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, 16 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/gen7_wm_surface_state.c b/src/mesa/drivers/dri/i965/gen7_wm_surface_state.c
index d84e075..5aa62bd 100644
--- a/src/mesa/drivers/dri/i965/gen7_wm_surface_state.c
+++ b/src/mesa/drivers/dri/i965/gen7_wm_surface_state.c
@@ -54,6 +54,20 @@ gen7_set_surface_tiling(struct gen7_surface_state *surf, uint32_t tiling)
    }
 }
 
+
+void
+gen7_set_surface_num_multisamples(struct gen7_surface_state *surf,
+                                  unsigned num_samples)
+{
+   if (num_samples > 4)
+      surf->ss4.num_multisamples = GEN7_SURFACE_MULTISAMPLECOUNT_8;
+   else if (num_samples > 0)
+      surf->ss4.num_multisamples = GEN7_SURFACE_MULTISAMPLECOUNT_4;
+   else
+      surf->ss4.num_multisamples = GEN7_SURFACE_MULTISAMPLECOUNT_1;
+}
+
+
 static void
 gen7_update_buffer_texture_surface(struct gl_context *ctx, GLuint unit)
 {
@@ -328,6 +342,8 @@ gen7_update_renderbuffer_surface(struct brw_context *brw,
    gen7_set_surface_tiling(surf, region->tiling);
    surf->ss3.pitch = (region->pitch * region->cpp) - 1;
 
+   gen7_set_surface_num_multisamples(surf, irb->mt->num_samples);
+
    if (intel->is_haswell) {
       surf->ss7.shader_chanel_select_r = HSW_SCS_RED;
       surf->ss7.shader_chanel_select_g = HSW_SCS_GREEN;