Add a basic CallGraph to Analysis.

The final graph contains a single root node, which is a parent of all externally available functions(and 'main'). As well as a list of Parentless/Unreachable functions, which are either truly unreachable or are unreachable due to our analyses imprecision.

The analyzer checkers debug.DumpCallGraph or debug.ViewGraph can be used to look at the produced graph.

Currently, the graph is not very precise, for example, it entirely skips edges resulted from ObjC method calls.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@152272 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Analysis/CallGraph.h

@@ -0,0 +1,216 @@
+//== CallGraph.h - AST-based Call graph  ------------------------*- C++ -*--==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file declares the AST-based CallGraph.
+//
+//  A call graph for functions whose definitions/bodies are available in the
+//  current translation unit. The graph has a "virtual" root node that contains
+//  edges to all externally available functions.
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_ANALYSIS_CALLGRAPH
+#define LLVM_CLANG_ANALYSIS_CALLGRAPH
+
+#include "clang/AST/DeclBase.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/GraphTraits.h"
+#include "llvm/ADT/SetVector.h"
+
+namespace clang {
+class CallGraphNode;
+
+class CallGraph {
+  friend class CallGraphNode;
+  typedef llvm::DenseMap<Decl *, CallGraphNode *> FunctionMapTy;
+
+  /// FunctionMap owns all CallGraphNodes.
+  FunctionMapTy FunctionMap;
+
+  /// This is a virtual root node that has edges to all the global functions -
+  /// 'main' or functions accessible from other translation units.
+  CallGraphNode *Root;
+
+  /// The list of nodes that have no parent. These are unreachable from Root.
+  /// Declarations can get to this list due to impressions in the graph, for
+  /// example, we do not track functions whose addresses were taken.
+  llvm::SetVector<CallGraphNode *> ParentlessNodes;
+
+public:
+  CallGraph();
+  ~CallGraph();
+
+  /// \brief Add the given declaration to the call graph.
+  void addToCallGraph(Decl *D, bool IsGlobal);
+
+  /// \brief Populate the call graph with the functions in the given DeclContext.
+  void addToCallGraph(DeclContext *DC);
+
+  /// \brief Lookup the node for the given declaration. If none found, insert
+  /// one into the graph.
+  CallGraphNode *getOrInsertFunction(Decl *);
+
+  /// Iterators through all the elements in the graph. Note, this gives
+  /// non-deterministic order.
+  typedef FunctionMapTy::iterator iterator;
+  typedef FunctionMapTy::const_iterator const_iterator;
+  iterator begin() { return FunctionMap.begin(); }
+  iterator end()   { return FunctionMap.end();   }
+  const_iterator begin() const { return FunctionMap.begin(); }
+  const_iterator end()   const { return FunctionMap.end();   }
+
+  /// \brief Get the number of nodes in the graph.
+  unsigned size() const { return FunctionMap.size(); }
+
+  /// \ brief Get the virtual root of the graph, all the functions available
+  /// externally are represented as callees of the node.
+  CallGraphNode *getRoot() const { return Root; }
+
+  /// Iterators through all the nodes of the graph that have no parent. These
+  /// are the unreachable nodes, which are either unused or are due to us
+  /// failing to add a call edge due to the analysis imprecision.
+  typedef llvm::SetVector<CallGraphNode *>::iterator nodes_iterator;
+  typedef llvm::SetVector<CallGraphNode *>::const_iterator const_nodes_iterator;
+  nodes_iterator parentless_begin() { return ParentlessNodes.begin(); }
+  nodes_iterator parentless_end() { return ParentlessNodes.end(); }
+  const_nodes_iterator
+    parentless_begin() const { return ParentlessNodes.begin(); }
+  const_nodes_iterator
+    parentless_end() const { return ParentlessNodes.end(); }
+
+  void print(raw_ostream &os) const;
+  void dump() const;
+  void viewGraph() const;
+};
+
+class CallGraphNode {
+public:
+  typedef CallGraphNode* CallRecord;
+
+private:
+  /// \brief The function/method declaration.
+  Decl *FD;
+
+  /// \brief The list of functions called from this node.
+  // Small vector might be more efficient since we are only tracking functions
+  // whose definition is in the current TU.
