LCOV - code coverage report
Current view: top level - include/llvm/CodeGen - MachineBasicBlock.h (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 102 102 100.0 %
Date: 2017-09-14 15:23:50 Functions: 5 5 100.0 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : //===- llvm/CodeGen/MachineBasicBlock.h -------------------------*- C++ -*-===//
       2             : //
       3             : //                     The LLVM Compiler Infrastructure
       4             : //
       5             : // This file is distributed under the University of Illinois Open Source
       6             : // License. See LICENSE.TXT for details.
       7             : //
       8             : //===----------------------------------------------------------------------===//
       9             : //
      10             : // Collect the sequence of machine instructions for a basic block.
      11             : //
      12             : //===----------------------------------------------------------------------===//
      13             : 
      14             : #ifndef LLVM_CODEGEN_MACHINEBASICBLOCK_H
      15             : #define LLVM_CODEGEN_MACHINEBASICBLOCK_H
      16             : 
      17             : #include "llvm/ADT/GraphTraits.h"
      18             : #include "llvm/ADT/ilist.h"
      19             : #include "llvm/ADT/ilist_node.h"
      20             : #include "llvm/ADT/iterator_range.h"
      21             : #include "llvm/ADT/simple_ilist.h"
      22             : #include "llvm/CodeGen/MachineInstr.h"
      23             : #include "llvm/CodeGen/MachineInstrBundleIterator.h"
      24             : #include "llvm/IR/DebugLoc.h"
      25             : #include "llvm/MC/LaneBitmask.h"
      26             : #include "llvm/MC/MCRegisterInfo.h"
      27             : #include "llvm/Support/BranchProbability.h"
      28             : #include <cassert>
      29             : #include <cstdint>
      30             : #include <functional>
      31             : #include <iterator>
      32             : #include <string>
      33             : #include <vector>
      34             : 
      35             : namespace llvm {
      36             : 
      37             : class BasicBlock;
      38             : class MachineFunction;
      39             : class MCSymbol;
      40             : class ModuleSlotTracker;
      41             : class Pass;
      42             : class SlotIndexes;
      43             : class StringRef;
      44             : class raw_ostream;
      45             : class TargetRegisterClass;
      46             : class TargetRegisterInfo;
      47             : 
      48             : template <> struct ilist_traits<MachineInstr> {
      49             : private:
      50             :   friend class MachineBasicBlock; // Set by the owning MachineBasicBlock.
      51             : 
      52             :   MachineBasicBlock *Parent;
      53             : 
      54             :   using instr_iterator =
      55             :       simple_ilist<MachineInstr, ilist_sentinel_tracking<true>>::iterator;
      56             : 
      57             : public:
      58             :   void addNodeToList(MachineInstr *N);
      59             :   void removeNodeFromList(MachineInstr *N);
      60             :   void transferNodesFromList(ilist_traits &OldList, instr_iterator First,
      61             :                              instr_iterator Last);
      62             :   void deleteNode(MachineInstr *MI);
      63             : };
      64             : 
      65             : class MachineBasicBlock
      66             :     : public ilist_node_with_parent<MachineBasicBlock, MachineFunction> {
      67             : public:
      68             :   /// Pair of physical register and lane mask.
      69             :   /// This is not simply a std::pair typedef because the members should be named
      70             :   /// clearly as they both have an integer type.
      71             :   struct RegisterMaskPair {
      72             :   public:
      73             :     MCPhysReg PhysReg;
      74             :     LaneBitmask LaneMask;
      75             : 
      76             :     RegisterMaskPair(MCPhysReg PhysReg, LaneBitmask LaneMask)
      77      694114 :         : PhysReg(PhysReg), LaneMask(LaneMask) {}
      78             :   };
      79             : 
      80             : private:
      81             :   using Instructions = ilist<MachineInstr, ilist_sentinel_tracking<true>>;
      82             : 
      83             :   Instructions Insts;
      84             :   const BasicBlock *BB;
      85             :   int Number;
      86             :   MachineFunction *xParent;
      87             : 
      88             :   /// Keep track of the predecessor / successor basic blocks.
      89             :   std::vector<MachineBasicBlock *> Predecessors;
      90             :   std::vector<MachineBasicBlock *> Successors;
      91             : 
      92             :   /// Keep track of the probabilities to the successors. This vector has the
      93             :   /// same order as Successors, or it is empty if we don't use it (disable
      94             :   /// optimization).
      95             :   std::vector<BranchProbability> Probs;
      96             :   using probability_iterator = std::vector<BranchProbability>::iterator;
      97             :   using const_probability_iterator =
      98             :       std::vector<BranchProbability>::const_iterator;
      99             : 
     100             :   /// Keep track of the physical registers that are livein of the basicblock.
     101             :   using LiveInVector = std::vector<RegisterMaskPair>;
     102             :   LiveInVector LiveIns;
     103             : 
     104             :   /// Alignment of the basic block. Zero if the basic block does not need to be
     105             :   /// aligned. The alignment is specified as log2(bytes).
     106             :   unsigned Alignment = 0;
     107             : 
     108             :   /// Indicate that this basic block is entered via an exception handler.
     109             :   bool IsEHPad = false;
     110             : 
     111             :   /// Indicate that this basic block is potentially the target of an indirect
     112             :   /// branch.
     113             :   bool AddressTaken = false;
     114             : 
     115             :   /// Indicate that this basic block is the entry block of an EH funclet.
     116             :   bool IsEHFuncletEntry = false;
     117             : 
     118             :   /// Indicate that this basic block is the entry block of a cleanup funclet.
     119             :   bool IsCleanupFuncletEntry = false;
     120             : 
     121             :   /// \brief since getSymbol is a relatively heavy-weight operation, the symbol
     122             :   /// is only computed once and is cached.
