fix: revert changes in castITensor

Signed-off-by: inocsin <vcheungyi@163.com>

Author: inocsin

core/conversion/converters/converter_util.cpp

@@ -129,24 +129,24 @@ nvinfer1::ITensor* applyIdentityOp(ConversionCtx* ctx, nvinfer1::ITensor* tensor
 }
 
 nvinfer1::ITensor* castITensor(ConversionCtx* ctx, nvinfer1::ITensor* tensor, nvinfer1::DataType dtype) {
-  // No matter whether tensor->getType() == dtype, identity layer is always needed.
-  // Otherwise will change the input tensor name in aten::to converter by AssociateValueAndTensor function
-  // When the input of aten::to is network input, will cause error
-  std::ostringstream tensor_id;
-  tensor_id << reinterpret_cast<int*>(tensor);
-
-  auto id_layer = ctx->net->addIdentity(*tensor);
-  TORCHTRT_CHECK(id_layer, "Unable to create identity layer for ITensor: " << tensor_id.str());
-  auto casted_tensor = id_layer->getOutput(0);
-  casted_tensor->setType(dtype);
+  if (tensor->getType() != dtype) {
+    std::ostringstream tensor_id;
+    tensor_id << reinterpret_cast<int*>(tensor);
 
-  LOG_DEBUG(ctx->logger, "Casting ITensor " << tensor_id.str() << " from " << tensor->getType() << " to " << dtype);
+    auto id_layer = ctx->net->addIdentity(*tensor);
+    TORCHTRT_CHECK(id_layer, "Unable to create identity layer for ITensor: " << tensor_id.str());
+    auto casted_tensor = id_layer->getOutput(0);
+    casted_tensor->setType(dtype);
 
-  std::stringstream ss;
-  ss << "[Cast ITensor " << tensor_id.str() << " from " << tensor->getType() << " to " << dtype << "]";
-  id_layer->setName(ss.str().c_str());
-  return casted_tensor;
+    LOG_DEBUG(ctx->logger, "Casting ITensor " << tensor_id.str() << " from " << tensor->getType() << " to " << dtype);
 
+    std::stringstream ss;
+    ss << "[Cast ITensor " << tensor_id.str() << " from " << tensor->getType() << " to " << dtype << "]";
+    id_layer->setName(ss.str().c_str());
+    return casted_tensor;
+  } else {
+    return tensor;
+  }
 }
 
 nvinfer1::ITensor* tensor_to_const(ConversionCtx* ctx, at::Tensor t, const std::string& name) {