Programming Languages Research Group: Git - IRC.git/blob

   1 package Analysis.Locality;
   2
   3 import java.util.*;
   4 import Analysis.CallGraph.CallGraph;
   5 import IR.SymbolTable;
   6 import IR.State;
   7 import IR.TypeUtil;
   8 import IR.MethodDescriptor;
   9 import IR.Flat.*;
  10
  11 public class LocalityAnalysis {
  12     State state;
  13     Stack lbtovisit;
  14     Hashtable<LocalityBinding,LocalityBinding> discovered;
  15     Hashtable<LocalityBinding, Set<LocalityBinding>> dependence;
  16     Hashtable<LocalityBinding, Hashtable<FlatNode,Hashtable<TempDescriptor, Integer>>> temptab;
  17     Hashtable<LocalityBinding, Hashtable<FlatNode, Integer>> atomictab;
  18     Hashtable<LocalityBinding, Hashtable<FlatAtomicEnterNode, Set<TempDescriptor>>> tempstosave;
  19
  20     CallGraph callgraph;
  21     TypeUtil typeutil;
  22     public static final Integer LOCAL=new Integer(0);
  23     public static final Integer GLOBAL=new Integer(1);
  24     public static final Integer EITHER=new Integer(2);
  25     public static final Integer CONFLICT=new Integer(3);
  26
  27     public LocalityAnalysis(State state, CallGraph callgraph, TypeUtil typeutil) {
  28         this.typeutil=typeutil;
  29         this.state=state;
  30         this.discovered=new Hashtable<LocalityBinding,LocalityBinding>();
  31         this.dependence=new Hashtable<LocalityBinding, Set<LocalityBinding>>();
  32         this.temptab=new Hashtable<LocalityBinding, Hashtable<FlatNode,Hashtable<TempDescriptor, Integer>>>();
  33         this.atomictab=new Hashtable<LocalityBinding, Hashtable<FlatNode, Integer>>();
  34         this.lbtovisit=new Stack();
  35         this.callgraph=callgraph;
  36         this.tempstosave=new Hashtable<LocalityBinding, Hashtable<FlatAtomicEnterNode, Set<TempDescriptor>>>();
  37
  38         doAnalysis();
  39     }
  40
  41     /** This method returns a set of LocalityBindings.  A
  42      * LocalityBinding specifies a context a method can be invoked in.
  43      * It specifies whether the method is in a transaction and whether
  44      * its parameter objects are locals or globals.  */
  45
  46     public Set<LocalityBinding> getLocalityBindings() {
  47         return discovered.keySet();
  48     }
  49
  50     /** This method returns a hashtable for a given LocalityBinding
  51      * that tells the current local/global status of temps at the each
  52      * node in the flat representation. */
  53
  54     public Hashtable<FlatNode, Hashtable<TempDescriptor, Integer>> getNodeTempInfo(LocalityBinding lb) {
  55         return temptab.get(lb);
  56     }
  57
  58     /** This method returns an hashtable for a given LocalitBinding
  59      * that tells whether a node in the flat represenation is in a
  60      * transaction or not.  Integer values greater than 0 indicate
  61      * that the node is in a transaction and give the nesting depth.