     123             :   mutable MCSymbol *CachedMCSymbol = nullptr;
     124             : 
     125             :   // Intrusive list support
     126             :   MachineBasicBlock() = default;
     127             : 
     128             :   explicit MachineBasicBlock(MachineFunction &MF, const BasicBlock *BB);
     129             : 
     130             :   ~MachineBasicBlock();
     131             : 
     132             :   // MachineBasicBlocks are allocated and owned by MachineFunction.
     133             :   friend class MachineFunction;
     134             : 
     135             : public:
     136             :   /// Return the LLVM basic block that this instance corresponded to originally.
     137             :   /// Note that this may be NULL if this instance does not correspond directly
     138             :   /// to an LLVM basic block.
     139             :   const BasicBlock *getBasicBlock() const { return BB; }
     140             : 
     141             :   /// Return the name of the corresponding LLVM basic block, or an empty string.
     142             :   StringRef getName() const;
     143             : 
     144             :   /// Return a formatted string to identify this block and its parent function.
     145             :   std::string getFullName() const;
     146             : 
     147             :   /// Test whether this block is potentially the target of an indirect branch.
     148             :   bool hasAddressTaken() const { return AddressTaken; }
     149             : 
     150             :   /// Set this block to reflect that it potentially is the target of an indirect
     151             :   /// branch.
     152         398 :   void setHasAddressTaken() { AddressTaken = true; }
     153             : 
     154             :   /// Return the MachineFunction containing this basic block.
     155             :   const MachineFunction *getParent() const { return xParent; }
     156             :   MachineFunction *getParent() { return xParent; }
     157             : 
     158             :   using instr_iterator = Instructions::iterator;
     159             :   using const_instr_iterator = Instructions::const_iterator;
     160             :   using reverse_instr_iterator = Instructions::reverse_iterator;
     161             :   using const_reverse_instr_iterator = Instructions::const_reverse_iterator;
     162             : 
     163             :   using iterator = MachineInstrBundleIterator<MachineInstr>;
     164             :   using const_iterator = MachineInstrBundleIterator<const MachineInstr>;
     165             :   using reverse_iterator = MachineInstrBundleIterator<MachineInstr, true>;
     166             :   using const_reverse_iterator =
     167             :       MachineInstrBundleIterator<const MachineInstr, true>;
     168             : 
     169     3295286 :   unsigned size() const { return (unsigned)Insts.size(); }
     170     8467794 :   bool empty() const { return Insts.empty(); }
     171             : 
     172             :   MachineInstr       &instr_front()       { return Insts.front(); }
     173             :   MachineInstr       &instr_back()        { return Insts.back();  }
     174             :   const MachineInstr &instr_front() const { return Insts.front(); }
     175     2589322 :   const MachineInstr &instr_back()  const { return Insts.back();  }
     176             : 
     177     1260884 :   MachineInstr       &front()             { return Insts.front(); }
     178     1223748 :   MachineInstr       &back()              { return *--end();      }
     179             :   const MachineInstr &front()       const { return Insts.front(); }
     180     8392290 :   const MachineInstr &back()        const { return *--end();      }
     181             : 
     182    76403098 :   instr_iterator                instr_begin()       { return Insts.begin();  }
     183    19777162 :   const_instr_iterator          instr_begin() const { return Insts.begin();  }
     184   150496974 :   instr_iterator                  instr_end()       { return Insts.end();    }
     185    25640312 :   const_instr_iterator            instr_end() const { return Insts.end();    }
     186     2272828 :   reverse_instr_iterator       instr_rbegin()       { return Insts.rbegin(); }
     187       22194 :   const_reverse_instr_iterator instr_rbegin() const { return Insts.rbegin(); }
     188     6832332 :   reverse_instr_iterator       instr_rend  ()       { return Insts.rend();   }
     189      105950 :   const_reverse_instr_iterator instr_rend  () const { return Insts.rend();   }
     190             : 
     191             :   using instr_range = iterator_range<instr_iterator>;
     192             :   using const_instr_range = iterator_range<const_instr_iterator>;
     193        9690 :   instr_range instrs() { return instr_range(instr_begin(), instr_end()); }
     194             :   const_instr_range instrs() const {
     195       36609 :     return const_instr_range(instr_begin(), instr_end());
     196             :   }
     197             : 
     198    35245078 :   iterator                begin()       { return instr_begin();  }
     199     8448069 :   const_iterator          begin() const { return instr_begin();  }
     200    55450603 :   iterator                end  ()       { return instr_end();    }
     201    11040458 :   const_iterator          end  () const { return instr_end();    }
     202             :   reverse_iterator rbegin() {
     203     2271886 :     return reverse_iterator::getAtBundleBegin(instr_rbegin());
     204             :   }
     205             :   const_reverse_iterator rbegin() const {
     206       22194 :     return const_reverse_iterator::getAtBundleBegin(instr_rbegin());
     207             :   }
     208     3420350 :   reverse_iterator rend() { return reverse_iterator(instr_rend()); }
     209             :   const_reverse_iterator rend() const {
     210       52975 :     return const_reverse_iterator(instr_rend());
     211             :   }
     212             : 
     213             :   /// Support for MachineInstr::getNextNode().
