llvm/unittests/Analysis/LazyCallGraphTest.cpp

//===- LazyCallGraphTest.cpp - Unit tests for the lazy CG analysis --------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "llvm/Analysis/LazyCallGraph.h"
#include "llvm/AsmParser/Parser.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/SourceMgr.h"
#include "gtest/gtest.h"
#include <memory>

using namespace llvm;

namespace {

std::unique_ptr<Module> parseAssembly(const char *Assembly) {
  auto M = make_unique<Module>("Module", getGlobalContext());

  SMDiagnostic Error;
  bool Parsed =
      ParseAssemblyString(Assembly, M.get(), Error, M->getContext()) == M.get();

  std::string ErrMsg;
  raw_string_ostream OS(ErrMsg);
  Error.print("", OS);

  // A failure here means that the test itself is buggy.
  if (!Parsed)
    report_fatal_error(OS.str().c_str());

  return M;
}

// IR forming a call graph with a diamond of triangle-shaped SCCs:
//
//         d1
//        /  \
//       d3--d2
//      /     \
//     b1     c1
//   /  \    /  \
//  b3--b2  c3--c2
//       \  /
//        a1
//       /  \
//      a3--a2
//
// All call edges go up between SCCs, and clockwise around the SCC.
static const char DiamondOfTriangles[] =
     "define void @a1() {\n"
     "entry:\n"
     "  call void @a2()\n"
     "  call void @b2()\n"
     "  call void @c3()\n"
     "  ret void\n"
     "}\n"
     "define void @a2() {\n"
     "entry:\n"
     "  call void @a3()\n"
     "  ret void\n"
     "}\n"
     "define void @a3() {\n"
     "entry:\n"
     "  call void @a1()\n"
     "  ret void\n"
     "}\n"
     "define void @b1() {\n"
     "entry:\n"
     "  call void @b2()\n"
     "  call void @d3()\n"
     "  ret void\n"
     "}\n"
     "define void @b2() {\n"
     "entry:\n"
     "  call void @b3()\n"
     "  ret void\n"
     "}\n"
     "define void @b3() {\n"
     "entry:\n"
     "  call void @b1()\n"
     "  ret void\n"
     "}\n"
     "define void @c1() {\n"
     "entry:\n"
     "  call void @c2()\n"
     "  call void @d2()\n"
     "  ret void\n"
     "}\n"
     "define void @c2() {\n"
     "entry:\n"
     "  call void @c3()\n"
     "  ret void\n"
     "}\n"
     "define void @c3() {\n"
     "entry:\n"
     "  call void @c1()\n"
     "  ret void\n"
     "}\n"
     "define void @d1() {\n"
     "entry:\n"
     "  call void @d2()\n"
     "  ret void\n"
     "}\n"
     "define void @d2() {\n"
     "entry:\n"
     "  call void @d3()\n"
     "  ret void\n"
     "}\n"
     "define void @d3() {\n"
     "entry:\n"
     "  call void @d1()\n"
     "  ret void\n"
     "}\n";

TEST(LazyCallGraphTest, BasicGraphFormation) {
  std::unique_ptr<Module> M = parseAssembly(DiamondOfTriangles);
  LazyCallGraph CG(*M);

  // The order of the entry nodes should be stable w.r.t. the source order of
  // the IR, and everything in our module is an entry node, so just directly
  // build variables for each node.
  auto I = CG.begin();
  LazyCallGraph::Node &A1 = *I++;
  EXPECT_EQ("a1", A1.getFunction().getName());
  LazyCallGraph::Node &A2 = *I++;
  EXPECT_EQ("a2", A2.getFunction().getName());
  LazyCallGraph::Node &A3 = *I++;
  EXPECT_EQ("a3", A3.getFunction().getName());
  LazyCallGraph::Node &B1 = *I++;
  EXPECT_EQ("b1", B1.getFunction().getName());
  LazyCallGraph::Node &B2 = *I++;
  EXPECT_EQ("b2", B2.getFunction().getName());
  LazyCallGraph::Node &B3 = *I++;
  EXPECT_EQ("b3", B3.getFunction().getName());
  LazyCallGraph::Node &C1 = *I++;
  EXPECT_EQ("c1", C1.getFunction().getName());
  LazyCallGraph::Node &C2 = *I++;
  EXPECT_EQ("c2", C2.getFunction().getName());
  LazyCallGraph::Node &C3 = *I++;
  EXPECT_EQ("c3", C3.getFunction().getName());
  LazyCallGraph::Node &D1 = *I++;
  EXPECT_EQ("d1", D1.getFunction().getName());
  LazyCallGraph::Node &D2 = *I++;
  EXPECT_EQ("d2", D2.getFunction().getName());
  LazyCallGraph::Node &D3 = *I++;
  EXPECT_EQ("d3", D3.getFunction().getName());
  EXPECT_EQ(CG.end(), I);

