[Impeller] use spec constant for decal support in morph filter. (#48288)

Don't branch on uniform for decal support in GLES backend.

Author: Jonah Williams

impeller/entity/contents/content_context.cc

@@ -322,7 +322,8 @@ ContentContext::ContentContext(
   gaussian_blur_noalpha_nodecal_pipelines_.CreateDefault(*context_,
                                                          options_trianglestrip);
   border_mask_blur_pipelines_.CreateDefault(*context_, options_trianglestrip);
-  morphology_filter_pipelines_.CreateDefault(*context_, options_trianglestrip);
+  morphology_filter_pipelines_.CreateDefault(*context_, options_trianglestrip,
+                                             {supports_decal});
   color_matrix_color_filter_pipelines_.CreateDefault(*context_,
                                                      options_trianglestrip);
   linear_to_srgb_filter_pipelines_.CreateDefault(*context_,

impeller/entity/contents/filters/morphology_filter_contents.cc

@@ -127,8 +127,6 @@ std::optional<Entity> DirectionalMorphologyFilterContents::RenderFilter(
       sampler_descriptor.width_address_mode = SamplerAddressMode::kDecal;
       sampler_descriptor.height_address_mode = SamplerAddressMode::kDecal;
     }
-    frag_info.supports_decal_sampler_address_mode =
-        renderer.GetDeviceCapabilities().SupportsDecalSamplerAddressMode();
 
     FS::BindTextureSampler(
         cmd, input_snapshot->texture,

impeller/entity/entity_unittests.cc

@@ -2514,6 +2514,19 @@ TEST_P(EntityTest, SpecializationConstantsAreAppliedToVariants) {
             expected_constants);
 }
 
+TEST_P(EntityTest, DecalSpecializationAppliedToMorphologyFilter) {
+  auto content_context =
+      ContentContext(GetContext(), TypographerContextSkia::Make());
+
+  auto default_color_burn = content_context.GetMorphologyFilterPipeline({});
+
+  auto decal_supported = static_cast<int32_t>(
+      GetContext()->GetCapabilities()->SupportsDecalSamplerAddressMode());
+  std::vector<int32_t> expected_constants = {decal_supported};
+  ASSERT_EQ(default_color_burn->GetDescriptor().GetSpecializationConstants(),
+            expected_constants);
+}
+
 }  // namespace testing
 }  // namespace impeller
 

impeller/entity/shaders/morphology_filter.frag

@@ -4,6 +4,8 @@
 
 precision mediump float;
 
+layout(constant_id = 0) const int supports_decal = 1;
+
 #include <impeller/constants.glsl>
 #include <impeller/texture.glsl>
 #include <impeller/types.glsl>
@@ -34,15 +36,11 @@ void main() {
     vec2 texture_coords = v_texture_coords + frag_info.uv_offset * i;
 
     f16vec4 color;
-#ifdef IMPELLER_TARGET_OPENGLES
-    if (frag_info.supports_decal_sampler_address_mode > 0.0) {
+    if (supports_decal == 1) {
       color = texture(texture_sampler, texture_coords);
     } else {
       color = IPHalfSampleDecal(texture_sampler, texture_coords);
     }
-#else
-    color = texture(texture_sampler, texture_coords);
-#endif
 
     if (frag_info.morph_type == kMorphTypeDilate) {
       result = max(color, result);

impeller/tools/malioc.json

@@ -4437,7 +4437,7 @@
       "uses_late_zs_update": false,
       "variants": {
         "Main": {
-          "fp16_arithmetic": 57,
+          "fp16_arithmetic": 80,
           "has_stack_spilling": false,
           "performance": {
             "longest_path_bound_pipelines": [
@@ -4475,22 +4475,23 @@
               0.0
             ],
             "total_bound_pipelines": [
+              "varying",
               "texture"
             ],
             "total_cycles": [
-              0.390625,
+              0.234375,
               0.078125,
-              0.390625,
-              0.0625,
+              0.234375,
+              0.0,
               0.0,
               0.25,
-              0.5
+              0.25
             ]
           },
           "stack_spill_bytes": 0,
           "thread_occupancy": 100,
           "uniform_registers_used": 8,
-          "work_registers_used": 20
+          "work_registers_used": 21
         }
       }
     },
@@ -4529,14 +4530,14 @@
               "arithmetic"
             ],
             "total_cycles": [
-              4.666666507720947,
+              2.6666667461395264,
               1.0,
-              2.0
+              1.0
             ]
           },
           "thread_occupancy": 100,
           "uniform_registers_used": 1,
-          "work_registers_used": 3
+          "work_registers_used": 4
         }
       }
     }