     214             :   static Instructions MachineBasicBlock::*getSublistAccess(MachineInstr *) {
     215             :     return &MachineBasicBlock::Insts;
     216             :   }
     217             : 
     218             :   inline iterator_range<iterator> terminators() {
     219      150084 :     return make_range(getFirstTerminator(), end());
     220             :   }
     221             :   inline iterator_range<const_iterator> terminators() const {
     222       20892 :     return make_range(getFirstTerminator(), end());
     223             :   }
     224             : 
     225             :   // Machine-CFG iterators
     226             :   using pred_iterator = std::vector<MachineBasicBlock *>::iterator;
     227             :   using const_pred_iterator = std::vector<MachineBasicBlock *>::const_iterator;
     228             :   using succ_iterator = std::vector<MachineBasicBlock *>::iterator;
     229             :   using const_succ_iterator = std::vector<MachineBasicBlock *>::const_iterator;
     230             :   using pred_reverse_iterator =
     231             :       std::vector<MachineBasicBlock *>::reverse_iterator;
     232             :   using const_pred_reverse_iterator =
     233             :       std::vector<MachineBasicBlock *>::const_reverse_iterator;
     234             :   using succ_reverse_iterator =
     235             :       std::vector<MachineBasicBlock *>::reverse_iterator;
     236             :   using const_succ_reverse_iterator =
     237             :       std::vector<MachineBasicBlock *>::const_reverse_iterator;
     238    15364018 :   pred_iterator        pred_begin()       { return Predecessors.begin(); }
     239     6787364 :   const_pred_iterator  pred_begin() const { return Predecessors.begin(); }
     240    13626646 :   pred_iterator        pred_end()         { return Predecessors.end();   }
     241     6700788 :   const_pred_iterator  pred_end()   const { return Predecessors.end();   }
     242             :   pred_reverse_iterator        pred_rbegin()
     243     1726016 :                                           { return Predecessors.rbegin();}
     244             :   const_pred_reverse_iterator  pred_rbegin() const
     245             :                                           { return Predecessors.rbegin();}
     246             :   pred_reverse_iterator        pred_rend()
     247     1726016 :                                           { return Predecessors.rend();  }
     248             :   const_pred_reverse_iterator  pred_rend()   const
     249             :                                           { return Predecessors.rend();  }
     250             :   unsigned             pred_size()  const {
     251    12850888 :     return (unsigned)Predecessors.size();
     252             :   }
     253     5353080 :   bool                 pred_empty() const { return Predecessors.empty(); }
     254    19992752 :   succ_iterator        succ_begin()       { return Successors.begin();   }
     255    17783697 :   const_succ_iterator  succ_begin() const { return Successors.begin();   }
     256    28296780 :   succ_iterator        succ_end()         { return Successors.end();     }
     257    18935602 :   const_succ_iterator  succ_end()   const { return Successors.end();     }
     258             :   succ_reverse_iterator        succ_rbegin()
     259           2 :                                           { return Successors.rbegin();  }
     260             :   const_succ_reverse_iterator  succ_rbegin() const
     261             :                                           { return Successors.rbegin();  }
     262             :   succ_reverse_iterator        succ_rend()
     263           2 :                                           { return Successors.rend();    }
     264             :   const_succ_reverse_iterator  succ_rend()   const
     265             :                                           { return Successors.rend();    }
     266             :   unsigned             succ_size()  const {
     267    10320268 :     return (unsigned)Successors.size();
     268             :   }
     269     4918950 :   bool                 succ_empty() const { return Successors.empty();   }
     270             : 
     271             :   inline iterator_range<pred_iterator> predecessors() {
     272     6970374 :     return make_range(pred_begin(), pred_end());
     273             :   }
     274             :   inline iterator_range<const_pred_iterator> predecessors() const {
     275      574944 :     return make_range(pred_begin(), pred_end());
     276             :   }
     277             :   inline iterator_range<succ_iterator> successors() {
     278     3513186 :     return make_range(succ_begin(), succ_end());
     279             :   }
     280             :   inline iterator_range<const_succ_iterator> successors() const {
     281    16112667 :     return make_range(succ_begin(), succ_end());
     282             :   }
     283             : 
     284             :   // LiveIn management methods.
     285             : 
     286             :   /// Adds the specified register as a live in. Note that it is an error to add
     287             :   /// the same register to the same set more than once unless the intention is
     288             :   /// to call sortUniqueLiveIns after all registers are added.
     289             :   void addLiveIn(MCPhysReg PhysReg,
     290             :                  LaneBitmask LaneMask = LaneBitmask::getAll()) {
     291     2067981 :     LiveIns.push_back(RegisterMaskPair(PhysReg, LaneMask));
     292             :   }
     293             :   void addLiveIn(const RegisterMaskPair &RegMaskPair) {
     294       16348 :     LiveIns.push_back(RegMaskPair);
     295             :   }
     296             : 
     297             :   /// Sorts and uniques the LiveIns vector. It can be significantly faster to do
     298             :   /// this than repeatedly calling isLiveIn before calling addLiveIn for every
     299             :   /// LiveIn insertion.
     300             :   void sortUniqueLiveIns();
     301             : 
     302             :   /// Clear live in list.
     303             :   void clearLiveIns();
     304             : 
     305             :   /// Add PhysReg as live in to this block, and ensure that there is a copy of
     306             :   /// PhysReg to a virtual register of class RC. Return the virtual register
     307             :   /// that is a copy of the live in PhysReg.
     308             :   unsigned addLiveIn(MCPhysReg PhysReg, const TargetRegisterClass *RC);
     309             : 
     310             :   /// Remove the specified register from the live in set.
     311             :   void removeLiveIn(MCPhysReg Reg,
     312             :                     LaneBitmask LaneMask = LaneBitmask::getAll());
     313             : 
     314             :   /// Return true if the specified register is in the live in set.
     315             :   bool isLiveIn(MCPhysReg Reg,
     316             :                 LaneBitmask LaneMask = LaneBitmask::getAll()) const;
     317             : 
     318             :   // Iteration support for live in sets.  These sets are kept in sorted
     319             :   // order by their register number.
     320             :   using livein_iterator = LiveInVector::const_iterator;
     321             : #ifndef NDEBUG
     322             :   /// Unlike livein_begin, this method does not check that the liveness
     323             :   /// information is accurate. Still for debug purposes it may be useful
     324             :   /// to have iterators that won't assert if the liveness information
     325             :   /// is not current.
