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