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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@8518 91177308-0d34-0410-b5e6-96231b3b80d8
192 lines
7.0 KiB
C++
192 lines
7.0 KiB
C++
//===- CallGraph.cpp - Build a Module's call graph ------------------------===//
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//
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// This interface is used to build and manipulate a call graph, which is a very
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// useful tool for interprocedural optimization.
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//
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// Every function in a module is represented as a node in the call graph. The
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// callgraph node keeps track of which functions the are called by the function
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// corresponding to the node.
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//
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// A call graph will contain nodes where the function that they correspond to is
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// null. This 'external' node is used to represent control flow that is not
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// represented (or analyzable) in the module. As such, the external node will
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// have edges to functions with the following properties:
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// 1. All functions in the module without internal linkage, since they could
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// be called by functions outside of the our analysis capability.
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// 2. All functions whose address is used for something more than a direct
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// call, for example being stored into a memory location. Since they may
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// be called by an unknown caller later, they must be tracked as such.
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//
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// Similarly, functions have a call edge to the external node iff:
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// 1. The function is external, reflecting the fact that they could call
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// anything without internal linkage or that has its address taken.
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// 2. The function contains an indirect function call.
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//
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// As an extension in the future, there may be multiple nodes with a null
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// function. These will be used when we can prove (through pointer analysis)
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// that an indirect call site can call only a specific set of functions.
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//
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// Because of these properties, the CallGraph captures a conservative superset
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// of all of the caller-callee relationships, which is useful for
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// transformations.
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//
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// The CallGraph class also attempts to figure out what the root of the
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// CallGraph is, which is currently does by looking for a function named 'main'.
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// If no function named 'main' is found, the external node is used as the entry
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// node, reflecting the fact that any function without internal linkage could
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// be called into (which is common for libraries).
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/CallGraph.h"
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#include "llvm/Module.h"
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#include "llvm/iOther.h"
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#include "llvm/iTerminators.h"
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#include "Support/STLExtras.h"
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#include <algorithm>
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static RegisterAnalysis<CallGraph> X("callgraph", "Call Graph Construction");
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// getNodeFor - Return the node for the specified function or create one if it
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// does not already exist.
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//
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CallGraphNode *CallGraph::getNodeFor(Function *F) {
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CallGraphNode *&CGN = FunctionMap[F];
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if (CGN) return CGN;
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assert((!F || F->getParent() == Mod) && "Function not in current module!");
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return CGN = new CallGraphNode(F);
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}
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// addToCallGraph - Add a function to the call graph, and link the node to all
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// of the functions that it calls.
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//
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void CallGraph::addToCallGraph(Function *F) {
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CallGraphNode *Node = getNodeFor(F);
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// If this function has external linkage, anything could call it...
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if (!F->hasInternalLinkage()) {
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ExternalNode->addCalledFunction(Node);
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// Found the entry point?
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if (F->getName() == "main") {
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if (Root)
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Root = ExternalNode; // Found multiple external mains? Don't pick one.
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else
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Root = Node; // Found a main, keep track of it!
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}
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}
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// If this function is not defined in this translation unit, it could call
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// anything.
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if (F->isExternal())
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Node->addCalledFunction(ExternalNode);
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// Loop over all of the users of the function... looking for callers...
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//
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for (Value::use_iterator I = F->use_begin(), E = F->use_end(); I != E; ++I) {
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User *U = *I;
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if (CallInst *CI = dyn_cast<CallInst>(U))
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getNodeFor(CI->getParent()->getParent())->addCalledFunction(Node);
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else if (InvokeInst *II = dyn_cast<InvokeInst>(U))
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getNodeFor(II->getParent()->getParent())->addCalledFunction(Node);
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else // Can't classify the user!
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ExternalNode->addCalledFunction(Node);
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}
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// Look for an indirect function call...
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for (Function::iterator BB = F->begin(), BBE = F->end(); BB != BBE; ++BB)
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for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); II != IE; ++II){
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Instruction &I = *II;
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if (CallInst *CI = dyn_cast<CallInst>(&I)) {
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if (CI->getCalledFunction() == 0)
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Node->addCalledFunction(ExternalNode);
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} else if (InvokeInst *II = dyn_cast<InvokeInst>(&I)) {
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if (II->getCalledFunction() == 0)
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Node->addCalledFunction(ExternalNode);
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}
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}
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}
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bool CallGraph::run(Module &M) {
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destroy();
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Mod = &M;
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ExternalNode = getNodeFor(0);
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Root = 0;
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// Add every function to the call graph...
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for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
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addToCallGraph(I);
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// If we didn't find a main function, use the external call graph node
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if (Root == 0) Root = ExternalNode;
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return false;
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}
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void CallGraph::destroy() {
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for (FunctionMapTy::iterator I = FunctionMap.begin(), E = FunctionMap.end();
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I != E; ++I)
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delete I->second;
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FunctionMap.clear();
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}
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static void WriteToOutput(const CallGraphNode *CGN, std::ostream &o) {
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if (CGN->getFunction())
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o << "Call graph node for function: '"
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<< CGN->getFunction()->getName() <<"'\n";
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else
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o << "Call graph node <<null function: 0x" << CGN << ">>:\n";
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for (unsigned i = 0; i < CGN->size(); ++i)
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if ((*CGN)[i]->getFunction())
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o << " Calls function '" << (*CGN)[i]->getFunction()->getName() << "'\n";
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else
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o << " Calls external node\n";
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o << "\n";
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}
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void CallGraph::print(std::ostream &o, const Module *M) const {
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o << "CallGraph Root is: ";
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if (getRoot()->getFunction())
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o << getRoot()->getFunction()->getName() << "\n";
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else
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o << "<<null function: 0x" << getRoot() << ">>\n";
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for (CallGraph::const_iterator I = begin(), E = end(); I != E; ++I)
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WriteToOutput(I->second, o);
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}
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//===----------------------------------------------------------------------===//
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// Implementations of public modification methods
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//
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// Functions to keep a call graph up to date with a function that has been
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// modified
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//
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void CallGraph::addFunctionToModule(Function *Meth) {
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assert(0 && "not implemented");
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abort();
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}
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// removeFunctionFromModule - Unlink the function from this module, returning
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// it. Because this removes the function from the module, the call graph node
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// is destroyed. This is only valid if the function does not call any other
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// functions (ie, there are no edges in it's CGN). The easiest way to do this
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// is to dropAllReferences before calling this.
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//
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Function *CallGraph::removeFunctionFromModule(CallGraphNode *CGN) {
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assert(CGN->CalledFunctions.empty() && "Cannot remove function from call "
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"graph if it references other functions!");
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Function *F = CGN->getFunction(); // Get the function for the call graph node
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delete CGN; // Delete the call graph node for this func
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FunctionMap.erase(F); // Remove the call graph node from the map
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Mod->getFunctionList().remove(F);
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return F;
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}
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