[Lite] Support Int8 Unpack Operator

Added support for Unpack Operator
Added relevant tests.

tensorflow/lite/tools/optimize/BUILD

@@ -242,6 +242,7 @@ tf_cc_test(
         "//tensorflow/lite/tools/optimize:testdata/single_conv_weights_min_minus_127_max_plus_127.bin",
         "//tensorflow/lite/tools/optimize:testdata/single_softmax_min_minus_5_max_plus_5.bin",
         "//tensorflow/lite/tools/optimize:testdata/split.bin",
+        "//tensorflow/lite/tools/optimize:testdata/unpack.bin",
     ],
     tags = [
         "tflite_not_portable_android",

tensorflow/lite/tools/optimize/operator_property.cc

@@ -70,9 +70,9 @@ OperatorProperty GetOperatorProperty(const ModelT* model, int subgraph_index,
       property.version = 2;
       break;
     case BuiltinOperator_SPLIT:
-      property.arbitrary_outputs = true;
       // We skip input 0 since it is the split dim which is not real valued.
       property.inputs = {{1, {}}};
+      property.arbitrary_outputs = true;
       property.restrict_same_input_output_scale = true;
       property.version = 2;
       break;
@@ -383,6 +383,12 @@ OperatorProperty GetOperatorProperty(const ModelT* model, int subgraph_index,
       property.restrict_same_input_output_scale = true;
       property.version = 2;
       break;
+    case BuiltinOperator_UNPACK:
+      property.inputs = {{0, {}}};
+      property.arbitrary_outputs = true;
+      property.restrict_same_input_output_scale = true;
+      property.version = 1;
+      break;
     default:
       // No quantized implementation exists for this operation.
       property.quantizable = false;

tensorflow/lite/tools/optimize/quantize_model_test.cc

@@ -1124,6 +1124,56 @@ TEST_F(QuantizeCustomOpTest, VerifyMixedQuantization) {
   }
 }
 
+class QuantizeUnpackTest : public QuantizeModelTest {
+protected:
+    QuantizeUnpackTest() {
+      input_model_ = ReadModel(internal::kModelWithUnpack);
+      readonly_model_ = input_model_->GetModel();
+      readonly_model_->UnPackTo(&model_);
+    }
+};
+
+TEST_F(QuantizeUnpackTest, VerifyUnpack) {
+  auto status = QuantizeModel(&builder_, &model_, &error_reporter_);
+
+  ASSERT_EQ(kTfLiteOk, status);
+
+  const auto subgraph = model_.subgraphs[0].get();
+  auto op = subgraph->operators[1].get();
+
+  auto float_graph = readonly_model_->subgraphs()->Get(0);
+
+  ASSERT_EQ(model_.operator_codes[op->opcode_index].get()->builtin_code,
+  BuiltinOperator_UNPACK);
+
+  // Get unpack input and output tensors
+  auto unpack_input = subgraph->tensors[op->inputs[0]].get();
+  auto unpack_output_0 = subgraph->tensors[op->outputs[0]].get();
+  auto unpack_output_1 = subgraph->tensors[op->outputs[1]].get();
+
+  // Verify Unpack input is quantized.
+  ASSERT_EQ(float_graph->tensors()->Get(op->inputs[0])->type(),
+          TensorType_FLOAT32);
+  EXPECT_EQ(unpack_input->type, TensorType_INT8);
+
+  // The model should only have one input and 2 outputs.
+  EXPECT_EQ(subgraph->inputs.size(), 1);
+  EXPECT_EQ(subgraph->outputs.size(), 2);
+
+  // Ensure quantization parameters before and after unpack
+  // are preserved after quantization for all outputs of
+  // unpack.
+  EXPECT_FLOAT_EQ(unpack_input->quantization->scale[0],
+          unpack_output_0->quantization->scale[0]);
+  EXPECT_FLOAT_EQ(unpack_input->quantization->scale[0],
+          unpack_output_1->quantization->scale[0]);
+  EXPECT_FLOAT_EQ(unpack_input->quantization->zero_point[0],
+          unpack_output_0->quantization->zero_point[0]);
+  EXPECT_FLOAT_EQ(unpack_input->quantization->zero_point[0],
+          unpack_output_1->quantization->zero_point[0]);
+
+}
+
 }  // namespace
 }  // namespace optimize
 }  // namespace tflite

tensorflow/lite/tools/optimize/test_util.cc

@@ -52,6 +52,8 @@ const char* kModelSplit = "split.bin";
 const char* kLstmCalibrated = "lstm_calibrated.bin";
 const char* kLstmQuantized = "lstm_quantized.bin";
 
+const char* kModelWithUnpack = "unpack.bin";
+
 int FailOnErrorReporter::Report(const char* format, va_list args) {
   char buf[1024];
   vsnprintf(buf, sizeof(buf), format, args);

tensorflow/lite/tools/optimize/test_util.h

@@ -80,6 +80,9 @@ extern const char* kModelSplit;
 extern const char* kLstmCalibrated;
 extern const char* kLstmQuantized;
 
+// Test model with an unpack op.
+extern const char* kModelWithUnpack;
+
 // An error reporter that fails on testing.
 class FailOnErrorReporter : public ErrorReporter {
  public: