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llvm-mirror/lib/LTO/ThinLTOCodeGenerator.cpp
Teresa Johnson 75870000ad [LTO] Prevent devirtualization for symbols dynamically exported 
Identify dynamically exported symbols (--export-dynamic[-symbol=],
--dynamic-list=, or definitions needed to preempt shared objects) and
prevent their LTO visibility from being upgraded.
This helps avoid use of whole program devirtualization when there may
be overrides in dynamic libraries.

Differential Revision: https://reviews.llvm.org/D91583
2021-01-27 15:54:13 -08:00

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//===-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/Statistic.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Analysis/ModuleSummaryAnalysis.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.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/LTO/SummaryBasedOptimizations.h"
#include "llvm/MC/SubtargetFeature.h"
#include "llvm/Object/IRObjectFile.h"
#include "llvm/Remarks/HotnessThresholdParser.h"
#include "llvm/Support/CachePruning.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/FileUtilities.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/SHA1.h"
#include "llvm/Support/SmallVectorMemoryBuffer.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/ThreadPool.h"
#include "llvm/Support/Threading.h"
#include "llvm/Support/ToolOutputFile.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/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
using namespace llvm;
#define DEBUG_TYPE "thinlto"
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<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) {
if (TempDir.empty())
return;
// User asked to save temps, let dump the bitcode file after import.
std::string SaveTempPath = (TempDir + llvm::Twine(count) + Suffix).str();
std::error_code EC;
raw_fd_ostream OS(SaveTempPath, EC, sys::fs::OF_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.SummaryList))
PrevailingCopy[I.first] =
getFirstDefinitionForLinker(I.second.SummaryList);
}
}
static StringMap<lto::InputFile *>
generateModuleMap(std::vector<std::unique_ptr<lto::InputFile>> &Modules) {
StringMap<lto::InputFile *> ModuleMap;
for (auto &M : Modules) {
assert(ModuleMap.find(M->getName()) == ModuleMap.end() &&
"Expect unique Buffer Identifier");
ModuleMap[M->getName()] = M.get();
}
return ModuleMap;
}
static void promoteModule(Module &TheModule, const ModuleSummaryIndex &Index,
bool ClearDSOLocalOnDeclarations) {
if (renameModuleForThinLTO(TheModule, Index, ClearDSOLocalOnDeclarations))
report_fatal_error("renameModuleForThinLTO failed");
}
namespace {
class ThinLTODiagnosticInfo : public DiagnosticInfo {
const Twine &Msg;
public:
ThinLTODiagnosticInfo(const Twine &DiagMsg,
DiagnosticSeverity Severity = DS_Error)
: DiagnosticInfo(DK_Linker, Severity), Msg(DiagMsg) {}
void print(DiagnosticPrinter &DP) const override { DP << Msg; }
};
}
/// Verify the module and strip broken debug info.
