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    9acb854c
    [ARM] Command-line options for embedded position-independent code · 9acb854c
    Oliver Stannard authored 
    This patch (with the corresponding ARM backend patch) adds support for
some new relocation models:

* Read-only position independence (ROPI): Code and read-only data is accessed
  PC-relative. The offsets between all code and RO data sections are known at
  static link time.
* Read-write position independence (RWPI): Read-write data is accessed relative
  to a static base register. The offsets between all writeable data sections
  are known at static link time.

These two modes are independent (they specify how different objects
should be addressed), so they can be used individually or together.

These modes are intended for bare-metal systems or systems with small
real-time operating systems. They are designed to avoid the need for a
dynamic linker, the only initialisation required is setting the static
base register to an appropriate value for RWPI code.

There is one C construct not currently supported by these modes: global
variables initialised to the address of another global variable or
function, where that address is not known at static-link time. There are
a few possible ways to solve this:

* Disallow this, and require the user to write their own initialisation
  function if they need variables like this.
* Emit dynamic initialisers for these variables in the compiler, called from
  the .init_array section (as is currently done for C++ dynamic initialisers).
  We have a patch to do this, described in my original RFC email
  (http://lists.llvm.org/pipermail/llvm-dev/2015-December/093022.html), but the
  feedback from that RFC thread was that this is not something that belongs in
  clang.
* Use a small dynamic loader to fix up these variables, by adding the
  difference between the load and execution address of the relevant section.
  This would require linker co-operation to generate a table of addresses that
  need fixing up.

Differential Revision: https://reviews.llvm.org/D23196



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@278016 91177308-0d34-0410-b5e6-96231b3b80d8
    9acb854c
    History
    [ARM] Command-line options for embedded position-independent code
    Oliver Stannard authored 
    This patch (with the corresponding ARM backend patch) adds support for
some new relocation models:

* Read-only position independence (ROPI): Code and read-only data is accessed
  PC-relative. The offsets between all code and RO data sections are known at
  static link time.
* Read-write position independence (RWPI): Read-write data is accessed relative
  to a static base register. The offsets between all writeable data sections
  are known at static link time.

These two modes are independent (they specify how different objects
should be addressed), so they can be used individually or together.

These modes are intended for bare-metal systems or systems with small
real-time operating systems. They are designed to avoid the need for a
dynamic linker, the only initialisation required is setting the static
base register to an appropriate value for RWPI code.

There is one C construct not currently supported by these modes: global
variables initialised to the address of another global variable or
function, where that address is not known at static-link time. There are
a few possible ways to solve this:

* Disallow this, and require the user to write their own initialisation
  function if they need variables like this.
* Emit dynamic initialisers for these variables in the compiler, called from
  the .init_array section (as is currently done for C++ dynamic initialisers).
  We have a patch to do this, described in my original RFC email
  (http://lists.llvm.org/pipermail/llvm-dev/2015-December/093022.html), but the
  feedback from that RFC thread was that this is not something that belongs in
  clang.
* Use a small dynamic loader to fix up these variables, by adding the
  difference between the load and execution address of the relevant section.
  This would require linker co-operation to generate a table of addresses that
  need fixing up.

Differential Revision: https://reviews.llvm.org/D23196



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@278016 91177308-0d34-0410-b5e6-96231b3b80d8
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BackendUtil.cpp 34.02 KiB 
//===--- BackendUtil.cpp - LLVM Backend Utilities -------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "clang/CodeGen/BackendUtil.h"
#include "clang/Basic/Diagnostic.h"
#include "clang/Basic/LangOptions.h"
#include "clang/Basic/TargetOptions.h"
#include "clang/Frontend/CodeGenOptions.h"
#include "clang/Frontend/FrontendDiagnostic.h"
#include "clang/Frontend/Utils.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Bitcode/BitcodeWriterPass.h"
#include "llvm/Bitcode/ReaderWriter.h"
#include "llvm/CodeGen/RegAllocRegistry.h"
#include "llvm/CodeGen/SchedulerRegistry.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/ModuleSummaryIndex.h"
#include "llvm/IR/IRPrintingPasses.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Verifier.h"
#include "llvm/MC/SubtargetFeature.h"
#include "llvm/Object/ModuleSummaryIndexObjectFile.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/PrettyStackTrace.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/Timer.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetSubtargetInfo.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/IPO/PassManagerBuilder.h"
#include "llvm/Transforms/Instrumentation.h"
#include "llvm/Transforms/ObjCARC.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Scalar/GVN.h"
#include "llvm/Transforms/Utils/SymbolRewriter.h"
#include <memory>
using namespace clang;
using namespace llvm;

namespace {

class EmitAssemblyHelper {
  DiagnosticsEngine &Diags;
  const CodeGenOptions &CodeGenOpts;
  const clang::TargetOptions &TargetOpts;
  const LangOptions &LangOpts;
  Module *TheModule;

  Timer CodeGenerationTime;

  std::unique_ptr<raw_pwrite_stream> OS;

private:
  TargetIRAnalysis getTargetIRAnalysis() const {
    if (TM)
      return TM->getTargetIRAnalysis();

    return TargetIRAnalysis();
  }

  /// Set LLVM command line options passed through -backend-option.
  void setCommandLineOpts();

  void CreatePasses(legacy::PassManager &MPM, legacy::FunctionPassManager &FPM,
                    ModuleSummaryIndex *ModuleSummary);

