1 //===-LTO.cpp - LLVM Link Time Optimizer ----------------------------------===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 // This file implements functions and classes used to support LTO.
11 //===----------------------------------------------------------------------===//
13 #include "llvm/LTO/LTO.h"
14 #include "llvm/ADT/Statistic.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/Config/llvm-config.h"
21 #include "llvm/IR/AutoUpgrade.h"
22 #include "llvm/IR/DiagnosticPrinter.h"
23 #include "llvm/IR/Intrinsics.h"
24 #include "llvm/IR/LegacyPassManager.h"
25 #include "llvm/IR/Mangler.h"
26 #include "llvm/IR/Metadata.h"
27 #include "llvm/IR/RemarkStreamer.h"
28 #include "llvm/LTO/LTOBackend.h"
29 #include "llvm/LTO/SummaryBasedOptimizations.h"
30 #include "llvm/Linker/IRMover.h"
31 #include "llvm/Object/IRObjectFile.h"
32 #include "llvm/Support/Error.h"
33 #include "llvm/Support/ManagedStatic.h"
34 #include "llvm/Support/MemoryBuffer.h"
35 #include "llvm/Support/Path.h"
36 #include "llvm/Support/SHA1.h"
37 #include "llvm/Support/SourceMgr.h"
38 #include "llvm/Support/TargetRegistry.h"
39 #include "llvm/Support/ThreadPool.h"
40 #include "llvm/Support/Threading.h"
41 #include "llvm/Support/VCSRevision.h"
42 #include "llvm/Support/raw_ostream.h"
43 #include "llvm/Target/TargetMachine.h"
44 #include "llvm/Target/TargetOptions.h"
45 #include "llvm/Transforms/IPO.h"
46 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
47 #include "llvm/Transforms/Utils/FunctionImportUtils.h"
48 #include "llvm/Transforms/Utils/SplitModule.h"
54 using namespace object;
56 #define DEBUG_TYPE "lto"
59 DumpThinCGSCCs("dump-thin-cg-sccs", cl::init(false), cl::Hidden,
60 cl::desc("Dump the SCCs in the ThinLTO index's callgraph"));
62 /// Enable global value internalization in LTO.
63 cl::opt<bool> EnableLTOInternalization(
64 "enable-lto-internalization", cl::init(true), cl::Hidden,
65 cl::desc("Enable global value internalization in LTO"));
67 // Computes a unique hash for the Module considering the current list of
68 // export/import and other global analysis results.
69 // The hash is produced in \p Key.
70 void llvm::computeLTOCacheKey(
71 SmallString<40> &Key, const Config &Conf, const ModuleSummaryIndex &Index,
72 StringRef ModuleID, const FunctionImporter::ImportMapTy &ImportList,
73 const FunctionImporter::ExportSetTy &ExportList,
74 const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes> &ResolvedODR,
75 const GVSummaryMapTy &DefinedGlobals,
76 const std::set<GlobalValue::GUID> &CfiFunctionDefs,
77 const std::set<GlobalValue::GUID> &CfiFunctionDecls) {
78 // Compute the unique hash for this entry.
79 // This is based on the current compiler version, the module itself, the
80 // export list, the hash for every single module in the import list, the
81 // list of ResolvedODR for the module, and the list of preserved symbols.
84 // Start with the compiler revision
85 Hasher.update(LLVM_VERSION_STRING);
87 Hasher.update(LLVM_REVISION);
90 // Include the parts of the LTO configuration that affect code generation.
91 auto AddString = [&](StringRef Str) {
93 Hasher.update(ArrayRef<uint8_t>{0});
95 auto AddUnsigned = [&](unsigned I) {
101 Hasher.update(ArrayRef<uint8_t>{Data, 4});
103 auto AddUint64 = [&](uint64_t I) {
113 Hasher.update(ArrayRef<uint8_t>{Data, 8});
116 // FIXME: Hash more of Options. For now all clients initialize Options from
117 // command-line flags (which is unsupported in production), but may set
118 // RelaxELFRelocations. The clang driver can also pass FunctionSections,
119 // DataSections and DebuggerTuning via command line flags.
120 AddUnsigned(Conf.Options.RelaxELFRelocations);
121 AddUnsigned(Conf.Options.FunctionSections);
122 AddUnsigned(Conf.Options.DataSections);
123 AddUnsigned((unsigned)Conf.Options.DebuggerTuning);
124 for (auto &A : Conf.MAttrs)
127 AddUnsigned(*Conf.RelocModel);
131 AddUnsigned(*Conf.CodeModel);
134 AddUnsigned(Conf.CGOptLevel);
135 AddUnsigned(Conf.CGFileType);
136 AddUnsigned(Conf.OptLevel);
137 AddUnsigned(Conf.UseNewPM);
138 AddUnsigned(Conf.Freestanding);
139 AddString(Conf.OptPipeline);
140 AddString(Conf.AAPipeline);
141 AddString(Conf.OverrideTriple);
142 AddString(Conf.DefaultTriple);
143 AddString(Conf.DwoDir);
145 // Include the hash for the current module
146 auto ModHash = Index.getModuleHash(ModuleID);
147 Hasher.update(ArrayRef<uint8_t>((uint8_t *)&ModHash[0], sizeof(ModHash)));
148 for (auto F : ExportList)
149 // The export list can impact the internalization, be conservative here
150 Hasher.update(ArrayRef<uint8_t>((uint8_t *)&F, sizeof(F)));
152 // Include the hash for every module we import functions from. The set of
153 // imported symbols for each module may affect code generation and is
154 // sensitive to link order, so include that as well.
155 for (auto &Entry : ImportList) {
156 auto ModHash = Index.getModuleHash(Entry.first());
157 Hasher.update(ArrayRef<uint8_t>((uint8_t *)&ModHash[0], sizeof(ModHash)));
159 AddUint64(Entry.second.size());
160 for (auto &Fn : Entry.second)
164 // Include the hash for the resolved ODR.
165 for (auto &Entry : ResolvedODR) {
166 Hasher.update(ArrayRef<uint8_t>((const uint8_t *)&Entry.first,
167 sizeof(GlobalValue::GUID)));
168 Hasher.update(ArrayRef<uint8_t>((const uint8_t *)&Entry.second,
169 sizeof(GlobalValue::LinkageTypes)));
172 // Members of CfiFunctionDefs and CfiFunctionDecls that are referenced or
173 // defined in this module.
174 std::set<GlobalValue::GUID> UsedCfiDefs;
175 std::set<GlobalValue::GUID> UsedCfiDecls;
177 // Typeids used in this module.
