llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp

//===-- SystemZInstrInfo.cpp - SystemZ instruction information ------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the SystemZ implementation of the TargetInstrInfo class.
//
//===----------------------------------------------------------------------===//

#include "MCTargetDesc/SystemZMCTargetDesc.h"
#include "SystemZ.h"
#include "SystemZInstrBuilder.h"
#include "SystemZInstrInfo.h"
#include "SystemZSubtarget.h"
#include "llvm/CodeGen/LiveInterval.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SlotIndexes.h"
#include "llvm/MC/MCInstrDesc.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/Support/BranchProbability.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetSubtargetInfo.h"
#include <cassert>
#include <cstdint>
#include <iterator>

using namespace llvm;

#define GET_INSTRINFO_CTOR_DTOR
#define GET_INSTRMAP_INFO
#include "SystemZGenInstrInfo.inc"

// Return a mask with Count low bits set.
static uint64_t allOnes(unsigned int Count) {
  return Count == 0 ? 0 : (uint64_t(1) << (Count - 1) << 1) - 1;
}

// Reg should be a 32-bit GPR.  Return true if it is a high register rather
// than a low register.
static bool isHighReg(unsigned int Reg) {
  if (SystemZ::GRH32BitRegClass.contains(Reg))
    return true;
  assert(SystemZ::GR32BitRegClass.contains(Reg) && "Invalid GRX32");
  return false;
}

// Pin the vtable to this file.
void SystemZInstrInfo::anchor() {}

SystemZInstrInfo::SystemZInstrInfo(SystemZSubtarget &sti)
  : SystemZGenInstrInfo(SystemZ::ADJCALLSTACKDOWN, SystemZ::ADJCALLSTACKUP),
    RI(), STI(sti) {
}

// MI is a 128-bit load or store.  Split it into two 64-bit loads or stores,
// each having the opcode given by NewOpcode.
void SystemZInstrInfo::splitMove(MachineBasicBlock::iterator MI,
                                 unsigned NewOpcode) const {
  MachineBasicBlock *MBB = MI->getParent();
  MachineFunction &MF = *MBB->getParent();

  // Get two load or store instructions.  Use the original instruction for one
  // of them (arbitrarily the second here) and create a clone for the other.
  MachineInstr *EarlierMI = MF.CloneMachineInstr(&*MI);
  MBB->insert(MI, EarlierMI);

  // Set up the two 64-bit registers.
  MachineOperand &HighRegOp = EarlierMI->getOperand(0);
  MachineOperand &LowRegOp = MI->getOperand(0);
  HighRegOp.setReg(RI.getSubReg(HighRegOp.getReg(), SystemZ::subreg_h64));
  LowRegOp.setReg(RI.getSubReg(LowRegOp.getReg(), SystemZ::subreg_l64));

  // The address in the first (high) instruction is already correct.
  // Adjust the offset in the second (low) instruction.
  MachineOperand &HighOffsetOp = EarlierMI->getOperand(2);
  MachineOperand &LowOffsetOp = MI->getOperand(2);
  LowOffsetOp.setImm(LowOffsetOp.getImm() + 8);

  // Clear the kill flags for the base and index registers in the first
  // instruction.
  EarlierMI->getOperand(1).setIsKill(false);
  EarlierMI->getOperand(3).setIsKill(false);

  // Set the opcodes.
  unsigned HighOpcode = getOpcodeForOffset(NewOpcode, HighOffsetOp.getImm());
  unsigned LowOpcode = getOpcodeForOffset(NewOpcode, LowOffsetOp.getImm());
  assert(HighOpcode && LowOpcode && "Both offsets should be in range");

  EarlierMI->setDesc(get(HighOpcode));
  MI->setDesc(get(LowOpcode));
}

// Split ADJDYNALLOC instruction MI.
void SystemZInstrInfo::splitAdjDynAlloc(MachineBasicBlock::iterator MI) const {
  MachineBasicBlock *MBB = MI->getParent();
  MachineFunction &MF = *MBB->getParent();
  MachineFrameInfo &MFFrame = MF.getFrameInfo();
  MachineOperand &OffsetMO = MI->getOperand(2);

  uint64_t Offset = (MFFrame.getMaxCallFrameSize() +
                     SystemZMC::CallFrameSize +
                     OffsetMO.getImm());
  unsigned NewOpcode = getOpcodeForOffset(SystemZ::LA, Offset);
  assert(NewOpcode && "No support for huge argument lists yet");
  MI->setDesc(get(NewOpcode));
  OffsetMO.setImm(Offset);
}

// MI is an RI-style pseudo instruction.  Replace it with LowOpcode
// if the first operand is a low GR32 and HighOpcode if the first operand
// is a high GR32.  ConvertHigh is true if LowOpcode takes a signed operand
// and HighOpcode takes an unsigned 32-bit operand.  In those cases,
// MI has the same kind of operand as LowOpcode, so needs to be converted
// if HighOpcode is used.
void SystemZInstrInfo::expandRIPseudo(MachineInstr &MI, unsigned LowOpcode,
                                      unsigned HighOpcode,
                                      bool ConvertHigh) const {
  unsigned Reg = MI.getOperand(0).getReg();
  bool IsHigh = isHighReg(Reg);
  MI.setDesc(get(IsHigh ? HighOpcode : LowOpcode));
  if (IsHigh && ConvertHigh)
    MI.getOperand(1).setImm(uint32_t(MI.getOperand(1).getImm()));
}

// MI is a three-operand RIE-style pseudo instruction.  Replace it with
// LowOpcodeK if the registers are both low GR32s, otherwise use a move
// followed by HighOpcode or LowOpcode, depending on whether the target
// is a high or low GR32.
void SystemZInstrInfo::expandRIEPseudo(MachineInstr &MI, unsigned LowOpcode,
                                       unsigned LowOpcodeK,
                                       unsigned HighOpcode) const {
  unsigned DestReg = MI.getOperand(0).getReg();
  unsigned SrcReg = MI.getOperand(1).getReg();
  bool DestIsHigh = isHighReg(DestReg);
  bool SrcIsHigh = isHighReg(SrcReg);
  if (!DestIsHigh && !SrcIsHigh)
    MI.setDesc(get(LowOpcodeK));
  else {
    emitGRX32Move(*MI.getParent(), MI, MI.getDebugLoc(), DestReg, SrcReg,
                  SystemZ::LR, 32, MI.getOperand(1).isKill(),
                  MI.getOperand(1).isUndef());
    MI.setDesc(get(DestIsHigh ? HighOpcode : LowOpcode));
    MI.getOperand(1).setReg(DestReg);
    MI.tieOperands(0, 1);
  }
}

// MI is an RXY-style pseudo instruction.  Replace it with LowOpcode
// if the first operand is a low GR32 and HighOpcode if the first operand
// is a high GR32.
void SystemZInstrInfo::expandRXYPseudo(MachineInstr &MI, unsigned LowOpcode,
                                       unsigned HighOpcode) const {
  unsigned Reg = MI.getOperand(0).getReg();
  unsigned Opcode = getOpcodeForOffset(isHighReg(Reg) ? HighOpcode : LowOpcode,
                                       MI.getOperand(2).getImm());
  MI.setDesc(get(Opcode));
}

// MI is a load-on-condition pseudo instruction with a single register
// (source or destination) operand.  Replace it with LowOpcode if the
// register is a low GR32 and HighOpcode if the register is a high GR32.
void SystemZInstrInfo::expandLOCPseudo(MachineInstr &MI, unsigned LowOpcode,
                                       unsigned HighOpcode) const {
  unsigned Reg = MI.getOperand(0).getReg();
  unsigned Opcode = isHighReg(Reg) ? HighOpcode : LowOpcode;
  MI.setDesc(get(Opcode));
}

// MI is a load-register-on-condition pseudo instruction.  Replace it with
// LowOpcode if source and destination are both low GR32s and HighOpcode if
// source and destination are both high GR32s.
void SystemZInstrInfo::expandLOCRPseudo(MachineInstr &MI, unsigned LowOpcode,
                                        unsigned HighOpcode) const {
  unsigned DestReg = MI.getOperand(0).getReg();
  unsigned SrcReg = MI.getOperand(2).getReg();
  bool DestIsHigh = isHighReg(DestReg);
  bool SrcIsHigh = isHighReg(SrcReg);

  if (!DestIsHigh && !SrcIsHigh)
    MI.setDesc(get(LowOpcode));
  else if (DestIsHigh && SrcIsHigh)
    MI.setDesc(get(HighOpcode));

  // If we were unable to implement the pseudo with a single instruction, we
  // need to convert it back into a branch sequence.  This cannot be done here
  // since the caller of expandPostRAPseudo does not handle changes to the CFG
  // correctly.  This change is defered to the SystemZExpandPseudo pass.
}

// MI is an RR-style pseudo instruction that zero-extends the low Size bits
// of one GRX32 into another.  Replace it with LowOpcode if both operands
// are low registers, otherwise use RISB[LH]G.
void SystemZInstrInfo::expandZExtPseudo(MachineInstr &MI, unsigned LowOpcode,
                                        unsigned Size) const {
  emitGRX32Move(*MI.getParent(), MI, MI.getDebugLoc(),
                MI.getOperand(0).getReg(), MI.getOperand(1).getReg(), LowOpcode,
                Size, MI.getOperand(1).isKill(), MI.getOperand(1).isUndef());
  MI.eraseFromParent();
}

void SystemZInstrInfo::expandLoadStackGuard(MachineInstr *MI) const {
  MachineBasicBlock *MBB = MI->getParent();
  MachineFunction &MF = *MBB->getParent();
  const unsigned Reg = MI->getOperand(0).getReg();

  // Conveniently, all 4 instructions are cloned from LOAD_STACK_GUARD,
  // so they already have operand 0 set to reg.