     326             :   livein_iterator livein_begin_dbg() const { return LiveIns.begin(); }
     327             :   iterator_range<livein_iterator> liveins_dbg() const {
     328             :     return make_range(livein_begin_dbg(), livein_end());
     329             :   }
     330             : #endif
     331             :   livein_iterator livein_begin() const;
     332     4229204 :   livein_iterator livein_end()   const { return LiveIns.end(); }
     333      387404 :   bool            livein_empty() const { return LiveIns.empty(); }
     334             :   iterator_range<livein_iterator> liveins() const {
     335     7930986 :     return make_range(livein_begin(), livein_end());
     336             :   }
     337             : 
     338             :   /// Remove entry from the livein set and return iterator to the next.
     339             :   livein_iterator removeLiveIn(livein_iterator I);
     340             : 
     341             :   /// Get the clobber mask for the start of this basic block. Funclets use this
     342             :   /// to prevent register allocation across funclet transitions.
     343             :   const uint32_t *getBeginClobberMask(const TargetRegisterInfo *TRI) const;
     344             : 
     345             :   /// Get the clobber mask for the end of the basic block.
     346             :   /// \see getBeginClobberMask()
     347             :   const uint32_t *getEndClobberMask(const TargetRegisterInfo *TRI) const;
     348             : 
     349             :   /// Return alignment of the basic block. The alignment is specified as
     350             :   /// log2(bytes).
     351             :   unsigned getAlignment() const { return Alignment; }
     352             : 
     353             :   /// Set alignment of the basic block. The alignment is specified as
     354             :   /// log2(bytes).
     355        7025 :   void setAlignment(unsigned Align) { Alignment = Align; }
     356             : 
     357             :   /// Returns true if the block is a landing pad. That is this basic block is
     358             :   /// entered via an exception handler.
     359             :   bool isEHPad() const { return IsEHPad; }
     360             : 
     361             :   /// Indicates the block is a landing pad.  That is this basic block is entered
     362             :   /// via an exception handler.
     363       51878 :   void setIsEHPad(bool V = true) { IsEHPad = V; }
     364             : 
     365             :   bool hasEHPadSuccessor() const;
     366             : 
     367             :   /// Returns true if this is the entry block of an EH funclet.
     368             :   bool isEHFuncletEntry() const { return IsEHFuncletEntry; }
     369             : 
     370             :   /// Indicates if this is the entry block of an EH funclet.
     371         266 :   void setIsEHFuncletEntry(bool V = true) { IsEHFuncletEntry = V; }
     372             : 
     373             :   /// Returns true if this is the entry block of a cleanup funclet.
     374             :   bool isCleanupFuncletEntry() const { return IsCleanupFuncletEntry; }
     375             : 
     376             :   /// Indicates if this is the entry block of a cleanup funclet.
     377          38 :   void setIsCleanupFuncletEntry(bool V = true) { IsCleanupFuncletEntry = V; }
     378             : 
     379             :   /// Returns true if it is legal to hoist instructions into this block.
     380             :   bool isLegalToHoistInto() const;
     381             : 
     382             :   // Code Layout methods.
     383             : 
     384             :   /// Move 'this' block before or after the specified block.  This only moves
     385             :   /// the block, it does not modify the CFG or adjust potential fall-throughs at
     386             :   /// the end of the block.
     387             :   void moveBefore(MachineBasicBlock *NewAfter);
     388             :   void moveAfter(MachineBasicBlock *NewBefore);
     389             : 
     390             :   /// Update the terminator instructions in block to account for changes to the
     391             :   /// layout. If the block previously used a fallthrough, it may now need a
     392             :   /// branch, and if it previously used branching it may now be able to use a
     393             :   /// fallthrough.
     394             :   void updateTerminator();
     395             : 
     396             :   // Machine-CFG mutators
     397             : 
     398             :   /// Add Succ as a successor of this MachineBasicBlock.  The Predecessors list
     399             :   /// of Succ is automatically updated. PROB parameter is stored in
     400             :   /// Probabilities list. The default probability is set as unknown. Mixing
     401             :   /// known and unknown probabilities in successor list is not allowed. When all
     402             :   /// successors have unknown probabilities, 1 / N is returned as the
     403             :   /// probability for each successor, where N is the number of successors.
     404             :   ///
     405             :   /// Note that duplicate Machine CFG edges are not allowed.
     406             :   void addSuccessor(MachineBasicBlock *Succ,
     407             :                     BranchProbability Prob = BranchProbability::getUnknown());
     408             : 
     409             :   /// Add Succ as a successor of this MachineBasicBlock.  The Predecessors list
     410             :   /// of Succ is automatically updated. The probability is not provided because
     411             :   /// BPI is not available (e.g. -O0 is used), in which case edge probabilities
     412             :   /// won't be used. Using this interface can save some space.
     413             :   void addSuccessorWithoutProb(MachineBasicBlock *Succ);
     414             : 
     415             :   /// Set successor probability of a given iterator.
     416             :   void setSuccProbability(succ_iterator I, BranchProbability Prob);
     417             : 
     418             :   /// Normalize probabilities of all successors so that the sum of them becomes
     419             :   /// one. This is usually done when the current update on this MBB is done, and
     420             :   /// the sum of its successors' probabilities is not guaranteed to be one. The
     421             :   /// user is responsible for the correct use of this function.
     422             :   /// MBB::removeSuccessor() has an option to do this automatically.
     423             :   void normalizeSuccProbs() {
     424      226032 :     BranchProbability::normalizeProbabilities(Probs.begin(), Probs.end());
     425             :   }
     426             : 
     427             :   /// Validate successors' probabilities and check if the sum of them is
     428             :   /// approximate one. This only works in DEBUG mode.
     429             :   void validateSuccProbs() const;
     430             : 
     431             :   /// Remove successor from the successors list of this MachineBasicBlock. The
     432             :   /// Predecessors list of Succ is automatically updated.
     433             :   /// If NormalizeSuccProbs is true, then normalize successors' probabilities
     434             :   /// after the successor is removed.