178 std::set<GlobalValue::GUID> UsedTypeIds;
180 auto AddUsedCfiGlobal = [&](GlobalValue::GUID ValueGUID) {
181 if (CfiFunctionDefs.count(ValueGUID))
182 UsedCfiDefs.insert(ValueGUID);
183 if (CfiFunctionDecls.count(ValueGUID))
184 UsedCfiDecls.insert(ValueGUID);
187 auto AddUsedThings = [&](GlobalValueSummary *GS) {
189 AddUnsigned(GS->isLive());
190 AddUnsigned(GS->canAutoHide());
191 for (const ValueInfo &VI : GS->refs()) {
192 AddUnsigned(VI.isDSOLocal());
193 AddUsedCfiGlobal(VI.getGUID());
195 if (auto *GVS = dyn_cast<GlobalVarSummary>(GS))
196 AddUnsigned(GVS->isReadOnly());
197 if (auto *FS = dyn_cast<FunctionSummary>(GS)) {
198 for (auto &TT : FS->type_tests())
199 UsedTypeIds.insert(TT);
200 for (auto &TT : FS->type_test_assume_vcalls())
201 UsedTypeIds.insert(TT.GUID);
202 for (auto &TT : FS->type_checked_load_vcalls())
203 UsedTypeIds.insert(TT.GUID);
204 for (auto &TT : FS->type_test_assume_const_vcalls())
205 UsedTypeIds.insert(TT.VFunc.GUID);
206 for (auto &TT : FS->type_checked_load_const_vcalls())
207 UsedTypeIds.insert(TT.VFunc.GUID);
208 for (auto &ET : FS->calls()) {
209 AddUnsigned(ET.first.isDSOLocal());
210 AddUsedCfiGlobal(ET.first.getGUID());
215 // Include the hash for the linkage type to reflect internalization and weak
216 // resolution, and collect any used type identifier resolutions.
217 for (auto &GS : DefinedGlobals) {
218 GlobalValue::LinkageTypes Linkage = GS.second->linkage();
220 ArrayRef<uint8_t>((const uint8_t *)&Linkage, sizeof(Linkage)));
221 AddUsedCfiGlobal(GS.first);
222 AddUsedThings(GS.second);
225 // Imported functions may introduce new uses of type identifier resolutions,
226 // so we need to collect their used resolutions as well.
227 for (auto &ImpM : ImportList)
228 for (auto &ImpF : ImpM.second) {
229 GlobalValueSummary *S = Index.findSummaryInModule(ImpF, ImpM.first());
231 // If this is an alias, we also care about any types/etc. that the aliasee
233 if (auto *AS = dyn_cast_or_null<AliasSummary>(S))
234 AddUsedThings(AS->getBaseObject());
237 auto AddTypeIdSummary = [&](StringRef TId, const TypeIdSummary &S) {
240 AddUnsigned(S.TTRes.TheKind);
241 AddUnsigned(S.TTRes.SizeM1BitWidth);
243 AddUint64(S.TTRes.AlignLog2);
244 AddUint64(S.TTRes.SizeM1);
245 AddUint64(S.TTRes.BitMask);
246 AddUint64(S.TTRes.InlineBits);
248 AddUint64(S.WPDRes.size());
249 for (auto &WPD : S.WPDRes) {
250 AddUnsigned(WPD.first);
251 AddUnsigned(WPD.second.TheKind);
252 AddString(WPD.second.SingleImplName);
254 AddUint64(WPD.second.ResByArg.size());
255 for (auto &ByArg : WPD.second.ResByArg) {
256 AddUint64(ByArg.first.size());
257 for (uint64_t Arg : ByArg.first)
259 AddUnsigned(ByArg.second.TheKind);
260 AddUint64(ByArg.second.Info);
261 AddUnsigned(ByArg.second.Byte);
262 AddUnsigned(ByArg.second.Bit);
267 // Include the hash for all type identifiers used by this module.
268 for (GlobalValue::GUID TId : UsedTypeIds) {
269 auto TidIter = Index.typeIds().equal_range(TId);
270 for (auto It = TidIter.first; It != TidIter.second; ++It)
271 AddTypeIdSummary(It->second.first, It->second.second);
274 AddUnsigned(UsedCfiDefs.size());
275 for (auto &V : UsedCfiDefs)
278 AddUnsigned(UsedCfiDecls.size());
279 for (auto &V : UsedCfiDecls)
282 if (!Conf.SampleProfile.empty()) {
283 auto FileOrErr = MemoryBuffer::getFile(Conf.SampleProfile);
285 Hasher.update(FileOrErr.get()->getBuffer());
287 if (!Conf.ProfileRemapping.empty()) {
288 FileOrErr = MemoryBuffer::getFile(Conf.ProfileRemapping);
290 Hasher.update(FileOrErr.get()->getBuffer());
295 Key = toHex(Hasher.result());
298 static void thinLTOResolvePrevailingGUID(
299 ValueInfo VI, DenseSet<GlobalValueSummary *> &GlobalInvolvedWithAlias,
300 function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
302 function_ref<void(StringRef, GlobalValue::GUID, GlobalValue::LinkageTypes)>
304 const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols) {
305 for (auto &S : VI.getSummaryList()) {
306 GlobalValue::LinkageTypes OriginalLinkage = S->linkage();
307 // Ignore local and appending linkage values since the linker
308 // doesn't resolve them.
309 if (GlobalValue::isLocalLinkage(OriginalLinkage) ||
310 GlobalValue::isAppendingLinkage(S->linkage()))
312 // We need to emit only one of these. The prevailing module will keep it,
313 // but turned into a weak, while the others will drop it when possible.
314 // This is both a compile-time optimization and a correctness
315 // transformation. This is necessary for correctness when we have exported
316 // a reference - we need to convert the linkonce to weak to
317 // ensure a copy is kept to satisfy the exported reference.
318 // FIXME: We may want to split the compile time and correctness
319 // aspects into separate routines.
320 if (isPrevailing(VI.getGUID(), S.get())) {
321 if (GlobalValue::isLinkOnceLinkage(OriginalLinkage)) {
322 S->setLinkage(GlobalValue::getWeakLinkage(
323 GlobalValue::isLinkOnceODRLinkage(OriginalLinkage)));
324 // The kept copy is eligible for auto-hiding (hidden visibility) if all
325 // copies were (i.e. they were all linkonce_odr global unnamed addr).
326 // If any copy is not (e.g. it was originally weak_odr), then the symbol
327 // must remain externally available (e.g. a weak_odr from an explicitly
328 // instantiated template). Additionally, if it is in the
329 // GUIDPreservedSymbols set, that means that it is visibile outside
330 // the summary (e.g. in a native object or a bitcode file without
331 // summary), and in that case we cannot hide it as it isn't possible to
333 S->setCanAutoHide(VI.canAutoHide() &&
334 !GUIDPreservedSymbols.count(VI.getGUID()));
337 // Alias and aliasee can't be turned into available_externally.
338 else if (!isa<AliasSummary>(S.get()) &&
339 !GlobalInvolvedWithAlias.count(S.get()))
340 S->setLinkage(GlobalValue::AvailableExternallyLinkage);
341 if (S->linkage() != OriginalLinkage)
342 recordNewLinkage(S->modulePath(), VI.getGUID(), S->linkage());
346 /// Resolve linkage for prevailing symbols in the \p Index.
