llvm/lib/CodeGen/VirtRegMap.h - toolchain/llvm-project - Gitiles

 //===-- llvm/CodeGen/VirtRegMap.h - Virtual Register Map -*- 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 a virtual register map. This maps virtual registers to
 // physical registers and virtual registers to stack slots. It is created and
 // updated by a register allocator and then used by a machine code rewriter that
 // adds spill code and rewrites virtual into physical register references.
 //
 //===----------------------------------------------------------------------===//

 #ifndef LLVM_CODEGEN_VIRTREGMAP_H
 #define LLVM_CODEGEN_VIRTREGMAP_H

 #include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/ADT/BitVector.h"
 #include "llvm/ADT/IndexedMap.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/Support/Streams.h"
 #include <map>

 namespace llvm {
   class MachineInstr;
   class MachineFunction;
   class TargetInstrInfo;

   class VirtRegMap {
   public:
     enum {
       NO_PHYS_REG = 0,
       NO_STACK_SLOT = (1L << 30)-1,
       MAX_STACK_SLOT = (1L << 18)-1
     };

     enum ModRef { isRef = 1, isMod = 2, isModRef = 3 };
     typedef std::multimap<MachineInstr*,
                           std::pair<unsigned, ModRef> > MI2VirtMapTy;

   private:
     const TargetInstrInfo &TII;

     MachineFunction &MF;
     /// Virt2PhysMap - This is a virtual to physical register
     /// mapping. Each virtual register is required to have an entry in
     /// it; even spilled virtual registers (the register mapped to a
     /// spilled register is the temporary used to load it from the
     /// stack).
     IndexedMap<unsigned, VirtReg2IndexFunctor> Virt2PhysMap;

     /// Virt2StackSlotMap - This is virtual register to stack slot
     /// mapping. Each spilled virtual register has an entry in it
     /// which corresponds to the stack slot this register is spilled
     /// at.
     IndexedMap<int, VirtReg2IndexFunctor> Virt2StackSlotMap;

     /// Virt2ReMatIdMap - This is virtual register to rematerialization id
     /// mapping. Each spilled virtual register that should be remat'd has an
     /// entry in it which corresponds to the remat id.
     IndexedMap<int, VirtReg2IndexFunctor> Virt2ReMatIdMap;

     /// Virt2SplitMap - This is virtual register to splitted virtual register
     /// mapping.
     IndexedMap<unsigned, VirtReg2IndexFunctor> Virt2SplitMap;

     /// Virt2SplitKillMap - This is splitted virtual register to its last use
     /// (kill) index mapping.
     IndexedMap<unsigned> Virt2SplitKillMap;

     /// ReMatMap - This is virtual register to re-materialized instruction
     /// mapping. Each virtual register whose definition is going to be
     /// re-materialized has an entry in it.
     IndexedMap<MachineInstr*, VirtReg2IndexFunctor> ReMatMap;

     /// MI2VirtMap - This is MachineInstr to virtual register
     /// mapping. In the case of memory spill code being folded into
     /// instructions, we need to know which virtual register was
     /// read/written by this instruction.
     MI2VirtMapTy MI2VirtMap;

     /// SpillPt2VirtMap - This records the virtual registers which should
     /// be spilled right after the MachineInstr due to live interval
     /// splitting.
     std::map<MachineInstr*, std::vector<std::pair<unsigned,bool> > >
     SpillPt2VirtMap;

     /// RestorePt2VirtMap - This records the virtual registers which should
     /// be restored right before the MachineInstr due to live interval
     /// splitting.
     std::map<MachineInstr*, std::vector<unsigned> > RestorePt2VirtMap;

     /// EmergencySpillMap - This records the physical registers that should
     /// be spilled / restored around the MachineInstr since the register
     /// allocator has run out of registers.
     std::map<MachineInstr*, std::vector<unsigned> > EmergencySpillMap;

     /// EmergencySpillSlots - This records emergency spill slots used to
     /// spill physical registers when the register allocator runs out of
     /// registers. Ideally only one stack slot is used per function per
     /// register class.
     std::map<const TargetRegisterClass*, int> EmergencySpillSlots;

     /// ReMatId - Instead of assigning a stack slot to a to be rematerialized
     /// virtual register, an unique id is being assigned. This keeps track of
     /// the highest id used so far. Note, this starts at (1<<18) to avoid
     /// conflicts with stack slot numbers.
     int ReMatId;

