1 //===-LTO.cpp - LLVM Link Time Optimizer ----------------------------------===//
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 functions and classes used to support LTO.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/LTO/LTO.h"
15 #include "llvm/Analysis/TargetLibraryInfo.h"
16 #include "llvm/Analysis/TargetTransformInfo.h"
17 #include "llvm/Bitcode/BitcodeReader.h"
18 #include "llvm/Bitcode/BitcodeWriter.h"
19 #include "llvm/CodeGen/Analysis.h"
20 #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
21 #include "llvm/IR/AutoUpgrade.h"
22 #include "llvm/IR/DiagnosticPrinter.h"
23 #include "llvm/IR/LegacyPassManager.h"
24 #include "llvm/IR/Mangler.h"
25 #include "llvm/IR/Metadata.h"
26 #include "llvm/LTO/LTOBackend.h"
27 #include "llvm/Linker/IRMover.h"
28 #include "llvm/Object/ModuleSummaryIndexObjectFile.h"
29 #include "llvm/Support/Error.h"
30 #include "llvm/Support/ManagedStatic.h"
31 #include "llvm/Support/MemoryBuffer.h"
32 #include "llvm/Support/Path.h"
33 #include "llvm/Support/SHA1.h"
34 #include "llvm/Support/SourceMgr.h"
35 #include "llvm/Support/TargetRegistry.h"
36 #include "llvm/Support/ThreadPool.h"
37 #include "llvm/Support/Threading.h"
38 #include "llvm/Support/raw_ostream.h"
39 #include "llvm/Target/TargetMachine.h"
40 #include "llvm/Target/TargetOptions.h"
41 #include "llvm/Transforms/IPO.h"
42 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
43 #include "llvm/Transforms/Utils/SplitModule.h"
49 using namespace object;
51 #define DEBUG_TYPE "lto"
53 // Returns a unique hash for the Module considering the current list of
54 // export/import and other global analysis results.
55 // The hash is produced in \p Key.
56 static void computeCacheKey(
57 SmallString<40> &Key, const Config &Conf, const ModuleSummaryIndex &Index,
58 StringRef ModuleID, const FunctionImporter::ImportMapTy &ImportList,
59 const FunctionImporter::ExportSetTy &ExportList,
60 const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes> &ResolvedODR,
61 const GVSummaryMapTy &DefinedGlobals) {
62 // Compute the unique hash for this entry.
63 // This is based on the current compiler version, the module itself, the
64 // export list, the hash for every single module in the import list, the
65 // list of ResolvedODR for the module, and the list of preserved symbols.
68 // Start with the compiler revision
69 Hasher.update(LLVM_VERSION_STRING);
70 #ifdef HAVE_LLVM_REVISION
71 Hasher.update(LLVM_REVISION);
74 // Include the parts of the LTO configuration that affect code generation.
75 auto AddString = [&](StringRef Str) {
77 Hasher.update(ArrayRef<uint8_t>{0});
79 auto AddUnsigned = [&](unsigned I) {
85 Hasher.update(ArrayRef<uint8_t>{Data, 4});
88 // FIXME: Hash more of Options. For now all clients initialize Options from
89 // command-line flags (which is unsupported in production), but may set
90 // RelaxELFRelocations. The clang driver can also pass FunctionSections,
91 // DataSections and DebuggerTuning via command line flags.
92 AddUnsigned(Conf.Options.RelaxELFRelocations);
93 AddUnsigned(Conf.Options.FunctionSections);
94 AddUnsigned(Conf.Options.DataSections);
95 AddUnsigned((unsigned)Conf.Options.DebuggerTuning);
96 for (auto &A : Conf.MAttrs)
98 AddUnsigned(Conf.RelocModel);
99 AddUnsigned(Conf.CodeModel);
100 AddUnsigned(Conf.CGOptLevel);
101 AddUnsigned(Conf.OptLevel);
102 AddString(Conf.OptPipeline);
103 AddString(Conf.AAPipeline);
104 AddString(Conf.OverrideTriple);
105 AddString(Conf.DefaultTriple);
107 // Include the hash for the current module
108 auto ModHash = Index.getModuleHash(ModuleID);
109 Hasher.update(ArrayRef<uint8_t>((uint8_t *)&ModHash[0], sizeof(ModHash)));
110 for (auto F : ExportList)
111 // The export list can impact the internalization, be conservative here
112 Hasher.update(ArrayRef<uint8_t>((uint8_t *)&F, sizeof(F)));
114 // Include the hash for every module we import functions from
115 for (auto &Entry : ImportList) {
116 auto ModHash = Index.getModuleHash(Entry.first());
117 Hasher.update(ArrayRef<uint8_t>((uint8_t *)&ModHash[0], sizeof(ModHash)));
120 // Include the hash for the resolved ODR.
