AArch64ExpandPseudoInsts.cpp

Go to the documentation of this file.

//===- AArch64ExpandPseudoInsts.cpp - Expand pseudo instructions ----------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains a pass that expands pseudo instructions into target
// instructions to allow proper scheduling and other late optimizations.  This
// pass should be run after register allocation but before the post-regalloc
// scheduling pass.
//
//===----------------------------------------------------------------------===//

#include "AArch64InstrInfo.h"
#include "AArch64Subtarget.h"
#include "MCTargetDesc/AArch64AddressingModes.h"
#include "Utils/AArch64BaseInfo.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Triple.h"
#include "llvm/CodeGen/LivePhysRegs.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/MC/MCInstrDesc.h"
#include "llvm/Pass.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Target/TargetMachine.h"
#include <cassert>
#include <cstdint>
#include <iterator>
#include <limits>
#include <utility>

using namespace llvm;

#define AARCH64_EXPAND_PSEUDO_NAME "AArch64 pseudo instruction expansion pass"

namespace {

class AArch64ExpandPseudo : public MachineFunctionPass {
public:
  const AArch64InstrInfo *TII;

  static char ID;

  AArch64ExpandPseudo() : MachineFunctionPass(ID) {
    initializeAArch64ExpandPseudoPass(*PassRegistry::getPassRegistry());
  }

  bool runOnMachineFunction(MachineFunction &Fn) override;

  StringRef getPassName() const override { return AARCH64_EXPAND_PSEUDO_NAME; }

private:
  bool expandMBB(MachineBasicBlock &MBB);
  bool expandMI(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
                MachineBasicBlock::iterator &NextMBBI);
  bool expandMOVImm(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
                    unsigned BitSize);
  bool expandMOVImmSimple(MachineBasicBlock &MBB,
                          MachineBasicBlock::iterator MBBI,
                          unsigned BitSize,
                          unsigned OneChunks,
                          unsigned ZeroChunks);

  bool expandCMP_SWAP(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
                      unsigned LdarOp, unsigned StlrOp, unsigned CmpOp,
                      unsigned ExtendImm, unsigned ZeroReg,
                      MachineBasicBlock::iterator &NextMBBI);
  bool expandCMP_SWAP_128(MachineBasicBlock &MBB,
                          MachineBasicBlock::iterator MBBI,
                          MachineBasicBlock::iterator &NextMBBI);
};

} // end anonymous namespace

char AArch64ExpandPseudo::ID = 0;

INITIALIZE_PASS(AArch64ExpandPseudo, "aarch64-expand-pseudo",
                AARCH64_EXPAND_PSEUDO_NAME, false, false)

/// Transfer implicit operands on the pseudo instruction to the
/// instructions created from the expansion.
static void transferImpOps(MachineInstr &OldMI, MachineInstrBuilder &UseMI,
                           MachineInstrBuilder &DefMI) {
  const MCInstrDesc &Desc = OldMI.getDesc();
  for (unsigned i = Desc.getNumOperands(), e = OldMI.getNumOperands(); i != e;
       ++i) {
    const MachineOperand &MO = OldMI.getOperand(i);
    assert(MO.isReg() && MO.getReg());
    if (MO.isUse())
      UseMI.add(MO);
    else
      DefMI.add(MO);
  }
}

/// Helper function which extracts the specified 16-bit chunk from a
/// 64-bit value.
static uint64_t getChunk(uint64_t Imm, unsigned ChunkIdx) {
  assert(ChunkIdx < 4 && "Out of range chunk index specified!");

  return (Imm >> (ChunkIdx * 16)) & 0xFFFF;
}

/// Check whether the given 16-bit chunk replicated to full 64-bit width
/// can be materialized with an ORR instruction.
static bool canUseOrr(uint64_t Chunk, uint64_t &Encoding) {
  Chunk = (Chunk << 48) | (Chunk << 32) | (Chunk << 16) | Chunk;

  return AArch64_AM::processLogicalImmediate(Chunk, 64, Encoding);
}

/// Check for identical 16-bit chunks within the constant and if so
/// materialize them with a single ORR instruction. The remaining one or two
/// 16-bit chunks will be materialized with MOVK instructions.
///
/// This allows us to materialize constants like |A|B|A|A| or |A|B|C|A| (order
/// of the chunks doesn't matter), assuming |A|A|A|A| can be materialized with
/// an ORR instruction.
static bool tryToreplicateChunks(uint64_t UImm, MachineInstr &MI,
                                 MachineBasicBlock &MBB,
                                 MachineBasicBlock::iterator &MBBI,
                                 const AArch64InstrInfo *TII) {
  using CountMap = DenseMap<uint64_t, unsigned>;

  CountMap Counts;

  // Scan the constant and count how often every chunk occurs.
  for (unsigned Idx = 0; Idx < 4; ++Idx)
    ++Counts[getChunk(UImm, Idx)];

  // Traverse the chunks to find one which occurs more than once.
  for (CountMap::const_iterator Chunk = Counts.begin(), End = Counts.end();
       Chunk != End; ++Chunk) {
    const uint64_t ChunkVal = Chunk->first;
    const unsigned Count = Chunk->second;

    uint64_t Encoding = 0;

