remove the unnecessary hidden_state variable

src/rewrite_rnn.cpp

@@ -104,11 +104,9 @@ void rewrite_rnn::apply_vanilla_rnn(program& prog, instruction_ref ins) const
         // The following logic is to ensure the last instruction rewritten from
         // rnn operator is a concat instruction
         // sequence len is 1
-        instruction_ref hidden_output{};
         if(ret_forward[0] == prog.end())
         {
-            hidden_output =
-                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
         {
@@ -116,8 +114,7 @@ void rewrite_rnn::apply_vanilla_rnn(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_output =
-                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
@@ -154,16 +151,15 @@ void rewrite_rnn::apply_vanilla_rnn(program& prog, instruction_ref ins) const
         // following logic is to ensure the last instruction is a
         // concat instruction
         // sequence len is 1
-        instruction_ref hidden_output{};
         if(ret[0] == prog.end())
         {
-            hidden_output = 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_output = prog.replace_instruction(ins, op::concat{0}, concat_arg0, concat_arg1);
+            prog.replace_instruction(ins, op::concat{0}, concat_arg0, concat_arg1);
         }
     }