  62      * The outermost AtomicEnterNode will have a value of 1 and the
  63      * outermost AtomicExitNode will have a value of 0. */
  64
  65     public Hashtable<FlatNode, Integer> getAtomic(LocalityBinding lb) {
  66         return atomictab.get(lb);
  67     }
  68
  69     /** This methods returns a hashtable for a given LocalityBinding
  70      * that tells which temps needs to be saved for each
  71      * AtomicEnterNode.  */
  72
  73     public Hashtable<FlatAtomicEnterNode, Set<TempDescriptor>> getTemps(LocalityBinding lb) {
  74         return tempstosave.get(lb);
  75     }
  76
  77     private void doAnalysis() {
  78         computeLocalityBindings();
  79         computeTempstoSave();
  80     }
  81
  82     private void computeLocalityBindings() {
  83         LocalityBinding lbmain=new LocalityBinding(typeutil.getMain(), false);
  84         lbmain.setGlobal(0, LOCAL);
  85         lbtovisit.add(lbmain);
  86         discovered.put(lbmain, lbmain);
  87
  88         while(!lbtovisit.empty()) {
  89             LocalityBinding lb=(LocalityBinding) lbtovisit.pop();
  90             Integer returnglobal=lb.getGlobalReturn();
  91             MethodDescriptor md=lb.getMethod();
  92             Hashtable<FlatNode,Hashtable<TempDescriptor, Integer>> temptable=new Hashtable<FlatNode,Hashtable<TempDescriptor, Integer>>();
  93             Hashtable<FlatNode, Integer> atomictable=new Hashtable<FlatNode, Integer>();
  94             computeCallsFlags(md, lb, temptable, atomictable);
  95             atomictab.put(lb, atomictable);
  96             temptab.put(lb, temptable);
  97
  98             if (!md.isStatic()&&!returnglobal.equals(lb.getGlobalReturn())) {
  99                 //return type is more precise now
 100                 //rerun everything that call us
 101                 lbtovisit.addAll(dependence.get(lb));
 102             }
 103         }
 104     }
 105
 106
 107     public void computeCallsFlags(MethodDescriptor md, LocalityBinding lb, Hashtable<FlatNode, Hashtable<TempDescriptor, Integer>> temptable, Hashtable<FlatNode, Integer> atomictable) {
 108         FlatMethod fm=state.getMethodFlat(md);
 109         HashSet<FlatNode> tovisit=new HashSet<FlatNode>();
 110         tovisit.add(fm.getNext(0));
 111         {
 112             // Build table for initial node
 113             Hashtable<TempDescriptor,Integer> table=new Hashtable<TempDescriptor,Integer>();
 114             temptable.put(fm, table);
 115             atomictable.put(fm, lb.isAtomic()?1:0);
 116             int offset=md.isStatic()?0:1;
 117             if (!md.isStatic()) {
 118                 table.put(fm.getParameter(0), lb.getGlobalThis());
 119             }
 120             for(int i=offset;i<fm.numParameters();i++) {
 121                 TempDescriptor temp=fm.getParameter(i);
 122                 Integer b=lb.isGlobal(i-offset);
 123                 table.put(temp,b);
 124             }
 125         }
 126
 127         while(!tovisit.isEmpty()) {
 128             FlatNode fn=tovisit.iterator().next();
 129             tovisit.remove(fn);
 130             Hashtable<TempDescriptor, Integer> currtable=new Hashtable<TempDescriptor, Integer>();
 131             int atomicstate=0;
 132             for(int i=0;i<fn.numPrev();i++) {
 133                 FlatNode prevnode=fn.getPrev(i);
 134                 if (atomictable.containsKey(prevnode)) {
 135                     atomicstate=atomictable.get(prevnode).intValue();
 136                 }
 137                 if (!temptable.containsKey(prevnode))
 138                     continue;
 139                 Hashtable<TempDescriptor, Integer> prevtable=temptable.get(prevnode);
 140                 for(Iterator<TempDescriptor> tempit=prevtable.keySet().iterator();tempit.hasNext();) {
 141                     TempDescriptor temp=tempit.next();
 142                     Integer tmpint=prevtable.get(temp);
 143                     Integer oldint=currtable.containsKey(temp)?currtable.get(temp):EITHER;
 144                     Integer newint=merge(tmpint, oldint);
 145                     currtable.put(temp, newint);
 146                 }
 147             }
 148             atomictable.put(fn, atomicstate);
 149             // Process this node
 150             switch(fn.kind()) {
 151             case FKind.FlatAtomicEnterNode:
 152                 processAtomicEnterNode((FlatAtomicEnterNode)fn, atomictable);
 153                 break;
 154             case FKind.FlatAtomicExitNode:
 155                 processAtomicExitNode((FlatAtomicExitNode)fn, atomictable);
 156                 break;
 157             case FKind.FlatCall:
 158                 processCallNode(lb, (FlatCall)fn, currtable, isAtomic(atomictable, fn));
 159                 break;
