AArch64RegisterBankInfo.cpp

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//===- AArch64RegisterBankInfo.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
//
//===----------------------------------------------------------------------===//
/// \file
/// This file implements the targeting of the RegisterBankInfo class for
/// AArch64.
/// \todo This should be generated by TableGen.
//===----------------------------------------------------------------------===//
 
#include "AArch64RegisterBankInfo.h"
#include "AArch64RegisterInfo.h"
#include "AArch64Subtarget.h"
#include "MCTargetDesc/AArch64MCTargetDesc.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/GlobalISel/GenericMachineInstrs.h"
#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
#include "llvm/CodeGen/GlobalISel/Utils.h"
#include "llvm/CodeGen/LowLevelTypeUtils.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterBank.h"
#include "llvm/CodeGen/RegisterBankInfo.h"
#include "llvm/CodeGen/TargetOpcodes.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/IntrinsicsAArch64.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Threading.h"
#include <cassert>
 
#define GET_TARGET_REGBANK_IMPL
#include "AArch64GenRegisterBank.inc"
 
// This file will be TableGen'ed at some point.
#include "AArch64GenRegisterBankInfo.def"
 
using namespace llvm;
static const unsigned CustomMappingID = 1;
 
AArch64RegisterBankInfo::AArch64RegisterBankInfo(
    const TargetRegisterInfo &TRI) {
  static llvm::once_flag InitializeRegisterBankFlag;
 
  static auto InitializeRegisterBankOnce = [&]() {
    // We have only one set of register banks, whatever the subtarget
    // is. Therefore, the initialization of the RegBanks table should be
    // done only once. Indeed the table of all register banks
    // (AArch64::RegBanks) is unique in the compiler. At some point, it
    // will get tablegen'ed and the whole constructor becomes empty.
 
    const RegisterBank &RBGPR = getRegBank(AArch64::GPRRegBankID);
    (void)RBGPR;
    assert(&AArch64::GPRRegBank == &RBGPR &&
           "The order in RegBanks is messed up");
 
    const RegisterBank &RBFPR = getRegBank(AArch64::FPRRegBankID);
    (void)RBFPR;
    assert(&AArch64::FPRRegBank == &RBFPR &&
           "The order in RegBanks is messed up");
 
    const RegisterBank &RBCCR = getRegBank(AArch64::CCRegBankID);
    (void)RBCCR;
    assert(&AArch64::CCRegBank == &RBCCR &&
           "The order in RegBanks is messed up");
 
    // The GPR register bank is fully defined by all the registers in
    // GR64all + its subclasses.
    assert(RBGPR.covers(*TRI.getRegClass(AArch64::GPR32RegClassID)) &&
           "Subclass not added?");
    assert(getMaximumSize(RBGPR.getID()) == 128 &&
           "GPRs should hold up to 128-bit");
 
    // The FPR register bank is fully defined by all the registers in
    // GR64all + its subclasses.
    assert(RBFPR.covers(*TRI.getRegClass(AArch64::QQRegClassID)) &&
           "Subclass not added?");
    assert(RBFPR.covers(*TRI.getRegClass(AArch64::FPR64RegClassID)) &&
           "Subclass not added?");
    assert(getMaximumSize(RBFPR.getID()) == 512 &&
           "FPRs should hold up to 512-bit via QQQQ sequence");
 
    assert(RBCCR.covers(*TRI.getRegClass(AArch64::CCRRegClassID)) &&
           "Class not added?");
    assert(getMaximumSize(RBCCR.getID()) == 32 &&
           "CCR should hold up to 32-bit");
 
    // Check that the TableGen'ed like file is in sync we our expectations.
    // First, the Idx.
    assert(checkPartialMappingIdx(PMI_FirstGPR, PMI_LastGPR,
                                  {PMI_GPR32, PMI_GPR64, PMI_GPR128}) &&
           "PartialMappingIdx's are incorrectly ordered");
    assert(checkPartialMappingIdx(PMI_FirstFPR, PMI_LastFPR,
                                  {PMI_FPR16, PMI_FPR32, PMI_FPR64, PMI_FPR128,
                                   PMI_FPR256, PMI_FPR512}) &&
           "PartialMappingIdx's are incorrectly ordered");
// Now, the content.
// Check partial mapping.
#define CHECK_PARTIALMAP(Idx, ValStartIdx, ValLength, RB)                      \
  do {                                                                         \
    assert(                                                                    \
        checkPartialMap(PartialMappingIdx::Idx, ValStartIdx, ValLength, RB) && \
        #Idx " is incorrectly initialized");                                   \
  } while (false)
 
    CHECK_PARTIALMAP(PMI_GPR32, 0, 32, RBGPR);
    CHECK_PARTIALMAP(PMI_GPR64, 0, 64, RBGPR);
    CHECK_PARTIALMAP(PMI_GPR128, 0, 128, RBGPR);
    CHECK_PARTIALMAP(PMI_FPR16, 0, 16, RBFPR);
    CHECK_PARTIALMAP(PMI_FPR32, 0, 32, RBFPR);
    CHECK_PARTIALMAP(PMI_FPR64, 0, 64, RBFPR);
    CHECK_PARTIALMAP(PMI_FPR128, 0, 128, RBFPR);
    CHECK_PARTIALMAP(PMI_FPR256, 0, 256, RBFPR);
    CHECK_PARTIALMAP(PMI_FPR512, 0, 512, RBFPR);
 
