chore: import upstream snapshot with attribution

paddle/phi/kernels/bmm_kernel.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 "paddle/phi/core/dense_tensor.h"
+
+namespace phi {
+
+/**
+ * @brief Bmm Kernel.
+ *        Applies batched matrix multiplication to two tensors.
+ *
+ *        Both of the two input tensors must be three-dimensional
+ *        and share the same batch size.
+ *        if x is a (b, m, k) tensor, y is a (b, k, n) tensor,
+ *        the output will be a (b, m, n) tensor.
+ *
+ * @param  ctx      device context
+ * @param  x        The input tensor
+ * @param  y        The input tensor
+ * @param  out      The product Tensor
+ */
+template <typename T, typename Context>
+void BmmKernel(const Context& dev_ctx,
+               const DenseTensor& x,
+               const DenseTensor& y,
+               DenseTensor* out);
+
+}  // namespace phi