LiveIntervalAnalysis.h   [plain text]

//===-- LiveIntervalAnalysis.h - Live Interval Analysis ---------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the LiveInterval analysis pass.  Given some numbering of
// each the machine instructions (in this implemention depth-first order) an
// interval [i, j) is said to be a live interval for register v if there is no
// instruction with number j' > j such that v is live at j' and there is no
// instruction with number i' < i such that v is live at i'. In this
// implementation intervals can have holes, i.e. an interval might look like
// [1,20), [50,65), [1000,1001).
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CODEGEN_LIVEINTERVAL_ANALYSIS_H
#define LLVM_CODEGEN_LIVEINTERVAL_ANALYSIS_H

#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/LiveInterval.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Support/Allocator.h"
#include <cmath>

namespace llvm {

  class AliasAnalysis;
  class LiveVariables;
  class MachineLoopInfo;
  class TargetRegisterInfo;
  class MachineRegisterInfo;
  class TargetInstrInfo;
  class TargetRegisterClass;
  class VirtRegMap;
  typedef std::pair<unsigned, MachineBasicBlock*> IdxMBBPair;

  inline bool operator<(unsigned V, const IdxMBBPair &IM) {
    return V < IM.first;
  }

  inline bool operator<(const IdxMBBPair &IM, unsigned V) {
    return IM.first < V;
  }

  struct Idx2MBBCompare {
    bool operator()(const IdxMBBPair &LHS, const IdxMBBPair &RHS) const {
      return LHS.first < RHS.first;
    }
  };
  
  class LiveIntervals : public MachineFunctionPass {
    MachineFunction* mf_;
    MachineRegisterInfo* mri_;
    const TargetMachine* tm_;
    const TargetRegisterInfo* tri_;
    const TargetInstrInfo* tii_;
    AliasAnalysis *aa_;
    LiveVariables* lv_;

    /// Special pool allocator for VNInfo's (LiveInterval val#).
    ///
    BumpPtrAllocator VNInfoAllocator;

    /// MBB2IdxMap - The indexes of the first and last instructions in the
    /// specified basic block.
    std::vector<std::pair<unsigned, unsigned> > MBB2IdxMap;

    /// Idx2MBBMap - Sorted list of pairs of index of first instruction
    /// and MBB id.
    std::vector<IdxMBBPair> Idx2MBBMap;

    /// FunctionSize - The number of instructions present in the function
    uint64_t FunctionSize;

    typedef DenseMap<MachineInstr*, unsigned> Mi2IndexMap;
    Mi2IndexMap mi2iMap_;

    typedef std::vector<MachineInstr*> Index2MiMap;
    Index2MiMap i2miMap_;

    typedef DenseMap<unsigned, LiveInterval*> Reg2IntervalMap;
    Reg2IntervalMap r2iMap_;

    BitVector allocatableRegs_;

    std::vector<MachineInstr*> ClonedMIs;

  public:
    static char ID; // Pass identification, replacement for typeid
    LiveIntervals() : MachineFunctionPass(&ID) {}

    struct InstrSlots {
      enum {
        LOAD  = 0,
        USE   = 1,
        DEF   = 2,
        STORE = 3,
        NUM   = 4
      };
    };

    static unsigned getBaseIndex(unsigned index) {
      return index - (index % InstrSlots::NUM);
    }
    static unsigned getBoundaryIndex(unsigned index) {
      return getBaseIndex(index + InstrSlots::NUM - 1);
    }
    static unsigned getLoadIndex(unsigned index) {
      return getBaseIndex(index) + InstrSlots::LOAD;
    }
    static unsigned getUseIndex(unsigned index) {
      return getBaseIndex(index) + InstrSlots::USE;
    }
    static unsigned getDefIndex(unsigned index) {
      return getBaseIndex(index) + InstrSlots::DEF;
    }
    static unsigned getStoreIndex(unsigned index) {
      return getBaseIndex(index) + InstrSlots::STORE;
    }

    static float getSpillWeight(bool isDef, bool isUse, unsigned loopDepth) {
      return (isDef + isUse) * powf(10.0F, (float)loopDepth);
    }

    typedef Reg2IntervalMap::iterator iterator;
    typedef Reg2IntervalMap::const_iterator const_iterator;
    const_iterator begin() const { return r2iMap_.begin(); }
    const_iterator end() const { return r2iMap_.end(); }
    iterator begin() { return r2iMap_.begin(); }
    iterator end() { return r2iMap_.end(); }
    unsigned getNumIntervals() const { return (unsigned)r2iMap_.size(); }

