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clang-p2996/lld/MachO/LTO.cpp
Tom Lin b4e000e600 [LLD][MachO] Enable plugin support for LTO (#115690) 
Add new CLI options for feature parity with ELF w.r.t pass plugins.
Most of the changes are ported directly from
0c86198b27.
With this change, it is now possible to load and run external pass
plugins during the LTO phase.
2024-11-22 15:01:59 -08:00

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//===- LTO.cpp ------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "LTO.h"
#include "Config.h"
#include "Driver.h"
#include "InputFiles.h"
#include "Symbols.h"
#include "Target.h"
#include "lld/Common/Args.h"
#include "lld/Common/CommonLinkerContext.h"
#include "lld/Common/Filesystem.h"
#include "lld/Common/Strings.h"
#include "lld/Common/TargetOptionsCommandFlags.h"
#include "llvm/Bitcode/BitcodeWriter.h"
#include "llvm/LTO/Config.h"
#include "llvm/LTO/LTO.h"
#include "llvm/Support/Caching.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/ObjCARC.h"
using namespace lld;
using namespace lld::macho;
using namespace llvm;
using namespace llvm::MachO;
using namespace llvm::sys;
static std::string getThinLTOOutputFile(StringRef modulePath) {
return lto::getThinLTOOutputFile(modulePath, config->thinLTOPrefixReplaceOld,
config->thinLTOPrefixReplaceNew);
}
static lto::Config createConfig() {
lto::Config c;
c.Options = initTargetOptionsFromCodeGenFlags();
c.Options.EmitAddrsig = config->icfLevel == ICFLevel::safe;
for (StringRef C : config->mllvmOpts)
c.MllvmArgs.emplace_back(C.str());
for (StringRef pluginFn : config->passPlugins)
c.PassPlugins.push_back(std::string(pluginFn));
c.OptPipeline = std::string(config->ltoNewPmPasses);
c.CodeModel = getCodeModelFromCMModel();
c.CPU = getCPUStr();
c.MAttrs = getMAttrs();
c.DiagHandler = diagnosticHandler;
c.AlwaysEmitRegularLTOObj = !config->ltoObjPath.empty();
c.TimeTraceEnabled = config->timeTraceEnabled;
c.TimeTraceGranularity = config->timeTraceGranularity;
c.DebugPassManager = config->ltoDebugPassManager;
c.CSIRProfile = std::string(config->csProfilePath);
c.RunCSIRInstr = config->csProfileGenerate;
c.PGOWarnMismatch = config->pgoWarnMismatch;
c.OptLevel = config->ltoo;
c.CGOptLevel = config->ltoCgo;
if (config->saveTemps)
checkError(c.addSaveTemps(config->outputFile.str() + ".",
/*UseInputModulePath=*/true));
return c;
}
// If `originalPath` exists, hardlinks `path` to `originalPath`. If that fails,
// or `originalPath` is not set, saves `buffer` to `path`.
static void saveOrHardlinkBuffer(StringRef buffer, const Twine &path,
std::optional<StringRef> originalPath) {
if (originalPath) {
auto err = fs::create_hard_link(*originalPath, path);
if (!err)
return;
}
saveBuffer(buffer, path);
}
BitcodeCompiler::BitcodeCompiler() {
// Initialize indexFile.
if (!config->thinLTOIndexOnlyArg.empty())
indexFile = openFile(config->thinLTOIndexOnlyArg);
// Initialize ltoObj.
lto::ThinBackend backend;
auto onIndexWrite = [&](StringRef S) { thinIndices.erase(S); };
if (config->thinLTOIndexOnly) {
backend = lto::createWriteIndexesThinBackend(
llvm::hardware_concurrency(config->thinLTOJobs),
std::string(config->thinLTOPrefixReplaceOld),
std::string(config->thinLTOPrefixReplaceNew),
std::string(config->thinLTOPrefixReplaceNativeObject),
config->thinLTOEmitImportsFiles, indexFile.get(), onIndexWrite);
} else {
backend = lto::createInProcessThinBackend(
llvm::heavyweight_hardware_concurrency(config->thinLTOJobs),
onIndexWrite, config->thinLTOEmitIndexFiles,
config->thinLTOEmitImportsFiles);
}
ltoObj = std::make_unique<lto::LTO>(createConfig(), backend);
}
void BitcodeCompiler::add(BitcodeFile &f) {
lto::InputFile &obj = *f.obj;
if (config->thinLTOEmitIndexFiles)
thinIndices.insert(obj.getName());
ArrayRef<lto::InputFile::Symbol> objSyms = obj.symbols();
std::vector<lto::SymbolResolution> resols;
resols.reserve(objSyms.size());
// Provide a resolution to the LTO API for each symbol.
bool exportDynamic =
config->outputType != MH_EXECUTE || config->exportDynamic;
auto symIt = f.symbols.begin();
for (const lto::InputFile::Symbol &objSym : objSyms) {
resols.emplace_back();
lto::SymbolResolution &r = resols.back();
Symbol *sym = *symIt++;
// 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;
if (const auto *defined = dyn_cast<Defined>(sym)) {
r.ExportDynamic =
defined->isExternal() && !defined->privateExtern && exportDynamic;
r.FinalDefinitionInLinkageUnit =
!defined->isExternalWeakDef() && !defined->interposable;
} else if (const auto *common = dyn_cast<CommonSymbol>(sym)) {
r.ExportDynamic = !common->privateExtern && exportDynamic;
r.FinalDefinitionInLinkageUnit = true;
}
r.VisibleToRegularObj =
sym->isUsedInRegularObj || (r.Prevailing && r.ExportDynamic);
// Un-define the symbol so that we don't get duplicate symbol errors when we
// load the ObjFile emitted by LTO compilation.
if (r.Prevailing)
replaceSymbol<Undefined>(sym, sym->getName(), sym->getFile(),
RefState::Strong, /*wasBitcodeSymbol=*/true);
// TODO: set the other resolution configs properly
}
checkError(ltoObj->add(std::move(f.obj), resols));
hasFiles = true;
}
// If LazyObjFile has not been added to link, emit empty index files.
