1 //===- FunctionImport.cpp - ThinLTO Summary-based Function Import ---------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements Function import based on summaries.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/Transforms/IPO/FunctionImport.h"
16 #include "llvm/ADT/StringSet.h"
17 #include "llvm/IR/AutoUpgrade.h"
18 #include "llvm/IR/DiagnosticPrinter.h"
19 #include "llvm/IR/IntrinsicInst.h"
20 #include "llvm/IR/Module.h"
21 #include "llvm/IRReader/IRReader.h"
22 #include "llvm/Linker/Linker.h"
23 #include "llvm/Object/FunctionIndexObjectFile.h"
24 #include "llvm/Support/CommandLine.h"
25 #include "llvm/Support/Debug.h"
26 #include "llvm/Support/SourceMgr.h"
32 #define DEBUG_TYPE "function-import"
34 /// Limit on instruction count of imported functions.
35 static cl::opt<unsigned> ImportInstrLimit(
36 "import-instr-limit", cl::init(100), cl::Hidden, cl::value_desc("N"),
37 cl::desc("Only import functions with less than N instructions"));
39 // Load lazily a module from \p FileName in \p Context.
40 static std::unique_ptr<Module> loadFile(const std::string &FileName,
41 LLVMContext &Context) {
43 DEBUG(dbgs() << "Loading '" << FileName << "'\n");
44 // Metadata isn't loaded or linked until after all functions are
45 // imported, after which it will be materialized and linked.
46 std::unique_ptr<Module> Result =
47 getLazyIRFileModule(FileName, Err, Context,
48 /* ShouldLazyLoadMetadata = */ true);
50 Err.print("function-import", errs());
58 /// Helper to load on demand a Module from file and cache it for subsequent
59 /// queries. It can be used with the FunctionImporter.
60 class ModuleLazyLoaderCache {
61 /// Cache of lazily loaded module for import.
62 StringMap<std::unique_ptr<Module>> ModuleMap;
64 /// Retrieve a Module from the cache or lazily load it on demand.
65 std::function<std::unique_ptr<Module>(StringRef FileName)> createLazyModule;
68 /// Create the loader, Module will be initialized in \p Context.
69 ModuleLazyLoaderCache(std::function<
70 std::unique_ptr<Module>(StringRef FileName)> createLazyModule)
71 : createLazyModule(createLazyModule) {}
73 /// Retrieve a Module from the cache or lazily load it on demand.
74 Module &operator()(StringRef FileName);
76 std::unique_ptr<Module> takeModule(StringRef FileName) {
77 auto I = ModuleMap.find(FileName);
78 assert(I != ModuleMap.end());
79 std::unique_ptr<Module> Ret = std::move(I->second);
85 // Get a Module for \p FileName from the cache, or load it lazily.
86 Module &ModuleLazyLoaderCache::operator()(StringRef Identifier) {
87 auto &Module = ModuleMap[Identifier];
89 Module = createLazyModule(Identifier);
92 } // anonymous namespace
94 /// Walk through the instructions in \p F looking for external
95 /// calls not already in the \p CalledFunctions set. If any are
96 /// found they are added to the \p Worklist for importing.
97 static void findExternalCalls(const Module &DestModule, Function &F,
98 const FunctionInfoIndex &Index,
99 StringSet<> &CalledFunctions,
100 SmallVector<StringRef, 64> &Worklist) {
101 // We need to suffix internal function calls imported from other modules,
102 // prepare the suffix ahead of time.
104 if (F.getParent() != &DestModule)
107 Twine(Index.getModuleId(F.getParent()->getModuleIdentifier()))).str();
111 if (isa<CallInst>(I)) {
112 auto CalledFunction = cast<CallInst>(I).getCalledFunction();
113 // Insert any new external calls that have not already been
114 // added to set/worklist.
115 if (!CalledFunction || !CalledFunction->hasName())
117 // Ignore intrinsics early
118 if (CalledFunction->isIntrinsic()) {
119 assert(CalledFunction->getIntrinsicID() != 0);
122 auto ImportedName = CalledFunction->getName();
123 auto Renamed = (ImportedName + Suffix).str();
124 // Rename internal functions
125 if (CalledFunction->hasInternalLinkage()) {
126 ImportedName = Renamed;
128 auto It = CalledFunctions.insert(ImportedName);
130 // This is a call to a function we already considered, skip.
