LegacyPassManager.cpp

//===- LegacyPassManager.cpp - LLVM Pass Infrastructure Implementation ----===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file implements the legacy LLVM Pass Manager infrastructure.
//
//===----------------------------------------------------------------------===//

#include "llvm/IR/LegacyPassManager.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/IRPrintingPasses.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/LegacyPassManagers.h"
#include "llvm/IR/LegacyPassNameParser.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PassTimingInfo.h"
#include "llvm/Support/Chrono.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/Mutex.h"
#include "llvm/Support/TimeProfiler.h"
#include "llvm/Support/Timer.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <unordered_set>
using namespace llvm;

// See PassManagers.h for Pass Manager infrastructure overview.

//===----------------------------------------------------------------------===//
// Pass debugging information.  Often it is useful to find out what pass is
// running when a crash occurs in a utility.  When this library is compiled with
// debugging on, a command line option (--debug-pass) is enabled that causes the
// pass name to be printed before it executes.
//

namespace {
// Different debug levels that can be enabled...
enum PassDebugLevel {
  Disabled, Arguments, Structure, Executions, Details
};
}

static cl::opt<enum PassDebugLevel>
PassDebugging("debug-pass", cl::Hidden,
                  cl::desc("Print PassManager debugging information"),
                  cl::values(
  clEnumVal(Disabled  , "disable debug output"),
  clEnumVal(Arguments , "print pass arguments to pass to 'opt'"),
  clEnumVal(Structure , "print pass structure before run()"),
  clEnumVal(Executions, "print pass name before it is executed"),
  clEnumVal(Details   , "print pass details when it is executed")));

namespace {
typedef llvm::cl::list<const llvm::PassInfo *, bool, PassNameParser>
PassOptionList;
}

// Print IR out before/after specified passes.
static PassOptionList
PrintBefore("print-before",
            llvm::cl::desc("Print IR before specified passes"),
            cl::Hidden);

static PassOptionList
PrintAfter("print-after",
           llvm::cl::desc("Print IR after specified passes"),
           cl::Hidden);

static cl::opt<bool> PrintBeforeAll("print-before-all",
                                    llvm::cl::desc("Print IR before each pass"),
                                    cl::init(false), cl::Hidden);
static cl::opt<bool> PrintAfterAll("print-after-all",
                                   llvm::cl::desc("Print IR after each pass"),
                                   cl::init(false), cl::Hidden);

static cl::opt<bool>
    PrintModuleScope("print-module-scope",
                     cl::desc("When printing IR for print-[before|after]{-all} "
                              "always print a module IR"),
                     cl::init(false), cl::Hidden);

static cl::list<std::string>
    PrintFuncsList("filter-print-funcs", cl::value_desc("function names"),
                   cl::desc("Only print IR for functions whose name "
                            "match this for all print-[before|after][-all] "
                            "options"),
                   cl::CommaSeparated, cl::Hidden);

/// This is a helper to determine whether to print IR before or
/// after a pass.

bool llvm::shouldPrintBeforePass() {
  return PrintBeforeAll || !PrintBefore.empty();
}

bool llvm::shouldPrintAfterPass() {
  return PrintAfterAll || !PrintAfter.empty();
}

static bool ShouldPrintBeforeOrAfterPass(StringRef PassID,
                                         PassOptionList &PassesToPrint) {
  for (auto *PassInf : PassesToPrint) {
    if (PassInf)
      if (PassInf->getPassArgument() == PassID) {
        return true;
      }
  }
  return false;
}

bool llvm::shouldPrintBeforePass(StringRef PassID) {
  return PrintBeforeAll || ShouldPrintBeforeOrAfterPass(PassID, PrintBefore);
}

bool llvm::shouldPrintAfterPass(StringRef PassID) {
  return PrintAfterAll || ShouldPrintBeforeOrAfterPass(PassID, PrintAfter);
}

bool llvm::forcePrintModuleIR() { return PrintModuleScope; }

bool llvm::isFunctionInPrintList(StringRef FunctionName) {
  static std::unordered_set<std::string> PrintFuncNames(PrintFuncsList.begin(),
                                                        PrintFuncsList.end());
  return PrintFuncNames.empty() ||
         PrintFuncNames.count(std::string(FunctionName));
}
/// isPassDebuggingExecutionsOrMore - Return true if -debug-pass=Executions
/// or higher is specified.
bool PMDataManager::isPassDebuggingExecutionsOrMore() const {
  return PassDebugging >= Executions;
}

unsigned PMDataManager::initSizeRemarkInfo(
    Module &M, StringMap<std::pair<unsigned, unsigned>> &FunctionToInstrCount) {
  // Only calculate getInstructionCount if the size-info remark is requested.
  unsigned InstrCount = 0;

  // Collect instruction counts for every function. We'll use this to emit
  // per-function size remarks later.
  for (Function &F : M) {
    unsigned FCount = F.getInstructionCount();

    // Insert a record into FunctionToInstrCount keeping track of the current
    // size of the function as the first member of a pair. Set the second
    // member to 0; if the function is deleted by the pass, then when we get
    // here, we'll be able to let the user know that F no longer contributes to
    // the module.
    FunctionToInstrCount[F.getName().str()] =
        std::pair<unsigned, unsigned>(FCount, 0);
    InstrCount += FCount;
  }
  return InstrCount;
}

void PMDataManager::emitInstrCountChangedRemark(
    Pass *P, Module &M, int64_t Delta, unsigned CountBefore,
    StringMap<std::pair<unsigned, unsigned>> &FunctionToInstrCount,
    Function *F) {
  // If it's a pass manager, don't emit a remark. (This hinges on the assumption
  // that the only passes that return non-null with getAsPMDataManager are pass
  // managers.) The reason we have to do this is to avoid emitting remarks for
  // CGSCC passes.
  if (P->getAsPMDataManager())
    return;

  // Set to true if this isn't a module pass or CGSCC pass.
  bool CouldOnlyImpactOneFunction = (F != nullptr);

  // Helper lambda that updates the changes to the size of some function.
  auto UpdateFunctionChanges =
      [&FunctionToInstrCount](Function &MaybeChangedFn) {
        // Update the total module count.
        unsigned FnSize = MaybeChangedFn.getInstructionCount();
        auto It = FunctionToInstrCount.find(MaybeChangedFn.getName());

        // If we created a new function, then we need to add it to the map and
        // say that it changed from 0 instructions to FnSize.
        if (It == FunctionToInstrCount.end()) {
          FunctionToInstrCount[MaybeChangedFn.getName()] =
              std::pair<unsigned, unsigned>(0, FnSize);
          return;
        }
        // Insert the new function size into the second member of the pair. This
        // tells us whether or not this function changed in size.
        It->second.second = FnSize;
      };

  // We need to initially update all of the function sizes.
  // If no function was passed in, then we're either a module pass or an
  // CGSCC pass.
  if (!CouldOnlyImpactOneFunction)
    std::for_each(M.begin(), M.end(), UpdateFunctionChanges);
  else
    UpdateFunctionChanges(*F);

  // Do we have a function we can use to emit a remark?
  if (!CouldOnlyImpactOneFunction) {
    // We need a function containing at least one basic block in order to output
    // remarks. Since it's possible that the first function in the module
    // doesn't actually contain a basic block, we have to go and find one that's
    // suitable for emitting remarks.
    auto It = std::find_if(M.begin(), M.end(),
                          [](const Function &Fn) { return !Fn.empty(); });

    // Didn't find a function. Quit.
    if (It == M.end())
      return;

    // We found a function containing at least one basic block.
    F = &*It;
  }
  int64_t CountAfter = static_cast<int64_t>(CountBefore) + Delta;
  BasicBlock &BB = *F->begin();
  OptimizationRemarkAnalysis R("size-info", "IRSizeChange",
                               DiagnosticLocation(), &BB);
  // FIXME: Move ore namespace to DiagnosticInfo so that we can use it. This
  // would let us use NV instead of DiagnosticInfoOptimizationBase::Argument.
  R << DiagnosticInfoOptimizationBase::Argument("Pass", P->getPassName())
    << ": IR instruction count changed from "
    << DiagnosticInfoOptimizationBase::Argument("IRInstrsBefore", CountBefore)
    << " to "
    << DiagnosticInfoOptimizationBase::Argument("IRInstrsAfter", CountAfter)
    << "; Delta: "
    << DiagnosticInfoOptimizationBase::Argument("DeltaInstrCount", Delta);
  F->getContext().diagnose(R); // Not using ORE for layering reasons.

  // Emit per-function size change remarks separately.
  std::string PassName = P->getPassName().str();

  // Helper lambda that emits a remark when the size of a function has changed.
  auto EmitFunctionSizeChangedRemark = [&FunctionToInstrCount, &F, &BB,
                                        &PassName](StringRef Fname) {
    unsigned FnCountBefore, FnCountAfter;
    std::pair<unsigned, unsigned> &Change = FunctionToInstrCount[Fname];
    std::tie(FnCountBefore, FnCountAfter) = Change;
    int64_t FnDelta = static_cast<int64_t>(FnCountAfter) -
                      static_cast<int64_t>(FnCountBefore);

    if (FnDelta == 0)
      return;

    // FIXME: We shouldn't use BB for the location here. Unfortunately, because
    // the function that we're looking at could have been deleted, we can't use
    // it for the source location. We *want* remarks when a function is deleted
    // though, so we're kind of stuck here as is. (This remark, along with the
    // whole-module size change remarks really ought not to have source
    // locations at all.)
    OptimizationRemarkAnalysis FR("size-info", "FunctionIRSizeChange",
                                  DiagnosticLocation(), &BB);
    FR << DiagnosticInfoOptimizationBase::Argument("Pass", PassName)
       << ": Function: "
       << DiagnosticInfoOptimizationBase::Argument("Function", Fname)
       << ": IR instruction count changed from "
       << DiagnosticInfoOptimizationBase::Argument("IRInstrsBefore",
                                                   FnCountBefore)
       << " to "
       << DiagnosticInfoOptimizationBase::Argument("IRInstrsAfter",
                                                   FnCountAfter)
       << "; Delta: "
       << DiagnosticInfoOptimizationBase::Argument("DeltaInstrCount", FnDelta);
    F->getContext().diagnose(FR);

    // Update the function size.
    Change.first = FnCountAfter;
  };

  // Are we looking at more than one function? If so, emit remarks for all of
  // the functions in the module. Otherwise, only emit one remark.
  if (!CouldOnlyImpactOneFunction)
    std::for_each(FunctionToInstrCount.keys().begin(),
                  FunctionToInstrCount.keys().end(),
                  EmitFunctionSizeChangedRemark);
  else
    EmitFunctionSizeChangedRemark(F->getName().str());
}

void PassManagerPrettyStackEntry::print(raw_ostream &OS) const {
  if (!V && !M)
    OS << "Releasing pass '";
  else
    OS << "Running pass '";

  OS << P->getPassName() << "'";

  if (M) {
    OS << " on module '" << M->getModuleIdentifier() << "'.\n";
    return;
  }
  if (!V) {
    OS << '\n';
    return;
  }

  OS << " on ";
  if (isa<Function>(V))
    OS << "function";
  else if (isa<BasicBlock>(V))
    OS << "basic block";
  else
    OS << "value";

  OS << " '";
  V->printAsOperand(OS, /*PrintType=*/false, M);
  OS << "'\n";
}

namespace llvm {
namespace legacy {
//===----------------------------------------------------------------------===//
// FunctionPassManagerImpl
//
/// FunctionPassManagerImpl manages FPPassManagers
class FunctionPassManagerImpl : public Pass,
                                public PMDataManager,
                                public PMTopLevelManager {
  virtual void anchor();
private:
  bool wasRun;
public:
  static char ID;
  explicit FunctionPassManagerImpl() :
    Pass(PT_PassManager, ID), PMDataManager(),
    PMTopLevelManager(new FPPassManager()), wasRun(false) {}

  /// \copydoc FunctionPassManager::add()
  void add(Pass *P) {
    schedulePass(P);
  }

  /// createPrinterPass - Get a function printer pass.
  Pass *createPrinterPass(raw_ostream &O,
                          const std::string &Banner) const override {
    return createPrintFunctionPass(O, Banner);
  }

  // Prepare for running an on the fly pass, freeing memory if needed
  // from a previous run.
  void releaseMemoryOnTheFly();

  /// run - Execute all of the passes scheduled for execution.  Keep track of
  /// whether any of the passes modifies the module, and if so, return true.
  bool run(Function &F);

  /// doInitialization - Run all of the initializers for the function passes.
  ///
  bool doInitialization(Module &M) override;

  /// doFinalization - Run all of the finalizers for the function passes.
  ///
  bool doFinalization(Module &M) override;


  PMDataManager *getAsPMDataManager() override { return this; }
  Pass *getAsPass() override { return this; }
  PassManagerType getTopLevelPassManagerType() override {
    return PMT_FunctionPassManager;
  }

  /// Pass Manager itself does not invalidate any analysis info.
  void getAnalysisUsage(AnalysisUsage &Info) const override {
    Info.setPreservesAll();
  }

  FPPassManager *getContainedManager(unsigned N) {
    assert(N < PassManagers.size() && "Pass number out of range!");
    FPPassManager *FP = static_cast<FPPassManager *>(PassManagers[N]);
    return FP;
  }

  void dumpPassStructure(unsigned Offset) override {
    for (unsigned I = 0; I < getNumContainedManagers(); ++I)
      getContainedManager(I)->dumpPassStructure(Offset);
  }
};

void FunctionPassManagerImpl::anchor() {}

char FunctionPassManagerImpl::ID = 0;

//===----------------------------------------------------------------------===//
// FunctionPassManagerImpl implementation
//
bool FunctionPassManagerImpl::doInitialization(Module &M) {
  bool Changed = false;

  dumpArguments();
  dumpPasses();

  for (ImmutablePass *ImPass : getImmutablePasses())
    Changed |= ImPass->doInitialization(M);

  for (unsigned Index = 0; Index < getNumContainedManagers(); ++Index)
    Changed |= getContainedManager(Index)->doInitialization(M);

  return Changed;
}

bool FunctionPassManagerImpl::doFinalization(Module &M) {
  bool Changed = false;

  for (int Index = getNumContainedManagers() - 1; Index >= 0; --Index)
    Changed |= getContainedManager(Index)->doFinalization(M);

  for (ImmutablePass *ImPass : getImmutablePasses())
    Changed |= ImPass->doFinalization(M);

  return Changed;
}

void FunctionPassManagerImpl::releaseMemoryOnTheFly() {
  if (!wasRun)
    return;
  for (unsigned Index = 0; Index < getNumContainedManagers(); ++Index) {
    FPPassManager *FPPM = getContainedManager(Index);
    for (unsigned Index = 0; Index < FPPM->getNumContainedPasses(); ++Index) {
      FPPM->getContainedPass(Index)->releaseMemory();
    }
  }
  wasRun = false;
}

// Execute all the passes managed by this top level manager.
// Return true if any function is modified by a pass.
bool FunctionPassManagerImpl::run(Function &F) {
  bool Changed = false;

  initializeAllAnalysisInfo();
  for (unsigned Index = 0; Index < getNumContainedManagers(); ++Index) {
    Changed |= getContainedManager(Index)->runOnFunction(F);
    F.getContext().yield();
  }

  for (unsigned Index = 0; Index < getNumContainedManagers(); ++Index)
    getContainedManager(Index)->cleanup();

  wasRun = true;
  return Changed;
}
} // namespace legacy
} // namespace llvm

namespace {
//===----------------------------------------------------------------------===//
// MPPassManager
//
/// MPPassManager manages ModulePasses and function pass managers.
/// It batches all Module passes and function pass managers together and
/// sequences them to process one module.
class MPPassManager : public Pass, public PMDataManager {
public:
  static char ID;
  explicit MPPassManager() :
    Pass(PT_PassManager, ID), PMDataManager() { }

  // Delete on the fly managers.
  ~MPPassManager() override {
    for (auto &OnTheFlyManager : OnTheFlyManagers) {
      legacy::FunctionPassManagerImpl *FPP = OnTheFlyManager.second;
      delete FPP;
    }
  }

  /// createPrinterPass - Get a module printer pass.
  Pass *createPrinterPass(raw_ostream &O,
                          const std::string &Banner) const override {
    return createPrintModulePass(O, Banner);
  }

  /// run - Execute all of the passes scheduled for execution.  Keep track of
  /// whether any of the passes modifies the module, and if so, return true.
  bool runOnModule(Module &M);

  using llvm::Pass::doInitialization;
  using llvm::Pass::doFinalization;

