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//===- llvm/CodeGen/MachineRegisterInfo.h -----------------------*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

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

//

// This file defines the MachineRegisterInfo class.

//

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

#ifndef LLVM_CODEGEN_MACHINEREGISTERINFO_H

#define LLVM_CODEGEN_MACHINEREGISTERINFO_H

#include "llvm/ADT/ArrayRef.h"

#include "llvm/ADT/BitVector.h"

#include "llvm/ADT/IndexedMap.h"

#include "llvm/ADT/PointerUnion.h"

#include "llvm/ADT/SmallPtrSet.h"

#include "llvm/ADT/SmallVector.h"

#include "llvm/ADT/StringSet.h"

#include "llvm/ADT/iterator_range.h"

#include "llvm/CodeGen/MachineBasicBlock.h"

#include "llvm/CodeGen/MachineFunction.h"

#include "llvm/CodeGen/MachineInstrBundle.h"

#include "llvm/CodeGen/MachineOperand.h"

#include "llvm/CodeGen/RegisterBank.h"

#include "llvm/CodeGen/TargetRegisterInfo.h"

#include "llvm/CodeGen/TargetSubtargetInfo.h"

#include "llvm/MC/LaneBitmask.h"

#include <cassert>

#include <cstddef>

#include <cstdint>

#include <iterator>

#include <memory>

#include <utility>

#include <vector>

namespace llvm {

class PSetIterator;

/// Convenient type to represent either a register class or a register bank.

using RegClassOrRegBank =

    PointerUnion<const TargetRegisterClass *, const RegisterBank *>;

/// MachineRegisterInfo - Keep track of information for virtual and physical

/// registers, including vreg register classes, use/def chains for registers,

/// etc.

class MachineRegisterInfo {

public:

  class Delegate {

    virtual void anchor();

  public:

    virtual ~Delegate() = default;

    virtual void MRI_NoteNewVirtualRegister(Register Reg) = 0;

    virtual void MRI_NotecloneVirtualRegister(Register NewReg,

                                              Register SrcReg) {

      MRI_NoteNewVirtualRegister(NewReg);

    }

  };

private:

  MachineFunction *MF;

  SmallPtrSet<Delegate *, 1> TheDelegates;

  /// True if subregister liveness is tracked.

  const bool TracksSubRegLiveness;

  /// VRegInfo - Information we keep for each virtual register.

  ///

  /// Each element in this list contains the register class of the vreg and the

  /// start of the use/def list for the register.

  IndexedMap<std::pair<RegClassOrRegBank, MachineOperand *>,

             VirtReg2IndexFunctor>

      VRegInfo;

  /// Map for recovering vreg name from vreg number.

  /// This map is used by the MIR Printer.

  IndexedMap<std::string, VirtReg2IndexFunctor> VReg2Name;

  /// StringSet that is used to unique vreg names.

  StringSet<> VRegNames;

  /// The flag is true upon \p UpdatedCSRs initialization

  /// and false otherwise.

  bool IsUpdatedCSRsInitialized = false;

  /// Contains the updated callee saved register list.

  /// As opposed to the static list defined in register info,

  /// all registers that were disabled are removed from the list.

  SmallVector<MCPhysReg, 16> UpdatedCSRs;

  /// RegAllocHints - This vector records register allocation hints for

  /// virtual registers. For each virtual register, it keeps a pair of hint

  /// type and hints vector making up the allocation hints. Only the first

  /// hint may be target specific, and in that case this is reflected by the

  /// first member of the pair being non-zero. If the hinted register is

  /// virtual, it means the allocator should prefer the physical register

  /// allocated to it if any.

  IndexedMap<std::pair<Register, SmallVector<Register, 4>>,

             VirtReg2IndexFunctor> RegAllocHints;

  /// PhysRegUseDefLists - This is an array of the head of the use/def list for

  /// physical registers.

  std::unique_ptr<MachineOperand *[]> PhysRegUseDefLists;

  /// getRegUseDefListHead - Return the head pointer for the register use/def

  /// list for the specified virtual or physical register.

