[Mesa-dev] [PATCH v3] i965: Implement GL_PRIMITIVES_GENERATED with non-zero streams.

[Chris Forbes]

Reviewed-by: Chris Forbes <chrisf at ijw.co.nz>

On Thu, Jun 26, 2014 at 6:24 PM, Iago Toral Quiroga <itoral at igalia.com> wrote:
> So far we have been using CL_INVOCATION_COUNT to resolve this query but this
> is no good with streams, as only stream 0 reaches the clipping stage. Instead
> we will use SO_PRIM_STORAGE_NEEDED which can keep track of the primitives sent
> to each individual stream.
>
> Since SO_PRIM_STORAGE_NEEDED is related to the SOL stage and according to
> ARB_transform_feedback3 we need to be able to query primitives generated in
> each stream whether transform feedback is active or not what we do is to
> enable the SOL unit even if transform feedback is not active but disable all
> output buffers in that case. This effectively disables transform feedback
> but permits activation of statistics enabling SO_PRIM_STORAGE_NEEDED even
> when transform feedback is not active.
> ---
>  src/mesa/drivers/dri/i965/gen6_queryobj.c  | 13 +++++++++----
>  src/mesa/drivers/dri/i965/gen7_sol_state.c | 20 +++++++++++++++++---
>  2 files changed, 26 insertions(+), 7 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/gen6_queryobj.c b/src/mesa/drivers/dri/i965/gen6_queryobj.c
> index 0cb64ca..b4b1509 100644
> --- a/src/mesa/drivers/dri/i965/gen6_queryobj.c
> +++ b/src/mesa/drivers/dri/i965/gen6_queryobj.c
> @@ -84,11 +84,16 @@ brw_store_register_mem64(struct brw_context *brw,
>
>  static void
>  write_primitives_generated(struct brw_context *brw,
> -                           drm_intel_bo *query_bo, int idx)
> +                           drm_intel_bo *query_bo, int stream, int idx)
>  {
>     intel_batchbuffer_emit_mi_flush(brw);
>
> -   brw_store_register_mem64(brw, query_bo, CL_INVOCATION_COUNT, idx);
> +   if (brw->gen >= 7) {
> +      brw_store_register_mem64(brw, query_bo,
> +                               GEN7_SO_PRIM_STORAGE_NEEDED(stream), idx);
> +   } else {
> +      brw_store_register_mem64(brw, query_bo, CL_INVOCATION_COUNT, idx);
> +   }
>  }
>
>  static void
> @@ -240,7 +245,7 @@ gen6_begin_query(struct gl_context *ctx, struct gl_query_object *q)
>        break;
>
>     case GL_PRIMITIVES_GENERATED:
> -      write_primitives_generated(brw, query->bo, 0);
> +      write_primitives_generated(brw, query->bo, query->Base.Stream, 0);
>        break;
>
>     case GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN:
> @@ -279,7 +284,7 @@ gen6_end_query(struct gl_context *ctx, struct gl_query_object *q)
>        break;
>
>     case GL_PRIMITIVES_GENERATED:
> -      write_primitives_generated(brw, query->bo, 1);
> +      write_primitives_generated(brw, query->bo, query->Base.Stream, 1);
>        break;
>
>     case GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN:
> diff --git a/src/mesa/drivers/dri/i965/gen7_sol_state.c b/src/mesa/drivers/dri/i965/gen7_sol_state.c
> index 11b2e2e..d2c3ae3 100644
> --- a/src/mesa/drivers/dri/i965/gen7_sol_state.c
> +++ b/src/mesa/drivers/dri/i965/gen7_sol_state.c
> @@ -223,14 +223,28 @@ upload_3dstate_streamout(struct brw_context *brw, bool active,
>     uint32_t dw1 = 0, dw2 = 0;
>     int i;
>
> +   /*
> +    * From ARB_transform_feedback3:
> +    *
> +    *   "When a generated primitive query for a vertex stream is active, the
> +    *   primitives-generated count is incremented every time a primitive
> +    *   emitted to that stream reaches the Discarding Rasterization stage
> +    *   (see Section 3.x) right before rasterization. This counter is
> +    *   incremented whether or not transform feedback is active."
> +    *
> +    * Since we can only keep track of generated primitives for each stream
> +    * in the SOL stage we need to make sure it is always active even if
> +    * transform beedback is not. This way we can track primitives generated
> +    * in each stream via SO_PRIMITIVE_STORAGE_NEEDED.
> +    */
> +   dw1 |= SO_FUNCTION_ENABLE;
> +   dw1 |= SO_STATISTICS_ENABLE;
> +
>     if (active) {
>        int urb_entry_read_offset = 0;
>        int urb_entry_read_length = (vue_map->num_slots + 1) / 2 -
>          urb_entry_read_offset;
>
> -      dw1 |= SO_FUNCTION_ENABLE;
> -      dw1 |= SO_STATISTICS_ENABLE;
> -
>        /* _NEW_LIGHT */
>        if (ctx->Light.ProvokingVertex != GL_FIRST_VERTEX_CONVENTION)
>          dw1 |= SO_REORDER_TRAILING;
> --
> 1.9.1
>
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