maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity
llvm-project/lld/ELF/LTO.cpp

305 lines
10 KiB
C++
Raw Blame History

//===- 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 "InputFiles.h"
#include "LinkerScript.h"
#include "SymbolTable.h"
#include "Symbols.h"
#include "lld/Common/Args.h"
#include "lld/Common/ErrorHandler.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/BinaryFormat/ELF.h"
#include "llvm/Bitcode/BitcodeReader.h"
#include "llvm/Bitcode/BitcodeWriter.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 <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;
// Creates an empty file to store a list of object files for final
// linking of distributed ThinLTO.
static std::unique_ptr<raw_fd_ostream> openFile(StringRef File) {
std::error_code EC;
auto Ret =
llvm::make_unique<raw_fd_ostream>(File, EC, sys::fs::OpenFlags::F_None);
if (EC) {
error("cannot open " + File + ": " + EC.message());
return nullptr;
}
return Ret;
}
static std::string getThinLTOOutputFile(StringRef ModulePath) {
return lto::getThinLTOOutputFile(ModulePath,
Config->ThinLTOPrefixReplace.first,
Config->ThinLTOPrefixReplace.second);
}
static lto::Config createConfig() {
lto::Config C;
// LLD supports the new relocations and address-significance tables.
C.Options = initTargetOptionsFromCodeGenFlags();
C.Options.RelaxELFRelocations = true;
C.Options.EmitAddrsig = true;
// Always emit a section per function/datum with LTO.
C.Options.FunctionSections = true;
C.Options.DataSections = true;
if (Config->Relocatable)
C.RelocModel = None;
else if (Config->Pic)
C.RelocModel = Reloc::PIC_;
else
C.RelocModel = Reloc::Static;
C.CodeModel = getCodeModelFromCMModel();
C.DisableVerify = Config->DisableVerify;
C.DiagHandler = diagnosticHandler;
C.OptLevel = Config->LTOO;
C.CPU = getCPUStr();
C.MAttrs = getMAttrs();
C.CGOptLevel = args::getCGOptLevel(Config->LTOO);
// Set up a custom pipeline if we've been asked to.
C.OptPipeline = Config->LTONewPmPasses;
C.AAPipeline = Config->LTOAAPipeline;
// Set up optimization remarks if we've been asked to.
C.RemarksFilename = Config->OptRemarksFilename;
C.RemarksPasses = Config->OptRemarksPasses;
C.RemarksWithHotness = Config->OptRemarksWithHotness;
C.SampleProfile = Config->LTOSampleProfile;
C.UseNewPM = Config->LTONewPassManager;
C.DebugPassManager = Config->LTODebugPassManager;
C.DwoDir = Config->DwoDir;
C.CSIRProfile = Config->LTOCSProfileFile;
C.RunCSIRInstr = Config->LTOCSProfileGenerate;
if (Config->EmitLLVM) {
C.PostInternalizeModuleHook = [](size_t Task, const Module &M) {
if (std::unique_ptr<raw_fd_ostream> OS = openFile(Config->OutputFile))
WriteBitcodeToFile(M, *OS, false);
return false;
};
}
if (Config->SaveTemps)
checkError(C.addSaveTemps(Config->OutputFile.str() + ".",
/*UseInputModulePath*/ true));
return C;
}
BitcodeCompiler::BitcodeCompiler() {
// Initialize IndexFile.
if (!Config->ThinLTOIndexOnlyArg.empty())
IndexFile = openFile(Config->ThinLTOIndexOnlyArg);
// Initialize LTOObj.
lto::ThinBackend Backend;
if (Config->ThinLTOIndexOnly) {
auto OnIndexWrite = [&](StringRef S) { ThinIndices.erase(S); };
Backend = lto::createWriteIndexesThinBackend(
Config->ThinLTOPrefixReplace.first, Config->ThinLTOPrefixReplace.second,
Config->ThinLTOEmitImportsFiles, IndexFile.get(), OnIndexWrite);
} else if (Config->ThinLTOJobs != -1U) {
Backend = lto::createInProcessThinBackend(Config->ThinLTOJobs);
}
LTOObj = llvm::make_unique<lto::LTO>(createConfig(), Backend,
Config->LTOPartitions);
// Initialize UsedStartStop.