  MachineOperand *&getRegUseDefListHead(Register RegNo) {

    if (RegNo.isVirtual())

      return VRegInfo[RegNo.id()].second;

    return PhysRegUseDefLists[RegNo.id()];

  }

  MachineOperand *getRegUseDefListHead(Register RegNo) const {

    if (RegNo.isVirtual())

      return VRegInfo[RegNo.id()].second;

    return PhysRegUseDefLists[RegNo.id()];

  }

  /// Get the next element in the use-def chain.

  static MachineOperand *getNextOperandForReg(const MachineOperand *MO) {

    assert(MO && MO->isReg() && "This is not a register operand!");

    return MO->Contents.Reg.Next;

  }

  /// UsedPhysRegMask - Additional used physregs including aliases.

  /// This bit vector represents all the registers clobbered by function calls.

  BitVector UsedPhysRegMask;

  /// ReservedRegs - This is a bit vector of reserved registers.  The target

  /// may change its mind about which registers should be reserved.  This

  /// vector is the frozen set of reserved registers when register allocation

  /// started.

  BitVector ReservedRegs;

  using VRegToTypeMap = IndexedMap<LLT, VirtReg2IndexFunctor>;

  /// Map generic virtual registers to their low-level type.

  VRegToTypeMap VRegToType;

  /// Keep track of the physical registers that are live in to the function.

  /// Live in values are typically arguments in registers.  LiveIn values are

  /// allowed to have virtual registers associated with them, stored in the

  /// second element.

  std::vector<std::pair<MCRegister, Register>> LiveIns;

public:

  explicit MachineRegisterInfo(MachineFunction *MF);

  MachineRegisterInfo(const MachineRegisterInfo &) = delete;

  MachineRegisterInfo &operator=(const MachineRegisterInfo &) = delete;

  const TargetRegisterInfo *getTargetRegisterInfo() const {

    return MF->getSubtarget().getRegisterInfo();

  }

  void resetDelegate(Delegate *delegate) {

    // Ensure another delegate does not take over unless the current

    // delegate first unattaches itself.

    assert(TheDelegates.count(delegate) &&

           "Only an existing delegate can perform reset!");

    TheDelegates.erase(delegate);

  }

  void addDelegate(Delegate *delegate) {

    assert(delegate && !TheDelegates.count(delegate) &&

           "Attempted to add null delegate, or to change it without "

           "first resetting it!");

    TheDelegates.insert(delegate);

  }

  void noteNewVirtualRegister(Register Reg) {

    for (auto *TheDelegate : TheDelegates)

      TheDelegate->MRI_NoteNewVirtualRegister(Reg);

  }

  void noteCloneVirtualRegister(Register NewReg, Register SrcReg) {

    for (auto *TheDelegate : TheDelegates)

      TheDelegate->MRI_NotecloneVirtualRegister(NewReg, SrcReg);

  }

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

  // Function State

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

  // isSSA - Returns true when the machine function is in SSA form. Early

  // passes require the machine function to be in SSA form where every virtual

  // register has a single defining instruction.

  //

  // The TwoAddressInstructionPass and PHIElimination passes take the machine

  // function out of SSA form when they introduce multiple defs per virtual

  // register.

  bool isSSA() const {

    return MF->getProperties().hasProperty(

        MachineFunctionProperties::Property::IsSSA);

  }

  // leaveSSA - Indicates that the machine function is no longer in SSA form.

  void leaveSSA() {

    MF->getProperties().reset(MachineFunctionProperties::Property::IsSSA);

  }

  /// tracksLiveness - Returns true when tracking register liveness accurately.

  /// (see MachineFUnctionProperties::Property description for details)

  bool tracksLiveness() const {

    return MF->getProperties().hasProperty(

        MachineFunctionProperties::Property::TracksLiveness);

  }

  /// invalidateLiveness - Indicates that register liveness is no longer being

  /// tracked accurately.

  ///

  /// This should be called by late passes that invalidate the liveness

  /// information.

  void invalidateLiveness() {

    MF->getProperties().reset(

        MachineFunctionProperties::Property::TracksLiveness);

  }

  /// Returns true if liveness for register class @p RC should be tracked at

  /// the subregister level.

  bool shouldTrackSubRegLiveness(const TargetRegisterClass &RC) const {

    return subRegLivenessEnabled() && RC.HasDisjunctSubRegs;

  }

  bool shouldTrackSubRegLiveness(Register VReg) const {

    assert(VReg.isVirtual() && "Must pass a VReg");

    return shouldTrackSubRegLiveness(*getRegClass(VReg));

