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Diffstat (limited to 'llvm/lib/LTO/LTOBackend.cpp')
| -rw-r--r-- | llvm/lib/LTO/LTOBackend.cpp | 547 |
1 files changed, 547 insertions, 0 deletions
diff --git a/llvm/lib/LTO/LTOBackend.cpp b/llvm/lib/LTO/LTOBackend.cpp new file mode 100644 index 0000000000000..2761f8367b0da --- /dev/null +++ b/llvm/lib/LTO/LTOBackend.cpp @@ -0,0 +1,547 @@ +//===-LTOBackend.cpp - LLVM Link Time Optimizer Backend -------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// This file implements the "backend" phase of LTO, i.e. it performs +// optimization and code generation on a loaded module. It is generally used +// internally by the LTO class but can also be used independently, for example +// to implement a standalone ThinLTO backend. +// +//===----------------------------------------------------------------------===// + +#include "llvm/LTO/LTOBackend.h" +#include "llvm/Analysis/AliasAnalysis.h" +#include "llvm/Analysis/CGSCCPassManager.h" +#include "llvm/Analysis/TargetLibraryInfo.h" +#include "llvm/Analysis/TargetTransformInfo.h" +#include "llvm/Bitcode/BitcodeReader.h" +#include "llvm/Bitcode/BitcodeWriter.h" +#include "llvm/IR/LegacyPassManager.h" +#include "llvm/IR/PassManager.h" +#include "llvm/IR/RemarkStreamer.h" +#include "llvm/IR/Verifier.h" +#include "llvm/LTO/LTO.h" +#include "llvm/MC/SubtargetFeature.h" +#include "llvm/Object/ModuleSymbolTable.h" +#include "llvm/Passes/PassBuilder.h" +#include "llvm/Passes/StandardInstrumentations.h" +#include "llvm/Support/Error.h" +#include "llvm/Support/FileSystem.h" +#include "llvm/Support/MemoryBuffer.h" +#include "llvm/Support/Path.h" +#include "llvm/Support/Program.h" +#include "llvm/Support/TargetRegistry.h" +#include "llvm/Support/ThreadPool.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/Target/TargetMachine.h" +#include "llvm/Transforms/IPO.h" +#include "llvm/Transforms/IPO/PassManagerBuilder.h" +#include "llvm/Transforms/Scalar/LoopPassManager.h" +#include "llvm/Transforms/Utils/FunctionImportUtils.h" +#include "llvm/Transforms/Utils/SplitModule.h" + +using namespace llvm; +using namespace lto; + +LLVM_ATTRIBUTE_NORETURN static void reportOpenError(StringRef Path, Twine Msg) { + errs() << "failed to open " << Path << ": " << Msg << '\n'; + errs().flush(); + exit(1); +} + +Error Config::addSaveTemps(std::string OutputFileName, + bool UseInputModulePath) { + ShouldDiscardValueNames = false; + + std::error_code EC; + ResolutionFile = std::make_unique<raw_fd_ostream>( + OutputFileName + "resolution.txt", EC, sys::fs::OpenFlags::OF_Text); + if (EC) + return errorCodeToError(EC); + + auto setHook = [&](std::string PathSuffix, ModuleHookFn &Hook) { + // Keep track of the hook provided by the linker, which also needs to run. + ModuleHookFn LinkerHook = Hook; + Hook = [=](unsigned Task, const Module &M) { + // If the linker's hook returned false, we need to pass that result + // through. + if (LinkerHook && !LinkerHook(Task, M)) + return false; + + std::string PathPrefix; + // If this is the combined module (not a ThinLTO backend compile) or the + // user hasn't requested using the input module's path, emit to a file + // named from the provided OutputFileName with the Task ID appended. + if (M.getModuleIdentifier() == "ld-temp.o" || !UseInputModulePath) { + PathPrefix = OutputFileName; + if (Task != (unsigned)-1) + PathPrefix += utostr(Task) + "."; + } else + PathPrefix = M.getModuleIdentifier() + "."; + std::string Path = PathPrefix + PathSuffix + ".bc"; + std::error_code EC; + raw_fd_ostream OS(Path, EC, sys::fs::OpenFlags::OF_None); + // Because -save-temps is a debugging feature, we report the error + // directly and exit. + if (EC) + reportOpenError(Path, EC.message()); + WriteBitcodeToFile(M, OS, /*ShouldPreserveUseListOrder=*/false); + return