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//===-LTOCodeGenerator.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 Link Time Optimization library. This library is
// intended to be used by linker to optimize code at link time.
//
//===----------------------------------------------------------------------===//
#include "llvm/LTO/legacy/LTOCodeGenerator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Bitcode/BitcodeWriter.h"
#include "llvm/CodeGen/ParallelCG.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/Config/config.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/DiagnosticPrinter.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/Mangler.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PassTimingInfo.h"
#include "llvm/IR/RemarkStreamer.h"
#include "llvm/IR/Verifier.h"
#include "llvm/InitializePasses.h"
#include "llvm/LTO/LTO.h"
#include "llvm/LTO/legacy/LTOModule.h"
#include "llvm/LTO/legacy/UpdateCompilerUsed.h"
#include "llvm/Linker/Linker.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/SubtargetFeature.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Signals.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Support/ToolOutputFile.h"
#include "llvm/Support/YAMLTraits.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/IPO/Internalize.h"
#include "llvm/Transforms/IPO/PassManagerBuilder.h"
#include "llvm/Transforms/ObjCARC.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
#include <system_error>
using namespace llvm;
const char* LTOCodeGenerator::getVersionString() {
#ifdef LLVM_VERSION_INFO
return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
#else
return PACKAGE_NAME " version " PACKAGE_VERSION;
#endif
}
namespace llvm {
cl::opt<bool> LTODiscardValueNames(
"lto-discard-value-names",
cl::desc("Strip names from Value during LTO (other than GlobalValue)."),
#ifdef NDEBUG
cl::init(true),
#else
cl::init(false),
#endif
cl::Hidden);
cl::opt<bool> RemarksWithHotness(
"lto-pass-remarks-with-hotness",
cl::desc("With PGO, include profile count in optimization remarks"),
cl::Hidden);
cl::opt<std::string>
RemarksFilename("lto-pass-remarks-output",
cl::desc("Output filename for pass remarks"),
cl::value_desc("filename"));
cl::opt<std::string>
RemarksPasses("lto-pass-remarks-filter",
cl::desc("Only record optimization remarks from passes whose "
"names match the given regular expression"),
cl::value_desc("regex"));
cl::opt<std::string> RemarksFormat(
"lto-pass-remarks-format",
cl::desc("The format used for serializing remarks (default: YAML)"),
cl::value_desc("format"), cl::init("yaml"));
cl::opt<std::string> LTOStatsFile(
"lto-stats-file",
cl::desc("Save statistics to the specified file"),
cl::Hidden);
}
LTOCodeGenerator::LTOCodeGenerator(LLVMContext &Context)
: Context(Context), MergedModule(new Module("ld-temp.o", Context)),
TheLinker(new Linker(*MergedModule)) {
Context.setDiscardValueNames(LTODiscardValueNames);
Context.enableDebugTypeODRUniquing();
initializeLTOPasses();
}
LTOCodeGenerator::~LTOCodeGenerator() {}
// Initialize LTO passes. Please keep this function in sync with
// PassManagerBuilder::populateLTOPassManager(), and make sure all LTO
// passes are initialized.