133 // Ignore functions already present in the destination module
134 auto *SrcGV = DestModule.getNamedValue(ImportedName);
136 if (GlobalAlias *SGA = dyn_cast<GlobalAlias>(SrcGV))
137 SrcGV = SGA->getBaseObject();
138 assert(isa<Function>(SrcGV) && "Name collision during import");
139 if (!cast<Function>(SrcGV)->isDeclaration()) {
140 DEBUG(dbgs() << DestModule.getModuleIdentifier() << ": Ignoring "
141 << ImportedName << " already in DestinationModule\n");
146 Worklist.push_back(It.first->getKey());
147 DEBUG(dbgs() << DestModule.getModuleIdentifier()
148 << ": Adding callee for : " << ImportedName << " : "
149 << F.getName() << "\n");
155 // Helper function: given a worklist and an index, will process all the worklist
156 // and decide what to import based on the summary information.
158 // Nothing is actually imported, functions are materialized in their source
159 // module and analyzed there.
161 // \p ModuleToFunctionsToImportMap is filled with the set of Function to import
163 static void GetImportList(Module &DestModule,
164 SmallVector<StringRef, 64> &Worklist,
165 StringSet<> &CalledFunctions,
166 std::map<StringRef, DenseSet<const GlobalValue *>>
167 &ModuleToFunctionsToImportMap,
168 const FunctionInfoIndex &Index,
169 ModuleLazyLoaderCache &ModuleLoaderCache) {
170 while (!Worklist.empty()) {
171 auto CalledFunctionName = Worklist.pop_back_val();
172 DEBUG(dbgs() << DestModule.getModuleIdentifier() << ": Process import for "
173 << CalledFunctionName << "\n");
175 // Try to get a summary for this function call.
176 auto InfoList = Index.findFunctionInfoList(CalledFunctionName);
177 if (InfoList == Index.end()) {
178 DEBUG(dbgs() << DestModule.getModuleIdentifier() << ": No summary for "
179 << CalledFunctionName << " Ignoring.\n");
182 assert(!InfoList->second.empty() && "No summary, error at import?");
184 // Comdat can have multiple entries, FIXME: what do we do with them?
185 auto &Info = InfoList->second[0];
186 assert(Info && "Nullptr in list, error importing summaries?\n");
188 auto *Summary = Info->functionSummary();
190 // FIXME: in case we are lazyloading summaries, we can do it now.
191 DEBUG(dbgs() << DestModule.getModuleIdentifier()
192 << ": Missing summary for " << CalledFunctionName
193 << ", error at import?\n");
194 llvm_unreachable("Missing summary");
197 if (Summary->instCount() > ImportInstrLimit) {
198 DEBUG(dbgs() << DestModule.getModuleIdentifier() << ": Skip import of "
199 << CalledFunctionName << " with " << Summary->instCount()
200 << " instructions (limit " << ImportInstrLimit << ")\n");
204 // Get the module path from the summary.
205 auto ModuleIdentifier = Summary->modulePath();
206 DEBUG(dbgs() << DestModule.getModuleIdentifier() << ": Importing "
207 << CalledFunctionName << " from " << ModuleIdentifier << "\n");
209 auto &SrcModule = ModuleLoaderCache(ModuleIdentifier);
211 // The function that we will import!
212 GlobalValue *SGV = SrcModule.getNamedValue(CalledFunctionName);
215 // The destination module is referencing function using their renamed name
216 // when importing a function that was originally local in the source
217 // module. The source module we have might not have been renamed so we try
218 // to remove the suffix added during the renaming to recover the original
219 // name in the source module.