121 for (auto &Entry : ResolvedODR) {
122 Hasher.update(ArrayRef<uint8_t>((const uint8_t *)&Entry.first,
123 sizeof(GlobalValue::GUID)));
124 Hasher.update(ArrayRef<uint8_t>((const uint8_t *)&Entry.second,
125 sizeof(GlobalValue::LinkageTypes)));
128 // Include the hash for the linkage type to reflect internalization and weak
130 for (auto &GS : DefinedGlobals) {
131 GlobalValue::LinkageTypes Linkage = GS.second->linkage();
133 ArrayRef<uint8_t>((const uint8_t *)&Linkage, sizeof(Linkage)));
136 if (!Conf.SampleProfile.empty()) {
137 auto FileOrErr = MemoryBuffer::getFile(Conf.SampleProfile);
139 Hasher.update(FileOrErr.get()->getBuffer());
142 Key = toHex(Hasher.result());
145 static void thinLTOResolveWeakForLinkerGUID(
146 GlobalValueSummaryList &GVSummaryList, GlobalValue::GUID GUID,
147 DenseSet<GlobalValueSummary *> &GlobalInvolvedWithAlias,
148 function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
150 function_ref<void(StringRef, GlobalValue::GUID, GlobalValue::LinkageTypes)>
152 for (auto &S : GVSummaryList) {
153 GlobalValue::LinkageTypes OriginalLinkage = S->linkage();
154 if (!GlobalValue::isWeakForLinker(OriginalLinkage))
156 // We need to emit only one of these. The prevailing module will keep it,
157 // but turned into a weak, while the others will drop it when possible.
158 // This is both a compile-time optimization and a correctness
159 // transformation. This is necessary for correctness when we have exported
160 // a reference - we need to convert the linkonce to weak to
161 // ensure a copy is kept to satisfy the exported reference.
162 // FIXME: We may want to split the compile time and correctness
163 // aspects into separate routines.
164 if (isPrevailing(GUID, S.get())) {
165 if (GlobalValue::isLinkOnceLinkage(OriginalLinkage))
166 S->setLinkage(GlobalValue::getWeakLinkage(
167 GlobalValue::isLinkOnceODRLinkage(OriginalLinkage)));
169 // Alias and aliasee can't be turned into available_externally.
170 else if (!isa<AliasSummary>(S.get()) &&
171 !GlobalInvolvedWithAlias.count(S.get()))
172 S->setLinkage(GlobalValue::AvailableExternallyLinkage);
173 if (S->linkage() != OriginalLinkage)
174 recordNewLinkage(S->modulePath(), GUID, S->linkage());
178 // Resolve Weak and LinkOnce values in the \p Index.
180 // We'd like to drop these functions if they are no longer referenced in the
181 // current module. However there is a chance that another module is still
182 // referencing them because of the import. We make sure we always emit at least
184 void llvm::thinLTOResolveWeakForLinkerInIndex(
185 ModuleSummaryIndex &Index,
186 function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
188 function_ref<void(StringRef, GlobalValue::GUID, GlobalValue::LinkageTypes)>
190 // We won't optimize the globals that are referenced by an alias for now
191 // Ideally we should turn the alias into a global and duplicate the definition
193 DenseSet<GlobalValueSummary *> GlobalInvolvedWithAlias;
194 for (auto &I : Index)
195 for (auto &S : I.second)
196 if (auto AS = dyn_cast<AliasSummary>(S.get()))
197 GlobalInvolvedWithAlias.insert(&AS->getAliasee());
199 for (auto &I : Index)
200 thinLTOResolveWeakForLinkerGUID(I.second, I.first, GlobalInvolvedWithAlias,
201 isPrevailing, recordNewLinkage);
204 static void thinLTOInternalizeAndPromoteGUID(
205 GlobalValueSummaryList &GVSummaryList, GlobalValue::GUID GUID,
206 function_ref<bool(StringRef, GlobalValue::GUID)> isExported) {
207 for (auto &S : GVSummaryList) {
208 if (isExported(S->modulePath(), GUID)) {
209 if (GlobalValue::isLocalLinkage(S->linkage()))
210 S->setLinkage(GlobalValue::ExternalLinkage);
211 } else if (!GlobalValue::isLocalLinkage(S->linkage()))
212 S->setLinkage(GlobalValue::InternalLinkage);
216 // Update the linkages in the given \p Index to mark exported values
217 // as external and non-exported values as internal.
218 void llvm::thinLTOInternalizeAndPromoteInIndex(
219 ModuleSummaryIndex &Index,
220 function_ref<bool(StringRef, GlobalValue::GUID)> isExported) {
221 for (auto &I : Index)
222 thinLTOInternalizeAndPromoteGUID(I.second, I.first, isExported);
225 struct InputFile::InputModule {
227 std::unique_ptr<Module> Mod;
229 // The range of ModuleSymbolTable entries for this input module.
230 size_t SymBegin, SymEnd;
233 // Requires a destructor for std::vector<InputModule>.
234 InputFile::~InputFile() = default;
236 Expected<std::unique_ptr<InputFile>> InputFile::create(MemoryBufferRef Object) {
237 std::unique_ptr<InputFile> File(new InputFile);
239 ErrorOr<MemoryBufferRef> BCOrErr =
240 IRObjectFile::findBitcodeInMemBuffer(Object);
242 return errorCodeToError(BCOrErr.getError());
244 Expected<std::vector<BitcodeModule>> BMsOrErr =
245 getBitcodeModuleList(*BCOrErr);
247 return BMsOrErr.takeError();
249 if (BMsOrErr->empty())
250 return make_error<StringError>("Bitcode file does not contain any modules",
251 inconvertibleErrorCode());
253 // Create an InputModule for each module in the InputFile, and add it to the
254 // ModuleSymbolTable.