void LTOCodeGenerator::initializeLTOPasses() {
PassRegistry &R = *PassRegistry::getPassRegistry();
initializeInternalizeLegacyPassPass(R);
initializeIPSCCPLegacyPassPass(R);
initializeGlobalOptLegacyPassPass(R);
initializeConstantMergeLegacyPassPass(R);
initializeDAHPass(R);
initializeInstructionCombiningPassPass(R);
initializeSimpleInlinerPass(R);
initializePruneEHPass(R);
initializeGlobalDCELegacyPassPass(R);
initializeArgPromotionPass(R);
initializeJumpThreadingPass(R);
initializeSROALegacyPassPass(R);
initializeAttributorLegacyPassPass(R);
initializePostOrderFunctionAttrsLegacyPassPass(R);
initializeReversePostOrderFunctionAttrsLegacyPassPass(R);
initializeGlobalsAAWrapperPassPass(R);
initializeLegacyLICMPassPass(R);
initializeMergedLoadStoreMotionLegacyPassPass(R);
initializeGVNLegacyPassPass(R);
initializeMemCpyOptLegacyPassPass(R);
initializeDCELegacyPassPass(R);
initializeCFGSimplifyPassPass(R);
}
void LTOCodeGenerator::setAsmUndefinedRefs(LTOModule *Mod) {
const std::vector<StringRef> &undefs = Mod->getAsmUndefinedRefs();
for (int i = 0, e = undefs.size(); i != e; ++i)
AsmUndefinedRefs.insert(undefs[i]);
}
bool LTOCodeGenerator::addModule(LTOModule *Mod) {
assert(&Mod->getModule().getContext() == &Context &&
"Expected module in same context");
bool ret = TheLinker->linkInModule(Mod->takeModule());
setAsmUndefinedRefs(Mod);
// We've just changed the input, so let's make sure we verify it.
HasVerifiedInput = false;
return !ret;
}
void LTOCodeGenerator::setModule(std::unique_ptr<LTOModule> Mod) {
assert(&Mod->getModule().getContext() == &Context &&
"Expected module in same context");
AsmUndefinedRefs.clear();
MergedModule = Mod->takeModule();
TheLinker = std::make_unique<Linker>(*MergedModule);
setAsmUndefinedRefs(&*Mod);
// We've just changed the input, so let's make sure we verify it.
HasVerifiedInput = false;
}
void LTOCodeGenerator::setTargetOptions(const TargetOptions &Options) {
this->Options = Options;
}
void LTOCodeGenerator::setDebugInfo(lto_debug_model Debug) {
switch (Debug) {
case LTO_DEBUG_MODEL_NONE:
EmitDwarfDebugInfo = false;
return;
case LTO_DEBUG_MODEL_DWARF:
EmitDwarfDebugInfo = true;
return;
}
llvm_unreachable("Unknown debug format!");
}
void LTOCodeGenerator::setOptLevel(unsigned Level) {
OptLevel = Level;
switch (OptLevel) {
case 0:
CGOptLevel = CodeGenOpt::None;
return;
case 1:
CGOptLevel = CodeGenOpt::Less;
return;
case 2:
CGOptLevel = CodeGenOpt::Default;
return;
case 3:
CGOptLevel = CodeGenOpt::Aggressive;
return;
}
llvm_unreachable("Unknown optimization level!");
}
bool LTOCodeGenerator::writeMergedModules(StringRef Path) {
if (!determineTarget())
return false;
// We always run the verifier once on the merged module.
verifyMergedModuleOnce();
// mark which symbols can not be internalized
applyScopeRestrictions();
// create output file
std::error_code EC;
ToolOutputFile Out(Path, EC, sys::fs::OF_None);
if (EC) {
std::string ErrMsg = "could not open bitcode file for writing: ";
ErrMsg += Path.str() + ": " + EC.message();
emitError(ErrMsg);
return false;
}
// write bitcode to it
WriteBitcodeToFile(*MergedModule, Out.os(), ShouldEmbedUselists);
Out.os().close();
if (Out.os().has_error()) {
std::string ErrMsg = "could not write bitcode file: ";
ErrMsg += Path.str() + ": " + Out.os().error().message();
emitError(ErrMsg);
Out.os().clear_error();
return false;
}
Out.keep();
return true;
}