  /// Pass Manager itself does not invalidate any analysis info.
  void getAnalysisUsage(AnalysisUsage &Info) const override {
    Info.setPreservesAll();
  }

  /// Add RequiredPass into list of lower level passes required by pass P.
  /// RequiredPass is run on the fly by Pass Manager when P requests it
  /// through getAnalysis interface.
  void addLowerLevelRequiredPass(Pass *P, Pass *RequiredPass) override;

  /// Return function pass corresponding to PassInfo PI, that is
  /// required by module pass MP. Instantiate analysis pass, by using
  /// its runOnFunction() for function F.
  std::tuple<Pass *, bool> getOnTheFlyPass(Pass *MP, AnalysisID PI,
                                           Function &F) override;

  StringRef getPassName() const override { return "Module Pass Manager"; }

  PMDataManager *getAsPMDataManager() override { return this; }
  Pass *getAsPass() override { return this; }

  // Print passes managed by this manager
  void dumpPassStructure(unsigned Offset) override {
    dbgs().indent(Offset*2) << "ModulePass Manager\n";
    for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
      ModulePass *MP = getContainedPass(Index);
      MP->dumpPassStructure(Offset + 1);
      MapVector<Pass *, legacy::FunctionPassManagerImpl *>::const_iterator I =
          OnTheFlyManagers.find(MP);
      if (I != OnTheFlyManagers.end())
        I->second->dumpPassStructure(Offset + 2);
      dumpLastUses(MP, Offset+1);
    }
  }

  ModulePass *getContainedPass(unsigned N) {
    assert(N < PassVector.size() && "Pass number out of range!");
    return static_cast<ModulePass *>(PassVector[N]);
  }

  PassManagerType getPassManagerType() const override {
    return PMT_ModulePassManager;
  }

 private:
  /// Collection of on the fly FPPassManagers. These managers manage
  /// function passes that are required by module passes.
   MapVector<Pass *, legacy::FunctionPassManagerImpl *> OnTheFlyManagers;
};

char MPPassManager::ID = 0;
} // End anonymous namespace

namespace llvm {
namespace legacy {
//===----------------------------------------------------------------------===//
// PassManagerImpl
//

/// PassManagerImpl manages MPPassManagers
class PassManagerImpl : public Pass,
                        public PMDataManager,
                        public PMTopLevelManager {
  virtual void anchor();

public:
  static char ID;
  explicit PassManagerImpl() :
    Pass(PT_PassManager, ID), PMDataManager(),
                              PMTopLevelManager(new MPPassManager()) {}

  /// \copydoc PassManager::add()
  void add(Pass *P) {
    schedulePass(P);
  }

  /// createPrinterPass - Get a module printer pass.
  Pass *createPrinterPass(raw_ostream &O,
                          const std::string &Banner) const override {
    return createPrintModulePass(O, Banner);
  }

  /// run - Execute all of the passes scheduled for execution.  Keep track of
  /// whether any of the passes modifies the module, and if so, return true.
  bool run(Module &M);

  using llvm::Pass::doInitialization;
  using llvm::Pass::doFinalization;

  /// Pass Manager itself does not invalidate any analysis info.
  void getAnalysisUsage(AnalysisUsage &Info) const override {
    Info.setPreservesAll();
  }

  PMDataManager *getAsPMDataManager() override { return this; }
  Pass *getAsPass() override { return this; }
  PassManagerType getTopLevelPassManagerType() override {
    return PMT_ModulePassManager;
  }

  MPPassManager *getContainedManager(unsigned N) {
    assert(N < PassManagers.size() && "Pass number out of range!");
    MPPassManager *MP = static_cast<MPPassManager *>(PassManagers[N]);
    return MP;
  }
};

void PassManagerImpl::anchor() {}

char PassManagerImpl::ID = 0;

//===----------------------------------------------------------------------===//
// PassManagerImpl implementation

//
/// run - Execute all of the passes scheduled for execution.  Keep track of
/// whether any of the passes modifies the module, and if so, return true.
bool PassManagerImpl::run(Module &M) {
  bool Changed = false;

  dumpArguments();
  dumpPasses();

  for (ImmutablePass *ImPass : getImmutablePasses())
    Changed |= ImPass->doInitialization(M);

  initializeAllAnalysisInfo();
  for (unsigned Index = 0; Index < getNumContainedManagers(); ++Index) {
    Changed |= getContainedManager(Index)->runOnModule(M);
    M.getContext().yield();
  }

  for (ImmutablePass *ImPass : getImmutablePasses())
    Changed |= ImPass->doFinalization(M);

  return Changed;
}
} // namespace legacy
} // namespace llvm

//===----------------------------------------------------------------------===//
// PMTopLevelManager implementation

/// Initialize top level manager. Create first pass manager.
PMTopLevelManager::PMTopLevelManager(PMDataManager *PMDM) {
  PMDM->setTopLevelManager(this);
  addPassManager(PMDM);
  activeStack.push(PMDM);
}

/// Set pass P as the last user of the given analysis passes.
void
PMTopLevelManager::setLastUser(ArrayRef<Pass*> AnalysisPasses, Pass *P) {
  unsigned PDepth = 0;
  if (P->getResolver())
    PDepth = P->getResolver()->getPMDataManager().getDepth();

  for (Pass *AP : AnalysisPasses) {
    LastUser[AP] = P;

    if (P == AP)
      continue;

    // Update the last users of passes that are required transitive by AP.
    AnalysisUsage *AnUsage = findAnalysisUsage(AP);
    const AnalysisUsage::VectorType &IDs = AnUsage->getRequiredTransitiveSet();
    SmallVector<Pass *, 12> LastUses;
    SmallVector<Pass *, 12> LastPMUses;
    for (AnalysisID ID : IDs) {
      Pass *AnalysisPass = findAnalysisPass(ID);
      assert(AnalysisPass && "Expected analysis pass to exist.");
      AnalysisResolver *AR = AnalysisPass->getResolver();
      assert(AR && "Expected analysis resolver to exist.");
      unsigned APDepth = AR->getPMDataManager().getDepth();

      if (PDepth == APDepth)
        LastUses.push_back(AnalysisPass);
      else if (PDepth > APDepth)
        LastPMUses.push_back(AnalysisPass);
    }

    setLastUser(LastUses, P);

    // If this pass has a corresponding pass manager, push higher level
    // analysis to this pass manager.
    if (P->getResolver())
      setLastUser(LastPMUses, P->getResolver()->getPMDataManager().getAsPass());


    // If AP is the last user of other passes then make P last user of
    // such passes.
    for (auto LU : LastUser) {
      if (LU.second == AP)
        // DenseMap iterator is not invalidated here because
        // this is just updating existing entries.
        LastUser[LU.first] = P;
    }
  }
}

/// Collect passes whose last user is P
void PMTopLevelManager::collectLastUses(SmallVectorImpl<Pass *> &LastUses,
                                        Pass *P) {
  DenseMap<Pass *, SmallPtrSet<Pass *, 8> >::iterator DMI =
    InversedLastUser.find(P);
  if (DMI == InversedLastUser.end())
    return;

  SmallPtrSet<Pass *, 8> &LU = DMI->second;
  for (Pass *LUP : LU) {
    LastUses.push_back(LUP);
  }

}

AnalysisUsage *PMTopLevelManager::findAnalysisUsage(Pass *P) {
  AnalysisUsage *AnUsage = nullptr;
  auto DMI = AnUsageMap.find(P);
  if (DMI != AnUsageMap.end())
    AnUsage = DMI->second;
  else {
    // Look up the analysis usage from the pass instance (different instances
    // of the same pass can produce different results), but unique the
    // resulting object to reduce memory usage.  This helps to greatly reduce
    // memory usage when we have many instances of only a few pass types
    // (e.g. instcombine, simplifycfg, etc...) which tend to share a fixed set
    // of dependencies.
    AnalysisUsage AU;
    P->getAnalysisUsage(AU);

    AUFoldingSetNode* Node = nullptr;
    FoldingSetNodeID ID;
    AUFoldingSetNode::Profile(ID, AU);
    void *IP = nullptr;
    if (auto *N = UniqueAnalysisUsages.FindNodeOrInsertPos(ID, IP))
      Node = N;
    else {
      Node = new (AUFoldingSetNodeAllocator.Allocate()) AUFoldingSetNode(AU);
      UniqueAnalysisUsages.InsertNode(Node, IP);
    }
    assert(Node && "cached analysis usage must be non null");

