text: //===-- llvm/CodeGen/MachineBasicBlock.h ------------------------*- C++ -*-===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // Collect the sequence of machine instructions for a basic block.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_CODEGEN_MACHINEBASICBLOCK_H
  #define LLVM_CODEGEN_MACHINEBASICBLOCK_H
  
  #include "llvm/ADT/GraphTraits.h"
  #include "llvm/CodeGen/MachineInstr.h"
  #include "llvm/Support/DataTypes.h"
  #include <functional>
  
  namespace llvm {
  
  class Pass;
  class BasicBlock;
  class MachineFunction;
  class MCSymbol;
  class SlotIndexes;
  class StringRef;
  class raw_ostream;
  class MachineBranchProbabilityInfo;
  
  template <>
  struct ilist_traits<MachineInstr> : public ilist_default_traits<MachineInstr> {
  private:
    mutable ilist_half_node<MachineInstr> Sentinel;
  
    // this is only set by the MachineBasicBlock owning the LiveList
    friend class MachineBasicBlock;
    MachineBasicBlock* Parent;
  
  public:
    MachineInstr *createSentinel() const {
      return static_cast<MachineInstr*>(&Sentinel);
    }
    void destroySentinel(MachineInstr *) const {}
  
    MachineInstr *provideInitialHead() const { return createSentinel(); }
    MachineInstr *ensureHead(MachineInstr*) const { return createSentinel(); }
    static void noteHead(MachineInstr*, MachineInstr*) {}
  
    void addNodeToList(MachineInstr* N);
    void removeNodeFromList(MachineInstr* N);
    void transferNodesFromList(ilist_traits &SrcTraits,
                               ilist_iterator<MachineInstr> first,
                               ilist_iterator<MachineInstr> last);
    void deleteNode(MachineInstr *N);
  private:
    void createNode(const MachineInstr &);
  };
  
  class MachineBasicBlock : public ilist_node<MachineBasicBlock> {
    typedef ilist<MachineInstr> Instructions;
    Instructions Insts;
    const BasicBlock *BB;
    int Number;
    MachineFunction *xParent;
  
    /// Predecessors/Successors - Keep track of the predecessor / successor
    /// basicblocks.
    std::vector<MachineBasicBlock *> Predecessors;
    std::vector<MachineBasicBlock *> Successors;
  
    /// Weights - Keep track of the weights to the successors. This vector
    /// has the same order as Successors, or it is empty if we don't use it
    /// (disable optimization).
    std::vector<uint32_t> Weights;
    typedef std::vector<uint32_t>::iterator weight_iterator;
    typedef std::vector<uint32_t>::const_iterator const_weight_iterator;
  
    /// LiveIns - Keep track of the physical registers that are livein of
    /// the basicblock.
    std::vector<unsigned> LiveIns;
  
    /// Alignment - Alignment of the basic block. Zero if the basic block does
    /// not need to be aligned.
    /// The alignment is specified as log2(bytes).
    unsigned Alignment;
  
    /// IsLandingPad - Indicate that this basic block is entered via an
    /// exception handler.
    bool IsLandingPad;
  
    /// AddressTaken - Indicate that this basic block is potentially the
    /// target of an indirect branch.
    bool AddressTaken;
  
    /// \brief since getSymbol is a relatively heavy-weight operation, the symbol
    /// is only computed once and is cached.
    mutable MCSymbol *CachedMCSymbol;
  
    // Intrusive list support
    MachineBasicBlock() {}
  
    explicit MachineBasicBlock(MachineFunction &mf, const BasicBlock *bb);
  
    ~MachineBasicBlock();
  
    // MachineBasicBlocks are allocated and owned by MachineFunction.
    friend class MachineFunction;
  
  public:
    /// getBasicBlock - Return the LLVM basic block that this instance
    /// corresponded to originally. Note that this may be NULL if this instance
    /// does not correspond directly to an LLVM basic block.
    ///
    const BasicBlock *getBasicBlock() const { return BB; }
  
    /// getName - Return the name of the corresponding LLVM basic block, or
    /// "(null)".
    StringRef getName() const;
  
    /// getFullName - Return a formatted string to identify this block and its
    /// parent function.
    std::string getFullName() const;
  
