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/3rd_party/llvm/include/llvm/Analysis/CallGraph.h

https://code.google.com/p/softart/
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  1//===- CallGraph.h - Build a Module's call graph ----------------*- C++ -*-===//
  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 interface is used to build and manipulate a call graph, which is a very
 11// useful tool for interprocedural optimization.
 12//
 13// Every function in a module is represented as a node in the call graph.  The
 14// callgraph node keeps track of which functions the are called by the function
 15// corresponding to the node.
 16//
 17// A call graph may contain nodes where the function that they correspond to is
 18// null.  These 'external' nodes are used to represent control flow that is not
 19// represented (or analyzable) in the module.  In particular, this analysis
 20// builds one external node such that:
 21//   1. All functions in the module without internal linkage will have edges
 22//      from this external node, indicating that they could be called by
 23//      functions outside of the module.
 24//   2. All functions whose address is used for something more than a direct
 25//      call, for example being stored into a memory location will also have an
 26//      edge from this external node.  Since they may be called by an unknown
 27//      caller later, they must be tracked as such.
 28//
 29// There is a second external node added for calls that leave this module.
 30// Functions have a call edge to the external node iff:
 31//   1. The function is external, reflecting the fact that they could call
 32//      anything without internal linkage or that has its address taken.
 33//   2. The function contains an indirect function call.
 34//
 35// As an extension in the future, there may be multiple nodes with a null
 36// function.  These will be used when we can prove (through pointer analysis)
 37// that an indirect call site can call only a specific set of functions.
 38//
 39// Because of these properties, the CallGraph captures a conservative superset
 40// of all of the caller-callee relationships, which is useful for
 41// transformations.
 42//
 43// The CallGraph class also attempts to figure out what the root of the
 44// CallGraph is, which it currently does by looking for a function named 'main'.
 45// If no function named 'main' is found, the external node is used as the entry
 46// node, reflecting the fact that any function without internal linkage could
 47// be called into (which is common for libraries).
 48//
 49//===----------------------------------------------------------------------===//
 50
 51#ifndef LLVM_ANALYSIS_CALLGRAPH_H
 52#define LLVM_ANALYSIS_CALLGRAPH_H
 53
 54#include "llvm/ADT/GraphTraits.h"
 55#include "llvm/ADT/STLExtras.h"
 56#include "llvm/IR/Function.h"
 57#include "llvm/Pass.h"
 58#include "llvm/Support/CallSite.h"
 59#include "llvm/Support/IncludeFile.h"
 60#include "llvm/Support/ValueHandle.h"
 61#include <map>
 62
 63namespace llvm {
 64
 65class Function;
 66class Module;
 67class CallGraphNode;
 68
 69//===----------------------------------------------------------------------===//
 70// CallGraph class definition
 71//
 72class CallGraph : public ModulePass {
 73  Module *Mod;              // The module this call graph represents
 74
 75  typedef std::map<const Function *, CallGraphNode *> FunctionMapTy;
 76  FunctionMapTy FunctionMap;    // Map from a function to its node
 77
 78  // Root is root of the call graph, or the external node if a 'main' function
 79  // couldn't be found.
 80  //
 81  CallGraphNode *Root;
 82
 83  // ExternalCallingNode - This node has edges to all external functions and
 84  // those internal functions that have their address taken.
 85  CallGraphNode *ExternalCallingNode;
 86
 87  // CallsExternalNode - This node has edges to it from all functions making
 88  // indirect calls or calling an external function.
 89  CallGraphNode *CallsExternalNode;
 90
 91  /// Replace the function represented by this node by another.
 92  /// This does not rescan the body of the function, so it is suitable when
 93  /// splicing the body of one function to another while also updating all
 94  /// callers from the old function to the new.
 95  ///
 96  void spliceFunction(const Function *From, const Function *To);
 97
 98  // Add a function to the call graph, and link the node to all of the functions
 99  // that it calls.
100  void addToCallGraph(Function *F);
101
102public:
103  static char ID; // Class identification, replacement for typeinfo
104  //===---------------------------------------------------------------------
105  // Accessors.
106  //
107  typedef FunctionMapTy::iterator iterator;
108  typedef FunctionMapTy::const_iterator const_iterator;
109
110  /// getModule - Return the module the call graph corresponds to.
111  ///
112  Module &getModule() const { return *Mod; }
113
114  inline       iterator begin()       { return FunctionMap.begin(); }
115  inline       iterator end()         { return FunctionMap.end();   }
116  inline const_iterator begin() const { return FunctionMap.begin(); }
117  inline const_iterator end()   const { return FunctionMap.end();   }
118
119  // Subscripting operators, return the call graph node for the provided
120  // function
121  inline const CallGraphNode *operator[](const Function *F) const {
122    const_iterator I = FunctionMap.find(F);
123    assert(I != FunctionMap.end() && "Function not in callgraph!");
124    return I->second;
125  }
126  inline CallGraphNode *operator[](const Function *F) {
127    const_iterator I = FunctionMap.find(F);
128    assert(I != FunctionMap.end() && "Function not in callgraph!");
129    return I->second;
130  }
131
132  /// Returns the CallGraphNode which is used to represent undetermined calls
133  /// into the callgraph.
