//===-- lib/CodeGen/GlobalISel/GICombinerHelper.cpp -----------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/GlobalISel/CombinerHelper.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallBitVector.h"
#include "llvm/Analysis/CmpInstAnalysis.h"
#include "llvm/CodeGen/GlobalISel/GISelChangeObserver.h"
#include "llvm/CodeGen/GlobalISel/GISelValueTracking.h"
#include "llvm/CodeGen/GlobalISel/GenericMachineInstrs.h"
#include "llvm/CodeGen/GlobalISel/LegalizerHelper.h"
#include "llvm/CodeGen/GlobalISel/LegalizerInfo.h"
#include "llvm/CodeGen/GlobalISel/MIPatternMatch.h"
#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
#include "llvm/CodeGen/GlobalISel/Utils.h"
#include "llvm/CodeGen/LowLevelTypeUtils.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Register.h"
#include "llvm/CodeGen/RegisterBankInfo.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetOpcodes.h"
#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/DivisionByConstantInfo.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Target/TargetMachine.h"
#include <cmath>
#include <optional>
#include <tuple>

#define DEBUG_TYPE "gi-combiner"

using namespace llvm;
using namespace MIPatternMatch;

// Option to allow testing of the combiner while no targets know about indexed
// addressing.
static cl::opt<bool>
    ForceLegalIndexing("force-legal-indexing", cl::Hidden, cl::init(false),
                       cl::desc("Force all indexed operations to be "
                                "legal for the GlobalISel combiner"));

CombinerHelper::CombinerHelper(GISelChangeObserver &Observer,
                               MachineIRBuilder &B, bool IsPreLegalize,
                               GISelValueTracking *VT,
                               MachineDominatorTree *MDT,
                               const LegalizerInfo *LI)
    : Builder(B), MRI(Builder.getMF().getRegInfo()), Observer(Observer), VT(VT),
      MDT(MDT), IsPreLegalize(IsPreLegalize), LI(LI),
      TII(Builder.getMF().getSubtarget().getInstrInfo()),
      RBI(Builder.getMF().getSubtarget().getRegBankInfo()),
      TRI(Builder.getMF().getSubtarget().getRegisterInfo()) {
  (void)this->VT;
}

const TargetLowering &CombinerHelper::getTargetLowering() const {
  return *Builder.getMF().getSubtarget().getTargetLowering();
}

const MachineFunction &CombinerHelper::getMachineFunction() const {
  return Builder.getMF();
}

LLVMContext &CombinerHelper::getContext() const { return Builder.getContext(); }

/// \returns The little endian in-memory byte position of byte \p I in a
/// \p ByteWidth bytes wide type.
///
/// E.g. Given a 4-byte type x, x[0] -> byte 0
static unsigned littleEndianByteAt(const unsigned ByteWidth, const unsigned I) {
  assert(I < ByteWidth && "I must be in [0, ByteWidth)");
  return I;
}

/// Determines the LogBase2 value for a non-null input value using the
/// transform: LogBase2(V) = (EltBits - 1) - ctlz(V).
static Register buildLogBase2(Register V, MachineIRBuilder &MIB) {
  auto &MRI = *MIB.getMRI();
  LLT Ty = MRI.getType(V);
  auto Ctlz = MIB.buildCTLZ(Ty, V);
  auto Base = MIB.buildConstant(Ty, Ty.getScalarSizeInBits() - 1);
  return MIB.buildSub(Ty, Base, Ctlz).getReg(0);
}

/// \returns The big endian in-memory byte position of byte \p I in a
/// \p ByteWidth bytes wide type.
///
/// E.g. Given a 4-byte type x, x[0] -> byte 3
static unsigned bigEndianByteAt(const unsigned ByteWidth, const unsigned I) {
  assert(I < ByteWidth && "I must be in [0, ByteWidth)");
  return ByteWidth - I - 1;
}

/// Given a map from byte offsets in memory to indices in a load/store,
/// determine if that map corresponds to a little or big endian byte pattern.
///
/// \param MemOffset2Idx maps memory offsets to address offsets.
/// \param LowestIdx is the lowest index in \p MemOffset2Idx.
///
/// \returns true if the map corresponds to a big endian byte pattern, false if
/// it corresponds to a little endian byte pattern, and std::nullopt otherwise.
///
/// E.g. given a 32-bit type x, and x[AddrOffset], the in-memory byte patterns
/// are as follows:
///
/// AddrOffset   Little endian    Big endian
/// 0            0                3
/// 1            1                2
/// 2            2                1
/// 3            3                0
static std::optional<bool>
isBigEndian(const SmallDenseMap<int64_t, int64_t, 8> &MemOffset2Idx,
            int64_t LowestIdx) {
  // Need at least two byte positions to decide on endianness.
  unsigned Width = MemOffset2Idx.size();
  if (Width < 2)
    return std::nullopt;
  bool BigEndian = true, LittleEndian = true;
  for (unsigned MemOffset = 0; MemOffset < Width; ++ MemOffset) {
    auto MemOffsetAndIdx = MemOffset2Idx.find(MemOffset);
    if (MemOffsetAndIdx == MemOffset2Idx.end())
      return std::nullopt;
    const int64_t Idx = MemOffsetAndIdx->second - LowestIdx;
    assert(Idx >= 0 && "Expected non-negative byte offset?");
    LittleEndian &= Idx == littleEndianByteAt(Width, MemOffset);
    BigEndian &= Idx == bigEndianByteAt(Width, MemOffset);
    if (!BigEndian && !LittleEndian)
      return std::nullopt;
  }

  assert((BigEndian != LittleEndian) &&
         "Pattern cannot be both big and little endian!");
  return BigEndian;
}

bool CombinerHelper::isPreLegalize() const { return IsPreLegalize; }

bool CombinerHelper::isLegal(const LegalityQuery &Query) const {
  assert(LI && "Must have LegalizerInfo to query isLegal!");
  return LI->getAction(Query).Action == LegalizeActions::Legal;
}

bool CombinerHelper::isLegalOrBeforeLegalizer(
    const LegalityQuery &Query) const {
  return isPreLegalize() || isLegal(Query);
}

bool CombinerHelper::isLegalOrHasWidenScalar(const LegalityQuery &Query) const {
  return isLegal(Query) ||
         LI->getAction(Query).Action == LegalizeActions::WidenScalar;
}

bool CombinerHelper::isLegalOrHasFewerElements(
    const LegalityQuery &Query) const {
  LegalizeAction Action = LI->getAction(Query).Action;
  return Action == LegalizeActions::Legal ||
         Action == LegalizeActions::FewerElements;
}

bool CombinerHelper::isConstantLegalOrBeforeLegalizer(const LLT Ty) const {
  if (!Ty.isVector())
    return isLegalOrBeforeLegalizer({TargetOpcode::G_CONSTANT, {Ty}});
  // Vector constants are represented as a G_BUILD_VECTOR of scalar G_CONSTANTs.
  if (isPreLegalize())
    return true;
  LLT EltTy = Ty.getElementType();
  return isLegal({TargetOpcode::G_BUILD_VECTOR, {Ty, EltTy}}) &&
         isLegal({TargetOpcode::G_CONSTANT, {EltTy}});
}

void CombinerHelper::replaceRegWith(MachineRegisterInfo &MRI, Register FromReg,
                                    Register ToReg) const {
  Observer.changingAllUsesOfReg(MRI, FromReg);

  if (MRI.constrainRegAttrs(ToReg, FromReg))
    MRI.replaceRegWith(FromReg, ToReg);
  else
    Builder.buildCopy(FromReg, ToReg);

  Observer.finishedChangingAllUsesOfReg();
}

void CombinerHelper::replaceRegOpWith(MachineRegisterInfo &MRI,
                                      MachineOperand &FromRegOp,
                                      Register ToReg) const {
  assert(FromRegOp.getParent() && "Expected an operand in an MI");
  Observer.changingInstr(*FromRegOp.getParent());

  FromRegOp.setReg(ToReg);

  Observer.changedInstr(*FromRegOp.getParent());
}

void CombinerHelper::replaceOpcodeWith(MachineInstr &FromMI,
                                       unsigned ToOpcode) const {
  Observer.changingInstr(FromMI);

  FromMI.setDesc(Builder.getTII().get(ToOpcode));

  Observer.changedInstr(FromMI);
}

const RegisterBank *CombinerHelper::getRegBank(Register Reg) const {
  return RBI->getRegBank(Reg, MRI, *TRI);
}

void CombinerHelper::setRegBank(Register Reg,
                                const RegisterBank *RegBank) const {
  if (RegBank)
    MRI.setRegBank(Reg, *RegBank);
}

bool CombinerHelper::matchCombineCopy(MachineInstr &MI) const {
  if (MI.getOpcode() != TargetOpcode::COPY)
    return false;
  Register DstReg = MI.getOperand(0).getReg();
  Register SrcReg = MI.getOperand(1).getReg();
  return canReplaceReg(DstReg, SrcReg, MRI);
}
void CombinerHelper::applyCombineCopy(MachineInstr &MI) const {
  Register DstReg = MI.getOperand(0).getReg();
  Register SrcReg = MI.getOperand(1).getReg();
  replaceRegWith(MRI, DstReg, SrcReg);
  MI.eraseFromParent();
}

bool CombinerHelper::matchFreezeOfSingleMaybePoisonOperand(
    MachineInstr &MI, BuildFnTy &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_FREEZE && "Invalid instruction");

  // Ported from InstCombinerImpl::pushFreezeToPreventPoisonFromPropagating.
  Register DstOp = MI.getOperand(0).getReg();
  Register OrigOp = MI.getOperand(1).getReg();

  if (!MRI.hasOneNonDBGUse(OrigOp))
    return false;

  MachineInstr *OrigDef;
  if (!mi_match(OrigOp, MRI, m_MInstr(OrigDef)))
    return false;
  // Even if only a single operand of the PHI is not guaranteed non-poison,
  // moving freeze() backwards across a PHI can cause optimization issues for
  // other users of that operand.
  //
  // Moving freeze() from one of the output registers of a G_UNMERGE_VALUES to
  // the source register is unprofitable because it makes the freeze() more
  // strict than is necessary (it would affect the whole register instead of
  // just the subreg being frozen).
  if (OrigDef->isPHI() || isa<GUnmerge>(OrigDef))
    return false;

  if (canCreateUndefOrPoison(OrigOp, MRI,
                             /*ConsiderFlagsAndMetadata=*/false))
    return false;

  std::optional<MachineOperand> MaybePoisonOperand;
  for (MachineOperand &Operand : OrigDef->uses()) {
    if (!Operand.isReg())
      return false;

    if (isGuaranteedNotToBeUndefOrPoison(Operand.getReg(), MRI))
      continue;

    if (!MaybePoisonOperand)
      MaybePoisonOperand = Operand;
    else {
      // We have more than one maybe-poison operand. Moving the freeze is
      // unsafe.
      return false;
    }
  }

  // Eliminate freeze if all operands are guaranteed non-poison.
  if (!MaybePoisonOperand) {
    MatchInfo = [=](MachineIRBuilder &B) {
      Observer.changingInstr(*OrigDef);
      cast<GenericMachineInstr>(OrigDef)->dropPoisonGeneratingFlags();
      Observer.changedInstr(*OrigDef);
      B.buildCopy(DstOp, OrigOp);
    };
    return true;
  }

  Register MaybePoisonOperandReg = MaybePoisonOperand->getReg();
  LLT MaybePoisonOperandRegTy = MRI.getType(MaybePoisonOperandReg);

  if (!isLegalOrBeforeLegalizer(
          {TargetOpcode::G_FREEZE, {MaybePoisonOperandRegTy}}))
    return false;

  MatchInfo = [=](MachineIRBuilder &B) mutable {
    Observer.changingInstr(*OrigDef);
    cast<GenericMachineInstr>(OrigDef)->dropPoisonGeneratingFlags();
    Observer.changedInstr(*OrigDef);
    B.setInsertPt(*OrigDef->getParent(), OrigDef->getIterator());
    auto Freeze = B.buildFreeze(MaybePoisonOperandRegTy, MaybePoisonOperandReg);
    replaceRegOpWith(
        MRI, *OrigDef->findRegisterUseOperand(MaybePoisonOperandReg, TRI),
        Freeze.getReg(0));
    replaceRegWith(MRI, DstOp, OrigOp);
  };
  return true;
}

bool CombinerHelper::matchCombineConcatVectors(
    MachineInstr &MI, SmallVector<Register> &Ops) const {
  assert(MI.getOpcode() == TargetOpcode::G_CONCAT_VECTORS &&
         "Invalid instruction");
  bool IsUndef = true;
  MachineInstr *Undef = nullptr;

  // Walk over all the operands of concat vectors and check if they are
  // build_vector themselves or undef.
  // Then collect their operands in Ops.
  for (const MachineOperand &MO : MI.uses()) {
    Register Reg = MO.getReg();
    MachineInstr *Def;
    if (!mi_match(Reg, MRI, m_MInstr(Def)))
      return false;
    if (!MRI.hasOneNonDBGUse(Reg))
      return false;
    switch (Def->getOpcode()) {
    case TargetOpcode::G_BUILD_VECTOR:
      IsUndef = false;
      // Remember the operands of the build_vector to fold
      // them into the yet-to-build flattened concat vectors.
      for (const MachineOperand &BuildVecMO : Def->uses())
        Ops.push_back(BuildVecMO.getReg());
      break;
    case TargetOpcode::G_IMPLICIT_DEF: {
      LLT OpType = MRI.getType(Reg);
      // Keep one undef value for all the undef operands.
      if (!Undef) {
        Builder.setInsertPt(*MI.getParent(), MI);
        Undef = Builder.buildUndef(OpType.getScalarType());
      }
      assert(MRI.getType(Undef->getOperand(0).getReg()) ==
                 OpType.getScalarType() &&
             "All undefs should have the same type");
      // Break the undef vector in as many scalar elements as needed
      // for the flattening.
      for (unsigned EltIdx = 0, EltEnd = OpType.getNumElements();
           EltIdx != EltEnd; ++EltIdx)
        Ops.push_back(Undef->getOperand(0).getReg());
      break;
    }
    default:
      return false;
    }
  }

  // Check if the combine is illegal
  LLT DstTy = MRI.getType(MI.getOperand(0).getReg());
  if (!isLegalOrBeforeLegalizer(
          {TargetOpcode::G_BUILD_VECTOR, {DstTy, MRI.getType(Ops[0])}})) {
    return false;
  }

  if (IsUndef)
    Ops.clear();

  return true;
}
void CombinerHelper::applyCombineConcatVectors(
    MachineInstr &MI, SmallVector<Register> &Ops) const {
  // We determined that the concat_vectors can be flatten.
  // Generate the flattened build_vector.
  Register DstReg = MI.getOperand(0).getReg();
  Builder.setInsertPt(*MI.getParent(), MI);
  Register NewDstReg = MRI.cloneVirtualRegister(DstReg);

  // Note: IsUndef is sort of redundant. We could have determine it by
  // checking that at all Ops are undef.  Alternatively, we could have
  // generate a build_vector of undefs and rely on another combine to
  // clean that up.  For now, given we already gather this information
  // in matchCombineConcatVectors, just save compile time and issue the
  // right thing.
  if (Ops.empty())
    Builder.buildUndef(NewDstReg);
  else
    Builder.buildBuildVector(NewDstReg, Ops);
  replaceRegWith(MRI, DstReg, NewDstReg);
  MI.eraseFromParent();
}

bool CombinerHelper::matchCombineBuildVectorOfBitcast(
    MachineInstr &MI, SmallVector<Register> &Ops) const {
  auto &BV = cast<GBuildVector>(MI);

  // Look at the first operand for a unmerge(bitcast) from a scalar type.
  GUnmerge *Unmerge = getOpcodeDef<GUnmerge>(BV.getSourceReg(0), MRI);
  if (!Unmerge || Unmerge->getReg(0) != BV.getSourceReg(0))
    return false;
  Register BCSrc;
  if (!mi_match(Unmerge->getSourceReg(), MRI, m_GBitcast(m_Reg(BCSrc))))
    return false;
  LLT InputTy = MRI.getType(BCSrc);
  unsigned Factor = Unmerge->getNumDefs();
  if (!InputTy.isScalar() || BV.getNumSources() % Factor != 0)
    return false;

  // Check if the build_vector is legal
  LLT BVDstTy = LLT::fixed_vector(BV.getNumSources() / Factor, InputTy);
  if (!isLegal({TargetOpcode::G_BUILD_VECTOR, {BVDstTy, InputTy}}))
    return false;

  // Check all other operands are bitcasts or undef.
  for (unsigned Idx = 0; Idx < BV.getNumSources(); Idx += Factor) {
    GUnmerge *Unmerge = getOpcodeDef<GUnmerge>(BV.getSourceReg(Idx), MRI);
    if (!all_of(iota_range<unsigned>(0, Factor, false), [&](unsigned J) {
          if (mi_match(BV.getSourceReg(Idx + J), MRI, m_GImplicitDef()))
            return true;
          return Unmerge && BV.getSourceReg(Idx + J) == Unmerge->getReg(J);
        }))
      return false;
    if (!Unmerge)
      Ops.push_back(0);
    else {
      Register BCSrc;
      if (!mi_match(
              Unmerge->getSourceReg(), MRI,
              m_GBitcast(m_all_of(m_Reg(BCSrc), m_SpecificType(InputTy)))))
        return false;
      Ops.push_back(BCSrc);
    }
  }

  return true;
}

void CombinerHelper::applyCombineBuildVectorOfBitcast(
    MachineInstr &MI, SmallVector<Register> &Ops) const {
  LLT SrcTy = MRI.getType(Ops[0]);
  // Build undef if any operations require it.
  Register Undef = 0;
  for (Register &Op : Ops) {
    if (!Op) {
      if (!Undef)
        Undef = Builder.buildUndef(SrcTy).getReg(0);
      Op = Undef;
    }
  }

  LLT BVDstTy = LLT::fixed_vector(Ops.size(), SrcTy);
  auto BV = Builder.buildBuildVector(BVDstTy, Ops);
  Builder.buildBitcast(MI.getOperand(0).getReg(), BV);
  MI.eraseFromParent();
}

void CombinerHelper::applyCombineShuffleToBuildVector(MachineInstr &MI) const {
  auto &Shuffle = cast<GShuffleVector>(MI);

  Register SrcVec1 = Shuffle.getSrc1Reg();
  Register SrcVec2 = Shuffle.getSrc2Reg();
  LLT EltTy = MRI.getType(SrcVec1).getElementType();
  int Width = MRI.getType(SrcVec1).getNumElements();

  auto Unmerge1 = Builder.buildUnmerge(EltTy, SrcVec1);
  auto Unmerge2 = Builder.buildUnmerge(EltTy, SrcVec2);

  SmallVector<Register> Extracts;
  // Select only applicable elements from unmerged values.
  for (int Val : Shuffle.getMask()) {
    if (Val == -1)
      Extracts.push_back(Builder.buildUndef(EltTy).getReg(0));
    else if (Val < Width)
      Extracts.push_back(Unmerge1.getReg(Val));
    else
      Extracts.push_back(Unmerge2.getReg(Val - Width));
  }
  assert(Extracts.size() > 0 && "Expected at least one element in the shuffle");
  if (Extracts.size() == 1)
    Builder.buildCopy(MI.getOperand(0).getReg(), Extracts[0]);
  else
    Builder.buildBuildVector(MI.getOperand(0).getReg(), Extracts);
  MI.eraseFromParent();
}

bool CombinerHelper::matchCombineShuffleConcat(
    MachineInstr &MI, SmallVector<Register> &Ops) const {
  ArrayRef<int> Mask = MI.getOperand(3).getShuffleMask();
  GConcatVectors *ConcatMI1, *ConcatMI2;
  if (!mi_match(MI.getOperand(1).getReg(), MRI, m_GConcatVectors(ConcatMI1)) ||
      !mi_match(MI.getOperand(2).getReg(), MRI, m_GConcatVectors(ConcatMI2)))
    return false;

  // Check that the sources of the Concat instructions have the same type
  if (MRI.getType(ConcatMI1->getSourceReg(0)) !=
      MRI.getType(ConcatMI2->getSourceReg(0)))
    return false;

  LLT ConcatSrcTy = MRI.getType(ConcatMI1->getReg(1));
  LLT ShuffleSrcTy1 = MRI.getType(MI.getOperand(1).getReg());
  unsigned ConcatSrcNumElt = ConcatSrcTy.getNumElements();
  for (unsigned i = 0; i < Mask.size(); i += ConcatSrcNumElt) {
    // Check if the index takes a whole source register from G_CONCAT_VECTORS
    // Assumes that all Sources of G_CONCAT_VECTORS are the same type
    if (Mask[i] == -1) {
      for (unsigned j = 1; j < ConcatSrcNumElt; j++) {
        if (i + j >= Mask.size())
          return false;
        if (Mask[i + j] != -1)
          return false;
      }
      if (!isLegalOrBeforeLegalizer(
              {TargetOpcode::G_IMPLICIT_DEF, {ConcatSrcTy}}))
        return false;
      Ops.push_back(0);
    } else if (Mask[i] % ConcatSrcNumElt == 0) {
      for (unsigned j = 1; j < ConcatSrcNumElt; j++) {
        if (i + j >= Mask.size())
          return false;
        if (Mask[i + j] != Mask[i] + static_cast<int>(j))
          return false;
      }
      // Retrieve the source register from its respective G_CONCAT_VECTORS
      // instruction
      if (Mask[i] < ShuffleSrcTy1.getNumElements()) {
        Ops.push_back(ConcatMI1->getSourceReg(Mask[i] / ConcatSrcNumElt));
      } else {
        Ops.push_back(ConcatMI2->getSourceReg(Mask[i] / ConcatSrcNumElt -
                                              ConcatMI1->getNumSources()));
      }
    } else {
      return false;
    }
  }

  if (!isLegalOrBeforeLegalizer(
          {TargetOpcode::G_CONCAT_VECTORS,
           {MRI.getType(MI.getOperand(0).getReg()), ConcatSrcTy}}))
    return false;

  return !Ops.empty();
}

void CombinerHelper::applyCombineShuffleConcat(
    MachineInstr &MI, SmallVector<Register> &Ops) const {
  LLT SrcTy;
  for (Register &Reg : Ops) {
    if (Reg != 0)
      SrcTy = MRI.getType(Reg);
  }
  assert(SrcTy.isValid() && "Unexpected full undef vector in concat combine");

  Register UndefReg = 0;

  for (Register &Reg : Ops) {
    if (Reg == 0) {
      if (UndefReg == 0)
        UndefReg = Builder.buildUndef(SrcTy).getReg(0);
      Reg = UndefReg;
    }
  }

  if (Ops.size() > 1)
    Builder.buildConcatVectors(MI.getOperand(0).getReg(), Ops);
  else
    Builder.buildCopy(MI.getOperand(0).getReg(), Ops[0]);
  MI.eraseFromParent();
}

bool CombinerHelper::matchCombineShuffleVector(
    MachineInstr &MI, SmallVectorImpl<Register> &Ops) const {
  assert(MI.getOpcode() == TargetOpcode::G_SHUFFLE_VECTOR &&
         "Invalid instruction kind");
  LLT DstType = MRI.getType(MI.getOperand(0).getReg());
  Register Src1 = MI.getOperand(1).getReg();
  LLT SrcType = MRI.getType(Src1);

  unsigned DstNumElts = DstType.getNumElements();
  unsigned SrcNumElts = SrcType.getNumElements();

  // If the resulting vector is smaller than the size of the source
  // vectors being concatenated, we won't be able to replace the
  // shuffle vector into a concat_vectors.
  //
  // Note: We may still be able to produce a concat_vectors fed by
  //       extract_vector_elt and so on. It is less clear that would
  //       be better though, so don't bother for now.
  //
  // If the destination is a scalar, the size of the sources doesn't
  // matter. we will lower the shuffle to a plain copy. This will
  // work only if the source and destination have the same size. But
  // that's covered by the next condition.
  //
  // TODO: If the size between the source and destination don't match
  //       we could still emit an extract vector element in that case.
  if (DstNumElts < 2 * SrcNumElts)
    return false;

  // Check that the shuffle mask can be broken evenly between the
  // different sources.
  if (DstNumElts % SrcNumElts != 0)
    return false;

  // Mask length is a multiple of the source vector length.
  // Check if the shuffle is some kind of concatenation of the input
  // vectors.
  unsigned NumConcat = DstNumElts / SrcNumElts;
  SmallVector<int, 8> ConcatSrcs(NumConcat, -1);
  ArrayRef<int> Mask = MI.getOperand(3).getShuffleMask();
  for (unsigned i = 0; i != DstNumElts; ++i) {
    int Idx = Mask[i];
    // Undef value.
    if (Idx < 0)
      continue;
    // Ensure the indices in each SrcType sized piece are sequential and that
    // the same source is used for the whole piece.
    if ((Idx % SrcNumElts != (i % SrcNumElts)) ||
        (ConcatSrcs[i / SrcNumElts] >= 0 &&
         ConcatSrcs[i / SrcNumElts] != (int)(Idx / SrcNumElts)))
      return false;
    // Remember which source this index came from.
    ConcatSrcs[i / SrcNumElts] = Idx / SrcNumElts;
  }

  // The shuffle is concatenating multiple vectors together.
  // Collect the different operands for that.
  Register UndefReg;
  Register Src2 = MI.getOperand(2).getReg();
  for (auto Src : ConcatSrcs) {
    if (Src < 0) {
      if (!UndefReg) {
        Builder.setInsertPt(*MI.getParent(), MI);
        UndefReg = Builder.buildUndef(SrcType).getReg(0);
      }
      Ops.push_back(UndefReg);
    } else if (Src == 0)
      Ops.push_back(Src1);
    else
      Ops.push_back(Src2);
  }
  return true;
}

void CombinerHelper::applyCombineShuffleVector(MachineInstr &MI,
                                               ArrayRef<Register> Ops) const {
  Register DstReg = MI.getOperand(0).getReg();
  Builder.setInsertPt(*MI.getParent(), MI);
  Register NewDstReg = MRI.cloneVirtualRegister(DstReg);

  if (Ops.size() == 1)
    Builder.buildCopy(NewDstReg, Ops[0]);
  else
    Builder.buildMergeLikeInstr(NewDstReg, Ops);

  replaceRegWith(MRI, DstReg, NewDstReg);
  MI.eraseFromParent();
}

namespace {

/// Select a preference between two uses. CurrentUse is the current preference
/// while *ForCandidate is attributes of the candidate under consideration.
PreferredTuple ChoosePreferredUse(MachineInstr &LoadMI,
                                  PreferredTuple &CurrentUse,
                                  const LLT TyForCandidate,
                                  unsigned OpcodeForCandidate,
                                  MachineInstr *MIForCandidate) {
  if (!CurrentUse.Ty.isValid()) {
    if (CurrentUse.ExtendOpcode == OpcodeForCandidate ||
        CurrentUse.ExtendOpcode == TargetOpcode::G_ANYEXT)
      return {TyForCandidate, OpcodeForCandidate, MIForCandidate};
    return CurrentUse;
  }

  // We permit the extend to hoist through basic blocks but this is only
  // sensible if the target has extending loads. If you end up lowering back
  // into a load and extend during the legalizer then the end result is
  // hoisting the extend up to the load.

  // Prefer defined extensions to undefined extensions as these are more
  // likely to reduce the number of instructions.
  if (OpcodeForCandidate == TargetOpcode::G_ANYEXT &&
      CurrentUse.ExtendOpcode != TargetOpcode::G_ANYEXT)
    return CurrentUse;
  else if (CurrentUse.ExtendOpcode == TargetOpcode::G_ANYEXT &&
           OpcodeForCandidate != TargetOpcode::G_ANYEXT)
    return {TyForCandidate, OpcodeForCandidate, MIForCandidate};

  // Prefer sign extensions to zero extensions as sign-extensions tend to be
  // more expensive. Don't do this if the load is already a zero-extend load
  // though, otherwise we'll rewrite a zero-extend load into a sign-extend
  // later.
  if (!isa<GZExtLoad>(LoadMI) && CurrentUse.Ty == TyForCandidate) {
    if (CurrentUse.ExtendOpcode == TargetOpcode::G_SEXT &&
        OpcodeForCandidate == TargetOpcode::G_ZEXT)
      return CurrentUse;
    else if (CurrentUse.ExtendOpcode == TargetOpcode::G_ZEXT &&
             OpcodeForCandidate == TargetOpcode::G_SEXT)
      return {TyForCandidate, OpcodeForCandidate, MIForCandidate};
  }

  // This is potentially target specific. We've chosen the largest type
  // because G_TRUNC is usually free. One potential catch with this is that
  // some targets have a reduced number of larger registers than smaller
  // registers and this choice potentially increases the live-range for the
  // larger value.
  if (TyForCandidate.getSizeInBits() > CurrentUse.Ty.getSizeInBits()) {
    return {TyForCandidate, OpcodeForCandidate, MIForCandidate};
  }
  return CurrentUse;
}

/// Find a suitable place to insert some instructions and insert them. This
/// function accounts for special cases like inserting before a PHI node.
/// The current strategy for inserting before PHI's is to duplicate the
/// instructions for each predecessor. However, while that's ok for G_TRUNC
/// on most targets since it generally requires no code, other targets/cases may
/// want to try harder to find a dominating block.
static void InsertInsnsWithoutSideEffectsBeforeUse(
    MachineIRBuilder &Builder, MachineInstr &DefMI, MachineOperand &UseMO,
    std::function<void(MachineBasicBlock *, MachineBasicBlock::iterator,
                       MachineOperand &UseMO)>
        Inserter) {
  MachineInstr &UseMI = *UseMO.getParent();

  MachineBasicBlock *InsertBB = UseMI.getParent();

  // If the use is a PHI then we want the predecessor block instead.
  if (UseMI.isPHI()) {
    MachineOperand *PredBB = std::next(&UseMO);
    InsertBB = PredBB->getMBB();
  }

  // If the block is the same block as the def then we want to insert just after
  // the def instead of at the start of the block.
  if (InsertBB == DefMI.getParent()) {
    MachineBasicBlock::iterator InsertPt = &DefMI;
    Inserter(InsertBB, std::next(InsertPt), UseMO);
    return;
  }

  // Otherwise we want the start of the BB
  Inserter(InsertBB, InsertBB->getFirstNonPHI(), UseMO);
}
} // end anonymous namespace

bool CombinerHelper::tryCombineExtendingLoads(MachineInstr &MI) const {
  PreferredTuple Preferred;
  if (matchCombineExtendingLoads(MI, Preferred)) {
    applyCombineExtendingLoads(MI, Preferred);
    return true;
  }
  return false;
}

static unsigned getExtLoadOpcForExtend(unsigned ExtOpc) {
  unsigned CandidateLoadOpc;
  switch (ExtOpc) {
  case TargetOpcode::G_ANYEXT:
    CandidateLoadOpc = TargetOpcode::G_LOAD;
    break;
  case TargetOpcode::G_SEXT:
    CandidateLoadOpc = TargetOpcode::G_SEXTLOAD;
    break;
  case TargetOpcode::G_ZEXT:
    CandidateLoadOpc = TargetOpcode::G_ZEXTLOAD;
    break;
  default:
    llvm_unreachable("Unexpected extend opc");
  }
  return CandidateLoadOpc;
}

bool CombinerHelper::matchCombineExtendingLoads(
    MachineInstr &MI, PreferredTuple &Preferred) const {
  // We match the loads and follow the uses to the extend instead of matching
  // the extends and following the def to the load. This is because the load
  // must remain in the same position for correctness (unless we also add code
  // to find a safe place to sink it) whereas the extend is freely movable.
  // It also prevents us from duplicating the load for the volatile case or just
  // for performance.
  GAnyLoad *LoadMI = dyn_cast<GAnyLoad>(&MI);
  if (!LoadMI)
    return false;

  Register LoadReg = LoadMI->getDstReg();

  LLT LoadValueTy = MRI.getType(LoadReg);
  if (!LoadValueTy.isScalar())
    return false;

  // Most architectures are going to legalize <s8 loads into at least a 1 byte
  // load, and the MMOs can only describe memory accesses in multiples of bytes.
  // If we try to perform extload combining on those, we can end up with
  // %a(s8) = extload %ptr (load 1 byte from %ptr)
  // ... which is an illegal extload instruction.
  if (LoadValueTy.getSizeInBits() < 8)
    return false;

  // For non power-of-2 types, they will very likely be legalized into multiple
  // loads. Don't bother trying to match them into extending loads.
  if (!llvm::has_single_bit<uint32_t>(LoadValueTy.getSizeInBits()))
    return false;

  // Find the preferred type aside from the any-extends (unless it's the only
  // one) and non-extending ops. We'll emit an extending load to that type and
  // and emit a variant of (extend (trunc X)) for the others according to the
  // relative type sizes. At the same time, pick an extend to use based on the
  // extend involved in the chosen type.
  unsigned PreferredOpcode =
      isa<GLoad>(&MI)
          ? TargetOpcode::G_ANYEXT
          : isa<GSExtLoad>(&MI) ? TargetOpcode::G_SEXT : TargetOpcode::G_ZEXT;
  Preferred = {LLT(), PreferredOpcode, nullptr};
  for (auto &UseMI : MRI.use_nodbg_instructions(LoadReg)) {
    if (UseMI.getOpcode() == TargetOpcode::G_SEXT ||
        UseMI.getOpcode() == TargetOpcode::G_ZEXT ||
        (UseMI.getOpcode() == TargetOpcode::G_ANYEXT)) {
      const auto &MMO = LoadMI->getMMO();
      // Don't do anything for atomics.
      if (MMO.isAtomic())
        continue;
      // Check for legality.
      if (!isPreLegalize()) {
        LegalityQuery::MemDesc MMDesc(MMO);
        unsigned CandidateLoadOpc = getExtLoadOpcForExtend(UseMI.getOpcode());
        LLT UseTy = MRI.getType(UseMI.getOperand(0).getReg());
        LLT SrcTy = MRI.getType(LoadMI->getPointerReg());
        if (LI->getAction({CandidateLoadOpc, {UseTy, SrcTy}, {MMDesc}})
                .Action != LegalizeActions::Legal)
          continue;
      }
      Preferred = ChoosePreferredUse(MI, Preferred,
                                     MRI.getType(UseMI.getOperand(0).getReg()),
                                     UseMI.getOpcode(), &UseMI);
    }
  }

  // There were no extends
  if (!Preferred.MI)
    return false;
  // It should be impossible to chose an extend without selecting a different
  // type since by definition the result of an extend is larger.
  assert(Preferred.Ty != LoadValueTy && "Extending to same type?");

  LLVM_DEBUG(dbgs() << "Preferred use is: " << *Preferred.MI);
  return true;
}

void CombinerHelper::applyCombineExtendingLoads(
    MachineInstr &MI, PreferredTuple &Preferred) const {
  // Rewrite the load to the chosen extending load.
  Register ChosenDstReg = Preferred.MI->getOperand(0).getReg();

  // Inserter to insert a truncate back to the original type at a given point
  // with some basic CSE to limit truncate duplication to one per BB.
  DenseMap<MachineBasicBlock *, MachineInstr *> EmittedInsns;
  auto InsertTruncAt = [&](MachineBasicBlock *InsertIntoBB,
                           MachineBasicBlock::iterator InsertBefore,
                           MachineOperand &UseMO) {
    MachineInstr *PreviouslyEmitted = EmittedInsns.lookup(InsertIntoBB);
    if (PreviouslyEmitted) {
      Observer.changingInstr(*UseMO.getParent());
      UseMO.setReg(PreviouslyEmitted->getOperand(0).getReg());
      Observer.changedInstr(*UseMO.getParent());
      return;
    }

    Builder.setInsertPt(*InsertIntoBB, InsertBefore);
    Register NewDstReg = MRI.cloneVirtualRegister(MI.getOperand(0).getReg());
    MachineInstr *NewMI = Builder.buildTrunc(NewDstReg, ChosenDstReg);
    EmittedInsns[InsertIntoBB] = NewMI;
    replaceRegOpWith(MRI, UseMO, NewDstReg);
  };

  Observer.changingInstr(MI);
  unsigned LoadOpc = getExtLoadOpcForExtend(Preferred.ExtendOpcode);
  MI.setDesc(Builder.getTII().get(LoadOpc));

  // Rewrite all the uses to fix up the types.
  auto &LoadValue = MI.getOperand(0);
  SmallVector<MachineOperand *, 4> Uses(
      llvm::make_pointer_range(MRI.use_operands(LoadValue.getReg())));

  for (auto *UseMO : Uses) {
    MachineInstr *UseMI = UseMO->getParent();

    // If the extend is compatible with the preferred extend then we should fix
    // up the type and extend so that it uses the preferred use.
    if (UseMI->getOpcode() == Preferred.ExtendOpcode ||
        UseMI->getOpcode() == TargetOpcode::G_ANYEXT) {
      Register UseDstReg = UseMI->getOperand(0).getReg();
      MachineOperand &UseSrcMO = UseMI->getOperand(1);
      const LLT UseDstTy = MRI.getType(UseDstReg);
      if (UseDstReg != ChosenDstReg) {
        if (Preferred.Ty == UseDstTy) {
          // If the use has the same type as the preferred use, then merge
          // the vregs and erase the extend. For example:
          //    %1:_(s8) = G_LOAD ...
          //    %2:_(s32) = G_SEXT %1(s8)
          //    %3:_(s32) = G_ANYEXT %1(s8)
          //    ... = ... %3(s32)
          // rewrites to:
          //    %2:_(s32) = G_SEXTLOAD ...
          //    ... = ... %2(s32)
          replaceRegWith(MRI, UseDstReg, ChosenDstReg);
          Observer.erasingInstr(*UseMO->getParent());
          UseMO->getParent()->eraseFromParent();
        } else if (Preferred.Ty.getSizeInBits() < UseDstTy.getSizeInBits()) {
          // If the preferred size is smaller, then keep the extend but extend
          // from the result of the extending load. For example:
          //    %1:_(s8) = G_LOAD ...
          //    %2:_(s32) = G_SEXT %1(s8)
          //    %3:_(s64) = G_ANYEXT %1(s8)
          //    ... = ... %3(s64)
          /// rewrites to:
          //    %2:_(s32) = G_SEXTLOAD ...
          //    %3:_(s64) = G_ANYEXT %2:_(s32)
          //    ... = ... %3(s64)
          replaceRegOpWith(MRI, UseSrcMO, ChosenDstReg);
        } else {
          // If the preferred size is large, then insert a truncate. For
          // example:
          //    %1:_(s8) = G_LOAD ...
          //    %2:_(s64) = G_SEXT %1(s8)
          //    %3:_(s32) = G_ZEXT %1(s8)
          //    ... = ... %3(s32)
          /// rewrites to:
          //    %2:_(s64) = G_SEXTLOAD ...
          //    %4:_(s8) = G_TRUNC %2:_(s32)
          //    %3:_(s64) = G_ZEXT %2:_(s8)
          //    ... = ... %3(s64)
          InsertInsnsWithoutSideEffectsBeforeUse(Builder, MI, *UseMO,
                                                 InsertTruncAt);
        }
        continue;
      }
      // The use is (one of) the uses of the preferred use we chose earlier.
      // We're going to update the load to def this value later so just erase
      // the old extend.
      Observer.erasingInstr(*UseMO->getParent());
      UseMO->getParent()->eraseFromParent();
      continue;
    }

    // The use isn't an extend. Truncate back to the type we originally loaded.
    // This is free on many targets.
    InsertInsnsWithoutSideEffectsBeforeUse(Builder, MI, *UseMO, InsertTruncAt);
  }

  MI.getOperand(0).setReg(ChosenDstReg);
  Observer.changedInstr(MI);
}

bool CombinerHelper::matchCombineLoadWithAndMask(MachineInstr &MI,
                                                 BuildFnTy &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_AND);

  // If we have the following code:
  //  %mask = G_CONSTANT 255
  //  %ld   = G_LOAD %ptr, (load s16)
  //  %and  = G_AND %ld, %mask
  //
  // Try to fold it into
  //   %ld = G_ZEXTLOAD %ptr, (load s8)

  Register Dst = MI.getOperand(0).getReg();
  if (MRI.getType(Dst).isVector())
    return false;

  auto MaybeMask =
      getIConstantVRegValWithLookThrough(MI.getOperand(2).getReg(), MRI);
  if (!MaybeMask)
    return false;

  APInt MaskVal = MaybeMask->Value;

  if (!MaskVal.isMask())
    return false;

  Register SrcReg = MI.getOperand(1).getReg();
  // Don't use getOpcodeDef() here since intermediate instructions may have
  // multiple users.
  GAnyLoad *LoadMI;
  Register PtrReg;
  const MachineMemOperand *MMO;
  if (!mi_match(SrcReg, MRI, m_GAnyLoad(LoadMI, m_Reg(PtrReg), m_MMO(MMO))))
    return false;

  Register LoadReg = LoadMI->getDstReg();
  LLT RegTy = MRI.getType(LoadReg);
  unsigned RegSize = RegTy.getSizeInBits();
  unsigned LoadSizeBits = MMO->getSizeInBits().getValue();
  unsigned MaskSizeBits = MaskVal.countr_one();

  if ((isa<GSExtLoad>(LoadMI) || MaskSizeBits < LoadSizeBits) &&
      !MRI.hasOneNonDBGUse(LoadReg))
    return false;

  // The mask may not be larger than the in-memory type, as it might cover sign
  // extended bits
  if (MaskSizeBits > LoadSizeBits)
    return false;

  // If the mask covers the whole destination register, there's nothing to
  // extend
  if (MaskSizeBits >= RegSize)
    return false;

  // Most targets cannot deal with loads of size < 8 and need to re-legalize to
  // at least byte loads. Avoid creating such loads here
  if (MaskSizeBits < 8 || !isPowerOf2_32(MaskSizeBits))
    return false;

  LegalityQuery::MemDesc MemDesc(*MMO);

  // Don't modify the memory access size if this is atomic/volatile, but we can
  // still adjust the opcode to indicate the high bit behavior.
  if (!MMO->isAtomic() && !MMO->isVolatile())
    MemDesc.MemoryTy = LLT::scalar(MaskSizeBits);
  else if (LoadSizeBits > MaskSizeBits || LoadSizeBits == RegSize)
    return false;

  // TODO: Could check if it's legal with the reduced or original memory size.
  if (!isLegalOrBeforeLegalizer(
          {TargetOpcode::G_ZEXTLOAD, {RegTy, MRI.getType(PtrReg)}, {MemDesc}}))
    return false;

  MatchInfo = [=](MachineIRBuilder &B) {
    B.setInstrAndDebugLoc(*LoadMI);
    auto &MF = B.getMF();
    auto PtrInfo = MMO->getPointerInfo();
    auto *NewMMO = MF.getMachineMemOperand(MMO, PtrInfo, MemDesc.MemoryTy);
    B.buildLoadInstr(TargetOpcode::G_ZEXTLOAD, Dst, PtrReg, *NewMMO);
    replaceRegWith(MRI, LoadReg, Dst);
    LoadMI->eraseFromParent();
  };
  return true;
}

bool CombinerHelper::isPredecessor(const MachineInstr &DefMI,
                                   const MachineInstr &UseMI) const {
  assert(!DefMI.isDebugInstr() && !UseMI.isDebugInstr() &&
         "shouldn't consider debug uses");
  assert(DefMI.getParent() == UseMI.getParent());
  if (&DefMI == &UseMI)
    return true;
  const MachineBasicBlock &MBB = *DefMI.getParent();
  auto DefOrUse = find_if(MBB, [&DefMI, &UseMI](const MachineInstr &MI) {
    return &MI == &DefMI || &MI == &UseMI;
  });
  if (DefOrUse == MBB.end())
    llvm_unreachable("Block must contain both DefMI and UseMI!");
  return &*DefOrUse == &DefMI;
}

bool CombinerHelper::dominates(const MachineInstr &DefMI,
                               const MachineInstr &UseMI) const {
  assert(!DefMI.isDebugInstr() && !UseMI.isDebugInstr() &&
         "shouldn't consider debug uses");
  if (MDT)
    return MDT->dominates(&DefMI, &UseMI);
  else if (DefMI.getParent() != UseMI.getParent())
    return false;

  return isPredecessor(DefMI, UseMI);
}

bool CombinerHelper::matchSextTruncSextLoad(MachineInstr &MI) const {
  assert(MI.getOpcode() == TargetOpcode::G_SEXT_INREG);
  Register SrcReg = MI.getOperand(1).getReg();
  Register LoadUser = SrcReg;

  if (MRI.getType(SrcReg).isVector())
    return false;

  Register TruncSrc;
  if (mi_match(SrcReg, MRI, m_GTrunc(m_Reg(TruncSrc))))
    LoadUser = TruncSrc;

  uint64_t SizeInBits = MI.getOperand(2).getImm();
  // If the source is a G_SEXTLOAD from the same bit width, then we don't
  // need any extend at all, just a truncate.
  if (auto *LoadMI = getOpcodeDef<GSExtLoad>(LoadUser, MRI)) {
    // If truncating more than the original extended value, abort.
    auto LoadSizeBits = LoadMI->getMemSizeInBits();
    if (TruncSrc &&
        MRI.getType(TruncSrc).getSizeInBits() < LoadSizeBits.getValue())
      return false;
    if (LoadSizeBits == SizeInBits)
      return true;
  }
  return false;
}

bool CombinerHelper::matchSextInRegOfLoad(
    MachineInstr &MI, std::tuple<Register, unsigned> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_SEXT_INREG);

  Register DstReg = MI.getOperand(0).getReg();
  LLT RegTy = MRI.getType(DstReg);

  // Only supports scalars for now.
  if (RegTy.isVector())
    return false;

  Register SrcReg = MI.getOperand(1).getReg();
  Register PtrReg;
  const MachineMemOperand *MMO;
  if (!mi_match(SrcReg, MRI, m_GLoad(m_Reg(PtrReg), m_MMO(MMO))))
    return false;

  uint64_t MemBits = MMO->getSizeInBits().getValue();
  uint64_t ExtFrom = MI.getOperand(2).getImm();

  if (MemBits > ExtFrom && !MRI.hasOneNonDBGUse(SrcReg))
    return false;

  // If the sign extend extends from a narrower width than the load's width,
  // then we can narrow the load width when we combine to a G_SEXTLOAD.
  // Avoid widening the load at all.
  unsigned NewSizeBits = std::min(ExtFrom, MemBits);

  // Don't generate G_SEXTLOADs with a < 1 byte width.
  if (NewSizeBits < 8)
    return false;
  // Don't bother creating a non-power-2 sextload, it will likely be broken up
  // anyway for most targets.
  if (!isPowerOf2_32(NewSizeBits))
    return false;

  LegalityQuery::MemDesc MMDesc(*MMO);

  // Don't modify the memory access size if this is atomic/volatile, but we can
  // still adjust the opcode to indicate the high bit behavior.
  if (!MMO->isAtomic() && !MMO->isVolatile())
    MMDesc.MemoryTy = LLT::scalar(NewSizeBits);
  else if (MemBits > NewSizeBits || MemBits == RegTy.getSizeInBits())
    return false;

  // TODO: Could check if it's legal with the reduced or original memory size.
  if (!isLegalOrBeforeLegalizer(
          {TargetOpcode::G_SEXTLOAD, {RegTy, MRI.getType(PtrReg)}, {MMDesc}}))
    return false;