 160             case FKind.FlatFieldNode:
 161                 processFieldNode(lb, (FlatFieldNode)fn, isAtomic(atomictable, fn), currtable);
 162                 break;
 163             case FKind.FlatSetFieldNode:
 164                 processSetFieldNode(lb, (FlatSetFieldNode)fn, isAtomic(atomictable,fn), currtable);
 165                 break;
 166             case FKind.FlatNew:
 167                 processNew(lb, (FlatNew)fn, isAtomic(atomictable, fn), currtable);
 168                 break;
 169             case FKind.FlatOpNode:
 170                 processOpNode((FlatOpNode)fn, currtable);
 171                 break;
 172             case FKind.FlatCastNode:
 173                 processCastNode((FlatCastNode)fn, currtable);
 174                 break;
 175             case FKind.FlatLiteralNode:
 176                 processLiteralNode((FlatLiteralNode)fn, currtable);
 177                 break;
 178             case FKind.FlatReturnNode:
 179                 processReturnNode(lb, (FlatReturnNode)fn, currtable);
 180                 break;
 181             case FKind.FlatSetElementNode:
 182                 processSetElementNode(lb, (FlatSetElementNode)fn, currtable, isAtomic(atomictable, fn));
 183                 break;
 184             case FKind.FlatElementNode:
 185                 processElementNode(lb, (FlatElementNode)fn, currtable, isAtomic(atomictable, fn));
 186                 break;
 187             case FKind.FlatCondBranch:
 188             case FKind.FlatBackEdge:
 189             case FKind.FlatNop:
 190                 //No action needed for these
 191                 break;
 192             case FKind.FlatFlagActionNode:
 193             case FKind.FlatCheckNode:
 194             case FKind.FlatTagDeclaration:
 195                 throw new Error("Incompatible with tasks!");
 196             case FKind.FlatMethod:
 197             default:
 198                 throw new Error();
 199             }
 200             Hashtable<TempDescriptor,Integer> oldtable=temptable.get(fn);
 201             if (oldtable==null||!oldtable.equals(currtable)) {
 202                 // Update table for this node
 203                 temptable.put(fn, currtable);
 204                 for(int i=0;i<fn.numNext();i++) {
 205                     tovisit.add(fn.getNext(i));
 206                 }
 207             }
 208         }
 209     }
 210
 211     private static boolean isAtomic(Hashtable<FlatNode, Integer> atomictable, FlatNode fn) {
 212         return atomictable.get(fn).intValue()>0;
 213     }
 214
 215     private static Integer merge(Integer a, Integer b) {
 216         if (a==null||a.equals(EITHER))
 217             return b;
 218         if (b==null||b.equals(EITHER))
 219             return a;
 220         if (a.equals(b))
 221             return a;
 222         return CONFLICT;
 223     }
 224
 225     void processCallNode(LocalityBinding currlb, FlatCall fc, Hashtable<TempDescriptor, Integer> currtable, boolean isatomic) {
 226         MethodDescriptor nodemd=fc.getMethod();
 227         Set methodset=fc.getThis()==null?callgraph.getMethods(nodemd):
 228             callgraph.getMethods(nodemd, fc.getThis().getType());
 229         Integer currreturnval=EITHER; //Start off with the either value
 230         for(Iterator methodit=methodset.iterator();methodit.hasNext();) {
 231             MethodDescriptor md=(MethodDescriptor) methodit.next();
 232             LocalityBinding lb=new LocalityBinding(md, isatomic);
 233             for(int i=0;i<fc.numArgs();i++) {
 234                 TempDescriptor arg=fc.getArg(i);
 235                 lb.setGlobal(i,currtable.get(arg));
 236             }
 237             if (fc.getThis()!=null) {
 238                 Integer thistype=currtable.get(fc.getThis());
 239                 if (thistype==null)
 240                     thistype=EITHER;
 241                 if(thistype.equals(CONFLICT))
 242                     throw new Error("Using type that can be either local or global in context:\n"+currlb.getExplanation());
 243                 if(thistype.equals(GLOBAL)&&!isatomic)
 244                     throw new Error("Using global object outside of transaction in context:\n"+currlb.getExplanation());
 245                 lb.setGlobalThis(thistype);
 246             } else
 247                 lb.setGlobalThis(EITHER);//default value
 248             //lb is built
 249             if (!discovered.containsKey(lb)) {
 250                 lb.setGlobalReturn(EITHER);
 251                 lb.setParent(currlb);
 252                 lbtovisit.add(lb);
 253                 discovered.put(lb, lb);
 254             } else
 255                 lb=discovered.get(lb);
 256             Integer returnval=lb.getGlobalReturn();