255 for (auto BM : *BMsOrErr) {
256 Expected<std::unique_ptr<Module>> MOrErr =
257 BM.getLazyModule(File->Ctx, /*ShouldLazyLoadMetadata*/ true,
258 /*IsImporting*/ false);
260 return MOrErr.takeError();
262 size_t SymBegin = File->SymTab.symbols().size();
263 File->SymTab.addModule(MOrErr->get());
264 size_t SymEnd = File->SymTab.symbols().size();
266 for (const auto &C : (*MOrErr)->getComdatSymbolTable()) {
267 auto P = File->ComdatMap.insert(
268 std::make_pair(&C.second, File->Comdats.size()));
271 File->Comdats.push_back(C.first());
274 File->Mods.push_back({BM, std::move(*MOrErr), SymBegin, SymEnd});
277 return std::move(File);
280 Expected<int> InputFile::Symbol::getComdatIndex() const {
283 const GlobalObject *GO = getGV()->getBaseObject();
285 return make_error<StringError>("Unable to determine comdat of alias!",
286 inconvertibleErrorCode());
287 if (const Comdat *C = GO->getComdat()) {
288 auto I = File->ComdatMap.find(C);
289 assert(I != File->ComdatMap.end());
295 Expected<std::string> InputFile::getLinkerOpts() {
296 std::string LinkerOpts;
297 raw_string_ostream LOS(LinkerOpts);
298 // Extract linker options from module metadata.
299 for (InputModule &Mod : Mods) {
300 std::unique_ptr<Module> &M = Mod.Mod;
301 if (auto E = M->materializeMetadata())
303 if (Metadata *Val = M->getModuleFlag("Linker Options")) {
304 MDNode *LinkerOptions = cast<MDNode>(Val);
305 for (const MDOperand &MDOptions : LinkerOptions->operands())
306 for (const MDOperand &MDOption : cast<MDNode>(MDOptions)->operands())
307 LOS << " " << cast<MDString>(MDOption)->getString();
311 // Synthesize export flags for symbols with dllexport storage.
312 const Triple TT(Mods[0].Mod->getTargetTriple());
314 for (const ModuleSymbolTable::Symbol &Sym : SymTab.symbols())
315 if (auto *GV = Sym.dyn_cast<GlobalValue*>())
316 emitLinkerFlagsForGlobalCOFF(LOS, GV, TT, M);
321 StringRef InputFile::getName() const {
322 return Mods[0].BM.getModuleIdentifier();
325 StringRef InputFile::getSourceFileName() const {
326 return Mods[0].Mod->getSourceFileName();
329 iterator_range<InputFile::symbol_iterator>
330 InputFile::module_symbols(InputModule &IM) {
331 return llvm::make_range(
332 symbol_iterator(SymTab.symbols().data() + IM.SymBegin, SymTab, this),
333 symbol_iterator(SymTab.symbols().data() + IM.SymEnd, SymTab, this));
336 LTO::RegularLTOState::RegularLTOState(unsigned ParallelCodeGenParallelismLevel,
338 : ParallelCodeGenParallelismLevel(ParallelCodeGenParallelismLevel),
341 LTO::ThinLTOState::ThinLTOState(ThinBackend Backend) : Backend(Backend) {
344 createInProcessThinBackend(llvm::heavyweight_hardware_concurrency());
347 LTO::LTO(Config Conf, ThinBackend Backend,
348 unsigned ParallelCodeGenParallelismLevel)
349 : Conf(std::move(Conf)),
350 RegularLTO(ParallelCodeGenParallelismLevel, this->Conf),
351 ThinLTO(std::move(Backend)) {}
353 // Requires a destructor for MapVector<BitcodeModule>.
354 LTO::~LTO() = default;
356 // Add the given symbol to the GlobalResolutions map, and resolve its partition.
357 void LTO::addSymbolToGlobalRes(SmallPtrSet<GlobalValue *, 8> &Used,
358 const InputFile::Symbol &Sym,
359 SymbolResolution Res, unsigned Partition) {
360 GlobalValue *GV = Sym.isGV() ? Sym.getGV() : nullptr;
362 auto &GlobalRes = GlobalResolutions[Sym.getName()];
364 GlobalRes.UnnamedAddr &= GV->hasGlobalUnnamedAddr();
366 GlobalRes.IRName = GV->getName();
368 // Set the partition to external if we know it is used elsewhere, e.g.
369 // it is visible to a regular object, is referenced from llvm.compiler_used,
370 // or was already recorded as being referenced from a different partition.
371 if (Res.VisibleToRegularObj || (GV && Used.count(GV)) ||
372 (GlobalRes.Partition != GlobalResolution::Unknown &&
373 GlobalRes.Partition != Partition)) {
374 GlobalRes.Partition = GlobalResolution::External;
376 // First recorded reference, save the current partition.
377 GlobalRes.Partition = Partition;
379 // Flag as visible outside of ThinLTO if visible from a regular object or
380 // if this is a reference in the regular LTO partition.