    /// hasAddressTaken - Test whether this block is potentially the target
    /// of an indirect branch.
    bool hasAddressTaken() const { return AddressTaken; }
  
    /// setHasAddressTaken - Set this block to reflect that it potentially
    /// is the target of an indirect branch.
    void setHasAddressTaken() { AddressTaken = true; }
  
    /// getParent - Return the MachineFunction containing this basic block.
    ///
    const MachineFunction *getParent() const { return xParent; }
    MachineFunction *getParent() { return xParent; }
  
  
    /// bundle_iterator - MachineBasicBlock iterator that automatically skips over
    /// MIs that are inside bundles (i.e. walk top level MIs only).
    template<typename Ty, typename IterTy>
    class bundle_iterator
      : public std::iterator<std::bidirectional_iterator_tag, Ty, ptrdiff_t> {
      IterTy MII;
  
    public:
      bundle_iterator(IterTy mii) : MII(mii) {}
  
      bundle_iterator(Ty &mi) : MII(mi) {
        assert(!mi.isBundledWithPred() &&
               "It's not legal to initialize bundle_iterator with a bundled MI");
      }
      bundle_iterator(Ty *mi) : MII(mi) {
        assert((!mi || !mi->isBundledWithPred()) &&
               "It's not legal to initialize bundle_iterator with a bundled MI");
      }
      // Template allows conversion from const to nonconst.
      template<class OtherTy, class OtherIterTy>
      bundle_iterator(const bundle_iterator<OtherTy, OtherIterTy> &I)
        : MII(I.getInstrIterator()) {}
      bundle_iterator() : MII(0) {}
  
      Ty &operator*() const { return *MII; }
      Ty *operator->() const { return &operator*(); }
  
      operator Ty*() const { return MII; }
  
      bool operator==(const bundle_iterator &x) const {
        return MII == x.MII;
      }
      bool operator!=(const bundle_iterator &x) const {
        return !operator==(x);
      }
  
      // Increment and decrement operators...
      bundle_iterator &operator--() {      // predecrement - Back up
        do --MII;
        while (MII->isBundledWithPred());
        return *this;
      }
      bundle_iterator &operator++() {      // preincrement - Advance
        while (MII->isBundledWithSucc())
          ++MII;
        ++MII;
        return *this;
      }
      bundle_iterator operator--(int) {    // postdecrement operators...
        bundle_iterator tmp = *this;
        --*this;
        return tmp;
      }
      bundle_iterator operator++(int) {    // postincrement operators...
        bundle_iterator tmp = *this;
        ++*this;
        return tmp;
      }
  
      IterTy getInstrIterator() const {
        return MII;
      }
    };
  
    typedef Instructions::iterator                                 instr_iterator;
    typedef Instructions::const_iterator                     const_instr_iterator;
    typedef std::reverse_iterator<instr_iterator>          reverse_instr_iterator;
    typedef
    std::reverse_iterator<const_instr_iterator>      const_reverse_instr_iterator;
  
    typedef
    bundle_iterator<MachineInstr,instr_iterator>                         iterator;
    typedef
    bundle_iterator<const MachineInstr,const_instr_iterator>       const_iterator;
    typedef std::reverse_iterator<const_iterator>          const_reverse_iterator;
    typedef std::reverse_iterator<iterator>                      reverse_iterator;
  
  
    unsigned size() const { return (unsigned)Insts.size(); }
    bool empty() const { return Insts.empty(); }
  
    MachineInstr& front() { return Insts.front(); }
    MachineInstr& back()  { return Insts.back(); }
    const MachineInstr& front() const { return Insts.front(); }
    const MachineInstr& back()  const { return Insts.back(); }
  
    instr_iterator                instr_begin()       { return Insts.begin();  }
    const_instr_iterator          instr_begin() const { return Insts.begin();  }
    instr_iterator                  instr_end()       { return Insts.end();    }
    const_instr_iterator            instr_end() const { return Insts.end();    }
    reverse_instr_iterator       instr_rbegin()       { return Insts.rbegin(); }
    const_reverse_instr_iterator instr_rbegin() const { return Insts.rbegin(); }
    reverse_instr_iterator       instr_rend  ()       { return Insts.rend();   }
    const_reverse_instr_iterator instr_rend  () const { return Insts.rend();   }
  
    iterator                begin()       { return instr_begin();  }
    const_iterator          begin() const { return instr_begin();  }
    iterator                end  ()       { return instr_end();    }
    const_iterator          end  () const { return instr_end();    }
    reverse_iterator       rbegin()       { return instr_rbegin(); }
    const_reverse_iterator rbegin() const { return instr_rbegin(); }
    reverse_iterator       rend  ()       { return instr_rend();   }
    const_reverse_iterator rend  () const { return instr_rend();   }
  
