Robust/src/Analysis/Loops/DeadCode.java

   1 package Analysis.Loops;
   2 import IR.Flat.*;
   3 import IR.Operation;
   4 import java.util.HashSet;
   5 import java.util.Iterator;
   6
   7 public class DeadCode {
   8   public DeadCode() {
   9   }
  10   public void optimize(FlatMethod fm) {
  11     UseDef ud=new UseDef(fm);
  12     HashSet useful=new HashSet();
  13     boolean changed=true;
  14     while(changed) {
  15       changed=false;
  16 nextfn:
  17       for(Iterator<FlatNode> it=fm.getNodeSet().iterator(); it.hasNext(); ) {
  18         FlatNode fn=it.next();
  19         switch(fn.kind()) {
  20         case FKind.FlatCall:
  21         case FKind.FlatFieldNode:
  22         case FKind.FlatSetFieldNode:
  23         case FKind.FlatNew:
  24         case FKind.FlatCastNode:
  25         case FKind.FlatReturnNode:
  26         case FKind.FlatCondBranch:
  27         case FKind.FlatSetElementNode:
  28         case FKind.FlatElementNode:
  29         case FKind.FlatFlagActionNode:
  30         case FKind.FlatCheckNode:
  31         case FKind.FlatBackEdge:
  32         case FKind.FlatExit:
  33         case FKind.FlatTagDeclaration:
  34         case FKind.FlatMethod:
  35         case FKind.FlatAtomicEnterNode:
  36         case FKind.FlatAtomicExitNode:
  37         case FKind.FlatPrefetchNode:
  38         case FKind.FlatSESEEnterNode:
  39         case FKind.FlatSESEExitNode:
  40         case FKind.FlatGenReachNode:
  41         case FKind.FlatGenDefReachNode:
  42           if (!useful.contains(fn)) {
  43             useful.add(fn);
  44             changed=true;
  45           }
  46           break;
  47
  48         case FKind.FlatOpNode:
  49           FlatOpNode fon=(FlatOpNode)fn;
  50           if (fon.getOp().getOp()==Operation.DIV||
  51               fon.getOp().getOp()==Operation.MOD) {
  52             if (!useful.contains(fn)) {
  53               useful.add(fn);
  54               changed=true;
  55             }
  56             break;
  57           }
  58
  59         default:
  60           TempDescriptor[] writes=fn.writesTemps();
  61           if (!useful.contains(fn))
  62             for(int i=0; i<writes.length; i++) {
  63               for(Iterator<FlatNode> uit=ud.useMap(fn,writes[i]).iterator(); uit.hasNext(); ) {
  64                 FlatNode ufn=uit.next();
  65                 if (useful.contains(ufn)) {
  66                   //we are useful
  67                   useful.add(fn);
  68                   changed=true;
  69                   continue nextfn;
  70                 }
  71               }
  72             }
  73         }
  74       }
  75     }
  76     //get rid of useless nodes
  77     for(Iterator<FlatNode> it=fm.getNodeSet().iterator(); it.hasNext(); ) {
  78       FlatNode fn=it.next();
  79       if (!useful.contains(fn)||isuseless(fn)) {
  80         //We have a useless node
  81         FlatNode fnnext=fn.getNext(0);
  82         for(int i=0; i<fn.numPrev(); i++) {
  83           FlatNode nprev=fn.getPrev(i);
  84
  85           for(int j=0; j<nprev.numNext(); j++) {
  86             if (nprev.getNext(j)==fn) {
  87               nprev.setnext(j, fnnext);
  88               fnnext.addPrev(nprev);
  89             }
  90           }
  91         }
  92         //fix up prev edge of fnnext
  93         fnnext.removePrev(fn);
  94       }
  95     }
  96   }
  97   public boolean isuseless(FlatNode fn) {
  98     if (fn.kind()==FKind.FlatOpNode) {
  99       FlatOpNode fon=(FlatOpNode)fn;
 100       if (fon.getOp().getOp()==Operation.ASSIGN&&fon.getLeft()==fon.getDest())
 101         return true;
 102     }
 103     return false;
 104   }
 105
 106 }