    AnUsageMap[P] = &Node->AU;
    AnUsage = &Node->AU;
  }
  return AnUsage;
}

/// Schedule pass P for execution. Make sure that passes required by
/// P are run before P is run. Update analysis info maintained by
/// the manager. Remove dead passes. This is a recursive function.
void PMTopLevelManager::schedulePass(Pass *P) {

  // TODO : Allocate function manager for this pass, other wise required set
  // may be inserted into previous function manager

  // Give pass a chance to prepare the stage.
  P->preparePassManager(activeStack);

  // If P is an analysis pass and it is available then do not
  // generate the analysis again. Stale analysis info should not be
  // available at this point.
  const PassInfo *PI = findAnalysisPassInfo(P->getPassID());
  if (PI && PI->isAnalysis() && findAnalysisPass(P->getPassID())) {
    // Remove any cached AnalysisUsage information.
    AnUsageMap.erase(P);
    delete P;
    return;
  }

  AnalysisUsage *AnUsage = findAnalysisUsage(P);

  bool checkAnalysis = true;
  while (checkAnalysis) {
    checkAnalysis = false;

    const AnalysisUsage::VectorType &RequiredSet = AnUsage->getRequiredSet();
    for (const AnalysisID ID : RequiredSet) {

      Pass *AnalysisPass = findAnalysisPass(ID);
      if (!AnalysisPass) {
        const PassInfo *PI = findAnalysisPassInfo(ID);

        if (!PI) {
          // Pass P is not in the global PassRegistry
          dbgs() << "Pass '"  << P->getPassName() << "' is not initialized." << "\n";
          dbgs() << "Verify if there is a pass dependency cycle." << "\n";
          dbgs() << "Required Passes:" << "\n";
          for (const AnalysisID ID2 : RequiredSet) {
            if (ID == ID2)
              break;
            Pass *AnalysisPass2 = findAnalysisPass(ID2);
            if (AnalysisPass2) {
              dbgs() << "\t" << AnalysisPass2->getPassName() << "\n";
            } else {
              dbgs() << "\t"   << "Error: Required pass not found! Possible causes:"  << "\n";
              dbgs() << "\t\t" << "- Pass misconfiguration (e.g.: missing macros)"    << "\n";
              dbgs() << "\t\t" << "- Corruption of the global PassRegistry"           << "\n";
            }
          }
        }

        assert(PI && "Expected required passes to be initialized");
        AnalysisPass = PI->createPass();
        if (P->getPotentialPassManagerType () ==
            AnalysisPass->getPotentialPassManagerType())
          // Schedule analysis pass that is managed by the same pass manager.
          schedulePass(AnalysisPass);
        else if (P->getPotentialPassManagerType () >
                 AnalysisPass->getPotentialPassManagerType()) {
          // Schedule analysis pass that is managed by a new manager.
          schedulePass(AnalysisPass);
          // Recheck analysis passes to ensure that required analyses that
          // are already checked are still available.
          checkAnalysis = true;
        } else
          // Do not schedule this analysis. Lower level analysis
          // passes are run on the fly.
          delete AnalysisPass;
      }
    }
  }

  // Now all required passes are available.
  if (ImmutablePass *IP = P->getAsImmutablePass()) {
    // P is a immutable pass and it will be managed by this
    // top level manager. Set up analysis resolver to connect them.
    PMDataManager *DM = getAsPMDataManager();
    AnalysisResolver *AR = new AnalysisResolver(*DM);
    P->setResolver(AR);
    DM->initializeAnalysisImpl(P);
    addImmutablePass(IP);
    DM->recordAvailableAnalysis(IP);
    return;
  }

  if (PI && !PI->isAnalysis() && shouldPrintBeforePass(PI->getPassArgument())) {
    Pass *PP = P->createPrinterPass(
        dbgs(), ("*** IR Dump Before " + P->getPassName() + " ***").str());
    PP->assignPassManager(activeStack, getTopLevelPassManagerType());
  }

  // Add the requested pass to the best available pass manager.
  P->assignPassManager(activeStack, getTopLevelPassManagerType());

  if (PI && !PI->isAnalysis() && shouldPrintAfterPass(PI->getPassArgument())) {
    Pass *PP = P->createPrinterPass(
        dbgs(), ("*** IR Dump After " + P->getPassName() + " ***").str());
    PP->assignPassManager(activeStack, getTopLevelPassManagerType());
  }
}

/// Find the pass that implements Analysis AID. Search immutable
/// passes and all pass managers. If desired pass is not found
/// then return NULL.
Pass *PMTopLevelManager::findAnalysisPass(AnalysisID AID) {
  // For immutable passes we have a direct mapping from ID to pass, so check
  // that first.
  if (Pass *P = ImmutablePassMap.lookup(AID))
    return P;

  // Check pass managers
  for (PMDataManager *PassManager : PassManagers)
    if (Pass *P = PassManager->findAnalysisPass(AID, false))
      return P;

  // Check other pass managers
  for (PMDataManager *IndirectPassManager : IndirectPassManagers)
    if (Pass *P = IndirectPassManager->findAnalysisPass(AID, false))
      return P;

  return nullptr;
}

const PassInfo *PMTopLevelManager::findAnalysisPassInfo(AnalysisID AID) const {
  const PassInfo *&PI = AnalysisPassInfos[AID];
  if (!PI)
    PI = PassRegistry::getPassRegistry()->getPassInfo(AID);
  else
    assert(PI == PassRegistry::getPassRegistry()->getPassInfo(AID) &&
           "The pass info pointer changed for an analysis ID!");

  return PI;
}

void PMTopLevelManager::addImmutablePass(ImmutablePass *P) {
  P->initializePass();
  ImmutablePasses.push_back(P);

  // Add this pass to the map from its analysis ID. We clobber any prior runs
  // of the pass in the map so that the last one added is the one found when
  // doing lookups.
  AnalysisID AID = P->getPassID();
  ImmutablePassMap[AID] = P;

  // Also add any interfaces implemented by the immutable pass to the map for
  // fast lookup.
  const PassInfo *PassInf = findAnalysisPassInfo(AID);
  assert(PassInf && "Expected all immutable passes to be initialized");
  for (const PassInfo *ImmPI : PassInf->getInterfacesImplemented())
    ImmutablePassMap[ImmPI->getTypeInfo()] = P;
}

// Print passes managed by this top level manager.
void PMTopLevelManager::dumpPasses() const {

  if (PassDebugging < Structure)
    return;

  // Print out the immutable passes
  for (unsigned i = 0, e = ImmutablePasses.size(); i != e; ++i) {
    ImmutablePasses[i]->dumpPassStructure(0);
  }

  // Every class that derives from PMDataManager also derives from Pass
  // (sometimes indirectly), but there's no inheritance relationship
  // between PMDataManager and Pass, so we have to getAsPass to get
  // from a PMDataManager* to a Pass*.
  for (PMDataManager *Manager : PassManagers)
    Manager->getAsPass()->dumpPassStructure(1);
}

void PMTopLevelManager::dumpArguments() const {

  if (PassDebugging < Arguments)
    return;

  dbgs() << "Pass Arguments: ";
  for (ImmutablePass *P : ImmutablePasses)
    if (const PassInfo *PI = findAnalysisPassInfo(P->getPassID())) {
      assert(PI && "Expected all immutable passes to be initialized");
      if (!PI->isAnalysisGroup())
        dbgs() << " -" << PI->getPassArgument();
    }
  for (PMDataManager *PM : PassManagers)
    PM->dumpPassArguments();
  dbgs() << "\n";
}

void PMTopLevelManager::initializeAllAnalysisInfo() {
  for (PMDataManager *PM : PassManagers)
    PM->initializeAnalysisInfo();

  // Initailize other pass managers
  for (PMDataManager *IPM : IndirectPassManagers)
    IPM->initializeAnalysisInfo();

  for (auto LU : LastUser) {
    SmallPtrSet<Pass *, 8> &L = InversedLastUser[LU.second];
    L.insert(LU.first);
  }
}

/// Destructor
PMTopLevelManager::~PMTopLevelManager() {
  for (PMDataManager *PM : PassManagers)
    delete PM;

  for (ImmutablePass *P : ImmutablePasses)
    delete P;
}

//===----------------------------------------------------------------------===//
// PMDataManager implementation

