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llvm-project/llvm/lib/LTO/ThinLTOCodeGenerator.cpp

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//===-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"
#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/LegacyPassManager.h"
#include "llvm/IR/Mangler.h"
#include "llvm/IR/Verifier.h"
#include "llvm/IRReader/IRReader.h"
#include "llvm/LTO/LTO.h"
#include "llvm/MC/SubtargetFeature.h"
#include "llvm/Object/IRObjectFile.h"
#include "llvm/Support/CachePruning.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Error.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/Support/VCSRevision.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;
extern cl::opt<std::string> LTORemarksFilename;
extern cl::opt<bool> LTOPassRemarksWithHotness;
}
namespace {
static cl::opt<int>
ThreadCount("threads", cl::init(llvm::heavyweight_hardware_concurrency()));
// 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::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.SummaryList))
PrevailingCopy[I.first] =
getFirstDefinitionForLinker(I.second.SummaryList);
}
}
static StringMap<MemoryBufferRef>
generateModuleMap(const std::vector<ThinLTOBuffer> &Modules) {
StringMap<MemoryBufferRef> ModuleMap;
for (auto &ModuleBuffer : Modules) {
assert(ModuleMap.find(ModuleBuffer.getBufferIdentifier()) ==
ModuleMap.end() &&
"Expect unique Buffer Identifier");
ModuleMap[ModuleBuffer.getBufferIdentifier()] = ModuleBuffer.getMemBuffer();
}
return ModuleMap;
}
static void promoteModule(Module &TheModule, const ModuleSummaryIndex &Index) {
if (renameModuleForThinLTO(TheModule, Index))
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>
loadModuleFromBuffer(const MemoryBufferRef &Buffer, LLVMContext &Context,
bool Lazy, bool IsImporting) {
SMDiagnostic Err;
Expected<std::unique_ptr<Module>> ModuleOrErr =
Lazy
? getLazyBitcodeModule(Buffer, Context,
/* ShouldLazyLoadMetadata */ true, IsImporting)
: parseBitcodeFile(Buffer, Context);
if (!ModuleOrErr) {
handleAllErrors(ModuleOrErr.takeError(), [&](ErrorInfoBase &EIB) {
SMDiagnostic Err = SMDiagnostic(Buffer.getBufferIdentifier(),
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.get());
}
static void
crossImportIntoModule(Module &TheModule, const ModuleSummaryIndex &Index,
StringMap<MemoryBufferRef> &ModuleMap,
const FunctionImporter::ImportMapTy &ImportList) {
auto Loader = [&](StringRef Identifier) {
return loadModuleFromBuffer(ModuleMap[Identifier], TheModule.getContext(),
/*Lazy=*/true, /*IsImporting*/ true);
};
FunctionImporter Importer(Index, Loader);
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) {
// 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;
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, nullptr, 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<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 &DefinedFunctions,
const DenseSet<GlobalValue::GUID> &PreservedSymbols, 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;
// 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.
// Include the hash for the current module
auto ModHash = Index.getModuleHash(ModuleID);
if (all_of(ModHash, [](uint32_t V) { return V == 0; }))
// No hash entry, no caching!
return;
SHA1 Hasher;
// Include the parts of the LTO configuration that affect code generation.
auto AddString = [&](StringRef Str) {
Hasher.update(Str);
Hasher.update(ArrayRef<uint8_t>{0});
};
auto AddUnsigned = [&](unsigned I) {
uint8_t Data[4];
Data[0] = I;
Data[1] = I >> 8;
Data[2] = I >> 16;
Data[3] = I >> 24;
Hasher.update(ArrayRef<uint8_t>{Data, 4});
};
// Start with the compiler revision
Hasher.update(LLVM_VERSION_STRING);
#ifdef LLVM_REVISION
Hasher.update(LLVM_REVISION);
#endif
// Hash the optimization level and the target machine settings.
AddString(TMBuilder.MCpu);
// FIXME: Hash more of Options. For now all clients initialize Options from
// command-line flags (which is unsupported in production), but may set
// RelaxELFRelocations. The clang driver can also pass FunctionSections,
// DataSections and DebuggerTuning via command line flags.
AddUnsigned(TMBuilder.Options.RelaxELFRelocations);
AddUnsigned(TMBuilder.Options.FunctionSections);
AddUnsigned(TMBuilder.Options.DataSections);
AddUnsigned((unsigned)TMBuilder.Options.DebuggerTuning);
AddString(TMBuilder.MAttr);
if (TMBuilder.RelocModel)
AddUnsigned(*TMBuilder.RelocModel);
AddUnsigned(TMBuilder.CGOptLevel);
AddUnsigned(OptLevel);
AddUnsigned(Freestanding);
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)));
}
// 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-" + 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
void write(const MemoryBuffer &OutputBuffer) {
if (EntryPath.empty())
return;
// Write to a temporary to avoid race condition
SmallString<128> TempFilename;
SmallString<128> CachePath(EntryPath);
int TempFD;
llvm::sys::path::remove_filename(CachePath);
sys::path::append(TempFilename, CachePath, "Thin-%%%%%%.tmp.o");
std::error_code EC =
sys::fs::createUniqueFile(TempFilename, 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 temp file to final destination; rename is atomic
EC = sys::fs::rename(TempFilename, EntryPath);
if (EC)
sys::fs::remove(TempFilename);
}
};
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,
bool Freestanding, unsigned OptLevel, 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, OptLevel, Freestanding);
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 make_unique<SmallVectorMemoryBuffer>(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) {
ThinLTOBuffer Buffer(Data, Identifier);
LLVMContext Context;
StringRef TripleStr;
ErrorOr<std::string> TripleOrErr = expectedToErrorOrAndEmitErrors(
Context, getBitcodeTargetTriple(Buffer.getMemBuffer()));
if (TripleOrErr)
TripleStr = *TripleOrErr;
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.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, None, CGOptLevel));
}
/**
* Produce the combined summary index from all the bitcode files:
* "thin-link".
