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llvm-mirror/lib/LTO/ThinLTOCodeGenerator.cpp
Teresa Johnson 525ee88977 [ThinLTO] Import local variables from the same module as caller 
Summary:
We can sometimes end up with multiple copies of a local variable that
have the same GUID in the index. This happens when there are local
variables with the same name that are in different source files having the
same name/path at compile time (but compiled into different bitcode objects).

In this case make sure we import the copy in the caller's module.
This enables importing both of the variables having the same GUID
(but which will have different promoted names since the module paths,
and therefore the module hashes, will be distinct).

Importing the wrong copy is particularly problematic for read only
variables, since we must import them as a local copy whenever
referenced. Otherwise we get undefs at link time.

Note that the llvm-lto.cpp and ThinLTOCodeGenerator changes are needed
for testing the distributed index case via clang, which will be sent as
a separate clang-side patch shortly. We were previously not doing the
dead code/read only computation before computing imports when testing
distributed index generation (like it was for testing importing and
other ThinLTO mechanisms alone).

Reviewers: evgeny777

Subscribers: mehdi_amini, inglorion, eraman, steven_wu, dexonsmith, dang, llvm-commits

Differential Revision: https://reviews.llvm.org/D55047

llvm-svn: 347886
2018-11-29 17:02:42 +00:00

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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/PassTimingInfo.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>
#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> 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 &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();
int FD;
SmallString<64> ResultPath;
std::error_code EC = sys::fs::openFileForRead(
Twine(EntryPath), FD, sys::fs::OF_UpdateAtime, &ResultPath);
if (EC)
return EC;
ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr =
MemoryBuffer::getOpenFile(FD, EntryPath,
/*FileSize*/ -1,
/*RequiresNullTerminator*/ false);
close(FD);
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);
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 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);
// 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 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) {
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;
};
thinLTOResolvePrevailingInIndex(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;
};
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) {
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 prevailing symbols
StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;
resolvePrevailingInIndex(Index, ResolvedODR);
thinLTOResolvePrevailingInModule(
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(
Module &TheModule, ModuleSummaryIndex &Index,
std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex) {
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(
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);
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) {
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(
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);
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. 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);
}
/// 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 = codegenModule(*TheModule, *TMBuilder.create());
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 prevailing symbols, this has to be computed early because it
// impacts the caching.
resolvePrevailingInIndex(*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, ImportList,
// GVSummary and ResolvedODR maps to enable threaded access to these maps
// below.
for (auto &Module : Modules) {
auto ModuleIdentifier = Module.getBufferIdentifier();
ExportLists[ModuleIdentifier];
ImportLists[ModuleIdentifier];
ResolvedODR[ModuleIdentifier];
ModuleToDefinedGVSummaries[ModuleIdentifier];
}
// 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, [&](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 &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, 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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