     435             :   void removeSuccessor(MachineBasicBlock *Succ,
     436             :                        bool NormalizeSuccProbs = false);
     437             : 
     438             :   /// Remove specified successor from the successors list of this
     439             :   /// MachineBasicBlock. The Predecessors list of Succ is automatically updated.
     440             :   /// If NormalizeSuccProbs is true, then normalize successors' probabilities
     441             :   /// after the successor is removed.
     442             :   /// Return the iterator to the element after the one removed.
     443             :   succ_iterator removeSuccessor(succ_iterator I,
     444             :                                 bool NormalizeSuccProbs = false);
     445             : 
     446             :   /// Replace successor OLD with NEW and update probability info.
     447             :   void replaceSuccessor(MachineBasicBlock *Old, MachineBasicBlock *New);
     448             : 
     449             :   /// Transfers all the successors from MBB to this machine basic block (i.e.,
     450             :   /// copies all the successors FromMBB and remove all the successors from
     451             :   /// FromMBB).
     452             :   void transferSuccessors(MachineBasicBlock *FromMBB);
     453             : 
     454             :   /// Transfers all the successors, as in transferSuccessors, and update PHI
     455             :   /// operands in the successor blocks which refer to FromMBB to refer to this.
     456             :   void transferSuccessorsAndUpdatePHIs(MachineBasicBlock *FromMBB);
     457             : 
     458             :   /// Return true if any of the successors have probabilities attached to them.
     459         696 :   bool hasSuccessorProbabilities() const { return !Probs.empty(); }
     460             : 
     461             :   /// Return true if the specified MBB is a predecessor of this block.
     462             :   bool isPredecessor(const MachineBasicBlock *MBB) const;
     463             : 
     464             :   /// Return true if the specified MBB is a successor of this block.
     465             :   bool isSuccessor(const MachineBasicBlock *MBB) const;
     466             : 
     467             :   /// Return true if the specified MBB will be emitted immediately after this
     468             :   /// block, such that if this block exits by falling through, control will
     469             :   /// transfer to the specified MBB. Note that MBB need not be a successor at
     470             :   /// all, for example if this block ends with an unconditional branch to some
     471             :   /// other block.
     472             :   bool isLayoutSuccessor(const MachineBasicBlock *MBB) const;
     473             : 
     474             :   /// Return the fallthrough block if the block can implicitly
     475             :   /// transfer control to the block after it by falling off the end of
     476             :   /// it.  This should return null if it can reach the block after
     477             :   /// it, but it uses an explicit branch to do so (e.g., a table
     478             :   /// jump).  Non-null return  is a conservative answer.
     479             :   MachineBasicBlock *getFallThrough();
     480             : 
     481             :   /// Return true if the block can implicitly transfer control to the
     482             :   /// block after it by falling off the end of it.  This should return
     483             :   /// false if it can reach the block after it, but it uses an
     484             :   /// explicit branch to do so (e.g., a table jump).  True is a
     485             :   /// conservative answer.
     486             :   bool canFallThrough();
     487             : 
     488             :   /// Returns a pointer to the first instruction in this block that is not a
     489             :   /// PHINode instruction. When adding instructions to the beginning of the
     490             :   /// basic block, they should be added before the returned value, not before
     491             :   /// the first instruction, which might be PHI.
     492             :   /// Returns end() is there's no non-PHI instruction.
     493             :   iterator getFirstNonPHI();
     494             : 
     495             :   /// Return the first instruction in MBB after I that is not a PHI or a label.
     496             :   /// This is the correct point to insert lowered copies at the beginning of a
     497             :   /// basic block that must be before any debugging information.
     498             :   iterator SkipPHIsAndLabels(iterator I);
     499             : 
     500             :   /// Return the first instruction in MBB after I that is not a PHI, label or
     501             :   /// debug.  This is the correct point to insert copies at the beginning of a
     502             :   /// basic block.
     503             :   iterator SkipPHIsLabelsAndDebug(iterator I);
     504             : 
     505             :   /// Returns an iterator to the first terminator instruction of this basic
     506             :   /// block. If a terminator does not exist, it returns end().
     507             :   iterator getFirstTerminator();
     508             :   const_iterator getFirstTerminator() const {
     509      137638 :     return const_cast<MachineBasicBlock *>(this)->getFirstTerminator();
     510             :   }
     511             : 
     512             :   /// Same getFirstTerminator but it ignores bundles and return an
     513             :   /// instr_iterator instead.
     514             :   instr_iterator getFirstInstrTerminator();
     515             : 
     516             :   /// Returns an iterator to the first non-debug instruction in the basic block,
     517             :   /// or end().
     518             :   iterator getFirstNonDebugInstr();
     519             :   const_iterator getFirstNonDebugInstr() const {
     520             :     return const_cast<MachineBasicBlock *>(this)->getFirstNonDebugInstr();
     521             :   }
     522             : 
     523             :   /// Returns an iterator to the last non-debug instruction in the basic block,
     524             :   /// or end().
     525             :   iterator getLastNonDebugInstr();
     526             :   const_iterator getLastNonDebugInstr() const {
     527     1329682 :     return const_cast<MachineBasicBlock *>(this)->getLastNonDebugInstr();
     528             :   }
     529             : 
     530             :   /// Convenience function that returns true if the block ends in a return
     531             :   /// instruction.
     532      846268 :   bool isReturnBlock() const {
     533     2524874 :     return !empty() && back().isReturn();
     534             :   }
     535             : 
     536             :   /// Split the critical edge from this block to the given successor block, and
     537             :   /// return the newly created block, or null if splitting is not possible.
     538             :   ///
     539             :   /// This function updates LiveVariables, MachineDominatorTree, and
     540             :   /// MachineLoopInfo, as applicable.