true; + }; + }; + + setHook("0.preopt", PreOptModuleHook); + setHook("1.promote", PostPromoteModuleHook); + setHook("2.internalize", PostInternalizeModuleHook); + setHook("3.import", PostImportModuleHook); + setHook("4.opt", PostOptModuleHook); + setHook("5.precodegen", PreCodeGenModuleHook); + + CombinedIndexHook = [=](const ModuleSummaryIndex &Index) { + std::string Path = OutputFileName + "index.bc"; + std::error_code EC; + raw_fd_ostream OS(Path, EC, sys::fs::OpenFlags::OF_None); + // Because -save-temps is a debugging feature, we report the error + // directly and exit. + if (EC) + reportOpenError(Path, EC.message()); + WriteIndexToFile(Index, OS); + + Path = OutputFileName + "index.dot"; + raw_fd_ostream OSDot(Path, EC, sys::fs::OpenFlags::OF_None); + if (EC) + reportOpenError(Path, EC.message()); + Index.exportToDot(OSDot); + return true; + }; + + return Error::success(); +} + +namespace { + +std::unique_ptr<TargetMachine> +createTargetMachine(Config &Conf, const Target *TheTarget, Module &M) { + StringRef TheTriple = M.getTargetTriple(); + SubtargetFeatures Features; + Features.getDefaultSubtargetFeatures(Triple(TheTriple)); + for (const std::string &A : Conf.MAttrs) + Features.AddFeature(A); + + Reloc::Model RelocModel; + if (Conf.RelocModel) + RelocModel = *Conf.RelocModel; + else + RelocModel = + M.getPICLevel() == PICLevel::NotPIC ? Reloc::Static : Reloc::PIC_; + + Optional<CodeModel::Model> CodeModel; + if (Conf.CodeModel) + CodeModel = *Conf.CodeModel; + else + CodeModel = M.getCodeModel(); + + return std::unique_ptr<TargetMachine>(TheTarget->createTargetMachine( + TheTriple, Conf.CPU, Features.getString(), Conf.Options, RelocModel, + CodeModel, Conf.CGOptLevel)); +} + +static void runNewPMPasses(Config &Conf, Module &Mod, TargetMachine *TM, + unsigned OptLevel, bool IsThinLTO, + ModuleSummaryIndex *ExportSummary, + const ModuleSummaryIndex *ImportSummary) { + Optional<PGOOptions> PGOOpt; + if (!Conf.SampleProfile.empty()) + PGOOpt = PGOOptions(Conf.SampleProfile, "", Conf.ProfileRemapping, + PGOOptions::SampleUse, PGOOptions::NoCSAction, true); + else if (Conf.RunCSIRInstr) { + PGOOpt = PGOOptions("", Conf.CSIRProfile, Conf.ProfileRemapping, + PGOOptions::IRUse, PGOOptions::CSIRInstr); + } else if (!Conf.CSIRProfile.empty()) { + PGOOpt = PGOOptions(Conf.CSIRProfile, "", Conf.ProfileRemapping, + PGOOptions::IRUse, PGOOptions::CSIRUse); + } + + PassInstrumentationCallbacks PIC; + StandardInstrumentations SI; + SI.registerCallbacks(PIC); + PassBuilder PB(TM, PipelineTuningOptions(),PGOOpt, &PIC); + AAManager AA; + + // Parse a custom AA pipeline if asked to. + if (auto Err = PB.parseAAPipeline(AA, "default")) + report_fatal_error("Error parsing default AA pipeline"); + + LoopAnalysisManager LAM(Conf.DebugPassManager); + FunctionAnalysisManager FAM(Conf.DebugPassManager); + CGSCCAnalysisManager CGAM(Conf.DebugPassManager); + ModuleAnalysisManager MAM(Conf.DebugPassManager); + + // Register the AA manager first so that our version is the one used. + FAM.registerPass([&] { return std::move(AA); }); + + // Register all the basic analyses with the managers. + PB.registerModuleAnalyses(MAM); + PB.registerCGSCCAnalyses(CGAM); + PB.registerFunctionAnalyses(FAM); + PB.registerLoopAnalyses(LAM); + PB.crossRegisterProxies(LAM, FAM, CGAM, MAM); + + ModulePassManager MPM(Conf.DebugPassManager); + // FIXME (davide): verify the input. + + PassBuilder::OptimizationLevel OL; + + switch (OptLevel) { + default: + llvm_unreachable("Invalid optimization level"); + case 0: + OL = PassBuilder::O0; + break; + case 1: + OL = PassBuilder::O1; + break; + case 2: + OL = PassBuilder::O2; + break; + case 3: + OL = PassBuilder::O3; + break; + } + + if (IsThinLTO) + MPM = PB.buildThinLTODefaultPipeline(OL, Conf.DebugPassManager, + ImportSummary); + else + MPM = PB.buildLTODefaultPipeline(OL, Conf.DebugPassManager, ExportSummary); + MPM.run(Mod, MAM); + + // FIXME (davide): verify the output. +} + +static void runNewPMCustomPasses(Module &Mod, TargetMachine *TM, + std::string PipelineDesc, + std::string AAPipelineDesc, + bool DisableVerify) { + PassBuilder PB(TM); + AAManager AA; + + // Parse a custom AA pipeline if asked to. + if (!AAPipelineDesc.empty()) + if (auto Err = PB.parseAAPipeline(AA, AAPipelineDesc)) + report_fatal_error("unable to parse AA pipeline description '" + + AAPipelineDesc + "': " + toString(std::move(Err))); + + LoopAnalysisManager LAM; + FunctionAnalysisManager FAM; + CGSCCAnalysisManager CGAM; + ModuleAnalysisManager MAM; + + // Register the AA manager first so that our version is the one used. + FAM.registerPass([&] { return std::move(AA); }); + + // Register all the basic analyses with the managers. + PB.registerModuleAnalyses(MAM); + PB.registerCGSCCAnalyses(CGAM); + PB.registerFunctionAnalyses(FAM); + PB.registerLoopAnalyses(LAM); + PB.crossRegisterProxies(LAM, FAM, CGAM, MAM); + + ModulePassManager MPM; + + // Always verify the input. + MPM.addPass(VerifierPass()); + + // Now, add all the passes we've been requested to. + if (auto Err = PB.parsePassPipeline(MPM, PipelineDesc)) + report_fatal_error("unable to parse pass pipeline description '" + + PipelineDesc + "': " + toString(std::move(Err))); + + if (!DisableVerify) + MPM.addPass(VerifierPass()); + MPM.run(Mod, MAM); +} + +static void runOldPMPasses(Config &Conf, Module &Mod, TargetMachine *TM, + bool IsThinLTO, ModuleSummaryIndex *ExportSummary, + const ModuleSummaryIndex *ImportSummary) { + legacy::PassManager passes; + passes.add(createTargetTransformInfoWrapperPass(TM->getTargetIRAnalysis())); + + PassManagerBuilder PMB; + PMB.LibraryInfo = new TargetLibraryInfoImpl(Triple(TM->getTargetTriple())); + PMB.Inliner = createFunctionInliningPass(); + PMB.ExportSummary = ExportSummary; + PMB.ImportSummary = ImportSummary; + // Unconditionally verify input since it is not verified before this + // point and has unknown origin. + PMB.VerifyInput = true; + PMB.VerifyOutput = !Conf.DisableVerify; + PMB.LoopVectorize = true; + PMB.SLPVectorize = true; + PMB.OptLevel = Conf.OptLevel; + PMB.PGOSampleUse = Conf.SampleProfile; + PMB.EnablePGOCSInstrGen = Conf.RunCSIRInstr; + if (!Conf.RunCSIRInstr && !Conf.CSIRProfile.empty()) { + PMB.EnablePGOCSInstrUse = true; + PMB.PGOInstrUse = Conf.CSIRProfile; + } + if (IsThinLTO) + PMB.populateThinLTOPassManager(passes); + else + PMB.populateLTOPassManager(passes); + passes.run(Mod); +} + +bool opt(Config &Conf, TargetMachine *TM, unsigned Task, Module &Mod, + bool IsThinLTO, ModuleSummaryIndex *ExportSummary, + const ModuleSummaryIndex *ImportSummary) { + // FIXME: Plumb the combined index into the new pass manager. + if (!Conf.OptPipeline.empty()) + runNewPMCustomPasses(Mod, TM, Conf.OptPipeline, Conf.AAPipeline, + Conf.DisableVerify); + else if (Conf.UseNewPM) + runNewPMPasses(Conf, Mod, TM, Conf.OptLevel, IsThinLTO, ExportSummary, + ImportSummary); + else + runOldPMPasses(Conf, Mod, TM, IsThinLTO, ExportSummary, ImportSummary); + return !Conf.PostOptModuleHook || Conf.PostOptModuleHook(Task, Mod); +} + +void codegen(Config &Conf, TargetMachine *TM, AddStreamFn AddStream, + unsigned Task, Module &Mod) { + if (Conf.PreCodeGenModuleHook && !Conf.PreCodeGenModuleHook(Task, Mod)) + return; + + std::unique_ptr<ToolOutputFile> DwoOut; + SmallString<1024> DwoFile(Conf.SplitDwarfOutput); + if (!Conf.DwoDir.empty()) { + std::error_code EC; + if (auto EC = llvm::sys::fs::create_directories(Conf.DwoDir)) + report_fatal_error("Failed to create directory " + Conf.DwoDir + ": " + + EC.message()); + + DwoFile = Conf.DwoDir; + sys::path::append(DwoFile, std::to_string(Task) + ".dwo"); + TM->Options.MCOptions.SplitDwarfFile = DwoFile.str().str(); + } else + TM->Options.MCOptions.SplitDwarfFile = Conf.SplitDwarfFile; + + if (!DwoFile.empty()) { + std::error_code EC; + DwoOut = std::make_unique<ToolOutputFile>(DwoFile, EC, sys::fs::OF_None); + if (EC) + report_fatal_error("Failed to open " + DwoFile + ": " + EC.message()); + } + + auto Stream = AddStream(Task); + legacy::PassManager CodeGenPasses; + if (TM->addPassesToEmitFile(CodeGenPasses, *Stream->OS, + DwoOut ? &DwoOut->os() : nullptr, + Conf.CGFileType)) + report_fatal_error("Failed to setup codegen"); + CodeGenPasses.run(Mod); + + if (DwoOut) + DwoOut->keep(); +} + +void splitCodeGen(Config &C, TargetMachine *TM, AddStreamFn AddStream, + unsigned ParallelCodeGenParallelismLevel, + std::unique_ptr<Module> Mod) { + ThreadPool CodegenThreadPool(ParallelCodeGenParallelismLevel); + unsigned ThreadCount = 0; + const Target *T = &TM->getTarget(); + + SplitModule( + std::move(Mod), ParallelCodeGenParallelismLevel, + [&](std::unique_ptr<Module> MPart) { + // We want to clone the module in a new context to multi-thread the + // codegen. We do it by serializing partition modules to bitcode + // (while still on the main thread, in order to avoid data races) and + // spinning up new threads which deserialize the partitions into + // separate contexts. + // FIXME: Provide a more direct way to do this in LLVM. + SmallString<0> BC; + raw_svector_ostream BCOS(BC); + WriteBitcodeToFile(*MPart, BCOS); + + // Enqueue the task + CodegenThreadPool.async( + [&](const SmallString<0> &BC, unsigned ThreadId) { + LTOLLVMContext Ctx(C); + Expected<std::unique_ptr<Module>> MOrErr = parseBitcodeFile( + MemoryBufferRef(StringRef(BC.data(), BC.size()), "ld-temp.o"), + Ctx); + if (!MOrErr) + report_fatal_error("Failed to read bitcode"); + std::unique_ptr<Module> MPartInCtx = std::move(MOrErr.get()); + + std::unique_ptr<TargetMachine> TM = + createTargetMachine(C, T, *MPartInCtx); + + codegen(C, TM.get(), AddStream, ThreadId, *MPartInCtx); + }, + // Pass BC using std::move to ensure that it get moved rather than + // copied into the thread's context. + std::move(BC), ThreadCount++); + }, + false); + + // Because the inner lambda (which runs in a worker thread) captures our local + // variables, we need to wait for the worker threads to terminate before we + // can leave the function scope. + CodegenThreadPool.wait(); +} + +Expected<const Target *> initAndLookupTarget(Config &C, Module &Mod) { + if (!C.OverrideTriple.empty()) + Mod.setTargetTriple(C.OverrideTriple); + else if (Mod.getTargetTriple().empty()) + Mod.setTargetTriple(C.DefaultTriple); + + std::string Msg; + const Target *T = TargetRegistry::lookupTarget(Mod.getTargetTriple(), Msg); + if (!T) + return make_error<StringError>(Msg, inconvertibleErrorCode()); + return T; +} + +} + +static Error +finalizeOptimizationRemarks(std::unique_ptr<ToolOutputFile> DiagOutputFile) { + // Make sure we flush the diagnostic remarks file in case the linker doesn't + // call the global destructors before exiting. + if (!DiagOutputFile) + return Error::success(); + DiagOutputFile->keep(); + DiagOutputFile->os().flush(); + return Error::success(); +} + +Error lto::backend(Config &C, AddStreamFn AddStream, + unsigned ParallelCodeGenParallelismLevel, + std::unique_ptr<Module> Mod, + ModuleSummaryIndex &CombinedIndex) { + Expected<const Target *> TOrErr = initAndLookupTarget(C, *Mod); + if (!TOrErr) + return TOrErr.takeError(); + + std::unique_ptr<TargetMachine> TM = createTargetMachine(C, *TOrErr, *Mod); + + // Setup optimization remarks. + auto DiagFileOrErr = lto::setupOptimizationRemarks( + Mod->getContext(), C.RemarksFilename, C.RemarksPasses, C.RemarksFormat, + C.RemarksWithHotness); + if (!DiagFileOrErr) + return DiagFileOrErr.takeError(); + auto DiagnosticOutputFile = std::move(*DiagFileOrErr); + + if (!C.CodeGenOnly) { + if (!opt(C, TM.get(), 0, *Mod, /*IsThinLTO=*/false, + /*ExportSummary=*/&CombinedIndex, /*ImportSummary=*/nullptr)) + return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile)); + } + + if (ParallelCodeGenParallelismLevel == 1) { + codegen(C, TM.get(), AddStream, 0, *Mod); + } else { + splitCodeGen(C, TM.get(), AddStream, ParallelCodeGenParallelismLevel, + std::move(Mod)); + } + return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile)); +} + +static void dropDeadSymbols(Module &Mod, const GVSummaryMapTy &DefinedGlobals, + const ModuleSummaryIndex &Index) { + std::vector<GlobalValue*> DeadGVs; + for (auto &GV : Mod.global_values()) + if (GlobalValueSummary *GVS = DefinedGlobals.lookup(GV.getGUID())) + if (!Index.isGlobalValueLive(GVS)) { + DeadGVs.push_back(&GV); + convertToDeclaration(GV); + } + + // Now that all dead bodies have been dropped, delete the actual objects + // themselves when possible. + for (GlobalValue *GV : DeadGVs) { + GV->removeDeadConstantUsers(); + // Might reference something defined in native object (i.e. dropped a + // non-prevailing IR def, but we need to keep the declaration). + if (GV->use_empty()) + GV->eraseFromParent(); + } +} + +Error lto::thinBackend(Config &Conf, unsigned Task, AddStreamFn AddStream, + Module &Mod, const ModuleSummaryIndex &CombinedIndex, + const FunctionImporter::ImportMapTy &ImportList, + const GVSummaryMapTy &DefinedGlobals, + MapVector<StringRef, BitcodeModule> &ModuleMap) { + Expected<const Target *> TOrErr = initAndLookupTarget(Conf, Mod); + if (!TOrErr) + return TOrErr.takeError(); + + std::unique_ptr<TargetMachine> TM = createTargetMachine(Conf, *TOrErr, Mod); + + // Setup optimization remarks. + auto DiagFileOrErr = lto::setupOptimizationRemarks( + Mod.getContext(), Conf.RemarksFilename, Conf.RemarksPasses, + Conf.RemarksFormat, Conf.RemarksWithHotness, Task); + if (!DiagFileOrErr) + return DiagFileOrErr.takeError(); + auto DiagnosticOutputFile = std::move(*DiagFileOrErr); + + if (Conf.CodeGenOnly) { + codegen(Conf, TM.get(), AddStream, Task, Mod); + return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile)); + } + + if (Conf.PreOptModuleHook && !Conf.PreOptModuleHook(Task, Mod)) + return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile)); + + renameModuleForThinLTO(Mod, CombinedIndex); + + dropDeadSymbols(Mod, DefinedGlobals, CombinedIndex); + + thinLTOResolvePrevailingInModule(Mod, DefinedGlobals); + + if (Conf.PostPromoteModuleHook && !Conf.PostPromoteModuleHook(Task, Mod)) + return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile)); + + if (!DefinedGlobals.empty()) + thinLTOInternalizeModule(Mod, DefinedGlobals); + + if (Conf.PostInternalizeModuleHook && + !Conf.PostInternalizeModuleHook(Task, Mod)) + return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile)); + + auto ModuleLoader = [&](StringRef Identifier) { + assert(Mod.getContext().isODRUniquingDebugTypes() && + "ODR Type uniquing should be enabled on the context"); + auto I = ModuleMap.find(Identifier); + assert(I != ModuleMap.end()); + return I->second.getLazyModule(Mod.getContext(), + /*ShouldLazyLoadMetadata=*/true, + /*IsImporting*/ true); + }; + + FunctionImporter Importer(CombinedIndex, ModuleLoader); + if (Error Err = Importer.importFunctions(Mod, ImportList).takeError()) + return Err; + + if (Conf.PostImportModuleHook && !Conf.PostImportModuleHook(Task, Mod)) + return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile)); + + if (!opt(Conf, TM.get(), Task, Mod, /*IsThinLTO=*/true, + /*ExportSummary=*/nullptr, /*ImportSummary=*/&CombinedIndex)) + return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile)); + + codegen(Conf, TM.get(), AddStream, Task, Mod); + return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile)); +} |