  }

  bool subRegLivenessEnabled() const {

    return TracksSubRegLiveness;

  }

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

  // Register Info

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

  /// Returns true if the updated CSR list was initialized and false otherwise.

  bool isUpdatedCSRsInitialized() const { return IsUpdatedCSRsInitialized; }

  /// Returns true if a register can be used as an argument to a function.

  bool isArgumentRegister(const MachineFunction &MF, MCRegister Reg) const;

  /// Returns true if a register is a fixed register.

  bool isFixedRegister(const MachineFunction &MF, MCRegister Reg) const;

  /// Returns true if a register is a general purpose register.

  bool isGeneralPurposeRegister(const MachineFunction &MF,

                                MCRegister Reg) const;

  /// Disables the register from the list of CSRs.

  /// I.e. the register will not appear as part of the CSR mask.

  /// \see UpdatedCalleeSavedRegs.

  void disableCalleeSavedRegister(MCRegister Reg);

  /// Returns list of callee saved registers.

  /// The function returns the updated CSR list (after taking into account

  /// registers that are disabled from the CSR list).

  const MCPhysReg *getCalleeSavedRegs() const;

  /// Sets the updated Callee Saved Registers list.

  /// Notice that it will override ant previously disabled/saved CSRs.

  void setCalleeSavedRegs(ArrayRef<MCPhysReg> CSRs);

  // Strictly for use by MachineInstr.cpp.

  void addRegOperandToUseList(MachineOperand *MO);

  // Strictly for use by MachineInstr.cpp.

  void removeRegOperandFromUseList(MachineOperand *MO);

  // Strictly for use by MachineInstr.cpp.

  void moveOperands(MachineOperand *Dst, MachineOperand *Src, unsigned NumOps);

  /// Verify the sanity of the use list for Reg.

  void verifyUseList(Register Reg) const;

  /// Verify the use list of all registers.

  void verifyUseLists() const;

  /// reg_begin/reg_end - Provide iteration support to walk over all definitions

  /// and uses of a register within the MachineFunction that corresponds to this

  /// MachineRegisterInfo object.

  template<bool Uses, bool Defs, bool SkipDebug,

           bool ByOperand, bool ByInstr, bool ByBundle>

  class defusechain_iterator;

  template<bool Uses, bool Defs, bool SkipDebug,

           bool ByOperand, bool ByInstr, bool ByBundle>

  class defusechain_instr_iterator;

  // Make it a friend so it can access getNextOperandForReg().

  template<bool, bool, bool, bool, bool, bool>

    friend class defusechain_iterator;

  template<bool, bool, bool, bool, bool, bool>

    friend class defusechain_instr_iterator;

  /// reg_iterator/reg_begin/reg_end - Walk all defs and uses of the specified

  /// register.

  using reg_iterator =

      defusechain_iterator<true, true, false, true, false, false>;

  reg_iterator reg_begin(Register RegNo) const {

    return reg_iterator(getRegUseDefListHead(RegNo));

  }

  static reg_iterator reg_end() { return reg_iterator(nullptr); }

  inline iterator_range<reg_iterator> reg_operands(Register Reg) const {

    return make_range(reg_begin(Reg), reg_end());

  }

  /// reg_instr_iterator/reg_instr_begin/reg_instr_end - Walk all defs and uses

  /// of the specified register, stepping by MachineInstr.

  using reg_instr_iterator =

      defusechain_instr_iterator<true, true, false, false, true, false>;

  reg_instr_iterator reg_instr_begin(Register RegNo) const {

    return reg_instr_iterator(getRegUseDefListHead(RegNo));

  }

  static reg_instr_iterator reg_instr_end() {

    return reg_instr_iterator(nullptr);

  }

  inline iterator_range<reg_instr_iterator>

  reg_instructions(Register Reg) const {

    return make_range(reg_instr_begin(Reg), reg_instr_end());

  }

  /// reg_bundle_iterator/reg_bundle_begin/reg_bundle_end - Walk all defs and uses

  /// of the specified register, stepping by bundle.

  using reg_bundle_iterator =

      defusechain_instr_iterator<true, true, false, false, false, true>;

  reg_bundle_iterator reg_bundle_begin(Register RegNo) const {

    return reg_bundle_iterator(getRegUseDefListHead(RegNo));

