Coverage Report

Created: 2018-01-17 21:32

/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/tools/lld/ELF/LTO.cpp
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//===- LTO.cpp ------------------------------------------------------------===//
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//
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//                             The LLVM Linker
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "LTO.h"
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#include "Config.h"
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#include "InputFiles.h"
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#include "LinkerScript.h"
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#include "SymbolTable.h"
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#include "Symbols.h"
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#include "lld/Common/ErrorHandler.h"
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#include "lld/Common/TargetOptionsCommandFlags.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/ADT/Twine.h"
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#include "llvm/BinaryFormat/ELF.h"
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#include "llvm/IR/DiagnosticPrinter.h"
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#include "llvm/LTO/Caching.h"
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#include "llvm/LTO/Config.h"
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#include "llvm/LTO/LTO.h"
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#include "llvm/Object/SymbolicFile.h"
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#include "llvm/Support/CodeGen.h"
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#include "llvm/Support/Error.h"
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#include "llvm/Support/FileSystem.h"
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#include "llvm/Support/MemoryBuffer.h"
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#include "llvm/Support/raw_ostream.h"
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#include <algorithm>
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#include <cstddef>
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#include <memory>
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#include <string>
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#include <system_error>
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#include <vector>
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using namespace llvm;
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using namespace llvm::object;
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using namespace llvm::ELF;
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using namespace lld;
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using namespace lld::elf;
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// This is for use when debugging LTO.
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static void saveBuffer(StringRef Buffer, const Twine &Path) {
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  std::error_code EC;
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  raw_fd_ostream OS(Path.str(), EC, sys::fs::OpenFlags::F_None);
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  if (EC)
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    error("cannot create " + Path + ": " + EC.message());
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  OS << Buffer;
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}
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static void diagnosticHandler(const DiagnosticInfo &DI) {
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  SmallString<128> ErrStorage;
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  raw_svector_ostream OS(ErrStorage);
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  DiagnosticPrinterRawOStream DP(OS);
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  DI.print(DP);
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  warn(ErrStorage);
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}
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static void checkError(Error E) {
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  handleAllErrors(std::move(E),
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                  [&](ErrorInfoBase &EIB) { error(EIB.message()); });
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}
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static std::unique_ptr<lto::LTO> createLTO() {
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  lto::Config Conf;
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  // LLD supports the new relocations.
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  Conf.Options = InitTargetOptionsFromCodeGenFlags();
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  Conf.Options.RelaxELFRelocations = true;
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  // Always emit a section per function/datum with LTO.
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  Conf.Options.FunctionSections = true;
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  Conf.Options.DataSections = true;
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  if (Config->Relocatable)
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    Conf.RelocModel = None;
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  else if (Config->Pic)
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    Conf.RelocModel = Reloc::PIC_;
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  else
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    Conf.RelocModel = Reloc::Static;
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  Conf.CodeModel = GetCodeModelFromCMModel();
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  Conf.DisableVerify = Config->DisableVerify;
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  Conf.DiagHandler = diagnosticHandler;
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  Conf.OptLevel = Config->LTOO;
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  // Set up a custom pipeline if we've been asked to.
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  Conf.OptPipeline = Config->LTONewPmPasses;
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  Conf.AAPipeline = Config->LTOAAPipeline;
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  // Set up optimization remarks if we've been asked to.
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  Conf.RemarksFilename = Config->OptRemarksFilename;
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  Conf.RemarksWithHotness = Config->OptRemarksWithHotness;
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  if (Config->SaveTemps)
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    checkError(Conf.addSaveTemps(std::string(Config->OutputFile) + ".",
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                                 /*UseInputModulePath*/ true));
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  lto::ThinBackend Backend;
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  if (Config->ThinLTOJobs != -1u)
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    Backend = lto::createInProcessThinBackend(Config->ThinLTOJobs);
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  return llvm::make_unique<lto::LTO>(std::move(Conf), Backend,
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                                     Config->LTOPartitions);
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}
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BitcodeCompiler::BitcodeCompiler() : LTOObj(createLTO()) {
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  for (Symbol *Sym : Symtab->getSymbols()) {
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    StringRef Name = Sym->getName();
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    for (StringRef Prefix : {"__start_", "__stop_"})
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      if (Name.startswith(Prefix))
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        UsedStartStop.insert(Name.substr(Prefix.size()));
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  }
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}
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BitcodeCompiler::~BitcodeCompiler() = default;
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static void undefine(Symbol *S) {
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  replaceSymbol<Undefined>(S, nullptr, S->getName(), STB_GLOBAL, STV_DEFAULT,
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                           S->Type);
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}
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void BitcodeCompiler::add(BitcodeFile &F) {
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  lto::InputFile &Obj = *F.Obj;
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  unsigned SymNum = 0;
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  std::vector<Symbol *> Syms = F.getSymbols();
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  std::vector<lto::SymbolResolution> Resols(Syms.size());
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  DenseSet<StringRef> ScriptSymbols;
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  for (BaseCommand *Base : Script->SectionCommands)
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    if (auto *Cmd = dyn_cast<SymbolAssignment>(Base))
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      ScriptSymbols.insert(Cmd->Name);
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  bool IsExecutable = !Config->Shared && 
!Config->Relocatable36
;
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  // Provide a resolution to the LTO API for each symbol.
