text: //===- PassManager.h - Pass management infrastructure -----------*- C++ -*-===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  /// \file
  ///
  /// This header defines various interfaces for pass management in LLVM. There
  /// is no "pass" interface in LLVM per se. Instead, an instance of any class
  /// which supports a method to 'run' it over a unit of IR can be used as
  /// a pass. A pass manager is generally a tool to collect a sequence of passes
  /// which run over a particular IR construct, and run each of them in sequence
  /// over each such construct in the containing IR construct. As there is no
  /// containing IR construct for a Module, a manager for passes over modules
  /// forms the base case which runs its managed passes in sequence over the
  /// single module provided.
  ///
  /// The core IR library provides managers for running passes over
  /// modules and functions.
  ///
  /// * FunctionPassManager can run over a Module, runs each pass over
  ///   a Function.
  /// * ModulePassManager must be directly run, runs each pass over the Module.
  ///
  /// Note that the implementations of the pass managers use concept-based
  /// polymorphism as outlined in the "Value Semantics and Concept-based
  /// Polymorphism" talk (or its abbreviated sibling "Inheritance Is The Base
  /// Class of Evil") by Sean Parent:
  /// * http://github.com/sean-parent/sean-parent.github.com/wiki/Papers-and-Presentations
  /// * http://www.youtube.com/watch?v=_BpMYeUFXv8
  /// * http://channel9.msdn.com/Events/GoingNative/2013/Inheritance-Is-The-Base-Class-of-Evil
  ///
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_IR_PASSMANAGER_H
  #define LLVM_IR_PASSMANAGER_H
  
  #include "llvm/ADT/DenseMap.h"
  #include "llvm/ADT/STLExtras.h"
  #include "llvm/ADT/SmallPtrSet.h"
  #include "llvm/ADT/TinyPtrVector.h"
  #include "llvm/IR/Function.h"
  #include "llvm/IR/Module.h"
  #include "llvm/IR/PassManagerInternal.h"
  #include "llvm/Support/Debug.h"
  #include "llvm/Support/TypeName.h"
  #include "llvm/Support/raw_ostream.h"
  #include "llvm/Support/type_traits.h"
  #include <list>
  #include <memory>
  #include <vector>
  
  namespace llvm {
  
  /// A special type used by analysis passes to provide an address that
  /// identifies that particular analysis pass type.
  ///
  /// Analysis passes should have a static data member of this type and derive
  /// from the \c AnalysisInfoMixin to get a static ID method used to identify
  /// the analysis in the pass management infrastructure.
  struct alignas(8) AnalysisKey {};
  
  /// A special type used to provide an address that identifies a set of related
  /// analyses.  These sets are primarily used below to mark sets of analyses as
  /// preserved.
  ///
  /// For example, a transformation can indicate that it preserves the CFG of a
  /// function by preserving the appropriate AnalysisSetKey.  An analysis that
  /// depends only on the CFG can then check if that AnalysisSetKey is preserved;
  /// if it is, the analysis knows that it itself is preserved.
  struct alignas(8) AnalysisSetKey {};
  
  /// A set of analyses that are preserved following a run of a transformation
  /// pass.
  ///
  /// Transformation passes build and return these objects to communicate which
  /// analyses are still valid after the transformation. For most passes this is
  /// fairly simple: if they don't change anything all analyses are preserved,
  /// otherwise only a short list of analyses that have been explicitly updated
  /// are preserved.
  ///
  /// This class also lets transformation passes mark abstract *sets* of analyses
  /// as preserved. A transformation that (say) does not alter the CFG can
  /// indicate such by marking a particular AnalysisSetKey as preserved, and
  /// then analyses can query whether that AnalysisSetKey is preserved.
  ///
  /// Finally, this class can represent an "abandoned" analysis, which is
  /// not preserved even if it would be covered by some abstract set of analyses.
  ///
  /// Given a `PreservedAnalyses` object, an analysis will typically want to
  /// figure out whether it is preserved. In the example below, MyAnalysisType is
  /// preserved if it's not abandoned, and (a) it's explicitly marked as
  /// preserved, (b), the set AllAnalysesOn<MyIRUnit> is preserved, or (c) both
  /// AnalysisSetA and AnalysisSetB are preserved.
  ///
  /// ```
  ///   auto PAC = PA.getChecker<MyAnalysisType>();
  ///   if (PAC.preserved() || PAC.preservedSet<AllAnalysesOn<MyIRUnit>>() ||
  ///       (PAC.preservedSet<AnalysisSetA>() &&
  ///        PAC.preservedSet<AnalysisSetB>())) {
  ///     // The analysis has been successfully preserved ...
  ///   }
  /// ```
  class PreservedAnalyses {
  public:
    /// \brief Convenience factory function for the empty preserved set.
    static PreservedAnalyses none() { return PreservedAnalyses(); }
  
    /// \brief Construct a special preserved set that preserves all passes.
    static PreservedAnalyses all() {
      PreservedAnalyses PA;
      PA.PreservedIDs.insert(&AllAnalysesKey);
      return PA;
    }
  
    /// Mark an analysis as preserved.
    template <typename AnalysisT> void preserve() { preserve(AnalysisT::ID()); }
  
    /// \brief Given an analysis's ID, mark the analysis as preserved, adding it
    /// to the set.
    void preserve(AnalysisKey *ID) {
      // Clear this ID from the explicit not-preserved set if present.
      NotPreservedAnalysisIDs.erase(ID);
  
      // If we're not already preserving all analyses (other than those in
      // NotPreservedAnalysisIDs).
      if (!areAllPreserved())
        PreservedIDs.insert(ID);
    }
  
    /// Mark an analysis set as preserved.
    template <typename AnalysisSetT> void preserveSet() {
      preserveSet(AnalysisSetT::ID());
    }
  
    /// Mark an analysis set as preserved using its ID.
    void preserveSet(AnalysisSetKey *ID) {
      // If we're not already in the saturated 'all' state, add this set.
      if (!areAllPreserved())
        PreservedIDs.insert(ID);
    }
  
    /// Mark an analysis as abandoned.
    ///
    /// An abandoned analysis is not preserved, even if it is nominally covered
    /// by some other set or was previously explicitly marked as preserved.
    ///
    /// Note that you can only abandon a specific analysis, not a *set* of
    /// analyses.
    template <typename AnalysisT> void abandon() { abandon(AnalysisT::ID()); }
  
    /// Mark an analysis as abandoned using its ID.
    ///
    /// An abandoned analysis is not preserved, even if it is nominally covered
    /// by some other set or was previously explicitly marked as preserved.
    ///
    /// Note that you can only abandon a specific analysis, not a *set* of
    /// analyses.
    void abandon(AnalysisKey *ID) {
      PreservedIDs.erase(ID);
      NotPreservedAnalysisIDs.insert(ID);
    }
  