static void verifyLoadedModule(Module &TheModule) {
bool BrokenDebugInfo = false;
if (verifyModule(TheModule, &dbgs(), &BrokenDebugInfo))
report_fatal_error("Broken module found, compilation aborted!");
if (BrokenDebugInfo) {
TheModule.getContext().diagnose(ThinLTODiagnosticInfo(
"Invalid debug info found, debug info will be stripped", DS_Warning));
StripDebugInfo(TheModule);
}
}
static std::unique_ptr<Module> loadModuleFromInput(lto::InputFile *Input,
LLVMContext &Context,
bool Lazy,
bool IsImporting) {
auto &Mod = Input->getSingleBitcodeModule();
SMDiagnostic Err;
Expected<std::unique_ptr<Module>> ModuleOrErr =
Lazy ? Mod.getLazyModule(Context,
/* ShouldLazyLoadMetadata */ true, IsImporting)
: Mod.parseModule(Context);
if (!ModuleOrErr) {
handleAllErrors(ModuleOrErr.takeError(), [&](ErrorInfoBase &EIB) {
SMDiagnostic Err = SMDiagnostic(Mod.getModuleIdentifier(),
SourceMgr::DK_Error, EIB.message());
Err.print("ThinLTO", errs());
});
report_fatal_error("Can't load module, abort.");
}
if (!Lazy)
verifyLoadedModule(*ModuleOrErr.get());
return std::move(*ModuleOrErr);
}
static void
crossImportIntoModule(Module &TheModule, const ModuleSummaryIndex &Index,
StringMap<lto::InputFile *> &ModuleMap,
const FunctionImporter::ImportMapTy &ImportList,
bool ClearDSOLocalOnDeclarations) {
auto Loader = [&](StringRef Identifier) {
auto &Input = ModuleMap[Identifier];
return loadModuleFromInput(Input, TheModule.getContext(),
/*Lazy=*/true, /*IsImporting*/ true);
};
FunctionImporter Importer(Index, Loader, ClearDSOLocalOnDeclarations);
Expected<bool> Result = Importer.importFunctions(TheModule, ImportList);
if (!Result) {
handleAllErrors(Result.takeError(), [&](ErrorInfoBase &EIB) {
SMDiagnostic Err = SMDiagnostic(TheModule.getModuleIdentifier(),
SourceMgr::DK_Error, EIB.message());
Err.print("ThinLTO", errs());
});
report_fatal_error("importFunctions failed");
}
// Verify again after cross-importing.
verifyLoadedModule(TheModule);
}
static void optimizeModule(Module &TheModule, TargetMachine &TM,
unsigned OptLevel, bool Freestanding,
ModuleSummaryIndex *Index) {
// Populate the PassManager
PassManagerBuilder PMB;
PMB.LibraryInfo = new TargetLibraryInfoImpl(TM.getTargetTriple());
if (Freestanding)
PMB.LibraryInfo->disableAllFunctions();
PMB.Inliner = createFunctionInliningPass();
// FIXME: should get it from the bitcode?
PMB.OptLevel = OptLevel;
PMB.LoopVectorize = true;
PMB.SLPVectorize = true;
// Already did this in verifyLoadedModule().
PMB.VerifyInput = false;
PMB.VerifyOutput = false;
PMB.ImportSummary = Index;
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);
}
static void
addUsedSymbolToPreservedGUID(const lto::InputFile &File,
DenseSet<GlobalValue::GUID> &PreservedGUID) {
for (const auto &Sym : File.symbols()) {
if (Sym.isUsed())
PreservedGUID.insert(GlobalValue::getGUID(Sym.getIRName()));
}
}
// 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) {
// Iterate the symbols in the input file and if the input has preserved symbol
// compute the GUID for the symbol.
for (const auto &Sym : File.symbols()) {
if (PreservedSymbols.count(Sym.getName()) && !Sym.getIRName().empty())
GUIDs.insert(GlobalValue::getGUID(GlobalValue::getGlobalIdentifier(
Sym.getIRName(), GlobalValue::ExternalLinkage, "")));
}
}
static DenseSet<GlobalValue::GUID>
computeGUIDPreservedSymbols(const lto::InputFile &File,
const StringSet<> &PreservedSymbols,
const Triple &TheTriple) {
DenseSet<GlobalValue::GUID> GUIDPreservedSymbols(PreservedSymbols.size());
computeGUIDPreservedSymbols(File, PreservedSymbols, TheTriple,
GUIDPreservedSymbols);
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, nullptr, CGFT_ObjectFile,
/* DisableVerify */ true))
report_fatal_error("Failed to setup codegen");
// Run codegen now. resulting binary is in OutputBuffer.