  // ear <reg>, %a0
  MachineInstr *Ear1MI = MF.CloneMachineInstr(MI);
  MBB->insert(MI, Ear1MI);
  Ear1MI->setDesc(get(SystemZ::EAR));
  MachineInstrBuilder(MF, Ear1MI).addReg(SystemZ::A0);

  // sllg <reg>, <reg>, 32
  MachineInstr *SllgMI = MF.CloneMachineInstr(MI);
  MBB->insert(MI, SllgMI);
  SllgMI->setDesc(get(SystemZ::SLLG));
  MachineInstrBuilder(MF, SllgMI).addReg(Reg).addReg(0).addImm(32);

  // ear <reg>, %a1
  MachineInstr *Ear2MI = MF.CloneMachineInstr(MI);
  MBB->insert(MI, Ear2MI);
  Ear2MI->setDesc(get(SystemZ::EAR));
  MachineInstrBuilder(MF, Ear2MI).addReg(SystemZ::A1);

  // lg <reg>, 40(<reg>)
  MI->setDesc(get(SystemZ::LG));
  MachineInstrBuilder(MF, MI).addReg(Reg).addImm(40).addReg(0);
}

// Emit a zero-extending move from 32-bit GPR SrcReg to 32-bit GPR
// DestReg before MBBI in MBB.  Use LowLowOpcode when both DestReg and SrcReg
// are low registers, otherwise use RISB[LH]G.  Size is the number of bits
// taken from the low end of SrcReg (8 for LLCR, 16 for LLHR and 32 for LR).
// KillSrc is true if this move is the last use of SrcReg.
void SystemZInstrInfo::emitGRX32Move(MachineBasicBlock &MBB,
                                     MachineBasicBlock::iterator MBBI,
                                     const DebugLoc &DL, unsigned DestReg,
                                     unsigned SrcReg, unsigned LowLowOpcode,
                                     unsigned Size, bool KillSrc,
                                     bool UndefSrc) const {
  unsigned Opcode;
  bool DestIsHigh = isHighReg(DestReg);
  bool SrcIsHigh = isHighReg(SrcReg);
  if (DestIsHigh && SrcIsHigh)
    Opcode = SystemZ::RISBHH;
  else if (DestIsHigh && !SrcIsHigh)
    Opcode = SystemZ::RISBHL;
  else if (!DestIsHigh && SrcIsHigh)
    Opcode = SystemZ::RISBLH;
  else {
    BuildMI(MBB, MBBI, DL, get(LowLowOpcode), DestReg)
      .addReg(SrcReg, getKillRegState(KillSrc) | getUndefRegState(UndefSrc));
    return;
  }
  unsigned Rotate = (DestIsHigh != SrcIsHigh ? 32 : 0);
  BuildMI(MBB, MBBI, DL, get(Opcode), DestReg)
    .addReg(DestReg, RegState::Undef)
    .addReg(SrcReg, getKillRegState(KillSrc) | getUndefRegState(UndefSrc))
    .addImm(32 - Size).addImm(128 + 31).addImm(Rotate);
}

MachineInstr *SystemZInstrInfo::commuteInstructionImpl(MachineInstr &MI,
                                                       bool NewMI,
                                                       unsigned OpIdx1,
                                                       unsigned OpIdx2) const {
  auto cloneIfNew = [NewMI](MachineInstr &MI) -> MachineInstr & {
    if (NewMI)
      return *MI.getParent()->getParent()->CloneMachineInstr(&MI);
    return MI;
  };

  switch (MI.getOpcode()) {
  case SystemZ::LOCRMux:
  case SystemZ::LOCFHR:
  case SystemZ::LOCR:
  case SystemZ::LOCGR: {
    auto &WorkingMI = cloneIfNew(MI);
    // Invert condition.
    unsigned CCValid = WorkingMI.getOperand(3).getImm();
    unsigned CCMask = WorkingMI.getOperand(4).getImm();
    WorkingMI.getOperand(4).setImm(CCMask ^ CCValid);
    return TargetInstrInfo::commuteInstructionImpl(WorkingMI, /*NewMI=*/false,
                                                   OpIdx1, OpIdx2);
  }
  default:
    return TargetInstrInfo::commuteInstructionImpl(MI, NewMI, OpIdx1, OpIdx2);
  }
}

// If MI is a simple load or store for a frame object, return the register
// it loads or stores and set FrameIndex to the index of the frame object.
// Return 0 otherwise.
//
// Flag is SimpleBDXLoad for loads and SimpleBDXStore for stores.
static int isSimpleMove(const MachineInstr &MI, int &FrameIndex,
                        unsigned Flag) {
  const MCInstrDesc &MCID = MI.getDesc();
  if ((MCID.TSFlags & Flag) && MI.getOperand(1).isFI() &&
      MI.getOperand(2).getImm() == 0 && MI.getOperand(3).getReg() == 0) {
    FrameIndex = MI.getOperand(1).getIndex();
    return MI.getOperand(0).getReg();
  }
  return 0;
}

unsigned SystemZInstrInfo::isLoadFromStackSlot(const MachineInstr &MI,
                                               int &FrameIndex) const {
  return isSimpleMove(MI, FrameIndex, SystemZII::SimpleBDXLoad);
}

unsigned SystemZInstrInfo::isStoreToStackSlot(const MachineInstr &MI,
                                              int &FrameIndex) const {
  return isSimpleMove(MI, FrameIndex, SystemZII::SimpleBDXStore);
}

bool SystemZInstrInfo::isStackSlotCopy(const MachineInstr &MI,
                                       int &DestFrameIndex,
                                       int &SrcFrameIndex) const {
  // Check for MVC 0(Length,FI1),0(FI2)
  const MachineFrameInfo &MFI = MI.getParent()->getParent()->getFrameInfo();
  if (MI.getOpcode() != SystemZ::MVC || !MI.getOperand(0).isFI() ||
      MI.getOperand(1).getImm() != 0 || !MI.getOperand(3).isFI() ||
      MI.getOperand(4).getImm() != 0)
    return false;

  // Check that Length covers the full slots.
  int64_t Length = MI.getOperand(2).getImm();
  unsigned FI1 = MI.getOperand(0).getIndex();
  unsigned FI2 = MI.getOperand(3).getIndex();
  if (MFI.getObjectSize(FI1) != Length ||
      MFI.getObjectSize(FI2) != Length)
    return false;

  DestFrameIndex = FI1;
  SrcFrameIndex = FI2;
  return true;
}

bool SystemZInstrInfo::analyzeBranch(MachineBasicBlock &MBB,
                                     MachineBasicBlock *&TBB,
                                     MachineBasicBlock *&FBB,
                                     SmallVectorImpl<MachineOperand> &Cond,
                                     bool AllowModify) const {
  // Most of the code and comments here are boilerplate.

  // Start from the bottom of the block and work up, examining the
  // terminator instructions.
  MachineBasicBlock::iterator I = MBB.end();
  while (I != MBB.begin()) {
    --I;
    if (I->isDebugValue())
      continue;

    // Working from the bottom, when we see a non-terminator instruction, we're
    // done.
    if (!isUnpredicatedTerminator(*I))
      break;

    // A terminator that isn't a branch can't easily be handled by this
    // analysis.
    if (!I->isBranch())
      return true;

    // Can't handle indirect branches.
    SystemZII::Branch Branch(getBranchInfo(*I));
    if (!Branch.Target->isMBB())
      return true;

    // Punt on compound branches.
    if (Branch.Type != SystemZII::BranchNormal)
      return true;

    if (Branch.CCMask == SystemZ::CCMASK_ANY) {
      // Handle unconditional branches.
      if (!AllowModify) {
        TBB = Branch.Target->getMBB();
        continue;
      }

      // If the block has any instructions after a JMP, delete them.
      while (std::next(I) != MBB.end())
        std::next(I)->eraseFromParent();

      Cond.clear();
      FBB = nullptr;

      // Delete the JMP if it's equivalent to a fall-through.
      if (MBB.isLayoutSuccessor(Branch.Target->getMBB())) {
        TBB = nullptr;
        I->eraseFromParent();
        I = MBB.end();
        continue;
      }

      // TBB is used to indicate the unconditinal destination.
      TBB = Branch.Target->getMBB();
      continue;
    }

    // Working from the bottom, handle the first conditional branch.
    if (Cond.empty()) {
      // FIXME: add X86-style branch swap
      FBB = TBB;
      TBB = Branch.Target->getMBB();
      Cond.push_back(MachineOperand::CreateImm(Branch.CCValid));
      Cond.push_back(MachineOperand::CreateImm(Branch.CCMask));
      continue;
    }

    // Handle subsequent conditional branches.
    assert(Cond.size() == 2 && TBB && "Should have seen a conditional branch");

