Re: [Caml-list] <DKIM> flambda for bytecode backend

[Pierre Chambart <pierre.chambart@ocamlpro.com>]

On 12/01/2018 19:36, Alexey Egorov wrote:
> Hello,
>
> I'm curious why flambda doesn't supported in bytecode compiler? It
> seems that js_of_ocaml can greatly benefit from such possibility.
>
It has been considered, and in fact Grégoire Henry did a version of the
bytecode compiler after flambda. But it was discarded as it was not very
useful. It couldn't work with js_of_ocaml, and there was no obvious way
how to do it properly.

The reason being that flambda takes place after closure conversion.
Hence after flambda, functions takes an explicit environment value. But
on the other hand, js_of_ocaml represents OCaml functions directly as
javascript function since the closures are working correctly.

The best we could do (without doing some magic) would look like:

let f x =
  let y = x + 1 in
  let g z = z + y in
  g

compiled to:

function f_code(x, env) {
  let y = x + 1;
  function g_code(y, env) {
    return(z + env.y);
  }
  let g = { code : g_code, env : { y: y };
  return(g);
}

let f = { code : f_code, env : { } }

This would probably be far slower than what js_of_ocaml currently does.
-- 
Pierre