// Check value mapping.
#define CHECK_VALUEMAP_IMPL(RBName, Size, Offset)                              \
  do {                                                                         \
    assert(checkValueMapImpl(PartialMappingIdx::PMI_##RBName##Size,            \
                             PartialMappingIdx::PMI_First##RBName, Size,       \
                             Offset) &&                                        \
           #RBName #Size " " #Offset " is incorrectly initialized");           \
  } while (false)
 
#define CHECK_VALUEMAP(RBName, Size) CHECK_VALUEMAP_IMPL(RBName, Size, 0)
 
    CHECK_VALUEMAP(GPR, 32);
    CHECK_VALUEMAP(GPR, 64);
    CHECK_VALUEMAP(GPR, 128);
    CHECK_VALUEMAP(FPR, 16);
    CHECK_VALUEMAP(FPR, 32);
    CHECK_VALUEMAP(FPR, 64);
    CHECK_VALUEMAP(FPR, 128);
    CHECK_VALUEMAP(FPR, 256);
    CHECK_VALUEMAP(FPR, 512);
 
// Check the value mapping for 3-operands instructions where all the operands
// map to the same value mapping.
#define CHECK_VALUEMAP_3OPS(RBName, Size)                                      \
  do {                                                                         \
    CHECK_VALUEMAP_IMPL(RBName, Size, 0);                                      \
    CHECK_VALUEMAP_IMPL(RBName, Size, 1);                                      \
    CHECK_VALUEMAP_IMPL(RBName, Size, 2);                                      \
  } while (false)
 
    CHECK_VALUEMAP_3OPS(GPR, 32);
    CHECK_VALUEMAP_3OPS(GPR, 64);
    CHECK_VALUEMAP_3OPS(GPR, 128);
    CHECK_VALUEMAP_3OPS(FPR, 32);
    CHECK_VALUEMAP_3OPS(FPR, 64);
    CHECK_VALUEMAP_3OPS(FPR, 128);
    CHECK_VALUEMAP_3OPS(FPR, 256);
    CHECK_VALUEMAP_3OPS(FPR, 512);
 
#define CHECK_VALUEMAP_CROSSREGCPY(RBNameDst, RBNameSrc, Size)                 \
  do {                                                                         \
    unsigned PartialMapDstIdx = PMI_##RBNameDst##Size - PMI_Min;               \
    unsigned PartialMapSrcIdx = PMI_##RBNameSrc##Size - PMI_Min;               \
    (void)PartialMapDstIdx;                                                    \
    (void)PartialMapSrcIdx;                                                    \
    const ValueMapping *Map = getCopyMapping(AArch64::RBNameDst##RegBankID,    \
                                             AArch64::RBNameSrc##RegBankID,    \
                                             TypeSize::getFixed(Size));        \
    (void)Map;                                                                 \
    assert(Map[0].BreakDown ==                                                 \
               &AArch64GenRegisterBankInfo::PartMappings[PartialMapDstIdx] &&  \
           Map[0].NumBreakDowns == 1 &&                                        \
           #RBNameDst #Size " Dst is incorrectly initialized");                \
    assert(Map[1].BreakDown ==                                                 \
               &AArch64GenRegisterBankInfo::PartMappings[PartialMapSrcIdx] &&  \
           Map[1].NumBreakDowns == 1 &&                                        \
           #RBNameSrc #Size " Src is incorrectly initialized");                \
                                                                               \
  } while (false)
 
    CHECK_VALUEMAP_CROSSREGCPY(GPR, GPR, 32);
    CHECK_VALUEMAP_CROSSREGCPY(GPR, FPR, 32);
    CHECK_VALUEMAP_CROSSREGCPY(GPR, GPR, 64);
    CHECK_VALUEMAP_CROSSREGCPY(GPR, FPR, 64);
    CHECK_VALUEMAP_CROSSREGCPY(FPR, FPR, 32);
    CHECK_VALUEMAP_CROSSREGCPY(FPR, GPR, 32);
    CHECK_VALUEMAP_CROSSREGCPY(FPR, FPR, 64);
    CHECK_VALUEMAP_CROSSREGCPY(FPR, GPR, 64);
 
#define CHECK_VALUEMAP_FPEXT(DstSize, SrcSize)                                 \
  do {                                                                         \
    unsigned PartialMapDstIdx = PMI_FPR##DstSize - PMI_Min;                    \
    unsigned PartialMapSrcIdx = PMI_FPR##SrcSize - PMI_Min;                    \
    (void)PartialMapDstIdx;                                                    \
    (void)PartialMapSrcIdx;                                                    \
    const ValueMapping *Map = getFPExtMapping(DstSize, SrcSize);               \
    (void)Map;                                                                 \
    assert(Map[0].BreakDown ==                                                 \
               &AArch64GenRegisterBankInfo::PartMappings[PartialMapDstIdx] &&  \
           Map[0].NumBreakDowns == 1 && "FPR" #DstSize                         \
                                        " Dst is incorrectly initialized");    \
    assert(Map[1].BreakDown ==                                                 \
               &AArch64GenRegisterBankInfo::PartMappings[PartialMapSrcIdx] &&  \
           Map[1].NumBreakDowns == 1 && "FPR" #SrcSize                         \
                                        " Src is incorrectly initialized");    \
                                                                               \
  } while (false)
 
