basicblocks.java

来自「编译原理大作业---tiger编译器 包括semant,translate,m」· Java 代码 · 共 50 行

package Canon;

public class BasicBlocks {
  public StmListList blocks;
  public Temp.Label done;

  private StmListList lastBlock;
  private Tree.StmList lastStm;

  private void addStm(Tree.Stm s) {
    lastStm = lastStm.tail = new Tree.StmList(s,null);
  }

  private void doStms(Tree.StmList l) {
      if (l==null)
    doStms(new Tree.StmList(new Tree.JUMP(done), null));
      else if (l.head instanceof Tree.JUMP
          || l.head instanceof Tree.CJUMP) {
    addStm(l.head);
    mkBlocks(l.tail);
      }
      else if (l.head instanceof Tree.LABEL)
           doStms(new Tree.StmList(new Tree.JUMP(((Tree.LABEL)l.head).label),
                   l));
      else {
    addStm(l.head);
    doStms(l.tail);
      }
  }

  void mkBlocks(Tree.StmList l) {
     if (l==null) return;
     else if (l.head instanceof Tree.LABEL) {
    lastStm = new Tree.StmList(l.head,null);
        if (lastBlock==null)
       lastBlock= blocks= new StmListList(lastStm,null);
        else
       lastBlock = lastBlock.tail = new StmListList(lastStm,null);
    doStms(l.tail);
     }
     else mkBlocks(new Tree.StmList(new Tree.LABEL(new Temp.Label()), l));
  }


  public BasicBlocks(Tree.StmList stms) {
    done = new Temp.Label();
    mkBlocks(stms);
  }
}