blob: 93f7ba3f9e4c760a112bb883019ba307e7ae37d1 [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 "InputFiles.h"
#include "Symbols.h"
#include "lld/Common/ErrorHandler.h"
#include "lld/Common/Strings.h"
#include "lld/Common/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/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 lld;
using namespace lld::coff;
static std::unique_ptr<lto::LTO> createLTO() {
lto::Config C;
C.Options = InitTargetOptionsFromCodeGenFlags();
// Always emit a section per function/datum with LTO. LLVM LTO should get most
// of the benefit of linker GC, but there are still opportunities for ICF.
C.Options.FunctionSections = true;
C.Options.DataSections = true;
// Use static reloc model on 32-bit x86 because it usually results in more
// compact code, and because there are also known code generation bugs when
// using the PIC model (see PR34306).
if (Config->Machine == COFF::IMAGE_FILE_MACHINE_I386)
C.RelocModel = Reloc::Static;
C.RelocModel = Reloc::PIC_;
C.DisableVerify = true;
C.DiagHandler = diagnosticHandler;
C.OptLevel = Config->LTOO;
if (Config->SaveTemps)
checkError(C.addSaveTemps(std::string(Config->OutputFile) + ".",
/*UseInputModulePath*/ true));
lto::ThinBackend Backend;
if (Config->ThinLTOJobs != 0)
Backend = lto::createInProcessThinBackend(Config->ThinLTOJobs);
return llvm::make_unique<lto::LTO>(std::move(C), Backend,
BitcodeCompiler::BitcodeCompiler() : LTOObj(createLTO()) {}
BitcodeCompiler::~BitcodeCompiler() = default;
static void undefine(Symbol *S) { replaceSymbol<Undefined>(S, S->getName()); }
void BitcodeCompiler::add(BitcodeFile &F) {
lto::InputFile &Obj = *F.Obj;
unsigned SymNum = 0;
std::vector<Symbol *> SymBodies = F.getSymbols();
std::vector<lto::SymbolResolution> Resols(SymBodies.size());
// Provide a resolution to the LTO API for each symbol.
for (const lto::InputFile::Symbol &ObjSym : Obj.symbols()) {
Symbol *Sym = SymBodies[SymNum];
lto::SymbolResolution &R = Resols[SymNum];
// 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() && Sym->getFile() == &F;
R.VisibleToRegularObj = Sym->IsUsedInRegularObj;
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 objects.
std::vector<StringRef> BitcodeCompiler::compile() {
unsigned MaxTasks = LTOObj->getMaxTasks();
// The /lldltocache 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->LTOCache.empty())
Cache = check(lto::localCache(
Config->LTOCache, [&](size_t Task, std::unique_ptr<MemoryBuffer> MB) {
Files[Task] = std::move(MB);
[&](size_t Task) {
return llvm::make_unique<lto::NativeObjectStream>(
if (!Config->LTOCache.empty())
pruneCache(Config->LTOCache, Config->LTOCachePolicy);
std::vector<StringRef> Ret;
for (unsigned I = 0; I != MaxTasks; ++I) {
if (Buf[I].empty())
if (Config->SaveTemps) {
if (I == 0)
saveBuffer(Buf[I], Config->OutputFile + ".lto.obj");
saveBuffer(Buf[I], Config->OutputFile + Twine(I) + ".lto.obj");
Ret.emplace_back(Buf[I].data(), Buf[I].size());
for (std::unique_ptr<MemoryBuffer> &File : Files)
if (File)
return Ret;