  MatchInfo = std::make_tuple(SrcReg, NewSizeBits);
  return true;
}

void CombinerHelper::applySextInRegOfLoad(
    MachineInstr &MI, std::tuple<Register, unsigned> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_SEXT_INREG);
  Register LoadReg;
  unsigned ScalarSizeBits;
  std::tie(LoadReg, ScalarSizeBits) = MatchInfo;
  GLoad *LoadDef = cast<GLoad>(MRI.getVRegDef(LoadReg));

  // If we have the following:
  // %ld = G_LOAD %ptr, (load 2)
  // %ext = G_SEXT_INREG %ld, 8
  //    ==>
  // %ld = G_SEXTLOAD %ptr (load 1)

  auto &MMO = LoadDef->getMMO();
  Builder.setInstrAndDebugLoc(*LoadDef);
  auto &MF = Builder.getMF();
  auto PtrInfo = MMO.getPointerInfo();
  auto *NewMMO = MF.getMachineMemOperand(&MMO, PtrInfo, ScalarSizeBits / 8);
  Builder.buildLoadInstr(TargetOpcode::G_SEXTLOAD, MI.getOperand(0).getReg(),
                         LoadDef->getPointerReg(), *NewMMO);
  replaceRegWith(MRI, LoadReg, MI.getOperand(0).getReg());
  MI.eraseFromParent();

  // Not all loads can be deleted, so make sure the old one is removed.
  LoadDef->eraseFromParent();
}

/// Return true if 'MI' is a load or a store that may be fold it's address
/// operand into the load / store addressing mode.
static bool canFoldInAddressingMode(GLoadStore *MI, const TargetLowering &TLI,
                                    MachineRegisterInfo &MRI) {
  TargetLowering::AddrMode AM;
  auto *MF = MI->getMF();
  auto *Addr = getOpcodeDef<GPtrAdd>(MI->getPointerReg(), MRI);
  if (!Addr)
    return false;

  AM.HasBaseReg = true;
  if (auto CstOff = getIConstantVRegVal(Addr->getOffsetReg(), MRI))
    AM.BaseOffs = CstOff->getSExtValue(); // [reg +/- imm]
  else
    AM.Scale = 1; // [reg +/- reg]

  return TLI.isLegalAddressingMode(
      MF->getDataLayout(), AM,
      getTypeForLLT(MI->getMMO().getMemoryType(),
                    MF->getFunction().getContext()),
      MI->getMMO().getAddrSpace());
}

static unsigned getIndexedOpc(unsigned LdStOpc) {
  switch (LdStOpc) {
  case TargetOpcode::G_LOAD:
    return TargetOpcode::G_INDEXED_LOAD;
  case TargetOpcode::G_STORE:
    return TargetOpcode::G_INDEXED_STORE;
  case TargetOpcode::G_ZEXTLOAD:
    return TargetOpcode::G_INDEXED_ZEXTLOAD;
  case TargetOpcode::G_SEXTLOAD:
    return TargetOpcode::G_INDEXED_SEXTLOAD;
  default:
    llvm_unreachable("Unexpected opcode");
  }
}

bool CombinerHelper::isIndexedLoadStoreLegal(GLoadStore &LdSt) const {
  // Check for legality.
  LLT PtrTy = MRI.getType(LdSt.getPointerReg());
  LLT Ty = MRI.getType(LdSt.getReg(0));
  LLT MemTy = LdSt.getMMO().getMemoryType();
  SmallVector<LegalityQuery::MemDesc, 2> MemDescrs(
      {{MemTy, MemTy.getSizeInBits().getKnownMinValue(),
        AtomicOrdering::NotAtomic, AtomicOrdering::NotAtomic}});
  unsigned IndexedOpc = getIndexedOpc(LdSt.getOpcode());
  SmallVector<LLT> OpTys;
  if (IndexedOpc == TargetOpcode::G_INDEXED_STORE)
    OpTys = {PtrTy, Ty, Ty};
  else
    OpTys = {Ty, PtrTy}; // For G_INDEXED_LOAD, G_INDEXED_[SZ]EXTLOAD

  LegalityQuery Q(IndexedOpc, OpTys, MemDescrs);
  return isLegal(Q);
}

static cl::opt<unsigned> PostIndexUseThreshold(
    "post-index-use-threshold", cl::Hidden, cl::init(32),
    cl::desc("Number of uses of a base pointer to check before it is no longer "
             "considered for post-indexing."));

bool CombinerHelper::findPostIndexCandidate(GLoadStore &LdSt, Register &Addr,
                                            Register &Base, Register &Offset,
                                            bool &RematOffset) const {
  // We're looking for the following pattern, for either load or store:
  // %baseptr:_(p0) = ...
  // G_STORE %val(s64), %baseptr(p0)
  // %offset:_(s64) = G_CONSTANT i64 -256
  // %new_addr:_(p0) = G_PTR_ADD %baseptr, %offset(s64)
  const auto &TLI = getTargetLowering();

  Register Ptr = LdSt.getPointerReg();
  // If the store is the only use, don't bother.
  if (MRI.hasOneNonDBGUse(Ptr))
    return false;

  if (!isIndexedLoadStoreLegal(LdSt))
    return false;

  if (getOpcodeDef(TargetOpcode::G_FRAME_INDEX, Ptr, MRI))
    return false;

  MachineInstr *StoredValDef = getDefIgnoringCopies(LdSt.getReg(0), MRI);
  MachineInstr *PtrDef;
  if (!mi_match(Ptr, MRI, m_MInstr(PtrDef)))
    return false;

  unsigned NumUsesChecked = 0;
  for (auto &Use : MRI.use_nodbg_instructions(Ptr)) {
    if (++NumUsesChecked > PostIndexUseThreshold)
      return false; // Try to avoid exploding compile time.

    auto *PtrAdd = dyn_cast<GPtrAdd>(&Use);
    // The use itself might be dead. This can happen during combines if DCE
    // hasn't had a chance to run yet. Don't allow it to form an indexed op.
    if (!PtrAdd || MRI.use_nodbg_empty(PtrAdd->getReg(0)))
      continue;

    // Check the user of this isn't the store, otherwise we'd be generate a
    // indexed store defining its own use.
    if (StoredValDef == &Use)
      continue;

    Offset = PtrAdd->getOffsetReg();
    if (!ForceLegalIndexing &&
        !TLI.isIndexingLegal(LdSt, PtrAdd->getBaseReg(), Offset,
                             /*IsPre*/ false, MRI))
      continue;

    // Make sure the offset calculation is before the potentially indexed op.
    MachineInstr *OffsetDef;
    if (!mi_match(Offset, MRI, m_MInstr(OffsetDef)))
      continue;
    RematOffset = false;
    if (!dominates(*OffsetDef, LdSt)) {
      // If the offset however is just a G_CONSTANT, we can always just
      // rematerialize it where we need it.
      if (OffsetDef->getOpcode() != TargetOpcode::G_CONSTANT)
        continue;
      RematOffset = true;
    }

    for (auto &BasePtrUse : MRI.use_nodbg_instructions(PtrAdd->getBaseReg())) {
      if (&BasePtrUse == PtrDef)
        continue;

      // If the user is a later load/store that can be post-indexed, then don't
      // combine this one.
      auto *BasePtrLdSt = dyn_cast<GLoadStore>(&BasePtrUse);
      if (BasePtrLdSt && BasePtrLdSt != &LdSt &&
          dominates(LdSt, *BasePtrLdSt) &&
          isIndexedLoadStoreLegal(*BasePtrLdSt))
        return false;

      // Now we're looking for the key G_PTR_ADD instruction, which contains
      // the offset add that we want to fold.
      if (auto *BasePtrUseDef = dyn_cast<GPtrAdd>(&BasePtrUse)) {
        Register PtrAddDefReg = BasePtrUseDef->getReg(0);
        for (auto &BaseUseUse : MRI.use_nodbg_instructions(PtrAddDefReg)) {
          // If the use is in a different block, then we may produce worse code
          // due to the extra register pressure.
          if (BaseUseUse.getParent() != LdSt.getParent())
            return false;

          if (auto *UseUseLdSt = dyn_cast<GLoadStore>(&BaseUseUse))
            if (canFoldInAddressingMode(UseUseLdSt, TLI, MRI))
              return false;
        }
        if (!dominates(LdSt, BasePtrUse))
          return false; // All use must be dominated by the load/store.
      }
    }

    Addr = PtrAdd->getReg(0);
    Base = PtrAdd->getBaseReg();
    return true;
  }

  return false;
}

bool CombinerHelper::findPreIndexCandidate(GLoadStore &LdSt, Register &Addr,
                                           Register &Base,
                                           Register &Offset) const {
  auto &MF = *LdSt.getParent()->getParent();
  const auto &TLI = *MF.getSubtarget().getTargetLowering();

  Addr = LdSt.getPointerReg();
  if (!mi_match(Addr, MRI, m_GPtrAdd(m_Reg(Base), m_Reg(Offset))) ||
      MRI.hasOneNonDBGUse(Addr))
    return false;

  if (!ForceLegalIndexing &&
      !TLI.isIndexingLegal(LdSt, Base, Offset, /*IsPre*/ true, MRI))
    return false;

  if (!isIndexedLoadStoreLegal(LdSt))
    return false;

  MachineInstr *BaseDef = getDefIgnoringCopies(Base, MRI);
  if (BaseDef->getOpcode() == TargetOpcode::G_FRAME_INDEX)
    return false;

  if (auto *St = dyn_cast<GStore>(&LdSt)) {
    // Would require a copy.
    if (Base == St->getValueReg())
      return false;

    // We're expecting one use of Addr in MI, but it could also be the
    // value stored, which isn't actually dominated by the instruction.
    if (St->getValueReg() == Addr)
      return false;
  }

  // Avoid increasing cross-block register pressure.
  for (auto &AddrUse : MRI.use_nodbg_instructions(Addr))
    if (AddrUse.getParent() != LdSt.getParent())
      return false;

  // FIXME: check whether all uses of the base pointer are constant PtrAdds.
  // That might allow us to end base's liveness here by adjusting the constant.
  bool RealUse = false;
  for (auto &AddrUse : MRI.use_nodbg_instructions(Addr)) {
    if (!dominates(LdSt, AddrUse))
      return false; // All use must be dominated by the load/store.

    // If Ptr may be folded in addressing mode of other use, then it's
    // not profitable to do this transformation.
    if (auto *UseLdSt = dyn_cast<GLoadStore>(&AddrUse)) {
      if (!canFoldInAddressingMode(UseLdSt, TLI, MRI))
        RealUse = true;
    } else {
      RealUse = true;
    }
  }
  return RealUse;
}

bool CombinerHelper::matchCombineExtractedVectorLoad(
    MachineInstr &MI, BuildFnTy &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_EXTRACT_VECTOR_ELT);

  // Check if there is a load that defines the vector being extracted from.
  auto *LoadMI = getOpcodeDef<GLoad>(MI.getOperand(1).getReg(), MRI);
  if (!LoadMI)
    return false;

  Register Vector = MI.getOperand(1).getReg();
  LLT VecEltTy = MRI.getType(Vector).getElementType();

  assert(MRI.getType(MI.getOperand(0).getReg()) == VecEltTy);

  // Checking whether we should reduce the load width.
  if (!MRI.hasOneNonDBGUse(Vector))
    return false;

  // Check if the defining load is simple.
  if (!LoadMI->isSimple())
    return false;

  // If the vector element type is not a multiple of a byte then we are unable
  // to correctly compute an address to load only the extracted element as a
  // scalar.
  if (!VecEltTy.isByteSized())
    return false;

  // Check for load fold barriers between the extraction and the load.
  if (MI.getParent() != LoadMI->getParent())
    return false;
  const unsigned MaxIter = 20;
  unsigned Iter = 0;
  for (auto II = LoadMI->getIterator(), IE = MI.getIterator(); II != IE; ++II) {
    if (II->isLoadFoldBarrier())
      return false;
    if (Iter++ == MaxIter)
      return false;
  }

  // Check if the new load that we are going to create is legal
  // if we are in the post-legalization phase.
  MachineMemOperand MMO = LoadMI->getMMO();
  Align Alignment = MMO.getAlign();
  MachinePointerInfo PtrInfo;
  uint64_t Offset;

  // Finding the appropriate PtrInfo if offset is a known constant.
  // This is required to create the memory operand for the narrowed load.
  // This machine memory operand object helps us infer about legality
  // before we proceed to combine the instruction.
  if (auto CVal = getIConstantVRegVal(Vector, MRI)) {
    int Elt = CVal->getZExtValue();
    // FIXME: should be (ABI size)*Elt.
    Offset = VecEltTy.getSizeInBits() * Elt / 8;
    PtrInfo = MMO.getPointerInfo().getWithOffset(Offset);
  } else {
    // Discard the pointer info except the address space because the memory
    // operand can't represent this new access since the offset is variable.
    Offset = VecEltTy.getSizeInBits() / 8;
    PtrInfo = MachinePointerInfo(MMO.getPointerInfo().getAddrSpace());
  }

  Alignment = commonAlignment(Alignment, Offset);

  Register VecPtr = LoadMI->getPointerReg();
  LLT PtrTy = MRI.getType(VecPtr);

  MachineFunction &MF = *MI.getMF();
  auto *NewMMO = MF.getMachineMemOperand(&MMO, PtrInfo, VecEltTy);

  LegalityQuery::MemDesc MMDesc(*NewMMO);

  if (!isLegalOrBeforeLegalizer(
          {TargetOpcode::G_LOAD, {VecEltTy, PtrTy}, {MMDesc}}))
    return false;

  // Load must be allowed and fast on the target.
  LLVMContext &C = MF.getFunction().getContext();
  auto &DL = MF.getDataLayout();
  unsigned Fast = 0;
  if (!getTargetLowering().allowsMemoryAccess(C, DL, VecEltTy, *NewMMO,
                                              &Fast) ||
      !Fast)
    return false;

  Register Result = MI.getOperand(0).getReg();
  Register Index = MI.getOperand(2).getReg();

  MatchInfo = [=](MachineIRBuilder &B) {
    GISelObserverWrapper DummyObserver;
    LegalizerHelper Helper(B.getMF(), DummyObserver, B);
    //// Get pointer to the vector element.
    Register finalPtr = Helper.getVectorElementPointer(
        LoadMI->getPointerReg(), MRI.getType(LoadMI->getOperand(0).getReg()),
        Index);
    // New G_LOAD instruction.
    B.buildLoad(Result, finalPtr, PtrInfo, Alignment);
    // Remove original GLOAD instruction.
    LoadMI->eraseFromParent();
  };

  return true;
}

bool CombinerHelper::matchCombineIndexedLoadStore(
    MachineInstr &MI, IndexedLoadStoreMatchInfo &MatchInfo) const {
  auto &LdSt = cast<GLoadStore>(MI);

  if (LdSt.isAtomic())
    return false;

  MatchInfo.IsPre = findPreIndexCandidate(LdSt, MatchInfo.Addr, MatchInfo.Base,
                                          MatchInfo.Offset);
  if (!MatchInfo.IsPre &&
      !findPostIndexCandidate(LdSt, MatchInfo.Addr, MatchInfo.Base,
                              MatchInfo.Offset, MatchInfo.RematOffset))
    return false;

  return true;
}

void CombinerHelper::applyCombineIndexedLoadStore(
    MachineInstr &MI, IndexedLoadStoreMatchInfo &MatchInfo) const {
  MachineInstr &AddrDef = *MRI.getVRegDef(MatchInfo.Addr);
  unsigned Opcode = MI.getOpcode();
  bool IsStore = Opcode == TargetOpcode::G_STORE;
  unsigned NewOpcode = getIndexedOpc(Opcode);

  // If the offset constant didn't happen to dominate the load/store, we can
  // just clone it as needed.
  if (MatchInfo.RematOffset) {
    auto *OldCst = MRI.getVRegDef(MatchInfo.Offset);
    auto NewCst = Builder.buildConstant(MRI.getType(MatchInfo.Offset),
                                        *OldCst->getOperand(1).getCImm());
    MatchInfo.Offset = NewCst.getReg(0);
  }

  auto MIB = Builder.buildInstr(NewOpcode);
  if (IsStore) {
    MIB.addDef(MatchInfo.Addr);
    MIB.addUse(MI.getOperand(0).getReg());
  } else {
    MIB.addDef(MI.getOperand(0).getReg());
    MIB.addDef(MatchInfo.Addr);
  }

  MIB.addUse(MatchInfo.Base);
  MIB.addUse(MatchInfo.Offset);
  MIB.addImm(MatchInfo.IsPre);
  MIB->cloneMemRefs(*MI.getMF(), MI);
  MI.eraseFromParent();
  AddrDef.eraseFromParent();

  LLVM_DEBUG(dbgs() << "    Combinined to indexed operation");
}

bool CombinerHelper::matchCombineDivRem(MachineInstr &MI,
                                        MachineInstr *&OtherMI) const {
  unsigned Opcode = MI.getOpcode();
  bool IsDiv, IsSigned;

  switch (Opcode) {
  default:
    llvm_unreachable("Unexpected opcode!");
  case TargetOpcode::G_SDIV:
  case TargetOpcode::G_UDIV: {
    IsDiv = true;
    IsSigned = Opcode == TargetOpcode::G_SDIV;
    break;
  }
  case TargetOpcode::G_SREM:
  case TargetOpcode::G_UREM: {
    IsDiv = false;
    IsSigned = Opcode == TargetOpcode::G_SREM;
    break;
  }
  }

  Register Src1 = MI.getOperand(1).getReg();
  unsigned DivOpcode, RemOpcode, DivremOpcode;
  if (IsSigned) {
    DivOpcode = TargetOpcode::G_SDIV;
    RemOpcode = TargetOpcode::G_SREM;
    DivremOpcode = TargetOpcode::G_SDIVREM;
  } else {
    DivOpcode = TargetOpcode::G_UDIV;
    RemOpcode = TargetOpcode::G_UREM;
    DivremOpcode = TargetOpcode::G_UDIVREM;
  }

  if (!isLegalOrBeforeLegalizer({DivremOpcode, {MRI.getType(Src1)}}))
    return false;

  // Combine:
  //   %div:_ = G_[SU]DIV %src1:_, %src2:_
  //   %rem:_ = G_[SU]REM %src1:_, %src2:_
  // into:
  //  %div:_, %rem:_ = G_[SU]DIVREM %src1:_, %src2:_

  // Combine:
  //   %rem:_ = G_[SU]REM %src1:_, %src2:_
  //   %div:_ = G_[SU]DIV %src1:_, %src2:_
  // into:
  //  %div:_, %rem:_ = G_[SU]DIVREM %src1:_, %src2:_

  for (auto &UseMI : MRI.use_nodbg_instructions(Src1)) {
    if (MI.getParent() == UseMI.getParent() &&
        ((IsDiv && UseMI.getOpcode() == RemOpcode) ||
         (!IsDiv && UseMI.getOpcode() == DivOpcode)) &&
        matchEqualDefs(MI.getOperand(2), UseMI.getOperand(2)) &&
        matchEqualDefs(MI.getOperand(1), UseMI.getOperand(1))) {
      OtherMI = &UseMI;
      return true;
    }
  }

  return false;
}

void CombinerHelper::applyCombineDivRem(MachineInstr &MI,
                                        MachineInstr *&OtherMI) const {
  unsigned Opcode = MI.getOpcode();
  assert(OtherMI && "OtherMI shouldn't be empty.");

  Register DestDivReg, DestRemReg;
  if (Opcode == TargetOpcode::G_SDIV || Opcode == TargetOpcode::G_UDIV) {
    DestDivReg = MI.getOperand(0).getReg();
    DestRemReg = OtherMI->getOperand(0).getReg();
  } else {
    DestDivReg = OtherMI->getOperand(0).getReg();
    DestRemReg = MI.getOperand(0).getReg();
  }

  bool IsSigned =
      Opcode == TargetOpcode::G_SDIV || Opcode == TargetOpcode::G_SREM;

  // Check which instruction is first in the block so we don't break def-use
  // deps by "moving" the instruction incorrectly. Also keep track of which
  // instruction is first so we pick it's operands, avoiding use-before-def
  // bugs.
  MachineInstr *FirstInst = dominates(MI, *OtherMI) ? &MI : OtherMI;
  Builder.setInstrAndDebugLoc(*FirstInst);

  Builder.buildInstr(IsSigned ? TargetOpcode::G_SDIVREM
                              : TargetOpcode::G_UDIVREM,
                     {DestDivReg, DestRemReg},
                     { FirstInst->getOperand(1), FirstInst->getOperand(2) });
  MI.eraseFromParent();
  OtherMI->eraseFromParent();
}

bool CombinerHelper::matchOptBrCondByInvertingCond(
    MachineInstr &MI, MachineInstr *&BrCond) const {
  assert(MI.getOpcode() == TargetOpcode::G_BR);

  // Try to match the following:
  // bb1:
  //   G_BRCOND %c1, %bb2
  //   G_BR %bb3
  // bb2:
  // ...
  // bb3:

  // The above pattern does not have a fall through to the successor bb2, always
  // resulting in a branch no matter which path is taken. Here we try to find
  // and replace that pattern with conditional branch to bb3 and otherwise
  // fallthrough to bb2. This is generally better for branch predictors.

  MachineBasicBlock *MBB = MI.getParent();
  MachineBasicBlock::iterator BrIt(MI);
  if (BrIt == MBB->begin())
    return false;
  assert(std::next(BrIt) == MBB->end() && "expected G_BR to be a terminator");

  BrCond = &*std::prev(BrIt);
  if (BrCond->getOpcode() != TargetOpcode::G_BRCOND)
    return false;

  // Check that the next block is the conditional branch target. Also make sure
  // that it isn't the same as the G_BR's target (otherwise, this will loop.)
  MachineBasicBlock *BrCondTarget = BrCond->getOperand(1).getMBB();
  return BrCondTarget != MI.getOperand(0).getMBB() &&
         MBB->isLayoutSuccessor(BrCondTarget);
}

void CombinerHelper::applyOptBrCondByInvertingCond(
    MachineInstr &MI, MachineInstr *&BrCond) const {
  MachineBasicBlock *BrTarget = MI.getOperand(0).getMBB();
  Builder.setInstrAndDebugLoc(*BrCond);
  LLT Ty = MRI.getType(BrCond->getOperand(0).getReg());
  // FIXME: Does int/fp matter for this? If so, we might need to restrict
  // this to i1 only since we might not know for sure what kind of
  // compare generated the condition value.
  auto True = Builder.buildConstant(
      Ty, getICmpTrueVal(getTargetLowering(), false, false));
  auto Xor = Builder.buildXor(Ty, BrCond->getOperand(0), True);

  auto *FallthroughBB = BrCond->getOperand(1).getMBB();
  Observer.changingInstr(MI);
  MI.getOperand(0).setMBB(FallthroughBB);
  Observer.changedInstr(MI);

  // Change the conditional branch to use the inverted condition and
  // new target block.
  Observer.changingInstr(*BrCond);
  BrCond->getOperand(0).setReg(Xor.getReg(0));
  BrCond->getOperand(1).setMBB(BrTarget);
  Observer.changedInstr(*BrCond);
}

bool CombinerHelper::matchCombineMemCpyFamily(
    MachineInstr &MI, MemCpyFamilyLoweringInfo &MatchInfo,
    unsigned MaxLen) const {
  auto &[Dst, Src, KnownLen, Alignment, DstAlignCanChange, MemOps] = MatchInfo;
  return canLowerMemCpyFamily(MI, MRI, MaxLen, Dst, Src, KnownLen, Alignment,
                              DstAlignCanChange, MemOps);
}

void CombinerHelper::applyCombineMemCpyFamily(
    MachineInstr &MI, MemCpyFamilyLoweringInfo &MatchInfo) const {
  auto &[Dst, Src, KnownLen, Alignment, DstAlignCanChange, MemOps] = MatchInfo;
  MachineIRBuilder HelperBuilder(MI);
  GISelObserverWrapper DummyObserver;
  LegalizerHelper Helper(HelperBuilder.getMF(), DummyObserver, HelperBuilder);
  bool Changed = Helper.lowerMemCpyFamily(MI, Dst, Src, KnownLen, Alignment,
                                          DstAlignCanChange, MemOps) ==
                 LegalizerHelper::LegalizeResult::Legalized;
  assert(Changed && "expected memcpy-family instruction to lower");
  (void)Changed;
}

bool CombinerHelper::tryCombineMemCpyFamily(MachineInstr &MI,
                                            unsigned MaxLen) const {
  MachineIRBuilder HelperBuilder(MI);
  GISelObserverWrapper DummyObserver;
  LegalizerHelper Helper(HelperBuilder.getMF(), DummyObserver, HelperBuilder);
  return Helper.lowerMemCpyFamily(MI, MaxLen) ==
         LegalizerHelper::LegalizeResult::Legalized;
}

static APFloat constantFoldFpUnary(const MachineInstr &MI,
                                   const MachineRegisterInfo &MRI,
                                   const APFloat &Val) {
  APFloat Result(Val);
  switch (MI.getOpcode()) {
  default:
    llvm_unreachable("Unexpected opcode!");
  case TargetOpcode::G_FNEG: {
    Result.changeSign();
    return Result;
  }
  case TargetOpcode::G_FABS: {
    Result.clearSign();
    return Result;
  }
  case TargetOpcode::G_FCEIL:
    Result.roundToIntegral(APFloat::rmTowardPositive);
    return Result;
  case TargetOpcode::G_FFLOOR:
    Result.roundToIntegral(APFloat::rmTowardNegative);
    return Result;
  case TargetOpcode::G_INTRINSIC_TRUNC:
    Result.roundToIntegral(APFloat::rmTowardZero);
    return Result;
  case TargetOpcode::G_INTRINSIC_ROUND:
    Result.roundToIntegral(APFloat::rmNearestTiesToAway);
    return Result;
  case TargetOpcode::G_INTRINSIC_ROUNDEVEN:
    Result.roundToIntegral(APFloat::rmNearestTiesToEven);
    return Result;
  case TargetOpcode::G_FRINT:
  case TargetOpcode::G_FNEARBYINT:
    // Use default rounding mode (round to nearest, ties to even)
    Result.roundToIntegral(APFloat::rmNearestTiesToEven);
    return Result;
  case TargetOpcode::G_FPEXT:
  case TargetOpcode::G_FPTRUNC: {
    bool Unused;
    LLT DstTy = MRI.getType(MI.getOperand(0).getReg());
    Result.convert(getFltSemanticForLLT(DstTy), APFloat::rmNearestTiesToEven,
                   &Unused);
    return Result;
  }
  case TargetOpcode::G_FSQRT: {
    bool Unused;
    Result.convert(APFloat::IEEEdouble(), APFloat::rmNearestTiesToEven,
                   &Unused);
    Result = APFloat(sqrt(Result.convertToDouble()));
    break;
  }
  case TargetOpcode::G_FLOG2: {
    bool Unused;
    Result.convert(APFloat::IEEEdouble(), APFloat::rmNearestTiesToEven,
                   &Unused);
    Result = APFloat(log2(Result.convertToDouble()));
    break;
  }
  }
  // Convert `APFloat` to appropriate IEEE type depending on `DstTy`. Otherwise,
  // `buildFConstant` will assert on size mismatch. Only `G_FSQRT`, and
  // `G_FLOG2` reach here.
  bool Unused;
  Result.convert(Val.getSemantics(), APFloat::rmNearestTiesToEven, &Unused);
  return Result;
}

void CombinerHelper::applyCombineConstantFoldFpUnary(
    MachineInstr &MI, const ConstantFP *Cst) const {
  APFloat Folded = constantFoldFpUnary(MI, MRI, Cst->getValue());
  const ConstantFP *NewCst = ConstantFP::get(Builder.getContext(), Folded);
  Builder.buildFConstant(MI.getOperand(0), *NewCst);
  MI.eraseFromParent();
}

bool CombinerHelper::matchPtrAddImmedChain(MachineInstr &MI,
                                           PtrAddChain &MatchInfo) const {
  // We're trying to match the following pattern:
  //   %t1 = G_PTR_ADD %base, G_CONSTANT imm1
  //   %root = G_PTR_ADD %t1, G_CONSTANT imm2
  // -->
  //   %root = G_PTR_ADD %base, G_CONSTANT (imm1 + imm2)

  if (MI.getOpcode() != TargetOpcode::G_PTR_ADD)
    return false;

  Register Add2 = MI.getOperand(1).getReg();
  Register Imm1 = MI.getOperand(2).getReg();
  auto MaybeImmVal = getIConstantVRegValWithLookThrough(Imm1, MRI);
  if (!MaybeImmVal)
    return false;

  Register Base, Imm2;
  uint32_t LHSPtrAddFlags;
  if (!mi_match(Add2, MRI,
                m_GPtrAdd(m_Reg(Base), m_Reg(Imm2), m_MIFlags(LHSPtrAddFlags))))
    return false;

  auto MaybeImm2Val = getIConstantVRegValWithLookThrough(Imm2, MRI);
  if (!MaybeImm2Val)
    return false;

  // Check if the new combined immediate forms an illegal addressing mode.
  // Do not combine if it was legal before but would get illegal.
  // To do so, we need to find a load/store user of the pointer to get
  // the access type.
  Type *AccessTy = nullptr;
  auto &MF = *MI.getMF();
  for (auto &UseMI : MRI.use_nodbg_instructions(MI.getOperand(0).getReg())) {
    if (auto *LdSt = dyn_cast<GLoadStore>(&UseMI)) {
      AccessTy = getTypeForLLT(MRI.getType(LdSt->getReg(0)),
                               MF.getFunction().getContext());
      break;
    }
  }
  TargetLoweringBase::AddrMode AMNew;
  APInt CombinedImm = MaybeImmVal->Value + MaybeImm2Val->Value;
  AMNew.BaseOffs = CombinedImm.getSExtValue();
  if (AccessTy) {
    AMNew.HasBaseReg = true;
    TargetLoweringBase::AddrMode AMOld;
    AMOld.BaseOffs = MaybeImmVal->Value.getSExtValue();
    AMOld.HasBaseReg = true;
    unsigned AS = MRI.getType(Add2).getAddressSpace();
    const auto &TLI = *MF.getSubtarget().getTargetLowering();
    if (TLI.isLegalAddressingMode(MF.getDataLayout(), AMOld, AccessTy, AS) &&
        !TLI.isLegalAddressingMode(MF.getDataLayout(), AMNew, AccessTy, AS))
      return false;
  }

  // Reassociating nuw additions preserves nuw. If both original G_PTR_ADDs are
  // inbounds, reaching the same result in one G_PTR_ADD is also inbounds.
  // The nusw constraints are satisfied because imm1+imm2 cannot exceed the
  // largest signed integer that fits into the index type, which is the maximum
  // size of allocated objects according to the IR Language Reference.
  unsigned PtrAddFlags = MI.getFlags();
  bool IsNoUWrap = PtrAddFlags & LHSPtrAddFlags & MachineInstr::MIFlag::NoUWrap;
  bool IsInBounds =
      PtrAddFlags & LHSPtrAddFlags & MachineInstr::MIFlag::InBounds;
  unsigned Flags = 0;
  if (IsNoUWrap)
    Flags |= MachineInstr::MIFlag::NoUWrap;
  if (IsInBounds) {
    Flags |= MachineInstr::MIFlag::InBounds;
    Flags |= MachineInstr::MIFlag::NoUSWrap;
  }

  // Pass the combined immediate to the apply function.
  MatchInfo.Imm = AMNew.BaseOffs;
  MatchInfo.Base = Base;
  MatchInfo.Bank = getRegBank(Imm2);
  MatchInfo.Flags = Flags;
  return true;
}

void CombinerHelper::applyPtrAddImmedChain(MachineInstr &MI,
                                           PtrAddChain &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_PTR_ADD && "Expected G_PTR_ADD");
  MachineIRBuilder MIB(MI);
  LLT OffsetTy = MRI.getType(MI.getOperand(2).getReg());
  auto NewOffset = MIB.buildConstant(OffsetTy, MatchInfo.Imm);
  setRegBank(NewOffset.getReg(0), MatchInfo.Bank);
  Observer.changingInstr(MI);
  MI.getOperand(1).setReg(MatchInfo.Base);
  MI.getOperand(2).setReg(NewOffset.getReg(0));
  MI.setFlags(MatchInfo.Flags);
  Observer.changedInstr(MI);
}

bool CombinerHelper::matchShiftImmedChain(MachineInstr &MI,
                                          RegisterImmPair &MatchInfo) const {
  // We're trying to match the following pattern with any of
  // G_SHL/G_ASHR/G_LSHR/G_SSHLSAT/G_USHLSAT shift instructions:
  //   %t1 = SHIFT %base, G_CONSTANT imm1
  //   %root = SHIFT %t1, G_CONSTANT imm2
  // -->
  //   %root = SHIFT %base, G_CONSTANT (imm1 + imm2)

  unsigned Opcode = MI.getOpcode();
  assert((Opcode == TargetOpcode::G_SHL || Opcode == TargetOpcode::G_ASHR ||
          Opcode == TargetOpcode::G_LSHR || Opcode == TargetOpcode::G_SSHLSAT ||
          Opcode == TargetOpcode::G_USHLSAT) &&
         "Expected G_SHL, G_ASHR, G_LSHR, G_SSHLSAT or G_USHLSAT");

  Register Shl2 = MI.getOperand(1).getReg();
  Register Imm1 = MI.getOperand(2).getReg();
  auto MaybeImmVal = getIConstantVRegValWithLookThrough(Imm1, MRI);
  if (!MaybeImmVal)
    return false;

  MachineInstr *Shl2Def;
  if (!mi_match(Shl2, MRI, m_MInstr(Shl2Def)) || Shl2Def->getOpcode() != Opcode)
    return false;

  Register Base = Shl2Def->getOperand(1).getReg();
  Register Imm2 = Shl2Def->getOperand(2).getReg();
  auto MaybeImm2Val = getIConstantVRegValWithLookThrough(Imm2, MRI);
  if (!MaybeImm2Val)
    return false;

  // Pass the combined immediate to the apply function.
  MatchInfo.Imm =
      (MaybeImmVal->Value.getZExtValue() + MaybeImm2Val->Value).getZExtValue();
  MatchInfo.Reg = Base;

  // There is no simple replacement for a saturating unsigned left shift that
  // exceeds the scalar size.
  if (Opcode == TargetOpcode::G_USHLSAT &&
      MatchInfo.Imm >= MRI.getType(Shl2).getScalarSizeInBits())
    return false;

  return true;
}

void CombinerHelper::applyShiftImmedChain(MachineInstr &MI,
                                          RegisterImmPair &MatchInfo) const {
  unsigned Opcode = MI.getOpcode();
  assert((Opcode == TargetOpcode::G_SHL || Opcode == TargetOpcode::G_ASHR ||
          Opcode == TargetOpcode::G_LSHR || Opcode == TargetOpcode::G_SSHLSAT ||
          Opcode == TargetOpcode::G_USHLSAT) &&
         "Expected G_SHL, G_ASHR, G_LSHR, G_SSHLSAT or G_USHLSAT");

  LLT Ty = MRI.getType(MI.getOperand(1).getReg());
  unsigned const ScalarSizeInBits = Ty.getScalarSizeInBits();
  auto Imm = MatchInfo.Imm;

  if (Imm >= ScalarSizeInBits) {
    // Any logical shift that exceeds scalar size will produce zero.
    if (Opcode == TargetOpcode::G_SHL || Opcode == TargetOpcode::G_LSHR) {
      Builder.buildConstant(MI.getOperand(0), 0);
      MI.eraseFromParent();
      return;
    }
    // Arithmetic shift and saturating signed left shift have no effect beyond
    // scalar size.
    Imm = ScalarSizeInBits - 1;
  }

  LLT ImmTy = MRI.getType(MI.getOperand(2).getReg());
  Register NewImm = Builder.buildConstant(ImmTy, Imm).getReg(0);
  Observer.changingInstr(MI);
  MI.getOperand(1).setReg(MatchInfo.Reg);
  MI.getOperand(2).setReg(NewImm);
  Observer.changedInstr(MI);
}

bool CombinerHelper::matchShiftOfShiftedLogic(
    MachineInstr &MI, ShiftOfShiftedLogic &MatchInfo) const {
  // We're trying to match the following pattern with any of
  // G_SHL/G_ASHR/G_LSHR/G_USHLSAT/G_SSHLSAT shift instructions in combination
  // with any of G_AND/G_OR/G_XOR logic instructions.
  //   %t1 = SHIFT %X, G_CONSTANT C0
  //   %t2 = LOGIC %t1, %Y
  //   %root = SHIFT %t2, G_CONSTANT C1
  // -->
  //   %t3 = SHIFT %X, G_CONSTANT (C0+C1)
  //   %t4 = SHIFT %Y, G_CONSTANT C1
  //   %root = LOGIC %t3, %t4
  unsigned ShiftOpcode = MI.getOpcode();
  assert((ShiftOpcode == TargetOpcode::G_SHL ||
          ShiftOpcode == TargetOpcode::G_ASHR ||
          ShiftOpcode == TargetOpcode::G_LSHR ||
          ShiftOpcode == TargetOpcode::G_USHLSAT ||
          ShiftOpcode == TargetOpcode::G_SSHLSAT) &&
         "Expected G_SHL, G_ASHR, G_LSHR, G_USHLSAT and G_SSHLSAT");

  // Match a one-use bitwise logic op.
  Register LogicDest = MI.getOperand(1).getReg();
  if (!MRI.hasOneNonDBGUse(LogicDest))
    return false;

  MachineInstr *LogicMI;
  if (!mi_match(LogicDest, MRI, m_MInstr(LogicMI)))
    return false;
  unsigned LogicOpcode = LogicMI->getOpcode();
  if (LogicOpcode != TargetOpcode::G_AND && LogicOpcode != TargetOpcode::G_OR &&
      LogicOpcode != TargetOpcode::G_XOR)
    return false;

  // Find a matching one-use shift by constant.
  const Register C1 = MI.getOperand(2).getReg();
  auto MaybeImmVal = getIConstantVRegValWithLookThrough(C1, MRI);
  if (!MaybeImmVal || MaybeImmVal->Value == 0)
    return false;

  const uint64_t C1Val = MaybeImmVal->Value.getZExtValue();

  auto matchFirstShift = [&](const MachineInstr *MI, uint64_t &ShiftVal) {
    // Shift should match previous one and should be a one-use.
    if (MI->getOpcode() != ShiftOpcode ||
        !MRI.hasOneNonDBGUse(MI->getOperand(0).getReg()))
      return false;

    // Must be a constant.
    auto MaybeImmVal =
        getIConstantVRegValWithLookThrough(MI->getOperand(2).getReg(), MRI);
    if (!MaybeImmVal)
      return false;

    ShiftVal = MaybeImmVal->Value.getSExtValue();
    return true;
  };

  // Logic ops are commutative, so check each operand for a match.
  Register LogicMIReg1 = LogicMI->getOperand(1).getReg();
  MachineInstr *LogicMIOp1;
  Register LogicMIReg2 = LogicMI->getOperand(2).getReg();
  MachineInstr *LogicMIOp2;
  if (!mi_match(LogicMIReg1, MRI, m_MInstr(LogicMIOp1)) ||
      !mi_match(LogicMIReg2, MRI, m_MInstr(LogicMIOp2)))
    return false;
  uint64_t C0Val;

  if (matchFirstShift(LogicMIOp1, C0Val)) {
    MatchInfo.LogicNonShiftReg = LogicMIReg2;
    MatchInfo.Shift2 = LogicMIOp1;
  } else if (matchFirstShift(LogicMIOp2, C0Val)) {
    MatchInfo.LogicNonShiftReg = LogicMIReg1;
    MatchInfo.Shift2 = LogicMIOp2;
  } else
    return false;

  MatchInfo.ValSum = C0Val + C1Val;

  // The fold is not valid if the sum of the shift values exceeds bitwidth.
  if (MatchInfo.ValSum >= MRI.getType(LogicDest).getScalarSizeInBits())
    return false;

  MatchInfo.Logic = LogicMI;
  return true;
}

void CombinerHelper::applyShiftOfShiftedLogic(
    MachineInstr &MI, ShiftOfShiftedLogic &MatchInfo) const {
  unsigned Opcode = MI.getOpcode();
  assert((Opcode == TargetOpcode::G_SHL || Opcode == TargetOpcode::G_ASHR ||
          Opcode == TargetOpcode::G_LSHR || Opcode == TargetOpcode::G_USHLSAT ||
          Opcode == TargetOpcode::G_SSHLSAT) &&
         "Expected G_SHL, G_ASHR, G_LSHR, G_USHLSAT and G_SSHLSAT");

  LLT ShlType = MRI.getType(MI.getOperand(2).getReg());
  LLT DestType = MRI.getType(MI.getOperand(0).getReg());

  Register Const = Builder.buildConstant(ShlType, MatchInfo.ValSum).getReg(0);

  Register Shift1Base = MatchInfo.Shift2->getOperand(1).getReg();
  Register Shift1 =
      Builder.buildInstr(Opcode, {DestType}, {Shift1Base, Const}).getReg(0);

  // If LogicNonShiftReg is the same to Shift1Base, and shift1 const is the same
  // to MatchInfo.Shift2 const, CSEMIRBuilder will reuse the old shift1 when
  // build shift2. So, if we erase MatchInfo.Shift2 at the end, actually we
  // remove old shift1. And it will cause crash later. So erase it earlier to
  // avoid the crash.
  MatchInfo.Shift2->eraseFromParent();

  Register Shift2Const = MI.getOperand(2).getReg();
  Register Shift2 = Builder
                        .buildInstr(Opcode, {DestType},
                                    {MatchInfo.LogicNonShiftReg, Shift2Const})
                        .getReg(0);

  Register Dest = MI.getOperand(0).getReg();
  Builder.buildInstr(MatchInfo.Logic->getOpcode(), {Dest}, {Shift1, Shift2});

  // This was one use so it's safe to remove it.
  MatchInfo.Logic->eraseFromParent();

  MI.eraseFromParent();
}

bool CombinerHelper::isDesirableToCommuteWithShift(
    const MachineInstr &MI) const {
  return getTargetLowering().isDesirableToCommuteWithShift(MI,
                                                           !isPreLegalize());
}

bool CombinerHelper::matchLshrOfTruncOfLshr(MachineInstr &MI,
                                            LshrOfTruncOfLshr &MatchInfo,
                                            MachineInstr &ShiftMI) const {
  assert(MI.getOpcode() == TargetOpcode::G_LSHR && "Expected a G_LSHR");

  Register N0 = MI.getOperand(1).getReg();
  Register N1 = MI.getOperand(2).getReg();
  unsigned OpSizeInBits = MRI.getType(N0).getScalarSizeInBits();

  APInt N1C, N001C;
  if (!mi_match(N1, MRI, m_ICstOrSplat(N1C)))
    return false;
  auto N001 = ShiftMI.getOperand(2).getReg();
  if (!mi_match(N001, MRI, m_ICstOrSplat(N001C)))
    return false;

  if (N001C.getBitWidth() > N1C.getBitWidth())
    N1C = N1C.zext(N001C.getBitWidth());
  else
    N001C = N001C.zext(N1C.getBitWidth());

  Register InnerShift = ShiftMI.getOperand(0).getReg();
  LLT InnerShiftTy = MRI.getType(InnerShift);
  uint64_t InnerShiftSize = InnerShiftTy.getScalarSizeInBits();
  if ((N1C + N001C).ult(InnerShiftSize)) {
    MatchInfo.Src = ShiftMI.getOperand(1).getReg();
    MatchInfo.ShiftAmt = N1C + N001C;
    MatchInfo.ShiftAmtTy = MRI.getType(N001);
    MatchInfo.InnerShiftTy = InnerShiftTy;

    if ((N001C + OpSizeInBits) == InnerShiftSize)
      return true;
    if (MRI.hasOneUse(N0) && MRI.hasOneUse(InnerShift)) {
      MatchInfo.Mask = true;
      MatchInfo.MaskVal = APInt(N1C.getBitWidth(), OpSizeInBits) - N1C;
      return true;
    }
  }
  return false;
}

void CombinerHelper::applyLshrOfTruncOfLshr(
    MachineInstr &MI, LshrOfTruncOfLshr &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_LSHR && "Expected a G_LSHR");

  Register Dst = MI.getOperand(0).getReg();
  auto ShiftAmt =
      Builder.buildConstant(MatchInfo.ShiftAmtTy, MatchInfo.ShiftAmt);
  auto Shift =
      Builder.buildLShr(MatchInfo.InnerShiftTy, MatchInfo.Src, ShiftAmt);
  if (MatchInfo.Mask == true) {
    APInt MaskVal =
        APInt::getLowBitsSet(MatchInfo.InnerShiftTy.getScalarSizeInBits(),
                             MatchInfo.MaskVal.getZExtValue());
    auto Mask = Builder.buildConstant(MatchInfo.InnerShiftTy, MaskVal);
    auto And = Builder.buildAnd(MatchInfo.InnerShiftTy, Shift, Mask);
    Builder.buildTrunc(Dst, And);
  } else
    Builder.buildTrunc(Dst, Shift);
  MI.eraseFromParent();
}

bool CombinerHelper::matchCombineMulToShl(MachineInstr &MI,
                                          unsigned &ShiftVal) const {
  assert(MI.getOpcode() == TargetOpcode::G_MUL && "Expected a G_MUL");
  auto MaybeImmVal =
      getIConstantVRegValWithLookThrough(MI.getOperand(2).getReg(), MRI);
  if (!MaybeImmVal)
    return false;

  ShiftVal = MaybeImmVal->Value.exactLogBase2();
  return (static_cast<int32_t>(ShiftVal) != -1);
}

void CombinerHelper::applyCombineMulToShl(MachineInstr &MI,
                                          unsigned &ShiftVal) const {
  assert(MI.getOpcode() == TargetOpcode::G_MUL && "Expected a G_MUL");
  MachineIRBuilder MIB(MI);
  LLT ShiftTy = MRI.getType(MI.getOperand(0).getReg());
  auto ShiftCst = MIB.buildConstant(ShiftTy, ShiftVal);
  Observer.changingInstr(MI);
  MI.setDesc(MIB.getTII().get(TargetOpcode::G_SHL));
  MI.getOperand(2).setReg(ShiftCst.getReg(0));
  if (ShiftVal == ShiftTy.getScalarSizeInBits() - 1)
    MI.clearFlag(MachineInstr::MIFlag::NoSWrap);
  Observer.changedInstr(MI);
}

bool CombinerHelper::matchCombineSubToAdd(MachineInstr &MI,
                                          BuildFnTy &MatchInfo) const {
  GSub &Sub = cast<GSub>(MI);

  LLT Ty = MRI.getType(Sub.getReg(0));

  if (!isLegalOrBeforeLegalizer({TargetOpcode::G_ADD, {Ty}}))
    return false;

  if (!isConstantLegalOrBeforeLegalizer(Ty))
    return false;

  APInt Imm = getIConstantFromReg(Sub.getRHSReg(), MRI);

  MatchInfo = [=, &MI](MachineIRBuilder &B) {
    auto NegCst = B.buildConstant(Ty, -Imm);
    Observer.changingInstr(MI);
    MI.setDesc(B.getTII().get(TargetOpcode::G_ADD));
    MI.getOperand(2).setReg(NegCst.getReg(0));
    MI.clearFlag(MachineInstr::MIFlag::NoUWrap);
    if (Imm.isMinSignedValue())
      MI.clearFlags(MachineInstr::MIFlag::NoSWrap);
    Observer.changedInstr(MI);
  };
  return true;
}