220 std::pair<StringRef, StringRef> Split =
221 CalledFunctionName.split(".llvm.");
222 SGV = SrcModule.getNamedValue(Split.first);
223 assert(SGV && "Can't find function to import in source module");
226 report_fatal_error(Twine("Can't load function '") + CalledFunctionName +
227 "' in Module '" + SrcModule.getModuleIdentifier() +
228 "', error in the summary?\n");
231 Function *F = dyn_cast<Function>(SGV);
232 if (!F && isa<GlobalAlias>(SGV)) {
233 auto *SGA = dyn_cast<GlobalAlias>(SGV);
234 F = dyn_cast<Function>(SGA->getBaseObject());
235 CalledFunctionName = F->getName();
237 assert(F && "Imported Function is ... not a Function");
239 // We cannot import weak_any functions/aliases without possibly affecting
240 // the order they are seen and selected by the linker, changing program
242 if (SGV->hasWeakAnyLinkage()) {
243 DEBUG(dbgs() << DestModule.getModuleIdentifier()
244 << ": Ignoring import request for weak-any "
245 << (isa<Function>(SGV) ? "function " : "alias ")
246 << CalledFunctionName << " from "
247 << SrcModule.getModuleIdentifier() << "\n");
251 // Add the function to the import list
252 auto &Entry = ModuleToFunctionsToImportMap[SrcModule.getModuleIdentifier()];
255 // Process the newly imported functions and add callees to the worklist.
257 findExternalCalls(DestModule, *F, Index, CalledFunctions, Worklist);
261 // Automatically import functions in Module \p DestModule based on the summaries
264 // The current implementation imports every called functions that exists in the
266 bool FunctionImporter::importFunctions(Module &DestModule) {
267 DEBUG(dbgs() << "Starting import for Module "
268 << DestModule.getModuleIdentifier() << "\n");
269 unsigned ImportedCount = 0;
271 /// First step is collecting the called external functions.
272 StringSet<> CalledFunctions;
273 SmallVector<StringRef, 64> Worklist;
274 for (auto &F : DestModule) {
275 if (F.isDeclaration() || F.hasFnAttribute(Attribute::OptimizeNone))
277 findExternalCalls(DestModule, F, Index, CalledFunctions, Worklist);
279 if (Worklist.empty())
282 /// Second step: for every call to an external function, try to import it.
284 // Linker that will be used for importing function
285 Linker TheLinker(DestModule);
287 // Map of Module -> List of Function to import from the Module
288 std::map<StringRef, DenseSet<const GlobalValue *>>
289 ModuleToFunctionsToImportMap;
291 // Analyze the summaries and get the list of functions to import by
292 // populating ModuleToFunctionsToImportMap
293 ModuleLazyLoaderCache ModuleLoaderCache(ModuleLoader);
294 GetImportList(DestModule, Worklist, CalledFunctions,
295 ModuleToFunctionsToImportMap, Index, ModuleLoaderCache);
296 assert(Worklist.empty() && "Worklist hasn't been flushed in GetImportList");
298 StringMap<std::unique_ptr<DenseMap<unsigned, MDNode *>>>
299 ModuleToTempMDValsMap;
301 // Do the actual import of functions now, one Module at a time
302 for (auto &FunctionsToImportPerModule : ModuleToFunctionsToImportMap) {
303 // Get the module for the import
304 auto &FunctionsToImport = FunctionsToImportPerModule.second;
305 std::unique_ptr<Module> SrcModule =
306 ModuleLoaderCache.takeModule(FunctionsToImportPerModule.first);
307 assert(&DestModule.getContext() == &SrcModule->getContext() &&
310 // Save the mapping of value ids to temporary metadata created when
311 // importing this function. If we have already imported from this module,
312 // add new temporary metadata to the existing mapping.
313 auto &TempMDVals = ModuleToTempMDValsMap[SrcModule->getModuleIdentifier()];
315 TempMDVals = llvm::make_unique<DenseMap<unsigned, MDNode *>>();
317 // Link in the specified functions.
318 if (TheLinker.linkInModule(std::move(SrcModule), Linker::Flags::None,
319 &Index, &FunctionsToImport, TempMDVals.get()))
320 report_fatal_error("Function Import: link error");
322 ImportedCount += FunctionsToImport.size();
325 // Now link in metadata for all modules from which we imported functions.
