[Mesa-dev] [PATCH 4/5] i965: Enable the ARB_transform_feedback3 extension on Gen7+.

Ian Romanick idr at freedesktop.org
Mon Oct 28 18:50:52 CET 2013


On 10/26/2013 01:33 PM, Kenneth Graunke wrote:
> This extension is written a bit strangely.  Although it introduces the
> concept of multiple transform feedback streams, it doesn't actually
> provide more than a single stream.
> 
> The ARB_gpu_shader5 extension is what introduces the ability to write to
> streams other than stream #0 and increases the required number of streams.
> 
> Since we don't yet support ARB_gpu_shader5, we can safely enable
> ARB_transform_feedback3 even though we only support a single stream.
> This does provide some useful functionality: applications can now use
> more than one interleaved transform feedback buffer.
> 
> I believe this extension can be enabled independently from
> ARB_transform_feedback2, so I've enabled it universally on Gen7+.

I think that's technically true, but I also think this will make our
implementation unjustly unique.  That's sure to uncover app bugs that I
don't think we want to chase.  I think I'd feel more comfortable only
enabling 3 when 2 is also enabled.

> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> ---
>  src/mesa/drivers/dri/i965/intel_extensions.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/src/mesa/drivers/dri/i965/intel_extensions.c b/src/mesa/drivers/dri/i965/intel_extensions.c
> index 0c6ed02..e08d93a 100644
> --- a/src/mesa/drivers/dri/i965/intel_extensions.c
> +++ b/src/mesa/drivers/dri/i965/intel_extensions.c
> @@ -230,6 +230,7 @@ intelInitExtensions(struct gl_context *ctx)
>        ctx->Extensions.ARB_conservative_depth = true;
>        if (can_do_pipelined_register_writes(brw))
>           ctx->Extensions.ARB_transform_feedback2 = true;
> +      ctx->Extensions.ARB_transform_feedback3 = true;
>     }
>  
>     if (ctx->API == API_OPENGL_CORE)
> 



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