// shl ([sza]ext x), y => zext (shl x, y), if shift does not overflow source
bool CombinerHelper::matchCombineShlOfExtend(MachineInstr &MI,
                                             RegisterImmPair &MatchData) const {
  assert(MI.getOpcode() == TargetOpcode::G_SHL && VT);
  if (!getTargetLowering().isDesirableToPullExtFromShl(MI))
    return false;

  Register LHS = MI.getOperand(1).getReg();

  Register ExtSrc;
  if (!mi_match(LHS, MRI, m_GAnyExt(m_Reg(ExtSrc))) &&
      !mi_match(LHS, MRI, m_GZExt(m_Reg(ExtSrc))) &&
      !mi_match(LHS, MRI, m_GSExt(m_Reg(ExtSrc))))
    return false;

  Register RHS = MI.getOperand(2).getReg();
  auto MaybeShiftAmtVal = isConstantOrConstantSplatVector(RHS, MRI);
  if (!MaybeShiftAmtVal)
    return false;

  if (LI) {
    LLT SrcTy = MRI.getType(ExtSrc);

    // We only really care about the legality with the shifted value. We can
    // pick any type the constant shift amount, so ask the target what to
    // use. Otherwise we would have to guess and hope it is reported as legal.
    LLT ShiftAmtTy = getTargetLowering().getPreferredShiftAmountTy(SrcTy);
    if (!isLegalOrBeforeLegalizer({TargetOpcode::G_SHL, {SrcTy, ShiftAmtTy}}))
      return false;
  }

  int64_t ShiftAmt = MaybeShiftAmtVal->getSExtValue();
  MatchData.Reg = ExtSrc;
  MatchData.Imm = ShiftAmt;

  unsigned MinLeadingZeros = VT->getKnownZeroes(ExtSrc).countl_one();
  unsigned SrcTySize = MRI.getType(ExtSrc).getScalarSizeInBits();
  return MinLeadingZeros >= ShiftAmt && ShiftAmt < SrcTySize;
}

void CombinerHelper::applyCombineShlOfExtend(
    MachineInstr &MI, const RegisterImmPair &MatchData) const {
  Register ExtSrcReg = MatchData.Reg;
  int64_t ShiftAmtVal = MatchData.Imm;

  LLT ExtSrcTy = MRI.getType(ExtSrcReg);
  auto ShiftAmt = Builder.buildConstant(ExtSrcTy, ShiftAmtVal);
  auto NarrowShift =
      Builder.buildShl(ExtSrcTy, ExtSrcReg, ShiftAmt, MI.getFlags());
  Builder.buildZExt(MI.getOperand(0), NarrowShift);
  MI.eraseFromParent();
}

static Register peekThroughBitcast(Register Reg,
                                   const MachineRegisterInfo &MRI) {
  while (mi_match(Reg, MRI, m_GBitcast(m_Reg(Reg))))
    ;

  return Reg;
}

bool CombinerHelper::matchCombineUnmergeMergeToPlainValues(
    MachineInstr &MI, SmallVectorImpl<Register> &Operands) const {
  assert(MI.getOpcode() == TargetOpcode::G_UNMERGE_VALUES &&
         "Expected an unmerge");
  auto &Unmerge = cast<GUnmerge>(MI);
  Register SrcReg = peekThroughBitcast(Unmerge.getSourceReg(), MRI);

  auto *SrcInstr = getOpcodeDef<GMergeLikeInstr>(SrcReg, MRI);
  if (!SrcInstr)
    return false;

  // Check the source type of the merge.
  LLT SrcMergeTy = MRI.getType(SrcInstr->getSourceReg(0));
  LLT Dst0Ty = MRI.getType(Unmerge.getReg(0));
  bool SameSize = Dst0Ty.getSizeInBits() == SrcMergeTy.getSizeInBits();
  if (SrcMergeTy != Dst0Ty && !SameSize)
    return false;
  // They are the same now (modulo a bitcast).
  // We can collect all the src registers.
  for (unsigned Idx = 0; Idx < SrcInstr->getNumSources(); ++Idx)
    Operands.push_back(SrcInstr->getSourceReg(Idx));
  return true;
}

void CombinerHelper::applyCombineUnmergeMergeToPlainValues(
    MachineInstr &MI, SmallVectorImpl<Register> &Operands) const {
  assert(MI.getOpcode() == TargetOpcode::G_UNMERGE_VALUES &&
         "Expected an unmerge");
  assert((MI.getNumOperands() - 1 == Operands.size()) &&
         "Not enough operands to replace all defs");
  unsigned NumElems = MI.getNumOperands() - 1;

  LLT SrcTy = MRI.getType(Operands[0]);
  LLT DstTy = MRI.getType(MI.getOperand(0).getReg());
  bool CanReuseInputDirectly = DstTy == SrcTy;
  for (unsigned Idx = 0; Idx < NumElems; ++Idx) {
    Register DstReg = MI.getOperand(Idx).getReg();
    Register SrcReg = Operands[Idx];

    // This combine may run after RegBankSelect, so we need to be aware of
    // register banks.
    const auto &DstCB = MRI.getRegClassOrRegBank(DstReg);
    if (!DstCB.isNull() && DstCB != MRI.getRegClassOrRegBank(SrcReg)) {
      SrcReg = Builder.buildCopy(MRI.getType(SrcReg), SrcReg).getReg(0);
      MRI.setRegClassOrRegBank(SrcReg, DstCB);
    }

    if (CanReuseInputDirectly)
      replaceRegWith(MRI, DstReg, SrcReg);
    else
      Builder.buildCast(DstReg, SrcReg);
  }
  MI.eraseFromParent();
}

bool CombinerHelper::matchCombineUnmergeConstant(
    MachineInstr &MI, SmallVectorImpl<APInt> &Csts) const {
  unsigned SrcIdx = MI.getNumOperands() - 1;
  Register SrcReg = MI.getOperand(SrcIdx).getReg();
  // Break down the big constant in smaller ones.
  APInt Val;
  if (!mi_match(SrcReg, MRI, m_GConstantOrFConstantBits(Val)))
    return false;

  LLT Dst0Ty = MRI.getType(MI.getOperand(0).getReg());
  unsigned ShiftAmt = Dst0Ty.getSizeInBits();
  // Unmerge a constant.
  for (unsigned Idx = 0; Idx != SrcIdx; ++Idx) {
    Csts.emplace_back(Val.trunc(ShiftAmt));
    Val = Val.lshr(ShiftAmt);
  }

  return true;
}

void CombinerHelper::applyCombineUnmergeConstant(
    MachineInstr &MI, SmallVectorImpl<APInt> &Csts) const {
  assert(MI.getOpcode() == TargetOpcode::G_UNMERGE_VALUES &&
         "Expected an unmerge");
  assert((MI.getNumOperands() - 1 == Csts.size()) &&
         "Not enough operands to replace all defs");
  unsigned NumElems = MI.getNumOperands() - 1;
  for (unsigned Idx = 0; Idx < NumElems; ++Idx) {
    Register DstReg = MI.getOperand(Idx).getReg();
    Builder.buildConstant(DstReg, Csts[Idx]);
  }

  MI.eraseFromParent();
}

bool CombinerHelper::matchCombineUnmergeUndef(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  unsigned SrcIdx = MI.getNumOperands() - 1;
  Register SrcReg = MI.getOperand(SrcIdx).getReg();
  MatchInfo = [&MI](MachineIRBuilder &B) {
    unsigned NumElems = MI.getNumOperands() - 1;
    for (unsigned Idx = 0; Idx < NumElems; ++Idx) {
      Register DstReg = MI.getOperand(Idx).getReg();
      B.buildUndef(DstReg);
    }
  };
  return mi_match(SrcReg, MRI, m_GImplicitDef());
}

bool CombinerHelper::matchCombineUnmergeWithDeadLanesToTrunc(
    MachineInstr &MI) const {
  assert(MI.getOpcode() == TargetOpcode::G_UNMERGE_VALUES &&
         "Expected an unmerge");
  if (!MRI.getType(MI.getOperand(0).getReg()).isScalar() ||
      !MRI.getType(MI.getOperand(MI.getNumDefs()).getReg()).isScalar())
    return false;
  // Check that all the lanes are dead except the first one.
  for (unsigned Idx = 1, EndIdx = MI.getNumDefs(); Idx != EndIdx; ++Idx) {
    if (!MRI.use_nodbg_empty(MI.getOperand(Idx).getReg()))
      return false;
  }
  return true;
}

void CombinerHelper::applyCombineUnmergeWithDeadLanesToTrunc(
    MachineInstr &MI) const {
  Register SrcReg = MI.getOperand(MI.getNumDefs()).getReg();
  Register Dst0Reg = MI.getOperand(0).getReg();
  Builder.buildTrunc(Dst0Reg, SrcReg);
  MI.eraseFromParent();
}

bool CombinerHelper::matchCombineUnmergeZExtToZExt(MachineInstr &MI) const {
  assert(MI.getOpcode() == TargetOpcode::G_UNMERGE_VALUES &&
         "Expected an unmerge");
  Register Dst0Reg = MI.getOperand(0).getReg();
  LLT Dst0Ty = MRI.getType(Dst0Reg);
  // G_ZEXT on vector applies to each lane, so it will
  // affect all destinations. Therefore we won't be able
  // to simplify the unmerge to just the first definition.
  if (Dst0Ty.isVector())
    return false;
  Register SrcReg = MI.getOperand(MI.getNumDefs()).getReg();
  LLT SrcTy = MRI.getType(SrcReg);
  if (SrcTy.isVector())
    return false;

  Register ZExtSrcReg;
  if (!mi_match(SrcReg, MRI, m_GZExt(m_Reg(ZExtSrcReg))))
    return false;

  // Finally we can replace the first definition with
  // a zext of the source if the definition is big enough to hold
  // all of ZExtSrc bits.
  LLT ZExtSrcTy = MRI.getType(ZExtSrcReg);
  return ZExtSrcTy.getSizeInBits() <= Dst0Ty.getSizeInBits();
}

void CombinerHelper::applyCombineUnmergeZExtToZExt(MachineInstr &MI) const {
  assert(MI.getOpcode() == TargetOpcode::G_UNMERGE_VALUES &&
         "Expected an unmerge");

  Register Dst0Reg = MI.getOperand(0).getReg();

  GZext *ZExtInstr =
      cast<GZext>(MRI.getVRegDef(MI.getOperand(MI.getNumDefs()).getReg()));
  Register ZExtSrcReg = ZExtInstr->getSrcReg();
  LLT Dst0Ty = MRI.getType(Dst0Reg);
  LLT ZExtSrcTy = MRI.getType(ZExtSrcReg);

  if (Dst0Ty.getSizeInBits() > ZExtSrcTy.getSizeInBits()) {
    Builder.buildZExt(Dst0Reg, ZExtSrcReg);
  } else {
    assert(Dst0Ty.getSizeInBits() == ZExtSrcTy.getSizeInBits() &&
           "ZExt src doesn't fit in destination");
    replaceRegWith(MRI, Dst0Reg, ZExtSrcReg);
  }

  Register ZeroReg;
  for (unsigned Idx = 1, EndIdx = MI.getNumDefs(); Idx != EndIdx; ++Idx) {
    if (!ZeroReg)
      ZeroReg = Builder.buildConstant(Dst0Ty, 0).getReg(0);
    replaceRegWith(MRI, MI.getOperand(Idx).getReg(), ZeroReg);
  }
  MI.eraseFromParent();
}

bool CombinerHelper::matchCombineShiftToUnmerge(MachineInstr &MI,
                                                unsigned TargetShiftSize,
                                                unsigned &ShiftVal) const {
  assert((MI.getOpcode() == TargetOpcode::G_SHL ||
          MI.getOpcode() == TargetOpcode::G_LSHR ||
          MI.getOpcode() == TargetOpcode::G_ASHR) && "Expected a shift");

  LLT Ty = MRI.getType(MI.getOperand(0).getReg());
  if (Ty.isVector()) // TODO:
    return false;

  // Don't narrow further than the requested size.
  unsigned Size = Ty.getSizeInBits();
  if (Size <= TargetShiftSize)
    return false;

  auto MaybeImmVal =
      getIConstantVRegValWithLookThrough(MI.getOperand(2).getReg(), MRI);
  if (!MaybeImmVal)
    return false;

  ShiftVal = MaybeImmVal->Value.getSExtValue();
  return ShiftVal >= Size / 2 && ShiftVal < Size;
}

void CombinerHelper::applyCombineShiftToUnmerge(
    MachineInstr &MI, const unsigned &ShiftVal) const {
  Register DstReg = MI.getOperand(0).getReg();
  Register SrcReg = MI.getOperand(1).getReg();
  LLT Ty = MRI.getType(SrcReg);
  unsigned Size = Ty.getSizeInBits();
  unsigned HalfSize = Size / 2;
  assert(ShiftVal >= HalfSize);

  LLT HalfTy = Ty.changeElementSize(HalfSize);

  auto Unmerge = Builder.buildUnmerge(HalfTy, SrcReg);
  unsigned NarrowShiftAmt = ShiftVal - HalfSize;

  if (MI.getOpcode() == TargetOpcode::G_LSHR) {
    Register Narrowed = Unmerge.getReg(1);

    //  dst = G_LSHR s64:x, C for C >= 32
    // =>
    //   lo, hi = G_UNMERGE_VALUES x
    //   dst = G_MERGE_VALUES (G_LSHR hi, C - 32), 0

    if (NarrowShiftAmt != 0) {
      Narrowed = Builder.buildLShr(HalfTy, Narrowed,
        Builder.buildConstant(HalfTy, NarrowShiftAmt)).getReg(0);
    }

    auto Zero = Builder.buildConstant(HalfTy, 0);
    Builder.buildMergeLikeInstr(DstReg, {Narrowed, Zero});
  } else if (MI.getOpcode() == TargetOpcode::G_SHL) {
    Register Narrowed = Unmerge.getReg(0);
    //  dst = G_SHL s64:x, C for C >= 32
    // =>
    //   lo, hi = G_UNMERGE_VALUES x
    //   dst = G_MERGE_VALUES 0, (G_SHL hi, C - 32)
    if (NarrowShiftAmt != 0) {
      Narrowed = Builder.buildShl(HalfTy, Narrowed,
        Builder.buildConstant(HalfTy, NarrowShiftAmt)).getReg(0);
    }

    auto Zero = Builder.buildConstant(HalfTy, 0);
    Builder.buildMergeLikeInstr(DstReg, {Zero, Narrowed});
  } else {
    assert(MI.getOpcode() == TargetOpcode::G_ASHR);
    auto Hi = Builder.buildAShr(
      HalfTy, Unmerge.getReg(1),
      Builder.buildConstant(HalfTy, HalfSize - 1));

    if (ShiftVal == HalfSize) {
      // (G_ASHR i64:x, 32) ->
      //   G_MERGE_VALUES hi_32(x), (G_ASHR hi_32(x), 31)
      Builder.buildMergeLikeInstr(DstReg, {Unmerge.getReg(1), Hi});
    } else if (ShiftVal == Size - 1) {
      // Don't need a second shift.
      // (G_ASHR i64:x, 63) ->
      //   %narrowed = (G_ASHR hi_32(x), 31)
      //   G_MERGE_VALUES %narrowed, %narrowed
      Builder.buildMergeLikeInstr(DstReg, {Hi, Hi});
    } else {
      auto Lo = Builder.buildAShr(
        HalfTy, Unmerge.getReg(1),
        Builder.buildConstant(HalfTy, ShiftVal - HalfSize));

      // (G_ASHR i64:x, C) ->, for C >= 32
      //   G_MERGE_VALUES (G_ASHR hi_32(x), C - 32), (G_ASHR hi_32(x), 31)
      Builder.buildMergeLikeInstr(DstReg, {Lo, Hi});
    }
  }

  MI.eraseFromParent();
}

bool CombinerHelper::tryCombineShiftToUnmerge(
    MachineInstr &MI, unsigned TargetShiftAmount) const {
  unsigned ShiftAmt;
  if (matchCombineShiftToUnmerge(MI, TargetShiftAmount, ShiftAmt)) {
    applyCombineShiftToUnmerge(MI, ShiftAmt);
    return true;
  }

  return false;
}

void CombinerHelper::applyCombineP2IToI2P(MachineInstr &MI,
                                          Register &Reg) const {
  assert(MI.getOpcode() == TargetOpcode::G_PTRTOINT && "Expected a G_PTRTOINT");
  Register DstReg = MI.getOperand(0).getReg();
  Builder.buildZExtOrTrunc(DstReg, Reg);
  MI.eraseFromParent();
}

bool CombinerHelper::matchCombineAnyExtTrunc(MachineInstr &MI,
                                             Register &Reg) const {
  assert(MI.getOpcode() == TargetOpcode::G_ANYEXT && "Expected a G_ANYEXT");
  Register DstReg = MI.getOperand(0).getReg();
  Register SrcReg = MI.getOperand(1).getReg();
  Register OriginalSrcReg = getSrcRegIgnoringCopies(SrcReg, MRI);
  if (OriginalSrcReg.isValid())
    SrcReg = OriginalSrcReg;
  LLT DstTy = MRI.getType(DstReg);
  return mi_match(SrcReg, MRI,
                  m_GTrunc(m_all_of(m_Reg(Reg), m_SpecificType(DstTy)))) &&
         canReplaceReg(DstReg, Reg, MRI);
}

bool CombinerHelper::matchCombineZextTrunc(MachineInstr &MI,
                                           Register &Reg) const {
  assert(MI.getOpcode() == TargetOpcode::G_ZEXT && "Expected a G_ZEXT");
  Register DstReg = MI.getOperand(0).getReg();
  Register SrcReg = MI.getOperand(1).getReg();
  LLT DstTy = MRI.getType(DstReg);
  if (mi_match(SrcReg, MRI,
               m_GTrunc(m_all_of(m_Reg(Reg), m_SpecificType(DstTy)))) &&
      canReplaceReg(DstReg, Reg, MRI)) {
    unsigned DstSize = DstTy.getScalarSizeInBits();
    unsigned SrcSize = MRI.getType(SrcReg).getScalarSizeInBits();
    return VT->getKnownBits(Reg).countMinLeadingZeros() >= DstSize - SrcSize;
  }
  return false;
}

static LLT getMidVTForTruncRightShiftCombine(LLT ShiftTy, LLT TruncTy) {
  const unsigned ShiftSize = ShiftTy.getScalarSizeInBits();
  const unsigned TruncSize = TruncTy.getScalarSizeInBits();

  // ShiftTy > 32 > TruncTy -> 32
  if (ShiftSize > 32 && TruncSize < 32)
    return ShiftTy.changeElementSize(32);

  // TODO: We could also reduce to 16 bits, but that's more target-dependent.
  //  Some targets like it, some don't, some only like it under certain
  //  conditions/processor versions, etc.
  //  A TL hook might be needed for this.

  // Don't combine
  return ShiftTy;
}

bool CombinerHelper::matchCombineTruncOfShift(
    MachineInstr &MI, std::pair<MachineInstr *, LLT> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_TRUNC && "Expected a G_TRUNC");
  Register DstReg = MI.getOperand(0).getReg();
  Register SrcReg = MI.getOperand(1).getReg();

  if (!MRI.hasOneNonDBGUse(SrcReg))
    return false;

  LLT SrcTy = MRI.getType(SrcReg);
  LLT DstTy = MRI.getType(DstReg);

  MachineInstr *SrcMI = getDefIgnoringCopies(SrcReg, MRI);
  const auto &TL = getTargetLowering();

  LLT NewShiftTy;
  switch (SrcMI->getOpcode()) {
  default:
    return false;
  case TargetOpcode::G_SHL: {
    NewShiftTy = DstTy;

    // Make sure new shift amount is legal.
    KnownBits Known = VT->getKnownBits(SrcMI->getOperand(2).getReg());
    if (Known.getMaxValue().uge(NewShiftTy.getScalarSizeInBits()))
      return false;
    break;
  }
  case TargetOpcode::G_LSHR:
  case TargetOpcode::G_ASHR: {
    // For right shifts, we conservatively do not do the transform if the TRUNC
    // has any STORE users. The reason is that if we change the type of the
    // shift, we may break the truncstore combine.
    //
    // TODO: Fix truncstore combine to handle (trunc(lshr (trunc x), k)).
    for (auto &User : MRI.use_instructions(DstReg))
      if (User.getOpcode() == TargetOpcode::G_STORE)
        return false;

    NewShiftTy = getMidVTForTruncRightShiftCombine(SrcTy, DstTy);
    if (NewShiftTy == SrcTy)
      return false;

    // Make sure we won't lose information by truncating the high bits.
    KnownBits Known = VT->getKnownBits(SrcMI->getOperand(2).getReg());
    if (Known.getMaxValue().ugt(NewShiftTy.getScalarSizeInBits() -
                                DstTy.getScalarSizeInBits()))
      return false;
    break;
  }
  }

  if (!isLegalOrBeforeLegalizer(
          {SrcMI->getOpcode(),
           {NewShiftTy, TL.getPreferredShiftAmountTy(NewShiftTy)}}))
    return false;

  MatchInfo = std::make_pair(SrcMI, NewShiftTy);
  return true;
}

void CombinerHelper::applyCombineTruncOfShift(
    MachineInstr &MI, std::pair<MachineInstr *, LLT> &MatchInfo) const {
  MachineInstr *ShiftMI = MatchInfo.first;
  LLT NewShiftTy = MatchInfo.second;

  Register Dst = MI.getOperand(0).getReg();
  LLT DstTy = MRI.getType(Dst);

  Register ShiftAmt = ShiftMI->getOperand(2).getReg();
  Register ShiftSrc = ShiftMI->getOperand(1).getReg();
  ShiftSrc = Builder.buildTrunc(NewShiftTy, ShiftSrc).getReg(0);

  const auto &TL = getTargetLowering();
  LLT PrefShiftTy = TL.getPreferredShiftAmountTy(NewShiftTy);
  if (MRI.getType(ShiftAmt) != PrefShiftTy)
    ShiftAmt = Builder.buildZExtOrTrunc(PrefShiftTy, ShiftAmt).getReg(0);

  Register NewShift =
      Builder
          .buildInstr(ShiftMI->getOpcode(), {NewShiftTy}, {ShiftSrc, ShiftAmt})
          .getReg(0);

  if (NewShiftTy == DstTy)
    replaceRegWith(MRI, Dst, NewShift);
  else
    Builder.buildTrunc(Dst, NewShift);

  eraseInst(MI);
}

bool CombinerHelper::matchAllExplicitUsesAreUndef(MachineInstr &MI) const {
  return all_of(MI.explicit_uses(), [this](const MachineOperand &MO) {
    return !MO.isReg() ||
           getOpcodeDef(TargetOpcode::G_IMPLICIT_DEF, MO.getReg(), MRI);
  });
}

bool CombinerHelper::matchUndefShuffleVectorMask(MachineInstr &MI) const {
  assert(MI.getOpcode() == TargetOpcode::G_SHUFFLE_VECTOR);
  ArrayRef<int> Mask = MI.getOperand(3).getShuffleMask();
  return all_of(Mask, [](int Elt) { return Elt < 0; });
}

bool CombinerHelper::matchUndefStore(MachineInstr &MI) const {
  if (!cast<GStore>(MI).isUnordered())
    return false;
  return getOpcodeDef(TargetOpcode::G_IMPLICIT_DEF, MI.getOperand(0).getReg(),
                      MRI);
}

bool CombinerHelper::matchInsertExtractVecEltOutOfBounds(
    MachineInstr &MI) const {
  assert((MI.getOpcode() == TargetOpcode::G_INSERT_VECTOR_ELT ||
          MI.getOpcode() == TargetOpcode::G_EXTRACT_VECTOR_ELT) &&
         "Expected an insert/extract element op");
  LLT VecTy = MRI.getType(MI.getOperand(1).getReg());
  if (VecTy.isScalableVector())
    return false;

  unsigned IdxIdx =
      MI.getOpcode() == TargetOpcode::G_EXTRACT_VECTOR_ELT ? 2 : 3;
  auto Idx = getIConstantVRegVal(MI.getOperand(IdxIdx).getReg(), MRI);
  if (!Idx)
    return false;
  return Idx->getZExtValue() >= VecTy.getNumElements();
}

bool CombinerHelper::matchConstantSelectCmp(MachineInstr &MI,
                                            unsigned &OpIdx) const {
  GSelect &SelMI = cast<GSelect>(MI);
  auto Cst = isConstantOrConstantSplatVector(SelMI.getCondReg(), MRI);
  if (!Cst)
    return false;
  OpIdx = Cst->isZero() ? 3 : 2;
  return true;
}

void CombinerHelper::eraseInst(MachineInstr &MI) const { MI.eraseFromParent(); }

bool CombinerHelper::matchEqualDefs(const MachineOperand &MOP1,
                                    const MachineOperand &MOP2) const {
  if (!MOP1.isReg() || !MOP2.isReg())
    return false;
  auto InstAndDef1 = getDefSrcRegIgnoringCopies(MOP1.getReg(), MRI);
  if (!InstAndDef1)
    return false;
  auto InstAndDef2 = getDefSrcRegIgnoringCopies(MOP2.getReg(), MRI);
  if (!InstAndDef2)
    return false;
  MachineInstr *I1 = InstAndDef1->MI;
  MachineInstr *I2 = InstAndDef2->MI;

  // Handle a case like this:
  //
  // %0:_(s64), %1:_(s64) = G_UNMERGE_VALUES %2:_(<2 x s64>)
  //
  // Even though %0 and %1 are produced by the same instruction they are not
  // the same values.
  if (I1 == I2)
    return MOP1.getReg() == MOP2.getReg();

  // If we have an instruction which loads or stores, we can't guarantee that
  // it is identical.
  //
  // For example, we may have
  //
  // %x1 = G_LOAD %addr (load N from @somewhere)
  // ...
  // call @foo
  // ...
  // %x2 = G_LOAD %addr (load N from @somewhere)
  // ...
  // %or = G_OR %x1, %x2
  //
  // It's possible that @foo will modify whatever lives at the address we're
  // loading from. To be safe, let's just assume that all loads and stores
  // are different (unless we have something which is guaranteed to not
  // change.)
  if (I1->mayLoadOrStore() && !I1->isDereferenceableInvariantLoad())
    return false;

  // If both instructions are loads or stores, they are equal only if both
  // are dereferenceable invariant loads with the same number of bits.
  if (I1->mayLoadOrStore() && I2->mayLoadOrStore()) {
    GLoadStore *LS1 = dyn_cast<GLoadStore>(I1);
    GLoadStore *LS2 = dyn_cast<GLoadStore>(I2);
    if (!LS1 || !LS2)
      return false;

    if (!I2->isDereferenceableInvariantLoad() ||
        (LS1->getMemSizeInBits() != LS2->getMemSizeInBits()))
      return false;
  }

  // Check for physical registers on the instructions first to avoid cases
  // like this:
  //
  // %a = COPY $physreg
  // ...
  // SOMETHING implicit-def $physreg
  // ...
  // %b = COPY $physreg
  //
  // These copies are not equivalent.
  if (any_of(I1->uses(), [](const MachineOperand &MO) {
        return MO.isReg() && MO.getReg().isPhysical();
      })) {
    // Check if we have a case like this:
    //
    // %a = COPY $physreg
    // %b = COPY %a
    //
    // In this case, I1 and I2 will both be equal to %a = COPY $physreg.
    // From that, we know that they must have the same value, since they must
    // have come from the same COPY.
    return I1->isIdenticalTo(*I2);
  }

  // We don't have any physical registers, so we don't necessarily need the
  // same vreg defs.
  //
  // On the off-chance that there's some target instruction feeding into the
  // instruction, let's use produceSameValue instead of isIdenticalTo.
  if (Builder.getTII().produceSameValue(*I1, *I2, &MRI)) {
    // Handle instructions with multiple defs that produce same values. Values
    // are same for operands with same index.
    // %0:_(s8), %1:_(s8), %2:_(s8), %3:_(s8) = G_UNMERGE_VALUES %4:_(<4 x s8>)
    // %5:_(s8), %6:_(s8), %7:_(s8), %8:_(s8) = G_UNMERGE_VALUES %4:_(<4 x s8>)
    // I1 and I2 are different instructions but produce same values,
    // %1 and %6 are same, %1 and %7 are not the same value.
    return I1->findRegisterDefOperandIdx(InstAndDef1->Reg, /*TRI=*/nullptr) ==
           I2->findRegisterDefOperandIdx(InstAndDef2->Reg, /*TRI=*/nullptr);
  }
  return false;
}

bool CombinerHelper::matchConstantFPOp(const MachineOperand &MOP,
                                       double C) const {
  if (!MOP.isReg())
    return false;
  std::optional<FPValueAndVReg> MaybeCst;
  if (!mi_match(MOP.getReg(), MRI, m_GFCstOrSplat(MaybeCst)))
    return false;

  return MaybeCst->Value.isExactlyValue(C);
}

void CombinerHelper::replaceSingleDefInstWithOperand(MachineInstr &MI,
                                                     unsigned OpIdx) const {
  assert(MI.getNumExplicitDefs() == 1 && "Expected one explicit def?");
  Register OldReg = MI.getOperand(0).getReg();
  Register Replacement = MI.getOperand(OpIdx).getReg();
  assert(canReplaceReg(OldReg, Replacement, MRI) && "Cannot replace register?");
  replaceRegWith(MRI, OldReg, Replacement);
  MI.eraseFromParent();
}

void CombinerHelper::replaceSingleDefInstWithReg(MachineInstr &MI,
                                                 Register Replacement) const {
  assert(MI.getNumExplicitDefs() == 1 && "Expected one explicit def?");
  Register OldReg = MI.getOperand(0).getReg();
  assert(canReplaceReg(OldReg, Replacement, MRI) && "Cannot replace register?");
  replaceRegWith(MRI, OldReg, Replacement);
  MI.eraseFromParent();
}

bool CombinerHelper::matchConstantLargerBitWidth(MachineInstr &MI,
                                                 unsigned ConstIdx) const {
  Register ConstReg = MI.getOperand(ConstIdx).getReg();
  LLT DstTy = MRI.getType(MI.getOperand(0).getReg());

  // Get the shift amount
  auto VRegAndVal = getIConstantVRegValWithLookThrough(ConstReg, MRI);
  if (!VRegAndVal)
    return false;

  // Return true of shift amount >= Bitwidth
  return (VRegAndVal->Value.uge(DstTy.getSizeInBits()));
}

void CombinerHelper::applyFunnelShiftConstantModulo(MachineInstr &MI) const {
  assert((MI.getOpcode() == TargetOpcode::G_FSHL ||
          MI.getOpcode() == TargetOpcode::G_FSHR) &&
         "This is not a funnel shift operation");

  Register ConstReg = MI.getOperand(3).getReg();
  LLT ConstTy = MRI.getType(ConstReg);
  LLT DstTy = MRI.getType(MI.getOperand(0).getReg());

  auto VRegAndVal = getIConstantVRegValWithLookThrough(ConstReg, MRI);
  assert((VRegAndVal) && "Value is not a constant");

  // Calculate the new Shift Amount = Old Shift Amount % BitWidth
  APInt NewConst = VRegAndVal->Value.urem(
      APInt(ConstTy.getSizeInBits(), DstTy.getScalarSizeInBits()));

  auto NewConstInstr = Builder.buildConstant(ConstTy, NewConst.getZExtValue());
  Builder.buildInstr(
      MI.getOpcode(), {MI.getOperand(0)},
      {MI.getOperand(1), MI.getOperand(2), NewConstInstr.getReg(0)});

  MI.eraseFromParent();
}

bool CombinerHelper::matchSelectSameVal(MachineInstr &MI) const {
  assert(MI.getOpcode() == TargetOpcode::G_SELECT);
  // Match (cond ? x : x)
  return matchEqualDefs(MI.getOperand(2), MI.getOperand(3)) &&
         canReplaceReg(MI.getOperand(0).getReg(), MI.getOperand(2).getReg(),
                       MRI);
}

bool CombinerHelper::matchOperandIsKnownToBeAPowerOfTwo(
    const MachineOperand &MO, bool OrNegative) const {
  return isKnownToBeAPowerOfTwo(MO.getReg(), MRI, VT, OrNegative);
}

void CombinerHelper::replaceInstWithFConstant(MachineInstr &MI,
                                              double C) const {
  assert(MI.getNumDefs() == 1 && "Expected only one def?");
  Builder.buildFConstant(MI.getOperand(0), C);
  MI.eraseFromParent();
}

void CombinerHelper::replaceInstWithConstant(MachineInstr &MI,
                                             int64_t C) const {
  assert(MI.getNumDefs() == 1 && "Expected only one def?");
  Builder.buildConstant(MI.getOperand(0), C);
  MI.eraseFromParent();
}

void CombinerHelper::replaceInstWithConstant(MachineInstr &MI, APInt C) const {
  assert(MI.getNumDefs() == 1 && "Expected only one def?");
  Builder.buildConstant(MI.getOperand(0), C);
  MI.eraseFromParent();
}

void CombinerHelper::replaceInstWithFConstant(MachineInstr &MI,
                                              ConstantFP *CFP) const {
  assert(MI.getNumDefs() == 1 && "Expected only one def?");
  Builder.buildFConstant(MI.getOperand(0), CFP->getValueAPF());
  MI.eraseFromParent();
}

void CombinerHelper::replaceInstWithUndef(MachineInstr &MI) const {
  assert(MI.getNumDefs() == 1 && "Expected only one def?");
  Builder.buildUndef(MI.getOperand(0));
  MI.eraseFromParent();
}

bool CombinerHelper::matchCombineInsertVecElts(
    MachineInstr &MI, SmallVectorImpl<Register> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_INSERT_VECTOR_ELT &&
         "Invalid opcode");
  Register DstReg = MI.getOperand(0).getReg();
  LLT DstTy = MRI.getType(DstReg);
  assert(DstTy.isVector() && "Invalid G_INSERT_VECTOR_ELT?");

  if (DstTy.isScalableVector())
    return false;

  unsigned NumElts = DstTy.getNumElements();
  // If this MI is part of a sequence of insert_vec_elts, then
  // don't do the combine in the middle of the sequence.
  if (MRI.hasOneUse(DstReg) && MRI.use_instr_begin(DstReg)->getOpcode() ==
                                   TargetOpcode::G_INSERT_VECTOR_ELT)
    return false;
  MachineInstr *CurrInst = &MI;
  MachineInstr *TmpInst;
  int64_t IntImm;
  Register TmpReg;
  MatchInfo.resize(NumElts);
  while (mi_match(
      *CurrInst, MRI,
      m_GInsertVecElt(m_MInstr(TmpInst), m_Reg(TmpReg), m_ICst(IntImm)))) {
    if (IntImm >= NumElts || IntImm < 0)
      return false;
    if (!MatchInfo[IntImm])
      MatchInfo[IntImm] = TmpReg;
    CurrInst = TmpInst;
  }
  // Variable index.
  if (CurrInst->getOpcode() == TargetOpcode::G_INSERT_VECTOR_ELT)
    return false;
  if (TmpInst->getOpcode() == TargetOpcode::G_BUILD_VECTOR) {
    for (unsigned I = 1; I < TmpInst->getNumOperands(); ++I) {
      if (!MatchInfo[I - 1].isValid())
        MatchInfo[I - 1] = TmpInst->getOperand(I).getReg();
    }
    return true;
  }
  // If we didn't end in a G_IMPLICIT_DEF and the source is not fully
  // overwritten, bail out.
  return TmpInst->getOpcode() == TargetOpcode::G_IMPLICIT_DEF ||
         all_of(MatchInfo, [](Register Reg) { return !!Reg; });
}

void CombinerHelper::applyCombineInsertVecElts(
    MachineInstr &MI, SmallVectorImpl<Register> &MatchInfo) const {
  Register UndefReg;
  auto GetUndef = [&]() {
    if (UndefReg)
      return UndefReg;
    LLT DstTy = MRI.getType(MI.getOperand(0).getReg());
    UndefReg = Builder.buildUndef(DstTy.getScalarType()).getReg(0);
    return UndefReg;
  };
  for (Register &Reg : MatchInfo) {
    if (!Reg)
      Reg = GetUndef();
  }
  Builder.buildBuildVector(MI.getOperand(0).getReg(), MatchInfo);
  MI.eraseFromParent();
}

bool CombinerHelper::matchBinopWithNegInner(Register MInner, Register Other,
                                            unsigned RootOpc, Register Dst,
                                            LLT Ty,
                                            BuildFnTy &MatchInfo) const {
  /// Helper function for matchBinopWithNeg: tries to match one commuted form
  /// of `a bitwiseop (~b +/- c)` -> `a bitwiseop ~(b -/+ c)`.
  MachineInstr *InnerDef;
  if (!mi_match(MInner, MRI, m_MInstr(InnerDef)))
    return false;

  unsigned InnerOpc = InnerDef->getOpcode();
  if (InnerOpc != TargetOpcode::G_ADD && InnerOpc != TargetOpcode::G_SUB)
    return false;

  if (!MRI.hasOneNonDBGUse(MInner))
    return false;

  Register InnerLHS = InnerDef->getOperand(1).getReg();
  Register InnerRHS = InnerDef->getOperand(2).getReg();
  Register NotSrc;
  Register B, C;

  // Check if either operand is ~b
  auto TryMatch = [&](Register MaybeNot, Register Other) {
    if (mi_match(MaybeNot, MRI, m_Not(m_Reg(NotSrc)))) {
      if (!MRI.hasOneNonDBGUse(MaybeNot))
        return false;
      B = NotSrc;
      C = Other;
      return true;
    }
    return false;
  };

  // For SUB, the not must be the LHS. For ADD, it can be either operand.
  if (!TryMatch(InnerLHS, InnerRHS) &&
      !(InnerOpc == TargetOpcode::G_ADD && TryMatch(InnerRHS, InnerLHS)))
    return false;

  // Flip add/sub
  unsigned FlippedOpc = (InnerOpc == TargetOpcode::G_ADD) ? TargetOpcode::G_SUB
                                                          : TargetOpcode::G_ADD;

  Register A = Other;
  MatchInfo = [=](MachineIRBuilder &Builder) {
    auto NewInner = Builder.buildInstr(FlippedOpc, {Ty}, {B, C});
    auto NewNot = Builder.buildNot(Ty, NewInner);
    Builder.buildInstr(RootOpc, {Dst}, {A, NewNot});
  };
  return true;
}

bool CombinerHelper::matchBinopWithNeg(MachineInstr &MI,
                                       BuildFnTy &MatchInfo) const {
  // Fold `a bitwiseop (~b +/- c)` -> `a bitwiseop ~(b -/+ c)`
  // Root MI is one of G_AND, G_OR, G_XOR.
  // We also look for commuted forms of operations. Pattern shouldn't apply
  // if there are multiple reasons of inner operations.

  unsigned RootOpc = MI.getOpcode();
  Register Dst = MI.getOperand(0).getReg();
  LLT Ty = MRI.getType(Dst);

  Register LHS = MI.getOperand(1).getReg();
  Register RHS = MI.getOperand(2).getReg();
  // Check the commuted and uncommuted forms of the operation.
  return matchBinopWithNegInner(LHS, RHS, RootOpc, Dst, Ty, MatchInfo) ||
         matchBinopWithNegInner(RHS, LHS, RootOpc, Dst, Ty, MatchInfo);
}

bool CombinerHelper::matchHoistLogicOpWithSameOpcodeHands(
    MachineInstr &MI, InstructionStepsMatchInfo &MatchInfo) const {
  // Matches: logic (hand x, ...), (hand y, ...) -> hand (logic x, y), ...
  //
  // Creates the new hand + logic instruction (but does not insert them.)
  //
  // On success, MatchInfo is populated with the new instructions. These are
  // inserted in applyHoistLogicOpWithSameOpcodeHands.
  unsigned LogicOpcode = MI.getOpcode();
  assert(LogicOpcode == TargetOpcode::G_AND ||
         LogicOpcode == TargetOpcode::G_OR ||
         LogicOpcode == TargetOpcode::G_XOR);
  MachineIRBuilder MIB(MI);
  Register Dst = MI.getOperand(0).getReg();
  Register LHSReg = MI.getOperand(1).getReg();
  Register RHSReg = MI.getOperand(2).getReg();

  // Don't recompute anything.
  if (!MRI.hasOneNonDBGUse(LHSReg) || !MRI.hasOneNonDBGUse(RHSReg))
    return false;

  // Make sure we have (hand x, ...), (hand y, ...)
  MachineInstr *LeftHandInst = getDefIgnoringCopies(LHSReg, MRI);
  MachineInstr *RightHandInst = getDefIgnoringCopies(RHSReg, MRI);
  if (!LeftHandInst || !RightHandInst)
    return false;
  unsigned HandOpcode = LeftHandInst->getOpcode();
  if (HandOpcode != RightHandInst->getOpcode())
    return false;
  if (LeftHandInst->getNumOperands() < 2 ||
      !LeftHandInst->getOperand(1).isReg() ||
      RightHandInst->getNumOperands() < 2 ||
      !RightHandInst->getOperand(1).isReg())
    return false;

  // Make sure the types match up, and if we're doing this post-legalization,
  // we end up with legal types.
  Register X = LeftHandInst->getOperand(1).getReg();
  Register Y = RightHandInst->getOperand(1).getReg();
  LLT XTy = MRI.getType(X);
  LLT YTy = MRI.getType(Y);
  if (!XTy.isValid() || XTy != YTy)
    return false;

  // Optional extra source register.
  Register ExtraHandOpSrcReg;
  switch (HandOpcode) {
  default:
    return false;
  case TargetOpcode::G_ANYEXT:
  case TargetOpcode::G_SEXT:
  case TargetOpcode::G_ZEXT: {
    // Match: logic (ext X), (ext Y) --> ext (logic X, Y)
    break;
  }
  case TargetOpcode::G_TRUNC: {
    // Match: logic (trunc X), (trunc Y) -> trunc (logic X, Y)
    const MachineFunction *MF = MI.getMF();
    LLVMContext &Ctx = MF->getFunction().getContext();

    LLT DstTy = MRI.getType(Dst);
    const TargetLowering &TLI = getTargetLowering();

    // Be extra careful sinking truncate. If it's free, there's no benefit in
    // widening a binop.
    if (TLI.isZExtFree(DstTy, XTy, Ctx) && TLI.isTruncateFree(XTy, DstTy, Ctx))
      return false;
    break;
  }
  case TargetOpcode::G_AND:
  case TargetOpcode::G_ASHR:
  case TargetOpcode::G_LSHR:
  case TargetOpcode::G_SHL: {
    // Match: logic (binop x, z), (binop y, z) -> binop (logic x, y), z
    MachineOperand &ZOp = LeftHandInst->getOperand(2);
    if (!matchEqualDefs(ZOp, RightHandInst->getOperand(2)))
      return false;
    ExtraHandOpSrcReg = ZOp.getReg();
    break;
  }
  }

  if (!isLegalOrBeforeLegalizer({LogicOpcode, {XTy, YTy}}))
    return false;

  // Record the steps to build the new instructions.
  //
  // Steps to build (logic x, y)
  auto NewLogicDst = MRI.createGenericVirtualRegister(XTy);
  OperandBuildSteps LogicBuildSteps = {
      [=](MachineInstrBuilder &MIB) { MIB.addDef(NewLogicDst); },
      [=](MachineInstrBuilder &MIB) { MIB.addReg(X); },
      [=](MachineInstrBuilder &MIB) { MIB.addReg(Y); }};
  InstructionBuildSteps LogicSteps(LogicOpcode, LogicBuildSteps);

  // Steps to build hand (logic x, y), ...z
  OperandBuildSteps HandBuildSteps = {
      [=](MachineInstrBuilder &MIB) { MIB.addDef(Dst); },
      [=](MachineInstrBuilder &MIB) { MIB.addReg(NewLogicDst); }};
  if (ExtraHandOpSrcReg.isValid())
    HandBuildSteps.push_back(
        [=](MachineInstrBuilder &MIB) { MIB.addReg(ExtraHandOpSrcReg); });
  InstructionBuildSteps HandSteps(HandOpcode, HandBuildSteps);

  MatchInfo = InstructionStepsMatchInfo({LogicSteps, HandSteps});
  return true;
}

void CombinerHelper::applyBuildInstructionSteps(
    MachineInstr &MI, InstructionStepsMatchInfo &MatchInfo) const {
  assert(MatchInfo.InstrsToBuild.size() &&
         "Expected at least one instr to build?");
  for (auto &InstrToBuild : MatchInfo.InstrsToBuild) {
    assert(InstrToBuild.Opcode && "Expected a valid opcode?");
    assert(InstrToBuild.OperandFns.size() && "Expected at least one operand?");
    MachineInstrBuilder Instr = Builder.buildInstr(InstrToBuild.Opcode);
    for (auto &OperandFn : InstrToBuild.OperandFns)
      OperandFn(Instr);
  }
  MI.eraseFromParent();
}

bool CombinerHelper::matchAshrShlToSextInreg(
    MachineInstr &MI, std::tuple<Register, int64_t> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_ASHR);
  int64_t ShlCst, AshrCst;
  Register Src;
  if (!mi_match(MI.getOperand(0).getReg(), MRI,
                m_GAShr(m_GShl(m_Reg(Src), m_ICstOrSplat(ShlCst)),
                        m_ICstOrSplat(AshrCst))))
    return false;
  if (ShlCst != AshrCst)
    return false;
  if (!isLegalOrBeforeLegalizer(
          {TargetOpcode::G_SEXT_INREG,
           {MRI.getType(Src)},
           {},
           {MRI.getType(Src).getScalarSizeInBits() - ShlCst}}))
    return false;
  MatchInfo = std::make_tuple(Src, ShlCst);
  return true;
}

void CombinerHelper::applyAshShlToSextInreg(
    MachineInstr &MI, std::tuple<Register, int64_t> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_ASHR);
  Register Src;
  int64_t ShiftAmt;
  std::tie(Src, ShiftAmt) = MatchInfo;
  unsigned Size = MRI.getType(Src).getScalarSizeInBits();
  Builder.buildSExtInReg(MI.getOperand(0).getReg(), Src, Size - ShiftAmt);
  MI.eraseFromParent();
}

/// and(and(x, C1), C2) -> C1&C2 ? and(x, C1&C2) : 0
bool CombinerHelper::matchOverlappingAnd(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_AND);

  Register Dst = MI.getOperand(0).getReg();
  LLT Ty = MRI.getType(Dst);

  Register R;
  int64_t C1;
  int64_t C2;
  if (!mi_match(
          Dst, MRI,
          m_GAnd(m_GAnd(m_Reg(R), m_ICst(C1)), m_ICst(C2))))
    return false;

  MatchInfo = [=](MachineIRBuilder &B) {
    if (C1 & C2) {
      B.buildAnd(Dst, R, B.buildConstant(Ty, C1 & C2));
      return;
    }
    auto Zero = B.buildConstant(Ty, 0);
    replaceRegWith(MRI, Dst, Zero->getOperand(0).getReg());
  };
  return true;
}

bool CombinerHelper::matchRedundantAnd(MachineInstr &MI,
                                       Register &Replacement) const {
  // Given
  //
  // %y:_(sN) = G_SOMETHING
  // %x:_(sN) = G_SOMETHING
  // %res:_(sN) = G_AND %x, %y
  //
  // Eliminate the G_AND when it is known that x & y == x or x & y == y.
  //
  // Patterns like this can appear as a result of legalization. E.g.
  //
  // %cmp:_(s32) = G_ICMP intpred(pred), %x(s32), %y
  // %one:_(s32) = G_CONSTANT i32 1
  // %and:_(s32) = G_AND %cmp, %one
  //
  // In this case, G_ICMP only produces a single bit, so x & 1 == x.
  assert(MI.getOpcode() == TargetOpcode::G_AND);
  if (!VT)
    return false;