// This is needed because this is what GNU gold plugin does and we have a
// distributed build system that depends on that behavior.
static void thinLTOCreateEmptyIndexFiles() {
DenseSet<StringRef> linkedBitCodeFiles;
for (InputFile *file : inputFiles)
if (auto *f = dyn_cast<BitcodeFile>(file))
if (!f->lazy)
linkedBitCodeFiles.insert(f->getName());
for (InputFile *file : inputFiles) {
if (auto *f = dyn_cast<BitcodeFile>(file)) {
if (!f->lazy)
continue;
if (linkedBitCodeFiles.contains(f->getName()))
continue;
std::string path =
replaceThinLTOSuffix(getThinLTOOutputFile(f->obj->getName()));
std::unique_ptr<raw_fd_ostream> os = openFile(path + ".thinlto.bc");
if (!os)
continue;
ModuleSummaryIndex m(/*HaveGVs=*/false);
m.setSkipModuleByDistributedBackend();
writeIndexToFile(m, *os);
if (config->thinLTOEmitImportsFiles)
openFile(path + ".imports");
}
}
}
// Merge all the bitcode files we have seen, codegen the result
// and return the resulting ObjectFile(s).
std::vector<ObjFile *> BitcodeCompiler::compile() {
unsigned maxTasks = ltoObj->getMaxTasks();
buf.resize(maxTasks);
files.resize(maxTasks);
// The -cache_path_lto 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.
FileCache cache;
if (!config->thinLTOCacheDir.empty())
cache = check(localCache("ThinLTO", "Thin", config->thinLTOCacheDir,
[&](size_t task, const Twine &moduleName,
std::unique_ptr<MemoryBuffer> mb) {
files[task] = std::move(mb);
}));
if (hasFiles)
checkError(ltoObj->run(
[&](size_t task, const Twine &moduleName) {
return std::make_unique<CachedFileStream>(
std::make_unique<raw_svector_ostream>(buf[task]));
},
cache));
// Emit empty index files for non-indexed files
for (StringRef s : thinIndices) {
std::string path = getThinLTOOutputFile(s);
openFile(path + ".thinlto.bc");
if (config->thinLTOEmitImportsFiles)
openFile(path + ".imports");
}
if (config->thinLTOEmitIndexFiles)
thinLTOCreateEmptyIndexFiles();
// In ThinLTO mode, Clang passes a temporary directory in -object_path_lto,
// while the argument is a single file in FullLTO mode.
bool objPathIsDir = true;
if (!config->ltoObjPath.empty()) {
if (std::error_code ec = fs::create_directories(config->ltoObjPath))
fatal("cannot create LTO object path " + config->ltoObjPath + ": " +
ec.message());
if (!fs::is_directory(config->ltoObjPath)) {
objPathIsDir = false;
unsigned objCount =
count_if(buf, [](const SmallString<0> &b) { return !b.empty(); });
if (objCount > 1)
fatal("-object_path_lto must specify a directory when using ThinLTO");
}
}
auto outputFilePath = [objPathIsDir](int i) {
SmallString<261> filePath("/tmp/lto.tmp");
if (!config->ltoObjPath.empty()) {
filePath = config->ltoObjPath;
if (objPathIsDir)
path::append(filePath, Twine(i) + "." +
getArchitectureName(config->arch()) +
".lto.o");
}
return filePath;
};
// ThinLTO with index only option is required to generate only the index
// files. After that, we exit from linker and ThinLTO backend runs in a
// distributed environment.
if (config->thinLTOIndexOnly) {
if (!config->ltoObjPath.empty())
saveBuffer(buf[0], outputFilePath(0));
if (indexFile)
indexFile->close();
return {};
}
if (!config->thinLTOCacheDir.empty())
pruneCache(config->thinLTOCacheDir, config->thinLTOCachePolicy, files);
std::vector<ObjFile *> ret;
for (unsigned i = 0; i < maxTasks; ++i) {
// Get the native object contents either from the cache or from memory. Do
// not use the cached MemoryBuffer directly to ensure dsymutil does not
// race with the cache pruner.
StringRef objBuf;
std::optional<StringRef> cachePath;
if (files[i]) {
objBuf = files[i]->getBuffer();
cachePath = files[i]->getBufferIdentifier();
} else {
objBuf = buf[i];
}
if (objBuf.empty())
continue;
// FIXME: should `saveTemps` and `ltoObjPath` use the same file name?
if (config->saveTemps)
saveBuffer(objBuf,
config->outputFile + ((i == 0) ? "" : Twine(i)) + ".lto.o");
auto filePath = outputFilePath(i);
uint32_t modTime = 0;
if (!config->ltoObjPath.empty()) {
saveOrHardlinkBuffer(objBuf, filePath, cachePath);
modTime = getModTime(filePath);
}
ret.push_back(make<ObjFile>(
MemoryBufferRef(objBuf, saver().save(filePath.str())), modTime,
/*archiveName=*/"", /*lazy=*/false,
/*forceHidden=*/false, /*compatArch=*/true, /*builtFromBitcode=*/true));
}
return ret;
}
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