//===- CallGraph.cpp - Build a Module's call graph ------------------------===//
//
-// This interface is used to build and manipulate a call graph, which is a very
-// useful tool for interprocedural optimization.
+// The LLVM Compiler Infrastructure
//
-// Every function in a module is represented as a node in the call graph. The
-// callgraph node keeps track of which functions the are called by the function
-// corresponding to the node.
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
-// A call graph will contain nodes where the function that they correspond to is
-// null. This 'external' node is used to represent control flow that is not
-// represented (or analyzable) in the module. As such, the external node will
-// have edges to functions with the following properties:
-// 1. All functions in the module without internal linkage, since they could
-// be called by functions outside of the our analysis capability.
-// 2. All functions whose address is used for something more than a direct
-// call, for example being stored into a memory location. Since they may
-// be called by an unknown caller later, they must be tracked as such.
-//
-// Similarly, functions have a call edge to the external node iff:
-// 1. The function is external, reflecting the fact that they could call
-// anything without internal linkage or that has its address taken.
-// 2. The function contains an indirect function call.
-//
-// As an extension in the future, there may be multiple nodes with a null
-// function. These will be used when we can prove (through pointer analysis)
-// that an indirect call site can call only a specific set of functions.
-//
-// Because of these properties, the CallGraph captures a conservative superset
-// of all of the caller-callee relationships, which is useful for
-// transformations.
+//===----------------------------------------------------------------------===//
//
-// The CallGraph class also attempts to figure out what the root of the
-// CallGraph is, which is currently does by looking for a function named 'main'.
-// If no function named 'main' is found, the external node is used as the entry
-// node, reflecting the fact that any function without internal linkage could
-// be called into (which is common for libraries).
+// This file implements the CallGraph class and provides the BasicCallGraph
+// default implementation.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Module.h"
-#include "llvm/iOther.h"
-#include "llvm/iTerminators.h"
-#include "Support/STLExtras.h"
-#include <algorithm>
+#include "llvm/Instructions.h"
+#include "llvm/Support/CallSite.h"
+#include <iostream>
+using namespace llvm;
+
+static bool isOnlyADirectCall(Function *F, CallSite CS) {
+ if (!CS.getInstruction()) return false;
+ for (CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end(); I != E; ++I)
+ if (*I == F) return false;
+ return true;
+}
-static RegisterAnalysis<CallGraph> X("callgraph", "Call Graph Construction");
+namespace {
-// getNodeFor - Return the node for the specified function or create one if it
-// does not already exist.
+//===----------------------------------------------------------------------===//
+// BasicCallGraph class definition
//
-CallGraphNode *CallGraph::getNodeFor(Function *F) {
- CallGraphNode *&CGN = FunctionMap[F];
- if (CGN) return CGN;
+class BasicCallGraph : public CallGraph, public ModulePass {
+ // Root is root of the call graph, or the external node if a 'main' function
+ // couldn't be found.
+ //
+ CallGraphNode *Root;
- assert((!F || F->getParent() == Mod) && "Function not in current module!");
- return CGN = new CallGraphNode(F);
-}
+ // ExternalCallingNode - This node has edges to all external functions and
+ // those internal functions that have their address taken.
+ CallGraphNode *ExternalCallingNode;
-// addToCallGraph - Add a function to the call graph, and link the node to all
-// of the functions that it calls.
-//
-void CallGraph::addToCallGraph(Function *F) {
- CallGraphNode *Node = getNodeFor(F);
-
- // If this function has external linkage, anything could call it...
- if (!F->hasInternalLinkage()) {
- ExternalNode->addCalledFunction(Node);
-
- // Found the entry point?
- if (F->getName() == "main") {
- if (Root)
- Root = ExternalNode; // Found multiple external mains? Don't pick one.
- else
- Root = Node; // Found a main, keep track of it!
- }
+ // CallsExternalNode - This node has edges to it from all functions making
+ // indirect calls or calling an external function.
+ CallGraphNode *CallsExternalNode;
+
+public:
+ BasicCallGraph() : Root(0), ExternalCallingNode(0), CallsExternalNode(0) {}
+ ~BasicCallGraph() { destroy(); }
+
+ // runOnModule - Compute the call graph for the specified module.
+ virtual bool runOnModule(Module &M) {
+ destroy();
+ CallGraph::initialize(M);
+
+ ExternalCallingNode = getOrInsertFunction(0);
+ CallsExternalNode = new CallGraphNode(0);
+ Root = 0;
+
+ // Add every function to the call graph...
+ for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
+ addToCallGraph(I);
+
+ // If we didn't find a main function, use the external call graph node
+ if (Root == 0) Root = ExternalCallingNode;
+
+ return false;
+ }
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesAll();
+ }
+
+ virtual void print(std::ostream &o, const Module *M) const {
+ o << "CallGraph Root is: ";
+ if (Function *F = getRoot()->getFunction())
+ o << F->getName() << "\n";
+ else
+ o << "<<null function: 0x" << getRoot() << ">>\n";
+
+ CallGraph::print(o, M);
+ }
+
+ virtual void releaseMemory() {
+ destroy();
}
- // If this function is not defined in this translation unit, it could call
- // anything.
