+namespace {
+
+/// MergeFunctions finds functions which will generate identical machine code,
+/// by considering all pointer types to be equivalent. Once identified,
+/// MergeFunctions will fold them by replacing a call to one to a call to a
+/// bitcast of the other.
+///
+class MergeFunctions : public ModulePass {
+public:
+ static char ID;
+ MergeFunctions()
+ : ModulePass(ID), HasGlobalAliases(false) {
+ initializeMergeFunctionsPass(*PassRegistry::getPassRegistry());
+ }
+
+ bool runOnModule(Module &M);
+
+private:
+ typedef DenseSet<ComparableFunction> FnSetType;
+
+ /// A work queue of functions that may have been modified and should be
+ /// analyzed again.
+ std::vector<WeakVH> Deferred;
+
+ /// Insert a ComparableFunction into the FnSet, or merge it away if it's
+ /// equal to one that's already present.
+ bool insert(ComparableFunction &NewF);
+
+ /// Remove a Function from the FnSet and queue it up for a second sweep of
+ /// analysis.
+ void remove(Function *F);
+
+ /// Find the functions that use this Value and remove them from FnSet and
+ /// queue the functions.
+ void removeUsers(Value *V);
+
+ /// Replace all direct calls of Old with calls of New. Will bitcast New if
+ /// necessary to make types match.
+ void replaceDirectCallers(Function *Old, Function *New);
+
+ /// Merge two equivalent functions. Upon completion, G may be deleted, or may
+ /// be converted into a thunk. In either case, it should never be visited
+ /// again.
+ void mergeTwoFunctions(Function *F, Function *G);
+
+ /// Replace G with a thunk or an alias to F. Deletes G.
+ void writeThunkOrAlias(Function *F, Function *G);
+
+ /// Replace G with a simple tail call to bitcast(F). Also replace direct uses
+ /// of G with bitcast(F). Deletes G.
+ void writeThunk(Function *F, Function *G);
+
+ /// Replace G with an alias to F. Deletes G.
+ void writeAlias(Function *F, Function *G);
+
+ /// The set of all distinct functions. Use the insert() and remove() methods
+ /// to modify it.
+ FnSetType FnSet;
+
+ /// TargetData for more accurate GEP comparisons. May be NULL.
+ TargetData *TD;
+
+ /// Whether or not the target supports global aliases.
+ bool HasGlobalAliases;
+};
+
+} // end anonymous namespace
+
+char MergeFunctions::ID = 0;
+INITIALIZE_PASS(MergeFunctions, "mergefunc", "Merge Functions", false, false)
+
+ModulePass *llvm::createMergeFunctionsPass() {
+ return new MergeFunctions();
+}
+
+bool MergeFunctions::runOnModule(Module &M) {
+ bool Changed = false;
+ TD = getAnalysisIfAvailable<TargetData>();
+
+ for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
+ if (!I->isDeclaration() && !I->hasAvailableExternallyLinkage())
+ Deferred.push_back(WeakVH(I));
+ }
+ FnSet.resize(Deferred.size());
+
+ do {
+ std::vector<WeakVH> Worklist;
+ Deferred.swap(Worklist);
+
+ DEBUG(dbgs() << "size of module: " << M.size() << '\n');
+ DEBUG(dbgs() << "size of worklist: " << Worklist.size() << '\n');
+
+ // Insert only strong functions and merge them. Strong function merging
+ // always deletes one of them.
+ for (std::vector<WeakVH>::iterator I = Worklist.begin(),
+ E = Worklist.end(); I != E; ++I) {
+ if (!*I) continue;
+ Function *F = cast<Function>(*I);
+ if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() &&
+ !F->mayBeOverridden()) {
+ ComparableFunction CF = ComparableFunction(F, TD);
+ Changed |= insert(CF);
+ }
+ }
+
+ // Insert only weak functions and merge them. By doing these second we
+ // create thunks to the strong function when possible. When two weak
+ // functions are identical, we create a new strong function with two weak
+ // weak thunks to it which are identical but not mergable.
+ for (std::vector<WeakVH>::iterator I = Worklist.begin(),
+ E = Worklist.end(); I != E; ++I) {
+ if (!*I) continue;
+ Function *F = cast<Function>(*I);
+ if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() &&
+ F->mayBeOverridden()) {
+ ComparableFunction CF = ComparableFunction(F, TD);
+ Changed |= insert(CF);
+ }
+ }
+ DEBUG(dbgs() << "size of FnSet: " << FnSet.size() << '\n');
+ } while (!Deferred.empty());
+
+ FnSet.clear();
+
+ return Changed;
+}
+
+bool DenseMapInfo<ComparableFunction>::isEqual(const ComparableFunction &LHS,
+ const ComparableFunction &RHS) {
+ if (LHS.getFunc() == RHS.getFunc() &&
+ LHS.getHash() == RHS.getHash())
+ return true;
+ if (!LHS.getFunc() || !RHS.getFunc())
+ return false;
+
+ // One of these is a special "underlying pointer comparison only" object.
+ if (LHS.getTD() == ComparableFunction::LookupOnly ||
+ RHS.getTD() == ComparableFunction::LookupOnly)
+ return false;
+
+ assert(LHS.getTD() == RHS.getTD() &&
+ "Comparing functions for different targets");
+
+ return FunctionComparator(LHS.getTD(), LHS.getFunc(),
+ RHS.getFunc()).compare();
+}
+
+// Replace direct callers of Old with New.
+void MergeFunctions::replaceDirectCallers(Function *Old, Function *New) {
+ Constant *BitcastNew = ConstantExpr::getBitCast(New, Old->getType());
+ for (Value::use_iterator UI = Old->use_begin(), UE = Old->use_end();
+ UI != UE;) {
+ Value::use_iterator TheIter = UI;
+ ++UI;
+ CallSite CS(*TheIter);
+ if (CS && CS.isCallee(TheIter)) {
+ remove(CS.getInstruction()->getParent()->getParent());
+ TheIter.getUse().set(BitcastNew);
+ }
+ }
+}
+
+// Replace G with an alias to F if possible, or else a thunk to F. Deletes G.
+void MergeFunctions::writeThunkOrAlias(Function *F, Function *G) {
+ if (HasGlobalAliases && G->hasUnnamedAddr()) {
+ if (G->hasExternalLinkage() || G->hasLocalLinkage() ||
+ G->hasWeakLinkage()) {
+ writeAlias(F, G);
+ return;
+ }
+ }
+
+ writeThunk(F, G);
+}
+
+// Replace G with a simple tail call to bitcast(F). Also replace direct uses
+// of G with bitcast(F). Deletes G.
+void MergeFunctions::writeThunk(Function *F, Function *G) {