348 // We'd like to drop these functions if they are no longer referenced in the
349 // current module. However there is a chance that another module is still
350 // referencing them because of the import. We make sure we always emit at least
352 void llvm::thinLTOResolvePrevailingInIndex(
353 ModuleSummaryIndex &Index,
354 function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
356 function_ref<void(StringRef, GlobalValue::GUID, GlobalValue::LinkageTypes)>
358 const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols) {
359 // We won't optimize the globals that are referenced by an alias for now
360 // Ideally we should turn the alias into a global and duplicate the definition
362 DenseSet<GlobalValueSummary *> GlobalInvolvedWithAlias;
363 for (auto &I : Index)
364 for (auto &S : I.second.SummaryList)
365 if (auto AS = dyn_cast<AliasSummary>(S.get()))
366 GlobalInvolvedWithAlias.insert(&AS->getAliasee());
368 for (auto &I : Index)
369 thinLTOResolvePrevailingGUID(Index.getValueInfo(I), GlobalInvolvedWithAlias,
370 isPrevailing, recordNewLinkage,
371 GUIDPreservedSymbols);
374 static bool isWeakWriteableObject(GlobalValueSummary *GVS) {
375 if (auto *VarSummary = dyn_cast<GlobalVarSummary>(GVS->getBaseObject()))
376 return !VarSummary->isReadOnly() &&
377 (VarSummary->linkage() == GlobalValue::WeakODRLinkage ||
378 VarSummary->linkage() == GlobalValue::LinkOnceODRLinkage);
382 static void thinLTOInternalizeAndPromoteGUID(
383 GlobalValueSummaryList &GVSummaryList, GlobalValue::GUID GUID,
384 function_ref<bool(StringRef, GlobalValue::GUID)> isExported) {
385 for (auto &S : GVSummaryList) {
386 if (isExported(S->modulePath(), GUID)) {
387 if (GlobalValue::isLocalLinkage(S->linkage()))
388 S->setLinkage(GlobalValue::ExternalLinkage);
389 } else if (EnableLTOInternalization &&
390 // Ignore local and appending linkage values since the linker
391 // doesn't resolve them.
392 !GlobalValue::isLocalLinkage(S->linkage()) &&
393 S->linkage() != GlobalValue::AppendingLinkage &&
394 // We can't internalize available_externally globals because this
395 // can break function pointer equality.
396 S->linkage() != GlobalValue::AvailableExternallyLinkage &&
397 // Functions and read-only variables with linkonce_odr and weak_odr
398 // linkage can be internalized. We can't internalize linkonce_odr
399 // and weak_odr variables which are modified somewhere in the
400 // program because reads and writes will become inconsistent.
401 !isWeakWriteableObject(S.get()))
402 S->setLinkage(GlobalValue::InternalLinkage);
406 // Update the linkages in the given \p Index to mark exported values
407 // as external and non-exported values as internal.
408 void llvm::thinLTOInternalizeAndPromoteInIndex(
409 ModuleSummaryIndex &Index,
410 function_ref<bool(StringRef, GlobalValue::GUID)> isExported) {
411 for (auto &I : Index)
412 thinLTOInternalizeAndPromoteGUID(I.second.SummaryList, I.first, isExported);
415 // Requires a destructor for std::vector<InputModule>.
416 InputFile::~InputFile() = default;
418 Expected<std::unique_ptr<InputFile>> InputFile::create(MemoryBufferRef Object) {
419 std::unique_ptr<InputFile> File(new InputFile);
421 Expected<IRSymtabFile> FOrErr = readIRSymtab(Object);
423 return FOrErr.takeError();
425 File->TargetTriple = FOrErr->TheReader.getTargetTriple();
426 File->SourceFileName = FOrErr->TheReader.getSourceFileName();
427 File->COFFLinkerOpts = FOrErr->TheReader.getCOFFLinkerOpts();
428 File->ComdatTable = FOrErr->TheReader.getComdatTable();
430 for (unsigned I = 0; I != FOrErr->Mods.size(); ++I) {
431 size_t Begin = File->Symbols.size();
432 for (const irsymtab::Reader::SymbolRef &Sym :
433 FOrErr->TheReader.module_symbols(I))
434 // Skip symbols that are irrelevant to LTO. Note that this condition needs
435 // to match the one in Skip() in LTO::addRegularLTO().
436 if (Sym.isGlobal() && !Sym.isFormatSpecific())
437 File->Symbols.push_back(Sym);
438 File->ModuleSymIndices.push_back({Begin, File->Symbols.size()});
441 File->Mods = FOrErr->Mods;
442 File->Strtab = std::move(FOrErr->Strtab);
443 return std::move(File);
446 StringRef InputFile::getName() const {
447 return Mods[0].getModuleIdentifier();
450 BitcodeModule &InputFile::getSingleBitcodeModule() {
451 assert(Mods.size() == 1 && "Expect only one bitcode module");
455 LTO::RegularLTOState::RegularLTOState(unsigned ParallelCodeGenParallelismLevel,
457 : ParallelCodeGenParallelismLevel(ParallelCodeGenParallelismLevel),
458 Ctx(Conf), CombinedModule(llvm::make_unique<Module>("ld-temp.o", Ctx)),
459 Mover(llvm::make_unique<IRMover>(*CombinedModule)) {}
461 LTO::ThinLTOState::ThinLTOState(ThinBackend Backend)
462 : Backend(Backend), CombinedIndex(/*HaveGVs*/ false) {
465 createInProcessThinBackend(llvm::heavyweight_hardware_concurrency());
468 LTO::LTO(Config Conf, ThinBackend Backend,
469 unsigned ParallelCodeGenParallelismLevel)
470 : Conf(std::move(Conf)),
471 RegularLTO(ParallelCodeGenParallelismLevel, this->Conf),
472 ThinLTO(std::move(Backend)) {}
474 // Requires a destructor for MapVector<BitcodeModule>.
475 LTO::~LTO() = default;
477 // Add the symbols in the given module to the GlobalResolutions map, and resolve
479 void LTO::addModuleToGlobalRes(ArrayRef<InputFile::Symbol> Syms,
480 ArrayRef<SymbolResolution> Res,
481 unsigned Partition, bool InSummary) {
482 auto *ResI = Res.begin();
483 auto *ResE = Res.end();
485 for (const InputFile::Symbol &Sym : Syms) {
486 assert(ResI != ResE);
487 SymbolResolution Res = *ResI++;
489 StringRef Name = Sym.getName();
490 Triple TT(RegularLTO.CombinedModule->getTargetTriple());
491 // Strip the __imp_ prefix from COFF dllimport symbols (similar to the
492 // way they are handled by lld), otherwise we can end up with two
493 // global resolutions (one with and one for a copy of the symbol without).
494 if (TT.isOSBinFormatCOFF() && Name.startswith("__imp_"))
495 Name = Name.substr(strlen("__imp_"));
496 auto &GlobalRes = GlobalResolutions[Name];
497 GlobalRes.UnnamedAddr &= Sym.isUnnamedAddr();
498 if (Res.Prevailing) {
499 assert(!GlobalRes.Prevailing &&
500 "Multiple prevailing defs are not allowed");
501 GlobalRes.Prevailing = true;
502 GlobalRes.IRName = Sym.getIRName();
503 } else if (!GlobalRes.Prevailing && GlobalRes.IRName.empty()) {
504 // Sometimes it can be two copies of symbol in a module and prevailing
505 // symbol can have no IR name. That might happen if symbol is defined in
506 // module level inline asm block. In case we have multiple modules with
507 // the same symbol we want to use IR name of the prevailing symbol.
508 // Otherwise, if we haven't seen a prevailing symbol, set the name so that
509 // we can later use it to check if there is any prevailing copy in IR.
510 GlobalRes.IRName = Sym.getIRName();
513 // Set the partition to external if we know it is re-defined by the linker
514 // with -defsym or -wrap options, used elsewhere, e.g. it is visible to a
515 // regular object, is referenced from llvm.compiler_used, or was already
516 // recorded as being referenced from a different partition.
517 if (Res.LinkerRedefined || Res.VisibleToRegularObj || Sym.isUsed() ||
518 (GlobalRes.Partition != GlobalResolution::Unknown &&
519 GlobalRes.Partition != Partition)) {
520 GlobalRes.Partition = GlobalResolution::External;
522 // First recorded reference, save the current partition.
523 GlobalRes.Partition = Partition;
525 // Flag as visible outside of summary if visible from a regular object or
526 // from a module that does not have a summary.