    LiveInterval &getInterval(unsigned reg) {
      Reg2IntervalMap::iterator I = r2iMap_.find(reg);
      assert(I != r2iMap_.end() && "Interval does not exist for register");
      return *I->second;
    }

    const LiveInterval &getInterval(unsigned reg) const {
      Reg2IntervalMap::const_iterator I = r2iMap_.find(reg);
      assert(I != r2iMap_.end() && "Interval does not exist for register");
      return *I->second;
    }

    bool hasInterval(unsigned reg) const {
      return r2iMap_.count(reg);
    }

    /// getMBBStartIdx - Return the base index of the first instruction in the
    /// specified MachineBasicBlock.
    unsigned getMBBStartIdx(MachineBasicBlock *MBB) const {
      return getMBBStartIdx(MBB->getNumber());
    }
    unsigned getMBBStartIdx(unsigned MBBNo) const {
      assert(MBBNo < MBB2IdxMap.size() && "Invalid MBB number!");
      return MBB2IdxMap[MBBNo].first;
    }

    /// getMBBEndIdx - Return the store index of the last instruction in the
    /// specified MachineBasicBlock.
    unsigned getMBBEndIdx(MachineBasicBlock *MBB) const {
      return getMBBEndIdx(MBB->getNumber());
    }
    unsigned getMBBEndIdx(unsigned MBBNo) const {
      assert(MBBNo < MBB2IdxMap.size() && "Invalid MBB number!");
      return MBB2IdxMap[MBBNo].second;
    }

    /// getScaledIntervalSize - get the size of an interval in "units,"
    /// where every function is composed of one thousand units.  This
    /// measure scales properly with empty index slots in the function.
    double getScaledIntervalSize(LiveInterval& I) {
      return (1000.0 / InstrSlots::NUM * I.getSize()) / i2miMap_.size();
    }
    
    /// getApproximateInstructionCount - computes an estimate of the number
    /// of instructions in a given LiveInterval.
    unsigned getApproximateInstructionCount(LiveInterval& I) {
      double IntervalPercentage = getScaledIntervalSize(I) / 1000.0;
      return (unsigned)(IntervalPercentage * FunctionSize);
    }

    /// getMBBFromIndex - given an index in any instruction of an
    /// MBB return a pointer the MBB
    MachineBasicBlock* getMBBFromIndex(unsigned index) const {
      std::vector<IdxMBBPair>::const_iterator I =
        std::lower_bound(Idx2MBBMap.begin(), Idx2MBBMap.end(), index);
      // Take the pair containing the index
      std::vector<IdxMBBPair>::const_iterator J =
        ((I != Idx2MBBMap.end() && I->first > index) ||
         (I == Idx2MBBMap.end() && Idx2MBBMap.size()>0)) ? (I-1): I;

      assert(J != Idx2MBBMap.end() && J->first < index+1 &&
             index <= getMBBEndIdx(J->second) &&
             "index does not correspond to an MBB");
      return J->second;
    }

    /// getInstructionIndex - returns the base index of instr
    unsigned getInstructionIndex(MachineInstr* instr) const {
      Mi2IndexMap::const_iterator it = mi2iMap_.find(instr);
      assert(it != mi2iMap_.end() && "Invalid instruction!");
      return it->second;
    }

    /// getInstructionFromIndex - given an index in any slot of an
    /// instruction return a pointer the instruction
    MachineInstr* getInstructionFromIndex(unsigned index) const {
      index /= InstrSlots::NUM; // convert index to vector index
      assert(index < i2miMap_.size() &&
             "index does not correspond to an instruction");
      return i2miMap_[index];
    }

    /// hasGapBeforeInstr - Return true if the previous instruction slot,
    /// i.e. Index - InstrSlots::NUM, is not occupied.
    bool hasGapBeforeInstr(unsigned Index) {
      Index = getBaseIndex(Index - InstrSlots::NUM);
      return getInstructionFromIndex(Index) == 0;
    }

    /// findGapBeforeInstr - Find an empty instruction slot before the
    /// specified index. If "Furthest" is true, find one that's furthest
    /// away from the index (but before any index that's occupied).
    unsigned findGapBeforeInstr(unsigned Index, bool Furthest = false) {
      Index = getBaseIndex(Index - InstrSlots::NUM);
      if (getInstructionFromIndex(Index))
        return 0;  // No gap!
      if (!Furthest)
        return Index;
      unsigned PrevIndex = getBaseIndex(Index - InstrSlots::NUM);
      while (getInstructionFromIndex(Index)) {
        Index = PrevIndex;
        PrevIndex = getBaseIndex(Index - InstrSlots::NUM);
      }
      return Index;
    }