    // Only handle the case where all conditional branches branch to the same
    // destination.
    if (TBB != Branch.Target->getMBB())
      return true;

    // If the conditions are the same, we can leave them alone.
    unsigned OldCCValid = Cond[0].getImm();
    unsigned OldCCMask = Cond[1].getImm();
    if (OldCCValid == Branch.CCValid && OldCCMask == Branch.CCMask)
      continue;

    // FIXME: Try combining conditions like X86 does.  Should be easy on Z!
    return false;
  }

  return false;
}

unsigned SystemZInstrInfo::removeBranch(MachineBasicBlock &MBB,
                                        int *BytesRemoved) const {
  assert(!BytesRemoved && "code size not handled");

  // Most of the code and comments here are boilerplate.
  MachineBasicBlock::iterator I = MBB.end();
  unsigned Count = 0;

  while (I != MBB.begin()) {
    --I;
    if (I->isDebugValue())
      continue;
    if (!I->isBranch())
      break;
    if (!getBranchInfo(*I).Target->isMBB())
      break;
    // Remove the branch.
    I->eraseFromParent();
    I = MBB.end();
    ++Count;
  }

  return Count;
}

bool SystemZInstrInfo::
reverseBranchCondition(SmallVectorImpl<MachineOperand> &Cond) const {
  assert(Cond.size() == 2 && "Invalid condition");
  Cond[1].setImm(Cond[1].getImm() ^ Cond[0].getImm());
  return false;
}

unsigned SystemZInstrInfo::insertBranch(MachineBasicBlock &MBB,
                                        MachineBasicBlock *TBB,
                                        MachineBasicBlock *FBB,
                                        ArrayRef<MachineOperand> Cond,
                                        const DebugLoc &DL,
                                        int *BytesAdded) const {
  // In this function we output 32-bit branches, which should always
  // have enough range.  They can be shortened and relaxed by later code
  // in the pipeline, if desired.

  // Shouldn't be a fall through.
  assert(TBB && "insertBranch must not be told to insert a fallthrough");
  assert((Cond.size() == 2 || Cond.size() == 0) &&
         "SystemZ branch conditions have one component!");
  assert(!BytesAdded && "code size not handled");

  if (Cond.empty()) {
    // Unconditional branch?
    assert(!FBB && "Unconditional branch with multiple successors!");
    BuildMI(&MBB, DL, get(SystemZ::J)).addMBB(TBB);
    return 1;
  }

  // Conditional branch.
  unsigned Count = 0;
  unsigned CCValid = Cond[0].getImm();
  unsigned CCMask = Cond[1].getImm();
  BuildMI(&MBB, DL, get(SystemZ::BRC))
    .addImm(CCValid).addImm(CCMask).addMBB(TBB);
  ++Count;

  if (FBB) {
    // Two-way Conditional branch. Insert the second branch.
    BuildMI(&MBB, DL, get(SystemZ::J)).addMBB(FBB);
    ++Count;
  }
  return Count;
}

bool SystemZInstrInfo::analyzeCompare(const MachineInstr &MI, unsigned &SrcReg,
                                      unsigned &SrcReg2, int &Mask,
                                      int &Value) const {
  assert(MI.isCompare() && "Caller should have checked for a comparison");

  if (MI.getNumExplicitOperands() == 2 && MI.getOperand(0).isReg() &&
      MI.getOperand(1).isImm()) {
    SrcReg = MI.getOperand(0).getReg();
    SrcReg2 = 0;
    Value = MI.getOperand(1).getImm();
    Mask = ~0;
    return true;
  }

  return false;
}

// If Reg is a virtual register, return its definition, otherwise return null.
static MachineInstr *getDef(unsigned Reg,
                            const MachineRegisterInfo *MRI) {
  if (TargetRegisterInfo::isPhysicalRegister(Reg))
    return nullptr;
  return MRI->getUniqueVRegDef(Reg);
}

// Return true if MI is a shift of type Opcode by Imm bits.
static bool isShift(MachineInstr *MI, unsigned Opcode, int64_t Imm) {
  return (MI->getOpcode() == Opcode &&
          !MI->getOperand(2).getReg() &&
          MI->getOperand(3).getImm() == Imm);
}

// If the destination of MI has no uses, delete it as dead.
static void eraseIfDead(MachineInstr *MI, const MachineRegisterInfo *MRI) {
  if (MRI->use_nodbg_empty(MI->getOperand(0).getReg()))
    MI->eraseFromParent();
}

// Compare compares SrcReg against zero.  Check whether SrcReg contains
// the result of an IPM sequence whose input CC survives until Compare,
// and whether Compare is therefore redundant.  Delete it and return
// true if so.
static bool removeIPMBasedCompare(MachineInstr &Compare, unsigned SrcReg,
                                  const MachineRegisterInfo *MRI,
                                  const TargetRegisterInfo *TRI) {
  MachineInstr *LGFR = nullptr;
  MachineInstr *RLL = getDef(SrcReg, MRI);
  if (RLL && RLL->getOpcode() == SystemZ::LGFR) {
    LGFR = RLL;
    RLL = getDef(LGFR->getOperand(1).getReg(), MRI);
  }
  if (!RLL || !isShift(RLL, SystemZ::RLL, 31))
    return false;

  MachineInstr *SRL = getDef(RLL->getOperand(1).getReg(), MRI);
  if (!SRL || !isShift(SRL, SystemZ::SRL, SystemZ::IPM_CC))
    return false;

  MachineInstr *IPM = getDef(SRL->getOperand(1).getReg(), MRI);
  if (!IPM || IPM->getOpcode() != SystemZ::IPM)
    return false;

  // Check that there are no assignments to CC between the IPM and Compare,
  if (IPM->getParent() != Compare.getParent())
    return false;
  MachineBasicBlock::iterator MBBI = IPM, MBBE = Compare.getIterator();
  for (++MBBI; MBBI != MBBE; ++MBBI) {
    MachineInstr &MI = *MBBI;
    if (MI.modifiesRegister(SystemZ::CC, TRI))
      return false;
  }

  Compare.eraseFromParent();
  if (LGFR)
    eraseIfDead(LGFR, MRI);
  eraseIfDead(RLL, MRI);
  eraseIfDead(SRL, MRI);
  eraseIfDead(IPM, MRI);

  return true;
}

bool SystemZInstrInfo::optimizeCompareInstr(
    MachineInstr &Compare, unsigned SrcReg, unsigned SrcReg2, int Mask,
    int Value, const MachineRegisterInfo *MRI) const {
  assert(!SrcReg2 && "Only optimizing constant comparisons so far");
  bool IsLogical = (Compare.getDesc().TSFlags & SystemZII::IsLogical) != 0;
  return Value == 0 && !IsLogical &&
         removeIPMBasedCompare(Compare, SrcReg, MRI, &RI);
}

bool SystemZInstrInfo::canInsertSelect(const MachineBasicBlock &MBB,
                                       ArrayRef<MachineOperand> Pred,
                                       unsigned TrueReg, unsigned FalseReg,
                                       int &CondCycles, int &TrueCycles,
                                       int &FalseCycles) const {
  // Not all subtargets have LOCR instructions.
  if (!STI.hasLoadStoreOnCond())
    return false;
  if (Pred.size() != 2)
    return false;

  // Check register classes.
  const MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
  const TargetRegisterClass *RC =
    RI.getCommonSubClass(MRI.getRegClass(TrueReg), MRI.getRegClass(FalseReg));
  if (!RC)
    return false;

  // We have LOCR instructions for 32 and 64 bit general purpose registers.
  if ((STI.hasLoadStoreOnCond2() &&
       SystemZ::GRX32BitRegClass.hasSubClassEq(RC)) ||
      SystemZ::GR32BitRegClass.hasSubClassEq(RC) ||
      SystemZ::GR64BitRegClass.hasSubClassEq(RC)) {
    CondCycles = 2;
    TrueCycles = 2;
    FalseCycles = 2;
    return true;
  }

  // Can't do anything else.
  return false;
}

void SystemZInstrInfo::insertSelect(MachineBasicBlock &MBB,
                                    MachineBasicBlock::iterator I,
                                    const DebugLoc &DL, unsigned DstReg,
                                    ArrayRef<MachineOperand> Pred,
                                    unsigned TrueReg,
                                    unsigned FalseReg) const {
  MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
  const TargetRegisterClass *RC = MRI.getRegClass(DstReg);

  assert(Pred.size() == 2 && "Invalid condition");
  unsigned CCValid = Pred[0].getImm();
  unsigned CCMask = Pred[1].getImm();

  unsigned Opc;
  if (SystemZ::GRX32BitRegClass.hasSubClassEq(RC)) {
    if (STI.hasLoadStoreOnCond2())
      Opc = SystemZ::LOCRMux;
    else {
      Opc = SystemZ::LOCR;
      MRI.constrainRegClass(DstReg, &SystemZ::GR32BitRegClass);
    }
  } else if (SystemZ::GR64BitRegClass.hasSubClassEq(RC))
    Opc = SystemZ::LOCGR;
  else
    llvm_unreachable("Invalid register class");