PM.run(TheModule);
}
return std::make_unique<SmallVectorMemoryBuffer>(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 &DefinedGVSummaries, unsigned OptLevel,
bool Freestanding, const TargetMachineBuilder &TMBuilder) {
if (CachePath.empty())
return;
if (!Index.modulePaths().count(ModuleID))
// The module does not have an entry, it can't have a hash at all
return;
if (all_of(Index.getModuleHash(ModuleID),
[](uint32_t V) { return V == 0; }))
// No hash entry, no caching!
return;
llvm::lto::Config Conf;
Conf.OptLevel = OptLevel;
Conf.Options = TMBuilder.Options;
Conf.CPU = TMBuilder.MCpu;
Conf.MAttrs.push_back(TMBuilder.MAttr);
Conf.RelocModel = TMBuilder.RelocModel;
Conf.CGOptLevel = TMBuilder.CGOptLevel;
Conf.Freestanding = Freestanding;
SmallString<40> Key;
computeLTOCacheKey(Key, Conf, Index, ModuleID, ImportList, ExportList,
ResolvedODR, DefinedGVSummaries);
// This choice of file name allows the cache to be pruned (see pruneCache()
// in include/llvm/Support/CachePruning.h).
sys::path::append(EntryPath, CachePath, "llvmcache-" + Key);
}
// 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();
SmallString<64> ResultPath;
Expected<sys::fs::file_t> FDOrErr = sys::fs::openNativeFileForRead(
Twine(EntryPath), sys::fs::OF_UpdateAtime, &ResultPath);
if (!FDOrErr)
return errorToErrorCode(FDOrErr.takeError());
ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = MemoryBuffer::getOpenFile(
*FDOrErr, EntryPath, /*FileSize=*/-1, /*RequiresNullTerminator=*/false);
sys::fs::closeFile(*FDOrErr);
return MBOrErr;
}
// Cache the Produced object file
void write(const MemoryBuffer &OutputBuffer) {
if (EntryPath.empty())
return;
// Write to a temporary to avoid race condition
SmallString<128> TempFilename;
SmallString<128> CachePath(EntryPath);
llvm::sys::path::remove_filename(CachePath);
sys::path::append(TempFilename, CachePath, "Thin-%%%%%%.tmp.o");
if (auto Err = handleErrors(
llvm::writeFileAtomically(TempFilename, EntryPath,
OutputBuffer.getBuffer()),
[](const llvm::AtomicFileWriteError &E) {
std::string ErrorMsgBuffer;
llvm::raw_string_ostream S(ErrorMsgBuffer);
E.log(S);
if (E.Error ==
llvm::atomic_write_error::failed_to_create_uniq_file) {
errs() << "Error: " << ErrorMsgBuffer << "\n";
report_fatal_error("ThinLTO: Can't get a temporary file");
}
})) {
// FIXME
consumeError(std::move(Err));
}
}
};
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) {
// "Benchmark"-like optimization: single-source case
bool SingleModule = (ModuleMap.size() == 1);
// When linking an ELF shared object, dso_local should be dropped. We
// conservatively do this for -fpic.
bool ClearDSOLocalOnDeclarations =
TM.getTargetTriple().isOSBinFormatELF() &&
TM.getRelocationModel() != Reloc::Static &&
TheModule.getPIELevel() == PIELevel::Default;
if (!SingleModule) {
promoteModule(TheModule, Index, ClearDSOLocalOnDeclarations);
// Apply summary-based prevailing-symbol resolution decisions.
thinLTOResolvePrevailingInModule(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,
ClearDSOLocalOnDeclarations);
// Save temps: after cross-module import.
saveTempBitcode(TheModule, SaveTempsDir, count, ".3.imported.bc");
}
optimizeModule(TheModule, TM, OptLevel, Freestanding, &Index);
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);
ProfileSummaryInfo PSI(TheModule);
auto Index = buildModuleSummaryIndex(TheModule, nullptr, &PSI);
WriteBitcodeToFile(TheModule, OS, true, &Index);
}
return std::make_unique<SmallVectorMemoryBuffer>(std::move(OutputBuffer));
}
return codegenModule(TheModule, TM);
}
/// 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) {
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;
};
// TODO Conf.VisibilityScheme can be lto::Config::ELF for ELF.