     /// LowSpillSlot, HighSpillSlot - Lowest and highest spill slot indexes.
     int LowSpillSlot, HighSpillSlot;

     /// SpillSlotToUsesMap - Records uses for each register spill slot.
     SmallVector<SmallPtrSet<MachineInstr*, 4>, 8> SpillSlotToUsesMap;

     /// ImplicitDefed - One bit for each virtual register. If set it indicates
     /// the register is implicitly defined.
     BitVector ImplicitDefed;

     VirtRegMap(const VirtRegMap&);     // DO NOT IMPLEMENT
     void operator=(const VirtRegMap&); // DO NOT IMPLEMENT

   public:
     explicit VirtRegMap(MachineFunction &mf);

     void grow();

     /// @brief returns true if the specified virtual register is
     /// mapped to a physical register
     bool hasPhys(unsigned virtReg) const {
       return getPhys(virtReg) != NO_PHYS_REG;
     }

     /// @brief returns the physical register mapped to the specified
     /// virtual register
     unsigned getPhys(unsigned virtReg) const {
       assert(TargetRegisterInfo::isVirtualRegister(virtReg));
       return Virt2PhysMap[virtReg];
     }

     /// @brief creates a mapping for the specified virtual register to
     /// the specified physical register
     void assignVirt2Phys(unsigned virtReg, unsigned physReg) {
       assert(TargetRegisterInfo::isVirtualRegister(virtReg) &&
              TargetRegisterInfo::isPhysicalRegister(physReg));
       assert(Virt2PhysMap[virtReg] == NO_PHYS_REG &&
              "attempt to assign physical register to already mapped "
              "virtual register");
       Virt2PhysMap[virtReg] = physReg;
     }

     /// @brief clears the specified virtual register's, physical
     /// register mapping
     void clearVirt(unsigned virtReg) {
       assert(TargetRegisterInfo::isVirtualRegister(virtReg));
       assert(Virt2PhysMap[virtReg] != NO_PHYS_REG &&
              "attempt to clear a not assigned virtual register");
       Virt2PhysMap[virtReg] = NO_PHYS_REG;
     }

     /// @brief clears all virtual to physical register mappings
     void clearAllVirt() {
       Virt2PhysMap.clear();
       grow();
     }

     /// @brief records virtReg is a split live interval from SReg.
     void setIsSplitFromReg(unsigned virtReg, unsigned SReg) {
       Virt2SplitMap[virtReg] = SReg;
     }

     /// @brief returns the live interval virtReg is split from.
     unsigned getPreSplitReg(unsigned virtReg) {
       return Virt2SplitMap[virtReg];
     }

     /// @brief returns true if the specified virtual register is not
     /// mapped to a stack slot or rematerialized.
     bool isAssignedReg(unsigned virtReg) const {
       if (getStackSlot(virtReg) == NO_STACK_SLOT &&
           getReMatId(virtReg) == NO_STACK_SLOT)
         return true;
       // Split register can be assigned a physical register as well as a
       // stack slot or remat id.
       return (Virt2SplitMap[virtReg] && Virt2PhysMap[virtReg] != NO_PHYS_REG);
     }

     /// @brief returns the stack slot mapped to the specified virtual
     /// register
     int getStackSlot(unsigned virtReg) const {
       assert(TargetRegisterInfo::isVirtualRegister(virtReg));
       return Virt2StackSlotMap[virtReg];
     }

     /// @brief returns the rematerialization id mapped to the specified virtual
     /// register
     int getReMatId(unsigned virtReg) const {
       assert(TargetRegisterInfo::isVirtualRegister(virtReg));
       return Virt2ReMatIdMap[virtReg];
     }

     /// @brief create a mapping for the specifed virtual register to
     /// the next available stack slot
     int assignVirt2StackSlot(unsigned virtReg);
     /// @brief create a mapping for the specified virtual register to
     /// the specified stack slot
     void assignVirt2StackSlot(unsigned virtReg, int frameIndex);

     /// @brief assign an unique re-materialization id to the specified
     /// virtual register.
     int assignVirtReMatId(unsigned virtReg);
     /// @brief assign an unique re-materialization id to the specified
     /// virtual register.
     void assignVirtReMatId(unsigned virtReg, int id);

     /// @brief returns true if the specified virtual register is being
     /// re-materialized.
     bool isReMaterialized(unsigned virtReg) const {
       return ReMatMap[virtReg] != NULL;
     }