    CHECK_VALUEMAP_FPEXT(32, 16);
    CHECK_VALUEMAP_FPEXT(64, 16);
    CHECK_VALUEMAP_FPEXT(64, 32);
    CHECK_VALUEMAP_FPEXT(128, 64);
 
    assert(verify(TRI) && "Invalid register bank information");
  };
 
  llvm::call_once(InitializeRegisterBankFlag, InitializeRegisterBankOnce);
}
 
unsigned AArch64RegisterBankInfo::copyCost(const RegisterBank &A,
                                           const RegisterBank &B,
                                           const TypeSize Size) const {
  // What do we do with different size?
  // copy are same size.
  // Will introduce other hooks for different size:
  // * extract cost.
  // * build_sequence cost.
 
  // Copy from (resp. to) GPR to (resp. from) FPR involves FMOV.
  // FIXME: This should be deduced from the scheduling model.
  if (&A == &AArch64::GPRRegBank && &B == &AArch64::FPRRegBank)
    // FMOVXDr or FMOVWSr.
    return 5;
  if (&A == &AArch64::FPRRegBank && &B == &AArch64::GPRRegBank)
    // FMOVDXr or FMOVSWr.
    return 4;
 
  return RegisterBankInfo::copyCost(A, B, Size);
}
 
const RegisterBank &
AArch64RegisterBankInfo::getRegBankFromRegClass(const TargetRegisterClass &RC,
                                                LLT Ty) const {
  switch (RC.getID()) {
  case AArch64::GPR64sponlyRegClassID:
    return getRegBank(AArch64::GPRRegBankID);
  default:
    return AArch64GenRegisterBankInfo::getRegBankFromRegClass(RC, Ty);
  }
}
 
RegisterBankInfo::InstructionMappings
AArch64RegisterBankInfo::getInstrAlternativeMappings(
    const MachineInstr &MI) const {
  const MachineFunction &MF = *MI.getParent()->getParent();
  const TargetSubtargetInfo &STI = MF.getSubtarget();
  const TargetRegisterInfo &TRI = *STI.getRegisterInfo();
  const MachineRegisterInfo &MRI = MF.getRegInfo();
 
  switch (MI.getOpcode()) {
  case TargetOpcode::G_OR: {
    // 32 and 64-bit or can be mapped on either FPR or
    // GPR for the same cost.
    TypeSize Size = getSizeInBits(MI.getOperand(0).getReg(), MRI, TRI);
    if (Size != 32 && Size != 64)
      break;
 
    // If the instruction has any implicit-defs or uses,
    // do not mess with it.
    if (MI.getNumOperands() != 3)
      break;
    InstructionMappings AltMappings;
    const InstructionMapping &GPRMapping = getInstructionMapping(
        /*ID*/ 1, /*Cost*/ 1, getValueMapping(PMI_FirstGPR, Size),
        /*NumOperands*/ 3);
    const InstructionMapping &FPRMapping = getInstructionMapping(
        /*ID*/ 2, /*Cost*/ 1, getValueMapping(PMI_FirstFPR, Size),
        /*NumOperands*/ 3);
 
    AltMappings.push_back(&GPRMapping);
    AltMappings.push_back(&FPRMapping);
    return AltMappings;
  }
  case TargetOpcode::G_BITCAST: {
    TypeSize Size = getSizeInBits(MI.getOperand(0).getReg(), MRI, TRI);
    if (Size != 32 && Size != 64)
      break;
 
    // If the instruction has any implicit-defs or uses,
    // do not mess with it.
    if (MI.getNumOperands() != 2)
      break;
 
    InstructionMappings AltMappings;
    const InstructionMapping &GPRMapping = getInstructionMapping(
        /*ID*/ 1, /*Cost*/ 1,
        getCopyMapping(AArch64::GPRRegBankID, AArch64::GPRRegBankID, Size),
        /*NumOperands*/ 2);
    const InstructionMapping &FPRMapping = getInstructionMapping(
        /*ID*/ 2, /*Cost*/ 1,
        getCopyMapping(AArch64::FPRRegBankID, AArch64::FPRRegBankID, Size),
        /*NumOperands*/ 2);
    const InstructionMapping &GPRToFPRMapping = getInstructionMapping(
        /*ID*/ 3,
        /*Cost*/
        copyCost(AArch64::GPRRegBank, AArch64::FPRRegBank,
                 TypeSize::getFixed(Size)),
        getCopyMapping(AArch64::FPRRegBankID, AArch64::GPRRegBankID, Size),
        /*NumOperands*/ 2);
    const InstructionMapping &FPRToGPRMapping = getInstructionMapping(
        /*ID*/ 3,
        /*Cost*/
        copyCost(AArch64::GPRRegBank, AArch64::FPRRegBank,
                 TypeSize::getFixed(Size)),
        getCopyMapping(AArch64::GPRRegBankID, AArch64::FPRRegBankID, Size),
        /*NumOperands*/ 2);
 
    AltMappings.push_back(&GPRMapping);
    AltMappings.push_back(&FPRMapping);
    AltMappings.push_back(&GPRToFPRMapping);
    AltMappings.push_back(&FPRToGPRMapping);
    return AltMappings;
  }
  case TargetOpcode::G_LOAD: {
    TypeSize Size = getSizeInBits(MI.getOperand(0).getReg(), MRI, TRI);
    if (Size != 64)
      break;
 
