There are several candidate translations. Which you might choose depends on those constraints on the actual problem (instead of this pretend one) that make "f x = 0" not an eminently better solution.

The one that probably most closely matches the semantics of the pseudo-code would be:

    let f0 x = unsafePerformIO $ do
        iRef <- newIORef 17
        whileM_ (fmap (>0) $ readIORef iRef) $ do
            modifyIORef iRef (\ i -> i - 1)

        readIORef iRef

Better would be to let Haskell help check that the mutation is local and no references escape:

    let f1 x = runST $ do
        iRef <- newSTRef 17
        whileM_ (fmap (>0) $ readSTRef iRef) $ do
            modifySTRef iRef (\ i -> i - 1)

        readSTRef iRef

There's the more idiomatic translation, where for something this simple we wouldn't bother with State:

    let f2 x = go 17
      where
        go i | i > 0 = go (i - 1)
             | otherwise = i

The literal translation using State is:

    let f3 x = execState countdown 17
      where
        countdown = whileM_ (>0) $ modify (\ i -> i - 1)

In all cases, the function as a whole is referentially transparent.

In your function, "while i > 0 { i := i - 1 }" is clearly not referentially transparent. Attempting to transliterate in a way that preserves this expression, it is unsurprising that we wind up with expressions that depend on state. The State monad is one way of encapsulating this. Note that f3 and f2 are actually very similar. The execState function doesn't do any deep voodoo - a value of type "State s a" is a thin wrapper around a function of type "s -> (a, s)"; execState simply extracts this function, applies it to a value, and returns the second part of the output.

The actual definitions are equivalent to these (albeit slightly more complicated to keep things DRY w/ transformers):

    newtype State s a = State (s -> (a, s))

    execState (State f) s = let (_, s') = f s in s'

What I don't see, in any of this, is a problem (conceptual or practical) involving "destructors". Is your objection to the need to call execState (or its friends)?