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// This file implements the CallGraph class and provides the BasicCallGraph
11// default implementation.
12//
13//===----------------------------------------------------------------------===//
14
15#include "llvm/Analysis/CallGraph.h"
16#include "llvm/Module.h"
17#include "llvm/Instructions.h"
18#include "llvm/IntrinsicInst.h"
19#include "llvm/Support/CallSite.h"
20#include "llvm/Support/Debug.h"
21#include "llvm/Support/raw_ostream.h"
22using namespace llvm;
23
24namespace {
25
26//===----------------------------------------------------------------------===//
27// BasicCallGraph class definition
28//
29class BasicCallGraph : public ModulePass, public CallGraph {
30  // Root is root of the call graph, or the external node if a 'main' function
31  // couldn't be found.
32  //
33  CallGraphNode *Root;
34
35  // ExternalCallingNode - This node has edges to all external functions and
36  // those internal functions that have their address taken.
37  CallGraphNode *ExternalCallingNode;
38
39  // CallsExternalNode - This node has edges to it from all functions making
40  // indirect calls or calling an external function.
41  CallGraphNode *CallsExternalNode;
42
43public:
44  static char ID; // Class identification, replacement for typeinfo
45  BasicCallGraph() : ModulePass(ID), Root(0),
46    ExternalCallingNode(0), CallsExternalNode(0) {
47      initializeBasicCallGraphPass(*PassRegistry::getPassRegistry());
48    }
49
50  // runOnModule - Compute the call graph for the specified module.
51  virtual bool runOnModule(Module &M) {
52    CallGraph::initialize(M);
53
54    ExternalCallingNode = getOrInsertFunction(0);
55    CallsExternalNode = new CallGraphNode(0);
56    Root = 0;
57
58    // Add every function to the call graph.
59    for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
60      addToCallGraph(I);
61
62    // If we didn't find a main function, use the external call graph node
63    if (Root == 0) Root = ExternalCallingNode;
64
65    return false;
66  }
67
68  virtual void getAnalysisUsage(AnalysisUsage &AU) const {
69    AU.setPreservesAll();
70  }
71
72  virtual void print(raw_ostream &OS, const Module *) const {
73    OS << "CallGraph Root is: ";
74    if (Function *F = getRoot()->getFunction())
75      OS << F->getName() << "\n";
76    else {
77      OS << "<<null function: 0x" << getRoot() << ">>\n";
78    }
79
80    CallGraph::print(OS, 0);
81  }
82
83  virtual void releaseMemory() {
84    destroy();
85  }
86
87  /// getAdjustedAnalysisPointer - This method is used when a pass implements
88  /// an analysis interface through multiple inheritance.  If needed, it should
89  /// override this to adjust the this pointer as needed for the specified pass
90  /// info.
91  virtual void *getAdjustedAnalysisPointer(AnalysisID PI) {
92    if (PI == &CallGraph::ID)
93      return (CallGraph*)this;
94    return this;
95  }
96
97  CallGraphNode* getExternalCallingNode() const { return ExternalCallingNode; }
98  CallGraphNode* getCallsExternalNode()   const { return CallsExternalNode; }
99
100  // getRoot - Return the root of the call graph, which is either main, or if
101  // main cannot be found, the external node.
102  //
103  CallGraphNode *getRoot()             { return Root; }
104  const CallGraphNode *getRoot() const { return Root; }
105
106private:
107  //===---------------------------------------------------------------------
108  // Implementation of CallGraph construction
109  //
110
111  // addToCallGraph - Add a function to the call graph, and link the node to all
112  // of the functions that it calls.
113  //
114  void addToCallGraph(Function *F) {
115    CallGraphNode *Node = getOrInsertFunction(F);
116
117    // If this function has external linkage, anything could call it.
118    if (!F->hasLocalLinkage()) {
119      ExternalCallingNode->addCalledFunction(CallSite(), Node);
120
121      // Found the entry point?