381 GlobalRes.VisibleOutsideThinLTO |=
382 (Res.VisibleToRegularObj || (Partition == GlobalResolution::RegularLTO));
385 static void writeToResolutionFile(raw_ostream &OS, InputFile *Input,
386 ArrayRef<SymbolResolution> Res) {
387 StringRef Path = Input->getName();
389 auto ResI = Res.begin();
390 for (const InputFile::Symbol &Sym : Input->symbols()) {
391 assert(ResI != Res.end());
392 SymbolResolution Res = *ResI++;
394 OS << "-r=" << Path << ',' << Sym.getName() << ',';
397 if (Res.FinalDefinitionInLinkageUnit)
399 if (Res.VisibleToRegularObj)
404 assert(ResI == Res.end());
407 Error LTO::add(std::unique_ptr<InputFile> Input,
408 ArrayRef<SymbolResolution> Res) {
409 assert(!CalledGetMaxTasks);
411 if (Conf.ResolutionFile)
412 writeToResolutionFile(*Conf.ResolutionFile, Input.get(), Res);
414 const SymbolResolution *ResI = Res.begin();
415 for (InputFile::InputModule &IM : Input->Mods)
416 if (Error Err = addModule(*Input, IM, ResI, Res.end()))
419 assert(ResI == Res.end());
420 return Error::success();
423 Error LTO::addModule(InputFile &Input, InputFile::InputModule &IM,
424 const SymbolResolution *&ResI,
425 const SymbolResolution *ResE) {
426 // FIXME: move to backend
429 if (M.getDataLayoutStr().empty())
430 return make_error<StringError>("input module has no datalayout",
431 inconvertibleErrorCode());
433 if (!Conf.OverrideTriple.empty())
434 M.setTargetTriple(Conf.OverrideTriple);
435 else if (M.getTargetTriple().empty())
436 M.setTargetTriple(Conf.DefaultTriple);
438 Expected<bool> HasThinLTOSummary = IM.BM.hasSummary();
439 if (!HasThinLTOSummary)
440 return HasThinLTOSummary.takeError();
442 if (*HasThinLTOSummary)
443 return addThinLTO(IM.BM, M, Input.module_symbols(IM), ResI, ResE);
445 return addRegularLTO(IM.BM, ResI, ResE);
448 // Add a regular LTO object to the link.
449 Error LTO::addRegularLTO(BitcodeModule BM, const SymbolResolution *&ResI,
450 const SymbolResolution *ResE) {
451 if (!RegularLTO.CombinedModule) {
452 RegularLTO.CombinedModule =
453 llvm::make_unique<Module>("ld-temp.o", RegularLTO.Ctx);
454 RegularLTO.Mover = llvm::make_unique<IRMover>(*RegularLTO.CombinedModule);
456 Expected<std::unique_ptr<Module>> MOrErr =
457 BM.getLazyModule(RegularLTO.Ctx, /*ShouldLazyLoadMetadata*/ true,
458 /*IsImporting*/ false);
460 return MOrErr.takeError();
462 Module &M = **MOrErr;
463 if (Error Err = M.materializeMetadata())
467 ModuleSymbolTable SymTab;
468 SymTab.addModule(&M);
470 SmallPtrSet<GlobalValue *, 8> Used;
471 collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ false);
473 std::vector<GlobalValue *> Keep;
475 for (GlobalVariable &GV : M.globals())
476 if (GV.hasAppendingLinkage())
479 DenseSet<GlobalObject *> AliasedGlobals;
480 for (auto &GA : M.aliases())
481 if (GlobalObject *GO = GA.getBaseObject())
482 AliasedGlobals.insert(GO);
484 for (const InputFile::Symbol &Sym :
485 make_range(InputFile::symbol_iterator(SymTab.symbols().begin(), SymTab,
487 InputFile::symbol_iterator(SymTab.symbols().end(), SymTab,
489 assert(ResI != ResE);
490 SymbolResolution Res = *ResI++;
491 addSymbolToGlobalRes(Used, Sym, Res, 0);
494 GlobalValue *GV = Sym.getGV();
495 if (Res.Prevailing) {
496 if (Sym.getFlags() & object::BasicSymbolRef::SF_Undefined)
499 switch (GV->getLinkage()) {
502 case GlobalValue::LinkOnceAnyLinkage:
503 GV->setLinkage(GlobalValue::WeakAnyLinkage);
505 case GlobalValue::LinkOnceODRLinkage:
506 GV->setLinkage(GlobalValue::WeakODRLinkage);
509 } else if (isa<GlobalObject>(GV) &&
510 (GV->hasLinkOnceODRLinkage() || GV->hasWeakODRLinkage() ||
511 GV->hasAvailableExternallyLinkage()) &&
512 !AliasedGlobals.count(cast<GlobalObject>(GV))) {
513 // Either of the above three types of linkage indicates that the
514 // chosen prevailing symbol will have the same semantics as this copy of
515 // the symbol, so we can link it with available_externally linkage. We
516 // only need to do this if the symbol is undefined.
517 GlobalValue *CombinedGV =
518 RegularLTO.CombinedModule->getNamedValue(GV->getName());
519 if (!CombinedGV || CombinedGV->isDeclaration()) {
521 GV->setLinkage(GlobalValue::AvailableExternallyLinkage);
522 cast<GlobalObject>(GV)->setComdat(nullptr);
526 // Common resolution: collect the maximum size/alignment over all commons.
