int paramIndex) {
-
-    assert og.paramIndex2id.containsKey(paramIndex);
-    Integer idParam = og.paramIndex2id.get(paramIndex);
-
-    HashSet<Integer> idSet = new HashSet<Integer>();
-    idSet.add(idParam);
-
-    return idSet;
-  }
-
-
-  private HashSet<Integer> getHeapRegionIDset(AllocationSite alloc) {
-
-    HashSet<Integer> idSet = new HashSet<Integer>();
-
-    for( int i = 0; i < alloc.getAllocationDepth(); ++i ) {
-      Integer id = alloc.getIthOldest(i);
-      idSet.add(id);
-    }
-
-    Integer idSummary = alloc.getSummary();
-    idSet.add(idSummary);
-
-    return idSet;
-  }
-
-  private HashSet<Integer> getHeapRegionIDset(HashSet<AllocationSite> allocSet) {
-
-    HashSet<Integer> idSet = new HashSet<Integer>();
-
-    Iterator allocItr = allocSet.iterator();
-    while( allocItr.hasNext() ) {
-      AllocationSite alloc = (AllocationSite) allocItr.next();
-
-      for( int i = 0; i < alloc.getAllocationDepth(); ++i ) {
-       Integer id = alloc.getIthOldest(i);
-       idSet.add(id);
-      }
-
-      Integer idSummary = alloc.getSummary();
-      idSet.add(idSummary);
-    }
-
-    return idSet;
-  }
-
-  private boolean createsPotentialAliases(OwnershipGraph og,
-                                          HashSet<Integer> idSetA,
-                                          HashSet<Integer> idSetB) {
-    boolean potentialAlias = false;
-
-    /*
-       // first expand set B into the set of all heap region node ID's
-       // reachable from the nodes in set B
-       HashSet<Integer> idSetReachableFromB = og.getReachableSet( idSetB );
-
-       // then see if anything in A can reach a node in the set reachable
-       // from B.  If so, there is a potential alias.
-       Iterator i = idSetA.iterator();
-       while( i.hasNext() ) {
-        Integer id = (Integer) i.next();
-        if( og.canIdReachSet( id, idSetB ) ) {
-            return true;
-        }
-       }
-     */
-
-    return false;
-  }
 }