122      if (F->getName() == "main") {
123        if (Root)    // Found multiple external mains?  Don't pick one.
124          Root = ExternalCallingNode;
125        else
126          Root = Node;          // Found a main, keep track of it!
127      }
128    }
129
130    // If this function has its address taken, anything could call it.
131    if (F->hasAddressTaken())
132      ExternalCallingNode->addCalledFunction(CallSite(), Node);
133
134    // If this function is not defined in this translation unit, it could call
135    // anything.
136    if (F->isDeclaration() && !F->isIntrinsic())
137      Node->addCalledFunction(CallSite(), CallsExternalNode);
138
139    // Look for calls by this function.
140    for (Function::iterator BB = F->begin(), BBE = F->end(); BB != BBE; ++BB)
141      for (BasicBlock::iterator II = BB->begin(), IE = BB->end();
142           II != IE; ++II) {
143        CallSite CS(cast<Value>(II));
144        if (CS && !isa<IntrinsicInst>(II)) {
145          const Function *Callee = CS.getCalledFunction();
146          if (Callee)
147            Node->addCalledFunction(CS, getOrInsertFunction(Callee));
148          else
149            Node->addCalledFunction(CS, CallsExternalNode);
150        }
151      }
152  }
153
154  //
155  // destroy - Release memory for the call graph
156  virtual void destroy() {
157    /// CallsExternalNode is not in the function map, delete it explicitly.
158    if (CallsExternalNode) {
159      CallsExternalNode->allReferencesDropped();
160      delete CallsExternalNode;
161      CallsExternalNode = 0;
162    }
163    CallGraph::destroy();
164  }
165};
166
167} //End anonymous namespace
168
169INITIALIZE_ANALYSIS_GROUP(CallGraph, "Call Graph", BasicCallGraph)
170INITIALIZE_AG_PASS(BasicCallGraph, CallGraph, "basiccg",
171                   "Basic CallGraph Construction", false, true, true)
172
173char CallGraph::ID = 0;
174char BasicCallGraph::ID = 0;
175
176void CallGraph::initialize(Module &M) {
177  Mod = &M;
178}
179
180void CallGraph::destroy() {
181  if (FunctionMap.empty()) return;
182
183  // Reset all node's use counts to zero before deleting them to prevent an
184  // assertion from firing.
185#ifndef NDEBUG
186  for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
187       I != E; ++I)
188    I->second->allReferencesDropped();
189#endif
190
191  for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
192      I != E; ++I)
193    delete I->second;
194  FunctionMap.clear();
195}
196
197void CallGraph::print(raw_ostream &OS, Module*) const {
198  for (CallGraph::const_iterator I = begin(), E = end(); I != E; ++I)
199    I->second->print(OS);
200}
201#ifndef NDEBUG
202void CallGraph::dump() const {
203  print(dbgs(), 0);
204}
205#endif
206
207//===----------------------------------------------------------------------===//
208// Implementations of public modification methods
209//
210
211// removeFunctionFromModule - Unlink the function from this module, returning
212// it.  Because this removes the function from the module, the call graph node
213// is destroyed.  This is only valid if the function does not call any other
214// functions (ie, there are no edges in it's CGN).  The easiest way to do this
215// is to dropAllReferences before calling this.
216//
217Function *CallGraph::removeFunctionFromModule(CallGraphNode *CGN) {
218  assert(CGN->empty() && "Cannot remove function from call "
219         "graph if it references other functions!");
220  Function *F = CGN->getFunction(); // Get the function for the call graph node
221  delete CGN;                       // Delete the call graph node for this func
222  FunctionMap.erase(F);             // Remove the call graph node from the map
223
224  Mod->getFunctionList().remove(F);
225  return F;
226}
227
228/// spliceFunction - Replace the function represented by this node by another.
229/// This does not rescan the body of the function, so it is suitable when
230/// splicing the body of the old function to the new while also updating all
231/// callers from old to new.
