1//===- CallGraph.cpp - Build a Module's call graph ------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#include "llvm/Analysis/CallGraph.h"
11#include "llvm/IR/CallSite.h"
12#include "llvm/IR/Instructions.h"
13#include "llvm/IR/IntrinsicInst.h"
14#include "llvm/IR/Module.h"
15#include "llvm/Support/Debug.h"
16#include "llvm/Support/raw_ostream.h"
17using namespace llvm;
18
19//===----------------------------------------------------------------------===//
20// Implementations of the CallGraph class methods.
21//
22
23CallGraph::CallGraph(Module &M)
24    : M(M), Root(nullptr), ExternalCallingNode(getOrInsertFunction(nullptr)),
25      CallsExternalNode(llvm::make_unique<CallGraphNode>(nullptr)) {
26  // Add every function to the call graph.
27  for (Function &F : M)
28    addToCallGraph(&F);
29
30  // If we didn't find a main function, use the external call graph node
31  if (!Root)
32    Root = ExternalCallingNode;
33}
34
35CallGraph::CallGraph(CallGraph &&Arg)
36    : M(Arg.M), FunctionMap(std::move(Arg.FunctionMap)), Root(Arg.Root),
37      ExternalCallingNode(Arg.ExternalCallingNode),
38      CallsExternalNode(std::move(Arg.CallsExternalNode)) {
39  Arg.FunctionMap.clear();
40  Arg.Root = nullptr;
41  Arg.ExternalCallingNode = nullptr;
42}
43
44CallGraph::~CallGraph() {
45  // CallsExternalNode is not in the function map, delete it explicitly.
46  if (CallsExternalNode)
47    CallsExternalNode->allReferencesDropped();
48
49// Reset all node's use counts to zero before deleting them to prevent an
50// assertion from firing.
51#ifndef NDEBUG
52  for (auto &I : FunctionMap)
53    I.second->allReferencesDropped();
54#endif
55}
56
57void CallGraph::addToCallGraph(Function *F) {
58  CallGraphNode *Node = getOrInsertFunction(F);
59
60  // If this function has external linkage, anything could call it.
61  if (!F->hasLocalLinkage()) {
62    ExternalCallingNode->addCalledFunction(CallSite(), Node);
63
64    // Found the entry point?
65    if (F->getName() == "main") {
66      if (Root) // Found multiple external mains?  Don't pick one.
67        Root = ExternalCallingNode;
68      else
69        Root = Node; // Found a main, keep track of it!
70    }
71  }
72
73  // If this function has its address taken, anything could call it.
74  if (F->hasAddressTaken())
75    ExternalCallingNode->addCalledFunction(CallSite(), Node);
76
77  // If this function is not defined in this translation unit, it could call
78  // anything.
79  if (F->isDeclaration() && !F->isIntrinsic())
80    Node->addCalledFunction(CallSite(), CallsExternalNode.get());
81
82  // Look for calls by this function.
83  for (BasicBlock &BB : *F)
84    for (Instruction &I : BB) {
85      if (auto CS = CallSite(&I)) {
86        const Function *Callee = CS.getCalledFunction();
87        if (!Callee || !Intrinsic::isLeaf(Callee->getIntrinsicID()))
88          // Indirect calls of intrinsics are not allowed so no need to check.
89          // We can be more precise here by using TargetArg returned by
90          // Intrinsic::isLeaf.
91          Node->addCalledFunction(CS, CallsExternalNode.get());
92        else if (!Callee->isIntrinsic())
93          Node->addCalledFunction(CS, getOrInsertFunction(Callee));
94      }
95    }
96}
97
98void CallGraph::print(raw_ostream &OS) const {
99  OS << "CallGraph Root is: ";
100  if (Function *F = Root->getFunction())
101    OS << F->getName() << "\n";
102  else {
103    OS << "<<null function: 0x" << Root << ">>\n";
104  }
105
106  // Print in a deterministic order by sorting CallGraphNodes by name.  We do
107  // this here to avoid slowing down the non-printing fast path.