  }

  static reg_bundle_iterator reg_bundle_end() {

    return reg_bundle_iterator(nullptr);

  }

  inline iterator_range<reg_bundle_iterator> reg_bundles(Register Reg) const {

    return make_range(reg_bundle_begin(Reg), reg_bundle_end());

  }

  /// reg_empty - Return true if there are no instructions using or defining the

  /// specified register (it may be live-in).

  bool reg_empty(Register RegNo) const { return reg_begin(RegNo) == reg_end(); }

  /// reg_nodbg_iterator/reg_nodbg_begin/reg_nodbg_end - Walk all defs and uses

  /// of the specified register, skipping those marked as Debug.

  using reg_nodbg_iterator =

      defusechain_iterator<true, true, true, true, false, false>;

  reg_nodbg_iterator reg_nodbg_begin(Register RegNo) const {

    return reg_nodbg_iterator(getRegUseDefListHead(RegNo));

  }

  static reg_nodbg_iterator reg_nodbg_end() {

    return reg_nodbg_iterator(nullptr);

  }

  inline iterator_range<reg_nodbg_iterator>

  reg_nodbg_operands(Register Reg) const {

    return make_range(reg_nodbg_begin(Reg), reg_nodbg_end());

  }

  /// reg_instr_nodbg_iterator/reg_instr_nodbg_begin/reg_instr_nodbg_end - Walk

  /// all defs and uses of the specified register, stepping by MachineInstr,

  /// skipping those marked as Debug.

  using reg_instr_nodbg_iterator =

      defusechain_instr_iterator<true, true, true, false, true, false>;

  reg_instr_nodbg_iterator reg_instr_nodbg_begin(Register RegNo) const {

    return reg_instr_nodbg_iterator(getRegUseDefListHead(RegNo));

  }

  static reg_instr_nodbg_iterator reg_instr_nodbg_end() {

    return reg_instr_nodbg_iterator(nullptr);

  }

  inline iterator_range<reg_instr_nodbg_iterator>

  reg_nodbg_instructions(Register Reg) const {

    return make_range(reg_instr_nodbg_begin(Reg), reg_instr_nodbg_end());

  }

  /// reg_bundle_nodbg_iterator/reg_bundle_nodbg_begin/reg_bundle_nodbg_end - Walk

  /// all defs and uses of the specified register, stepping by bundle,

  /// skipping those marked as Debug.

  using reg_bundle_nodbg_iterator =

      defusechain_instr_iterator<true, true, true, false, false, true>;

  reg_bundle_nodbg_iterator reg_bundle_nodbg_begin(Register RegNo) const {

    return reg_bundle_nodbg_iterator(getRegUseDefListHead(RegNo));

  }

  static reg_bundle_nodbg_iterator reg_bundle_nodbg_end() {

    return reg_bundle_nodbg_iterator(nullptr);

  }

  inline iterator_range<reg_bundle_nodbg_iterator>

  reg_nodbg_bundles(Register Reg) const {

    return make_range(reg_bundle_nodbg_begin(Reg), reg_bundle_nodbg_end());

  }

  /// reg_nodbg_empty - Return true if the only instructions using or defining

  /// Reg are Debug instructions.

  bool reg_nodbg_empty(Register RegNo) const {

    return reg_nodbg_begin(RegNo) == reg_nodbg_end();

  }

  /// def_iterator/def_begin/def_end - Walk all defs of the specified register.

  using def_iterator =

      defusechain_iterator<false, true, false, true, false, false>;

  def_iterator def_begin(Register RegNo) const {

    return def_iterator(getRegUseDefListHead(RegNo));

  }

  static def_iterator def_end() { return def_iterator(nullptr); }

  inline iterator_range<def_iterator> def_operands(Register Reg) const {

    return make_range(def_begin(Reg), def_end());

  }

  /// def_instr_iterator/def_instr_begin/def_instr_end - Walk all defs of the

  /// specified register, stepping by MachineInst.

  using def_instr_iterator =

      defusechain_instr_iterator<false, true, false, false, true, false>;

  def_instr_iterator def_instr_begin(Register RegNo) const {

    return def_instr_iterator(getRegUseDefListHead(RegNo));

  }

  static def_instr_iterator def_instr_end() {

    return def_instr_iterator(nullptr);