    // We are looking for chunks which have two or three instances and can be
    // materialized with an ORR instruction.
    if ((Count != 2 && Count != 3) || !canUseOrr(ChunkVal, Encoding))
      continue;

    const bool CountThree = Count == 3;
    // Create the ORR-immediate instruction.
    MachineInstrBuilder MIB =
        BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(AArch64::ORRXri))
            .add(MI.getOperand(0))
            .addReg(AArch64::XZR)
            .addImm(Encoding);

    const unsigned DstReg = MI.getOperand(0).getReg();
    const bool DstIsDead = MI.getOperand(0).isDead();

    unsigned ShiftAmt = 0;
    uint64_t Imm16 = 0;
    // Find the first chunk not materialized with the ORR instruction.
    for (; ShiftAmt < 64; ShiftAmt += 16) {
      Imm16 = (UImm >> ShiftAmt) & 0xFFFF;

      if (Imm16 != ChunkVal)
        break;
    }

    // Create the first MOVK instruction.
    MachineInstrBuilder MIB1 =
        BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(AArch64::MOVKXi))
            .addReg(DstReg,
                    RegState::Define | getDeadRegState(DstIsDead && CountThree))
            .addReg(DstReg)
            .addImm(Imm16)
            .addImm(AArch64_AM::getShifterImm(AArch64_AM::LSL, ShiftAmt));

    // In case we have three instances the whole constant is now materialized
    // and we can exit.
    if (CountThree) {
      transferImpOps(MI, MIB, MIB1);
      MI.eraseFromParent();
      return true;
    }

    // Find the remaining chunk which needs to be materialized.
    for (ShiftAmt += 16; ShiftAmt < 64; ShiftAmt += 16) {
      Imm16 = (UImm >> ShiftAmt) & 0xFFFF;

      if (Imm16 != ChunkVal)
        break;
    }

    // Create the second MOVK instruction.
    MachineInstrBuilder MIB2 =
        BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(AArch64::MOVKXi))
            .addReg(DstReg, RegState::Define | getDeadRegState(DstIsDead))
            .addReg(DstReg)
            .addImm(Imm16)
            .addImm(AArch64_AM::getShifterImm(AArch64_AM::LSL, ShiftAmt));

    transferImpOps(MI, MIB, MIB2);
    MI.eraseFromParent();
    return true;
  }

  return false;
}

/// Check whether this chunk matches the pattern '1...0...'. This pattern
/// starts a contiguous sequence of ones if we look at the bits from the LSB
/// towards the MSB.
static bool isStartChunk(uint64_t Chunk) {
  if (Chunk == 0 || Chunk == std::numeric_limits<uint64_t>::max())
    return false;

  return isMask_64(~Chunk);
}

/// Check whether this chunk matches the pattern '0...1...' This pattern
/// ends a contiguous sequence of ones if we look at the bits from the LSB
/// towards the MSB.
static bool isEndChunk(uint64_t Chunk) {
  if (Chunk == 0 || Chunk == std::numeric_limits<uint64_t>::max())
    return false;

  return isMask_64(Chunk);
}

/// Clear or set all bits in the chunk at the given index.
static uint64_t updateImm(uint64_t Imm, unsigned Idx, bool Clear) {
  const uint64_t Mask = 0xFFFF;

  if (Clear)
    // Clear chunk in the immediate.
    Imm &= ~(Mask << (Idx * 16));
  else
    // Set all bits in the immediate for the particular chunk.
    Imm |= Mask << (Idx * 16);

  return Imm;
}

/// Check whether the constant contains a sequence of contiguous ones,
/// which might be interrupted by one or two chunks. If so, materialize the
/// sequence of contiguous ones with an ORR instruction.
/// Materialize the chunks which are either interrupting the sequence or outside
/// of the sequence with a MOVK instruction.
///
/// Assuming S is a chunk which starts the sequence (1...0...), E is a chunk
/// which ends the sequence (0...1...). Then we are looking for constants which
/// contain at least one S and E chunk.
/// E.g. |E|A|B|S|, |A|E|B|S| or |A|B|E|S|.
///
/// We are also looking for constants like |S|A|B|E| where the contiguous
/// sequence of ones wraps around the MSB into the LSB.
static bool trySequenceOfOnes(uint64_t UImm, MachineInstr &MI,
                              MachineBasicBlock &MBB,
                              MachineBasicBlock::iterator &MBBI,
                              const AArch64InstrInfo *TII) {
  const int NotSet = -1;
  const uint64_t Mask = 0xFFFF;

  int StartIdx = NotSet;
  int EndIdx = NotSet;
  // Try to find the chunks which start/end a contiguous sequence of ones.
  for (int Idx = 0; Idx < 4; ++Idx) {
    int64_t Chunk = getChunk(UImm, Idx);
    // Sign extend the 16-bit chunk to 64-bit.
    Chunk = (Chunk << 48) >> 48;

    if (isStartChunk(Chunk))
      StartIdx = Idx;
    else if (isEndChunk(Chunk))
      EndIdx = Idx;
  }

  // Early exit in case we can't find a start/end chunk.
  if (StartIdx == NotSet || EndIdx == NotSet)
    return false;

  // Outside of the contiguous sequence of ones everything needs to be zero.
  uint64_t Outside = 0;
  // Chunks between the start and end chunk need to have all their bits set.
  uint64_t Inside = Mask;

  // If our contiguous sequence of ones wraps around from the MSB into the LSB,
  // just swap indices and pretend we are materializing a contiguous sequence
  // of zeros surrounded by a contiguous sequence of ones.
  if (StartIdx > EndIdx) {
    std::swap(StartIdx, EndIdx);
    std::swap(Outside, Inside);
  }

  uint64_t OrrImm = UImm;
  int FirstMovkIdx = NotSet;
  int SecondMovkIdx = NotSet;