    // If the instruction has any implicit-defs or uses,
    // do not mess with it.
    if (MI.getNumOperands() != 2)
      break;
 
    InstructionMappings AltMappings;
    const InstructionMapping &GPRMapping = getInstructionMapping(
        /*ID*/ 1, /*Cost*/ 1,
        getOperandsMapping(
            {getValueMapping(PMI_FirstGPR, Size),
             // Addresses are GPR 64-bit.
             getValueMapping(PMI_FirstGPR, TypeSize::getFixed(64))}),
        /*NumOperands*/ 2);
    const InstructionMapping &FPRMapping = getInstructionMapping(
        /*ID*/ 2, /*Cost*/ 1,
        getOperandsMapping(
            {getValueMapping(PMI_FirstFPR, Size),
             // Addresses are GPR 64-bit.
             getValueMapping(PMI_FirstGPR, TypeSize::getFixed(64))}),
        /*NumOperands*/ 2);
 
    AltMappings.push_back(&GPRMapping);
    AltMappings.push_back(&FPRMapping);
    return AltMappings;
  }
  default:
    break;
  }
  return RegisterBankInfo::getInstrAlternativeMappings(MI);
}
 
void AArch64RegisterBankInfo::applyMappingImpl(
    MachineIRBuilder &Builder, const OperandsMapper &OpdMapper) const {
  MachineInstr &MI = OpdMapper.getMI();
  MachineRegisterInfo &MRI = OpdMapper.getMRI();
 
  switch (MI.getOpcode()) {
  case TargetOpcode::G_OR:
  case TargetOpcode::G_BITCAST:
  case TargetOpcode::G_LOAD:
    // Those ID must match getInstrAlternativeMappings.
    assert((OpdMapper.getInstrMapping().getID() >= 1 &&
            OpdMapper.getInstrMapping().getID() <= 4) &&
           "Don't know how to handle that ID");
    return applyDefaultMapping(OpdMapper);
  case TargetOpcode::G_INSERT_VECTOR_ELT: {
    // Extend smaller gpr operands to 32 bit.
    Builder.setInsertPt(*MI.getParent(), MI.getIterator());
    auto Ext = Builder.buildAnyExt(LLT::scalar(32), MI.getOperand(2).getReg());
    MRI.setRegBank(Ext.getReg(0), getRegBank(AArch64::GPRRegBankID));
    MI.getOperand(2).setReg(Ext.getReg(0));
    return applyDefaultMapping(OpdMapper);
  }
  case AArch64::G_DUP: {
    // Extend smaller gpr to 32-bits
    assert(MRI.getType(MI.getOperand(1).getReg()).getSizeInBits() < 32 &&
           "Expected sources smaller than 32-bits");
    Builder.setInsertPt(*MI.getParent(), MI.getIterator());
 
    Register ConstReg;
    auto ConstMI = MRI.getVRegDef(MI.getOperand(1).getReg());
    if (ConstMI->getOpcode() == TargetOpcode::G_CONSTANT) {
      auto CstVal = ConstMI->getOperand(1).getCImm()->getValue();
      ConstReg =
          Builder.buildConstant(LLT::scalar(32), CstVal.sext(32)).getReg(0);
    } else {
      ConstReg = Builder.buildAnyExt(LLT::scalar(32), MI.getOperand(1).getReg())
                     .getReg(0);
    }
    MRI.setRegBank(ConstReg, getRegBank(AArch64::GPRRegBankID));
    MI.getOperand(1).setReg(ConstReg);
    return applyDefaultMapping(OpdMapper);
  }
  default:
    llvm_unreachable("Don't know how to handle that operation");
  }
}
 
const RegisterBankInfo::InstructionMapping &
AArch64RegisterBankInfo::getSameKindOfOperandsMapping(
    const MachineInstr &MI) const {
  const unsigned Opc = MI.getOpcode();
  const MachineFunction &MF = *MI.getParent()->getParent();
  const MachineRegisterInfo &MRI = MF.getRegInfo();
 
  unsigned NumOperands = MI.getNumOperands();
  assert(NumOperands <= 3 &&
         "This code is for instructions with 3 or less operands");
 
  LLT Ty = MRI.getType(MI.getOperand(0).getReg());
  TypeSize Size = Ty.getSizeInBits();
  bool IsFPR = Ty.isVector() || isPreISelGenericFloatingPointOpcode(Opc);
 
  PartialMappingIdx RBIdx = IsFPR ? PMI_FirstFPR : PMI_FirstGPR;
 
#ifndef NDEBUG
  // Make sure all the operands are using similar size and type.
  // Should probably be checked by the machine verifier.
  // This code won't catch cases where the number of lanes is
  // different between the operands.
  // If we want to go to that level of details, it is probably
  // best to check that the types are the same, period.
  // Currently, we just check that the register banks are the same
  // for each types.
  for (unsigned Idx = 1; Idx != NumOperands; ++Idx) {
    LLT OpTy = MRI.getType(MI.getOperand(Idx).getReg());
    assert(
        AArch64GenRegisterBankInfo::getRegBankBaseIdxOffset(
            RBIdx, OpTy.getSizeInBits()) ==
            AArch64GenRegisterBankInfo::getRegBankBaseIdxOffset(RBIdx, Size) &&
        "Operand has incompatible size");
    bool OpIsFPR = OpTy.isVector() || isPreISelGenericFloatingPointOpcode(Opc);
    (void)OpIsFPR;
    assert(IsFPR == OpIsFPR && "Operand has incompatible type");
  }
#endif // End NDEBUG.
 
