Fix quant dequant fuse pass (#2190)

* fix bug for accessing the removed node, test=develop

lite/core/mir/fusion/quant_dequant_fuse_pass.cc

@@ -30,47 +30,52 @@ void QuantDequantFusePass::Apply(const std::unique_ptr<SSAGraph>& graph) {
   // releated nodes
   std::unordered_set<std::string> quant_types = {
       "fake_quantize_range_abs_max", "fake_quantize_moving_average_abs_max"};
+  std::vector<Node*> quant_nodes;
   for (auto& cur_node : graph->mutable_nodes()) {
     if (cur_node.IsStmt() && quant_types.count(cur_node.stmt()->op_type())) {
-      // find input nodes and output nodes
-      std::list<Node*> input_nodes = cur_node.inlinks;
-      std::list<Node*> output_nodes = cur_node.outlinks;
-      CHECK_EQ(input_nodes.size(), 2);
-      CHECK_EQ(output_nodes.size(), 2);
-
-      bool front_is_scale = input_nodes.front()->arg()->is_weight;
-      Node* input_scale_node =
-          front_is_scale ? input_nodes.front() : input_nodes.back();
-      Node* input_act_node =
-          front_is_scale ? input_nodes.back() : input_nodes.front();
-      front_is_scale = output_nodes.front()->arg()->is_weight;
-      Node* output_scale_node =
-          front_is_scale ? output_nodes.front() : output_nodes.back();
-      Node* output_act_node =
-          front_is_scale ? output_nodes.back() : output_nodes.front();
+      quant_nodes.push_back(&cur_node);
+    }
+  }
+  for (auto quant_node : quant_nodes) {
+    // find input nodes and output nodes
+    std::list<Node*> input_nodes = quant_node->inlinks;
+    std::list<Node*> output_nodes = quant_node->outlinks;
+    CHECK_EQ(input_nodes.size(), 2);
+    CHECK_EQ(output_nodes.size(), 2);
 
-      // relink nodes and save value to quantized_node
-      int bit_length = cur_node.stmt()->op_info()->GetAttr<int>("bit_length");
-      int range = ((1 << (bit_length - 1)) - 1);
-      auto* scope = cur_node.stmt()->op()->scope();
-      auto scale_tensor = scope->FindVar(output_scale_node->arg()->name)
-                              ->GetMutable<lite::Tensor>();
-      float scale_value = scale_tensor->data<float>()[0] / range;
+    bool front_is_scale = input_nodes.front()->arg()->is_weight;
+    Node* input_scale_node =
+        front_is_scale ? input_nodes.front() : input_nodes.back();
+    Node* input_act_node =
+        front_is_scale ? input_nodes.back() : input_nodes.front();
+    front_is_scale = output_nodes.front()->arg()->is_weight;
+    Node* output_scale_node =
+        front_is_scale ? output_nodes.front() : output_nodes.back();
+    Node* output_act_node =
+        front_is_scale ? output_nodes.back() : output_nodes.front();
 
-      for (auto* quantized_node_ptr : output_act_node->outlinks) {
-        quantized_node_ptr->stmt()->mutable_op_info()->SetAttr<int>(
-            "bit_length", bit_length);
-        quantized_node_ptr->stmt()->mutable_op_info()->SetAttr<float>(
-            "input_scale", scale_value);
-        IR_NODE_LINK_TO(input_act_node, quantized_node_ptr)
-        RemoveDirectedLink(output_act_node, quantized_node_ptr);
-      }
+    // relink nodes and save value to quantized_node
+    int bit_length = quant_node->stmt()->op_info()->GetAttr<int>("bit_length");
+    int range = ((1 << (bit_length - 1)) - 1);
+    auto* scope = quant_node->stmt()->op()->scope();
+    auto scale_tensor = scope->FindVar(output_scale_node->arg()->name)
+                            ->GetMutable<lite::Tensor>();
+    float scale_value = scale_tensor->data<float>()[0] / range;
 
-      // delete nodes and edges
-      std::unordered_set<const Node*> nodes2rm = {
-          input_scale_node, &cur_node, output_scale_node, output_act_node};
-      GraphSafeRemoveNodes(graph.get(), nodes2rm);
+    auto outlinks = output_act_node->outlinks;
+    for (auto* quantized_node_ptr : outlinks) {
+      quantized_node_ptr->stmt()->mutable_op_info()->SetAttr<int>("bit_length",
+                                                                  bit_length);
+      quantized_node_ptr->stmt()->mutable_op_info()->SetAttr<float>(
+          "input_scale", scale_value);
+      IR_NODE_LINK_TO(input_act_node, quantized_node_ptr)
+      RemoveDirectedLink(output_act_node, quantized_node_ptr);
     }
+
+    // delete nodes and edges
+    std::unordered_set<const Node*> nodes2rm = {
+        input_scale_node, quant_node, output_scale_node, output_act_node};
+    GraphSafeRemoveNodes(graph.get(), nodes2rm);
   }
 
   // fuse quantized node and dequant node