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 <eocallaghan@alterapraxis.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/mesa/state_tracker/st_context.c b/src/mesa/state_tracker/st_context.c
index ff9135f..6c50a31 100644
--- a/src/mesa/state_tracker/st_context.c
+++ b/src/mesa/state_tracker/st_context.c
@@ -136,6 +136,7 @@ st_destroy_context_priv(struct st_context *st)
    st_destroy_drawpix(st);
    st_destroy_drawtex(st);
    st_destroy_perfmon(st);
+   st_destroy_pbo_upload(st);
 
    for (shader = 0; shader < ARRAY_SIZE(st->state.sampler_views); shader++) {
       for (i = 0; i < ARRAY_SIZE(st->state.sampler_views[0]); i++) {
@@ -209,6 +210,7 @@ st_create_context_priv( struct gl_context *ctx, struct pipe_context *pipe,
    st_init_bitmap(st);
    st_init_clear(st);
    st_init_draw( st );
+   st_init_pbo_upload(st);
 
    /* Choose texture target for glDrawPixels, glBitmap, renderbuffers */
    if (pipe->screen->get_param(pipe->screen, PIPE_CAP_NPOT_TEXTURES))