     /// @brief returns the original machine instruction being re-issued
     /// to re-materialize the specified virtual register.
     MachineInstr *getReMaterializedMI(unsigned virtReg) const {
       return ReMatMap[virtReg];
     }

     /// @brief records the specified virtual register will be
     /// re-materialized and the original instruction which will be re-issed
     /// for this purpose.  If parameter all is true, then all uses of the
     /// registers are rematerialized and it's safe to delete the definition.
     void setVirtIsReMaterialized(unsigned virtReg, MachineInstr *def) {
       ReMatMap[virtReg] = def;
     }

     /// @brief record the last use (kill) of a split virtual register.
     void addKillPoint(unsigned virtReg, unsigned index) {
       Virt2SplitKillMap[virtReg] = index;
     }

     unsigned getKillPoint(unsigned virtReg) const {
       return Virt2SplitKillMap[virtReg];
     }

     /// @brief remove the last use (kill) of a split virtual register.
     void removeKillPoint(unsigned virtReg) {
       Virt2SplitKillMap[virtReg] = 0;
     }

     /// @brief returns true if the specified MachineInstr is a spill point.
     bool isSpillPt(MachineInstr *Pt) const {
       return SpillPt2VirtMap.find(Pt) != SpillPt2VirtMap.end();
     }

     /// @brief returns the virtual registers that should be spilled due to
     /// splitting right after the specified MachineInstr.
     std::vector<std::pair<unsigned,bool> > &getSpillPtSpills(MachineInstr *Pt) {
       return SpillPt2VirtMap[Pt];
     }

     /// @brief records the specified MachineInstr as a spill point for virtReg.
     void addSpillPoint(unsigned virtReg, bool isKill, MachineInstr *Pt) {
       if (SpillPt2VirtMap.find(Pt) != SpillPt2VirtMap.end())
         SpillPt2VirtMap[Pt].push_back(std::make_pair(virtReg, isKill));
       else {
         std::vector<std::pair<unsigned,bool> > Virts;
         Virts.push_back(std::make_pair(virtReg, isKill));
         SpillPt2VirtMap.insert(std::make_pair(Pt, Virts));
       }
     }

     /// @brief - transfer spill point information from one instruction to
     /// another.
     void transferSpillPts(MachineInstr *Old, MachineInstr *New) {
       std::map<MachineInstr*,std::vector<std::pair<unsigned,bool> > >::iterator
         I = SpillPt2VirtMap.find(Old);
       if (I == SpillPt2VirtMap.end())
         return;
       while (!I->second.empty()) {
         unsigned virtReg = I->second.back().first;
         bool isKill = I->second.back().second;
         I->second.pop_back();
         addSpillPoint(virtReg, isKill, New);
       }
       SpillPt2VirtMap.erase(I);
     }

     /// @brief returns true if the specified MachineInstr is a restore point.
     bool isRestorePt(MachineInstr *Pt) const {
       return RestorePt2VirtMap.find(Pt) != RestorePt2VirtMap.end();
     }

     /// @brief returns the virtual registers that should be restoreed due to
     /// splitting right after the specified MachineInstr.
     std::vector<unsigned> &getRestorePtRestores(MachineInstr *Pt) {
       return RestorePt2VirtMap[Pt];
     }

     /// @brief records the specified MachineInstr as a restore point for virtReg.
     void addRestorePoint(unsigned virtReg, MachineInstr *Pt) {
       if (RestorePt2VirtMap.find(Pt) != RestorePt2VirtMap.end())
         RestorePt2VirtMap[Pt].push_back(virtReg);
       else {
         std::vector<unsigned> Virts;
         Virts.push_back(virtReg);
         RestorePt2VirtMap.insert(std::make_pair(Pt, Virts));
       }
     }

     /// @brief - transfer restore point information from one instruction to
     /// another.
     void transferRestorePts(MachineInstr *Old, MachineInstr *New) {
       std::map<MachineInstr*,std::vector<unsigned> >::iterator I =
         RestorePt2VirtMap.find(Old);
       if (I == RestorePt2VirtMap.end())
         return;
       while (!I->second.empty()) {
         unsigned virtReg = I->second.back();
         I->second.pop_back();
         addRestorePoint(virtReg, New);
       }
       RestorePt2VirtMap.erase(I);
     }