  BuildMI(MBB, I, DL, get(Opc), DstReg)
    .addReg(FalseReg).addReg(TrueReg)
    .addImm(CCValid).addImm(CCMask);
}

bool SystemZInstrInfo::FoldImmediate(MachineInstr &UseMI, MachineInstr &DefMI,
                                     unsigned Reg,
                                     MachineRegisterInfo *MRI) const {
  unsigned DefOpc = DefMI.getOpcode();
  if (DefOpc != SystemZ::LHIMux && DefOpc != SystemZ::LHI &&
      DefOpc != SystemZ::LGHI)
    return false;
  if (DefMI.getOperand(0).getReg() != Reg)
    return false;
  int32_t ImmVal = (int32_t)DefMI.getOperand(1).getImm();

  unsigned UseOpc = UseMI.getOpcode();
  unsigned NewUseOpc;
  unsigned UseIdx;
  int CommuteIdx = -1;
  switch (UseOpc) {
  case SystemZ::LOCRMux:
    if (!STI.hasLoadStoreOnCond2())
      return false;
    NewUseOpc = SystemZ::LOCHIMux;
    if (UseMI.getOperand(2).getReg() == Reg)
      UseIdx = 2;
    else if (UseMI.getOperand(1).getReg() == Reg)
      UseIdx = 2, CommuteIdx = 1;
    else
      return false;
    break;
  case SystemZ::LOCGR:
    if (!STI.hasLoadStoreOnCond2())
      return false;
    NewUseOpc = SystemZ::LOCGHI;
    if (UseMI.getOperand(2).getReg() == Reg)
      UseIdx = 2;
    else if (UseMI.getOperand(1).getReg() == Reg)
      UseIdx = 2, CommuteIdx = 1;
    else
      return false;
    break;
  default:
    return false;
  }

  if (CommuteIdx != -1)
    if (!commuteInstruction(UseMI, false, CommuteIdx, UseIdx))
      return false;

  bool DeleteDef = MRI->hasOneNonDBGUse(Reg);
  UseMI.setDesc(get(NewUseOpc));
  UseMI.getOperand(UseIdx).ChangeToImmediate(ImmVal);
  if (DeleteDef)
    DefMI.eraseFromParent();

  return true;
}

bool SystemZInstrInfo::isPredicable(const MachineInstr &MI) const {
  unsigned Opcode = MI.getOpcode();
  if (Opcode == SystemZ::Return ||
      Opcode == SystemZ::Trap ||
      Opcode == SystemZ::CallJG ||
      Opcode == SystemZ::CallBR)
    return true;
  return false;
}

bool SystemZInstrInfo::
isProfitableToIfCvt(MachineBasicBlock &MBB,
                    unsigned NumCycles, unsigned ExtraPredCycles,
                    BranchProbability Probability) const {
  // Avoid using conditional returns at the end of a loop (since then
  // we'd need to emit an unconditional branch to the beginning anyway,
  // making the loop body longer).  This doesn't apply for low-probability
  // loops (eg. compare-and-swap retry), so just decide based on branch
  // probability instead of looping structure.
  // However, since Compare and Trap instructions cost the same as a regular
  // Compare instruction, we should allow the if conversion to convert this
  // into a Conditional Compare regardless of the branch probability.
  if (MBB.getLastNonDebugInstr()->getOpcode() != SystemZ::Trap &&
      MBB.succ_empty() && Probability < BranchProbability(1, 8))
    return false;
  // For now only convert single instructions.
  return NumCycles == 1;
}

bool SystemZInstrInfo::
isProfitableToIfCvt(MachineBasicBlock &TMBB,
                    unsigned NumCyclesT, unsigned ExtraPredCyclesT,
                    MachineBasicBlock &FMBB,
                    unsigned NumCyclesF, unsigned ExtraPredCyclesF,
                    BranchProbability Probability) const {
  // For now avoid converting mutually-exclusive cases.
  return false;
}

bool SystemZInstrInfo::
isProfitableToDupForIfCvt(MachineBasicBlock &MBB, unsigned NumCycles,
                          BranchProbability Probability) const {
  // For now only duplicate single instructions.
  return NumCycles == 1;
}

bool SystemZInstrInfo::PredicateInstruction(
    MachineInstr &MI, ArrayRef<MachineOperand> Pred) const {
  assert(Pred.size() == 2 && "Invalid condition");
  unsigned CCValid = Pred[0].getImm();
  unsigned CCMask = Pred[1].getImm();
  assert(CCMask > 0 && CCMask < 15 && "Invalid predicate");
  unsigned Opcode = MI.getOpcode();
  if (Opcode == SystemZ::Trap) {
    MI.setDesc(get(SystemZ::CondTrap));
    MachineInstrBuilder(*MI.getParent()->getParent(), MI)
      .addImm(CCValid).addImm(CCMask)
      .addReg(SystemZ::CC, RegState::Implicit);
    return true;
  }
  if (Opcode == SystemZ::Return) {
    MI.setDesc(get(SystemZ::CondReturn));
    MachineInstrBuilder(*MI.getParent()->getParent(), MI)
      .addImm(CCValid).addImm(CCMask)
      .addReg(SystemZ::CC, RegState::Implicit);
    return true;
  }
  if (Opcode == SystemZ::CallJG) {
    MachineOperand FirstOp = MI.getOperand(0);
    const uint32_t *RegMask = MI.getOperand(1).getRegMask();
    MI.RemoveOperand(1);
    MI.RemoveOperand(0);
    MI.setDesc(get(SystemZ::CallBRCL));
    MachineInstrBuilder(*MI.getParent()->getParent(), MI)
        .addImm(CCValid)
        .addImm(CCMask)
        .add(FirstOp)
        .addRegMask(RegMask)
        .addReg(SystemZ::CC, RegState::Implicit);
    return true;
  }
  if (Opcode == SystemZ::CallBR) {
    const uint32_t *RegMask = MI.getOperand(0).getRegMask();
    MI.RemoveOperand(0);
    MI.setDesc(get(SystemZ::CallBCR));
    MachineInstrBuilder(*MI.getParent()->getParent(), MI)
      .addImm(CCValid).addImm(CCMask)
      .addRegMask(RegMask)
      .addReg(SystemZ::CC, RegState::Implicit);
    return true;
  }
  return false;
}

void SystemZInstrInfo::copyPhysReg(MachineBasicBlock &MBB,
                                   MachineBasicBlock::iterator MBBI,
                                   const DebugLoc &DL, unsigned DestReg,
                                   unsigned SrcReg, bool KillSrc) const {
  // Split 128-bit GPR moves into two 64-bit moves.  This handles ADDR128 too.
  if (SystemZ::GR128BitRegClass.contains(DestReg, SrcReg)) {
    copyPhysReg(MBB, MBBI, DL, RI.getSubReg(DestReg, SystemZ::subreg_h64),
                RI.getSubReg(SrcReg, SystemZ::subreg_h64), KillSrc);
    copyPhysReg(MBB, MBBI, DL, RI.getSubReg(DestReg, SystemZ::subreg_l64),
                RI.getSubReg(SrcReg, SystemZ::subreg_l64), KillSrc);
    return;
  }

  if (SystemZ::GRX32BitRegClass.contains(DestReg, SrcReg)) {
    emitGRX32Move(MBB, MBBI, DL, DestReg, SrcReg, SystemZ::LR, 32, KillSrc,
                  false);
    return;
  }

  // Everything else needs only one instruction.
  unsigned Opcode;
  if (SystemZ::GR64BitRegClass.contains(DestReg, SrcReg))
    Opcode = SystemZ::LGR;
  else if (SystemZ::FP32BitRegClass.contains(DestReg, SrcReg))
    // For z13 we prefer LDR over LER to avoid partial register dependencies.
    Opcode = STI.hasVector() ? SystemZ::LDR32 : SystemZ::LER;
  else if (SystemZ::FP64BitRegClass.contains(DestReg, SrcReg))
    Opcode = SystemZ::LDR;
  else if (SystemZ::FP128BitRegClass.contains(DestReg, SrcReg))
    Opcode = SystemZ::LXR;
  else if (SystemZ::VR32BitRegClass.contains(DestReg, SrcReg))
    Opcode = SystemZ::VLR32;
  else if (SystemZ::VR64BitRegClass.contains(DestReg, SrcReg))
    Opcode = SystemZ::VLR64;
  else if (SystemZ::VR128BitRegClass.contains(DestReg, SrcReg))
    Opcode = SystemZ::VLR;
  else if (SystemZ::AR32BitRegClass.contains(DestReg, SrcReg))
    Opcode = SystemZ::CPYA;
  else if (SystemZ::AR32BitRegClass.contains(DestReg) &&
           SystemZ::GR32BitRegClass.contains(SrcReg))
    Opcode = SystemZ::SAR;
  else if (SystemZ::GR32BitRegClass.contains(DestReg) &&
           SystemZ::AR32BitRegClass.contains(SrcReg))
    Opcode = SystemZ::EAR;
  else
    llvm_unreachable("Impossible reg-to-reg copy");

  BuildMI(MBB, MBBI, DL, get(Opcode), DestReg)
    .addReg(SrcReg, getKillRegState(KillSrc));
}

void SystemZInstrInfo::storeRegToStackSlot(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI, unsigned SrcReg,
    bool isKill, int FrameIdx, const TargetRegisterClass *RC,
    const TargetRegisterInfo *TRI) const {
  DebugLoc DL = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();