  // Find out which chunks we need to patch up to obtain a contiguous sequence
  // of ones.
  for (int Idx = 0; Idx < 4; ++Idx) {
    const uint64_t Chunk = getChunk(UImm, Idx);

    // Check whether we are looking at a chunk which is not part of the
    // contiguous sequence of ones.
    if ((Idx < StartIdx || EndIdx < Idx) && Chunk != Outside) {
      OrrImm = updateImm(OrrImm, Idx, Outside == 0);

      // Remember the index we need to patch.
      if (FirstMovkIdx == NotSet)
        FirstMovkIdx = Idx;
      else
        SecondMovkIdx = Idx;

      // Check whether we are looking a chunk which is part of the contiguous
      // sequence of ones.
    } else if (Idx > StartIdx && Idx < EndIdx && Chunk != Inside) {
      OrrImm = updateImm(OrrImm, Idx, Inside != Mask);

      // Remember the index we need to patch.
      if (FirstMovkIdx == NotSet)
        FirstMovkIdx = Idx;
      else
        SecondMovkIdx = Idx;
    }
  }
  assert(FirstMovkIdx != NotSet && "Constant materializable with single ORR!");

  // Create the ORR-immediate instruction.
  uint64_t Encoding = 0;
  AArch64_AM::processLogicalImmediate(OrrImm, 64, Encoding);
  MachineInstrBuilder MIB =
      BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(AArch64::ORRXri))
          .add(MI.getOperand(0))
          .addReg(AArch64::XZR)
          .addImm(Encoding);

  const unsigned DstReg = MI.getOperand(0).getReg();
  const bool DstIsDead = MI.getOperand(0).isDead();

  const bool SingleMovk = SecondMovkIdx == NotSet;
  // Create the first MOVK instruction.
  MachineInstrBuilder MIB1 =
      BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(AArch64::MOVKXi))
          .addReg(DstReg,
                  RegState::Define | getDeadRegState(DstIsDead && SingleMovk))
          .addReg(DstReg)
          .addImm(getChunk(UImm, FirstMovkIdx))
          .addImm(
              AArch64_AM::getShifterImm(AArch64_AM::LSL, FirstMovkIdx * 16));

  // Early exit in case we only need to emit a single MOVK instruction.
  if (SingleMovk) {
    transferImpOps(MI, MIB, MIB1);
    MI.eraseFromParent();
    return true;
  }

  // Create the second MOVK instruction.
  MachineInstrBuilder MIB2 =
      BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(AArch64::MOVKXi))
          .addReg(DstReg, RegState::Define | getDeadRegState(DstIsDead))
          .addReg(DstReg)
          .addImm(getChunk(UImm, SecondMovkIdx))
          .addImm(
              AArch64_AM::getShifterImm(AArch64_AM::LSL, SecondMovkIdx * 16));

  transferImpOps(MI, MIB, MIB2);
  MI.eraseFromParent();
  return true;
}

/// Expand a MOVi32imm or MOVi64imm pseudo instruction to one or more
/// real move-immediate instructions to synthesize the immediate.
bool AArch64ExpandPseudo::expandMOVImm(MachineBasicBlock &MBB,
                                       MachineBasicBlock::iterator MBBI,
                                       unsigned BitSize) {
  MachineInstr &MI = *MBBI;
  unsigned DstReg = MI.getOperand(0).getReg();
  uint64_t Imm = MI.getOperand(1).getImm();
  const unsigned Mask = 0xFFFF;

  if (DstReg == AArch64::XZR || DstReg == AArch64::WZR) {
    // Useless def, and we don't want to risk creating an invalid ORR (which
    // would really write to sp).
    MI.eraseFromParent();
    return true;
  }

  // Scan the immediate and count the number of 16-bit chunks which are either
  // all ones or all zeros.
  unsigned OneChunks = 0;
  unsigned ZeroChunks = 0;
  for (unsigned Shift = 0; Shift < BitSize; Shift += 16) {
    const unsigned Chunk = (Imm >> Shift) & Mask;
    if (Chunk == Mask)
      OneChunks++;
    else if (Chunk == 0)
      ZeroChunks++;
  }

  // FIXME: Prefer MOVZ/MOVN over ORR because of the rules for the "mov"
  // alias.

  // Try a single ORR.
  uint64_t UImm = Imm << (64 - BitSize) >> (64 - BitSize);
  uint64_t Encoding;
  if (AArch64_AM::processLogicalImmediate(UImm, BitSize, Encoding)) {
    unsigned Opc = (BitSize == 32 ? AArch64::ORRWri : AArch64::ORRXri);
    MachineInstrBuilder MIB =
        BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(Opc))
            .add(MI.getOperand(0))
            .addReg(BitSize == 32 ? AArch64::WZR : AArch64::XZR)
            .addImm(Encoding);
    transferImpOps(MI, MIB, MIB);
    MI.eraseFromParent();
    return true;
  }

  // Two instruction sequences.
  //
  // Prefer MOVZ/MOVN followed by MOVK; it's more readable, and possibly the
  // fastest sequence with fast literal generation.
  if (OneChunks >= (BitSize / 16) - 2 || ZeroChunks >= (BitSize / 16) - 2)
    return expandMOVImmSimple(MBB, MBBI, BitSize, OneChunks, ZeroChunks);

  assert(BitSize == 64 && "All 32-bit immediates can be expanded with a"
                          "MOVZ/MOVK pair");

  // Try other two-instruction sequences.