     /// @brief records that the specified physical register must be spilled
     /// around the specified machine instr.
     void addEmergencySpill(unsigned PhysReg, MachineInstr *MI) {
       if (EmergencySpillMap.find(MI) != EmergencySpillMap.end())
         EmergencySpillMap[MI].push_back(PhysReg);
       else {
         std::vector<unsigned> PhysRegs;
         PhysRegs.push_back(PhysReg);
         EmergencySpillMap.insert(std::make_pair(MI, PhysRegs));
       }
     }

     /// @brief returns true if one or more physical registers must be spilled
     /// around the specified instruction.
     bool hasEmergencySpills(MachineInstr *MI) const {
       return EmergencySpillMap.find(MI) != EmergencySpillMap.end();
     }

     /// @brief returns the physical registers to be spilled and restored around
     /// the instruction.
     std::vector<unsigned> &getEmergencySpills(MachineInstr *MI) {
       return EmergencySpillMap[MI];
     }

     /// @brief - transfer emergency spill information from one instruction to
     /// another.
     void transferEmergencySpills(MachineInstr *Old, MachineInstr *New) {
       std::map<MachineInstr*,std::vector<unsigned> >::iterator I =
         EmergencySpillMap.find(Old);
       if (I == EmergencySpillMap.end())
         return;
       while (!I->second.empty()) {
         unsigned virtReg = I->second.back();
         I->second.pop_back();
         addEmergencySpill(virtReg, New);
       }
       EmergencySpillMap.erase(I);
     }

     /// @brief return or get a emergency spill slot for the register class.
     int getEmergencySpillSlot(const TargetRegisterClass *RC);

     /// @brief Return lowest spill slot index.
     int getLowSpillSlot() const {
       return LowSpillSlot;
     }

     /// @brief Return highest spill slot index.
     int getHighSpillSlot() const {
       return HighSpillSlot;
     }

     /// @brief Records a spill slot use.
     void addSpillSlotUse(int FrameIndex, MachineInstr *MI);

     /// @brief Returns true if spill slot has been used.
     bool isSpillSlotUsed(int FrameIndex) const {
       assert(FrameIndex >= 0 && "Spill slot index should not be negative!");
       return !SpillSlotToUsesMap[FrameIndex-LowSpillSlot].empty();
     }

     /// @brief Mark the specified register as being implicitly defined.
     void setIsImplicitlyDefined(unsigned VirtReg) {
       ImplicitDefed.set(VirtReg-TargetRegisterInfo::FirstVirtualRegister);
     }

     /// @brief Returns true if the virtual register is implicitly defined.
     bool isImplicitlyDefined(unsigned VirtReg) const {
       return ImplicitDefed[VirtReg-TargetRegisterInfo::FirstVirtualRegister];
     }

     /// @brief Updates information about the specified virtual register's value
     /// folded into newMI machine instruction.
     void virtFolded(unsigned VirtReg, MachineInstr *OldMI, MachineInstr *NewMI,
                     ModRef MRInfo);

     /// @brief Updates information about the specified virtual register's value
     /// folded into the specified machine instruction.
     void virtFolded(unsigned VirtReg, MachineInstr *MI, ModRef MRInfo);

     /// @brief returns the virtual registers' values folded in memory
     /// operands of this instruction
     std::pair<MI2VirtMapTy::const_iterator, MI2VirtMapTy::const_iterator>
     getFoldedVirts(MachineInstr* MI) const {
       return MI2VirtMap.equal_range(MI);
     }

     /// RemoveMachineInstrFromMaps - MI is being erased, remove it from the
     /// the folded instruction map and spill point map.
     void RemoveMachineInstrFromMaps(MachineInstr *MI);

     void print(std::ostream &OS) const;
     void print(std::ostream *OS) const { if (OS) print(*OS); }
     void dump() const;
   };

   inline std::ostream *operator<<(std::ostream *OS, const VirtRegMap &VRM) {
     VRM.print(OS);
     return OS;
   }
   inline std::ostream &operator<<(std::ostream &OS, const VirtRegMap &VRM) {
     VRM.print(OS);
     return OS;
   }

   /// Spiller interface: Implementations of this interface assign spilled
   /// virtual registers to stack slots, rewriting the code.
   struct Spiller {
     virtual ~Spiller();
     virtual bool runOnMachineFunction(MachineFunction &MF,
                                       VirtRegMap &VRM) = 0;
   };

   /// createSpiller - Create an return a spiller object, as specified on the
   /// command line.
   Spiller* createSpiller();

