chore: import upstream snapshot with attribution

paddle/phi/kernels/impl/numel_kernel_impl.h

@@ -0,0 +1,39 @@
+// 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/tensor_utils.h"
+
+namespace phi {
+
+template <typename T, typename Context>
+void NumelKernel(const Context& dev_ctx,
+                 const DenseTensor& input,
+                 DenseTensor* out) {
+  auto place = dev_ctx.GetPlace();
+  auto out_data = dev_ctx.template Alloc<int64_t>(out);
+
+  if (place == CPUPlace()) {
+    out_data[0] = input.numel();
+  } else {
+    DenseTensor cpu_tensor;
+    cpu_tensor.Resize(out->dims());
+    auto cpu_data = dev_ctx.template HostAlloc<int64_t>(&cpu_tensor);
+    cpu_data[0] = input.numel();
+    Copy(dev_ctx, cpu_tensor, place, false, out);
+  }
+}
+
+}  // namespace phi