[Caml-list] Status of Flambda in OCaml 4.03

[Markus Mottl <markus.mottl@gmail.com>]

Hi,

I'm trying out OCaml 4.03.0+beta1 right now and wanted to test Flambda
optimizations.  But looking at the generated assembly, it doesn't seem
to be doing much if anything on the simple test examples that I
thought would benefit.

To give an example of what I expected to see, lets consider this code:

-----
let map_pair f (x, y) = f x, f y

let succ x = x + 1
let map_pair_succ1 pair = map_pair succ pair
let map_pair_succ2 (x, y) = succ x, succ y
-----

I would have thought that the "succ" function would be inlined in
"map_pair_succ1" as the compiler would do for "map_pair_succ2".
But the generated code looks like this:

-----
L101:
  movq  %rax, %rdi
  movq  %rdi, 8(%rsp)
  movq  %rbx, (%rsp)
  movq  8(%rbx), %rax
  movq  (%rdi), %rsi
  movq  %rdi, %rbx
  call  *%rsi
L102:
  movq  %rax, 16(%rsp)
  movq  (%rsp), %rax
  movq  (%rax), %rax
  movq  8(%rsp), %rbx
  movq  (%rbx), %rdi
  call  *%rdi
-----

Is Flambda supposed to work out of the box with the current beta?
What flags or annotations should I use for testing?  Any showcase
examples I should try out that are expected to be improved?

Regards,
Markus

-- 
Markus Mottl        http://www.ocaml.info        markus.mottl@gmail.com