chore: import upstream snapshot with attribution

paddle/phi/kernels/erf_kernel.h

@@ -0,0 +1,37 @@
+/* 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/core/dense_tensor.h"
+
+namespace phi {
+
+/**
+ * @brief Erf Kernel.
+ *        The equation is:
+ *        $$
+ *        f(x) = \frac{2}{\sqrt{\pi}} \int_{0}^{x}e^{- \eta^{2}}d\eta
+ *        $$
+ *
+ *        The input `x` can carry the LoD (Level of Details) information,
+ *        or not. And the output shares the LoD information with input `x`.
+ * @param  ctx   device context
+ * @param  x     The input tensor of erf kernel
+ * @param  out   The output tensor of erf kernel
+ */
+template <typename T, typename Context>
+void ErfKernel(const Context& dev_ctx, const DenseTensor& x, DenseTensor* out);
+
+}  // namespace phi