blob: 615b4c9dc944c03118ba42a18782b783b9cf159e [file] [log] [blame]
//===- LTO.cpp ------------------------------------------------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "LTO.h"
#include "Config.h"
#include "InputFiles.h"
#include "Symbols.h"
#include "lld/Common/Args.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;
namespace lld {
namespace wasm {
static std::unique_ptr<lto::LTO> createLTO() {
lto::Config c;
c.Options = initTargetOptionsFromCodeGenFlags();
// Always emit a section per function/data with LTO.
c.Options.FunctionSections = true;
c.Options.DataSections = true;
c.DisableVerify = config->disableVerify;
c.DiagHandler = diagnosticHandler;
c.OptLevel = config->ltoo;
c.MAttrs = getMAttrs();
c.CGOptLevel = args::getCGOptLevel(config->ltoo);
if (config->relocatable)
c.RelocModel = None;
else if (config->isPic)
c.RelocModel = Reloc::PIC_;
c.RelocModel = Reloc::Static;
if (config->saveTemps)
checkError(c.addSaveTemps(config->outputFile.str() + ".",
/*UseInputModulePath*/ true));
lto::ThinBackend backend;
if (config->thinLTOJobs != -1U)
backend = lto::createInProcessThinBackend(config->thinLTOJobs);
return std::make_unique<lto::LTO>(std::move(c), backend,
BitcodeCompiler::BitcodeCompiler() : ltoObj(createLTO()) {}
BitcodeCompiler::~BitcodeCompiler() = default;
static void undefine(Symbol *s) {
if (auto f = dyn_cast<DefinedFunction>(s))
replaceSymbol<UndefinedFunction>(f, f->getName(), "", "", 0, f->getFile(),
else if (isa<DefinedData>(s))
replaceSymbol<UndefinedData>(s, s->getName(), 0, s->getFile());
llvm_unreachable("unexpected symbol kind");
void BitcodeCompiler::add(BitcodeFile &f) {
lto::InputFile &obj = *f.obj;
unsigned symNum = 0;
ArrayRef<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];
// 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 = config->relocatable || sym->isUsedInRegularObj ||
sym->isNoStrip() ||
(r.Prevailing && sym->isExported());
if (r.Prevailing)
// We tell LTO to not apply interprocedural optimization for wrapped
// (with --wrap) symbols because otherwise LTO would inline them while
// their values are still not final.
r.LinkerRedefined = !sym->canInline;
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 --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 std::make_unique<lto::NativeObjectStream>(
if (!config->thinLTOCacheDir.empty())
pruneCache(config->thinLTOCacheDir, config->thinLTOCachePolicy);
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.o");
saveBuffer(buf[i], config->outputFile + Twine(i) + ".lto.o");
ret.emplace_back(buf[i].data(), buf[i].size());
for (std::unique_ptr<MemoryBuffer> &file : files)
if (file)
return ret;
} // namespace wasm
} // namespace lld