Add more documentation to classes/functions and remove some dead code.

PiperOrigin-RevId: 314821136
Change-Id: I2e19f4b68939fd972914471c4373044ac45dc1e8

tensorflow/lite/experimental/delegates/hexagon/builders/op_builder.h

@@ -32,6 +32,7 @@ namespace tflite {
 namespace delegates {
 namespace hexagon {
 
+// Wrapper that holds all data representing a single node in the Hexagon graph.
 struct OpNode {
   std::vector<hexagon_nn_input> inputs;
   std::vector<hexagon_nn_output> outputs;
@@ -48,6 +49,15 @@ struct OpNode {
 
 class GraphBuilder;
 
+// Represents a single Op in the TFLite graph.
+// For each op in TFLite there should be an OpBuidler, this builder is
+// responsible for constructing equivalent node(s) in the hexagon graph. A
+// single builder can create one or more ops in the hexagon graph. When adding
+// new op* users should inherit from this class and implement
+// - PopulateSubgraph: which given inputs/outputs should construct the
+// equivalent hexagon nodes.
+// - RegisterOutputs: Which should have logic that maps final outputs from a
+// given node to the equivalent in Hexagon graph.
 class OpBuilder {
  public:
   // Const representing the shape of a scalar value.
@@ -65,30 +75,59 @@ class OpBuilder {
 
   virtual ~OpBuilder() {}
 
-  // TODO(karimnosseir): Do we need to have builder pattern, or they are few not
-  // worth it ?
+  // Sets the op type in the hexagon graph.
   void SetOpType(int op_type) { op_node_.op_type = op_type; }
 
+  // Sets the node id in the hexagon graph.
   void SetNodeId(int node_id) { op_node_.node_id = node_id; }
 
+  // Sets the TfLite node index in the TfLite graph.
   void SetTFLiteNodeId(int node_index) {
     op_node_.tflite_node_index = node_index;
   }
 
+  // Marks this node as Const node.
   void SetConstNode() { op_node_.op_type = OP_Const; }
 
+  // Sets the padding type of the current node.
   void SetPaddingType(hexagon_nn_padding_type padding_type) {
     op_node_.padding_type = padding_type;
   }
 
+  // Sets the builtin_data of TFLite node that this Builder is responsible for.
   void SetBuiltinData(void* builtin_data) { builtin_data_ = builtin_data; }
 
+  // Returns true if the current op is a const Op.
   bool IsConstNode() const { return op_node_.op_type == OP_Const; }
 
-  void print() {}
+  // Subclasses should override it and have logic which handles initializing
+  // hexagon node(s) for the current op, given 'inputs' 'outputs'
+  virtual TfLiteStatus PopulateSubGraph(const TfLiteIntArray* inputs,
+                                        const TfLiteIntArray* outputs,
+                                        TfLiteContext* context) {
+    return kTfLiteOk;
+  }
 
+  // Subclasses should override it and register the final output(s) from the
+  // node to the equivalent in hexagon graph.
+  virtual TfLiteStatus RegisterOutputs(const TfLiteIntArray* outputs,
+                                       TfLiteContext* context) {
+    return kTfLiteOk;
+  }
+
+  // Constructs OpNode which represents a node in the Hexagon graph.
   const OpNode* Build();
 
+  // Returns the Node index in TFLite graph.
+  int GetTFLiteNodeID() const { return op_node_.tflite_node_index; }
+
+  // Returns the Op type of the current Op (in Hexagon graph)
+  int GetOpType() const { return op_node_.op_type; }
+
+  // Returns the node id in the hexagon graph.
+  int GetID() const { return op_node_.node_id; }
+
+  // Adds tensor identified by 'tensor_id' as input to the current Op.
   void AddInput(const TensorID& tensor_id) { input_ids_.push_back(tensor_id); }
 
   // Adds Output to the current node, the output has shape defined in 'dims'.
@@ -106,25 +145,13 @@ class OpBuilder {
   // Same as above but accepts pointer instead of std::vector.
   TensorID AddOutput(int elementsize, int rank, const int* max_sizes_vect);
 
-  int GetID() const { return op_node_.node_id; }
-
-  int GetTFLiteNodeID() const { return op_node_.tflite_node_index; }
-
-  int GetOpType() const { return op_node_.op_type; }
-
+  // Sets the node that corresponds to this builder in TFLite graph.
   void SetTfLiteNode(const TfLiteNode* node) { tflite_node_ = node; }
 
-  virtual TfLiteStatus PopulateSubGraph(const TfLiteIntArray* inputs,
-                                        const TfLiteIntArray* outputs,
-                                        TfLiteContext* context) {
-    return kTfLiteOk;
-  }
-
-  virtual TfLiteStatus RegisterOutputs(const TfLiteIntArray* outputs,
-                                       TfLiteContext* context) {
-    return kTfLiteOk;
-  }
-
+  // Static
+  // Computes the min/max values of 'tensor' and sets the values in
+  // the out params 'min' and 'max'.
+  // Returns kTfLiteOk on success.
   static TfLiteStatus ComputeMinAndMaxQuantValues(const TfLiteTensor& tensor,
                                                   float* min, float* max) {
     if (tensor.type == kTfLiteUInt8) {