| //===- CallGraph.cpp - Build a Module's call graph ------------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // 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. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This interface is used to build and manipulate a call graph, which is a very |
| // useful tool for interprocedural optimization. |
| // |
| // 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. |
| // |
| // 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). |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Analysis/CallGraph.h" |
| #include "llvm/Constants.h" // Remove when ConstantPointerRefs are gone |
| #include "llvm/Module.h" |
| #include "llvm/iOther.h" |
| #include "llvm/iTerminators.h" |
| #include "llvm/Support/CallSite.h" |
| #include "Support/STLExtras.h" |
| |
| namespace llvm { |
| |
| static RegisterAnalysis<CallGraph> X("callgraph", "Call Graph Construction"); |
| |
| static const char * const KnownExternalFunctions[] = { |
| // Low-level system calls |
| "open", |
| "read", |
| "write", |
| "writev", |
| "lseek", |
| "poll", |
| "ioctl", |
| |
| // Low-level stdc library functions |
| "abort", "exit", |
| "getenv", "putenv", |
| |
| // Standard IO functions |
| "printf", |
| "sprintf", |
| "fopen", |
| "freopen", |
| "fclose", |
| "fwrite", |
| "puts", |
| "fputs", |
| "getc", |
| "ungetc", |
| "putc", |
| "putchar", |
| "fread", |
| "fileno", |
| "ftell", |
| "fflush", |
| "fseek", |
| "fileno", |
| "ferror", |
| "feof", |
| "fdopen", |
| "__fxstat", |
| "setbuf", |
| "setbuffer", |
| "etlinebuf", |
| "setvbuf", |
| |
| // Memory functions |
| "malloc", |
| "free", |
| "realloc", |
| "calloc", |
| "memalign", |
| |
| // String functions |
| "atoi", |
| "memmove", |
| "memset", |
| "memchr", |
| "memcmp", |
| "strchr", |
| "strncpy", |
| "strncmp", |
| "strcmp", |
| "strtok", |
| "__strcoll_l", |
| "__strxfrm_l", |
| "__strftime_l", |
| "__strtol_l", |
| "__strtoul_l", |
| "__strtoll_l", |
| "__strtoull_l", |
| "__strtof_l", |
| "__strtod_l", |
| "__strtold_l", |
| "isalpha", |
| |
| // Math functions |
| "exp", "sqrt", "cbrt", "hypot", |
| "log", "log10", "pow", |
| "sin", "cos", "tan", |
| "asin", "acos", "atan", "atan2", |
| |
| // Locale functions |
| "__uselocale", |
| "__newlocale", |
| "__freelocale", |
| "__duplocale", |
| "__nl_langinfo_l", |
| |
| // gettext functions used by libstdc++ |
| "gettext", |
| "dgettext", |
| "dcgettext", |
| "textdomain", |
| "bindtextdomain", |
| |
| // Random stuff |
| "__assert_fail", |
| "__errno_location", |
| "clock", "time", |
| "__main", |
| }; |
| |
| |
| /// ExternalFunctionDoesntCallIntoProgram - This hack is used to indicate to the |
| /// call graph that the specified external function is _KNOWN_ to not call back |
| /// into the program. This is important, because otherwise functions which call |
| /// "printf" for example, end up in a great big SCC that goes from the function |
| /// through main. |
| /// |
| static bool ExternalFunctionDoesntCallIntoProgram(const std::string &Name) { |
| static std::vector<std::string> Funcs; |
| |
| // First time this is called? |
| if (Funcs.empty()) { |
| // Add a whole bunch of functions which are often used... |
| Funcs.insert(Funcs.end(), KnownExternalFunctions, |
| KnownExternalFunctions+ |
| sizeof(KnownExternalFunctions)/sizeof(KnownExternalFunctions[0])); |
| // Sort the list for efficient access |
| std::sort(Funcs.begin(), Funcs.end()); |
| } |
| |
| if (Name.size() > 7 && !memcmp("__llvm_", Name.c_str(), 7)) |
| return true; |
| |
| // Binary search for the function name... |
| std::vector<std::string>::iterator I = |
| std::lower_bound(Funcs.begin(), Funcs.end(), Name); |
| |
| // Found it? |
| return I != Funcs.end() && *I == Name; |
| } |
| |
| |
| |
| // getNodeFor - Return the node for the specified function or create one if it |
| // does not already exist. |
| // |
| CallGraphNode *CallGraph::getNodeFor(Function *F) { |
| CallGraphNode *&CGN = FunctionMap[F]; |
| if (CGN) return CGN; |
| |
| assert((!F || F->getParent() == Mod) && "Function not in current module!"); |
| return CGN = new CallGraphNode(F); |
| } |
| |
| 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; |
| } |
| |
| // 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! |
| } |
| } |
| |
| // If this function is not defined in this translation unit, it could call |
| // anything. |
| if (F->isExternal() && !F->getIntrinsicID() && |
| !ExternalFunctionDoesntCallIntoProgram(F->getName())) |
| Node->addCalledFunction(ExternalNode); |
| |
| // 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)) { |
| if (isOnlyADirectCall(F, CallSite::get(Inst))) |
| getNodeFor(Inst->getParent()->getParent())->addCalledFunction(Node); |
| else |
| isUsedExternally = true; |
| } else if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(*I)) { |
| // THIS IS A DISGUSTING HACK. Brought to you by the power of |
| // ConstantPointerRefs! |
| for (Value::use_iterator I = CPR->use_begin(), E = CPR->use_end(); |
| I != E; ++I) |
| if (Instruction *Inst = dyn_cast<Instruction>(*I)) { |
| if (isOnlyADirectCall(F, CallSite::get(Inst))) |
| getNodeFor(Inst->getParent()->getParent())->addCalledFunction(Node); |
| else |
| isUsedExternally = true; |
| } else { |
| isUsedExternally = true; |
| } |
| } else { // Can't classify the user! |
| isUsedExternally = true; |
| } |
| } |
| if (isUsedExternally) |
| ExternalNode->addCalledFunction(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){ |
| CallSite CS = CallSite::get(II); |
| if (CS.getInstruction() && !CS.getCalledFunction()) |
| Node->addCalledFunction(ExternalNode); |
| } |
| } |
| |
| bool CallGraph::run(Module &M) { |
| destroy(); |
| |
| Mod = &M; |
| ExternalNode = getNodeFor(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 = ExternalNode; |
| |
| return false; |
| } |
| |
| void CallGraph::destroy() { |
| for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end(); |
| I != E; ++I) |
| delete I->second; |
| FunctionMap.clear(); |
| } |
| |
| 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"; |
| |
| 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::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"; |
| |
| for (CallGraph::const_iterator I = begin(), E = end(); I != E; ++I) |
| WriteToOutput(I->second, o); |
| } |
| |
| |
| //===----------------------------------------------------------------------===// |
| // 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 |
| // functions (ie, there are no edges in it's CGN). The easiest way to do this |
| // is to dropAllReferences before calling this. |
| // |
| Function *CallGraph::removeFunctionFromModule(CallGraphNode *CGN) { |
| assert(CGN->CalledFunctions.empty() && "Cannot remove function from call " |
| "graph if it references other functions!"); |
| Function *F = CGN->getFunction(); // Get the function for the call graph node |
| delete CGN; // Delete the call graph node for this func |
| FunctionMap.erase(F); // Remove the call graph node from the map |
| |
| Mod->getFunctionList().remove(F); |
| return F; |
| } |
| |
| void CallGraph::stub() {} |
| |
| } // End llvm namespace |