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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/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 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.
   ///
   /// @param Regions A vector of regions.
   /// @return The smallest region that contains all regions in Regions.
   RegionT *getCommonRegion(SmallVectorImpl<RegionT *> &Regions) const;
 
   /// Find the smallest region that contains a set of basic blocks.
   ///
   /// @param BBs A vector of basic blocks.
   /// @return The smallest region that contains all basic blocks in BBS.
   RegionT *getCommonRegion(SmallVectorImpl<BlockT *> &BBs) const;
 
   RegionT *getTopLevelRegion() const { return TopLevelRegion; }
 
   /// Clear the Node Cache for all Regions.
   ///
   /// @see Region::clearNodeCache()
   void clearNodeCache() {
     if (TopLevelRegion)
       TopLevelRegion->clearNodeCache();
   }
 
   void verifyAnalysis() const;
 };
 
 class RegionNode : public RegionNodeBase<RegionTraits<Function>> {
 public:
   inline RegionNode(Region *Parent, BasicBlock *Entry, bool isSubRegion = false)
       : RegionNodeBase<RegionTraits<Function>>(Parent, Entry, isSubRegion) {}
 
   bool operator==(const Region &RN) const {
     return this == reinterpret_cast<const RegionNode *>(&RN);
   }
 };
 
 class Region : public RegionBase<RegionTraits<Function>> {
 public:
   Region(BasicBlock *Entry, BasicBlock *Exit, RegionInfo *RI, DominatorTree *DT,
          Region *Parent = nullptr);
   ~Region();
 
   bool operator==(const RegionNode &RN) const {
     return &RN == reinterpret_cast<const RegionNode *>(this);
   }
 };
 
 class RegionInfo : public RegionInfoBase<RegionTraits<Function>> {
 public:
   using Base = RegionInfoBase<RegionTraits<Function>>;
 
   explicit RegionInfo();
 
   RegionInfo(RegionInfo &&Arg) : Base(std::move(static_cast<Base &>(Arg))) {
     updateRegionTree(*this, TopLevelRegion);
   }
 
   RegionInfo &operator=(RegionInfo &&RHS) {
     Base::operator=(std::move(static_cast<Base &>(RHS)));
     updateRegionTree(*this, TopLevelRegion);
     return *this;
   }
 
   ~RegionInfo() override;
 
   /// Handle invalidation explicitly.
   bool invalidate(Function &F, const PreservedAnalyses &PA,
                   FunctionAnalysisManager::Invalidator &);
 
   // updateStatistics - Update statistic about created regions.
   void updateStatistics(Region *R) final;
 
   void recalculate(Function &F, DominatorTree *DT, PostDominatorTree *PDT,
                    DominanceFrontier *DF);
 
 #ifndef NDEBUG
   /// Opens a viewer to show the GraphViz visualization of the regions.
   ///
   /// Useful during debugging as an alternative to dump().
   void view();
 
   /// Opens a viewer to show the GraphViz visualization of this region
   /// without instructions in the BasicBlocks.
   ///
   /// Useful during debugging as an alternative to dump().
   void viewOnly();
 #endif
 };
 
 class RegionInfoPass : public FunctionPass {
   RegionInfo RI;
 
 public:
   static char ID;
 
   explicit RegionInfoPass();
   ~RegionInfoPass() override;
 
   RegionInfo &getRegionInfo() { return RI; }
 
   const RegionInfo &getRegionInfo() const { return RI; }
 
   /// @name FunctionPass interface
   //@{
   bool runOnFunction(Function &F) override;
   void releaseMemory() override;
   void verifyAnalysis() const override;
   void getAnalysisUsage(AnalysisUsage &AU) const override;
   void print(raw_ostream &OS, const Module *) const override;
   void dump() const;
   //@}
 };
 
 /// Analysis pass that exposes the \c RegionInfo for a function.
 class RegionInfoAnalysis : public AnalysisInfoMixin<RegionInfoAnalysis> {
   friend AnalysisInfoMixin<RegionInfoAnalysis>;
 
   static AnalysisKey Key;
 
 public:
   using Result = RegionInfo;
 
   RegionInfo run(Function &F, FunctionAnalysisManager &AM);
 };
 
 /// Printer pass for the \c RegionInfo.
 class RegionInfoPrinterPass : public PassInfoMixin<RegionInfoPrinterPass> {
   raw_ostream &OS;
 
 public:
   explicit RegionInfoPrinterPass(raw_ostream &OS);
 
   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
 
   static bool isRequired() { return true; }
 };
 
 /// Verifier pass for the \c RegionInfo.
 struct RegionInfoVerifierPass : PassInfoMixin<RegionInfoVerifierPass> {
   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
   static bool isRequired() { return true; }
 };
 
 template <>
 template <>
 inline BasicBlock *
 RegionNodeBase<RegionTraits<Function>>::getNodeAs<BasicBlock>() const {
   assert(!isSubRegion() && "This is not a BasicBlock RegionNode!");
   return getEntry();
 }
 
 template <>
 template <>
 inline Region *
 RegionNodeBase<RegionTraits<Function>>::getNodeAs<Region>() const {
   assert(isSubRegion() && "This is not a subregion RegionNode!");
   auto Unconst = const_cast<RegionNodeBase<RegionTraits<Function>> *>(this);
   return reinterpret_cast<Region *>(Unconst);
 }
 
 template <class Tr>
 inline raw_ostream &operator<<(raw_ostream &OS,
                                const RegionNodeBase<Tr> &Node) {
   using BlockT = typename Tr::BlockT;
   using RegionT = typename Tr::RegionT;
 
   if (Node.isSubRegion())
     return OS << Node.template getNodeAs<RegionT>()->getNameStr();
   else
     return OS << Node.template getNodeAs<BlockT>()->getName();
 }
 
 extern template class RegionBase<RegionTraits<Function>>;
 extern template class RegionNodeBase<RegionTraits<Function>>;
 extern template class RegionInfoBase<RegionTraits<Function>>;
 
 } // end namespace llvm
 
 #endif // LLVM_ANALYSIS_REGIONINFO_H

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