for (Symbol *Sym : Symtab->getSymbols()) {
StringRef S = Sym->getName();
for (StringRef Prefix : {"__start_", "__stop_"})
if (S.startswith(Prefix))
UsedStartStop.insert(S.substr(Prefix.size()));
}
}
BitcodeCompiler::~BitcodeCompiler() = default;
static void undefine(Symbol *S) {
replaceSymbol<Undefined>(S, nullptr, S->getName(), STB_GLOBAL, STV_DEFAULT,
S->Type);
}
void BitcodeCompiler::add(BitcodeFile &F) {
lto::InputFile &Obj = *F.Obj;
bool IsExec = !Config->Shared && !Config->Relocatable;
if (Config->ThinLTOIndexOnly)
ThinIndices.insert(Obj.getName());
ArrayRef<Symbol *> Syms = F.getSymbols();
ArrayRef<lto::InputFile::Symbol> ObjSyms = Obj.symbols();
std::vector<lto::SymbolResolution> Resols(Syms.size());
// Provide a resolution to the LTO API for each symbol.
for (size_t I = 0, E = Syms.size(); I != E; ++I) {
Symbol *Sym = Syms[I];
const lto::InputFile::Symbol &ObjSym = ObjSyms[I];
lto::SymbolResolution &R = Resols[I];
// 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->File == &F;
// We ask LTO to preserve following global symbols:
// 1) All symbols when doing relocatable link, so that them can be used
// for doing final link.
// 2) Symbols that are used in regular objects.
// 3) C named sections if we have corresponding __start_/__stop_ symbol.
// 4) Symbols that are defined in bitcode files and used for dynamic linking.
R.VisibleToRegularObj = Config->Relocatable || Sym->IsUsedInRegularObj ||
(R.Prevailing && Sym->includeInDynsym()) ||
UsedStartStop.count(ObjSym.getSectionName());
const auto *DR = dyn_cast<Defined>(Sym);
R.FinalDefinitionInLinkageUnit =
(IsExec || Sym->Visibility != STV_DEFAULT) && DR &&
// Skip absolute symbols from ELF objects, otherwise PC-rel relocations
// will be generated by for them, triggering linker errors.
// Symbol section is always null for bitcode symbols, hence the check
// for isElf(). Skip linker script defined symbols as well: they have
// no File defined.
!(DR->Section == nullptr && (!Sym->File || Sym->File->isElf()));
if (R.Prevailing)
undefine(Sym);
// 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));
}
static void createEmptyIndex(StringRef ModulePath) {
std::string Path = replaceThinLTOSuffix(getThinLTOOutputFile(ModulePath));
std::unique_ptr<raw_fd_ostream> OS = openFile(Path + ".thinlto.bc");
if (!OS)
return;
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<InputFile *> BitcodeCompiler::compile() {
unsigned MaxTasks = LTOObj->getMaxTasks();
Buf.resize(MaxTasks);
Files.resize(MaxTasks);
// 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(
lto::localCache(Config->ThinLTOCacheDir,
[&](size_t Task, std::unique_ptr<MemoryBuffer> MB) {
Files[Task] = std::move(MB);
}));
checkError(LTOObj->run(
[&](size_t Task) {
return llvm::make_unique<lto::NativeObjectStream>(
llvm::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 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.
if (Config->ThinLTOIndexOnly) {
for (LazyObjFile *F : LazyObjFiles)
if (!F->AddedToLink && isBitcode(F->MB))
createEmptyIndex(F->getName());
if (!Config->LTOObjPath.empty())
saveBuffer(Buf[0], Config->LTOObjPath);
// 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 (IndexFile)
IndexFile->close();
return {};
}
if (!Config->ThinLTOCacheDir.empty())
pruneCache(Config->ThinLTOCacheDir, Config->ThinLTOCachePolicy);
if (!Config->LTOObjPath.empty()) {
saveBuffer(Buf[0], Config->LTOObjPath);
for (unsigned I = 1; I != MaxTasks; ++I)
saveBuffer(Buf[I], Config->LTOObjPath + Twine(I));
}
if (Config->SaveTemps) {
saveBuffer(Buf[0], Config->OutputFile + ".lto.o");
for (unsigned I = 1; I != MaxTasks; ++I)
saveBuffer(Buf[I], Config->OutputFile + Twine(I) + ".lto.o");
}
std::vector<InputFile *> Ret;
for (unsigned I = 0; I != MaxTasks; ++I)
if (!Buf[I].empty())
Ret.push_back(createObjectFile(MemoryBufferRef(Buf[I], "lto.tmp")));
for (std::unique_ptr<MemoryBuffer> &File : Files)
if (File)
Ret.push_back(createObjectFile(*File));
return Ret;
}
Reference in New Issue View Git Blame Copy Permalink