  }

  inline iterator_range<def_instr_iterator>

  def_instructions(Register Reg) const {

    return make_range(def_instr_begin(Reg), def_instr_end());

  }

  /// def_bundle_iterator/def_bundle_begin/def_bundle_end - Walk all defs of the

  /// specified register, stepping by bundle.

  using def_bundle_iterator =

      defusechain_instr_iterator<false, true, false, false, false, true>;

  def_bundle_iterator def_bundle_begin(Register RegNo) const {

    return def_bundle_iterator(getRegUseDefListHead(RegNo));

  }

  static def_bundle_iterator def_bundle_end() {

    return def_bundle_iterator(nullptr);

  }

  inline iterator_range<def_bundle_iterator> def_bundles(Register Reg) const {

    return make_range(def_bundle_begin(Reg), def_bundle_end());

  }

  /// def_empty - Return true if there are no instructions defining the

  /// specified register (it may be live-in).

  bool def_empty(Register RegNo) const { return def_begin(RegNo) == def_end(); }

  StringRef getVRegName(Register Reg) const {

    return VReg2Name.inBounds(Reg) ? StringRef(VReg2Name[Reg]) : "";

  }

  void insertVRegByName(StringRef Name, Register Reg) {

    assert((Name.empty() || VRegNames.find(Name) == VRegNames.end()) &&

           "Named VRegs Must be Unique.");

    if (!Name.empty()) {

      VRegNames.insert(Name);

      VReg2Name.grow(Reg);

      VReg2Name[Reg] = Name.str();

    }

  }

  /// Return true if there is exactly one operand defining the specified

  /// register.

  bool hasOneDef(Register RegNo) const {

    return hasSingleElement(def_operands(RegNo));

  }

  /// Returns the defining operand if there is exactly one operand defining the

  /// specified register, otherwise nullptr.

  MachineOperand *getOneDef(Register Reg) const {

    def_iterator DI = def_begin(Reg);

    if (DI == def_end()) // No defs.

      return nullptr;

    def_iterator OneDef = DI;

    if (++DI == def_end())

      return &*OneDef;

    return nullptr; // Multiple defs.

  }

  /// use_iterator/use_begin/use_end - Walk all uses of the specified register.

  using use_iterator =

      defusechain_iterator<true, false, false, true, false, false>;

  use_iterator use_begin(Register RegNo) const {

    return use_iterator(getRegUseDefListHead(RegNo));

  }

  static use_iterator use_end() { return use_iterator(nullptr); }

  inline iterator_range<use_iterator> use_operands(Register Reg) const {

    return make_range(use_begin(Reg), use_end());

  }

  /// use_instr_iterator/use_instr_begin/use_instr_end - Walk all uses of the

  /// specified register, stepping by MachineInstr.

  using use_instr_iterator =

      defusechain_instr_iterator<true, false, false, false, true, false>;

  use_instr_iterator use_instr_begin(Register RegNo) const {

    return use_instr_iterator(getRegUseDefListHead(RegNo));

  }

  static use_instr_iterator use_instr_end() {

    return use_instr_iterator(nullptr);

  }

  inline iterator_range<use_instr_iterator>

  use_instructions(Register Reg) const {

    return make_range(use_instr_begin(Reg), use_instr_end());

  }

  /// use_bundle_iterator/use_bundle_begin/use_bundle_end - Walk all uses of the

  /// specified register, stepping by bundle.

  using use_bundle_iterator =

      defusechain_instr_iterator<true, false, false, false, false, true>;

  use_bundle_iterator use_bundle_begin(Register RegNo) const {

    return use_bundle_iterator(getRegUseDefListHead(RegNo));

  }

  static use_bundle_iterator use_bundle_end() {

    return use_bundle_iterator(nullptr);

  }

  inline iterator_range<use_bundle_iterator> use_bundles(Register Reg) const {

    return make_range(use_bundle_begin(Reg), use_bundle_end());

  }

  /// use_empty - Return true if there are no instructions using the specified

  /// register.

  bool use_empty(Register RegNo) const { return use_begin(RegNo) == use_end(); }

  /// hasOneUse - Return true if there is exactly one instruction using the

  /// specified register.

  bool hasOneUse(Register RegNo) const {

    return hasSingleElement(use_operands(RegNo));

  }

  /// use_nodbg_iterator/use_nodbg_begin/use_nodbg_end - Walk all uses of the

  /// specified register, skipping those marked as Debug.

