struct a
    {   align(16) int[4] test = [1,2,3,4];
    }
    a test;

    asm
    {
            movdqa XMM0, test   ;
            addps XMM0, XMM0    ;
            movdpa test, XMM0   ;
    }

This works fine with unaligned movdqu but throws an access violation exception with movdqa. Why isn't align letting me do an aligned read? How should I do an aligned read?

On Monday, 11 June 2012 at 03:19:08 UTC, ixid wrote:
>     struct a
>     {   align(16) int[4] test = [1,2,3,4];
>     }
>     a test;
>
>     asm
>     {
>             movdqa XMM0, test   ;
>             addps XMM0, XMM0    ;
>             movdpa test, XMM0   ;
>     }
>
> This works fine with unaligned movdqu but throws an access violation exception with movdqa. Why isn't align letting me do an aligned read? How should I do an aligned read?

One way would be to a vector type:

import core.simd;
int4 test;

That doesn't work for me, hence using assembler. I get:
Internal error: ..\ztc\cgcod.c 1447

test code please

import std.stdio, core.simd;

void main()
{   int4 v;
}

Internal error: ..\ztc\cgcod.c 1447
Building Debug\dtest1.exe failed!

> import std.stdio, core.simd;
>
> void main()
> {   int4 v;
> }
>
> Internal error: ..\ztc\cgcod.c 1447
> Building Debug\dtest1.exe failed!

Works fine on Linux.

Maybe the 32Bit check doesn't work for Windoze?
-m32 on Linux yields Error: SIMD vector types not supported on this platform

I think it has been fixed for the next version of DMD already. Any idea why align isn't letting me use movdqa?

> I think it has been fixed for the next version of DMD already. Any idea why align isn't letting me use movdqa?

Cause align doesn't work the way you think it does.
In fact I still don't understand how it works at all.

On 6/11/2012 7:15 AM, Trass3r wrote:
>> I think it has been fixed for the next version of DMD already. Any
>> idea why align isn't letting me use movdqa?
>
> Cause align doesn't work the way you think it does.
> In fact I still don't understand how it works at all.

The language align keyword can only reduce the alignment from the platform default (typically 8).  A serious flaw if you ask me . . . .

On Thursday, June 14, 2012 00:17:25 Sean Cavanaugh wrote:
> On 6/11/2012 7:15 AM, Trass3r wrote:
> >> I think it has been fixed for the next version of DMD already. Any idea why align isn't letting me use movdqa?
> > 
> > Cause align doesn't work the way you think it does.
> > In fact I still don't understand how it works at all.
> 
> The language align keyword can only reduce the alignment from the platform default (typically 8).  A serious flaw if you ask me . . . .

Then open an enhancement request. If there's a good enough reason that align should work the way that you want it to and not a sufficiently good reason why it shouldn't, then Walter may be willing to make the change. It may be that nothing will change, but it doesn't hurt to ask.

- Jonathan M Davis