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, 1 insertions, 3 deletions

diff --git a/src/gallium/drivers/radeonsi/r600_blit.c b/src/gallium/drivers/radeonsi/r600_blit.c
index cea7e128018..30736fcf8a7 100644
--- a/src/gallium/drivers/radeonsi/r600_blit.c
+++ b/src/gallium/drivers/radeonsi/r600_blit.c
@@ -61,9 +61,7 @@ static void r600_blitter_begin(struct pipe_context *ctx, enum r600_blitter_op op
 	if (rctx->queued.named.viewport) {
 		util_blitter_save_viewport(rctx->blitter, &rctx->queued.named.viewport->viewport);
 	}
-	util_blitter_save_vertex_buffers(rctx->blitter,
-					 rctx->nr_vertex_buffers,
-					 rctx->vertex_buffer);
+	util_blitter_save_vertex_buffer_slot(rctx->blitter, rctx->vertex_buffer);
 	util_blitter_save_so_targets(rctx->blitter, rctx->num_so_targets,
 				     (struct pipe_stream_output_target**)rctx->so_targets);