    /// InsertMachineInstrInMaps - Insert the specified machine instruction
    /// into the instruction index map at the given index.
    void InsertMachineInstrInMaps(MachineInstr *MI, unsigned Index) {
      i2miMap_[Index / InstrSlots::NUM] = MI;
      Mi2IndexMap::iterator it = mi2iMap_.find(MI);
      assert(it == mi2iMap_.end() && "Already in map!");
      mi2iMap_[MI] = Index;
    }

    /// conflictsWithPhysRegDef - Returns true if the specified register
    /// is defined during the duration of the specified interval.
    bool conflictsWithPhysRegDef(const LiveInterval &li, VirtRegMap &vrm,
                                 unsigned reg);

    /// conflictsWithPhysRegRef - Similar to conflictsWithPhysRegRef except
    /// it can check use as well.
    bool conflictsWithPhysRegRef(LiveInterval &li, unsigned Reg,
                                 bool CheckUse,
                                 SmallPtrSet<MachineInstr*,32> &JoinedCopies);

    /// findLiveInMBBs - Given a live range, if the value of the range
    /// is live in any MBB returns true as well as the list of basic blocks
    /// in which the value is live.
    bool findLiveInMBBs(unsigned Start, unsigned End,
                        SmallVectorImpl<MachineBasicBlock*> &MBBs) const;

    /// findReachableMBBs - Return a list MBB that can be reached via any
    /// branch or fallthroughs. Return true if the list is not empty.
    bool findReachableMBBs(unsigned Start, unsigned End,
                        SmallVectorImpl<MachineBasicBlock*> &MBBs) const;

    // Interval creation

    LiveInterval &getOrCreateInterval(unsigned reg) {
      Reg2IntervalMap::iterator I = r2iMap_.find(reg);
      if (I == r2iMap_.end())
        I = r2iMap_.insert(std::make_pair(reg, createInterval(reg))).first;
      return *I->second;
    }

    /// dupInterval - Duplicate a live interval. The caller is responsible for
    /// managing the allocated memory.
    LiveInterval *dupInterval(LiveInterval *li);
    
    /// addLiveRangeToEndOfBlock - Given a register and an instruction,
    /// adds a live range from that instruction to the end of its MBB.
    LiveRange addLiveRangeToEndOfBlock(unsigned reg,
                                        MachineInstr* startInst);

    // Interval removal

    void removeInterval(unsigned Reg) {
      DenseMap<unsigned, LiveInterval*>::iterator I = r2iMap_.find(Reg);
      delete I->second;
      r2iMap_.erase(I);
    }

    /// isNotInMIMap - returns true if the specified machine instr has been
    /// removed or was never entered in the map.
    bool isNotInMIMap(MachineInstr* instr) const {
      return !mi2iMap_.count(instr);
    }

    /// RemoveMachineInstrFromMaps - This marks the specified machine instr as
    /// deleted.
    void RemoveMachineInstrFromMaps(MachineInstr *MI) {
      // remove index -> MachineInstr and
      // MachineInstr -> index mappings
      Mi2IndexMap::iterator mi2i = mi2iMap_.find(MI);
      if (mi2i != mi2iMap_.end()) {
        i2miMap_[mi2i->second/InstrSlots::NUM] = 0;
        mi2iMap_.erase(mi2i);
      }
    }

    /// ReplaceMachineInstrInMaps - Replacing a machine instr with a new one in
    /// maps used by register allocator.
    void ReplaceMachineInstrInMaps(MachineInstr *MI, MachineInstr *NewMI) {
      Mi2IndexMap::iterator mi2i = mi2iMap_.find(MI);
      if (mi2i == mi2iMap_.end())
        return;
      i2miMap_[mi2i->second/InstrSlots::NUM] = NewMI;
      Mi2IndexMap::iterator it = mi2iMap_.find(MI);
      assert(it != mi2iMap_.end() && "Invalid instruction!");
      unsigned Index = it->second;
      mi2iMap_.erase(it);
      mi2iMap_[NewMI] = Index;
    }

    BumpPtrAllocator& getVNInfoAllocator() { return VNInfoAllocator; }

    /// getVNInfoSourceReg - Helper function that parses the specified VNInfo
    /// copy field and returns the source register that defines it.
    unsigned getVNInfoSourceReg(const VNInfo *VNI) const;

    virtual void getAnalysisUsage(AnalysisUsage &AU) const;
    virtual void releaseMemory();

    /// runOnMachineFunction - pass entry point
    virtual bool runOnMachineFunction(MachineFunction&);