  // 64-bit ORR followed by MOVK.
  // We try to construct the ORR immediate in three different ways: either we
  // zero out the chunk which will be replaced, we fill the chunk which will
  // be replaced with ones, or we take the bit pattern from the other half of
  // the 64-bit immediate. This is comprehensive because of the way ORR
  // immediates are constructed.
  for (unsigned Shift = 0; Shift < BitSize; Shift += 16) {
    uint64_t ShiftedMask = (0xFFFFULL << Shift);
    uint64_t ZeroChunk = UImm & ~ShiftedMask;
    uint64_t OneChunk = UImm | ShiftedMask;
    uint64_t RotatedImm = (UImm << 32) | (UImm >> 32);
    uint64_t ReplicateChunk = ZeroChunk | (RotatedImm & ShiftedMask);
    if (AArch64_AM::processLogicalImmediate(ZeroChunk, BitSize, Encoding) ||
        AArch64_AM::processLogicalImmediate(OneChunk, BitSize, Encoding) ||
        AArch64_AM::processLogicalImmediate(ReplicateChunk,
                                            BitSize, Encoding)) {
      // Create the ORR-immediate instruction.
      MachineInstrBuilder MIB =
          BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(AArch64::ORRXri))
              .add(MI.getOperand(0))
              .addReg(AArch64::XZR)
              .addImm(Encoding);

      // Create the MOVK instruction.
      const unsigned Imm16 = getChunk(UImm, Shift / 16);
      const unsigned DstReg = MI.getOperand(0).getReg();
      const bool DstIsDead = MI.getOperand(0).isDead();
      MachineInstrBuilder MIB1 =
          BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(AArch64::MOVKXi))
              .addReg(DstReg, RegState::Define | getDeadRegState(DstIsDead))
              .addReg(DstReg)
              .addImm(Imm16)
              .addImm(AArch64_AM::getShifterImm(AArch64_AM::LSL, Shift));

      transferImpOps(MI, MIB, MIB1);
      MI.eraseFromParent();
      return true;
    }
  }

  // FIXME: Add more two-instruction sequences.

  // Three instruction sequences.
  //
  // Prefer MOVZ/MOVN followed by two MOVK; it's more readable, and possibly
  // the fastest sequence with fast literal generation. (If neither MOVK is
  // part of a fast literal generation pair, it could be slower than the
  // four-instruction sequence, but we won't worry about that for now.)
  if (OneChunks || ZeroChunks)
    return expandMOVImmSimple(MBB, MBBI, BitSize, OneChunks, ZeroChunks);

  // Check for identical 16-bit chunks within the constant and if so materialize
  // them with a single ORR instruction. The remaining one or two 16-bit chunks
  // will be materialized with MOVK instructions.
  if (BitSize == 64 && tryToreplicateChunks(UImm, MI, MBB, MBBI, TII))
    return true;

  // Check whether the constant contains a sequence of contiguous ones, which
  // might be interrupted by one or two chunks. If so, materialize the sequence
  // of contiguous ones with an ORR instruction. Materialize the chunks which
  // are either interrupting the sequence or outside of the sequence with a
  // MOVK instruction.
  if (BitSize == 64 && trySequenceOfOnes(UImm, MI, MBB, MBBI, TII))
    return true;

  // We found no possible two or three instruction sequence; use the general
  // four-instruction sequence.
  return expandMOVImmSimple(MBB, MBBI, BitSize, OneChunks, ZeroChunks);
}

/// \brief Expand a MOVi32imm or MOVi64imm pseudo instruction to a
/// MOVZ or MOVN of width BitSize followed by up to 3 MOVK instructions.
bool AArch64ExpandPseudo::expandMOVImmSimple(MachineBasicBlock &MBB,
                                             MachineBasicBlock::iterator MBBI,
                                             unsigned BitSize,
                                             unsigned OneChunks,
                                             unsigned ZeroChunks) {
  MachineInstr &MI = *MBBI;
  unsigned DstReg = MI.getOperand(0).getReg();
  uint64_t Imm = MI.getOperand(1).getImm();
  const unsigned Mask = 0xFFFF;

  // Use a MOVZ or MOVN instruction to set the high bits, followed by one or
  // more MOVK instructions to insert additional 16-bit portions into the
  // lower bits.
  bool isNeg = false;

  // Use MOVN to materialize the high bits if we have more all one chunks
  // than all zero chunks.
  if (OneChunks > ZeroChunks) {
    isNeg = true;
    Imm = ~Imm;
  }

  unsigned FirstOpc;
  if (BitSize == 32) {
    Imm &= (1LL << 32) - 1;
    FirstOpc = (isNeg ? AArch64::MOVNWi : AArch64::MOVZWi);
  } else {
    FirstOpc = (isNeg ? AArch64::MOVNXi : AArch64::MOVZXi);
  }
  unsigned Shift = 0;     // LSL amount for high bits with MOVZ/MOVN
  unsigned LastShift = 0; // LSL amount for last MOVK
  if (Imm != 0) {
    unsigned LZ = countLeadingZeros(Imm);
    unsigned TZ = countTrailingZeros(Imm);
    Shift = (TZ / 16) * 16;
    LastShift = ((63 - LZ) / 16) * 16;
  }
  unsigned Imm16 = (Imm >> Shift) & Mask;
  bool DstIsDead = MI.getOperand(0).isDead();
  MachineInstrBuilder MIB1 =
      BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(FirstOpc))
          .addReg(DstReg, RegState::Define |
                  getDeadRegState(DstIsDead && Shift == LastShift))
          .addImm(Imm16)
          .addImm(AArch64_AM::getShifterImm(AArch64_AM::LSL, Shift));