lto::Config Conf;
thinLTOResolvePrevailingInIndex(Conf, Index, isPrevailing, recordNewLinkage,
GUIDPreservedSymbols);
}
// 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 ||
TheTriple.getArch() == llvm::Triple::aarch64_32)
TMBuilder.MCpu = "cyclone";
}
TMBuilder.TheTriple = std::move(TheTriple);
}
} // end anonymous namespace
void ThinLTOCodeGenerator::addModule(StringRef Identifier, StringRef Data) {
MemoryBufferRef Buffer(Data, Identifier);
auto InputOrError = lto::InputFile::create(Buffer);
if (!InputOrError)
report_fatal_error("ThinLTO cannot create input file: " +
toString(InputOrError.takeError()));
auto TripleStr = (*InputOrError)->getTargetTriple();
Triple TheTriple(TripleStr);
if (Modules.empty())
initTMBuilder(TMBuilder, Triple(TheTriple));
else if (TMBuilder.TheTriple != TheTriple) {
if (!TMBuilder.TheTriple.isCompatibleWith(TheTriple))
report_fatal_error("ThinLTO modules with incompatible triples not "
"supported");
initTMBuilder(TMBuilder, Triple(TMBuilder.TheTriple.merge(TheTriple)));
}
Modules.emplace_back(std::move(*InputOrError));
}
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();
std::unique_ptr<TargetMachine> TM(
TheTarget->createTargetMachine(TheTriple.str(), MCpu, FeatureStr, Options,
RelocModel, None, CGOptLevel));
assert(TM && "Cannot create target machine");
return TM;
}
/**
* Produce the combined summary index from all the bitcode files:
* "thin-link".
*/
std::unique_ptr<ModuleSummaryIndex> ThinLTOCodeGenerator::linkCombinedIndex() {
std::unique_ptr<ModuleSummaryIndex> CombinedIndex =
std::make_unique<ModuleSummaryIndex>(/*HaveGVs=*/false);
uint64_t NextModuleId = 0;
for (auto &Mod : Modules) {
auto &M = Mod->getSingleBitcodeModule();
if (Error Err =
M.readSummary(*CombinedIndex, Mod->getName(), NextModuleId++)) {
// FIXME diagnose
logAllUnhandledErrors(
std::move(Err), errs(),
"error: can't create module summary index for buffer: ");
return nullptr;
}
}
return CombinedIndex;
}
namespace {
struct IsExported {
const StringMap<FunctionImporter::ExportSetTy> &ExportLists;
const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols;
IsExported(const StringMap<FunctionImporter::ExportSetTy> &ExportLists,
const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols)
: ExportLists(ExportLists), GUIDPreservedSymbols(GUIDPreservedSymbols) {}
bool operator()(StringRef ModuleIdentifier, ValueInfo VI) const {
const auto &ExportList = ExportLists.find(ModuleIdentifier);
return (ExportList != ExportLists.end() && ExportList->second.count(VI)) ||
GUIDPreservedSymbols.count(VI.getGUID());
}
};
struct IsPrevailing {
const DenseMap<GlobalValue::GUID, const GlobalValueSummary *> &PrevailingCopy;
IsPrevailing(const DenseMap<GlobalValue::GUID, const GlobalValueSummary *>
&PrevailingCopy)
: PrevailingCopy(PrevailingCopy) {}
bool operator()(GlobalValue::GUID GUID, const GlobalValueSummary *S) const {
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;
};
};
} // namespace
static void computeDeadSymbolsInIndex(
ModuleSummaryIndex &Index,
const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols) {
// We have no symbols resolution available. And can't do any better now in the
// case where the prevailing symbol is in a native object. It can be refined
// with linker information in the future.
auto isPrevailing = [&](GlobalValue::GUID G) {
return PrevailingType::Unknown;
};
computeDeadSymbolsWithConstProp(Index, GUIDPreservedSymbols, isPrevailing,
/* ImportEnabled = */ true);
}
/**
* 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) {
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);
// Convert the preserved symbols set from string to GUID
auto GUIDPreservedSymbols = computeGUIDPreservedSymbols(
File, PreservedSymbols, Triple(TheModule.getTargetTriple()));
// Add used symbol to the preserved symbols.