527 // We also record if we see an instance of a common as prevailing, so that
528 // if none is prevailing we can ignore it later.
529 if (Sym.getFlags() & object::BasicSymbolRef::SF_Common) {
530 // FIXME: We should figure out what to do about commons defined by asm.
531 // For now they aren't reported correctly by ModuleSymbolTable.
532 auto &CommonRes = RegularLTO.Commons[Sym.getGV()->getName()];
533 CommonRes.Size = std::max(CommonRes.Size, Sym.getCommonSize());
534 CommonRes.Align = std::max(CommonRes.Align, Sym.getCommonAlignment());
535 CommonRes.Prevailing |= Res.Prevailing;
538 // FIXME: use proposed local attribute for FinalDefinitionInLinkageUnit.
541 return RegularLTO.Mover->move(std::move(*MOrErr), Keep,
542 [](GlobalValue &, IRMover::ValueAdder) {},
543 /* LinkModuleInlineAsm */ true,
544 /* IsPerformingImport */ false);
547 // Add a ThinLTO object to the link.
548 // FIXME: This function should not need to take as many parameters once we have
549 // a bitcode symbol table.
550 Error LTO::addThinLTO(BitcodeModule BM, Module &M,
551 iterator_range<InputFile::symbol_iterator> Syms,
552 const SymbolResolution *&ResI,
553 const SymbolResolution *ResE) {
554 SmallPtrSet<GlobalValue *, 8> Used;
555 collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ false);
557 Expected<std::unique_ptr<ModuleSummaryIndex>> SummaryOrErr = BM.getSummary();
559 return SummaryOrErr.takeError();
560 ThinLTO.CombinedIndex.mergeFrom(std::move(*SummaryOrErr),
561 ThinLTO.ModuleMap.size());
563 for (const InputFile::Symbol &Sym : Syms) {
564 assert(ResI != ResE);
565 SymbolResolution Res = *ResI++;
566 addSymbolToGlobalRes(Used, Sym, Res, ThinLTO.ModuleMap.size() + 1);
568 if (Res.Prevailing && Sym.isGV())
569 ThinLTO.PrevailingModuleForGUID[Sym.getGV()->getGUID()] =
570 BM.getModuleIdentifier();
573 if (!ThinLTO.ModuleMap.insert({BM.getModuleIdentifier(), BM}).second)
574 return make_error<StringError>(
575 "Expected at most one ThinLTO module per bitcode file",
576 inconvertibleErrorCode());
578 return Error::success();
581 unsigned LTO::getMaxTasks() const {
582 CalledGetMaxTasks = true;
583 return RegularLTO.ParallelCodeGenParallelismLevel + ThinLTO.ModuleMap.size();
586 Error LTO::run(AddStreamFn AddStream, NativeObjectCache Cache) {
587 // Save the status of having a regularLTO combined module, as
588 // this is needed for generating the ThinLTO Task ID, and
589 // the CombinedModule will be moved at the end of runRegularLTO.
590 bool HasRegularLTO = RegularLTO.CombinedModule != nullptr;
591 // Invoke regular LTO if there was a regular LTO module to start with.
593 if (auto E = runRegularLTO(AddStream))
595 return runThinLTO(AddStream, Cache, HasRegularLTO);
598 Error LTO::runRegularLTO(AddStreamFn AddStream) {
599 // Make sure commons have the right size/alignment: we kept the largest from
600 // all the prevailing when adding the inputs, and we apply it here.
601 const DataLayout &DL = RegularLTO.CombinedModule->getDataLayout();
602 for (auto &I : RegularLTO.Commons) {
603 if (!I.second.Prevailing)
604 // Don't do anything if no instance of this common was prevailing.
606 GlobalVariable *OldGV = RegularLTO.CombinedModule->getNamedGlobal(I.first);
607 if (OldGV && DL.getTypeAllocSize(OldGV->getValueType()) == I.second.Size) {
608 // Don't create a new global if the type is already correct, just make
609 // sure the alignment is correct.
610 OldGV->setAlignment(I.second.Align);
614 ArrayType::get(Type::getInt8Ty(RegularLTO.Ctx), I.second.Size);
615 auto *GV = new GlobalVariable(*RegularLTO.CombinedModule, Ty, false,
616 GlobalValue::CommonLinkage,
617 ConstantAggregateZero::get(Ty), "");
618 GV->setAlignment(I.second.Align);
620 OldGV->replaceAllUsesWith(ConstantExpr::getBitCast(GV, OldGV->getType()));
622 OldGV->eraseFromParent();
624 GV->setName(I.first);
628 if (Conf.PreOptModuleHook &&
629 !Conf.PreOptModuleHook(0, *RegularLTO.CombinedModule))
630 return Error::success();
632 if (!Conf.CodeGenOnly) {
633 for (const auto &R : GlobalResolutions) {
634 if (R.second.IRName.empty())
636 if (R.second.Partition != 0 &&
637 R.second.Partition != GlobalResolution::External)
641 RegularLTO.CombinedModule->getNamedValue(R.second.IRName);
642 // Ignore symbols defined in other partitions.
