public void addPhiOperand(RegisterSpec registerSpec,SsaBasicBlock predBlock){
  operands.add(new Operand(registerSpec,predBlock.getIndex(),predBlock.getRopLabel()));
  sources=null;
}

public void addPhiOperand ( RegisterSpec registerSpec , SsaBasicBlock predBlock ) { operands . add ( new Operand ( registerSpec , predBlock . getIndex ( ) , predBlock . getRopLabel ( ) ) ) ; sources = null ; }
adds an operand to this phi instruction .
