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//===- RegionInfo.h - SESE region analysis ----------------------*- C++ -*-===//

//

// 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

//

//===----------------------------------------------------------------------===//

//

// Calculate a program structure tree built out of single entry single exit

// regions.

// The basic ideas are taken from "The Program Structure Tree - Richard Johnson,

// David Pearson, Keshav Pingali - 1994", however enriched with ideas from "The

// Refined Process Structure Tree - Jussi Vanhatalo, Hagen Voelyer, Jana

// Koehler - 2009".

// The algorithm to calculate these data structures however is completely

// different, as it takes advantage of existing information already available

// in (Post)dominace tree and dominance frontier passes. This leads to a simpler

// and in practice hopefully better performing algorithm. The runtime of the

// algorithms described in the papers above are both linear in graph size,

// O(V+E), whereas this algorithm is not, as the dominance frontier information

// itself is not, but in practice runtime seems to be in the order of magnitude

// of dominance tree calculation.

//

// WARNING: LLVM is generally very concerned about compile time such that

//          the use of additional analysis passes in the default

//          optimization sequence is avoided as much as possible.

//          Specifically, if you do not need the RegionInfo, but dominance

//          information could be sufficient please base your work only on

//          the dominator tree. Most passes maintain it, such that using

//          it has often near zero cost. In contrast RegionInfo is by

//          default not available, is not maintained by existing

//          transformations and there is no intention to do so.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_ANALYSIS_REGIONINFO_H

#define LLVM_ANALYSIS_REGIONINFO_H

#include "llvm/ADT/DenseMap.h"

#include "llvm/ADT/DepthFirstIterator.h"

#include "llvm/ADT/GraphTraits.h"

#include "llvm/ADT/PointerIntPair.h"

#include "llvm/ADT/iterator_range.h"

#include "llvm/Config/llvm-config.h"

#include "llvm/IR/Dominators.h"

#include "llvm/IR/PassManager.h"

#include "llvm/Pass.h"

#include <algorithm>

#include <cassert>

#include <map>

#include <memory>

#include <set>

#include <string>

#include <type_traits>

#include <vector>

namespace llvm {

class BasicBlock;

class DominanceFrontier;

class Loop;

class LoopInfo;

class PostDominatorTree;

class Region;

template <class RegionTr> class RegionBase;

class RegionInfo;

template <class RegionTr> class RegionInfoBase;

class RegionNode;

class raw_ostream;

// Class to be specialized for different users of RegionInfo

// (i.e. BasicBlocks or MachineBasicBlocks). This is only to avoid needing to

// pass around an unreasonable number of template parameters.

template <class FuncT_>

struct RegionTraits {

  // FuncT

  // BlockT

  // RegionT

  // RegionNodeT

  // RegionInfoT

  using BrokenT = typename FuncT_::UnknownRegionTypeError;

};

template <>

struct RegionTraits<Function> {

  using FuncT = Function;

  using BlockT = BasicBlock;

  using RegionT = Region;

  using RegionNodeT = RegionNode;

  using RegionInfoT = RegionInfo;

  using DomTreeT = DominatorTree;

  using DomTreeNodeT = DomTreeNode;

  using DomFrontierT = DominanceFrontier;

  using PostDomTreeT = PostDominatorTree;

  using InstT = Instruction;

  using LoopT = Loop;

  using LoopInfoT = LoopInfo;

  static unsigned getNumSuccessors(BasicBlock *BB) {

    return BB->getTerminator()->getNumSuccessors();

  }

};

/// Marker class to iterate over the elements of a Region in flat mode.

///

/// The class is used to either iterate in Flat mode or by not using it to not

/// iterate in Flat mode.  During a Flat mode iteration all Regions are entered

/// and the iteration returns every BasicBlock.  If the Flat mode is not

/// selected for SubRegions just one RegionNode containing the subregion is

/// returned.

template <class GraphType>

class FlatIt {};

/// A RegionNode represents a subregion or a BasicBlock that is part of a

/// Region.

template <class Tr>

class RegionNodeBase {

  friend class RegionBase<Tr>;

public:

  using BlockT = typename Tr::BlockT;

  using RegionT = typename Tr::RegionT;

private:

  /// This is the entry basic block that starts this region node.  If this is a

  /// BasicBlock RegionNode, then entry is just the basic block, that this

  /// RegionNode represents.  Otherwise it is the entry of this (Sub)RegionNode.

