code cleanup

src/rewrite_rnn.cpp

@@ -313,9 +313,10 @@ void rewrite_rnn::apply_gru(program& prog, instruction_ref ins) const
 {
     assert(ins->name() == "gru");
     const auto actv_funcs = gru_actv_funcs(ins);
-    // could be 3 to 5 inputs (though onnx::rnn has 6 inputs,
-    // the 5th one is undefined and ignored by protobuf. so
-    // we need to process up to 5 inputs
+    // could be 3 to 6 inputs, but the parse_gru function will
+    // append undefined operators to make 6 arguments when parsing
+    // an onnx file. Another case is user can have num of arguments
+    // when writing their program.
     auto args = ins->inputs();
 
     shape seq_shape         = args[0]->get_shape();
@@ -383,11 +384,9 @@ void rewrite_rnn::apply_gru(program& prog, instruction_ref ins) const
 
         // The following logic is to ensure the last instruction rewritten
         // from gru operator is a concat
-        instruction_ref hidden_state{};
         if(ret_forward[0] == prog.end())
         {
-            hidden_state =
-                prog.replace_instruction(ins, op::concat{1}, ret_forward[1], ret_reverse[1]);
+            prog.replace_instruction(ins, op::concat{1}, ret_forward[1], ret_reverse[1]);
         }
         else
         {
@@ -395,8 +394,7 @@ void rewrite_rnn::apply_gru(program& prog, instruction_ref ins) const
                 prog.insert_instruction(ins, op::concat{0}, ret_forward[0], ret_forward[1]);
             ret_reverse[0] =
                 prog.insert_instruction(ins, op::concat{0}, ret_reverse[1], ret_reverse[0]);
-            hidden_state =
-                prog.replace_instruction(ins, op::concat{1}, {ret_forward[0], ret_reverse[0]});
+            prog.replace_instruction(ins, op::concat{1}, {ret_forward[0], ret_reverse[0]});
         }
     }
     else
@@ -434,16 +432,15 @@ void rewrite_rnn::apply_gru(program& prog, instruction_ref ins) const
 
         last_output = prog.insert_instruction(ins, op::squeeze{{0}}, ret[1]);
 
-        instruction_ref hidden_state{};
         if(ret[0] == prog.end())
         {
-            hidden_state = prog.replace_instruction(ins, op::concat{0}, ret[1]);
+            prog.replace_instruction(ins, op::concat{0}, ret[1]);
         }
         else
         {
             auto concat_arg0 = is_forward ? ret[0] : ret[1];
             auto concat_arg1 = is_forward ? ret[1] : ret[0];
-            hidden_state = prog.replace_instruction(ins, op::concat{0}, concat_arg0, concat_arg1);
+            prog.replace_instruction(ins, op::concat{0}, concat_arg0, concat_arg1);
         }
     }