 } // End llvm namespace

 #endif
	//===-- llvm/CodeGen/VirtRegMap.h - Virtual Register Map -- 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 a virtual register map. This maps virtual registers to
	// physical registers and virtual registers to stack slots. It is created and
	// updated by a register allocator and then used by a machine code rewriter that
	// adds spill code and rewrites virtual into physical register references.
	//
	//===----------------------------------------------------------------------===//

	#ifndef LLVM_CODEGEN_VIRTREGMAP_H
	#define LLVM_CODEGEN_VIRTREGMAP_H

	#include "llvm/Target/TargetRegisterInfo.h"
	#include "llvm/ADT/BitVector.h"
	#include "llvm/ADT/IndexedMap.h"
	#include "llvm/ADT/SmallPtrSet.h"
	#include "llvm/Support/Streams.h"
	#include <map>

	namespace llvm {
	class MachineInstr;
	class MachineFunction;
	class TargetInstrInfo;

	class VirtRegMap {
	public:
	enum {
	NO_PHYS_REG = 0,
	NO_STACK_SLOT = (1L << 30)-1,
	MAX_STACK_SLOT = (1L << 18)-1
	};

	enum ModRef { isRef = 1, isMod = 2, isModRef = 3 };
	typedef std::multimap<MachineInstr*,
	std::pair<unsigned, ModRef> > MI2VirtMapTy;

	private:
	const TargetInstrInfo &TII;

	MachineFunction &MF;
	/// Virt2PhysMap - This is a virtual to physical register
	/// mapping. Each virtual register is required to have an entry in
	/// it; even spilled virtual registers (the register mapped to a
	/// spilled register is the temporary used to load it from the
	/// stack).
	IndexedMap<unsigned, VirtReg2IndexFunctor> Virt2PhysMap;

	/// Virt2StackSlotMap - This is virtual register to stack slot
	/// mapping. Each spilled virtual register has an entry in it
	/// which corresponds to the stack slot this register is spilled
	/// at.
	IndexedMap<int, VirtReg2IndexFunctor> Virt2StackSlotMap;

	/// Virt2ReMatIdMap - This is virtual register to rematerialization id
	/// mapping. Each spilled virtual register that should be remat'd has an
	/// entry in it which corresponds to the remat id.
	IndexedMap<int, VirtReg2IndexFunctor> Virt2ReMatIdMap;

	/// Virt2SplitMap - This is virtual register to splitted virtual register
	/// mapping.
	IndexedMap<unsigned, VirtReg2IndexFunctor> Virt2SplitMap;

	/// Virt2SplitKillMap - This is splitted virtual register to its last use
	/// (kill) index mapping.
	IndexedMap<unsigned> Virt2SplitKillMap;

	/// ReMatMap - This is virtual register to re-materialized instruction
	/// mapping. Each virtual register whose definition is going to be
	/// re-materialized has an entry in it.
	IndexedMap<MachineInstr*, VirtReg2IndexFunctor> ReMatMap;

	/// MI2VirtMap - This is MachineInstr to virtual register
	/// mapping. In the case of memory spill code being folded into
	/// instructions, we need to know which virtual register was
	/// read/written by this instruction.
	MI2VirtMapTy MI2VirtMap;

	/// SpillPt2VirtMap - This records the virtual registers which should
	/// be spilled right after the MachineInstr due to live interval
	/// splitting.
	std::map<MachineInstr*, std::vector<std::pair<unsigned,bool> > >
	SpillPt2VirtMap;

	/// RestorePt2VirtMap - This records the virtual registers which should
	/// be restored right before the MachineInstr due to live interval
	/// splitting.
	std::map<MachineInstr*, std::vector<unsigned> > RestorePt2VirtMap;

	/// EmergencySpillMap - This records the physical registers that should
	/// be spilled / restored around the MachineInstr since the register
	/// allocator has run out of registers.
	std::map<MachineInstr*, std::vector<unsigned> > EmergencySpillMap;

	/// EmergencySpillSlots - This records emergency spill slots used to
	/// spill physical registers when the register allocator runs out of
	/// registers. Ideally only one stack slot is used per function per
	/// register class.
	std::map<const TargetRegisterClass*, int> EmergencySpillSlots;

	/// ReMatId - Instead of assigning a stack slot to a to be rematerialized
	/// virtual register, an unique id is being assigned. This keeps track of
	/// the highest id used so far. Note, this starts at (1<<18) to avoid
	/// conflicts with stack slot numbers.
	int ReMatId;

