i965/gen6: Initial implementation of MSAA.

This patch enables MSAA for Gen6, by modifying intel_mipmap_tree to
understand multisampled buffers, adapting the rendering pipeline setup
to enable multisampled rendering, and adding multisample resolve
operations to brw_blorp_blit.cpp. Some preparation work is also
included for Gen7, but it is not yet enabled.

MSAA support is still fairly preliminary.  In particular, the
following are not yet supported:
- Fully general blits between MSAA and non-MSAA buffers.
- Formats other than RGBA8, DEPTH24, and STENCIL8.
- Centroid interpolation.
- Coverage parameters (glSampleCoverage, GL_SAMPLE_ALPHA_TO_COVERAGE,
  GL_SAMPLE_ALPHA_TO_ONE, GL_SAMPLE_COVERAGE, GL_SAMPLE_COVERAGE_VALUE,
  GL_SAMPLE_COVERAGE_INVERT).

Fixes piglit tests "EXT_framebuffer_multisample/accuracy" on
i965/Gen6.

v2:
- In intel_alloc_renderbuffer_storage(), quantize the requested number
  of samples to the next higher sample count supported by the
  hardware.  This ensures that a query of GL_SAMPLES will return the
  correct value.  It also ensures that MSAA is fully disabled on Gen7
  for now (since Gen7 MSAA support doesn't work yet).
- When reading from a non-MSAA surface, ensure that s_is_zero is true
  so that we won't try to read from a nonexistent sample.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_state_upload.c b/src/mesa/drivers/dri/i965/brw_state_upload.c
index b02e1600d62..551fa6a5df1 100644
--- a/src/mesa/drivers/dri/i965/brw_state_upload.c
+++ b/src/mesa/drivers/dri/i965/brw_state_upload.c
@@ -153,6 +153,7 @@ static const struct brw_tracked_state *gen6_atoms[] =
 
    &brw_samplers,
    &gen6_sampler_state,
+   &gen6_multisample_state, /* TODO: is this the right spot? */
 
    &gen6_vs_state,
    &gen6_gs_state,
@@ -221,6 +222,7 @@ const struct brw_tracked_state *gen7_atoms[] =
    &brw_wm_binding_table,
 
    &gen7_samplers,
+   &gen6_multisample_state, /* TODO: is this the right spot? */
 
    &gen7_disable_stages,
    &gen7_vs_state,