1 //===----- llvm/unittest/ADT/SCCIteratorTest.cpp - SCCIterator tests ------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "llvm/ADT/SCCIterator.h"
11 #include "llvm/ADT/GraphTraits.h"
12 #include "gtest/gtest.h"
19 /// Graph<N> - A graph with N nodes. Note that N can be at most 8.
25 Graph& operator=(const Graph&);
27 static void ValidateIndex(unsigned Idx) {
28 assert(Idx < N && "Invalid node index!");
32 /// NodeSubset - A subset of the graph's nodes.
34 typedef unsigned char BitVector; // Where the limitation N <= 8 comes from.
36 NodeSubset(BitVector e) : Elements(e) {}
38 /// NodeSubset - Default constructor, creates an empty subset.
39 NodeSubset() : Elements(0) {
40 assert(N <= sizeof(BitVector)*CHAR_BIT && "Graph too big!");
43 /// Comparison operators.
44 bool operator==(const NodeSubset &other) const {
45 return other.Elements == this->Elements;
47 bool operator!=(const NodeSubset &other) const {
48 return !(*this == other);
51 /// AddNode - Add the node with the given index to the subset.
52 void AddNode(unsigned Idx) {
54 Elements |= 1U << Idx;
57 /// DeleteNode - Remove the node with the given index from the subset.
58 void DeleteNode(unsigned Idx) {
60 Elements &= ~(1U << Idx);
63 /// count - Return true if the node with the given index is in the subset.
64 bool count(unsigned Idx) {
66 return (Elements & (1U << Idx)) != 0;
69 /// isEmpty - Return true if this is the empty set.
70 bool isEmpty() const {
74 /// isSubsetOf - Return true if this set is a subset of the given one.
75 bool isSubsetOf(const NodeSubset &other) const {
76 return (this->Elements | other.Elements) == other.Elements;
79 /// Complement - Return the complement of this subset.
80 NodeSubset Complement() const {
81 return ~(unsigned)this->Elements & ((1U << N) - 1);
84 /// Join - Return the union of this subset and the given one.
85 NodeSubset Join(const NodeSubset &other) const {
86 return this->Elements | other.Elements;
89 /// Meet - Return the intersection of this subset and the given one.
90 NodeSubset Meet(const NodeSubset &other) const {
91 return this->Elements & other.Elements;
95 /// NodeType - Node index and set of children of the node.
96 typedef std::pair<unsigned, NodeSubset> NodeType;
99 /// Nodes - The list of nodes for this graph.
103 /// Graph - Default constructor. Creates an empty graph.
105 // Let each node know which node it is. This allows us to find the start of
106 // the Nodes array given a pointer to any element of it.
107 for (unsigned i = 0; i != N; ++i)
111 /// AddEdge - Add an edge from the node with index FromIdx to the node with
113 void AddEdge(unsigned FromIdx, unsigned ToIdx) {
114 ValidateIndex(FromIdx);
115 Nodes[FromIdx].second.AddNode(ToIdx);
118 /// DeleteEdge - Remove the edge (if any) from the node with index FromIdx to
119 /// the node with index ToIdx.
120 void DeleteEdge(unsigned FromIdx, unsigned ToIdx) {
121 ValidateIndex(FromIdx);
122 Nodes[FromIdx].second.DeleteNode(ToIdx);
125 /// AccessNode - Get a pointer to the node with the given index.
126 NodeType *AccessNode(unsigned Idx) const {
128 // The constant cast is needed when working with GraphTraits, which insists
129 // on taking a constant Graph.
130 return const_cast<NodeType *>(&Nodes[Idx]);
133 /// NodesReachableFrom - Return the set of all nodes reachable from the given
135 NodeSubset NodesReachableFrom(unsigned Idx) const {
136 // This algorithm doesn't scale, but that doesn't matter given the small
137 // size of our graphs.
138 NodeSubset Reachable;
140 // The initial node is reachable.
141 Reachable.AddNode(Idx);
143 NodeSubset Previous(Reachable);
145 // Add in all nodes which are children of a reachable node.
146 for (unsigned i = 0; i != N; ++i)
147 if (Previous.count(i))
148 Reachable = Reachable.Join(Nodes[i].second);
150 // If nothing changed then we have found all reachable nodes.
151 if (Reachable == Previous)
158 /// ChildIterator - Visit all children of a node.
159 class ChildIterator {
162 /// FirstNode - Pointer to first node in the graph's Nodes array.
164 /// Children - Set of nodes which are children of this one and that haven't
165 /// yet been visited.
168 ChildIterator(); // Disable default constructor.
170 ChildIterator(NodeType *F, NodeSubset C) : FirstNode(F), Children(C) {}
173 /// ChildIterator - Copy constructor.
174 ChildIterator(const ChildIterator& other) : FirstNode(other.FirstNode),
175 Children(other.Children) {}
177 /// Comparison operators.
178 bool operator==(const ChildIterator &other) const {
179 return other.FirstNode == this->FirstNode &&
180 other.Children == this->Children;
182 bool operator!=(const ChildIterator &other) const {
183 return !(*this == other);
186 /// Prefix increment operator.
187 ChildIterator& operator++() {
188 // Find the next unvisited child node.
189 for (unsigned i = 0; i != N; ++i)
190 if (Children.count(i)) {
191 // Remove that child - it has been visited. This is the increment!
192 Children.DeleteNode(i);
195 assert(false && "Incrementing end iterator!");
196 return *this; // Avoid compiler warnings.
199 /// Postfix increment operator.
200 ChildIterator operator++(int) {
201 ChildIterator Result(*this);
206 /// Dereference operator.