+  llvm::SmallVector<CallRecord, 5> CalledFunctions;
+
+public:
+  CallGraphNode(Decl *D) : FD(D) {}
+
+  typedef llvm::SmallVector<CallRecord, 5>::iterator iterator;
+  typedef llvm::SmallVector<CallRecord, 5>::const_iterator const_iterator;
+
+  /// Iterators through all the callees/children of the node.
+  inline iterator begin() { return CalledFunctions.begin(); }
+  inline iterator end()   { return CalledFunctions.end(); }
+  inline const_iterator begin() const { return CalledFunctions.begin(); }
+  inline const_iterator end()   const { return CalledFunctions.end();   }
+
+  inline bool empty() const {return CalledFunctions.empty(); }
+  inline unsigned size() const {return CalledFunctions.size(); }
+
+  void addCallee(CallGraphNode *N, CallGraph *CG) {
+    CalledFunctions.push_back(N);
+    CG->ParentlessNodes.remove(N);
+  }
+
+  Decl *getDecl() const { return FD; }
+
+  StringRef getName() const;
+
+  void print(raw_ostream &os) const;
+  void dump() const;
+};
+
+} // end clang namespace
+
+// Graph traits for iteration, viewing.
+namespace llvm {
+template <> struct GraphTraits<clang::CallGraphNode*> {
+  typedef clang::CallGraphNode NodeType;
+  typedef clang::CallGraphNode::CallRecord CallRecordTy;
+  typedef std::pointer_to_unary_function<CallRecordTy,
+                                         clang::CallGraphNode*> CGNDerefFun;
+  static NodeType *getEntryNode(clang::CallGraphNode *CGN) { return CGN; }
+  typedef mapped_iterator<NodeType::iterator, CGNDerefFun> ChildIteratorType;
+  static inline ChildIteratorType child_begin(NodeType *N) {
+    return map_iterator(N->begin(), CGNDerefFun(CGNDeref));
+  }
+  static inline ChildIteratorType child_end  (NodeType *N) {
+    return map_iterator(N->end(), CGNDerefFun(CGNDeref));
+  }
+  static clang::CallGraphNode *CGNDeref(CallRecordTy P) {
+    return P;
+  }
+};
+
+template <> struct GraphTraits<const clang::CallGraphNode*> {
+  typedef const clang::CallGraphNode NodeType;
+  typedef NodeType::const_iterator ChildIteratorType;
+  static NodeType *getEntryNode(const clang::CallGraphNode *CGN) { return CGN; }
+  static inline ChildIteratorType child_begin(NodeType *N) { return N->begin();}
+  static inline ChildIteratorType child_end  (NodeType *N) { return N->end(); }
+};
+
+template <> struct GraphTraits<clang::CallGraph*>
+  : public GraphTraits<clang::CallGraphNode*> {
+
+  static NodeType *getEntryNode(clang::CallGraph *CGN) {
+    return CGN->getRoot();  // Start at the external node!
+  }
+  typedef std::pair<clang::Decl*, clang::CallGraphNode*> PairTy;
+  typedef std::pointer_to_unary_function<PairTy, clang::CallGraphNode&> DerefFun;
+  // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
+  typedef mapped_iterator<clang::CallGraph::iterator, DerefFun> nodes_iterator;
+
+  static nodes_iterator nodes_begin(clang::CallGraph *CG) {
+    return map_iterator(CG->begin(), DerefFun(CGdereference));
+  }
+  static nodes_iterator nodes_end  (clang::CallGraph *CG) {
+    return map_iterator(CG->end(), DerefFun(CGdereference));
+  }
+  static clang::CallGraphNode &CGdereference(PairTy P) {
+    return *(P.second);
+  }
+
+  static unsigned size(clang::CallGraph *CG) {
+    return CG->size();
+  }
+};
+
+template <> struct GraphTraits<const clang::CallGraph*> :
+  public GraphTraits<const clang::CallGraphNode*> {
+  static NodeType *getEntryNode(const clang::CallGraph *CGN) {
+    return CGN->getRoot();
+  }
+  typedef std::pair<clang::Decl*, clang::CallGraphNode*> PairTy;
+  typedef std::pointer_to_unary_function<PairTy, clang::CallGraphNode&> DerefFun;
+  // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
+  typedef mapped_iterator<clang::CallGraph::const_iterator,
+                          DerefFun> nodes_iterator;
+
+  static nodes_iterator nodes_begin(const clang::CallGraph *CG) {
+    return map_iterator(CG->begin(), DerefFun(CGdereference));
+  }
+  static nodes_iterator nodes_end(const clang::CallGraph *CG) {
+    return map_iterator(CG->end(), DerefFun(CGdereference));
+  }
+  static clang::CallGraphNode &CGdereference(PairTy P) {
+    return *(P.second);
+  }
+
+  static unsigned size(const clang::CallGraph *CG) {
+    return CG->size();
+  }
+};
+
+} // end llvm namespace
+
+#endif