*/
std::unique_ptr<ModuleSummaryIndex> ThinLTOCodeGenerator::linkCombinedIndex() {
std::unique_ptr<ModuleSummaryIndex> CombinedIndex =
llvm::make_unique<ModuleSummaryIndex>(/*HaveGVs=*/false);
uint64_t NextModuleId = 0;
for (auto &ModuleBuffer : Modules) {
if (Error Err = readModuleSummaryIndex(ModuleBuffer.getMemBuffer(),
*CombinedIndex, NextModuleId++)) {
// FIXME diagnose
logAllUnhandledErrors(
std::move(Err), errs(),
"error: can't create module summary index for buffer: ");
return nullptr;
}
}
return CombinedIndex;
}
static void internalizeAndPromoteInIndex(
const StringMap<FunctionImporter::ExportSetTy> &ExportLists,
const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols,
ModuleSummaryIndex &Index) {
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);
}
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;
};
computeDeadSymbols(Index, GUIDPreservedSymbols, isPrevailing);
}
/**
* 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);
// Convert the preserved symbols set from string to GUID
auto GUIDPreservedSymbols = computeGUIDPreservedSymbols(
PreservedSymbols, Triple(TheModule.getTargetTriple()));
// 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);
// Resolve LinkOnce/Weak symbols.
StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;
resolveWeakForLinkerInIndex(Index, ResolvedODR);
thinLTOResolveWeakForLinkerModule(
TheModule, ModuleToDefinedGVSummaries[ModuleIdentifier]);
// Promote the exported values in the index, so that they are promoted
// in the module.
internalizeAndPromoteInIndex(ExportLists, GUIDPreservedSymbols, Index);
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);
// Convert the preserved symbols set from string to GUID
auto GUIDPreservedSymbols = computeGUIDPreservedSymbols(
PreservedSymbols, Triple(TheModule.getTargetTriple()));
// 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()];
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[ModulePath],
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[ModulePath])))
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);
// 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;
// Internalization
internalizeAndPromoteInIndex(ExportLists, GUIDPreservedSymbols, Index);
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);
}
/**
* Perform ThinLTO CodeGen.
*/
std::unique_ptr<MemoryBuffer> ThinLTOCodeGenerator::codegen(Module &TheModule) {
initTMBuilder(TMBuilder, Triple(TheModule.getTargetTriple()));
return codegenModule(TheModule, *TMBuilder.create());
}
/// 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.
static std::string writeGeneratedObject(int count, StringRef CacheEntryPath,
StringRef SavedObjectsDirectoryPath,
const MemoryBuffer &OutputBuffer) {
SmallString<128> OutputPath(SavedObjectsDirectoryPath);
llvm::sys::path::append(OutputPath, Twine(count) + ".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 OutputPath.str();
// Hard linking failed, try to copy.
Err = sys::fs::copy_file(CacheEntryPath, OutputPath);
if (!Err)
return 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() << "error: 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::F_None);
if (Err)
report_fatal_error("Can't open output '" + OutputPath + "'\n");
OS << OutputBuffer.getBuffer();
return 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 &ModuleBuffer : Modules) {
Pool.async([&](int count) {
LLVMContext Context;
Context.setDiscardValueNames(LTODiscardValueNames);
// Parse module now
auto TheModule =
loadModuleFromBuffer(ModuleBuffer.getMemBuffer(), Context, false,
/*IsImporting*/ false);
// CodeGen
auto OutputBuffer = codegen(*TheModule);
if (SavedObjectsDirectoryPath.empty())
ProducedBinaries[count] = std::move(OutputBuffer);
else
ProducedBinaryFiles[count] = writeGeneratedObject(
count, "", SavedObjectsDirectoryPath, *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::F_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.
auto GUIDPreservedSymbols =
computeGUIDPreservedSymbols(PreservedSymbols, TMBuilder.TheTriple);
// Compute "dead" symbols, we don't want to import/export these!
computeDeadSymbolsInIndex(*Index, GUIDPreservedSymbols);
// 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;
// Resolve LinkOnce/Weak symbols, this has to be computed early because it
// impacts the caching.
resolveWeakForLinkerInIndex(*Index, ResolvedODR);
// 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.
internalizeAndPromoteInIndex(ExportLists, GUIDPreservedSymbols, *Index);
// 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);
llvm::sort(ModulesOrdering.begin(), ModulesOrdering.end(),
[&](int LeftIndex, int RightIndex) {
auto LSize = Modules[LeftIndex].getBuffer().size();
auto RSize = Modules[RightIndex].getBuffer().size();
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,
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, SavedObjectsDirectoryPath,
*ErrOrBuffer.get());
return;
}
}
LLVMContext Context;
Context.setDiscardValueNames(LTODiscardValueNames);
Context.enableDebugTypeODRUniquing();
auto DiagFileOrErr = lto::setupOptimizationRemarks(
Context, LTORemarksFilename, LTOPassRemarksWithHotness, 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 =
loadModuleFromBuffer(ModuleBuffer.getMemBuffer(), 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() << "error: 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, SavedObjectsDirectoryPath, *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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