  // Callers may expect a single instruction, so keep 128-bit moves
  // together for now and lower them after register allocation.
  unsigned LoadOpcode, StoreOpcode;
  getLoadStoreOpcodes(RC, LoadOpcode, StoreOpcode);
  addFrameReference(BuildMI(MBB, MBBI, DL, get(StoreOpcode))
                        .addReg(SrcReg, getKillRegState(isKill)),
                    FrameIdx);
}

void SystemZInstrInfo::loadRegFromStackSlot(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI, unsigned DestReg,
    int FrameIdx, const TargetRegisterClass *RC,
    const TargetRegisterInfo *TRI) const {
  DebugLoc DL = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();

  // Callers may expect a single instruction, so keep 128-bit moves
  // together for now and lower them after register allocation.
  unsigned LoadOpcode, StoreOpcode;
  getLoadStoreOpcodes(RC, LoadOpcode, StoreOpcode);
  addFrameReference(BuildMI(MBB, MBBI, DL, get(LoadOpcode), DestReg),
                    FrameIdx);
}

// Return true if MI is a simple load or store with a 12-bit displacement
// and no index.  Flag is SimpleBDXLoad for loads and SimpleBDXStore for stores.
static bool isSimpleBD12Move(const MachineInstr *MI, unsigned Flag) {
  const MCInstrDesc &MCID = MI->getDesc();
  return ((MCID.TSFlags & Flag) &&
          isUInt<12>(MI->getOperand(2).getImm()) &&
          MI->getOperand(3).getReg() == 0);
}

namespace {

struct LogicOp {
  LogicOp() = default;
  LogicOp(unsigned regSize, unsigned immLSB, unsigned immSize)
    : RegSize(regSize), ImmLSB(immLSB), ImmSize(immSize) {}

  explicit operator bool() const { return RegSize; }

  unsigned RegSize = 0;
  unsigned ImmLSB = 0;
  unsigned ImmSize = 0;
};

} // end anonymous namespace

static LogicOp interpretAndImmediate(unsigned Opcode) {
  switch (Opcode) {
  case SystemZ::NILMux: return LogicOp(32,  0, 16);
  case SystemZ::NIHMux: return LogicOp(32, 16, 16);
  case SystemZ::NILL64: return LogicOp(64,  0, 16);
  case SystemZ::NILH64: return LogicOp(64, 16, 16);
  case SystemZ::NIHL64: return LogicOp(64, 32, 16);
  case SystemZ::NIHH64: return LogicOp(64, 48, 16);
  case SystemZ::NIFMux: return LogicOp(32,  0, 32);
  case SystemZ::NILF64: return LogicOp(64,  0, 32);
  case SystemZ::NIHF64: return LogicOp(64, 32, 32);
  default:              return LogicOp();
  }
}

static void transferDeadCC(MachineInstr *OldMI, MachineInstr *NewMI) {
  if (OldMI->registerDefIsDead(SystemZ::CC)) {
    MachineOperand *CCDef = NewMI->findRegisterDefOperand(SystemZ::CC);
    if (CCDef != nullptr)
      CCDef->setIsDead(true);
  }
}

// Used to return from convertToThreeAddress after replacing two-address
// instruction OldMI with three-address instruction NewMI.
static MachineInstr *finishConvertToThreeAddress(MachineInstr *OldMI,
                                                 MachineInstr *NewMI,
                                                 LiveVariables *LV) {
  if (LV) {
    unsigned NumOps = OldMI->getNumOperands();
    for (unsigned I = 1; I < NumOps; ++I) {
      MachineOperand &Op = OldMI->getOperand(I);
      if (Op.isReg() && Op.isKill())
        LV->replaceKillInstruction(Op.getReg(), *OldMI, *NewMI);
    }
  }
  transferDeadCC(OldMI, NewMI);
  return NewMI;
}

MachineInstr *SystemZInstrInfo::convertToThreeAddress(
    MachineFunction::iterator &MFI, MachineInstr &MI, LiveVariables *LV) const {
  MachineBasicBlock *MBB = MI.getParent();
  MachineFunction *MF = MBB->getParent();
  MachineRegisterInfo &MRI = MF->getRegInfo();

  unsigned Opcode = MI.getOpcode();
  unsigned NumOps = MI.getNumOperands();

  // Try to convert something like SLL into SLLK, if supported.
  // We prefer to keep the two-operand form where possible both
  // because it tends to be shorter and because some instructions
  // have memory forms that can be used during spilling.
  if (STI.hasDistinctOps()) {
    MachineOperand &Dest = MI.getOperand(0);
    MachineOperand &Src = MI.getOperand(1);
    unsigned DestReg = Dest.getReg();
    unsigned SrcReg = Src.getReg();
    // AHIMux is only really a three-operand instruction when both operands
    // are low registers.  Try to constrain both operands to be low if
    // possible.
    if (Opcode == SystemZ::AHIMux &&
        TargetRegisterInfo::isVirtualRegister(DestReg) &&
        TargetRegisterInfo::isVirtualRegister(SrcReg) &&
        MRI.getRegClass(DestReg)->contains(SystemZ::R1L) &&
        MRI.getRegClass(SrcReg)->contains(SystemZ::R1L)) {
      MRI.constrainRegClass(DestReg, &SystemZ::GR32BitRegClass);
      MRI.constrainRegClass(SrcReg, &SystemZ::GR32BitRegClass);
    }
    int ThreeOperandOpcode = SystemZ::getThreeOperandOpcode(Opcode);
    if (ThreeOperandOpcode >= 0) {
      // Create three address instruction without adding the implicit
      // operands. Those will instead be copied over from the original
      // instruction by the loop below.
      MachineInstrBuilder MIB(
          *MF, MF->CreateMachineInstr(get(ThreeOperandOpcode), MI.getDebugLoc(),
                                      /*NoImplicit=*/true));
      MIB.add(Dest);
      // Keep the kill state, but drop the tied flag.
      MIB.addReg(Src.getReg(), getKillRegState(Src.isKill()), Src.getSubReg());
      // Keep the remaining operands as-is.
      for (unsigned I = 2; I < NumOps; ++I)
        MIB.add(MI.getOperand(I));
      MBB->insert(MI, MIB);
      return finishConvertToThreeAddress(&MI, MIB, LV);
    }
  }

  // Try to convert an AND into an RISBG-type instruction.
  if (LogicOp And = interpretAndImmediate(Opcode)) {
    uint64_t Imm = MI.getOperand(2).getImm() << And.ImmLSB;
    // AND IMMEDIATE leaves the other bits of the register unchanged.
    Imm |= allOnes(And.RegSize) & ~(allOnes(And.ImmSize) << And.ImmLSB);
    unsigned Start, End;
    if (isRxSBGMask(Imm, And.RegSize, Start, End)) {
      unsigned NewOpcode;
      if (And.RegSize == 64) {
        NewOpcode = SystemZ::RISBG;
        // Prefer RISBGN if available, since it does not clobber CC.
        if (STI.hasMiscellaneousExtensions())
          NewOpcode = SystemZ::RISBGN;
      } else {
        NewOpcode = SystemZ::RISBMux;
        Start &= 31;
        End &= 31;
      }
      MachineOperand &Dest = MI.getOperand(0);
      MachineOperand &Src = MI.getOperand(1);
      MachineInstrBuilder MIB =
          BuildMI(*MBB, MI, MI.getDebugLoc(), get(NewOpcode))
              .add(Dest)
              .addReg(0)
              .addReg(Src.getReg(), getKillRegState(Src.isKill()),
                      Src.getSubReg())
              .addImm(Start)
              .addImm(End + 128)
              .addImm(0);
      return finishConvertToThreeAddress(&MI, MIB, LV);
    }
  }
  return nullptr;
}

MachineInstr *SystemZInstrInfo::foldMemoryOperandImpl(
    MachineFunction &MF, MachineInstr &MI, ArrayRef<unsigned> Ops,
    MachineBasicBlock::iterator InsertPt, int FrameIndex,
    LiveIntervals *LIS) const {
  const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
  const MachineFrameInfo &MFI = MF.getFrameInfo();
  unsigned Size = MFI.getObjectSize(FrameIndex);
  unsigned Opcode = MI.getOpcode();

  if (Ops.size() == 2 && Ops[0] == 0 && Ops[1] == 1) {
    if (LIS != nullptr && (Opcode == SystemZ::LA || Opcode == SystemZ::LAY) &&
        isInt<8>(MI.getOperand(2).getImm()) && !MI.getOperand(3).getReg()) {

      // Check CC liveness, since new instruction introduces a dead
      // def of CC.
      MCRegUnitIterator CCUnit(SystemZ::CC, TRI);
      LiveRange &CCLiveRange = LIS->getRegUnit(*CCUnit);
      ++CCUnit;
      assert(!CCUnit.isValid() && "CC only has one reg unit.");
      SlotIndex MISlot =
          LIS->getSlotIndexes()->getInstructionIndex(MI).getRegSlot();
      if (!CCLiveRange.liveAt(MISlot)) {
        // LA(Y) %reg, CONST(%reg) -> AGSI %mem, CONST
        MachineInstr *BuiltMI = BuildMI(*InsertPt->getParent(), InsertPt,
                                        MI.getDebugLoc(), get(SystemZ::AGSI))
                                    .addFrameIndex(FrameIndex)
                                    .addImm(0)
                                    .addImm(MI.getOperand(2).getImm());
        BuiltMI->findRegisterDefOperand(SystemZ::CC)->setIsDead(true);
        CCLiveRange.createDeadDef(MISlot, LIS->getVNInfoAllocator());
        return BuiltMI;
      }
    }
    return nullptr;
  }

