[Mesa-dev] [PATCH] mesa: Ensure stack is realigned on x86.

[Brian Paul]

On 12/02/2014 01:27 PM, Jose Fonseca wrote:
> From: José Fonseca <jfonseca at vmware.com>
>
> Nowadays GCC assumes stack pointer is 16-byte aligned even on 32-bits,
> but that is an assumption OpenGL drivers (or any dynamic library for
> that matter) can affort to make as there are many closed- and open-

can or cannot?

affort -> afford


> source application binaries out there that only assume 4-byte stack
> alignment.
>
> This fix uses force_align_arg_pointer GCC attribute, and is only a
> stop-gap measure.
>
> The right fix would be to pass -mstackrealign or
> -mincoming-stack-boundary=2 to all source fails that use any -msse*
> option, as there is no way to guarantee if/when GCC will decide to spill
> SSE registers to the stack.
>
> https://bugs.freedesktop.org/show_bug.cgi?id=86788
> ---
>   src/mesa/main/sse_minmax.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/src/mesa/main/sse_minmax.c b/src/mesa/main/sse_minmax.c
> index 222ac14..93cf2a6 100644
> --- a/src/mesa/main/sse_minmax.c
> +++ b/src/mesa/main/sse_minmax.c
> @@ -31,6 +31,9 @@
>   #include <stdint.h>
>
>   void
> +#if !defined(__x86_64__)
> +   __attribute__((force_align_arg_pointer))
> +#endif
>   _mesa_uint_array_min_max(const unsigned *ui_indices, unsigned *min_index,
>                            unsigned *max_index, const unsigned count)
>   {
>

I don't remember if this code is compiled with MSVC.  If so, do you also 
need a gcc check for the __attribute__ part?

-Brian