bool LTOCodeGenerator::compileOptimizedToFile(const char **Name) {
// make unique temp output file to put generated code
SmallString<128> Filename;
int FD;
StringRef Extension
(FileType == CGFT_AssemblyFile ? "s" : "o");
std::error_code EC =
sys::fs::createTemporaryFile("lto-llvm", Extension, FD, Filename);
if (EC) {
emitError(EC.message());
return false;
}
// generate object file
ToolOutputFile objFile(Filename, FD);
bool genResult = compileOptimized(&objFile.os());
objFile.os().close();
if (objFile.os().has_error()) {
emitError((Twine("could not write object file: ") + Filename + ": " +
objFile.os().error().message())
.str());
objFile.os().clear_error();
sys::fs::remove(Twine(Filename));
return false;
}
objFile.keep();
if (!genResult) {
sys::fs::remove(Twine(Filename));
return false;
}
NativeObjectPath = Filename.c_str();
*Name = NativeObjectPath.c_str();
return true;
}
std::unique_ptr<MemoryBuffer>
LTOCodeGenerator::compileOptimized() {
const char *name;
if (!compileOptimizedToFile(&name))
return nullptr;
// read .o file into memory buffer
ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
MemoryBuffer::getFile(name, -1, false);
if (std::error_code EC = BufferOrErr.getError()) {
emitError(EC.message());
sys::fs::remove(NativeObjectPath);
return nullptr;
}
// remove temp files
sys::fs::remove(NativeObjectPath);
return std::move(*BufferOrErr);
}
bool LTOCodeGenerator::compile_to_file(const char **Name, bool DisableVerify,
bool DisableInline,
bool DisableGVNLoadPRE,
bool DisableVectorization) {
if (!optimize(DisableVerify, DisableInline, DisableGVNLoadPRE,
DisableVectorization))
return false;
return compileOptimizedToFile(Name);
}
std::unique_ptr<MemoryBuffer>
LTOCodeGenerator::compile(bool DisableVerify, bool DisableInline,
bool DisableGVNLoadPRE, bool DisableVectorization) {
if (!optimize(DisableVerify, DisableInline, DisableGVNLoadPRE,
DisableVectorization))
return nullptr;
return compileOptimized();
}
bool LTOCodeGenerator::determineTarget() {
if (TargetMach)
return true;
TripleStr = MergedModule->getTargetTriple();
if (TripleStr.empty()) {
TripleStr = sys::getDefaultTargetTriple();
MergedModule->setTargetTriple(TripleStr);
}
llvm::Triple Triple(TripleStr);
// create target machine from info for merged modules
std::string ErrMsg;
MArch = TargetRegistry::lookupTarget(TripleStr, ErrMsg);
if (!MArch) {
emitError(ErrMsg);
return false;
}
// Construct LTOModule, hand over ownership of module and target. Use MAttr as
// the default set of features.
SubtargetFeatures Features(MAttr);
Features.getDefaultSubtargetFeatures(Triple);
FeatureStr = Features.getString();
// Set a default CPU for Darwin triples.
if (MCpu.empty() && Triple.isOSDarwin()) {
if (Triple.getArch() == llvm::Triple::x86_64)
MCpu = "core2";
else if (Triple.getArch() == llvm::Triple::x86)
MCpu = "yonah";
else if (Triple.getArch() == llvm::Triple::aarch64 ||
Triple.getArch() == llvm::Triple::aarch64_32)
MCpu = "cyclone";
}
TargetMach = createTargetMachine();
return true;
}
std::unique_ptr<TargetMachine> LTOCodeGenerator::createTargetMachine() {
return std::unique_ptr<TargetMachine>(MArch->createTargetMachine(
TripleStr, MCpu, FeatureStr, Options, RelocModel, None, CGOptLevel));
}
// If a linkonce global is present in the MustPreserveSymbols, we need to make
// sure we honor this. To force the compiler to not drop it, we add it to the
// "llvm.compiler.used" global.
