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Diffstat (limited to 'lib/LTO/ThinLTOCodeGenerator.cpp')
| -rw-r--r-- | lib/LTO/ThinLTOCodeGenerator.cpp | 835 |
1 files changed, 835 insertions, 0 deletions
diff --git a/lib/LTO/ThinLTOCodeGenerator.cpp b/lib/LTO/ThinLTOCodeGenerator.cpp new file mode 100644 index 000000000000..bfb0980bc165 --- /dev/null +++ b/lib/LTO/ThinLTOCodeGenerator.cpp @@ -0,0 +1,835 @@ +//===-ThinLTOCodeGenerator.cpp - LLVM Link Time Optimizer -----------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implements the Thin Link Time Optimization library. This library is +// intended to be used by linker to optimize code at link time. +// +//===----------------------------------------------------------------------===// + +#include "llvm/LTO/legacy/ThinLTOCodeGenerator.h" + +#ifdef HAVE_LLVM_REVISION +#include "LLVMLTORevision.h" +#endif + +#include "llvm/ADT/Statistic.h" +#include "llvm/ADT/StringExtras.h" +#include "llvm/Analysis/ModuleSummaryAnalysis.h" +#include "llvm/Analysis/TargetLibraryInfo.h" +#include "llvm/Analysis/TargetTransformInfo.h" +#include "llvm/Bitcode/BitcodeWriterPass.h" +#include "llvm/Bitcode/ReaderWriter.h" +#include "llvm/ExecutionEngine/ObjectMemoryBuffer.h" +#include "llvm/IR/DiagnosticPrinter.h" +#include "llvm/IR/LLVMContext.h" +#include "llvm/IR/LegacyPassManager.h" +#include "llvm/IR/Mangler.h" +#include "llvm/IRReader/IRReader.h" +#include "llvm/LTO/LTO.h" +#include "llvm/Linker/Linker.h" +#include "llvm/MC/SubtargetFeature.h" +#include "llvm/Object/IRObjectFile.h" +#include "llvm/Object/ModuleSummaryIndexObjectFile.h" +#include "llvm/Support/CachePruning.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/Path.h" +#include "llvm/Support/SHA1.h" +#include "llvm/Support/TargetRegistry.h" +#include "llvm/Support/ThreadPool.h" +#include "llvm/Target/TargetMachine.h" +#include "llvm/Transforms/IPO.h" +#include "llvm/Transforms/IPO/FunctionImport.h" +#include "llvm/Transforms/IPO/Internalize.h" +#include "llvm/Transforms/IPO/PassManagerBuilder.h" +#include "llvm/Transforms/ObjCARC.h" +#include "llvm/Transforms/Utils/FunctionImportUtils.h" + +#include <numeric> + +using namespace llvm; + +#define DEBUG_TYPE "thinlto" + +namespace llvm { +// Flags -discard-value-names, defined in LTOCodeGenerator.cpp +extern cl::opt<bool> LTODiscardValueNames; +} + +namespace { + +static cl::opt<int> ThreadCount("threads", + cl::init(std::thread::hardware_concurrency())); + +static void diagnosticHandler(const DiagnosticInfo &DI) { + DiagnosticPrinterRawOStream DP(errs()); + DI.print(DP); + errs() << '\n'; +} + +// Simple helper to save temporary files for debug. +static void saveTempBitcode(const Module &TheModule, StringRef TempDir, + unsigned count, StringRef Suffix) { + if (TempDir.empty()) + return; + // User asked to save temps, let dump the bitcode file after import. + auto SaveTempPath = TempDir + llvm::utostr(count) + Suffix; + std::error_code EC; + raw_fd_ostream OS(SaveTempPath.str(), EC, sys::fs::F_None); + if (EC) + report_fatal_error(Twine("Failed to open ") + SaveTempPath + + " to save optimized bitcode\n"); + WriteBitcodeToFile(&TheModule, OS, /* ShouldPreserveUseListOrder */ true); +} + +static const GlobalValueSummary * +getFirstDefinitionForLinker(const GlobalValueSummaryList &GVSummaryList) { + // If there is any strong definition anywhere, get it. + auto StrongDefForLinker = llvm::find_if( + GVSummaryList, [](const std::unique_ptr<GlobalValueSummary> &Summary) { + auto Linkage = Summary->linkage(); + return !GlobalValue::isAvailableExternallyLinkage(Linkage) && + !GlobalValue::isWeakForLinker(Linkage); + }); + if (StrongDefForLinker != GVSummaryList.end()) + return StrongDefForLinker->get(); + // Get the first *linker visible* definition for this global in the summary + // list. + auto FirstDefForLinker = llvm::find_if( + GVSummaryList, [](const std::unique_ptr<GlobalValueSummary> &Summary) { + auto Linkage = Summary->linkage(); + return !GlobalValue::isAvailableExternallyLinkage(Linkage); + }); + // Extern templates can be emitted as available_externally. + if (FirstDefForLinker == GVSummaryList.end()) + return nullptr; + return FirstDefForLinker->get(); +} + +// Populate map of GUID to the prevailing copy for any multiply defined +// symbols. Currently assume first copy is prevailing, or any strong +// definition. Can be refined with Linker information in the future. +static void computePrevailingCopies( + const ModuleSummaryIndex &Index, + DenseMap<GlobalValue::GUID, const GlobalValueSummary *> &PrevailingCopy) { + auto HasMultipleCopies = [&](const GlobalValueSummaryList &GVSummaryList) { + return GVSummaryList.size() > 1; + }; + + for (auto &I : Index) { + if (HasMultipleCopies(I.second)) + PrevailingCopy[I.first] = getFirstDefinitionForLinker(I.second); + } +} + +static StringMap<MemoryBufferRef> +generateModuleMap(const std::vector<MemoryBufferRef> &Modules) { + StringMap<MemoryBufferRef> ModuleMap; + for (auto &ModuleBuffer : Modules) { + assert(ModuleMap.find(ModuleBuffer.getBufferIdentifier()) == + ModuleMap.end() && + "Expect unique Buffer Identifier"); + ModuleMap[ModuleBuffer.getBufferIdentifier()] = ModuleBuffer; + } + return ModuleMap; +} + +static void promoteModule(Module &TheModule, const ModuleSummaryIndex &Index) { + if (renameModuleForThinLTO(TheModule, Index)) + report_fatal_error("renameModuleForThinLTO failed"); +} + +static void +crossImportIntoModule(Module &TheModule, const ModuleSummaryIndex &Index, + StringMap<MemoryBufferRef> &ModuleMap, + const FunctionImporter::ImportMapTy &ImportList) { + ModuleLoader Loader(TheModule.getContext(), ModuleMap); + FunctionImporter Importer(Index, Loader); + Importer.importFunctions(TheModule, ImportList); +} + +static void optimizeModule(Module &TheModule, TargetMachine &TM) { + // Populate the PassManager + PassManagerBuilder PMB; + PMB.LibraryInfo = new TargetLibraryInfoImpl(TM.getTargetTriple()); + PMB.Inliner = createFunctionInliningPass(); + // FIXME: should get it from the bitcode? + PMB.OptLevel = 3; + PMB.LoopVectorize = true; + PMB.SLPVectorize = true; + PMB.VerifyInput = true; + PMB.VerifyOutput = false; + + legacy::PassManager PM; + + // Add the TTI (required to inform the vectorizer about register size for + // instance) + PM.add(createTargetTransformInfoWrapperPass(TM.getTargetIRAnalysis())); + + // Add optimizations + PMB.populateThinLTOPassManager(PM); + + PM.run(TheModule); +} + +// Convert the PreservedSymbols map from "Name" based to "GUID" based. +static DenseSet<GlobalValue::GUID> +computeGUIDPreservedSymbols(const StringSet<> &PreservedSymbols, + const Triple &TheTriple) { + DenseSet<GlobalValue::GUID> GUIDPreservedSymbols(PreservedSymbols.size()); + for (auto &Entry : PreservedSymbols) { + StringRef Name = Entry.first(); + if (TheTriple.isOSBinFormatMachO() && Name.size() > 0 && Name[0] == '_') + Name = Name.drop_front(); + GUIDPreservedSymbols.insert(GlobalValue::getGUID(Name)); + } + return GUIDPreservedSymbols; +} + +std::unique_ptr<MemoryBuffer> codegenModule(Module &TheModule, + TargetMachine &TM) { + SmallVector<char, 128> OutputBuffer; + + // CodeGen + { + raw_svector_ostream OS(OutputBuffer); + legacy::PassManager PM; + + // If the bitcode files contain ARC code and were compiled with optimization, + // the ObjCARCContractPass must be run, so do it unconditionally here. + PM.add(createObjCARCContractPass()); + + // Setup the codegen now. + if (TM.addPassesToEmitFile(PM, OS, TargetMachine::CGFT_ObjectFile, + /* DisableVerify */ true)) + report_fatal_error("Failed to setup codegen"); + + // Run codegen now. resulting binary is in OutputBuffer. + PM.run(TheModule); + } + return make_unique<ObjectMemoryBuffer>(std::move(OutputBuffer)); +} + +/// Manage caching for a single Module. +class ModuleCacheEntry { + SmallString<128> EntryPath; + +public: + // Create a cache entry. This compute a unique hash for the Module considering + // the current list of export/import, and offer an interface to query to + // access the content in the cache. + ModuleCacheEntry( + StringRef CachePath, const ModuleSummaryIndex &Index, StringRef ModuleID, + const FunctionImporter::ImportMapTy &ImportList, + const FunctionImporter::ExportSetTy &ExportList, + const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes> &ResolvedODR, + const GVSummaryMapTy &DefinedFunctions, + const DenseSet<GlobalValue::GUID> &PreservedSymbols) { + if (CachePath.empty()) + return; + + // Compute the unique hash for this entry + // This is based on the current compiler version, the module itself, the + // export list, the hash for every single module in the import list, the + // list of ResolvedODR for the module, and the list of preserved symbols. + + SHA1 Hasher; + + // Start with the compiler revision + Hasher.update(LLVM_VERSION_STRING); +#ifdef HAVE_LLVM_REVISION + Hasher.update(LLVM_REVISION); +#endif + + // Include the hash for the current module + auto ModHash = Index.getModuleHash(ModuleID); + Hasher.update(ArrayRef<uint8_t>((uint8_t *)&ModHash[0], sizeof(ModHash))); + for (auto F : ExportList) + // The export list can impact the internalization, be conservative here + Hasher.update(ArrayRef<uint8_t>((uint8_t *)&F, sizeof(F))); + + // Include the hash for every module we import functions from + for (auto &Entry : ImportList) { + auto ModHash = Index.getModuleHash(Entry.first()); + Hasher.update(ArrayRef<uint8_t>((uint8_t *)&ModHash[0], sizeof(ModHash))); + } + + // Include the hash for the resolved ODR. + for (auto &Entry : ResolvedODR) { + Hasher.update(ArrayRef<uint8_t>((const uint8_t *)&Entry.first, + sizeof(GlobalValue::GUID))); + Hasher.update(ArrayRef<uint8_t>((const uint8_t *)&Entry.second, + sizeof(GlobalValue::LinkageTypes))); + } + + // Include the hash for the preserved symbols. + for (auto &Entry : PreservedSymbols) { + if (DefinedFunctions.count(Entry)) + Hasher.update( + ArrayRef<uint8_t>((const uint8_t *)&Entry, sizeof(GlobalValue::GUID))); + } + + sys::path::append(EntryPath, CachePath, toHex(Hasher.result())); + } + + // Access the path to this entry in the cache. + StringRef getEntryPath() { return EntryPath; } + + // Try loading the buffer for this cache entry. + ErrorOr<std::unique_ptr<MemoryBuffer>> tryLoadingBuffer() { + if (EntryPath.empty()) + return std::error_code(); + return MemoryBuffer::getFile(EntryPath); + } + + // Cache the Produced object file + std::unique_ptr<MemoryBuffer> + write(std::unique_ptr<MemoryBuffer> OutputBuffer) { + if (EntryPath.empty()) + return OutputBuffer; + + // Write to a temporary to avoid race condition + SmallString<128> TempFilename; + int TempFD; + std::error_code EC = + sys::fs::createTemporaryFile("Thin", "tmp.o", TempFD, TempFilename); + if (EC) { + errs() << "Error: " << EC.message() << "\n"; + report_fatal_error("ThinLTO: Can't get a temporary file"); + } + { + raw_fd_ostream OS(TempFD, /* ShouldClose */ true); + OS << OutputBuffer->getBuffer(); + } + // Rename to final destination (hopefully race condition won't matter here) + EC = sys::fs::rename(TempFilename, EntryPath); + if (EC) { + sys::fs::remove(TempFilename); + raw_fd_ostream OS(EntryPath, EC, sys::fs::F_None); + if (EC) + report_fatal_error(Twine("Failed to open ") + EntryPath + + " to save cached entry\n"); + OS << OutputBuffer->getBuffer(); + } + auto ReloadedBufferOrErr = MemoryBuffer::getFile(EntryPath); + if (auto EC = ReloadedBufferOrErr.getError()) { + // FIXME diagnose + errs() << "error: can't reload cached file '" << EntryPath + << "': " << EC.message() << "\n"; + return OutputBuffer; + } + return std::move(*ReloadedBufferOrErr); + } +}; + +static std::unique_ptr<MemoryBuffer> +ProcessThinLTOModule(Module &TheModule, ModuleSummaryIndex &Index, + StringMap<MemoryBufferRef> &ModuleMap, TargetMachine &TM, + const FunctionImporter::ImportMapTy &ImportList, + const FunctionImporter::ExportSetTy &ExportList, + const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols, + const GVSummaryMapTy &DefinedGlobals, + const ThinLTOCodeGenerator::CachingOptions &CacheOptions, + bool DisableCodeGen, StringRef SaveTempsDir, + unsigned count) { + + // "Benchmark"-like optimization: single-source case + bool SingleModule = (ModuleMap.size() == 1); + + if (!SingleModule) { + promoteModule(TheModule, Index); + + // Apply summary-based LinkOnce/Weak resolution decisions. + thinLTOResolveWeakForLinkerModule(TheModule, DefinedGlobals); + + // Save temps: after promotion. + saveTempBitcode(TheModule, SaveTempsDir, count, ".1.promoted.bc"); + } + + // Be friendly and don't nuke totally the module when the client didn't + // supply anything to preserve. + if (!ExportList.empty() || !GUIDPreservedSymbols.empty()) { + // Apply summary-based internalization decisions. + thinLTOInternalizeModule(TheModule, DefinedGlobals); + } + + // Save internalized bitcode + saveTempBitcode(TheModule, SaveTempsDir, count, ".2.internalized.bc"); + + if (!SingleModule) { + crossImportIntoModule(TheModule, Index, ModuleMap, ImportList); + + // Save temps: after cross-module import. + saveTempBitcode(TheModule, SaveTempsDir, count, ".3.imported.bc"); + } + + optimizeModule(TheModule, TM); + + saveTempBitcode(TheModule, SaveTempsDir, count, ".4.opt.bc"); + + if (DisableCodeGen) { + // Configured to stop before CodeGen, serialize the bitcode and return. + SmallVector<char, 128> OutputBuffer; + { + raw_svector_ostream OS(OutputBuffer); + ModuleSummaryIndexBuilder IndexBuilder(&TheModule); + WriteBitcodeToFile(&TheModule, OS, true, &IndexBuilder.getIndex()); + } + return make_unique<ObjectMemoryBuffer>(std::move(OutputBuffer)); + } + + return codegenModule(TheModule, TM); +} + +/// Resolve LinkOnce/Weak symbols. Record resolutions in the \p ResolvedODR map +/// for caching, and in the \p Index for application during the ThinLTO +/// backends. This is needed for correctness for exported symbols (ensure +/// at least one copy kept) and a compile-time optimization (to drop duplicate +/// copies when possible). +static void resolveWeakForLinkerInIndex( + ModuleSummaryIndex &Index, + StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> + &ResolvedODR) { + + DenseMap<GlobalValue::GUID, const GlobalValueSummary *> PrevailingCopy; + computePrevailingCopies(Index, PrevailingCopy); + + auto isPrevailing = [&](GlobalValue::GUID GUID, const GlobalValueSummary *S) { + const auto &Prevailing = PrevailingCopy.find(GUID); + // Not in map means that there was only one copy, which must be prevailing. + if (Prevailing == PrevailingCopy.end()) + return true; + return Prevailing->second == S; + }; + + auto recordNewLinkage = [&](StringRef ModuleIdentifier, + GlobalValue::GUID GUID, + GlobalValue::LinkageTypes NewLinkage) { + ResolvedODR[ModuleIdentifier][GUID] = NewLinkage; + }; + + thinLTOResolveWeakForLinkerInIndex(Index, isPrevailing, recordNewLinkage); +} + +// Initialize the TargetMachine builder for a given Triple +static void initTMBuilder(TargetMachineBuilder &TMBuilder, + const