  using use_nodbg_iterator =

      defusechain_iterator<true, false, true, true, false, false>;

  use_nodbg_iterator use_nodbg_begin(Register RegNo) const {

    return use_nodbg_iterator(getRegUseDefListHead(RegNo));

  }

  static use_nodbg_iterator use_nodbg_end() {

    return use_nodbg_iterator(nullptr);

  }

  inline iterator_range<use_nodbg_iterator>

  use_nodbg_operands(Register Reg) const {

    return make_range(use_nodbg_begin(Reg), use_nodbg_end());

  }

  /// use_instr_nodbg_iterator/use_instr_nodbg_begin/use_instr_nodbg_end - Walk

  /// all uses of the specified register, stepping by MachineInstr, skipping

  /// those marked as Debug.

  using use_instr_nodbg_iterator =

      defusechain_instr_iterator<true, false, true, false, true, false>;

  use_instr_nodbg_iterator use_instr_nodbg_begin(Register RegNo) const {

    return use_instr_nodbg_iterator(getRegUseDefListHead(RegNo));

  }

  static use_instr_nodbg_iterator use_instr_nodbg_end() {

    return use_instr_nodbg_iterator(nullptr);

  }

  inline iterator_range<use_instr_nodbg_iterator>

  use_nodbg_instructions(Register Reg) const {

    return make_range(use_instr_nodbg_begin(Reg), use_instr_nodbg_end());

  }

  /// use_bundle_nodbg_iterator/use_bundle_nodbg_begin/use_bundle_nodbg_end - Walk

  /// all uses of the specified register, stepping by bundle, skipping

  /// those marked as Debug.

  using use_bundle_nodbg_iterator =

      defusechain_instr_iterator<true, false, true, false, false, true>;

  use_bundle_nodbg_iterator use_bundle_nodbg_begin(Register RegNo) const {

    return use_bundle_nodbg_iterator(getRegUseDefListHead(RegNo));

  }

  static use_bundle_nodbg_iterator use_bundle_nodbg_end() {

    return use_bundle_nodbg_iterator(nullptr);

  }

  inline iterator_range<use_bundle_nodbg_iterator>

  use_nodbg_bundles(Register Reg) const {

    return make_range(use_bundle_nodbg_begin(Reg), use_bundle_nodbg_end());

  }

  /// use_nodbg_empty - Return true if there are no non-Debug instructions

  /// using the specified register.

  bool use_nodbg_empty(Register RegNo) const {

    return use_nodbg_begin(RegNo) == use_nodbg_end();

  }

  /// hasOneNonDBGUse - Return true if there is exactly one non-Debug

  /// use of the specified register.

  bool hasOneNonDBGUse(Register RegNo) const;

  /// hasOneNonDBGUse - Return true if there is exactly one non-Debug

  /// instruction using the specified register. Said instruction may have

  /// multiple uses.

  bool hasOneNonDBGUser(Register RegNo) const;

  /// hasAtMostUses - Return true if the given register has at most \p MaxUsers

  /// non-debug user instructions.

  bool hasAtMostUserInstrs(Register Reg, unsigned MaxUsers) const;

  /// replaceRegWith - Replace all instances of FromReg with ToReg in the

  /// machine function.  This is like llvm-level X->replaceAllUsesWith(Y),

  /// except that it also changes any definitions of the register as well.

  ///

  /// Note that it is usually necessary to first constrain ToReg's register

  /// class and register bank to match the FromReg constraints using one of the

  /// methods:

  ///

  ///   constrainRegClass(ToReg, getRegClass(FromReg))

  ///   constrainRegAttrs(ToReg, FromReg)

  ///   RegisterBankInfo::constrainGenericRegister(ToReg,

  ///       *MRI.getRegClass(FromReg), MRI)

  ///

  /// These functions will return a falsy result if the virtual registers have

  /// incompatible constraints.

  ///

  /// Note that if ToReg is a physical register the function will replace and

  /// apply sub registers to ToReg in order to obtain a final/proper physical

  /// register.

  void replaceRegWith(Register FromReg, Register ToReg);

  /// getVRegDef - Return the machine instr that defines the specified virtual

  /// register or null if none is found.  This assumes that the code is in SSA

  /// form, so there should only be one definition.