  return getInstructionMapping(DefaultMappingID, 1,
                               getValueMapping(RBIdx, Size), NumOperands);
}
 
/// \returns true if a given intrinsic only uses and defines FPRs.
static bool isFPIntrinsic(const MachineRegisterInfo &MRI,
                          const MachineInstr &MI) {
  // TODO: Add more intrinsics.
  switch (cast<GIntrinsic>(MI).getIntrinsicID()) {
  default:
    return false;
  case Intrinsic::aarch64_neon_uaddlv:
  case Intrinsic::aarch64_neon_uaddv:
  case Intrinsic::aarch64_neon_saddv:
  case Intrinsic::aarch64_neon_umaxv:
  case Intrinsic::aarch64_neon_smaxv:
  case Intrinsic::aarch64_neon_uminv:
  case Intrinsic::aarch64_neon_sminv:
  case Intrinsic::aarch64_neon_faddv:
  case Intrinsic::aarch64_neon_fmaxv:
  case Intrinsic::aarch64_neon_fminv:
  case Intrinsic::aarch64_neon_fmaxnmv:
  case Intrinsic::aarch64_neon_fminnmv:
  case Intrinsic::aarch64_neon_fmulx:
  case Intrinsic::aarch64_neon_frecpe:
  case Intrinsic::aarch64_neon_frecps:
  case Intrinsic::aarch64_neon_frecpx:
  case Intrinsic::aarch64_neon_frsqrte:
  case Intrinsic::aarch64_neon_frsqrts:
  case Intrinsic::aarch64_neon_facge:
  case Intrinsic::aarch64_neon_facgt:
  case Intrinsic::aarch64_neon_fabd:
  case Intrinsic::aarch64_sisd_fabd:
  case Intrinsic::aarch64_neon_sqrdmlah:
  case Intrinsic::aarch64_neon_sqrdmlsh:
  case Intrinsic::aarch64_neon_sqrdmulh:
  case Intrinsic::aarch64_neon_sqadd:
  case Intrinsic::aarch64_neon_sqsub:
  case Intrinsic::aarch64_crypto_sha1h:
  case Intrinsic::aarch64_crypto_sha1c:
  case Intrinsic::aarch64_crypto_sha1p:
  case Intrinsic::aarch64_crypto_sha1m:
  case Intrinsic::aarch64_sisd_fcvtxn:
    return true;
  case Intrinsic::aarch64_neon_saddlv: {
    const LLT SrcTy = MRI.getType(MI.getOperand(2).getReg());
    return SrcTy.getElementType().getSizeInBits() >= 16 &&
           SrcTy.getElementCount().getFixedValue() >= 4;
  }
  }
}
 
bool AArch64RegisterBankInfo::isPHIWithFPConstraints(
    const MachineInstr &MI, const MachineRegisterInfo &MRI,
    const AArch64RegisterInfo &TRI, const unsigned Depth) const {
  if (!MI.isPHI() || Depth > MaxFPRSearchDepth)
    return false;
 
  return any_of(MRI.use_nodbg_instructions(MI.getOperand(0).getReg()),
                [&](const MachineInstr &UseMI) {
                  if (onlyUsesFP(UseMI, MRI, TRI, Depth + 1))
                    return true;
                  return isPHIWithFPConstraints(UseMI, MRI, TRI, Depth + 1);
                });
}
 
bool AArch64RegisterBankInfo::hasFPConstraints(const MachineInstr &MI,
                                               const MachineRegisterInfo &MRI,
                                               const AArch64RegisterInfo &TRI,
                                               unsigned Depth) const {
  unsigned Op = MI.getOpcode();
  if (Op == TargetOpcode::G_INTRINSIC && isFPIntrinsic(MRI, MI))
    return true;
 
  // Do we have an explicit floating point instruction?
  if (isPreISelGenericFloatingPointOpcode(Op))
    return true;
 
  // No. Check if we have a copy-like instruction. If we do, then we could
  // still be fed by floating point instructions.
  if (Op != TargetOpcode::COPY && !MI.isPHI() &&
      !isPreISelGenericOptimizationHint(Op))
    return false;
 
  // Check if we already know the register bank.
  auto *RB = getRegBank(MI.getOperand(0).getReg(), MRI, TRI);
  if (RB == &AArch64::FPRRegBank)
    return true;
  if (RB == &AArch64::GPRRegBank)
    return false;
 
