Mesa (main): turnip: force sample interpolations for sample shading

[GitLab Mirror]

Module: Mesa
Branch: main
Commit: 3933752c7f7b224185c5c8ff999dcc85526f9441
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=3933752c7f7b224185c5c8ff999dcc85526f9441

Author: Chia-I Wu <olvaffe at gmail.com>
Date:   Tue May 24 15:26:42 2022 -0700

turnip: force sample interpolations for sample shading

Sample shading has similiar definitions in Vulkan and OpenGL, and they
both require unique associated data.  While the definition for Vulkan
might change, we should stick to the current definition until the change
takes place and until apps (i.e., ANGLE) are updated.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16700>

---

 src/freedreno/vulkan/tu_pipeline.c | 29 +++++++++++++++++++++++++++--
 src/freedreno/vulkan/tu_private.h  |  1 +
 src/freedreno/vulkan/tu_shader.c   |  7 +++++++
 3 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/src/freedreno/vulkan/tu_pipeline.c b/src/freedreno/vulkan/tu_pipeline.c
index d7cdc7936ca..9ad4a39db0e 100644
--- a/src/freedreno/vulkan/tu_pipeline.c
+++ b/src/freedreno/vulkan/tu_pipeline.c
@@ -2360,8 +2360,32 @@ tu_pipeline_shader_key_init(struct ir3_shader_key *key,
       key->msaa = true;
    }
 
-   /* note: not actually used by ir3, just checked in tu6_emit_fs_inputs */
-   if (msaa_info->sampleShadingEnable)
+   /* The 1.3.215 spec says:
+    *
+    *    Sample shading can be used to specify a minimum number of unique
+    *    samples to process for each fragment. If sample shading is enabled,
+    *    an implementation must provide a minimum of
+    *
+    *       max(ceil(minSampleShadingFactor * totalSamples), 1)
+    *
+    *    unique associated data for each fragment, where
+    *    minSampleShadingFactor is the minimum fraction of sample shading.
+    *
+    * The definition is pretty much the same as OpenGL's GL_SAMPLE_SHADING.
+    * They both require unique associated data.
+    *
+    * There are discussions to change the definition, such that
+    * sampleShadingEnable does not imply unique associated data.  Before the
+    * discussions are settled and before apps (i.e., ANGLE) are fixed to
+    * follow the new and incompatible definition, we should stick to the
+    * current definition.
+    *
+    * Note that ir3_shader_key::sample_shading is not actually used by ir3,
+    * just checked in tu6_emit_fs_inputs.  We will also copy the value to
+    * tu_shader_key::force_sample_interp in a bit.
+    */
+   if (msaa_info->sampleShadingEnable &&
+       (msaa_info->minSampleShading * msaa_info->rasterizationSamples) > 1.0f)
       key->sample_shading = true;
 
    /* We set this after we compile to NIR because we need the prim mode */
@@ -2739,6 +2763,7 @@ tu_pipeline_builder_compile_shaders(struct tu_pipeline_builder *builder,
 
    keys[MESA_SHADER_VERTEX].multiview_mask = builder->multiview_mask;
    keys[MESA_SHADER_FRAGMENT].multiview_mask = builder->multiview_mask;
+   keys[MESA_SHADER_FRAGMENT].force_sample_interp = ir3_key.sample_shading;
 
    unsigned char pipeline_sha1[20];
    tu_hash_shaders(pipeline_sha1, stage_infos, builder->layout, keys, &ir3_key, compiler);
diff --git a/src/freedreno/vulkan/tu_private.h b/src/freedreno/vulkan/tu_private.h
index c38eb756a17..8bf74d365d0 100644
--- a/src/freedreno/vulkan/tu_private.h
+++ b/src/freedreno/vulkan/tu_private.h
@@ -1360,6 +1360,7 @@ struct tu_shader
 
 struct tu_shader_key {
    unsigned multiview_mask;
+   bool force_sample_interp;
    enum ir3_wavesize_option api_wavesize, real_wavesize;
 };
 
diff --git a/src/freedreno/vulkan/tu_shader.c b/src/freedreno/vulkan/tu_shader.c
index bf298ef5103..41c8a4f8dd5 100644
--- a/src/freedreno/vulkan/tu_shader.c
+++ b/src/freedreno/vulkan/tu_shader.c
@@ -747,6 +747,13 @@ tu_shader_create(struct tu_device *dev,
                              &shader->multi_pos_output, dev);
    }
 
+   if (nir->info.stage == MESA_SHADER_FRAGMENT && key->force_sample_interp) {
+      nir_foreach_shader_in_variable(var, nir) {
+         if (!var->data.centroid)
+            var->data.sample = true;
+      }
+   }
+
    NIR_PASS_V(nir, nir_lower_explicit_io, nir_var_mem_push_const,
               nir_address_format_32bit_offset);