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 <[email protected]>

2 files changed, 7 insertions, 6 deletions

diff --git a/src/gallium/auxiliary/draw/draw_context.c b/src/gallium/auxiliary/draw/draw_context.c
index 48b5db34027..91dd2e1a20a 100644
--- a/src/gallium/auxiliary/draw/draw_context.c
+++ b/src/gallium/auxiliary/draw/draw_context.c
@@ -36,6 +36,7 @@
 #include "util/u_math.h"
 #include "util/u_cpu_detect.h"
 #include "util/u_inlines.h"
+#include "util/u_helpers.h"
 #include "draw_context.h"
 #include "draw_vs.h"
 #include "draw_gs.h"
@@ -318,14 +319,14 @@ void draw_set_viewport_state( struct draw_context *draw,
 
 void
 draw_set_vertex_buffers(struct draw_context *draw,
-                        unsigned count,
+                        unsigned start_slot, unsigned count,
                         const struct pipe_vertex_buffer *buffers)
 {
-   assert(count <= PIPE_MAX_ATTRIBS);
+   assert(start_slot + count <= PIPE_MAX_ATTRIBS);
 
-   util_copy_vertex_buffers(draw->pt.vertex_buffer,
-                            &draw->pt.nr_vertex_buffers,
-                            buffers, count);
+   util_set_vertex_buffers_count(draw->pt.vertex_buffer,
+                                 &draw->pt.nr_vertex_buffers,
+                                 buffers, start_slot, count);
 }
 
 
diff --git a/src/gallium/auxiliary/draw/draw_context.h b/src/gallium/auxiliary/draw/draw_context.h
index 4a73ec8c37d..30633233fb0 100644
--- a/src/gallium/auxiliary/draw/draw_context.h
+++ b/src/gallium/auxiliary/draw/draw_context.h
@@ -200,7 +200,7 @@ void draw_delete_geometry_shader(struct draw_context *draw,
  */
 
 void draw_set_vertex_buffers(struct draw_context *draw,
-                             unsigned count,
+                             unsigned start_slot, unsigned count,
                              const struct pipe_vertex_buffer *buffers);
 
 void draw_set_vertex_elements(struct draw_context *draw,