// VisitStack - Used to maintain the ordering. Top = current block
// First element is node pointer, second is the 'next child' to visit
// if the int in PointerIntTy is 0, the 'next child' to visit is invalid
// VisitStack - Used to maintain the ordering. Top = current block
// First element is node pointer, second is the 'next child' to visit
// if the int in PointerIntTy is 0, the 'next child' to visit is invalid