/// Augement AvailableAnalysis by adding analysis made available by pass P.
void PMDataManager::recordAvailableAnalysis(Pass *P) {
  AnalysisID PI = P->getPassID();

  AvailableAnalysis[PI] = P;

  assert(!AvailableAnalysis.empty());

  // This pass is the current implementation of all of the interfaces it
  // implements as well.
  const PassInfo *PInf = TPM->findAnalysisPassInfo(PI);
  if (!PInf) return;
  const std::vector<const PassInfo*> &II = PInf->getInterfacesImplemented();
  for (unsigned i = 0, e = II.size(); i != e; ++i)
    AvailableAnalysis[II[i]->getTypeInfo()] = P;
}

// Return true if P preserves high level analysis used by other
// passes managed by this manager
bool PMDataManager::preserveHigherLevelAnalysis(Pass *P) {
  AnalysisUsage *AnUsage = TPM->findAnalysisUsage(P);
  if (AnUsage->getPreservesAll())
    return true;

  const AnalysisUsage::VectorType &PreservedSet = AnUsage->getPreservedSet();
  for (Pass *P1 : HigherLevelAnalysis) {
    if (P1->getAsImmutablePass() == nullptr &&
        !is_contained(PreservedSet, P1->getPassID()))
      return false;
  }

  return true;
}

/// verifyPreservedAnalysis -- Verify analysis preserved by pass P.
void PMDataManager::verifyPreservedAnalysis(Pass *P) {
  // Don't do this unless assertions are enabled.
#ifdef NDEBUG
  return;
#endif
  AnalysisUsage *AnUsage = TPM->findAnalysisUsage(P);
  const AnalysisUsage::VectorType &PreservedSet = AnUsage->getPreservedSet();

  // Verify preserved analysis
  for (AnalysisID AID : PreservedSet) {
    if (Pass *AP = findAnalysisPass(AID, true)) {
      TimeRegion PassTimer(getPassTimer(AP));
      AP->verifyAnalysis();
    }
  }
}

/// Remove Analysis not preserved by Pass P
void PMDataManager::removeNotPreservedAnalysis(Pass *P) {
  AnalysisUsage *AnUsage = TPM->findAnalysisUsage(P);
  if (AnUsage->getPreservesAll())
    return;

  const AnalysisUsage::VectorType &PreservedSet = AnUsage->getPreservedSet();
  for (DenseMap<AnalysisID, Pass*>::iterator I = AvailableAnalysis.begin(),
         E = AvailableAnalysis.end(); I != E; ) {
    DenseMap<AnalysisID, Pass*>::iterator Info = I++;
    if (Info->second->getAsImmutablePass() == nullptr &&
        !is_contained(PreservedSet, Info->first)) {
      // Remove this analysis
      if (PassDebugging >= Details) {
        Pass *S = Info->second;
        dbgs() << " -- '" <<  P->getPassName() << "' is not preserving '";
        dbgs() << S->getPassName() << "'\n";
      }
      AvailableAnalysis.erase(Info);
    }
  }

  // Check inherited analysis also. If P is not preserving analysis
  // provided by parent manager then remove it here.
  for (unsigned Index = 0; Index < PMT_Last; ++Index) {

    if (!InheritedAnalysis[Index])
      continue;

    for (DenseMap<AnalysisID, Pass*>::iterator
           I = InheritedAnalysis[Index]->begin(),
           E = InheritedAnalysis[Index]->end(); I != E; ) {
      DenseMap<AnalysisID, Pass *>::iterator Info = I++;
      if (Info->second->getAsImmutablePass() == nullptr &&
          !is_contained(PreservedSet, Info->first)) {
        // Remove this analysis
        if (PassDebugging >= Details) {
          Pass *S = Info->second;
          dbgs() << " -- '" <<  P->getPassName() << "' is not preserving '";
          dbgs() << S->getPassName() << "'\n";
        }
        InheritedAnalysis[Index]->erase(Info);
      }
    }
  }
}

/// Remove analysis passes that are not used any longer
void PMDataManager::removeDeadPasses(Pass *P, StringRef Msg,
                                     enum PassDebuggingString DBG_STR) {

  SmallVector<Pass *, 12> DeadPasses;

  // If this is a on the fly manager then it does not have TPM.
  if (!TPM)
    return;

  TPM->collectLastUses(DeadPasses, P);

  if (PassDebugging >= Details && !DeadPasses.empty()) {
    dbgs() << " -*- '" <<  P->getPassName();
    dbgs() << "' is the last user of following pass instances.";
    dbgs() << " Free these instances\n";
  }

  for (Pass *P : DeadPasses)
    freePass(P, Msg, DBG_STR);
}

void PMDataManager::freePass(Pass *P, StringRef Msg,
                             enum PassDebuggingString DBG_STR) {
  dumpPassInfo(P, FREEING_MSG, DBG_STR, Msg);

  {
    // If the pass crashes releasing memory, remember this.
    PassManagerPrettyStackEntry X(P);
    TimeRegion PassTimer(getPassTimer(P));

    P->releaseMemory();
  }

  AnalysisID PI = P->getPassID();
  if (const PassInfo *PInf = TPM->findAnalysisPassInfo(PI)) {
    // Remove the pass itself (if it is not already removed).
    AvailableAnalysis.erase(PI);

    // Remove all interfaces this pass implements, for which it is also
    // listed as the available implementation.
    const std::vector<const PassInfo*> &II = PInf->getInterfacesImplemented();
    for (unsigned i = 0, e = II.size(); i != e; ++i) {
      DenseMap<AnalysisID, Pass*>::iterator Pos =
        AvailableAnalysis.find(II[i]->getTypeInfo());
      if (Pos != AvailableAnalysis.end() && Pos->second == P)
        AvailableAnalysis.erase(Pos);
    }
  }
}

/// Add pass P into the PassVector. Update
/// AvailableAnalysis appropriately if ProcessAnalysis is true.
void PMDataManager::add(Pass *P, bool ProcessAnalysis) {
  // This manager is going to manage pass P. Set up analysis resolver
  // to connect them.
  AnalysisResolver *AR = new AnalysisResolver(*this);
  P->setResolver(AR);

  // If a FunctionPass F is the last user of ModulePass info M
  // then the F's manager, not F, records itself as a last user of M.
  SmallVector<Pass *, 12> TransferLastUses;

  if (!ProcessAnalysis) {
    // Add pass
    PassVector.push_back(P);
    return;
  }

  // At the moment, this pass is the last user of all required passes.
  SmallVector<Pass *, 12> LastUses;
  SmallVector<Pass *, 8> UsedPasses;
  SmallVector<AnalysisID, 8> ReqAnalysisNotAvailable;

  unsigned PDepth = this->getDepth();

  collectRequiredAndUsedAnalyses(UsedPasses, ReqAnalysisNotAvailable, P);
  for (Pass *PUsed : UsedPasses) {
    unsigned RDepth = 0;

    assert(PUsed->getResolver() && "Analysis Resolver is not set");
    PMDataManager &DM = PUsed->getResolver()->getPMDataManager();
    RDepth = DM.getDepth();

    if (PDepth == RDepth)
      LastUses.push_back(PUsed);
    else if (PDepth > RDepth) {
      // Let the parent claim responsibility of last use
      TransferLastUses.push_back(PUsed);
      // Keep track of higher level analysis used by this manager.
      HigherLevelAnalysis.push_back(PUsed);
    } else
      llvm_unreachable("Unable to accommodate Used Pass");
  }

  // Set P as P's last user until someone starts using P.
  // However, if P is a Pass Manager then it does not need
  // to record its last user.
  if (!P->getAsPMDataManager())
    LastUses.push_back(P);
  TPM->setLastUser(LastUses, P);

  if (!TransferLastUses.empty()) {
    Pass *My_PM = getAsPass();
    TPM->setLastUser(TransferLastUses, My_PM);
    TransferLastUses.clear();
  }

  // Now, take care of required analyses that are not available.
  for (AnalysisID ID : ReqAnalysisNotAvailable) {
    const PassInfo *PI = TPM->findAnalysisPassInfo(ID);
    Pass *AnalysisPass = PI->createPass();
    this->addLowerLevelRequiredPass(P, AnalysisPass);
  }

  // Take a note of analysis required and made available by this pass.
  // Remove the analysis not preserved by this pass
  removeNotPreservedAnalysis(P);
  recordAvailableAnalysis(P);

