gl_shader_decompiler: Stub input attribute Unknown_63.

src/video_core/engines/shader_bytecode.h

@@ -78,6 +78,8 @@ union Attribute {
         // shader, and a tuple of (TessCoord.x, TessCoord.y, TessCoord.z, ~) when inside a Tess Eval
         // shader.
         TessCoordInstanceIDVertexID = 47,
+        // TODO(bunnei): Figure out what this is used for. Super Mario Odyssey uses this.
+        Unknown_63 = 63,
     };
 
     union {

src/video_core/renderer_opengl/gl_shader_decompiler.cpp

@@ -523,6 +523,11 @@ private:
             // shader.
             ASSERT(stage == Maxwell3D::Regs::ShaderStage::Vertex);
             return "vec4(0, 0, uintBitsToFloat(gl_InstanceID), uintBitsToFloat(gl_VertexID))";
+        case Attribute::Index::Unknown_63:
+            // TODO(bunnei): Figure out what this is used for. Super Mario Odyssey uses this.
+            LOG_CRITICAL(HW_GPU, "Unhandled input attribute Unknown_63");
+            UNREACHABLE();
+            break;
         default:
             const u32 index{static_cast<u32>(attribute) -
                             static_cast<u32>(Attribute::Index::Attribute_0)};
@@ -534,6 +539,8 @@ private:
             LOG_CRITICAL(HW_GPU, "Unhandled input attribute: {}", index);
             UNREACHABLE();
         }
+
+        return "vec4(0, 0, 0, 0)";
     }
 
     /// Generates code representing an output attribute register.