chore: import upstream snapshot with attribution

test/cpp/cinn/common/dfs_walker_test.cc

@@ -0,0 +1,72 @@
+// Copyright (c) 2023 CINN 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/cinn/common/dfs_walker.h"
+
+#include <glog/logging.h>
+#include <gtest/gtest.h>
+
+namespace cinn {
+namespace common {
+
+TEST(DfsWalker, simple_on_push) {
+  DfsWalker<int> visitor(
+      [](int node, const std::function<void(int)>& NodeHandler) {
+        if (node == 0) {
+          NodeHandler(3);
+        } else if (node == 1) {
+          NodeHandler(2);
+          NodeHandler(3);
+        } else if (node == 2 || node == 3) {
+          NodeHandler(4);
+        }
+      });
+  std::vector<int> sources{0, 1};
+  std::vector<int> outputs;
+  visitor(sources.begin(), sources.end(), [&](int node) {
+    LOG(ERROR) << node;
+    outputs.push_back(node);
+  });
+  std::vector<int> expected{0, 3, 4, 1, 2};
+  EXPECT_TRUE((outputs == expected));
+}
+
+TEST(DfsWalker, simple_on_pop) {
+  DfsWalker<int> visitor(
+      [](int node, const std::function<void(int)>& NodeHandler) {
+        if (node == 0) {
+          NodeHandler(3);
+        } else if (node == 1) {
+          NodeHandler(2);
+          NodeHandler(3);
+        } else if (node == 2 || node == 3) {
+          NodeHandler(4);
+        }
+      });
+  std::vector<int> sources{0, 1};
+  std::vector<int> outputs;
+  visitor(
+      sources.begin(),
+      sources.end(),
+      [](int) {},
+      [&](int node) {
+        LOG(ERROR) << node;
+        outputs.push_back(node);
+      });
+  std::vector<int> expected{4, 3, 0, 2, 1};
+  EXPECT_TRUE((outputs == expected));
+}
+
+}  // namespace common
+}  // namespace cinn