  // Build vectors and sort them for the rest of the assertions to make them
  // independent of order.
  std::vector<std::string> Nodes;

  for (LazyCallGraph::Node &N : A1)
    Nodes.push_back(N.getFunction().getName());
  std::sort(Nodes.begin(), Nodes.end());
  EXPECT_EQ("a2", Nodes[0]);
  EXPECT_EQ("b2", Nodes[1]);
  EXPECT_EQ("c3", Nodes[2]);
  Nodes.clear();

  EXPECT_EQ(A2.end(), std::next(A2.begin()));
  EXPECT_EQ("a3", A2.begin()->getFunction().getName());
  EXPECT_EQ(A3.end(), std::next(A3.begin()));
  EXPECT_EQ("a1", A3.begin()->getFunction().getName());

  for (LazyCallGraph::Node &N : B1)
    Nodes.push_back(N.getFunction().getName());
  std::sort(Nodes.begin(), Nodes.end());
  EXPECT_EQ("b2", Nodes[0]);
  EXPECT_EQ("d3", Nodes[1]);
  Nodes.clear();

  EXPECT_EQ(B2.end(), std::next(B2.begin()));
  EXPECT_EQ("b3", B2.begin()->getFunction().getName());
  EXPECT_EQ(B3.end(), std::next(B3.begin()));
  EXPECT_EQ("b1", B3.begin()->getFunction().getName());

  for (LazyCallGraph::Node &N : C1)
    Nodes.push_back(N.getFunction().getName());
  std::sort(Nodes.begin(), Nodes.end());
  EXPECT_EQ("c2", Nodes[0]);
  EXPECT_EQ("d2", Nodes[1]);
  Nodes.clear();

  EXPECT_EQ(C2.end(), std::next(C2.begin()));
  EXPECT_EQ("c3", C2.begin()->getFunction().getName());
  EXPECT_EQ(C3.end(), std::next(C3.begin()));
  EXPECT_EQ("c1", C3.begin()->getFunction().getName());

  EXPECT_EQ(D1.end(), std::next(D1.begin()));
  EXPECT_EQ("d2", D1.begin()->getFunction().getName());
  EXPECT_EQ(D2.end(), std::next(D2.begin()));
  EXPECT_EQ("d3", D2.begin()->getFunction().getName());
  EXPECT_EQ(D3.end(), std::next(D3.begin()));
  EXPECT_EQ("d1", D3.begin()->getFunction().getName());

  // Now lets look at the SCCs.
  auto SCCI = CG.postorder_scc_begin();

  LazyCallGraph::SCC &D = *SCCI++;
  for (LazyCallGraph::Node *N : D)
    Nodes.push_back(N->getFunction().getName());
  std::sort(Nodes.begin(), Nodes.end());
  EXPECT_EQ(3u, Nodes.size());
  EXPECT_EQ("d1", Nodes[0]);
  EXPECT_EQ("d2", Nodes[1]);
  EXPECT_EQ("d3", Nodes[2]);
  Nodes.clear();

  LazyCallGraph::SCC &C = *SCCI++;
  for (LazyCallGraph::Node *N : C)
    Nodes.push_back(N->getFunction().getName());
  std::sort(Nodes.begin(), Nodes.end());
  EXPECT_EQ(3u, Nodes.size());
  EXPECT_EQ("c1", Nodes[0]);
  EXPECT_EQ("c2", Nodes[1]);
  EXPECT_EQ("c3", Nodes[2]);
  Nodes.clear();

  LazyCallGraph::SCC &B = *SCCI++;
  for (LazyCallGraph::Node *N : B)
    Nodes.push_back(N->getFunction().getName());
  std::sort(Nodes.begin(), Nodes.end());
  EXPECT_EQ(3u, Nodes.size());
  EXPECT_EQ("b1", Nodes[0]);
  EXPECT_EQ("b2", Nodes[1]);
  EXPECT_EQ("b3", Nodes[2]);
  Nodes.clear();

