blob: dd435173101a5a853935e8b37e9674cf4a2666e9 [file] [log] [blame]
//===- LTO.cpp ------------------------------------------------------------===//
// The LLVM Linker
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
#include "LTO.h"
#include "Config.h"
#include "Error.h"
#include "InputFiles.h"
#include "Symbols.h"
#include "lld/Core/TargetOptionsCommandFlags.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/IR/DiagnosticPrinter.h"
#include "llvm/LTO/Caching.h"
#include "llvm/LTO/Config.h"
#include "llvm/LTO/LTO.h"
#include "llvm/Object/SymbolicFile.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/ELF.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cstddef>
#include <memory>
#include <string>
#include <system_error>
#include <vector>
using namespace llvm;
using namespace llvm::object;
using namespace llvm::ELF;
using namespace lld;
using namespace lld::elf;
// This is for use when debugging LTO.
static void saveBuffer(StringRef Buffer, const Twine &Path) {
std::error_code EC;
raw_fd_ostream OS(Path.str(), EC, sys::fs::OpenFlags::F_None);
if (EC)
error("cannot create " + Path + ": " + EC.message());
OS << Buffer;
static void diagnosticHandler(const DiagnosticInfo &DI) {
SmallString<128> ErrStorage;
raw_svector_ostream OS(ErrStorage);
DiagnosticPrinterRawOStream DP(OS);
static void checkError(Error E) {
handleAllErrors(std::move(E), [&](ErrorInfoBase &EIB) -> Error {
return Error::success();
static std::unique_ptr<lto::LTO> createLTO() {
lto::Config Conf;
// LLD supports the new relocations.
Conf.Options = InitTargetOptionsFromCodeGenFlags();
Conf.Options.RelaxELFRelocations = true;
Conf.RelocModel = Config->Pic ? Reloc::PIC_ : Reloc::Static;
Conf.CodeModel = GetCodeModelFromCMModel();
Conf.DisableVerify = Config->DisableVerify;
Conf.DiagHandler = diagnosticHandler;
Conf.OptLevel = Config->LTOO;
// Set up a custom pipeline if we've been asked to.
Conf.OptPipeline = Config->LTONewPmPasses;
Conf.AAPipeline = Config->LTOAAPipeline;
// Set up optimization remarks if we've been asked to.
Conf.RemarksFilename = Config->OptRemarksFilename;
Conf.RemarksWithHotness = Config->OptRemarksWithHotness;
if (Config->SaveTemps)
checkError(Conf.addSaveTemps(std::string(Config->OutputFile) + ".",
/*UseInputModulePath*/ true));
lto::ThinBackend Backend;
if (Config->ThinLTOJobs != -1u)
Backend = lto::createInProcessThinBackend(Config->ThinLTOJobs);
return llvm::make_unique<lto::LTO>(std::move(Conf), Backend,
BitcodeCompiler::BitcodeCompiler() : LTOObj(createLTO()) {}
BitcodeCompiler::~BitcodeCompiler() = default;
static void undefine(Symbol *S) {
replaceBody<Undefined>(S, S->body()->getName(), /*IsLocal=*/false,
STV_DEFAULT, S->body()->Type, nullptr);
void BitcodeCompiler::add(BitcodeFile &F) {
lto::InputFile &Obj = *F.Obj;
unsigned SymNum = 0;
std::vector<Symbol *> Syms = F.getSymbols();
std::vector<lto::SymbolResolution> Resols(Syms.size());
// Provide a resolution to the LTO API for each symbol.
for (const lto::InputFile::Symbol &ObjSym : Obj.symbols()) {
Symbol *Sym = Syms[SymNum];
lto::SymbolResolution &R = Resols[SymNum];
SymbolBody *B = Sym->body();
// Ideally we shouldn't check for SF_Undefined but currently IRObjectFile
// reports two symbols for module ASM defined. Without this check, lld
// flags an undefined in IR with a definition in ASM as prevailing.
// Once IRObjectFile is fixed to report only one symbol this hack can
// be removed.
R.Prevailing = !ObjSym.isUndefined() && B->File == &F;
R.VisibleToRegularObj =
Sym->IsUsedInRegularObj || (R.Prevailing && Sym->includeInDynsym());
if (R.Prevailing)
checkError(LTOObj->add(std::move(F.Obj), Resols));
// Merge all the bitcode files we have seen, codegen the result
// and return the resulting ObjectFile(s).
std::vector<InputFile *> BitcodeCompiler::compile() {
std::vector<InputFile *> Ret;
unsigned MaxTasks = LTOObj->getMaxTasks();
// The --thinlto-cache-dir option specifies the path to a directory in which
// to cache native object files for ThinLTO incremental builds. If a path was
// specified, configure LTO to use it as the cache directory.
lto::NativeObjectCache Cache;
if (!Config->ThinLTOCacheDir.empty())
Cache = check(
[&](size_t Task, std::unique_ptr<MemoryBuffer> MB) {
Files[Task] = std::move(MB);
[&](size_t Task) {
return llvm::make_unique<lto::NativeObjectStream>(
if (!Config->ThinLTOCacheDir.empty())
pruneCache(Config->ThinLTOCacheDir, Config->ThinLTOCachePolicy);
for (unsigned I = 0; I != MaxTasks; ++I) {
if (Buff[I].empty())
if (Config->SaveTemps) {
if (I == 0)
saveBuffer(Buff[I], Config->OutputFile + ".lto.o");
saveBuffer(Buff[I], Config->OutputFile + Twine(I) + ".lto.o");
InputFile *Obj = createObjectFile(MemoryBufferRef(Buff[I], "lto.tmp"));
for (std::unique_ptr<MemoryBuffer> &File : Files)
if (File)
return Ret;