527 GlobalRes.VisibleOutsideSummary |=
528 (Res.VisibleToRegularObj || Sym.isUsed() || !InSummary);
532 static void writeToResolutionFile(raw_ostream &OS, InputFile *Input,
533 ArrayRef<SymbolResolution> Res) {
534 StringRef Path = Input->getName();
536 auto ResI = Res.begin();
537 for (const InputFile::Symbol &Sym : Input->symbols()) {
538 assert(ResI != Res.end());
539 SymbolResolution Res = *ResI++;
541 OS << "-r=" << Path << ',' << Sym.getName() << ',';
544 if (Res.FinalDefinitionInLinkageUnit)
546 if (Res.VisibleToRegularObj)
548 if (Res.LinkerRedefined)
553 assert(ResI == Res.end());
556 Error LTO::add(std::unique_ptr<InputFile> Input,
557 ArrayRef<SymbolResolution> Res) {
558 assert(!CalledGetMaxTasks);
560 if (Conf.ResolutionFile)
561 writeToResolutionFile(*Conf.ResolutionFile, Input.get(), Res);
563 if (RegularLTO.CombinedModule->getTargetTriple().empty())
564 RegularLTO.CombinedModule->setTargetTriple(Input->getTargetTriple());
566 const SymbolResolution *ResI = Res.begin();
567 for (unsigned I = 0; I != Input->Mods.size(); ++I)
568 if (Error Err = addModule(*Input, I, ResI, Res.end()))
571 assert(ResI == Res.end());
572 return Error::success();
575 Error LTO::addModule(InputFile &Input, unsigned ModI,
576 const SymbolResolution *&ResI,
577 const SymbolResolution *ResE) {
578 Expected<BitcodeLTOInfo> LTOInfo = Input.Mods[ModI].getLTOInfo();
580 return LTOInfo.takeError();
582 if (EnableSplitLTOUnit.hasValue()) {
583 // If only some modules were split, flag this in the index so that
584 // we can skip or error on optimizations that need consistently split
585 // modules (whole program devirt and lower type tests).
586 if (EnableSplitLTOUnit.getValue() != LTOInfo->EnableSplitLTOUnit)
587 ThinLTO.CombinedIndex.setPartiallySplitLTOUnits();
589 EnableSplitLTOUnit = LTOInfo->EnableSplitLTOUnit;
591 BitcodeModule BM = Input.Mods[ModI];
592 auto ModSyms = Input.module_symbols(ModI);
593 addModuleToGlobalRes(ModSyms, {ResI, ResE},
594 LTOInfo->IsThinLTO ? ThinLTO.ModuleMap.size() + 1 : 0,
595 LTOInfo->HasSummary);
597 if (LTOInfo->IsThinLTO)
598 return addThinLTO(BM, ModSyms, ResI, ResE);
600 Expected<RegularLTOState::AddedModule> ModOrErr =
601 addRegularLTO(BM, ModSyms, ResI, ResE);
603 return ModOrErr.takeError();
605 if (!LTOInfo->HasSummary)
606 return linkRegularLTO(std::move(*ModOrErr), /*LivenessFromIndex=*/false);
608 // Regular LTO module summaries are added to a dummy module that represents
609 // the combined regular LTO module.
610 if (Error Err = BM.readSummary(ThinLTO.CombinedIndex, "", -1ull))
612 RegularLTO.ModsWithSummaries.push_back(std::move(*ModOrErr));
613 return Error::success();
616 // Checks whether the given global value is in a non-prevailing comdat
617 // (comdat containing values the linker indicated were not prevailing,
618 // which we then dropped to available_externally), and if so, removes
619 // it from the comdat. This is called for all global values to ensure the
620 // comdat is empty rather than leaving an incomplete comdat. It is needed for
621 // regular LTO modules, in case we are in a mixed-LTO mode (both regular
622 // and thin LTO modules) compilation. Since the regular LTO module will be
623 // linked first in the final native link, we want to make sure the linker
624 // doesn't select any of these incomplete comdats that would be left
625 // in the regular LTO module without this cleanup.
627 handleNonPrevailingComdat(GlobalValue &GV,
628 std::set<const Comdat *> &NonPrevailingComdats) {
629 Comdat *C = GV.getComdat();
633 if (!NonPrevailingComdats.count(C))
636 // Additionally need to drop externally visible global values from the comdat
637 // to available_externally, so that there aren't multiply defined linker
639 if (!GV.hasLocalLinkage())
640 GV.setLinkage(GlobalValue::AvailableExternallyLinkage);
642 if (auto GO = dyn_cast<GlobalObject>(&GV))
643 GO->setComdat(nullptr);
646 // Add a regular LTO object to the link.
647 // The resulting module needs to be linked into the combined LTO module with
649 Expected<LTO::RegularLTOState::AddedModule>
650 LTO::addRegularLTO(BitcodeModule BM, ArrayRef<InputFile::Symbol> Syms,
651 const SymbolResolution *&ResI,
652 const SymbolResolution *ResE) {
653 RegularLTOState::AddedModule Mod;
654 Expected<std::unique_ptr<Module>> MOrErr =
655 BM.getLazyModule(RegularLTO.Ctx, /*ShouldLazyLoadMetadata*/ true,
656 /*IsImporting*/ false);
658 return MOrErr.takeError();
659 Module &M = **MOrErr;
660 Mod.M = std::move(*MOrErr);
662 if (Error Err = M.materializeMetadata())
663 return std::move(Err);
666 ModuleSymbolTable SymTab;
667 SymTab.addModule(&M);
669 for (GlobalVariable &GV : M.globals())
670 if (GV.hasAppendingLinkage())
671 Mod.Keep.push_back(&GV);
673 DenseSet<GlobalObject *> AliasedGlobals;
674 for (auto &GA : M.aliases())
675 if (GlobalObject *GO = GA.getBaseObject())
676 AliasedGlobals.insert(GO);
678 // In this function we need IR GlobalValues matching the symbols in Syms
679 // (which is not backed by a module), so we need to enumerate them in the same
680 // order. The symbol enumeration order of a ModuleSymbolTable intentionally
681 // matches the order of an irsymtab, but when we read the irsymtab in
682 // InputFile::create we omit some symbols that are irrelevant to LTO. The
683 // Skip() function skips the same symbols from the module as InputFile does
684 // from the symbol table.
685 auto MsymI = SymTab.symbols().begin(), MsymE = SymTab.symbols().end();
687 while (MsymI != MsymE) {
688 auto Flags = SymTab.getSymbolFlags(*MsymI);
689 if ((Flags & object::BasicSymbolRef::SF_Global) &&
690 !(Flags & object::BasicSymbolRef::SF_FormatSpecific))
697 std::set<const Comdat *> NonPrevailingComdats;
698 for (const InputFile::Symbol &Sym : Syms) {
699 assert(ResI != ResE);
700 SymbolResolution Res = *ResI++;
702 assert(MsymI != MsymE);
703 ModuleSymbolTable::Symbol Msym = *MsymI++;
706 if (GlobalValue *GV = Msym.dyn_cast<GlobalValue *>()) {
707 if (Res.Prevailing) {
708 if (Sym.isUndefined())
710 Mod.Keep.push_back(GV);
711 // For symbols re-defined with linker -wrap and -defsym options,
712 // set the linkage to weak to inhibit IPO. The linkage will be
713 // restored by the linker.
