3 files changed, 38 insertions, 0 deletions
diff --git a/source/blender/gpu/GPU_material.h b/source/blender/gpu/GPU_material.h
index 3ca465fa57a..ddd8300bf0f 100644
--- a/source/blender/gpu/GPU_material.h
+++ b/source/blender/gpu/GPU_material.h
@@ -77,12 +77,20 @@ typedef enum eGPUMaterialFlag {
   GPU_MATFLAG_HOLDOUT = (1 << 6),
   GPU_MATFLAG_SHADER_TO_RGBA = (1 << 7),
   GPU_MATFLAG_AO = (1 << 8),
+  GPU_MATFLAG_CLEARCOAT = (1 << 9),
 
   GPU_MATFLAG_OBJECT_INFO = (1 << 10),
   GPU_MATFLAG_AOV = (1 << 11),
 
   GPU_MATFLAG_BARYCENTRIC = (1 << 20),
 
+  /* Optimization to only add the branches of the principled shader that are necessary. */
+  GPU_MATFLAG_PRINCIPLED_CLEARCOAT = (1 << 21),
+  GPU_MATFLAG_PRINCIPLED_METALLIC = (1 << 22),
+  GPU_MATFLAG_PRINCIPLED_DIELECTRIC = (1 << 23),
+  GPU_MATFLAG_PRINCIPLED_GLASS = (1 << 24),
+  GPU_MATFLAG_PRINCIPLED_ANY = (1 << 25),
+
   /* Tells the render engine the material was just compiled or updated. */
   GPU_MATFLAG_UPDATED = (1 << 29),
 
diff --git a/source/blender/gpu/intern/gpu_codegen.cc b/source/blender/gpu/intern/gpu_codegen.cc
index 82441c3c89c..a05bf51242f 100644
--- a/source/blender/gpu/intern/gpu_codegen.cc
+++ b/source/blender/gpu/intern/gpu_codegen.cc
@@ -351,6 +351,24 @@ void GPUCodegen::generate_resources()
 {
   GPUCodegenCreateInfo &info = *create_info;
 
+  /* Ref. T98190: Defines are optimizations for old compilers.
+   * Might become unecessary with EEVEE-Next. */
+  if (GPU_material_flag_get(&mat, GPU_MATFLAG_PRINCIPLED_CLEARCOAT)) {
+    info.define("PRINCIPLED_CLEARCOAT");
+  }
+  if (GPU_material_flag_get(&mat, GPU_MATFLAG_PRINCIPLED_METALLIC)) {
+    info.define("PRINCIPLED_METALLIC");
+  }
+  if (GPU_material_flag_get(&mat, GPU_MATFLAG_PRINCIPLED_DIELECTRIC)) {
+    info.define("PRINCIPLED_DIELECTRIC");
+  }
+  if (GPU_material_flag_get(&mat, GPU_MATFLAG_PRINCIPLED_GLASS)) {
+    info.define("PRINCIPLED_GLASS");
+  }
+  if (GPU_material_flag_get(&mat, GPU_MATFLAG_PRINCIPLED_ANY)) {
+    info.define("PRINCIPLED_ANY");
+  }
+
   std::stringstream ss;
 
   /* Textures. */
diff --git a/source/blender/gpu/shaders/material/gpu_shader_material_principled.glsl b/source/blender/gpu/shaders/material/gpu_shader_material_principled.glsl
index 2e695fa3e14..0d8f2272c10 100644
--- a/source/blender/gpu/shaders/material/gpu_shader_material_principled.glsl
+++ b/source/blender/gpu/shaders/material/gpu_shader_material_principled.glsl
@@ -149,25 +149,37 @@ void node_bsdf_principled(vec4 base_color,
                                                        max(roughness, transmission_roughness);
   refraction_data.ior = ior;
 
+  /* Ref. T98190: Defines are optimizations for old compilers.
+   * Might become unecessary with EEVEE-Next. */
   if (do_diffuse == 0.0 && do_refraction == 0.0 && do_clearcoat != 0.0) {
+#ifdef PRINCIPLED_CLEARCOAT
     /* Metallic & Clearcoat case. */
     result = closure_eval(reflection_data, clearcoat_data);
+#endif
   }
   else if (do_diffuse == 0.0 && do_refraction == 0.0 && do_clearcoat == 0.0) {
+#ifdef PRINCIPLED_METALLIC
     /* Metallic case. */
     result = closure_eval(reflection_data);
+#endif
   }
   else if (do_diffuse != 0.0 && do_refraction == 0.0 && do_clearcoat == 0.0) {
+#ifdef PRINCIPLED_DIELECTRIC
     /* Dielectric case. */
     result = closure_eval(diffuse_data, reflection_data);
+#endif
   }
   else if (do_diffuse == 0.0 && do_refraction != 0.0 && do_clearcoat == 0.0) {
+#ifdef PRINCIPLED_GLASS
     /* Glass case. */
     result = closure_eval(reflection_data, refraction_data);
+#endif
   }
   else {
+#ifdef PRINCIPLED_ANY
     /* Un-optimized case. */
     result = closure_eval(diffuse_data, reflection_data, clearcoat_data, refraction_data);
+#endif
   }
   Closure emission_cl = closure_eval(emission_data);
   Closure transparency_cl = closure_eval(transparency_data);