- if (F->isExternal())
- Node->addCalledFunction(ExternalNode);
+ /// dump - Print out this call graph.
+ ///
+ inline void dump() const {
+ print(std::cerr, Mod);
+ }
- // Loop over all of the users of the function... looking for callers...
+ CallGraphNode* getExternalCallingNode() const { return ExternalCallingNode; }
+ CallGraphNode* getCallsExternalNode() const { return CallsExternalNode; }
+
+ // getRoot - Return the root of the call graph, which is either main, or if
+ // main cannot be found, the external node.
//
- for (Value::use_iterator I = F->use_begin(), E = F->use_end(); I != E; ++I) {
- User *U = *I;
- if (CallInst *CI = dyn_cast<CallInst>(U))
- getNodeFor(CI->getParent()->getParent())->addCalledFunction(Node);
- else if (InvokeInst *II = dyn_cast<InvokeInst>(U))
- getNodeFor(II->getParent()->getParent())->addCalledFunction(Node);
- else // Can't classify the user!
- ExternalNode->addCalledFunction(Node);
- }
+ CallGraphNode *getRoot() { return Root; }
+ const CallGraphNode *getRoot() const { return Root; }
+
+private:
+ //===---------------------------------------------------------------------
+ // Implementation of CallGraph construction
+ //
+
+ // addToCallGraph - Add a function to the call graph, and link the node to all
+ // of the functions that it calls.
+ //
+ void addToCallGraph(Function *F) {
+ CallGraphNode *Node = getOrInsertFunction(F);
+
+ // If this function has external linkage, anything could call it.
+ if (!F->hasInternalLinkage()) {
+ ExternalCallingNode->addCalledFunction(CallSite(), Node);
- // Look for an indirect function call...
- for (Function::iterator BB = F->begin(), BBE = F->end(); BB != BBE; ++BB)
- for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); II != IE; ++II){
- Instruction &I = *II;
-
- if (CallInst *CI = dyn_cast<CallInst>(&I)) {
- if (CI->getCalledFunction() == 0)
- Node->addCalledFunction(ExternalNode);
- } else if (InvokeInst *II = dyn_cast<InvokeInst>(&I)) {
- if (II->getCalledFunction() == 0)
- Node->addCalledFunction(ExternalNode);
+ // Found the entry point?
+ if (F->getName() == "main") {
+ if (Root) // Found multiple external mains? Don't pick one.
+ Root = ExternalCallingNode;
+ else
+ Root = Node; // Found a main, keep track of it!
}
}
-}
-bool CallGraph::run(Module &M) {
- destroy();
+ // If this function is not defined in this translation unit, it could call
+ // anything.
+ if (F->isExternal() && !F->getIntrinsicID())
+ Node->addCalledFunction(CallSite(), CallsExternalNode);
- Mod = &M;
- ExternalNode = getNodeFor(0);
- Root = 0;
+ // Loop over all of the users of the function... looking for callers...
+ //
+ bool isUsedExternally = false;
+ for (Value::use_iterator I = F->use_begin(), E = F->use_end(); I != E; ++I){
+ if (Instruction *Inst = dyn_cast<Instruction>(*I)) {
+ CallSite CS = CallSite::get(Inst);
+ if (isOnlyADirectCall(F, CS))
+ getOrInsertFunction(Inst->getParent()->getParent())
+ ->addCalledFunction(CS, Node);
+ else
+ isUsedExternally = true;
+ } else if (GlobalValue *GV = dyn_cast<GlobalValue>(*I)) {
+ for (Value::use_iterator I = GV->use_begin(), E = GV->use_end();
+ I != E; ++I)
+ if (Instruction *Inst = dyn_cast<Instruction>(*I)) {
+ CallSite CS = CallSite::get(Inst);
+ if (isOnlyADirectCall(F, CS))
+ getOrInsertFunction(Inst->getParent()->getParent())
+ ->addCalledFunction(CS, Node);
+ else
+ isUsedExternally = true;
+ } else {
+ isUsedExternally = true;
+ }
+ } else { // Can't classify the user!
+ isUsedExternally = true;
+ }
+ }
+ if (isUsedExternally)
+ ExternalCallingNode->addCalledFunction(CallSite(), Node);
- // Add every function to the call graph...
- for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
- addToCallGraph(I);
+ // Look for an indirect function call.
