gallium: add start_slot parameter to set_vertex_buffers

This allows updating only a subrange of buffer bindings.

set_vertex_buffers(pipe, start_slot, count, NULL) unbinds buffers in that
range. Binding NULL resources unbinds buffers too (both buffer and user_buffer
must be NULL).

The meta ops are adapted to only save, change, and restore the single slot
they use. The cso_context can save and restore only one vertex buffer slot.
The clients can query which one it is using cso_get_aux_vertex_buffer_slot.
It's currently set to 0. (the Draw module breaks if it's set to non-zero)

It should decrease the CPU overhead when using a lot of meta ops, but
the drivers must be able to treat each vertex buffer slot as a separate
state (only r600g does so at the moment).

I can imagine this also being useful for optimizing some OpenGL use cases.

Reviewed-by: Brian Paul <brianp@vmware.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/src/gallium/auxiliary/cso_cache/cso_context.h b/src/gallium/auxiliary/cso_cache/cso_context.h
index f49b2b7..16158ed 100644
--- a/src/gallium/auxiliary/cso_cache/cso_context.h
+++ b/src/gallium/auxiliary/cso_cache/cso_context.h
@@ -102,10 +102,14 @@ void cso_restore_vertex_elements(struct cso_context *ctx);
 
 
 void cso_set_vertex_buffers(struct cso_context *ctx,
-                            unsigned count,
+                            unsigned start_slot, unsigned count,
                             const struct pipe_vertex_buffer *buffers);
-void cso_save_vertex_buffers(struct cso_context *ctx);
-void cso_restore_vertex_buffers(struct cso_context *ctx);
+
+/* One vertex buffer slot is provided with the save/restore functionality.
+ * cso_context chooses the slot, it can be non-zero. */
+void cso_save_aux_vertex_buffer_slot(struct cso_context *ctx);
+void cso_restore_aux_vertex_buffer_slot(struct cso_context *ctx);
+unsigned cso_get_aux_vertex_buffer_slot(struct cso_context *ctx);
 
 
 void cso_set_stream_outputs(struct cso_context *ctx,