  LazyCallGraph::SCC &A = *SCCI++;
  for (LazyCallGraph::Node *N : A)
    Nodes.push_back(N->getFunction().getName());
  std::sort(Nodes.begin(), Nodes.end());
  EXPECT_EQ(3u, Nodes.size());
  EXPECT_EQ("a1", Nodes[0]);
  EXPECT_EQ("a2", Nodes[1]);
  EXPECT_EQ("a3", Nodes[2]);
  Nodes.clear();

  EXPECT_EQ(CG.postorder_scc_end(), SCCI);
}

static Function &lookupFunction(Module &M, StringRef Name) {
  for (Function &F : M)
    if (F.getName() == Name)
      return F;
  report_fatal_error("Couldn't find function!");
}

TEST(LazyCallGraphTest, BasicGraphMutation) {
  std::unique_ptr<Module> M = parseAssembly(
      "define void @a() {\n"
      "entry:\n"
      "  call void @b()\n"
      "  call void @c()\n"
      "  ret void\n"
      "}\n"
      "define void @b() {\n"
      "entry:\n"
      "  ret void\n"
      "}\n"
      "define void @c() {\n"
      "entry:\n"
      "  ret void\n"
      "}\n");
  LazyCallGraph CG(*M);

  LazyCallGraph::Node &A = CG.get(lookupFunction(*M, "a"));
  LazyCallGraph::Node &B = CG.get(lookupFunction(*M, "b"));
  EXPECT_EQ(2, std::distance(A.begin(), A.end()));
  EXPECT_EQ(0, std::distance(B.begin(), B.end()));

  CG.insertEdge(B, lookupFunction(*M, "c"));
  EXPECT_EQ(1, std::distance(B.begin(), B.end()));
  LazyCallGraph::Node &C = *B.begin();
  EXPECT_EQ(0, std::distance(C.begin(), C.end()));

  CG.insertEdge(C, B.getFunction());
  EXPECT_EQ(1, std::distance(C.begin(), C.end()));
  EXPECT_EQ(&B, &*C.begin());

  CG.insertEdge(C, C.getFunction());
  EXPECT_EQ(2, std::distance(C.begin(), C.end()));
  EXPECT_EQ(&B, &*C.begin());
  EXPECT_EQ(&C, &*(C.begin() + 1));
}

TEST(LazyCallGraphTest, MultiArmSCC) {
  // Two interlocking cycles. The really useful thing about this SCC is that it
  // will require Tarjan's DFS to backtrack and finish processing all of the
  // children of each node in the SCC.
  std::unique_ptr<Module> M = parseAssembly(
      "define void @a() {\n"
      "entry:\n"
      "  call void @b()\n"
      "  call void @d()\n"
      "  ret void\n"
      "}\n"
      "define void @b() {\n"
      "entry:\n"
      "  call void @c()\n"
      "  ret void\n"
      "}\n"
      "define void @c() {\n"
      "entry:\n"
      "  call void @a()\n"
      "  ret void\n"
      "}\n"
      "define void @d() {\n"
      "entry:\n"
      "  call void @e()\n"
      "  ret void\n"
      "}\n"
      "define void @e() {\n"
      "entry:\n"
      "  call void @a()\n"
      "  ret void\n"
      "}\n");
  LazyCallGraph CG(*M);

  // Force the graph to be fully expanded.
  auto SCCI = CG.postorder_scc_begin();
  LazyCallGraph::SCC &SCC = *SCCI++;
  EXPECT_EQ(CG.postorder_scc_end(), SCCI);

  LazyCallGraph::Node &A = *CG.lookup(lookupFunction(*M, "a"));
  LazyCallGraph::Node &B = *CG.lookup(lookupFunction(*M, "b"));
  LazyCallGraph::Node &C = *CG.lookup(lookupFunction(*M, "c"));
  LazyCallGraph::Node &D = *CG.lookup(lookupFunction(*M, "d"));
  LazyCallGraph::Node &E = *CG.lookup(lookupFunction(*M, "e"));
  EXPECT_EQ(&SCC, CG.lookupSCC(A));
  EXPECT_EQ(&SCC, CG.lookupSCC(B));
  EXPECT_EQ(&SCC, CG.lookupSCC(C));
  EXPECT_EQ(&SCC, CG.lookupSCC(D));
  EXPECT_EQ(&SCC, CG.lookupSCC(E));
}

