[Mesa-dev] [PATCH] llvmpipe: fix lp_rast_plane alignment on 32bit

[Jose Fonseca]

On 15/03/16 04:41, sroland at vmware.com wrote:
> From: Roland Scheidegger <sroland at vmware.com>
>
> Some rasterization code relies (for sse) on the first and third planes
> (but not the second for now) being 128bit aligned, and we didn't get that
> on 32bit - I mistakenly thought the 64bit number in the struct would get
> the thing aligned to 64bit even on 32bit archs.
> Stephane Marchesin really figured this out.
>
> This fixes https://bugs.freedesktop.org/show_bug.cgi?id=94522
>
> CC: <mesa-stable at lists.freedesktop.org>
> ---
>   src/gallium/drivers/llvmpipe/lp_rast.h | 6 ++++++
>   1 file changed, 6 insertions(+)
>
> diff --git a/src/gallium/drivers/llvmpipe/lp_rast.h b/src/gallium/drivers/llvmpipe/lp_rast.h
> index 34008e1..d9be7f3 100644
> --- a/src/gallium/drivers/llvmpipe/lp_rast.h
> +++ b/src/gallium/drivers/llvmpipe/lp_rast.h
> @@ -116,6 +116,12 @@ struct lp_rast_plane {
>
>      /* one-pixel sized trivial reject offsets for each plane */
>      uint32_t eo;
> +   /*
> +    * We rely on this struct being 64bit aligned (ideally it would be 128bit
> +    * but that's quite the waste) and therefore on 32bit we need padding
> +    * since otherwise (even with the 64bit number in there) it wouldn't be.
> +    */
> +   uint32_t pad;
>   };
>
>   /**
>

Looks good, but lets add

    STATIC_ASSERT(sizeof(struct lp_rast_plane) % 8 == 0);

somewhere, and move the comment there (as the "pad" might come and go if 
the structure is ever changed again, but the static assertion should 
remain.)

Jose