  // We don't know anything.
  //
  // If we have a phi, we may be able to infer that it will be assigned a FPR
  // based off of its inputs.
  if (!MI.isPHI() || Depth > MaxFPRSearchDepth)
    return false;
 
  return any_of(MI.explicit_uses(), [&](const MachineOperand &Op) {
    return Op.isReg() &&
           onlyDefinesFP(*MRI.getVRegDef(Op.getReg()), MRI, TRI, Depth + 1);
  });
}
 
bool AArch64RegisterBankInfo::onlyUsesFP(const MachineInstr &MI,
                                         const MachineRegisterInfo &MRI,
                                         const AArch64RegisterInfo &TRI,
                                         unsigned Depth) const {
  switch (MI.getOpcode()) {
  case TargetOpcode::G_FPTOSI:
  case TargetOpcode::G_FPTOUI:
  case TargetOpcode::G_FPTOSI_SAT:
  case TargetOpcode::G_FPTOUI_SAT:
  case TargetOpcode::G_FCMP:
  case TargetOpcode::G_LROUND:
  case TargetOpcode::G_LLROUND:
  case AArch64::G_PMULL:
    return true;
  case TargetOpcode::G_INTRINSIC:
    switch (cast<GIntrinsic>(MI).getIntrinsicID()) {
    case Intrinsic::aarch64_neon_fcvtas:
    case Intrinsic::aarch64_neon_fcvtau:
    case Intrinsic::aarch64_neon_fcvtzs:
    case Intrinsic::aarch64_neon_fcvtzu:
    case Intrinsic::aarch64_neon_fcvtms:
    case Intrinsic::aarch64_neon_fcvtmu:
    case Intrinsic::aarch64_neon_fcvtns:
    case Intrinsic::aarch64_neon_fcvtnu:
    case Intrinsic::aarch64_neon_fcvtps:
    case Intrinsic::aarch64_neon_fcvtpu:
      return true;
    default:
      break;
    }
    break;
  default:
    break;
  }
  return hasFPConstraints(MI, MRI, TRI, Depth);
}
 
bool AArch64RegisterBankInfo::onlyDefinesFP(const MachineInstr &MI,
                                            const MachineRegisterInfo &MRI,
                                            const AArch64RegisterInfo &TRI,
                                            unsigned Depth) const {
  switch (MI.getOpcode()) {
  case AArch64::G_DUP:
  case AArch64::G_SADDLP:
  case AArch64::G_UADDLP:
  case TargetOpcode::G_SITOFP:
  case TargetOpcode::G_UITOFP:
  case TargetOpcode::G_EXTRACT_VECTOR_ELT:
  case TargetOpcode::G_INSERT_VECTOR_ELT:
  case TargetOpcode::G_BUILD_VECTOR:
  case TargetOpcode::G_BUILD_VECTOR_TRUNC:
    return true;
  case TargetOpcode::G_INTRINSIC_W_SIDE_EFFECTS:
    switch (cast<GIntrinsic>(MI).getIntrinsicID()) {
    case Intrinsic::aarch64_neon_ld1x2:
    case Intrinsic::aarch64_neon_ld1x3:
    case Intrinsic::aarch64_neon_ld1x4:
    case Intrinsic::aarch64_neon_ld2:
    case Intrinsic::aarch64_neon_ld2lane:
    case Intrinsic::aarch64_neon_ld2r:
    case Intrinsic::aarch64_neon_ld3:
    case Intrinsic::aarch64_neon_ld3lane:
    case Intrinsic::aarch64_neon_ld3r:
    case Intrinsic::aarch64_neon_ld4:
    case Intrinsic::aarch64_neon_ld4lane:
    case Intrinsic::aarch64_neon_ld4r:
      return true;
    default:
      break;
    }
    break;
  default:
    break;
  }
  return hasFPConstraints(MI, MRI, TRI, Depth);
}
 
bool AArch64RegisterBankInfo::prefersFPUse(const MachineInstr &MI,
                                           const MachineRegisterInfo &MRI,
                                           const AArch64RegisterInfo &TRI,
                                           unsigned Depth) const {
  switch (MI.getOpcode()) {
  case TargetOpcode::G_SITOFP:
  case TargetOpcode::G_UITOFP:
    return MRI.getType(MI.getOperand(0).getReg()).getSizeInBits() ==
           MRI.getType(MI.getOperand(1).getReg()).getSizeInBits();
  }
  return onlyDefinesFP(MI, MRI, TRI, Depth);
}
 
bool AArch64RegisterBankInfo::isLoadFromFPType(const MachineInstr &MI) const {
  // GMemOperation because we also want to match indexed loads.
  auto *MemOp = cast<GMemOperation>(&MI);
  const Value *LdVal = MemOp->getMMO().getValue();
  if (!LdVal)
    return false;
 
  Type *EltTy = nullptr;
  if (const GlobalValue *GV = dyn_cast<GlobalValue>(LdVal)) {
    EltTy = GV->getValueType();
    // Look at the first element of the struct to determine the type we are
    // loading
    while (StructType *StructEltTy = dyn_cast<StructType>(EltTy)) {
      if (StructEltTy->getNumElements() == 0)
        break;
      EltTy = StructEltTy->getTypeAtIndex(0U);
    }
    // Look at the first element of the array to determine its type
    if (isa<ArrayType>(EltTy))
      EltTy = EltTy->getArrayElementType();
  } else if (!isa<Constant>(LdVal)) {
    // FIXME: grubbing around uses is pretty ugly, but with no more
    // `getPointerElementType` there's not much else we can do.
    for (const auto *LdUser : LdVal->users()) {
      if (isa<LoadInst>(LdUser)) {
        EltTy = LdUser->getType();
        break;
      }
      if (isa<StoreInst>(LdUser) && LdUser->getOperand(1) == LdVal) {
        EltTy = LdUser->getOperand(0)->getType();
        break;
      }
    }
  }
  return EltTy && EltTy->isFPOrFPVectorTy();
}
 
const RegisterBankInfo::InstructionMapping &
AArch64RegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
  const unsigned Opc = MI.getOpcode();
 
