let num_defs stm =
match stm.skind with
Instr(il) -> List.fold_left (fun s i ->
let _, d = UD.computeUseDefInstr i in
s + UD.VS.cardinal d) 0 [il]
| _ -> let _, d = UD.computeUseDefStmtKind stm.skind in
UD.VS.cardinal d