  Register AndDst = MI.getOperand(0).getReg();
  Register LHS = MI.getOperand(1).getReg();
  Register RHS = MI.getOperand(2).getReg();

  // Check the RHS (maybe a constant) first, and if we have no KnownBits there,
  // we can't do anything. If we do, then it depends on whether we have
  // KnownBits on the LHS.
  KnownBits RHSBits = VT->getKnownBits(RHS);
  if (RHSBits.isUnknown())
    return false;

  KnownBits LHSBits = VT->getKnownBits(LHS);

  // Check that x & Mask == x.
  // x & 1 == x, always
  // x & 0 == x, only if x is also 0
  // Meaning Mask has no effect if every bit is either one in Mask or zero in x.
  //
  // Check if we can replace AndDst with the LHS of the G_AND
  if (canReplaceReg(AndDst, LHS, MRI) &&
      (LHSBits.Zero | RHSBits.One).isAllOnes()) {
    Replacement = LHS;
    return true;
  }

  // Check if we can replace AndDst with the RHS of the G_AND
  if (canReplaceReg(AndDst, RHS, MRI) &&
      (LHSBits.One | RHSBits.Zero).isAllOnes()) {
    Replacement = RHS;
    return true;
  }

  return false;
}

bool CombinerHelper::matchRedundantOr(MachineInstr &MI,
                                      Register &Replacement) const {
  // Given
  //
  // %y:_(sN) = G_SOMETHING
  // %x:_(sN) = G_SOMETHING
  // %res:_(sN) = G_OR %x, %y
  //
  // Eliminate the G_OR when it is known that x | y == x or x | y == y.
  assert(MI.getOpcode() == TargetOpcode::G_OR);
  if (!VT)
    return false;

  Register OrDst = MI.getOperand(0).getReg();
  Register LHS = MI.getOperand(1).getReg();
  Register RHS = MI.getOperand(2).getReg();

  KnownBits LHSBits = VT->getKnownBits(LHS);
  KnownBits RHSBits = VT->getKnownBits(RHS);

  // Check that x | Mask == x.
  // x | 0 == x, always
  // x | 1 == x, only if x is also 1
  // Meaning Mask has no effect if every bit is either zero in Mask or one in x.
  //
  // Check if we can replace OrDst with the LHS of the G_OR
  if (canReplaceReg(OrDst, LHS, MRI) &&
      (LHSBits.One | RHSBits.Zero).isAllOnes()) {
    Replacement = LHS;
    return true;
  }

  // Check if we can replace OrDst with the RHS of the G_OR
  if (canReplaceReg(OrDst, RHS, MRI) &&
      (LHSBits.Zero | RHSBits.One).isAllOnes()) {
    Replacement = RHS;
    return true;
  }

  return false;
}

bool CombinerHelper::matchRedundantSExtInReg(MachineInstr &MI) const {
  // If the input is already sign extended, just drop the extension.
  Register Src = MI.getOperand(1).getReg();
  unsigned ExtBits = MI.getOperand(2).getImm();
  unsigned TypeSize = MRI.getType(Src).getScalarSizeInBits();
  return VT->computeNumSignBits(Src) >= (TypeSize - ExtBits + 1);
}

static bool isConstValidTrue(const TargetLowering &TLI, unsigned ScalarSizeBits,
                             int64_t Cst, bool IsVector, bool IsFP) {
  // For i1, Cst will always be -1 regardless of boolean contents.
  return (ScalarSizeBits == 1 && Cst == -1) ||
         isConstTrueVal(TLI, Cst, IsVector, IsFP);
}

// This pattern aims to match the following shape to avoid extra mov
// instructions
// G_BUILD_VECTOR(
//   G_UNMERGE_VALUES(src, 0)
//   G_UNMERGE_VALUES(src, 1)
//   G_IMPLICIT_DEF
//   G_IMPLICIT_DEF
// )
// ->
// G_CONCAT_VECTORS(
//   src,
//   undef
// )
bool CombinerHelper::matchCombineBuildUnmerge(MachineInstr &MI,
                                              MachineRegisterInfo &MRI,
                                              Register &UnmergeSrc) const {
  auto &BV = cast<GBuildVector>(MI);

  unsigned BuildUseCount = BV.getNumSources();
  if (BuildUseCount % 2 != 0)
    return false;

  unsigned NumUnmerge = BuildUseCount / 2;

  auto *Unmerge = getOpcodeDef<GUnmerge>(BV.getSourceReg(0), MRI);

  // Check the first operand is an unmerge and has the correct number of
  // operands
  if (!Unmerge || Unmerge->getNumDefs() != NumUnmerge)
    return false;

  UnmergeSrc = Unmerge->getSourceReg();

  LLT DstTy = MRI.getType(MI.getOperand(0).getReg());
  LLT UnmergeSrcTy = MRI.getType(UnmergeSrc);

  if (!UnmergeSrcTy.isVector())
    return false;

  // Ensure we only generate legal instructions post-legalizer
  if (!IsPreLegalize &&
      !isLegal({TargetOpcode::G_CONCAT_VECTORS, {DstTy, UnmergeSrcTy}}))
    return false;

  // Check that all of the operands before the midpoint come from the same
  // unmerge and are in the same order as they are used in the build_vector
  for (unsigned I = 0; I < NumUnmerge; ++I) {
    auto MaybeUnmergeReg = BV.getSourceReg(I);
    auto *LoopUnmerge = getOpcodeDef<GUnmerge>(MaybeUnmergeReg, MRI);

    if (!LoopUnmerge || LoopUnmerge != Unmerge)
      return false;

    if (LoopUnmerge->getOperand(I).getReg() != MaybeUnmergeReg)
      return false;
  }

  // Check that all of the unmerged values are used
  if (Unmerge->getNumDefs() != NumUnmerge)
    return false;

  // Check that all of the operands after the mid point are undefs.
  for (unsigned I = NumUnmerge; I < BuildUseCount; ++I) {
    auto *Undef = getDefIgnoringCopies(BV.getSourceReg(I), MRI);

    if (Undef->getOpcode() != TargetOpcode::G_IMPLICIT_DEF)
      return false;
  }

  return true;
}

void CombinerHelper::applyCombineBuildUnmerge(MachineInstr &MI,
                                              MachineRegisterInfo &MRI,
                                              MachineIRBuilder &B,
                                              Register &UnmergeSrc) const {
  assert(UnmergeSrc && "Expected there to be one matching G_UNMERGE_VALUES");
  B.setInstrAndDebugLoc(MI);

  Register UndefVec = B.buildUndef(MRI.getType(UnmergeSrc)).getReg(0);
  B.buildConcatVectors(MI.getOperand(0), {UnmergeSrc, UndefVec});

  MI.eraseFromParent();
}

// This combine tries to reduce the number of scalarised G_TRUNC instructions by
// using vector truncates instead
//
// EXAMPLE:
// %a(i32), %b(i32) = G_UNMERGE_VALUES %src(<2 x i32>)
// %T_a(i16) = G_TRUNC %a(i32)
// %T_b(i16) = G_TRUNC %b(i32)
// %Undef(i16) = G_IMPLICIT_DEF(i16)
// %dst(v4i16) = G_BUILD_VECTORS %T_a(i16), %T_b(i16), %Undef(i16), %Undef(i16)
//
// ===>
// %Undef(<2 x i32>) = G_IMPLICIT_DEF(<2 x i32>)
// %Mid(<4 x s32>) = G_CONCAT_VECTORS %src(<2 x i32>), %Undef(<2 x i32>)
// %dst(<4 x s16>) = G_TRUNC %Mid(<4 x s32>)
//
// Only matches sources made up of G_TRUNCs followed by G_IMPLICIT_DEFs
bool CombinerHelper::matchUseVectorTruncate(MachineInstr &MI,
                                            Register &MatchInfo) const {
  auto BuildMI = cast<GBuildVector>(&MI);
  unsigned NumOperands = BuildMI->getNumSources();
  LLT DstTy = MRI.getType(BuildMI->getReg(0));

  // Check the G_BUILD_VECTOR sources
  unsigned I;
  GUnmerge *UnmergeMI = nullptr;

  // Check all source TRUNCs come from the same UNMERGE instruction
  // and that the element order matches (BUILD_VECTOR position I
  // corresponds to UNMERGE result I)
  for (I = 0; I < NumOperands; ++I) {
    // Check if the G_TRUNC instructions all come from the same MI
    Register TruncSrcReg;
    if (!mi_match(BuildMI->getSourceReg(I), MRI, m_GTrunc(m_Reg(TruncSrcReg))))
      break;

    if (!UnmergeMI) {
      if (!mi_match(TruncSrcReg, MRI, m_GUnmerge(UnmergeMI)))
        return false;
    } else {
      MachineInstr *UnmergeSrcMI;
      if (!mi_match(TruncSrcReg, MRI, m_MInstr(UnmergeSrcMI)) ||
          UnmergeMI != UnmergeSrcMI)
        return false;
    }
    // Element order must match: position I must use UNMERGE result I.
    if (UnmergeMI->getOperand(I).getReg() != TruncSrcReg)
      return false;
  }
  if (I < 2)
    return false;

  // Check the remaining source elements are only G_IMPLICIT_DEF
  for (; I < NumOperands; ++I) {
    if (!mi_match(BuildMI->getSourceReg(I), MRI, m_GImplicitDef()))
      return false;
  }

  // Check the size of unmerge source
  MatchInfo = UnmergeMI->getSourceReg();
  LLT UnmergeSrcTy = MRI.getType(MatchInfo);
  if (!DstTy.getElementCount().isKnownMultipleOf(UnmergeSrcTy.getNumElements()))
    return false;

  // Check the unmerge source and destination element types match
  LLT UnmergeSrcEltTy = UnmergeSrcTy.getElementType();
  Register UnmergeDstReg = UnmergeMI->getOperand(0).getReg();
  LLT UnmergeDstEltTy = MRI.getType(UnmergeDstReg);
  if (UnmergeSrcEltTy != UnmergeDstEltTy)
    return false;

  // Only generate legal instructions post-legalizer
  if (!IsPreLegalize) {
    LLT MidTy = DstTy.changeElementType(UnmergeSrcTy.getScalarType());

    if (DstTy.getElementCount() != UnmergeSrcTy.getElementCount() &&
        !isLegal({TargetOpcode::G_CONCAT_VECTORS, {MidTy, UnmergeSrcTy}}))
      return false;

    if (!isLegal({TargetOpcode::G_TRUNC, {DstTy, MidTy}}))
      return false;
  }

  return true;
}

void CombinerHelper::applyUseVectorTruncate(MachineInstr &MI,
                                            Register &MatchInfo) const {
  Register MidReg;
  auto BuildMI = cast<GBuildVector>(&MI);
  Register DstReg = BuildMI->getReg(0);
  LLT DstTy = MRI.getType(DstReg);
  LLT UnmergeSrcTy = MRI.getType(MatchInfo);
  unsigned DstTyNumElt = DstTy.getNumElements();
  unsigned UnmergeSrcTyNumElt = UnmergeSrcTy.getNumElements();

  // No need to pad vector if only G_TRUNC is needed
  if (DstTyNumElt / UnmergeSrcTyNumElt == 1) {
    MidReg = MatchInfo;
  } else {
    Register UndefReg = Builder.buildUndef(UnmergeSrcTy).getReg(0);
    SmallVector<Register> ConcatRegs = {MatchInfo};
    for (unsigned I = 1; I < DstTyNumElt / UnmergeSrcTyNumElt; ++I)
      ConcatRegs.push_back(UndefReg);

    auto MidTy = DstTy.changeElementType(UnmergeSrcTy.getScalarType());
    MidReg = Builder.buildConcatVectors(MidTy, ConcatRegs).getReg(0);
  }

  Builder.buildTrunc(DstReg, MidReg);
  MI.eraseFromParent();
}

bool CombinerHelper::matchNotCmp(
    MachineInstr &MI, SmallVectorImpl<Register> &RegsToNegate) const {
  assert(MI.getOpcode() == TargetOpcode::G_XOR);
  LLT Ty = MRI.getType(MI.getOperand(0).getReg());
  const auto &TLI = *Builder.getMF().getSubtarget().getTargetLowering();
  Register XorSrc;
  Register CstReg;
  // We match xor(src, true) here.
  if (!mi_match(MI.getOperand(0).getReg(), MRI,
                m_GXor(m_Reg(XorSrc), m_Reg(CstReg))))
    return false;

  if (!MRI.hasOneNonDBGUse(XorSrc))
    return false;

  // Check that XorSrc is the root of a tree of comparisons combined with ANDs
  // and ORs. The suffix of RegsToNegate starting from index I is used a work
  // list of tree nodes to visit.
  RegsToNegate.push_back(XorSrc);
  // Remember whether the comparisons are all integer or all floating point.
  bool IsInt = false;
  bool IsFP = false;
  for (unsigned I = 0; I < RegsToNegate.size(); ++I) {
    Register Reg = RegsToNegate[I];
    if (!MRI.hasOneNonDBGUse(Reg))
      return false;
    MachineInstr *Def;
    if (!mi_match(Reg, MRI, m_MInstr(Def)))
      return false;
    switch (Def->getOpcode()) {
    default:
      // Don't match if the tree contains anything other than ANDs, ORs and
      // comparisons.
      return false;
    case TargetOpcode::G_ICMP:
      if (IsFP)
        return false;
      IsInt = true;
      // When we apply the combine we will invert the predicate.
      break;
    case TargetOpcode::G_FCMP:
      if (IsInt)
        return false;
      IsFP = true;
      // When we apply the combine we will invert the predicate.
      break;
    case TargetOpcode::G_AND:
    case TargetOpcode::G_OR:
      // Implement De Morgan's laws:
      // ~(x & y) -> ~x | ~y
      // ~(x | y) -> ~x & ~y
      // When we apply the combine we will change the opcode and recursively
      // negate the operands.
      RegsToNegate.push_back(Def->getOperand(1).getReg());
      RegsToNegate.push_back(Def->getOperand(2).getReg());
      break;
    }
  }

  // Now we know whether the comparisons are integer or floating point, check
  // the constant in the xor.
  int64_t Cst;
  if (Ty.isVector()) {
    int64_t SplatCst;
    if (!mi_match(CstReg, MRI, m_ICstOrSplat(SplatCst)))
      return false;
    if (!isConstValidTrue(TLI, Ty.getScalarSizeInBits(), SplatCst, true, IsFP))
      return false;
  } else {
    if (!mi_match(CstReg, MRI, m_ICst(Cst)))
      return false;
    if (!isConstValidTrue(TLI, Ty.getSizeInBits(), Cst, false, IsFP))
      return false;
  }

  return true;
}

void CombinerHelper::applyNotCmp(
    MachineInstr &MI, SmallVectorImpl<Register> &RegsToNegate) const {
  for (Register Reg : RegsToNegate) {
    MachineInstr *Def = MRI.getVRegDef(Reg);
    Observer.changingInstr(*Def);
    // For each comparison, invert the opcode. For each AND and OR, change the
    // opcode.
    switch (Def->getOpcode()) {
    default:
      llvm_unreachable("Unexpected opcode");
    case TargetOpcode::G_ICMP:
    case TargetOpcode::G_FCMP: {
      MachineOperand &PredOp = Def->getOperand(1);
      CmpInst::Predicate NewP = CmpInst::getInversePredicate(
          (CmpInst::Predicate)PredOp.getPredicate());
      PredOp.setPredicate(NewP);
      break;
    }
    case TargetOpcode::G_AND:
      Def->setDesc(Builder.getTII().get(TargetOpcode::G_OR));
      break;
    case TargetOpcode::G_OR:
      Def->setDesc(Builder.getTII().get(TargetOpcode::G_AND));
      break;
    }
    Observer.changedInstr(*Def);
  }

  replaceRegWith(MRI, MI.getOperand(0).getReg(), MI.getOperand(1).getReg());
  MI.eraseFromParent();
}

bool CombinerHelper::matchXorOfAndWithSameReg(
    MachineInstr &MI, std::pair<Register, Register> &MatchInfo) const {
  // Match (xor (and x, y), y) (or any of its commuted cases)
  assert(MI.getOpcode() == TargetOpcode::G_XOR);
  Register &X = MatchInfo.first;
  Register &Y = MatchInfo.second;
  Register AndReg = MI.getOperand(1).getReg();
  Register SharedReg = MI.getOperand(2).getReg();

  // Find a G_AND on either side of the G_XOR.
  // Look for one of
  //
  // (xor (and x, y), SharedReg)
  // (xor SharedReg, (and x, y))
  if (!mi_match(AndReg, MRI, m_GAnd(m_Reg(X), m_Reg(Y)))) {
    std::swap(AndReg, SharedReg);
    if (!mi_match(AndReg, MRI, m_GAnd(m_Reg(X), m_Reg(Y))))
      return false;
  }

  // Only do this if we'll eliminate the G_AND.
  if (!MRI.hasOneNonDBGUse(AndReg))
    return false;

  // We can combine if SharedReg is the same as either the LHS or RHS of the
  // G_AND.
  if (Y != SharedReg)
    std::swap(X, Y);
  return Y == SharedReg;
}

void CombinerHelper::applyXorOfAndWithSameReg(
    MachineInstr &MI, std::pair<Register, Register> &MatchInfo) const {
  // Fold (xor (and x, y), y) -> (and (not x), y)
  Register X, Y;
  std::tie(X, Y) = MatchInfo;
  auto Not = Builder.buildNot(MRI.getType(X), X);
  Observer.changingInstr(MI);
  MI.setDesc(Builder.getTII().get(TargetOpcode::G_AND));
  MI.getOperand(1).setReg(Not->getOperand(0).getReg());
  MI.getOperand(2).setReg(Y);
  Observer.changedInstr(MI);
}

bool CombinerHelper::matchPtrAddZero(MachineInstr &MI) const {
  auto &PtrAdd = cast<GPtrAdd>(MI);
  Register DstReg = PtrAdd.getReg(0);
  LLT Ty = MRI.getType(DstReg);
  const DataLayout &DL = Builder.getMF().getDataLayout();

  if (DL.isNonIntegralAddressSpace(Ty.getScalarType().getAddressSpace()))
    return false;

  if (Ty.isPointer()) {
    auto ConstVal = getIConstantVRegVal(PtrAdd.getBaseReg(), MRI);
    return ConstVal && *ConstVal == 0;
  }

  assert(Ty.isVector() && "Expecting a vector type");
  const MachineInstr *VecMI;
  if (!mi_match(PtrAdd.getBaseReg(), MRI, m_MInstr(VecMI)))
    return false;
  return isBuildVectorAllZeros(*VecMI, MRI);
}

/// The second source operand is known to be a power of 2.
void CombinerHelper::applySimplifyURemByPow2(MachineInstr &MI) const {
  Register DstReg = MI.getOperand(0).getReg();
  Register Src0 = MI.getOperand(1).getReg();
  Register Pow2Src1 = MI.getOperand(2).getReg();
  LLT Ty = MRI.getType(DstReg);

  // Fold (urem x, pow2) -> (and x, pow2-1)
  auto NegOne = Builder.buildConstant(Ty, -1);
  auto Add = Builder.buildAdd(Ty, Pow2Src1, NegOne);
  Builder.buildAnd(DstReg, Src0, Add);
  MI.eraseFromParent();
}

bool CombinerHelper::matchFoldBinOpIntoSelect(MachineInstr &MI,
                                              unsigned &SelectOpNo) const {
  Register LHS = MI.getOperand(1).getReg();
  Register RHS = MI.getOperand(2).getReg();

  Register OtherOperandReg = RHS;
  SelectOpNo = 1;
  Register SelectTrue, SelectFalse;

  // Don't do this unless the old select is going away. We want to eliminate the
  // binary operator, not replace a binop with a select.
  if (!mi_match(LHS, MRI,
                m_GISelect(m_Reg(), m_Reg(SelectTrue), m_Reg(SelectFalse))) ||
      !MRI.hasOneNonDBGUse(LHS)) {
    OtherOperandReg = LHS;
    SelectOpNo = 2;
    if (!mi_match(RHS, MRI,
                  m_GISelect(m_Reg(), m_Reg(SelectTrue), m_Reg(SelectFalse))) ||
        !MRI.hasOneNonDBGUse(RHS))
      return false;
  }

  MachineInstr *SelectLHS, *SelectRHS;
  if (!mi_match(SelectTrue, MRI, m_MInstr(SelectLHS)) ||
      !mi_match(SelectFalse, MRI, m_MInstr(SelectRHS)))
    return false;

  if (!isConstantOrConstantVector(*SelectLHS, MRI,
                                  /*AllowFP*/ true,
                                  /*AllowOpaqueConstants*/ false))
    return false;
  if (!isConstantOrConstantVector(*SelectRHS, MRI,
                                  /*AllowFP*/ true,
                                  /*AllowOpaqueConstants*/ false))
    return false;

  unsigned BinOpcode = MI.getOpcode();

  // We know that one of the operands is a select of constants. Now verify that
  // the other binary operator operand is either a constant, or we can handle a
  // variable.
  bool CanFoldNonConst =
      (BinOpcode == TargetOpcode::G_AND || BinOpcode == TargetOpcode::G_OR) &&
      (isNullOrNullSplat(*SelectLHS, MRI) ||
       isAllOnesOrAllOnesSplat(*SelectLHS, MRI)) &&
      (isNullOrNullSplat(*SelectRHS, MRI) ||
       isAllOnesOrAllOnesSplat(*SelectRHS, MRI));
  if (CanFoldNonConst)
    return true;

  MachineInstr *OtherOperandDef;
  if (!mi_match(OtherOperandReg, MRI, m_MInstr(OtherOperandDef)))
    return false;
  return isConstantOrConstantVector(*OtherOperandDef, MRI,
                                    /*AllowFP*/ true,
                                    /*AllowOpaqueConstants*/ false);
}

/// \p SelectOperand is the operand in binary operator \p MI that is the select
/// to fold.
void CombinerHelper::applyFoldBinOpIntoSelect(
    MachineInstr &MI, const unsigned &SelectOperand) const {
  Register Dst = MI.getOperand(0).getReg();
  Register LHS = MI.getOperand(1).getReg();
  Register RHS = MI.getOperand(2).getReg();
  GSelect *Select =
      cast<GSelect>(MRI.getVRegDef(MI.getOperand(SelectOperand).getReg()));

  Register SelectCond = Select->getCondReg();
  Register SelectTrue = Select->getTrueReg();
  Register SelectFalse = Select->getFalseReg();

  LLT Ty = MRI.getType(Dst);
  unsigned BinOpcode = MI.getOpcode();

  Register FoldTrue, FoldFalse;

  // We have a select-of-constants followed by a binary operator with a
  // constant. Eliminate the binop by pulling the constant math into the select.
  // Example: add (select Cond, CT, CF), CBO --> select Cond, CT + CBO, CF + CBO
  if (SelectOperand == 1) {
    // TODO: SelectionDAG verifies this actually constant folds before
    // committing to the combine.

    FoldTrue = Builder.buildInstr(BinOpcode, {Ty}, {SelectTrue, RHS}).getReg(0);
    FoldFalse =
        Builder.buildInstr(BinOpcode, {Ty}, {SelectFalse, RHS}).getReg(0);
  } else {
    FoldTrue = Builder.buildInstr(BinOpcode, {Ty}, {LHS, SelectTrue}).getReg(0);
    FoldFalse =
        Builder.buildInstr(BinOpcode, {Ty}, {LHS, SelectFalse}).getReg(0);
  }

  Builder.buildSelect(Dst, SelectCond, FoldTrue, FoldFalse, MI.getFlags());
  MI.eraseFromParent();
}

std::optional<SmallVector<Register, 8>>
CombinerHelper::findCandidatesForLoadOrCombine(const MachineInstr *Root) const {
  assert(Root->getOpcode() == TargetOpcode::G_OR && "Expected G_OR only!");
  // We want to detect if Root is part of a tree which represents a bunch
  // of loads being merged into a larger load. We'll try to recognize patterns
  // like, for example:
  //
  //  Reg   Reg
  //   \    /
  //    OR_1   Reg
  //     \    /
  //      OR_2
  //        \     Reg
  //         .. /
  //        Root
  //
  //  Reg   Reg   Reg   Reg
  //     \ /       \   /
  //     OR_1      OR_2
  //       \       /
  //        \    /
  //         ...
  //         Root
  //
  // Each "Reg" may have been produced by a load + some arithmetic. This
  // function will save each of them.
  SmallVector<Register, 8> RegsToVisit;
  SmallVector<const MachineInstr *, 7> Ors = {Root};

  // In the "worst" case, we're dealing with a load for each byte. So, there
  // are at most #bytes - 1 ORs.
  const unsigned MaxIter =
      MRI.getType(Root->getOperand(0).getReg()).getSizeInBytes() - 1;
  for (unsigned Iter = 0; Iter < MaxIter; ++Iter) {
    if (Ors.empty())
      break;
    const MachineInstr *Curr = Ors.pop_back_val();
    Register OrLHS = Curr->getOperand(1).getReg();
    Register OrRHS = Curr->getOperand(2).getReg();

    // In the combine, we want to elimate the entire tree.
    if (!MRI.hasOneNonDBGUse(OrLHS) || !MRI.hasOneNonDBGUse(OrRHS))
      return std::nullopt;

    // If it's a G_OR, save it and continue to walk. If it's not, then it's
    // something that may be a load + arithmetic.
    if (const MachineInstr *Or = getOpcodeDef(TargetOpcode::G_OR, OrLHS, MRI))
      Ors.push_back(Or);
    else
      RegsToVisit.push_back(OrLHS);
    if (const MachineInstr *Or = getOpcodeDef(TargetOpcode::G_OR, OrRHS, MRI))
      Ors.push_back(Or);
    else
      RegsToVisit.push_back(OrRHS);
  }

  // We're going to try and merge each register into a wider power-of-2 type,
  // so we ought to have an even number of registers.
  if (RegsToVisit.empty() || RegsToVisit.size() % 2 != 0)
    return std::nullopt;
  return RegsToVisit;
}

/// Helper function for findLoadOffsetsForLoadOrCombine.
///
/// Check if \p Reg is the result of loading a \p MemSizeInBits wide value,
/// and then moving that value into a specific byte offset.
///
/// e.g. x[i] << 24
///
/// \returns The load instruction and the byte offset it is moved into.
static std::optional<std::pair<GZExtLoad *, int64_t>>
matchLoadAndBytePosition(Register Reg, unsigned MemSizeInBits,
                         const MachineRegisterInfo &MRI) {
  assert(MRI.hasOneNonDBGUse(Reg) &&
         "Expected Reg to only have one non-debug use?");
  Register MaybeLoad;
  int64_t Shift;
  if (!mi_match(Reg, MRI,
                m_OneNonDBGUse(m_GShl(m_Reg(MaybeLoad), m_ICst(Shift))))) {
    Shift = 0;
    MaybeLoad = Reg;
  }

  if (Shift % MemSizeInBits != 0)
    return std::nullopt;

  // TODO: Handle other types of loads.
  auto *Load = getOpcodeDef<GZExtLoad>(MaybeLoad, MRI);
  if (!Load)
    return std::nullopt;

  if (!Load->isUnordered() || Load->getMemSizeInBits() != MemSizeInBits)
    return std::nullopt;

  return std::make_pair(Load, Shift / MemSizeInBits);
}

std::optional<std::tuple<GZExtLoad *, int64_t, GZExtLoad *>>
CombinerHelper::findLoadOffsetsForLoadOrCombine(
    SmallDenseMap<int64_t, int64_t, 8> &MemOffset2Idx,
    const SmallVector<Register, 8> &RegsToVisit,
    const unsigned MemSizeInBits) const {

  // Each load found for the pattern. There should be one for each RegsToVisit.
  SmallSetVector<const MachineInstr *, 8> Loads;

  // The lowest index used in any load. (The lowest "i" for each x[i].)
  int64_t LowestIdx = INT64_MAX;

  // The load which uses the lowest index.
  GZExtLoad *LowestIdxLoad = nullptr;

  // Keeps track of the load indices we see. We shouldn't see any indices twice.
  SmallSet<int64_t, 8> SeenIdx;

  // Ensure each load is in the same MBB.
  // TODO: Support multiple MachineBasicBlocks.
  MachineBasicBlock *MBB = nullptr;
  const MachineMemOperand *MMO = nullptr;

  // Earliest instruction-order load in the pattern.
  GZExtLoad *EarliestLoad = nullptr;

  // Latest instruction-order load in the pattern.
  GZExtLoad *LatestLoad = nullptr;

  // Base pointer which every load should share.
  Register BasePtr;

  // We want to find a load for each register. Each load should have some
  // appropriate bit twiddling arithmetic. During this loop, we will also keep
  // track of the load which uses the lowest index. Later, we will check if we
  // can use its pointer in the final, combined load.
  for (auto Reg : RegsToVisit) {
    // Find the load, and find the position that it will end up in (e.g. a
    // shifted) value.
    auto LoadAndPos = matchLoadAndBytePosition(Reg, MemSizeInBits, MRI);
    if (!LoadAndPos)
      return std::nullopt;
    GZExtLoad *Load;
    int64_t DstPos;
    std::tie(Load, DstPos) = *LoadAndPos;

    // TODO: Handle multiple MachineBasicBlocks. Currently not handled because
    // it is difficult to check for stores/calls/etc between loads.
    MachineBasicBlock *LoadMBB = Load->getParent();
    if (!MBB)
      MBB = LoadMBB;
    if (LoadMBB != MBB)
      return std::nullopt;

    // Make sure that the MachineMemOperands of every seen load are compatible.
    auto &LoadMMO = Load->getMMO();
    if (!MMO)
      MMO = &LoadMMO;
    if (MMO->getAddrSpace() != LoadMMO.getAddrSpace())
      return std::nullopt;

    // Find out what the base pointer and index for the load is.
    Register LoadPtr;
    int64_t Idx;
    if (!mi_match(Load->getOperand(1).getReg(), MRI,
                  m_GPtrAdd(m_Reg(LoadPtr), m_ICst(Idx)))) {
      LoadPtr = Load->getOperand(1).getReg();
      Idx = 0;
    }

    // Don't combine things like a[i], a[i] -> a bigger load.
    if (!SeenIdx.insert(Idx).second)
      return std::nullopt;

    // Every load must share the same base pointer; don't combine things like:
    //
    // a[i], b[i + 1] -> a bigger load.
    if (!BasePtr.isValid())
      BasePtr = LoadPtr;
    if (BasePtr != LoadPtr)
      return std::nullopt;

    if (Idx < LowestIdx) {
      LowestIdx = Idx;
      LowestIdxLoad = Load;
    }

    // Keep track of the byte offset that this load ends up at. If we have seen
    // the byte offset, then stop here. We do not want to combine:
    //
    // a[i] << 16, a[i + k] << 16 -> a bigger load.
    if (!MemOffset2Idx.try_emplace(DstPos, Idx).second)
      return std::nullopt;
    Loads.insert(Load);

    // Keep track of the position of the earliest/latest loads in the pattern.
    // We will check that there are no load fold barriers between them later
    // on.
    //
    // FIXME: Is there a better way to check for load fold barriers?
    if (!EarliestLoad || dominates(*Load, *EarliestLoad))
      EarliestLoad = Load;
    if (!LatestLoad || dominates(*LatestLoad, *Load))
      LatestLoad = Load;
  }

  // We found a load for each register. Let's check if each load satisfies the
  // pattern.
  assert(Loads.size() == RegsToVisit.size() &&
         "Expected to find a load for each register?");
  assert(EarliestLoad != LatestLoad && EarliestLoad &&
         LatestLoad && "Expected at least two loads?");

  // Check if there are any stores, calls, etc. between any of the loads. If
  // there are, then we can't safely perform the combine.
  //
  // MaxIter is chosen based off the (worst case) number of iterations it
  // typically takes to succeed in the LLVM test suite plus some padding.
  //
  // FIXME: Is there a better way to check for load fold barriers?
  const unsigned MaxIter = 20;
  unsigned Iter = 0;
  for (const auto &MI : instructionsWithoutDebug(EarliestLoad->getIterator(),
                                                 LatestLoad->getIterator())) {
    if (Loads.count(&MI))
      continue;
    if (MI.isLoadFoldBarrier())
      return std::nullopt;
    if (Iter++ == MaxIter)
      return std::nullopt;
  }

  return std::make_tuple(LowestIdxLoad, LowestIdx, LatestLoad);
}

bool CombinerHelper::matchLoadOrCombine(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_OR);
  MachineFunction &MF = *MI.getMF();
  // Assuming a little-endian target, transform:
  //  s8 *a = ...
  //  s32 val = a[0] | (a[1] << 8) | (a[2] << 16) | (a[3] << 24)
  // =>
  //  s32 val = *((i32)a)
  //
  //  s8 *a = ...
  //  s32 val = (a[0] << 24) | (a[1] << 16) | (a[2] << 8) | a[3]
  // =>
  //  s32 val = BSWAP(*((s32)a))
  Register Dst = MI.getOperand(0).getReg();
  LLT Ty = MRI.getType(Dst);
  if (Ty.isVector())
    return false;

  // We need to combine at least two loads into this type. Since the smallest
  // possible load is into a byte, we need at least a 16-bit wide type.
  const unsigned WideMemSizeInBits = Ty.getSizeInBits();
  if (WideMemSizeInBits < 16 || WideMemSizeInBits % 8 != 0)
    return false;

  // Match a collection of non-OR instructions in the pattern.
  auto RegsToVisit = findCandidatesForLoadOrCombine(&MI);
  if (!RegsToVisit)
    return false;

  // We have a collection of non-OR instructions. Figure out how wide each of
  // the small loads should be based off of the number of potential loads we
  // found.
  const unsigned NarrowMemSizeInBits = WideMemSizeInBits / RegsToVisit->size();
  if (NarrowMemSizeInBits % 8 != 0)
    return false;

  // Check if each register feeding into each OR is a load from the same
  // base pointer + some arithmetic.
  //
  // e.g. a[0], a[1] << 8, a[2] << 16, etc.
  //
  // Also verify that each of these ends up putting a[i] into the same memory
  // offset as a load into a wide type would.
  SmallDenseMap<int64_t, int64_t, 8> MemOffset2Idx;
  GZExtLoad *LowestIdxLoad, *LatestLoad;
  int64_t LowestIdx;
  auto MaybeLoadInfo = findLoadOffsetsForLoadOrCombine(
      MemOffset2Idx, *RegsToVisit, NarrowMemSizeInBits);
  if (!MaybeLoadInfo)
    return false;
  std::tie(LowestIdxLoad, LowestIdx, LatestLoad) = *MaybeLoadInfo;

  // We have a bunch of loads being OR'd together. Using the addresses + offsets
  // we found before, check if this corresponds to a big or little endian byte
  // pattern. If it does, then we can represent it using a load + possibly a
  // BSWAP.
  bool IsBigEndianTarget = MF.getDataLayout().isBigEndian();
  std::optional<bool> IsBigEndian = isBigEndian(MemOffset2Idx, LowestIdx);
  if (!IsBigEndian)
    return false;
  bool NeedsBSwap = IsBigEndianTarget != *IsBigEndian;
  if (NeedsBSwap && !isLegalOrBeforeLegalizer({TargetOpcode::G_BSWAP, {Ty}}))
    return false;

  // Make sure that the load from the lowest index produces offset 0 in the
  // final value.
  //
  // This ensures that we won't combine something like this:
  //
  // load x[i] -> byte 2
  // load x[i+1] -> byte 0 ---> wide_load x[i]
  // load x[i+2] -> byte 1
  const unsigned NumLoadsInTy = WideMemSizeInBits / NarrowMemSizeInBits;
  const unsigned ZeroByteOffset =
      *IsBigEndian
          ? bigEndianByteAt(NumLoadsInTy, 0)
          : littleEndianByteAt(NumLoadsInTy, 0);
  auto ZeroOffsetIdx = MemOffset2Idx.find(ZeroByteOffset);
  if (ZeroOffsetIdx == MemOffset2Idx.end() ||
      ZeroOffsetIdx->second != LowestIdx)
    return false;

  // We wil reuse the pointer from the load which ends up at byte offset 0. It
  // may not use index 0.
  Register Ptr = LowestIdxLoad->getPointerReg();
  const MachineMemOperand &MMO = LowestIdxLoad->getMMO();
  LegalityQuery::MemDesc MMDesc(MMO);
  MMDesc.MemoryTy = Ty;
  if (!isLegalOrBeforeLegalizer(
          {TargetOpcode::G_LOAD, {Ty, MRI.getType(Ptr)}, {MMDesc}}))
    return false;
  auto PtrInfo = MMO.getPointerInfo();
  auto *NewMMO = MF.getMachineMemOperand(&MMO, PtrInfo, WideMemSizeInBits / 8);

  // Load must be allowed and fast on the target.
  LLVMContext &C = MF.getFunction().getContext();
  auto &DL = MF.getDataLayout();
  unsigned Fast = 0;
  if (!getTargetLowering().allowsMemoryAccess(C, DL, Ty, *NewMMO, &Fast) ||
      !Fast)
    return false;

  MatchInfo = [=](MachineIRBuilder &MIB) {
    MIB.setInstrAndDebugLoc(*LatestLoad);
    Register LoadDst = NeedsBSwap ? MRI.cloneVirtualRegister(Dst) : Dst;
    MIB.buildLoad(LoadDst, Ptr, *NewMMO);
    if (NeedsBSwap)
      MIB.buildBSwap(Dst, LoadDst);
  };
  return true;
}

bool CombinerHelper::matchExtendThroughPhis(MachineInstr &MI,
                                            MachineInstr *&ExtMI) const {
  auto &PHI = cast<GPhi>(MI);
  Register DstReg = PHI.getReg(0);

  // TODO: Extending a vector may be expensive, don't do this until heuristics
  // are better.
  if (MRI.getType(DstReg).isVector())
    return false;

  // Try to match a phi, whose only use is an extend.
  if (!MRI.hasOneNonDBGUse(DstReg))
    return false;
  ExtMI = &*MRI.use_instr_nodbg_begin(DstReg);
  switch (ExtMI->getOpcode()) {
  case TargetOpcode::G_ANYEXT:
    return true; // G_ANYEXT is usually free.
  case TargetOpcode::G_ZEXT:
  case TargetOpcode::G_SEXT:
    break;
  default:
    return false;
  }

  // If the target is likely to fold this extend away, don't propagate.
  if (Builder.getTII().isExtendLikelyToBeFolded(*ExtMI, MRI))
    return false;

  // We don't want to propagate the extends unless there's a good chance that
  // they'll be optimized in some way.
  // Collect the unique incoming values.
  SmallPtrSet<MachineInstr *, 4> InSrcs;
  for (unsigned I = 0; I < PHI.getNumIncomingValues(); ++I) {
    auto *DefMI = getDefIgnoringCopies(PHI.getIncomingValue(I), MRI);
    switch (DefMI->getOpcode()) {
    case TargetOpcode::G_LOAD:
    case TargetOpcode::G_TRUNC:
    case TargetOpcode::G_SEXT:
    case TargetOpcode::G_ZEXT:
    case TargetOpcode::G_ANYEXT:
    case TargetOpcode::G_CONSTANT:
      InSrcs.insert(DefMI);
      // Don't try to propagate if there are too many places to create new
      // extends, chances are it'll increase code size.
      if (InSrcs.size() > 2)
        return false;
      break;
    default:
      return false;
    }
  }
  return true;
}

void CombinerHelper::applyExtendThroughPhis(MachineInstr &MI,
                                            MachineInstr *&ExtMI) const {
  auto &PHI = cast<GPhi>(MI);
  Register DstReg = ExtMI->getOperand(0).getReg();
  LLT ExtTy = MRI.getType(DstReg);

  // Propagate the extension into the block of each incoming reg's block.
  // Use a SetVector here because PHIs can have duplicate edges, and we want
  // deterministic iteration order.
  SmallSetVector<MachineInstr *, 8> SrcMIs;
  SmallDenseMap<MachineInstr *, MachineInstr *, 8> OldToNewSrcMap;
  for (unsigned I = 0; I < PHI.getNumIncomingValues(); ++I) {
    auto SrcReg = PHI.getIncomingValue(I);
    MachineInstr *SrcMI;
    if (!mi_match(SrcReg, MRI, m_MInstr(SrcMI)))
      continue;
    if (!SrcMIs.insert(SrcMI))
      continue;

    // Build an extend after each src inst.
    auto *MBB = SrcMI->getParent();
    MachineBasicBlock::iterator InsertPt = ++SrcMI->getIterator();
    if (InsertPt != MBB->end() && InsertPt->isPHI())
      InsertPt = MBB->getFirstNonPHI();

    Builder.setInsertPt(*SrcMI->getParent(), InsertPt);
    Builder.setDebugLoc(MI.getDebugLoc());
    auto NewExt = Builder.buildExtOrTrunc(ExtMI->getOpcode(), ExtTy, SrcReg);
    OldToNewSrcMap[SrcMI] = NewExt;
  }

  // Create a new phi with the extended inputs.
  Builder.setInstrAndDebugLoc(MI);
  auto NewPhi = Builder.buildInstrNoInsert(TargetOpcode::G_PHI);
  NewPhi.addDef(DstReg);
  for (const MachineOperand &MO : llvm::drop_begin(MI.operands())) {
    if (!MO.isReg()) {
      NewPhi.addMBB(MO.getMBB());
      continue;
    }
    auto *NewSrc = OldToNewSrcMap[MRI.getVRegDef(MO.getReg())];
    NewPhi.addUse(NewSrc->getOperand(0).getReg());
  }
  Builder.insertInstr(NewPhi);
  ExtMI->eraseFromParent();
}

bool CombinerHelper::matchExtractVecEltBuildVec(MachineInstr &MI,
                                                Register &Reg) const {
  assert(MI.getOpcode() == TargetOpcode::G_EXTRACT_VECTOR_ELT);
  // If we have a constant index, look for a G_BUILD_VECTOR source
  // and find the source register that the index maps to.
  Register SrcVec = MI.getOperand(1).getReg();
  LLT SrcTy = MRI.getType(SrcVec);
  if (SrcTy.isScalableVector())
    return false;

  auto Cst = getIConstantVRegValWithLookThrough(MI.getOperand(2).getReg(), MRI);
  if (!Cst || Cst->Value.getZExtValue() >= SrcTy.getNumElements())
    return false;

  unsigned VecIdx = Cst->Value.getZExtValue();

  // Check if we have a build_vector or build_vector_trunc with an optional
  // trunc in front.
  MachineInstr *SrcVecMI;
  Register TruncSrc;
  if (mi_match(SrcVec, MRI, m_GTrunc(m_Reg(TruncSrc)))) {
    if (!mi_match(TruncSrc, MRI, m_MInstr(SrcVecMI)))
      return false;
  } else if (!mi_match(SrcVec, MRI, m_MInstr(SrcVecMI)))
    return false;

  if (SrcVecMI->getOpcode() != TargetOpcode::G_BUILD_VECTOR &&
      SrcVecMI->getOpcode() != TargetOpcode::G_BUILD_VECTOR_TRUNC)
    return false;

  EVT Ty(getMVTForLLT(SrcTy));
  if (!MRI.hasOneNonDBGUse(SrcVec) &&
      !getTargetLowering().aggressivelyPreferBuildVectorSources(Ty))
    return false;

  Reg = SrcVecMI->getOperand(VecIdx + 1).getReg();
  return true;
}

void CombinerHelper::applyExtractVecEltBuildVec(MachineInstr &MI,
                                                Register &Reg) const {
  // Check the type of the register, since it may have come from a
  // G_BUILD_VECTOR_TRUNC.
  LLT ScalarTy = MRI.getType(Reg);
  Register DstReg = MI.getOperand(0).getReg();
  LLT DstTy = MRI.getType(DstReg);

  if (ScalarTy != DstTy) {
    assert(ScalarTy.getSizeInBits() > DstTy.getSizeInBits());
    Builder.buildTrunc(DstReg, Reg);
    MI.eraseFromParent();
    return;
  }
  replaceSingleDefInstWithReg(MI, Reg);
}

bool CombinerHelper::matchExtractAllEltsFromBuildVector(
    MachineInstr &MI,
    SmallVectorImpl<std::pair<Register, MachineInstr *>> &SrcDstPairs) const {
  assert(MI.getOpcode() == TargetOpcode::G_BUILD_VECTOR);
  // This combine tries to find build_vector's which have every source element
  // extracted using G_EXTRACT_VECTOR_ELT. This can happen when transforms like
  // the masked load scalarization is run late in the pipeline. There's already
  // a combine for a similar pattern starting from the extract, but that
  // doesn't attempt to do it if there are multiple uses of the build_vector,
  // which in this case is true. Starting the combine from the build_vector
  // feels more natural than trying to find sibling nodes of extracts.
  // E.g.
  //  %vec(<4 x s32>) = G_BUILD_VECTOR %s1(s32), %s2, %s3, %s4
  //  %ext1 = G_EXTRACT_VECTOR_ELT %vec, 0
  //  %ext2 = G_EXTRACT_VECTOR_ELT %vec, 1
  //  %ext3 = G_EXTRACT_VECTOR_ELT %vec, 2
  //  %ext4 = G_EXTRACT_VECTOR_ELT %vec, 3
  // ==>
  // replace ext{1,2,3,4} with %s{1,2,3,4}

  Register DstReg = MI.getOperand(0).getReg();
  LLT DstTy = MRI.getType(DstReg);
  unsigned NumElts = DstTy.getNumElements();

  SmallBitVector ExtractedElts(NumElts);
  for (MachineInstr &II : MRI.use_nodbg_instructions(DstReg)) {
    if (II.getOpcode() != TargetOpcode::G_EXTRACT_VECTOR_ELT)
      return false;
    auto Cst = getIConstantVRegVal(II.getOperand(2).getReg(), MRI);
    if (!Cst)
      return false;
    unsigned Idx = Cst->getZExtValue();
    if (Idx >= NumElts)
      return false; // Out of range.
    ExtractedElts.set(Idx);
    SrcDstPairs.emplace_back(
        std::make_pair(MI.getOperand(Idx + 1).getReg(), &II));
  }
  // Match if every element was extracted.
  return ExtractedElts.all();
}

void CombinerHelper::applyExtractAllEltsFromBuildVector(
    MachineInstr &MI,
    SmallVectorImpl<std::pair<Register, MachineInstr *>> &SrcDstPairs) const {
  assert(MI.getOpcode() == TargetOpcode::G_BUILD_VECTOR);
  for (auto &Pair : SrcDstPairs) {
    auto *ExtMI = Pair.second;
    replaceRegWith(MRI, ExtMI->getOperand(0).getReg(), Pair.first);
    ExtMI->eraseFromParent();
  }
  MI.eraseFromParent();
}

void CombinerHelper::applyBuildFn(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  applyBuildFnNoErase(MI, MatchInfo);
  MI.eraseFromParent();
}

void CombinerHelper::applyBuildFnNoErase(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  MatchInfo(Builder);
}

bool CombinerHelper::matchOrShiftToFunnelShift(MachineInstr &MI,
                                               bool AllowScalarConstants,
                                               BuildFnTy &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_OR);

