i965: Add i965 plumbing for ARB_post_depth_coverage for i965 (gen9+).

This extension allows the fragment shader to control whether values in
gl_SampleMaskIn[] reflect the coverage after application of the early
depth and stencil tests.

Signed-off-by: Plamena Manolova <plamena.manolova@intel.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

docs/features.txt

@@ -287,7 +287,7 @@ Khronos, ARB, and OES extensions that are not part of any OpenGL or OpenGL ES ve
   GL_ARB_indirect_parameters                            DONE (nvc0, radeonsi)
   GL_ARB_parallel_shader_compile                        not started, but Chia-I Wu did some related work in 2014
   GL_ARB_pipeline_statistics_query                      DONE (i965, nvc0, radeonsi, softpipe, swr)
-  GL_ARB_post_depth_coverage                            not started
+  GL_ARB_post_depth_coverage                            DONE (i965)
   GL_ARB_robustness_isolation                           not started
   GL_ARB_sample_locations                               not started
   GL_ARB_seamless_cubemap_per_texture                   DONE (i965, nvc0, radeonsi, r600, softpipe, swr)

docs/relnotes/13.1.0.html

@@ -44,6 +44,7 @@ Note: some of the new features are only available with certain drivers.
 </p>
 
 <ul>
+<li>GL_ARB_post_depth_coverage on i965/gen9+</li>
 <li>GL_NV_image_formats on any driver supporting GL_ARB_shader_image_load_store (i965, nvc0, radeonsi, softpipe)</li>
 </ul>
 

src/mesa/drivers/dri/i965/brw_compiler.h

@@ -397,6 +397,7 @@ struct brw_wm_prog_data {
    bool computed_stencil;
 
    bool early_fragment_tests;
+   bool post_depth_coverage;
    bool dispatch_8;
    bool dispatch_16;
    bool dual_src_blend;

src/mesa/drivers/dri/i965/brw_fs.cpp

@@ -6454,6 +6454,7 @@ brw_compile_fs(const struct brw_compiler *compiler, void *log_data,
        shader->info->outputs_read);
 
    prog_data->early_fragment_tests = shader->info->fs.early_fragment_tests;
+   prog_data->post_depth_coverage = shader->info->fs.post_depth_coverage;
 
    prog_data->barycentric_interp_modes =
       brw_compute_barycentric_interp_modes(compiler->devinfo, shader);

src/mesa/drivers/dri/i965/gen8_ps_state.c

@@ -53,10 +53,17 @@ gen8_upload_ps_extra(struct brw_context *brw,
       dw1 |= GEN8_PSX_SHADER_IS_PER_SAMPLE;
 
    if (prog_data->uses_sample_mask) {
-      if (brw->gen >= 9)
-         dw1 |= BRW_PSICMS_INNER << GEN9_PSX_SHADER_NORMAL_COVERAGE_MASK_SHIFT;
-      else
+      if (brw->gen >= 9) {
+         if (prog_data->post_depth_coverage) {
+            dw1 |= BRW_PCICMS_DEPTH << GEN9_PSX_SHADER_NORMAL_COVERAGE_MASK_SHIFT;
+         }
+         else {
+            dw1 |= BRW_PSICMS_INNER << GEN9_PSX_SHADER_NORMAL_COVERAGE_MASK_SHIFT;
+         }
+      }
+      else {
          dw1 |= GEN8_PSX_SHADER_USES_INPUT_COVERAGE_MASK;
+      }
    }
 
    if (prog_data->uses_omask)

src/mesa/drivers/dri/i965/intel_extensions.c

@@ -415,6 +415,7 @@ intelInitExtensions(struct gl_context *ctx)
       ctx->Extensions.KHR_texture_compression_astc_ldr = true;
       ctx->Extensions.KHR_texture_compression_astc_sliced_3d = true;
       ctx->Extensions.MESA_shader_framebuffer_fetch = true;
+      ctx->Extensions.ARB_post_depth_coverage = true;
    }
 
    if (ctx->API == API_OPENGL_CORE)