  ///

  /// In the BBtoRegionNode map of the parent of this node, BB will always map

  /// to this node no matter which kind of node this one is.

  ///

  /// The node can hold either a Region or a BasicBlock.

  /// Use one bit to save, if this RegionNode is a subregion or BasicBlock

  /// RegionNode.

  PointerIntPair<BlockT *, 1, bool> entry;

  /// The parent Region of this RegionNode.

  /// @see getParent()

  RegionT *parent;

protected:

  /// Create a RegionNode.

  ///

  /// @param Parent      The parent of this RegionNode.

  /// @param Entry       The entry BasicBlock of the RegionNode.  If this

  ///                    RegionNode represents a BasicBlock, this is the

  ///                    BasicBlock itself.  If it represents a subregion, this

  ///                    is the entry BasicBlock of the subregion.

  /// @param isSubRegion If this RegionNode represents a SubRegion.

  inline RegionNodeBase(RegionT *Parent, BlockT *Entry,

                        bool isSubRegion = false)

      : entry(Entry, isSubRegion), parent(Parent) {}

public:

  RegionNodeBase(const RegionNodeBase &) = delete;

  RegionNodeBase &operator=(const RegionNodeBase &) = delete;

  /// Get the parent Region of this RegionNode.

  ///

  /// The parent Region is the Region this RegionNode belongs to. If for

  /// example a BasicBlock is element of two Regions, there exist two

  /// RegionNodes for this BasicBlock. Each with the getParent() function

  /// pointing to the Region this RegionNode belongs to.

  ///

  /// @return Get the parent Region of this RegionNode.

  inline RegionT *getParent() const { return parent; }

  /// Get the entry BasicBlock of this RegionNode.

  ///

  /// If this RegionNode represents a BasicBlock this is just the BasicBlock

  /// itself, otherwise we return the entry BasicBlock of the Subregion

  ///

  /// @return The entry BasicBlock of this RegionNode.

  inline BlockT *getEntry() const { return entry.getPointer(); }

  /// Get the content of this RegionNode.

  ///

  /// This can be either a BasicBlock or a subregion. Before calling getNodeAs()

  /// check the type of the content with the isSubRegion() function call.

  ///

  /// @return The content of this RegionNode.

  template <class T> inline T *getNodeAs() const;

  /// Is this RegionNode a subregion?

  ///

  /// @return True if it contains a subregion. False if it contains a

  ///         BasicBlock.

  inline bool isSubRegion() const { return entry.getInt(); }

};

//===----------------------------------------------------------------------===//

/// A single entry single exit Region.

///

/// A Region is a connected subgraph of a control flow graph that has exactly

/// two connections to the remaining graph. It can be used to analyze or

/// optimize parts of the control flow graph.

///

/// A <em> simple Region </em> is connected to the remaining graph by just two

/// edges. One edge entering the Region and another one leaving the Region.

///

/// An <em> extended Region </em> (or just Region) is a subgraph that can be

/// transform into a simple Region. The transformation is done by adding

/// BasicBlocks that merge several entry or exit edges so that after the merge

/// just one entry and one exit edge exists.

///

/// The \e Entry of a Region is the first BasicBlock that is passed after

/// entering the Region. It is an element of the Region. The entry BasicBlock

/// dominates all BasicBlocks in the Region.

///

/// The \e Exit of a Region is the first BasicBlock that is passed after

/// leaving the Region. It is not an element of the Region. The exit BasicBlock,

/// postdominates all BasicBlocks in the Region.

///

/// A <em> canonical Region </em> cannot be constructed by combining smaller

/// Regions.

///

/// Region A is the \e parent of Region B, if B is completely contained in A.

///

/// Two canonical Regions either do not intersect at all or one is

/// the parent of the other.

///

/// The <em> Program Structure Tree</em> is a graph (V, E) where V is the set of

/// Regions in the control flow graph and E is the \e parent relation of these

/// Regions.

///

/// Example:

///

/// \verbatim

/// A simple control flow graph, that contains two regions.

///

///        1

///       / |

///      2   |

///     / \   3

///    4   5  |

///    |   |  |

///    6   7  8

///     \  | /

///      \ |/       Region A: 1 -> 9 {1,2,3,4,5,6,7,8}

///        9        Region B: 2 -> 9 {2,4,5,6,7}

/// \endverbatim

///

/// You can obtain more examples by either calling

///

/// <tt> "opt -passes='print<regions>' anyprogram.ll" </tt>

/// or

/// <tt> "opt -view-regions-only anyprogram.ll" </tt>

///

/// on any LLVM file you are interested in.

