alignment on stack-allocated arrays/structs

[Tomas Lindquist Olsen]

On Tue, Nov 17, 2009 at 9:12 PM, Trass3r <mrmocool at gmx.de> wrote:
> I originally posted a question about this in D.learn. bearophile advised me
> to ask for that feature here.
>
>
> Original post:
> ==============
>
> OpenCL requires all types to be naturally aligned.
>
> The D specs state:
> "AlignAttribute is ignored when applied to declarations that are not struct
> members."
>
> Could there arise any problems translating the following
>
> /*
>  * Vector types
>  *
>  *  Note:   OpenCL requires that all types be naturally aligned.
>  *          This means that vector types must be naturally aligned.
>  *          For example, a vector of four floats must be aligned to
>  *          a 16 byte boundary (calculated as 4 * the natural 4-byte
>  *          alignment of the float).  The alignment qualifiers here
>  *          will only function properly if your compiler supports them
>  *          and if you don't actively work to defeat them.  For example,
>  *          in order for a cl_float4 to be 16 byte aligned in a struct,
>  *          the start of the struct must itself be 16-byte aligned.
>  *
>  *          Maintaining proper alignment is the user's responsibility.
>  */
>
> typedef double          cl_double2[2]   __attribute__((aligned(16)));
> typedef double          cl_double4[4]   __attribute__((aligned(32)));
> typedef double          cl_double8[8]   __attribute__((aligned(64)));
> typedef double          cl_double16[16] __attribute__((aligned(128)));
>
>
>
> into just
>
>
> alias double[2]    cl_double2;
> alias double[4]    cl_double4;
> alias double[8]    cl_double8;
> alias double[16]   cl_double16;
>
> ?
>

yep, D provides no way to do this, they'd all align to 4 bytes (at
least on x86-32)