	/// LowSpillSlot, HighSpillSlot - Lowest and highest spill slot indexes.
	int LowSpillSlot, HighSpillSlot;

	/// SpillSlotToUsesMap - Records uses for each register spill slot.
	SmallVector<SmallPtrSet<MachineInstr*, 4>, 8> SpillSlotToUsesMap;

	/// ImplicitDefed - One bit for each virtual register. If set it indicates
	/// the register is implicitly defined.
	BitVector ImplicitDefed;

	VirtRegMap(const VirtRegMap&); // DO NOT IMPLEMENT
	void operator=(const VirtRegMap&); // DO NOT IMPLEMENT

	public:
	explicit VirtRegMap(MachineFunction &mf);

	void grow();

	/// @brief returns true if the specified virtual register is
	/// mapped to a physical register
	bool hasPhys(unsigned virtReg) const {
	return getPhys(virtReg) != NO_PHYS_REG;
	}

	/// @brief returns the physical register mapped to the specified
	/// virtual register
	unsigned getPhys(unsigned virtReg) const {
	assert(TargetRegisterInfo::isVirtualRegister(virtReg));
	return Virt2PhysMap[virtReg];
	}

	/// @brief creates a mapping for the specified virtual register to
	/// the specified physical register
	void assignVirt2Phys(unsigned virtReg, unsigned physReg) {
	assert(TargetRegisterInfo::isVirtualRegister(virtReg) &&
	TargetRegisterInfo::isPhysicalRegister(physReg));
	assert(Virt2PhysMap[virtReg] == NO_PHYS_REG &&
	"attempt to assign physical register to already mapped "
	"virtual register");
	Virt2PhysMap[virtReg] = physReg;
	}

	/// @brief clears the specified virtual register's, physical
	/// register mapping
	void clearVirt(unsigned virtReg) {
	assert(TargetRegisterInfo::isVirtualRegister(virtReg));
	assert(Virt2PhysMap[virtReg] != NO_PHYS_REG &&
	"attempt to clear a not assigned virtual register");
	Virt2PhysMap[virtReg] = NO_PHYS_REG;
	}

	/// @brief clears all virtual to physical register mappings
	void clearAllVirt() {
	Virt2PhysMap.clear();
	grow();
	}

	/// @brief records virtReg is a split live interval from SReg.
	void setIsSplitFromReg(unsigned virtReg, unsigned SReg) {
	Virt2SplitMap[virtReg] = SReg;
	}

	/// @brief returns the live interval virtReg is split from.
	unsigned getPreSplitReg(unsigned virtReg) {
	return Virt2SplitMap[virtReg];
	}

	/// @brief returns true if the specified virtual register is not
	/// mapped to a stack slot or rematerialized.
	bool isAssignedReg(unsigned virtReg) const {
	if (getStackSlot(virtReg) == NO_STACK_SLOT &&
	getReMatId(virtReg) == NO_STACK_SLOT)
	return true;
	// Split register can be assigned a physical register as well as a
	// stack slot or remat id.
	return (Virt2SplitMap[virtReg] && Virt2PhysMap[virtReg] != NO_PHYS_REG);
	}

	/// @brief returns the stack slot mapped to the specified virtual
	/// register
	int getStackSlot(unsigned virtReg) const {
	assert(TargetRegisterInfo::isVirtualRegister(virtReg));
	return Virt2StackSlotMap[virtReg];
	}

	/// @brief returns the rematerialization id mapped to the specified virtual
	/// register
	int getReMatId(unsigned virtReg) const {
	assert(TargetRegisterInfo::isVirtualRegister(virtReg));
	return Virt2ReMatIdMap[virtReg];
	}

	/// @brief create a mapping for the specifed virtual register to
	/// the next available stack slot
	int assignVirt2StackSlot(unsigned virtReg);
	/// @brief create a mapping for the specified virtual register to
	/// the specified stack slot
	void assignVirt2StackSlot(unsigned virtReg, int frameIndex);

	/// @brief assign an unique re-materialization id to the specified
	/// virtual register.
	int assignVirtReMatId(unsigned virtReg);
	/// @brief assign an unique re-materialization id to the specified
	/// virtual register.
	void assignVirtReMatId(unsigned virtReg, int id);

	/// @brief returns true if the specified virtual register is being
	/// re-materialized.
	bool isReMaterialized(unsigned virtReg) const {
	return ReMatMap[virtReg] != NULL;
	}