134  CallGraphNode *getExternalCallingNode() const { return ExternalCallingNode; }
135  CallGraphNode *getCallsExternalNode() const { return CallsExternalNode; }
136
137  /// Return the root/main method in the module, or some other root node, such
138  /// as the externalcallingnode.
139  CallGraphNode *getRoot() { return Root; }
140  const CallGraphNode *getRoot() const { return Root; }
141
142  //===---------------------------------------------------------------------
143  // Functions to keep a call graph up to date with a function that has been
144  // modified.
145  //
146
147  /// removeFunctionFromModule - Unlink the function from this module, returning
148  /// it.  Because this removes the function from the module, the call graph
149  /// node is destroyed.  This is only valid if the function does not call any
150  /// other functions (ie, there are no edges in it's CGN).  The easiest way to
151  /// do this is to dropAllReferences before calling this.
152  ///
153  Function *removeFunctionFromModule(CallGraphNode *CGN);
154
155  /// getOrInsertFunction - This method is identical to calling operator[], but
156  /// it will insert a new CallGraphNode for the specified function if one does
157  /// not already exist.
158  CallGraphNode *getOrInsertFunction(const Function *F);
159
160  CallGraph();
161  virtual ~CallGraph() { releaseMemory(); }
162  virtual void getAnalysisUsage(AnalysisUsage &AU) const;
163  virtual bool runOnModule(Module &M);
164  virtual void releaseMemory();
165
166  void print(raw_ostream &o, const Module *) const;
167  void dump() const;
168};
169
170//===----------------------------------------------------------------------===//
171// CallGraphNode class definition.
172//
173class CallGraphNode {
174  friend class CallGraph;
175  
176  AssertingVH<Function> F;
177
178  // CallRecord - This is a pair of the calling instruction (a call or invoke)
179  // and the callgraph node being called.
180public:
181  typedef std::pair<WeakVH, CallGraphNode*> CallRecord;
182private:
183  std::vector<CallRecord> CalledFunctions;
184  
185  /// NumReferences - This is the number of times that this CallGraphNode occurs
186  /// in the CalledFunctions array of this or other CallGraphNodes.
187  unsigned NumReferences;
188
189  CallGraphNode(const CallGraphNode &) LLVM_DELETED_FUNCTION;
190  void operator=(const CallGraphNode &) LLVM_DELETED_FUNCTION;
191 
192  void DropRef() { --NumReferences; }
193  void AddRef() { ++NumReferences; }
194public:
195  typedef std::vector<CallRecord> CalledFunctionsVector;
196
197  
198  // CallGraphNode ctor - Create a node for the specified function.
199  inline CallGraphNode(Function *f) : F(f), NumReferences(0) {}
200  ~CallGraphNode() {
201    assert(NumReferences == 0 && "Node deleted while references remain");
202  }
203  
204  //===---------------------------------------------------------------------
205  // Accessor methods.
206  //
207
208  typedef std::vector<CallRecord>::iterator iterator;
209  typedef std::vector<CallRecord>::const_iterator const_iterator;
210
211  // getFunction - Return the function that this call graph node represents.
212  Function *getFunction() const { return F; }
213
214  inline iterator begin() { return CalledFunctions.begin(); }
215  inline iterator end()   { return CalledFunctions.end();   }
216  inline const_iterator begin() const { return CalledFunctions.begin(); }
217  inline const_iterator end()   const { return CalledFunctions.end();   }
218  inline bool empty() const { return CalledFunctions.empty(); }
219  inline unsigned size() const { return (unsigned)CalledFunctions.size(); }
220
221  /// getNumReferences - Return the number of other CallGraphNodes in this
222  /// CallGraph that reference this node in their callee list.
223  unsigned getNumReferences() const { return NumReferences; }
224  
225  // Subscripting operator - Return the i'th called function.
226  //
227  CallGraphNode *operator[](unsigned i) const {
228    assert(i < CalledFunctions.size() && "Invalid index");
229    return CalledFunctions[i].second;
230  }
231
232  /// dump - Print out this call graph node.
233  ///
234  void dump() const;
235  void print(raw_ostream &OS) const;
236
237  //===---------------------------------------------------------------------
238  // Methods to keep a call graph up to date with a function that has been
239  // modified
240  //
241
242  /// removeAllCalledFunctions - As the name implies, this removes all edges
243  /// from this CallGraphNode to any functions it calls.
244  void removeAllCalledFunctions() {
245    while (!CalledFunctions.empty()) {
246      CalledFunctions.back().second->DropRef();
247      CalledFunctions.pop_back();
248    }
249  }
250  
251  /// stealCalledFunctionsFrom - Move all the callee information from N to this
252  /// node.
