ThinLTOCodeGenerator.cpp | Explore in Territory

//===-ThinLTOCodeGenerator.cpp - LLVM Link Time Optimizer -----------------===//
//
// 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 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"
#include "llvm/Support/CommandLine.h"

#include "llvm/ADT/ScopeExit.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/ModuleSummaryAnalysis.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Bitcode/BitcodeReader.h"
#include "llvm/Bitcode/BitcodeWriter.h"
#include "llvm/Bitcode/BitcodeWriterPass.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/DiagnosticPrinter.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/LLVMRemarkStreamer.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/Mangler.h"
#include "llvm/IR/PassTimingInfo.h"
#include "llvm/IR/Verifier.h"
#include "llvm/IRReader/IRReader.h"
#include "llvm/LTO/LTO.h"
#include "llvm/MC/TargetRegistry.h"
#include "llvm/Object/IRObjectFile.h"
#include "llvm/Passes/PassBuilder.h"
#include "llvm/Passes/StandardInstrumentations.h"
#include "llvm/Remarks/HotnessThresholdParser.h"
#include "llvm/Support/CachePruning.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/FormatVariadic.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/SHA1.h"
#include "llvm/Support/SmallVectorMemoryBuffer.h"
#include "llvm/Support/ThreadPool.h"
#include "llvm/Support/Threading.h"
#include "llvm/Support/ToolOutputFile.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/TargetParser/SubtargetFeature.h"
#include "llvm/Transforms/IPO/FunctionAttrs.h"
#include "llvm/Transforms/IPO/FunctionImport.h"
#include "llvm/Transforms/IPO/Internalize.h"
#include "llvm/Transforms/IPO/WholeProgramDevirt.h"
#include "llvm/Transforms/ObjCARC.h"
#include "llvm/Transforms/Utils/FunctionImportUtils.h"

#include <numeric>

#if !defined(_MSC_VER) && !defined(__MINGW32__)
#include <unistd.h>
#else
#include <io.h>
#endif

usingnamespacellvm;

#define DEBUG_TYPE …

namespace llvm {
// Flags -discard-value-names, defined in LTOCodeGenerator.cpp
extern cl::opt<bool> LTODiscardValueNames;
extern cl::opt<std::string> RemarksFilename;
extern cl::opt<std::string> RemarksPasses;
extern cl::opt<bool> RemarksWithHotness;
extern cl::opt<std::optional<uint64_t>, false, remarks::HotnessThresholdParser>
    RemarksHotnessThreshold;
extern cl::opt<std::string> RemarksFormat;
}

namespace {

// Default to using all available threads in the system, but using only one
// thred per core, as indicated by the usage of
// heavyweight_hardware_concurrency() below.
static cl::opt<int> ThreadCount("threads", cl::init(0));

// Simple helper to save temporary files for debug.
static void saveTempBitcode(const Module &TheModule, StringRef TempDir,
                            unsigned count, StringRef Suffix) { … }

static const GlobalValueSummary *
getFirstDefinitionForLinker(const GlobalValueSummaryList &GVSummaryList) { … }

// 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) { … }

static StringMap<lto::InputFile *>
generateModuleMap(std::vector<std::unique_ptr<lto::InputFile>> &Modules) { … }

static void promoteModule(Module &TheModule, const ModuleSummaryIndex &Index,
                          bool ClearDSOLocalOnDeclarations) { … }

namespace {
class ThinLTODiagnosticInfo : public DiagnosticInfo { … };
}

/// Verify the module and strip broken debug info.
static void verifyLoadedModule(Module &TheModule) { … }

static std::unique_ptr<Module> loadModuleFromInput(lto::InputFile *Input,
                                                   LLVMContext &Context,
                                                   bool Lazy,
                                                   bool IsImporting) { … }

static void
crossImportIntoModule(Module &TheModule, const ModuleSummaryIndex &Index,
                      StringMap<lto::InputFile *> &ModuleMap,
                      const FunctionImporter::ImportMapTy &ImportList,
                      bool ClearDSOLocalOnDeclarations) { … }

static void optimizeModule(Module &TheModule, TargetMachine &TM,
                           unsigned OptLevel, bool Freestanding,
                           bool DebugPassManager, ModuleSummaryIndex *Index) { … }

static void
addUsedSymbolToPreservedGUID(const lto::InputFile &File,
                             DenseSet<GlobalValue::GUID> &PreservedGUID) { … }