     541             :   MachineBasicBlock *SplitCriticalEdge(MachineBasicBlock *Succ, Pass &P);
     542             : 
     543             :   /// Check if the edge between this block and the given successor \p
     544             :   /// Succ, can be split. If this returns true a subsequent call to
     545             :   /// SplitCriticalEdge is guaranteed to return a valid basic block if
     546             :   /// no changes occured in the meantime.
     547             :   bool canSplitCriticalEdge(const MachineBasicBlock *Succ) const;
     548             : 
     549             :   void pop_front() { Insts.pop_front(); }
     550             :   void pop_back() { Insts.pop_back(); }
     551        2624 :   void push_back(MachineInstr *MI) { Insts.push_back(MI); }
     552             : 
     553             :   /// Insert MI into the instruction list before I, possibly inside a bundle.
     554             :   ///
     555             :   /// If the insertion point is inside a bundle, MI will be added to the bundle,
     556             :   /// otherwise MI will not be added to any bundle. That means this function
     557             :   /// alone can't be used to prepend or append instructions to bundles. See
     558             :   /// MIBundleBuilder::insert() for a more reliable way of doing that.
     559             :   instr_iterator insert(instr_iterator I, MachineInstr *M);
     560             : 
     561             :   /// Insert a range of instructions into the instruction list before I.
     562             :   template<typename IT>
     563             :   void insert(iterator I, IT S, IT E) {
     564             :     assert((I == end() || I->getParent() == this) &&
     565             :            "iterator points outside of basic block");
     566        7600 :     Insts.insert(I.getInstrIterator(), S, E);
     567             :   }
     568             : 
     569             :   /// Insert MI into the instruction list before I.
     570             :   iterator insert(iterator I, MachineInstr *MI) {
     571             :     assert((I == end() || I->getParent() == this) &&
     572             :            "iterator points outside of basic block");
     573             :     assert(!MI->isBundledWithPred() && !MI->isBundledWithSucc() &&
     574             :            "Cannot insert instruction with bundle flags");
     575     6421220 :     return Insts.insert(I.getInstrIterator(), MI);
     576             :   }
     577             : 
     578             :   /// Insert MI into the instruction list after I.
     579             :   iterator insertAfter(iterator I, MachineInstr *MI) {
     580             :     assert((I == end() || I->getParent() == this) &&
     581             :            "iterator points outside of basic block");
     582             :     assert(!MI->isBundledWithPred() && !MI->isBundledWithSucc() &&
     583             :            "Cannot insert instruction with bundle flags");
     584         172 :     return Insts.insertAfter(I.getInstrIterator(), MI);
     585             :   }
     586             : 
     587             :   /// Remove an instruction from the instruction list and delete it.
     588             :   ///
     589             :   /// If the instruction is part of a bundle, the other instructions in the
     590             :   /// bundle will still be bundled after removing the single instruction.
     591             :   instr_iterator erase(instr_iterator I);
     592             : 
     593             :   /// Remove an instruction from the instruction list and delete it.
     594             :   ///
     595             :   /// If the instruction is part of a bundle, the other instructions in the
     596             :   /// bundle will still be bundled after removing the single instruction.
     597             :   instr_iterator erase_instr(MachineInstr *I) {
     598      553771 :     return erase(instr_iterator(I));
     599             :   }
     600             : 
     601             :   /// Remove a range of instructions from the instruction list and delete them.
     602             :   iterator erase(iterator I, iterator E) {
     603     5359520 :     return Insts.erase(I.getInstrIterator(), E.getInstrIterator());
     604             :   }
     605             : 
     606             :   /// Remove an instruction or bundle from the instruction list and delete it.
     607             :   ///
     608             :   /// If I points to a bundle of instructions, they are all erased.
     609     2664417 :   iterator erase(iterator I) {
     610     5328834 :     return erase(I, std::next(I));
     611             :   }
     612             : 
     613             :   /// Remove an instruction from the instruction list and delete it.
     614             :   ///
     615             :   /// If I is the head of a bundle of instructions, the whole bundle will be
     616             :   /// erased.
     617             :   iterator erase(MachineInstr *I) {
     618     2086838 :     return erase(iterator(I));
     619             :   }
     620             : 
     621             :   /// Remove the unbundled instruction from the instruction list without
     622             :   /// deleting it.
     623             :   ///
     624             :   /// This function can not be used to remove bundled instructions, use
     625             :   /// remove_instr to remove individual instructions from a bundle.
     626             :   MachineInstr *remove(MachineInstr *I) {
     627             :     assert(!I->isBundled() && "Cannot remove bundled instructions");
     628      118785 :     return Insts.remove(instr_iterator(I));
     629             :   }
     630             : 
     631             :   /// Remove the possibly bundled instruction from the instruction list
     632             :   /// without deleting it.
     633             :   ///
     634             :   /// If the instruction is part of a bundle, the other instructions in the
     635             :   /// bundle will still be bundled after removing the single instruction.
     636             :   MachineInstr *remove_instr(MachineInstr *I);
     637             : 
     638             :   void clear() {
     639         166 :     Insts.clear();
     640             :   }
     641             : 
     642             :   /// Take an instruction from MBB 'Other' at the position From, and insert it
     643             :   /// into this MBB right before 'Where'.
     644             :   ///
     645             :   /// If From points to a bundle of instructions, the whole bundle is moved.
     646     1122607 :   void splice(iterator Where, MachineBasicBlock *Other, iterator From) {
     647             :     // The range splice() doesn't allow noop moves, but this one does.
     648     1122607 :     if (Where != From)
     649     1103915 :       splice(Where, Other, From, std::next(From));
     650     1122607 :   }
     651             : 
     652             :   /// Take a block of instructions from MBB 'Other' in the range [From, To),
     653             :   /// and insert them into this MBB right before 'Where'.
     654             :   ///
     655             :   /// The instruction at 'Where' must not be included in the range of
     656             :   /// instructions to move.