addUsedSymbolToPreservedGUID(File, GUIDPreservedSymbols);
// Compute "dead" symbols, we don't want to import/export these!
computeDeadSymbolsInIndex(Index, GUIDPreservedSymbols);
// Generate import/export list
StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount);
ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists,
ExportLists);
DenseMap<GlobalValue::GUID, const GlobalValueSummary *> PrevailingCopy;
computePrevailingCopies(Index, PrevailingCopy);
// Resolve prevailing symbols
StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;
resolvePrevailingInIndex(Index, ResolvedODR, GUIDPreservedSymbols,
PrevailingCopy);
thinLTOResolvePrevailingInModule(
TheModule, ModuleToDefinedGVSummaries[ModuleIdentifier]);
// Promote the exported values in the index, so that they are promoted
// in the module.
thinLTOInternalizeAndPromoteInIndex(
Index, IsExported(ExportLists, GUIDPreservedSymbols),
IsPrevailing(PrevailingCopy));
// FIXME Set ClearDSOLocalOnDeclarations.
promoteModule(TheModule, Index, /*ClearDSOLocalOnDeclarations=*/false);
}
/**
* Perform cross-module importing for the module identified by ModuleIdentifier.
*/
void ThinLTOCodeGenerator::crossModuleImport(Module &TheModule,
ModuleSummaryIndex &Index,
const lto::InputFile &File) {
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);
// Convert the preserved symbols set from string to GUID
auto GUIDPreservedSymbols = computeGUIDPreservedSymbols(
File, PreservedSymbols, Triple(TheModule.getTargetTriple()));
addUsedSymbolToPreservedGUID(File, GUIDPreservedSymbols);
// Compute "dead" symbols, we don't want to import/export these!
computeDeadSymbolsInIndex(Index, GUIDPreservedSymbols);
// Generate import/export list
StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount);
ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists,
ExportLists);
auto &ImportList = ImportLists[TheModule.getModuleIdentifier()];
// FIXME Set ClearDSOLocalOnDeclarations.
crossImportIntoModule(TheModule, Index, ModuleMap, ImportList,
/*ClearDSOLocalOnDeclarations=*/false);
}
/**
* Compute the list of summaries needed for importing into module.
*/
void ThinLTOCodeGenerator::gatherImportedSummariesForModule(
Module &TheModule, ModuleSummaryIndex &Index,
std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex,
const lto::InputFile &File) {
auto ModuleCount = Index.modulePaths().size();
auto ModuleIdentifier = TheModule.getModuleIdentifier();
// Collect for each module the list of function it defines (GUID -> Summary).
StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount);
Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
// Convert the preserved symbols set from string to GUID
auto GUIDPreservedSymbols = computeGUIDPreservedSymbols(
File, PreservedSymbols, Triple(TheModule.getTargetTriple()));
addUsedSymbolToPreservedGUID(File, GUIDPreservedSymbols);
// Compute "dead" symbols, we don't want to import/export these!
computeDeadSymbolsInIndex(Index, GUIDPreservedSymbols);
// Generate import/export list
StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount);
ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists,
ExportLists);
llvm::gatherImportedSummariesForModule(
ModuleIdentifier, ModuleToDefinedGVSummaries,
ImportLists[ModuleIdentifier], ModuleToSummariesForIndex);
}
/**
* Emit the list of files needed for importing into module.
*/
void ThinLTOCodeGenerator::emitImports(Module &TheModule, StringRef OutputName,
ModuleSummaryIndex &Index,
const lto::InputFile &File) {
auto ModuleCount = Index.modulePaths().size();
auto ModuleIdentifier = TheModule.getModuleIdentifier();
// Collect for each module the list of function it defines (GUID -> Summary).
StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount);
Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
// Convert the preserved symbols set from string to GUID
auto GUIDPreservedSymbols = computeGUIDPreservedSymbols(
File, PreservedSymbols, Triple(TheModule.getTargetTriple()));
addUsedSymbolToPreservedGUID(File, GUIDPreservedSymbols);
// Compute "dead" symbols, we don't want to import/export these!
computeDeadSymbolsInIndex(Index, GUIDPreservedSymbols);
// Generate import/export list
StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount);
ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists,
ExportLists);
std::map<std::string, GVSummaryMapTy> ModuleToSummariesForIndex;
llvm::gatherImportedSummariesForModule(
ModuleIdentifier, ModuleToDefinedGVSummaries,
ImportLists[ModuleIdentifier], ModuleToSummariesForIndex);
std::error_code EC;
if ((EC = EmitImportsFiles(ModuleIdentifier, OutputName,
ModuleToSummariesForIndex)))
report_fatal_error(Twine("Failed to open ") + OutputName +
" to save imports lists\n");
}
/**
* 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) {
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(File, PreservedSymbols, TMBuilder.TheTriple);
addUsedSymbolToPreservedGUID(File, GUIDPreservedSymbols);
// Collect for each module the list of function it defines (GUID -> Summary).
StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount);
Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
// Compute "dead" symbols, we don't want to import/export these!
computeDeadSymbolsInIndex(Index, GUIDPreservedSymbols);
// 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;
DenseMap<GlobalValue::GUID, const GlobalValueSummary *> PrevailingCopy;
computePrevailingCopies(Index, PrevailingCopy);
// Resolve prevailing symbols
StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;
resolvePrevailingInIndex(Index, ResolvedODR, GUIDPreservedSymbols,
PrevailingCopy);
// Promote the exported values in the index, so that they are promoted
// in the module.
thinLTOInternalizeAndPromoteInIndex(
Index, IsExported(ExportLists, GUIDPreservedSymbols),
IsPrevailing(PrevailingCopy));
// FIXME Set ClearDSOLocalOnDeclarations.
promoteModule(TheModule, Index, /*ClearDSOLocalOnDeclarations=*/false);
// Internalization
thinLTOResolvePrevailingInModule(
TheModule, ModuleToDefinedGVSummaries[ModuleIdentifier]);
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(), OptLevel, Freestanding,
nullptr);
}
/// 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) {
auto ArchName = TMBuilder.TheTriple.getArchName();
SmallString<128> OutputPath(SavedObjectsDirectoryPath);
llvm::sys::path::append(OutputPath,
Twine(count) + "." + ArchName + ".thinlto.o");
OutputPath.c_str(); // Ensure the string is null terminated.
if (sys::fs::exists(OutputPath))
sys::fs::remove(OutputPath);
// We don't return a memory buffer to the linker, just a list of files.
if (!CacheEntryPath.empty()) {
// Cache is enabled, hard-link the entry (or copy if hard-link fails).
auto Err = sys::fs::create_hard_link(CacheEntryPath, OutputPath);
if (!Err)
return std::string(OutputPath.str());
// Hard linking failed, try to copy.
Err = sys::fs::copy_file(CacheEntryPath, OutputPath);
if (!Err)
return std::string(OutputPath.str());
// Copy failed (could be because the CacheEntry was removed from the cache
// in the meantime by another process), fall back and try to write down the
// buffer to the output.
errs() << "remark: can't link or copy from cached entry '" << CacheEntryPath
<< "' to '" << OutputPath << "'\n";
}
// No cache entry, just write out the buffer.
std::error_code Err;
raw_fd_ostream OS(OutputPath, Err, sys::fs::OF_None);
if (Err)
report_fatal_error("Can't open output '" + OutputPath + "'\n");
OS << OutputBuffer.getBuffer();
return std::string(OutputPath.str());
}
// Main entry point for the ThinLTO processing
void ThinLTOCodeGenerator::run() {
// Prepare the resulting object vector
assert(ProducedBinaries.empty() && "The generator should not be reused");
if (SavedObjectsDirectoryPath.empty())
ProducedBinaries.resize(Modules.size());
else {
sys::fs::create_directories(SavedObjectsDirectoryPath);
bool IsDir;
sys::fs::is_directory(SavedObjectsDirectoryPath, IsDir);
if (!IsDir)
report_fatal_error("Unexistent dir: '" + SavedObjectsDirectoryPath + "'");
ProducedBinaryFiles.resize(Modules.size());
}
if (CodeGenOnly) {
// Perform only parallel codegen and return.