TEST(LazyCallGraphTest, InterSCCEdgeRemoval) {
  std::unique_ptr<Module> M = parseAssembly(
      "define void @a() {\n"
      "entry:\n"
      "  call void @b()\n"
      "  ret void\n"
      "}\n"
      "define void @b() {\n"
      "entry:\n"
      "  ret void\n"
      "}\n");
  LazyCallGraph CG(*M);

  // Force the graph to be fully expanded.
  for (LazyCallGraph::SCC &C : CG.postorder_sccs())
    (void)C;

  LazyCallGraph::Node &A = *CG.lookup(lookupFunction(*M, "a"));
  LazyCallGraph::Node &B = *CG.lookup(lookupFunction(*M, "b"));
  LazyCallGraph::SCC &AC = *CG.lookupSCC(A);
  LazyCallGraph::SCC &BC = *CG.lookupSCC(B);

  EXPECT_EQ("b", A.begin()->getFunction().getName());
  EXPECT_EQ(B.end(), B.begin());
  EXPECT_EQ(&AC, &*BC.parent_begin());

  AC.removeInterSCCEdge(A, B);

  EXPECT_EQ(A.end(), A.begin());
  EXPECT_EQ(B.end(), B.begin());
  EXPECT_EQ(BC.parent_end(), BC.parent_begin());
}

TEST(LazyCallGraphTest, IntraSCCEdgeRemoval) {
  // A nice fully connected (including self-edges) SCC.
  std::unique_ptr<Module> M1 = parseAssembly(
      "define void @a() {\n"
      "entry:\n"
      "  call void @a()\n"
      "  call void @b()\n"
      "  call void @c()\n"
      "  ret void\n"
      "}\n"
      "define void @b() {\n"
      "entry:\n"
      "  call void @a()\n"
      "  call void @b()\n"
      "  call void @c()\n"
      "  ret void\n"
      "}\n"
      "define void @c() {\n"
      "entry:\n"
      "  call void @a()\n"
      "  call void @b()\n"
      "  call void @c()\n"
      "  ret void\n"
      "}\n");
  LazyCallGraph CG1(*M1);

  // Force the graph to be fully expanded.
  auto SCCI = CG1.postorder_scc_begin();
  LazyCallGraph::SCC &SCC = *SCCI++;
  EXPECT_EQ(CG1.postorder_scc_end(), SCCI);

  LazyCallGraph::Node &A = *CG1.lookup(lookupFunction(*M1, "a"));
  LazyCallGraph::Node &B = *CG1.lookup(lookupFunction(*M1, "b"));
  LazyCallGraph::Node &C = *CG1.lookup(lookupFunction(*M1, "c"));
  EXPECT_EQ(&SCC, CG1.lookupSCC(A));
  EXPECT_EQ(&SCC, CG1.lookupSCC(B));
  EXPECT_EQ(&SCC, CG1.lookupSCC(C));

  // Remove the edge from b -> a, which should leave the 3 functions still in
  // a single connected component because of a -> b -> c -> a.
  SmallVector<LazyCallGraph::SCC *, 1> NewSCCs = SCC.removeIntraSCCEdge(B, A);
  EXPECT_EQ(0u, NewSCCs.size());
  EXPECT_EQ(&SCC, CG1.lookupSCC(A));
  EXPECT_EQ(&SCC, CG1.lookupSCC(B));
  EXPECT_EQ(&SCC, CG1.lookupSCC(C));

  // Remove the edge from c -> a, which should leave 'a' in the original SCC
  // and form a new SCC for 'b' and 'c'.
  NewSCCs = SCC.removeIntraSCCEdge(C, A);
  EXPECT_EQ(1u, NewSCCs.size());
  EXPECT_EQ(&SCC, CG1.lookupSCC(A));
  EXPECT_EQ(1, std::distance(SCC.begin(), SCC.end()));
  LazyCallGraph::SCC *SCC2 = CG1.lookupSCC(B);
  EXPECT_EQ(SCC2, CG1.lookupSCC(C));
  EXPECT_EQ(SCC2, NewSCCs[0]);
}

}