232///
233void CallGraph::spliceFunction(const Function *From, const Function *To) {
234  assert(FunctionMap.count(From) && "No CallGraphNode for function!");
235  assert(!FunctionMap.count(To) &&
236         "Pointing CallGraphNode at a function that already exists");
237  FunctionMapTy::iterator I = FunctionMap.find(From);
238  I->second->F = const_cast<Function*>(To);
239  FunctionMap[To] = I->second;
240  FunctionMap.erase(I);
241}
242
243// getOrInsertFunction - This method is identical to calling operator[], but
244// it will insert a new CallGraphNode for the specified function if one does
245// not already exist.
246CallGraphNode *CallGraph::getOrInsertFunction(const Function *F) {
247  CallGraphNode *&CGN = FunctionMap[F];
248  if (CGN) return CGN;
249
250  assert((!F || F->getParent() == Mod) && "Function not in current module!");
251  return CGN = new CallGraphNode(const_cast<Function*>(F));
252}
253
254void CallGraphNode::print(raw_ostream &OS) const {
255  if (Function *F = getFunction())
256    OS << "Call graph node for function: '" << F->getName() << "'";
257  else
258    OS << "Call graph node <<null function>>";
259
260  OS << "<<" << this << ">>  #uses=" << getNumReferences() << '\n';
261
262  for (const_iterator I = begin(), E = end(); I != E; ++I) {
263    OS << "  CS<" << I->first << "> calls ";
264    if (Function *FI = I->second->getFunction())
265      OS << "function '" << FI->getName() <<"'\n";
266    else
267      OS << "external node\n";
268  }
269  OS << '\n';
270}
271
272#ifndef NDEBUG
273void CallGraphNode::dump() const { print(dbgs()); }
274#endif
275
276/// removeCallEdgeFor - This method removes the edge in the node for the
277/// specified call site.  Note that this method takes linear time, so it
278/// should be used sparingly.
279void CallGraphNode::removeCallEdgeFor(CallSite CS) {
280  for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
281    assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
282    if (I->first == CS.getInstruction()) {
283      I->second->DropRef();
284      *I = CalledFunctions.back();
285      CalledFunctions.pop_back();
286      return;
287    }
288  }
289}
290
291// removeAnyCallEdgeTo - This method removes any call edges from this node to
292// the specified callee function.  This takes more time to execute than
293// removeCallEdgeTo, so it should not be used unless necessary.
294void CallGraphNode::removeAnyCallEdgeTo(CallGraphNode *Callee) {
295  for (unsigned i = 0, e = CalledFunctions.size(); i != e; ++i)
296    if (CalledFunctions[i].second == Callee) {
297      Callee->DropRef();
298      CalledFunctions[i] = CalledFunctions.back();
299      CalledFunctions.pop_back();
300      --i; --e;
301    }
302}
303
304/// removeOneAbstractEdgeTo - Remove one edge associated with a null callsite
305/// from this node to the specified callee function.
306void CallGraphNode::removeOneAbstractEdgeTo(CallGraphNode *Callee) {
307  for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
308    assert(I != CalledFunctions.end() && "Cannot find callee to remove!");
309    CallRecord &CR = *I;
310    if (CR.second == Callee && CR.first == 0) {
311      Callee->DropRef();
312      *I = CalledFunctions.back();
313      CalledFunctions.pop_back();
314      return;
315    }
316  }
317}
318
319/// replaceCallEdge - This method replaces the edge in the node for the
320/// specified call site with a new one.  Note that this method takes linear
321/// time, so it should be used sparingly.
322void CallGraphNode::replaceCallEdge(CallSite CS,
323                                    CallSite NewCS, CallGraphNode *NewNode){
324  for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
325    assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
326    if (I->first == CS.getInstruction()) {
327      I->second->DropRef();
328      I->first = NewCS.getInstruction();
329      I->second = NewNode;
330      NewNode->AddRef();
331      return;
332    }
333  }
334}
335
336// Enuse that users of CallGraph.h also link with this file
337DEFINING_FILE_FOR(CallGraph)
338