1 files changed, 44 insertions, 0 deletions
diff --git a/tensorflow/contrib/lite/toco/import_tensorflow.cc b/tensorflow/contrib/lite/toco/import_tensorflow.cc
index 32f22e1ea0..6b195cc992 100644
--- a/tensorflow/contrib/lite/toco/import_tensorflow.cc
+++ b/tensorflow/contrib/lite/toco/import_tensorflow.cc
@@ -43,6 +43,7 @@ limitations under the License.
 #include "tensorflow/core/framework/tensor_shape.pb.h"
 #include "tensorflow/core/framework/types.pb.h"
 #include "tensorflow/core/graph/graph_constructor.h"
+#include "tensorflow/core/lib/core/errors.h"
 #include "tensorflow/core/lib/core/status.h"
 #include "tensorflow/core/platform/logging.h"
 #include "tensorflow/core/public/session_options.h"
@@ -2002,6 +2003,48 @@ tensorflow::Status ConvertCTCBeamSearchDecoderOperator(
   return tensorflow::Status::OK();
 }
 
+// This isn't a TensorFlow builtin op. Currently this node can only be generated
+// with TfLite OpHint API.
+tensorflow::Status ConvertUnidirectionalSequenceLstm(
+    const NodeDef& node, const TensorFlowImportFlags& tf_import_flags,
+    Model* model) {
+  DCHECK_EQ(node.op(), "UnidirectionalSequenceLstm");
+
+  auto* op = new UnidirectionalSequenceLstmOperator();
+  const auto& indices = GetListAttr(node, "_tflite_input_indices");
+  if (indices.i_size() != node.input().size()) {
+    return tensorflow::errors::InvalidArgument("Input size does not match.");
+  }
+
+  // The input size needs to be the same as the TfLite UniDirectionalSequence
+  // Lstm implementation.
+  const int kInputsSize = 20;
+
+  op->inputs.resize(kInputsSize);
+  std::vector<bool> done(kInputsSize);
+  int idx = 0;
+  for (const string& input : node.input()) {
+    int real_index = indices.i(idx);
+    op->inputs[real_index] = (input);
+    done[real_index] = true;
+    idx++;
+  }
+
+  for (int idx = 0; idx < done.size(); idx++) {
+    if (!done[idx]) {
+      string optional_name = node.name() + "_" + std::to_string(idx);
+      model->CreateOptionalArray(optional_name);
+      op->inputs[idx] = optional_name;
+    }
+  }
+
+  // There're three outputs, only the last one is required.
+  op->outputs.push_back(node.name() + ":2");
+  model->operators.emplace_back(op);
+
+  return tensorflow::Status::OK();
+}
+
 }  // namespace
 
 namespace internal {
@@ -2121,6 +2164,7 @@ ConverterMapType GetTensorFlowNodeConverterMap() {
       {"Transpose", ConvertSimpleOperator<TransposeOperator, 2>},
       {"Unpack", ConvertUnpackOperator},
       {"ZerosLike", ConvertSimpleOperator<TensorFlowZerosLikeOperator, 1>},
+      {"UnidirectionalSequenceLstm", ConvertUnidirectionalSequenceLstm},
   });
 }