chore: import upstream snapshot with attribution

paddle/phi/kernels/funcs/index_elementwise_utils.h

@@ -0,0 +1,64 @@
+/* Copyright (c) 2025 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 <array>
+#include <cstdint>
+#include <type_traits>
+#include <vector>
+
+#include "paddle/phi/common/memory_utils.h"
+#include "paddle/phi/common/place.h"
+#include "paddle/phi/core/dense_tensor.h"
+#include "paddle/phi/kernels/funcs/math_function.h"
+#include "paddle/phi/kernels/funcs/stride_utils.h"
+
+namespace phi {
+namespace funcs {
+
+constexpr int MAX_DIMS = DDim::kMaxRank;
+
+template <int N>
+struct alignas(N) OpaqueType {
+  char data[N];
+};
+
+template <typename IndexT>
+std::array<char*, DDim::kMaxRank> GetIndexDataPtrs(
+    const std::vector<const DenseTensor*>& index) {
+  std::array<char*, DDim::kMaxRank> index_ptrs{};
+
+  PADDLE_ENFORCE_LE(index.size(),
+                    DDim::kMaxRank,
+                    "The number of index tensors exceeds the maximum rank.");
+
+  for (size_t i = 0; i < index.size(); ++i) {
+    const IndexT* p_index = index[i]->data<IndexT>();
+
+    PADDLE_ENFORCE_NOT_NULL(
+        p_index,
+        ::common::errors::InvalidArgument(
+            "The pointer p_index is nullptr, "
+            "please check whether the index tensor is valid and "
+            "its data is correctly initialized."));
+
+    index_ptrs[i] = reinterpret_cast<char*>(const_cast<IndexT*>(p_index));
+  }
+
+  return index_ptrs;
+}
+
+}  // namespace funcs
+}  // namespace phi