108
109  SmallVector<CallGraphNode *, 16> Nodes;
110  Nodes.reserve(FunctionMap.size());
111
112  for (const auto &I : *this)
113    Nodes.push_back(I.second.get());
114
115  std::sort(Nodes.begin(), Nodes.end(),
116            [](CallGraphNode *LHS, CallGraphNode *RHS) {
117    if (Function *LF = LHS->getFunction())
118      if (Function *RF = RHS->getFunction())
119        return LF->getName() < RF->getName();
120
121    return RHS->getFunction() != nullptr;
122  });
123
124  for (CallGraphNode *CN : Nodes)
125    CN->print(OS);
126}
127
128LLVM_DUMP_METHOD
129void CallGraph::dump() const { print(dbgs()); }
130
131// removeFunctionFromModule - Unlink the function from this module, returning
132// it.  Because this removes the function from the module, the call graph node
133// is destroyed.  This is only valid if the function does not call any other
134// functions (ie, there are no edges in it's CGN).  The easiest way to do this
135// is to dropAllReferences before calling this.
136//
137Function *CallGraph::removeFunctionFromModule(CallGraphNode *CGN) {
138  assert(CGN->empty() && "Cannot remove function from call "
139         "graph if it references other functions!");
140  Function *F = CGN->getFunction(); // Get the function for the call graph node
141  FunctionMap.erase(F);             // Remove the call graph node from the map
142
143  M.getFunctionList().remove(F);
144  return F;
145}
146
147/// spliceFunction - Replace the function represented by this node by another.
148/// This does not rescan the body of the function, so it is suitable when
149/// splicing the body of the old function to the new while also updating all
150/// callers from old to new.
151///
152void CallGraph::spliceFunction(const Function *From, const Function *To) {
153  assert(FunctionMap.count(From) && "No CallGraphNode for function!");
154  assert(!FunctionMap.count(To) &&
155         "Pointing CallGraphNode at a function that already exists");
156  FunctionMapTy::iterator I = FunctionMap.find(From);
157  I->second->F = const_cast<Function*>(To);
158  FunctionMap[To] = std::move(I->second);
159  FunctionMap.erase(I);
160}
161
162// getOrInsertFunction - This method is identical to calling operator[], but
163// it will insert a new CallGraphNode for the specified function if one does
164// not already exist.
165CallGraphNode *CallGraph::getOrInsertFunction(const Function *F) {
166  auto &CGN = FunctionMap[F];
167  if (CGN)
168    return CGN.get();
169
170  assert((!F || F->getParent() == &M) && "Function not in current module!");
171  CGN = llvm::make_unique<CallGraphNode>(const_cast<Function *>(F));
172  return CGN.get();
173}
174
175//===----------------------------------------------------------------------===//
176// Implementations of the CallGraphNode class methods.
177//
178
179void CallGraphNode::print(raw_ostream &OS) const {
180  if (Function *F = getFunction())
181    OS << "Call graph node for function: '" << F->getName() << "'";
182  else
183    OS << "Call graph node <<null function>>";
184
185  OS << "<<" << this << ">>  #uses=" << getNumReferences() << '\n';
186
187  for (const auto &I : *this) {
188    OS << "  CS<" << I.first << "> calls ";
189    if (Function *FI = I.second->getFunction())
190      OS << "function '" << FI->getName() <<"'\n";
191    else
192      OS << "external node\n";
193  }
194  OS << '\n';
195}
196
197LLVM_DUMP_METHOD
198void CallGraphNode::dump() const { print(dbgs()); }
199
200/// removeCallEdgeFor - This method removes the edge in the node for the
201/// specified call site.  Note that this method takes linear time, so it
202/// should be used sparingly.
203void CallGraphNode::removeCallEdgeFor(CallSite CS) {
204  for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
205    assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
206    if (I->first == CS.getInstruction()) {
207      I->second->DropRef();
208      *I = CalledFunctions.back();
209      CalledFunctions.pop_back();
210      return;
211    }
212  }
213}
214
215// removeAnyCallEdgeTo - This method removes any call edges from this node to
216// the specified callee function.  This takes more time to execute than
217// removeCallEdgeTo, so it should not be used unless necessary.
