fix a bug in gru pass.

src/rewrite_gru.cpp

@@ -276,18 +276,18 @@ std::vector<instruction_ref> rewrite_gru::gru_oper(bool is_forward,
         auto z1tht = prog.insert_instruction(ins, op::mul{}, z1t, ht);
         auto ztht1 = prog.insert_instruction(ins, op::mul{}, zt, ih);
         ih         = prog.insert_instruction(ins, op::add{}, z1tht, ztht1);
-        final_out  = ih;
+        final_out = prog.insert_instruction(ins, op::unsqueeze{{0}}, ih);
 
         if(is_forward)
         {
             hidden_out =
-                (seq_index == 0) ? ih : prog.insert_instruction(ins, op::concat{0}, hidden_out, ih);
+                (seq_index == 0) ? final_out : prog.insert_instruction(ins, op::concat{0}, hidden_out, final_out);
         }
         else
         {
             hidden_out = (seq_index == seq_len - 1)
-                             ? ih
-                             : prog.insert_instruction(ins, op::concat{0}, ih, hidden_out);
+                             ? final_out
+                             : prog.insert_instruction(ins, op::concat{0}, final_out, hidden_out);
         }
         seq_index = is_forward ? (seq_index + 1) : (seq_index - 1);
     }