    /// \brief Intersect this set with another in place.
    ///
    /// This is a mutating operation on this preserved set, removing all
    /// preserved passes which are not also preserved in the argument.
    void intersect(const PreservedAnalyses &Arg) {
      if (Arg.areAllPreserved())
        return;
      if (areAllPreserved()) {
        *this = Arg;
        return;
      }
      // The intersection requires the *union* of the explicitly not-preserved
      // IDs and the *intersection* of the preserved IDs.
      for (auto ID : Arg.NotPreservedAnalysisIDs) {
        PreservedIDs.erase(ID);
        NotPreservedAnalysisIDs.insert(ID);
      }
      for (auto ID : PreservedIDs)
        if (!Arg.PreservedIDs.count(ID))
          PreservedIDs.erase(ID);
    }
  
    /// \brief Intersect this set with a temporary other set in place.
    ///
    /// This is a mutating operation on this preserved set, removing all
    /// preserved passes which are not also preserved in the argument.
    void intersect(PreservedAnalyses &&Arg) {
      if (Arg.areAllPreserved())
        return;
      if (areAllPreserved()) {
        *this = std::move(Arg);
        return;
      }
      // The intersection requires the *union* of the explicitly not-preserved
      // IDs and the *intersection* of the preserved IDs.
      for (auto ID : Arg.NotPreservedAnalysisIDs) {
        PreservedIDs.erase(ID);
        NotPreservedAnalysisIDs.insert(ID);
      }
      for (auto ID : PreservedIDs)
        if (!Arg.PreservedIDs.count(ID))
          PreservedIDs.erase(ID);
    }
  
    /// A checker object that makes it easy to query for whether an analysis or
    /// some set covering it is preserved.
    class PreservedAnalysisChecker {
      friend class PreservedAnalyses;
  
      const PreservedAnalyses &PA;
      AnalysisKey *const ID;
      const bool IsAbandoned;
  
      /// A PreservedAnalysisChecker is tied to a particular Analysis because
      /// `preserved()` and `preservedSet()` both return false if the Analysis
      /// was abandoned.
      PreservedAnalysisChecker(const PreservedAnalyses &PA, AnalysisKey *ID)
          : PA(PA), ID(ID), IsAbandoned(PA.NotPreservedAnalysisIDs.count(ID)) {}
  
    public:
      /// Returns true if the checker's analysis was not abandoned and either
      ///  - the analysis is explicitly preserved or
      ///  - all analyses are preserved.
      bool preserved() {
        return !IsAbandoned && (PA.PreservedIDs.count(&AllAnalysesKey) ||
                                PA.PreservedIDs.count(ID));
      }
  
      /// Returns true if the checker's analysis was not abandoned and either
      ///  - \p AnalysisSetT is explicitly preserved or
      ///  - all analyses are preserved.
      template <typename AnalysisSetT> bool preservedSet() {
        AnalysisSetKey *SetID = AnalysisSetT::ID();
        return !IsAbandoned && (PA.PreservedIDs.count(&AllAnalysesKey) ||
                                PA.PreservedIDs.count(SetID));
      }
    };
  
    /// Build a checker for this `PreservedAnalyses` and the specified analysis
    /// type.
    ///
    /// You can use the returned object to query whether an analysis was
    /// preserved. See the example in the comment on `PreservedAnalysis`.
    template <typename AnalysisT> PreservedAnalysisChecker getChecker() const {
      return PreservedAnalysisChecker(*this, AnalysisT::ID());
    }
  
    /// Build a checker for this `PreservedAnalyses` and the specified analysis
    /// ID.
    ///
    /// You can use the returned object to query whether an analysis was
    /// preserved. See the example in the comment on `PreservedAnalysis`.
    PreservedAnalysisChecker getChecker(AnalysisKey *ID) const {
      return PreservedAnalysisChecker(*this, ID);
    }
  
    /// Test whether all analyses are preserved (and none are abandoned).
    ///
    /// This is used primarily to optimize for the common case of a transformation
    /// which makes no changes to the IR.
    bool areAllPreserved() const {
      return NotPreservedAnalysisIDs.empty() &&
             PreservedIDs.count(&AllAnalysesKey);
    }
  
    /// Directly test whether a set of analyses is preserved.
    ///
    /// This is only true when no analyses have been explicitly abandoned.
    template <typename AnalysisSetT> bool allAnalysesInSetPreserved() const {
      return allAnalysesInSetPreserved(AnalysisSetT::ID());
    }
  
    /// Directly test whether a set of analyses is preserved.
    ///
    /// This is only true when no analyses have been explicitly abandoned.
    bool allAnalysesInSetPreserved(AnalysisSetKey *SetID) const {
      return NotPreservedAnalysisIDs.empty() &&
             (PreservedIDs.count(&AllAnalysesKey) || PreservedIDs.count(SetID));
    }
  
  private:
    /// A special key used to indicate all analyses.
    static AnalysisSetKey AllAnalysesKey;
  
    /// The IDs of analyses and analysis sets that are preserved.
    SmallPtrSet<void *, 2> PreservedIDs;
  
    /// The IDs of explicitly not-preserved analyses.
    ///
    /// If an analysis in this set is covered by a set in `PreservedIDs`, we
    /// consider it not-preserved. That is, `NotPreservedAnalysisIDs` always
    /// "wins" over analysis sets in `PreservedIDs`.
    ///
    /// Also, a given ID should never occur both here and in `PreservedIDs`.
    SmallPtrSet<AnalysisKey *, 2> NotPreservedAnalysisIDs;
  };
  
  // Forward declare the analysis manager template.
  template <typename IRUnitT, typename... ExtraArgTs> class AnalysisManager;
  
  /// A CRTP mix-in to automatically provide informational APIs needed for
  /// passes.
  ///
  /// This provides some boilerplate for types that are passes.
  template <typename DerivedT> struct PassInfoMixin {
    /// Gets the name of the pass we are mixed into.
    static StringRef name() {
      static_assert(std::is_base_of<PassInfoMixin, DerivedT>::value,
                    "Must pass the derived type as the template argument!");
      StringRef Name = getTypeName<DerivedT>();
      if (Name.startswith("llvm::"))
        Name = Name.drop_front(strlen("llvm::"));
      return Name;
    }
  };
  
  /// A CRTP mix-in that provides informational APIs needed for analysis passes.
  ///
  /// This provides some boilerplate for types that are analysis passes. It
  /// automatically mixes in \c PassInfoMixin.
  template <typename DerivedT>
  struct AnalysisInfoMixin : PassInfoMixin<DerivedT> {
    /// Returns an opaque, unique ID for this analysis type.
    ///
    /// This ID is a pointer type that is guaranteed to be 8-byte aligned and thus
    /// suitable for use in sets, maps, and other data structures that use the low
    /// bits of pointers.
    ///
    /// Note that this requires the derived type provide a static \c AnalysisKey
    /// member called \c Key.
    ///
    /// FIXME: The only reason the mixin type itself can't declare the Key value
    /// is that some compilers cannot correctly unique a templated static variable
    /// so it has the same addresses in each instantiation. The only currently
    /// known platform with this limitation is Windows DLL builds, specifically
    /// building each part of LLVM as a DLL. If we ever remove that build
    /// configuration, this mixin can provide the static key as well.
    static AnalysisKey *ID() {
      static_assert(std::is_base_of<AnalysisInfoMixin, DerivedT>::value,
                    "Must pass the derived type as the template argument!");
      return &DerivedT::Key;
    }
  };
  
  /// This templated class represents "all analyses that operate over \<a
  /// particular IR unit\>" (e.g. a Function or a Module) in instances of
  /// PreservedAnalysis.
  ///
  /// This lets a transformation say e.g. "I preserved all function analyses".
  ///
  /// Note that you must provide an explicit instantiation declaration and
  /// definition for this template in order to get the correct behavior on
  /// Windows. Otherwise, the address of SetKey will not be stable.
  template <typename IRUnitT>
  class AllAnalysesOn {
  public:
    static AnalysisSetKey *ID() { return &SetKey; }
  
  private:
    static AnalysisSetKey SetKey;
  };
  
  template <typename IRUnitT> AnalysisSetKey AllAnalysesOn<IRUnitT>::SetKey;
  
  extern template class AllAnalysesOn<Module>;
  extern template class AllAnalysesOn<Function>;
  
  /// \brief Manages a sequence of passes over a particular unit of IR.
  ///
  /// A pass manager contains a sequence of passes to run over a particular unit
  /// of IR (e.g. Functions, Modules). It is itself a valid pass over that unit of
  /// IR, and when run over some given IR will run each of its contained passes in
  /// sequence. Pass managers are the primary and most basic building block of a
  /// pass pipeline.
  ///
  /// When you run a pass manager, you provide an \c AnalysisManager<IRUnitT>
  /// argument. The pass manager will propagate that analysis manager to each
  /// pass it runs, and will call the analysis manager's invalidation routine with
  /// the PreservedAnalyses of each pass it runs.
  template <typename IRUnitT,
            typename AnalysisManagerT = AnalysisManager<IRUnitT>,
            typename... ExtraArgTs>
  class PassManager : public PassInfoMixin<
                          PassManager<IRUnitT, AnalysisManagerT, ExtraArgTs...>> {
  public:
    /// \brief Construct a pass manager.
    ///
    /// If \p DebugLogging is true, we'll log our progress to llvm::dbgs().
    explicit PassManager(bool DebugLogging = false) : DebugLogging(DebugLogging) {}
  
    // FIXME: These are equivalent to the default move constructor/move
    // assignment. However, using = default triggers linker errors due to the
    // explicit instantiations below. Find away to use the default and remove the
    // duplicated code here.
    PassManager(PassManager &&Arg)
        : Passes(std::move(Arg.Passes)),
          DebugLogging(std::move(Arg.DebugLogging)) {}
  
    PassManager &operator=(PassManager &&RHS) {
      Passes = std::move(RHS.Passes);
      DebugLogging = std::move(RHS.DebugLogging);
      return *this;
    }
  
    /// \brief Run all of the passes in this manager over the given unit of IR.
    /// ExtraArgs are passed to each pass.
    PreservedAnalyses run(IRUnitT &IR, AnalysisManagerT &AM,
                          ExtraArgTs... ExtraArgs) {
      PreservedAnalyses PA = PreservedAnalyses::all();
  
      if (DebugLogging)
        dbgs() << "Starting " << getTypeName<IRUnitT>() << " pass manager run.\n";
  
      for (unsigned Idx = 0, Size = Passes.size(); Idx != Size; ++Idx) {
        if (DebugLogging)
          dbgs() << "Running pass: " << Passes[Idx]->name() << " on "
                 << IR.getName() << "\n";
  
        PreservedAnalyses PassPA = Passes[Idx]->run(IR, AM, ExtraArgs...);
  
        // Update the analysis manager as each pass runs and potentially
        // invalidates analyses.
        AM.invalidate(IR, PassPA);
  
        // Finally, intersect the preserved analyses to compute the aggregate
        // preserved set for this pass manager.
        PA.intersect(std::move(PassPA));
  
        // FIXME: Historically, the pass managers all called the LLVM context's
        // yield function here. We don't have a generic way to acquire the
        // context and it isn't yet clear what the right pattern is for yielding
        // in the new pass manager so it is currently omitted.
        //IR.getContext().yield();
      }
  
      // Invaliadtion was handled after each pass in the above loop for the
      // current unit of IR. Therefore, the remaining analysis results in the
      // AnalysisManager are preserved. We mark this with a set so that we don't
      // need to inspect each one individually.
      PA.preserveSet<AllAnalysesOn<IRUnitT>>();
  
      if (DebugLogging)
        dbgs() << "Finished " << getTypeName<IRUnitT>() << " pass manager run.\n";
  
      return PA;
    }
  
    template <typename PassT> void addPass(PassT Pass) {
      typedef detail::PassModel<IRUnitT, PassT, PreservedAnalyses,
                                AnalysisManagerT, ExtraArgTs...>
          PassModelT;
      Passes.emplace_back(new PassModelT(std::move(Pass)));
    }
  
  private:
    typedef detail::PassConcept<IRUnitT, AnalysisManagerT, ExtraArgTs...>
        PassConceptT;
  
    std::vector<std::unique_ptr<PassConceptT>> Passes;
  
    /// \brief Flag indicating whether we should do debug logging.
    bool DebugLogging;
  };
  
  extern template class PassManager<Module>;
  /// \brief Convenience typedef for a pass manager over modules.
  typedef PassManager<Module> ModulePassManager;
  
  extern template class PassManager<Function>;
  /// \brief Convenience typedef for a pass manager over functions.
  typedef PassManager<Function> FunctionPassManager;
  
  /// \brief A container for analyses that lazily runs them and caches their
  /// results.
  ///
  /// This class can manage analyses for any IR unit where the address of the IR
  /// unit sufficies as its identity.
  template <typename IRUnitT, typename... ExtraArgTs> class AnalysisManager {
  public:
    class Invalidator;
  
  private:
    // Now that we've defined our invalidator, we can define the concept types.
    typedef detail::AnalysisResultConcept<IRUnitT, PreservedAnalyses, Invalidator>
        ResultConceptT;
    typedef detail::AnalysisPassConcept<IRUnitT, PreservedAnalyses, Invalidator,
                                        ExtraArgTs...>
        PassConceptT;
  
    /// \brief List of analysis pass IDs and associated concept pointers.
    ///
    /// Requires iterators to be valid across appending new entries and arbitrary
    /// erases. Provides the analysis ID to enable finding iterators to a given
    /// entry in maps below, and provides the storage for the actual result
    /// concept.
    typedef std::list<std::pair<AnalysisKey *, std::unique_ptr<ResultConceptT>>>
        AnalysisResultListT;
  
    /// \brief Map type from IRUnitT pointer to our custom list type.
    typedef DenseMap<IRUnitT *, AnalysisResultListT> AnalysisResultListMapT;
  
    /// \brief Map type from a pair of analysis ID and IRUnitT pointer to an
    /// iterator into a particular result list (which is where the actual analysis
    /// result is stored).
    typedef DenseMap<std::pair<AnalysisKey *, IRUnitT *>,
                     typename AnalysisResultListT::iterator>
        AnalysisResultMapT;
  
  public:
    /// API to communicate dependencies between analyses during invalidation.
    ///
    /// When an analysis result embeds handles to other analysis results, it
    /// needs to be invalidated both when its own information isn't preserved and
    /// when any of its embedded analysis results end up invalidated. We pass an
    /// \c Invalidator object as an argument to \c invalidate() in order to let
    /// the analysis results themselves define the dependency graph on the fly.
    /// This lets us avoid building building an explicit representation of the
    /// dependencies between analysis results.
    class Invalidator {
    public:
      /// Trigger the invalidation of some other analysis pass if not already
      /// handled and return whether it was in fact invalidated.
      ///
      /// This is expected to be called from within a given analysis result's \c
      /// invalidate method to trigger a depth-first walk of all inter-analysis
      /// dependencies. The same \p IR unit and \p PA passed to that result's \c
      /// invalidate method should in turn be provided to this routine.
      ///
      /// The first time this is called for a given analysis pass, it will call
      /// the corresponding result's \c invalidate method.  Subsequent calls will
      /// use a cache of the results of that initial call.  It is an error to form
      /// cyclic dependencies between analysis results.
      ///
      /// This returns true if the given analysis's result is invalid. Any
      /// dependecies on it will become invalid as a result.
      template <typename PassT>
      bool invalidate(IRUnitT &IR, const PreservedAnalyses &PA) {
        typedef detail::AnalysisResultModel<IRUnitT, PassT,
                                            typename PassT::Result,
                                            PreservedAnalyses, Invalidator>
            ResultModelT;
        return invalidateImpl<ResultModelT>(PassT::ID(), IR, PA);
      }
  
      /// A type-erased variant of the above invalidate method with the same core
      /// API other than passing an analysis ID rather than an analysis type
      /// parameter.
      ///
      /// This is sadly less efficient than the above routine, which leverages
      /// the type parameter to avoid the type erasure overhead.
      bool invalidate(AnalysisKey *ID, IRUnitT &IR, const PreservedAnalyses &PA) {
        return invalidateImpl<>(ID, IR, PA);
      }
  
    private:
      friend class AnalysisManager;
  
      template <typename ResultT = ResultConceptT>
      bool invalidateImpl(AnalysisKey *ID, IRUnitT &IR,
                          const PreservedAnalyses &PA) {
        // If we've already visited this pass, return true if it was invalidated
        // and false otherwise.
        auto IMapI = IsResultInvalidated.find(ID);
        if (IMapI != IsResultInvalidated.end())
          return IMapI->second;
  
        // Otherwise look up the result object.
        auto RI = Results.find({ID, &IR});
        assert(RI != Results.end() &&
               "Trying to invalidate a dependent result that isn't in the "
               "manager's cache is always an error, likely due to a stale result "
               "handle!");
  
        auto &Result = static_cast<ResultT &>(*RI->second->second);
  
        // Insert into the map whether the result should be invalidated and return
        // that. Note that we cannot reuse IMapI and must do a fresh insert here,
        // as calling invalidate could (recursively) insert things into the map,
        // making any iterator or reference invalid.
        bool Inserted;
        std::tie(IMapI, Inserted) =
            IsResultInvalidated.insert({ID, Result.invalidate(IR, PA, *this)});
        (void)Inserted;
        assert(Inserted && "Should not have already inserted this ID, likely "
                           "indicates a dependency cycle!");
        return IMapI->second;
      }
  
      Invalidator(SmallDenseMap<AnalysisKey *, bool, 8> &IsResultInvalidated,
                  const AnalysisResultMapT &Results)
          : IsResultInvalidated(IsResultInvalidated), Results(Results) {}
  
      SmallDenseMap<AnalysisKey *, bool, 8> &IsResultInvalidated;
      const AnalysisResultMapT &Results;
    };
  
    /// \brief Construct an empty analysis manager.
    ///
    /// If \p DebugLogging is true, we'll log our progress to llvm::dbgs().
    AnalysisManager(bool DebugLogging = false) : DebugLogging(DebugLogging) {}
    AnalysisManager(AnalysisManager &&) = default;
    AnalysisManager &operator=(AnalysisManager &&) = default;
  
    /// \brief Returns true if the analysis manager has an empty results cache.
    bool empty() const {
      assert(AnalysisResults.empty() == AnalysisResultLists.empty() &&
             "The storage and index of analysis results disagree on how many "
             "there are!");
      return AnalysisResults.empty();
    }
  
    /// \brief Clear any cached analysis results for a single unit of IR.
    ///
    /// This doesn't invalidate, but instead simply deletes, the relevant results.
    /// It is useful when the IR is being removed and we want to clear out all the
    /// memory pinned for it.
    void clear(IRUnitT &IR) {
      if (DebugLogging)
        dbgs() << "Clearing all analysis results for: " << IR.getName() << "\n";
  
      auto ResultsListI = AnalysisResultLists.find(&IR);
      if (ResultsListI == AnalysisResultLists.end())
        return;
      // Delete the map entries that point into the results list.
      for (auto &IDAndResult : ResultsListI->second)
        AnalysisResults.erase({IDAndResult.first, &IR});
  
      // And actually destroy and erase the results associated with this IR.
      AnalysisResultLists.erase(ResultsListI);
    }
  
