Update LayerNorm with Welford online algorithm

src/ATen/native/xpu/LayerNorm.cpp

@@ -49,18 +49,19 @@ ::std::tuple<at::Tensor, at::Tensor, at::Tensor> layer_norm_xpu(
 
   Tensor Y = at::native::empty_like(
       *X,
-      c10::nullopt /* dtype */,
-      c10::nullopt /* layout */,
-      c10::nullopt /* device */,
-      c10::nullopt /* pin_memory */,
+      std::nullopt /* dtype */,
+      std::nullopt /* layout */,
+      std::nullopt /* device */,
+      std::nullopt /* pin_memory */,
       LEGACY_CONTIGUOUS_MEMORY_FORMAT);
+
   auto acc_type = at::toAccumulateType(input.scalar_type(), true);
 
   Tensor mean = at::empty({M}, X->options().dtype(acc_type));
   Tensor rstd = at::empty({M}, X->options().dtype(acc_type));
 
   native::xpu::layer_norm_kernel(
-      *X, *gamma, *beta, M, N, epsilon, Y, mean, rstd);
+      *X, *gamma, *beta, M, N, epsilon, &Y, &mean, &rstd);
 
   const auto input_shape = input.sizes();
   const size_t axis = input.dim() - normalized_shape.size();