  // All other cases require a single operand.
  if (Ops.size() != 1)
    return nullptr;

  unsigned OpNum = Ops[0];
  assert(Size ==
             MF.getRegInfo()
                 .getRegClass(MI.getOperand(OpNum).getReg())
                 ->getSize() &&
         "Invalid size combination");

  if ((Opcode == SystemZ::AHI || Opcode == SystemZ::AGHI) && OpNum == 0 &&
      isInt<8>(MI.getOperand(2).getImm())) {
    // A(G)HI %reg, CONST -> A(G)SI %mem, CONST
    Opcode = (Opcode == SystemZ::AHI ? SystemZ::ASI : SystemZ::AGSI);
    MachineInstr *BuiltMI =
        BuildMI(*InsertPt->getParent(), InsertPt, MI.getDebugLoc(), get(Opcode))
            .addFrameIndex(FrameIndex)
            .addImm(0)
            .addImm(MI.getOperand(2).getImm());
    transferDeadCC(&MI, BuiltMI);
    return BuiltMI;
  }

  if (Opcode == SystemZ::LGDR || Opcode == SystemZ::LDGR) {
    bool Op0IsGPR = (Opcode == SystemZ::LGDR);
    bool Op1IsGPR = (Opcode == SystemZ::LDGR);
    // If we're spilling the destination of an LDGR or LGDR, store the
    // source register instead.
    if (OpNum == 0) {
      unsigned StoreOpcode = Op1IsGPR ? SystemZ::STG : SystemZ::STD;
      return BuildMI(*InsertPt->getParent(), InsertPt, MI.getDebugLoc(),
                     get(StoreOpcode))
          .add(MI.getOperand(1))
          .addFrameIndex(FrameIndex)
          .addImm(0)
          .addReg(0);
    }
    // If we're spilling the source of an LDGR or LGDR, load the
    // destination register instead.
    if (OpNum == 1) {
      unsigned LoadOpcode = Op0IsGPR ? SystemZ::LG : SystemZ::LD;
      unsigned Dest = MI.getOperand(0).getReg();
      return BuildMI(*InsertPt->getParent(), InsertPt, MI.getDebugLoc(),
                     get(LoadOpcode), Dest)
          .addFrameIndex(FrameIndex)
          .addImm(0)
          .addReg(0);
    }
  }

  // Look for cases where the source of a simple store or the destination
  // of a simple load is being spilled.  Try to use MVC instead.
  //
  // Although MVC is in practice a fast choice in these cases, it is still
  // logically a bytewise copy.  This means that we cannot use it if the
  // load or store is volatile.  We also wouldn't be able to use MVC if
  // the two memories partially overlap, but that case cannot occur here,
  // because we know that one of the memories is a full frame index.
  //
  // For performance reasons, we also want to avoid using MVC if the addresses
  // might be equal.  We don't worry about that case here, because spill slot
  // coloring happens later, and because we have special code to remove
  // MVCs that turn out to be redundant.
  if (OpNum == 0 && MI.hasOneMemOperand()) {
    MachineMemOperand *MMO = *MI.memoperands_begin();
    if (MMO->getSize() == Size && !MMO->isVolatile()) {
      // Handle conversion of loads.
      if (isSimpleBD12Move(&MI, SystemZII::SimpleBDXLoad)) {
        return BuildMI(*InsertPt->getParent(), InsertPt, MI.getDebugLoc(),
                       get(SystemZ::MVC))
            .addFrameIndex(FrameIndex)
            .addImm(0)
            .addImm(Size)
            .add(MI.getOperand(1))
            .addImm(MI.getOperand(2).getImm())
            .addMemOperand(MMO);
      }
      // Handle conversion of stores.
      if (isSimpleBD12Move(&MI, SystemZII::SimpleBDXStore)) {
        return BuildMI(*InsertPt->getParent(), InsertPt, MI.getDebugLoc(),
                       get(SystemZ::MVC))
            .add(MI.getOperand(1))
            .addImm(MI.getOperand(2).getImm())
            .addImm(Size)
            .addFrameIndex(FrameIndex)
            .addImm(0)
            .addMemOperand(MMO);
      }
    }
  }

  // If the spilled operand is the final one, try to change <INSN>R
  // into <INSN>.
  int MemOpcode = SystemZ::getMemOpcode(Opcode);
  if (MemOpcode >= 0) {
    unsigned NumOps = MI.getNumExplicitOperands();
    if (OpNum == NumOps - 1) {
      const MCInstrDesc &MemDesc = get(MemOpcode);
      uint64_t AccessBytes = SystemZII::getAccessSize(MemDesc.TSFlags);
      assert(AccessBytes != 0 && "Size of access should be known");
      assert(AccessBytes <= Size && "Access outside the frame index");
      uint64_t Offset = Size - AccessBytes;
      MachineInstrBuilder MIB = BuildMI(*InsertPt->getParent(), InsertPt,
                                        MI.getDebugLoc(), get(MemOpcode));
      for (unsigned I = 0; I < OpNum; ++I)
        MIB.add(MI.getOperand(I));
      MIB.addFrameIndex(FrameIndex).addImm(Offset);
      if (MemDesc.TSFlags & SystemZII::HasIndex)
        MIB.addReg(0);
      transferDeadCC(&MI, MIB);
      return MIB;
    }
  }

  return nullptr;
}

MachineInstr *SystemZInstrInfo::foldMemoryOperandImpl(
    MachineFunction &MF, MachineInstr &MI, ArrayRef<unsigned> Ops,
    MachineBasicBlock::iterator InsertPt, MachineInstr &LoadMI,
    LiveIntervals *LIS) const {
  return nullptr;
}

bool SystemZInstrInfo::expandPostRAPseudo(MachineInstr &MI) const {
  switch (MI.getOpcode()) {
  case SystemZ::L128:
    splitMove(MI, SystemZ::LG);
    return true;

  case SystemZ::ST128:
    splitMove(MI, SystemZ::STG);
    return true;

  case SystemZ::LX:
    splitMove(MI, SystemZ::LD);
    return true;

  case SystemZ::STX:
    splitMove(MI, SystemZ::STD);
    return true;

  case SystemZ::LBMux:
    expandRXYPseudo(MI, SystemZ::LB, SystemZ::LBH);
    return true;

  case SystemZ::LHMux:
    expandRXYPseudo(MI, SystemZ::LH, SystemZ::LHH);
    return true;

  case SystemZ::LLCRMux:
    expandZExtPseudo(MI, SystemZ::LLCR, 8);
    return true;

  case SystemZ::LLHRMux:
    expandZExtPseudo(MI, SystemZ::LLHR, 16);
    return true;

  case SystemZ::LLCMux:
    expandRXYPseudo(MI, SystemZ::LLC, SystemZ::LLCH);
    return true;

  case SystemZ::LLHMux:
    expandRXYPseudo(MI, SystemZ::LLH, SystemZ::LLHH);
    return true;

  case SystemZ::LMux:
    expandRXYPseudo(MI, SystemZ::L, SystemZ::LFH);
    return true;

  case SystemZ::LOCMux:
    expandLOCPseudo(MI, SystemZ::LOC, SystemZ::LOCFH);
    return true;

  case SystemZ::LOCHIMux:
    expandLOCPseudo(MI, SystemZ::LOCHI, SystemZ::LOCHHI);
    return true;

  case SystemZ::LOCRMux:
    expandLOCRPseudo(MI, SystemZ::LOCR, SystemZ::LOCFHR);
    return true;

  case SystemZ::STCMux:
    expandRXYPseudo(MI, SystemZ::STC, SystemZ::STCH);
    return true;

  case SystemZ::STHMux:
    expandRXYPseudo(MI, SystemZ::STH, SystemZ::STHH);
    return true;

  case SystemZ::STMux:
    expandRXYPseudo(MI, SystemZ::ST, SystemZ::STFH);
    return true;

  case SystemZ::STOCMux:
    expandLOCPseudo(MI, SystemZ::STOC, SystemZ::STOCFH);
    return true;

  case SystemZ::LHIMux:
    expandRIPseudo(MI, SystemZ::LHI, SystemZ::IIHF, true);
    return true;

  case SystemZ::IIFMux:
    expandRIPseudo(MI, SystemZ::IILF, SystemZ::IIHF, false);
    return true;

  case SystemZ::IILMux:
    expandRIPseudo(MI, SystemZ::IILL, SystemZ::IIHL, false);
    return true;

  case SystemZ::IIHMux:
    expandRIPseudo(MI, SystemZ::IILH, SystemZ::IIHH, false);
    return true;

  case SystemZ::NIFMux:
    expandRIPseudo(MI, SystemZ::NILF, SystemZ::NIHF, false);
    return true;

  case SystemZ::NILMux:
    expandRIPseudo(MI, SystemZ::NILL, SystemZ::NIHL, false);
    return true;

  case SystemZ::NIHMux:
    expandRIPseudo(MI, SystemZ::NILH, SystemZ::NIHH, false);
    return true;