207 NodeType *operator*() {
208 // Find the next unvisited child node.
209 for (unsigned i = 0; i != N; ++i)
210 if (Children.count(i))
211 // Return a pointer to it.
212 return FirstNode + i;
213 assert(false && "Dereferencing end iterator!");
214 return nullptr; // Avoid compiler warning.
218 /// child_begin - Return an iterator pointing to the first child of the given
220 static ChildIterator child_begin(NodeType *Parent) {
221 return ChildIterator(Parent - Parent->first, Parent->second);
224 /// child_end - Return the end iterator for children of the given node.
225 static ChildIterator child_end(NodeType *Parent) {
226 return ChildIterator(Parent - Parent->first, NodeSubset());
230 template <unsigned N>
231 struct GraphTraits<Graph<N> > {
232 typedef typename Graph<N>::NodeType NodeType;
233 typedef typename Graph<N>::ChildIterator ChildIteratorType;
235 static inline NodeType *getEntryNode(const Graph<N> &G) { return G.AccessNode(0); }
236 static inline ChildIteratorType child_begin(NodeType *Node) {
237 return Graph<N>::child_begin(Node);
239 static inline ChildIteratorType child_end(NodeType *Node) {
240 return Graph<N>::child_end(Node);
244 TEST(SCCIteratorTest, AllSmallGraphs) {
245 // Test SCC computation against every graph with NUM_NODES nodes or less.
246 // Since SCC considers every node to have an implicit self-edge, we only
247 // create graphs for which every node has a self-edge.
249 #define NUM_GRAPHS (NUM_NODES * (NUM_NODES - 1))
250 typedef Graph<NUM_NODES> GT;
252 /// Enumerate all graphs using NUM_GRAPHS bits.
253 static_assert(NUM_GRAPHS < sizeof(unsigned) * CHAR_BIT, "Too many graphs!");
254 for (unsigned GraphDescriptor = 0; GraphDescriptor < (1U << NUM_GRAPHS);
258 // Add edges as specified by the descriptor.
259 unsigned DescriptorCopy = GraphDescriptor;
260 for (unsigned i = 0; i != NUM_NODES; ++i)
261 for (unsigned j = 0; j != NUM_NODES; ++j) {
262 // Always add a self-edge.
267 if (DescriptorCopy & 1)
269 DescriptorCopy >>= 1;
272 // Test the SCC logic on this graph.
274 /// NodesInSomeSCC - Those nodes which are in some SCC.
275 GT::NodeSubset NodesInSomeSCC;
277 for (scc_iterator<GT> I = scc_begin(G), E = scc_end(G); I != E; ++I) {
278 const std::vector<GT::NodeType *> &SCC = *I;
280 // Get the nodes in this SCC as a NodeSubset rather than a vector.
281 GT::NodeSubset NodesInThisSCC;
282 for (unsigned i = 0, e = SCC.size(); i != e; ++i)
283 NodesInThisSCC.AddNode(SCC[i]->first);
285 // There should be at least one node in every SCC.
286 EXPECT_FALSE(NodesInThisSCC.isEmpty());
288 // Check that every node in the SCC is reachable from every other node in
290 for (unsigned i = 0; i != NUM_NODES; ++i)
291 if (NodesInThisSCC.count(i))
292 EXPECT_TRUE(NodesInThisSCC.isSubsetOf(G.NodesReachableFrom(i)));
294 // OK, now that we now that every node in the SCC is reachable from every
295 // other, this means that the set of nodes reachable from any node in the
296 // SCC is the same as the set of nodes reachable from every node in the
297 // SCC. Check that for every node N not in the SCC but reachable from the
298 // SCC, no element of the SCC is reachable from N.
299 for (unsigned i = 0; i != NUM_NODES; ++i)
300 if (NodesInThisSCC.count(i)) {
301 GT::NodeSubset NodesReachableFromSCC = G.NodesReachableFrom(i);
302 GT::NodeSubset ReachableButNotInSCC =
303 NodesReachableFromSCC.Meet(NodesInThisSCC.Complement());
305 for (unsigned j = 0; j != NUM_NODES; ++j)
306 if (ReachableButNotInSCC.count(j))
307 EXPECT_TRUE(G.NodesReachableFrom(j).Meet(NodesInThisSCC).isEmpty());
309 // The result must be the same for all other nodes in this SCC, so
310 // there is no point in checking them.
314 // This is indeed a SCC: a maximal set of nodes for which each node is
315 // reachable from every other.
317 // Check that we didn't already see this SCC.
318 EXPECT_TRUE(NodesInSomeSCC.Meet(NodesInThisSCC).isEmpty());
320 NodesInSomeSCC = NodesInSomeSCC.Join(NodesInThisSCC);
322 // Check a property that is specific to the LLVM SCC iterator and
323 // guaranteed by it: if a node in SCC S1 has an edge to a node in
324 // SCC S2, then S1 is visited *after* S2. This means that the set
325 // of nodes reachable from this SCC must be contained either in the
326 // union of this SCC and all previously visited SCC's.
328 for (unsigned i = 0; i != NUM_NODES; ++i)
329 if (NodesInThisSCC.count(i)) {
330 GT::NodeSubset NodesReachableFromSCC = G.NodesReachableFrom(i);
331 EXPECT_TRUE(NodesReachableFromSCC.isSubsetOf(NodesInSomeSCC));
332 // The result must be the same for all other nodes in this SCC, so
333 // there is no point in checking them.
338 // Finally, check that the nodes in some SCC are exactly those that are
339 // reachable from the initial node.
340 EXPECT_EQ(NodesInSomeSCC, G.NodesReachableFrom(0));