This looks good. I recommend porting all_varyings_in_vbos from
st_draw.c to vbo_all_varyings_in_vbos, because it also takes instanced
arrays into account.
Reviewed-by: Marek Olšák <marek.ol...@amd.com>
Marek
On Sat, Oct 26, 2013 at 7:35 AM, Kenneth Graunke <kenn...@whitecape.org> wrote:
> DrawTransformFeedback() needs to obtain the number of vertices written
> to a particular stream during the last Begin/EndTransformFeedback block.
> The new driver hook returns exactly that information.
>
> Gallium drivers already implement this by passing the transform feedback
> object to the drawing function, counting the number of vertices written
> on the GPU, and using draw indirect. This is efficient, but doesn't
> always work:
>
> If vertex data comes from user arrays, then the VBO module needs to
> know how many vertices to upload, so we need to synchronously count.
> Gallium drivers are currently broken in this case.
>
> It also doesn't work if primitive restart is done in software. For
> normal drawing, vbo_draw_arrays() performs software primitive restart,
> splitting the draw call in two. vbo_draw_transform_feedback() currently
> doesn't because it has no idea how many vertices need to be drawn.
>
> The new driver hook gives it that information, allowing us to reuse
> the existing vbo_draw_arrays() code to do everything right.
>
> On Intel hardware (at least Ivybridge), using the draw indirect approach
> is difficult since the hardware counts primitives, rather than vertices,
> which requires doing some simple math. So we always use this hook.
>
> Gallium drivers will likely want to use this hook in some cases, but
> want to use the existing draw indirect approach where possible. Hence,
> I've added a flag to allow drivers to opt-in to this call.
>
> v2: Make it possible to implement this hook but only use this path
> when necessary (suggested by Marek).
>
> Cc: Marek Olšák <mar...@gmail.com>
> Cc: Eric Anholt <e...@anholt.net>
> Signed-off-by: Kenneth Graunke <kenn...@whitecape.org>
> ---
> src/mesa/drivers/dri/i965/brw_context.c | 2 ++
> src/mesa/main/dd.h | 8 ++++++++
> src/mesa/main/mtypes.h | 6 ++++++
> src/mesa/vbo/vbo_exec_array.c | 10 ++++++++++
> 4 files changed, 26 insertions(+)
>
> Marek,
>
> Does this look like what you wanted? I feel a bit silly adding all of this
> seeing as the later conditions are totally untested - i965 sets the "always
> use this hook" flag, so it short-circuits them, and Gallium drivers don't
> yet implement the hook, so they don't hit it either. :)
>
> But I think this is probably roughly what you're going to want...
>
> Eric, does this look reasonable?
>
> Thanks for everything!
>
> diff --git a/src/mesa/drivers/dri/i965/brw_context.c
> b/src/mesa/drivers/dri/i965/brw_context.c
> index 90d9be4..623273c 100644
> --- a/src/mesa/drivers/dri/i965/brw_context.c
> +++ b/src/mesa/drivers/dri/i965/brw_context.c
> @@ -329,6 +329,8 @@ brw_initialize_context_constants(struct brw_context *brw)
> ctx->Const.MaxTransformFeedbackSeparateComponents =
> BRW_MAX_SOL_BINDINGS / BRW_MAX_SOL_BUFFERS;
>
> + ctx->Const.AlwaysUseGetTransformFeedbackVertexCount = true;
> +
> if (brw->gen == 6) {
> ctx->Const.MaxSamples = 4;
> ctx->Const.MaxColorTextureSamples = 4;
> diff --git a/src/mesa/main/dd.h b/src/mesa/main/dd.h
> index 29469ce..11d5a9e 100644
> --- a/src/mesa/main/dd.h
> +++ b/src/mesa/main/dd.h
> @@ -843,6 +843,14 @@ struct dd_function_table {
> struct gl_transform_feedback_object *obj);
>
> /**
> + * Return the number of vertices written to a stream during the last
> + * Begin/EndTransformFeedback block.
> + */
> + GLsizei (*GetTransformFeedbackVertexCount)(struct gl_context *ctx,
> + struct
> gl_transform_feedback_object *obj,
> + GLuint stream);
> +
> + /**
> * \name GL_NV_texture_barrier interface
> */
> void (*TextureBarrier)(struct gl_context *ctx);
> diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
> index 97ed1bd..f5e1f01 100644
> --- a/src/mesa/main/mtypes.h
> +++ b/src/mesa/main/mtypes.h
> @@ -3131,6 +3131,12 @@ struct gl_constants
> */
> GLboolean PrimitiveRestartInSoftware;
>
> + /**
> + * Always use the GetTransformFeedbackVertexCount() driver hook, rather
> + * than passing the transform feedback object to the drawing function.
> + */
> + GLboolean AlwaysUseGetTransformFeedbackVertexCount;
> +
> /** GL_ARB_map_buffer_alignment */
> GLuint MinMapBufferAlignment;
>
> diff --git a/src/mesa/vbo/vbo_exec_array.c b/src/mesa/vbo/vbo_exec_array.c
> index 1670409..f25a9de 100644
> --- a/src/mesa/vbo/vbo_exec_array.c
> +++ b/src/mesa/vbo/vbo_exec_array.c
> @@ -1464,6 +1464,16 @@ vbo_draw_transform_feedback(struct gl_context *ctx,
> GLenum mode,
> return;
> }
>
> + if (ctx->Driver.GetTransformFeedbackVertexCount &&
> + (ctx->Const.AlwaysUseGetTransformFeedbackVertexCount ||
> + (ctx->Const.PrimitiveRestartInSoftware &&
> + ctx->Array._PrimitiveRestart) ||
> + !vbo_all_varyings_in_vbos(exec->array.inputs))) {
> + GLsizei n = ctx->Driver.GetTransformFeedbackVertexCount(ctx, obj,
> stream);
> + vbo_draw_arrays(ctx, mode, 0, n, numInstances, 0);
> + return;
> + }
> +
> vbo_bind_arrays(ctx);
>
> /* init most fields to zero */
> --
> 1.8.3.2
>
_______________________________________________
mesa-dev mailing list
mesa-dev@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/mesa-dev