  case SystemZ::OIFMux:
    expandRIPseudo(MI, SystemZ::OILF, SystemZ::OIHF, false);
    return true;

  case SystemZ::OILMux:
    expandRIPseudo(MI, SystemZ::OILL, SystemZ::OIHL, false);
    return true;

  case SystemZ::OIHMux:
    expandRIPseudo(MI, SystemZ::OILH, SystemZ::OIHH, false);
    return true;

  case SystemZ::XIFMux:
    expandRIPseudo(MI, SystemZ::XILF, SystemZ::XIHF, false);
    return true;

  case SystemZ::TMLMux:
    expandRIPseudo(MI, SystemZ::TMLL, SystemZ::TMHL, false);
    return true;

  case SystemZ::TMHMux:
    expandRIPseudo(MI, SystemZ::TMLH, SystemZ::TMHH, false);
    return true;

  case SystemZ::AHIMux:
    expandRIPseudo(MI, SystemZ::AHI, SystemZ::AIH, false);
    return true;

  case SystemZ::AHIMuxK:
    expandRIEPseudo(MI, SystemZ::AHI, SystemZ::AHIK, SystemZ::AIH);
    return true;

  case SystemZ::AFIMux:
    expandRIPseudo(MI, SystemZ::AFI, SystemZ::AIH, false);
    return true;

  case SystemZ::CHIMux:
    expandRIPseudo(MI, SystemZ::CHI, SystemZ::CIH, false);
    return true;

  case SystemZ::CFIMux:
    expandRIPseudo(MI, SystemZ::CFI, SystemZ::CIH, false);
    return true;

  case SystemZ::CLFIMux:
    expandRIPseudo(MI, SystemZ::CLFI, SystemZ::CLIH, false);
    return true;

  case SystemZ::CMux:
    expandRXYPseudo(MI, SystemZ::C, SystemZ::CHF);
    return true;

  case SystemZ::CLMux:
    expandRXYPseudo(MI, SystemZ::CL, SystemZ::CLHF);
    return true;

  case SystemZ::RISBMux: {
    bool DestIsHigh = isHighReg(MI.getOperand(0).getReg());
    bool SrcIsHigh = isHighReg(MI.getOperand(2).getReg());
    if (SrcIsHigh == DestIsHigh)
      MI.setDesc(get(DestIsHigh ? SystemZ::RISBHH : SystemZ::RISBLL));
    else {
      MI.setDesc(get(DestIsHigh ? SystemZ::RISBHL : SystemZ::RISBLH));
      MI.getOperand(5).setImm(MI.getOperand(5).getImm() ^ 32);
    }
    return true;
  }

  case SystemZ::ADJDYNALLOC:
    splitAdjDynAlloc(MI);
    return true;

  case TargetOpcode::LOAD_STACK_GUARD:
    expandLoadStackGuard(&MI);
    return true;

  default:
    return false;
  }
}

unsigned SystemZInstrInfo::getInstSizeInBytes(const MachineInstr &MI) const {
  if (MI.getOpcode() == TargetOpcode::INLINEASM) {
    const MachineFunction *MF = MI.getParent()->getParent();
    const char *AsmStr = MI.getOperand(0).getSymbolName();
    return getInlineAsmLength(AsmStr, *MF->getTarget().getMCAsmInfo());
  }
  return MI.getDesc().getSize();
}

SystemZII::Branch
SystemZInstrInfo::getBranchInfo(const MachineInstr &MI) const {
  switch (MI.getOpcode()) {
  case SystemZ::BR:
  case SystemZ::J:
  case SystemZ::JG:
    return SystemZII::Branch(SystemZII::BranchNormal, SystemZ::CCMASK_ANY,
                             SystemZ::CCMASK_ANY, &MI.getOperand(0));

  case SystemZ::BRC:
  case SystemZ::BRCL:
    return SystemZII::Branch(SystemZII::BranchNormal, MI.getOperand(0).getImm(),
                             MI.getOperand(1).getImm(), &MI.getOperand(2));

  case SystemZ::BRCT:
  case SystemZ::BRCTH:
    return SystemZII::Branch(SystemZII::BranchCT, SystemZ::CCMASK_ICMP,
                             SystemZ::CCMASK_CMP_NE, &MI.getOperand(2));

  case SystemZ::BRCTG:
    return SystemZII::Branch(SystemZII::BranchCTG, SystemZ::CCMASK_ICMP,
                             SystemZ::CCMASK_CMP_NE, &MI.getOperand(2));

  case SystemZ::CIJ:
  case SystemZ::CRJ:
    return SystemZII::Branch(SystemZII::BranchC, SystemZ::CCMASK_ICMP,
                             MI.getOperand(2).getImm(), &MI.getOperand(3));

  case SystemZ::CLIJ:
  case SystemZ::CLRJ:
    return SystemZII::Branch(SystemZII::BranchCL, SystemZ::CCMASK_ICMP,
                             MI.getOperand(2).getImm(), &MI.getOperand(3));

  case SystemZ::CGIJ:
  case SystemZ::CGRJ:
    return SystemZII::Branch(SystemZII::BranchCG, SystemZ::CCMASK_ICMP,
                             MI.getOperand(2).getImm(), &MI.getOperand(3));

  case SystemZ::CLGIJ:
  case SystemZ::CLGRJ:
    return SystemZII::Branch(SystemZII::BranchCLG, SystemZ::CCMASK_ICMP,
                             MI.getOperand(2).getImm(), &MI.getOperand(3));

  default:
    llvm_unreachable("Unrecognized branch opcode");
  }
}

void SystemZInstrInfo::getLoadStoreOpcodes(const TargetRegisterClass *RC,
                                           unsigned &LoadOpcode,
                                           unsigned &StoreOpcode) const {
  if (RC == &SystemZ::GR32BitRegClass || RC == &SystemZ::ADDR32BitRegClass) {
    LoadOpcode = SystemZ::L;
    StoreOpcode = SystemZ::ST;
  } else if (RC == &SystemZ::GRH32BitRegClass) {
    LoadOpcode = SystemZ::LFH;
    StoreOpcode = SystemZ::STFH;
  } else if (RC == &SystemZ::GRX32BitRegClass) {
    LoadOpcode = SystemZ::LMux;
    StoreOpcode = SystemZ::STMux;
  } else if (RC == &SystemZ::GR64BitRegClass ||
             RC == &SystemZ::ADDR64BitRegClass) {
    LoadOpcode = SystemZ::LG;
    StoreOpcode = SystemZ::STG;
  } else if (RC == &SystemZ::GR128BitRegClass ||
             RC == &SystemZ::ADDR128BitRegClass) {
    LoadOpcode = SystemZ::L128;
    StoreOpcode = SystemZ::ST128;
  } else if (RC == &SystemZ::FP32BitRegClass) {
    LoadOpcode = SystemZ::LE;
    StoreOpcode = SystemZ::STE;
  } else if (RC == &SystemZ::FP64BitRegClass) {
    LoadOpcode = SystemZ::LD;
    StoreOpcode = SystemZ::STD;
  } else if (RC == &SystemZ::FP128BitRegClass) {
    LoadOpcode = SystemZ::LX;
    StoreOpcode = SystemZ::STX;
  } else if (RC == &SystemZ::VR32BitRegClass) {
    LoadOpcode = SystemZ::VL32;
    StoreOpcode = SystemZ::VST32;
  } else if (RC == &SystemZ::VR64BitRegClass) {
    LoadOpcode = SystemZ::VL64;
    StoreOpcode = SystemZ::VST64;
  } else if (RC == &SystemZ::VF128BitRegClass ||
             RC == &SystemZ::VR128BitRegClass) {
    LoadOpcode = SystemZ::VL;
    StoreOpcode = SystemZ::VST;
  } else
    llvm_unreachable("Unsupported regclass to load or store");
}

unsigned SystemZInstrInfo::getOpcodeForOffset(unsigned Opcode,
                                              int64_t Offset) const {
  const MCInstrDesc &MCID = get(Opcode);
  int64_t Offset2 = (MCID.TSFlags & SystemZII::Is128Bit ? Offset + 8 : Offset);
  if (isUInt<12>(Offset) && isUInt<12>(Offset2)) {
    // Get the instruction to use for unsigned 12-bit displacements.
    int Disp12Opcode = SystemZ::getDisp12Opcode(Opcode);
    if (Disp12Opcode >= 0)
      return Disp12Opcode;

    // All address-related instructions can use unsigned 12-bit
    // displacements.
    return Opcode;
  }
  if (isInt<20>(Offset) && isInt<20>(Offset2)) {
    // Get the instruction to use for signed 20-bit displacements.
    int Disp20Opcode = SystemZ::getDisp20Opcode(Opcode);
    if (Disp20Opcode >= 0)
      return Disp20Opcode;