 257             currreturnval=merge(returnval, currreturnval);
 258             if (!dependence.containsKey(lb))
 259                 dependence.put(lb, new HashSet<LocalityBinding>());
 260             dependence.get(lb).add(currlb);
 261         }
 262         if (fc.getReturnTemp()!=null) {
 263             currtable.put(fc.getReturnTemp(), currreturnval);
 264         }
 265     }
 266
 267     void processFieldNode(LocalityBinding lb, FlatFieldNode ffn, boolean transaction, Hashtable<TempDescriptor, Integer> currtable) {
 268         Integer type=currtable.get(ffn.getSrc());
 269         TempDescriptor dst=ffn.getDst();
 270         if (type.equals(LOCAL)) {
 271             if (ffn.getField().isGlobal())
 272                 currtable.put(dst,GLOBAL);
 273             else
 274                 currtable.put(dst,LOCAL);
 275         } else if (type.equals(GLOBAL)) {
 276             if (!transaction)
 277                 throw new Error("Global access outside of a transaction in context:\n"+lb.getExplanation());
 278             if (ffn.getField().getType().isPrimitive())
 279                 currtable.put(dst, LOCAL); // primitives are local
 280             else
 281                 currtable.put(dst, GLOBAL);
 282         } else if (type.equals(EITHER)) {
 283             if (ffn.getField().getType().isPrimitive())
 284                 currtable.put(dst, LOCAL); // primitives are local
 285             else
 286                 currtable.put(dst, EITHER);
 287         } else if (type.equals(CONFLICT)) {
 288             throw new Error("Access to object that could be either global or local in context:\n"+lb.getExplanation());
 289         }
 290     }
 291
 292     //need to handle primitives
 293     void processSetFieldNode(LocalityBinding lb, FlatSetFieldNode fsfn, boolean transaction, Hashtable<TempDescriptor, Integer> currtable) {
 294         Integer srctype=currtable.get(fsfn.getSrc());
 295         Integer dsttype=currtable.get(fsfn.getDst());
 296
 297         if (dsttype.equals(LOCAL)) {
 298             if (fsfn.getField().isGlobal()) {
 299                 if (!(srctype.equals(GLOBAL)||srctype.equals(EITHER)))
 300                     throw new Error("Writing possible local reference to global field in context: \n"+lb.getExplanation());
 301             } else {
 302                 if (!(srctype.equals(LOCAL)||srctype.equals(EITHER)))
 303                     throw new Error("Writing possible global reference to local object in context: \n"+lb.getExplanation());
 304             }
 305         } else if (dsttype.equals(GLOBAL)) {
 306             if (!transaction)
 307                 throw new Error("Global access outside of a transaction in context:\n"+lb.getExplanation());
 308             //okay to store primitives in global object
 309             if (srctype.equals(LOCAL) && fsfn.getField().getType().isPrimitive())
 310                 return;
 311             if (!(srctype.equals(GLOBAL)||srctype.equals(EITHER)))
 312                 throw new Error("Writing possible local reference to global object in context:\n"+lb.getExplanation());
 313         } else if (dsttype.equals(EITHER)) {
 314             if (srctype.equals(CONFLICT))
 315                 throw new Error("Using reference that could be local or global in context:\n"+lb.getExplanation());
 316         } else if (dsttype.equals(CONFLICT)) {
 317             throw new Error("Access to object that could be either global or local in context:\n"+lb.getExplanation());
 318         }
 319     }
 320
 321     void processNew(LocalityBinding lb, FlatNew fn, boolean transaction, Hashtable<TempDescriptor, Integer> currtable) {
 322         if (fn.isGlobal()&&!transaction) {
 323             throw new Error("Allocating global object outside of transaction in context:"+lb.getExplanation());
 324         }
 325         if (fn.isGlobal())
 326             currtable.put(fn.getDst(), GLOBAL);
 327         else
 328             currtable.put(fn.getDst(), LOCAL);
 329     }
 330
 331     void processOpNode(FlatOpNode fon, Hashtable<TempDescriptor, Integer> currtable) {
 332         /* Just propagate value */
 333         currtable.put(fon.getDest(), currtable.get(fon.getLeft()));
 334     }
 335
 336     void processCastNode(FlatCastNode fcn, Hashtable<TempDescriptor, Integer> currtable) {
 337         currtable.put(fcn.getDst(), currtable.get(fcn.getSrc()));
 338     }
 339
 340     void processLiteralNode(FlatLiteralNode fln, Hashtable<TempDescriptor, Integer> currtable) {
 341         //null is either
 342         if (fln.getValue()==null)
 343             currtable.put(fln.getDst(), EITHER);
 344         else
 345             currtable.put(fln.getDst(), LOCAL);
 346     }
 347
