Files
clang-p2996/llvm/lib/LTO/LTOCodeGenerator.cpp
Noah Shutty d788c44f5c [Support] Improve Caching conformance with Support library behavior
This diff makes several amendments to the local file caching mechanism
which was migrated from ThinLTO to Support in
rGe678c51177102845c93529d457b020f969125373 in response to follow-up
discussion on that commit.

Patch By: noajshu

Differential Revision: https://reviews.llvm.org/D113080
2021-11-04 13:00:44 -07:00

692 lines
22 KiB
C++

//===-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/LLVMRemarkStreamer.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/Mangler.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PassTimingInfo.h"
#include "llvm/IR/Verifier.h"
#include "llvm/InitializePasses.h"
#include "llvm/LTO/LTO.h"
#include "llvm/LTO/LTOBackend.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/MC/TargetRegistry.h"
#include "llvm/Remarks/HotnessThresholdParser.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/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/IPO/WholeProgramDevirt.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<Optional<uint64_t>, false, remarks::HotnessThresholdParser>
RemarksHotnessThreshold(
"lto-pass-remarks-hotness-threshold",
cl::desc("Minimum profile count required for an "
"optimization remark to be output."
" Use 'auto' to apply the threshold from profile summary."),
cl::value_desc("uint or 'auto'"), cl::init(0), 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();
Config.CodeModel = None;
Config.StatsFile = LTOStatsFile;
Config.PreCodeGenPassesHook = [](legacy::PassManager &PM) {
PM.add(createObjCARCContractPass());
};
}
LTOCodeGenerator::~LTOCodeGenerator() {}
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) {
Config.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) {
Config.OptLevel = Level;
Config.PTO.LoopVectorization = Config.OptLevel > 1;
Config.PTO.SLPVectorization = Config.OptLevel > 1;
switch (Config.OptLevel) {
case 0:
Config.CGOptLevel = CodeGenOpt::None;
return;
case 1:
Config.CGOptLevel = CodeGenOpt::Less;
return;
case 2:
Config.CGOptLevel = CodeGenOpt::Default;
return;
case 3:
Config.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;
auto AddStream = [&](size_t Task) -> std::unique_ptr<CachedFileStream> {
StringRef Extension(Config.CGFileType == CGFT_AssemblyFile ? "s" : "o");
int FD;
std::error_code EC =
sys::fs::createTemporaryFile("lto-llvm", Extension, FD, Filename);
if (EC)
emitError(EC.message());
return std::make_unique<CachedFileStream>(
std::make_unique<llvm::raw_fd_ostream>(FD, true));
};
bool genResult = compileOptimized(AddStream, 1);
if (!genResult) {
sys::fs::remove(Twine(Filename));
return false;
}
// 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();
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, /*IsText=*/false, /*RequiresNullTerminator=*/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) {
if (!optimize())
return false;
return compileOptimizedToFile(Name);
}
std::unique_ptr<MemoryBuffer> LTOCodeGenerator::compile() {
if (!optimize())
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(join(Config.MAttrs, ""));
Features.getDefaultSubtargetFeatures(Triple);
FeatureStr = Features.getString();
// Set a default CPU for Darwin triples.
if (Config.CPU.empty() && Triple.isOSDarwin()) {
if (Triple.getArch() == llvm::Triple::x86_64)
Config.CPU = "core2";
else if (Triple.getArch() == llvm::Triple::x86)
Config.CPU = "yonah";
else if (Triple.isArm64e())
Config.CPU = "apple-a12";
else if (Triple.getArch() == llvm::Triple::aarch64 ||
Triple.getArch() == llvm::Triple::aarch64_32)
Config.CPU = "cyclone";
}
TargetMach = createTargetMachine();
assert(TargetMach && "Unable to create target machine");
return true;
}
std::unique_ptr<TargetMachine> LTOCodeGenerator::createTargetMachine() {
assert(MArch && "MArch is not set!");
return std::unique_ptr<TargetMachine>(MArch->createTargetMachine(
TripleStr, Config.CPU, FeatureStr, Config.Options, Config.RelocModel,
None, Config.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);
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() {
if (!this->determineTarget())
return false;
auto DiagFileOrErr = lto::setupLLVMOptimizationRemarks(
Context, RemarksFilename, RemarksPasses, RemarksFormat,
RemarksWithHotness, RemarksHotnessThreshold);
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());
// Currently there is no support for enabling whole program visibility via a
// linker option in the old LTO API, but this call allows it to be specified
// via the internal option. Must be done before WPD invoked via the optimizer
// pipeline run below.
updateVCallVisibilityInModule(*MergedModule,
/* WholeProgramVisibilityEnabledInLTO */ false,
// FIXME: This needs linker information via a
// TBD new interface.
/* DynamicExportSymbols */ {});
// 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();
// Write LTOPostLink flag for passes that require all the modules.
MergedModule->addModuleFlag(Module::Error, "LTOPostLink", 1);
// Add an appropriate DataLayout instance for this module...
MergedModule->setDataLayout(TargetMach->createDataLayout());
ModuleSummaryIndex CombinedIndex(false);
TargetMach = createTargetMachine();
if (!opt(Config, TargetMach.get(), 0, *MergedModule, /*IsThinLTO=*/false,
/*ExportSummary=*/&CombinedIndex, /*ImportSummary=*/nullptr,
/*CmdArgs*/ std::vector<uint8_t>())) {
emitError("LTO middle-end optimizations failed");
return false;
}
return true;
}
bool LTOCodeGenerator::compileOptimized(AddStreamFn AddStream,
unsigned ParallelismLevel) {
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();
// Re-externalize globals that may have been internalized to increase scope
// for splitting
restoreLinkageForExternals();
ModuleSummaryIndex CombinedIndex(false);
Config.CodeGenOnly = true;
Error Err = backend(Config, AddStream, ParallelismLevel, *MergedModule,
CombinedIndex);
assert(!Err && "unexpected code-generation failure");
(void)Err;
// 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<StringRef> Options) {
for (StringRef Option : Options)
CodegenOptions.push_back(Option.str());
}
void LTOCodeGenerator::parseCodeGenDebugOptions() {
if (!CodegenOptions.empty())
llvm::parseCommandLineOptions(CodegenOptions);
}
void llvm::parseCommandLineOptions(std::vector<std::string> &Options) {
if (!Options.empty()) {
// ParseCommandLineOptions() expects argv[0] to be program name.
std::vector<const char *> CodegenArgv(1, "libLLVMLTO");
for (std::string &Arg : Options)
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));
}