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, 9 insertions, 2 deletions

diff --git a/src/gallium/drivers/nv30/nv30_push.c b/src/gallium/drivers/nv30/nv30_push.c
index c5867bfa11a..5ec2d462a68 100644
--- a/src/gallium/drivers/nv30/nv30_push.c
+++ b/src/gallium/drivers/nv30/nv30_push.c
@@ -211,6 +211,10 @@ nv30_push_vbo(struct nv30_context *nv30, const struct pipe_draw_info *info)
       struct pipe_vertex_buffer *vb = &nv30->vtxbuf[i];
       struct nv04_resource *res = nv04_resource(vb->buffer);
 
+      if (!vb->buffer && !vb->user_buffer) {
+         continue;
+      }
+
       data = nouveau_resource_map_offset(&nv30->base, res,
                                          vb->buffer_offset, NOUVEAU_BO_RD);
 
@@ -276,8 +280,11 @@ nv30_push_vbo(struct nv30_context *nv30, const struct pipe_draw_info *info)
    if (info->indexed)
       nouveau_resource_unmap(nv04_resource(nv30->idxbuf.buffer));
 
-   for (i = 0; i < nv30->num_vtxbufs; ++i)
-      nouveau_resource_unmap(nv04_resource(nv30->vtxbuf[i].buffer));
+   for (i = 0; i < nv30->num_vtxbufs; ++i) {
+      if (nv30->vtxbuf[i].buffer) {
+         nouveau_resource_unmap(nv04_resource(nv30->vtxbuf[i].buffer));
+      }
+   }
 
    nv30_state_release(nv30);
 }