  // If a MOVN was used for the high bits of a negative value, flip the rest
  // of the bits back for use with MOVK.
  if (isNeg)
    Imm = ~Imm;

  if (Shift == LastShift) {
    transferImpOps(MI, MIB1, MIB1);
    MI.eraseFromParent();
    return true;
  }

  MachineInstrBuilder MIB2;
  unsigned Opc = (BitSize == 32 ? AArch64::MOVKWi : AArch64::MOVKXi);
  while (Shift < LastShift) {
    Shift += 16;
    Imm16 = (Imm >> Shift) & Mask;
    if (Imm16 == (isNeg ? Mask : 0))
      continue; // This 16-bit portion is already set correctly.
    MIB2 = BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(Opc))
               .addReg(DstReg,
                       RegState::Define |
                       getDeadRegState(DstIsDead && Shift == LastShift))
               .addReg(DstReg)
               .addImm(Imm16)
               .addImm(AArch64_AM::getShifterImm(AArch64_AM::LSL, Shift));
  }

  transferImpOps(MI, MIB1, MIB2);
  MI.eraseFromParent();
  return true;
}

bool AArch64ExpandPseudo::expandCMP_SWAP(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI, unsigned LdarOp,
    unsigned StlrOp, unsigned CmpOp, unsigned ExtendImm, unsigned ZeroReg,
    MachineBasicBlock::iterator &NextMBBI) {
  MachineInstr &MI = *MBBI;
  DebugLoc DL = MI.getDebugLoc();
  const MachineOperand &Dest = MI.getOperand(0);
  unsigned StatusReg = MI.getOperand(1).getReg();
  bool StatusDead = MI.getOperand(1).isDead();
  // Duplicating undef operands into 2 instructions does not guarantee the same
  // value on both; However undef should be replaced by xzr anyway.
  assert(!MI.getOperand(2).isUndef() && "cannot handle undef");
  unsigned AddrReg = MI.getOperand(2).getReg();
  unsigned DesiredReg = MI.getOperand(3).getReg();
  unsigned NewReg = MI.getOperand(4).getReg();

  MachineFunction *MF = MBB.getParent();
  auto LoadCmpBB = MF->CreateMachineBasicBlock(MBB.getBasicBlock());
  auto StoreBB = MF->CreateMachineBasicBlock(MBB.getBasicBlock());
  auto DoneBB = MF->CreateMachineBasicBlock(MBB.getBasicBlock());

  MF->insert(++MBB.getIterator(), LoadCmpBB);
  MF->insert(++LoadCmpBB->getIterator(), StoreBB);
  MF->insert(++StoreBB->getIterator(), DoneBB);

  // .Lloadcmp:
  //     mov wStatus, 0
  //     ldaxr xDest, [xAddr]
  //     cmp xDest, xDesired
  //     b.ne .Ldone
  if (!StatusDead)
    BuildMI(LoadCmpBB, DL, TII->get(AArch64::MOVZWi), StatusReg)
      .addImm(0).addImm(0);
  BuildMI(LoadCmpBB, DL, TII->get(LdarOp), Dest.getReg())
      .addReg(AddrReg);
  BuildMI(LoadCmpBB, DL, TII->get(CmpOp), ZeroReg)
      .addReg(Dest.getReg(), getKillRegState(Dest.isDead()))
      .addReg(DesiredReg)
      .addImm(ExtendImm);
  BuildMI(LoadCmpBB, DL, TII->get(AArch64::Bcc))
      .addImm(AArch64CC::NE)
      .addMBB(DoneBB)
      .addReg(AArch64::NZCV, RegState::Implicit | RegState::Kill);
  LoadCmpBB->addSuccessor(DoneBB);
  LoadCmpBB->addSuccessor(StoreBB);

  // .Lstore:
  //     stlxr wStatus, xNew, [xAddr]
  //     cbnz wStatus, .Lloadcmp
  BuildMI(StoreBB, DL, TII->get(StlrOp), StatusReg)
      .addReg(NewReg)
      .addReg(AddrReg);
  BuildMI(StoreBB, DL, TII->get(AArch64::CBNZW))
      .addReg(StatusReg, getKillRegState(StatusDead))
      .addMBB(LoadCmpBB);
  StoreBB->addSuccessor(LoadCmpBB);
  StoreBB->addSuccessor(DoneBB);

  DoneBB->splice(DoneBB->end(), &MBB, MI, MBB.end());
  DoneBB->transferSuccessors(&MBB);

  MBB.addSuccessor(LoadCmpBB);

  NextMBBI = MBB.end();
  MI.eraseFromParent();

  // Recompute livein lists.
  LivePhysRegs LiveRegs;
  computeAndAddLiveIns(LiveRegs, *DoneBB);
  computeAndAddLiveIns(LiveRegs, *StoreBB);
  computeAndAddLiveIns(LiveRegs, *LoadCmpBB);
  // Do an extra pass around the loop to get loop carried registers right.
  StoreBB->clearLiveIns();
  computeAndAddLiveIns(LiveRegs, *StoreBB);
  LoadCmpBB->clearLiveIns();
  computeAndAddLiveIns(LiveRegs, *LoadCmpBB);

  return true;
}

bool AArch64ExpandPseudo::expandCMP_SWAP_128(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
    MachineBasicBlock::iterator &NextMBBI) {
  MachineInstr &MI = *MBBI;
  DebugLoc DL = MI.getDebugLoc();
  MachineOperand &DestLo = MI.getOperand(0);
  MachineOperand &DestHi = MI.getOperand(1);
  unsigned StatusReg = MI.getOperand(2).getReg();
  bool StatusDead = MI.getOperand(2).isDead();
  // Duplicating undef operands into 2 instructions does not guarantee the same
  // value on both; However undef should be replaced by xzr anyway.
  assert(!MI.getOperand(3).isUndef() && "cannot handle undef");
  unsigned AddrReg = MI.getOperand(3).getReg();
  unsigned DesiredLoReg = MI.getOperand(4).getReg();
  unsigned DesiredHiReg = MI.getOperand(5).getReg();
  unsigned NewLoReg = MI.getOperand(6).getReg();
  unsigned NewHiReg = MI.getOperand(7).getReg();