    /// print - Implement the dump method.
    virtual void print(std::ostream &O, const Module* = 0) const;
    void print(std::ostream *O, const Module* M = 0) const {
      if (O) print(*O, M);
    }

    /// addIntervalsForSpills - Create new intervals for spilled defs / uses of
    /// the given interval. FIXME: It also returns the weight of the spill slot
    /// (if any is created) by reference. This is temporary.
    std::vector<LiveInterval*>
    addIntervalsForSpills(const LiveInterval& i,
                          SmallVectorImpl<LiveInterval*> &SpillIs,
                          const MachineLoopInfo *loopInfo, VirtRegMap& vrm);
    
    /// addIntervalsForSpillsFast - Quickly create new intervals for spilled
    /// defs / uses without remat or splitting.
    std::vector<LiveInterval*>
    addIntervalsForSpillsFast(const LiveInterval &li,
                              const MachineLoopInfo *loopInfo, VirtRegMap &vrm);

    /// spillPhysRegAroundRegDefsUses - Spill the specified physical register
    /// around all defs and uses of the specified interval. Return true if it
    /// was able to cut its interval.
    bool spillPhysRegAroundRegDefsUses(const LiveInterval &li,
                                       unsigned PhysReg, VirtRegMap &vrm);

    /// isReMaterializable - Returns true if every definition of MI of every
    /// val# of the specified interval is re-materializable. Also returns true
    /// by reference if all of the defs are load instructions.
    bool isReMaterializable(const LiveInterval &li,
                            SmallVectorImpl<LiveInterval*> &SpillIs,
                            bool &isLoad);

    /// isReMaterializable - Returns true if the definition MI of the specified
    /// val# of the specified interval is re-materializable.
    bool isReMaterializable(const LiveInterval &li, const VNInfo *ValNo,
                            MachineInstr *MI);

    /// getRepresentativeReg - Find the largest super register of the specified
    /// physical register.
    unsigned getRepresentativeReg(unsigned Reg) const;

    /// getNumConflictsWithPhysReg - Return the number of uses and defs of the
    /// specified interval that conflicts with the specified physical register.
    unsigned getNumConflictsWithPhysReg(const LiveInterval &li,
                                        unsigned PhysReg) const;

    /// computeNumbering - Compute the index numbering.
    void computeNumbering();

    /// intervalIsInOneMBB - Returns true if the specified interval is entirely
    /// within a single basic block.
    bool intervalIsInOneMBB(const LiveInterval &li) const;

  private:      
    /// computeIntervals - Compute live intervals.
    void computeIntervals();
    
    /// handleRegisterDef - update intervals for a register def
    /// (calls handlePhysicalRegisterDef and
    /// handleVirtualRegisterDef)
    void handleRegisterDef(MachineBasicBlock *MBB,
                           MachineBasicBlock::iterator MI, unsigned MIIdx,
                           MachineOperand& MO, unsigned MOIdx);

    /// handleVirtualRegisterDef - update intervals for a virtual
    /// register def
    void handleVirtualRegisterDef(MachineBasicBlock *MBB,
                                  MachineBasicBlock::iterator MI,
                                  unsigned MIIdx, MachineOperand& MO,
                                  unsigned MOIdx, LiveInterval& interval);

    /// handlePhysicalRegisterDef - update intervals for a physical register
    /// def.
    void handlePhysicalRegisterDef(MachineBasicBlock* mbb,
                                   MachineBasicBlock::iterator mi,
                                   unsigned MIIdx, MachineOperand& MO,
                                   LiveInterval &interval,
                                   MachineInstr *CopyMI);

    /// handleLiveInRegister - Create interval for a livein register.
    void handleLiveInRegister(MachineBasicBlock* mbb,
                              unsigned MIIdx,
                              LiveInterval &interval, bool isAlias = false);

    /// getReMatImplicitUse - If the remat definition MI has one (for now, we
    /// only allow one) virtual register operand, then its uses are implicitly
    /// using the register. Returns the virtual register.
    unsigned getReMatImplicitUse(const LiveInterval &li,
                                 MachineInstr *MI) const;

    /// isValNoAvailableAt - Return true if the val# of the specified interval
    /// which reaches the given instruction also reaches the specified use
    /// index.
    bool isValNoAvailableAt(const LiveInterval &li, MachineInstr *MI,
                            unsigned UseIdx) const;

    /// isReMaterializable - Returns true if the definition MI of the specified
    /// val# of the specified interval is re-materializable. Also returns true
    /// by reference if the def is a load.
    bool isReMaterializable(const LiveInterval &li, const VNInfo *ValNo,
                            MachineInstr *MI,
                            SmallVectorImpl<LiveInterval*> &SpillIs,
                            bool &isLoad);