    /// \brief Clear all analysis results cached by this AnalysisManager.
    ///
    /// Like \c clear(IRUnitT&), this doesn't invalidate the results; it simply
    /// deletes them.  This lets you clean up the AnalysisManager when the set of
    /// IR units itself has potentially changed, and thus we can't even look up a
    /// a result and invalidate/clear it directly.
    void clear() {
      AnalysisResults.clear();
      AnalysisResultLists.clear();
    }
  
    /// \brief Get the result of an analysis pass for a given IR unit.
    ///
    /// Runs the analysis if a cached result is not available.
    template <typename PassT>
    typename PassT::Result &getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs) {
      assert(AnalysisPasses.count(PassT::ID()) &&
             "This analysis pass was not registered prior to being queried");
      ResultConceptT &ResultConcept =
          getResultImpl(PassT::ID(), IR, ExtraArgs...);
      typedef detail::AnalysisResultModel<IRUnitT, PassT, typename PassT::Result,
                                          PreservedAnalyses, Invalidator>
          ResultModelT;
      return static_cast<ResultModelT &>(ResultConcept).Result;
    }
  
    /// \brief Get the cached result of an analysis pass for a given IR unit.
    ///
    /// This method never runs the analysis.
    ///
    /// \returns null if there is no cached result.
    template <typename PassT>
    typename PassT::Result *getCachedResult(IRUnitT &IR) const {
      assert(AnalysisPasses.count(PassT::ID()) &&
             "This analysis pass was not registered prior to being queried");
  
      ResultConceptT *ResultConcept = getCachedResultImpl(PassT::ID(), IR);
      if (!ResultConcept)
        return nullptr;
  
      typedef detail::AnalysisResultModel<IRUnitT, PassT, typename PassT::Result,
                                          PreservedAnalyses, Invalidator>
          ResultModelT;
      return &static_cast<ResultModelT *>(ResultConcept)->Result;
    }
  
    /// \brief Register an analysis pass with the manager.
    ///
    /// The parameter is a callable whose result is an analysis pass. This allows
    /// passing in a lambda to construct the analysis.
    ///
    /// The analysis type to register is the type returned by calling the \c
    /// PassBuilder argument. If that type has already been registered, then the
    /// argument will not be called and this function will return false.
    /// Otherwise, we register the analysis returned by calling \c PassBuilder(),
    /// and this function returns true.
    ///
    /// (Note: Although the return value of this function indicates whether or not
    /// an analysis was previously registered, there intentionally isn't a way to
    /// query this directly.  Instead, you should just register all the analyses
    /// you might want and let this class run them lazily.  This idiom lets us
    /// minimize the number of times we have to look up analyses in our
    /// hashtable.)
    template <typename PassBuilderT>
    bool registerPass(PassBuilderT &&PassBuilder) {
      typedef decltype(PassBuilder()) PassT;
      typedef detail::AnalysisPassModel<IRUnitT, PassT, PreservedAnalyses,
                                        Invalidator, ExtraArgTs...>
          PassModelT;
  
      auto &PassPtr = AnalysisPasses[PassT::ID()];
      if (PassPtr)
        // Already registered this pass type!
        return false;
  
      // Construct a new model around the instance returned by the builder.
      PassPtr.reset(new PassModelT(PassBuilder()));
      return true;
    }
  
    /// \brief Invalidate a specific analysis pass for an IR module.
    ///
    /// Note that the analysis result can disregard invalidation, if it determines
    /// it is in fact still valid.
    template <typename PassT> void invalidate(IRUnitT &IR) {
      assert(AnalysisPasses.count(PassT::ID()) &&
             "This analysis pass was not registered prior to being invalidated");
      invalidateImpl(PassT::ID(), IR);
    }
  
    /// \brief Invalidate cached analyses for an IR unit.
    ///
    /// Walk through all of the analyses pertaining to this unit of IR and
    /// invalidate them, unless they are preserved by the PreservedAnalyses set.
    void invalidate(IRUnitT &IR, const PreservedAnalyses &PA) {
      // We're done if all analyses on this IR unit are preserved.
      if (PA.allAnalysesInSetPreserved<AllAnalysesOn<IRUnitT>>())
        return;
  
      if (DebugLogging)
        dbgs() << "Invalidating all non-preserved analyses for: " << IR.getName()
               << "\n";
  
      // Track whether each analysis's result is invalidated in
      // IsResultInvalidated.
      SmallDenseMap<AnalysisKey *, bool, 8> IsResultInvalidated;
      Invalidator Inv(IsResultInvalidated, AnalysisResults);
      AnalysisResultListT &ResultsList = AnalysisResultLists[&IR];
      for (auto &AnalysisResultPair : ResultsList) {
        // This is basically the same thing as Invalidator::invalidate, but we
        // can't call it here because we're operating on the type-erased result.
        // Moreover if we instead called invalidate() directly, it would do an
        // unnecessary look up in ResultsList.
        AnalysisKey *ID = AnalysisResultPair.first;
        auto &Result = *AnalysisResultPair.second;
  
        auto IMapI = IsResultInvalidated.find(ID);
        if (IMapI != IsResultInvalidated.end())
          // This result was already handled via the Invalidator.
          continue;
  
        // Try to invalidate the result, giving it the Invalidator so it can
        // recursively query for any dependencies it has and record the result.
        // Note that we cannot reuse 'IMapI' here or pre-insert the ID, as
        // Result.invalidate may insert things into the map, invalidating our
        // iterator.
        bool Inserted =
            IsResultInvalidated.insert({ID, Result.invalidate(IR, PA, Inv)})
                .second;
        (void)Inserted;
        assert(Inserted && "Should never have already inserted this ID, likely "
                           "indicates a cycle!");
      }
  
      // Now erase the results that were marked above as invalidated.
      if (!IsResultInvalidated.empty()) {
        for (auto I = ResultsList.begin(), E = ResultsList.end(); I != E;) {
          AnalysisKey *ID = I->first;
          if (!IsResultInvalidated.lookup(ID)) {
            ++I;
            continue;
          }
  
          if (DebugLogging)
            dbgs() << "Invalidating analysis: " << this->lookUpPass(ID).name()
                   << "\n";
  
          I = ResultsList.erase(I);
          AnalysisResults.erase({ID, &IR});
        }
      }
  
      if (ResultsList.empty())
        AnalysisResultLists.erase(&IR);
    }
  
  private:
    /// \brief Look up a registered analysis pass.
    PassConceptT &lookUpPass(AnalysisKey *ID) {
      typename AnalysisPassMapT::iterator PI = AnalysisPasses.find(ID);
      assert(PI != AnalysisPasses.end() &&
             "Analysis passes must be registered prior to being queried!");
      return *PI->second;
    }
  
