Re: [Caml-list] Tail recursion detection

[Alain Frisch <frisch@clipper.ens.fr>]

On Mon, 20 May 2002, John Max Skaller wrote:

> I'm in the process of writing a tail recursion detector for
> Felix, and many of the routines are tail recursive (heh!).
> However, in a few places, there are multi-way branches
> each of which terminate in identical tail calls:
>
> let rec f x y = match .. with
>    | .. ->
>       if .. then
>       if .. then
>       if .. then
> 	f x' y'
>       else f x' y'
>       else f x' y'
>       else f x' y'
> ..


These would be tail calls even with different x' and y' ...

> My question is: how smart is the Ocaml tail call detector?

As far as I can tell, the detection is quite easy: just replace
during (some kind of intermediate) code generation any call followed
by a return with a tail call (after replacing any jump to a return
with the return). This is enough to detect tail call in your example.
Have a look at the OCaml bytecode generator, it is easy enough to get the
idea.


Does this answer your question ?

-- Alain

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