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-rw-r--r--src/support/disjoint_sets.h87
-rw-r--r--test/gtest/CMakeLists.txt1
-rw-r--r--test/gtest/disjoint_sets.cpp106
3 files changed, 194 insertions, 0 deletions
diff --git a/src/support/disjoint_sets.h b/src/support/disjoint_sets.h
new file mode 100644
index 000000000..198e5cb67
--- /dev/null
+++ b/src/support/disjoint_sets.h
@@ -0,0 +1,87 @@
+/*
+ * Copyright 2024 WebAssembly Community Group participants
+ *
+ * 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.
+ */
+
+#ifndef wasm_support_disjoint_sets_h
+#define wasm_support_disjoint_sets_h
+
+#include <cassert>
+#include <cstddef>
+#include <vector>
+
+namespace wasm {
+
+// A disjoint set forest (a.k.a. union-find) implementation. See
+// https://en.wikipedia.org/wiki/Disjoint-set_data_structure.
+struct DisjointSets {
+ struct ElemInfo {
+ // The index of the parent element, or the index of the element itself if it
+ // has no parent.
+ size_t parent;
+ // An upper bound on the height of the tree rooted at this element.
+ size_t rank;
+ };
+ std::vector<ElemInfo> info;
+
+ // Add an element and return its index.
+ size_t addSet() {
+ size_t ret = info.size();
+ info.push_back({ret, 0});
+ return ret;
+ }
+
+ // Get the representative element of the set to which `elem` belongs.
+ size_t getRoot(size_t elem) {
+ assert(elem < info.size());
+ size_t root = elem;
+ // Follow parent pointers up to the root.
+ for (; info[root].parent != root; root = info[root].parent) {
+ }
+ // Compress the path to make subsequent getRoots of this set faster.
+ while (elem != root) {
+ size_t parent = info[elem].parent;
+ info[elem].parent = root;
+ elem = parent;
+ }
+ return root;
+ }
+
+ // Join the sets to which the elements belong and return the representative
+ // element of the union.
+ size_t getUnion(size_t elem1, size_t elem2) {
+ assert(elem1 < info.size() && elem2 < info.size());
+ size_t root1 = getRoot(elem1);
+ size_t root2 = getRoot(elem2);
+ if (root1 == root2) {
+ // Already in the same set.
+ return root1;
+ }
+ // Canonicalize so that root1 has the greater rank.
+ if (info[root1].rank < info[root2].rank) {
+ std::swap(root1, root2);
+ }
+ // Merge the trees, smaller into larger.
+ info[root2].parent = root1;
+ // If the ranks were equal, the new root has a larger rank.
+ if (info[root1].rank == info[root2].rank) {
+ ++info[root1].rank;
+ }
+ return root1;
+ }
+};
+
+} // namespace wasm
+
+#endif // wasm_support_disjoint_sets_h
diff --git a/test/gtest/CMakeLists.txt b/test/gtest/CMakeLists.txt
index 4604eea77..538ec1cdc 100644
--- a/test/gtest/CMakeLists.txt
+++ b/test/gtest/CMakeLists.txt
@@ -4,6 +4,7 @@ include_directories(../../src/wasm)
set(unittest_SOURCES
cfg.cpp
dfa_minimization.cpp
+ disjoint_sets.cpp
json.cpp
lattices.cpp
possible-contents.cpp
diff --git a/test/gtest/disjoint_sets.cpp b/test/gtest/disjoint_sets.cpp
new file mode 100644
index 000000000..f974957a3
--- /dev/null
+++ b/test/gtest/disjoint_sets.cpp
@@ -0,0 +1,106 @@
+/*
+ * Copyright 2024 WebAssembly Community Group participants
+ *
+ * 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 "support/disjoint_sets.h"
+#include "gtest/gtest.h"
+
+using namespace wasm;
+
+TEST(DisjointSetsTest, NewSets) {
+ DisjointSets sets;
+ auto elem1 = sets.addSet();
+ auto elem2 = sets.addSet();
+ EXPECT_NE(elem1, elem2);
+
+ auto root1 = sets.getRoot(elem1);
+ EXPECT_EQ(elem1, root1);
+
+ auto root2 = sets.getRoot(elem2);
+ EXPECT_EQ(elem2, root2);
+}
+
+TEST(DisjointSetsTest, Union) {
+ DisjointSets sets;
+ auto elem1 = sets.addSet();
+ auto elem2 = sets.addSet();
+ auto root = sets.getUnion(elem1, elem2);
+ EXPECT_TRUE(root == elem1 || root == elem2);
+
+ auto root1 = sets.getRoot(elem1);
+ auto root2 = sets.getRoot(elem2);
+ EXPECT_EQ(root1, root);
+ EXPECT_EQ(root2, root);
+}
+
+TEST(DisjointSetsTest, TwoUnions) {
+ DisjointSets sets;
+ auto elem1 = sets.addSet();
+ auto elem2 = sets.addSet();
+ auto elem3 = sets.addSet();
+ auto elem4 = sets.addSet();
+
+ auto rootA = sets.getUnion(elem1, elem3);
+ auto rootB = sets.getUnion(elem2, elem4);
+ EXPECT_EQ(sets.getRoot(elem1), rootA);
+ EXPECT_EQ(sets.getRoot(elem2), rootB);
+ EXPECT_EQ(sets.getRoot(elem3), rootA);
+ EXPECT_EQ(sets.getRoot(elem4), rootB);
+ EXPECT_NE(rootA, rootB);
+}
+
+TEST(DisjointSetsTest, UnionList) {
+ constexpr size_t count = 16;
+ DisjointSets sets;
+ size_t elems[count];
+ for (size_t i = 0; i < count; ++i) {
+ elems[i] = sets.addSet();
+ }
+
+ for (size_t i = 1; i < count; ++i) {
+ sets.getUnion(elems[i], elems[i - 1]);
+ }
+
+ auto root = sets.getRoot(elems[0]);
+ for (size_t rep = 0; rep < 2; ++rep) {
+ for (size_t i = 0; i < count; ++i) {
+ auto currRoot = sets.getRoot(elems[i]);
+ EXPECT_EQ(currRoot, root);
+ }
+ }
+}
+
+TEST(DisjointSetsTest, UnionTree) {
+ constexpr size_t count = 16;
+ DisjointSets sets;
+ size_t elems[count];
+ for (size_t i = 0; i < count; ++i) {
+ elems[i] = sets.addSet();
+ }
+
+ for (size_t stride = 2; stride <= count; stride *= 2) {
+ for (size_t i = 0; i < count; i += stride) {
+ sets.getUnion(elems[i], elems[i + stride / 2]);
+ }
+ }
+
+ auto root = sets.getRoot(elems[0]);
+ for (size_t rep = 0; rep < 2; ++rep) {
+ for (size_t i = 0; i < count; ++i) {
+ auto currRoot = sets.getRoot(elems[i]);
+ EXPECT_EQ(currRoot, root);
+ }
+ }
+}
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