void LTOCodeGenerator::preserveDiscardableGVs(
Module &TheModule,
llvm::function_ref<bool(const GlobalValue &)> mustPreserveGV) {
std::vector<GlobalValue *> Used;
auto mayPreserveGlobal = [&](GlobalValue &GV) {
if (!GV.isDiscardableIfUnused() || GV.isDeclaration() ||
!mustPreserveGV(GV))
return;
if (GV.hasAvailableExternallyLinkage())
return emitWarning(
(Twine("Linker asked to preserve available_externally global: '") +
GV.getName() + "'").str());
if (GV.hasInternalLinkage())
return emitWarning((Twine("Linker asked to preserve internal global: '") +
GV.getName() + "'").str());
Used.push_back(&GV);
};
for (auto &GV : TheModule)
mayPreserveGlobal(GV);
for (auto &GV : TheModule.globals())
mayPreserveGlobal(GV);
for (auto &GV : TheModule.aliases())
mayPreserveGlobal(GV);
if (Used.empty())
return;
appendToCompilerUsed(TheModule, Used);
}
void LTOCodeGenerator::applyScopeRestrictions() {
if (ScopeRestrictionsDone)
return;
// Declare a callback for the internalize pass that will ask for every
// candidate GlobalValue if it can be internalized or not.
Mangler Mang;
SmallString<64> MangledName;
auto mustPreserveGV = [&](const GlobalValue &GV) -> bool {
// Unnamed globals can't be mangled, but they can't be preserved either.
if (!GV.hasName())
return false;
// Need to mangle the GV as the "MustPreserveSymbols" StringSet is filled
// with the linker supplied name, which on Darwin includes a leading
// underscore.
MangledName.clear();
MangledName.reserve(GV.getName().size() + 1);
Mang.getNameWithPrefix(MangledName, &GV, /*CannotUsePrivateLabel=*/false);
return MustPreserveSymbols.count(MangledName);
};
// Preserve linkonce value on linker request
preserveDiscardableGVs(*MergedModule, mustPreserveGV);
if (!ShouldInternalize)
return;
if (ShouldRestoreGlobalsLinkage) {
// Record the linkage type of non-local symbols so they can be restored
// prior
// to module splitting.
auto RecordLinkage = [&](const GlobalValue &GV) {
if (!GV.hasAvailableExternallyLinkage() && !GV.hasLocalLinkage() &&
GV.hasName())
ExternalSymbols.insert(std::make_pair(GV.getName(), GV.getLinkage()));
};
for (auto &GV : *MergedModule)
RecordLinkage(GV);
for (auto &GV : MergedModule->globals())
RecordLinkage(GV);
for (auto &GV : MergedModule->aliases())
RecordLinkage(GV);
}
// Update the llvm.compiler_used globals to force preserving libcalls and
// symbols referenced from asm
updateCompilerUsed(*MergedModule, *TargetMach, AsmUndefinedRefs);
internalizeModule(*MergedModule, mustPreserveGV);
MergedModule->addModuleFlag(Module::Error, "LTOPostLink", 1);
ScopeRestrictionsDone = true;
}
/// Restore original linkage for symbols that may have been internalized
void LTOCodeGenerator::restoreLinkageForExternals() {
if (!ShouldInternalize || !ShouldRestoreGlobalsLinkage)
return;
assert(ScopeRestrictionsDone &&
"Cannot externalize without internalization!");
if (ExternalSymbols.empty())
return;
auto externalize = [this](GlobalValue &GV) {
if (!GV.hasLocalLinkage() || !GV.hasName())
return;
auto I = ExternalSymbols.find(GV.getName());
if (I == ExternalSymbols.end())
return;
GV.setLinkage(I->second);
};
llvm::for_each(MergedModule->functions(), externalize);
llvm::for_each(MergedModule->globals(), externalize);
llvm::for_each(MergedModule->aliases(), externalize);
}
void LTOCodeGenerator::verifyMergedModuleOnce() {
// Only run on the first call.