253  void stealCalledFunctionsFrom(CallGraphNode *N) {
254    assert(CalledFunctions.empty() &&
255           "Cannot steal callsite information if I already have some");
256    std::swap(CalledFunctions, N->CalledFunctions);
257  }
258  
259
260  /// addCalledFunction - Add a function to the list of functions called by this
261  /// one.
262  void addCalledFunction(CallSite CS, CallGraphNode *M) {
263    assert(!CS.getInstruction() ||
264           !CS.getCalledFunction() ||
265           !CS.getCalledFunction()->isIntrinsic());
266    CalledFunctions.push_back(std::make_pair(CS.getInstruction(), M));
267    M->AddRef();
268  }
269
270  void removeCallEdge(iterator I) {
271    I->second->DropRef();
272    *I = CalledFunctions.back();
273    CalledFunctions.pop_back();
274  }
275  
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.
280  void removeCallEdgeFor(CallSite CS);
281
282  /// removeAnyCallEdgeTo - This method removes all call edges from this node
283  /// to the specified callee function.  This takes more time to execute than
284  /// removeCallEdgeTo, so it should not be used unless necessary.
285  void removeAnyCallEdgeTo(CallGraphNode *Callee);
286
287  /// removeOneAbstractEdgeTo - Remove one edge associated with a null callsite
288  /// from this node to the specified callee function.
289  void removeOneAbstractEdgeTo(CallGraphNode *Callee);
290  
291  /// replaceCallEdge - This method replaces the edge in the node for the
292  /// specified call site with a new one.  Note that this method takes linear
293  /// time, so it should be used sparingly.
294  void replaceCallEdge(CallSite CS, CallSite NewCS, CallGraphNode *NewNode);
295  
296  /// allReferencesDropped - This is a special function that should only be
297  /// used by the CallGraph class.
298  void allReferencesDropped() {
299    NumReferences = 0;
300  }
301};
302
303//===----------------------------------------------------------------------===//
304// GraphTraits specializations for call graphs so that they can be treated as
305// graphs by the generic graph algorithms.
306//
307
308// Provide graph traits for tranversing call graphs using standard graph
309// traversals.
310template <> struct GraphTraits<CallGraphNode*> {
311  typedef CallGraphNode NodeType;
312
313  typedef CallGraphNode::CallRecord CGNPairTy;
314  typedef std::pointer_to_unary_function<CGNPairTy, CallGraphNode*> CGNDerefFun;
315
316  static NodeType *getEntryNode(CallGraphNode *CGN) { return CGN; }
317
318  typedef mapped_iterator<NodeType::iterator, CGNDerefFun> ChildIteratorType;
319
320  static inline ChildIteratorType child_begin(NodeType *N) {
321    return map_iterator(N->begin(), CGNDerefFun(CGNDeref));
322  }
323  static inline ChildIteratorType child_end  (NodeType *N) {
324    return map_iterator(N->end(), CGNDerefFun(CGNDeref));
325  }
326
327  static CallGraphNode *CGNDeref(CGNPairTy P) {
328    return P.second;
329  }
330
331};
332
333template <> struct GraphTraits<const CallGraphNode*> {
334  typedef const CallGraphNode NodeType;
335  typedef NodeType::const_iterator ChildIteratorType;
336
337  static NodeType *getEntryNode(const CallGraphNode *CGN) { return CGN; }
338  static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();}
339  static inline ChildIteratorType child_end  (NodeType *N) { return N->end(); }
340};
341
342template<> struct GraphTraits<CallGraph*> : public GraphTraits<CallGraphNode*> {
343  static NodeType *getEntryNode(CallGraph *CGN) {
344    return CGN->getExternalCallingNode();  // Start at the external node!
345  }
346  typedef std::pair<const Function*, CallGraphNode*> PairTy;
347  typedef std::pointer_to_unary_function<PairTy, CallGraphNode&> DerefFun;
348
349  // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
350  typedef mapped_iterator<CallGraph::iterator, DerefFun> nodes_iterator;
351  static nodes_iterator nodes_begin(CallGraph *CG) {
352    return map_iterator(CG->begin(), DerefFun(CGdereference));
353  }
354  static nodes_iterator nodes_end  (CallGraph *CG) {
355    return map_iterator(CG->end(), DerefFun(CGdereference));
356  }
357
358  static CallGraphNode &CGdereference(PairTy P) {
359    return *P.second;
360  }
361};
362
363template<> struct GraphTraits<const CallGraph*> :
364  public GraphTraits<const CallGraphNode*> {
365  static NodeType *getEntryNode(const CallGraph *CGN) {
366    return CGN->getExternalCallingNode();
367  }
368  // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
369  typedef CallGraph::const_iterator nodes_iterator;
370  static nodes_iterator nodes_begin(const CallGraph *CG) { return CG->begin(); }
371  static nodes_iterator nodes_end  (const CallGraph *CG) { return CG->end(); }
372};
373
374} // End llvm namespace
375
376// Make sure that any clients of this file link in CallGraph.cpp
377FORCE_DEFINING_FILE_TO_BE_LINKED(CallGraph)
378
379#endif