///

/// The first call returns a textual representation of the program structure

/// tree, the second one creates a graphical representation using graphviz.

template <class Tr>

class RegionBase : public RegionNodeBase<Tr> {

  friend class RegionInfoBase<Tr>;

  using FuncT = typename Tr::FuncT;

  using BlockT = typename Tr::BlockT;

  using RegionInfoT = typename Tr::RegionInfoT;

  using RegionT = typename Tr::RegionT;

  using RegionNodeT = typename Tr::RegionNodeT;

  using DomTreeT = typename Tr::DomTreeT;

  using LoopT = typename Tr::LoopT;

  using LoopInfoT = typename Tr::LoopInfoT;

  using InstT = typename Tr::InstT;

  using BlockTraits = GraphTraits<BlockT *>;

  using InvBlockTraits = GraphTraits<Inverse<BlockT *>>;

  using SuccIterTy = typename BlockTraits::ChildIteratorType;

  using PredIterTy = typename InvBlockTraits::ChildIteratorType;

  // Information necessary to manage this Region.

  RegionInfoT *RI;

  DomTreeT *DT;

  // The exit BasicBlock of this region.

  // (The entry BasicBlock is part of RegionNode)

  BlockT *exit;

  using RegionSet = std::vector<std::unique_ptr<RegionT>>;

  // The subregions of this region.

  RegionSet children;

  using BBNodeMapT = std::map<BlockT *, std::unique_ptr<RegionNodeT>>;

  // Save the BasicBlock RegionNodes that are element of this Region.

  mutable BBNodeMapT BBNodeMap;

  /// Check if a BB is in this Region. This check also works

  /// if the region is incorrectly built. (EXPENSIVE!)

  void verifyBBInRegion(BlockT *BB) const;

  /// Walk over all the BBs of the region starting from BB and

  /// verify that all reachable basic blocks are elements of the region.

  /// (EXPENSIVE!)

  void verifyWalk(BlockT *BB, std::set<BlockT *> *visitedBB) const;

  /// Verify if the region and its children are valid regions (EXPENSIVE!)

  void verifyRegionNest() const;

public:

  /// Create a new region.

  ///

  /// @param Entry  The entry basic block of the region.

  /// @param Exit   The exit basic block of the region.

  /// @param RI     The region info object that is managing this region.

  /// @param DT     The dominator tree of the current function.

  /// @param Parent The surrounding region or NULL if this is a top level

  ///               region.

  RegionBase(BlockT *Entry, BlockT *Exit, RegionInfoT *RI, DomTreeT *DT,

             RegionT *Parent = nullptr);

  RegionBase(const RegionBase &) = delete;

  RegionBase &operator=(const RegionBase &) = delete;

  /// Delete the Region and all its subregions.

  ~RegionBase();

  /// Get the entry BasicBlock of the Region.

  /// @return The entry BasicBlock of the region.

  BlockT *getEntry() const {

    return RegionNodeBase<Tr>::getEntry();

  }

  /// Replace the entry basic block of the region with the new basic

  ///        block.

  ///

  /// @param BB  The new entry basic block of the region.

  void replaceEntry(BlockT *BB);

  /// Replace the exit basic block of the region with the new basic

  ///        block.

  ///

  /// @param BB  The new exit basic block of the region.

  void replaceExit(BlockT *BB);

  /// Recursively replace the entry basic block of the region.

  ///

  /// This function replaces the entry basic block with a new basic block. It

  /// also updates all child regions that have the same entry basic block as

  /// this region.

  ///

  /// @param NewEntry The new entry basic block.

  void replaceEntryRecursive(BlockT *NewEntry);

  /// Recursively replace the exit basic block of the region.

  ///

  /// This function replaces the exit basic block with a new basic block. It

  /// also updates all child regions that have the same exit basic block as

  /// this region.

  ///

  /// @param NewExit The new exit basic block.

  void replaceExitRecursive(BlockT *NewExit);

  /// Get the exit BasicBlock of the Region.

  /// @return The exit BasicBlock of the Region, NULL if this is the TopLevel

  ///         Region.

  BlockT *getExit() const { return exit; }

  /// Get the parent of the Region.

  /// @return The parent of the Region or NULL if this is a top level

  ///         Region.

  RegionT *getParent() const {

    return RegionNodeBase<Tr>::getParent();

  }

  /// Get the RegionNode representing the current Region.

  /// @return The RegionNode representing the current Region.

  RegionNodeT *getNode() const {

    return const_cast<RegionNodeT *>(

        reinterpret_cast<const RegionNodeT *>(this));

  }

  /// Get the nesting level of this Region.

  ///

  /// An toplevel Region has depth 0.

  ///

  /// @return The depth of the region.

  unsigned getDepth() const;

  /// Check if a Region is the TopLevel region.

  ///

  /// The toplevel region represents the whole function.

  bool isTopLevelRegion() const { return exit == nullptr; }

  /// Return a new (non-canonical) region, that is obtained by joining

  ///        this region with its predecessors.

  ///

  /// @return A region also starting at getEntry(), but reaching to the next

  ///         basic block that forms with getEntry() a (non-canonical) region.

  ///         NULL if such a basic block does not exist.

  RegionT *getExpandedRegion() const;

  /// Return the first block of this region's single entry edge,

  ///        if existing.

  ///

  /// @return The BasicBlock starting this region's single entry edge,

  ///         else NULL.

  BlockT *getEnteringBlock() const;

  /// Return the first block of this region's single exit edge,

  ///        if existing.

  ///

  /// @return The BasicBlock starting this region's single exit edge,

  ///         else NULL.

  BlockT *getExitingBlock() const;

  /// Collect all blocks of this region's single exit edge, if existing.

  ///

  /// @return True if this region contains all the predecessors of the exit.

  bool getExitingBlocks(SmallVectorImpl<BlockT *> &Exitings) const;

  /// Is this a simple region?

  ///

  /// A region is simple if it has exactly one exit and one entry edge.

  ///

  /// @return True if the Region is simple.

  bool isSimple() const;

  /// Returns the name of the Region.

  /// @return The Name of the Region.

  std::string getNameStr() const;

  /// Return the RegionInfo object, that belongs to this Region.

  RegionInfoT *getRegionInfo() const { return RI; }

  /// PrintStyle - Print region in difference ways.

  enum PrintStyle { PrintNone, PrintBB, PrintRN };

  /// Print the region.

  ///

  /// @param OS The output stream the Region is printed to.

  /// @param printTree Print also the tree of subregions.

  /// @param level The indentation level used for printing.

  void print(raw_ostream &OS, bool printTree = true, unsigned level = 0,

             PrintStyle Style = PrintNone) const;

#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)

  /// Print the region to stderr.

  void dump() const;

#endif

  /// Check if the region contains a BasicBlock.

  ///

  /// @param BB The BasicBlock that might be contained in this Region.

  /// @return True if the block is contained in the region otherwise false.

  bool contains(const BlockT *BB) const;

  /// Check if the region contains another region.

  ///

  /// @param SubRegion The region that might be contained in this Region.

  /// @return True if SubRegion is contained in the region otherwise false.

  bool contains(const RegionT *SubRegion) const {

    // Toplevel Region.

    if (!getExit())

      return true;

    return contains(SubRegion->getEntry()) &&

           (contains(SubRegion->getExit()) ||

            SubRegion->getExit() == getExit());

  }

  /// Check if the region contains an Instruction.

  ///

  /// @param Inst The Instruction that might be contained in this region.

  /// @return True if the Instruction is contained in the region otherwise

  /// false.

  bool contains(const InstT *Inst) const { return contains(Inst->getParent()); }

  /// Check if the region contains a loop.

  ///

  /// @param L The loop that might be contained in this region.

  /// @return True if the loop is contained in the region otherwise false.

  ///         In case a NULL pointer is passed to this function the result

  ///         is false, except for the region that describes the whole function.

  ///         In that case true is returned.

  bool contains(const LoopT *L) const;

  /// Get the outermost loop in the region that contains a loop.

  ///

  /// Find for a Loop L the outermost loop OuterL that is a parent loop of L

  /// and is itself contained in the region.

  ///

  /// @param L The loop the lookup is started.

  /// @return The outermost loop in the region, NULL if such a loop does not

  ///         exist or if the region describes the whole function.

  LoopT *outermostLoopInRegion(LoopT *L) const;

  /// Get the outermost loop in the region that contains a basic block.

  ///

  /// Find for a basic block BB the outermost loop L that contains BB and is

  /// itself contained in the region.