  /// Generates the TargetMachine.
  /// Leaves TM unchanged if it is unable to create the target machine.
  /// Some of our clang tests specify triples which are not built
  /// into clang. This is okay because these tests check the generated
  /// IR, and they require DataLayout which depends on the triple.
  /// In this case, we allow this method to fail and not report an error.
  /// When MustCreateTM is used, we print an error if we are unable to load
  /// the requested target.
  void CreateTargetMachine(bool MustCreateTM);

  /// Add passes necessary to emit assembly or LLVM IR.
  ///
  /// \return True on success.
  bool AddEmitPasses(legacy::PassManager &CodeGenPasses, BackendAction Action,
                     raw_pwrite_stream &OS);

public:
  EmitAssemblyHelper(DiagnosticsEngine &_Diags, const CodeGenOptions &CGOpts,
                     const clang::TargetOptions &TOpts,
                     const LangOptions &LOpts, Module *M)
      : Diags(_Diags), CodeGenOpts(CGOpts), TargetOpts(TOpts), LangOpts(LOpts),
        TheModule(M), CodeGenerationTime("Code Generation Time") {}

  ~EmitAssemblyHelper() {
    if (CodeGenOpts.DisableFree)
      BuryPointer(std::move(TM));
  }

  std::unique_ptr<TargetMachine> TM;

  void EmitAssembly(BackendAction Action,
                    std::unique_ptr<raw_pwrite_stream> OS);
};

// We need this wrapper to access LangOpts and CGOpts from extension functions
// that we add to the PassManagerBuilder.
class PassManagerBuilderWrapper : public PassManagerBuilder {
public:
  PassManagerBuilderWrapper(const CodeGenOptions &CGOpts,
                            const LangOptions &LangOpts)
      : PassManagerBuilder(), CGOpts(CGOpts), LangOpts(LangOpts) {}
  const CodeGenOptions &getCGOpts() const { return CGOpts; }
  const LangOptions &getLangOpts() const { return LangOpts; }
private:
  const CodeGenOptions &CGOpts;
  const LangOptions &LangOpts;
};

}

static void addObjCARCAPElimPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
  if (Builder.OptLevel > 0)
    PM.add(createObjCARCAPElimPass());
}

static void addObjCARCExpandPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
  if (Builder.OptLevel > 0)
    PM.add(createObjCARCExpandPass());
}

static void addObjCARCOptPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
  if (Builder.OptLevel > 0)
    PM.add(createObjCARCOptPass());
}

static void addAddDiscriminatorsPass(const PassManagerBuilder &Builder,
                                     legacy::PassManagerBase &PM) {
  PM.add(createAddDiscriminatorsPass());
}

static void addCleanupPassesForSampleProfiler(
    const PassManagerBuilder &Builder, legacy::PassManagerBase &PM) {
  // instcombine is needed before sample profile annotation because it converts
  // certain function calls to be inlinable. simplifycfg and sroa are needed
  // before instcombine for necessary preparation. E.g. load store is eliminated
  // properly so that instcombine will not introduce unecessary liverange.
  PM.add(createCFGSimplificationPass());
  PM.add(createSROAPass());
  PM.add(createInstructionCombiningPass());
}

static void addBoundsCheckingPass(const PassManagerBuilder &Builder,
                                  legacy::PassManagerBase &PM) {
  PM.add(createBoundsCheckingPass());
}

static void addSanitizerCoveragePass(const PassManagerBuilder &Builder,
                                     legacy::PassManagerBase &PM) {
  const PassManagerBuilderWrapper &BuilderWrapper =
      static_cast<const PassManagerBuilderWrapper&>(Builder);
  const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
  SanitizerCoverageOptions Opts;
  Opts.CoverageType =
      static_cast<SanitizerCoverageOptions::Type>(CGOpts.SanitizeCoverageType);
  Opts.IndirectCalls = CGOpts.SanitizeCoverageIndirectCalls;
  Opts.TraceBB = CGOpts.SanitizeCoverageTraceBB;
  Opts.TraceCmp = CGOpts.SanitizeCoverageTraceCmp;
  Opts.Use8bitCounters = CGOpts.SanitizeCoverage8bitCounters;
  Opts.TracePC = CGOpts.SanitizeCoverageTracePC;
  PM.add(createSanitizerCoverageModulePass(Opts));
}

static void addAddressSanitizerPasses(const PassManagerBuilder &Builder,
                                      legacy::PassManagerBase &PM) {
  const PassManagerBuilderWrapper &BuilderWrapper =
      static_cast<const PassManagerBuilderWrapper&>(Builder);
  const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
  bool Recover = CGOpts.SanitizeRecover.has(SanitizerKind::Address);
  bool UseAfterScope = CGOpts.SanitizeAddressUseAfterScope;
  PM.add(createAddressSanitizerFunctionPass(/*CompileKernel*/ false, Recover,
                                            UseAfterScope));
  PM.add(createAddressSanitizerModulePass(/*CompileKernel*/false, Recover));
}

static void addKernelAddressSanitizerPasses(const PassManagerBuilder &Builder,
                                            legacy::PassManagerBase &PM) {
  PM.add(createAddressSanitizerFunctionPass(
      /*CompileKernel*/ true,
      /*Recover*/ true, /*UseAfterScope*/ false));
  PM.add(createAddressSanitizerModulePass(/*CompileKernel*/true,
                                          /*Recover*/true));
}

static void addMemorySanitizerPass(const PassManagerBuilder &Builder,
                                   legacy::PassManagerBase &PM) {
  const PassManagerBuilderWrapper &BuilderWrapper =
      static_cast<const PassManagerBuilderWrapper&>(Builder);
  const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
  PM.add(createMemorySanitizerPass(CGOpts.SanitizeMemoryTrackOrigins));

