Merge pull request #13080 from reyoung/fix_scale_grad_bug

Fix bug when loss@GRAD is reused. (Release Branch)

Author: panyx0718

paddle/fluid/framework/details/multi_devices_graph_pass.cc

@@ -625,19 +625,11 @@ int MultiDevSSAGraphBuilder::GetVarDeviceID(const ir::Graph &graph,
 void MultiDevSSAGraphBuilder::CreateScaleLossGradOp(
     ir::Graph *result, const std::string &loss_grad_name) const {
   for (size_t i = 0; i < places_.size(); ++i) {
-// Insert ScaleCost OpHandle
-#ifdef PADDLE_WITH_CUDA
-    auto *communication_dev_ctx =
-        nccl_ctxs_ ? nccl_ctxs_->DevCtx(places_[i])
-                   : platform::DeviceContextPool::Instance().Get(places_[i]);
-#else
-    auto *communication_dev_ctx =
-        platform::DeviceContextPool::Instance().Get(platform::CPUPlace());
-#endif
+    // Insert ScaleCost OpHandle
+    auto *dev_ctx = platform::DeviceContextPool::Instance().Get(places_[i]);
     auto *op_handle = new ScaleLossGradOpHandle(
         result->CreateEmptyNode("scale_loss_grad", ir::Node::Type::kOperation),
-        local_scopes_.size(), local_scopes_[i], places_[i],
-        communication_dev_ctx);
+        local_scopes_.size(), local_scopes_[i], places_[i], dev_ctx);
     result->Get<GraphOps>(kGraphOps).emplace_back(op_handle);
 
     // FIXME: Currently ScaleLossGradOp only use device_count as scale