chore: import upstream snapshot with attribution

paddle/phi/kernels/gpu/unstack_kernel.cu

@@ -0,0 +1,57 @@
+// 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.
+
+#include "paddle/phi/kernels/unstack_kernel.h"
+
+#include "paddle/phi/backends/gpu/gpu_context.h"
+#include "paddle/phi/core/kernel_registry.h"
+#include "paddle/phi/kernels/funcs/stack_and_unstack.h"
+
+namespace phi {
+
+template <typename T, typename Context>
+void UnStackKernel(const Context& dev_ctx,
+                   const DenseTensor& x,
+                   int axis,
+                   int num,
+                   std::vector<DenseTensor*> outs) {
+  if (axis < 0) axis += x.dims().size();
+
+  int64_t split_dim = x.dims()[axis];
+  PADDLE_ENFORCE_EQ(
+      split_dim,
+      outs.size(),
+      common::errors::InvalidArgument(
+          "Output outs's size should be equal to the split_dim, but"
+          " received split_dim is:%d outs's size is:%d.",
+          split_dim,
+          outs.size()));
+
+  funcs::UnStackRawKernel<T, Context>(dev_ctx, x, axis, &outs);
+}
+
+}  // namespace phi
+
+PD_REGISTER_KERNEL(unstack,
+                   GPU,
+                   ALL_LAYOUT,
+                   phi::UnStackKernel,
+                   float,
+                   double,
+                   int64_t,
+                   int,
+                   phi::float16,
+                   phi::bfloat16,
+                   phi::complex64,
+                   phi::complex128) {}