lib/Analysis/CMakeLists.txt

@@ -2,6 +2,7 @@ set(LLVM_USED_LIBS clangBasic clangAST clangIndex)
 
 add_clang_library(clangAnalysis
   AnalysisDeclContext.cpp
+  CallGraph.cpp
   CFG.cpp
   CFGReachabilityAnalysis.cpp
   CFGStmtMap.cpp

lib/Analysis/CallGraph.cpp

@@ -0,0 +1,207 @@
+//== CallGraph.cpp - AST-based Call graph  ----------------------*- C++ -*--==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines the AST-based CallGraph.
+//
+//===----------------------------------------------------------------------===//
+#include "clang/Analysis/CallGraph.h"
+
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/StmtVisitor.h"
+
+#include "llvm/Support/GraphWriter.h"
+
+using namespace clang;
+
+/// Determine if a declaration should be included in the graph.
+static bool includeInGraph(const Decl *D) {
+  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
+    // We skip function template definitions, as their semantics is
+    // only determined when they are instantiated.
+    if (!FD->isThisDeclarationADefinition() ||
+        FD->isDependentContext())
+      return false;
+
+    IdentifierInfo *II = FD->getIdentifier();
+    if (II && II->getName().startswith("__inline"))
+      return false;
+  }
+
+  if (const ObjCMethodDecl *ID = dyn_cast<ObjCMethodDecl>(D)) {
+    if (!ID->isThisDeclarationADefinition())
+      return false;
+  }
+
+  return true;
+}
+
+namespace {
+/// A helper class, which walks the AST and locates all the call sites in the
+/// given function body.
+class CGBuilder : public StmtVisitor<CGBuilder> {
+  CallGraph *G;
+  const Decl *FD;
+  CallGraphNode *CallerNode;
+
+public:
+  CGBuilder(CallGraph *g, const Decl *D, CallGraphNode *N)
+    : G(g), FD(D), CallerNode(N) {}
+
+  void VisitStmt(Stmt *S) { VisitChildren(S); }
+
+  void VisitCallExpr(CallExpr *CE) {
+    // TODO: We need to handle ObjC method calls as well.
+    if (FunctionDecl *CalleeDecl = CE->getDirectCallee())
+      if (includeInGraph(CalleeDecl)) {
+        CallGraphNode *CalleeNode = G->getOrInsertFunction(CalleeDecl);
+        CallerNode->addCallee(CalleeNode, G);
+      }
+  };
+
+  void VisitChildren(Stmt *S) {
+    for (Stmt::child_range I = S->children(); I; ++I)
+      if (*I)
+        static_cast<CGBuilder*>(this)->Visit(*I);
+  }
+};
+} // end anonymous namespace
+
+CallGraph::CallGraph() {
+  Root = getOrInsertFunction(0);
+}
+
+CallGraph::~CallGraph() {
+  if (!FunctionMap.empty()) {
+    for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
+        I != E; ++I)
+      delete I->second;
+    FunctionMap.clear();
+  }
+}
+
+void CallGraph::addToCallGraph(Decl* D, bool IsGlobal) {
+  CallGraphNode *Node = getOrInsertFunction(D);
+
+  if (IsGlobal)
+    Root->addCallee(Node, this);
+
+  // Process all the calls by this function as well.
+  CGBuilder builder(this, D, Node);
+  builder.Visit(D->getBody());
+}
+
+void CallGraph::addToCallGraph(DeclContext *DC) {
+  for (DeclContext::decl_iterator I = DC->decls_begin(), E = DC->decls_end();
+       I != E; ++I) {
+    Decl *D = *I;
+    switch (D->getKind()) {
+    case Decl::CXXConstructor:
+    case Decl::CXXDestructor:
+    case Decl::CXXConversion:
+    case Decl::CXXMethod:
+    case Decl::Function: {
+      FunctionDecl *FD = cast<FunctionDecl>(D);
+      // We skip function template definitions, as their semantics is
+      // only determined when they are instantiated.
+      if (includeInGraph(FD))
+        // If this function has external linkage, anything could call it.
+        // Note, we are not precise here. For example, the function could have
+        // its address taken.
+        addToCallGraph(FD, FD->isGlobal());
+      break;
+    }
+
+    case Decl::ObjCCategoryImpl:
+    case Decl::ObjCImplementation: {
+      ObjCImplDecl *ID = cast<ObjCImplDecl>(D);
+      for (ObjCContainerDecl::method_iterator MI = ID->meth_begin(),
+          ME = ID->meth_end(); MI != ME; ++MI) {
+        if (includeInGraph(*MI))
+          addToCallGraph(*MI, true);
+      }
+      break;
+    }
+
+    default:
+      break;
+    }
+  }
+}
+
+CallGraphNode *CallGraph::getOrInsertFunction(Decl *F) {
+  CallGraphNode *&Node = FunctionMap[F];
+  if (Node)
+    return Node;
+
+  Node = new CallGraphNode(F);
+  ParentlessNodes.insert(Node);
+  return Node;
+}
+
+void CallGraph::print(raw_ostream &OS) const {
+  OS << " --- Call graph Dump --- \n";
+  for (const_iterator I = begin(), E = end(); I != E; ++I) {
+    OS << "  Function: ";
+    if (I->second == Root)
+      OS << "< root >";
+    else
+      I->second->print(OS);
+    OS << " calls: ";
+    for (CallGraphNode::iterator CI = I->second->begin(),
+        CE = I->second->end(); CI != CE; ++CI) {
+      assert(*CI != Root && "No one can call the root node.");
+      (*CI)->print(OS);
+      OS << " ";
+    }
+    OS << '\n';
+  }
+  OS.flush();
+}
+
+void CallGraph::dump() const {
+  print(llvm::errs());
+}
+
+void CallGraph::viewGraph() const {
+  llvm::ViewGraph(this, "CallGraph");
+}
+
+StringRef CallGraphNode::getName() const {
+  if (const FunctionDecl *D = dyn_cast_or_null<FunctionDecl>(FD))
+    if (const IdentifierInfo *II = D->getIdentifier())
+      return II->getName();
+    return "< >";
+}
+
+void CallGraphNode::print(raw_ostream &os) const {
+  os << getName();
+}
+
+void CallGraphNode::dump() const {
+  print(llvm::errs());
+}
+
+namespace llvm {
+
+template <>
+struct DOTGraphTraits<const CallGraph*> : public DefaultDOTGraphTraits {
+
+  DOTGraphTraits (bool isSimple=false) : DefaultDOTGraphTraits(isSimple) {}
+
+  static std::string getNodeLabel(const CallGraphNode *Node,
+                                  const CallGraph *CG) {
+    if (CG->getRoot() == Node) {
+      return "< root >";
+    }
+    return Node->getName();
+  }
+
+};
+}