  ///

  /// @param LI A pointer to a LoopInfo analysis.

  /// @param BB The basic block surrounded by the loop.

  /// @return The outermost loop in the region, NULL if such a loop does not

  ///         exist or if the region describes the whole function.

  LoopT *outermostLoopInRegion(LoopInfoT *LI, BlockT *BB) const;

  /// Get the subregion that starts at a BasicBlock

  ///

  /// @param BB The BasicBlock the subregion should start.

  /// @return The Subregion if available, otherwise NULL.

  RegionT *getSubRegionNode(BlockT *BB) const;

  /// Get the RegionNode for a BasicBlock

  ///

  /// @param BB The BasicBlock at which the RegionNode should start.

  /// @return If available, the RegionNode that represents the subregion

  ///         starting at BB. If no subregion starts at BB, the RegionNode

  ///         representing BB.

  RegionNodeT *getNode(BlockT *BB) const;

  /// Get the BasicBlock RegionNode for a BasicBlock

  ///

  /// @param BB The BasicBlock for which the RegionNode is requested.

  /// @return The RegionNode representing the BB.

  RegionNodeT *getBBNode(BlockT *BB) const;

  /// Add a new subregion to this Region.

  ///

  /// @param SubRegion The new subregion that will be added.

  /// @param moveChildren Move the children of this region, that are also

  ///                     contained in SubRegion into SubRegion.

  void addSubRegion(RegionT *SubRegion, bool moveChildren = false);

  /// Remove a subregion from this Region.

  ///

  /// The subregion is not deleted, as it will probably be inserted into another

  /// region.

  /// @param SubRegion The SubRegion that will be removed.

  RegionT *removeSubRegion(RegionT *SubRegion);

  /// Move all direct child nodes of this Region to another Region.

  ///

  /// @param To The Region the child nodes will be transferred to.

  void transferChildrenTo(RegionT *To);

  /// Verify if the region is a correct region.

  ///

  /// Check if this is a correctly build Region. This is an expensive check, as

  /// the complete CFG of the Region will be walked.

  void verifyRegion() const;

  /// Clear the cache for BB RegionNodes.

  ///

  /// After calling this function the BasicBlock RegionNodes will be stored at

  /// different memory locations. RegionNodes obtained before this function is

  /// called are therefore not comparable to RegionNodes abtained afterwords.

  void clearNodeCache();

  /// @name Subregion Iterators

  ///

  /// These iterators iterator over all subregions of this Region.

  //@{

  using iterator = typename RegionSet::iterator;

  using const_iterator = typename RegionSet::const_iterator;

  iterator begin() { return children.begin(); }

  iterator end() { return children.end(); }

  const_iterator begin() const { return children.begin(); }

  const_iterator end() const { return children.end(); }

  //@}

  /// @name BasicBlock Iterators

  ///

  /// These iterators iterate over all BasicBlocks that are contained in this

  /// Region. The iterator also iterates over BasicBlocks that are elements of

  /// a subregion of this Region. It is therefore called a flat iterator.

  //@{

  template <bool IsConst>

  class block_iterator_wrapper

      : public df_iterator<

            std::conditional_t<IsConst, const BlockT, BlockT> *> {

    using super =

        df_iterator<std::conditional_t<IsConst, const BlockT, BlockT> *>;

  public:

    using Self = block_iterator_wrapper<IsConst>;

    using value_type = typename super::value_type;

    // Construct the begin iterator.

    block_iterator_wrapper(value_type Entry, value_type Exit)

        : super(df_begin(Entry)) {

      // Mark the exit of the region as visited, so that the children of the

      // exit and the exit itself, i.e. the block outside the region will never

      // be visited.

      super::Visited.insert(Exit);

    }

    // Construct the end iterator.

    block_iterator_wrapper() : super(df_end<value_type>((BlockT *)nullptr)) {}

    /*implicit*/ block_iterator_wrapper(super I) : super(I) {}

    // FIXME: Even a const_iterator returns a non-const BasicBlock pointer.

    //        This was introduced for backwards compatibility, but should

    //        be removed as soon as all users are fixed.