  Register Dst = MI.getOperand(0).getReg();
  LLT Ty = MRI.getType(Dst);
  unsigned BitWidth = Ty.getScalarSizeInBits();

  Register ShlSrc, ShlAmt, LShrSrc, LShrAmt, Amt;
  unsigned FshOpc = 0;

  // Match (or (shl ...), (lshr ...)).
  if (!mi_match(Dst, MRI,
                // m_GOr() handles the commuted version as well.
                m_GOr(m_GShl(m_Reg(ShlSrc), m_Reg(ShlAmt)),
                      m_GLShr(m_Reg(LShrSrc), m_Reg(LShrAmt)))))
    return false;

  // Given constants C0 and C1 such that C0 + C1 is bit-width:
  // (or (shl x, C0), (lshr y, C1)) -> (fshl x, y, C0) or (fshr x, y, C1)
  int64_t CstShlAmt = 0, CstLShrAmt;
  if (mi_match(ShlAmt, MRI, m_ICstOrSplat(CstShlAmt)) &&
      mi_match(LShrAmt, MRI, m_ICstOrSplat(CstLShrAmt)) &&
      CstShlAmt + CstLShrAmt == BitWidth) {
    FshOpc = TargetOpcode::G_FSHR;
    Amt = LShrAmt;
  } else if (mi_match(LShrAmt, MRI,
                      m_GSub(m_SpecificICstOrSplat(BitWidth), m_Reg(Amt))) &&
             ShlAmt == Amt) {
    // (or (shl x, amt), (lshr y, (sub bw, amt))) -> (fshl x, y, amt)
    FshOpc = TargetOpcode::G_FSHL;
  } else if (mi_match(ShlAmt, MRI,
                      m_GSub(m_SpecificICstOrSplat(BitWidth), m_Reg(Amt))) &&
             LShrAmt == Amt) {
    // (or (shl x, (sub bw, amt)), (lshr y, amt)) -> (fshr x, y, amt)
    FshOpc = TargetOpcode::G_FSHR;
  } else {
    return false;
  }

  LLT AmtTy = MRI.getType(Amt);
  if (!isLegalOrBeforeLegalizer({FshOpc, {Ty, AmtTy}}) &&
      (!AllowScalarConstants || CstShlAmt == 0 || !Ty.isScalar()))
    return false;

  MatchInfo = [=](MachineIRBuilder &B) {
    B.buildInstr(FshOpc, {Dst}, {ShlSrc, LShrSrc, Amt});
  };
  return true;
}

/// Match an FSHL or FSHR that can be combined to a ROTR or ROTL rotate.
bool CombinerHelper::matchFunnelShiftToRotate(MachineInstr &MI) const {
  unsigned Opc = MI.getOpcode();
  assert(Opc == TargetOpcode::G_FSHL || Opc == TargetOpcode::G_FSHR);
  Register X = MI.getOperand(1).getReg();
  Register Y = MI.getOperand(2).getReg();
  if (X != Y)
    return false;
  unsigned RotateOpc =
      Opc == TargetOpcode::G_FSHL ? TargetOpcode::G_ROTL : TargetOpcode::G_ROTR;
  return isLegalOrBeforeLegalizer({RotateOpc, {MRI.getType(X), MRI.getType(Y)}});
}

void CombinerHelper::applyFunnelShiftToRotate(MachineInstr &MI) const {
  unsigned Opc = MI.getOpcode();
  assert(Opc == TargetOpcode::G_FSHL || Opc == TargetOpcode::G_FSHR);
  bool IsFSHL = Opc == TargetOpcode::G_FSHL;
  Observer.changingInstr(MI);
  MI.setDesc(Builder.getTII().get(IsFSHL ? TargetOpcode::G_ROTL
                                         : TargetOpcode::G_ROTR));
  MI.removeOperand(2);
  Observer.changedInstr(MI);
}

// Fold (rot x, c) -> (rot x, c % BitSize)
bool CombinerHelper::matchRotateOutOfRange(MachineInstr &MI) const {
  assert(MI.getOpcode() == TargetOpcode::G_ROTL ||
         MI.getOpcode() == TargetOpcode::G_ROTR);
  unsigned Bitsize =
      MRI.getType(MI.getOperand(0).getReg()).getScalarSizeInBits();
  Register AmtReg = MI.getOperand(2).getReg();
  bool OutOfRange = false;
  auto MatchOutOfRange = [Bitsize, &OutOfRange](const Constant *C) {
    if (auto *CI = dyn_cast<ConstantInt>(C))
      OutOfRange |= CI->getValue().uge(Bitsize);
    return true;
  };
  return matchUnaryPredicate(MRI, AmtReg, MatchOutOfRange) && OutOfRange;
}

void CombinerHelper::applyRotateOutOfRange(MachineInstr &MI) const {
  assert(MI.getOpcode() == TargetOpcode::G_ROTL ||
         MI.getOpcode() == TargetOpcode::G_ROTR);
  unsigned Bitsize =
      MRI.getType(MI.getOperand(0).getReg()).getScalarSizeInBits();
  Register Amt = MI.getOperand(2).getReg();
  LLT AmtTy = MRI.getType(Amt);
  auto Bits = Builder.buildConstant(AmtTy, Bitsize);
  Amt = Builder.buildURem(AmtTy, MI.getOperand(2).getReg(), Bits).getReg(0);
  Observer.changingInstr(MI);
  MI.getOperand(2).setReg(Amt);
  Observer.changedInstr(MI);
}

bool CombinerHelper::matchICmpToTrueFalseKnownBits(MachineInstr &MI,
                                                   int64_t &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_ICMP);
  auto Pred = static_cast<CmpInst::Predicate>(MI.getOperand(1).getPredicate());

  // We want to avoid calling KnownBits on the LHS if possible, as this combine
  // has no filter and runs on every G_ICMP instruction. We can avoid calling
  // KnownBits on the LHS in two cases:
  //
  //  - The RHS is unknown: Constants are always on RHS. If the RHS is unknown
  //  we cannot do any transforms so we can safely bail out early.
  //  - The RHS is zero: we don't need to know the LHS to do unsigned <0 and
  //  >=0.
  auto KnownRHS = VT->getKnownBits(MI.getOperand(3).getReg());
  if (KnownRHS.isUnknown())
    return false;

  std::optional<bool> KnownVal;
  if (KnownRHS.isZero()) {
    // ? uge 0 -> always true
    // ? ult 0 -> always false
    if (Pred == CmpInst::ICMP_UGE)
      KnownVal = true;
    else if (Pred == CmpInst::ICMP_ULT)
      KnownVal = false;
  }

  if (!KnownVal) {
    auto KnownLHS = VT->getKnownBits(MI.getOperand(2).getReg());
    KnownVal = ICmpInst::compare(KnownLHS, KnownRHS, Pred);
  }

  if (!KnownVal)
    return false;
  MatchInfo =
      *KnownVal
          ? getICmpTrueVal(getTargetLowering(),
                           /*IsVector = */
                           MRI.getType(MI.getOperand(0).getReg()).isVector(),
                           /* IsFP = */ false)
          : 0;
  return true;
}

bool CombinerHelper::matchICmpToLHSKnownBits(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_ICMP);
  // Given:
  //
  // %x = G_WHATEVER (... x is known to be 0 or 1 ...)
  // %cmp = G_ICMP ne %x, 0
  //
  // Or:
  //
  // %x = G_WHATEVER (... x is known to be 0 or 1 ...)
  // %cmp = G_ICMP eq %x, 1
  //
  // We can replace %cmp with %x assuming true is 1 on the target.
  auto Pred = static_cast<CmpInst::Predicate>(MI.getOperand(1).getPredicate());
  if (!CmpInst::isEquality(Pred))
    return false;
  Register Dst = MI.getOperand(0).getReg();
  LLT DstTy = MRI.getType(Dst);
  if (getICmpTrueVal(getTargetLowering(), DstTy.isVector(),
                     /* IsFP = */ false) != 1)
    return false;
  int64_t OneOrZero = Pred == CmpInst::ICMP_EQ;
  if (!mi_match(MI.getOperand(3).getReg(), MRI, m_SpecificICst(OneOrZero)))
    return false;
  Register LHS = MI.getOperand(2).getReg();
  auto KnownLHS = VT->getKnownBits(LHS);
  if (KnownLHS.getMinValue() != 0 || KnownLHS.getMaxValue() != 1)
    return false;
  // Make sure replacing Dst with the LHS is a legal operation.
  LLT LHSTy = MRI.getType(LHS);
  unsigned LHSSize = LHSTy.getSizeInBits();
  unsigned DstSize = DstTy.getSizeInBits();
  unsigned Op = TargetOpcode::COPY;
  if (DstSize != LHSSize)
    Op = DstSize < LHSSize ? TargetOpcode::G_TRUNC : TargetOpcode::G_ZEXT;
  if (!isLegalOrBeforeLegalizer({Op, {DstTy, LHSTy}}))
    return false;
  MatchInfo = [=](MachineIRBuilder &B) { B.buildInstr(Op, {Dst}, {LHS}); };
  return true;
}

// Replace (and (or x, c1), c2) with (and x, c2) iff c1 & c2 == 0
bool CombinerHelper::matchAndOrDisjointMask(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_AND);

  // Ignore vector types to simplify matching the two constants.
  // TODO: do this for vectors and scalars via a demanded bits analysis.
  LLT Ty = MRI.getType(MI.getOperand(0).getReg());
  if (Ty.isVector())
    return false;

  Register Src;
  Register AndMaskReg;
  int64_t AndMaskBits;
  int64_t OrMaskBits;
  if (!mi_match(MI, MRI,
                m_GAnd(m_GOr(m_Reg(Src), m_ICst(OrMaskBits)),
                       m_all_of(m_ICst(AndMaskBits), m_Reg(AndMaskReg)))))
    return false;

  // Check if OrMask could turn on any bits in Src.
  if (AndMaskBits & OrMaskBits)
    return false;

  MatchInfo = [=, &MI](MachineIRBuilder &B) {
    Observer.changingInstr(MI);
    // Canonicalize the result to have the constant on the RHS.
    if (MI.getOperand(1).getReg() == AndMaskReg)
      MI.getOperand(2).setReg(AndMaskReg);
    MI.getOperand(1).setReg(Src);
    Observer.changedInstr(MI);
  };
  return true;
}

/// Form a G_SBFX from a G_SEXT_INREG fed by a right shift.
bool CombinerHelper::matchBitfieldExtractFromSExtInReg(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_SEXT_INREG);
  Register Dst = MI.getOperand(0).getReg();
  Register Src = MI.getOperand(1).getReg();
  LLT Ty = MRI.getType(Src);
  LLT ExtractTy = getTargetLowering().getPreferredShiftAmountTy(Ty);
  if (!LI || !LI->isLegalOrCustom({TargetOpcode::G_SBFX, {Ty, ExtractTy}}))
    return false;
  int64_t Width = MI.getOperand(2).getImm();
  Register ShiftSrc;
  int64_t ShiftImm;
  if (!mi_match(
          Src, MRI,
          m_OneNonDBGUse(m_any_of(m_GAShr(m_Reg(ShiftSrc), m_ICst(ShiftImm)),
                                  m_GLShr(m_Reg(ShiftSrc), m_ICst(ShiftImm))))))
    return false;
  if (ShiftImm < 0 || ShiftImm + Width > Ty.getScalarSizeInBits())
    return false;

  MatchInfo = [=](MachineIRBuilder &B) {
    auto Cst1 = B.buildConstant(ExtractTy, ShiftImm);
    auto Cst2 = B.buildConstant(ExtractTy, Width);
    B.buildSbfx(Dst, ShiftSrc, Cst1, Cst2);
  };
  return true;
}

/// Form a G_UBFX from "(a srl b) & mask", where b and mask are constants.
bool CombinerHelper::matchBitfieldExtractFromAnd(MachineInstr &MI,
                                                 BuildFnTy &MatchInfo) const {
  GAnd *And = cast<GAnd>(&MI);
  Register Dst = And->getReg(0);
  LLT Ty = MRI.getType(Dst);
  LLT ExtractTy = getTargetLowering().getPreferredShiftAmountTy(Ty);
  // Note that isLegalOrBeforeLegalizer is stricter and does not take custom
  // into account.
  if (LI && !LI->isLegalOrCustom({TargetOpcode::G_UBFX, {Ty, ExtractTy}}))
    return false;

  int64_t AndImm, LSBImm;
  Register ShiftSrc;
  const unsigned Size = Ty.getScalarSizeInBits();
  if (!mi_match(And->getReg(0), MRI,
                m_GAnd(m_OneNonDBGUse(m_GLShr(m_Reg(ShiftSrc), m_ICst(LSBImm))),
                       m_ICst(AndImm))))
    return false;

  // AndImm is sign-extended to 64 bits by m_ICst; restrict it to the operand
  // width so an all-ones mask (a redundant AND) is not misread as a wider mask.
  uint64_t MaybeMask = static_cast<uint64_t>(AndImm);
  if (Size < 64)
    MaybeMask &= maskTrailingOnes<uint64_t>(Size);

  // The mask is a mask of the low bits iff imm & (imm+1) == 0.
  if (MaybeMask & (MaybeMask + 1))
    return false;

  // LSB must fit within the register.
  if (static_cast<uint64_t>(LSBImm) >= Size)
    return false;

  uint64_t Width = APInt(Size, MaybeMask).countr_one();
  // The extracted field [LSB, LSB+Width) must fit within the register.
  // Otherwise this is a redundant AND (e.g. an all-ones mask combined with a
  // non-zero shift) that is better handled by other combines, and would form
  // an out-of-range bitfield extract.
  if (static_cast<uint64_t>(LSBImm) + Width > Size)
    return false;

  MatchInfo = [=](MachineIRBuilder &B) {
    auto WidthCst = B.buildConstant(ExtractTy, Width);
    auto LSBCst = B.buildConstant(ExtractTy, LSBImm);
    B.buildInstr(TargetOpcode::G_UBFX, {Dst}, {ShiftSrc, LSBCst, WidthCst});
  };
  return true;
}

bool CombinerHelper::matchBitfieldExtractFromShr(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  const unsigned Opcode = MI.getOpcode();
  assert(Opcode == TargetOpcode::G_ASHR || Opcode == TargetOpcode::G_LSHR);

  const Register Dst = MI.getOperand(0).getReg();

  const unsigned ExtrOpcode = Opcode == TargetOpcode::G_ASHR
                                  ? TargetOpcode::G_SBFX
                                  : TargetOpcode::G_UBFX;

  // Check if the type we would use for the extract is legal
  LLT Ty = MRI.getType(Dst);
  LLT ExtractTy = getTargetLowering().getPreferredShiftAmountTy(Ty);
  if (!LI || !LI->isLegalOrCustom({ExtrOpcode, {Ty, ExtractTy}}))
    return false;

  Register ShlSrc;
  int64_t ShrAmt;
  int64_t ShlAmt;
  const unsigned Size = Ty.getScalarSizeInBits();

  // Try to match shr (shl x, c1), c2
  if (!mi_match(Dst, MRI,
                m_BinOp(Opcode,
                        m_OneNonDBGUse(m_GShl(m_Reg(ShlSrc), m_ICst(ShlAmt))),
                        m_ICst(ShrAmt))))
    return false;

  // Make sure that the shift sizes can fit a bitfield extract
  if (ShlAmt < 0 || ShlAmt > ShrAmt || ShrAmt >= Size)
    return false;

  // Skip this combine if the G_SEXT_INREG combine could handle it
  if (Opcode == TargetOpcode::G_ASHR && ShlAmt == ShrAmt)
    return false;

  // Calculate start position and width of the extract
  const int64_t Pos = ShrAmt - ShlAmt;
  const int64_t Width = Size - ShrAmt;

  MatchInfo = [=](MachineIRBuilder &B) {
    auto WidthCst = B.buildConstant(ExtractTy, Width);
    auto PosCst = B.buildConstant(ExtractTy, Pos);
    B.buildInstr(ExtrOpcode, {Dst}, {ShlSrc, PosCst, WidthCst});
  };
  return true;
}

bool CombinerHelper::matchBitfieldExtractFromShrAnd(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  const unsigned Opcode = MI.getOpcode();
  assert(Opcode == TargetOpcode::G_LSHR || Opcode == TargetOpcode::G_ASHR);

  const Register Dst = MI.getOperand(0).getReg();
  LLT Ty = MRI.getType(Dst);
  LLT ExtractTy = getTargetLowering().getPreferredShiftAmountTy(Ty);
  if (LI && !LI->isLegalOrCustom({TargetOpcode::G_UBFX, {Ty, ExtractTy}}))
    return false;

  // Try to match shr (and x, c1), c2
  Register AndSrc;
  int64_t ShrAmt;
  int64_t SMask;
  if (!mi_match(Dst, MRI,
                m_BinOp(Opcode,
                        m_OneNonDBGUse(m_GAnd(m_Reg(AndSrc), m_ICst(SMask))),
                        m_ICst(ShrAmt))))
    return false;

  const unsigned Size = Ty.getScalarSizeInBits();
  if (ShrAmt < 0 || ShrAmt >= Size)
    return false;

  // If the shift subsumes the mask, emit the 0 directly.
  if (0 == (SMask >> ShrAmt)) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.buildConstant(Dst, 0);
    };
    return true;
  }

  // Check that ubfx can do the extraction, with no holes in the mask.
  uint64_t UMask = SMask;
  UMask |= maskTrailingOnes<uint64_t>(ShrAmt);
  UMask &= maskTrailingOnes<uint64_t>(Size);
  if (!isMask_64(UMask))
    return false;

  // Calculate start position and width of the extract.
  const int64_t Pos = ShrAmt;
  const int64_t Width = llvm::countr_one(UMask) - ShrAmt;

  // It's preferable to keep the shift, rather than form G_SBFX.
  // TODO: remove the G_AND via demanded bits analysis.
  if (Opcode == TargetOpcode::G_ASHR && Width + ShrAmt == Size)
    return false;

  MatchInfo = [=](MachineIRBuilder &B) {
    auto WidthCst = B.buildConstant(ExtractTy, Width);
    auto PosCst = B.buildConstant(ExtractTy, Pos);
    B.buildInstr(TargetOpcode::G_UBFX, {Dst}, {AndSrc, PosCst, WidthCst});
  };
  return true;
}

bool CombinerHelper::reassociationCanBreakAddressingModePattern(
    MachineInstr &MI) const {
  auto &PtrAdd = cast<GPtrAdd>(MI);

  Register Src1Reg = PtrAdd.getBaseReg();
  auto *Src1Def = getOpcodeDef<GPtrAdd>(Src1Reg, MRI);
  if (!Src1Def)
    return false;

  Register Src2Reg = PtrAdd.getOffsetReg();

  if (MRI.hasOneNonDBGUse(Src1Reg))
    return false;

  auto C1 = getIConstantVRegVal(Src1Def->getOffsetReg(), MRI);
  if (!C1)
    return false;
  auto C2 = getIConstantVRegVal(Src2Reg, MRI);
  if (!C2)
    return false;

  const APInt &C1APIntVal = *C1;
  const APInt &C2APIntVal = *C2;
  const int64_t CombinedValue = (C1APIntVal + C2APIntVal).getSExtValue();

  for (auto &UseMI : MRI.use_nodbg_instructions(PtrAdd.getReg(0))) {
    // This combine may end up running before ptrtoint/inttoptr combines
    // manage to eliminate redundant conversions, so try to look through them.
    MachineInstr *ConvUseMI = &UseMI;
    unsigned ConvUseOpc = ConvUseMI->getOpcode();
    while (ConvUseOpc == TargetOpcode::G_INTTOPTR ||
           ConvUseOpc == TargetOpcode::G_PTRTOINT) {
      Register DefReg = ConvUseMI->getOperand(0).getReg();
      if (!MRI.hasOneNonDBGUse(DefReg))
        break;
      ConvUseMI = &*MRI.use_instr_nodbg_begin(DefReg);
      ConvUseOpc = ConvUseMI->getOpcode();
    }
    auto *LdStMI = dyn_cast<GLoadStore>(ConvUseMI);
    if (!LdStMI)
      continue;
    // Is x[offset2] already not a legal addressing mode? If so then
    // reassociating the constants breaks nothing (we test offset2 because
    // that's the one we hope to fold into the load or store).
    TargetLoweringBase::AddrMode AM;
    AM.HasBaseReg = true;
    AM.BaseOffs = C2APIntVal.getSExtValue();
    unsigned AS = MRI.getType(LdStMI->getPointerReg()).getAddressSpace();
    Type *AccessTy = getTypeForLLT(LdStMI->getMMO().getMemoryType(),
                                   PtrAdd.getMF()->getFunction().getContext());
    const auto &TLI = *PtrAdd.getMF()->getSubtarget().getTargetLowering();
    if (!TLI.isLegalAddressingMode(PtrAdd.getMF()->getDataLayout(), AM,
                                   AccessTy, AS))
      continue;

    // Would x[offset1+offset2] still be a legal addressing mode?
    AM.BaseOffs = CombinedValue;
    if (!TLI.isLegalAddressingMode(PtrAdd.getMF()->getDataLayout(), AM,
                                   AccessTy, AS))
      return true;
  }

  return false;
}

bool CombinerHelper::matchReassocConstantInnerRHS(GPtrAdd &MI,
                                                  MachineInstr *RHS,
                                                  BuildFnTy &MatchInfo) const {
  // G_PTR_ADD(BASE, G_ADD(X, C)) -> G_PTR_ADD(G_PTR_ADD(BASE, X), C)
  Register Src1Reg = MI.getOperand(1).getReg();
  if (RHS->getOpcode() != TargetOpcode::G_ADD)
    return false;
  auto C2 = getIConstantVRegVal(RHS->getOperand(2).getReg(), MRI);
  if (!C2)
    return false;

  // If both additions are nuw, the reassociated additions are also nuw.
  // If the original G_PTR_ADD is additionally nusw, X and C are both not
  // negative, so BASE+X is between BASE and BASE+(X+C). The new G_PTR_ADDs are
  // therefore also nusw.
  // If the original G_PTR_ADD is additionally inbounds (which implies nusw),
  // the new G_PTR_ADDs are then also inbounds.
  unsigned PtrAddFlags = MI.getFlags();
  unsigned AddFlags = RHS->getFlags();
  bool IsNoUWrap = PtrAddFlags & AddFlags & MachineInstr::MIFlag::NoUWrap;
  bool IsNoUSWrap = IsNoUWrap && (PtrAddFlags & MachineInstr::MIFlag::NoUSWrap);
  bool IsInBounds = IsNoUWrap && (PtrAddFlags & MachineInstr::MIFlag::InBounds);
  unsigned Flags = 0;
  if (IsNoUWrap)
    Flags |= MachineInstr::MIFlag::NoUWrap;
  if (IsNoUSWrap)
    Flags |= MachineInstr::MIFlag::NoUSWrap;
  if (IsInBounds)
    Flags |= MachineInstr::MIFlag::InBounds;

  MatchInfo = [=, &MI](MachineIRBuilder &B) {
    LLT PtrTy = MRI.getType(MI.getOperand(0).getReg());

    auto NewBase =
        Builder.buildPtrAdd(PtrTy, Src1Reg, RHS->getOperand(1).getReg(), Flags);
    Observer.changingInstr(MI);
    MI.getOperand(1).setReg(NewBase.getReg(0));
    MI.getOperand(2).setReg(RHS->getOperand(2).getReg());
    MI.setFlags(Flags);
    Observer.changedInstr(MI);
  };
  return !reassociationCanBreakAddressingModePattern(MI);
}

bool CombinerHelper::matchReassocConstantInnerLHS(GPtrAdd &MI,
                                                  MachineInstr *LHS,
                                                  MachineInstr *RHS,
                                                  BuildFnTy &MatchInfo) const {
  // G_PTR_ADD (G_PTR_ADD X, C), Y) -> (G_PTR_ADD (G_PTR_ADD(X, Y), C)
  // if and only if (G_PTR_ADD X, C) has one use.
  Register LHSBase;
  std::optional<ValueAndVReg> LHSCstOff;
  if (!mi_match(MI.getBaseReg(), MRI,
                m_OneNonDBGUse(m_GPtrAdd(m_Reg(LHSBase), m_GCst(LHSCstOff)))))
    return false;

  auto *LHSPtrAdd = cast<GPtrAdd>(LHS);

  // Reassociating nuw additions preserves nuw. If both original G_PTR_ADDs are
  // nuw and inbounds (which implies nusw), the offsets are both non-negative,
  // so the new G_PTR_ADDs are also inbounds.
  unsigned PtrAddFlags = MI.getFlags();
  unsigned LHSPtrAddFlags = LHSPtrAdd->getFlags();
  bool IsNoUWrap = PtrAddFlags & LHSPtrAddFlags & MachineInstr::MIFlag::NoUWrap;
  bool IsNoUSWrap = IsNoUWrap && (PtrAddFlags & LHSPtrAddFlags &
                                  MachineInstr::MIFlag::NoUSWrap);
  bool IsInBounds = IsNoUWrap && (PtrAddFlags & LHSPtrAddFlags &
                                  MachineInstr::MIFlag::InBounds);
  unsigned Flags = 0;
  if (IsNoUWrap)
    Flags |= MachineInstr::MIFlag::NoUWrap;
  if (IsNoUSWrap)
    Flags |= MachineInstr::MIFlag::NoUSWrap;
  if (IsInBounds)
    Flags |= MachineInstr::MIFlag::InBounds;

  MatchInfo = [=, &MI](MachineIRBuilder &B) {
    // When we change LHSPtrAdd's offset register we might cause it to use a reg
    // before its def. Sink the instruction so the outer PTR_ADD to ensure this
    // doesn't happen.
    LHSPtrAdd->moveBefore(&MI);
    Register RHSReg = MI.getOffsetReg();
    // set VReg will cause type mismatch if it comes from extend/trunc
    auto NewCst = B.buildConstant(MRI.getType(RHSReg), LHSCstOff->Value);
    Observer.changingInstr(MI);
    MI.getOperand(2).setReg(NewCst.getReg(0));
    MI.setFlags(Flags);
    Observer.changedInstr(MI);
    Observer.changingInstr(*LHSPtrAdd);
    LHSPtrAdd->getOperand(2).setReg(RHSReg);
    LHSPtrAdd->setFlags(Flags);
    Observer.changedInstr(*LHSPtrAdd);
  };
  return !reassociationCanBreakAddressingModePattern(MI);
}

bool CombinerHelper::matchReassocFoldConstantsInSubTree(
    GPtrAdd &MI, MachineInstr *LHS, MachineInstr *RHS,
    BuildFnTy &MatchInfo) const {
  // G_PTR_ADD(G_PTR_ADD(BASE, C1), C2) -> G_PTR_ADD(BASE, C1+C2)
  auto *LHSPtrAdd = dyn_cast<GPtrAdd>(LHS);
  if (!LHSPtrAdd)
    return false;

  Register Src2Reg = MI.getOperand(2).getReg();
  Register LHSSrc1 = LHSPtrAdd->getBaseReg();
  Register LHSSrc2 = LHSPtrAdd->getOffsetReg();
  auto C1 = getIConstantVRegVal(LHSSrc2, MRI);
  if (!C1)
    return false;
  auto C2 = getIConstantVRegVal(Src2Reg, MRI);
  if (!C2)
    return false;

  // Reassociating nuw additions preserves nuw. If both original G_PTR_ADDs are
  // inbounds, reaching the same result in one G_PTR_ADD is also inbounds.
  // The nusw constraints are satisfied because imm1+imm2 cannot exceed the
  // largest signed integer that fits into the index type, which is the maximum
  // size of allocated objects according to the IR Language Reference.
  unsigned PtrAddFlags = MI.getFlags();
  unsigned LHSPtrAddFlags = LHSPtrAdd->getFlags();
  bool IsNoUWrap = PtrAddFlags & LHSPtrAddFlags & MachineInstr::MIFlag::NoUWrap;
  bool IsInBounds =
      PtrAddFlags & LHSPtrAddFlags & MachineInstr::MIFlag::InBounds;
  unsigned Flags = 0;
  if (IsNoUWrap)
    Flags |= MachineInstr::MIFlag::NoUWrap;
  if (IsInBounds) {
    Flags |= MachineInstr::MIFlag::InBounds;
    Flags |= MachineInstr::MIFlag::NoUSWrap;
  }

  MatchInfo = [=, &MI](MachineIRBuilder &B) {
    auto NewCst = B.buildConstant(MRI.getType(Src2Reg), *C1 + *C2);
    Observer.changingInstr(MI);
    MI.getOperand(1).setReg(LHSSrc1);
    MI.getOperand(2).setReg(NewCst.getReg(0));
    MI.setFlags(Flags);
    Observer.changedInstr(MI);
  };
  return !reassociationCanBreakAddressingModePattern(MI);
}

bool CombinerHelper::matchReassocPtrAdd(MachineInstr &MI,
                                        BuildFnTy &MatchInfo) const {
  auto &PtrAdd = cast<GPtrAdd>(MI);
  // We're trying to match a few pointer computation patterns here for
  // re-association opportunities.
  // 1) Isolating a constant operand to be on the RHS, e.g.:
  // G_PTR_ADD(BASE, G_ADD(X, C)) -> G_PTR_ADD(G_PTR_ADD(BASE, X), C)
  //
  // 2) Folding two constants in each sub-tree as long as such folding
  // doesn't break a legal addressing mode.
  // G_PTR_ADD(G_PTR_ADD(BASE, C1), C2) -> G_PTR_ADD(BASE, C1+C2)
  //
  // 3) Move a constant from the LHS of an inner op to the RHS of the outer.
  // G_PTR_ADD (G_PTR_ADD X, C), Y) -> G_PTR_ADD (G_PTR_ADD(X, Y), C)
  // iif (G_PTR_ADD X, C) has one use.
  MachineInstr *LHS, *RHS;
  if (!mi_match(PtrAdd.getBaseReg(), MRI, m_MInstr(LHS)) ||
      !mi_match(PtrAdd.getOffsetReg(), MRI, m_MInstr(RHS)))
    return false;

  // Try to match example 2.
  if (matchReassocFoldConstantsInSubTree(PtrAdd, LHS, RHS, MatchInfo))
    return true;

  // Try to match example 3.
  if (matchReassocConstantInnerLHS(PtrAdd, LHS, RHS, MatchInfo))
    return true;

  // Try to match example 1.
  if (matchReassocConstantInnerRHS(PtrAdd, RHS, MatchInfo))
    return true;

  return false;
}
bool CombinerHelper::tryReassocBinOp(unsigned Opc, Register DstReg,
                                     Register OpLHS, Register OpRHS,
                                     BuildFnTy &MatchInfo) const {
  LLT OpRHSTy = MRI.getType(OpRHS);
  MachineInstr *OpLHSDef;
  if (!mi_match(OpLHS, MRI, m_MInstr(OpLHSDef)) || OpLHSDef->getOpcode() != Opc)
    return false;

  Register OpLHSLHS = OpLHSDef->getOperand(1).getReg();
  Register OpLHSRHS = OpLHSDef->getOperand(2).getReg();

  // If the inner op is (X op C), pull the constant out so it can be folded with
  // other constants in the expression tree. Folding is not guaranteed so we
  // might have (C1 op C2). In that case do not pull a constant out because it
  // won't help and can lead to infinite loops.
  if (isConstantOrConstantSplatVector(OpLHSRHS, MRI) &&
      !isConstantOrConstantSplatVector(OpLHSLHS, MRI)) {
    if (isConstantOrConstantSplatVector(OpRHS, MRI)) {
      // (Opc (Opc X, C1), C2) -> (Opc X, (Opc C1, C2))
      MatchInfo = [=](MachineIRBuilder &B) {
        auto NewCst = B.buildInstr(Opc, {OpRHSTy}, {OpLHSRHS, OpRHS});
        B.buildInstr(Opc, {DstReg}, {OpLHSLHS, NewCst});
      };
      return true;
    }
    if (getTargetLowering().isReassocProfitable(MRI, OpLHS, OpRHS)) {
      // Reassociate: (op (op x, c1), y) -> (op (op x, y), c1)
      //              iff (op x, c1) has one use
      MatchInfo = [=](MachineIRBuilder &B) {
        auto NewLHSLHS = B.buildInstr(Opc, {OpRHSTy}, {OpLHSLHS, OpRHS});
        B.buildInstr(Opc, {DstReg}, {NewLHSLHS, OpLHSRHS});
      };
      return true;
    }
  }

  return false;
}

bool CombinerHelper::matchReassocCommBinOp(MachineInstr &MI,
                                           BuildFnTy &MatchInfo) const {
  // We don't check if the reassociation will break a legal addressing mode
  // here since pointer arithmetic is handled by G_PTR_ADD.
  unsigned Opc = MI.getOpcode();
  Register DstReg = MI.getOperand(0).getReg();
  Register LHSReg = MI.getOperand(1).getReg();
  Register RHSReg = MI.getOperand(2).getReg();

  if (tryReassocBinOp(Opc, DstReg, LHSReg, RHSReg, MatchInfo))
    return true;
  if (tryReassocBinOp(Opc, DstReg, RHSReg, LHSReg, MatchInfo))
    return true;
  return false;
}

bool CombinerHelper::matchConstantFoldCastOp(MachineInstr &MI,
                                             APInt &MatchInfo) const {
  LLT DstTy = MRI.getType(MI.getOperand(0).getReg());
  Register SrcOp = MI.getOperand(1).getReg();

  if (auto MaybeCst = ConstantFoldCastOp(MI.getOpcode(), DstTy, SrcOp, MRI)) {
    MatchInfo = *MaybeCst;
    return true;
  }

  return false;
}

bool CombinerHelper::matchConstantFoldUnaryIntOp(MachineInstr &MI,
                                                 BuildFnTy &MatchInfo) const {
  Register Dst = MI.getOperand(0).getReg();
  auto Csts = ConstantFoldUnaryIntOp(MI.getOpcode(), MRI.getType(Dst),
                                     MI.getOperand(1).getReg(), MRI);
  if (Csts.empty())
    return false;

  MatchInfo = [Dst, Csts = std::move(Csts)](MachineIRBuilder &B) {
    if (Csts.size() == 1)
      B.buildConstant(Dst, Csts[0]);
    else
      B.buildBuildVectorConstant(Dst, Csts);
  };
  return true;
}

bool CombinerHelper::matchConstantFoldBinOp(MachineInstr &MI,
                                            APInt &MatchInfo) const {
  Register Op1 = MI.getOperand(1).getReg();
  Register Op2 = MI.getOperand(2).getReg();
  auto MaybeCst = ConstantFoldBinOp(MI.getOpcode(), Op1, Op2, MRI);
  if (!MaybeCst)
    return false;
  MatchInfo = *MaybeCst;
  return true;
}

bool CombinerHelper::matchConstantFoldFPBinOp(MachineInstr &MI,
                                              ConstantFP *&MatchInfo) const {
  Register Op1 = MI.getOperand(1).getReg();
  Register Op2 = MI.getOperand(2).getReg();
  auto MaybeCst = ConstantFoldFPBinOp(MI.getOpcode(), Op1, Op2, MRI);
  if (!MaybeCst)
    return false;
  MatchInfo =
      ConstantFP::get(MI.getMF()->getFunction().getContext(), *MaybeCst);
  return true;
}

bool CombinerHelper::matchConstantFoldFMA(MachineInstr &MI,
                                          ConstantFP *&MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_FMA ||
         MI.getOpcode() == TargetOpcode::G_FMAD);
  auto [_, Op1, Op2, Op3] = MI.getFirst4Regs();

  const ConstantFP *Op3Cst = getConstantFPVRegVal(Op3, MRI);
  if (!Op3Cst)
    return false;

  const ConstantFP *Op2Cst = getConstantFPVRegVal(Op2, MRI);
  if (!Op2Cst)
    return false;

  const ConstantFP *Op1Cst = getConstantFPVRegVal(Op1, MRI);
  if (!Op1Cst)
    return false;

  APFloat Op1F = Op1Cst->getValueAPF();
  Op1F.fusedMultiplyAdd(Op2Cst->getValueAPF(), Op3Cst->getValueAPF(),
                        APFloat::rmNearestTiesToEven);
  MatchInfo = ConstantFP::get(MI.getMF()->getFunction().getContext(), Op1F);
  return true;
}

bool CombinerHelper::matchNarrowBinopFeedingAnd(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  // Look for a binop feeding into an AND with a mask:
  //
  // %add = G_ADD %lhs, %rhs
  // %and = G_AND %add, 000...11111111
  //
  // Check if it's possible to perform the binop at a narrower width and zext
  // back to the original width like so:
  //
  // %narrow_lhs = G_TRUNC %lhs
  // %narrow_rhs = G_TRUNC %rhs
  // %narrow_add = G_ADD %narrow_lhs, %narrow_rhs
  // %new_add = G_ZEXT %narrow_add
  // %and = G_AND %new_add, 000...11111111
  //
  // This can allow later combines to eliminate the G_AND if it turns out
  // that the mask is irrelevant.
  assert(MI.getOpcode() == TargetOpcode::G_AND);
  Register Dst = MI.getOperand(0).getReg();
  Register AndLHS = MI.getOperand(1).getReg();
  Register AndRHS = MI.getOperand(2).getReg();
  LLT WideTy = MRI.getType(Dst);

  // If the potential binop has more than one use, then it's possible that one
  // of those uses will need its full width.
  if (!WideTy.isScalar() || !MRI.hasOneNonDBGUse(AndLHS))
    return false;

  // Check if the LHS feeding the AND is impacted by the high bits that we're
  // masking out.
  //
  // e.g. for 64-bit x, y:
  //
  // add_64(x, y) & 65535 == zext(add_16(trunc(x), trunc(y))) & 65535
  MachineInstr *LHSInst = getDefIgnoringCopies(AndLHS, MRI);
  if (!LHSInst)
    return false;
  unsigned LHSOpc = LHSInst->getOpcode();
  switch (LHSOpc) {
  default:
    return false;
  case TargetOpcode::G_ADD:
  case TargetOpcode::G_SUB:
  case TargetOpcode::G_MUL:
  case TargetOpcode::G_AND:
  case TargetOpcode::G_OR:
  case TargetOpcode::G_XOR:
    break;
  }

  // Find the mask on the RHS.
  auto Cst = getIConstantVRegValWithLookThrough(AndRHS, MRI);
  if (!Cst)
    return false;
  auto Mask = Cst->Value;
  if (!Mask.isMask())
    return false;

  // No point in combining if there's nothing to truncate.
  unsigned NarrowWidth = Mask.countr_one();
  if (NarrowWidth == WideTy.getSizeInBits())
    return false;
  LLT NarrowTy = LLT::integer(NarrowWidth);

  // Check if adding the zext + truncates could be harmful.
  auto &MF = *MI.getMF();
  const auto &TLI = getTargetLowering();
  LLVMContext &Ctx = MF.getFunction().getContext();
  if (!TLI.isTruncateFree(WideTy, NarrowTy, Ctx) ||
      !TLI.isZExtFree(NarrowTy, WideTy, Ctx))
    return false;
  if (!isLegalOrBeforeLegalizer({TargetOpcode::G_TRUNC, {NarrowTy, WideTy}}) ||
      !isLegalOrBeforeLegalizer({TargetOpcode::G_ZEXT, {WideTy, NarrowTy}}))
    return false;
  Register BinOpLHS = LHSInst->getOperand(1).getReg();
  Register BinOpRHS = LHSInst->getOperand(2).getReg();
  MatchInfo = [=, &MI](MachineIRBuilder &B) {
    auto NarrowLHS = Builder.buildTrunc(NarrowTy, BinOpLHS);
    auto NarrowRHS = Builder.buildTrunc(NarrowTy, BinOpRHS);
    auto NarrowBinOp =
        Builder.buildInstr(LHSOpc, {NarrowTy}, {NarrowLHS, NarrowRHS});
    auto Ext = Builder.buildZExt(WideTy, NarrowBinOp);
    Observer.changingInstr(MI);
    MI.getOperand(1).setReg(Ext.getReg(0));
    Observer.changedInstr(MI);
  };
  return true;
}

bool CombinerHelper::matchMulOBy2(MachineInstr &MI,
                                  BuildFnTy &MatchInfo) const {
  unsigned Opc = MI.getOpcode();
  assert(Opc == TargetOpcode::G_UMULO || Opc == TargetOpcode::G_SMULO);

  if (!mi_match(MI.getOperand(3).getReg(), MRI, m_SpecificICstOrSplat(2)))
    return false;

  MatchInfo = [=, &MI](MachineIRBuilder &B) {
    Observer.changingInstr(MI);
    unsigned NewOpc = Opc == TargetOpcode::G_UMULO ? TargetOpcode::G_UADDO
                                                   : TargetOpcode::G_SADDO;
    MI.setDesc(Builder.getTII().get(NewOpc));
    MI.getOperand(3).setReg(MI.getOperand(2).getReg());
    Observer.changedInstr(MI);
  };
  return true;
}

bool CombinerHelper::matchMulOBy0(MachineInstr &MI,
                                  BuildFnTy &MatchInfo) const {
  // (G_*MULO x, 0) -> 0 + no carry out
  assert(MI.getOpcode() == TargetOpcode::G_UMULO ||
         MI.getOpcode() == TargetOpcode::G_SMULO);
  if (!mi_match(MI.getOperand(3).getReg(), MRI, m_SpecificICstOrSplat(0)))
    return false;
  Register Dst = MI.getOperand(0).getReg();
  Register Carry = MI.getOperand(1).getReg();
  if (!isConstantLegalOrBeforeLegalizer(MRI.getType(Dst)) ||
      !isConstantLegalOrBeforeLegalizer(MRI.getType(Carry)))
    return false;
  MatchInfo = [=](MachineIRBuilder &B) {
    B.buildConstant(Dst, 0);
    B.buildConstant(Carry, 0);
  };
  return true;
}

bool CombinerHelper::matchAddEToAddO(MachineInstr &MI,
                                     BuildFnTy &MatchInfo) const {
  // (G_*ADDE x, y, 0) -> (G_*ADDO x, y)
  // (G_*SUBE x, y, 0) -> (G_*SUBO x, y)
  assert(MI.getOpcode() == TargetOpcode::G_UADDE ||
         MI.getOpcode() == TargetOpcode::G_SADDE ||
         MI.getOpcode() == TargetOpcode::G_USUBE ||
         MI.getOpcode() == TargetOpcode::G_SSUBE);
  if (!mi_match(MI.getOperand(4).getReg(), MRI, m_SpecificICstOrSplat(0)))
    return false;
  MatchInfo = [&](MachineIRBuilder &B) {
    unsigned NewOpcode;
    switch (MI.getOpcode()) {
    case TargetOpcode::G_UADDE:
      NewOpcode = TargetOpcode::G_UADDO;
      break;
    case TargetOpcode::G_SADDE:
      NewOpcode = TargetOpcode::G_SADDO;
      break;
    case TargetOpcode::G_USUBE:
      NewOpcode = TargetOpcode::G_USUBO;
      break;
    case TargetOpcode::G_SSUBE:
      NewOpcode = TargetOpcode::G_SSUBO;
      break;
    }
    Observer.changingInstr(MI);
    MI.setDesc(B.getTII().get(NewOpcode));
    MI.removeOperand(4);
    Observer.changedInstr(MI);
  };
  return true;
}

bool CombinerHelper::matchSubAddSameReg(MachineInstr &MI,
                                        BuildFnTy &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_SUB);
  Register Dst = MI.getOperand(0).getReg();
  // (x + y) - z -> x (if y == z)
  // (x + y) - z -> y (if x == z)
  Register X, Y, Z;
  if (mi_match(Dst, MRI, m_GSub(m_GAdd(m_Reg(X), m_Reg(Y)), m_Reg(Z)))) {
    Register ReplaceReg;
    int64_t CstX, CstY;
    if (Y == Z || (mi_match(Y, MRI, m_ICstOrSplat(CstY)) &&
                   mi_match(Z, MRI, m_SpecificICstOrSplat(CstY))))
      ReplaceReg = X;
    else if (X == Z || (mi_match(X, MRI, m_ICstOrSplat(CstX)) &&
                        mi_match(Z, MRI, m_SpecificICstOrSplat(CstX))))
      ReplaceReg = Y;
    if (ReplaceReg) {
      MatchInfo = [=](MachineIRBuilder &B) { B.buildCopy(Dst, ReplaceReg); };
      return true;
    }
  }

  // x - (y + z) -> 0 - y (if x == z)
  // x - (y + z) -> 0 - z (if x == y)
  if (mi_match(Dst, MRI, m_GSub(m_Reg(X), m_GAdd(m_Reg(Y), m_Reg(Z))))) {
    Register ReplaceReg;
    int64_t CstX;
    if (X == Z || (mi_match(X, MRI, m_ICstOrSplat(CstX)) &&
                   mi_match(Z, MRI, m_SpecificICstOrSplat(CstX))))
      ReplaceReg = Y;
    else if (X == Y || (mi_match(X, MRI, m_ICstOrSplat(CstX)) &&
                        mi_match(Y, MRI, m_SpecificICstOrSplat(CstX))))
      ReplaceReg = Z;
    if (ReplaceReg) {
      MatchInfo = [=](MachineIRBuilder &B) {
        auto Zero = B.buildConstant(MRI.getType(Dst), 0);
        B.buildSub(Dst, Zero, ReplaceReg);
      };
      return true;
    }
  }
  return false;
}

MachineInstr *CombinerHelper::buildUDivOrURemUsingMul(MachineInstr &MI) const {
  unsigned Opcode = MI.getOpcode();
  assert(Opcode == TargetOpcode::G_UDIV || Opcode == TargetOpcode::G_UREM);
  auto &UDivorRem = cast<GenericMachineInstr>(MI);
  Register Dst = UDivorRem.getReg(0);
  Register LHS = UDivorRem.getReg(1);
  Register RHS = UDivorRem.getReg(2);
  LLT Ty = MRI.getType(Dst);
  LLT ScalarTy = Ty.getScalarType();
  const unsigned EltBits = ScalarTy.getScalarSizeInBits();
  LLT ShiftAmtTy = getTargetLowering().getPreferredShiftAmountTy(Ty);
  LLT ScalarShiftAmtTy = ShiftAmtTy.getScalarType();

  auto &MIB = Builder;

  bool UseSRL = false;
  SmallVector<Register, 16> Shifts, Factors;
  auto *RHSDefInstr = cast<GenericMachineInstr>(getDefIgnoringCopies(RHS, MRI));
  bool IsSplat = getIConstantSplatVal(*RHSDefInstr, MRI).has_value();

  auto BuildExactUDIVPattern = [&](const Constant *C) {
    // Don't recompute inverses for each splat element.
    if (IsSplat && !Factors.empty()) {
      Shifts.push_back(Shifts[0]);
      Factors.push_back(Factors[0]);
      return true;
    }

    auto *CI = cast<ConstantInt>(C);
    APInt Divisor = CI->getValue();
    unsigned Shift = Divisor.countr_zero();
    if (Shift) {
      Divisor.lshrInPlace(Shift);
      UseSRL = true;
    }

    // Calculate the multiplicative inverse modulo BW.
    APInt Factor = Divisor.multiplicativeInverse();
    Shifts.push_back(MIB.buildConstant(ScalarShiftAmtTy, Shift).getReg(0));
    Factors.push_back(MIB.buildConstant(ScalarTy, Factor).getReg(0));
    return true;
  };

  if (MI.getFlag(MachineInstr::MIFlag::IsExact)) {
    // Collect all magic values from the build vector.
    if (!matchUnaryPredicate(MRI, RHS, BuildExactUDIVPattern))
      llvm_unreachable("Expected unary predicate match to succeed");