  MachineFunction *MF = MBB.getParent();
  auto LoadCmpBB = MF->CreateMachineBasicBlock(MBB.getBasicBlock());
  auto StoreBB = MF->CreateMachineBasicBlock(MBB.getBasicBlock());
  auto DoneBB = MF->CreateMachineBasicBlock(MBB.getBasicBlock());

  MF->insert(++MBB.getIterator(), LoadCmpBB);
  MF->insert(++LoadCmpBB->getIterator(), StoreBB);
  MF->insert(++StoreBB->getIterator(), DoneBB);

  // .Lloadcmp:
  //     ldaxp xDestLo, xDestHi, [xAddr]
  //     cmp xDestLo, xDesiredLo
  //     sbcs xDestHi, xDesiredHi
  //     b.ne .Ldone
  BuildMI(LoadCmpBB, DL, TII->get(AArch64::LDAXPX))
      .addReg(DestLo.getReg(), RegState::Define)
      .addReg(DestHi.getReg(), RegState::Define)
      .addReg(AddrReg);
  BuildMI(LoadCmpBB, DL, TII->get(AArch64::SUBSXrs), AArch64::XZR)
      .addReg(DestLo.getReg(), getKillRegState(DestLo.isDead()))
      .addReg(DesiredLoReg)
      .addImm(0);
  BuildMI(LoadCmpBB, DL, TII->get(AArch64::CSINCWr), StatusReg)
    .addUse(AArch64::WZR)
    .addUse(AArch64::WZR)
    .addImm(AArch64CC::EQ);
  BuildMI(LoadCmpBB, DL, TII->get(AArch64::SUBSXrs), AArch64::XZR)
      .addReg(DestHi.getReg(), getKillRegState(DestHi.isDead()))
      .addReg(DesiredHiReg)
      .addImm(0);
  BuildMI(LoadCmpBB, DL, TII->get(AArch64::CSINCWr), StatusReg)
      .addUse(StatusReg, RegState::Kill)
      .addUse(StatusReg, RegState::Kill)
      .addImm(AArch64CC::EQ);
  BuildMI(LoadCmpBB, DL, TII->get(AArch64::CBNZW))
      .addUse(StatusReg, getKillRegState(StatusDead))
      .addMBB(DoneBB);
  LoadCmpBB->addSuccessor(DoneBB);
  LoadCmpBB->addSuccessor(StoreBB);

  // .Lstore:
  //     stlxp wStatus, xNewLo, xNewHi, [xAddr]
  //     cbnz wStatus, .Lloadcmp
  BuildMI(StoreBB, DL, TII->get(AArch64::STLXPX), StatusReg)
      .addReg(NewLoReg)
      .addReg(NewHiReg)
      .addReg(AddrReg);
  BuildMI(StoreBB, DL, TII->get(AArch64::CBNZW))
      .addReg(StatusReg, getKillRegState(StatusDead))
      .addMBB(LoadCmpBB);
  StoreBB->addSuccessor(LoadCmpBB);
  StoreBB->addSuccessor(DoneBB);

  DoneBB->splice(DoneBB->end(), &MBB, MI, MBB.end());
  DoneBB->transferSuccessors(&MBB);

  MBB.addSuccessor(LoadCmpBB);

  NextMBBI = MBB.end();
  MI.eraseFromParent();

  // Recompute liveness bottom up.
  LivePhysRegs LiveRegs;
  computeAndAddLiveIns(LiveRegs, *DoneBB);
  computeAndAddLiveIns(LiveRegs, *StoreBB);
  computeAndAddLiveIns(LiveRegs, *LoadCmpBB);
  // Do an extra pass in the loop to get the loop carried dependencies right.
  StoreBB->clearLiveIns();
  computeAndAddLiveIns(LiveRegs, *StoreBB);
  LoadCmpBB->clearLiveIns();
  computeAndAddLiveIns(LiveRegs, *LoadCmpBB);

  return true;
}

/// If MBBI references a pseudo instruction that should be expanded here,
/// do the expansion and return true.  Otherwise return false.
bool AArch64ExpandPseudo::expandMI(MachineBasicBlock &MBB,
                                   MachineBasicBlock::iterator MBBI,
                                   MachineBasicBlock::iterator &NextMBBI) {
  MachineInstr &MI = *MBBI;
  unsigned Opcode = MI.getOpcode();
  switch (Opcode) {
  default:
    break;