    BlockT *operator*() const {

      return const_cast<BlockT *>(super::operator*());

    }

  };

  using block_iterator = block_iterator_wrapper<false>;

  using const_block_iterator = block_iterator_wrapper<true>;

  block_iterator block_begin() { return block_iterator(getEntry(), getExit()); }

  block_iterator block_end() { return block_iterator(); }

  const_block_iterator block_begin() const {

    return const_block_iterator(getEntry(), getExit());

  }

  const_block_iterator block_end() const { return const_block_iterator(); }

  using block_range = iterator_range<block_iterator>;

  using const_block_range = iterator_range<const_block_iterator>;

  /// Returns a range view of the basic blocks in the region.

  inline block_range blocks() {

    return block_range(block_begin(), block_end());

  }

  /// Returns a range view of the basic blocks in the region.

  ///

  /// This is the 'const' version of the range view.

  inline const_block_range blocks() const {

    return const_block_range(block_begin(), block_end());

  }

  //@}

  /// @name Element Iterators

  ///

  /// These iterators iterate over all BasicBlock and subregion RegionNodes that

  /// are direct children of this Region. It does not iterate over any

  /// RegionNodes that are also element of a subregion of this Region.

  //@{

  using element_iterator =

      df_iterator<RegionNodeT *, df_iterator_default_set<RegionNodeT *>, false,

                  GraphTraits<RegionNodeT *>>;

  using const_element_iterator =

      df_iterator<const RegionNodeT *,

                  df_iterator_default_set<const RegionNodeT *>, false,

                  GraphTraits<const RegionNodeT *>>;

  element_iterator element_begin();

  element_iterator element_end();

  iterator_range<element_iterator> elements() {

    return make_range(element_begin(), element_end());

  }

  const_element_iterator element_begin() const;

  const_element_iterator element_end() const;

  iterator_range<const_element_iterator> elements() const {

    return make_range(element_begin(), element_end());

  }

  //@}

};

/// Print a RegionNode.

template <class Tr>

inline raw_ostream &operator<<(raw_ostream &OS, const RegionNodeBase<Tr> &Node);

//===----------------------------------------------------------------------===//

/// Analysis that detects all canonical Regions.

///

/// The RegionInfo pass detects all canonical regions in a function. The Regions

/// are connected using the parent relation. This builds a Program Structure

/// Tree.

template <class Tr>

class RegionInfoBase {

  friend class RegionInfo;

  friend class MachineRegionInfo;

  using BlockT = typename Tr::BlockT;

  using FuncT = typename Tr::FuncT;

  using RegionT = typename Tr::RegionT;

  using RegionInfoT = typename Tr::RegionInfoT;

  using DomTreeT = typename Tr::DomTreeT;

  using DomTreeNodeT = typename Tr::DomTreeNodeT;

  using PostDomTreeT = typename Tr::PostDomTreeT;

  using DomFrontierT = typename Tr::DomFrontierT;

  using BlockTraits = GraphTraits<BlockT *>;

  using InvBlockTraits = GraphTraits<Inverse<BlockT *>>;

  using SuccIterTy = typename BlockTraits::ChildIteratorType;

  using PredIterTy = typename InvBlockTraits::ChildIteratorType;

  using BBtoBBMap = DenseMap<BlockT *, BlockT *>;

  using BBtoRegionMap = DenseMap<BlockT *, RegionT *>;

  RegionInfoBase();

  RegionInfoBase(RegionInfoBase &&Arg)

    : DT(std::move(Arg.DT)), PDT(std::move(Arg.PDT)), DF(std::move(Arg.DF)),

      TopLevelRegion(std::move(Arg.TopLevelRegion)),

      BBtoRegion(std::move(Arg.BBtoRegion)) {

    Arg.wipe();

  }

  RegionInfoBase &operator=(RegionInfoBase &&RHS) {

    DT = std::move(RHS.DT);

    PDT = std::move(RHS.PDT);

    DF = std::move(RHS.DF);

    TopLevelRegion = std::move(RHS.TopLevelRegion);

    BBtoRegion = std::move(RHS.BBtoRegion);

    RHS.wipe();

    return *this;

  }

  virtual ~RegionInfoBase();

  DomTreeT *DT;

  PostDomTreeT *PDT;

  DomFrontierT *DF;

  /// The top level region.

  RegionT *TopLevelRegion = nullptr;

  /// Map every BB to the smallest region, that contains BB.

  BBtoRegionMap BBtoRegion;

protected:

  /// Update refences to a RegionInfoT held by the RegionT managed here

  ///

  /// This is a post-move helper. Regions hold references to the owning

  /// RegionInfo object. After a move these need to be fixed.

  template<typename TheRegionT>

  void updateRegionTree(RegionInfoT &RI, TheRegionT *R) {

    if (!R)

      return;

    R->RI = &RI;

    for (auto &SubR : *R)

      updateRegionTree(RI, SubR.get());

  }

private:

  /// Wipe this region tree's state without releasing any resources.

