On Wednesday, 8 September 2021 at 04:32:50 UTC, james.p.leblanc
wrote:
Dear All,
In searching through the forum archives (going back to 2013,
2016
etc), and experiments, it **appears to me** that LDC does indeed
respect the standard "align" properties. (Meaning: proper
alignment
for using AVX with static arrays can be guaranteed).
Experiments (and forum discussions) also lead me to believe that
DMD does NOT respect this alignment.
So, what is the "official status" of AVX alignment
possibilities?
Succinctly:
1) Can we truly rely on LDC's alignment for AVX ?
2) Is DMD presently **not** respecting alignment? (Or have I
misunderstood?)
This has important impact on performance of numerical
computations.
Thanks for all illumination!
James
Yes you are correct (to my understanding)
DMD only respects `align` keyword upto the value 16,ie, until
`align(16)`, the code behaves the way you expect it to. It is
100% a bug(don't have the link on me right now)
Try the following code on DMD, then LDC. See for yourself
```d
import std.stdio:writeln;
void main()
{
align(16) int[100] a;
align(1024) int[100] b;
writeln(cast(ulong)&a[0] % 16);
writeln(cast(ulong)&b[0] % 1024);
}
```
