Refine GetTensorFromVar (#14160)

* fix GetTensorFromVar
test=release/1.1

* refine GetTensorFromVar
test=develop

Author: chengduo

paddle/fluid/framework/operator.cc

@@ -354,18 +354,18 @@ void OperatorBase::GenerateTemporaryNames() {
   }
 }
 
-static bool VarIsTensor(const Variable* var) {
-  return var->IsType<LoDTensor>() || var->IsType<SelectedRows>();
+static bool VarIsTensor(const Variable& var) {
+  return var.IsType<LoDTensor>() || var.IsType<SelectedRows>();
 }
 
-const Tensor* GetTensorFromVar(Variable* var) {
-  if (var->IsType<LoDTensor>()) {
-    return var->GetMutable<LoDTensor>();
-  } else if (var->IsType<SelectedRows>()) {
-    return var->GetMutable<SelectedRows>()->mutable_value();
+const Tensor* GetTensorFromVar(const Variable& var) {
+  if (var.IsType<LoDTensor>()) {
+    return static_cast<const Tensor*>(&(var.Get<LoDTensor>()));
+  } else if (var.IsType<SelectedRows>()) {
+    return &(var.Get<SelectedRows>().value());
   } else {
     PADDLE_THROW("Variable type_id %s, expect LoDTensor/SelectedRows.",
-                 var->Type().name());
+                 var.Type().name());
   }
 }
 
@@ -415,8 +415,7 @@ bool ExecutionContext::HasOutput(const std::string& name) const {
 template <>
 const Tensor* ExecutionContext::Input<Tensor>(const std::string& name) const {
   auto* var = InputVar(name);
-  return var == nullptr ? nullptr
-                        : GetTensorFromVar(const_cast<Variable*>(var));
+  return var == nullptr ? nullptr : GetTensorFromVar(*var);
 }
 
 template <>
@@ -428,7 +427,7 @@ const std::vector<const Tensor*> ExecutionContext::MultiInput<Tensor>(
   std::transform(names.begin(), names.end(), std::back_inserter(res),
                  [&](const std::string& sub_name) {
                    auto var = scope_.FindVar(sub_name);
-                   return var == nullptr ? nullptr : GetTensorFromVar(var);
+                   return var == nullptr ? nullptr : GetTensorFromVar(*var);
                  });
   return res;
 }
@@ -770,8 +769,10 @@ void OperatorWithKernel::TransferInplaceVarsBack(
   for (auto& var_name : inplace_vars) {
     VLOG(3) << "share inplace var " + var_name + " back to it's original scope";
     auto* original_tensor = GetMutableTensorFromVar(scope.FindVar(var_name));
-    auto* transformed_tensor =
-        GetTensorFromVar(transfer_scope.FindVar(var_name));
+    auto* var = transfer_scope.FindVar(var_name);
+    PADDLE_ENFORCE(var != nullptr, "The var[%s] should not be nullptr",
+                   var_name);
+    auto* transformed_tensor = GetTensorFromVar(*var);
     original_tensor->ShareDataWith(*transformed_tensor);
   }
 }
@@ -784,11 +785,11 @@ Scope* OperatorWithKernel::TryTransferData(
     for (auto& var_name : var_name_item.second) {
       auto* var = scope.FindVar(var_name);
       // Only tensor can be tranfer to another device.
-      if (var == nullptr || !VarIsTensor(var)) {
+      if (var == nullptr || !VarIsTensor(*var)) {
         continue;
       }
 
-      auto* tensor_in = GetTensorFromVar(var);
+      auto* tensor_in = GetTensorFromVar(*var);
       if (!tensor_in->IsInitialized()) {
         continue;
       }

paddle/fluid/framework/operator.h

@@ -63,7 +63,7 @@ inline std::string GradVarName(const std::string& var_name) {
 }
 
 proto::VarType::Type GetDataTypeOfVar(const Variable* var);
-const Tensor* GetTensorFromVar(Variable* var);
+const Tensor* GetTensorFromVar(const Variable& var);
 
 class OperatorBase;
 class ExecutionContext;

paddle/fluid/operators/sum_op.cc

@@ -67,6 +67,7 @@ class SumOp : public framework::OperatorWithKernel {
   framework::OpKernelType GetExpectedKernelType(
       const framework::ExecutionContext& ctx) const override {
     auto x_vars = ctx.MultiInputVar("X");
+    auto x_vars_name = ctx.Inputs("X");
 
     framework::LibraryType library{framework::LibraryType::kPlain};
     framework::DataLayout layout{framework::DataLayout::kAnyLayout};
@@ -81,10 +82,11 @@ class SumOp : public framework::OperatorWithKernel {
 
     if (x_vars[0]->IsType<framework::LoDTensor>()) {
       int dtype = -1;
-      for (auto& x_var : x_vars) {
+      for (size_t idx = 0; idx < x_vars.size(); ++idx) {
+        PADDLE_ENFORCE(x_vars[idx] != nullptr,
+                       "Input var[%s] should not be nullptr", x_vars_name[idx]);
         // FIXME(zcd): The input x_var may be SelectedRows or LoDTensor.
-        auto tensor = framework::GetTensorFromVar(
-            const_cast<framework::Variable*>(x_var));
+        auto tensor = framework::GetTensorFromVar(*x_vars[idx]);
         if (tensor->numel() == 0) {
           continue;
         }