Populate gl_InstanceID attribute information explicitly

src/compiler/translator/VariableInfo.cpp

@@ -336,7 +336,25 @@ void CollectVariablesTraverser::visitSymbol(TIntermSymbol *symbol)
                 recordBuiltInVaryingUsed("gl_PointCoord", &mPointCoordAdded);
                 return;
             case EvqInstanceID:
-                recordBuiltInAttributeUsed("gl_InstanceID", &mInstanceIDAdded);
+                // Whenever the SH_INITIALIZE_BUILTINS_FOR_INSTANCED_MULTIVIEW option is set,
+                // gl_InstanceID is added inside expressions to initialize ViewID_OVR and
+                // InstanceID. gl_InstanceID is not added to the symbol table for ESSL1 shaders
+                // which makes it necessary to populate the type information explicitly instead of
+                // extracting it from the symbol table.
+                if (!mInstanceIDAdded)
+                {
+                    Attribute info;
+                    const char kName[] = "gl_InstanceID";
+                    info.name          = kName;
+                    info.mappedName    = kName;
+                    info.type          = GL_INT;
+                    info.arraySize     = 0;
+                    info.precision     = GL_HIGH_INT;  // Defined by spec.
+                    info.staticUse     = true;
+                    info.location      = -1;
+                    mAttribs->push_back(info);
+                    mInstanceIDAdded = true;
+                }
                 return;
             case EvqVertexID:
                 recordBuiltInAttributeUsed("gl_VertexID", &mVertexIDAdded);

src/tests/compiler_tests/WEBGL_multiview_test.cpp

@@ -717,3 +717,28 @@ TEST_F(WEBGLMultiviewVertexShaderOutputCodeTest, StrippedOVRMultiviewDirective)
     compile(shaderString);
     EXPECT_TRUE(foundInESSLCode("GL_OVR_multiview"));
 }
+
+// Test that gl_InstanceID is collected in an ESSL1 shader if the
+// SH_INITIALIZE_BUILTINS_FOR_INSTANCED_MULTIVIEW option is set.
+TEST_F(WEBGLMultiviewVertexShaderTest, InstaceIDCollectedESSL1)
+{
+    const std::string &shaderString =
+        "#extension GL_OVR_multiview2 : require\n"
+        "layout(num_views = 2) in;\n"
+        "void main()\n"
+        "{\n"
+        "   gl_Position.x = gl_ViewID_OVR == 0 ? 0. : 1.;\n"
+        "   gl_Position.yzw = vec3(0., 0., 1.);\n"
+        "}\n";
+    mExtraCompileOptions |= SH_INITIALIZE_BUILTINS_FOR_INSTANCED_MULTIVIEW;
+    mExtraCompileOptions |= SH_VARIABLES;
+    compileAssumeSuccess(shaderString);
+
+    const std::vector<Attribute> &attributes = getAttributes();
+    bool isGLInstanceIDFound                 = false;
+    for (size_t i = 0u; i < attributes.size() && !isGLInstanceIDFound; ++i)
+    {
+        isGLInstanceIDFound = (attributes[i].name == "gl_InstanceID");
+    }
+    EXPECT_TRUE(isGLInstanceIDFound);
+}
\ No newline at end of file

src/tests/test_utils/ShaderCompileTreeTest.cpp

@@ -153,12 +153,18 @@ bool ShaderCompileTreeTest::hasWarning() const
     return mInfoLog.find("WARNING: ") != std::string::npos;
 }
 
-const std::vector<sh::Uniform> ShaderCompileTreeTest::getUniforms()
+const std::vector<sh::Uniform> &ShaderCompileTreeTest::getUniforms() const
 {
     ASSERT(mExtraCompileOptions & SH_VARIABLES);
     return mTranslator->getUniforms();
 }
 
+const std::vector<sh::Attribute> &ShaderCompileTreeTest::getAttributes() const
+{
+    ASSERT(mExtraCompileOptions & SH_VARIABLES);
+    return mTranslator->getAttributes();
+}
+
 bool IsZero(TIntermNode *node)
 {
     if (!node->getAsTyped())

src/tests/test_utils/ShaderCompileTreeTest.h

@@ -38,7 +38,8 @@ class ShaderCompileTreeTest : public testing::Test
 
     bool hasWarning() const;
 
-    const std::vector<sh::Uniform> getUniforms();
+    const std::vector<sh::Uniform> &getUniforms() const;
+    const std::vector<sh::Attribute> &getAttributes() const;
 
     virtual void initResources(ShBuiltInResources *resources) {}
     virtual ::GLenum getShaderType() const     = 0;