Track that indices of l-values are not required to be l-values

src/compiler/translator/IntermNode.h

@@ -694,8 +694,9 @@ class TIntermTraverser : angle::NonCopyable
     TIntermSequence *getFunctionParameters(const TIntermAggregate *callNode);
 
     // Track whether an l-value is required inside a function call.
-    // This function is intended to be called only from traversal functions, not from traverers.
+    // These functions are intended to be called only from traversal functions, not from traverers.
     void setInFunctionCallOutParameter(bool inOutParameter);
+    bool isInFunctionCallOutParameter() const;
 
     bool isLValueRequiredHere() const
     {

src/compiler/translator/IntermTraverse.cpp

@@ -118,6 +118,11 @@ void TIntermTraverser::setInFunctionCallOutParameter(bool inOutParameter)
     mInFunctionCallOutParameter = inOutParameter;
 }
 
+bool TIntermTraverser::isInFunctionCallOutParameter() const
+{
+    return mInFunctionCallOutParameter;
+}
+
 //
 // Traverse the intermediate representation tree, and
 // call a node type specific function for each node.
@@ -162,11 +167,13 @@ void TIntermBinary::traverse(TIntermTraverser *it)
     {
         it->incrementDepth(this);
 
+        // Some binary operations like indexing can be inside an expression which must be an
+        // l-value.
+        bool parentOperatorRequiresLValue     = it->operatorRequiresLValue();
+        bool parentInFunctionCallOutParameter = it->isInFunctionCallOutParameter();
         if (isAssignment())
         {
-            // Some binary operations like indexing can be inside an l-value.
-            // TODO(oetuaho@nvidia.com): Now the code doesn't unset operatorRequiresLValue for the
-            // index, fix this.
+            ASSERT(!it->isLValueRequiredHere());
             it->setOperatorRequiresLValue(true);
         }
 
@@ -179,9 +186,21 @@ void TIntermBinary::traverse(TIntermTraverser *it)
         if (isAssignment())
             it->setOperatorRequiresLValue(false);
 
+        // Index is not required to be an l-value even when the surrounding expression is required
+        // to be an l-value.
+        if (mOp == EOpIndexDirect || mOp == EOpIndexDirectInterfaceBlock ||
+            mOp == EOpIndexDirectStruct || mOp == EOpIndexIndirect)
+        {
+            it->setOperatorRequiresLValue(false);
+            it->setInFunctionCallOutParameter(false);
+        }
+
         if (visit && mRight)
             mRight->traverse(it);
 
+        it->setOperatorRequiresLValue(parentOperatorRequiresLValue);
+        it->setInFunctionCallOutParameter(parentInFunctionCallOutParameter);
+
         it->decrementDepth();
     }
 
@@ -207,6 +226,7 @@ void TIntermUnary::traverse(TIntermTraverser *it)
     {
         it->incrementDepth(this);
 
+        ASSERT(!it->operatorRequiresLValue());
         switch (getOp())
         {
             case EOpPostIncrement:

src/tests/compiler_tests/DebugShaderPrecision_test.cpp

@@ -771,3 +771,35 @@ TEST_F(DebugShaderPrecisionTest, NestedFunctionCalls)
     // Test nested calls
     ASSERT_TRUE(foundInCode("v2 = add(compound_add(v, angle_frm(u2)), angle_frm(fract(angle_frm(u3))))"));
 }
+
+// Test that code inside an index of a function out parameter gets processed.
+TEST_F(DebugShaderPrecisionTest, OpInIndexOfFunctionOutParameter)
+{
+    const std::string &shaderString =
+        "precision mediump float;\n"
+        "void foo(out vec4 f) { f.x = 0.0; }\n"
+        "uniform float u2;\n"
+        "void main() {\n"
+        "   vec4 v[2];\n"
+        "   foo(v[int(exp2(u2))]);\n"
+        "   gl_FragColor = v[0];\n"
+        "}\n";
+    compile(shaderString);
+    ASSERT_TRUE(foundInCode("angle_frm(exp2(angle_frm(u2)))"));
+}
+
+// Test that code inside an index of an l-value gets processed.
+TEST_F(DebugShaderPrecisionTest, OpInIndexOfLValue)
+{
+    const std::string &shaderString =
+        "precision mediump float;\n"
+        "uniform vec4 u1;\n"
+        "uniform float u2;\n"
+        "void main() {\n"
+        "   vec4 v[2];\n"
+        "   v[int(exp2(u2))] = u1;\n"
+        "   gl_FragColor = v[0];\n"
+        "}\n";
+    compile(shaderString);
+    ASSERT_TRUE(foundInCode("angle_frm(exp2(angle_frm(u2)))"));
+}