  // MemorySanitizer inserts complex instrumentation that mostly follows
  // the logic of the original code, but operates on "shadow" values.
  // It can benefit from re-running some general purpose optimization passes.
  if (Builder.OptLevel > 0) {
    PM.add(createEarlyCSEPass());
    PM.add(createReassociatePass());
    PM.add(createLICMPass());
    PM.add(createGVNPass());
    PM.add(createInstructionCombiningPass());
    PM.add(createDeadStoreEliminationPass());
  }
}

static void addThreadSanitizerPass(const PassManagerBuilder &Builder,
                                   legacy::PassManagerBase &PM) {
  PM.add(createThreadSanitizerPass());
}

static void addDataFlowSanitizerPass(const PassManagerBuilder &Builder,
                                     legacy::PassManagerBase &PM) {
  const PassManagerBuilderWrapper &BuilderWrapper =
      static_cast<const PassManagerBuilderWrapper&>(Builder);
  const LangOptions &LangOpts = BuilderWrapper.getLangOpts();
  PM.add(createDataFlowSanitizerPass(LangOpts.SanitizerBlacklistFiles));
}

static void addEfficiencySanitizerPass(const PassManagerBuilder &Builder,
                                       legacy::PassManagerBase &PM) {
  const PassManagerBuilderWrapper &BuilderWrapper =
      static_cast<const PassManagerBuilderWrapper&>(Builder);
  const LangOptions &LangOpts = BuilderWrapper.getLangOpts();
  EfficiencySanitizerOptions Opts;
  if (LangOpts.Sanitize.has(SanitizerKind::EfficiencyCacheFrag))
    Opts.ToolType = EfficiencySanitizerOptions::ESAN_CacheFrag;
  else if (LangOpts.Sanitize.has(SanitizerKind::EfficiencyWorkingSet))
    Opts.ToolType = EfficiencySanitizerOptions::ESAN_WorkingSet;
  PM.add(createEfficiencySanitizerPass(Opts));
}

static TargetLibraryInfoImpl *createTLII(llvm::Triple &TargetTriple,
                                         const CodeGenOptions &CodeGenOpts) {
  TargetLibraryInfoImpl *TLII = new TargetLibraryInfoImpl(TargetTriple);
  if (!CodeGenOpts.SimplifyLibCalls)
    TLII->disableAllFunctions();
  else {
    // Disable individual libc/libm calls in TargetLibraryInfo.
    LibFunc::Func F;
    for (auto &FuncName : CodeGenOpts.getNoBuiltinFuncs())
      if (TLII->getLibFunc(FuncName, F))
        TLII->setUnavailable(F);
  }

  switch (CodeGenOpts.getVecLib()) {
  case CodeGenOptions::Accelerate:
    TLII->addVectorizableFunctionsFromVecLib(TargetLibraryInfoImpl::Accelerate);
    break;
  case CodeGenOptions::SVML:
    TLII->addVectorizableFunctionsFromVecLib(TargetLibraryInfoImpl::SVML);
    break;
  default:
    break;
  }
  return TLII;
}

static void addSymbolRewriterPass(const CodeGenOptions &Opts,
                                  legacy::PassManager *MPM) {
  llvm::SymbolRewriter::RewriteDescriptorList DL;

  llvm::SymbolRewriter::RewriteMapParser MapParser;
  for (const auto &MapFile : Opts.RewriteMapFiles)
    MapParser.parse(MapFile, &DL);

  MPM->add(createRewriteSymbolsPass(DL));
}

void EmitAssemblyHelper::CreatePasses(legacy::PassManager &MPM,
                                      legacy::FunctionPassManager &FPM,
                                      ModuleSummaryIndex *ModuleSummary) {
  if (CodeGenOpts.DisableLLVMPasses)
    return;

  unsigned OptLevel = CodeGenOpts.OptimizationLevel;
  CodeGenOptions::InliningMethod Inlining = CodeGenOpts.getInlining();

  // Handle disabling of LLVM optimization, where we want to preserve the
  // internal module before any optimization.
  if (CodeGenOpts.DisableLLVMOpts) {
    OptLevel = 0;
    Inlining = CodeGenOpts.NoInlining;
  }

  PassManagerBuilderWrapper PMBuilder(CodeGenOpts, LangOpts);

