chore: import upstream snapshot with attribution

paddle/phi/kernels/impl/erf_grad_kernel_impl.h

@@ -0,0 +1,40 @@
+/* Copyright (c) 2022 PaddlePaddle Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License. */
+
+#pragma once
+
+#include "paddle/phi/backends/all_context.h"
+#include "paddle/phi/core/kernel_registry.h"
+#include "paddle/phi/kernels/erf_grad_kernel.h"
+#include "paddle/phi/kernels/funcs/eigen/common.h"
+#include "paddle/phi/kernels/funcs/eigen/eigen_function.h"
+
+namespace phi {
+
+template <typename T, typename Context>
+void ErfGradKernel(const Context& dev_ctx,
+                   const DenseTensor& x,
+                   const DenseTensor& out_grad,
+                   DenseTensor* x_grad) {
+  dev_ctx.template Alloc<T>(x_grad);
+
+  auto eigen_x = EigenVector<T>::Flatten(x);
+  auto eigen_dout = EigenVector<T>::Flatten(out_grad);
+  auto eigen_dx = EigenVector<T>::Flatten(*x_grad);
+  auto& place = *dev_ctx.eigen_device();
+  funcs::EigenErfGrad<std::decay_t<decltype(place)>, T>::Eval(
+      place, eigen_dx, eigen_x, eigen_dout);
+}
+
+}  // namespace phi