st/mesa: Accelerate PBO uploads

Create a PIPE_BUFFER sampler view on the pixel-unpack buffer, and draw
the image on the texture with a fragment shader that maps fragment
coordinates to buffer coordinates.

Modifications by Nicolai Hähnle:
- various cleanups and fixes (e.g. error handling, corner cases)
- split try_pbo_upload into two functions, which will allow code to be
  shared with compressed texture uploads
- modify the source format selection to only test for support against
  the PIPE_BUFFER target

v2:
- update handling of TGSI_SEMANTIC_POSITION for recent changes in master
- MaxTextureBufferSize is number of texels, not bytes (Ilia Mirkin)
- only enable when integers are supported (Marek Olšák)
- try harder to hit the TextureBufferOffsetAlignment
- remove unnecessary MOV from the fragment shader

Reviewed-by: Edward O'Callaghan <[email protected]>

1 files changed, 10 insertions, 0 deletions

diff --git a/src/mesa/state_tracker/st_context.h b/src/mesa/state_tracker/st_context.h
index 9c6980fc425..fa0fa104a9a 100644
--- a/src/mesa/state_tracker/st_context.h
+++ b/src/mesa/state_tracker/st_context.h
@@ -204,6 +204,16 @@ struct st_context
       void *gs_layered;
    } clear;
 
+   /* For gl(Compressed)Tex(Sub)Image */
+   struct {
+      struct pipe_rasterizer_state raster;
+      struct pipe_blend_state blend;
+      void *vs;
+      void *fs;
+      bool enabled;
+      bool rgba_only;
+   } pbo_upload;
+
    /** used for anything using util_draw_vertex_buffer */
    struct pipe_vertex_element velems_util_draw[3];