1//===- CallGraph.cpp - Build a Module's call graph ------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "llvm/Analysis/CallGraph.h"
10#include "llvm/ADT/STLExtras.h"
11#include "llvm/ADT/SmallVector.h"
12#include "llvm/Config/llvm-config.h"
13#include "llvm/IR/Function.h"
14#include "llvm/IR/Intrinsics.h"
15#include "llvm/IR/Module.h"
16#include "llvm/IR/PassManager.h"
17#include "llvm/InitializePasses.h"
18#include "llvm/Pass.h"
19#include "llvm/Support/Compiler.h"
20#include "llvm/Support/Debug.h"
21#include "llvm/Support/raw_ostream.h"
22#include <algorithm>
23#include <cassert>
24
25using namespace llvm;
26
27//===----------------------------------------------------------------------===//
28// Implementations of the CallGraph class methods.
29//
30
31CallGraph::CallGraph(Module &M)
32    : M(M), ExternalCallingNode(getOrInsertFunction(nullptr)),
33      CallsExternalNode(std::make_unique<CallGraphNode>(nullptr)) {
34  // Add every function to the call graph.
35  for (Function &F : M)
36    addToCallGraph(&F);
37}
38
39CallGraph::CallGraph(CallGraph &&Arg)
40    : M(Arg.M), FunctionMap(std::move(Arg.FunctionMap)),
41      ExternalCallingNode(Arg.ExternalCallingNode),
42      CallsExternalNode(std::move(Arg.CallsExternalNode)) {
43  Arg.FunctionMap.clear();
44  Arg.ExternalCallingNode = nullptr;
45}
46
47CallGraph::~CallGraph() {
48  // CallsExternalNode is not in the function map, delete it explicitly.
49  if (CallsExternalNode)
50    CallsExternalNode->allReferencesDropped();
51
52// Reset all node's use counts to zero before deleting them to prevent an
53// assertion from firing.
54#ifndef NDEBUG
55  for (auto &I : FunctionMap)
56    I.second->allReferencesDropped();
57#endif
58}
59
60void CallGraph::addToCallGraph(Function *F) {
61  CallGraphNode *Node = getOrInsertFunction(F);
62
63  // If this function has external linkage or has its address taken, anything
64  // could call it.
65  if (!F->hasLocalLinkage() || F->hasAddressTaken())
66    ExternalCallingNode->addCalledFunction(nullptr, Node);
67
68  // If this function is not defined in this translation unit, it could call
69  // anything.
70  if (F->isDeclaration() && !F->isIntrinsic())
71    Node->addCalledFunction(nullptr, CallsExternalNode.get());
72
73  // Look for calls by this function.
74  for (BasicBlock &BB : *F)
75    for (Instruction &I : BB) {
76      if (auto *Call = dyn_cast<CallBase>(&I)) {
77        const Function *Callee = Call->getCalledFunction();
78        if (!Callee || !Intrinsic::isLeaf(Callee->getIntrinsicID()))
79          // Indirect calls of intrinsics are not allowed so no need to check.
80          // We can be more precise here by using TargetArg returned by
81          // Intrinsic::isLeaf.
82          Node->addCalledFunction(Call, CallsExternalNode.get());
83        else if (!Callee->isIntrinsic())
84          Node->addCalledFunction(Call, getOrInsertFunction(Callee));
85      }
86    }
87}
88
89void CallGraph::print(raw_ostream &OS) const {
90  // Print in a deterministic order by sorting CallGraphNodes by name.  We do
91  // this here to avoid slowing down the non-printing fast path.