Triple &TheTriple) { + // Set a default CPU for Darwin triples (copied from LTOCodeGenerator). + // FIXME this looks pretty terrible... + if (TMBuilder.MCpu.empty() && TheTriple.isOSDarwin()) { + if (TheTriple.getArch() == llvm::Triple::x86_64) + TMBuilder.MCpu = "core2"; + else if (TheTriple.getArch() == llvm::Triple::x86) + TMBuilder.MCpu = "yonah"; + else if (TheTriple.getArch() == llvm::Triple::aarch64) + TMBuilder.MCpu = "cyclone"; + } + TMBuilder.TheTriple = std::move(TheTriple); +} + +} // end anonymous namespace + +void ThinLTOCodeGenerator::addModule(StringRef Identifier, StringRef Data) { + MemoryBufferRef Buffer(Data, Identifier); + if (Modules.empty()) { + // First module added, so initialize the triple and some options + LLVMContext Context; + Triple TheTriple(getBitcodeTargetTriple(Buffer, Context)); + initTMBuilder(TMBuilder, Triple(TheTriple)); + } +#ifndef NDEBUG + else { + LLVMContext Context; + assert(TMBuilder.TheTriple.str() == + getBitcodeTargetTriple(Buffer, Context) && + "ThinLTO modules with different triple not supported"); + } +#endif + Modules.push_back(Buffer); +} + +void ThinLTOCodeGenerator::preserveSymbol(StringRef Name) { + PreservedSymbols.insert(Name); +} + +void ThinLTOCodeGenerator::crossReferenceSymbol(StringRef Name) { + // FIXME: At the moment, we don't take advantage of this extra information, + // we're conservatively considering cross-references as preserved. + // CrossReferencedSymbols.insert(Name); + PreservedSymbols.insert(Name); +} + +// TargetMachine factory +std::unique_ptr<TargetMachine> TargetMachineBuilder::create() const { + std::string ErrMsg; + const Target *TheTarget = + TargetRegistry::lookupTarget(TheTriple.str(), ErrMsg); + if (!TheTarget) { + report_fatal_error("Can't load target for this Triple: " + ErrMsg); + } + + // Use MAttr as the default set of features. + SubtargetFeatures Features(MAttr); + Features.getDefaultSubtargetFeatures(TheTriple); + std::string FeatureStr = Features.getString(); + return std::unique_ptr<TargetMachine>(TheTarget->createTargetMachine( + TheTriple.str(), MCpu, FeatureStr, Options, RelocModel, + CodeModel::Default, CGOptLevel)); +} + +/** + * Produce the combined summary index from all the bitcode files: + * "thin-link". + */ +std::unique_ptr<ModuleSummaryIndex> ThinLTOCodeGenerator::linkCombinedIndex() { + std::unique_ptr<ModuleSummaryIndex> CombinedIndex; + uint64_t NextModuleId = 0; + for (auto &ModuleBuffer : Modules) { + ErrorOr<std::unique_ptr<object::ModuleSummaryIndexObjectFile>> ObjOrErr = + object::ModuleSummaryIndexObjectFile::create(ModuleBuffer, + diagnosticHandler); + if (std::error_code EC = ObjOrErr.getError()) { + // FIXME diagnose + errs() << "error: can't create ModuleSummaryIndexObjectFile for buffer: " + << EC.message() << "\n"; + return nullptr; + } + auto Index = (*ObjOrErr)->takeIndex(); + if (CombinedIndex) { + CombinedIndex->mergeFrom(std::move(Index), ++NextModuleId); + } else { + CombinedIndex = std::move(Index); + } + } + return CombinedIndex; +} + +/** + * Perform promotion and renaming of exported internal functions. + * Index is updated to reflect linkage changes from weak resolution. + */ +void ThinLTOCodeGenerator::promote(Module &TheModule, + ModuleSummaryIndex &Index) { + auto ModuleCount = Index.modulePaths().size(); + auto ModuleIdentifier = TheModule.getModuleIdentifier(); + // Collect for each module the list of function it defines (GUID -> Summary). + StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries; + Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries); + + // Generate import/export list + StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount); + StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount); + ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists, + ExportLists); + + // Resolve LinkOnce/Weak symbols. + StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR; + resolveWeakForLinkerInIndex(Index, ResolvedODR); + + thinLTOResolveWeakForLinkerModule( + TheModule, ModuleToDefinedGVSummaries[ModuleIdentifier]); + + promoteModule(TheModule, Index); +} + +/** + * Perform cross-module importing for the module identified by ModuleIdentifier. + */ +void ThinLTOCodeGenerator::crossModuleImport(Module &TheModule, + ModuleSummaryIndex &Index) { + auto ModuleMap = generateModuleMap(Modules); + auto ModuleCount = Index.modulePaths().size(); + + // Collect for each module the list of function it defines (GUID -> Summary). + StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount); + Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries); + + // Generate import/export list + StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount); + StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount); + ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists, + ExportLists); + auto &ImportList = ImportLists[TheModule.getModuleIdentifier()]; + + crossImportIntoModule(TheModule, Index, ModuleMap, ImportList); +} + +/** + * Compute the list of summaries needed for importing into module. + */ +void ThinLTOCodeGenerator::gatherImportedSummariesForModule( + StringRef ModulePath, ModuleSummaryIndex &Index, + std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex) { + auto ModuleCount = Index.modulePaths().size(); + + // Collect for each module the list of function it defines (GUID -> Summary). + StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount); + Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries); + + // Generate import/export list + StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount); + StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount); + ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists, + ExportLists); + + llvm::gatherImportedSummariesForModule(ModulePath, ModuleToDefinedGVSummaries, + ImportLists, + ModuleToSummariesForIndex); +} + +/** + * Emit the list of files needed for importing into module. + */ +void ThinLTOCodeGenerator::emitImports(StringRef ModulePath, + StringRef OutputName, + ModuleSummaryIndex &Index) { + auto ModuleCount = Index.modulePaths().size(); + + // Collect for each module the list of function it defines (GUID -> Summary). + StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount); + Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries); + + // Generate import/export list + StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount); + StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount); + ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists, + ExportLists); + + std::error_code EC; + if ((EC = EmitImportsFiles(ModulePath, OutputName, ImportLists))) + report_fatal_error(Twine("Failed to open ") + OutputName + + " to save imports lists\n"); +} + +/** + * Perform internalization. Index is updated to reflect linkage changes. + */ +void ThinLTOCodeGenerator::internalize(Module &TheModule, + ModuleSummaryIndex &Index) { + initTMBuilder(TMBuilder, Triple(TheModule.getTargetTriple())); + auto ModuleCount = Index.modulePaths().size(); + auto ModuleIdentifier = TheModule.getModuleIdentifier(); + + // Convert the preserved symbols set from string to GUID + auto GUIDPreservedSymbols = + computeGUIDPreservedSymbols(PreservedSymbols, TMBuilder.TheTriple); + + // Collect for each module the list of function it defines (GUID -> Summary). + StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount); + Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries); + + // Generate import/export list + StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount); + StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount); + ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists, + ExportLists); + auto &ExportList = ExportLists[ModuleIdentifier]; + + // Be friendly and don't nuke totally the module when the client didn't + // supply anything to preserve. + if (ExportList.empty() && GUIDPreservedSymbols.empty()) + return; + + // Internalization + auto isExported = [&](StringRef ModuleIdentifier, GlobalValue::GUID GUID) { + const auto &ExportList = ExportLists.find(ModuleIdentifier); + return (ExportList != ExportLists.end() && + ExportList->second.count(GUID)) || + GUIDPreservedSymbols.count(GUID); + }; + thinLTOInternalizeAndPromoteInIndex(Index, isExported); + thinLTOInternalizeModule(TheModule, + ModuleToDefinedGVSummaries[ModuleIdentifier]); +} + +/** + * Perform post-importing ThinLTO optimizations. + */ +void ThinLTOCodeGenerator::optimize(Module &TheModule) { + initTMBuilder(TMBuilder, Triple(TheModule.getTargetTriple())); + + // Optimize now + optimizeModule(TheModule, *TMBuilder.create()); +} + +/** + * Perform ThinLTO CodeGen. + */ +std::unique_ptr<MemoryBuffer> ThinLTOCodeGenerator::codegen(Module &TheModule) { + initTMBuilder(TMBuilder, Triple(TheModule.getTargetTriple())); + return codegenModule(TheModule, *TMBuilder.create()); +} + +// Main entry point for the ThinLTO processing +void ThinLTOCodeGenerator::run() { + if (CodeGenOnly) { + // Perform only parallel codegen and return. + ThreadPool Pool; + assert(ProducedBinaries.empty() && "The generator should not be reused"); + ProducedBinaries.resize(Modules.size()); + int count = 0; + for (auto &ModuleBuffer : Modules) { + Pool.async([&](int count) { + LLVMContext Context; + Context.setDiscardValueNames(LTODiscardValueNames); + + // Parse module now + auto TheModule = loadModuleFromBuffer(ModuleBuffer, Context, false); + + // CodeGen + ProducedBinaries[count] = codegen(*TheModule); + }, count++); + } + + return; + } + + // Sequential linking phase + auto Index = linkCombinedIndex(); + + // Save temps: index. + if (!SaveTempsDir.empty()) { + auto SaveTempPath = SaveTempsDir + "index.bc"; + std::error_code EC; + raw_fd_ostream OS(SaveTempPath, EC, sys::fs::F_None); + if (EC) + report_fatal_error(Twine("Failed to open ") + SaveTempPath + + " to save optimized bitcode\n"); + WriteIndexToFile(*Index, OS); + } + + // Prepare the resulting object vector + assert(ProducedBinaries.empty() && "The generator should not be reused"); + ProducedBinaries.resize(Modules.size()); + + // Prepare the module map. + auto ModuleMap = generateModuleMap(Modules); + auto ModuleCount = Modules.size(); + + // Collect for each module the list of function it defines (GUID -> Summary). + StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount); + Index->collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries); + + // Collect the import/export lists for all modules from the call-graph in the + // combined index. + StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount); + StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount); + ComputeCrossModuleImport(*Index, ModuleToDefinedGVSummaries, ImportLists, + ExportLists); + + // Convert the preserved symbols set from string to GUID, this is needed for + // computing the caching hash and the internalization. + auto GUIDPreservedSymbols = + computeGUIDPreservedSymbols(PreservedSymbols, TMBuilder.TheTriple); + + // We use a std::map here to be able to have a defined ordering when + // producing a hash for the cache entry. + // FIXME: we should be able to compute the caching hash for the entry based + // on the index, and nuke this map. + StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR; + + // Resolve LinkOnce/Weak symbols, this has to be computed early because it + // impacts the caching. + resolveWeakForLinkerInIndex(*Index, ResolvedODR); + + auto isExported = [&](StringRef ModuleIdentifier, GlobalValue::GUID GUID) { + const auto &ExportList = ExportLists.find(ModuleIdentifier); + return (ExportList != ExportLists.end() && + ExportList->second.count(GUID)) || + GUIDPreservedSymbols.count(GUID); + }; + + // Use global summary-based analysis to identify symbols that can be + // internalized (because they aren't exported or preserved as per callback). + // Changes are made in the index, consumed in the ThinLTO backends. + thinLTOInternalizeAndPromoteInIndex(*Index, isExported); + + // Make sure that every module has an entry in the ExportLists and + // ResolvedODR maps to enable threaded access to these maps below. + for (auto &DefinedGVSummaries : ModuleToDefinedGVSummaries) { + ExportLists[DefinedGVSummaries.first()]; + ResolvedODR[DefinedGVSummaries.first()]; + } + + // Compute the ordering we will process the inputs: the rough heuristic here + // is to sort them per size so that the largest module get schedule as soon as + // possible. This is purely a compile-time optimization. + std::vector<int> ModulesOrdering; + ModulesOrdering.resize(Modules.size()); + std::iota(ModulesOrdering.begin(), ModulesOrdering.end(), 0); + std::sort(ModulesOrdering.begin(), ModulesOrdering.end(), + [&](int LeftIndex, int RightIndex) { + auto LSize = Modules[LeftIndex].getBufferSize(); + auto RSize = Modules[RightIndex].getBufferSize(); + return LSize > RSize; + }); + + // Parallel optimizer + codegen + { + ThreadPool Pool(ThreadCount); + for (auto IndexCount : ModulesOrdering) { + auto &ModuleBuffer = Modules[IndexCount]; + Pool.async([&](int count) { + auto ModuleIdentifier = ModuleBuffer.getBufferIdentifier(); + auto &ExportList = ExportLists[ModuleIdentifier]; + + auto &DefinedFunctions = ModuleToDefinedGVSummaries[ModuleIdentifier]; + + // The module may be cached, this helps handling it. + ModuleCacheEntry CacheEntry(CacheOptions.Path, *Index, ModuleIdentifier, + ImportLists[ModuleIdentifier], ExportList, + ResolvedODR[ModuleIdentifier], + DefinedFunctions, GUIDPreservedSymbols); + + { + auto ErrOrBuffer = CacheEntry.tryLoadingBuffer(); + DEBUG(dbgs() << "Cache " << (ErrOrBuffer ? "hit" : "miss") << " '" + << CacheEntry.getEntryPath() << "' for buffer " << count + << " " << ModuleIdentifier << "\n"); + + if (ErrOrBuffer) { + // Cache Hit! + ProducedBinaries[count] = std::move(ErrOrBuffer.get()); + return; + } + } + + LLVMContext Context; + Context.setDiscardValueNames(LTODiscardValueNames); + Context.enableDebugTypeODRUniquing(); + + // Parse module now + auto TheModule = loadModuleFromBuffer(ModuleBuffer, Context, false); + + // Save temps: original file. + saveTempBitcode(*TheModule, SaveTempsDir, count, ".0.original.bc"); + + auto &ImportList = ImportLists[ModuleIdentifier]; + // Run the main process now, and generates a binary + auto OutputBuffer = ProcessThinLTOModule( + *TheModule, *Index, ModuleMap, *TMBuilder.create(), ImportList, + ExportList, GUIDPreservedSymbols, + ModuleToDefinedGVSummaries[ModuleIdentifier], CacheOptions, + DisableCodeGen, SaveTempsDir, count); + + OutputBuffer = CacheEntry.write(std::move(OutputBuffer)); + ProducedBinaries[count] = std::move(OutputBuffer); + }, IndexCount); + } + } + + CachePruning(CacheOptions.Path) + .setPruningInterval(CacheOptions.PruningInterval) + .setEntryExpiration(CacheOptions.Expiration) + .setMaxSize(CacheOptions.MaxPercentageOfAvailableSpace) + .prune(); + + // If statistics were requested, print them out now. + if (llvm::AreStatisticsEnabled()) + llvm::PrintStatistics(); +} |