218void CallGraphNode::removeAnyCallEdgeTo(CallGraphNode *Callee) {
219  for (unsigned i = 0, e = CalledFunctions.size(); i != e; ++i)
220    if (CalledFunctions[i].second == Callee) {
221      Callee->DropRef();
222      CalledFunctions[i] = CalledFunctions.back();
223      CalledFunctions.pop_back();
224      --i; --e;
225    }
226}
227
228/// removeOneAbstractEdgeTo - Remove one edge associated with a null callsite
229/// from this node to the specified callee function.
230void CallGraphNode::removeOneAbstractEdgeTo(CallGraphNode *Callee) {
231  for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
232    assert(I != CalledFunctions.end() && "Cannot find callee to remove!");
233    CallRecord &CR = *I;
234    if (CR.second == Callee && CR.first == nullptr) {
235      Callee->DropRef();
236      *I = CalledFunctions.back();
237      CalledFunctions.pop_back();
238      return;
239    }
240  }
241}
242
243/// replaceCallEdge - This method replaces the edge in the node for the
244/// specified call site with a new one.  Note that this method takes linear
245/// time, so it should be used sparingly.
246void CallGraphNode::replaceCallEdge(CallSite CS,
247                                    CallSite NewCS, CallGraphNode *NewNode){
248  for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
249    assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
250    if (I->first == CS.getInstruction()) {
251      I->second->DropRef();
252      I->first = NewCS.getInstruction();
253      I->second = NewNode;
254      NewNode->AddRef();
255      return;
256    }
257  }
258}
259
260// Provide an explicit template instantiation for the static ID.
261char CallGraphAnalysis::PassID;
262
263PreservedAnalyses CallGraphPrinterPass::run(Module &M,
264                                            AnalysisManager<Module> &AM) {
265  AM.getResult<CallGraphAnalysis>(M).print(OS);
266  return PreservedAnalyses::all();
267}
268
269//===----------------------------------------------------------------------===//
270// Out-of-line definitions of CallGraphAnalysis class members.
271//
272
273//===----------------------------------------------------------------------===//
274// Implementations of the CallGraphWrapperPass class methods.
275//
276
277CallGraphWrapperPass::CallGraphWrapperPass() : ModulePass(ID) {
278  initializeCallGraphWrapperPassPass(*PassRegistry::getPassRegistry());
279}
280
281CallGraphWrapperPass::~CallGraphWrapperPass() {}
282
283void CallGraphWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
284  AU.setPreservesAll();
285}
286
287bool CallGraphWrapperPass::runOnModule(Module &M) {
288  // All the real work is done in the constructor for the CallGraph.
289  G.reset(new CallGraph(M));
290  return false;
291}
292
293INITIALIZE_PASS(CallGraphWrapperPass, "basiccg", "CallGraph Construction",
294                false, true)
295
296char CallGraphWrapperPass::ID = 0;
297
298void CallGraphWrapperPass::releaseMemory() { G.reset(); }
299
300void CallGraphWrapperPass::print(raw_ostream &OS, const Module *) const {
301  if (!G) {
302    OS << "No call graph has been built!\n";
303    return;
304  }
305
306  // Just delegate.
307  G->print(OS);
308}
309
310LLVM_DUMP_METHOD
311void CallGraphWrapperPass::dump() const { print(dbgs(), nullptr); }
312
313namespace {
314struct CallGraphPrinterLegacyPass : public ModulePass {
315  static char ID; // Pass ID, replacement for typeid
316  CallGraphPrinterLegacyPass() : ModulePass(ID) {
317    initializeCallGraphPrinterLegacyPassPass(*PassRegistry::getPassRegistry());
318  }
319
320  void getAnalysisUsage(AnalysisUsage &AU) const override {
321    AU.setPreservesAll();
322    AU.addRequiredTransitive<CallGraphWrapperPass>();
323  }
324  bool runOnModule(Module &M) override {
325    getAnalysis<CallGraphWrapperPass>().print(errs(), &M);
326    return false;
327  }
328};
329}
330
331char CallGraphPrinterLegacyPass::ID = 0;
332
333INITIALIZE_PASS_BEGIN(CallGraphPrinterLegacyPass, "print-callgraph",
334                      "Print a call graph", true, true)
335INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
336INITIALIZE_PASS_END(CallGraphPrinterLegacyPass, "print-callgraph",
337                    "Print a call graph", true, true)
338