v3d: use the GPU to record primitives written to transform feedback

We can use the PRIMITIVE_COUNTS_FEEDBACK packet to write various primitive
counts to a buffer, including the number of primives written to transform
feedback buffers, which will handle buffer overflow correctly.

There are a couple of caveats with this:

Primitive counters are reset when we emit a 'Tile Binning Mode Configuration'
packet, which can happen in the middle of a primitives query, so we need to
read the buffer when we submit a job and accumulate the counts in the context
so we don't lose them.

We also need to do the same when we switch primitive type during transform
feedback so we can compute the correct number of recorded vertices from
the number of primitives. This is necessary so we can provide an accurate
vertex count for draw from transform feedback.

v2:
 - When computing the number of vertices for a primitive, pass in the base
   primitive, since that is what the hardware will count.
 - No need to update primitive counts when switching primitive types if
   the base primitives are the same.
 - Log perf warning when mapping the primitive counts BO for readback (Eric).
 - Only emit the primitive counts packet once at job end (Eric).
 - Use u_upload mechanism for the primitive counts buffer (Eric).
 - Use the XML to generate indices into the primitive counters buffer (Eric).

Fixes piglit tests:
spec/ext_transform_feedback/overflow-edge-cases
spec/ext_transform_feedback/query-primitives_written-bufferrange
spec/ext_transform_feedback/query-primitives_written-bufferrange-discard
spec/ext_transform_feedback/change-size base-shrink
spec/ext_transform_feedback/change-size base-grow
spec/ext_transform_feedback/change-size offset-shrink
spec/ext_transform_feedback/change-size offset-grow
spec/ext_transform_feedback/change-size range-shrink
spec/ext_transform_feedback/change-size range-grow
spec/ext_transform_feedback/intervening-read prims-written

Reviewed-by: Eric Anholt <[email protected]>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/gallium/drivers/v3d/v3d_context.h b/src/gallium/drivers/v3d/v3d_context.h
index 5f19504dbae..b2c917df240 100644
--- a/src/gallium/drivers/v3d/v3d_context.h
+++ b/src/gallium/drivers/v3d/v3d_context.h
@@ -498,6 +498,8 @@ struct v3d_context {
         struct v3d_vertexbuf_stateobj vertexbuf;
         struct v3d_streamout_stateobj streamout;
         struct v3d_bo *current_oq;
+        struct pipe_resource *prim_counts;
+        uint32_t prim_counts_offset;
         struct pipe_debug_callback debug;
         /** @} */
 };
@@ -652,6 +654,8 @@ bool v3d_generate_mipmap(struct pipe_context *pctx,
 
 struct v3d_fence *v3d_fence_create(struct v3d_context *v3d);
 
+void v3d_tf_update_counters(struct v3d_context *v3d);
+
 #ifdef v3dX
 #  include "v3dx_context.h"
 #else