if (HasVerifiedInput)
return;
HasVerifiedInput = true;
bool BrokenDebugInfo = false;
if (verifyModule(*MergedModule, &dbgs(), &BrokenDebugInfo))
report_fatal_error("Broken module found, compilation aborted!");
if (BrokenDebugInfo) {
emitWarning("Invalid debug info found, debug info will be stripped");
StripDebugInfo(*MergedModule);
}
}
void LTOCodeGenerator::finishOptimizationRemarks() {
if (DiagnosticOutputFile) {
DiagnosticOutputFile->keep();
// FIXME: LTOCodeGenerator dtor is not invoked on Darwin
DiagnosticOutputFile->os().flush();
}
}
/// Optimize merged modules using various IPO passes
bool LTOCodeGenerator::optimize(bool DisableVerify, bool DisableInline,
bool DisableGVNLoadPRE,
bool DisableVectorization) {
if (!this->determineTarget())
return false;
auto DiagFileOrErr =
lto::setupOptimizationRemarks(Context, RemarksFilename, RemarksPasses,
RemarksFormat, RemarksWithHotness);
if (!DiagFileOrErr) {
errs() << "Error: " << toString(DiagFileOrErr.takeError()) << "\n";
report_fatal_error("Can't get an output file for the remarks");
}
DiagnosticOutputFile = std::move(*DiagFileOrErr);
// Setup output file to emit statistics.
auto StatsFileOrErr = lto::setupStatsFile(LTOStatsFile);
if (!StatsFileOrErr) {
errs() << "Error: " << toString(StatsFileOrErr.takeError()) << "\n";
report_fatal_error("Can't get an output file for the statistics");
}
StatsFile = std::move(StatsFileOrErr.get());
// We always run the verifier once on the merged module, the `DisableVerify`
// parameter only applies to subsequent verify.
verifyMergedModuleOnce();
// Mark which symbols can not be internalized
this->applyScopeRestrictions();
// Instantiate the pass manager to organize the passes.
legacy::PassManager passes;
// Add an appropriate DataLayout instance for this module...
MergedModule->setDataLayout(TargetMach->createDataLayout());
passes.add(
createTargetTransformInfoWrapperPass(TargetMach->getTargetIRAnalysis()));
Triple TargetTriple(TargetMach->getTargetTriple());
PassManagerBuilder PMB;
PMB.DisableGVNLoadPRE = DisableGVNLoadPRE;
PMB.LoopVectorize = !DisableVectorization;
PMB.SLPVectorize = !DisableVectorization;
if (!DisableInline)
PMB.Inliner = createFunctionInliningPass();
PMB.LibraryInfo = new TargetLibraryInfoImpl(TargetTriple);
if (Freestanding)
PMB.LibraryInfo->disableAllFunctions();
PMB.OptLevel = OptLevel;
PMB.VerifyInput = !DisableVerify;
PMB.VerifyOutput = !DisableVerify;
PMB.populateLTOPassManager(passes);
// Run our queue of passes all at once now, efficiently.
passes.run(*MergedModule);
return true;
}
bool LTOCodeGenerator::compileOptimized(ArrayRef<raw_pwrite_stream *> Out) {
if (!this->determineTarget())
return false;
// We always run the verifier once on the merged module. If it has already
// been called in optimize(), this call will return early.
verifyMergedModuleOnce();
legacy::PassManager preCodeGenPasses;
// If the bitcode files contain ARC code and were compiled with optimization,
// the ObjCARCContractPass must be run, so do it unconditionally here.
preCodeGenPasses.add(createObjCARCContractPass());
preCodeGenPasses.run(*MergedModule);
// Re-externalize globals that may have been internalized to increase scope
// for splitting
restoreLinkageForExternals();
// Do code generation. We need to preserve the module in case the client calls
// writeMergedModules() after compilation, but we only need to allow this at
// parallelism level 1. This is achieved by having splitCodeGen return the
// original module at parallelism level 1 which we then assign back to
// MergedModule.