+ for (Function::iterator BB = F->begin(), BBE = F->end(); BB != BBE; ++BB)
+ for (BasicBlock::iterator II = BB->begin(), IE = BB->end();
+ II != IE; ++II) {
+ CallSite CS = CallSite::get(II);
+ if (CS.getInstruction() && !CS.getCalledFunction())
+ Node->addCalledFunction(CS, CallsExternalNode);
+ }
+ }
- // If we didn't find a main function, use the external call graph node
- if (Root == 0) Root = ExternalNode;
-
- return false;
-}
+ //
+ // destroy - Release memory for the call graph
+ virtual void destroy() {
+ if (!CallsExternalNode) {
+ delete CallsExternalNode;
+ CallsExternalNode = 0;
+ }
+ }
+};
-void CallGraph::destroy() {
- for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
- I != E; ++I)
- delete I->second;
- FunctionMap.clear();
-}
+RegisterAnalysisGroup<CallGraph> X("Call Graph");
+RegisterPass<BasicCallGraph> Y("basiccg", "Basic CallGraph Construction");
+RegisterAnalysisGroup<CallGraph, true> Z(Y);
-static void WriteToOutput(const CallGraphNode *CGN, std::ostream &o) {
- if (CGN->getFunction())
- o << "Call graph node for function: '"
- << CGN->getFunction()->getName() <<"'\n";
- else
- o << "Call graph node <<null function: 0x" << CGN << ">>:\n";
+} //End anonymous namespace
- for (unsigned i = 0; i < CGN->size(); ++i)
- if ((*CGN)[i]->getFunction())
- o << " Calls function '" << (*CGN)[i]->getFunction()->getName() << "'\n";
- else
- o << " Calls external node\n";
- o << "\n";
+void CallGraph::initialize(Module &M) {
+ destroy();
+ Mod = &M;
}
-void CallGraph::print(std::ostream &o, const Module *M) const {
- o << "CallGraph Root is: ";
- if (getRoot()->getFunction())
- o << getRoot()->getFunction()->getName() << "\n";
- else
- o << "<<null function: 0x" << getRoot() << ">>\n";
-
+void CallGraph::destroy() {
+ if (!FunctionMap.empty()) {
+ for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
+ I != E; ++I)
+ delete I->second;
+ FunctionMap.clear();
+ }
+}
+
+void CallGraph::print(std::ostream &OS, const Module *M) const {
for (CallGraph::const_iterator I = begin(), E = end(); I != E; ++I)
- WriteToOutput(I->second, o);
+ I->second->print(OS);
}
+void CallGraph::dump() const {
+ print(std::cerr, 0);
+}
//===----------------------------------------------------------------------===//
// Implementations of public modification methods
//
-// Functions to keep a call graph up to date with a function that has been
-// modified
-//
-void CallGraph::addFunctionToModule(Function *Meth) {
- assert(0 && "not implemented");
- abort();
-}
-
// removeFunctionFromModule - Unlink the function from this module, returning
// it. Because this removes the function from the module, the call graph node
// is destroyed. This is only valid if the function does not call any other
return F;
}
+// changeFunction - This method changes the function associated with this
+// CallGraphNode, for use by transformations that need to change the prototype
+// of a Function (thus they must create a new Function and move the old code
+// over).
+void CallGraph::changeFunction(Function *OldF, Function *NewF) {
+ iterator I = FunctionMap.find(OldF);
+ CallGraphNode *&New = FunctionMap[NewF];
+ assert(I != FunctionMap.end() && I->second && !New &&
+ "OldF didn't exist in CG or NewF already does!");
+ New = I->second;
+ New->F = NewF;
+ FunctionMap.erase(I);
+}
+
+// getOrInsertFunction - This method is identical to calling operator[], but
+// it will insert a new CallGraphNode for the specified function if one does
+// not already exist.
+CallGraphNode *CallGraph::getOrInsertFunction(const Function *F) {
+ CallGraphNode *&CGN = FunctionMap[F];
+ if (CGN) return CGN;
+
+ assert((!F || F->getParent() == Mod) && "Function not in current module!");
+ return CGN = new CallGraphNode(const_cast<Function*>(F));
+}
+
+void CallGraphNode::print(std::ostream &OS) const {
+ if (Function *F = getFunction())
+ OS << "Call graph node for function: '" << F->getName() <<"'\n";
+ else
+ OS << "Call graph node <<null function: 0x" << this << ">>:\n";
+
+ for (const_iterator I = begin(), E = end(); I != E; ++I)
+ if (I->second->getFunction())
+ OS << " Calls function '" << I->second->getFunction()->getName() <<"'\n";
+ else
+ OS << " Calls external node\n";
+ OS << "\n";
+}
+
+void CallGraphNode::dump() const { print(std::cerr); }
+
+void CallGraphNode::removeCallEdgeTo(CallGraphNode *Callee) {
+ for (unsigned i = CalledFunctions.size(); ; --i) {
+ assert(i && "Cannot find callee to remove!");
+ if (CalledFunctions[i-1].second == Callee) {
+ CalledFunctions.erase(CalledFunctions.begin()+i-1);
+ return;
+ }
+ }
+}
+
+// removeAnyCallEdgeTo - This method removes any call edges from this node to
+// the specified callee function. This takes more time to execute than
+// removeCallEdgeTo, so it should not be used unless necessary.
+void CallGraphNode::removeAnyCallEdgeTo(CallGraphNode *Callee) {
+ for (unsigned i = 0, e = CalledFunctions.size(); i != e; ++i)
+ if (CalledFunctions[i].second == Callee) {
+ CalledFunctions[i] = CalledFunctions.back();
+ CalledFunctions.pop_back();
+ --i; --e;
+ }
+}
+
+// Enuse that users of CallGraph.h also link with this file
+DEFINING_FILE_FOR(CallGraph)
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