  case AArch64::ADDWrr:
  case AArch64::SUBWrr:
  case AArch64::ADDXrr:
  case AArch64::SUBXrr:
  case AArch64::ADDSWrr:
  case AArch64::SUBSWrr:
  case AArch64::ADDSXrr:
  case AArch64::SUBSXrr:
  case AArch64::ANDWrr:
  case AArch64::ANDXrr:
  case AArch64::BICWrr:
  case AArch64::BICXrr:
  case AArch64::ANDSWrr:
  case AArch64::ANDSXrr:
  case AArch64::BICSWrr:
  case AArch64::BICSXrr:
  case AArch64::EONWrr:
  case AArch64::EONXrr:
  case AArch64::EORWrr:
  case AArch64::EORXrr:
  case AArch64::ORNWrr:
  case AArch64::ORNXrr:
  case AArch64::ORRWrr:
  case AArch64::ORRXrr: {
    unsigned Opcode;
    switch (MI.getOpcode()) {
    default:
      return false;
    case AArch64::ADDWrr:      Opcode = AArch64::ADDWrs; break;
    case AArch64::SUBWrr:      Opcode = AArch64::SUBWrs; break;
    case AArch64::ADDXrr:      Opcode = AArch64::ADDXrs; break;
    case AArch64::SUBXrr:      Opcode = AArch64::SUBXrs; break;
    case AArch64::ADDSWrr:     Opcode = AArch64::ADDSWrs; break;
    case AArch64::SUBSWrr:     Opcode = AArch64::SUBSWrs; break;
    case AArch64::ADDSXrr:     Opcode = AArch64::ADDSXrs; break;
    case AArch64::SUBSXrr:     Opcode = AArch64::SUBSXrs; break;
    case AArch64::ANDWrr:      Opcode = AArch64::ANDWrs; break;
    case AArch64::ANDXrr:      Opcode = AArch64::ANDXrs; break;
    case AArch64::BICWrr:      Opcode = AArch64::BICWrs; break;
    case AArch64::BICXrr:      Opcode = AArch64::BICXrs; break;
    case AArch64::ANDSWrr:     Opcode = AArch64::ANDSWrs; break;
    case AArch64::ANDSXrr:     Opcode = AArch64::ANDSXrs; break;
    case AArch64::BICSWrr:     Opcode = AArch64::BICSWrs; break;
    case AArch64::BICSXrr:     Opcode = AArch64::BICSXrs; break;
    case AArch64::EONWrr:      Opcode = AArch64::EONWrs; break;
    case AArch64::EONXrr:      Opcode = AArch64::EONXrs; break;
    case AArch64::EORWrr:      Opcode = AArch64::EORWrs; break;
    case AArch64::EORXrr:      Opcode = AArch64::EORXrs; break;
    case AArch64::ORNWrr:      Opcode = AArch64::ORNWrs; break;
    case AArch64::ORNXrr:      Opcode = AArch64::ORNXrs; break;
    case AArch64::ORRWrr:      Opcode = AArch64::ORRWrs; break;
    case AArch64::ORRXrr:      Opcode = AArch64::ORRXrs; break;
    }
    MachineInstrBuilder MIB1 =
        BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(Opcode),
                MI.getOperand(0).getReg())
            .add(MI.getOperand(1))
            .add(MI.getOperand(2))
            .addImm(AArch64_AM::getShifterImm(AArch64_AM::LSL, 0));
    transferImpOps(MI, MIB1, MIB1);
    MI.eraseFromParent();
    return true;
  }

  case AArch64::LOADgot: {
    MachineFunction *MF = MBB.getParent();
    unsigned DstReg = MI.getOperand(0).getReg();
    const MachineOperand &MO1 = MI.getOperand(1);
    unsigned Flags = MO1.getTargetFlags();

    if (MF->getTarget().getCodeModel() == CodeModel::Tiny) {
      // Tiny codemodel expand to LDR
      MachineInstrBuilder MIB = BuildMI(MBB, MBBI, MI.getDebugLoc(),
                                        TII->get(AArch64::LDRXl), DstReg);

      if (MO1.isGlobal()) {
        MIB.addGlobalAddress(MO1.getGlobal(), 0, Flags);
      } else if (MO1.isSymbol()) {
        MIB.addExternalSymbol(MO1.getSymbolName(), Flags);
      } else {
        assert(MO1.isCPI() &&
               "Only expect globals, externalsymbols, or constant pools");
        MIB.addConstantPoolIndex(MO1.getIndex(), MO1.getOffset(), Flags);
      }
    } else {
      // Small codemodel expand into ADRP + LDR.
      MachineInstrBuilder MIB1 =
          BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(AArch64::ADRP), DstReg);
      MachineInstrBuilder MIB2 =
          BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(AArch64::LDRXui))
              .add(MI.getOperand(0))
              .addReg(DstReg);

      if (MO1.isGlobal()) {
        MIB1.addGlobalAddress(MO1.getGlobal(), 0, Flags | AArch64II::MO_PAGE);
        MIB2.addGlobalAddress(MO1.getGlobal(), 0,
                              Flags | AArch64II::MO_PAGEOFF | AArch64II::MO_NC);
      } else if (MO1.isSymbol()) {
        MIB1.addExternalSymbol(MO1.getSymbolName(), Flags | AArch64II::MO_PAGE);
        MIB2.addExternalSymbol(MO1.getSymbolName(), Flags |
                                                        AArch64II::MO_PAGEOFF |
                                                        AArch64II::MO_NC);
      } else {
        assert(MO1.isCPI() &&
               "Only expect globals, externalsymbols, or constant pools");
        MIB1.addConstantPoolIndex(MO1.getIndex(), MO1.getOffset(),
                                  Flags | AArch64II::MO_PAGE);
        MIB2.addConstantPoolIndex(MO1.getIndex(), MO1.getOffset(),
                                  Flags | AArch64II::MO_PAGEOFF |
                                      AArch64II::MO_NC);
      }

      transferImpOps(MI, MIB1, MIB2);
    }
    MI.eraseFromParent();
    return true;
  }

  case AArch64::MOVaddr:
  case AArch64::MOVaddrJT:
  case AArch64::MOVaddrCP:
  case AArch64::MOVaddrBA:
  case AArch64::MOVaddrTLS:
  case AArch64::MOVaddrEXT: {
    // Expand into ADRP + ADD.
    unsigned DstReg = MI.getOperand(0).getReg();
    MachineInstrBuilder MIB1 =
        BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(AArch64::ADRP), DstReg)
            .add(MI.getOperand(1));

