typedef struct _tr {
  char *pc;
  int type;
  struct _tr *list_next;
  struct _tr *left;
  struct _tr *right;
} TRnode;

enum tr_idents {
  IDENT,
  NOP,
  PTR,
  LABEL,
  STORAGE_CLASS,
  TYPE,
  OP
  };

#define TOP 1
#define BOTTOM 2