Add greedy verification kernel (#4383)

sgl-kernel/csrc/speculative/packbit.cu

@@ -0,0 +1,47 @@
+// This is only a pluggin used for flashinfer 0.1.6. The new version does not need it.
+/*
+ * Copyright (c) 2025 by SGLang team.
+ * Copyright (c) 2025 by FlashInfer team.
+ *
+ * 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 <flashinfer/quantization.cuh>
+
+#include "pytorch_extension_utils.h"
+
+using namespace flashinfer;
+
+// bitorder = "little"
+void segment_packbits(
+    at::Tensor x, at::Tensor input_indptr, at::Tensor output_indptr, at::Tensor y, int64_t cuda_stream) {
+  CHECK_INPUT(x);
+  CHECK_INPUT(input_indptr);
+  CHECK_INPUT(output_indptr);
+  auto device = x.device();
+  CHECK_EQ(input_indptr.device(), device);
+  CHECK_EQ(output_indptr.device(), device);
+  CHECK_EQ(y.device(), device);
+  unsigned int batch_size = input_indptr.size(0) - 1;
+  CHECK_EQ(output_indptr.size(0), batch_size + 1);
+
+  cudaStream_t stream = reinterpret_cast<cudaStream_t>(cuda_stream);
+  cudaError_t status = quantization::SegmentPackBits(
+      static_cast<bool*>(x.data_ptr()),
+      static_cast<uint8_t*>(y.data_ptr()),
+      static_cast<int32_t*>(input_indptr.data_ptr()),
+      static_cast<int32_t*>(output_indptr.data_ptr()),
+      batch_size,
+      quantization::BitOrder::kLittle,
+      stream);
+}