fact function in WebAssembly

fact.wat

(module
  (export "fact" (func $fact))

  (func $fact (param $n i32) (result i32)
    (local $result i32)
    (set_local $result (i32.const 1))
    (if (get_local $n)
       (loop $start
          (set_local $result (i32.mul (get_local $n) (get_local $result)))
          (tee_local $n      (i32.sub (get_local $n) (i32.const 1)))
          (br_if $start) 
       )
    )
    (get_local $result)
  )
)