	/// @brief returns the original machine instruction being re-issued
	/// to re-materialize the specified virtual register.
	MachineInstr *getReMaterializedMI(unsigned virtReg) const {
	return ReMatMap[virtReg];
	}

	/// @brief records the specified virtual register will be
	/// re-materialized and the original instruction which will be re-issed
	/// for this purpose. If parameter all is true, then all uses of the
	/// registers are rematerialized and it's safe to delete the definition.
	void setVirtIsReMaterialized(unsigned virtReg, MachineInstr *def) {
	ReMatMap[virtReg] = def;
	}

	/// @brief record the last use (kill) of a split virtual register.
	void addKillPoint(unsigned virtReg, unsigned index) {
	Virt2SplitKillMap[virtReg] = index;
	}

	unsigned getKillPoint(unsigned virtReg) const {
	return Virt2SplitKillMap[virtReg];
	}

	/// @brief remove the last use (kill) of a split virtual register.
	void removeKillPoint(unsigned virtReg) {
	Virt2SplitKillMap[virtReg] = 0;
	}

	/// @brief returns true if the specified MachineInstr is a spill point.
	bool isSpillPt(MachineInstr *Pt) const {
	return SpillPt2VirtMap.find(Pt) != SpillPt2VirtMap.end();
	}

	/// @brief returns the virtual registers that should be spilled due to
	/// splitting right after the specified MachineInstr.
	std::vector<std::pair<unsigned,bool> > &getSpillPtSpills(MachineInstr *Pt) {
	return SpillPt2VirtMap[Pt];
	}

	/// @brief records the specified MachineInstr as a spill point for virtReg.
	void addSpillPoint(unsigned virtReg, bool isKill, MachineInstr *Pt) {
	if (SpillPt2VirtMap.find(Pt) != SpillPt2VirtMap.end())
	SpillPt2VirtMap[Pt].push_back(std::make_pair(virtReg, isKill));
	else {
	std::vector<std::pair<unsigned,bool> > Virts;
	Virts.push_back(std::make_pair(virtReg, isKill));
	SpillPt2VirtMap.insert(std::make_pair(Pt, Virts));
	}
	}

	/// @brief - transfer spill point information from one instruction to
	/// another.
	void transferSpillPts(MachineInstr Old, MachineInstr New) {
	std::map<MachineInstr*,std::vector<std::pair<unsigned,bool> > >::iterator
	I = SpillPt2VirtMap.find(Old);
	if (I == SpillPt2VirtMap.end())
	return;
	while (!I->second.empty()) {
	unsigned virtReg = I->second.back().first;
	bool isKill = I->second.back().second;
	I->second.pop_back();
	addSpillPoint(virtReg, isKill, New);
	}
	SpillPt2VirtMap.erase(I);
	}

	/// @brief returns true if the specified MachineInstr is a restore point.
	bool isRestorePt(MachineInstr *Pt) const {
	return RestorePt2VirtMap.find(Pt) != RestorePt2VirtMap.end();
	}

	/// @brief returns the virtual registers that should be restoreed due to
	/// splitting right after the specified MachineInstr.
	std::vector<unsigned> &getRestorePtRestores(MachineInstr *Pt) {
	return RestorePt2VirtMap[Pt];
	}

	/// @brief records the specified MachineInstr as a restore point for virtReg.
	void addRestorePoint(unsigned virtReg, MachineInstr *Pt) {
	if (RestorePt2VirtMap.find(Pt) != RestorePt2VirtMap.end())
	RestorePt2VirtMap[Pt].push_back(virtReg);
	else {
	std::vector<unsigned> Virts;
	Virts.push_back(virtReg);
	RestorePt2VirtMap.insert(std::make_pair(Pt, Virts));
	}
	}

	/// @brief - transfer restore point information from one instruction to
	/// another.
	void transferRestorePts(MachineInstr Old, MachineInstr New) {
	std::map<MachineInstr*,std::vector<unsigned> >::iterator I =
	RestorePt2VirtMap.find(Old);
	if (I == RestorePt2VirtMap.end())
	return;
	while (!I->second.empty()) {
	unsigned virtReg = I->second.back();
	I->second.pop_back();
	addRestorePoint(virtReg, New);
	}
	RestorePt2VirtMap.erase(I);
	}