    Register Shift, Factor;
    if (Ty.isVector()) {
      Shift = MIB.buildBuildVector(ShiftAmtTy, Shifts).getReg(0);
      Factor = MIB.buildBuildVector(Ty, Factors).getReg(0);
    } else {
      Shift = Shifts[0];
      Factor = Factors[0];
    }

    Register Res = LHS;

    if (UseSRL)
      Res = MIB.buildLShr(Ty, Res, Shift, MachineInstr::IsExact).getReg(0);

    return MIB.buildMul(Ty, Res, Factor);
  }

  unsigned KnownLeadingZeros =
      VT ? VT->getKnownBits(LHS).countMinLeadingZeros() : 0;

  bool UseNPQ = false;
  SmallVector<Register, 16> PreShifts, PostShifts, MagicFactors, NPQFactors;
  auto BuildUDIVPattern = [&](const Constant *C) {
    auto *CI = cast<ConstantInt>(C);
    const APInt &Divisor = CI->getValue();

    bool SelNPQ = false;
    APInt Magic(Divisor.getBitWidth(), 0);
    unsigned PreShift = 0, PostShift = 0;

    // Magic algorithm doesn't work for division by 1. We need to emit a select
    // at the end.
    // TODO: Use undef values for divisor of 1.
    if (!Divisor.isOne()) {

      // UnsignedDivisionByConstantInfo doesn't work correctly if leading zeros
      // in the dividend exceeds the leading zeros for the divisor.
      UnsignedDivisionByConstantInfo magics =
          UnsignedDivisionByConstantInfo::get(
              Divisor, std::min(KnownLeadingZeros, Divisor.countl_zero()));

      Magic = std::move(magics.Magic);

      assert(magics.PreShift < Divisor.getBitWidth() &&
             "We shouldn't generate an undefined shift!");
      assert(magics.PostShift < Divisor.getBitWidth() &&
             "We shouldn't generate an undefined shift!");
      assert((!magics.IsAdd || magics.PreShift == 0) && "Unexpected pre-shift");
      PreShift = magics.PreShift;
      PostShift = magics.PostShift;
      SelNPQ = magics.IsAdd;
    }

    PreShifts.push_back(
        MIB.buildConstant(ScalarShiftAmtTy, PreShift).getReg(0));
    MagicFactors.push_back(MIB.buildConstant(ScalarTy, Magic).getReg(0));
    NPQFactors.push_back(
        MIB.buildConstant(ScalarTy,
                          SelNPQ ? APInt::getOneBitSet(EltBits, EltBits - 1)
                                 : APInt::getZero(EltBits))
            .getReg(0));
    PostShifts.push_back(
        MIB.buildConstant(ScalarShiftAmtTy, PostShift).getReg(0));
    UseNPQ |= SelNPQ;
    return true;
  };

  // Collect the shifts/magic values from each element.
  bool Matched = matchUnaryPredicate(MRI, RHS, BuildUDIVPattern);
  (void)Matched;
  assert(Matched && "Expected unary predicate match to succeed");

  Register PreShift, PostShift, MagicFactor, NPQFactor;
  auto *RHSDef = getOpcodeDef<GBuildVector>(RHS, MRI);
  if (RHSDef) {
    PreShift = MIB.buildBuildVector(ShiftAmtTy, PreShifts).getReg(0);
    MagicFactor = MIB.buildBuildVector(Ty, MagicFactors).getReg(0);
    NPQFactor = MIB.buildBuildVector(Ty, NPQFactors).getReg(0);
    PostShift = MIB.buildBuildVector(ShiftAmtTy, PostShifts).getReg(0);
  } else {
    assert(MRI.getType(RHS).isScalar() &&
           "Non-build_vector operation should have been a scalar");
    PreShift = PreShifts[0];
    MagicFactor = MagicFactors[0];
    PostShift = PostShifts[0];
  }

  Register Q = LHS;
  Q = MIB.buildLShr(Ty, Q, PreShift).getReg(0);

  // Multiply the numerator (operand 0) by the magic value.
  Q = MIB.buildUMulH(Ty, Q, MagicFactor).getReg(0);

  if (UseNPQ) {
    Register NPQ = MIB.buildSub(Ty, LHS, Q).getReg(0);

    // For vectors we might have a mix of non-NPQ/NPQ paths, so use
    // G_UMULH to act as a SRL-by-1 for NPQ, else multiply by zero.
    if (Ty.isVector())
      NPQ = MIB.buildUMulH(Ty, NPQ, NPQFactor).getReg(0);
    else
      NPQ = MIB.buildLShr(Ty, NPQ, MIB.buildConstant(ShiftAmtTy, 1)).getReg(0);

    Q = MIB.buildAdd(Ty, NPQ, Q).getReg(0);
  }

  Q = MIB.buildLShr(Ty, Q, PostShift).getReg(0);
  auto One = MIB.buildConstant(Ty, 1);
  auto IsOne = MIB.buildICmp(
      CmpInst::Predicate::ICMP_EQ,
      Ty.isScalar() ? LLT::integer(1) : Ty.changeElementType(LLT::integer(1)),
      RHS, One);
  auto ret = MIB.buildSelect(Ty, IsOne, LHS, Q);

  if (Opcode == TargetOpcode::G_UREM) {
    auto Prod = MIB.buildMul(Ty, ret, RHS);
    return MIB.buildSub(Ty, LHS, Prod);
  }
  return ret;
}

bool CombinerHelper::matchUDivOrURemByConst(MachineInstr &MI) const {
  unsigned Opcode = MI.getOpcode();
  assert(Opcode == TargetOpcode::G_UDIV || Opcode == TargetOpcode::G_UREM);
  Register Dst = MI.getOperand(0).getReg();
  Register RHS = MI.getOperand(2).getReg();
  LLT DstTy = MRI.getType(Dst);

  auto &MF = *MI.getMF();
  AttributeList Attr = MF.getFunction().getAttributes();
  const auto &TLI = getTargetLowering();
  LLVMContext &Ctx = MF.getFunction().getContext();
  if (DstTy.getScalarSizeInBits() == 1 ||
      TLI.isIntDivCheap(getApproximateEVTForLLT(DstTy, Ctx), Attr))
    return false;

  // Don't do this for minsize because the instruction sequence is usually
  // larger.
  if (MF.getFunction().hasMinSize())
    return false;

  if (Opcode == TargetOpcode::G_UDIV &&
      MI.getFlag(MachineInstr::MIFlag::IsExact)) {
    return matchUnaryPredicate(
        MRI, RHS, [](const Constant *C) { return C && !C->isNullValue(); });
  }

  MachineInstr *RHSDef;
  if (!mi_match(RHS, MRI, m_MInstr(RHSDef)) ||
      !isConstantOrConstantVector(*RHSDef, MRI))
    return false;

  // Don't do this if the types are not going to be legal.
  if (LI) {
    if (!isLegalOrBeforeLegalizer({TargetOpcode::G_MUL, {DstTy, DstTy}}))
      return false;
    if (!isLegalOrBeforeLegalizer({TargetOpcode::G_UMULH, {DstTy}}))
      return false;
    if (!isLegalOrBeforeLegalizer(
            {TargetOpcode::G_ICMP,
             {DstTy.isVector() ? DstTy.changeElementSize(1) : LLT::scalar(1),
              DstTy}}))
      return false;
    if (Opcode == TargetOpcode::G_UREM &&
        !isLegalOrBeforeLegalizer({TargetOpcode::G_SUB, {DstTy, DstTy}}))
      return false;
  }

  return matchUnaryPredicate(
      MRI, RHS, [](const Constant *C) { return C && !C->isNullValue(); });
}

void CombinerHelper::applyUDivOrURemByConst(MachineInstr &MI) const {
  auto *NewMI = buildUDivOrURemUsingMul(MI);
  replaceSingleDefInstWithReg(MI, NewMI->getOperand(0).getReg());
}

bool CombinerHelper::matchSDivOrSRemByConst(MachineInstr &MI) const {
  unsigned Opcode = MI.getOpcode();
  assert(Opcode == TargetOpcode::G_SDIV || Opcode == TargetOpcode::G_SREM);
  Register Dst = MI.getOperand(0).getReg();
  Register RHS = MI.getOperand(2).getReg();
  LLT DstTy = MRI.getType(Dst);
  auto SizeInBits = DstTy.getScalarSizeInBits();
  LLT WideTy = DstTy.changeElementSize(SizeInBits * 2);

  auto &MF = *MI.getMF();
  AttributeList Attr = MF.getFunction().getAttributes();
  const auto &TLI = getTargetLowering();
  LLVMContext &Ctx = MF.getFunction().getContext();
  if (DstTy.getScalarSizeInBits() < 3 ||
      TLI.isIntDivCheap(getApproximateEVTForLLT(DstTy, Ctx), Attr))
    return false;

  // Don't do this for minsize because the instruction sequence is usually
  // larger.
  if (MF.getFunction().hasMinSize())
    return false;

  // If the sdiv has an 'exact' flag we can use a simpler lowering.
  if (Opcode == TargetOpcode::G_SDIV &&
      MI.getFlag(MachineInstr::MIFlag::IsExact)) {
    return matchUnaryPredicate(
        MRI, RHS, [](const Constant *C) { return C && !C->isNullValue(); });
  }

  MachineInstr *RHSDef;
  if (!mi_match(RHS, MRI, m_MInstr(RHSDef)) ||
      !isConstantOrConstantVector(*RHSDef, MRI))
    return false;

  // Don't do this if the types are not going to be legal.
  if (LI) {
    if (!isLegalOrBeforeLegalizer({TargetOpcode::G_MUL, {DstTy, DstTy}}))
      return false;
    if (!isLegal({TargetOpcode::G_SMULH, {DstTy}}) &&
        !isLegalOrHasWidenScalar({TargetOpcode::G_MUL, {WideTy, WideTy}}))
      return false;
    if (Opcode == TargetOpcode::G_SREM &&
        !isLegalOrBeforeLegalizer({TargetOpcode::G_SUB, {DstTy, DstTy}}))
      return false;
  }

  return matchUnaryPredicate(
      MRI, RHS, [](const Constant *C) { return C && !C->isNullValue(); });
}

void CombinerHelper::applySDivOrSRemByConst(MachineInstr &MI) const {
  auto *NewMI = buildSDivOrSRemUsingMul(MI);
  replaceSingleDefInstWithReg(MI, NewMI->getOperand(0).getReg());
}

MachineInstr *CombinerHelper::buildSDivOrSRemUsingMul(MachineInstr &MI) const {
  unsigned Opcode = MI.getOpcode();
  assert(MI.getOpcode() == TargetOpcode::G_SDIV ||
         Opcode == TargetOpcode::G_SREM);
  auto &SDivorRem = cast<GenericMachineInstr>(MI);
  Register Dst = SDivorRem.getReg(0);
  Register LHS = SDivorRem.getReg(1);
  Register RHS = SDivorRem.getReg(2);
  LLT Ty = MRI.getType(Dst);
  LLT ScalarTy = Ty.getScalarType();
  const unsigned EltBits = ScalarTy.getScalarSizeInBits();
  LLT ShiftAmtTy = getTargetLowering().getPreferredShiftAmountTy(Ty);
  LLT ScalarShiftAmtTy = ShiftAmtTy.getScalarType();
  auto &MIB = Builder;

  bool UseSRA = false;
  SmallVector<Register, 16> ExactShifts, ExactFactors;

  auto *RHSDefInstr = cast<GenericMachineInstr>(getDefIgnoringCopies(RHS, MRI));
  bool IsSplat = getIConstantSplatVal(*RHSDefInstr, MRI).has_value();

  auto BuildExactSDIVPattern = [&](const Constant *C) {
    // Don't recompute inverses for each splat element.
    if (IsSplat && !ExactFactors.empty()) {
      ExactShifts.push_back(ExactShifts[0]);
      ExactFactors.push_back(ExactFactors[0]);
      return true;
    }

    auto *CI = cast<ConstantInt>(C);
    APInt Divisor = CI->getValue();
    unsigned Shift = Divisor.countr_zero();
    if (Shift) {
      Divisor.ashrInPlace(Shift);
      UseSRA = true;
    }

    // Calculate the multiplicative inverse modulo BW.
    // 2^W requires W + 1 bits, so we have to extend and then truncate.
    APInt Factor = Divisor.multiplicativeInverse();
    ExactShifts.push_back(MIB.buildConstant(ScalarShiftAmtTy, Shift).getReg(0));
    ExactFactors.push_back(MIB.buildConstant(ScalarTy, Factor).getReg(0));
    return true;
  };

  if (MI.getFlag(MachineInstr::MIFlag::IsExact)) {
    // Collect all magic values from the build vector.
    bool Matched = matchUnaryPredicate(MRI, RHS, BuildExactSDIVPattern);
    (void)Matched;
    assert(Matched && "Expected unary predicate match to succeed");

    Register Shift, Factor;
    if (Ty.isVector()) {
      Shift = MIB.buildBuildVector(ShiftAmtTy, ExactShifts).getReg(0);
      Factor = MIB.buildBuildVector(Ty, ExactFactors).getReg(0);
    } else {
      Shift = ExactShifts[0];
      Factor = ExactFactors[0];
    }

    Register Res = LHS;

    if (UseSRA)
      Res = MIB.buildAShr(Ty, Res, Shift, MachineInstr::IsExact).getReg(0);

    return MIB.buildMul(Ty, Res, Factor);
  }

  SmallVector<Register, 16> MagicFactors, Factors, Shifts, ShiftMasks;

  auto BuildSDIVPattern = [&](const Constant *C) {
    auto *CI = cast<ConstantInt>(C);
    const APInt &Divisor = CI->getValue();

    SignedDivisionByConstantInfo Magics =
        SignedDivisionByConstantInfo::get(Divisor);
    int NumeratorFactor = 0;
    int ShiftMask = -1;

    if (Divisor.isOne() || Divisor.isAllOnes()) {
      // If d is +1/-1, we just multiply the numerator by +1/-1.
      NumeratorFactor = Divisor.getSExtValue();
      Magics.Magic = 0;
      Magics.ShiftAmount = 0;
      ShiftMask = 0;
    } else if (Divisor.isStrictlyPositive() && Magics.Magic.isNegative()) {
      // If d > 0 and m < 0, add the numerator.
      NumeratorFactor = 1;
    } else if (Divisor.isNegative() && Magics.Magic.isStrictlyPositive()) {
      // If d < 0 and m > 0, subtract the numerator.
      NumeratorFactor = -1;
    }

    MagicFactors.push_back(MIB.buildConstant(ScalarTy, Magics.Magic).getReg(0));
    Factors.push_back(MIB.buildConstant(ScalarTy, NumeratorFactor).getReg(0));
    Shifts.push_back(
        MIB.buildConstant(ScalarShiftAmtTy, Magics.ShiftAmount).getReg(0));
    ShiftMasks.push_back(MIB.buildConstant(ScalarTy, ShiftMask).getReg(0));

    return true;
  };

  // Collect the shifts/magic values from each element.
  bool Matched = matchUnaryPredicate(MRI, RHS, BuildSDIVPattern);
  (void)Matched;
  assert(Matched && "Expected unary predicate match to succeed");

  Register MagicFactor, Factor, Shift, ShiftMask;
  auto *RHSDef = getOpcodeDef<GBuildVector>(RHS, MRI);
  if (RHSDef) {
    MagicFactor = MIB.buildBuildVector(Ty, MagicFactors).getReg(0);
    Factor = MIB.buildBuildVector(Ty, Factors).getReg(0);
    Shift = MIB.buildBuildVector(ShiftAmtTy, Shifts).getReg(0);
    ShiftMask = MIB.buildBuildVector(Ty, ShiftMasks).getReg(0);
  } else {
    assert(MRI.getType(RHS).isScalar() &&
           "Non-build_vector operation should have been a scalar");
    MagicFactor = MagicFactors[0];
    Factor = Factors[0];
    Shift = Shifts[0];
    ShiftMask = ShiftMasks[0];
  }

  Register Q = LHS;
  Q = MIB.buildSMulH(Ty, LHS, MagicFactor).getReg(0);

  // (Optionally) Add/subtract the numerator using Factor.
  Factor = MIB.buildMul(Ty, LHS, Factor).getReg(0);
  Q = MIB.buildAdd(Ty, Q, Factor).getReg(0);

  // Shift right algebraic by shift value.
  Q = MIB.buildAShr(Ty, Q, Shift).getReg(0);

  // Extract the sign bit, mask it and add it to the quotient.
  auto SignShift = MIB.buildConstant(ShiftAmtTy, EltBits - 1);
  auto T = MIB.buildLShr(Ty, Q, SignShift);
  T = MIB.buildAnd(Ty, T, ShiftMask);
  auto ret = MIB.buildAdd(Ty, Q, T);

  if (Opcode == TargetOpcode::G_SREM) {
    auto Prod = MIB.buildMul(Ty, ret, RHS);
    return MIB.buildSub(Ty, LHS, Prod);
  }
  return ret;
}

bool CombinerHelper::matchDivByPow2(MachineInstr &MI, bool IsSigned) const {
  assert((MI.getOpcode() == TargetOpcode::G_SDIV ||
          MI.getOpcode() == TargetOpcode::G_UDIV) &&
         "Expected SDIV or UDIV");
  auto &Div = cast<GenericMachineInstr>(MI);
  Register RHS = Div.getReg(2);
  auto MatchPow2 = [&](const Constant *C) {
    auto *CI = dyn_cast<ConstantInt>(C);
    return CI && (CI->getValue().isPowerOf2() ||
                  (IsSigned && CI->getValue().isNegatedPowerOf2()));
  };
  return matchUnaryPredicate(MRI, RHS, MatchPow2, /*AllowUndefs=*/false);
}

void CombinerHelper::applySDivByPow2(MachineInstr &MI) const {
  assert(MI.getOpcode() == TargetOpcode::G_SDIV && "Expected SDIV");
  auto &SDiv = cast<GenericMachineInstr>(MI);
  Register Dst = SDiv.getReg(0);
  Register LHS = SDiv.getReg(1);
  Register RHS = SDiv.getReg(2);
  LLT Ty = MRI.getType(Dst);
  LLT ShiftAmtTy = getTargetLowering().getPreferredShiftAmountTy(Ty);
  LLT CCVT = Ty.isVector() ? LLT::vector(Ty.getElementCount(), LLT::integer(1))
                           : LLT::integer(1);

  // Effectively we want to lower G_SDIV %lhs, %rhs, where %rhs is a power of 2,
  // to the following version:
  //
  // %c1 = G_CTTZ %rhs
  // %inexact = G_SUB $bitwidth, %c1
  // %sign = %G_ASHR %lhs, $(bitwidth - 1)
  // %lshr = G_LSHR %sign, %inexact
  // %add = G_ADD %lhs, %lshr
  // %ashr = G_ASHR %add, %c1
  // %ashr = G_SELECT, %isoneorallones, %lhs, %ashr
  // %zero = G_CONSTANT $0
  // %neg = G_NEG %ashr
  // %isneg = G_ICMP SLT %rhs, %zero
  // %res = G_SELECT %isneg, %neg, %ashr

  unsigned BitWidth = Ty.getScalarSizeInBits();
  auto Zero = Builder.buildConstant(Ty, 0);

  auto Bits = Builder.buildConstant(ShiftAmtTy, BitWidth);
  auto C1 = Builder.buildCTTZ(ShiftAmtTy, RHS);
  auto Inexact = Builder.buildSub(ShiftAmtTy, Bits, C1);
  // Splat the sign bit into the register
  auto Sign = Builder.buildAShr(
      Ty, LHS, Builder.buildConstant(ShiftAmtTy, BitWidth - 1));

  // Add (LHS < 0) ? abs2 - 1 : 0;
  auto LSrl = Builder.buildLShr(Ty, Sign, Inexact);
  auto Add = Builder.buildAdd(Ty, LHS, LSrl);
  auto AShr = Builder.buildAShr(Ty, Add, C1);

  // Special case: (sdiv X, 1) -> X
  // Special Case: (sdiv X, -1) -> 0-X
  auto One = Builder.buildConstant(Ty, 1);
  auto MinusOne = Builder.buildConstant(Ty, -1);
  auto IsOne = Builder.buildICmp(CmpInst::Predicate::ICMP_EQ, CCVT, RHS, One);
  auto IsMinusOne =
      Builder.buildICmp(CmpInst::Predicate::ICMP_EQ, CCVT, RHS, MinusOne);
  auto IsOneOrMinusOne = Builder.buildOr(CCVT, IsOne, IsMinusOne);
  AShr = Builder.buildSelect(Ty, IsOneOrMinusOne, LHS, AShr);

  // If divided by a positive value, we're done. Otherwise, the result must be
  // negated.
  auto Neg = Builder.buildNeg(Ty, AShr);
  auto IsNeg = Builder.buildICmp(CmpInst::Predicate::ICMP_SLT, CCVT, RHS, Zero);
  Builder.buildSelect(MI.getOperand(0).getReg(), IsNeg, Neg, AShr);
  MI.eraseFromParent();
}

void CombinerHelper::applyUDivByPow2(MachineInstr &MI) const {
  assert(MI.getOpcode() == TargetOpcode::G_UDIV && "Expected UDIV");
  auto &UDiv = cast<GenericMachineInstr>(MI);
  Register Dst = UDiv.getReg(0);
  Register LHS = UDiv.getReg(1);
  Register RHS = UDiv.getReg(2);
  LLT Ty = MRI.getType(Dst);
  LLT ShiftAmtTy = getTargetLowering().getPreferredShiftAmountTy(Ty);

  auto C1 = Builder.buildCTTZ(ShiftAmtTy, RHS);
  Builder.buildLShr(MI.getOperand(0).getReg(), LHS, C1);
  MI.eraseFromParent();
}

void CombinerHelper::applySimplifySRemByPow2(MachineInstr &MI) const {
  assert(MI.getOpcode() == TargetOpcode::G_SREM && "Expected SREM");
  auto &SRem = cast<GBinOp>(MI);
  Register Dst = SRem.getReg(0);
  Register LHS = SRem.getLHSReg();
  Register RHS = SRem.getRHSReg();
  LLT Ty = MRI.getType(Dst);
  LLT ShiftAmtTy = getTargetLowering().getPreferredShiftAmountTy(Ty);

  // Effectively we want to lower G_SREM %lhs, %rhs, where %rhs is +/- a power
  // of 2, to the following branch-free bias-and-mask version:
  //
  // %abs = G_ABS %rhs
  // %mask = G_SUB %abs, 1
  // %sign = G_ASHR %lhs, $(bitwidth - 1)
  // %bias = G_AND %sign, %mask
  // %biased = G_ADD %lhs, %bias
  // %masked = G_AND %biased, %mask
  // %res = G_SUB %masked, %bias
  //
  // The bias adds (|%rhs| - 1) for negative %lhs, correcting rounding towards
  // zero (instead of towards -inf that a plain mask would give). Constant
  // divisors collapse %mask to a single G_CONSTANT via the CSEMIRBuilder folds
  // for G_ABS and G_SUB.

  unsigned BitWidth = Ty.getScalarSizeInBits();
  auto AbsRHS = Builder.buildAbs(Ty, RHS);
  auto Mask = Builder.buildSub(Ty, AbsRHS, Builder.buildConstant(Ty, 1));
  auto BWMinusOne = Builder.buildConstant(ShiftAmtTy, BitWidth - 1);
  auto Sign = Builder.buildAShr(Ty, LHS, BWMinusOne);
  auto Bias = Builder.buildAnd(Ty, Sign, Mask);
  auto Biased = Builder.buildAdd(Ty, LHS, Bias);
  auto Masked = Builder.buildAnd(Ty, Biased, Mask);
  Builder.buildSub(Dst, Masked, Bias);
  MI.eraseFromParent();
}

bool CombinerHelper::matchUMulHToLShr(MachineInstr &MI) const {
  assert(MI.getOpcode() == TargetOpcode::G_UMULH);
  Register RHS = MI.getOperand(2).getReg();
  Register Dst = MI.getOperand(0).getReg();
  LLT Ty = MRI.getType(Dst);
  LLT RHSTy = MRI.getType(RHS);
  LLT ShiftAmtTy = getTargetLowering().getPreferredShiftAmountTy(Ty);
  auto MatchPow2ExceptOne = [&](const Constant *C) {
    if (auto *CI = dyn_cast<ConstantInt>(C))
      return CI->getValue().isPowerOf2() && !CI->getValue().isOne();
    return false;
  };
  if (!matchUnaryPredicate(MRI, RHS, MatchPow2ExceptOne, false))
    return false;
  // We need to check both G_LSHR and G_CTLZ because the combine uses G_CTLZ to
  // get log base 2, and it is not always legal for on a target.
  return isLegalOrBeforeLegalizer({TargetOpcode::G_LSHR, {Ty, ShiftAmtTy}}) &&
         isLegalOrBeforeLegalizer({TargetOpcode::G_CTLZ, {RHSTy, RHSTy}});
}

void CombinerHelper::applyUMulHToLShr(MachineInstr &MI) const {
  Register LHS = MI.getOperand(1).getReg();
  Register RHS = MI.getOperand(2).getReg();
  Register Dst = MI.getOperand(0).getReg();
  LLT Ty = MRI.getType(Dst);
  LLT ShiftAmtTy = getTargetLowering().getPreferredShiftAmountTy(Ty);
  unsigned NumEltBits = Ty.getScalarSizeInBits();

  auto LogBase2 = buildLogBase2(RHS, Builder);
  auto ShiftAmt =
      Builder.buildSub(Ty, Builder.buildConstant(Ty, NumEltBits), LogBase2);
  auto Trunc = Builder.buildZExtOrTrunc(ShiftAmtTy, ShiftAmt);
  Builder.buildLShr(Dst, LHS, Trunc);
  MI.eraseFromParent();
}

bool CombinerHelper::matchTruncSSatS(MachineInstr &MI,
                                     Register &MatchInfo) const {
  Register Dst = MI.getOperand(0).getReg();
  Register Src = MI.getOperand(1).getReg();
  LLT DstTy = MRI.getType(Dst);
  LLT SrcTy = MRI.getType(Src);
  unsigned NumDstBits = DstTy.getScalarSizeInBits();
  unsigned NumSrcBits = SrcTy.getScalarSizeInBits();
  assert(NumSrcBits > NumDstBits && "Unexpected types for truncate operation");

  if (!LI || !isLegalOrHasFewerElements(
                 {TargetOpcode::G_TRUNC_SSAT_S, {DstTy, SrcTy}}))
    return false;

  APInt SignedMax = APInt::getSignedMaxValue(NumDstBits).sext(NumSrcBits);
  APInt SignedMin = APInt::getSignedMinValue(NumDstBits).sext(NumSrcBits);
  if (mi_match(
          Src, MRI,
          m_GSMin(m_GSMax(m_Reg(MatchInfo), m_SpecificICstOrSplat(SignedMin)),
                  m_SpecificICstOrSplat(SignedMax))))
    return true;
  if (mi_match(
          Src, MRI,
          m_GSMax(m_GSMin(m_Reg(MatchInfo), m_SpecificICstOrSplat(SignedMax)),
                  m_SpecificICstOrSplat(SignedMin))))
    return true;

  // CVP in the midend will often transform trunc(smin(smax(..)) into
  // trunc nsw(smin(..)) as the smax against INT_MIN never saturates.
  if (MI.getFlag(MachineInstr::MIFlag::NoSWrap) &&
      mi_match(Src, MRI,
               m_GSMin(m_Reg(MatchInfo), m_SpecificICstOrSplat(SignedMax))))
    return true;

  return false;
}

void CombinerHelper::applyTruncSSatS(MachineInstr &MI,
                                     Register &MatchInfo) const {
  Register Dst = MI.getOperand(0).getReg();
  Builder.buildTruncSSatS(Dst, MatchInfo);
  MI.eraseFromParent();
}

bool CombinerHelper::matchTruncSSatU(MachineInstr &MI,
                                     Register &MatchInfo) const {
  Register Dst = MI.getOperand(0).getReg();
  Register Src = MI.getOperand(1).getReg();
  LLT DstTy = MRI.getType(Dst);
  LLT SrcTy = MRI.getType(Src);
  unsigned NumDstBits = DstTy.getScalarSizeInBits();
  unsigned NumSrcBits = SrcTy.getScalarSizeInBits();
  assert(NumSrcBits > NumDstBits && "Unexpected types for truncate operation");

  if (!LI || !isLegalOrHasFewerElements(
                 {TargetOpcode::G_TRUNC_SSAT_U, {DstTy, SrcTy}}))
    return false;
  APInt UnsignedMax = APInt::getMaxValue(NumDstBits).zext(NumSrcBits);
  return mi_match(Src, MRI,
                  m_GSMin(m_GSMax(m_Reg(MatchInfo), m_SpecificICstOrSplat(0)),
                          m_SpecificICstOrSplat(UnsignedMax))) ||
         mi_match(Src, MRI,
                  m_GSMax(m_GSMin(m_Reg(MatchInfo),
                                  m_SpecificICstOrSplat(UnsignedMax)),
                          m_SpecificICstOrSplat(0))) ||
         mi_match(Src, MRI,
                  m_GUMin(m_GSMax(m_Reg(MatchInfo), m_SpecificICstOrSplat(0)),
                          m_SpecificICstOrSplat(UnsignedMax)));
}

void CombinerHelper::applyTruncSSatU(MachineInstr &MI,
                                     Register &MatchInfo) const {
  Register Dst = MI.getOperand(0).getReg();
  Builder.buildTruncSSatU(Dst, MatchInfo);
  MI.eraseFromParent();
}

bool CombinerHelper::matchTruncUSatU(MachineInstr &MI,
                                     MachineInstr &MinMI) const {
  Register Min = MinMI.getOperand(2).getReg();
  Register Val = MinMI.getOperand(1).getReg();
  LLT DstTy = MRI.getType(MI.getOperand(0).getReg());
  LLT SrcTy = MRI.getType(Val);
  unsigned NumDstBits = DstTy.getScalarSizeInBits();
  unsigned NumSrcBits = SrcTy.getScalarSizeInBits();
  assert(NumSrcBits > NumDstBits && "Unexpected types for truncate operation");

  if (!LI || !isLegalOrHasFewerElements(
                 {TargetOpcode::G_TRUNC_SSAT_U, {DstTy, SrcTy}}))
    return false;
  APInt UnsignedMax = APInt::getMaxValue(NumDstBits).zext(NumSrcBits);
  return mi_match(Min, MRI, m_SpecificICstOrSplat(UnsignedMax)) &&
         !mi_match(Val, MRI, m_GSMax(m_Reg(), m_Reg()));
}

bool CombinerHelper::matchTruncUSatUToFPTOUISat(MachineInstr &MI,
                                                MachineInstr &SrcMI) const {
  LLT DstTy = MRI.getType(MI.getOperand(0).getReg());
  LLT SrcTy = MRI.getType(SrcMI.getOperand(1).getReg());

  return LI &&
         isLegalOrBeforeLegalizer({TargetOpcode::G_FPTOUI_SAT, {DstTy, SrcTy}});
}

bool CombinerHelper::matchRedundantNegOperands(MachineInstr &MI,
                                               BuildFnTy &MatchInfo) const {
  unsigned Opc = MI.getOpcode();
  assert(Opc == TargetOpcode::G_FADD || Opc == TargetOpcode::G_FSUB);

  Register Dst = MI.getOperand(0).getReg();
  Register X = MI.getOperand(1).getReg();
  Register Y = MI.getOperand(2).getReg();
  LLT Type = MRI.getType(Dst);

  // fold (fadd x, fneg(y)) -> (fsub x, y)
  // fold (fadd fneg(y), x) -> (fsub x, y)
  // G_ADD is commutative so both cases are checked by m_GFAdd
  if (mi_match(Dst, MRI, m_GFAdd(m_Reg(X), m_GFNeg(m_Reg(Y)))) &&
      isLegalOrBeforeLegalizer({TargetOpcode::G_FSUB, {Type}})) {
    Opc = TargetOpcode::G_FSUB;
  }
  /// fold (fsub x, fneg(y)) -> (fadd x, y)
  else if (mi_match(Dst, MRI, m_GFSub(m_Reg(X), m_GFNeg(m_Reg(Y)))) &&
           isLegalOrBeforeLegalizer({TargetOpcode::G_FADD, {Type}})) {
    Opc = TargetOpcode::G_FADD;
  } else
    return false;

  MatchInfo = [=, &MI](MachineIRBuilder &B) {
    Observer.changingInstr(MI);
    MI.setDesc(B.getTII().get(Opc));
    MI.getOperand(1).setReg(X);
    MI.getOperand(2).setReg(Y);
    Observer.changedInstr(MI);
  };
  return true;
}

bool CombinerHelper::matchFsubToFneg(MachineInstr &MI,
                                     Register &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_FSUB);

  Register LHS = MI.getOperand(1).getReg();
  MatchInfo = MI.getOperand(2).getReg();
  LLT Ty = MRI.getType(MI.getOperand(0).getReg());

  const auto LHSCst = Ty.isVector()
                          ? getFConstantSplat(LHS, MRI, /* allowUndef */ true)
                          : getFConstantVRegValWithLookThrough(LHS, MRI);
  if (!LHSCst)
    return false;

  // -0.0 is always allowed
  if (LHSCst->Value.isNegZero())
    return true;

  // +0.0 is only allowed if nsz is set.
  if (LHSCst->Value.isPosZero())
    return MI.getFlag(MachineInstr::FmNsz);

  return false;
}

void CombinerHelper::applyFsubToFneg(MachineInstr &MI,
                                     Register &MatchInfo) const {
  Register Dst = MI.getOperand(0).getReg();
  Builder.buildFNeg(
      Dst, Builder.buildFCanonicalize(MRI.getType(Dst), MatchInfo).getReg(0));
  eraseInst(MI);
}

/// Checks if \p MI is TargetOpcode::G_FMUL and contractable either
/// due to global flags or MachineInstr flags.
static bool isContractableFMul(MachineInstr &MI, bool AllowFusionGlobally) {
  if (MI.getOpcode() != TargetOpcode::G_FMUL)
    return false;
  return AllowFusionGlobally || MI.getFlag(MachineInstr::MIFlag::FmContract);
}

static bool hasMoreUses(const MachineInstr &MI0, const MachineInstr &MI1,
                        const MachineRegisterInfo &MRI) {
  return std::distance(MRI.use_instr_nodbg_begin(MI0.getOperand(0).getReg()),
                       MRI.use_instr_nodbg_end()) >
         std::distance(MRI.use_instr_nodbg_begin(MI1.getOperand(0).getReg()),
                       MRI.use_instr_nodbg_end());
}

bool CombinerHelper::canCombineFMadOrFMA(MachineInstr &MI,
                                         bool &AllowFusionGlobally,
                                         bool &HasFMAD, bool &Aggressive,
                                         bool CanReassociate) const {

  auto *MF = MI.getMF();
  const auto &TLI = *MF->getSubtarget().getTargetLowering();
  LLT DstType = MRI.getType(MI.getOperand(0).getReg());

  if (CanReassociate && !MI.getFlag(MachineInstr::MIFlag::FmReassoc))
    return false;

  // Floating-point multiply-add with intermediate rounding.
  HasFMAD = (!isPreLegalize() && TLI.isFMADLegal(MI, DstType));
  // Floating-point multiply-add without intermediate rounding.
  bool HasFMA = TLI.isFMAFasterThanFMulAndFAdd(*MF, DstType) &&
                isLegalOrBeforeLegalizer({TargetOpcode::G_FMA, {DstType}});
  // No valid opcode, do not combine.
  if (!HasFMAD && !HasFMA)
    return false;

  // FMAD (with intermediate rounding) is always safe to form; FMA requires the
  // contract fast-math flag.
  AllowFusionGlobally = HasFMAD;
  // If the addition is not contractable, do not combine.
  if (!AllowFusionGlobally && !MI.getFlag(MachineInstr::MIFlag::FmContract))
    return false;

  Aggressive = TLI.enableAggressiveFMAFusion(DstType);
  return true;
}

bool CombinerHelper::matchCombineFAddFMulToFMadOrFMA(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_FADD);

  bool AllowFusionGlobally, HasFMAD, Aggressive;
  if (!canCombineFMadOrFMA(MI, AllowFusionGlobally, HasFMAD, Aggressive))
    return false;

  Register Op1 = MI.getOperand(1).getReg();
  Register Op2 = MI.getOperand(2).getReg();
  MachineInstr *Op1Def, *Op2Def;
  if (!mi_match(Op1, MRI, m_MInstr(Op1Def)) ||
      !mi_match(Op2, MRI, m_MInstr(Op2Def)))
    return false;
  DefinitionAndSourceRegister LHS = {Op1Def, Op1};
  DefinitionAndSourceRegister RHS = {Op2Def, Op2};
  unsigned PreferredFusedOpcode =
      HasFMAD ? TargetOpcode::G_FMAD : TargetOpcode::G_FMA;

  // If we have two choices trying to fold (fadd (fmul u, v), (fmul x, y)),
  // prefer to fold the multiply with fewer uses.
  if (Aggressive && isContractableFMul(*LHS.MI, AllowFusionGlobally) &&
      isContractableFMul(*RHS.MI, AllowFusionGlobally)) {
    if (hasMoreUses(*LHS.MI, *RHS.MI, MRI))
      std::swap(LHS, RHS);
  }

  // fold (fadd (fmul x, y), z) -> (fma x, y, z)
  if (isContractableFMul(*LHS.MI, AllowFusionGlobally) &&
      (Aggressive || MRI.hasOneNonDBGUse(LHS.Reg))) {
    unsigned Flags = MI.getFlags() & LHS.MI->getFlags();
    MatchInfo = [=, &MI](MachineIRBuilder &B) {
      B.buildInstr(PreferredFusedOpcode, {MI.getOperand(0).getReg()},
                   {LHS.MI->getOperand(1).getReg(),
                    LHS.MI->getOperand(2).getReg(), RHS.Reg},
                   Flags);
    };
    return true;
  }

  // fold (fadd x, (fmul y, z)) -> (fma y, z, x)
  if (isContractableFMul(*RHS.MI, AllowFusionGlobally) &&
      (Aggressive || MRI.hasOneNonDBGUse(RHS.Reg))) {
    unsigned Flags = MI.getFlags() & RHS.MI->getFlags();
    MatchInfo = [=, &MI](MachineIRBuilder &B) {
      B.buildInstr(PreferredFusedOpcode, {MI.getOperand(0).getReg()},
                   {RHS.MI->getOperand(1).getReg(),
                    RHS.MI->getOperand(2).getReg(), LHS.Reg},
                   Flags);
    };
    return true;
  }

  return false;
}

bool CombinerHelper::matchCombineFAddFpExtFMulToFMadOrFMA(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_FADD);

  bool AllowFusionGlobally, HasFMAD, Aggressive;
  if (!canCombineFMadOrFMA(MI, AllowFusionGlobally, HasFMAD, Aggressive))
    return false;

  const auto &TLI = *MI.getMF()->getSubtarget().getTargetLowering();
  Register Op1 = MI.getOperand(1).getReg();
  Register Op2 = MI.getOperand(2).getReg();
  MachineInstr *Op1Def, *Op2Def;
  if (!mi_match(Op1, MRI, m_MInstr(Op1Def)) ||
      !mi_match(Op2, MRI, m_MInstr(Op2Def)))
    return false;
  DefinitionAndSourceRegister LHS = {Op1Def, Op1};
  DefinitionAndSourceRegister RHS = {Op2Def, Op2};
  LLT DstType = MRI.getType(MI.getOperand(0).getReg());

  unsigned PreferredFusedOpcode =
      HasFMAD ? TargetOpcode::G_FMAD : TargetOpcode::G_FMA;

  MachineInstr *LHSFpExtSrc;
  bool LHSContractable =
      mi_match(LHS.Reg, MRI, m_GFPExt(m_MInstr(LHSFpExtSrc))) &&
      isContractableFMul(*LHSFpExtSrc, AllowFusionGlobally) &&
      TLI.isFPExtFoldable(MI, PreferredFusedOpcode, DstType,
                          MRI.getType(LHSFpExtSrc->getOperand(1).getReg()));
  MachineInstr *RHSFpExtSrc;
  bool RHSContractable =
      mi_match(RHS.Reg, MRI, m_GFPExt(m_MInstr(RHSFpExtSrc))) &&
      isContractableFMul(*RHSFpExtSrc, AllowFusionGlobally) &&
      TLI.isFPExtFoldable(MI, PreferredFusedOpcode, DstType,
                          MRI.getType(RHSFpExtSrc->getOperand(1).getReg()));

  //  fold (fadd (fpext (fmul x, y)), z) -> (fma (fpext x), (fpext y), z)
  if (LHSContractable || RHSContractable) {
    // Ensure that the contractable fmul with the fewest uses (if both are
    // contractable) is the LHS operand.
    if (!LHSContractable ||
        (RHSContractable && hasMoreUses(*LHSFpExtSrc, *RHSFpExtSrc, MRI))) {
      std::swap(LHS, RHS);
      LHSFpExtSrc = RHSFpExtSrc;
    }

    unsigned Flags = MI.getFlags() & LHSFpExtSrc->getFlags();
    MatchInfo = [=, &MI](MachineIRBuilder &B) {
      auto FpExtX = B.buildFPExt(DstType, LHSFpExtSrc->getOperand(1).getReg());
      auto FpExtY = B.buildFPExt(DstType, LHSFpExtSrc->getOperand(2).getReg());
      B.buildInstr(PreferredFusedOpcode, {MI.getOperand(0).getReg()},
                   {FpExtX.getReg(0), FpExtY.getReg(0), RHS.Reg}, Flags);
    };
    return true;
  }

  return false;
}

bool CombinerHelper::matchCombineFAddFMAFMulToFMadOrFMA(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_FADD);

  bool AllowFusionGlobally, HasFMAD, Aggressive;
  if (!canCombineFMadOrFMA(MI, AllowFusionGlobally, HasFMAD, Aggressive, true))
    return false;

  Register Op1 = MI.getOperand(1).getReg();
  Register Op2 = MI.getOperand(2).getReg();
  MachineInstr *Op1Def, *Op2Def;
  if (!mi_match(Op1, MRI, m_MInstr(Op1Def)) ||
      !mi_match(Op2, MRI, m_MInstr(Op2Def)))
    return false;
  DefinitionAndSourceRegister LHS = {Op1Def, Op1};
  DefinitionAndSourceRegister RHS = {Op2Def, Op2};
  LLT DstTy = MRI.getType(MI.getOperand(0).getReg());

  unsigned PreferredFusedOpcode =
      HasFMAD ? TargetOpcode::G_FMAD : TargetOpcode::G_FMA;

  MachineInstr *FMA = nullptr;
  Register Z;
  // fold (fadd (fma x, y, (fmul u, v)), z) -> (fma x, y, (fma u, v, z))
  if (LHS.MI->getOpcode() == PreferredFusedOpcode &&
      mi_match(LHS.MI->getOperand(3).getReg(), MRI,
               m_GFMul(m_Reg(), m_Reg())) &&
      MRI.hasOneNonDBGUse(LHS.MI->getOperand(0).getReg()) &&
      MRI.hasOneNonDBGUse(LHS.MI->getOperand(3).getReg())) {
    FMA = LHS.MI;
    Z = RHS.Reg;
  }
  // fold (fadd z, (fma x, y, (fmul u, v))) -> (fma x, y, (fma u, v, z))
  else if (RHS.MI->getOpcode() == PreferredFusedOpcode &&
           mi_match(RHS.MI->getOperand(3).getReg(), MRI,
                    m_GFMul(m_Reg(), m_Reg())) &&
           MRI.hasOneNonDBGUse(RHS.MI->getOperand(0).getReg()) &&
           MRI.hasOneNonDBGUse(RHS.MI->getOperand(3).getReg())) {
    Z = LHS.Reg;
    FMA = RHS.MI;
  }

  if (FMA) {
    MachineInstr *FMulMI;
    if (!mi_match(FMA->getOperand(3).getReg(), MRI, m_MInstr(FMulMI)))
      return false;
    Register X = FMA->getOperand(1).getReg();
    Register Y = FMA->getOperand(2).getReg();
    Register U = FMulMI->getOperand(1).getReg();
    Register V = FMulMI->getOperand(2).getReg();
    unsigned InnerFlags = MI.getFlags() & FMulMI->getFlags();
    unsigned OuterFlags = MI.getFlags() & FMA->getFlags();

    MatchInfo = [=, &MI](MachineIRBuilder &B) {
      Register InnerFMA = MRI.createGenericVirtualRegister(DstTy);
      B.buildInstr(PreferredFusedOpcode, {InnerFMA}, {U, V, Z}, InnerFlags);
      B.buildInstr(PreferredFusedOpcode, {MI.getOperand(0).getReg()},
                   {X, Y, InnerFMA}, OuterFlags);
    };
    return true;
  }

  return false;
}

bool CombinerHelper::matchCombineFAddFpExtFMulToFMadOrFMAAggressive(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_FADD);

  bool AllowFusionGlobally, HasFMAD, Aggressive;
  if (!canCombineFMadOrFMA(MI, AllowFusionGlobally, HasFMAD, Aggressive))
    return false;

  if (!Aggressive)
    return false;

  const auto &TLI = *MI.getMF()->getSubtarget().getTargetLowering();
  LLT DstType = MRI.getType(MI.getOperand(0).getReg());
  Register Op1 = MI.getOperand(1).getReg();
  Register Op2 = MI.getOperand(2).getReg();
  MachineInstr *Op1Def, *Op2Def;
  if (!mi_match(Op1, MRI, m_MInstr(Op1Def)) ||
      !mi_match(Op2, MRI, m_MInstr(Op2Def)))
    return false;
  DefinitionAndSourceRegister LHS = {Op1Def, Op1};
  DefinitionAndSourceRegister RHS = {Op2Def, Op2};

  unsigned PreferredFusedOpcode =
      HasFMAD ? TargetOpcode::G_FMAD : TargetOpcode::G_FMA;

  // If we have two choices trying to fold (fadd (fmul u, v), (fmul x, y)),
  // prefer to fold the multiply with fewer uses.
  if (Aggressive && isContractableFMul(*LHS.MI, AllowFusionGlobally) &&
      isContractableFMul(*RHS.MI, AllowFusionGlobally)) {
    if (hasMoreUses(*LHS.MI, *RHS.MI, MRI))
      std::swap(LHS, RHS);
  }

  // Builds: (fma x, y, (fma (fpext u), (fpext v), z))
  auto buildMatchInfo = [=, &MI](Register U, Register V, Register Z, Register X,
                                 Register Y, unsigned InnerFlags,
                                 unsigned OuterFlags, MachineIRBuilder &B) {
    Register FpExtU = B.buildFPExt(DstType, U).getReg(0);
    Register FpExtV = B.buildFPExt(DstType, V).getReg(0);
    Register InnerFMA = B.buildInstr(PreferredFusedOpcode, {DstType},
                                     {FpExtU, FpExtV, Z}, InnerFlags)
                            .getReg(0);
    B.buildInstr(PreferredFusedOpcode, {MI.getOperand(0).getReg()},
                 {X, Y, InnerFMA}, OuterFlags);
  };

