//===- FunctionImport.cpp - ThinLTO Summary-based Function Import ---------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements Function import based on summaries. // //===----------------------------------------------------------------------===// #include "llvm/Transforms/IPO/FunctionImport.h" #include "llvm/ADT/StringSet.h" #include "llvm/IR/AutoUpgrade.h" #include "llvm/IR/DiagnosticPrinter.h" #include "llvm/IR/IntrinsicInst.h" #include "llvm/IR/Module.h" #include "llvm/IRReader/IRReader.h" #include "llvm/Linker/Linker.h" #include "llvm/Object/FunctionIndexObjectFile.h" #include "llvm/Support/CommandLine.h" #include "llvm/Support/Debug.h" #include "llvm/Support/SourceMgr.h" #include <map> using namespace llvm; #define DEBUG_TYPE "function-import" /// Limit on instruction count of imported functions. static cl::opt<unsigned> ImportInstrLimit( "import-instr-limit", cl::init(100), cl::Hidden, cl::value_desc("N"), cl::desc("Only import functions with less than N instructions")); // Load lazily a module from \p FileName in \p Context. static std::unique_ptr<Module> loadFile(const std::string &FileName, LLVMContext &Context) { SMDiagnostic Err; DEBUG(dbgs() << "Loading '" << FileName << "'\n"); std::unique_ptr<Module> Result = getLazyIRFileModule(FileName, Err, Context); if (!Result) { Err.print("function-import", errs()); return nullptr; } Result->materializeMetadata(); UpgradeDebugInfo(*Result); return Result; } namespace { /// Helper to load on demand a Module from file and cache it for subsequent /// queries. It can be used with the FunctionImporter. class ModuleLazyLoaderCache { /// Cache of lazily loaded module for import. StringMap<std::unique_ptr<Module>> ModuleMap; /// Retrieve a Module from the cache or lazily load it on demand. std::function<std::unique_ptr<Module>(StringRef FileName)> createLazyModule; public: /// Create the loader, Module will be initialized in \p Context. ModuleLazyLoaderCache(std::function< std::unique_ptr<Module>(StringRef FileName)> createLazyModule) : createLazyModule(createLazyModule) {} /// Retrieve a Module from the cache or lazily load it on demand. Module &operator()(StringRef FileName); std::unique_ptr<Module> takeModule(StringRef FileName) { auto I = ModuleMap.find(FileName); assert(I != ModuleMap.end()); std::unique_ptr<Module> Ret = std::move(I->second); ModuleMap.erase(I); return Ret; } }; // Get a Module for \p FileName from the cache, or load it lazily. Module &ModuleLazyLoaderCache::operator()(StringRef Identifier) { auto &Module = ModuleMap[Identifier]; if (!Module) Module = createLazyModule(Identifier); return *Module; } } // anonymous namespace /// Walk through the instructions in \p F looking for external /// calls not already in the \p CalledFunctions set. If any are /// found they are added to the \p Worklist for importing. static void findExternalCalls(const Module &DestModule, Function &F, const FunctionInfoIndex &Index, StringSet<> &CalledFunctions, SmallVector<StringRef, 64> &Worklist) { // We need to suffix internal function calls imported from other modules, // prepare the suffix ahead of time. std::string Suffix; if (F.getParent() != &DestModule) Suffix = (Twine(".llvm.") + Twine(Index.getModuleId(F.getParent()->getModuleIdentifier()))).str(); for (auto &BB : F) { for (auto &I : BB) { if (isa<CallInst>(I)) { auto CalledFunction = cast<CallInst>(I).getCalledFunction(); // Insert any new external calls that have not already been // added to set/worklist. if (!CalledFunction || !CalledFunction->hasName()) continue; // Ignore intrinsics early if (CalledFunction->isIntrinsic()) { assert(CalledFunction->getIntrinsicID() != 0); continue; } auto ImportedName = CalledFunction->getName(); auto Renamed = (ImportedName + Suffix).str(); // Rename internal functions if (CalledFunction->hasInternalLinkage()) { ImportedName = Renamed; } auto It = CalledFunctions.insert(ImportedName); if (!It.second) { // This is a call to a function we already considered, skip. continue; } // Ignore functions already present in the destination module auto *SrcGV = DestModule.getNamedValue(ImportedName); if (SrcGV) { assert(isa<Function>(SrcGV) && "Name collision during import"); if (!cast<Function>(SrcGV)->isDeclaration()) { DEBUG(dbgs() << DestModule.getModuleIdentifier() << ": Ignoring " << ImportedName << " already in DestinationModule\n"); continue; } } Worklist.push_back(It.first->getKey()); DEBUG(dbgs() << DestModule.getModuleIdentifier() << ": Adding callee for : " << ImportedName << " : " << F.getName() << "\n"); } } } } // Helper function: given a worklist and an index, will process all the worklist // and decide what to import based on the summary information. // // Nothing is actually imported, functions are materialized in their source // module and analyzed there. // // \p ModuleToFunctionsToImportMap is filled with the set of Function to import // per Module. static void GetImportList(Module &DestModule, SmallVector<StringRef, 64> &Worklist, StringSet<> &CalledFunctions, std::map<StringRef, DenseSet<const GlobalValue *>> &ModuleToFunctionsToImportMap, const FunctionInfoIndex &Index, ModuleLazyLoaderCache &ModuleLoaderCache) { while (!Worklist.empty()) { auto CalledFunctionName = Worklist.pop_back_val(); DEBUG(dbgs() << DestModule.getModuleIdentifier() << ": Process import for " << CalledFunctionName << "\n"); // Try to get a summary for this function call. auto InfoList = Index.findFunctionInfoList(CalledFunctionName); if (InfoList == Index.end()) { DEBUG(dbgs() << DestModule.getModuleIdentifier() << ": No summary for " << CalledFunctionName << " Ignoring.\n"); continue; } assert(!InfoList->second.empty() && "No summary, error at import?"); // Comdat can have multiple entries, FIXME: what do we do with them? auto &Info = InfoList->second[0]; assert(Info && "Nullptr in list, error importing summaries?\n"); auto *Summary = Info->functionSummary(); if (!Summary) { // FIXME: in case we are lazyloading summaries, we can do it now. DEBUG(dbgs() << DestModule.getModuleIdentifier() << ": Missing summary for " << CalledFunctionName << ", error at import?\n"); llvm_unreachable("Missing summary"); } if (Summary->instCount() > ImportInstrLimit) { DEBUG(dbgs() << DestModule.getModuleIdentifier() << ": Skip import of " << CalledFunctionName << " with " << Summary->instCount() << " instructions (limit " << ImportInstrLimit << ")\n"); continue; } // Get the module path from the summary. auto ModuleIdentifier = Summary->modulePath(); DEBUG(dbgs() << DestModule.getModuleIdentifier() << ": Importing " << CalledFunctionName << " from " << ModuleIdentifier << "\n"); auto &SrcModule = ModuleLoaderCache(ModuleIdentifier); // The function that we will import! GlobalValue *SGV = SrcModule.getNamedValue(CalledFunctionName); if (!SGV) { // The destination module is referencing function using their renamed name // when importing a function that was originally local in the source // module. The source module we have might not have been renamed so we try // to remove the suffix added during the renaming to recover the original // name in the source module. std::pair<StringRef, StringRef> Split = CalledFunctionName.split(".llvm."); SGV = SrcModule.getNamedValue(Split.first); assert(SGV && "Can't find function to import in source module"); } if (!SGV) { report_fatal_error(Twine("Can't load function '") + CalledFunctionName + "' in Module '" + SrcModule.getModuleIdentifier() + "', error in the summary?\n"); } Function *F = dyn_cast<Function>(SGV); if (!F && isa<GlobalAlias>(SGV)) { auto *SGA = dyn_cast<GlobalAlias>(SGV); F = dyn_cast<Function>(SGA->getBaseObject()); CalledFunctionName = F->getName(); } assert(F && "Imported Function is ... not a Function"); // We cannot import weak_any functions/aliases without possibly affecting // the order they are seen and selected by the linker, changing program // semantics. if (SGV->hasWeakAnyLinkage()) { DEBUG(dbgs() << DestModule.getModuleIdentifier() << ": Ignoring import request for weak-any " << (isa<Function>(SGV) ? "function " : "alias ") << CalledFunctionName << " from " << SrcModule.getModuleIdentifier() << "\n"); continue; } // Add the function to the import list auto &Entry = ModuleToFunctionsToImportMap[SrcModule.getModuleIdentifier()]; Entry.insert(F); // Process the newly imported functions and add callees to the worklist. F->materialize(); findExternalCalls(DestModule, *F, Index, CalledFunctions, Worklist); } } // Automatically import functions in Module \p DestModule based on the summaries // index. // // The current implementation imports every called functions that exists in the // summaries index. bool FunctionImporter::importFunctions(Module &DestModule) { DEBUG(dbgs() << "Starting import for Module " << DestModule.getModuleIdentifier() << "\n"); unsigned ImportedCount = 0; /// First step is collecting the called external functions. StringSet<> CalledFunctions; SmallVector<StringRef, 64> Worklist; for (auto &F : DestModule) { if (F.isDeclaration() || F.hasFnAttribute(Attribute::OptimizeNone)) continue; findExternalCalls(DestModule, F, Index, CalledFunctions, Worklist); } if (Worklist.empty()) return false; /// Second step: for every call to an external function, try to import it. // Linker that will be used for importing function Linker TheLinker(DestModule); // Map of Module -> List of Function to import from the Module std::map<StringRef, DenseSet<const GlobalValue *>> ModuleToFunctionsToImportMap; // Analyze the summaries and get the list of functions to import by // populating ModuleToFunctionsToImportMap ModuleLazyLoaderCache ModuleLoaderCache(ModuleLoader); GetImportList(DestModule, Worklist, CalledFunctions, ModuleToFunctionsToImportMap, Index, ModuleLoaderCache); assert(Worklist.empty() && "Worklist hasn't been flushed in GetImportList"); StringMap<std::unique_ptr<DenseMap<unsigned, MDNode *>>> ModuleToTempMDValsMap; // Do the actual import of functions now, one Module at a time for (auto &FunctionsToImportPerModule : ModuleToFunctionsToImportMap) { // Get the module for the import auto &FunctionsToImport = FunctionsToImportPerModule.second; std::unique_ptr<Module> SrcModule = ModuleLoaderCache.takeModule(FunctionsToImportPerModule.first); assert(&DestModule.getContext() == &SrcModule->getContext() && "Context mismatch"); // Save the mapping of value ids to temporary metadata created when // importing this function. If we have already imported from this module, // add new temporary metadata to the existing mapping. auto &TempMDVals = ModuleToTempMDValsMap[SrcModule->getModuleIdentifier()]; if (!TempMDVals) TempMDVals = llvm::make_unique<DenseMap<unsigned, MDNode *>>(); // Link in the specified functions. if (TheLinker.linkInModule(std::move(SrcModule), Linker::Flags::None, &Index, &FunctionsToImport, TempMDVals.get())) report_fatal_error("Function Import: link error"); ImportedCount += FunctionsToImport.size(); } // Now link in metadata for all modules from which we imported functions. for (StringMapEntry<std::unique_ptr<DenseMap<unsigned, MDNode *>>> &SME : ModuleToTempMDValsMap) { // Load the specified source module. auto &SrcModule = ModuleLoaderCache(SME.getKey()); // Link in all necessary metadata from this module. if (TheLinker.linkInMetadata(SrcModule, SME.getValue().get())) return false; } DEBUG(dbgs() << "Imported " << ImportedCount << " functions for Module " << DestModule.getModuleIdentifier() << "\n"); return ImportedCount; } /// Summary file to use for function importing when using -function-import from /// the command line. static cl::opt<std::string> SummaryFile("summary-file", cl::desc("The summary file to use for function importing.")); static void diagnosticHandler(const DiagnosticInfo &DI) { raw_ostream &OS = errs(); DiagnosticPrinterRawOStream DP(OS); DI.print(DP); OS << '\n'; } /// Parse the function index out of an IR file and return the function /// index object if found, or nullptr if not. static std::unique_ptr<FunctionInfoIndex> getFunctionIndexForFile(StringRef Path, std::string &Error, DiagnosticHandlerFunction DiagnosticHandler) { std::unique_ptr<MemoryBuffer> Buffer; ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr = MemoryBuffer::getFile(Path); if (std::error_code EC = BufferOrErr.getError()) { Error = EC.message(); return nullptr; } Buffer = std::move(BufferOrErr.get()); ErrorOr<std::unique_ptr<object::FunctionIndexObjectFile>> ObjOrErr = object::FunctionIndexObjectFile::create(Buffer->getMemBufferRef(), DiagnosticHandler); if (std::error_code EC = ObjOrErr.getError()) { Error = EC.message(); return nullptr; } return (*ObjOrErr)->takeIndex(); } /// Pass that performs cross-module function import provided a summary file. class FunctionImportPass : public ModulePass { /// Optional function summary index to use for importing, otherwise /// the summary-file option must be specified. const FunctionInfoIndex *Index; public: /// Pass identification, replacement for typeid static char ID; /// Specify pass name for debug output const char *getPassName() const override { return "Function Importing"; } explicit FunctionImportPass(const FunctionInfoIndex *Index = nullptr) : ModulePass(ID), Index(Index) {} bool runOnModule(Module &M) override { if (SummaryFile.empty() && !Index) report_fatal_error("error: -function-import requires -summary-file or " "file from frontend\n"); std::unique_ptr<FunctionInfoIndex> IndexPtr; if (!SummaryFile.empty()) { if (Index) report_fatal_error("error: -summary-file and index from frontend\n"); std::string Error; IndexPtr = getFunctionIndexForFile(SummaryFile, Error, diagnosticHandler); if (!IndexPtr) { errs() << "Error loading file '" << SummaryFile << "': " << Error << "\n"; return false; } Index = IndexPtr.get(); } // Perform the import now. auto ModuleLoader = [&M](StringRef Identifier) { return loadFile(Identifier, M.getContext()); }; FunctionImporter Importer(*Index, ModuleLoader); return Importer.importFunctions(M); return false; } }; char FunctionImportPass::ID = 0; INITIALIZE_PASS_BEGIN(FunctionImportPass, "function-import", "Summary Based Function Import", false, false) INITIALIZE_PASS_END(FunctionImportPass, "function-import", "Summary Based Function Import", false, false) namespace llvm { Pass *createFunctionImportPass(const FunctionInfoIndex *Index = nullptr) { return new FunctionImportPass(Index); } }