chore: import upstream snapshot with attribution

paddle/phi/kernels/impl/pad_kernel_impl.h

@@ -0,0 +1,41 @@
+// 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 <utility>
+#include <vector>
+
+#include "paddle/phi/common/scalar.h"
+#include "paddle/phi/core/dense_tensor.h"
+#include "paddle/phi/kernels/full_kernel.h"
+#include "paddle/phi/kernels/funcs/padding.h"
+namespace phi {
+template <typename T, typename Context>
+void PadKernel(const Context& dev_ctx,
+               const DenseTensor& x,
+               const std::vector<int>& paddings,
+               const Scalar& pad_value,
+               DenseTensor* out) {
+  dev_ctx.template Alloc<T>(out);
+  if (x.numel() == 0) {
+    if (out) {
+      Full<T, Context>(dev_ctx, out->dims(), pad_value, out);
+    }
+    return;
+  }
+  int rank = x.dims().size();
+  funcs::PaddingFunctor<Context, T>(
+      rank, dev_ctx, paddings, pad_value.to<T>(), x, out);
+}
+}  // namespace phi