  MachineInstr *getVRegDef(Register Reg) const;

  /// getUniqueVRegDef - Return the unique machine instr that defines the

  /// specified virtual register or null if none is found.  If there are

  /// multiple definitions or no definition, return null.

  MachineInstr *getUniqueVRegDef(Register Reg) const;

  /// clearKillFlags - Iterate over all the uses of the given register and

  /// clear the kill flag from the MachineOperand. This function is used by

  /// optimization passes which extend register lifetimes and need only

  /// preserve conservative kill flag information.

  void clearKillFlags(Register Reg) const;

  void dumpUses(Register RegNo) const;

  /// Returns true if PhysReg is unallocatable and constant throughout the

  /// function. Writing to a constant register has no effect.

  bool isConstantPhysReg(MCRegister PhysReg) const;

  /// Get an iterator over the pressure sets affected by the given physical or

  /// virtual register. If RegUnit is physical, it must be a register unit (from

  /// MCRegUnitIterator).

  PSetIterator getPressureSets(Register RegUnit) const;

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

  // Virtual Register Info

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

  /// Return the register class of the specified virtual register.

  /// This shouldn't be used directly unless \p Reg has a register class.

  /// \see getRegClassOrNull when this might happen.

  const TargetRegisterClass *getRegClass(Register Reg) const {

    assert(VRegInfo[Reg.id()].first.is<const TargetRegisterClass *>() &&

           "Register class not set, wrong accessor");

    return VRegInfo[Reg.id()].first.get<const TargetRegisterClass *>();

  }

  /// Return the register class of \p Reg, or null if Reg has not been assigned

  /// a register class yet.

  ///

  /// \note A null register class can only happen when these two

  /// conditions are met:

  /// 1. Generic virtual registers are created.

  /// 2. The machine function has not completely been through the

  ///    instruction selection process.

  /// None of this condition is possible without GlobalISel for now.

  /// In other words, if GlobalISel is not used or if the query happens after

  /// the select pass, using getRegClass is safe.

  const TargetRegisterClass *getRegClassOrNull(Register Reg) const {

    const RegClassOrRegBank &Val = VRegInfo[Reg].first;

    return Val.dyn_cast<const TargetRegisterClass *>();

  }

  /// Return the register bank of \p Reg, or null if Reg has not been assigned

  /// a register bank or has been assigned a register class.

  /// \note It is possible to get the register bank from the register class via

  /// RegisterBankInfo::getRegBankFromRegClass.

  const RegisterBank *getRegBankOrNull(Register Reg) const {

    const RegClassOrRegBank &Val = VRegInfo[Reg].first;

    return Val.dyn_cast<const RegisterBank *>();

  }

  /// Return the register bank or register class of \p Reg.

  /// \note Before the register bank gets assigned (i.e., before the

  /// RegBankSelect pass) \p Reg may not have either.

  const RegClassOrRegBank &getRegClassOrRegBank(Register Reg) const {

    return VRegInfo[Reg].first;

  }

  /// setRegClass - Set the register class of the specified virtual register.

  void setRegClass(Register Reg, const TargetRegisterClass *RC);

  /// Set the register bank to \p RegBank for \p Reg.

  void setRegBank(Register Reg, const RegisterBank &RegBank);

  void setRegClassOrRegBank(Register Reg,

                            const RegClassOrRegBank &RCOrRB){

    VRegInfo[Reg].first = RCOrRB;

  }

  /// constrainRegClass - Constrain the register class of the specified virtual

  /// register to be a common subclass of RC and the current register class,

  /// but only if the new class has at least MinNumRegs registers.  Return the

  /// new register class, or NULL if no such class exists.

  /// This should only be used when the constraint is known to be trivial, like

  /// GR32 -> GR32_NOSP. Beware of increasing register pressure.

  ///

  /// \note Assumes that the register has a register class assigned.

  /// Use RegisterBankInfo::constrainGenericRegister in GlobalISel's

  /// InstructionSelect pass and constrainRegAttrs in every other pass,

  /// including non-select passes of GlobalISel, instead.

  const TargetRegisterClass *constrainRegClass(Register Reg,

                                               const TargetRegisterClass *RC,

                                               unsigned MinNumRegs = 0);

  /// Constrain the register class or the register bank of the virtual register

  /// \p Reg (and low-level type) to be a common subclass or a common bank of

  /// both registers provided respectively (and a common low-level type). Do

  /// nothing if any of the attributes (classes, banks, or low-level types) of

  /// the registers are deemed incompatible, or if the resulting register will

  /// have a class smaller than before and of size less than \p MinNumRegs.