  
    // Machine-CFG iterators
    typedef std::vector<MachineBasicBlock *>::iterator       pred_iterator;
    typedef std::vector<MachineBasicBlock *>::const_iterator const_pred_iterator;
    typedef std::vector<MachineBasicBlock *>::iterator       succ_iterator;
    typedef std::vector<MachineBasicBlock *>::const_iterator const_succ_iterator;
    typedef std::vector<MachineBasicBlock *>::reverse_iterator
                                                           pred_reverse_iterator;
    typedef std::vector<MachineBasicBlock *>::const_reverse_iterator
                                                     const_pred_reverse_iterator;
    typedef std::vector<MachineBasicBlock *>::reverse_iterator
                                                           succ_reverse_iterator;
    typedef std::vector<MachineBasicBlock *>::const_reverse_iterator
                                                     const_succ_reverse_iterator;
  
    pred_iterator        pred_begin()       { return Predecessors.begin(); }
    const_pred_iterator  pred_begin() const { return Predecessors.begin(); }
    pred_iterator        pred_end()         { return Predecessors.end();   }
    const_pred_iterator  pred_end()   const { return Predecessors.end();   }
    pred_reverse_iterator        pred_rbegin()
                                            { return Predecessors.rbegin();}
    const_pred_reverse_iterator  pred_rbegin() const
                                            { return Predecessors.rbegin();}
    pred_reverse_iterator        pred_rend()
                                            { return Predecessors.rend();  }
    const_pred_reverse_iterator  pred_rend()   const
                                            { return Predecessors.rend();  }
    unsigned             pred_size()  const {
      return (unsigned)Predecessors.size();
    }
    bool                 pred_empty() const { return Predecessors.empty(); }
    succ_iterator        succ_begin()       { return Successors.begin();   }
    const_succ_iterator  succ_begin() const { return Successors.begin();   }
    succ_iterator        succ_end()         { return Successors.end();     }
    const_succ_iterator  succ_end()   const { return Successors.end();     }
    succ_reverse_iterator        succ_rbegin()
                                            { return Successors.rbegin();  }
    const_succ_reverse_iterator  succ_rbegin() const
                                            { return Successors.rbegin();  }
    succ_reverse_iterator        succ_rend()
                                            { return Successors.rend();    }
    const_succ_reverse_iterator  succ_rend()   const
                                            { return Successors.rend();    }
    unsigned             succ_size()  const {
      return (unsigned)Successors.size();
    }
    bool                 succ_empty() const { return Successors.empty();   }
  
    // LiveIn management methods.
  
    /// addLiveIn - Add the specified register as a live in.  Note that it
    /// is an error to add the same register to the same set more than once.
    void addLiveIn(unsigned Reg)  { LiveIns.push_back(Reg); }
  
    /// removeLiveIn - Remove the specified register from the live in set.
    ///
    void removeLiveIn(unsigned Reg);
  
    /// isLiveIn - Return true if the specified register is in the live in set.
    ///
    bool isLiveIn(unsigned Reg) const;
  
    // Iteration support for live in sets.  These sets are kept in sorted
    // order by their register number.
    typedef std::vector<unsigned>::const_iterator livein_iterator;
    livein_iterator livein_begin() const { return LiveIns.begin(); }
    livein_iterator livein_end()   const { return LiveIns.end(); }
    bool            livein_empty() const { return LiveIns.empty(); }
  
    /// getAlignment - Return alignment of the basic block.
    /// The alignment is specified as log2(bytes).
    ///
    unsigned getAlignment() const { return Alignment; }
  
    /// setAlignment - Set alignment of the basic block.
    /// The alignment is specified as log2(bytes).
    ///
    void setAlignment(unsigned Align) { Alignment = Align; }
  
    /// isLandingPad - Returns true if the block is a landing pad. That is
    /// this basic block is entered via an exception handler.
    bool isLandingPad() const { return IsLandingPad; }
  
    /// setIsLandingPad - Indicates the block is a landing pad.  That is
    /// this basic block is entered via an exception handler.
    void setIsLandingPad(bool V = true) { IsLandingPad = V; }
  
    /// getLandingPadSuccessor - If this block has a successor that is a landing
    /// pad, return it. Otherwise return NULL.
    const MachineBasicBlock *getLandingPadSuccessor() const;
  
    // Code Layout methods.
  
