if (!didSomething) {  return; }
  private void rectifyPhiTypes() {    if (DEBUG) System.out.println("Rectify phi types.");    while (!scalarPhis.isEmpty()) {      for (Iterator i = scalarPhis.iterator(); i.hasNext(); ) {        OPT_Instruction phi = (OPT_Instruction)i.next();        phi.scratch = NO_NULL_TYPE;        if (DEBUG) System.out.println("PHI: " + phi);        VM_Type meet = meetPhiType(phi);        if (DEBUG) System.out.println("MEET: " + meet);        if (meet != null) {          if (phi.scratch == NO_NULL_TYPE) i.remove();          OPT_RegisterOperand result = (OPT_RegisterOperand)Phi.getResult(phi);          result.type = meet;          for (Enumeration e = OPT_DefUse.uses(result.register);               e.hasMoreElements(); ) {             OPT_RegisterOperand rop = (OPT_RegisterOperand)e.nextElement();            rop.type = meet;          }        }      }    }  }