vectorization of a simple loop -- not in DMD?

[max haughton]

On Monday, 11 July 2022 at 18:15:16 UTC, Ivan Kazmenko wrote:
> Hi.
>
> I'm looking at the compiler output of DMD (-O -release), LDC 
> (-O -release), and GDC (-O3) for a simple array operation:
>
> ```
> void add1 (int [] a)
> {
>     foreach (i; 0..a.length)
>         a[i] += 1;
> }
> ```
>
> Here are the outputs: https://godbolt.org/z/GcznbjEaf
>
> From what I gather at the view linked above, DMD does not use 
> XMM registers for speedup, and does not unroll the loop either. 
>  Switching between 32bit and 64bit doesn't help either.  
> However, I recall in the past it was capable of at least some 
> of these optimizations.  So, how do I enable them for such a 
> function?
>
> Ivan Kazmenko.

How long ago is the past? The godbolt.org dmd is quite old.

The dmd backend is ancient, it isn't really capable of these 
kinds of loop optimizations.