    /// \brief Look up a registered analysis pass.
    const PassConceptT &lookUpPass(AnalysisKey *ID) const {
      typename AnalysisPassMapT::const_iterator PI = AnalysisPasses.find(ID);
      assert(PI != AnalysisPasses.end() &&
             "Analysis passes must be registered prior to being queried!");
      return *PI->second;
    }
  
    /// \brief Get an analysis result, running the pass if necessary.
    ResultConceptT &getResultImpl(AnalysisKey *ID, IRUnitT &IR,
                                  ExtraArgTs... ExtraArgs) {
      typename AnalysisResultMapT::iterator RI;
      bool Inserted;
      std::tie(RI, Inserted) = AnalysisResults.insert(std::make_pair(
          std::make_pair(ID, &IR), typename AnalysisResultListT::iterator()));
  
      // If we don't have a cached result for this function, look up the pass and
      // run it to produce a result, which we then add to the cache.
      if (Inserted) {
        auto &P = this->lookUpPass(ID);
        if (DebugLogging)
          dbgs() << "Running analysis: " << P.name() << "\n";
        AnalysisResultListT &ResultList = AnalysisResultLists[&IR];
        ResultList.emplace_back(ID, P.run(IR, *this, ExtraArgs...));
  
        // P.run may have inserted elements into AnalysisResults and invalidated
        // RI.
        RI = AnalysisResults.find({ID, &IR});
        assert(RI != AnalysisResults.end() && "we just inserted it!");
  
        RI->second = std::prev(ResultList.end());
      }
  
      return *RI->second->second;
    }
  
    /// \brief Get a cached analysis result or return null.
    ResultConceptT *getCachedResultImpl(AnalysisKey *ID, IRUnitT &IR) const {
      typename AnalysisResultMapT::const_iterator RI =
          AnalysisResults.find({ID, &IR});
      return RI == AnalysisResults.end() ? nullptr : &*RI->second->second;
    }
  
    /// \brief Invalidate a function pass result.
    void invalidateImpl(AnalysisKey *ID, IRUnitT &IR) {
      typename AnalysisResultMapT::iterator RI =
          AnalysisResults.find({ID, &IR});
      if (RI == AnalysisResults.end())
        return;
  
      if (DebugLogging)
        dbgs() << "Invalidating analysis: " << this->lookUpPass(ID).name()
               << "\n";
      AnalysisResultLists[&IR].erase(RI->second);
      AnalysisResults.erase(RI);
    }
  
    /// \brief Map type from module analysis pass ID to pass concept pointer.
    typedef DenseMap<AnalysisKey *, std::unique_ptr<PassConceptT>> AnalysisPassMapT;
  
    /// \brief Collection of module analysis passes, indexed by ID.
    AnalysisPassMapT AnalysisPasses;
  
    /// \brief Map from function to a list of function analysis results.
    ///
    /// Provides linear time removal of all analysis results for a function and
    /// the ultimate storage for a particular cached analysis result.
    AnalysisResultListMapT AnalysisResultLists;
  
    /// \brief Map from an analysis ID and function to a particular cached
    /// analysis result.
    AnalysisResultMapT AnalysisResults;
  
    /// \brief Indicates whether we log to \c llvm::dbgs().
    bool DebugLogging;
  };
  
  extern template class AnalysisManager<Module>;
  /// \brief Convenience typedef for the Module analysis manager.
  typedef AnalysisManager<Module> ModuleAnalysisManager;
  
  extern template class AnalysisManager<Function>;
  /// \brief Convenience typedef for the Function analysis manager.
  typedef AnalysisManager<Function> FunctionAnalysisManager;
  
  /// \brief An analysis over an "outer" IR unit that provides access to an
  /// analysis manager over an "inner" IR unit.  The inner unit must be contained
  /// in the outer unit.
  ///
  /// Fore example, InnerAnalysisManagerProxy<FunctionAnalysisManager, Module> is
  /// an analysis over Modules (the "outer" unit) that provides access to a
  /// Function analysis manager.  The FunctionAnalysisManager is the "inner"
  /// manager being proxied, and Functions are the "inner" unit.  The inner/outer
  /// relationship is valid because each Function is contained in one Module.
  ///
  /// If you're (transitively) within a pass manager for an IR unit U that
  /// contains IR unit V, you should never use an analysis manager over V, except
  /// via one of these proxies.
  ///
  /// Note that the proxy's result is a move-only RAII object.  The validity of
  /// the analyses in the inner analysis manager is tied to its lifetime.
  template <typename AnalysisManagerT, typename IRUnitT, typename... ExtraArgTs>
  class InnerAnalysisManagerProxy
      : public AnalysisInfoMixin<
            InnerAnalysisManagerProxy<AnalysisManagerT, IRUnitT>> {
  public:
    class Result {
    public:
      explicit Result(AnalysisManagerT &InnerAM) : InnerAM(&InnerAM) {}
      Result(Result &&Arg) : InnerAM(std::move(Arg.InnerAM)) {
        // We have to null out the analysis manager in the moved-from state
        // because we are taking ownership of the responsibilty to clear the
        // analysis state.
        Arg.InnerAM = nullptr;
      }
      Result &operator=(Result &&RHS) {
        InnerAM = RHS.InnerAM;
        // We have to null out the analysis manager in the moved-from state
        // because we are taking ownership of the responsibilty to clear the
        // analysis state.
        RHS.InnerAM = nullptr;
        return *this;
      }
      ~Result() {
        // InnerAM is cleared in a moved from state where there is nothing to do.
        if (!InnerAM)
          return;
  
        // Clear out the analysis manager if we're being destroyed -- it means we
        // didn't even see an invalidate call when we got invalidated.
        InnerAM->clear();
      }
  
      /// \brief Accessor for the analysis manager.
      AnalysisManagerT &getManager() { return *InnerAM; }
  
      /// \brief Handler for invalidation of the outer IR unit, \c IRUnitT.
      ///
      /// If the proxy analysis itself is not preserved, we assume that the set of
      /// inner IR objects contained in IRUnit may have changed.  In this case,
      /// we have to call \c clear() on the inner analysis manager, as it may now
      /// have stale pointers to its inner IR objects.
      ///
      /// Regardless of whether the proxy analysis is marked as preserved, all of
      /// the analyses in the inner analysis manager are potentially invalidated
      /// based on the set of preserved analyses.
      bool invalidate(
          IRUnitT &IR, const PreservedAnalyses &PA,
          typename AnalysisManager<IRUnitT, ExtraArgTs...>::Invalidator &Inv);
  
    private:
      AnalysisManagerT *InnerAM;
    };
  
    explicit InnerAnalysisManagerProxy(AnalysisManagerT &InnerAM)
        : InnerAM(&InnerAM) {}
  
