Fix fc padding bug during inference fusion (#22860) (#22921)

* fix fc padding during fusion, test=develop

* fix optim model inference after SaveOptimModel, test=develop

paddle/fluid/framework/ir/fc_fuse_pass.cc

@@ -100,22 +100,31 @@ int FCFusePass::ApplyFCPattern(Graph* graph, bool with_relu) const {
     bool use_gpu = Has("use_gpu") ? Get<bool>("use_gpu") : false;
     bool use_fc_padding =
         Has("use_fc_padding") ? Get<bool>("use_fc_padding") : true;
+    const std::string& w_name = patterns::UniqueKey(w->Name());
+    VarDesc w_key(w_name);
+    w_key.SetPersistable(true);
+    auto* w_node = g->CreateVarNode(&w_key);
     if (!use_gpu && use_fc_padding) {
       if (w_h % 128 == 0 && w_w % 128 == 0) {
+        auto* w_var = scope->Var(w_name);
+        auto* w_tensor = w_var->GetMutable<framework::LoDTensor>();
+
         auto* weight_data_tmp = new float[weight_num];
         for (int i = 0; i < w_h; i++) {
           memcpy(weight_data_tmp + i * w_w, weight_data + i * w_w,
                  w_w * sizeof(float));
         }
-        weight->Resize(DDim{weight_dims[0] + 4, weight_dims[1] + 4});
+        w_tensor->Resize(DDim{weight_dims[0] + 4, weight_dims[1] + 4});
         auto* weight_data_new =
-            weight->mutable_data<float>(platform::CPUPlace());
+            w_tensor->mutable_data<float>(platform::CPUPlace());
         for (int i = 0; i < w_h; i++) {
           memcpy(weight_data_new + i * (w_w + 4), weight_data_tmp + i * w_w,
                  w_w * sizeof(float));
         }
         delete[] weight_data_tmp;
+        desc.SetInput("W", {w_name});
         desc.SetAttr("padding_weights", true);
+        desc.Flush();
       }
     }
 
@@ -147,7 +156,12 @@ int FCFusePass::ApplyFCPattern(Graph* graph, bool with_relu) const {
     }
 
     IR_NODE_LINK_TO(subgraph.at(x), fc_node);
+    if (desc.GetAttrIfExists<bool>("padding_weights")) {
+      IR_NODE_LINK_TO(w_node, fc_node);
+    } else {
+      GraphSafeRemoveNodes(g, {w_node});
       IR_NODE_LINK_TO(w, fc_node);
+    }
     IR_NODE_LINK_TO(bias, fc_node);
     if (with_relu) {
       IR_NODE_LINK_TO(fc_node, relu_out);