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]>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/mesa/state_tracker/st_draw_feedback.c b/src/mesa/state_tracker/st_draw_feedback.c
index a6c7d0eec85..ae87fb28dbf 100644
--- a/src/mesa/state_tracker/st_draw_feedback.c
+++ b/src/mesa/state_tracker/st_draw_feedback.c
@@ -205,7 +205,7 @@ st_feedback_draw_vbo(struct gl_context *ctx,
 #endif
    }
 
-   draw_set_vertex_buffers(draw, vp->num_inputs, vbuffers);
+   draw_set_vertex_buffers(draw, 0, vp->num_inputs, vbuffers);
    draw_set_vertex_elements(draw, vp->num_inputs, velements);
 
    memset(&ibuffer, 0, sizeof(ibuffer));
@@ -264,5 +264,5 @@ st_feedback_draw_vbo(struct gl_context *ctx,
       draw_set_mapped_vertex_buffer(draw, attr, NULL);
       pipe_resource_reference(&vbuffers[attr].buffer, NULL);
    }
-   draw_set_vertex_buffers(draw, 0, NULL);
+   draw_set_vertex_buffers(draw, 0, vp->num_inputs, NULL);
 }