  MachineInstr *FMulMI, *FMAMI;
  // fold (fadd (fma x, y, (fpext (fmul u, v))), z)
  //   -> (fma x, y, (fma (fpext u), (fpext v), z))
  if (LHS.MI->getOpcode() == PreferredFusedOpcode &&
      mi_match(LHS.MI->getOperand(3).getReg(), MRI,
               m_GFPExt(m_MInstr(FMulMI))) &&
      isContractableFMul(*FMulMI, AllowFusionGlobally) &&
      TLI.isFPExtFoldable(MI, PreferredFusedOpcode, DstType,
                          MRI.getType(FMulMI->getOperand(0).getReg()))) {
    unsigned InnerFlags = MI.getFlags() & FMulMI->getFlags();
    unsigned OuterFlags = MI.getFlags() & LHS.MI->getFlags();
    MatchInfo = [=](MachineIRBuilder &B) {
      buildMatchInfo(FMulMI->getOperand(1).getReg(),
                     FMulMI->getOperand(2).getReg(), RHS.Reg,
                     LHS.MI->getOperand(1).getReg(),
                     LHS.MI->getOperand(2).getReg(), InnerFlags, OuterFlags, B);
    };
    return true;
  }

  // fold (fadd (fpext (fma x, y, (fmul u, v))), z)
  //   -> (fma (fpext x), (fpext y), (fma (fpext u), (fpext v), z))
  // FIXME: This turns two single-precision and one double-precision
  // operation into two double-precision operations, which might not be
  // interesting for all targets, especially GPUs.
  if (mi_match(LHS.Reg, MRI, m_GFPExt(m_MInstr(FMAMI))) &&
      FMAMI->getOpcode() == PreferredFusedOpcode) {
    MachineInstr *FMulMI;
    if (!mi_match(FMAMI->getOperand(3).getReg(), MRI, m_MInstr(FMulMI)))
      return false;
    if (isContractableFMul(*FMulMI, AllowFusionGlobally) &&
        TLI.isFPExtFoldable(MI, PreferredFusedOpcode, DstType,
                            MRI.getType(FMAMI->getOperand(0).getReg()))) {
      unsigned InnerFlags = MI.getFlags() & FMulMI->getFlags();
      unsigned OuterFlags = MI.getFlags() & FMAMI->getFlags();
      MatchInfo = [=](MachineIRBuilder &B) {
        Register X = FMAMI->getOperand(1).getReg();
        Register Y = FMAMI->getOperand(2).getReg();
        X = B.buildFPExt(DstType, X).getReg(0);
        Y = B.buildFPExt(DstType, Y).getReg(0);
        buildMatchInfo(FMulMI->getOperand(1).getReg(),
                       FMulMI->getOperand(2).getReg(), RHS.Reg, X, Y,
                       InnerFlags, OuterFlags, B);
      };

      return true;
    }
  }

  // fold (fadd z, (fma x, y, (fpext (fmul u, v)))
  //   -> (fma x, y, (fma (fpext u), (fpext v), z))
  if (RHS.MI->getOpcode() == PreferredFusedOpcode &&
      mi_match(RHS.MI->getOperand(3).getReg(), MRI,
               m_GFPExt(m_MInstr(FMulMI))) &&
      isContractableFMul(*FMulMI, AllowFusionGlobally) &&
      TLI.isFPExtFoldable(MI, PreferredFusedOpcode, DstType,
                          MRI.getType(FMulMI->getOperand(0).getReg()))) {
    unsigned InnerFlags = MI.getFlags() & FMulMI->getFlags();
    unsigned OuterFlags = MI.getFlags() & RHS.MI->getFlags();
    MatchInfo = [=](MachineIRBuilder &B) {
      buildMatchInfo(FMulMI->getOperand(1).getReg(),
                     FMulMI->getOperand(2).getReg(), LHS.Reg,
                     RHS.MI->getOperand(1).getReg(),
                     RHS.MI->getOperand(2).getReg(), InnerFlags, OuterFlags, B);
    };
    return true;
  }

  // fold (fadd z, (fpext (fma x, y, (fmul u, v)))
  //   -> (fma (fpext x), (fpext y), (fma (fpext u), (fpext v), z))
  // FIXME: This turns two single-precision and one double-precision
  // operation into two double-precision operations, which might not be
  // interesting for all targets, especially GPUs.
  if (mi_match(RHS.Reg, MRI, m_GFPExt(m_MInstr(FMAMI))) &&
      FMAMI->getOpcode() == PreferredFusedOpcode) {
    MachineInstr *FMulMI;
    if (!mi_match(FMAMI->getOperand(3).getReg(), MRI, m_MInstr(FMulMI)))
      return false;
    if (isContractableFMul(*FMulMI, AllowFusionGlobally) &&
        TLI.isFPExtFoldable(MI, PreferredFusedOpcode, DstType,
                            MRI.getType(FMAMI->getOperand(0).getReg()))) {
      unsigned InnerFlags = MI.getFlags() & FMulMI->getFlags();
      unsigned OuterFlags = MI.getFlags() & FMAMI->getFlags();
      MatchInfo = [=](MachineIRBuilder &B) {
        Register X = FMAMI->getOperand(1).getReg();
        Register Y = FMAMI->getOperand(2).getReg();
        X = B.buildFPExt(DstType, X).getReg(0);
        Y = B.buildFPExt(DstType, Y).getReg(0);
        buildMatchInfo(FMulMI->getOperand(1).getReg(),
                       FMulMI->getOperand(2).getReg(), LHS.Reg, X, Y,
                       InnerFlags, OuterFlags, B);
      };
      return true;
    }
  }

  return false;
}

bool CombinerHelper::matchCombineFSubFMulToFMadOrFMA(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_FSUB);

  bool AllowFusionGlobally, HasFMAD, Aggressive;
  if (!canCombineFMadOrFMA(MI, AllowFusionGlobally, HasFMAD, Aggressive))
    return false;

  Register Op1 = MI.getOperand(1).getReg();
  Register Op2 = MI.getOperand(2).getReg();
  MachineInstr *Op1Def, *Op2Def;
  if (!mi_match(Op1, MRI, m_MInstr(Op1Def)) ||
      !mi_match(Op2, MRI, m_MInstr(Op2Def)))
    return false;
  DefinitionAndSourceRegister LHS = {Op1Def, Op1};
  DefinitionAndSourceRegister RHS = {Op2Def, Op2};
  LLT DstTy = MRI.getType(MI.getOperand(0).getReg());

  // If we have two choices trying to fold (fsub (fmul u, v), (fmul x, y)),
  // prefer to fold the multiply with fewer uses.
  int FirstMulHasFewerUses = true;
  if (isContractableFMul(*LHS.MI, AllowFusionGlobally) &&
      isContractableFMul(*RHS.MI, AllowFusionGlobally) &&
      hasMoreUses(*LHS.MI, *RHS.MI, MRI))
    FirstMulHasFewerUses = false;

  unsigned PreferredFusedOpcode =
      HasFMAD ? TargetOpcode::G_FMAD : TargetOpcode::G_FMA;

  // fold (fsub (fmul x, y), z) -> (fma x, y, -z)
  if (FirstMulHasFewerUses &&
      (isContractableFMul(*LHS.MI, AllowFusionGlobally) &&
       (Aggressive || MRI.hasOneNonDBGUse(LHS.Reg)))) {
    unsigned Flags = MI.getFlags() & LHS.MI->getFlags();
    MatchInfo = [=, &MI](MachineIRBuilder &B) {
      Register NegZ = B.buildFNeg(DstTy, RHS.Reg).getReg(0);
      B.buildInstr(PreferredFusedOpcode, {MI.getOperand(0).getReg()},
                   {LHS.MI->getOperand(1).getReg(),
                    LHS.MI->getOperand(2).getReg(), NegZ},
                   Flags);
    };
    return true;
  }
  // fold (fsub x, (fmul y, z)) -> (fma -y, z, x)
  else if ((isContractableFMul(*RHS.MI, AllowFusionGlobally) &&
            (Aggressive || MRI.hasOneNonDBGUse(RHS.Reg)))) {
    unsigned Flags = MI.getFlags() & RHS.MI->getFlags();
    MatchInfo = [=, &MI](MachineIRBuilder &B) {
      Register NegY =
          B.buildFNeg(DstTy, RHS.MI->getOperand(1).getReg()).getReg(0);
      B.buildInstr(PreferredFusedOpcode, {MI.getOperand(0).getReg()},
                   {NegY, RHS.MI->getOperand(2).getReg(), LHS.Reg}, Flags);
    };
    return true;
  }

  return false;
}

bool CombinerHelper::matchCombineFSubFNegFMulToFMadOrFMA(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_FSUB);

  bool AllowFusionGlobally, HasFMAD, Aggressive;
  if (!canCombineFMadOrFMA(MI, AllowFusionGlobally, HasFMAD, Aggressive))
    return false;

  Register LHSReg = MI.getOperand(1).getReg();
  Register RHSReg = MI.getOperand(2).getReg();
  LLT DstTy = MRI.getType(MI.getOperand(0).getReg());

  unsigned PreferredFusedOpcode =
      HasFMAD ? TargetOpcode::G_FMAD : TargetOpcode::G_FMA;

  MachineInstr *FMulMI;
  // fold (fsub (fneg (fmul x, y)), z) -> (fma (fneg x), y, (fneg z))
  if (mi_match(LHSReg, MRI, m_GFNeg(m_MInstr(FMulMI))) &&
      (Aggressive || (MRI.hasOneNonDBGUse(LHSReg) &&
                      MRI.hasOneNonDBGUse(FMulMI->getOperand(0).getReg()))) &&
      isContractableFMul(*FMulMI, AllowFusionGlobally)) {
    unsigned Flags = MI.getFlags() & FMulMI->getFlags();
    MatchInfo = [=, &MI](MachineIRBuilder &B) {
      Register NegX =
          B.buildFNeg(DstTy, FMulMI->getOperand(1).getReg()).getReg(0);
      Register NegZ = B.buildFNeg(DstTy, RHSReg).getReg(0);
      B.buildInstr(PreferredFusedOpcode, {MI.getOperand(0).getReg()},
                   {NegX, FMulMI->getOperand(2).getReg(), NegZ}, Flags);
    };
    return true;
  }

  // fold (fsub x, (fneg (fmul, y, z))) -> (fma y, z, x)
  if (mi_match(RHSReg, MRI, m_GFNeg(m_MInstr(FMulMI))) &&
      (Aggressive || (MRI.hasOneNonDBGUse(RHSReg) &&
                      MRI.hasOneNonDBGUse(FMulMI->getOperand(0).getReg()))) &&
      isContractableFMul(*FMulMI, AllowFusionGlobally)) {
    unsigned Flags = MI.getFlags() & FMulMI->getFlags();
    MatchInfo = [=, &MI](MachineIRBuilder &B) {
      B.buildInstr(PreferredFusedOpcode, {MI.getOperand(0).getReg()},
                   {FMulMI->getOperand(1).getReg(),
                    FMulMI->getOperand(2).getReg(), LHSReg},
                   Flags);
    };
    return true;
  }

  return false;
}

bool CombinerHelper::matchCombineFSubFpExtFMulToFMadOrFMA(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_FSUB);

  bool AllowFusionGlobally, HasFMAD, Aggressive;
  if (!canCombineFMadOrFMA(MI, AllowFusionGlobally, HasFMAD, Aggressive))
    return false;

  Register LHSReg = MI.getOperand(1).getReg();
  Register RHSReg = MI.getOperand(2).getReg();
  LLT DstTy = MRI.getType(MI.getOperand(0).getReg());

  unsigned PreferredFusedOpcode =
      HasFMAD ? TargetOpcode::G_FMAD : TargetOpcode::G_FMA;

  MachineInstr *FMulMI;
  // fold (fsub (fpext (fmul x, y)), z) -> (fma (fpext x), (fpext y), (fneg z))
  if (mi_match(LHSReg, MRI, m_GFPExt(m_MInstr(FMulMI))) &&
      isContractableFMul(*FMulMI, AllowFusionGlobally) &&
      (Aggressive || MRI.hasOneNonDBGUse(LHSReg))) {
    unsigned Flags = MI.getFlags() & FMulMI->getFlags();
    MatchInfo = [=, &MI](MachineIRBuilder &B) {
      Register FpExtX =
          B.buildFPExt(DstTy, FMulMI->getOperand(1).getReg()).getReg(0);
      Register FpExtY =
          B.buildFPExt(DstTy, FMulMI->getOperand(2).getReg()).getReg(0);
      Register NegZ = B.buildFNeg(DstTy, RHSReg).getReg(0);
      B.buildInstr(PreferredFusedOpcode, {MI.getOperand(0).getReg()},
                   {FpExtX, FpExtY, NegZ}, Flags);
    };
    return true;
  }

  // fold (fsub x, (fpext (fmul y, z))) -> (fma (fneg (fpext y)), (fpext z), x)
  if (mi_match(RHSReg, MRI, m_GFPExt(m_MInstr(FMulMI))) &&
      isContractableFMul(*FMulMI, AllowFusionGlobally) &&
      (Aggressive || MRI.hasOneNonDBGUse(RHSReg))) {
    unsigned Flags = MI.getFlags() & FMulMI->getFlags();
    MatchInfo = [=, &MI](MachineIRBuilder &B) {
      Register FpExtY =
          B.buildFPExt(DstTy, FMulMI->getOperand(1).getReg()).getReg(0);
      Register NegY = B.buildFNeg(DstTy, FpExtY).getReg(0);
      Register FpExtZ =
          B.buildFPExt(DstTy, FMulMI->getOperand(2).getReg()).getReg(0);
      B.buildInstr(PreferredFusedOpcode, {MI.getOperand(0).getReg()},
                   {NegY, FpExtZ, LHSReg}, Flags);
    };
    return true;
  }

  return false;
}

bool CombinerHelper::matchCombineFSubFpExtFNegFMulToFMadOrFMA(
    MachineInstr &MI,
    std::function<void(MachineIRBuilder &)> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_FSUB);

  bool AllowFusionGlobally, HasFMAD, Aggressive;
  if (!canCombineFMadOrFMA(MI, AllowFusionGlobally, HasFMAD, Aggressive))
    return false;

  const auto &TLI = *MI.getMF()->getSubtarget().getTargetLowering();
  LLT DstTy = MRI.getType(MI.getOperand(0).getReg());
  Register LHSReg = MI.getOperand(1).getReg();
  Register RHSReg = MI.getOperand(2).getReg();

  unsigned PreferredFusedOpcode =
      HasFMAD ? TargetOpcode::G_FMAD : TargetOpcode::G_FMA;

  auto buildMatchInfo = [=](Register Dst, Register X, Register Y, Register Z,
                            unsigned Flags, MachineIRBuilder &B) {
    Register FpExtX = B.buildFPExt(DstTy, X).getReg(0);
    Register FpExtY = B.buildFPExt(DstTy, Y).getReg(0);
    B.buildInstr(PreferredFusedOpcode, {Dst}, {FpExtX, FpExtY, Z}, Flags);
  };

  MachineInstr *FMulMI;
  // fold (fsub (fpext (fneg (fmul x, y))), z) ->
  //      (fneg (fma (fpext x), (fpext y), z))
  // fold (fsub (fneg (fpext (fmul x, y))), z) ->
  //      (fneg (fma (fpext x), (fpext y), z))
  if ((mi_match(LHSReg, MRI, m_GFPExt(m_GFNeg(m_MInstr(FMulMI)))) ||
       mi_match(LHSReg, MRI, m_GFNeg(m_GFPExt(m_MInstr(FMulMI))))) &&
      isContractableFMul(*FMulMI, AllowFusionGlobally) &&
      TLI.isFPExtFoldable(MI, PreferredFusedOpcode, DstTy,
                          MRI.getType(FMulMI->getOperand(0).getReg()))) {
    unsigned Flags = MI.getFlags() & FMulMI->getFlags();
    MatchInfo = [=, &MI](MachineIRBuilder &B) {
      Register FMAReg = MRI.createGenericVirtualRegister(DstTy);
      buildMatchInfo(FMAReg, FMulMI->getOperand(1).getReg(),
                     FMulMI->getOperand(2).getReg(), RHSReg, Flags, B);
      B.buildFNeg(MI.getOperand(0).getReg(), FMAReg);
    };
    return true;
  }

  // fold (fsub x, (fpext (fneg (fmul y, z)))) -> (fma (fpext y), (fpext z), x)
  // fold (fsub x, (fneg (fpext (fmul y, z)))) -> (fma (fpext y), (fpext z), x)
  if ((mi_match(RHSReg, MRI, m_GFPExt(m_GFNeg(m_MInstr(FMulMI)))) ||
       mi_match(RHSReg, MRI, m_GFNeg(m_GFPExt(m_MInstr(FMulMI))))) &&
      isContractableFMul(*FMulMI, AllowFusionGlobally) &&
      TLI.isFPExtFoldable(MI, PreferredFusedOpcode, DstTy,
                          MRI.getType(FMulMI->getOperand(0).getReg()))) {
    unsigned Flags = MI.getFlags() & FMulMI->getFlags();
    MatchInfo = [=, &MI](MachineIRBuilder &B) {
      buildMatchInfo(MI.getOperand(0).getReg(), FMulMI->getOperand(1).getReg(),
                     FMulMI->getOperand(2).getReg(), LHSReg, Flags, B);
    };
    return true;
  }

  return false;
}

bool CombinerHelper::matchCombineFMinMaxNaN(MachineInstr &MI,
                                            unsigned &IdxToPropagate) const {
  bool PropagateNaN;
  switch (MI.getOpcode()) {
  default:
    return false;
  case TargetOpcode::G_FMINNUM:
  case TargetOpcode::G_FMAXNUM:
    PropagateNaN = false;
    break;
  case TargetOpcode::G_FMINIMUM:
  case TargetOpcode::G_FMAXIMUM:
    PropagateNaN = true;
    break;
  }

  auto MatchNaN = [&](unsigned Idx) {
    Register MaybeNaNReg = MI.getOperand(Idx).getReg();
    const ConstantFP *MaybeCst = getConstantFPVRegVal(MaybeNaNReg, MRI);
    if (!MaybeCst || !MaybeCst->getValueAPF().isNaN())
      return false;
    IdxToPropagate = PropagateNaN ? Idx : (Idx == 1 ? 2 : 1);
    return true;
  };

  return MatchNaN(1) || MatchNaN(2);
}

// Combine multiple FDIVs with the same divisor into multiple FMULs by the
// reciprocal.
// E.g., (a / Y; b / Y;) -> (recip = 1.0 / Y; a * recip; b * recip)
bool CombinerHelper::matchRepeatedFPDivisor(
    MachineInstr &MI, SmallVector<MachineInstr *> &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_FDIV);

  Register X = MI.getOperand(1).getReg();
  Register Y = MI.getOperand(2).getReg();

  if (!MI.getFlag(MachineInstr::MIFlag::FmArcp))
    return false;

  auto IsOne = [this](Register X) {
    auto N0CFP = isConstantOrConstantSplatVectorFP(X, MRI);
    return N0CFP && (N0CFP->isOne() || N0CFP->isMinusOne());
  };

  // Skip if current node is a reciprocal/fneg-reciprocal.
  if (IsOne(X))
    return false;

  // Exit early if the target does not want this transform or if there can't
  // possibly be enough uses of the divisor to make the transform worthwhile.
  unsigned MinUses = getTargetLowering().combineRepeatedFPDivisors();
  if (!MinUses)
    return false;

  // Find all FDIV users of the same divisor. For the moment we limit all
  // instructions to a single BB and use the first Instr in MatchInfo as the
  // dominating position.
  MatchInfo.push_back(&MI);
  for (auto &U : MRI.use_nodbg_instructions(Y)) {
    if (&U == &MI || U.getParent() != MI.getParent())
      continue;
    if (U.getOpcode() == TargetOpcode::G_FDIV &&
        U.getOperand(2).getReg() == Y && U.getOperand(1).getReg() != Y &&
        !IsOne(U.getOperand(1).getReg())) {
      // This division is eligible for optimization only if global unsafe math
      // is enabled or if this division allows reciprocal formation.
      if (U.getFlag(MachineInstr::MIFlag::FmArcp)) {
        MatchInfo.push_back(&U);
        if (dominates(U, *MatchInfo[0]))
          std::swap(MatchInfo[0], MatchInfo.back());
      }
    }
  }

  // Now that we have the actual number of divisor uses, make sure it meets
  // the minimum threshold specified by the target.
  return MatchInfo.size() >= MinUses;
}

void CombinerHelper::applyRepeatedFPDivisor(
    SmallVector<MachineInstr *> &MatchInfo) const {
  // Generate the new div at the position of the first instruction, that we have
  // ensured will dominate all other instructions.
  Builder.setInsertPt(*MatchInfo[0]->getParent(), MatchInfo[0]);
  LLT Ty = MRI.getType(MatchInfo[0]->getOperand(0).getReg());
  auto Div = Builder.buildFDiv(Ty, Builder.buildFConstant(Ty, 1.0),
                               MatchInfo[0]->getOperand(2).getReg(),
                               MatchInfo[0]->getFlags());

  // Replace all found div's with fmul instructions.
  for (MachineInstr *MI : MatchInfo) {
    Builder.setInsertPt(*MI->getParent(), MI);
    Builder.buildFMul(MI->getOperand(0).getReg(), MI->getOperand(1).getReg(),
                      Div->getOperand(0).getReg(), MI->getFlags());
    MI->eraseFromParent();
  }
}

bool CombinerHelper::matchBuildVectorIdentityFold(MachineInstr &MI,
                                                  Register &MatchInfo) const {
  // This combine folds the following patterns:
  //
  //  G_BUILD_VECTOR_TRUNC (G_BITCAST(x), G_LSHR(G_BITCAST(x), k))
  //  G_BUILD_VECTOR(G_TRUNC(G_BITCAST(x)), G_TRUNC(G_LSHR(G_BITCAST(x), k)))
  //    into
  //      x
  //    if
  //      k == sizeof(VecEltTy)/2
  //      type(x) == type(dst)
  //
  //  G_BUILD_VECTOR(G_TRUNC(G_BITCAST(x)), undef)
  //    into
  //      x
  //    if
  //      type(x) == type(dst)

  LLT DstVecTy = MRI.getType(MI.getOperand(0).getReg());
  LLT DstEltTy = DstVecTy.getElementType();

  Register Lo, Hi;

  if (mi_match(
          MI, MRI,
          m_GBuildVector(m_GTrunc(m_GBitcast(m_Reg(Lo))), m_GImplicitDef()))) {
    MatchInfo = Lo;
    return MRI.getType(MatchInfo) == DstVecTy;
  }

  std::optional<ValueAndVReg> ShiftAmount;
  const auto LoPattern = m_GBitcast(m_Reg(Lo));
  const auto HiPattern = m_GLShr(m_GBitcast(m_Reg(Hi)), m_GCst(ShiftAmount));
  if (mi_match(
          MI, MRI,
          m_any_of(m_GBuildVectorTrunc(LoPattern, HiPattern),
                   m_GBuildVector(m_GTrunc(LoPattern), m_GTrunc(HiPattern))))) {
    if (Lo == Hi && ShiftAmount->Value == DstEltTy.getSizeInBits()) {
      MatchInfo = Lo;
      return MRI.getType(MatchInfo) == DstVecTy;
    }
  }

  return false;
}

bool CombinerHelper::matchTruncBuildVectorFold(MachineInstr &MI,
                                               Register &MatchInfo) const {
  // Replace (G_TRUNC (G_BITCAST (G_BUILD_VECTOR x, y)) with just x
  // if type(x) == type(G_TRUNC)
  if (!mi_match(MI.getOperand(1).getReg(), MRI,
                m_GBitcast(m_GBuildVector(m_Reg(MatchInfo), m_Reg()))))
    return false;

  return MRI.getType(MatchInfo) == MRI.getType(MI.getOperand(0).getReg());
}

bool CombinerHelper::matchTruncLshrBuildVectorFold(MachineInstr &MI,
                                                   Register &MatchInfo) const {
  // Replace (G_TRUNC (G_LSHR (G_BITCAST (G_BUILD_VECTOR x, y)), K)) with
  //    y if K == size of vector element type
  std::optional<ValueAndVReg> ShiftAmt;
  if (!mi_match(MI.getOperand(1).getReg(), MRI,
                m_GLShr(m_GBitcast(m_GBuildVector(m_Reg(), m_Reg(MatchInfo))),
                        m_GCst(ShiftAmt))))
    return false;

  LLT MatchTy = MRI.getType(MatchInfo);
  return ShiftAmt->Value.getZExtValue() == MatchTy.getSizeInBits() &&
         MatchTy == MRI.getType(MI.getOperand(0).getReg());
}

unsigned CombinerHelper::getFPMinMaxOpcForSelect(
    CmpInst::Predicate Pred, LLT DstTy,
    SelectPatternNaNBehaviour VsNaNRetVal) const {
  assert(VsNaNRetVal != SelectPatternNaNBehaviour::NOT_APPLICABLE &&
         "Expected a NaN behaviour?");
  // Choose an opcode based off of legality or the behaviour when one of the
  // LHS/RHS may be NaN.
  switch (Pred) {
  default:
    return 0;
  case CmpInst::FCMP_UGT:
  case CmpInst::FCMP_UGE:
  case CmpInst::FCMP_OGT:
  case CmpInst::FCMP_OGE:
    if (VsNaNRetVal == SelectPatternNaNBehaviour::RETURNS_OTHER)
      return TargetOpcode::G_FMAXNUM;
    if (VsNaNRetVal == SelectPatternNaNBehaviour::RETURNS_NAN)
      return TargetOpcode::G_FMAXIMUM;
    if (isLegal({TargetOpcode::G_FMAXNUM, {DstTy}}))
      return TargetOpcode::G_FMAXNUM;
    if (isLegal({TargetOpcode::G_FMAXIMUM, {DstTy}}))
      return TargetOpcode::G_FMAXIMUM;
    return 0;
  case CmpInst::FCMP_ULT:
  case CmpInst::FCMP_ULE:
  case CmpInst::FCMP_OLT:
  case CmpInst::FCMP_OLE:
    if (VsNaNRetVal == SelectPatternNaNBehaviour::RETURNS_OTHER)
      return TargetOpcode::G_FMINNUM;
    if (VsNaNRetVal == SelectPatternNaNBehaviour::RETURNS_NAN)
      return TargetOpcode::G_FMINIMUM;
    if (isLegal({TargetOpcode::G_FMINNUM, {DstTy}}))
      return TargetOpcode::G_FMINNUM;
    if (!isLegal({TargetOpcode::G_FMINIMUM, {DstTy}}))
      return 0;
    return TargetOpcode::G_FMINIMUM;
  }
}

CombinerHelper::SelectPatternNaNBehaviour
CombinerHelper::computeRetValAgainstNaN(Register LHS, Register RHS,
                                        bool IsOrderedComparison) const {
  bool LHSSafe = VT->isKnownNeverNaN(LHS);
  bool RHSSafe = VT->isKnownNeverNaN(RHS);
  // Completely unsafe.
  if (!LHSSafe && !RHSSafe)
    return SelectPatternNaNBehaviour::NOT_APPLICABLE;
  if (LHSSafe && RHSSafe)
    return SelectPatternNaNBehaviour::RETURNS_ANY;
  // An ordered comparison will return false when given a NaN, so it
  // returns the RHS.
  if (IsOrderedComparison)
    return LHSSafe ? SelectPatternNaNBehaviour::RETURNS_NAN
                   : SelectPatternNaNBehaviour::RETURNS_OTHER;
  // An unordered comparison will return true when given a NaN, so it
  // returns the LHS.
  return LHSSafe ? SelectPatternNaNBehaviour::RETURNS_OTHER
                 : SelectPatternNaNBehaviour::RETURNS_NAN;
}

bool CombinerHelper::matchFPSelectToMinMax(Register Dst, Register Cond,
                                           Register TrueVal, Register FalseVal,
                                           BuildFnTy &MatchInfo) const {
  // Match: select (fcmp cond x, y) x, y
  //        select (fcmp cond x, y) y, x
  // And turn it into fminnum/fmaxnum or fmin/fmax based off of the condition.
  LLT DstTy = MRI.getType(Dst);
  // Bail out early on pointers, since we'll never want to fold to a min/max.
  if (DstTy.isPointer())
    return false;
  // Match a floating point compare with a less-than/greater-than predicate.
  // TODO: Allow multiple users of the compare if they are all selects.
  CmpInst::Predicate Pred;
  Register CmpLHS, CmpRHS;
  if (!mi_match(Cond, MRI,
                m_OneNonDBGUse(
                    m_GFCmp(m_Pred(Pred), m_Reg(CmpLHS), m_Reg(CmpRHS)))) ||
      CmpInst::isEquality(Pred))
    return false;
  SelectPatternNaNBehaviour ResWithKnownNaNInfo =
      computeRetValAgainstNaN(CmpLHS, CmpRHS, CmpInst::isOrdered(Pred));
  if (ResWithKnownNaNInfo == SelectPatternNaNBehaviour::NOT_APPLICABLE)
    return false;
  if (TrueVal == CmpRHS && FalseVal == CmpLHS) {
    std::swap(CmpLHS, CmpRHS);
    Pred = CmpInst::getSwappedPredicate(Pred);
    if (ResWithKnownNaNInfo == SelectPatternNaNBehaviour::RETURNS_NAN)
      ResWithKnownNaNInfo = SelectPatternNaNBehaviour::RETURNS_OTHER;
    else if (ResWithKnownNaNInfo == SelectPatternNaNBehaviour::RETURNS_OTHER)
      ResWithKnownNaNInfo = SelectPatternNaNBehaviour::RETURNS_NAN;
  }
  if (TrueVal != CmpLHS || FalseVal != CmpRHS)
    return false;
  // Decide what type of max/min this should be based off of the predicate.
  unsigned Opc = getFPMinMaxOpcForSelect(Pred, DstTy, ResWithKnownNaNInfo);
  if (!Opc || !isLegal({Opc, {DstTy}}))
    return false;
  // Comparisons between signed zero and zero may have different results...
  // unless we have fmaximum/fminimum. In that case, we know -0 < 0.
  if (Opc != TargetOpcode::G_FMAXIMUM && Opc != TargetOpcode::G_FMINIMUM) {
    // We don't know if a comparison between two 0s will give us a consistent
    // result. Be conservative and only proceed if at least one side is
    // non-zero.
    auto KnownNonZeroSide = getFConstantVRegValWithLookThrough(CmpLHS, MRI);
    if (!KnownNonZeroSide || !KnownNonZeroSide->Value.isNonZero()) {
      KnownNonZeroSide = getFConstantVRegValWithLookThrough(CmpRHS, MRI);
      if (!KnownNonZeroSide || !KnownNonZeroSide->Value.isNonZero())
        return false;
    }
  }
  MatchInfo = [=](MachineIRBuilder &B) {
    B.buildInstr(Opc, {Dst}, {CmpLHS, CmpRHS});
  };
  return true;
}

bool CombinerHelper::matchSimplifySelectToMinMax(MachineInstr &MI,
                                                 BuildFnTy &MatchInfo) const {
  // TODO: Handle integer cases.
  assert(MI.getOpcode() == TargetOpcode::G_SELECT);
  // Condition may be fed by a truncated compare.
  Register Cond = MI.getOperand(1).getReg();
  Register MaybeTrunc;
  if (mi_match(Cond, MRI, m_OneNonDBGUse(m_GTrunc(m_Reg(MaybeTrunc)))))
    Cond = MaybeTrunc;
  Register Dst = MI.getOperand(0).getReg();
  Register TrueVal = MI.getOperand(2).getReg();
  Register FalseVal = MI.getOperand(3).getReg();
  return matchFPSelectToMinMax(Dst, Cond, TrueVal, FalseVal, MatchInfo);
}

bool CombinerHelper::matchRedundantBinOpInEquality(MachineInstr &MI,
                                                   BuildFnTy &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_ICMP);
  // (X + Y) == X --> Y == 0
  // (X + Y) != X --> Y != 0
  // (X - Y) == X --> Y == 0
  // (X - Y) != X --> Y != 0
  // (X ^ Y) == X --> Y == 0
  // (X ^ Y) != X --> Y != 0
  Register Dst = MI.getOperand(0).getReg();
  CmpInst::Predicate Pred;
  Register X, Y, OpLHS, OpRHS;
  bool MatchedSub = mi_match(
      Dst, MRI,
      m_c_GICmp(m_Pred(Pred), m_Reg(X), m_GSub(m_Reg(OpLHS), m_Reg(Y))));
  if (MatchedSub && X != OpLHS)
    return false;
  if (!MatchedSub) {
    if (!mi_match(Dst, MRI,
                  m_c_GICmp(m_Pred(Pred), m_Reg(X),
                            m_any_of(m_GAdd(m_Reg(OpLHS), m_Reg(OpRHS)),
                                     m_GXor(m_Reg(OpLHS), m_Reg(OpRHS))))))
      return false;
    Y = X == OpLHS ? OpRHS : X == OpRHS ? OpLHS : Register();
  }
  MatchInfo = [=](MachineIRBuilder &B) {
    auto Zero = B.buildConstant(MRI.getType(Y), 0);
    B.buildICmp(Pred, Dst, Y, Zero);
  };
  return CmpInst::isEquality(Pred) && Y.isValid();
}

/// Return the minimum useless shift amount that results in complete loss of the
/// source value. Return std::nullopt when it cannot determine a value.
static std::optional<unsigned>
getMinUselessShift(KnownBits ValueKB, unsigned Opcode,
                   std::optional<int64_t> &Result) {
  assert((Opcode == TargetOpcode::G_SHL || Opcode == TargetOpcode::G_LSHR ||
          Opcode == TargetOpcode::G_ASHR) &&
         "Expect G_SHL, G_LSHR or G_ASHR.");
  auto SignificantBits = 0;
  switch (Opcode) {
  case TargetOpcode::G_SHL:
    SignificantBits = ValueKB.countMinTrailingZeros();
    Result = 0;
    break;
  case TargetOpcode::G_LSHR:
    Result = 0;
    SignificantBits = ValueKB.countMinLeadingZeros();
    break;
  case TargetOpcode::G_ASHR:
    if (ValueKB.isNonNegative()) {
      SignificantBits = ValueKB.countMinLeadingZeros();
      Result = 0;
    } else if (ValueKB.isNegative()) {
      SignificantBits = ValueKB.countMinLeadingOnes();
      Result = -1;
    } else {
      // Cannot determine shift result.
      Result = std::nullopt;
    }
    break;
  default:
    break;
  }
  return ValueKB.getBitWidth() - SignificantBits;
}

bool CombinerHelper::matchShiftsTooBig(
    MachineInstr &MI, std::optional<int64_t> &MatchInfo) const {
  Register ShiftVal = MI.getOperand(1).getReg();
  Register ShiftReg = MI.getOperand(2).getReg();
  LLT ResTy = MRI.getType(MI.getOperand(0).getReg());
  auto IsShiftTooBig = [&](const Constant *C) {
    auto *CI = dyn_cast<ConstantInt>(C);
    if (!CI)
      return false;
    if (CI->uge(ResTy.getScalarSizeInBits())) {
      MatchInfo = std::nullopt;
      return true;
    }
    auto OptMaxUsefulShift = getMinUselessShift(VT->getKnownBits(ShiftVal),
                                                MI.getOpcode(), MatchInfo);
    return OptMaxUsefulShift && CI->uge(*OptMaxUsefulShift);
  };
  return matchUnaryPredicate(MRI, ShiftReg, IsShiftTooBig);
}

bool CombinerHelper::matchCommuteConstantToRHS(MachineInstr &MI) const {
  unsigned LHSOpndIdx = 1;
  unsigned RHSOpndIdx = 2;
  switch (MI.getOpcode()) {
  case TargetOpcode::G_UADDO:
  case TargetOpcode::G_SADDO:
  case TargetOpcode::G_UMULO:
  case TargetOpcode::G_SMULO:
    LHSOpndIdx = 2;
    RHSOpndIdx = 3;
    break;
  default:
    break;
  }
  Register LHS = MI.getOperand(LHSOpndIdx).getReg();
  Register RHS = MI.getOperand(RHSOpndIdx).getReg();
  MachineInstr *LHSDef, *RHSDef;
  if (!mi_match(LHS, MRI, m_MInstr(LHSDef)) ||
      !mi_match(RHS, MRI, m_MInstr(RHSDef)))
    return false;

  if (!getIConstantVRegVal(LHS, MRI)) {
    // Skip commuting if LHS is not a constant. But, LHS may be a
    // G_CONSTANT_FOLD_BARRIER. If so we commute as long as we don't already
    // have a constant on the RHS.
    if (LHSDef->getOpcode() != TargetOpcode::G_CONSTANT_FOLD_BARRIER)
      return false;
  }
  // Commute as long as RHS is not a constant or G_CONSTANT_FOLD_BARRIER.
  return RHSDef->getOpcode() != TargetOpcode::G_CONSTANT_FOLD_BARRIER &&
         !getIConstantVRegVal(RHS, MRI);
}

bool CombinerHelper::matchCommuteFPConstantToRHS(MachineInstr &MI) const {
  Register LHS = MI.getOperand(1).getReg();
  Register RHS = MI.getOperand(2).getReg();
  std::optional<FPValueAndVReg> ValAndVReg;
  if (!mi_match(LHS, MRI, m_GFCstOrSplat(ValAndVReg)))
    return false;
  return !mi_match(RHS, MRI, m_GFCstOrSplat(ValAndVReg));
}

void CombinerHelper::applyCommuteBinOpOperands(MachineInstr &MI) const {
  Observer.changingInstr(MI);
  unsigned LHSOpndIdx = 1;
  unsigned RHSOpndIdx = 2;
  switch (MI.getOpcode()) {
  case TargetOpcode::G_UADDO:
  case TargetOpcode::G_SADDO:
  case TargetOpcode::G_UMULO:
  case TargetOpcode::G_SMULO:
    LHSOpndIdx = 2;
    RHSOpndIdx = 3;
    break;
  default:
    break;
  }
  Register LHSReg = MI.getOperand(LHSOpndIdx).getReg();
  Register RHSReg = MI.getOperand(RHSOpndIdx).getReg();
  MI.getOperand(LHSOpndIdx).setReg(RHSReg);
  MI.getOperand(RHSOpndIdx).setReg(LHSReg);
  Observer.changedInstr(MI);
}

bool CombinerHelper::isOneOrOneSplat(Register Src, bool AllowUndefs) const {
  LLT SrcTy = MRI.getType(Src);
  if (SrcTy.isFixedVector())
    return isConstantSplatVector(Src, 1, AllowUndefs);
  if (SrcTy.isScalar()) {
    if (AllowUndefs && getOpcodeDef<GImplicitDef>(Src, MRI) != nullptr)
      return true;
    auto IConstant = getIConstantVRegValWithLookThrough(Src, MRI);
    return IConstant && IConstant->Value == 1;
  }
  return false; // scalable vector
}

bool CombinerHelper::isZeroOrZeroSplat(Register Src, bool AllowUndefs) const {
  LLT SrcTy = MRI.getType(Src);
  if (SrcTy.isFixedVector())
    return isConstantSplatVector(Src, 0, AllowUndefs);
  if (SrcTy.isScalar()) {
    if (AllowUndefs && getOpcodeDef<GImplicitDef>(Src, MRI) != nullptr)
      return true;
    auto IConstant = getIConstantVRegValWithLookThrough(Src, MRI);
    return IConstant && IConstant->Value == 0;
  }
  return false; // scalable vector
}

// Ignores COPYs during conformance checks.
// FIXME scalable vectors.
bool CombinerHelper::isConstantSplatVector(Register Src, int64_t SplatValue,
                                           bool AllowUndefs) const {
  GBuildVector *BuildVector = getOpcodeDef<GBuildVector>(Src, MRI);
  if (!BuildVector)
    return false;
  unsigned NumSources = BuildVector->getNumSources();

  for (unsigned I = 0; I < NumSources; ++I) {
    GImplicitDef *ImplicitDef =
        getOpcodeDef<GImplicitDef>(BuildVector->getSourceReg(I), MRI);
    if (ImplicitDef && AllowUndefs)
      continue;
    if (ImplicitDef && !AllowUndefs)
      return false;
    std::optional<ValueAndVReg> IConstant =
        getIConstantVRegValWithLookThrough(BuildVector->getSourceReg(I), MRI);
    if (IConstant && IConstant->Value == SplatValue)
      continue;
    return false;
  }
  return true;
}

// Ignores COPYs during lookups.
// FIXME scalable vectors
std::optional<APInt>
CombinerHelper::getConstantOrConstantSplatVector(Register Src) const {
  auto IConstant = getIConstantVRegValWithLookThrough(Src, MRI);
  if (IConstant)
    return IConstant->Value;

  GBuildVector *BuildVector = getOpcodeDef<GBuildVector>(Src, MRI);
  if (!BuildVector)
    return std::nullopt;
  unsigned NumSources = BuildVector->getNumSources();

  std::optional<APInt> Value = std::nullopt;
  for (unsigned I = 0; I < NumSources; ++I) {
    std::optional<ValueAndVReg> IConstant =
        getIConstantVRegValWithLookThrough(BuildVector->getSourceReg(I), MRI);
    if (!IConstant)
      return std::nullopt;
    if (!Value)
      Value = IConstant->Value;
    else if (*Value != IConstant->Value)
      return std::nullopt;
  }
  return Value;
}

// FIXME G_SPLAT_VECTOR
bool CombinerHelper::isConstantOrConstantVectorI(Register Src) const {
  auto IConstant = getIConstantVRegValWithLookThrough(Src, MRI);
  if (IConstant)
    return true;

  GBuildVector *BuildVector = getOpcodeDef<GBuildVector>(Src, MRI);
  if (!BuildVector)
    return false;

  unsigned NumSources = BuildVector->getNumSources();
  for (unsigned I = 0; I < NumSources; ++I) {
    std::optional<ValueAndVReg> IConstant =
        getIConstantVRegValWithLookThrough(BuildVector->getSourceReg(I), MRI);
    if (!IConstant)
      return false;
  }
  return true;
}

// TODO: use knownbits to determine zeros
bool CombinerHelper::tryFoldSelectOfConstants(GSelect *Select,
                                              BuildFnTy &MatchInfo) const {
  uint32_t Flags = Select->getFlags();
  Register Dest = Select->getReg(0);
  Register Cond = Select->getCondReg();
  Register True = Select->getTrueReg();
  Register False = Select->getFalseReg();
  LLT CondTy = MRI.getType(Select->getCondReg());
  LLT TrueTy = MRI.getType(Select->getTrueReg());

  // We only do this combine for scalar boolean conditions.
  if (CondTy != LLT::scalar(1))
    return false;

  if (TrueTy.isPointer())
    return false;

  // Both are scalars.
  std::optional<ValueAndVReg> TrueOpt =
      getIConstantVRegValWithLookThrough(True, MRI);
  std::optional<ValueAndVReg> FalseOpt =
      getIConstantVRegValWithLookThrough(False, MRI);

  if (!TrueOpt || !FalseOpt)
    return false;

  APInt TrueValue = TrueOpt->Value;
  APInt FalseValue = FalseOpt->Value;

  // select Cond, 1, 0 --> zext (Cond)
  if (TrueValue.isOne() && FalseValue.isZero()) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.setInstrAndDebugLoc(*Select);
      B.buildZExtOrTrunc(Dest, Cond);
    };
    return true;
  }

  // select Cond, -1, 0 --> sext (Cond)
  if (TrueValue.isAllOnes() && FalseValue.isZero()) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.setInstrAndDebugLoc(*Select);
      B.buildSExtOrTrunc(Dest, Cond);
    };
    return true;
  }

  // select Cond, 0, 1 --> zext (!Cond)
  if (TrueValue.isZero() && FalseValue.isOne()) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.setInstrAndDebugLoc(*Select);
      Register Inner = MRI.createGenericVirtualRegister(CondTy);
      B.buildNot(Inner, Cond);
      B.buildZExtOrTrunc(Dest, Inner);
    };
    return true;
  }

  // select Cond, 0, -1 --> sext (!Cond)
  if (TrueValue.isZero() && FalseValue.isAllOnes()) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.setInstrAndDebugLoc(*Select);
      Register Inner = MRI.createGenericVirtualRegister(CondTy);
      B.buildNot(Inner, Cond);
      B.buildSExtOrTrunc(Dest, Inner);
    };
    return true;
  }

  // select Cond, C1, C1-1 --> add (zext Cond), C1-1
  if (TrueValue - 1 == FalseValue) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.setInstrAndDebugLoc(*Select);
      Register Inner = MRI.createGenericVirtualRegister(TrueTy);
      B.buildZExtOrTrunc(Inner, Cond);
      B.buildAdd(Dest, Inner, False);
    };
    return true;
  }

  // select Cond, C1, C1+1 --> add (sext Cond), C1+1
  if (TrueValue + 1 == FalseValue) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.setInstrAndDebugLoc(*Select);
      Register Inner = MRI.createGenericVirtualRegister(TrueTy);
      B.buildSExtOrTrunc(Inner, Cond);
      B.buildAdd(Dest, Inner, False);
    };
    return true;
  }

  // select Cond, Pow2, 0 --> (zext Cond) << log2(Pow2)
  if (TrueValue.isPowerOf2() && FalseValue.isZero()) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.setInstrAndDebugLoc(*Select);
      Register Inner = MRI.createGenericVirtualRegister(TrueTy);
      B.buildZExtOrTrunc(Inner, Cond);
      // The shift amount must be scalar.
      LLT ShiftTy = TrueTy.isVector() ? TrueTy.getElementType() : TrueTy;
      auto ShAmtC = B.buildConstant(ShiftTy, TrueValue.exactLogBase2());
      B.buildShl(Dest, Inner, ShAmtC, Flags);
    };
    return true;
  }

  // select Cond, 0, Pow2 --> (zext (!Cond)) << log2(Pow2)
  if (FalseValue.isPowerOf2() && TrueValue.isZero()) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.setInstrAndDebugLoc(*Select);
      Register Not = MRI.createGenericVirtualRegister(CondTy);
      B.buildNot(Not, Cond);
      Register Inner = MRI.createGenericVirtualRegister(TrueTy);
      B.buildZExtOrTrunc(Inner, Not);
      // The shift amount must be scalar.
      LLT ShiftTy = TrueTy.isVector() ? TrueTy.getElementType() : TrueTy;
      auto ShAmtC = B.buildConstant(ShiftTy, FalseValue.exactLogBase2());
      B.buildShl(Dest, Inner, ShAmtC, Flags);
    };
    return true;
  }

  // select Cond, -1, C --> or (sext Cond), C
  if (TrueValue.isAllOnes()) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.setInstrAndDebugLoc(*Select);
      Register Inner = MRI.createGenericVirtualRegister(TrueTy);
      B.buildSExtOrTrunc(Inner, Cond);
      B.buildOr(Dest, Inner, False, Flags);
    };
    return true;
  }

  // select Cond, C, -1 --> or (sext (not Cond)), C
  if (FalseValue.isAllOnes()) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.setInstrAndDebugLoc(*Select);
      Register Not = MRI.createGenericVirtualRegister(CondTy);
      B.buildNot(Not, Cond);
      Register Inner = MRI.createGenericVirtualRegister(TrueTy);
      B.buildSExtOrTrunc(Inner, Not);
      B.buildOr(Dest, Inner, True, Flags);
    };
    return true;
  }

  return false;
}

// TODO: use knownbits to determine zeros
bool CombinerHelper::tryFoldBoolSelectToLogic(GSelect *Select,
                                              BuildFnTy &MatchInfo) const {
  uint32_t Flags = Select->getFlags();
  Register DstReg = Select->getReg(0);
  Register Cond = Select->getCondReg();
  Register True = Select->getTrueReg();
  Register False = Select->getFalseReg();
  LLT CondTy = MRI.getType(Select->getCondReg());
  LLT TrueTy = MRI.getType(Select->getTrueReg());