  // Try the default logic for non-generic instructions that are either copies
  // or already have some operands assigned to banks.
  if ((Opc != TargetOpcode::COPY && !isPreISelGenericOpcode(Opc)) ||
      Opc == TargetOpcode::G_PHI) {
    const RegisterBankInfo::InstructionMapping &Mapping =
        getInstrMappingImpl(MI);
    if (Mapping.isValid())
      return Mapping;
  }
 
  const MachineFunction &MF = *MI.getParent()->getParent();
  const MachineRegisterInfo &MRI = MF.getRegInfo();
  const AArch64Subtarget &STI = MF.getSubtarget<AArch64Subtarget>();
  const AArch64RegisterInfo &TRI = *STI.getRegisterInfo();
 
  switch (Opc) {
    // G_{F|S|U}REM are not listed because they are not legal.
    // Arithmetic ops.
  case TargetOpcode::G_ADD:
  case TargetOpcode::G_SUB:
  case TargetOpcode::G_PTR_ADD:
  case TargetOpcode::G_MUL:
  case TargetOpcode::G_SDIV:
  case TargetOpcode::G_UDIV:
    // Bitwise ops.
  case TargetOpcode::G_AND:
  case TargetOpcode::G_OR:
  case TargetOpcode::G_XOR:
    // Floating point ops.
  case TargetOpcode::G_FADD:
  case TargetOpcode::G_FSUB:
  case TargetOpcode::G_FMUL:
  case TargetOpcode::G_FDIV:
  case TargetOpcode::G_FMAXIMUM:
  case TargetOpcode::G_FMINIMUM:
    return getSameKindOfOperandsMapping(MI);
  case TargetOpcode::G_FPEXT: {
    LLT DstTy = MRI.getType(MI.getOperand(0).getReg());
    LLT SrcTy = MRI.getType(MI.getOperand(1).getReg());
    return getInstructionMapping(
        DefaultMappingID, /*Cost*/ 1,
        getFPExtMapping(DstTy.getSizeInBits(), SrcTy.getSizeInBits()),
        /*NumOperands*/ 2);
  }
    // Shifts.
  case TargetOpcode::G_SHL:
  case TargetOpcode::G_LSHR:
  case TargetOpcode::G_ASHR: {
    LLT ShiftAmtTy = MRI.getType(MI.getOperand(2).getReg());
    LLT SrcTy = MRI.getType(MI.getOperand(1).getReg());
    if (ShiftAmtTy.getSizeInBits() == 64 && SrcTy.getSizeInBits() == 32)
      return getInstructionMapping(DefaultMappingID, 1,
                                   &ValMappings[Shift64Imm], 3);
    return getSameKindOfOperandsMapping(MI);
  }
  case TargetOpcode::COPY: {
    Register DstReg = MI.getOperand(0).getReg();
    Register SrcReg = MI.getOperand(1).getReg();
    // Check if one of the register is not a generic register.
    if ((DstReg.isPhysical() || !MRI.getType(DstReg).isValid()) ||
        (SrcReg.isPhysical() || !MRI.getType(SrcReg).isValid())) {
      const RegisterBank *DstRB = getRegBank(DstReg, MRI, TRI);
      const RegisterBank *SrcRB = getRegBank(SrcReg, MRI, TRI);
      if (!DstRB)
        DstRB = SrcRB;
      else if (!SrcRB)
        SrcRB = DstRB;
      // If both RB are null that means both registers are generic.
      // We shouldn't be here.
      assert(DstRB && SrcRB && "Both RegBank were nullptr");
      TypeSize Size = getSizeInBits(DstReg, MRI, TRI);
      return getInstructionMapping(
          DefaultMappingID, copyCost(*DstRB, *SrcRB, Size),
          getCopyMapping(DstRB->getID(), SrcRB->getID(), Size),
          // We only care about the mapping of the destination.
          /*NumOperands*/ 1);
    }
    // Both registers are generic, use G_BITCAST.
    [[fallthrough]];
  }
  case TargetOpcode::G_BITCAST: {
    LLT DstTy = MRI.getType(MI.getOperand(0).getReg());
    LLT SrcTy = MRI.getType(MI.getOperand(1).getReg());
    TypeSize Size = DstTy.getSizeInBits();
    bool DstIsGPR = !DstTy.isVector() && DstTy.getSizeInBits() <= 64;
    bool SrcIsGPR = !SrcTy.isVector() && SrcTy.getSizeInBits() <= 64;
    const RegisterBank &DstRB =
        DstIsGPR ? AArch64::GPRRegBank : AArch64::FPRRegBank;
    const RegisterBank &SrcRB =
        SrcIsGPR ? AArch64::GPRRegBank : AArch64::FPRRegBank;
    return getInstructionMapping(
        DefaultMappingID, copyCost(DstRB, SrcRB, Size),
        getCopyMapping(DstRB.getID(), SrcRB.getID(), Size),
        // We only care about the mapping of the destination for COPY.
        /*NumOperands*/ Opc == TargetOpcode::G_BITCAST ? 2 : 1);
  }
  default:
    break;
  }
 
  unsigned NumOperands = MI.getNumOperands();
  unsigned MappingID = DefaultMappingID;
 