643 if (!GV || GV->hasLocalLinkage())
645 GV->setUnnamedAddr(R.second.UnnamedAddr ? GlobalValue::UnnamedAddr::Global
646 : GlobalValue::UnnamedAddr::None);
647 if (R.second.Partition == 0)
648 GV->setLinkage(GlobalValue::InternalLinkage);
651 if (Conf.PostInternalizeModuleHook &&
652 !Conf.PostInternalizeModuleHook(0, *RegularLTO.CombinedModule))
653 return Error::success();
655 return backend(Conf, AddStream, RegularLTO.ParallelCodeGenParallelismLevel,
656 std::move(RegularLTO.CombinedModule), ThinLTO.CombinedIndex);
659 /// This class defines the interface to the ThinLTO backend.
660 class lto::ThinBackendProc {
663 ModuleSummaryIndex &CombinedIndex;
664 const StringMap<GVSummaryMapTy> &ModuleToDefinedGVSummaries;
667 ThinBackendProc(Config &Conf, ModuleSummaryIndex &CombinedIndex,
668 const StringMap<GVSummaryMapTy> &ModuleToDefinedGVSummaries)
669 : Conf(Conf), CombinedIndex(CombinedIndex),
670 ModuleToDefinedGVSummaries(ModuleToDefinedGVSummaries) {}
672 virtual ~ThinBackendProc() {}
674 unsigned Task, BitcodeModule BM,
675 const FunctionImporter::ImportMapTy &ImportList,
676 const FunctionImporter::ExportSetTy &ExportList,
677 const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes> &ResolvedODR,
678 MapVector<StringRef, BitcodeModule> &ModuleMap) = 0;
679 virtual Error wait() = 0;
683 class InProcessThinBackend : public ThinBackendProc {
684 ThreadPool BackendThreadPool;
685 AddStreamFn AddStream;
686 NativeObjectCache Cache;
692 InProcessThinBackend(
693 Config &Conf, ModuleSummaryIndex &CombinedIndex,
694 unsigned ThinLTOParallelismLevel,
695 const StringMap<GVSummaryMapTy> &ModuleToDefinedGVSummaries,
696 AddStreamFn AddStream, NativeObjectCache Cache)
697 : ThinBackendProc(Conf, CombinedIndex, ModuleToDefinedGVSummaries),
698 BackendThreadPool(ThinLTOParallelismLevel),
699 AddStream(std::move(AddStream)), Cache(std::move(Cache)) {}
701 Error runThinLTOBackendThread(
702 AddStreamFn AddStream, NativeObjectCache Cache, unsigned Task,
703 BitcodeModule BM, ModuleSummaryIndex &CombinedIndex,
704 const FunctionImporter::ImportMapTy &ImportList,
705 const FunctionImporter::ExportSetTy &ExportList,
706 const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes> &ResolvedODR,
707 const GVSummaryMapTy &DefinedGlobals,
708 MapVector<StringRef, BitcodeModule> &ModuleMap) {
709 auto RunThinBackend = [&](AddStreamFn AddStream) {
710 LTOLLVMContext BackendContext(Conf);
711 Expected<std::unique_ptr<Module>> MOrErr = BM.parseModule(BackendContext);
713 return MOrErr.takeError();
715 return thinBackend(Conf, Task, AddStream, **MOrErr, CombinedIndex,
716 ImportList, DefinedGlobals, ModuleMap);
719 auto ModuleID = BM.getModuleIdentifier();
721 if (!Cache || !CombinedIndex.modulePaths().count(ModuleID) ||
722 all_of(CombinedIndex.getModuleHash(ModuleID),
723 [](uint32_t V) { return V == 0; }))
724 // Cache disabled or no entry for this module in the combined index or
726 return RunThinBackend(AddStream);
729 // The module may be cached, this helps handling it.
730 computeCacheKey(Key, Conf, CombinedIndex, ModuleID, ImportList, ExportList,
731 ResolvedODR, DefinedGlobals);
732 if (AddStreamFn CacheAddStream = Cache(Task, Key))
733 return RunThinBackend(CacheAddStream);
735 return Error::success();
739 unsigned Task, BitcodeModule BM,
740 const FunctionImporter::ImportMapTy &ImportList,
741 const FunctionImporter::ExportSetTy &ExportList,
742 const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes> &ResolvedODR,
743 MapVector<StringRef, BitcodeModule> &ModuleMap) override {
744 StringRef ModulePath = BM.getModuleIdentifier();
745 assert(ModuleToDefinedGVSummaries.count(ModulePath));
746 const GVSummaryMapTy &DefinedGlobals =
747 ModuleToDefinedGVSummaries.find(ModulePath)->second;
748 BackendThreadPool.async(
749 [=](BitcodeModule BM, ModuleSummaryIndex &CombinedIndex,
750 const FunctionImporter::ImportMapTy &ImportList,
751 const FunctionImporter::ExportSetTy &ExportList,
752 const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>
754 const GVSummaryMapTy &DefinedGlobals,
755 MapVector<StringRef, BitcodeModule> &ModuleMap) {
756 Error E = runThinLTOBackendThread(
757 AddStream, Cache, Task, BM, CombinedIndex, ImportList,
758 ExportList, ResolvedODR, DefinedGlobals, ModuleMap);
760 std::unique_lock<std::mutex> L(ErrMu);
762 Err = joinErrors(std::move(*Err), std::move(E));
767 BM, std::ref(CombinedIndex), std::ref(ImportList),
768 std::ref(ExportList), std::ref(ResolvedODR), std::ref(DefinedGlobals),
769 std::ref(ModuleMap));
770 return Error::success();
773 Error wait() override {
774 BackendThreadPool.wait();
776 return std::move(*Err);
778 return Error::success();
781 } // end anonymous namespace
783 ThinBackend lto::createInProcessThinBackend(unsigned ParallelismLevel) {
784 return [=](Config &Conf, ModuleSummaryIndex &CombinedIndex,
785 const StringMap<GVSummaryMapTy> &ModuleToDefinedGVSummaries,
786 AddStreamFn AddStream, NativeObjectCache Cache) {
787 return llvm::make_unique<InProcessThinBackend>(
788 Conf, CombinedIndex, ParallelismLevel, ModuleToDefinedGVSummaries,
793 // Given the original \p Path to an output file, replace any path
794 // prefix matching \p OldPrefix with \p NewPrefix. Also, create the
795 // resulting directory if it does not yet exist.