326 for (StringMapEntry<std::unique_ptr<DenseMap<unsigned, MDNode *>>> &SME :
327 ModuleToTempMDValsMap) {
328 // Load the specified source module.
329 auto &SrcModule = ModuleLoaderCache(SME.getKey());
330 // The modules were created with lazy metadata loading. Materialize it
331 // now, before linking it.
332 SrcModule.materializeMetadata();
333 UpgradeDebugInfo(SrcModule);
335 // Link in all necessary metadata from this module.
336 if (TheLinker.linkInMetadata(SrcModule, SME.getValue().get()))
340 DEBUG(dbgs() << "Imported " << ImportedCount << " functions for Module "
341 << DestModule.getModuleIdentifier() << "\n");
342 return ImportedCount;
345 /// Summary file to use for function importing when using -function-import from
346 /// the command line.
347 static cl::opt<std::string>
348 SummaryFile("summary-file",
349 cl::desc("The summary file to use for function importing."));
351 static void diagnosticHandler(const DiagnosticInfo &DI) {
352 raw_ostream &OS = errs();
353 DiagnosticPrinterRawOStream DP(OS);
358 /// Parse the function index out of an IR file and return the function
359 /// index object if found, or nullptr if not.
360 static std::unique_ptr<FunctionInfoIndex>
361 getFunctionIndexForFile(StringRef Path, std::string &Error,
362 DiagnosticHandlerFunction DiagnosticHandler) {
363 std::unique_ptr<MemoryBuffer> Buffer;
364 ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
365 MemoryBuffer::getFile(Path);
366 if (std::error_code EC = BufferOrErr.getError()) {
367 Error = EC.message();
370 Buffer = std::move(BufferOrErr.get());
371 ErrorOr<std::unique_ptr<object::FunctionIndexObjectFile>> ObjOrErr =
372 object::FunctionIndexObjectFile::create(Buffer->getMemBufferRef(),
374 if (std::error_code EC = ObjOrErr.getError()) {
375 Error = EC.message();
378 return (*ObjOrErr)->takeIndex();
382 /// Pass that performs cross-module function import provided a summary file.
383 class FunctionImportPass : public ModulePass {
384 /// Optional function summary index to use for importing, otherwise
385 /// the summary-file option must be specified.
386 const FunctionInfoIndex *Index;
389 /// Pass identification, replacement for typeid
392 /// Specify pass name for debug output
393 const char *getPassName() const override {
394 return "Function Importing";
397 explicit FunctionImportPass(const FunctionInfoIndex *Index = nullptr)
398 : ModulePass(ID), Index(Index) {}
400 bool runOnModule(Module &M) override {
401 if (SummaryFile.empty() && !Index)
402 report_fatal_error("error: -function-import requires -summary-file or "
403 "file from frontend\n");
404 std::unique_ptr<FunctionInfoIndex> IndexPtr;
405 if (!SummaryFile.empty()) {
407 report_fatal_error("error: -summary-file and index from frontend\n");
409 IndexPtr = getFunctionIndexForFile(SummaryFile, Error, diagnosticHandler);
411 errs() << "Error loading file '" << SummaryFile << "': " << Error
415 Index = IndexPtr.get();
418 // First we need to promote to global scope and rename any local values that
419 // are potentially exported to other modules.
420 if (renameModuleForThinLTO(M, Index)) {
421 errs() << "Error renaming module\n";
425 // Perform the import now.
426 auto ModuleLoader = [&M](StringRef Identifier) {
427 return loadFile(Identifier, M.getContext());
429 FunctionImporter Importer(*Index, ModuleLoader);
430 return Importer.importFunctions(M);
433 } // anonymous namespace
435 char FunctionImportPass::ID = 0;
436 INITIALIZE_PASS_BEGIN(FunctionImportPass, "function-import",
437 "Summary Based Function Import", false, false)
438 INITIALIZE_PASS_END(FunctionImportPass, "function-import",
439 "Summary Based Function Import", false, false)
442 Pass *createFunctionImportPass(const FunctionInfoIndex *Index = nullptr) {
443 return new FunctionImportPass(Index);