[Mesa-dev] [PATCH 2/2] st/mesa: Handle GL_MAP_INVALIDATE_BUFFER_BIT in st_bufferobj_map_range().

[Henri Verbeet]

Alternatively, individual drivers could actually implement
PIPE_TRANSFER_DISCARD_WHOLE_RESOURCE. As far as I can tell only svga
currently implements that, and st_bufferobj_map_range() seems to be the main
user. I wonder if in general PIPE_TRANSFER_DISCARD_WHOLE_RESOURCE is something
that should just be handled by the state trackers.

As for the actual implementation, we could also try a map with
PIPE_TRANSFER_DONTBLOCK first, and avoid invalidating _NEW_BUFFER_OBJECT in
some cases. I'm not sure if that's worth it without doing more benchmarking
though, since in the typical case GL_MAP_INVALIDATE_BUFFER_BIT will probably
imply that the buffer is in use.

Signed-off-by: Henri Verbeet <hverbeet at gmail.com>
---
 src/mesa/state_tracker/st_cb_bufferobjects.c |   15 +++++++++++++++
 1 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/src/mesa/state_tracker/st_cb_bufferobjects.c b/src/mesa/state_tracker/st_cb_bufferobjects.c
index 7374bb0..7aa859e 100644
--- a/src/mesa/state_tracker/st_cb_bufferobjects.c
+++ b/src/mesa/state_tracker/st_cb_bufferobjects.c
@@ -332,6 +332,21 @@ st_bufferobj_map_range(struct gl_context *ctx, GLenum target,
       obj->Pointer = &st_bufferobj_zero_length;
    }
    else {
+      if (flags & PIPE_TRANSFER_DISCARD_WHOLE_RESOURCE) {
+         struct pipe_resource *buffer;
+
+         buffer = pipe_buffer_create(pipe->screen,
+                                     st_obj->buffer->bind,
+                                     st_obj->buffer->usage,
+                                     st_obj->buffer->width0);
+         if (buffer) {
+            st_invalidate_state(ctx, _NEW_BUFFER_OBJECT);
+            pipe_resource_reference(&st_obj->buffer, NULL);
+            st_obj->buffer = buffer;
+            flags &= ~PIPE_TRANSFER_DISCARD_WHOLE_RESOURCE;
+         }
+      }
+
       obj->Pointer = pipe_buffer_map_range(pipe, 
                                            st_obj->buffer,
                                            offset, length,
-- 
1.7.2.5