714 if (Res.LinkerRedefined)
715 GV->setLinkage(GlobalValue::WeakAnyLinkage);
717 GlobalValue::LinkageTypes OriginalLinkage = GV->getLinkage();
718 if (GlobalValue::isLinkOnceLinkage(OriginalLinkage))
719 GV->setLinkage(GlobalValue::getWeakLinkage(
720 GlobalValue::isLinkOnceODRLinkage(OriginalLinkage)));
721 } else if (isa<GlobalObject>(GV) &&
722 (GV->hasLinkOnceODRLinkage() || GV->hasWeakODRLinkage() ||
723 GV->hasAvailableExternallyLinkage()) &&
724 !AliasedGlobals.count(cast<GlobalObject>(GV))) {
725 // Any of the above three types of linkage indicates that the
726 // chosen prevailing symbol will have the same semantics as this copy of
727 // the symbol, so we may be able to link it with available_externally
728 // linkage. We will decide later whether to do that when we link this
729 // module (in linkRegularLTO), based on whether it is undefined.
730 Mod.Keep.push_back(GV);
731 GV->setLinkage(GlobalValue::AvailableExternallyLinkage);
733 NonPrevailingComdats.insert(GV->getComdat());
734 cast<GlobalObject>(GV)->setComdat(nullptr);
737 // Set the 'local' flag based on the linker resolution for this symbol.
738 if (Res.FinalDefinitionInLinkageUnit) {
739 GV->setDSOLocal(true);
740 if (GV->hasDLLImportStorageClass())
741 GV->setDLLStorageClass(GlobalValue::DLLStorageClassTypes::
742 DefaultStorageClass);
745 // Common resolution: collect the maximum size/alignment over all commons.
746 // We also record if we see an instance of a common as prevailing, so that
747 // if none is prevailing we can ignore it later.
748 if (Sym.isCommon()) {
749 // FIXME: We should figure out what to do about commons defined by asm.
750 // For now they aren't reported correctly by ModuleSymbolTable.
751 auto &CommonRes = RegularLTO.Commons[Sym.getIRName()];
752 CommonRes.Size = std::max(CommonRes.Size, Sym.getCommonSize());
753 CommonRes.Align = std::max(CommonRes.Align, Sym.getCommonAlignment());
754 CommonRes.Prevailing |= Res.Prevailing;
758 if (!M.getComdatSymbolTable().empty())
759 for (GlobalValue &GV : M.global_values())
760 handleNonPrevailingComdat(GV, NonPrevailingComdats);
761 assert(MsymI == MsymE);
762 return std::move(Mod);
765 Error LTO::linkRegularLTO(RegularLTOState::AddedModule Mod,
766 bool LivenessFromIndex) {
767 std::vector<GlobalValue *> Keep;
768 for (GlobalValue *GV : Mod.Keep) {
769 if (LivenessFromIndex && !ThinLTO.CombinedIndex.isGUIDLive(GV->getGUID()))
772 if (!GV->hasAvailableExternallyLinkage()) {
777 // Only link available_externally definitions if we don't already have a
779 GlobalValue *CombinedGV =
780 RegularLTO.CombinedModule->getNamedValue(GV->getName());
781 if (CombinedGV && !CombinedGV->isDeclaration())
787 return RegularLTO.Mover->move(std::move(Mod.M), Keep,
788 [](GlobalValue &, IRMover::ValueAdder) {},
789 /* IsPerformingImport */ false);
792 // Add a ThinLTO module to the link.
793 Error LTO::addThinLTO(BitcodeModule BM, ArrayRef<InputFile::Symbol> Syms,
794 const SymbolResolution *&ResI,
795 const SymbolResolution *ResE) {
797 BM.readSummary(ThinLTO.CombinedIndex, BM.getModuleIdentifier(),
798 ThinLTO.ModuleMap.size()))
801 for (const InputFile::Symbol &Sym : Syms) {
802 assert(ResI != ResE);
803 SymbolResolution Res = *ResI++;
805 if (!Sym.getIRName().empty()) {
806 auto GUID = GlobalValue::getGUID(GlobalValue::getGlobalIdentifier(
807 Sym.getIRName(), GlobalValue::ExternalLinkage, ""));
808 if (Res.Prevailing) {
809 ThinLTO.PrevailingModuleForGUID[GUID] = BM.getModuleIdentifier();
811 // For linker redefined symbols (via --wrap or --defsym) we want to
812 // switch the linkage to `weak` to prevent IPOs from happening.
813 // Find the summary in the module for this very GV and record the new
814 // linkage so that we can switch it when we import the GV.
815 if (Res.LinkerRedefined)
816 if (auto S = ThinLTO.CombinedIndex.findSummaryInModule(
817 GUID, BM.getModuleIdentifier()))
818 S->setLinkage(GlobalValue::WeakAnyLinkage);
821 // If the linker resolved the symbol to a local definition then mark it
822 // as local in the summary for the module we are adding.
823 if (Res.FinalDefinitionInLinkageUnit) {
824 if (auto S = ThinLTO.CombinedIndex.findSummaryInModule(
825 GUID, BM.getModuleIdentifier())) {
826 S->setDSOLocal(true);
832 if (!ThinLTO.ModuleMap.insert({BM.getModuleIdentifier(), BM}).second)
833 return make_error<StringError>(
834 "Expected at most one ThinLTO module per bitcode file",
835 inconvertibleErrorCode());
837 return Error::success();
840 unsigned LTO::getMaxTasks() const {
841 CalledGetMaxTasks = true;
842 return RegularLTO.ParallelCodeGenParallelismLevel + ThinLTO.ModuleMap.size();
845 // If only some of the modules were split, we cannot correctly handle
846 // code that contains type tests or type checked loads.
847 Error LTO::checkPartiallySplit() {
848 if (!ThinLTO.CombinedIndex.partiallySplitLTOUnits())
849 return Error::success();
851 Function *TypeTestFunc = RegularLTO.CombinedModule->getFunction(
852 Intrinsic::getName(Intrinsic::type_test));
853 Function *TypeCheckedLoadFunc = RegularLTO.CombinedModule->getFunction(
854 Intrinsic::getName(Intrinsic::type_checked_load));
856 // First check if there are type tests / type checked loads in the
857 // merged regular LTO module IR.
858 if ((TypeTestFunc && !TypeTestFunc->use_empty()) ||
859 (TypeCheckedLoadFunc && !TypeCheckedLoadFunc->use_empty()))
860 return make_error<StringError>(
861 "inconsistent LTO Unit splitting (recompile with -fsplit-lto-unit)",
862 inconvertibleErrorCode());
864 // Otherwise check if there are any recorded in the combined summary from the
866 for (auto &P : ThinLTO.CombinedIndex) {
867 for (auto &S : P.second.SummaryList) {
868 auto *FS = dyn_cast<FunctionSummary>(S.get());
871 if (!FS->type_test_assume_vcalls().empty() ||
872 !FS->type_checked_load_vcalls().empty() ||
873 !FS->type_test_assume_const_vcalls().empty() ||
874 !FS->type_checked_load_const_vcalls().empty() ||
875 !FS->type_tests().empty())
876 return make_error<StringError>(
877 "inconsistent LTO Unit splitting (recompile with -fsplit-lto-unit)",
878 inconvertibleErrorCode());
881 return Error::success();
884 Error LTO::run(AddStreamFn AddStream, NativeObjectCache Cache) {
885 // Compute "dead" symbols, we don't want to import/export these!
