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.FlatTagDeclaration:
  33         case FKind.FlatMethod:
  34         case FKind.FlatAtomicEnterNode:
  35         case FKind.FlatAtomicExitNode:
  36         case FKind.FlatPrefetchNode:
  37         case FKind.FlatSESEEnterNode:
  38         case FKind.FlatSESEExitNode:
  39           if (!useful.contains(fn)) {
  40             useful.add(fn);
  41             changed=true;
  42           }
  43           break;
  44         case FKind.FlatOpNode:
  45           FlatOpNode fon=(FlatOpNode)fn;
  46           if (fon.getOp().getOp()==Operation.DIV||
  47               fon.getOp().getOp()==Operation.MOD) {
  48             if (!useful.contains(fn)) {
  49               useful.add(fn);
  50               changed=true;
  51             }
  52             break;
  53           }
  54         default:
  55           TempDescriptor[] writes=fn.writesTemps();
  56           if (!useful.contains(fn))
  57             for(int i=0;i<writes.length;i++) {
  58               for(Iterator<FlatNode> uit=ud.useMap(fn,writes[i]).iterator();uit.hasNext();) {
  59                 FlatNode ufn=uit.next();
  60                 if (useful.contains(ufn)) {
  61                   //we are useful
  62                   useful.add(fn);
  63                   changed=true;
  64                   continue nextfn;
  65                 }
  66               }
  67             }
  68         }
  69       }
  70     }
  71     //get rid of useless nodes
  72     for(Iterator<FlatNode> it=fm.getNodeSet().iterator();it.hasNext();) {
  73       FlatNode fn=it.next();
  74       if (!useful.contains(fn)) {
  75         //We have a useless node
  76         FlatNode fnnext=fn.getNext(0);
  77         for(int i=0;i<fn.numPrev();i++) {
  78           FlatNode nprev=fn.getPrev(i);
  79           for(int j=0;j<nprev.numNext();j++) {
  80             if (nprev.getNext(j)==fn) {
  81               nprev.setnext(j, fnnext);
  82               fnnext.addPrev(nprev);
  83             }
  84           }
  85         }
  86         //fix up prev edge of fnnext
  87         fnnext.removePrev(fn);
  88       }
  89     }
  90   }
  91 }