    // Check whether Opcode allows signed 20-bit displacements.
    if (MCID.TSFlags & SystemZII::Has20BitOffset)
      return Opcode;
  }
  return 0;
}

unsigned SystemZInstrInfo::getLoadAndTest(unsigned Opcode) const {
  switch (Opcode) {
  case SystemZ::L:      return SystemZ::LT;
  case SystemZ::LY:     return SystemZ::LT;
  case SystemZ::LG:     return SystemZ::LTG;
  case SystemZ::LGF:    return SystemZ::LTGF;
  case SystemZ::LR:     return SystemZ::LTR;
  case SystemZ::LGFR:   return SystemZ::LTGFR;
  case SystemZ::LGR:    return SystemZ::LTGR;
  case SystemZ::LER:    return SystemZ::LTEBR;
  case SystemZ::LDR:    return SystemZ::LTDBR;
  case SystemZ::LXR:    return SystemZ::LTXBR;
  case SystemZ::LCDFR:  return SystemZ::LCDBR;
  case SystemZ::LPDFR:  return SystemZ::LPDBR;
  case SystemZ::LNDFR:  return SystemZ::LNDBR;
  case SystemZ::LCDFR_32:  return SystemZ::LCEBR;
  case SystemZ::LPDFR_32:  return SystemZ::LPEBR;
  case SystemZ::LNDFR_32:  return SystemZ::LNEBR;
  // On zEC12 we prefer to use RISBGN.  But if there is a chance to
  // actually use the condition code, we may turn it back into RISGB.
  // Note that RISBG is not really a "load-and-test" instruction,
  // but sets the same condition code values, so is OK to use here.
  case SystemZ::RISBGN: return SystemZ::RISBG;
  default:              return 0;
  }
}

// Return true if Mask matches the regexp 0*1+0*, given that zero masks
// have already been filtered out.  Store the first set bit in LSB and
// the number of set bits in Length if so.
static bool isStringOfOnes(uint64_t Mask, unsigned &LSB, unsigned &Length) {
  unsigned First = findFirstSet(Mask);
  uint64_t Top = (Mask >> First) + 1;
  if ((Top & -Top) == Top) {
    LSB = First;
    Length = findFirstSet(Top);
    return true;
  }
  return false;
}

bool SystemZInstrInfo::isRxSBGMask(uint64_t Mask, unsigned BitSize,
                                   unsigned &Start, unsigned &End) const {
  // Reject trivial all-zero masks.
  Mask &= allOnes(BitSize);
  if (Mask == 0)
    return false;

  // Handle the 1+0+ or 0+1+0* cases.  Start then specifies the index of
  // the msb and End specifies the index of the lsb.
  unsigned LSB, Length;
  if (isStringOfOnes(Mask, LSB, Length)) {
    Start = 63 - (LSB + Length - 1);
    End = 63 - LSB;
    return true;
  }

  // Handle the wrap-around 1+0+1+ cases.  Start then specifies the msb
  // of the low 1s and End specifies the lsb of the high 1s.
  if (isStringOfOnes(Mask ^ allOnes(BitSize), LSB, Length)) {
    assert(LSB > 0 && "Bottom bit must be set");
    assert(LSB + Length < BitSize && "Top bit must be set");
    Start = 63 - (LSB - 1);
    End = 63 - (LSB + Length);
    return true;
  }

  return false;
}

unsigned SystemZInstrInfo::getFusedCompare(unsigned Opcode,
                                           SystemZII::FusedCompareType Type,
                                           const MachineInstr *MI) const {
  switch (Opcode) {
  case SystemZ::CHI:
  case SystemZ::CGHI:
    if (!(MI && isInt<8>(MI->getOperand(1).getImm())))
      return 0;
    break;
  case SystemZ::CLFI:
  case SystemZ::CLGFI:
    if (!(MI && isUInt<8>(MI->getOperand(1).getImm())))
      return 0;
    break;
  case SystemZ::CL:
  case SystemZ::CLG:
    if (!STI.hasMiscellaneousExtensions())
      return 0;
    if (!(MI && MI->getOperand(3).getReg() == 0))
      return 0;
    break;
  }
  switch (Type) {
  case SystemZII::CompareAndBranch:
    switch (Opcode) {
    case SystemZ::CR:
      return SystemZ::CRJ;
    case SystemZ::CGR:
      return SystemZ::CGRJ;
    case SystemZ::CHI:
      return SystemZ::CIJ;
    case SystemZ::CGHI:
      return SystemZ::CGIJ;
    case SystemZ::CLR:
      return SystemZ::CLRJ;
    case SystemZ::CLGR:
      return SystemZ::CLGRJ;
    case SystemZ::CLFI:
      return SystemZ::CLIJ;
    case SystemZ::CLGFI:
      return SystemZ::CLGIJ;
    default:
      return 0;
    }
  case SystemZII::CompareAndReturn:
    switch (Opcode) {
    case SystemZ::CR:
      return SystemZ::CRBReturn;
    case SystemZ::CGR:
      return SystemZ::CGRBReturn;
    case SystemZ::CHI:
      return SystemZ::CIBReturn;
    case SystemZ::CGHI:
      return SystemZ::CGIBReturn;
    case SystemZ::CLR:
      return SystemZ::CLRBReturn;
    case SystemZ::CLGR:
      return SystemZ::CLGRBReturn;
    case SystemZ::CLFI:
      return SystemZ::CLIBReturn;
    case SystemZ::CLGFI:
      return SystemZ::CLGIBReturn;
    default:
      return 0;
    }
  case SystemZII::CompareAndSibcall:
    switch (Opcode) {
    case SystemZ::CR:
      return SystemZ::CRBCall;
    case SystemZ::CGR:
      return SystemZ::CGRBCall;
    case SystemZ::CHI:
      return SystemZ::CIBCall;
    case SystemZ::CGHI:
      return SystemZ::CGIBCall;
    case SystemZ::CLR:
      return SystemZ::CLRBCall;
    case SystemZ::CLGR:
      return SystemZ::CLGRBCall;
    case SystemZ::CLFI:
      return SystemZ::CLIBCall;
    case SystemZ::CLGFI:
      return SystemZ::CLGIBCall;
    default:
      return 0;
    }
  case SystemZII::CompareAndTrap:
    switch (Opcode) {
    case SystemZ::CR:
      return SystemZ::CRT;
    case SystemZ::CGR:
      return SystemZ::CGRT;
    case SystemZ::CHI:
      return SystemZ::CIT;
    case SystemZ::CGHI:
      return SystemZ::CGIT;
    case SystemZ::CLR:
      return SystemZ::CLRT;
    case SystemZ::CLGR:
      return SystemZ::CLGRT;
    case SystemZ::CLFI:
      return SystemZ::CLFIT;
    case SystemZ::CLGFI:
      return SystemZ::CLGIT;
    case SystemZ::CL:
      return SystemZ::CLT;
    case SystemZ::CLG:
      return SystemZ::CLGT;
    default:
      return 0;
    }
  }
  return 0;
}

unsigned SystemZInstrInfo::getLoadAndTrap(unsigned Opcode) const {
  if (!STI.hasLoadAndTrap())
    return 0;
  switch (Opcode) {
  case SystemZ::L:
  case SystemZ::LY:
    return SystemZ::LAT;
  case SystemZ::LG:
    return SystemZ::LGAT;
  case SystemZ::LFH:
    return SystemZ::LFHAT;
  case SystemZ::LLGF:
    return SystemZ::LLGFAT;
  case SystemZ::LLGT:
    return SystemZ::LLGTAT;
  }
  return 0;
}

void SystemZInstrInfo::loadImmediate(MachineBasicBlock &MBB,
                                     MachineBasicBlock::iterator MBBI,
                                     unsigned Reg, uint64_t Value) const {
  DebugLoc DL = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
  unsigned Opcode;
  if (isInt<16>(Value))
    Opcode = SystemZ::LGHI;
  else if (SystemZ::isImmLL(Value))
    Opcode = SystemZ::LLILL;
  else if (SystemZ::isImmLH(Value)) {
    Opcode = SystemZ::LLILH;
    Value >>= 16;
  } else {
    assert(isInt<32>(Value) && "Huge values not handled yet");
    Opcode = SystemZ::LGFI;
  }
  BuildMI(MBB, MBBI, DL, get(Opcode), Reg).addImm(Value);
}

bool SystemZInstrInfo::
areMemAccessesTriviallyDisjoint(MachineInstr &MIa, MachineInstr &MIb,
                                AliasAnalysis *AA) const {

  if (!MIa.hasOneMemOperand() || !MIb.hasOneMemOperand())
    return false;

  // If mem-operands show that the same address Value is used by both
  // instructions, check for non-overlapping offsets and widths. Not
  // sure if a register based analysis would be an improvement...

  MachineMemOperand *MMOa = *MIa.memoperands_begin();
  MachineMemOperand *MMOb = *MIb.memoperands_begin();
  const Value *VALa = MMOa->getValue();
  const Value *VALb = MMOb->getValue();
  bool SameVal = (VALa && VALb && (VALa == VALb));
  if (!SameVal) {
    const PseudoSourceValue *PSVa = MMOa->getPseudoValue();
    const PseudoSourceValue *PSVb = MMOb->getPseudoValue();
    if (PSVa && PSVb && (PSVa == PSVb))
      SameVal = true;
  }
  if (SameVal) {
    int OffsetA = MMOa->getOffset(), OffsetB = MMOb->getOffset();
    int WidthA = MMOa->getSize(), WidthB = MMOb->getSize();
    int LowOffset = OffsetA < OffsetB ? OffsetA : OffsetB;
    int HighOffset = OffsetA < OffsetB ? OffsetB : OffsetA;
    int LowWidth = (LowOffset == OffsetA) ? WidthA : WidthB;
    if (LowOffset + LowWidth <= HighOffset)
      return true;
  }

  return false;
}