ThreadPool Pool;
int count = 0;
for (auto &Mod : Modules) {
Pool.async([&](int count) {
LLVMContext Context;
Context.setDiscardValueNames(LTODiscardValueNames);
// Parse module now
auto TheModule = loadModuleFromInput(Mod.get(), Context, false,
/*IsImporting*/ false);
// CodeGen
auto OutputBuffer = codegenModule(*TheModule, *TMBuilder.create());
if (SavedObjectsDirectoryPath.empty())
ProducedBinaries[count] = std::move(OutputBuffer);
else
ProducedBinaryFiles[count] =
writeGeneratedObject(count, "", *OutputBuffer);
}, 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::OF_None);
if (EC)
report_fatal_error(Twine("Failed to open ") + SaveTempPath +
" to save optimized bitcode\n");
WriteIndexToFile(*Index, OS);
}
// 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);
// Convert the preserved symbols set from string to GUID, this is needed for
// computing the caching hash and the internalization.
DenseSet<GlobalValue::GUID> GUIDPreservedSymbols;
for (const auto &M : Modules)
computeGUIDPreservedSymbols(*M, PreservedSymbols, TMBuilder.TheTriple,
GUIDPreservedSymbols);
// Add used symbol from inputs to the preserved symbols.
for (const auto &M : Modules)
addUsedSymbolToPreservedGUID(*M, GUIDPreservedSymbols);
// Compute "dead" symbols, we don't want to import/export these!
computeDeadSymbolsInIndex(*Index, GUIDPreservedSymbols);
// Synthesize entry counts for functions in the combined index.
computeSyntheticCounts(*Index);
// Currently there is no support for enabling whole program visibility via a
// linker option in the old LTO API, but this call allows it to be specified
// via the internal option. Must be done before WPD below.
updateVCallVisibilityInIndex(*Index,
/* WholeProgramVisibilityEnabledInLTO */ false,
// FIXME: This needs linker information via a
// TBD new interface.
/* DynamicExportSymbols */ {});
// Perform index-based WPD. This will return immediately if there are
// no index entries in the typeIdMetadata map (e.g. if we are instead
// performing IR-based WPD in hybrid regular/thin LTO mode).
std::map<ValueInfo, std::vector<VTableSlotSummary>> LocalWPDTargetsMap;
std::set<GlobalValue::GUID> ExportedGUIDs;
runWholeProgramDevirtOnIndex(*Index, ExportedGUIDs, LocalWPDTargetsMap);
for (auto GUID : ExportedGUIDs)
GUIDPreservedSymbols.insert(GUID);
// 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);
// 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;
DenseMap<GlobalValue::GUID, const GlobalValueSummary *> PrevailingCopy;
computePrevailingCopies(*Index, PrevailingCopy);
// Resolve prevailing symbols, this has to be computed early because it
// impacts the caching.
resolvePrevailingInIndex(*Index, ResolvedODR, GUIDPreservedSymbols,
PrevailingCopy);
// 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.
updateIndexWPDForExports(*Index,
IsExported(ExportLists, GUIDPreservedSymbols),
LocalWPDTargetsMap);
thinLTOInternalizeAndPromoteInIndex(
*Index, IsExported(ExportLists, GUIDPreservedSymbols),
IsPrevailing(PrevailingCopy));
// Make sure that every module has an entry in the ExportLists, ImportList,
// GVSummary and ResolvedODR maps to enable threaded access to these maps
// below.