886 DenseSet<GlobalValue::GUID> GUIDPreservedSymbols;
887 DenseMap<GlobalValue::GUID, PrevailingType> GUIDPrevailingResolutions;
888 for (auto &Res : GlobalResolutions) {
889 // Normally resolution have IR name of symbol. We can do nothing here
890 // otherwise. See comments in GlobalResolution struct for more details.
891 if (Res.second.IRName.empty())
894 GlobalValue::GUID GUID = GlobalValue::getGUID(
895 GlobalValue::dropLLVMManglingEscape(Res.second.IRName));
897 if (Res.second.VisibleOutsideSummary && Res.second.Prevailing)
898 GUIDPreservedSymbols.insert(GlobalValue::getGUID(
899 GlobalValue::dropLLVMManglingEscape(Res.second.IRName)));
901 GUIDPrevailingResolutions[GUID] =
902 Res.second.Prevailing ? PrevailingType::Yes : PrevailingType::No;
905 auto isPrevailing = [&](GlobalValue::GUID G) {
906 auto It = GUIDPrevailingResolutions.find(G);
907 if (It == GUIDPrevailingResolutions.end())
908 return PrevailingType::Unknown;
911 computeDeadSymbolsWithConstProp(ThinLTO.CombinedIndex, GUIDPreservedSymbols,
912 isPrevailing, Conf.OptLevel > 0);
914 // Setup output file to emit statistics.
915 auto StatsFileOrErr = setupStatsFile(Conf.StatsFile);
917 return StatsFileOrErr.takeError();
918 std::unique_ptr<ToolOutputFile> StatsFile = std::move(StatsFileOrErr.get());
920 // Finalize linking of regular LTO modules containing summaries now that
921 // we have computed liveness information.
922 for (auto &M : RegularLTO.ModsWithSummaries)
923 if (Error Err = linkRegularLTO(std::move(M),
924 /*LivenessFromIndex=*/true))
927 // Ensure we don't have inconsistently split LTO units with type tests.
928 if (Error Err = checkPartiallySplit())
931 Error Result = runRegularLTO(AddStream);
933 Result = runThinLTO(AddStream, Cache, GUIDPreservedSymbols);
936 PrintStatisticsJSON(StatsFile->os());
941 Error LTO::runRegularLTO(AddStreamFn AddStream) {
942 // Make sure commons have the right size/alignment: we kept the largest from
943 // all the prevailing when adding the inputs, and we apply it here.
944 const DataLayout &DL = RegularLTO.CombinedModule->getDataLayout();
945 for (auto &I : RegularLTO.Commons) {
946 if (!I.second.Prevailing)
947 // Don't do anything if no instance of this common was prevailing.
949 GlobalVariable *OldGV = RegularLTO.CombinedModule->getNamedGlobal(I.first);
950 if (OldGV && DL.getTypeAllocSize(OldGV->getValueType()) == I.second.Size) {
951 // Don't create a new global if the type is already correct, just make
952 // sure the alignment is correct.
953 OldGV->setAlignment(I.second.Align);
957 ArrayType::get(Type::getInt8Ty(RegularLTO.Ctx), I.second.Size);
958 auto *GV = new GlobalVariable(*RegularLTO.CombinedModule, Ty, false,
959 GlobalValue::CommonLinkage,
960 ConstantAggregateZero::get(Ty), "");
961 GV->setAlignment(I.second.Align);
963 OldGV->replaceAllUsesWith(ConstantExpr::getBitCast(GV, OldGV->getType()));
965 OldGV->eraseFromParent();
967 GV->setName(I.first);
971 if (Conf.PreOptModuleHook &&
972 !Conf.PreOptModuleHook(0, *RegularLTO.CombinedModule))
973 return Error::success();
975 if (!Conf.CodeGenOnly) {
976 for (const auto &R : GlobalResolutions) {
977 if (!R.second.isPrevailingIRSymbol())
979 if (R.second.Partition != 0 &&
980 R.second.Partition != GlobalResolution::External)
984 RegularLTO.CombinedModule->getNamedValue(R.second.IRName);
985 // Ignore symbols defined in other partitions.
986 // Also skip declarations, which are not allowed to have internal linkage.
987 if (!GV || GV->hasLocalLinkage() || GV->isDeclaration())
989 GV->setUnnamedAddr(R.second.UnnamedAddr ? GlobalValue::UnnamedAddr::Global
990 : GlobalValue::UnnamedAddr::None);
991 if (EnableLTOInternalization && R.second.Partition == 0)
992 GV->setLinkage(GlobalValue::InternalLinkage);
995 if (Conf.PostInternalizeModuleHook &&
996 !Conf.PostInternalizeModuleHook(0, *RegularLTO.CombinedModule))
997 return Error::success();
999 return backend(Conf, AddStream, RegularLTO.ParallelCodeGenParallelismLevel,
1000 std::move(RegularLTO.CombinedModule), ThinLTO.CombinedIndex);
1003 /// This class defines the interface to the ThinLTO backend.
1004 class lto::ThinBackendProc {
1007 ModuleSummaryIndex &CombinedIndex;
1008 const StringMap<GVSummaryMapTy> &ModuleToDefinedGVSummaries;
1011 ThinBackendProc(Config &Conf, ModuleSummaryIndex &CombinedIndex,
1012 const StringMap<GVSummaryMapTy> &ModuleToDefinedGVSummaries)
1013 : Conf(Conf), CombinedIndex(CombinedIndex),
1014 ModuleToDefinedGVSummaries(ModuleToDefinedGVSummaries) {}
1016 virtual ~ThinBackendProc() {}
1017 virtual Error start(
1018 unsigned Task, BitcodeModule BM,
1019 const FunctionImporter::ImportMapTy &ImportList,
1020 const FunctionImporter::ExportSetTy &ExportList,
1021 const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes> &ResolvedODR,
1022 MapVector<StringRef, BitcodeModule> &ModuleMap) = 0;
1023 virtual Error wait() = 0;
1027 class InProcessThinBackend : public ThinBackendProc {
1028 ThreadPool BackendThreadPool;
1029 AddStreamFn AddStream;
1030 NativeObjectCache Cache;
1031 std::set<GlobalValue::GUID> CfiFunctionDefs;
1032 std::set<GlobalValue::GUID> CfiFunctionDecls;
1034 Optional<Error> Err;
1038 InProcessThinBackend(
1039 Config &Conf, ModuleSummaryIndex &CombinedIndex,
1040 unsigned ThinLTOParallelismLevel,
1041 const StringMap<GVSummaryMapTy> &ModuleToDefinedGVSummaries,
1042 AddStreamFn AddStream, NativeObjectCache Cache)
1043 : ThinBackendProc(Conf, CombinedIndex, ModuleToDefinedGVSummaries),
1044 BackendThreadPool(ThinLTOParallelismLevel),
1045 AddStream(std::move(AddStream)), Cache(std::move(Cache)) {
1046 for (auto &Name : CombinedIndex.cfiFunctionDefs())
1047 CfiFunctionDefs.insert(
1048 GlobalValue::getGUID(GlobalValue::dropLLVMManglingEscape(Name)));
1049 for (auto &Name : CombinedIndex.cfiFunctionDecls())
1050 CfiFunctionDecls.insert(
1051 GlobalValue::getGUID(GlobalValue::dropLLVMManglingEscape(Name)));
1054 Error runThinLTOBackendThread(
1055 AddStreamFn AddStream, NativeObjectCache Cache, unsigned Task,
1056 BitcodeModule BM, ModuleSummaryIndex &CombinedIndex,
1057 const FunctionImporter::ImportMapTy &ImportList,
1058 const FunctionImporter::ExportSetTy &ExportList,
1059 const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes> &ResolvedODR,
1060 const GVSummaryMapTy &DefinedGlobals,
1061 MapVector<StringRef, BitcodeModule> &ModuleMap) {
1062 auto RunThinBackend = [&](AddStreamFn AddStream) {
1063 LTOLLVMContext BackendContext(Conf);
1064 Expected<std::unique_ptr<Module>> MOrErr = BM.parseModule(BackendContext);
1066 return MOrErr.takeError();
1068 return thinBackend(Conf, Task, AddStream, **MOrErr, CombinedIndex,
1069 ImportList, DefinedGlobals, ModuleMap);
1072 auto ModuleID = BM.getModuleIdentifier();
1074 if (!Cache || !CombinedIndex.modulePaths().count(ModuleID) ||
1075 all_of(CombinedIndex.getModuleHash(ModuleID),
1076 [](uint32_t V) { return V == 0; }))
1077 // Cache disabled or no entry for this module in the combined index or
1079 return RunThinBackend(AddStream);
1081 SmallString<40> Key;
1082 // The module may be cached, this helps handling it.