// Convert the PreservedSymbols map from "Name" based to "GUID" based.
static void computeGUIDPreservedSymbols(const lto::InputFile &File,
                                        const StringSet<> &PreservedSymbols,
                                        const Triple &TheTriple,
                                        DenseSet<GlobalValue::GUID> &GUIDs) { … }

static DenseSet<GlobalValue::GUID>
computeGUIDPreservedSymbols(const lto::InputFile &File,
                            const StringSet<> &PreservedSymbols,
                            const Triple &TheTriple) { … }

std::unique_ptr<MemoryBuffer> codegenModule(Module &TheModule,
                                            TargetMachine &TM) { … }

/// Manage caching for a single Module.
class ModuleCacheEntry { … };

static std::unique_ptr<MemoryBuffer>
ProcessThinLTOModule(Module &TheModule, ModuleSummaryIndex &Index,
                     StringMap<lto::InputFile *> &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,
                     bool Freestanding, unsigned OptLevel, unsigned count,
                     bool DebugPassManager) { … }

/// Resolve prevailing 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 resolvePrevailingInIndex(
    ModuleSummaryIndex &Index,
    StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>>
        &ResolvedODR,
    const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols,
    const DenseMap<GlobalValue::GUID, const GlobalValueSummary *>
        &PrevailingCopy) { … }

// Initialize the TargetMachine builder for a given Triple
static void initTMBuilder(TargetMachineBuilder &TMBuilder,
                          const Triple &TheTriple) { … }

} // end anonymous namespace

void ThinLTOCodeGenerator::addModule(StringRef Identifier, StringRef Data) { … }

void ThinLTOCodeGenerator::preserveSymbol(StringRef Name) { … }

void ThinLTOCodeGenerator::crossReferenceSymbol(StringRef Name) { … }

// TargetMachine factory
std::unique_ptr<TargetMachine> TargetMachineBuilder::create() const { … }

/**
 * Produce the combined summary index from all the bitcode files:
 * "thin-link".
 */
std::unique_ptr<ModuleSummaryIndex> ThinLTOCodeGenerator::linkCombinedIndex() { … }

namespace {
struct IsExported { … };

struct IsPrevailing { … };
} // namespace

static void computeDeadSymbolsInIndex(
    ModuleSummaryIndex &Index,
    const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols) { … }

/**
 * 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,
                                   const lto::InputFile &File) { … }

/**
 * Perform cross-module importing for the module identified by ModuleIdentifier.
 */
void ThinLTOCodeGenerator::crossModuleImport(Module &TheModule,
                                             ModuleSummaryIndex &Index,
                                             const lto::InputFile &File) { … }

/**
 * Compute the list of summaries needed for importing into module.
 */
void ThinLTOCodeGenerator::gatherImportedSummariesForModule(
    Module &TheModule, ModuleSummaryIndex &Index,
    ModuleToSummariesForIndexTy &ModuleToSummariesForIndex,
    GVSummaryPtrSet &DecSummaries, const lto::InputFile &File) { … }

/**
 * Emit the list of files needed for importing into module.
 */
void ThinLTOCodeGenerator::emitImports(Module &TheModule, StringRef OutputName,
                                       ModuleSummaryIndex &Index,
                                       const lto::InputFile &File) { … }

/**
 * Perform internalization. Runs promote and internalization together.
 * Index is updated to reflect linkage changes.
 */
void ThinLTOCodeGenerator::internalize(Module &TheModule,
                                       ModuleSummaryIndex &Index,
                                       const lto::InputFile &File) { … }

/**
 * Perform post-importing ThinLTO optimizations.
 */
void ThinLTOCodeGenerator::optimize(Module &TheModule) { … }

/// Write out the generated object file, either from CacheEntryPath or from
/// OutputBuffer, preferring hard-link when possible.
/// Returns the path to the generated file in SavedObjectsDirectoryPath.
std::string
ThinLTOCodeGenerator::writeGeneratedObject(int count, StringRef CacheEntryPath,
                                           const MemoryBuffer &OutputBuffer) { … }

// Main entry point for the ThinLTO processing
void ThinLTOCodeGenerator::run() { … }
llvm/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