    MachineInstrBuilder MIB2 =
        BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(AArch64::ADDXri))
            .add(MI.getOperand(0))
            .addReg(DstReg)
            .add(MI.getOperand(2))
            .addImm(0);

    transferImpOps(MI, MIB1, MIB2);
    MI.eraseFromParent();
    return true;
  }
  case AArch64::ADDlowTLS:
    // Produce a plain ADD
    BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(AArch64::ADDXri))
        .add(MI.getOperand(0))
        .add(MI.getOperand(1))
        .add(MI.getOperand(2))
        .addImm(0);
    MI.eraseFromParent();
    return true;

  case AArch64::MOVbaseTLS: {
    unsigned DstReg = MI.getOperand(0).getReg();
    auto SysReg = AArch64SysReg::TPIDR_EL0;
    MachineFunction *MF = MBB.getParent();
    if (MF->getTarget().getTargetTriple().isOSFuchsia() &&
        MF->getTarget().getCodeModel() == CodeModel::Kernel)
      SysReg = AArch64SysReg::TPIDR_EL1;
    BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(AArch64::MRS), DstReg)
        .addImm(SysReg);
    MI.eraseFromParent();
    return true;
  }

  case AArch64::MOVi32imm:
    return expandMOVImm(MBB, MBBI, 32);
  case AArch64::MOVi64imm:
    return expandMOVImm(MBB, MBBI, 64);
  case AArch64::RET_ReallyLR: {
    // Hiding the LR use with RET_ReallyLR may lead to extra kills in the
    // function and missing live-ins. We are fine in practice because callee
    // saved register handling ensures the register value is restored before
    // RET, but we need the undef flag here to appease the MachineVerifier
    // liveness checks.
    MachineInstrBuilder MIB =
        BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(AArch64::RET))
          .addReg(AArch64::LR, RegState::Undef);
    transferImpOps(MI, MIB, MIB);
    MI.eraseFromParent();
    return true;
  }
  case AArch64::CMP_SWAP_8:
    return expandCMP_SWAP(MBB, MBBI, AArch64::LDAXRB, AArch64::STLXRB,
                          AArch64::SUBSWrx,
                          AArch64_AM::getArithExtendImm(AArch64_AM::UXTB, 0),
                          AArch64::WZR, NextMBBI);
  case AArch64::CMP_SWAP_16:
    return expandCMP_SWAP(MBB, MBBI, AArch64::LDAXRH, AArch64::STLXRH,
                          AArch64::SUBSWrx,
                          AArch64_AM::getArithExtendImm(AArch64_AM::UXTH, 0),
                          AArch64::WZR, NextMBBI);
  case AArch64::CMP_SWAP_32:
    return expandCMP_SWAP(MBB, MBBI, AArch64::LDAXRW, AArch64::STLXRW,
                          AArch64::SUBSWrs,
                          AArch64_AM::getShifterImm(AArch64_AM::LSL, 0),
                          AArch64::WZR, NextMBBI);
  case AArch64::CMP_SWAP_64:
    return expandCMP_SWAP(MBB, MBBI,
                          AArch64::LDAXRX, AArch64::STLXRX, AArch64::SUBSXrs,
                          AArch64_AM::getShifterImm(AArch64_AM::LSL, 0),
                          AArch64::XZR, NextMBBI);
  case AArch64::CMP_SWAP_128:
    return expandCMP_SWAP_128(MBB, MBBI, NextMBBI);

  case AArch64::AESMCrrTied:
  case AArch64::AESIMCrrTied: {
    MachineInstrBuilder MIB =
    BuildMI(MBB, MBBI, MI.getDebugLoc(),
            TII->get(Opcode == AArch64::AESMCrrTied ? AArch64::AESMCrr :
                                                      AArch64::AESIMCrr))
      .add(MI.getOperand(0))
      .add(MI.getOperand(1));
    transferImpOps(MI, MIB, MIB);
    MI.eraseFromParent();
    return true;
   }
  }
  return false;
}

/// Iterate over the instructions in basic block MBB and expand any
/// pseudo instructions.  Return true if anything was modified.
bool AArch64ExpandPseudo::expandMBB(MachineBasicBlock &MBB) {
  bool Modified = false;

  MachineBasicBlock::iterator MBBI = MBB.begin(), E = MBB.end();
  while (MBBI != E) {
    MachineBasicBlock::iterator NMBBI = std::next(MBBI);
    Modified |= expandMI(MBB, MBBI, NMBBI);
    MBBI = NMBBI;
  }

  return Modified;
}

bool AArch64ExpandPseudo::runOnMachineFunction(MachineFunction &MF) {
  TII = static_cast<const AArch64InstrInfo *>(MF.getSubtarget().getInstrInfo());

  bool Modified = false;
  for (auto &MBB : MF)
    Modified |= expandMBB(MBB);
  return Modified;
}

/// Returns an instance of the pseudo instruction expansion pass.
FunctionPass *llvm::createAArch64ExpandPseudoPass() {
  return new AArch64ExpandPseudo();
}