1083 computeLTOCacheKey(Key, Conf, CombinedIndex, ModuleID, ImportList,
1084 ExportList, ResolvedODR, DefinedGlobals, CfiFunctionDefs,
1086 if (AddStreamFn CacheAddStream = Cache(Task, Key))
1087 return RunThinBackend(CacheAddStream);
1089 return Error::success();
1093 unsigned Task, BitcodeModule BM,
1094 const FunctionImporter::ImportMapTy &ImportList,
1095 const FunctionImporter::ExportSetTy &ExportList,
1096 const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes> &ResolvedODR,
1097 MapVector<StringRef, BitcodeModule> &ModuleMap) override {
1098 StringRef ModulePath = BM.getModuleIdentifier();
1099 assert(ModuleToDefinedGVSummaries.count(ModulePath));
1100 const GVSummaryMapTy &DefinedGlobals =
1101 ModuleToDefinedGVSummaries.find(ModulePath)->second;
1102 BackendThreadPool.async(
1103 [=](BitcodeModule BM, ModuleSummaryIndex &CombinedIndex,
1104 const FunctionImporter::ImportMapTy &ImportList,
1105 const FunctionImporter::ExportSetTy &ExportList,
1106 const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>
1108 const GVSummaryMapTy &DefinedGlobals,
1109 MapVector<StringRef, BitcodeModule> &ModuleMap) {
1110 Error E = runThinLTOBackendThread(
1111 AddStream, Cache, Task, BM, CombinedIndex, ImportList, ExportList,
1112 ResolvedODR, DefinedGlobals, ModuleMap);
1114 std::unique_lock<std::mutex> L(ErrMu);
1116 Err = joinErrors(std::move(*Err), std::move(E));
1121 BM, std::ref(CombinedIndex), std::ref(ImportList), std::ref(ExportList),
1122 std::ref(ResolvedODR), std::ref(DefinedGlobals), std::ref(ModuleMap));
1123 return Error::success();
1126 Error wait() override {
1127 BackendThreadPool.wait();
1129 return std::move(*Err);
1131 return Error::success();
1134 } // end anonymous namespace
1136 ThinBackend lto::createInProcessThinBackend(unsigned ParallelismLevel) {
1137 return [=](Config &Conf, ModuleSummaryIndex &CombinedIndex,
1138 const StringMap<GVSummaryMapTy> &ModuleToDefinedGVSummaries,
1139 AddStreamFn AddStream, NativeObjectCache Cache) {
1140 return llvm::make_unique<InProcessThinBackend>(
1141 Conf, CombinedIndex, ParallelismLevel, ModuleToDefinedGVSummaries,
1146 // Given the original \p Path to an output file, replace any path
1147 // prefix matching \p OldPrefix with \p NewPrefix. Also, create the
1148 // resulting directory if it does not yet exist.
1149 std::string lto::getThinLTOOutputFile(const std::string &Path,
1150 const std::string &OldPrefix,
1151 const std::string &NewPrefix) {
1152 if (OldPrefix.empty() && NewPrefix.empty())
1154 SmallString<128> NewPath(Path);
1155 llvm::sys::path::replace_path_prefix(NewPath, OldPrefix, NewPrefix);
1156 StringRef ParentPath = llvm::sys::path::parent_path(NewPath.str());
1157 if (!ParentPath.empty()) {
1158 // Make sure the new directory exists, creating it if necessary.
1159 if (std::error_code EC = llvm::sys::fs::create_directories(ParentPath))
1160 llvm::errs() << "warning: could not create directory '" << ParentPath
1161 << "': " << EC.message() << '\n';
1163 return NewPath.str();
1167 class WriteIndexesThinBackend : public ThinBackendProc {
1168 std::string OldPrefix, NewPrefix;
1169 bool ShouldEmitImportsFiles;
1170 raw_fd_ostream *LinkedObjectsFile;
1171 lto::IndexWriteCallback OnWrite;
1174 WriteIndexesThinBackend(
1175 Config &Conf, ModuleSummaryIndex &CombinedIndex,
1176 const StringMap<GVSummaryMapTy> &ModuleToDefinedGVSummaries,
1177 std::string OldPrefix, std::string NewPrefix, bool ShouldEmitImportsFiles,
1178 raw_fd_ostream *LinkedObjectsFile, lto::IndexWriteCallback OnWrite)
1179 : ThinBackendProc(Conf, CombinedIndex, ModuleToDefinedGVSummaries),
1180 OldPrefix(OldPrefix), NewPrefix(NewPrefix),
1181 ShouldEmitImportsFiles(ShouldEmitImportsFiles),
1182 LinkedObjectsFile(LinkedObjectsFile), OnWrite(OnWrite) {}
1185 unsigned Task, BitcodeModule BM,
1186 const FunctionImporter::ImportMapTy &ImportList,
1187 const FunctionImporter::ExportSetTy &ExportList,
1188 const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes> &ResolvedODR,
1189 MapVector<StringRef, BitcodeModule> &ModuleMap) override {
1190 StringRef ModulePath = BM.getModuleIdentifier();
1191 std::string NewModulePath =
1192 getThinLTOOutputFile(ModulePath, OldPrefix, NewPrefix);
1194 if (LinkedObjectsFile)
1195 *LinkedObjectsFile << NewModulePath << '\n';
1197 std::map<std::string, GVSummaryMapTy> ModuleToSummariesForIndex;
1198 gatherImportedSummariesForModule(ModulePath, ModuleToDefinedGVSummaries,
1199 ImportList, ModuleToSummariesForIndex);
1202 raw_fd_ostream OS(NewModulePath + ".thinlto.bc", EC,
1203 sys::fs::OpenFlags::F_None);
1205 return errorCodeToError(EC);
1206 WriteIndexToFile(CombinedIndex, OS, &ModuleToSummariesForIndex);
1208 if (ShouldEmitImportsFiles) {
1209 EC = EmitImportsFiles(ModulePath, NewModulePath + ".imports",
1210 ModuleToSummariesForIndex);
1212 return errorCodeToError(EC);
1216 OnWrite(ModulePath);
1217 return Error::success();
1220 Error wait() override { return Error::success(); }
1222 } // end anonymous namespace
1224 ThinBackend lto::createWriteIndexesThinBackend(
1225 std::string OldPrefix, std::string NewPrefix, bool ShouldEmitImportsFiles,
1226 raw_fd_ostream *LinkedObjectsFile, IndexWriteCallback OnWrite) {
1227 return [=](Config &Conf, ModuleSummaryIndex &CombinedIndex,
1228 const StringMap<GVSummaryMapTy> &ModuleToDefinedGVSummaries,
1229 AddStreamFn AddStream, NativeObjectCache Cache) {
1230 return llvm::make_unique<WriteIndexesThinBackend>(
1231 Conf, CombinedIndex, ModuleToDefinedGVSummaries, OldPrefix, NewPrefix,
1232 ShouldEmitImportsFiles, LinkedObjectsFile, OnWrite);
1236 Error LTO::runThinLTO(AddStreamFn AddStream, NativeObjectCache Cache,
1237 const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols) {
1238 if (ThinLTO.ModuleMap.empty())
1239 return Error::success();
1241 if (Conf.CombinedIndexHook && !Conf.CombinedIndexHook(ThinLTO.CombinedIndex))
1242 return Error::success();
1244 // Collect for each module the list of function it defines (GUID ->
1246 StringMap<GVSummaryMapTy>
1247 ModuleToDefinedGVSummaries(ThinLTO.ModuleMap.size());
1248 ThinLTO.CombinedIndex.collectDefinedGVSummariesPerModule(
1249 ModuleToDefinedGVSummaries);
1250 // Create entries for any modules that didn't have any GV summaries
1251 // (either they didn't have any GVs to start with, or we suppressed
1252 // generation of the summaries because they e.g. had inline assembly
1253 // uses that couldn't be promoted/renamed on export). This is so
1254 // InProcessThinBackend::start can still launch a backend thread, which
1255 // is passed the map of summaries for the module, without any special
1256 // handling for this case.
