let node_stmt_opt v = match node_type v with
| Vstart | Vtest (false, _, _)
| VfctIn | VfctOut | Vend | Vexit | Vloop2 _ -> None
| VblkIn (bk, _) | VblkOut (bk, _) -> bkind_stmt bk
| Vstmt s | Vtest (true, s, _) | Vloop (_, s) | Vswitch (s,_)
| Vcall (s, _, _, _)
-> Some s