 348     void processReturnNode(LocalityBinding lb, FlatReturnNode frn, Hashtable<TempDescriptor, Integer> currtable) {
 349         if(frn.getReturnTemp()!=null) {
 350             Integer returntype=currtable.get(frn.getReturnTemp());
 351             lb.setGlobalReturn(merge(returntype, lb.getGlobalReturn()));
 352         }
 353     }
 354
 355     void processSetElementNode(LocalityBinding lb, FlatSetElementNode fsen, Hashtable<TempDescriptor, Integer> currtable, boolean isatomic) {
 356         Integer srctype=currtable.get(fsen.getSrc());
 357         Integer dsttype=currtable.get(fsen.getDst());
 358
 359         if (dsttype.equals(LOCAL)) {
 360             if (!(srctype.equals(LOCAL)||srctype.equals(EITHER)))
 361                 throw new Error("Writing possible global reference to local object in context:\n"+lb.getExplanation());
 362         } else if (dsttype.equals(GLOBAL)) {
 363             if (!(srctype.equals(GLOBAL)||srctype.equals(EITHER)))
 364                 throw new Error("Writing possible local reference to global object in context:\n"+lb.getExplanation());
 365             if (!isatomic)
 366                 throw new Error("Global access outside of a transaction in context:\n"+lb.getExplanation());
 367         } else if (dsttype.equals(EITHER)) {
 368             if (srctype.equals(CONFLICT))
 369                 throw new Error("Using reference that could be local or global in context:\n"+lb.getExplanation());
 370         } else if (dsttype.equals(CONFLICT)) {
 371             throw new Error("Access to object that could be either global or local in context:\n"+lb.getExplanation());
 372         }
 373     }
 374
 375     void processElementNode(LocalityBinding lb, FlatElementNode fen, Hashtable<TempDescriptor, Integer> currtable, boolean isatomic) {
 376         Integer type=currtable.get(fen.getSrc());
 377         TempDescriptor dst=fen.getDst();
 378         if (type.equals(LOCAL)) {
 379             currtable.put(dst,LOCAL);
 380         } else if (type.equals(GLOBAL)) {
 381             if (!isatomic)
 382                 throw new Error("Global access outside of a transaction in context:\n"+lb.getExplanation());
 383             currtable.put(dst, GLOBAL);
 384         } else if (type.equals(EITHER)) {
 385             currtable.put(dst, EITHER);
 386         } else if (type.equals(CONFLICT)) {
 387             throw new Error("Access to object that could be either global or local in context:\n"+lb.getExplanation());
 388         }
 389     }
 390
 391     void processAtomicEnterNode(FlatAtomicEnterNode fen, Hashtable<FlatNode, Integer> atomictable) {
 392         int atomic=atomictable.get(fen).intValue();
 393         atomictable.put(fen, new Integer(atomic+1));
 394     }
 395
 396     void processAtomicExitNode(FlatAtomicExitNode fen, Hashtable<FlatNode, Integer> atomictable) {
 397         int atomic=atomictable.get(fen).intValue();
 398         atomictable.put(fen, new Integer(atomic-1));
 399     }
 400
 401     private Hashtable<FlatNode, Set<TempDescriptor>> computeLiveTemps(FlatMethod fm) {
 402         Hashtable<FlatNode, Set<TempDescriptor>> nodetotemps=new Hashtable<FlatNode, Set<TempDescriptor>>();
 403
 404         Set<FlatNode> toprocess=fm.getNodeSet();
 405
 406         while(!toprocess.isEmpty()) {
 407             FlatNode fn=toprocess.iterator().next();
 408             toprocess.remove(fn);
 409
 410             List<TempDescriptor> reads=Arrays.asList(fn.readsTemps());
 411             List<TempDescriptor> writes=Arrays.asList(fn.readsTemps());
 412
 413             HashSet<TempDescriptor> tempset=new HashSet<TempDescriptor>();
 414             for(int i=0;i<fn.numNext();i++) {
 415                 FlatNode fnnext=fn.getNext(i);
 416                 if (nodetotemps.containsKey(fnnext))
 417                     tempset.addAll(nodetotemps.get(fnnext));
 418             }
 419             tempset.removeAll(writes);
 420             tempset.addAll(reads);
 421             if (!nodetotemps.containsKey(fn)||
 422                 nodetotemps.get(fn).equals(tempset)) {
 423                 nodetotemps.put(fn, tempset);
 424                 for(int i=0;i<fn.numPrev();i++)
 425                     toprocess.add(fn.getPrev(i));
 426             }
 427         }
 428         return nodetotemps;
 429     }
 430
 431     private void computeTempstoSave() {
 432         for(Iterator<LocalityBinding> lbit=getLocalityBindings().iterator();lbit.hasNext();) {
 433             LocalityBinding lb=lbit.next();
 434             computeTempstoSave(lb);
 435         }
 436     }
 437
 438     /* Need to checkpoint all temps that could be read from along any
 439      * path that are either:
 440        1) Written to by any assignment inside the transaction
 441        2) Read from a global temp.