lib/StaticAnalyzer/Checkers/Checkers.td

@@ -467,6 +467,14 @@ def CFGDumper : Checker<"DumpCFG">,
   HelpText<"Display Control-Flow Graphs">,
   DescFile<"DebugCheckers.cpp">;
 
+def CallGraphViewer : Checker<"ViewCallGraph">,
+  HelpText<"View Call Graph using GraphViz">,
+  DescFile<"DebugCheckers.cpp">;
+
+def CallGraphDumper : Checker<"DumpCallGraph">,
+  HelpText<"Display Call Graph">,
+  DescFile<"DebugCheckers.cpp">;
+
 def AnalyzerStatsChecker : Checker<"Stats">,
   HelpText<"Emit warnings with analyzer statistics">,
   DescFile<"AnalyzerStatsChecker.cpp">;

lib/StaticAnalyzer/Checkers/DebugCheckers.cpp

@@ -16,6 +16,7 @@
 #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
 #include "clang/Analysis/Analyses/LiveVariables.h"
 #include "clang/Analysis/Analyses/Dominators.h"
+#include "clang/Analysis/CallGraph.h"
 #include "llvm/Support/Process.h"
 
 using namespace clang;
@@ -103,3 +104,43 @@ public:
 void ento::registerCFGDumper(CheckerManager &mgr) {
   mgr.registerChecker<CFGDumper>();
 }
+
+//===----------------------------------------------------------------------===//
+// CallGraphViewer
+//===----------------------------------------------------------------------===//
+
+namespace {
+class CallGraphViewer : public Checker< check::ASTDecl<TranslationUnitDecl> > {
+public:
+  void checkASTDecl(const TranslationUnitDecl *TU, AnalysisManager& mgr,
+                    BugReporter &BR) const {
+    CallGraph CG;
+    CG.addToCallGraph(const_cast<TranslationUnitDecl*>(TU));
+    CG.viewGraph();
+  }
+};
+}
+
+void ento::registerCallGraphViewer(CheckerManager &mgr) {
+  mgr.registerChecker<CallGraphViewer>();
+}
+
+//===----------------------------------------------------------------------===//
+// CallGraphDumper
+//===----------------------------------------------------------------------===//
+
+namespace {
+class CallGraphDumper : public Checker< check::ASTDecl<TranslationUnitDecl> > {
+public:
+  void checkASTDecl(const TranslationUnitDecl *TU, AnalysisManager& mgr,
+                    BugReporter &BR) const {
+    CallGraph CG;
+    CG.addToCallGraph(const_cast<TranslationUnitDecl*>(TU));
+    CG.dump();
+  }
+};
+}
+
+void ento::registerCallGraphDumper(CheckerManager &mgr) {
+  mgr.registerChecker<CallGraphDumper>();
+}

test/Analysis/debug-CallGraph.c

@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -analyze -analyzer-checker=debug.DumpCallGraph %s 2>&1 | FileCheck %s
+
+static void mmm(int y) {
+  if (y != 0)
+      y++;
+  y = y/0;
+}
+
+static int foo(int x, int y) {
+    mmm(y);
+    if (x != 0)
+      x++;
+    return 5/x;
+}
+
+void aaa() {
+  foo(1,2);
+}
+
+// CHECK:--- Call graph Dump ---
+// CHECK: Function: < root > calls: aaa