  // Add pass
  PassVector.push_back(P);
}


/// Populate UP with analysis pass that are used or required by
/// pass P and are available. Populate RP_NotAvail with analysis
/// pass that are required by pass P but are not available.
void PMDataManager::collectRequiredAndUsedAnalyses(
    SmallVectorImpl<Pass *> &UP, SmallVectorImpl<AnalysisID> &RP_NotAvail,
    Pass *P) {
  AnalysisUsage *AnUsage = TPM->findAnalysisUsage(P);

  for (const auto &UsedID : AnUsage->getUsedSet())
    if (Pass *AnalysisPass = findAnalysisPass(UsedID, true))
      UP.push_back(AnalysisPass);

  for (const auto &RequiredID : AnUsage->getRequiredSet())
    if (Pass *AnalysisPass = findAnalysisPass(RequiredID, true))
      UP.push_back(AnalysisPass);
    else
      RP_NotAvail.push_back(RequiredID);

  for (const auto &RequiredID : AnUsage->getRequiredTransitiveSet())
    if (Pass *AnalysisPass = findAnalysisPass(RequiredID, true))
      UP.push_back(AnalysisPass);
    else
      RP_NotAvail.push_back(RequiredID);
}

// All Required analyses should be available to the pass as it runs!  Here
// we fill in the AnalysisImpls member of the pass so that it can
// successfully use the getAnalysis() method to retrieve the
// implementations it needs.
//
void PMDataManager::initializeAnalysisImpl(Pass *P) {
  AnalysisUsage *AnUsage = TPM->findAnalysisUsage(P);

  for (const AnalysisID ID : AnUsage->getRequiredSet()) {
    Pass *Impl = findAnalysisPass(ID, true);
    if (!Impl)
      // This may be analysis pass that is initialized on the fly.
      // If that is not the case then it will raise an assert when it is used.
      continue;
    AnalysisResolver *AR = P->getResolver();
    assert(AR && "Analysis Resolver is not set");
    AR->addAnalysisImplsPair(ID, Impl);
  }
}

/// Find the pass that implements Analysis AID. If desired pass is not found
/// then return NULL.
Pass *PMDataManager::findAnalysisPass(AnalysisID AID, bool SearchParent) {

  // Check if AvailableAnalysis map has one entry.
  DenseMap<AnalysisID, Pass*>::const_iterator I =  AvailableAnalysis.find(AID);

  if (I != AvailableAnalysis.end())
    return I->second;

  // Search Parents through TopLevelManager
  if (SearchParent)
    return TPM->findAnalysisPass(AID);

  return nullptr;
}

// Print list of passes that are last used by P.
void PMDataManager::dumpLastUses(Pass *P, unsigned Offset) const{

  SmallVector<Pass *, 12> LUses;

  // If this is a on the fly manager then it does not have TPM.
  if (!TPM)
    return;

  TPM->collectLastUses(LUses, P);

  for (Pass *P : LUses) {
    dbgs() << "--" << std::string(Offset*2, ' ');
    P->dumpPassStructure(0);
  }
}

void PMDataManager::dumpPassArguments() const {
  for (Pass *P : PassVector) {
    if (PMDataManager *PMD = P->getAsPMDataManager())
      PMD->dumpPassArguments();
    else
      if (const PassInfo *PI =
            TPM->findAnalysisPassInfo(P->getPassID()))
        if (!PI->isAnalysisGroup())
          dbgs() << " -" << PI->getPassArgument();
  }
}

void PMDataManager::dumpPassInfo(Pass *P, enum PassDebuggingString S1,
                                 enum PassDebuggingString S2,
                                 StringRef Msg) {
  if (PassDebugging < Executions)
    return;
  dbgs() << "[" << std::chrono::system_clock::now() << "] " << (void *)this
         << std::string(getDepth() * 2 + 1, ' ');
  switch (S1) {
  case EXECUTION_MSG:
    dbgs() << "Executing Pass '" << P->getPassName();
    break;
  case MODIFICATION_MSG:
    dbgs() << "Made Modification '" << P->getPassName();
    break;
  case FREEING_MSG:
    dbgs() << " Freeing Pass '" << P->getPassName();
    break;
  default:
    break;
  }
  switch (S2) {
  case ON_FUNCTION_MSG:
    dbgs() << "' on Function '" << Msg << "'...\n";
    break;
  case ON_MODULE_MSG:
    dbgs() << "' on Module '"  << Msg << "'...\n";
    break;
  case ON_REGION_MSG:
    dbgs() << "' on Region '"  << Msg << "'...\n";
    break;
  case ON_LOOP_MSG:
    dbgs() << "' on Loop '" << Msg << "'...\n";
    break;
  case ON_CG_MSG:
    dbgs() << "' on Call Graph Nodes '" << Msg << "'...\n";
    break;
  default:
    break;
  }
}

void PMDataManager::dumpRequiredSet(const Pass *P) const {
  if (PassDebugging < Details)
    return;

  AnalysisUsage analysisUsage;
  P->getAnalysisUsage(analysisUsage);
  dumpAnalysisUsage("Required", P, analysisUsage.getRequiredSet());
}

void PMDataManager::dumpPreservedSet(const Pass *P) const {
  if (PassDebugging < Details)
    return;

  AnalysisUsage analysisUsage;
  P->getAnalysisUsage(analysisUsage);
  dumpAnalysisUsage("Preserved", P, analysisUsage.getPreservedSet());
}

void PMDataManager::dumpUsedSet(const Pass *P) const {
  if (PassDebugging < Details)
    return;

  AnalysisUsage analysisUsage;
  P->getAnalysisUsage(analysisUsage);
  dumpAnalysisUsage("Used", P, analysisUsage.getUsedSet());
}

void PMDataManager::dumpAnalysisUsage(StringRef Msg, const Pass *P,
                                   const AnalysisUsage::VectorType &Set) const {
  assert(PassDebugging >= Details);
  if (Set.empty())
    return;
  dbgs() << (const void*)P << std::string(getDepth()*2+3, ' ') << Msg << " Analyses:";
  for (unsigned i = 0; i != Set.size(); ++i) {
    if (i) dbgs() << ',';
    const PassInfo *PInf = TPM->findAnalysisPassInfo(Set[i]);
    if (!PInf) {
      // Some preserved passes, such as AliasAnalysis, may not be initialized by
      // all drivers.
      dbgs() << " Uninitialized Pass";
      continue;
    }
    dbgs() << ' ' << PInf->getPassName();
  }
  dbgs() << '\n';
}

/// Add RequiredPass into list of lower level passes required by pass P.
/// RequiredPass is run on the fly by Pass Manager when P requests it
/// through getAnalysis interface.
/// This should be handled by specific pass manager.
void PMDataManager::addLowerLevelRequiredPass(Pass *P, Pass *RequiredPass) {
  if (TPM) {
    TPM->dumpArguments();
    TPM->dumpPasses();
  }

  // Module Level pass may required Function Level analysis info
  // (e.g. dominator info). Pass manager uses on the fly function pass manager
  // to provide this on demand. In that case, in Pass manager terminology,
  // module level pass is requiring lower level analysis info managed by
  // lower level pass manager.

  // When Pass manager is not able to order required analysis info, Pass manager
  // checks whether any lower level manager will be able to provide this
  // analysis info on demand or not.
#ifndef NDEBUG
  dbgs() << "Unable to schedule '" << RequiredPass->getPassName();
  dbgs() << "' required by '" << P->getPassName() << "'\n";
#endif
  llvm_unreachable("Unable to schedule pass");
}

std::tuple<Pass *, bool> PMDataManager::getOnTheFlyPass(Pass *P, AnalysisID PI,
                                                        Function &F) {
  llvm_unreachable("Unable to find on the fly pass");
}

// Destructor
PMDataManager::~PMDataManager() {
  for (Pass *P : PassVector)
    delete P;
}

//===----------------------------------------------------------------------===//
// NOTE: Is this the right place to define this method ?
// getAnalysisIfAvailable - Return analysis result or null if it doesn't exist.
Pass *AnalysisResolver::getAnalysisIfAvailable(AnalysisID ID, bool dir) const {
  return PM.findAnalysisPass(ID, dir);
}

std::tuple<Pass *, bool>
AnalysisResolver::findImplPass(Pass *P, AnalysisID AnalysisPI, Function &F) {
  return PM.getOnTheFlyPass(P, AnalysisPI, F);
}

namespace llvm {
namespace legacy {

//===----------------------------------------------------------------------===//
// FunctionPassManager implementation