 442
 443        Generate tempstosave map from
 444        localitybinding->flatatomicenternode->Set<TempDescriptors>
 445     */
 446
 447     private void computeTempstoSave(LocalityBinding lb) {
 448         if (lb.isAtomic())
 449             return;
 450         Hashtable<FlatNode, Integer> atomictab=getAtomic(lb);
 451         Hashtable<FlatNode, Hashtable<TempDescriptor, Integer>> temptab=getNodeTempInfo(lb);
 452         MethodDescriptor md=lb.getMethod();
 453         FlatMethod fm=state.getMethodFlat(md);
 454
 455         Hashtable<FlatNode, Set<TempDescriptor>> nodetotemps=computeLiveTemps(fm);
 456         Hashtable<FlatAtomicEnterNode, Set<TempDescriptor>> nodetosavetemps=new Hashtable<FlatAtomicEnterNode, Set<TempDescriptor>>();
 457         tempstosave.put(lb, nodetosavetemps);
 458
 459         Hashtable<FlatNode, FlatAtomicEnterNode> nodemap=new Hashtable<FlatNode, FlatAtomicEnterNode>();
 460
 461         HashSet<FlatNode> toprocess=new HashSet<FlatNode>();
 462         HashSet<FlatNode> discovered=new HashSet<FlatNode>();
 463         toprocess.add(fm);
 464         discovered.add(fm);
 465         while(!toprocess.isEmpty()) {
 466             FlatNode fn=toprocess.iterator().next();
 467             toprocess.remove(fn);
 468             boolean isatomic=atomictab.get(fn).intValue()>0;
 469             if (isatomic&&
 470                 atomictab.get(fn.getPrev(0)).intValue()==0) {
 471                 assert(fn.getPrev(0).kind()==FKind.FlatAtomicEnterNode);
 472                 nodemap.put(fn, (FlatAtomicEnterNode)fn);
 473                 nodetosavetemps.put((FlatAtomicEnterNode)fn, new HashSet<TempDescriptor>());
 474             } else if (isatomic) {
 475                 FlatAtomicEnterNode atomicnode=nodemap.get(fn);
 476                 Set<TempDescriptor> livetemps=nodetotemps.get(fn);
 477                 List<TempDescriptor> reads=Arrays.asList(fn.readsTemps());
 478                 List<TempDescriptor> writes=Arrays.asList(fn.readsTemps());
 479
 480                 for(Iterator<TempDescriptor> tempit=livetemps.iterator();tempit.hasNext();) {
 481                     TempDescriptor tmp=tempit.next();
 482                     if (writes.contains(tmp)) {
 483                         nodetosavetemps.get(fn).add(tmp);
 484                     } else if (reads.contains(tmp)&&temptab.get(fn).get(tmp)==GLOBAL) {
 485                         nodetosavetemps.get(fn).add(tmp);
 486                     }
 487                 }
 488             }
 489             for(int i=0;i<fn.numNext();i++) {
 490                 FlatNode fnnext=fn.getNext(i);
 491                 if (!discovered.contains(fnnext)) {
 492                     discovered.add(fnnext);
 493                     toprocess.add(fnnext);
 494                     if(isatomic) {
 495                         nodemap.put(fnnext, nodemap.get(fn));
 496                     }
 497                 }
 498             }
 499         }
 500     }
 501 }