for (auto &Module : Modules) {
auto ModuleIdentifier = Module->getName();
ExportLists[ModuleIdentifier];
ImportLists[ModuleIdentifier];
ResolvedODR[ModuleIdentifier];
ModuleToDefinedGVSummaries[ModuleIdentifier];
}
std::vector<BitcodeModule *> ModulesVec;
ModulesVec.reserve(Modules.size());
for (auto &Mod : Modules)
ModulesVec.push_back(&Mod->getSingleBitcodeModule());
std::vector<int> ModulesOrdering = lto::generateModulesOrdering(ModulesVec);
// Parallel optimizer + codegen
{
ThreadPool Pool(heavyweight_hardware_concurrency(ThreadCount));
for (auto IndexCount : ModulesOrdering) {
auto &Mod = Modules[IndexCount];
Pool.async([&](int count) {
auto ModuleIdentifier = Mod->getName();
auto &ExportList = ExportLists[ModuleIdentifier];
auto &DefinedGVSummaries = ModuleToDefinedGVSummaries[ModuleIdentifier];
// The module may be cached, this helps handling it.
ModuleCacheEntry CacheEntry(CacheOptions.Path, *Index, ModuleIdentifier,
ImportLists[ModuleIdentifier], ExportList,
ResolvedODR[ModuleIdentifier],
DefinedGVSummaries, OptLevel, Freestanding,
TMBuilder);
auto CacheEntryPath = CacheEntry.getEntryPath();
{
auto ErrOrBuffer = CacheEntry.tryLoadingBuffer();
LLVM_DEBUG(dbgs() << "Cache " << (ErrOrBuffer ? "hit" : "miss")
<< " '" << CacheEntryPath << "' for buffer "
<< count << " " << ModuleIdentifier << "\n");
if (ErrOrBuffer) {
// Cache Hit!
if (SavedObjectsDirectoryPath.empty())
ProducedBinaries[count] = std::move(ErrOrBuffer.get());
else
ProducedBinaryFiles[count] = writeGeneratedObject(
count, CacheEntryPath, *ErrOrBuffer.get());
return;
}
}
LLVMContext Context;
Context.setDiscardValueNames(LTODiscardValueNames);
Context.enableDebugTypeODRUniquing();
auto DiagFileOrErr = lto::setupLLVMOptimizationRemarks(
Context, RemarksFilename, RemarksPasses, RemarksFormat,
RemarksWithHotness, RemarksHotnessThreshold, count);
if (!DiagFileOrErr) {
errs() << "Error: " << toString(DiagFileOrErr.takeError()) << "\n";
report_fatal_error("ThinLTO: Can't get an output file for the "
"remarks");
}
// Parse module now
auto TheModule = loadModuleFromInput(Mod.get(), Context, false,
/*IsImporting*/ 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, Freestanding, OptLevel, count);
// Commit to the cache (if enabled)
CacheEntry.write(*OutputBuffer);
if (SavedObjectsDirectoryPath.empty()) {
// We need to generated a memory buffer for the linker.
if (!CacheEntryPath.empty()) {
// When cache is enabled, reload from the cache if possible.
// Releasing the buffer from the heap and reloading it from the
// cache file with mmap helps us to lower memory pressure.
// The freed memory can be used for the next input file.
// The final binary link will read from the VFS cache (hopefully!)
// or from disk (if the memory pressure was too high).
auto ReloadedBufferOrErr = CacheEntry.tryLoadingBuffer();
if (auto EC = ReloadedBufferOrErr.getError()) {
// On error, keep the preexisting buffer and print a diagnostic.
errs() << "remark: can't reload cached file '" << CacheEntryPath
<< "': " << EC.message() << "\n";
} else {
OutputBuffer = std::move(*ReloadedBufferOrErr);
}
}
ProducedBinaries[count] = std::move(OutputBuffer);
return;
}
ProducedBinaryFiles[count] = writeGeneratedObject(
count, CacheEntryPath, *OutputBuffer);
}, IndexCount);
}
}
pruneCache(CacheOptions.Path, CacheOptions.Policy);
// If statistics were requested, print them out now.
if (llvm::AreStatisticsEnabled())
llvm::PrintStatistics();
reportAndResetTimings();
}
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