	/// @brief records that the specified physical register must be spilled
	/// around the specified machine instr.
	void addEmergencySpill(unsigned PhysReg, MachineInstr *MI) {
	if (EmergencySpillMap.find(MI) != EmergencySpillMap.end())
	EmergencySpillMap[MI].push_back(PhysReg);
	else {
	std::vector<unsigned> PhysRegs;
	PhysRegs.push_back(PhysReg);
	EmergencySpillMap.insert(std::make_pair(MI, PhysRegs));
	}
	}

	/// @brief returns true if one or more physical registers must be spilled
	/// around the specified instruction.
	bool hasEmergencySpills(MachineInstr *MI) const {
	return EmergencySpillMap.find(MI) != EmergencySpillMap.end();
	}

	/// @brief returns the physical registers to be spilled and restored around
	/// the instruction.
	std::vector<unsigned> &getEmergencySpills(MachineInstr *MI) {
	return EmergencySpillMap[MI];
	}

	/// @brief - transfer emergency spill information from one instruction to
	/// another.
	void transferEmergencySpills(MachineInstr Old, MachineInstr New) {
	std::map<MachineInstr*,std::vector<unsigned> >::iterator I =
	EmergencySpillMap.find(Old);
	if (I == EmergencySpillMap.end())
	return;
	while (!I->second.empty()) {
	unsigned virtReg = I->second.back();
	I->second.pop_back();
	addEmergencySpill(virtReg, New);
	}
	EmergencySpillMap.erase(I);
	}

	/// @brief return or get a emergency spill slot for the register class.
	int getEmergencySpillSlot(const TargetRegisterClass *RC);

	/// @brief Return lowest spill slot index.
	int getLowSpillSlot() const {
	return LowSpillSlot;
	}

	/// @brief Return highest spill slot index.
	int getHighSpillSlot() const {
	return HighSpillSlot;
	}

	/// @brief Records a spill slot use.
	void addSpillSlotUse(int FrameIndex, MachineInstr *MI);

	/// @brief Returns true if spill slot has been used.
	bool isSpillSlotUsed(int FrameIndex) const {
	assert(FrameIndex >= 0 && "Spill slot index should not be negative!");
	return !SpillSlotToUsesMap[FrameIndex-LowSpillSlot].empty();
	}

	/// @brief Mark the specified register as being implicitly defined.
	void setIsImplicitlyDefined(unsigned VirtReg) {
	ImplicitDefed.set(VirtReg-TargetRegisterInfo::FirstVirtualRegister);
	}

	/// @brief Returns true if the virtual register is implicitly defined.
	bool isImplicitlyDefined(unsigned VirtReg) const {
	return ImplicitDefed[VirtReg-TargetRegisterInfo::FirstVirtualRegister];
	}

	/// @brief Updates information about the specified virtual register's value
	/// folded into newMI machine instruction.
	void virtFolded(unsigned VirtReg, MachineInstr OldMI, MachineInstr NewMI,
	ModRef MRInfo);

	/// @brief Updates information about the specified virtual register's value
	/// folded into the specified machine instruction.
	void virtFolded(unsigned VirtReg, MachineInstr *MI, ModRef MRInfo);

	/// @brief returns the virtual registers' values folded in memory
	/// operands of this instruction
	std::pair<MI2VirtMapTy::const_iterator, MI2VirtMapTy::const_iterator>
	getFoldedVirts(MachineInstr* MI) const {
	return MI2VirtMap.equal_range(MI);
	}

	/// RemoveMachineInstrFromMaps - MI is being erased, remove it from the
	/// the folded instruction map and spill point map.
	void RemoveMachineInstrFromMaps(MachineInstr *MI);

	void print(std::ostream &OS) const;
	void print(std::ostream OS) const { if (OS) print(OS); }
	void dump() const;
	};

	inline std::ostream operator<<(std::ostream OS, const VirtRegMap &VRM) {
	VRM.print(OS);
	return OS;
	}
	inline std::ostream &operator<<(std::ostream &OS, const VirtRegMap &VRM) {
	VRM.print(OS);
	return OS;
	}

	/// Spiller interface: Implementations of this interface assign spilled
	/// virtual registers to stack slots, rewriting the code.
	struct Spiller {
	virtual ~Spiller();
	virtual bool runOnMachineFunction(MachineFunction &MF,
	VirtRegMap &VRM) = 0;
	};

	/// createSpiller - Create an return a spiller object, as specified on the
	/// command line.
	Spiller* createSpiller();

	} // End llvm namespace

	#endif