  // Figure out TargetLibraryInfo.
  Triple TargetTriple(TheModule->getTargetTriple());
  PMBuilder.LibraryInfo = createTLII(TargetTriple, CodeGenOpts);

  switch (Inlining) {
  case CodeGenOptions::NoInlining:
    break;
  case CodeGenOptions::NormalInlining:
  case CodeGenOptions::OnlyHintInlining: {
    PMBuilder.Inliner =
        createFunctionInliningPass(OptLevel, CodeGenOpts.OptimizeSize);
    break;
  }
  case CodeGenOptions::OnlyAlwaysInlining:
    // Respect always_inline.
    if (OptLevel == 0)
      // Do not insert lifetime intrinsics at -O0.
      PMBuilder.Inliner = createAlwaysInlinerPass(false);
    else
      PMBuilder.Inliner = createAlwaysInlinerPass();
    break;
  }

  PMBuilder.OptLevel = OptLevel;
  PMBuilder.SizeLevel = CodeGenOpts.OptimizeSize;
  PMBuilder.BBVectorize = CodeGenOpts.VectorizeBB;
  PMBuilder.SLPVectorize = CodeGenOpts.VectorizeSLP;
  PMBuilder.LoopVectorize = CodeGenOpts.VectorizeLoop;

  PMBuilder.DisableUnrollLoops = !CodeGenOpts.UnrollLoops;
  PMBuilder.MergeFunctions = CodeGenOpts.MergeFunctions;
  PMBuilder.PrepareForThinLTO = CodeGenOpts.EmitSummaryIndex;
  PMBuilder.PrepareForLTO = CodeGenOpts.PrepareForLTO;
  PMBuilder.RerollLoops = CodeGenOpts.RerollLoops;

  // If we are performing a ThinLTO importing compile, invoke the LTO
  // pipeline and pass down the in-memory module summary index.
  if (ModuleSummary) {
    PMBuilder.ModuleSummary = ModuleSummary;
    PMBuilder.populateThinLTOPassManager(MPM);
    return;
  }

  // Add target-specific passes that need to run as early as possible.
  if (TM)
    PMBuilder.addExtension(
        PassManagerBuilder::EP_EarlyAsPossible,
        [&](const PassManagerBuilder &, legacy::PassManagerBase &PM) {
          TM->addEarlyAsPossiblePasses(PM);
        });

  PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,
                         addAddDiscriminatorsPass);

  // In ObjC ARC mode, add the main ARC optimization passes.
  if (LangOpts.ObjCAutoRefCount) {
    PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,
                           addObjCARCExpandPass);
    PMBuilder.addExtension(PassManagerBuilder::EP_ModuleOptimizerEarly,
                           addObjCARCAPElimPass);
    PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
                           addObjCARCOptPass);
  }

  if (LangOpts.Sanitize.has(SanitizerKind::LocalBounds)) {
    PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
                           addBoundsCheckingPass);
    PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
                           addBoundsCheckingPass);
  }

  if (CodeGenOpts.SanitizeCoverageType ||
      CodeGenOpts.SanitizeCoverageIndirectCalls ||
      CodeGenOpts.SanitizeCoverageTraceCmp) {
    PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
                           addSanitizerCoveragePass);
    PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
                           addSanitizerCoveragePass);
  }

  if (LangOpts.Sanitize.has(SanitizerKind::Address)) {
    PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
                           addAddressSanitizerPasses);
    PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
                           addAddressSanitizerPasses);
  }

  if (LangOpts.Sanitize.has(SanitizerKind::KernelAddress)) {
    PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
                           addKernelAddressSanitizerPasses);
    PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
                           addKernelAddressSanitizerPasses);
  }

  if (LangOpts.Sanitize.has(SanitizerKind::Memory)) {
    PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
                           addMemorySanitizerPass);
    PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
                           addMemorySanitizerPass);
  }

  if (LangOpts.Sanitize.has(SanitizerKind::Thread)) {
    PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
                           addThreadSanitizerPass);
    PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
                           addThreadSanitizerPass);
  }

  if (LangOpts.Sanitize.has(SanitizerKind::DataFlow)) {
    PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
                           addDataFlowSanitizerPass);
    PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
                           addDataFlowSanitizerPass);
  }

  if (LangOpts.Sanitize.hasOneOf(SanitizerKind::Efficiency)) {
    PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
                           addEfficiencySanitizerPass);
    PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
                           addEfficiencySanitizerPass);
  }

  // Set up the per-function pass manager.
  if (CodeGenOpts.VerifyModule)
    FPM.add(createVerifierPass());

  // Set up the per-module pass manager.
  if (!CodeGenOpts.RewriteMapFiles.empty())
    addSymbolRewriterPass(CodeGenOpts, &MPM);

  if (!CodeGenOpts.DisableGCov &&
      (CodeGenOpts.EmitGcovArcs || CodeGenOpts.EmitGcovNotes)) {
    // Not using 'GCOVOptions::getDefault' allows us to avoid exiting if
    // LLVM's -default-gcov-version flag is set to something invalid.
    GCOVOptions Options;
    Options.EmitNotes = CodeGenOpts.EmitGcovNotes;
    Options.EmitData = CodeGenOpts.EmitGcovArcs;
    memcpy(Options.Version, CodeGenOpts.CoverageVersion, 4);
    Options.UseCfgChecksum = CodeGenOpts.CoverageExtraChecksum;
    Options.NoRedZone = CodeGenOpts.DisableRedZone;
    Options.FunctionNamesInData =
        !CodeGenOpts.CoverageNoFunctionNamesInData;
    Options.ExitBlockBeforeBody = CodeGenOpts.CoverageExitBlockBeforeBody;
    MPM.add(createGCOVProfilerPass(Options));
    if (CodeGenOpts.getDebugInfo() == codegenoptions::NoDebugInfo)
      MPM.add(createStripSymbolsPass(true));
  }