    /// tryFoldMemoryOperand - Attempts to fold either a spill / restore from
    /// slot / to reg or any rematerialized load into ith operand of specified
    /// MI. If it is successul, MI is updated with the newly created MI and
    /// returns true.
    bool tryFoldMemoryOperand(MachineInstr* &MI, VirtRegMap &vrm,
                              MachineInstr *DefMI, unsigned InstrIdx,
                              SmallVector<unsigned, 2> &Ops,
                              bool isSS, int Slot, unsigned Reg);

    /// canFoldMemoryOperand - Return true if the specified load / store
    /// folding is possible.
    bool canFoldMemoryOperand(MachineInstr *MI,
                              SmallVector<unsigned, 2> &Ops,
                              bool ReMatLoadSS) const;

    /// anyKillInMBBAfterIdx - Returns true if there is a kill of the specified
    /// VNInfo that's after the specified index but is within the basic block.
    bool anyKillInMBBAfterIdx(const LiveInterval &li, const VNInfo *VNI,
                              MachineBasicBlock *MBB, unsigned Idx) const;

    /// hasAllocatableSuperReg - Return true if the specified physical register
    /// has any super register that's allocatable.
    bool hasAllocatableSuperReg(unsigned Reg) const;

    /// SRInfo - Spill / restore info.
    struct SRInfo {
      int index;
      unsigned vreg;
      bool canFold;
      SRInfo(int i, unsigned vr, bool f) : index(i), vreg(vr), canFold(f) {};
    };

    bool alsoFoldARestore(int Id, int index, unsigned vr,
                          BitVector &RestoreMBBs,
                          DenseMap<unsigned,std::vector<SRInfo> >&RestoreIdxes);
    void eraseRestoreInfo(int Id, int index, unsigned vr,
                          BitVector &RestoreMBBs,
                          DenseMap<unsigned,std::vector<SRInfo> >&RestoreIdxes);

    /// handleSpilledImpDefs - Remove IMPLICIT_DEF instructions which are being
    /// spilled and create empty intervals for their uses.
    void handleSpilledImpDefs(const LiveInterval &li, VirtRegMap &vrm,
                              const TargetRegisterClass* rc,
                              std::vector<LiveInterval*> &NewLIs);

    /// rewriteImplicitOps - Rewrite implicit use operands of MI (i.e. uses of
    /// interval on to-be re-materialized operands of MI) with new register.
    void rewriteImplicitOps(const LiveInterval &li,
                           MachineInstr *MI, unsigned NewVReg, VirtRegMap &vrm);

    /// rewriteInstructionForSpills, rewriteInstructionsForSpills - Helper
    /// functions for addIntervalsForSpills to rewrite uses / defs for the given
    /// live range.
    bool rewriteInstructionForSpills(const LiveInterval &li, const VNInfo *VNI,
        bool TrySplit, unsigned index, unsigned end, MachineInstr *MI,
        MachineInstr *OrigDefMI, MachineInstr *DefMI, unsigned Slot, int LdSlot,
        bool isLoad, bool isLoadSS, bool DefIsReMat, bool CanDelete,
        VirtRegMap &vrm, const TargetRegisterClass* rc,
        SmallVector<int, 4> &ReMatIds, const MachineLoopInfo *loopInfo,
        unsigned &NewVReg, unsigned ImpUse, bool &HasDef, bool &HasUse,
        DenseMap<unsigned,unsigned> &MBBVRegsMap,
        std::vector<LiveInterval*> &NewLIs);
    void rewriteInstructionsForSpills(const LiveInterval &li, bool TrySplit,
        LiveInterval::Ranges::const_iterator &I,
        MachineInstr *OrigDefMI, MachineInstr *DefMI, unsigned Slot, int LdSlot,
        bool isLoad, bool isLoadSS, bool DefIsReMat, bool CanDelete,
        VirtRegMap &vrm, const TargetRegisterClass* rc,
        SmallVector<int, 4> &ReMatIds, const MachineLoopInfo *loopInfo,
        BitVector &SpillMBBs,
        DenseMap<unsigned,std::vector<SRInfo> > &SpillIdxes,
        BitVector &RestoreMBBs,
        DenseMap<unsigned,std::vector<SRInfo> > &RestoreIdxes,
        DenseMap<unsigned,unsigned> &MBBVRegsMap,
        std::vector<LiveInterval*> &NewLIs);

    static LiveInterval* createInterval(unsigned Reg);

    void printRegName(unsigned reg) const;
  };

} // End llvm namespace

#endif