796 std::string lto::getThinLTOOutputFile(const std::string &Path,
797 const std::string &OldPrefix,
798 const std::string &NewPrefix) {
799 if (OldPrefix.empty() && NewPrefix.empty())
801 SmallString<128> NewPath(Path);
802 llvm::sys::path::replace_path_prefix(NewPath, OldPrefix, NewPrefix);
803 StringRef ParentPath = llvm::sys::path::parent_path(NewPath.str());
804 if (!ParentPath.empty()) {
805 // Make sure the new directory exists, creating it if necessary.
806 if (std::error_code EC = llvm::sys::fs::create_directories(ParentPath))
807 llvm::errs() << "warning: could not create directory '" << ParentPath
808 << "': " << EC.message() << '\n';
810 return NewPath.str();
814 class WriteIndexesThinBackend : public ThinBackendProc {
815 std::string OldPrefix, NewPrefix;
816 bool ShouldEmitImportsFiles;
818 std::string LinkedObjectsFileName;
819 std::unique_ptr<llvm::raw_fd_ostream> LinkedObjectsFile;
822 WriteIndexesThinBackend(
823 Config &Conf, ModuleSummaryIndex &CombinedIndex,
824 const StringMap<GVSummaryMapTy> &ModuleToDefinedGVSummaries,
825 std::string OldPrefix, std::string NewPrefix, bool ShouldEmitImportsFiles,
826 std::string LinkedObjectsFileName)
827 : ThinBackendProc(Conf, CombinedIndex, ModuleToDefinedGVSummaries),
828 OldPrefix(OldPrefix), NewPrefix(NewPrefix),
829 ShouldEmitImportsFiles(ShouldEmitImportsFiles),
830 LinkedObjectsFileName(LinkedObjectsFileName) {}
833 unsigned Task, BitcodeModule BM,
834 const FunctionImporter::ImportMapTy &ImportList,
835 const FunctionImporter::ExportSetTy &ExportList,
836 const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes> &ResolvedODR,
837 MapVector<StringRef, BitcodeModule> &ModuleMap) override {
838 StringRef ModulePath = BM.getModuleIdentifier();
839 std::string NewModulePath =
840 getThinLTOOutputFile(ModulePath, OldPrefix, NewPrefix);
843 if (!LinkedObjectsFileName.empty()) {
844 if (!LinkedObjectsFile) {
845 LinkedObjectsFile = llvm::make_unique<raw_fd_ostream>(
846 LinkedObjectsFileName, EC, sys::fs::OpenFlags::F_None);
848 return errorCodeToError(EC);
850 *LinkedObjectsFile << NewModulePath << '\n';
853 std::map<std::string, GVSummaryMapTy> ModuleToSummariesForIndex;
854 gatherImportedSummariesForModule(ModulePath, ModuleToDefinedGVSummaries,
855 ImportList, ModuleToSummariesForIndex);
857 raw_fd_ostream OS(NewModulePath + ".thinlto.bc", EC,
858 sys::fs::OpenFlags::F_None);
860 return errorCodeToError(EC);
861 WriteIndexToFile(CombinedIndex, OS, &ModuleToSummariesForIndex);
863 if (ShouldEmitImportsFiles)
864 return errorCodeToError(
865 EmitImportsFiles(ModulePath, NewModulePath + ".imports", ImportList));
866 return Error::success();
869 Error wait() override { return Error::success(); }
871 } // end anonymous namespace
873 ThinBackend lto::createWriteIndexesThinBackend(std::string OldPrefix,
874 std::string NewPrefix,
875 bool ShouldEmitImportsFiles,
876 std::string LinkedObjectsFile) {
877 return [=](Config &Conf, ModuleSummaryIndex &CombinedIndex,
878 const StringMap<GVSummaryMapTy> &ModuleToDefinedGVSummaries,
879 AddStreamFn AddStream, NativeObjectCache Cache) {
880 return llvm::make_unique<WriteIndexesThinBackend>(
881 Conf, CombinedIndex, ModuleToDefinedGVSummaries, OldPrefix, NewPrefix,
882 ShouldEmitImportsFiles, LinkedObjectsFile);
886 Error LTO::runThinLTO(AddStreamFn AddStream, NativeObjectCache Cache,
887 bool HasRegularLTO) {
888 if (ThinLTO.ModuleMap.empty())
889 return Error::success();
891 if (Conf.CombinedIndexHook && !Conf.CombinedIndexHook(ThinLTO.CombinedIndex))
892 return Error::success();
894 // Collect for each module the list of function it defines (GUID ->
896 StringMap<std::map<GlobalValue::GUID, GlobalValueSummary *>>
897 ModuleToDefinedGVSummaries(ThinLTO.ModuleMap.size());
898 ThinLTO.CombinedIndex.collectDefinedGVSummariesPerModule(
899 ModuleToDefinedGVSummaries);
900 // Create entries for any modules that didn't have any GV summaries
901 // (either they didn't have any GVs to start with, or we suppressed
902 // generation of the summaries because they e.g. had inline assembly
903 // uses that couldn't be promoted/renamed on export). This is so
904 // InProcessThinBackend::start can still launch a backend thread, which
905 // is passed the map of summaries for the module, without any special
906 // handling for this case.