  if (CodeGenOpts.hasProfileClangInstr()) {
    InstrProfOptions Options;
    Options.NoRedZone = CodeGenOpts.DisableRedZone;
    Options.InstrProfileOutput = CodeGenOpts.InstrProfileOutput;
    MPM.add(createInstrProfilingLegacyPass(Options));
  }
  if (CodeGenOpts.hasProfileIRInstr()) {
    PMBuilder.EnablePGOInstrGen = true;
    if (!CodeGenOpts.InstrProfileOutput.empty())
      PMBuilder.PGOInstrGen = CodeGenOpts.InstrProfileOutput;
    else
      PMBuilder.PGOInstrGen = "default_%m.profraw";
  }
  if (CodeGenOpts.hasProfileIRUse())
    PMBuilder.PGOInstrUse = CodeGenOpts.ProfileInstrumentUsePath;

  if (!CodeGenOpts.SampleProfileFile.empty()) {
    MPM.add(createPruneEHPass());
    MPM.add(createSampleProfileLoaderPass(CodeGenOpts.SampleProfileFile));
    PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,
                           addCleanupPassesForSampleProfiler);
  }

  PMBuilder.populateFunctionPassManager(FPM);
  PMBuilder.populateModulePassManager(MPM);
}

void EmitAssemblyHelper::setCommandLineOpts() {
  SmallVector<const char *, 16> BackendArgs;
  BackendArgs.push_back("clang"); // Fake program name.
  if (!CodeGenOpts.DebugPass.empty()) {
    BackendArgs.push_back("-debug-pass");
    BackendArgs.push_back(CodeGenOpts.DebugPass.c_str());
  }
  if (!CodeGenOpts.LimitFloatPrecision.empty()) {
    BackendArgs.push_back("-limit-float-precision");
    BackendArgs.push_back(CodeGenOpts.LimitFloatPrecision.c_str());
  }
  for (const std::string &BackendOption : CodeGenOpts.BackendOptions)
    BackendArgs.push_back(BackendOption.c_str());
  BackendArgs.push_back(nullptr);
  llvm::cl::ParseCommandLineOptions(BackendArgs.size() - 1,
                                    BackendArgs.data());
}

void EmitAssemblyHelper::CreateTargetMachine(bool MustCreateTM) {
  // Create the TargetMachine for generating code.
  std::string Error;
  std::string Triple = TheModule->getTargetTriple();
  const llvm::Target *TheTarget = TargetRegistry::lookupTarget(Triple, Error);
  if (!TheTarget) {
    if (MustCreateTM)
      Diags.Report(diag::err_fe_unable_to_create_target) << Error;
    return;
  }

  unsigned CodeModel =
    llvm::StringSwitch<unsigned>(CodeGenOpts.CodeModel)
      .Case("small", llvm::CodeModel::Small)
      .Case("kernel", llvm::CodeModel::Kernel)
      .Case("medium", llvm::CodeModel::Medium)
      .Case("large", llvm::CodeModel::Large)
      .Case("default", llvm::CodeModel::Default)
      .Default(~0u);
  assert(CodeModel != ~0u && "invalid code model!");
  llvm::CodeModel::Model CM = static_cast<llvm::CodeModel::Model>(CodeModel);

  std::string FeaturesStr =
      llvm::join(TargetOpts.Features.begin(), TargetOpts.Features.end(), ",");

  // Keep this synced with the equivalent code in tools/driver/cc1as_main.cpp.
  llvm::Optional<llvm::Reloc::Model> RM;
  if (CodeGenOpts.RelocationModel == "static") {
    RM = llvm::Reloc::Static;
  } else if (CodeGenOpts.RelocationModel == "pic") {
    RM = llvm::Reloc::PIC_;
  } else if (CodeGenOpts.RelocationModel == "ropi") {
    RM = llvm::Reloc::ROPI;
  } else if (CodeGenOpts.RelocationModel == "rwpi") {
    RM = llvm::Reloc::RWPI;
  } else if (CodeGenOpts.RelocationModel == "ropi-rwpi") {
    RM = llvm::Reloc::ROPI_RWPI;
  } else {
    assert(CodeGenOpts.RelocationModel == "dynamic-no-pic" &&
           "Invalid PIC model!");
    RM = llvm::Reloc::DynamicNoPIC;
  }

  CodeGenOpt::Level OptLevel = CodeGenOpt::Default;
  switch (CodeGenOpts.OptimizationLevel) {
  default: break;
  case 0: OptLevel = CodeGenOpt::None; break;
  case 3: OptLevel = CodeGenOpt::Aggressive; break;
  }

  llvm::TargetOptions Options;

  if (!TargetOpts.Reciprocals.empty())
    Options.Reciprocals = TargetRecip(TargetOpts.Reciprocals);

  Options.ThreadModel =
    llvm::StringSwitch<llvm::ThreadModel::Model>(CodeGenOpts.ThreadModel)
      .Case("posix", llvm::ThreadModel::POSIX)
      .Case("single", llvm::ThreadModel::Single);