    /// \brief Run the analysis pass and create our proxy result object.
    ///
    /// This doesn't do any interesting work; it is primarily used to insert our
    /// proxy result object into the outer analysis cache so that we can proxy
    /// invalidation to the inner analysis manager.
    Result run(IRUnitT &IR, AnalysisManager<IRUnitT, ExtraArgTs...> &AM,
               ExtraArgTs...) {
      return Result(*InnerAM);
    }
  
  private:
    friend AnalysisInfoMixin<
        InnerAnalysisManagerProxy<AnalysisManagerT, IRUnitT>>;
    static AnalysisKey Key;
  
    AnalysisManagerT *InnerAM;
  };
  
  template <typename AnalysisManagerT, typename IRUnitT, typename... ExtraArgTs>
  AnalysisKey
      InnerAnalysisManagerProxy<AnalysisManagerT, IRUnitT, ExtraArgTs...>::Key;
  
  /// Provide the \c FunctionAnalysisManager to \c Module proxy.
  typedef InnerAnalysisManagerProxy<FunctionAnalysisManager, Module>
      FunctionAnalysisManagerModuleProxy;
  
  /// Specialization of the invalidate method for the \c
  /// FunctionAnalysisManagerModuleProxy's result.
  template <>
  bool FunctionAnalysisManagerModuleProxy::Result::invalidate(
      Module &M, const PreservedAnalyses &PA,
      ModuleAnalysisManager::Invalidator &Inv);
  
  // Ensure the \c FunctionAnalysisManagerModuleProxy is provided as an extern
  // template.
  extern template class InnerAnalysisManagerProxy<FunctionAnalysisManager,
                                                  Module>;
  
  /// \brief An analysis over an "inner" IR unit that provides access to an
  /// analysis manager over a "outer" IR unit.  The inner unit must be contained
  /// in the outer unit.
  ///
  /// For example OuterAnalysisManagerProxy<ModuleAnalysisManager, Function> is an
  /// analysis over Functions (the "inner" unit) which provides access to a Module
  /// analysis manager.  The ModuleAnalysisManager is the "outer" manager being
  /// proxied, and Modules are the "outer" IR unit.  The inner/outer relationship
  /// is valid because each Function is contained in one Module.
  ///
  /// This proxy only exposes the const interface of the outer analysis manager,
  /// to indicate that you cannot cause an outer analysis to run from within an
  /// inner pass.  Instead, you must rely on the \c getCachedResult API.
  ///
  /// This proxy doesn't manage invalidation in any way -- that is handled by the
  /// recursive return path of each layer of the pass manager.  A consequence of
  /// this is the outer analyses may be stale.  We invalidate the outer analyses
  /// only when we're done running passes over the inner IR units.
  template <typename AnalysisManagerT, typename IRUnitT, typename... ExtraArgTs>
  class OuterAnalysisManagerProxy
      : public AnalysisInfoMixin<
            OuterAnalysisManagerProxy<AnalysisManagerT, IRUnitT, ExtraArgTs...>> {
  public:
    /// \brief Result proxy object for \c OuterAnalysisManagerProxy.
    class Result {
    public:
      explicit Result(const AnalysisManagerT &AM) : AM(&AM) {}
  
      const AnalysisManagerT &getManager() const { return *AM; }
  
      /// \brief Handle invalidation by ignoring it; this pass is immutable.
      bool invalidate(
          IRUnitT &, const PreservedAnalyses &,
          typename AnalysisManager<IRUnitT, ExtraArgTs...>::Invalidator &) {
        return false;
      }
  
      /// Register a deferred invalidation event for when the outer analysis
      /// manager processes its invalidations.
      template <typename OuterAnalysisT, typename InvalidatedAnalysisT>
      void registerOuterAnalysisInvalidation() {
        AnalysisKey *OuterID = OuterAnalysisT::ID();
        AnalysisKey *InvalidatedID = InvalidatedAnalysisT::ID();
  
        auto &InvalidatedIDList = OuterAnalysisInvalidationMap[OuterID];
        // Note, this is a linear scan. If we end up with large numbers of
        // analyses that all trigger invalidation on the same outer analysis,
        // this entire system should be changed to some other deterministic
        // data structure such as a `SetVector` of a pair of pointers.
        auto InvalidatedIt = std::find(InvalidatedIDList.begin(),
                                       InvalidatedIDList.end(), InvalidatedID);
        if (InvalidatedIt == InvalidatedIDList.end())
          InvalidatedIDList.push_back(InvalidatedID);
      }
  
      /// Access the map from outer analyses to deferred invalidation requiring
      /// analyses.
      const SmallDenseMap<AnalysisKey *, TinyPtrVector<AnalysisKey *>, 2> &
      getOuterInvalidations() const {
        return OuterAnalysisInvalidationMap;
      }
  
    private:
      const AnalysisManagerT *AM;
  
      /// A map from an outer analysis ID to the set of this IR-unit's analyses
      /// which need to be invalidated.
      SmallDenseMap<AnalysisKey *, TinyPtrVector<AnalysisKey *>, 2>
          OuterAnalysisInvalidationMap;
    };
  
    OuterAnalysisManagerProxy(const AnalysisManagerT &AM) : AM(&AM) {}
  
    /// \brief Run the analysis pass and create our proxy result object.
    /// Nothing to see here, it just forwards the \c AM reference into the
    /// result.
    Result run(IRUnitT &, AnalysisManager<IRUnitT, ExtraArgTs...> &,
               ExtraArgTs...) {
      return Result(*AM);
    }
  
  private:
    friend AnalysisInfoMixin<
        OuterAnalysisManagerProxy<AnalysisManagerT, IRUnitT, ExtraArgTs...>>;
    static AnalysisKey Key;
  
    const AnalysisManagerT *AM;
  };
  
  template <typename AnalysisManagerT, typename IRUnitT, typename... ExtraArgTs>
  AnalysisKey
      OuterAnalysisManagerProxy<AnalysisManagerT, IRUnitT, ExtraArgTs...>::Key;
  
  extern template class OuterAnalysisManagerProxy<ModuleAnalysisManager,
                                                  Function>;
  /// Provide the \c ModuleAnalysisManager to \c Function proxy.
  typedef OuterAnalysisManagerProxy<ModuleAnalysisManager, Function>
      ModuleAnalysisManagerFunctionProxy;
  