/// Create new Function pass manager
FunctionPassManager::FunctionPassManager(Module *m) : M(m) {
  FPM = new legacy::FunctionPassManagerImpl();
  // FPM is the top level manager.
  FPM->setTopLevelManager(FPM);

  AnalysisResolver *AR = new AnalysisResolver(*FPM);
  FPM->setResolver(AR);
}

FunctionPassManager::~FunctionPassManager() {
  delete FPM;
}

void FunctionPassManager::add(Pass *P) {
  FPM->add(P);
}

/// run - Execute all of the passes scheduled for execution.  Keep
/// track of whether any of the passes modifies the function, and if
/// so, return true.
///
bool FunctionPassManager::run(Function &F) {
  handleAllErrors(F.materialize(), [&](ErrorInfoBase &EIB) {
    report_fatal_error("Error reading bitcode file: " + EIB.message());
  });
  return FPM->run(F);
}


/// doInitialization - Run all of the initializers for the function passes.
///
bool FunctionPassManager::doInitialization() {
  return FPM->doInitialization(*M);
}

/// doFinalization - Run all of the finalizers for the function passes.
///
bool FunctionPassManager::doFinalization() {
  return FPM->doFinalization(*M);
}
} // namespace legacy
} // namespace llvm

/// cleanup - After running all passes, clean up pass manager cache.
void FPPassManager::cleanup() {
 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
    FunctionPass *FP = getContainedPass(Index);
    AnalysisResolver *AR = FP->getResolver();
    assert(AR && "Analysis Resolver is not set");
    AR->clearAnalysisImpls();
 }
}


//===----------------------------------------------------------------------===//
// FPPassManager implementation

char FPPassManager::ID = 0;
/// Print passes managed by this manager
void FPPassManager::dumpPassStructure(unsigned Offset) {
  dbgs().indent(Offset*2) << "FunctionPass Manager\n";
  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
    FunctionPass *FP = getContainedPass(Index);
    FP->dumpPassStructure(Offset + 1);
    dumpLastUses(FP, Offset+1);
  }
}

#ifdef EXPENSIVE_CHECKS
namespace {
namespace details {

// Basic hashing mechanism to detect structural change to the IR, used to verify
// pass return status consistency with actual change. Loosely copied from
// llvm/lib/Transforms/Utils/FunctionComparator.cpp

class StructuralHash {
  uint64_t Hash = 0x6acaa36bef8325c5ULL;

  void update(uint64_t V) { Hash = hashing::detail::hash_16_bytes(Hash, V); }

public:
  StructuralHash() = default;

  void update(Function &F) {
    if (F.empty())
      return;

    update(F.isVarArg());
    update(F.arg_size());

    SmallVector<const BasicBlock *, 8> BBs;
    SmallPtrSet<const BasicBlock *, 16> VisitedBBs;

    BBs.push_back(&F.getEntryBlock());
    VisitedBBs.insert(BBs[0]);
    while (!BBs.empty()) {
      const BasicBlock *BB = BBs.pop_back_val();
      update(45798); // Block header
      for (auto &Inst : *BB)
        update(Inst.getOpcode());

      const Instruction *Term = BB->getTerminator();
      for (unsigned i = 0, e = Term->getNumSuccessors(); i != e; ++i) {
        if (!VisitedBBs.insert(Term->getSuccessor(i)).second)
          continue;
        BBs.push_back(Term->getSuccessor(i));
      }
    }
  }

  void update(Module &M) {
    for (Function &F : M)
      update(F);
  }

  uint64_t getHash() const { return Hash; }
};

} // namespace details

uint64_t StructuralHash(Function &F) {
  details::StructuralHash H;
  H.update(F);
  return H.getHash();
}

uint64_t StructuralHash(Module &M) {
  details::StructuralHash H;
  H.update(M);
  return H.getHash();
}

} // end anonymous namespace

#endif

/// Execute all of the passes scheduled for execution by invoking
/// runOnFunction method.  Keep track of whether any of the passes modifies
/// the function, and if so, return true.
bool FPPassManager::runOnFunction(Function &F) {
  if (F.isDeclaration())
    return false;

  bool Changed = false;
  Module &M = *F.getParent();
  // Collect inherited analysis from Module level pass manager.
  populateInheritedAnalysis(TPM->activeStack);

  unsigned InstrCount, FunctionSize = 0;
  StringMap<std::pair<unsigned, unsigned>> FunctionToInstrCount;
  bool EmitICRemark = M.shouldEmitInstrCountChangedRemark();
  // Collect the initial size of the module.
  if (EmitICRemark) {
    InstrCount = initSizeRemarkInfo(M, FunctionToInstrCount);
    FunctionSize = F.getInstructionCount();
  }

  llvm::TimeTraceScope FunctionScope("OptFunction", F.getName());

  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
    FunctionPass *FP = getContainedPass(Index);
    bool LocalChanged = false;

    llvm::TimeTraceScope PassScope("RunPass", FP->getPassName());

    dumpPassInfo(FP, EXECUTION_MSG, ON_FUNCTION_MSG, F.getName());
    dumpRequiredSet(FP);

    initializeAnalysisImpl(FP);

    {
      PassManagerPrettyStackEntry X(FP, F);
      TimeRegion PassTimer(getPassTimer(FP));
#ifdef EXPENSIVE_CHECKS
      uint64_t RefHash = StructuralHash(F);
#endif
      LocalChanged |= FP->runOnFunction(F);

#ifdef EXPENSIVE_CHECKS
      assert((LocalChanged || (RefHash == StructuralHash(F))) &&
             "Pass modifies its input and doesn't report it.");
#endif

      if (EmitICRemark) {
        unsigned NewSize = F.getInstructionCount();

        // Update the size of the function, emit a remark, and update the size
        // of the module.
        if (NewSize != FunctionSize) {
          int64_t Delta = static_cast<int64_t>(NewSize) -
                          static_cast<int64_t>(FunctionSize);
          emitInstrCountChangedRemark(FP, M, Delta, InstrCount,
                                      FunctionToInstrCount, &F);
          InstrCount = static_cast<int64_t>(InstrCount) + Delta;
          FunctionSize = NewSize;
        }
      }
    }

    Changed |= LocalChanged;
    if (LocalChanged)
      dumpPassInfo(FP, MODIFICATION_MSG, ON_FUNCTION_MSG, F.getName());
    dumpPreservedSet(FP);
    dumpUsedSet(FP);

    verifyPreservedAnalysis(FP);
    removeNotPreservedAnalysis(FP);
    recordAvailableAnalysis(FP);
    removeDeadPasses(FP, F.getName(), ON_FUNCTION_MSG);
  }

  return Changed;
}

bool FPPassManager::runOnModule(Module &M) {
  bool Changed = false;

  for (Function &F : M)
    Changed |= runOnFunction(F);

  return Changed;
}

bool FPPassManager::doInitialization(Module &M) {
  bool Changed = false;

  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index)
    Changed |= getContainedPass(Index)->doInitialization(M);

  return Changed;
}

bool FPPassManager::doFinalization(Module &M) {
  bool Changed = false;

  for (int Index = getNumContainedPasses() - 1; Index >= 0; --Index)
    Changed |= getContainedPass(Index)->doFinalization(M);

  return Changed;
}

//===----------------------------------------------------------------------===//
// MPPassManager implementation

/// Execute all of the passes scheduled for execution by invoking
/// runOnModule method.  Keep track of whether any of the passes modifies
/// the module, and if so, return true.
bool
MPPassManager::runOnModule(Module &M) {
  llvm::TimeTraceScope TimeScope("OptModule", M.getName());

  bool Changed = false;

  // Initialize on-the-fly passes
  for (auto &OnTheFlyManager : OnTheFlyManagers) {
    legacy::FunctionPassManagerImpl *FPP = OnTheFlyManager.second;
    Changed |= FPP->doInitialization(M);
  }

  // Initialize module passes
  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index)
    Changed |= getContainedPass(Index)->doInitialization(M);

  unsigned InstrCount;
  StringMap<std::pair<unsigned, unsigned>> FunctionToInstrCount;
  bool EmitICRemark = M.shouldEmitInstrCountChangedRemark();
  // Collect the initial size of the module.
  if (EmitICRemark)
    InstrCount = initSizeRemarkInfo(M, FunctionToInstrCount);

