st/mesa: treat resource-less xfb buffers as if they weren't there

If a transform feedback buffer's size is 0, st_bufferobj_data doesn't
end up creating a buffer for it. There's no point in trying to write to
such a buffer, so just pretend as if it's not really there.

This fixes arb_gpu_shader5-xfb-streams-without-invocations on nvc0.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Cc: "10.4 10.5" <mesa-stable@lists.freedesktop.org>
(cherry picked from commit 80d373ed5b1d90a5e71747ee5b8951baac62f750)

diff --git a/src/mesa/state_tracker/st_cb_xformfb.c b/src/mesa/state_tracker/st_cb_xformfb.c
index 8f75eda..a2bd86a 100644 (file)
--- a/src/mesa/state_tracker/st_cb_xformfb.c
+++ b/src/mesa/state_tracker/st_cb_xformfb.c
@@ -122,7 +122,7 @@ st_begin_transform_feedback(struct gl_context *ctx, GLenum mode,
    for (i = 0; i < max_num_targets; i++) {
       struct st_buffer_object *bo = st_buffer_object(sobj->base.Buffers[i]);
 
-      if (bo) {
+      if (bo && bo->buffer) {
          /* Check whether we need to recreate the target. */
          if (!sobj->targets[i] ||
              sobj->targets[i] == sobj->draw_count ||