92
93  SmallVector<CallGraphNode *, 16> Nodes;
94  Nodes.reserve(FunctionMap.size());
95
96  for (const auto &I : *this)
97    Nodes.push_back(I.second.get());
98
99  llvm::sort(Nodes, [](CallGraphNode *LHS, CallGraphNode *RHS) {
100    if (Function *LF = LHS->getFunction())
101      if (Function *RF = RHS->getFunction())
102        return LF->getName() < RF->getName();
103
104    return RHS->getFunction() != nullptr;
105  });
106
107  for (CallGraphNode *CN : Nodes)
108    CN->print(OS);
109}
110
111#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
112LLVM_DUMP_METHOD void CallGraph::dump() const { print(dbgs()); }
113#endif
114
115// removeFunctionFromModule - Unlink the function from this module, returning
116// it.  Because this removes the function from the module, the call graph node
117// is destroyed.  This is only valid if the function does not call any other
118// functions (ie, there are no edges in it's CGN).  The easiest way to do this
119// is to dropAllReferences before calling this.
120//
121Function *CallGraph::removeFunctionFromModule(CallGraphNode *CGN) {
122  assert(CGN->empty() && "Cannot remove function from call "
123         "graph if it references other functions!");
124  Function *F = CGN->getFunction(); // Get the function for the call graph node
125  FunctionMap.erase(F);             // Remove the call graph node from the map
126
127  M.getFunctionList().remove(F);
128  return F;
129}
130
131/// spliceFunction - Replace the function represented by this node by another.
132/// This does not rescan the body of the function, so it is suitable when
133/// splicing the body of the old function to the new while also updating all
134/// callers from old to new.
135void CallGraph::spliceFunction(const Function *From, const Function *To) {
136  assert(FunctionMap.count(From) && "No CallGraphNode for function!");
137  assert(!FunctionMap.count(To) &&
138         "Pointing CallGraphNode at a function that already exists");
139  FunctionMapTy::iterator I = FunctionMap.find(From);
140  I->second->F = const_cast<Function*>(To);
141  FunctionMap[To] = std::move(I->second);
142  FunctionMap.erase(I);
143}
144
145// getOrInsertFunction - This method is identical to calling operator[], but
146// it will insert a new CallGraphNode for the specified function if one does
147// not already exist.
148CallGraphNode *CallGraph::getOrInsertFunction(const Function *F) {
149  auto &CGN = FunctionMap[F];
150  if (CGN)
151    return CGN.get();
152
153  assert((!F || F->getParent() == &M) && "Function not in current module!");
154  CGN = std::make_unique<CallGraphNode>(const_cast<Function *>(F));
155  return CGN.get();
156}
157
158//===----------------------------------------------------------------------===//
159// Implementations of the CallGraphNode class methods.
160//
161
162void CallGraphNode::print(raw_ostream &OS) const {
163  if (Function *F = getFunction())
164    OS << "Call graph node for function: '" << F->getName() << "'";
165  else
166    OS << "Call graph node <<null function>>";
167
168  OS << "<<" << this << ">>  #uses=" << getNumReferences() << '\n';
169
170  for (const auto &I : *this) {
171    OS << "  CS<" << I.first << "> calls ";
172    if (Function *FI = I.second->getFunction())
173      OS << "function '" << FI->getName() <<"'\n";
174    else
175      OS << "external node\n";
176  }
177  OS << '\n';
178}
179
180#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
181LLVM_DUMP_METHOD void CallGraphNode::dump() const { print(dbgs()); }
182#endif
183
184/// removeCallEdgeFor - This method removes the edge in the node for the
185/// specified call site.  Note that this method takes linear time, so it
186/// should be used sparingly.
187void CallGraphNode::removeCallEdgeFor(CallBase &Call) {
188  for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
189    assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
190    if (I->first == &Call) {
191      I->second->DropRef();
192      *I = CalledFunctions.back();
193      CalledFunctions.pop_back();
194      return;
195    }
196  }
197}
198
199// removeAnyCallEdgeTo - This method removes any call edges from this node to
200// the specified callee function.  This takes more time to execute than
201// removeCallEdgeTo, so it should not be used unless necessary.
202void CallGraphNode::removeAnyCallEdgeTo(CallGraphNode *Callee) {
203  for (unsigned i = 0, e = CalledFunctions.size(); i != e; ++i)
204    if (CalledFunctions[i].second == Callee) {
205      Callee->DropRef();
206      CalledFunctions[i] = CalledFunctions.back();
207      CalledFunctions.pop_back();
208      --i; --e;
209    }
210}
211
212/// removeOneAbstractEdgeTo - Remove one edge associated with a null callsite
213/// from this node to the specified callee function.