  /// \brief Trivial adaptor that maps from a module to its functions.
  ///
  /// Designed to allow composition of a FunctionPass(Manager) and
  /// a ModulePassManager, by running the FunctionPass(Manager) over every
  /// function in the module.
  ///
  /// Function passes run within this adaptor can rely on having exclusive access
  /// to the function they are run over. They should not read or modify any other
  /// functions! Other threads or systems may be manipulating other functions in
  /// the module, and so their state should never be relied on.
  /// FIXME: Make the above true for all of LLVM's actual passes, some still
  /// violate this principle.
  ///
  /// Function passes can also read the module containing the function, but they
  /// should not modify that module outside of the use lists of various globals.
  /// For example, a function pass is not permitted to add functions to the
  /// module.
  /// FIXME: Make the above true for all of LLVM's actual passes, some still
  /// violate this principle.
  ///
  /// Note that although function passes can access module analyses, module
  /// analyses are not invalidated while the function passes are running, so they
  /// may be stale.  Function analyses will not be stale.
  template <typename FunctionPassT>
  class ModuleToFunctionPassAdaptor
      : public PassInfoMixin<ModuleToFunctionPassAdaptor<FunctionPassT>> {
  public:
    explicit ModuleToFunctionPassAdaptor(FunctionPassT Pass)
        : Pass(std::move(Pass)) {}
  
    /// \brief Runs the function pass across every function in the module.
    PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM) {
      FunctionAnalysisManager &FAM =
          AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
  
      PreservedAnalyses PA = PreservedAnalyses::all();
      for (Function &F : M) {
        if (F.isDeclaration())
          continue;
  
        PreservedAnalyses PassPA = Pass.run(F, FAM);
  
        // We know that the function pass couldn't have invalidated any other
        // function's analyses (that's the contract of a function pass), so
        // directly handle the function analysis manager's invalidation here.
        FAM.invalidate(F, PassPA);
  
        // Then intersect the preserved set so that invalidation of module
        // analyses will eventually occur when the module pass completes.
        PA.intersect(std::move(PassPA));
      }
  
      // The FunctionAnalysisManagerModuleProxy is preserved because (we assume)
      // the function passes we ran didn't add or remove any functions.
      //
      // We also preserve all analyses on Functions, because we did all the
      // invalidation we needed to do above.
      PA.preserveSet<AllAnalysesOn<Function>>();
      PA.preserve<FunctionAnalysisManagerModuleProxy>();
      return PA;
    }
  
  private:
    FunctionPassT Pass;
  };
  
  /// \brief A function to deduce a function pass type and wrap it in the
  /// templated adaptor.
  template <typename FunctionPassT>
  ModuleToFunctionPassAdaptor<FunctionPassT>
  createModuleToFunctionPassAdaptor(FunctionPassT Pass) {
    return ModuleToFunctionPassAdaptor<FunctionPassT>(std::move(Pass));
  }
  
  /// \brief A utility pass template to force an analysis result to be available.
  ///
  /// If there are extra arguments at the pass's run level there may also be
  /// extra arguments to the analysis manager's \c getResult routine. We can't
  /// guess how to effectively map the arguments from one to the other, and so
  /// this specialization just ignores them.
  ///
  /// Specific patterns of run-method extra arguments and analysis manager extra
  /// arguments will have to be defined as appropriate specializations.
  template <typename AnalysisT, typename IRUnitT,
            typename AnalysisManagerT = AnalysisManager<IRUnitT>,
            typename... ExtraArgTs>
  struct RequireAnalysisPass
      : PassInfoMixin<RequireAnalysisPass<AnalysisT, IRUnitT, AnalysisManagerT,
                                          ExtraArgTs...>> {
    /// \brief Run this pass over some unit of IR.
    ///
    /// This pass can be run over any unit of IR and use any analysis manager
    /// provided they satisfy the basic API requirements. When this pass is
    /// created, these methods can be instantiated to satisfy whatever the
    /// context requires.
    PreservedAnalyses run(IRUnitT &Arg, AnalysisManagerT &AM,
                          ExtraArgTs &&... Args) {
      (void)AM.template getResult<AnalysisT>(Arg,
                                             std::forward<ExtraArgTs>(Args)...);
  
      return PreservedAnalyses::all();
    }
  };
  
  /// \brief A no-op pass template which simply forces a specific analysis result
  /// to be invalidated.
  template <typename AnalysisT>
  struct InvalidateAnalysisPass
      : PassInfoMixin<InvalidateAnalysisPass<AnalysisT>> {
    /// \brief Run this pass over some unit of IR.
    ///
    /// This pass can be run over any unit of IR and use any analysis manager,
    /// provided they satisfy the basic API requirements. When this pass is
    /// created, these methods can be instantiated to satisfy whatever the
    /// context requires.
    template <typename IRUnitT, typename AnalysisManagerT, typename... ExtraArgTs>
    PreservedAnalyses run(IRUnitT &Arg, AnalysisManagerT &AM, ExtraArgTs &&...) {
      auto PA = PreservedAnalyses::all();
      PA.abandon<AnalysisT>();
      return PA;
    }
  };
  
  /// \brief A utility pass that does nothing, but preserves no analyses.
  ///
  /// Because this preserves no analyses, any analysis passes queried after this
  /// pass runs will recompute fresh results.
  struct InvalidateAllAnalysesPass : PassInfoMixin<InvalidateAllAnalysesPass> {
    /// \brief Run this pass over some unit of IR.
    template <typename IRUnitT, typename AnalysisManagerT, typename... ExtraArgTs>
    PreservedAnalyses run(IRUnitT &, AnalysisManagerT &, ExtraArgTs &&...) {
      return PreservedAnalyses::none();
    }
  };
  
  /// A utility pass template that simply runs another pass multiple times.
  ///
  /// This can be useful when debugging or testing passes. It also serves as an
  /// example of how to extend the pass manager in ways beyond composition.
  template <typename PassT>
  class RepeatedPass : public PassInfoMixin<RepeatedPass<PassT>> {
  public:
    RepeatedPass(int Count, PassT P) : Count(Count), P(std::move(P)) {}
  
    template <typename IRUnitT, typename AnalysisManagerT, typename... Ts>
    PreservedAnalyses run(IRUnitT &Arg, AnalysisManagerT &AM, Ts &&... Args) {
      auto PA = PreservedAnalyses::all();
      for (int i = 0; i < Count; ++i)
        PA.intersect(P.run(Arg, AM, std::forward<Ts>(Args)...));
      return PA;
    }
  
  private:
    int Count;
    PassT P;
  };
  
  template <typename PassT>
  RepeatedPass<PassT> createRepeatedPass(int Count, PassT P) {
    return RepeatedPass<PassT>(Count, std::move(P));
  }
  
  }
  
  #endif
  