1257 for (auto &Mod : ThinLTO.ModuleMap)
1258 if (!ModuleToDefinedGVSummaries.count(Mod.first))
1259 ModuleToDefinedGVSummaries.try_emplace(Mod.first);
1261 // Synthesize entry counts for functions in the CombinedIndex.
1262 computeSyntheticCounts(ThinLTO.CombinedIndex);
1264 StringMap<FunctionImporter::ImportMapTy> ImportLists(
1265 ThinLTO.ModuleMap.size());
1266 StringMap<FunctionImporter::ExportSetTy> ExportLists(
1267 ThinLTO.ModuleMap.size());
1268 StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;
1271 ThinLTO.CombinedIndex.dumpSCCs(outs());
1273 if (Conf.OptLevel > 0)
1274 ComputeCrossModuleImport(ThinLTO.CombinedIndex, ModuleToDefinedGVSummaries,
1275 ImportLists, ExportLists);
1277 // Figure out which symbols need to be internalized. This also needs to happen
1278 // at -O0 because summary-based DCE is implemented using internalization, and
1279 // we must apply DCE consistently with the full LTO module in order to avoid
1280 // undefined references during the final link.
1281 std::set<GlobalValue::GUID> ExportedGUIDs;
1282 for (auto &Res : GlobalResolutions) {
1283 // If the symbol does not have external references or it is not prevailing,
1284 // then not need to mark it as exported from a ThinLTO partition.
1285 if (Res.second.Partition != GlobalResolution::External ||
1286 !Res.second.isPrevailingIRSymbol())
1288 auto GUID = GlobalValue::getGUID(
1289 GlobalValue::dropLLVMManglingEscape(Res.second.IRName));
1290 // Mark exported unless index-based analysis determined it to be dead.
1291 if (ThinLTO.CombinedIndex.isGUIDLive(GUID))
1292 ExportedGUIDs.insert(GUID);
1295 // Any functions referenced by the jump table in the regular LTO object must
1297 for (auto &Def : ThinLTO.CombinedIndex.cfiFunctionDefs())
1298 ExportedGUIDs.insert(
1299 GlobalValue::getGUID(GlobalValue::dropLLVMManglingEscape(Def)));
1301 auto isExported = [&](StringRef ModuleIdentifier, GlobalValue::GUID GUID) {
1302 const auto &ExportList = ExportLists.find(ModuleIdentifier);
1303 return (ExportList != ExportLists.end() &&
1304 ExportList->second.count(GUID)) ||
1305 ExportedGUIDs.count(GUID);
1307 thinLTOInternalizeAndPromoteInIndex(ThinLTO.CombinedIndex, isExported);
1309 auto isPrevailing = [&](GlobalValue::GUID GUID,
1310 const GlobalValueSummary *S) {
1311 return ThinLTO.PrevailingModuleForGUID[GUID] == S->modulePath();
1313 auto recordNewLinkage = [&](StringRef ModuleIdentifier,
1314 GlobalValue::GUID GUID,
1315 GlobalValue::LinkageTypes NewLinkage) {
1316 ResolvedODR[ModuleIdentifier][GUID] = NewLinkage;
1318 thinLTOResolvePrevailingInIndex(ThinLTO.CombinedIndex, isPrevailing,
1319 recordNewLinkage, GUIDPreservedSymbols);
1321 std::unique_ptr<ThinBackendProc> BackendProc =
1322 ThinLTO.Backend(Conf, ThinLTO.CombinedIndex, ModuleToDefinedGVSummaries,
1325 // Tasks 0 through ParallelCodeGenParallelismLevel-1 are reserved for combined
1326 // module and parallel code generation partitions.
1327 unsigned Task = RegularLTO.ParallelCodeGenParallelismLevel;
1328 for (auto &Mod : ThinLTO.ModuleMap) {
1329 if (Error E = BackendProc->start(Task, Mod.second, ImportLists[Mod.first],
1330 ExportLists[Mod.first],
1331 ResolvedODR[Mod.first], ThinLTO.ModuleMap))
1336 return BackendProc->wait();
1339 Expected<std::unique_ptr<ToolOutputFile>>
1340 lto::setupOptimizationRemarks(LLVMContext &Context,
1341 StringRef LTORemarksFilename,
1342 StringRef LTORemarksPasses,
1343 bool LTOPassRemarksWithHotness, int Count) {
1344 if (LTOPassRemarksWithHotness)
1345 Context.setDiagnosticsHotnessRequested(true);
1346 if (LTORemarksFilename.empty())
1349 std::string Filename = LTORemarksFilename;
1351 Filename += ".thin." + llvm::utostr(Count) + ".yaml";
1354 auto DiagnosticFile =
1355 llvm::make_unique<ToolOutputFile>(Filename, EC, sys::fs::F_None);
1357 return errorCodeToError(EC);
1358 Context.setRemarkStreamer(
1359 llvm::make_unique<RemarkStreamer>(Filename, DiagnosticFile->os()));
1361 if (!LTORemarksPasses.empty())
1362 if (Error E = Context.getRemarkStreamer()->setFilter(LTORemarksPasses))
1363 return std::move(E);
1365 DiagnosticFile->keep();
1366 return std::move(DiagnosticFile);
1369 Expected<std::unique_ptr<ToolOutputFile>>
1370 lto::setupStatsFile(StringRef StatsFilename) {
1371 // Setup output file to emit statistics.
1372 if (StatsFilename.empty())
1375 llvm::EnableStatistics(false);
1378 llvm::make_unique<ToolOutputFile>(StatsFilename, EC, sys::fs::F_None);
1380 return errorCodeToError(EC);
1383 return std::move(StatsFile);