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/IR/Instructions.h"
17#include "llvm/IR/IntrinsicInst.h"
18#include "llvm/IR/Module.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) {
145          const Function *Callee = CS.getCalledFunction();
146          if (!Callee)
147            // Indirect calls of intrinsics are not allowed so no need to check.
148            Node->addCalledFunction(CS, CallsExternalNode);
149          else if (!Callee->isIntrinsic())
150            Node->addCalledFunction(CS, getOrInsertFunction(Callee));
151        }
152      }
153  }
154
155  //
156  // destroy - Release memory for the call graph
157  virtual void destroy() {
158    /// CallsExternalNode is not in the function map, delete it explicitly.
159    if (CallsExternalNode) {
160      CallsExternalNode->allReferencesDropped();
161      delete CallsExternalNode;
162      CallsExternalNode = 0;
163    }
164    CallGraph::destroy();
165  }
166};
167
168} //End anonymous namespace
169
170INITIALIZE_ANALYSIS_GROUP(CallGraph, "Call Graph", BasicCallGraph)
171INITIALIZE_AG_PASS(BasicCallGraph, CallGraph, "basiccg",
172                   "Basic CallGraph Construction", false, true, true)
173
174char CallGraph::ID = 0;
175char BasicCallGraph::ID = 0;
176
177void CallGraph::initialize(Module &M) {
178  Mod = &M;
179}
180
181void CallGraph::destroy() {
182  if (FunctionMap.empty()) return;
183
184  // Reset all node's use counts to zero before deleting them to prevent an
185  // assertion from firing.
186#ifndef NDEBUG
187  for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
188       I != E; ++I)
189    I->second->allReferencesDropped();
190#endif
191
192  for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
193      I != E; ++I)
194    delete I->second;
195  FunctionMap.clear();
196}
197
198void CallGraph::print(raw_ostream &OS, Module*) const {
199  for (CallGraph::const_iterator I = begin(), E = end(); I != E; ++I)
200    I->second->print(OS);
201}
202#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
203void CallGraph::dump() const {
204  print(dbgs(), 0);
205}
206#endif
207
208//===----------------------------------------------------------------------===//
209// Implementations of public modification methods
210//
211
212// removeFunctionFromModule - Unlink the function from this module, returning
213// it.  Because this removes the function from the module, the call graph node
214// is destroyed.  This is only valid if the function does not call any other
215// functions (ie, there are no edges in it's CGN).  The easiest way to do this
216// is to dropAllReferences before calling this.
217//
218Function *CallGraph::removeFunctionFromModule(CallGraphNode *CGN) {
219  assert(CGN->empty() && "Cannot remove function from call "
220         "graph if it references other functions!");
221  Function *F = CGN->getFunction(); // Get the function for the call graph node
222  delete CGN;                       // Delete the call graph node for this func
223  FunctionMap.erase(F);             // Remove the call graph node from the map
224
225  Mod->getFunctionList().remove(F);
226  return F;
227}
228
229/// spliceFunction - Replace the function represented by this node by another.
230/// This does not rescan the body of the function, so it is suitable when
231/// splicing the body of the old function to the new while also updating all
232/// callers from old to new.
233///
234void CallGraph::spliceFunction(const Function *From, const Function *To) {
235  assert(FunctionMap.count(From) && "No CallGraphNode for function!");
236  assert(!FunctionMap.count(To) &&
237         "Pointing CallGraphNode at a function that already exists");
238  FunctionMapTy::iterator I = FunctionMap.find(From);
239  I->second->F = const_cast<Function*>(To);
240  FunctionMap[To] = I->second;
241  FunctionMap.erase(I);
242}
243
244// getOrInsertFunction - This method is identical to calling operator[], but
245// it will insert a new CallGraphNode for the specified function if one does
246// not already exist.
247CallGraphNode *CallGraph::getOrInsertFunction(const Function *F) {
248  CallGraphNode *&CGN = FunctionMap[F];
249  if (CGN) return CGN;
250
251  assert((!F || F->getParent() == Mod) && "Function not in current module!");
252  return CGN = new CallGraphNode(const_cast<Function*>(F));
253}
254
255void CallGraphNode::print(raw_ostream &OS) const {
256  if (Function *F = getFunction())
257    OS << "Call graph node for function: '" << F->getName() << "'";
258  else
259    OS << "Call graph node <<null function>>";
260
261  OS << "<<" << this << ">>  #uses=" << getNumReferences() << '\n';
262
263  for (const_iterator I = begin(), E = end(); I != E; ++I) {
264    OS << "  CS<" << I->first << "> calls ";
265    if (Function *FI = I->second->getFunction())
266      OS << "function '" << FI->getName() <<"'\n";
267    else
268      OS << "external node\n";
269  }
270  OS << '\n';
271}
272
273#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
274void CallGraphNode::dump() const { print(dbgs()); }
275#endif
276
277/// removeCallEdgeFor - This method removes the edge in the node for the
278/// specified call site.  Note that this method takes linear time, so it
279/// should be used sparingly.
280void CallGraphNode::removeCallEdgeFor(CallSite CS) {
281  for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
282    assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
283    if (I->first == CS.getInstruction()) {
284      I->second->DropRef();
285      *I = CalledFunctions.back();
286      CalledFunctions.pop_back();
287      return;
288    }
289  }
290}
291
292// removeAnyCallEdgeTo - This method removes any call edges from this node to
293// the specified callee function.  This takes more time to execute than
294// removeCallEdgeTo, so it should not be used unless necessary.
295void CallGraphNode::removeAnyCallEdgeTo(CallGraphNode *Callee) {
296  for (unsigned i = 0, e = CalledFunctions.size(); i != e; ++i)
297    if (CalledFunctions[i].second == Callee) {
298      Callee->DropRef();
299      CalledFunctions[i] = CalledFunctions.back();
300      CalledFunctions.pop_back();
301      --i; --e;
302    }
303}
304
305/// removeOneAbstractEdgeTo - Remove one edge associated with a null callsite
306/// from this node to the specified callee function.
307void CallGraphNode::removeOneAbstractEdgeTo(CallGraphNode *Callee) {
308  for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
309    assert(I != CalledFunctions.end() && "Cannot find callee to remove!");
310    CallRecord &CR = *I;
311    if (CR.second == Callee && CR.first == 0) {
312      Callee->DropRef();
313      *I = CalledFunctions.back();
314      CalledFunctions.pop_back();
315      return;
316    }
317  }
318}
319
320/// replaceCallEdge - This method replaces the edge in the node for the
321/// specified call site with a new one.  Note that this method takes linear
322/// time, so it should be used sparingly.
323void CallGraphNode::replaceCallEdge(CallSite CS,
324                                    CallSite NewCS, CallGraphNode *NewNode){
325  for (CalledFunctionsVector::iterator I = CalledFunctions.begin(); ; ++I) {
326    assert(I != CalledFunctions.end() && "Cannot find callsite to remove!");
327    if (I->first == CS.getInstruction()) {
328      I->second->DropRef();
329      I->first = NewCS.getInstruction();
330      I->second = NewNode;
331      NewNode->AddRef();
332      return;
333    }
334  }
335}
336
337// Enuse that users of CallGraph.h also link with this file
338DEFINING_FILE_FOR(CallGraph)
339