vectorization of a simple loop -- not in DMD?

[Ivan Kazmenko via Digitalmars-d-learn]

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.