     657             :   void splice(iterator Where, MachineBasicBlock *Other,
     658             :               iterator From, iterator To) {
     659     1179792 :     Insts.splice(Where.getInstrIterator(), Other->Insts,
     660             :                  From.getInstrIterator(), To.getInstrIterator());
     661             :   }
     662             : 
     663             :   /// This method unlinks 'this' from the containing function, and returns it,
     664             :   /// but does not delete it.
     665             :   MachineBasicBlock *removeFromParent();
     666             : 
     667             :   /// This method unlinks 'this' from the containing function and deletes it.
     668             :   void eraseFromParent();
     669             : 
     670             :   /// Given a machine basic block that branched to 'Old', change the code and
     671             :   /// CFG so that it branches to 'New' instead.
     672             :   void ReplaceUsesOfBlockWith(MachineBasicBlock *Old, MachineBasicBlock *New);
     673             : 
     674             :   /// Various pieces of code can cause excess edges in the CFG to be inserted.
     675             :   /// If we have proven that MBB can only branch to DestA and DestB, remove any
     676             :   /// other MBB successors from the CFG. DestA and DestB can be null. Besides
     677             :   /// DestA and DestB, retain other edges leading to LandingPads (currently
     678             :   /// there can be only one; we don't check or require that here). Note it is
     679             :   /// possible that DestA and/or DestB are LandingPads.
     680             :   bool CorrectExtraCFGEdges(MachineBasicBlock *DestA,
     681             :                             MachineBasicBlock *DestB,
     682             :                             bool IsCond);
     683             : 
     684             :   /// Find the next valid DebugLoc starting at MBBI, skipping any DBG_VALUE
     685             :   /// instructions.  Return UnknownLoc if there is none.
     686             :   DebugLoc findDebugLoc(instr_iterator MBBI);
     687             :   DebugLoc findDebugLoc(iterator MBBI) {
     688      381671 :     return findDebugLoc(MBBI.getInstrIterator());
     689             :   }
     690             : 
     691             :   /// Find and return the merged DebugLoc of the branch instructions of the
     692             :   /// block. Return UnknownLoc if there is none.
     693             :   DebugLoc findBranchDebugLoc();
     694             : 
     695             :   /// Possible outcome of a register liveness query to computeRegisterLiveness()
     696             :   enum LivenessQueryResult {
     697             :     LQR_Live,   ///< Register is known to be (at least partially) live.
     698             :     LQR_Dead,   ///< Register is known to be fully dead.
     699             :     LQR_Unknown ///< Register liveness not decidable from local neighborhood.
     700             :   };
     701             : 
     702             :   /// Return whether (physical) register \p Reg has been <def>ined and not
     703             :   /// <kill>ed as of just before \p Before.
     704             :   ///
     705             :   /// Search is localised to a neighborhood of \p Neighborhood instructions
     706             :   /// before (searching for defs or kills) and \p Neighborhood instructions
     707             :   /// after (searching just for defs) \p Before.
     708             :   ///
     709             :   /// \p Reg must be a physical register.
     710             :   LivenessQueryResult computeRegisterLiveness(const TargetRegisterInfo *TRI,
     711             :                                               unsigned Reg,
     712             :                                               const_iterator Before,
     713             :                                               unsigned Neighborhood = 10) const;
     714             : 
     715             :   // Debugging methods.
     716             :   void dump() const;
     717             :   void print(raw_ostream &OS, const SlotIndexes* = nullptr) const;
     718             :   void print(raw_ostream &OS, ModuleSlotTracker &MST,
     719             :              const SlotIndexes* = nullptr) const;
     720             : 
     721             :   // Printing method used by LoopInfo.
     722             :   void printAsOperand(raw_ostream &OS, bool PrintType = true) const;
     723             : 
     724             :   /// MachineBasicBlocks are uniquely numbered at the function level, unless
     725             :   /// they're not in a MachineFunction yet, in which case this will return -1.
     726             :   int getNumber() const { return Number; }
     727      569580 :   void setNumber(int N) { Number = N; }
     728             : 
     729             :   /// Return the MCSymbol for this basic block.
     730             :   MCSymbol *getSymbol() const;
     731             : 
     732             : private:
     733             :   /// Return probability iterator corresponding to the I successor iterator.
     734             :   probability_iterator getProbabilityIterator(succ_iterator I);
     735             :   const_probability_iterator
     736             :   getProbabilityIterator(const_succ_iterator I) const;
     737             : 
     738             :   friend class MachineBranchProbabilityInfo;
     739             :   friend class MIPrinter;
     740             : 
     741             :   /// Return probability of the edge from this block to MBB. This method should
     742             :   /// NOT be called directly, but by using getEdgeProbability method from
     743             :   /// MachineBranchProbabilityInfo class.
     744             :   BranchProbability getSuccProbability(const_succ_iterator Succ) const;
     745             : 
     746             :   // Methods used to maintain doubly linked list of blocks...
     747             :   friend struct ilist_callback_traits<MachineBasicBlock>;
     748             : 
     749             :   // Machine-CFG mutators
     750             : 
     751             :   /// Add Pred as a predecessor of this MachineBasicBlock. Don't do this
     752             :   /// unless you know what you're doing, because it doesn't update Pred's
     753             :   /// successors list. Use Pred->addSuccessor instead.
     754             :   void addPredecessor(MachineBasicBlock *Pred);
     755             : 
     756             :   /// Remove Pred as a predecessor of this MachineBasicBlock. Don't do this
     757             :   /// unless you know what you're doing, because it doesn't update Pred's
     758             :   /// successors list. Use Pred->removeSuccessor instead.
     759             :   void removePredecessor(MachineBasicBlock *Pred);
     760             : };
     761             : 
     762             : raw_ostream& operator<<(raw_ostream &OS, const MachineBasicBlock &MBB);
     763             : 
     764             : // This is useful when building IndexedMaps keyed on basic block pointers.