  // Set float ABI type.
  assert((CodeGenOpts.FloatABI == "soft" || CodeGenOpts.FloatABI == "softfp" ||
          CodeGenOpts.FloatABI == "hard" || CodeGenOpts.FloatABI.empty()) &&
         "Invalid Floating Point ABI!");
  Options.FloatABIType =
      llvm::StringSwitch<llvm::FloatABI::ABIType>(CodeGenOpts.FloatABI)
          .Case("soft", llvm::FloatABI::Soft)
          .Case("softfp", llvm::FloatABI::Soft)
          .Case("hard", llvm::FloatABI::Hard)
          .Default(llvm::FloatABI::Default);

  // Set FP fusion mode.
  switch (CodeGenOpts.getFPContractMode()) {
  case CodeGenOptions::FPC_Off:
    Options.AllowFPOpFusion = llvm::FPOpFusion::Strict;
    break;
  case CodeGenOptions::FPC_On:
    Options.AllowFPOpFusion = llvm::FPOpFusion::Standard;
    break;
  case CodeGenOptions::FPC_Fast:
    Options.AllowFPOpFusion = llvm::FPOpFusion::Fast;
    break;
  }

  Options.UseInitArray = CodeGenOpts.UseInitArray;
  Options.DisableIntegratedAS = CodeGenOpts.DisableIntegratedAS;
  Options.CompressDebugSections = CodeGenOpts.CompressDebugSections;
  Options.RelaxELFRelocations = CodeGenOpts.RelaxELFRelocations;

  // Set EABI version.
  Options.EABIVersion = llvm::StringSwitch<llvm::EABI>(TargetOpts.EABIVersion)
                            .Case("4", llvm::EABI::EABI4)
                            .Case("5", llvm::EABI::EABI5)
                            .Case("gnu", llvm::EABI::GNU)
                            .Default(llvm::EABI::Default);

  if (LangOpts.SjLjExceptions)
    Options.ExceptionModel = llvm::ExceptionHandling::SjLj;

  Options.LessPreciseFPMADOption = CodeGenOpts.LessPreciseFPMAD;
  Options.NoInfsFPMath = CodeGenOpts.NoInfsFPMath;
  Options.NoNaNsFPMath = CodeGenOpts.NoNaNsFPMath;
  Options.NoZerosInBSS = CodeGenOpts.NoZeroInitializedInBSS;
  Options.UnsafeFPMath = CodeGenOpts.UnsafeFPMath;
  Options.StackAlignmentOverride = CodeGenOpts.StackAlignment;
  Options.FunctionSections = CodeGenOpts.FunctionSections;
  Options.DataSections = CodeGenOpts.DataSections;
  Options.UniqueSectionNames = CodeGenOpts.UniqueSectionNames;
  Options.EmulatedTLS = CodeGenOpts.EmulatedTLS;
  Options.DebuggerTuning = CodeGenOpts.getDebuggerTuning();

  Options.MCOptions.MCRelaxAll = CodeGenOpts.RelaxAll;
  Options.MCOptions.MCSaveTempLabels = CodeGenOpts.SaveTempLabels;
  Options.MCOptions.MCUseDwarfDirectory = !CodeGenOpts.NoDwarfDirectoryAsm;
  Options.MCOptions.MCNoExecStack = CodeGenOpts.NoExecStack;
  Options.MCOptions.MCIncrementalLinkerCompatible =
      CodeGenOpts.IncrementalLinkerCompatible;
  Options.MCOptions.MCFatalWarnings = CodeGenOpts.FatalWarnings;
  Options.MCOptions.AsmVerbose = CodeGenOpts.AsmVerbose;
  Options.MCOptions.PreserveAsmComments = CodeGenOpts.PreserveAsmComments;
  Options.MCOptions.ABIName = TargetOpts.ABI;

  TM.reset(TheTarget->createTargetMachine(Triple, TargetOpts.CPU, FeaturesStr,
                                          Options, RM, CM, OptLevel));
}

bool EmitAssemblyHelper::AddEmitPasses(legacy::PassManager &CodeGenPasses,
                                       BackendAction Action,
                                       raw_pwrite_stream &OS) {
  // Add LibraryInfo.
  llvm::Triple TargetTriple(TheModule->getTargetTriple());
  std::unique_ptr<TargetLibraryInfoImpl> TLII(
      createTLII(TargetTriple, CodeGenOpts));
  CodeGenPasses.add(new TargetLibraryInfoWrapperPass(*TLII));

  // Normal mode, emit a .s or .o file by running the code generator. Note,
  // this also adds codegenerator level optimization passes.
  TargetMachine::CodeGenFileType CGFT = TargetMachine::CGFT_AssemblyFile;
  if (Action == Backend_EmitObj)
    CGFT = TargetMachine::CGFT_ObjectFile;
  else if (Action == Backend_EmitMCNull)
    CGFT = TargetMachine::CGFT_Null;
  else
    assert(Action == Backend_EmitAssembly && "Invalid action!");

