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OCaml defunctorization and other optimizations
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Date: -- (:)
From: Török_Edwin <edwintorok@g...>
Subject: Re: [Caml-list] OCaml defunctorization and other optimizations
On 05/20/2010 11:41 AM, Julien Signoles wrote:
> Hello,
> 
> 2010/5/19 Török Edwin <edwintorok@gmail.com <mailto:edwintorok@gmail.com>>
> 
>     I was able to find the sources via the wayback machine.
>     Unsurprisingly it doesn't build with OCaml 3.11.2 (it wants OCaml 3.06).
>     Is there a more up to date variant of ocamldefun? Would it be possible
>     to port it to 3.11.2?
> 
> 
> As far as I know, there is no up to date variant of ocamldefun.
> For porting to 3.11.2, you have at least to:
> - update the caml AST
> - migrate all the camlp4 stuff to new camlp4 or camlp5
> - update the different analyses to take into account AST changes (in
> particular the new caml constructs like recursive modules).
> 
> Besides ocamldefun could be hugely improved in order to generate more
> efficient caml code. I know (I knew?) what to do for this purpose

Thanks, this sounds good so far.

>, but I
> have no time from a while ago in order to implement myself a new version
> of ocamldefun.

Yes time is an issue for me too.

> I could provide some helps to someone motivated...

I think that'll have to be someone else than me, as I consider myself
just a beginner in OCaml.
However if you think that implementing AST transforms would be possible
for a beginner (in OCaml, I do have experience with compilers), I'm
willing to give it a try.

> 
>     Is it possible to implement ocamldefun-like functionality via Camlp4's
>     AST filters?
> 
> 
> Defunctorisation is a fully syntactic task (that's not so true in
> presence of recursive modules). But, among other thinks,
> defunctorisation requires to perform the very same scope analysis than
> ocaml for binding each use of variable to its declaration. I am not an
> expert of Camlp4 possibilities, but defunctorisation requires to
> manipulate the full caml AST.

It looks like there is access to AST, I don't know if it is the full AST
or just a simplified view:
http://brion.inria.fr/gallium/index.php/Abstract_Syntax_Tree
http://brion.inria.fr/gallium/index.php/Camlp4MapGenerator

>  
> 
>     Also is it possible to implement function specialization
>     (monomorphization?) using an AST filter?
>     The example from the OCaml tutorial is not optimized by
>     http://www.ocaml-tutorial.org/performance_and_profiling.
> 
> 
> I'm not an expert (again) but typing information should be required,
> isn't it? 

Right, so I would need an AST that has all the infered type information.
I don't know if Camlp4 can offer that.

>  
> 
>     Or is it possible to get access to the OCaml compiler's IL
>     representation and make optimizations on that?
> 
> 
> At this day, there is no public interface to the internal modules of the
> caml compiler. But, depending on the context (possible license issues),
> you could embed some parts of the caml compiler in your tool.

I think that if there is a defunctorizer written it should live in the
OCaml distribution itself (maybe in contrib/).
I certainly don't intend to write an external tool that uses OCaml
internal modules.

Best regards,
--Edwin