D3D11: Fix unreferenced XFB vars getting dropped.

src/libANGLE/renderer/d3d/VaryingPacking.cpp

@@ -267,33 +267,37 @@ bool VaryingPacking::packVaryings(gl::InfoLog &infoLog,
             continue;
         }
 
+        bool found = false;
         for (const PackedVarying &packedVarying : packedVaryings)
         {
             const auto &varying = *packedVarying.varying;
 
             // Make sure transform feedback varyings aren't optimized out.
-            if (uniqueVaryingNames.count(transformFeedbackVaryingName) == 0)
+            if (uniqueVaryingNames.count(transformFeedbackVaryingName) > 0)
             {
-                bool found = false;
-                if (transformFeedbackVaryingName == varying.name)
-                {
-                    if (!packVarying(packedVarying))
-                    {
-                        infoLog << "Could not pack varying " << varying.name;
-                        return false;
-                    }
-
-                    found = true;
-                    break;
-                }
-                if (!found)
+                found = true;
+                break;
+            }
+
+            if (transformFeedbackVaryingName == varying.name)
+            {
+                if (!packVarying(packedVarying))
                 {
-                    infoLog << "Transform feedback varying " << transformFeedbackVaryingName
-                            << " does not exist in the vertex shader.";
+                    infoLog << "Could not pack varying " << varying.name;
                     return false;
                 }
+
+                found = true;
+                break;
             }
         }
+
+        if (!found)
+        {
+            infoLog << "Transform feedback varying " << transformFeedbackVaryingName
+                    << " does not exist in the vertex shader.";
+            return false;
+        }
     }
 
     // Sort the packed register list

src/tests/gl_tests/TransformFeedbackTest.cpp

@@ -823,6 +823,69 @@ TEST_P(TransformFeedbackTest, OptimizedVaryings)
     ASSERT_NE(0u, mProgram);
 }
 
+// Test an edge case where two varyings are unreferenced in the frag shader.
+TEST_P(TransformFeedbackTest, TwoUnreferencedInFragShader)
+{
+    // TODO(jmadill): With points and rasterizer discard?
+    const std::string &vertexShaderSource =
+        "#version 300 es\n"
+        "in vec3 position;\n"
+        "out vec3 outAttrib1;\n"
+        "out vec3 outAttrib2;\n"
+        "void main() {"
+        "  outAttrib1 = position;\n"
+        "  outAttrib2 = position;\n"
+        "  gl_Position = vec4(position, 1);\n"
+        "}";
+
+    const std::string &fragmentShaderSource =
+        "#version 300 es\n"
+        "precision mediump float;\n"
+        "out vec4 color;\n"
+        "in vec3 outAttrib1;\n"
+        "in vec3 outAttrib2;\n"
+        "void main() {\n"
+        "  color = vec4(0);\n"
+        "}";
+
+    std::vector<std::string> tfVaryings;
+    tfVaryings.push_back("outAttrib1");
+    tfVaryings.push_back("outAttrib2");
+
+    mProgram = CompileProgramWithTransformFeedback(vertexShaderSource, fragmentShaderSource,
+                                                   tfVaryings, GL_INTERLEAVED_ATTRIBS);
+    ASSERT_NE(0u, mProgram);
+
+    glBindBuffer(GL_TRANSFORM_FEEDBACK_BUFFER, mTransformFeedbackBuffer);
+    glBufferData(GL_TRANSFORM_FEEDBACK_BUFFER, sizeof(Vector3) * 2 * 6, nullptr, GL_STREAM_DRAW);
+
+    glBindTransformFeedback(GL_TRANSFORM_FEEDBACK, mTransformFeedback);
+    glBindBufferBase(GL_TRANSFORM_FEEDBACK_BUFFER, 0, mTransformFeedbackBuffer);
+
+    glUseProgram(mProgram);
+    glBeginTransformFeedback(GL_TRIANGLES);
+    drawQuad(mProgram, "position", 0.5f);
+    glEndTransformFeedback();
+    glUseProgram(0);
+    ASSERT_GL_NO_ERROR();
+
+    const GLvoid *mapPointer =
+        glMapBufferRange(GL_TRANSFORM_FEEDBACK_BUFFER, 0, sizeof(Vector2) * 2 * 6, GL_MAP_READ_BIT);
+    ASSERT_NE(nullptr, mapPointer);
+
+    const auto &quadVertices = GetQuadVertices();
+
+    const Vector3 *vecPointer = static_cast<const Vector3 *>(mapPointer);
+    for (unsigned int vectorIndex = 0; vectorIndex < 3; ++vectorIndex)
+    {
+        unsigned int stream1Index = vectorIndex * 2;
+        unsigned int stream2Index = vectorIndex * 2 + 1;
+        EXPECT_EQ(quadVertices[vectorIndex], vecPointer[stream1Index]);
+        EXPECT_EQ(quadVertices[vectorIndex], vecPointer[stream2Index]);
+    }
+
+    ASSERT_GL_NO_ERROR();
+}
 class TransformFeedbackLifetimeTest : public TransformFeedbackTest
 {
   protected:

util/Vector.cpp

@@ -132,6 +132,16 @@ Vector3 operator-(const Vector3 &a, const Vector3 &b)
     return Vector3(a.x - b.x, a.y - b.y, a.z - b.z);
 }
 
+bool operator==(const Vector3 &a, const Vector3 &b)
+{
+    return (a.x == b.x && a.y == b.y && a.z == b.z);
+}
+
+bool operator!=(const Vector3 &a, const Vector3 &b)
+{
+    return !(a == b);
+}
+
 Vector4::Vector4() : x(0.0f), y(0.0f), z(0.0f), w(0.0f)
 {
 }

util/Vector.h

@@ -60,6 +60,8 @@ ANGLE_EXPORT Vector3 operator/(const Vector3 &a, const Vector3 &b);
 ANGLE_EXPORT Vector3 operator/(const Vector3 &a, const float &b);
 ANGLE_EXPORT Vector3 operator+(const Vector3 &a, const Vector3 &b);
 ANGLE_EXPORT Vector3 operator-(const Vector3 &a, const Vector3 &b);
+ANGLE_EXPORT bool operator==(const Vector3 &a, const Vector3 &b);
+ANGLE_EXPORT bool operator!=(const Vector3 &a, const Vector3 &b);
 
 struct ANGLE_EXPORT Vector4
 {