  ///

  /// This is essentially a post-move helper only. It leaves the object in an

  /// assignable and destroyable state, but otherwise invalid.

  void wipe() {

    DT = nullptr;

    PDT = nullptr;

    DF = nullptr;

    TopLevelRegion = nullptr;

    BBtoRegion.clear();

  }

  // Check whether the entries of BBtoRegion for the BBs of region

  // SR are correct. Triggers an assertion if not. Calls itself recursively for

  // subregions.

  void verifyBBMap(const RegionT *SR) const;

  // Returns true if BB is in the dominance frontier of

  // entry, because it was inherited from exit. In the other case there is an

  // edge going from entry to BB without passing exit.

  bool isCommonDomFrontier(BlockT *BB, BlockT *entry, BlockT *exit) const;

  // Check if entry and exit surround a valid region, based on

  // dominance tree and dominance frontier.

  bool isRegion(BlockT *entry, BlockT *exit) const;

  // Saves a shortcut pointing from entry to exit.

  // This function may extend this shortcut if possible.

  void insertShortCut(BlockT *entry, BlockT *exit, BBtoBBMap *ShortCut) const;

  // Returns the next BB that postdominates N, while skipping

  // all post dominators that cannot finish a canonical region.

  DomTreeNodeT *getNextPostDom(DomTreeNodeT *N, BBtoBBMap *ShortCut) const;

  // A region is trivial, if it contains only one BB.

  bool isTrivialRegion(BlockT *entry, BlockT *exit) const;

  // Creates a single entry single exit region.

  RegionT *createRegion(BlockT *entry, BlockT *exit);

  // Detect all regions starting with bb 'entry'.

  void findRegionsWithEntry(BlockT *entry, BBtoBBMap *ShortCut);

  // Detects regions in F.

  void scanForRegions(FuncT &F, BBtoBBMap *ShortCut);

  // Get the top most parent with the same entry block.

  RegionT *getTopMostParent(RegionT *region);

  // Build the region hierarchy after all region detected.

  void buildRegionsTree(DomTreeNodeT *N, RegionT *region);

  // Update statistic about created regions.

  virtual void updateStatistics(RegionT *R) = 0;

  // Detect all regions in function and build the region tree.

  void calculate(FuncT &F);

public:

  RegionInfoBase(const RegionInfoBase &) = delete;

  RegionInfoBase &operator=(const RegionInfoBase &) = delete;

  static bool VerifyRegionInfo;

  static typename RegionT::PrintStyle printStyle;

  void print(raw_ostream &OS) const;

#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)

  void dump() const;

#endif

  void releaseMemory();

  /// Get the smallest region that contains a BasicBlock.

  ///

  /// @param BB The basic block.

  /// @return The smallest region, that contains BB or NULL, if there is no

  /// region containing BB.

  RegionT *getRegionFor(BlockT *BB) const;

  ///  Set the smallest region that surrounds a basic block.

  ///

  /// @param BB The basic block surrounded by a region.

  /// @param R The smallest region that surrounds BB.

  void setRegionFor(BlockT *BB, RegionT *R);

  /// A shortcut for getRegionFor().

  ///

  /// @param BB The basic block.

  /// @return The smallest region, that contains BB or NULL, if there is no

  /// region containing BB.

  RegionT *operator[](BlockT *BB) const;

  /// Return the exit of the maximal refined region, that starts at a

  /// BasicBlock.

  ///

  /// @param BB The BasicBlock the refined region starts.

  BlockT *getMaxRegionExit(BlockT *BB) const;

  /// Find the smallest region that contains two regions.

  ///

  /// @param A The first region.

  /// @param B The second region.

  /// @return The smallest region containing A and B.

  RegionT *getCommonRegion(RegionT *A, RegionT *B) const;

  /// Find the smallest region that contains two basic blocks.

  ///

  /// @param A The first basic block.

  /// @param B The second basic block.

  /// @return The smallest region that contains A and B.

  RegionT *getCommonRegion(BlockT *A, BlockT *B) const {

    return getCommonRegion(getRegionFor(A), getRegionFor(B));

  }

  /// Find the smallest region that contains a set of regions.

  ///