    /// moveBefore/moveAfter - move 'this' block before or after the specified
    /// block.  This only moves the block, it does not modify the CFG or adjust
    /// potential fall-throughs at the end of the block.
    void moveBefore(MachineBasicBlock *NewAfter);
    void moveAfter(MachineBasicBlock *NewBefore);
  
    /// updateTerminator - Update the terminator instructions in block to account
    /// for changes to the layout. If the block previously used a fallthrough,
    /// it may now need a branch, and if it previously used branching it may now
    /// be able to use a fallthrough.
    void updateTerminator();
  
    // Machine-CFG mutators
  
    /// addSuccessor - Add succ as a successor of this MachineBasicBlock.
    /// The Predecessors list of succ is automatically updated. WEIGHT
    /// parameter is stored in Weights list and it may be used by
    /// MachineBranchProbabilityInfo analysis to calculate branch probability.
    ///
    /// Note that duplicate Machine CFG edges are not allowed.
    ///
    void addSuccessor(MachineBasicBlock *succ, uint32_t weight = 0);
  
    /// removeSuccessor - Remove successor from the successors list of this
    /// MachineBasicBlock. The Predecessors list of succ is automatically updated.
    ///
    void removeSuccessor(MachineBasicBlock *succ);
  
    /// removeSuccessor - Remove specified successor from the successors list of
    /// this MachineBasicBlock. The Predecessors list of succ is automatically
    /// updated.  Return the iterator to the element after the one removed.
    ///
    succ_iterator removeSuccessor(succ_iterator I);
  
    /// replaceSuccessor - Replace successor OLD with NEW and update weight info.
    ///
    void replaceSuccessor(MachineBasicBlock *Old, MachineBasicBlock *New);
  
  
    /// transferSuccessors - Transfers all the successors from MBB to this
    /// machine basic block (i.e., copies all the successors fromMBB and
    /// remove all the successors from fromMBB).
    void transferSuccessors(MachineBasicBlock *fromMBB);
  
    /// transferSuccessorsAndUpdatePHIs - Transfers all the successors, as
    /// in transferSuccessors, and update PHI operands in the successor blocks
    /// which refer to fromMBB to refer to this.
    void transferSuccessorsAndUpdatePHIs(MachineBasicBlock *fromMBB);
  
    /// isPredecessor - Return true if the specified MBB is a predecessor of this
    /// block.
    bool isPredecessor(const MachineBasicBlock *MBB) const;
  
    /// isSuccessor - Return true if the specified MBB is a successor of this
    /// block.
    bool isSuccessor(const MachineBasicBlock *MBB) const;
  
    /// isLayoutSuccessor - Return true if the specified MBB will be emitted
    /// immediately after this block, such that if this block exits by
    /// falling through, control will transfer to the specified MBB. Note
    /// that MBB need not be a successor at all, for example if this block
    /// ends with an unconditional branch to some other block.
    bool isLayoutSuccessor(const MachineBasicBlock *MBB) const;
  
    /// canFallThrough - Return true if the block can implicitly transfer
    /// control to the block after it by falling off the end of it.  This should
    /// return false if it can reach the block after it, but it uses an explicit
    /// branch to do so (e.g., a table jump).  True is a conservative answer.
    bool canFallThrough();
  
    /// Returns a pointer to the first instructon in this block that is not a
    /// PHINode instruction. When adding instruction to the beginning of the
    /// basic block, they should be added before the returned value, not before
    /// the first instruction, which might be PHI.
    /// Returns end() is there's no non-PHI instruction.
    iterator getFirstNonPHI();
  
    /// SkipPHIsAndLabels - Return the first instruction in MBB after I that is
    /// not a PHI or a label. This is the correct point to insert copies at the
    /// beginning of a basic block.
    iterator SkipPHIsAndLabels(iterator I);
  
    /// getFirstTerminator - returns an iterator to the first terminator
    /// instruction of this basic block. If a terminator does not exist,
    /// it returns end()
    iterator getFirstTerminator();
    const_iterator getFirstTerminator() const;
  
    /// getFirstInstrTerminator - Same getFirstTerminator but it ignores bundles
    /// and return an instr_iterator instead.
    instr_iterator getFirstInstrTerminator();
  
    /// getLastNonDebugInstr - returns an iterator to the last non-debug
    /// instruction in the basic block, or end()
    iterator getLastNonDebugInstr();
    const_iterator getLastNonDebugInstr() const;
  
    /// SplitCriticalEdge - Split the critical edge from this block to the
    /// given successor block, and return the newly created block, or null
    /// if splitting is not possible.
    ///
    /// This function updates LiveVariables, MachineDominatorTree, and
    /// MachineLoopInfo, as applicable.
    MachineBasicBlock *SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P);
  
    void pop_front() { Insts.pop_front(); }
    void pop_back() { Insts.pop_back(); }
    void push_back(MachineInstr *MI) { Insts.push_back(MI); }
  
    /// Insert MI into the instruction list before I, possibly inside a bundle.
    ///
    /// If the insertion point is inside a bundle, MI will be added to the bundle,
    /// otherwise MI will not be added to any bundle. That means this function
    /// alone can't be used to prepend or append instructions to bundles. See
    /// MIBundleBuilder::insert() for a more reliable way of doing that.
    instr_iterator insert(instr_iterator I, MachineInstr *M);
  
    /// Insert a range of instructions into the instruction list before I.
    template<typename IT>
    void insert(iterator I, IT S, IT E) {
      Insts.insert(I.getInstrIterator(), S, E);
    }
  
    /// Insert MI into the instruction list before I.
    iterator insert(iterator I, MachineInstr *MI) {
      assert(!MI->isBundledWithPred() && !MI->isBundledWithSucc() &&
             "Cannot insert instruction with bundle flags");
      return Insts.insert(I.getInstrIterator(), MI);
    }
  
    /// Insert MI into the instruction list after I.
    iterator insertAfter(iterator I, MachineInstr *MI) {
      assert(!MI->isBundledWithPred() && !MI->isBundledWithSucc() &&
             "Cannot insert instruction with bundle flags");
      return Insts.insertAfter(I.getInstrIterator(), MI);
    }
  
    /// Remove an instruction from the instruction list and delete it.
    ///
    /// If the instruction is part of a bundle, the other instructions in the
    /// bundle will still be bundled after removing the single instruction.
    instr_iterator erase(instr_iterator I);
  
    /// Remove an instruction from the instruction list and delete it.
    ///
    /// If the instruction is part of a bundle, the other instructions in the
    /// bundle will still be bundled after removing the single instruction.
    instr_iterator erase_instr(MachineInstr *I) {
      return erase(instr_iterator(I));
    }
  
    /// Remove a range of instructions from the instruction list and delete them.
    iterator erase(iterator I, iterator E) {
      return Insts.erase(I.getInstrIterator(), E.getInstrIterator());
    }
  
    /// Remove an instruction or bundle from the instruction list and delete it.
    ///
    /// If I points to a bundle of instructions, they are all erased.
    iterator erase(iterator I) {
      return erase(I, llvm::next(I));
    }
  
    /// Remove an instruction from the instruction list and delete it.
    ///
    /// If I is the head of a bundle of instructions, the whole bundle will be
    /// erased.
    iterator erase(MachineInstr *I) {
      return erase(iterator(I));
    }
  
    /// Remove the unbundled instruction from the instruction list without
    /// deleting it.
    ///
    /// This function can not be used to remove bundled instructions, use
    /// remove_instr to remove individual instructions from a bundle.
    MachineInstr *remove(MachineInstr *I) {
      assert(!I->isBundled() && "Cannot remove bundled instructions");
      return Insts.remove(I);
    }
  
    /// Remove the possibly bundled instruction from the instruction list
    /// without deleting it.
    ///
    /// If the instruction is part of a bundle, the other instructions in the
    /// bundle will still be bundled after removing the single instruction.
    MachineInstr *remove_instr(MachineInstr *I);
  
    void clear() {
      Insts.clear();
    }
  
    /// Take an instruction from MBB 'Other' at the position From, and insert it
    /// into this MBB right before 'Where'.
    ///
    /// If From points to a bundle of instructions, the whole bundle is moved.
    void splice(iterator Where, MachineBasicBlock *Other, iterator From) {
      // The range splice() doesn't allow noop moves, but this one does.
      if (Where != From)
        splice(Where, Other, From, llvm::next(From));
    }
  
    /// Take a block of instructions from MBB 'Other' in the range [From, To),
    /// and insert them into this MBB right before 'Where'.
    ///
    /// The instruction at 'Where' must not be included in the range of
    /// instructions to move.
    void splice(iterator Where, MachineBasicBlock *Other,
                iterator From, iterator To) {
      Insts.splice(Where.getInstrIterator(), Other->Insts,
                   From.getInstrIterator(), To.getInstrIterator());
    }
  
    /// removeFromParent - This method unlinks 'this' from the containing
    /// function, and returns it, but does not delete it.
    MachineBasicBlock *removeFromParent();
  
    /// eraseFromParent - This method unlinks 'this' from the containing
    /// function and deletes it.
    void eraseFromParent();
  
    /// ReplaceUsesOfBlockWith - Given a machine basic block that branched to
    /// 'Old', change the code and CFG so that it branches to 'New' instead.
    void ReplaceUsesOfBlockWith(MachineBasicBlock *Old, MachineBasicBlock *New);
  
    /// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in
    /// the CFG to be inserted.  If we have proven that MBB can only branch to
    /// DestA and DestB, remove any other MBB successors from the CFG. DestA and
    /// DestB can be null. Besides DestA and DestB, retain other edges leading
    /// to LandingPads (currently there can be only one; we don't check or require
    /// that here). Note it is possible that DestA and/or DestB are LandingPads.
    bool CorrectExtraCFGEdges(MachineBasicBlock *DestA,
                              MachineBasicBlock *DestB,
                              bool isCond);
  
    /// findDebugLoc - find the next valid DebugLoc starting at MBBI, skipping
    /// any DBG_VALUE instructions.  Return UnknownLoc if there is none.
    DebugLoc findDebugLoc(instr_iterator MBBI);
    DebugLoc findDebugLoc(iterator MBBI) {
      return findDebugLoc(MBBI.getInstrIterator());
    }
  
    /// Possible outcome of a register liveness query to computeRegisterLiveness()
    enum LivenessQueryResult {
      LQR_Live,            ///< Register is known to be live.
      LQR_OverlappingLive, ///< Register itself is not live, but some overlapping
                           ///< register is.
      LQR_Dead,            ///< Register is known to be dead.
      LQR_Unknown          ///< Register liveness not decidable from local
                           ///< neighborhood.
    };
  
    /// computeRegisterLiveness - Return whether (physical) register \c Reg
    /// has been <def>ined and not <kill>ed as of just before \c MI.
    /// 
    /// Search is localised to a neighborhood of
    /// \c Neighborhood instructions before (searching for defs or kills) and
    /// Neighborhood instructions after (searching just for defs) MI.
    ///
    /// \c Reg must be a physical register.
    LivenessQueryResult computeRegisterLiveness(const TargetRegisterInfo *TRI,
                                                unsigned Reg, MachineInstr *MI,
                                                unsigned Neighborhood=10);
  
    // Debugging methods.
    void dump() const;
    void print(raw_ostream &OS, SlotIndexes* = 0) const;
  
    /// getNumber - MachineBasicBlocks are uniquely numbered at the function
    /// level, unless they're not in a MachineFunction yet, in which case this
    /// will return -1.
    ///
    int getNumber() const { return Number; }
    void setNumber(int N) { Number = N; }
  
    /// getSymbol - Return the MCSymbol for this basic block.
    ///
    MCSymbol *getSymbol() const;
  
  
  private:
    /// getWeightIterator - Return weight iterator corresponding to the I
    /// successor iterator.
    weight_iterator getWeightIterator(succ_iterator I);
    const_weight_iterator getWeightIterator(const_succ_iterator I) const;
  
    friend class MachineBranchProbabilityInfo;
  
    /// getSuccWeight - Return weight of the edge from this block to MBB. This
    /// method should NOT be called directly, but by using getEdgeWeight method
    /// from MachineBranchProbabilityInfo class.
    uint32_t getSuccWeight(const_succ_iterator Succ) const;
  
  
    // Methods used to maintain doubly linked list of blocks...
    friend struct ilist_traits<MachineBasicBlock>;
  
    // Machine-CFG mutators
  
    /// addPredecessor - Remove pred as a predecessor of this MachineBasicBlock.
    /// Don't do this unless you know what you're doing, because it doesn't
    /// update pred's successors list. Use pred->addSuccessor instead.
    ///
    void addPredecessor(MachineBasicBlock *pred);
  
    /// removePredecessor - Remove pred as a predecessor of this
    /// MachineBasicBlock. Don't do this unless you know what you're
    /// doing, because it doesn't update pred's successors list. Use
    /// pred->removeSuccessor instead.
    ///
    void removePredecessor(MachineBasicBlock *pred);
  };
  
  raw_ostream& operator<<(raw_ostream &OS, const MachineBasicBlock &MBB);
  
  void WriteAsOperand(raw_ostream &, const MachineBasicBlock*, bool t);
  
  // This is useful when building IndexedMaps keyed on basic block pointers.
  struct MBB2NumberFunctor :
    public std::unary_function<const MachineBasicBlock*, unsigned> {
    unsigned operator()(const MachineBasicBlock *MBB) const {
      return MBB->getNumber();
    }
  };
  
  //===--------------------------------------------------------------------===//
  // GraphTraits specializations for machine basic block graphs (machine-CFGs)
  //===--------------------------------------------------------------------===//
  
  // Provide specializations of GraphTraits to be able to treat a
  // MachineFunction as a graph of MachineBasicBlocks...
  //
  
  template <> struct GraphTraits<MachineBasicBlock *> {
    typedef MachineBasicBlock NodeType;
    typedef MachineBasicBlock::succ_iterator ChildIteratorType;
  
    static NodeType *getEntryNode(MachineBasicBlock *BB) { return BB; }
    static inline ChildIteratorType child_begin(NodeType *N) {
      return N->succ_begin();
    }
    static inline ChildIteratorType child_end(NodeType *N) {
      return N->succ_end();
    }
  };
  
  template <> struct GraphTraits<const MachineBasicBlock *> {
    typedef const MachineBasicBlock NodeType;
    typedef MachineBasicBlock::const_succ_iterator ChildIteratorType;
  
    static NodeType *getEntryNode(const MachineBasicBlock *BB) { return BB; }
    static inline ChildIteratorType child_begin(NodeType *N) {
      return N->succ_begin();
    }
    static inline ChildIteratorType child_end(NodeType *N) {
      return N->succ_end();
    }
  };
  
  // Provide specializations of GraphTraits to be able to treat a
  // MachineFunction as a graph of MachineBasicBlocks... and to walk it
  // in inverse order.  Inverse order for a function is considered
  // to be when traversing the predecessor edges of a MBB
  // instead of the successor edges.
  //
  template <> struct GraphTraits<Inverse<MachineBasicBlock*> > {
    typedef MachineBasicBlock NodeType;
    typedef MachineBasicBlock::pred_iterator ChildIteratorType;
    static NodeType *getEntryNode(Inverse<MachineBasicBlock *> G) {
      return G.Graph;
    }
    static inline ChildIteratorType child_begin(NodeType *N) {
      return N->pred_begin();
    }
    static inline ChildIteratorType child_end(NodeType *N) {
      return N->pred_end();
    }
  };
  
  template <> struct GraphTraits<Inverse<const MachineBasicBlock*> > {
    typedef const MachineBasicBlock NodeType;
    typedef MachineBasicBlock::const_pred_iterator ChildIteratorType;
    static NodeType *getEntryNode(Inverse<const MachineBasicBlock*> G) {
      return G.Graph;
    }
    static inline ChildIteratorType child_begin(NodeType *N) {
      return N->pred_begin();
    }
    static inline ChildIteratorType child_end(NodeType *N) {
      return N->pred_end();
    }
  };
  
  } // End llvm namespace
  
  #endif
  