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  for (const lto::InputFile::Symbol &ObjSym : Obj.symbols()) {
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    Symbol *Sym = Syms[SymNum];
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    lto::SymbolResolution &R = Resols[SymNum];
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    ++SymNum;
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    // Ideally we shouldn't check for SF_Undefined but currently IRObjectFile
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    // reports two symbols for module ASM defined. Without this check, lld
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    // flags an undefined in IR with a definition in ASM as prevailing.
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    // Once IRObjectFile is fixed to report only one symbol this hack can
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    // be removed.
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    R.Prevailing = !ObjSym.isUndefined() && 
Sym->File == &F101
;
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    // We ask LTO to preserve following global symbols:
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    // 1) All symbols when doing relocatable link, so that them can be used
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    //    for doing final link.
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    // 2) Symbols that are used in regular objects.
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    // 3) C named sections if we have corresponding __start_/__stop_ symbol.
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    // 4) Symbols that are defined in bitcode files and used for dynamic linking.
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    R.VisibleToRegularObj = Config->Relocatable || 
Sym->IsUsedInRegularObj139
||
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(98
R.Prevailing98
&&
Sym->includeInDynsym()64
) ||
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UsedStartStop.count(ObjSym.getSectionName())62
;
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    R.FinalDefinitionInLinkageUnit =
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        Sym->isDefined() && 
(122
IsExecutable122
||
Sym->Visibility != STV_DEFAULT72
);
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    if (R.Prevailing)
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      undefine(Sym);
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    // We tell LTO to not apply interprocedural optimization for following
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    // symbols because otherwise LTO would inline them while their values are
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    // still not final:
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    // 1) Aliased (with --defsym) or wrapped (with --wrap) symbols.
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    // 2) Symbols redefined in linker script.
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    R.LinkerRedefined = !Sym->CanInline || 
ScriptSymbols.count(Sym->getName())134
;
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  }
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  checkError(LTOObj->add(std::move(F.Obj), Resols));
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}
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// Merge all the bitcode files we have seen, codegen the result
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// and return the resulting ObjectFile(s).
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std::vector<InputFile *> BitcodeCompiler::compile() {
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  std::vector<InputFile *> Ret;
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  unsigned MaxTasks = LTOObj->getMaxTasks();
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  Buff.resize(MaxTasks);
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  Files.resize(MaxTasks);
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  // The --thinlto-cache-dir option specifies the path to a directory in which
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  // to cache native object files for ThinLTO incremental builds. If a path was
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  // specified, configure LTO to use it as the cache directory.
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  lto::NativeObjectCache Cache;
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  if (!Config->ThinLTOCacheDir.empty())
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    Cache = check(
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        lto::localCache(Config->ThinLTOCacheDir,
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                        [&](size_t Task, std::unique_ptr<MemoryBuffer> MB,
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                            StringRef Path) { Files[Task] = std::move(MB); }));
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  checkError(LTOObj->run(
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      [&](size_t Task) {
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        return llvm::make_unique<lto::NativeObjectStream>(
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            llvm::make_unique<raw_svector_ostream>(Buff[Task]));
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      },
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      Cache));
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  if (!Config->ThinLTOCacheDir.empty())
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    pruneCache(Config->ThinLTOCacheDir, Config->ThinLTOCachePolicy);
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  for (unsigned I = 0; I != MaxTasks; 
++I76
) {
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    if (Buff[I].empty())
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      continue;
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    if (Config->SaveTemps) {
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      if (I == 0)
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        saveBuffer(Buff[I], Config->OutputFile + ".lto.o");
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      else
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        saveBuffer(Buff[I], Config->OutputFile + Twine(I) + ".lto.o");
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    }
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    InputFile *Obj = createObjectFile(MemoryBufferRef(Buff[I], "lto.tmp"));
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    Ret.push_back(Obj);
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  }
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  for (std::unique_ptr<MemoryBuffer> &File : Files)
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    if (File)
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      Ret.push_back(createObjectFile(*File));
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  return Ret;
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}