  // Add ObjC ARC final-cleanup optimizations. This is done as part of the
  // "codegen" passes so that it isn't run multiple times when there is
  // inlining happening.
  if (CodeGenOpts.OptimizationLevel > 0)
    CodeGenPasses.add(createObjCARCContractPass());

  if (TM->addPassesToEmitFile(CodeGenPasses, OS, CGFT,
                              /*DisableVerify=*/!CodeGenOpts.VerifyModule)) {
    Diags.Report(diag::err_fe_unable_to_interface_with_target);
    return false;
  }

  return true;
}

void EmitAssemblyHelper::EmitAssembly(BackendAction Action,
                                      std::unique_ptr<raw_pwrite_stream> OS) {
  TimeRegion Region(llvm::TimePassesIsEnabled ? &CodeGenerationTime : nullptr);

  setCommandLineOpts();

  bool UsesCodeGen = (Action != Backend_EmitNothing &&
                      Action != Backend_EmitBC &&
                      Action != Backend_EmitLL);
  CreateTargetMachine(UsesCodeGen);

  if (UsesCodeGen && !TM)
    return;
  if (TM)
    TheModule->setDataLayout(TM->createDataLayout());

  // If we are performing a ThinLTO importing compile, load the function
  // index into memory and pass it into CreatePasses, which will add it
  // to the PassManagerBuilder and invoke LTO passes.
  std::unique_ptr<ModuleSummaryIndex> ModuleSummary;
  if (!CodeGenOpts.ThinLTOIndexFile.empty()) {
    ErrorOr<std::unique_ptr<ModuleSummaryIndex>> IndexOrErr =
        llvm::getModuleSummaryIndexForFile(
            CodeGenOpts.ThinLTOIndexFile, [&](const DiagnosticInfo &DI) {
              TheModule->getContext().diagnose(DI);
            });
    if (std::error_code EC = IndexOrErr.getError()) {
      std::string Error = EC.message();
      errs() << "Error loading index file '" << CodeGenOpts.ThinLTOIndexFile
             << "': " << Error << "\n";
      return;
    }
    ModuleSummary = std::move(IndexOrErr.get());
    assert(ModuleSummary && "Expected non-empty module summary index");
  }

  legacy::PassManager PerModulePasses;
  PerModulePasses.add(
      createTargetTransformInfoWrapperPass(getTargetIRAnalysis()));

  legacy::FunctionPassManager PerFunctionPasses(TheModule);
  PerFunctionPasses.add(
      createTargetTransformInfoWrapperPass(getTargetIRAnalysis()));

  CreatePasses(PerModulePasses, PerFunctionPasses, ModuleSummary.get());

  legacy::PassManager CodeGenPasses;
  CodeGenPasses.add(
      createTargetTransformInfoWrapperPass(getTargetIRAnalysis()));

  switch (Action) {
  case Backend_EmitNothing:
    break;

  case Backend_EmitBC:
    PerModulePasses.add(createBitcodeWriterPass(
        *OS, CodeGenOpts.EmitLLVMUseLists, CodeGenOpts.EmitSummaryIndex,
        CodeGenOpts.EmitSummaryIndex));
    break;

  case Backend_EmitLL:
    PerModulePasses.add(
        createPrintModulePass(*OS, "", CodeGenOpts.EmitLLVMUseLists));
    break;

  default:
    if (!AddEmitPasses(CodeGenPasses, Action, *OS))
      return;
  }

  // Before executing passes, print the final values of the LLVM options.
  cl::PrintOptionValues();

  // Run passes. For now we do all passes at once, but eventually we
  // would like to have the option of streaming code generation.

  {
    PrettyStackTraceString CrashInfo("Per-function optimization");

    PerFunctionPasses.doInitialization();
    for (Function &F : *TheModule)
      if (!F.isDeclaration())
        PerFunctionPasses.run(F);
    PerFunctionPasses.doFinalization();
  }

  {
    PrettyStackTraceString CrashInfo("Per-module optimization passes");
    PerModulePasses.run(*TheModule);
  }

  {
    PrettyStackTraceString CrashInfo("Code generation");
    CodeGenPasses.run(*TheModule);
  }
}

void clang::EmitBackendOutput(DiagnosticsEngine &Diags,
                              const CodeGenOptions &CGOpts,
                              const clang::TargetOptions &TOpts,
                              const LangOptions &LOpts, const llvm::DataLayout &TDesc,
                              Module *M, BackendAction Action,
                              std::unique_ptr<raw_pwrite_stream> OS) {
  EmitAssemblyHelper AsmHelper(Diags, CGOpts, TOpts, LOpts, M);

  AsmHelper.EmitAssembly(Action, std::move(OS));

  // Verify clang's TargetInfo DataLayout against the LLVM TargetMachine's
  // DataLayout.
  if (AsmHelper.TM) {
    std::string DLDesc = M->getDataLayout().getStringRepresentation();
    if (DLDesc != TDesc.getStringRepresentation()) {
      unsigned DiagID = Diags.getCustomDiagID(
          DiagnosticsEngine::Error, "backend data layout '%0' does not match "
                                    "expected target description '%1'");
      Diags.Report(DiagID) << DLDesc << TDesc.getStringRepresentation();
    }
  }
}

static const char* getSectionNameForBitcode(const Triple &T) {
  switch (T.getObjectFormat()) {
  case Triple::MachO:
    return "__LLVM,__bitcode";
  case Triple::COFF:
  case Triple::ELF:
  case Triple::UnknownObjectFormat:
    return ".llvmbc";
  }
  llvm_unreachable("Unimplemented ObjectFormatType");
}

static const char* getSectionNameForCommandline(const Triple &T) {
  switch (T.getObjectFormat()) {
  case Triple::MachO:
    return "__LLVM,__cmdline";
  case Triple::COFF:
  case Triple::ELF:
  case Triple::UnknownObjectFormat:
    return ".llvmcmd";
  }
  llvm_unreachable("Unimplemented ObjectFormatType");
}

