| //===----- llvm/unittest/ADT/SCCIteratorTest.cpp - SCCIterator tests ------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/ADT/SCCIterator.h" |
| #include "TestGraph.h" |
| #include "gtest/gtest.h" |
| #include <limits.h> |
| |
| using namespace llvm; |
| |
| namespace llvm { |
| |
| TEST(SCCIteratorTest, AllSmallGraphs) { |
| // Test SCC computation against every graph with NUM_NODES nodes or less. |
| // Since SCC considers every node to have an implicit self-edge, we only |
| // create graphs for which every node has a self-edge. |
| #define NUM_NODES 4 |
| #define NUM_GRAPHS (NUM_NODES * (NUM_NODES - 1)) |
| typedef Graph<NUM_NODES> GT; |
| |
| /// Enumerate all graphs using NUM_GRAPHS bits. |
| static_assert(NUM_GRAPHS < sizeof(unsigned) * CHAR_BIT, "Too many graphs!"); |
| for (unsigned GraphDescriptor = 0; GraphDescriptor < (1U << NUM_GRAPHS); |
| ++GraphDescriptor) { |
| GT G; |
| |
| // Add edges as specified by the descriptor. |
| unsigned DescriptorCopy = GraphDescriptor; |
| for (unsigned i = 0; i != NUM_NODES; ++i) |
| for (unsigned j = 0; j != NUM_NODES; ++j) { |
| // Always add a self-edge. |
| if (i == j) { |
| G.AddEdge(i, j); |
| continue; |
| } |
| if (DescriptorCopy & 1) |
| G.AddEdge(i, j); |
| DescriptorCopy >>= 1; |
| } |
| |
| // Test the SCC logic on this graph. |
| |
| /// NodesInSomeSCC - Those nodes which are in some SCC. |
| GT::NodeSubset NodesInSomeSCC; |
| |
| for (scc_iterator<GT> I = scc_begin(G), E = scc_end(G); I != E; ++I) { |
| const std::vector<GT::NodeType *> &SCC = *I; |
| |
| // Get the nodes in this SCC as a NodeSubset rather than a vector. |
| GT::NodeSubset NodesInThisSCC; |
| for (unsigned i = 0, e = SCC.size(); i != e; ++i) |
| NodesInThisSCC.AddNode(SCC[i]->first); |
| |
| // There should be at least one node in every SCC. |
| EXPECT_FALSE(NodesInThisSCC.isEmpty()); |
| |
| // Check that every node in the SCC is reachable from every other node in |
| // the SCC. |
| for (unsigned i = 0; i != NUM_NODES; ++i) |
| if (NodesInThisSCC.count(i)) { |
| EXPECT_TRUE(NodesInThisSCC.isSubsetOf(G.NodesReachableFrom(i))); |
| } |
| |
| // OK, now that we now that every node in the SCC is reachable from every |
| // other, this means that the set of nodes reachable from any node in the |
| // SCC is the same as the set of nodes reachable from every node in the |
| // SCC. Check that for every node N not in the SCC but reachable from the |
| // SCC, no element of the SCC is reachable from N. |
| for (unsigned i = 0; i != NUM_NODES; ++i) |
| if (NodesInThisSCC.count(i)) { |
| GT::NodeSubset NodesReachableFromSCC = G.NodesReachableFrom(i); |
| GT::NodeSubset ReachableButNotInSCC = |
| NodesReachableFromSCC.Meet(NodesInThisSCC.Complement()); |
| |
| for (unsigned j = 0; j != NUM_NODES; ++j) |
| if (ReachableButNotInSCC.count(j)) { |
| EXPECT_TRUE(G.NodesReachableFrom(j).Meet(NodesInThisSCC).isEmpty()); |
| } |
| |
| // The result must be the same for all other nodes in this SCC, so |
| // there is no point in checking them. |
| break; |
| } |
| |
| // This is indeed a SCC: a maximal set of nodes for which each node is |
| // reachable from every other. |
| |
| // Check that we didn't already see this SCC. |
| EXPECT_TRUE(NodesInSomeSCC.Meet(NodesInThisSCC).isEmpty()); |
| |
| NodesInSomeSCC = NodesInSomeSCC.Join(NodesInThisSCC); |
| |
| // Check a property that is specific to the LLVM SCC iterator and |
| // guaranteed by it: if a node in SCC S1 has an edge to a node in |
| // SCC S2, then S1 is visited *after* S2. This means that the set |
| // of nodes reachable from this SCC must be contained either in the |
| // union of this SCC and all previously visited SCC's. |
| |
| for (unsigned i = 0; i != NUM_NODES; ++i) |
| if (NodesInThisSCC.count(i)) { |
| GT::NodeSubset NodesReachableFromSCC = G.NodesReachableFrom(i); |
| EXPECT_TRUE(NodesReachableFromSCC.isSubsetOf(NodesInSomeSCC)); |
| // The result must be the same for all other nodes in this SCC, so |
| // there is no point in checking them. |
| break; |
| } |
| } |
| |
| // Finally, check that the nodes in some SCC are exactly those that are |
| // reachable from the initial node. |
| EXPECT_EQ(NodesInSomeSCC, G.NodesReachableFrom(0)); |
| } |
| } |
| |
| } |