  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
    ModulePass *MP = getContainedPass(Index);
    bool LocalChanged = false;

    dumpPassInfo(MP, EXECUTION_MSG, ON_MODULE_MSG, M.getModuleIdentifier());
    dumpRequiredSet(MP);

    initializeAnalysisImpl(MP);

    {
      PassManagerPrettyStackEntry X(MP, M);
      TimeRegion PassTimer(getPassTimer(MP));

#ifdef EXPENSIVE_CHECKS
      uint64_t RefHash = StructuralHash(M);
#endif

      LocalChanged |= MP->runOnModule(M);

#ifdef EXPENSIVE_CHECKS
      assert((LocalChanged || (RefHash == StructuralHash(M))) &&
             "Pass modifies its input and doesn't report it.");
#endif

      if (EmitICRemark) {
        // Update the size of the module.
        unsigned ModuleCount = M.getInstructionCount();
        if (ModuleCount != InstrCount) {
          int64_t Delta = static_cast<int64_t>(ModuleCount) -
                          static_cast<int64_t>(InstrCount);
          emitInstrCountChangedRemark(MP, M, Delta, InstrCount,
                                      FunctionToInstrCount);
          InstrCount = ModuleCount;
        }
      }
    }

    Changed |= LocalChanged;
    if (LocalChanged)
      dumpPassInfo(MP, MODIFICATION_MSG, ON_MODULE_MSG,
                   M.getModuleIdentifier());
    dumpPreservedSet(MP);
    dumpUsedSet(MP);

    verifyPreservedAnalysis(MP);
    removeNotPreservedAnalysis(MP);
    recordAvailableAnalysis(MP);
    removeDeadPasses(MP, M.getModuleIdentifier(), ON_MODULE_MSG);
  }

  // Finalize module passes
  for (int Index = getNumContainedPasses() - 1; Index >= 0; --Index)
    Changed |= getContainedPass(Index)->doFinalization(M);

  // Finalize on-the-fly passes
  for (auto &OnTheFlyManager : OnTheFlyManagers) {
    legacy::FunctionPassManagerImpl *FPP = OnTheFlyManager.second;
    // We don't know when is the last time an on-the-fly pass is run,
    // so we need to releaseMemory / finalize here
    FPP->releaseMemoryOnTheFly();
    Changed |= FPP->doFinalization(M);
  }

  return Changed;
}

/// Add RequiredPass into list of lower level passes required by pass P.
/// RequiredPass is run on the fly by Pass Manager when P requests it
/// through getAnalysis interface.
void MPPassManager::addLowerLevelRequiredPass(Pass *P, Pass *RequiredPass) {
  assert(RequiredPass && "No required pass?");
  assert(P->getPotentialPassManagerType() == PMT_ModulePassManager &&
         "Unable to handle Pass that requires lower level Analysis pass");
  assert((P->getPotentialPassManagerType() <
          RequiredPass->getPotentialPassManagerType()) &&
         "Unable to handle Pass that requires lower level Analysis pass");

  legacy::FunctionPassManagerImpl *FPP = OnTheFlyManagers[P];
  if (!FPP) {
    FPP = new legacy::FunctionPassManagerImpl();
    // FPP is the top level manager.
    FPP->setTopLevelManager(FPP);

    OnTheFlyManagers[P] = FPP;
  }
  const PassInfo *RequiredPassPI =
      TPM->findAnalysisPassInfo(RequiredPass->getPassID());

  Pass *FoundPass = nullptr;
  if (RequiredPassPI && RequiredPassPI->isAnalysis()) {
    FoundPass =
      ((PMTopLevelManager*)FPP)->findAnalysisPass(RequiredPass->getPassID());
  }
  if (!FoundPass) {
    FoundPass = RequiredPass;
    // This should be guaranteed to add RequiredPass to the passmanager given
    // that we checked for an available analysis above.
    FPP->add(RequiredPass);
  }
  // Register P as the last user of FoundPass or RequiredPass.
  SmallVector<Pass *, 1> LU;
  LU.push_back(FoundPass);
  FPP->setLastUser(LU,  P);
}

/// Return function pass corresponding to PassInfo PI, that is
/// required by module pass MP. Instantiate analysis pass, by using
/// its runOnFunction() for function F.
std::tuple<Pass *, bool> MPPassManager::getOnTheFlyPass(Pass *MP, AnalysisID PI,
                                                        Function &F) {
  legacy::FunctionPassManagerImpl *FPP = OnTheFlyManagers[MP];
  assert(FPP && "Unable to find on the fly pass");

  FPP->releaseMemoryOnTheFly();
  bool Changed = FPP->run(F);
  return std::make_tuple(((PMTopLevelManager *)FPP)->findAnalysisPass(PI),
                         Changed);
}

namespace llvm {
namespace legacy {

//===----------------------------------------------------------------------===//
// PassManager implementation

/// Create new pass manager
PassManager::PassManager() {
  PM = new PassManagerImpl();
  // PM is the top level manager
  PM->setTopLevelManager(PM);
}

PassManager::~PassManager() {
  delete PM;
}

void PassManager::add(Pass *P) {
  PM->add(P);
}

/// run - Execute all of the passes scheduled for execution.  Keep track of
/// whether any of the passes modifies the module, and if so, return true.
bool PassManager::run(Module &M) {
  return PM->run(M);
}
} // namespace legacy
} // namespace llvm

//===----------------------------------------------------------------------===//
// PMStack implementation
//

// Pop Pass Manager from the stack and clear its analysis info.
void PMStack::pop() {

  PMDataManager *Top = this->top();
  Top->initializeAnalysisInfo();

  S.pop_back();
}

// Push PM on the stack and set its top level manager.
void PMStack::push(PMDataManager *PM) {
  assert(PM && "Unable to push. Pass Manager expected");
  assert(PM->getDepth()==0 && "Pass Manager depth set too early");

  if (!this->empty()) {
    assert(PM->getPassManagerType() > this->top()->getPassManagerType()
           && "pushing bad pass manager to PMStack");
    PMTopLevelManager *TPM = this->top()->getTopLevelManager();

    assert(TPM && "Unable to find top level manager");
    TPM->addIndirectPassManager(PM);
    PM->setTopLevelManager(TPM);
    PM->setDepth(this->top()->getDepth()+1);
  } else {
    assert((PM->getPassManagerType() == PMT_ModulePassManager
           || PM->getPassManagerType() == PMT_FunctionPassManager)
           && "pushing bad pass manager to PMStack");
    PM->setDepth(1);
  }

  S.push_back(PM);
}

// Dump content of the pass manager stack.
LLVM_DUMP_METHOD void PMStack::dump() const {
  for (PMDataManager *Manager : S)
    dbgs() << Manager->getAsPass()->getPassName() << ' ';

  if (!S.empty())
    dbgs() << '\n';
}

/// Find appropriate Module Pass Manager in the PM Stack and
/// add self into that manager.
void ModulePass::assignPassManager(PMStack &PMS,
                                   PassManagerType PreferredType) {
  // Find Module Pass Manager
  PassManagerType T;
  while ((T = PMS.top()->getPassManagerType()) > PMT_ModulePassManager &&
         T != PreferredType)
    PMS.pop();
  PMS.top()->add(this);
}

/// Find appropriate Function Pass Manager or Call Graph Pass Manager
/// in the PM Stack and add self into that manager.
void FunctionPass::assignPassManager(PMStack &PMS,
                                     PassManagerType /*PreferredType*/) {
  // Find Function Pass Manager
  PMDataManager *PM;
  while (PM = PMS.top(), PM->getPassManagerType() > PMT_FunctionPassManager)
    PMS.pop();

  // Create new Function Pass Manager if needed.
  if (PM->getPassManagerType() != PMT_FunctionPassManager) {
    // [1] Create new Function Pass Manager
    auto *FPP = new FPPassManager;
    FPP->populateInheritedAnalysis(PMS);

    // [2] Set up new manager's top level manager
    PM->getTopLevelManager()->addIndirectPassManager(FPP);

    // [3] Assign manager to manage this new manager. This may create
    // and push new managers into PMS
    FPP->assignPassManager(PMS, PM->getPassManagerType());

    // [4] Push new manager into PMS
    PMS.push(FPP);
    PM = FPP;
  }

  // Assign FPP as the manager of this pass.
  PM->add(this);
}

legacy::PassManagerBase::~PassManagerBase() {}