[onert] Generate BackPropAccumulator only if necessary (#13570)

This commit changes BackPropAccumulators to be generated only if the correspoding dispoable tensors exist.

ONE-DCO-1.0-Signed-off-by: ragmani <[email protected]>

runtime/onert/backend/train/KernelGenerator.cc

@@ -80,21 +80,22 @@ generateBackPropAccumulator(const IPortableTensor *disposable, BackPropTensor *g
   return update_fn;
 }
 
-void appendBackPropAccumulator(const ir::train::ITrainableOperation &op,
-                               const ir::OperationIndex &op_index, TensorRegistry *tensor_reg,
-                               exec::train::TrainableFnSequence *seq)
+void appendBackPropAccumulators(const ir::train::ITrainableOperation &op,
+                                const ir::OperationIndex &op_index, TensorRegistry *tensor_reg,
+                                exec::train::TrainableFnSequence *seq)
 {
+  if (!op.isRequiredForBackward())
+    return;
+
   for (const auto &input_index : (op.getInputs() | ir::Remove::UNDEFINED))
   {
-    if (op.isRequiredForBackward())
+    const auto disposable =
+      tensor_reg->getDisposableBackPropTensor(DisposableTensorIndex{op_index, input_index});
+    if (disposable != nullptr)
     {
-      const auto disposable =
-        tensor_reg->getDisposableBackPropTensor(DisposableTensorIndex{op_index, input_index});
-      if (disposable != nullptr)
-      {
-        auto back_prop = tensor_reg->getBackPropTensor(input_index);
-        seq->append(generateBackPropAccumulator(disposable, back_prop));
-      }
+      auto back_prop = tensor_reg->getBackPropTensor(input_index);
+      assert(back_prop);
+      seq->append(generateBackPropAccumulator(disposable, back_prop));
     }
   }
 }
@@ -111,13 +112,16 @@ generateGradientApplier(const exec::train::optimizer::Optimizer *optimizer,
 
 std::unique_ptr<exec::train::TrainableFnSequence> KernelGenerator::generate(ir::OperationIndex idx)
 {
+  // NOTE This function is related to planning tensors. If you change this function, you should
+  //      also consider to change planning tensors.
+
   auto ret = std::make_unique<exec::train::TrainableFnSequence>();
 
   const auto &op = _tgraph.operation(idx);
 
-  // NOTE appendBackPropAccumulator() must be called before appending _return_fn to
+  // NOTE appendBackPropAccumulators() must be called before appending _return_fn to
   //      TrainableFnSequence as long as both are appended to the same TrainableFnSequence.
-  appendBackPropAccumulator(op, idx, _tensor_reg.get(), ret.get());
+  appendBackPropAccumulators(op, idx, _tensor_reg.get(), ret.get());
 
   op.accept(*this);
   assert(_return_fn);
@@ -604,19 +608,28 @@ void KernelGenerator::visit(const ir::train::operation::Softmax &node)
   _return_fn = std::move(fn);
 }
 
-IPortableTensor *KernelGenerator::getBackPropIn(const ir::Operation &node,
+IPortableTensor *KernelGenerator::getBackPropIn(const ir::IOperation &node,
                                                 const ir::OperandIndex &operand_index)
 {
   const auto &op_index = _node_to_idx[&node];
+  const auto backwarding_operand_index = ir::train::TrainingOperandIndex{operand_index, false};
 
-  auto temp_tensor =
+  const auto disposable_tensor =
     _tensor_reg->getDisposableBackPropTensor(DisposableTensorIndex{op_index, operand_index});
-  if (temp_tensor == nullptr)
+  if (disposable_tensor != nullptr)
   {
-    temp_tensor = _tensor_reg->getBackPropTensor(operand_index);
+    const auto &training_usedefs = _tgraph.trainingUseDefs().at(backwarding_operand_index);
+    UNUSED_RELEASE(training_usedefs);
+    assert(std::count_if(training_usedefs.getTrainingDefs().begin(),
+                         training_usedefs.getTrainingDefs().end(),
+                         [&](const ir::train::TrainingOperationIndex &op_index) {
+                           return _tgraph.operation(op_index.index()).isRequiredForBackward();
+                         }) > 1);
+
+    return disposable_tensor;
   }
-
-  return temp_tensor;
+  else
+    return _tensor_reg->getBackPropTensor(operand_index);
 }
 
 IPortableTensor *KernelGenerator::getBackPropOut(const ir::OperandIndex &output_index)

runtime/onert/backend/train/KernelGenerator.h

@@ -59,8 +59,7 @@ class KernelGenerator : public backend::train::KernelGeneratorBase
   void visit(const ir::train::operation::Softmax &node) override;
 
 private:
-  IPortableTensor *getBackPropIn(const ir::Operation &op_index,
-                                 const ir::OperandIndex &operand_index);
+  IPortableTensor *getBackPropIn(const ir::IOperation &node, const ir::OperandIndex &operand_index);
   IPortableTensor *getBackPropOut(const ir::OperandIndex &index);
 
 private: