llvm/CodeGen/MachineBasicBlock.h

//===-- 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/CodeGen/MachineInstr.h"
#include "llvm/ADT/GraphTraits.h"

namespace llvm {

class BasicBlock;
class MachineFunction;
class raw_ostream;

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;

  /// 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.
  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;

  // 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;

  /// 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; }

  typedef Instructions::iterator                              iterator;
  typedef Instructions::const_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(); }

  iterator                begin()       { return Insts.begin();  }
  const_iterator          begin() const { return Insts.begin();  }
  iterator                  end()       { return Insts.end();    }
  const_iterator            end() const { return Insts.end();    }
  reverse_iterator       rbegin()       { return Insts.rbegin(); }
  const_reverse_iterator rbegin() const { return Insts.rbegin(); }
  reverse_iterator       rend  ()       { return Insts.rend();   }
  const_reverse_iterator rend  () const { return Insts.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>::iterator       livein_iterator;
  typedef std::vector<unsigned>::const_iterator const_livein_iterator;
  livein_iterator       livein_begin()       { return LiveIns.begin(); }
  const_livein_iterator livein_begin() const { return LiveIns.begin(); }
  livein_iterator       livein_end()         { return LiveIns.end(); }
  const_livein_iterator livein_end()   const { return LiveIns.end(); }
  bool            livein_empty() const { return LiveIns.empty(); }

  /// getAlignment - Return alignment of the basic block.
  ///
  unsigned getAlignment() const { return Alignment; }

  /// setAlignment - Set alignment of the basic block.
  ///
  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() { IsLandingPad = true; }

  // 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.
  ///
  void addSuccessor(MachineBasicBlock *succ);

  /// 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);

  /// 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);

  /// 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();

  /// getFirstTerminator - returns an iterator to the first terminator
  /// instruction of this basic block. If a terminator does not exist,
  /// it returns end()
  iterator getFirstTerminator();

  /// isOnlyReachableViaFallthough - Return true if this basic block has
  /// exactly one predecessor and the control transfer mechanism between
  /// the predecessor and this block is a fall-through.
  bool isOnlyReachableByFallthrough() const;

  void pop_front() { Insts.pop_front(); }
  void pop_back() { Insts.pop_back(); }
  void push_back(MachineInstr *MI) { Insts.push_back(MI); }
  template<typename IT>
  void insert(iterator I, IT S, IT E) { Insts.insert(I, S, E); }
  iterator insert(iterator I, MachineInstr *M) { return Insts.insert(I, M); }

  // erase - Remove the specified element or range from the instruction list.
  // These functions delete any instructions removed.
  //
  iterator erase(iterator I)             { return Insts.erase(I); }
  iterator erase(iterator I, iterator E) { return Insts.erase(I, E); }
  MachineInstr *remove(MachineInstr *I)  { return Insts.remove(I); }
  void clear()                           { Insts.clear(); }

  /// splice - Take an instruction from MBB 'Other' at the position From,
  /// and insert it into this MBB right before 'where'.
  void splice(iterator where, MachineBasicBlock *Other, iterator From) {
    Insts.splice(where, Other->Insts, From);
  }

  /// splice - Take a block of instructions from MBB 'Other' in the range [From,
  /// To), and insert them into this MBB right before 'where'.
  void splice(iterator where, MachineBasicBlock *Other, iterator From,
              iterator To) {
    Insts.splice(where, Other->Insts, From, To);
  }

  /// 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);

  /// BranchesToLandingPad - The basic block is a landing pad or branches only
  /// to a landing pad. No other instructions are present other than the
  /// unconditional branch.
  bool BranchesToLandingPad(const MachineBasicBlock *MBB) const;

  /// 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);

  // Debugging methods.
  void dump() const;
  void print(raw_ostream &OS) 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; }

private:   // 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);

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