     765             : struct MBB2NumberFunctor :
     766             :   public std::unary_function<const MachineBasicBlock*, unsigned> {
     767             :   unsigned operator()(const MachineBasicBlock *MBB) const {
     768     3476958 :     return MBB->getNumber();
     769             :   }
     770             : };
     771             : 
     772             : //===--------------------------------------------------------------------===//
     773             : // GraphTraits specializations for machine basic block graphs (machine-CFGs)
     774             : //===--------------------------------------------------------------------===//
     775             : 
     776             : // Provide specializations of GraphTraits to be able to treat a
     777             : // MachineFunction as a graph of MachineBasicBlocks.
     778             : //
     779             : 
     780             : template <> struct GraphTraits<MachineBasicBlock *> {
     781             :   using NodeRef = MachineBasicBlock *;
     782             :   using ChildIteratorType = MachineBasicBlock::succ_iterator;
     783             : 
     784             :   static NodeRef getEntryNode(MachineBasicBlock *BB) { return BB; }
     785     6231528 :   static ChildIteratorType child_begin(NodeRef N) { return N->succ_begin(); }
     786     8695230 :   static ChildIteratorType child_end(NodeRef N) { return N->succ_end(); }
     787             : };
     788             : 
     789             : template <> struct GraphTraits<const MachineBasicBlock *> {
     790             :   using NodeRef = const MachineBasicBlock *;
     791             :   using ChildIteratorType = MachineBasicBlock::const_succ_iterator;
     792             : 
     793             :   static NodeRef getEntryNode(const MachineBasicBlock *BB) { return BB; }
     794     4027159 :   static ChildIteratorType child_begin(NodeRef N) { return N->succ_begin(); }
     795     5307723 :   static ChildIteratorType child_end(NodeRef N) { return N->succ_end(); }
     796             : };
     797             : 
     798             : // Provide specializations of GraphTraits to be able to treat a
     799             : // MachineFunction as a graph of MachineBasicBlocks and to walk it
     800             : // in inverse order.  Inverse order for a function is considered
     801             : // to be when traversing the predecessor edges of a MBB
     802             : // instead of the successor edges.
     803             : //
     804             : template <> struct GraphTraits<Inverse<MachineBasicBlock*>> {
     805             :   using NodeRef = MachineBasicBlock *;
     806             :   using ChildIteratorType = MachineBasicBlock::pred_iterator;
     807             : 
     808             :   static NodeRef getEntryNode(Inverse<MachineBasicBlock *> G) {
     809          17 :     return G.Graph;
     810             :   }
     811             : 
     812     3685717 :   static ChildIteratorType child_begin(NodeRef N) { return N->pred_begin(); }
     813     3685724 :   static ChildIteratorType child_end(NodeRef N) { return N->pred_end(); }
     814             : };
     815             : 
     816             : template <> struct GraphTraits<Inverse<const MachineBasicBlock*>> {
     817             :   using NodeRef = const MachineBasicBlock *;
     818             :   using ChildIteratorType = MachineBasicBlock::const_pred_iterator;
     819             : 
     820             :   static NodeRef getEntryNode(Inverse<const MachineBasicBlock *> G) {
     821         787 :     return G.Graph;
     822             :   }
     823             : 
     824         879 :   static ChildIteratorType child_begin(NodeRef N) { return N->pred_begin(); }
     825        1181 :   static ChildIteratorType child_end(NodeRef N) { return N->pred_end(); }
     826             : };
     827             : 
     828             : /// MachineInstrSpan provides an interface to get an iteration range
     829             : /// containing the instruction it was initialized with, along with all
     830             : /// those instructions inserted prior to or following that instruction
     831             : /// at some point after the MachineInstrSpan is constructed.
     832             : class MachineInstrSpan {
     833             :   MachineBasicBlock &MBB;
     834             :   MachineBasicBlock::iterator I, B, E;
     835             : 
     836             : public:
     837       61522 :   MachineInstrSpan(MachineBasicBlock::iterator I)
     838      123044 :     : MBB(*I->getParent()),
     839             :       I(I),
     840      189292 :       B(I == MBB.begin() ? MBB.end() : std::prev(I)),
     841      246088 :       E(std::next(I)) {}
     842             : 
     843       42958 :   MachineBasicBlock::iterator begin() {
     844      171832 :     return B == MBB.end() ? MBB.begin() : std::next(B);
     845             :   }
     846             :   MachineBasicBlock::iterator end() { return E; }
     847             :   bool empty() { return begin() == end(); }
     848             : 
     849             :   MachineBasicBlock::iterator getInitial() { return I; }
     850             : };
     851             : 
     852             : /// Increment \p It until it points to a non-debug instruction or to \p End
     853             : /// and return the resulting iterator. This function should only be used
     854             : /// MachineBasicBlock::{iterator, const_iterator, instr_iterator,
     855             : /// const_instr_iterator} and the respective reverse iterators.
     856             : template<typename IterT>
     857             : inline IterT skipDebugInstructionsForward(IterT It, IterT End) {
     858    10199832 :   while (It != End && It->isDebugValue())
     859       15645 :     It++;
     860             :   return It;
     861             : }
     862             : 
     863             : /// Decrement \p It until it points to a non-debug instruction or to \p Begin
     864             : /// and return the resulting iterator. This function should only be used
     865             : /// MachineBasicBlock::{iterator, const_iterator, instr_iterator,
     866             : /// const_instr_iterator} and the respective reverse iterators.
     867             : template<class IterT>
     868             : inline IterT skipDebugInstructionsBackward(IterT It, IterT Begin) {
     869     7989427 :   while (It != Begin && It->isDebugValue())
     870        8709 :     It--;
     871             :   return It;
     872             : }
     873             : 
     874             : } // end namespace llvm
     875             : 
     876             : #endif // LLVM_CODEGEN_MACHINEBASICBLOCK_H

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