  // Boolean or fixed vector of booleans.
  if (CondTy.isScalableVector() ||
      (CondTy.isFixedVector() &&
       CondTy.getElementType().getScalarSizeInBits() != 1) ||
      CondTy.getScalarSizeInBits() != 1)
    return false;

  if (CondTy != TrueTy)
    return false;

  // select Cond, Cond, F --> or Cond, F
  // select Cond, 1, F    --> or Cond, F
  if ((Cond == True) || isOneOrOneSplat(True, /* AllowUndefs */ true)) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.setInstrAndDebugLoc(*Select);
      Register Ext = MRI.createGenericVirtualRegister(TrueTy);
      B.buildZExtOrTrunc(Ext, Cond);
      auto FreezeFalse = B.buildFreeze(TrueTy, False);
      B.buildOr(DstReg, Ext, FreezeFalse, Flags);
    };
    return true;
  }

  // select Cond, T, Cond --> and Cond, T
  // select Cond, T, 0    --> and Cond, T
  if ((Cond == False) || isZeroOrZeroSplat(False, /* AllowUndefs */ true)) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.setInstrAndDebugLoc(*Select);
      Register Ext = MRI.createGenericVirtualRegister(TrueTy);
      B.buildZExtOrTrunc(Ext, Cond);
      auto FreezeTrue = B.buildFreeze(TrueTy, True);
      B.buildAnd(DstReg, Ext, FreezeTrue);
    };
    return true;
  }

  // select Cond, T, 1 --> or (not Cond), T
  if (isOneOrOneSplat(False, /* AllowUndefs */ true)) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.setInstrAndDebugLoc(*Select);
      // First the not.
      Register Inner = MRI.createGenericVirtualRegister(CondTy);
      B.buildNot(Inner, Cond);
      // Then an ext to match the destination register.
      Register Ext = MRI.createGenericVirtualRegister(TrueTy);
      B.buildZExtOrTrunc(Ext, Inner);
      auto FreezeTrue = B.buildFreeze(TrueTy, True);
      B.buildOr(DstReg, Ext, FreezeTrue, Flags);
    };
    return true;
  }

  // select Cond, 0, F --> and (not Cond), F
  if (isZeroOrZeroSplat(True, /* AllowUndefs */ true)) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.setInstrAndDebugLoc(*Select);
      // First the not.
      Register Inner = MRI.createGenericVirtualRegister(CondTy);
      B.buildNot(Inner, Cond);
      // Then an ext to match the destination register.
      Register Ext = MRI.createGenericVirtualRegister(TrueTy);
      B.buildZExtOrTrunc(Ext, Inner);
      auto FreezeFalse = B.buildFreeze(TrueTy, False);
      B.buildAnd(DstReg, Ext, FreezeFalse);
    };
    return true;
  }

  return false;
}

bool CombinerHelper::matchSelectIMinMax(const MachineOperand &MO,
                                        BuildFnTy &MatchInfo) const {
  Register DstReg = MO.getReg();
  Register CondReg, True, False;
  if (!mi_match(DstReg, MRI,
                m_GISelect(m_Reg(CondReg), m_Reg(True), m_Reg(False))))
    return false;

  CmpInst::Predicate Pred;
  Register CmpLHS, CmpRHS;
  if (!mi_match(CondReg, MRI,
                m_GICmp(m_Pred(Pred), m_Reg(CmpLHS), m_Reg(CmpRHS))))
    return false;

  LLT DstTy = MRI.getType(DstReg);
  if (DstTy.isPointerOrPointerVector())
    return false;

  // We want to fold the icmp and replace the select.
  if (!MRI.hasOneNonDBGUse(CondReg))
    return false;

  // We need a larger or smaller predicate for
  // canonicalization.
  if (CmpInst::isEquality(Pred))
    return false;

  // We can swap CmpLHS and CmpRHS for higher hitrate.
  if (True == CmpRHS && False == CmpLHS) {
    std::swap(CmpLHS, CmpRHS);
    Pred = CmpInst::getSwappedPredicate(Pred);
  }

  // (icmp X, Y) ? X : Y -> integer minmax.
  // see matchSelectPattern in ValueTracking.
  // Legality between G_SELECT and integer minmax can differ.
  if (True != CmpLHS || False != CmpRHS)
    return false;

  switch (Pred) {
  case ICmpInst::ICMP_UGT:
  case ICmpInst::ICMP_UGE: {
    if (!isLegalOrBeforeLegalizer({TargetOpcode::G_UMAX, DstTy}))
      return false;
    MatchInfo = [=](MachineIRBuilder &B) { B.buildUMax(DstReg, True, False); };
    return true;
  }
  case ICmpInst::ICMP_SGT:
  case ICmpInst::ICMP_SGE: {
    if (!isLegalOrBeforeLegalizer({TargetOpcode::G_SMAX, DstTy}))
      return false;
    MatchInfo = [=](MachineIRBuilder &B) { B.buildSMax(DstReg, True, False); };
    return true;
  }
  case ICmpInst::ICMP_ULT:
  case ICmpInst::ICMP_ULE: {
    if (!isLegalOrBeforeLegalizer({TargetOpcode::G_UMIN, DstTy}))
      return false;
    MatchInfo = [=](MachineIRBuilder &B) { B.buildUMin(DstReg, True, False); };
    return true;
  }
  case ICmpInst::ICMP_SLT:
  case ICmpInst::ICMP_SLE: {
    if (!isLegalOrBeforeLegalizer({TargetOpcode::G_SMIN, DstTy}))
      return false;
    MatchInfo = [=](MachineIRBuilder &B) { B.buildSMin(DstReg, True, False); };
    return true;
  }
  default:
    return false;
  }
}

// (neg (min/max x, (neg x))) --> (max/min x, (neg x))
bool CombinerHelper::matchSimplifyNegMinMax(MachineInstr &MI,
                                            BuildFnTy &MatchInfo) const {
  assert(MI.getOpcode() == TargetOpcode::G_SUB);
  Register DestReg = MI.getOperand(0).getReg();
  LLT DestTy = MRI.getType(DestReg);

  Register X;
  Register Sub0;
  auto NegPattern = m_all_of(m_Neg(m_DeferredReg(X)), m_Reg(Sub0));
  if (mi_match(DestReg, MRI,
               m_Neg(m_OneUse(m_any_of(m_GSMin(m_Reg(X), NegPattern),
                                       m_GSMax(m_Reg(X), NegPattern),
                                       m_GUMin(m_Reg(X), NegPattern),
                                       m_GUMax(m_Reg(X), NegPattern)))))) {
    MachineInstr *MinMaxMI;
    if (!mi_match(MI.getOperand(2).getReg(), MRI, m_MInstr(MinMaxMI)))
      return false;
    unsigned NewOpc = getInverseGMinMaxOpcode(MinMaxMI->getOpcode());
    if (isLegal({NewOpc, {DestTy}})) {
      MatchInfo = [=](MachineIRBuilder &B) {
        B.buildInstr(NewOpc, {DestReg}, {X, Sub0});
      };
      return true;
    }
  }

  return false;
}

bool CombinerHelper::matchSelect(MachineInstr &MI, BuildFnTy &MatchInfo) const {
  GSelect *Select = cast<GSelect>(&MI);

  if (tryFoldSelectOfConstants(Select, MatchInfo))
    return true;

  if (tryFoldBoolSelectToLogic(Select, MatchInfo))
    return true;

  return false;
}

/// Fold (icmp Pred1 V1, C1) && (icmp Pred2 V2, C2)
/// or   (icmp Pred1 V1, C1) || (icmp Pred2 V2, C2)
/// into a single comparison using range-based reasoning.
/// see InstCombinerImpl::foldAndOrOfICmpsUsingRanges.
bool CombinerHelper::tryFoldAndOrOrICmpsUsingRanges(
    GLogicalBinOp *Logic, BuildFnTy &MatchInfo) const {
  assert(Logic->getOpcode() != TargetOpcode::G_XOR && "unexpected xor");
  bool IsAnd = Logic->getOpcode() == TargetOpcode::G_AND;
  Register DstReg = Logic->getReg(0);
  Register LHS = Logic->getLHSReg();
  Register RHS = Logic->getRHSReg();
  unsigned Flags = Logic->getFlags();

  // We need an G_ICMP on the LHS register.
  GICmp *Cmp1 = getOpcodeDef<GICmp>(LHS, MRI);
  if (!Cmp1)
    return false;

  // We need an G_ICMP on the RHS register.
  GICmp *Cmp2 = getOpcodeDef<GICmp>(RHS, MRI);
  if (!Cmp2)
    return false;

  // We want to fold the icmps.
  if (!MRI.hasOneNonDBGUse(Cmp1->getReg(0)) ||
      !MRI.hasOneNonDBGUse(Cmp2->getReg(0)))
    return false;

  APInt C1;
  APInt C2;
  std::optional<ValueAndVReg> MaybeC1 =
      getIConstantVRegValWithLookThrough(Cmp1->getRHSReg(), MRI);
  if (!MaybeC1)
    return false;
  C1 = MaybeC1->Value;

  std::optional<ValueAndVReg> MaybeC2 =
      getIConstantVRegValWithLookThrough(Cmp2->getRHSReg(), MRI);
  if (!MaybeC2)
    return false;
  C2 = MaybeC2->Value;

  Register R1 = Cmp1->getLHSReg();
  Register R2 = Cmp2->getLHSReg();
  CmpInst::Predicate Pred1 = Cmp1->getCond();
  CmpInst::Predicate Pred2 = Cmp2->getCond();
  LLT CmpTy = MRI.getType(Cmp1->getReg(0));
  LLT CmpOperandTy = MRI.getType(R1);

  if (CmpOperandTy.isPointer())
    return false;

  // We build ands, adds, and constants of type CmpOperandTy.
  // They must be legal to build.
  if (!isLegalOrBeforeLegalizer({TargetOpcode::G_AND, CmpOperandTy}) ||
      !isLegalOrBeforeLegalizer({TargetOpcode::G_ADD, CmpOperandTy}) ||
      !isConstantLegalOrBeforeLegalizer(CmpOperandTy))
    return false;

  // Look through add of a constant offset on R1, R2, or both operands. This
  // allows us to interpret the R + C' < C'' range idiom into a proper range.
  std::optional<APInt> Offset1;
  std::optional<APInt> Offset2;
  if (R1 != R2) {
    if (GAdd *Add = getOpcodeDef<GAdd>(R1, MRI)) {
      std::optional<ValueAndVReg> MaybeOffset1 =
          getIConstantVRegValWithLookThrough(Add->getRHSReg(), MRI);
      if (MaybeOffset1) {
        R1 = Add->getLHSReg();
        Offset1 = MaybeOffset1->Value;
      }
    }
    if (GAdd *Add = getOpcodeDef<GAdd>(R2, MRI)) {
      std::optional<ValueAndVReg> MaybeOffset2 =
          getIConstantVRegValWithLookThrough(Add->getRHSReg(), MRI);
      if (MaybeOffset2) {
        R2 = Add->getLHSReg();
        Offset2 = MaybeOffset2->Value;
      }
    }
  }

  if (R1 != R2)
    return false;

  // We calculate the icmp ranges including maybe offsets.
  ConstantRange CR1 = ConstantRange::makeExactICmpRegion(
      IsAnd ? ICmpInst::getInversePredicate(Pred1) : Pred1, C1);
  if (Offset1)
    CR1 = CR1.subtract(*Offset1);

  ConstantRange CR2 = ConstantRange::makeExactICmpRegion(
      IsAnd ? ICmpInst::getInversePredicate(Pred2) : Pred2, C2);
  if (Offset2)
    CR2 = CR2.subtract(*Offset2);

  bool CreateMask = false;
  APInt LowerDiff;
  std::optional<ConstantRange> CR = CR1.exactUnionWith(CR2);
  if (!CR) {
    // We need non-wrapping ranges.
    if (CR1.isWrappedSet() || CR2.isWrappedSet())
      return false;

    // Check whether we have equal-size ranges that only differ by one bit.
    // In that case we can apply a mask to map one range onto the other.
    LowerDiff = CR1.getLower() ^ CR2.getLower();
    APInt UpperDiff = (CR1.getUpper() - 1) ^ (CR2.getUpper() - 1);
    APInt CR1Size = CR1.getUpper() - CR1.getLower();
    if (!LowerDiff.isPowerOf2() || LowerDiff != UpperDiff ||
        CR1Size != CR2.getUpper() - CR2.getLower())
      return false;

    CR = CR1.getLower().ult(CR2.getLower()) ? CR1 : CR2;
    CreateMask = true;
  }

  if (IsAnd)
    CR = CR->inverse();

  CmpInst::Predicate NewPred;
  APInt NewC, Offset;
  CR->getEquivalentICmp(NewPred, NewC, Offset);

  // We take the result type of one of the original icmps, CmpTy, for
  // the to be build icmp. The operand type, CmpOperandTy, is used for
  // the other instructions and constants to be build. The types of
  // the parameters and output are the same for add and and.  CmpTy
  // and the type of DstReg might differ. That is why we zext or trunc
  // the icmp into the destination register.

  MatchInfo = [=](MachineIRBuilder &B) {
    if (CreateMask && Offset != 0) {
      auto TildeLowerDiff = B.buildConstant(CmpOperandTy, ~LowerDiff);
      auto And = B.buildAnd(CmpOperandTy, R1, TildeLowerDiff); // the mask.
      auto OffsetC = B.buildConstant(CmpOperandTy, Offset);
      auto Add = B.buildAdd(CmpOperandTy, And, OffsetC, Flags);
      auto NewCon = B.buildConstant(CmpOperandTy, NewC);
      auto ICmp = B.buildICmp(NewPred, CmpTy, Add, NewCon);
      B.buildZExtOrTrunc(DstReg, ICmp);
    } else if (CreateMask && Offset == 0) {
      auto TildeLowerDiff = B.buildConstant(CmpOperandTy, ~LowerDiff);
      auto And = B.buildAnd(CmpOperandTy, R1, TildeLowerDiff); // the mask.
      auto NewCon = B.buildConstant(CmpOperandTy, NewC);
      auto ICmp = B.buildICmp(NewPred, CmpTy, And, NewCon);
      B.buildZExtOrTrunc(DstReg, ICmp);
    } else if (!CreateMask && Offset != 0) {
      auto OffsetC = B.buildConstant(CmpOperandTy, Offset);
      auto Add = B.buildAdd(CmpOperandTy, R1, OffsetC, Flags);
      auto NewCon = B.buildConstant(CmpOperandTy, NewC);
      auto ICmp = B.buildICmp(NewPred, CmpTy, Add, NewCon);
      B.buildZExtOrTrunc(DstReg, ICmp);
    } else if (!CreateMask && Offset == 0) {
      auto NewCon = B.buildConstant(CmpOperandTy, NewC);
      auto ICmp = B.buildICmp(NewPred, CmpTy, R1, NewCon);
      B.buildZExtOrTrunc(DstReg, ICmp);
    } else {
      llvm_unreachable("unexpected configuration of CreateMask and Offset");
    }
  };
  return true;
}

bool CombinerHelper::tryFoldLogicOfFCmps(GLogicalBinOp *Logic,
                                         BuildFnTy &MatchInfo) const {
  assert(Logic->getOpcode() != TargetOpcode::G_XOR && "unexpecte xor");
  Register DestReg = Logic->getReg(0);
  Register LHS = Logic->getLHSReg();
  Register RHS = Logic->getRHSReg();
  bool IsAnd = Logic->getOpcode() == TargetOpcode::G_AND;

  // We need a compare on the LHS register.
  GFCmp *Cmp1 = getOpcodeDef<GFCmp>(LHS, MRI);
  if (!Cmp1)
    return false;

  // We need a compare on the RHS register.
  GFCmp *Cmp2 = getOpcodeDef<GFCmp>(RHS, MRI);
  if (!Cmp2)
    return false;

  LLT CmpTy = MRI.getType(Cmp1->getReg(0));
  LLT CmpOperandTy = MRI.getType(Cmp1->getLHSReg());

  // We build one fcmp, want to fold the fcmps, replace the logic op,
  // and the fcmps must have the same shape.
  if (!isLegalOrBeforeLegalizer(
          {TargetOpcode::G_FCMP, {CmpTy, CmpOperandTy}}) ||
      !MRI.hasOneNonDBGUse(Logic->getReg(0)) ||
      !MRI.hasOneNonDBGUse(Cmp1->getReg(0)) ||
      !MRI.hasOneNonDBGUse(Cmp2->getReg(0)) ||
      MRI.getType(Cmp1->getLHSReg()) != MRI.getType(Cmp2->getLHSReg()))
    return false;

  CmpInst::Predicate PredL = Cmp1->getCond();
  CmpInst::Predicate PredR = Cmp2->getCond();
  Register LHS0 = Cmp1->getLHSReg();
  Register LHS1 = Cmp1->getRHSReg();
  Register RHS0 = Cmp2->getLHSReg();
  Register RHS1 = Cmp2->getRHSReg();

  if (LHS0 == RHS1 && LHS1 == RHS0) {
    // Swap RHS operands to match LHS.
    PredR = CmpInst::getSwappedPredicate(PredR);
    std::swap(RHS0, RHS1);
  }

  if (LHS0 == RHS0 && LHS1 == RHS1) {
    // We determine the new predicate.
    unsigned CmpCodeL = getFCmpCode(PredL);
    unsigned CmpCodeR = getFCmpCode(PredR);
    unsigned NewPred = IsAnd ? CmpCodeL & CmpCodeR : CmpCodeL | CmpCodeR;
    unsigned Flags = Cmp1->getFlags() | Cmp2->getFlags();
    MatchInfo = [=](MachineIRBuilder &B) {
      // The fcmp predicates fill the lower part of the enum.
      FCmpInst::Predicate Pred = static_cast<FCmpInst::Predicate>(NewPred);
      if (Pred == FCmpInst::FCMP_FALSE &&
          isConstantLegalOrBeforeLegalizer(CmpTy)) {
        auto False = B.buildConstant(CmpTy, 0);
        B.buildZExtOrTrunc(DestReg, False);
      } else if (Pred == FCmpInst::FCMP_TRUE &&
                 isConstantLegalOrBeforeLegalizer(CmpTy)) {
        auto True =
            B.buildConstant(CmpTy, getICmpTrueVal(getTargetLowering(),
                                                  CmpTy.isVector() /*isVector*/,
                                                  true /*isFP*/));
        B.buildZExtOrTrunc(DestReg, True);
      } else { // We take the predicate without predicate optimizations.
        auto Cmp = B.buildFCmp(Pred, CmpTy, LHS0, LHS1, Flags);
        B.buildZExtOrTrunc(DestReg, Cmp);
      }
    };
    return true;
  }

  return false;
}

bool CombinerHelper::matchAnd(MachineInstr &MI, BuildFnTy &MatchInfo) const {
  GAnd *And = cast<GAnd>(&MI);

  if (tryFoldAndOrOrICmpsUsingRanges(And, MatchInfo))
    return true;

  if (tryFoldLogicOfFCmps(And, MatchInfo))
    return true;

  return false;
}

bool CombinerHelper::matchOr(MachineInstr &MI, BuildFnTy &MatchInfo) const {
  GOr *Or = cast<GOr>(&MI);

  if (tryFoldAndOrOrICmpsUsingRanges(Or, MatchInfo))
    return true;

  if (tryFoldLogicOfFCmps(Or, MatchInfo))
    return true;

  return false;
}

bool CombinerHelper::matchAddOverflow(MachineInstr &MI,
                                      BuildFnTy &MatchInfo) const {
  GAddCarryOut *Add = cast<GAddCarryOut>(&MI);

  // Addo has no flags
  Register Dst = Add->getReg(0);
  Register Carry = Add->getReg(1);
  Register LHS = Add->getLHSReg();
  Register RHS = Add->getRHSReg();
  bool IsSigned = Add->isSigned();
  LLT DstTy = MRI.getType(Dst);
  LLT CarryTy = MRI.getType(Carry);

  // Fold addo, if the carry is dead -> add, undef.
  if (MRI.use_nodbg_empty(Carry) &&
      isLegalOrBeforeLegalizer({TargetOpcode::G_ADD, {DstTy}})) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.buildAdd(Dst, LHS, RHS);
      B.buildUndef(Carry);
    };
    return true;
  }

  // Canonicalize constant to RHS.
  if (isConstantOrConstantVectorI(LHS) && !isConstantOrConstantVectorI(RHS)) {
    if (IsSigned) {
      MatchInfo = [=](MachineIRBuilder &B) {
        B.buildSAddo(Dst, Carry, RHS, LHS);
      };
      return true;
    }
    // !IsSigned
    MatchInfo = [=](MachineIRBuilder &B) {
      B.buildUAddo(Dst, Carry, RHS, LHS);
    };
    return true;
  }

  std::optional<APInt> MaybeLHS = getConstantOrConstantSplatVector(LHS);
  std::optional<APInt> MaybeRHS = getConstantOrConstantSplatVector(RHS);

  // Fold addo(c1, c2) -> c3, carry.
  if (MaybeLHS && MaybeRHS && isConstantLegalOrBeforeLegalizer(DstTy) &&
      isConstantLegalOrBeforeLegalizer(CarryTy)) {
    bool Overflow;
    APInt Result = IsSigned ? MaybeLHS->sadd_ov(*MaybeRHS, Overflow)
                            : MaybeLHS->uadd_ov(*MaybeRHS, Overflow);
    MatchInfo = [=](MachineIRBuilder &B) {
      B.buildConstant(Dst, Result);
      B.buildConstant(Carry, Overflow);
    };
    return true;
  }

  // Fold (addo x, 0) -> x, no carry
  if (MaybeRHS && *MaybeRHS == 0 && isConstantLegalOrBeforeLegalizer(CarryTy)) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.buildCopy(Dst, LHS);
      B.buildConstant(Carry, 0);
    };
    return true;
  }

  // Given 2 constant operands whose sum does not overflow:
  // uaddo (X +nuw C0), C1 -> uaddo X, C0 + C1
  // saddo (X +nsw C0), C1 -> saddo X, C0 + C1
  GAdd *AddLHS = getOpcodeDef<GAdd>(LHS, MRI);
  if (MaybeRHS && AddLHS && MRI.hasOneNonDBGUse(Add->getReg(0)) &&
      ((IsSigned && AddLHS->getFlag(MachineInstr::MIFlag::NoSWrap)) ||
       (!IsSigned && AddLHS->getFlag(MachineInstr::MIFlag::NoUWrap)))) {
    std::optional<APInt> MaybeAddRHS =
        getConstantOrConstantSplatVector(AddLHS->getRHSReg());
    if (MaybeAddRHS) {
      bool Overflow;
      APInt NewC = IsSigned ? MaybeAddRHS->sadd_ov(*MaybeRHS, Overflow)
                            : MaybeAddRHS->uadd_ov(*MaybeRHS, Overflow);
      if (!Overflow && isConstantLegalOrBeforeLegalizer(DstTy)) {
        if (IsSigned) {
          MatchInfo = [=](MachineIRBuilder &B) {
            auto ConstRHS = B.buildConstant(DstTy, NewC);
            B.buildSAddo(Dst, Carry, AddLHS->getLHSReg(), ConstRHS);
          };
          return true;
        }
        // !IsSigned
        MatchInfo = [=](MachineIRBuilder &B) {
          auto ConstRHS = B.buildConstant(DstTy, NewC);
          B.buildUAddo(Dst, Carry, AddLHS->getLHSReg(), ConstRHS);
        };
        return true;
      }
    }
  };

  // We try to combine addo to non-overflowing add.
  if (!isLegalOrBeforeLegalizer({TargetOpcode::G_ADD, {DstTy}}) ||
      !isConstantLegalOrBeforeLegalizer(CarryTy))
    return false;

  // We try to combine uaddo to non-overflowing add.
  if (!IsSigned) {
    ConstantRange CRLHS =
        ConstantRange::fromKnownBits(VT->getKnownBits(LHS), /*IsSigned=*/false);
    ConstantRange CRRHS =
        ConstantRange::fromKnownBits(VT->getKnownBits(RHS), /*IsSigned=*/false);

    switch (CRLHS.unsignedAddMayOverflow(CRRHS)) {
    case ConstantRange::OverflowResult::MayOverflow:
      return false;
    case ConstantRange::OverflowResult::NeverOverflows: {
      MatchInfo = [=](MachineIRBuilder &B) {
        B.buildAdd(Dst, LHS, RHS, MachineInstr::MIFlag::NoUWrap);
        B.buildConstant(Carry, 0);
      };
      return true;
    }
    case ConstantRange::OverflowResult::AlwaysOverflowsLow:
    case ConstantRange::OverflowResult::AlwaysOverflowsHigh: {
      MatchInfo = [=](MachineIRBuilder &B) {
        B.buildAdd(Dst, LHS, RHS);
        B.buildConstant(Carry, 1);
      };
      return true;
    }
    }
    return false;
  }

  // We try to combine saddo to non-overflowing add.

  // If LHS and RHS each have at least two sign bits, then there is no signed
  // overflow.
  if (VT->computeNumSignBits(RHS) > 1 && VT->computeNumSignBits(LHS) > 1) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.buildAdd(Dst, LHS, RHS, MachineInstr::MIFlag::NoSWrap);
      B.buildConstant(Carry, 0);
    };
    return true;
  }

  ConstantRange CRLHS =
      ConstantRange::fromKnownBits(VT->getKnownBits(LHS), /*IsSigned=*/true);
  ConstantRange CRRHS =
      ConstantRange::fromKnownBits(VT->getKnownBits(RHS), /*IsSigned=*/true);

  switch (CRLHS.signedAddMayOverflow(CRRHS)) {
  case ConstantRange::OverflowResult::MayOverflow:
    return false;
  case ConstantRange::OverflowResult::NeverOverflows: {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.buildAdd(Dst, LHS, RHS, MachineInstr::MIFlag::NoSWrap);
      B.buildConstant(Carry, 0);
    };
    return true;
  }
  case ConstantRange::OverflowResult::AlwaysOverflowsLow:
  case ConstantRange::OverflowResult::AlwaysOverflowsHigh: {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.buildAdd(Dst, LHS, RHS);
      B.buildConstant(Carry, 1);
    };
    return true;
  }
  }

  return false;
}

void CombinerHelper::applyBuildFnMO(const MachineOperand &MO,
                                    BuildFnTy &MatchInfo) const {
  MachineInstr *Root = getDefIgnoringCopies(MO.getReg(), MRI);
  MatchInfo(Builder);
  Root->eraseFromParent();
}

bool CombinerHelper::matchFPowIExpansion(MachineInstr &MI,
                                         int64_t Exponent) const {
  bool OptForSize = MI.getMF()->getFunction().hasOptSize();
  return getTargetLowering().isBeneficialToExpandPowI(Exponent, OptForSize);
}

void CombinerHelper::applyExpandFPowI(MachineInstr &MI,
                                      int64_t Exponent) const {
  auto [Dst, Base] = MI.getFirst2Regs();
  LLT Ty = MRI.getType(Dst);
  int64_t ExpVal = Exponent;

  if (ExpVal == 0) {
    Builder.buildFConstant(Dst, 1.0);
    MI.removeFromParent();
    return;
  }

  if (ExpVal < 0)
    ExpVal = -ExpVal;

  // We use the simple binary decomposition method from SelectionDAG ExpandPowI
  // to generate the multiply sequence. There are more optimal ways to do this
  // (for example, powi(x,15) generates one more multiply than it should), but
  // this has the benefit of being both really simple and much better than a
  // libcall.
  std::optional<SrcOp> Res;
  SrcOp CurSquare = Base;
  while (ExpVal > 0) {
    if (ExpVal & 1) {
      if (!Res)
        Res = CurSquare;
      else
        Res = Builder.buildFMul(Ty, *Res, CurSquare);
    }

    CurSquare = Builder.buildFMul(Ty, CurSquare, CurSquare);
    ExpVal >>= 1;
  }

  // If the original exponent was negative, invert the result, producing
  // 1/(x*x*x).
  if (Exponent < 0)
    Res = Builder.buildFDiv(Ty, Builder.buildFConstant(Ty, 1.0), *Res,
                            MI.getFlags());

  Builder.buildCopy(Dst, *Res);
  MI.eraseFromParent();
}

bool CombinerHelper::matchFoldAPlusC1MinusC2(const MachineInstr &MI,
                                             BuildFnTy &MatchInfo) const {
  // fold (A+C1)-C2 -> A+(C1-C2)
  const GSub *Sub = cast<GSub>(&MI);
  Register A, C1Reg;
  if (!mi_match(Sub->getLHSReg(), MRI, m_GAdd(m_Reg(A), m_Reg(C1Reg))))
    return false;

  if (!MRI.hasOneNonDBGUse(Sub->getLHSReg()))
    return false;

  APInt C2 = getIConstantFromReg(Sub->getRHSReg(), MRI);
  APInt C1 = getIConstantFromReg(C1Reg, MRI);

  Register Dst = Sub->getReg(0);
  LLT DstTy = MRI.getType(Dst);

  MatchInfo = [=](MachineIRBuilder &B) {
    auto Const = B.buildConstant(DstTy, C1 - C2);
    B.buildAdd(Dst, A, Const);
  };

  return true;
}

bool CombinerHelper::matchFoldC2MinusAPlusC1(const MachineInstr &MI,
                                             BuildFnTy &MatchInfo) const {
  // fold C2-(A+C1) -> (C2-C1)-A
  const GSub *Sub = cast<GSub>(&MI);
  Register A, C1Reg;
  if (!mi_match(Sub->getRHSReg(), MRI, m_GAdd(m_Reg(A), m_Reg(C1Reg))))
    return false;

  if (!MRI.hasOneNonDBGUse(Sub->getRHSReg()))
    return false;

  APInt C2 = getIConstantFromReg(Sub->getLHSReg(), MRI);
  APInt C1 = getIConstantFromReg(C1Reg, MRI);

  Register Dst = Sub->getReg(0);
  LLT DstTy = MRI.getType(Dst);

  MatchInfo = [=](MachineIRBuilder &B) {
    auto Const = B.buildConstant(DstTy, C2 - C1);
    B.buildSub(Dst, Const, A);
  };

  return true;
}

bool CombinerHelper::matchFoldAMinusC1MinusC2(const MachineInstr &MI,
                                              BuildFnTy &MatchInfo) const {
  // fold (A-C1)-C2 -> A-(C1+C2)
  const GSub *Sub1 = cast<GSub>(&MI);
  Register A, C1Reg;
  if (!mi_match(Sub1->getLHSReg(), MRI, m_GSub(m_Reg(A), m_Reg(C1Reg))))
    return false;

  if (!MRI.hasOneNonDBGUse(Sub1->getLHSReg()))
    return false;

  APInt C2 = getIConstantFromReg(Sub1->getRHSReg(), MRI);
  APInt C1 = getIConstantFromReg(C1Reg, MRI);

  Register Dst = Sub1->getReg(0);
  LLT DstTy = MRI.getType(Dst);

  MatchInfo = [=](MachineIRBuilder &B) {
    auto Const = B.buildConstant(DstTy, C1 + C2);
    B.buildSub(Dst, A, Const);
  };

  return true;
}

bool CombinerHelper::matchFoldC1Minus2MinusC2(const MachineInstr &MI,
                                              BuildFnTy &MatchInfo) const {
  // fold (C1-A)-C2 -> (C1-C2)-A
  const GSub *Sub1 = cast<GSub>(&MI);
  Register C1Reg, A;
  if (!mi_match(Sub1->getLHSReg(), MRI, m_GSub(m_Reg(C1Reg), m_Reg(A))))
    return false;

  if (!MRI.hasOneNonDBGUse(Sub1->getLHSReg()))
    return false;

  APInt C2 = getIConstantFromReg(Sub1->getRHSReg(), MRI);
  APInt C1 = getIConstantFromReg(C1Reg, MRI);

  Register Dst = Sub1->getReg(0);
  LLT DstTy = MRI.getType(Dst);

  MatchInfo = [=](MachineIRBuilder &B) {
    auto Const = B.buildConstant(DstTy, C1 - C2);
    B.buildSub(Dst, Const, A);
  };

  return true;
}

bool CombinerHelper::matchFoldAMinusC1PlusC2(const MachineInstr &MI,
                                             BuildFnTy &MatchInfo) const {
  // fold ((A-C1)+C2) -> (A+(C2-C1))
  const GAdd *Add = cast<GAdd>(&MI);
  Register A, C1Reg;
  if (!mi_match(Add->getLHSReg(), MRI, m_GSub(m_Reg(A), m_Reg(C1Reg))))
    return false;

  if (!MRI.hasOneNonDBGUse(Add->getLHSReg()))
    return false;

  APInt C2 = getIConstantFromReg(Add->getRHSReg(), MRI);
  APInt C1 = getIConstantFromReg(C1Reg, MRI);

  Register Dst = Add->getReg(0);
  LLT DstTy = MRI.getType(Dst);

  MatchInfo = [=](MachineIRBuilder &B) {
    auto Const = B.buildConstant(DstTy, C2 - C1);
    B.buildAdd(Dst, A, Const);
  };

  return true;
}

bool CombinerHelper::matchUnmergeValuesAnyExtBuildVector(
    const MachineInstr &MI, BuildFnTy &MatchInfo) const {
  const GUnmerge *Unmerge = cast<GUnmerge>(&MI);

  if (!MRI.hasOneNonDBGUse(Unmerge->getSourceReg()))
    return false;

  LLT DstTy = MRI.getType(Unmerge->getReg(0));

  // $bv:_(<8 x s8>) = G_BUILD_VECTOR ....
  // $any:_(<8 x s16>) = G_ANYEXT $bv
  // $uv:_(<4 x s16>), $uv1:_(<4 x s16>) = G_UNMERGE_VALUES $any
  //
  // ->
  //
  // $any:_(s16) = G_ANYEXT $bv[0]
  // $any1:_(s16) = G_ANYEXT $bv[1]
  // $any2:_(s16) = G_ANYEXT $bv[2]
  // $any3:_(s16) = G_ANYEXT $bv[3]
  // $any4:_(s16) = G_ANYEXT $bv[4]
  // $any5:_(s16) = G_ANYEXT $bv[5]
  // $any6:_(s16) = G_ANYEXT $bv[6]
  // $any7:_(s16) = G_ANYEXT $bv[7]
  // $uv:_(<4 x s16>) = G_BUILD_VECTOR $any, $any1, $any2, $any3
  // $uv1:_(<4 x s16>) = G_BUILD_VECTOR $any4, $any5, $any6, $any7

  // We want to unmerge into vectors.
  if (!DstTy.isFixedVector())
    return false;

  Register AnySrcReg;
  if (!mi_match(Unmerge->getSourceReg(), MRI, m_GAnyExt(m_Reg(AnySrcReg))))
    return false;

  GBuildVector *BV;
  if (mi_match(AnySrcReg, MRI, m_GBuildVector(BV))) {
    // G_UNMERGE_VALUES G_ANYEXT G_BUILD_VECTOR

    if (!MRI.hasOneNonDBGUse(BV->getReg(0)))
      return false;

    // FIXME: check element types?
    if (BV->getNumSources() % Unmerge->getNumDefs() != 0)
      return false;

    LLT BigBvTy = MRI.getType(BV->getReg(0));
    LLT SmallBvTy = DstTy;
    LLT SmallBvElemenTy = SmallBvTy.getElementType();

    if (!isLegalOrBeforeLegalizer(
            {TargetOpcode::G_BUILD_VECTOR, {SmallBvTy, SmallBvElemenTy}}))
      return false;

    // We check the legality of scalar anyext.
    if (!isLegalOrBeforeLegalizer(
            {TargetOpcode::G_ANYEXT,
             {SmallBvElemenTy, BigBvTy.getElementType()}}))
      return false;

    MatchInfo = [=](MachineIRBuilder &B) {
      // Build into each G_UNMERGE_VALUES def
      // a small build vector with anyext from the source build vector.
      for (unsigned I = 0; I < Unmerge->getNumDefs(); ++I) {
        SmallVector<Register> Ops;
        for (unsigned J = 0; J < SmallBvTy.getNumElements(); ++J) {
          Register SourceArray =
              BV->getSourceReg(I * SmallBvTy.getNumElements() + J);
          auto AnyExt = B.buildAnyExt(SmallBvElemenTy, SourceArray);
          Ops.push_back(AnyExt.getReg(0));
        }
        B.buildBuildVector(Unmerge->getOperand(I).getReg(), Ops);
      };
    };
    return true;
  };

  return false;
}

bool CombinerHelper::matchShuffleUndefRHS(MachineInstr &MI,
                                          BuildFnTy &MatchInfo) const {

  bool Changed = false;
  auto &Shuffle = cast<GShuffleVector>(MI);
  ArrayRef<int> OrigMask = Shuffle.getMask();
  SmallVector<int, 16> NewMask;
  const LLT SrcTy = MRI.getType(Shuffle.getSrc1Reg());
  const unsigned NumSrcElems = SrcTy.isVector() ? SrcTy.getNumElements() : 1;
  const unsigned NumDstElts = OrigMask.size();
  for (unsigned i = 0; i != NumDstElts; ++i) {
    int Idx = OrigMask[i];
    if (Idx >= (int)NumSrcElems) {
      Idx = -1;
      Changed = true;
    }
    NewMask.push_back(Idx);
  }

  if (!Changed)
    return false;

  MatchInfo = [&, NewMask = std::move(NewMask)](MachineIRBuilder &B) {
    B.buildShuffleVector(MI.getOperand(0), MI.getOperand(1), MI.getOperand(2),
                         std::move(NewMask));
  };

  return true;
}

static void commuteMask(MutableArrayRef<int> Mask, const unsigned NumElems) {
  const unsigned MaskSize = Mask.size();
  for (unsigned I = 0; I < MaskSize; ++I) {
    int Idx = Mask[I];
    if (Idx < 0)
      continue;

    if (Idx < (int)NumElems)
      Mask[I] = Idx + NumElems;
    else
      Mask[I] = Idx - NumElems;
  }
}

bool CombinerHelper::matchShuffleDisjointMask(MachineInstr &MI,
                                              BuildFnTy &MatchInfo) const {

  auto &Shuffle = cast<GShuffleVector>(MI);
  // If any of the two inputs is already undef, don't check the mask again to
  // prevent infinite loop
  if (getOpcodeDef(TargetOpcode::G_IMPLICIT_DEF, Shuffle.getSrc1Reg(), MRI))
    return false;

  if (getOpcodeDef(TargetOpcode::G_IMPLICIT_DEF, Shuffle.getSrc2Reg(), MRI))
    return false;

  const LLT DstTy = MRI.getType(Shuffle.getReg(0));
  const LLT Src1Ty = MRI.getType(Shuffle.getSrc1Reg());
  if (!isLegalOrBeforeLegalizer(
          {TargetOpcode::G_SHUFFLE_VECTOR, {DstTy, Src1Ty}}))
    return false;

  ArrayRef<int> Mask = Shuffle.getMask();
  const unsigned NumSrcElems = Src1Ty.getNumElements();

  bool TouchesSrc1 = false;
  bool TouchesSrc2 = false;
  const unsigned NumElems = Mask.size();
  for (unsigned Idx = 0; Idx < NumElems; ++Idx) {
    if (Mask[Idx] < 0)
      continue;

    if (Mask[Idx] < (int)NumSrcElems)
      TouchesSrc1 = true;
    else
      TouchesSrc2 = true;
  }

  if (TouchesSrc1 == TouchesSrc2)
    return false;

  Register NewSrc1 = Shuffle.getSrc1Reg();
  SmallVector<int, 16> NewMask(Mask);
  if (TouchesSrc2) {
    NewSrc1 = Shuffle.getSrc2Reg();
    commuteMask(NewMask, NumSrcElems);
  }

  MatchInfo = [=, &Shuffle](MachineIRBuilder &B) {
    auto Undef = B.buildUndef(Src1Ty);
    B.buildShuffleVector(Shuffle.getReg(0), NewSrc1, Undef, NewMask);
  };

  return true;
}

bool CombinerHelper::matchSuboCarryOut(const MachineInstr &MI,
                                       BuildFnTy &MatchInfo) const {
  const GSubCarryOut *Subo = cast<GSubCarryOut>(&MI);

  Register Dst = Subo->getReg(0);
  Register LHS = Subo->getLHSReg();
  Register RHS = Subo->getRHSReg();
  Register Carry = Subo->getCarryOutReg();
  LLT DstTy = MRI.getType(Dst);
  LLT CarryTy = MRI.getType(Carry);

  // Check legality before known bits.
  if (!isLegalOrBeforeLegalizer({TargetOpcode::G_SUB, {DstTy}}) ||
      !isConstantLegalOrBeforeLegalizer(CarryTy))
    return false;

  ConstantRange KBLHS =
      ConstantRange::fromKnownBits(VT->getKnownBits(LHS),
                                   /* IsSigned=*/Subo->isSigned());
  ConstantRange KBRHS =
      ConstantRange::fromKnownBits(VT->getKnownBits(RHS),
                                   /* IsSigned=*/Subo->isSigned());

  if (Subo->isSigned()) {
    // G_SSUBO
    switch (KBLHS.signedSubMayOverflow(KBRHS)) {
    case ConstantRange::OverflowResult::MayOverflow:
      return false;
    case ConstantRange::OverflowResult::NeverOverflows: {
      MatchInfo = [=](MachineIRBuilder &B) {
        B.buildSub(Dst, LHS, RHS, MachineInstr::MIFlag::NoSWrap);
        B.buildConstant(Carry, 0);
      };
      return true;
    }
    case ConstantRange::OverflowResult::AlwaysOverflowsLow:
    case ConstantRange::OverflowResult::AlwaysOverflowsHigh: {
      MatchInfo = [=](MachineIRBuilder &B) {
        B.buildSub(Dst, LHS, RHS);
        B.buildConstant(Carry, getICmpTrueVal(getTargetLowering(),
                                              /*isVector=*/CarryTy.isVector(),
                                              /*isFP=*/false));
      };
      return true;
    }
    }
    return false;
  }

  // G_USUBO
  switch (KBLHS.unsignedSubMayOverflow(KBRHS)) {
  case ConstantRange::OverflowResult::MayOverflow:
    return false;
  case ConstantRange::OverflowResult::NeverOverflows: {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.buildSub(Dst, LHS, RHS, MachineInstr::MIFlag::NoUWrap);
      B.buildConstant(Carry, 0);
    };
    return true;
  }
  case ConstantRange::OverflowResult::AlwaysOverflowsLow:
  case ConstantRange::OverflowResult::AlwaysOverflowsHigh: {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.buildSub(Dst, LHS, RHS);
      B.buildConstant(Carry, getICmpTrueVal(getTargetLowering(),
                                            /*isVector=*/CarryTy.isVector(),
                                            /*isFP=*/false));
    };
    return true;
  }
  }

  return false;
}

// Fold (ctlz (xor x, (sra x, bitwidth-1))) -> (add (ctls x), 1).
// Fold (ctlz (or (shl (xor x, (sra x, bitwidth-1)), 1), 1) -> (ctls x)
bool CombinerHelper::matchCtls(MachineInstr &CtlzMI,
                               BuildFnTy &MatchInfo) const {
  assert((CtlzMI.getOpcode() == TargetOpcode::G_CTLZ ||
          CtlzMI.getOpcode() == TargetOpcode::G_CTLZ_ZERO_POISON) &&
         "Expected G_CTLZ variant");

  const Register Dst = CtlzMI.getOperand(0).getReg();
  Register Src = CtlzMI.getOperand(1).getReg();

  LLT Ty = MRI.getType(Dst);
  LLT SrcTy = MRI.getType(Src);

  if (!(Ty.isValid() && Ty.isScalar()))
    return false;

  if (!LI)
    return false;

  SmallVector<LLT, 2> QueryTypes = {Ty, SrcTy};
  LegalityQuery Query(TargetOpcode::G_CTLS, QueryTypes);

  switch (LI->getAction(Query).Action) {
  default:
    return false;
  case LegalizeActions::Legal:
  case LegalizeActions::Custom:
  case LegalizeActions::WidenScalar:
    break;
  }

  //  Src = or(shl(V, 1), 1) -> Src=V; NeedAdd = False
  Register V;
  bool NeedAdd = true;
  if (mi_match(Src, MRI,
               m_OneUse(m_GOr(m_OneUse(m_GShl(m_Reg(V), m_SpecificICst(1))),
                              m_SpecificICst(1))))) {
    NeedAdd = false;
    Src = V;
  }

  unsigned BitWidth = Ty.getScalarSizeInBits();

  Register X;
  if (!mi_match(Src, MRI,
                m_OneUse(m_GXor(m_Reg(X), m_OneUse(m_GAShr(
                                              m_DeferredReg(X),
                                              m_SpecificICst(BitWidth - 1)))))))
    return false;

  MatchInfo = [=](MachineIRBuilder &B) {
    if (!NeedAdd) {
      B.buildCTLS(Dst, X);
      return;
    }

    auto Ctls = B.buildCTLS(Ty, X);
    auto One = B.buildConstant(Ty, 1);

    B.buildAdd(Dst, Ctls, One);
  };

  return true;
}

// Fold shr ( add ( ext X, ext Y ), 1 ) -> avgfloor ( x, y )
// Fold shr ( add ( ext X, ext Y, 1 ), 1 ) -> avgceil ( x, y )
bool CombinerHelper::matchAVG(MachineInstr &MI, MachineRegisterInfo &MRI,
                              Register X, Register Y,
                              unsigned TargetOpc) const {
  assert((MI.getOpcode() == TargetOpcode::G_LSHR ||
          MI.getOpcode() == TargetOpcode::G_ASHR) &&
         "Expected G_LSHR/G_ASHR");

  LLT XTy = MRI.getType(X);
  return XTy == MRI.getType(Y) && isLegal({TargetOpc, {XTy}});
}

static unsigned getCountZeroPoisonOpcode(const MachineInstr &MI) {
  assert((MI.getOpcode() == TargetOpcode::G_CTLZ ||
          MI.getOpcode() == TargetOpcode::G_CTTZ) &&
         "Expected count-zero opcode");
  switch (MI.getOpcode()) {
  case TargetOpcode::G_CTLZ:
    return TargetOpcode::G_CTLZ_ZERO_POISON;
  case TargetOpcode::G_CTTZ:
    return TargetOpcode::G_CTTZ_ZERO_POISON;
  default:
    llvm_unreachable("Unexpected count-zero opcode");
  }
}

bool CombinerHelper::matchCountZeroToZeroPoison(MachineInstr &MI) const {
  if (!VT)
    return false;

  unsigned ZPOpc = getCountZeroPoisonOpcode(MI);
  Register Src = MI.getOperand(1).getReg();
  if (!VT->isKnownNeverZero(Src))
    return false;

  LLT DstTy = MRI.getType(MI.getOperand(0).getReg());
  LLT SrcTy = MRI.getType(Src);
  return isLegalOrBeforeLegalizer({ZPOpc, {DstTy, SrcTy}});
}

void CombinerHelper::applyCountZeroToZeroPoison(MachineInstr &MI) const {
  replaceOpcodeWith(MI, getCountZeroPoisonOpcode(MI));
}