  /// Return true if such register attributes exist, false otherwise.

  ///

  /// \note Use this method instead of constrainRegClass and

  /// RegisterBankInfo::constrainGenericRegister everywhere but SelectionDAG

  /// ISel / FastISel and GlobalISel's InstructionSelect pass respectively.

  bool constrainRegAttrs(Register Reg, Register ConstrainingReg,

                         unsigned MinNumRegs = 0);

  /// recomputeRegClass - Try to find a legal super-class of Reg's register

  /// class that still satisfies the constraints from the instructions using

  /// Reg.  Returns true if Reg was upgraded.

  ///

  /// This method can be used after constraints have been removed from a

  /// virtual register, for example after removing instructions or splitting

  /// the live range.

  bool recomputeRegClass(Register Reg);

  /// createVirtualRegister - Create and return a new virtual register in the

  /// function with the specified register class.

  Register createVirtualRegister(const TargetRegisterClass *RegClass,

                                 StringRef Name = "");

  /// Create and return a new virtual register in the function with the same

  /// attributes as the given register.

  Register cloneVirtualRegister(Register VReg, StringRef Name = "");

  /// Get the low-level type of \p Reg or LLT{} if Reg is not a generic

  /// (target independent) virtual register.

  LLT getType(Register Reg) const {

    if (Reg.isVirtual() && VRegToType.inBounds(Reg))

      return VRegToType[Reg];

    return LLT{};

  }

  /// Set the low-level type of \p VReg to \p Ty.

  void setType(Register VReg, LLT Ty);

  /// Create and return a new generic virtual register with low-level

  /// type \p Ty.

  Register createGenericVirtualRegister(LLT Ty, StringRef Name = "");

  /// Remove all types associated to virtual registers (after instruction

  /// selection and constraining of all generic virtual registers).

  void clearVirtRegTypes();

  /// Creates a new virtual register that has no register class, register bank

  /// or size assigned yet. This is only allowed to be used

  /// temporarily while constructing machine instructions. Most operations are

  /// undefined on an incomplete register until one of setRegClass(),

  /// setRegBank() or setSize() has been called on it.

  Register createIncompleteVirtualRegister(StringRef Name = "");

  /// getNumVirtRegs - Return the number of virtual registers created.

  unsigned getNumVirtRegs() const { return VRegInfo.size(); }

  /// clearVirtRegs - Remove all virtual registers (after physreg assignment).

  void clearVirtRegs();

  /// setRegAllocationHint - Specify a register allocation hint for the

  /// specified virtual register. This is typically used by target, and in case

  /// of an earlier hint it will be overwritten.

  void setRegAllocationHint(Register VReg, unsigned Type, Register PrefReg) {

    assert(VReg.isVirtual());

    RegAllocHints[VReg].first  = Type;

    RegAllocHints[VReg].second.clear();

    RegAllocHints[VReg].second.push_back(PrefReg);

  }

  /// addRegAllocationHint - Add a register allocation hint to the hints

  /// vector for VReg.

  void addRegAllocationHint(Register VReg, Register PrefReg) {

    assert(VReg.isVirtual());

    RegAllocHints[VReg].second.push_back(PrefReg);

  }

  /// Specify the preferred (target independent) register allocation hint for

  /// the specified virtual register.

  void setSimpleHint(Register VReg, Register PrefReg) {

    setRegAllocationHint(VReg, /*Type=*/0, PrefReg);

  }

  void clearSimpleHint(Register VReg) {

    assert (!RegAllocHints[VReg].first &&

            "Expected to clear a non-target hint!");

    RegAllocHints[VReg].second.clear();

  }

  /// getRegAllocationHint - Return the register allocation hint for the

  /// specified virtual register. If there are many hints, this returns the

  /// one with the greatest weight.

  std::pair<Register, Register>

  getRegAllocationHint(Register VReg) const {

    assert(VReg.isVirtual());

    Register BestHint = (RegAllocHints[VReg.id()].second.size() ?

                         RegAllocHints[VReg.id()].second[0] : Register());