MergedModule = splitCodeGen(std::move(MergedModule), Out, {},
[&]() { return createTargetMachine(); }, FileType,
ShouldRestoreGlobalsLinkage);
// If statistics were requested, save them to the specified file or
// print them out after codegen.
if (StatsFile)
PrintStatisticsJSON(StatsFile->os());
else if (AreStatisticsEnabled())
PrintStatistics();
reportAndResetTimings();
finishOptimizationRemarks();
return true;
}
void LTOCodeGenerator::setCodeGenDebugOptions(ArrayRef<const char *> Options) {
for (StringRef Option : Options)
CodegenOptions.push_back(Option);
}
void LTOCodeGenerator::parseCodeGenDebugOptions() {
// if options were requested, set them
if (!CodegenOptions.empty()) {
// ParseCommandLineOptions() expects argv[0] to be program name.
std::vector<const char *> CodegenArgv(1, "libLLVMLTO");
for (std::string &Arg : CodegenOptions)
CodegenArgv.push_back(Arg.c_str());
cl::ParseCommandLineOptions(CodegenArgv.size(), CodegenArgv.data());
}
}
void LTOCodeGenerator::DiagnosticHandler(const DiagnosticInfo &DI) {
// Map the LLVM internal diagnostic severity to the LTO diagnostic severity.
lto_codegen_diagnostic_severity_t Severity;
switch (DI.getSeverity()) {
case DS_Error:
Severity = LTO_DS_ERROR;
break;
case DS_Warning:
Severity = LTO_DS_WARNING;
break;
case DS_Remark:
Severity = LTO_DS_REMARK;
break;
case DS_Note:
Severity = LTO_DS_NOTE;
break;
}
// Create the string that will be reported to the external diagnostic handler.
std::string MsgStorage;
raw_string_ostream Stream(MsgStorage);
DiagnosticPrinterRawOStream DP(Stream);
DI.print(DP);
Stream.flush();
// If this method has been called it means someone has set up an external
// diagnostic handler. Assert on that.
assert(DiagHandler && "Invalid diagnostic handler");
(*DiagHandler)(Severity, MsgStorage.c_str(), DiagContext);
}
namespace {
struct LTODiagnosticHandler : public DiagnosticHandler {
LTOCodeGenerator *CodeGenerator;
LTODiagnosticHandler(LTOCodeGenerator *CodeGenPtr)
: CodeGenerator(CodeGenPtr) {}
bool handleDiagnostics(const DiagnosticInfo &DI) override {
CodeGenerator->DiagnosticHandler(DI);
return true;
}
};
}
void
LTOCodeGenerator::setDiagnosticHandler(lto_diagnostic_handler_t DiagHandler,
void *Ctxt) {
this->DiagHandler = DiagHandler;
this->DiagContext = Ctxt;
if (!DiagHandler)
return Context.setDiagnosticHandler(nullptr);
// Register the LTOCodeGenerator stub in the LLVMContext to forward the
// diagnostic to the external DiagHandler.
Context.setDiagnosticHandler(std::make_unique<LTODiagnosticHandler>(this),
true);
}
namespace {
class LTODiagnosticInfo : public DiagnosticInfo {
const Twine &Msg;
public:
LTODiagnosticInfo(const Twine &DiagMsg, DiagnosticSeverity Severity=DS_Error)
: DiagnosticInfo(DK_Linker, Severity), Msg(DiagMsg) {}
void print(DiagnosticPrinter &DP) const override { DP << Msg; }
};
}
void LTOCodeGenerator::emitError(const std::string &ErrMsg) {
if (DiagHandler)
(*DiagHandler)(LTO_DS_ERROR, ErrMsg.c_str(), DiagContext);
else
Context.diagnose(LTODiagnosticInfo(ErrMsg));
}
void LTOCodeGenerator::emitWarning(const std::string &ErrMsg) {
if (DiagHandler)
(*DiagHandler)(LTO_DS_WARNING, ErrMsg.c_str(), DiagContext);
else
Context.diagnose(LTODiagnosticInfo(ErrMsg, DS_Warning));
}