[None][feat] Add customized topk and related unit tests for DSA (#8882)

Signed-off-by: Christina Zhang <83400082+ChristinaZ@users.noreply.github.com>

Author: ChristinaZ

cpp/tensorrt_llm/kernels/IndexerTopK.h

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2019-2025, NVIDIA CORPORATION.  All rights reserved.
+ * Copyright (c) 2021, NAVER Corp.  Authored by CLOVA.
+ *
+ * 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 <cuda_bf16.h>
+#include <cuda_fp16.h>
+
+#include "tensorrt_llm/common/cudaUtils.h"
+
+namespace tensorrt_llm::kernels
+{
+void invokeIndexerTopKDecode(float const* logits, int const* seqLens, int* outIndices, float* auxLogits,
+    int* auxIndices, int const splitWorkThreshold, int const numRows, int const numColumns, int const stride0,
+    int const stride1, int const next_n, int const index_topk = 2048, cudaStream_t const stream = 0);
+
+void invokeIndexerTopKPrefill(float const* logits, int const* rowStarts, int const* rowEnds, int* outIndices,
+    int const numRows, int const numColumns, int const stride0, int const stride1, int const index_topk = 2048,
+    cudaStream_t const stream = 0);
+
+} // namespace tensorrt_llm::kernels