907 for (auto &Mod : ThinLTO.ModuleMap)
908 if (!ModuleToDefinedGVSummaries.count(Mod.first))
909 ModuleToDefinedGVSummaries.try_emplace(Mod.first);
911 StringMap<FunctionImporter::ImportMapTy> ImportLists(
912 ThinLTO.ModuleMap.size());
913 StringMap<FunctionImporter::ExportSetTy> ExportLists(
914 ThinLTO.ModuleMap.size());
915 StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;
917 if (Conf.OptLevel > 0) {
918 // Compute "dead" symbols, we don't want to import/export these!
919 DenseSet<GlobalValue::GUID> GUIDPreservedSymbols;
920 for (auto &Res : GlobalResolutions) {
921 if (Res.second.VisibleOutsideThinLTO &&
922 // IRName will be defined if we have seen the prevailing copy of
923 // this value. If not, no need to preserve any ThinLTO copies.
924 !Res.second.IRName.empty())
925 GUIDPreservedSymbols.insert(GlobalValue::getGUID(Res.second.IRName));
929 computeDeadSymbols(ThinLTO.CombinedIndex, GUIDPreservedSymbols);
931 ComputeCrossModuleImport(ThinLTO.CombinedIndex, ModuleToDefinedGVSummaries,
932 ImportLists, ExportLists, &DeadSymbols);
934 std::set<GlobalValue::GUID> ExportedGUIDs;
935 for (auto &Res : GlobalResolutions) {
936 // First check if the symbol was flagged as having external references.
937 if (Res.second.Partition != GlobalResolution::External)
939 // IRName will be defined if we have seen the prevailing copy of
940 // this value. If not, no need to mark as exported from a ThinLTO
941 // partition (and we can't get the GUID).
942 if (Res.second.IRName.empty())
944 auto GUID = GlobalValue::getGUID(Res.second.IRName);
945 // Mark exported unless index-based analysis determined it to be dead.
946 if (!DeadSymbols.count(GUID))
947 ExportedGUIDs.insert(GlobalValue::getGUID(Res.second.IRName));
950 auto isPrevailing = [&](GlobalValue::GUID GUID,
951 const GlobalValueSummary *S) {
952 return ThinLTO.PrevailingModuleForGUID[GUID] == S->modulePath();
954 auto isExported = [&](StringRef ModuleIdentifier, GlobalValue::GUID GUID) {
955 const auto &ExportList = ExportLists.find(ModuleIdentifier);
956 return (ExportList != ExportLists.end() &&
957 ExportList->second.count(GUID)) ||
958 ExportedGUIDs.count(GUID);
960 thinLTOInternalizeAndPromoteInIndex(ThinLTO.CombinedIndex, isExported);
962 auto recordNewLinkage = [&](StringRef ModuleIdentifier,
963 GlobalValue::GUID GUID,
964 GlobalValue::LinkageTypes NewLinkage) {
965 ResolvedODR[ModuleIdentifier][GUID] = NewLinkage;
968 thinLTOResolveWeakForLinkerInIndex(ThinLTO.CombinedIndex, isPrevailing,
972 std::unique_ptr<ThinBackendProc> BackendProc =
973 ThinLTO.Backend(Conf, ThinLTO.CombinedIndex, ModuleToDefinedGVSummaries,
976 // Task numbers start at ParallelCodeGenParallelismLevel if an LTO
977 // module is present, as tasks 0 through ParallelCodeGenParallelismLevel-1
978 // are reserved for parallel code generation partitions.
980 HasRegularLTO ? RegularLTO.ParallelCodeGenParallelismLevel : 0;
981 for (auto &Mod : ThinLTO.ModuleMap) {
982 if (Error E = BackendProc->start(Task, Mod.second, ImportLists[Mod.first],
983 ExportLists[Mod.first],
984 ResolvedODR[Mod.first], ThinLTO.ModuleMap))
989 return BackendProc->wait();