Re: [Caml-list] Int32 vs float unboxing

[Alain Frisch <alain.frisch@lexifi.com>]

On 08/22/2011 09:19 AM, Dmitry Bely wrote:
> In the code below "s" reference is unboxed in sum_float loop, but not
> in sum_in32. Why?
>
> let sum_int32 v =
>    let s = ref 0l in
>    for i=0 to (Array.length v)-1 do
>      s := Int32.add !s (Array.unsafe_get v i)
>    done;
>    Int32.add !s Int32.zero
>
> let sum_float v =
>    let s = ref 0. in
>    for i=0 to (Array.length v)-1 do
>      s := !s +. (Array.unsafe_get v i)
>    done;
>    !s +. 0.

A random guess: since adding Int32.zero is the identity (contrary to 
adding 0.), the compiler is clever enough to optimize away this useless 
operation; unfortunately, this optimization breaks the unboxing pass.

-- Alain