// With -fembed-bitcode, save a copy of the llvm IR as data in the
// __LLVM,__bitcode section.
void clang::EmbedBitcode(llvm::Module *M, const CodeGenOptions &CGOpts,
                         llvm::MemoryBufferRef Buf) {
  if (CGOpts.getEmbedBitcode() == CodeGenOptions::Embed_Off)
    return;

  // Save llvm.compiler.used and remote it.
  SmallVector<Constant*, 2> UsedArray;
  SmallSet<GlobalValue*, 4> UsedGlobals;
  Type *UsedElementType = Type::getInt8Ty(M->getContext())->getPointerTo(0);
  GlobalVariable *Used = collectUsedGlobalVariables(*M, UsedGlobals, true);
  for (auto *GV : UsedGlobals) {
    if (GV->getName() != "llvm.embedded.module" &&
        GV->getName() != "llvm.cmdline")
      UsedArray.push_back(
          ConstantExpr::getPointerBitCastOrAddrSpaceCast(GV, UsedElementType));
  }
  if (Used)
    Used->eraseFromParent();

  // Embed the bitcode for the llvm module.
  std::string Data;
  ArrayRef<uint8_t> ModuleData;
  Triple T(M->getTargetTriple());
  // Create a constant that contains the bitcode.
  // In case of embedding a marker, ignore the input Buf and use the empty
  // ArrayRef. It is also legal to create a bitcode marker even Buf is empty.
  if (CGOpts.getEmbedBitcode() != CodeGenOptions::Embed_Marker) {
    if (!isBitcode((const unsigned char *)Buf.getBufferStart(),
                   (const unsigned char *)Buf.getBufferEnd())) {
      // If the input is LLVM Assembly, bitcode is produced by serializing
      // the module. Use-lists order need to be perserved in this case.
      llvm::raw_string_ostream OS(Data);
      llvm::WriteBitcodeToFile(M, OS, /* ShouldPreserveUseListOrder */ true);
      ModuleData =
          ArrayRef<uint8_t>((const uint8_t *)OS.str().data(), OS.str().size());
    } else
      // If the input is LLVM bitcode, write the input byte stream directly.
      ModuleData = ArrayRef<uint8_t>((const uint8_t *)Buf.getBufferStart(),
                                     Buf.getBufferSize());
  }
  llvm::Constant *ModuleConstant =
      llvm::ConstantDataArray::get(M->getContext(), ModuleData);
  llvm::GlobalVariable *GV = new llvm::GlobalVariable(
      *M, ModuleConstant->getType(), true, llvm::GlobalValue::PrivateLinkage,
      ModuleConstant);
  GV->setSection(getSectionNameForBitcode(T));
  UsedArray.push_back(
      ConstantExpr::getPointerBitCastOrAddrSpaceCast(GV, UsedElementType));
  if (llvm::GlobalVariable *Old =
          M->getGlobalVariable("llvm.embedded.module", true)) {
    assert(Old->hasOneUse() &&
           "llvm.embedded.module can only be used once in llvm.compiler.used");
    GV->takeName(Old);
    Old->eraseFromParent();
  } else {
    GV->setName("llvm.embedded.module");
  }

  // Skip if only bitcode needs to be embedded.
  if (CGOpts.getEmbedBitcode() != CodeGenOptions::Embed_Bitcode) {
    // Embed command-line options.
    ArrayRef<uint8_t> CmdData(const_cast<uint8_t *>(CGOpts.CmdArgs.data()),
                              CGOpts.CmdArgs.size());
    llvm::Constant *CmdConstant =
      llvm::ConstantDataArray::get(M->getContext(), CmdData);
    GV = new llvm::GlobalVariable(*M, CmdConstant->getType(), true,
                                  llvm::GlobalValue::PrivateLinkage,
                                  CmdConstant);
    GV->setSection(getSectionNameForCommandline(T));
    UsedArray.push_back(
        ConstantExpr::getPointerBitCastOrAddrSpaceCast(GV, UsedElementType));
    if (llvm::GlobalVariable *Old =
            M->getGlobalVariable("llvm.cmdline", true)) {
      assert(Old->hasOneUse() &&
             "llvm.cmdline can only be used once in llvm.compiler.used");
      GV->takeName(Old);
      Old->eraseFromParent();
    } else {
      GV->setName("llvm.cmdline");
    }
  }

  if (UsedArray.empty())
    return;

  // Recreate llvm.compiler.used.
  ArrayType *ATy = ArrayType::get(UsedElementType, UsedArray.size());
  auto *NewUsed = new GlobalVariable(
      *M, ATy, false, llvm::GlobalValue::AppendingLinkage,
      llvm::ConstantArray::get(ATy, UsedArray), "llvm.compiler.used");
  NewUsed->setSection("llvm.metadata");
}