214void CallGraphNode::removeOneAbstractEdgeTo(CallGraphNode *Callee) {
215  for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
216    assert(I != CalledFunctions.end() && "Cannot find callee to remove!");
217    CallRecord &CR = *I;
218    if (CR.second == Callee && CR.first == nullptr) {
219      Callee->DropRef();
220      *I = CalledFunctions.back();
221      CalledFunctions.pop_back();
222      return;
223    }
224  }
225}
226
227/// replaceCallEdge - This method replaces the edge in the node for the
228/// specified call site with a new one.  Note that this method takes linear
229/// time, so it should be used sparingly.
230void CallGraphNode::replaceCallEdge(CallBase &Call, CallBase &NewCall,
231                                    CallGraphNode *NewNode) {
232  for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
233    assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
234    if (I->first == &Call) {
235      I->second->DropRef();
236      I->first = &NewCall;
237      I->second = NewNode;
238      NewNode->AddRef();
239      return;
240    }
241  }
242}
243
244// Provide an explicit template instantiation for the static ID.
245AnalysisKey CallGraphAnalysis::Key;
246
247PreservedAnalyses CallGraphPrinterPass::run(Module &M,
248                                            ModuleAnalysisManager &AM) {
249  AM.getResult<CallGraphAnalysis>(M).print(OS);
250  return PreservedAnalyses::all();
251}
252
253//===----------------------------------------------------------------------===//
254// Out-of-line definitions of CallGraphAnalysis class members.
255//
256
257//===----------------------------------------------------------------------===//
258// Implementations of the CallGraphWrapperPass class methods.
259//
260
261CallGraphWrapperPass::CallGraphWrapperPass() : ModulePass(ID) {
262  initializeCallGraphWrapperPassPass(*PassRegistry::getPassRegistry());
263}
264
265CallGraphWrapperPass::~CallGraphWrapperPass() = default;
266
267void CallGraphWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
268  AU.setPreservesAll();
269}
270
271bool CallGraphWrapperPass::runOnModule(Module &M) {
272  // All the real work is done in the constructor for the CallGraph.
273  G.reset(new CallGraph(M));
274  return false;
275}
276
277INITIALIZE_PASS(CallGraphWrapperPass, "basiccg", "CallGraph Construction",
278                false, true)
279
280char CallGraphWrapperPass::ID = 0;
281
282void CallGraphWrapperPass::releaseMemory() { G.reset(); }
283
284void CallGraphWrapperPass::print(raw_ostream &OS, const Module *) const {
285  if (!G) {
286    OS << "No call graph has been built!\n";
287    return;
288  }
289
290  // Just delegate.
291  G->print(OS);
292}
293
294#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
295LLVM_DUMP_METHOD
296void CallGraphWrapperPass::dump() const { print(dbgs(), nullptr); }
297#endif
298
299namespace {
300
301struct CallGraphPrinterLegacyPass : public ModulePass {
302  static char ID; // Pass ID, replacement for typeid
303
304  CallGraphPrinterLegacyPass() : ModulePass(ID) {
305    initializeCallGraphPrinterLegacyPassPass(*PassRegistry::getPassRegistry());
306  }
307
308  void getAnalysisUsage(AnalysisUsage &AU) const override {
309    AU.setPreservesAll();
310    AU.addRequiredTransitive<CallGraphWrapperPass>();
311  }
312
313  bool runOnModule(Module &M) override {
314    getAnalysis<CallGraphWrapperPass>().print(errs(), &M);
315    return false;
316  }
317};
318
319} // end anonymous namespace
320
321char CallGraphPrinterLegacyPass::ID = 0;
322
323INITIALIZE_PASS_BEGIN(CallGraphPrinterLegacyPass, "print-callgraph",
324                      "Print a call graph", true, true)
325INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
326INITIALIZE_PASS_END(CallGraphPrinterLegacyPass, "print-callgraph",
327                    "Print a call graph", true, true)
328