  // Track the size and bank of each register.  We don't do partial mappings.
  SmallVector<unsigned, 4> OpSize(NumOperands);
  SmallVector<PartialMappingIdx, 4> OpRegBankIdx(NumOperands);
  for (unsigned Idx = 0; Idx < NumOperands; ++Idx) {
    auto &MO = MI.getOperand(Idx);
    if (!MO.isReg() || !MO.getReg())
      continue;
 
    LLT Ty = MRI.getType(MO.getReg());
    if (!Ty.isValid())
      continue;
    OpSize[Idx] = Ty.getSizeInBits().getKnownMinValue();
 
    // As a top-level guess, vectors including both scalable and non-scalable
    // ones go in FPRs, scalars and pointers in GPRs.
    // For floating-point instructions, scalars go in FPRs.
    if (Ty.isVector())
      OpRegBankIdx[Idx] = PMI_FirstFPR;
    else if (isPreISelGenericFloatingPointOpcode(Opc) ||
             (MO.isDef() && onlyDefinesFP(MI, MRI, TRI)) ||
             (MO.isUse() && onlyUsesFP(MI, MRI, TRI)) ||
             Ty.getSizeInBits() > 64)
      OpRegBankIdx[Idx] = PMI_FirstFPR;
    else
      OpRegBankIdx[Idx] = PMI_FirstGPR;
  }
 
  unsigned Cost = 1;
  // Some of the floating-point instructions have mixed GPR and FPR operands:
  // fine-tune the computed mapping.
  switch (Opc) {
  case AArch64::G_DUP: {
    Register ScalarReg = MI.getOperand(1).getReg();
    LLT ScalarTy = MRI.getType(ScalarReg);
    auto ScalarDef = MRI.getVRegDef(ScalarReg);
    // We want to select dup(load) into LD1R.
    if (ScalarDef->getOpcode() == TargetOpcode::G_LOAD)
      OpRegBankIdx = {PMI_FirstFPR, PMI_FirstFPR};
    // s8 is an exception for G_DUP, which we always want on gpr.
    else if (ScalarTy.getSizeInBits() != 8 &&
             (getRegBank(ScalarReg, MRI, TRI) == &AArch64::FPRRegBank ||
              onlyDefinesFP(*ScalarDef, MRI, TRI)))
      OpRegBankIdx = {PMI_FirstFPR, PMI_FirstFPR};
    else {
      if (ScalarTy.getSizeInBits() < 32 &&
          getRegBank(ScalarReg, MRI, TRI) == &AArch64::GPRRegBank) {
        // Calls applyMappingImpl()
        MappingID = CustomMappingID;
      }
      OpRegBankIdx = {PMI_FirstFPR, PMI_FirstGPR};
    }
    break;
  }
  case TargetOpcode::G_TRUNC: {
    LLT SrcTy = MRI.getType(MI.getOperand(1).getReg());
    if (!SrcTy.isVector() && SrcTy.getSizeInBits() == 128)
      OpRegBankIdx = {PMI_FirstFPR, PMI_FirstFPR};
    break;
  }
  case TargetOpcode::G_SITOFP:
  case TargetOpcode::G_UITOFP: {
    if (MRI.getType(MI.getOperand(0).getReg()).isVector())
      break;
    // Integer to FP conversions don't necessarily happen between GPR -> FPR
    // regbanks. They can also be done within an FPR register.
    Register SrcReg = MI.getOperand(1).getReg();
    if (getRegBank(SrcReg, MRI, TRI) == &AArch64::FPRRegBank &&
        MRI.getType(SrcReg).getSizeInBits() ==
            MRI.getType(MI.getOperand(0).getReg()).getSizeInBits())
      OpRegBankIdx = {PMI_FirstFPR, PMI_FirstFPR};
    else
      OpRegBankIdx = {PMI_FirstFPR, PMI_FirstGPR};
    break;
  }
  case TargetOpcode::G_FPTOSI_SAT:
  case TargetOpcode::G_FPTOUI_SAT:
  case TargetOpcode::G_FPTOSI:
  case TargetOpcode::G_FPTOUI: {
    LLT DstType = MRI.getType(MI.getOperand(0).getReg());
    if (DstType.isVector())
      break;
    if (DstType == LLT::scalar(16)) {
      OpRegBankIdx = {PMI_FirstFPR, PMI_FirstFPR};
      break;
    }
    TypeSize DstSize = getSizeInBits(MI.getOperand(0).getReg(), MRI, TRI);
    TypeSize SrcSize = getSizeInBits(MI.getOperand(1).getReg(), MRI, TRI);
    if (((DstSize == SrcSize) || STI.hasFeature(AArch64::FeatureFPRCVT)) &&
        all_of(MRI.use_nodbg_instructions(MI.getOperand(0).getReg()),
               [&](const MachineInstr &UseMI) {
                 return onlyUsesFP(UseMI, MRI, TRI) ||
                        prefersFPUse(UseMI, MRI, TRI);
               }))
      OpRegBankIdx = {PMI_FirstFPR, PMI_FirstFPR};
    else
      OpRegBankIdx = {PMI_FirstGPR, PMI_FirstFPR};
    break;
  }
  case TargetOpcode::G_INTRINSIC_LRINT:
  case TargetOpcode::G_INTRINSIC_LLRINT:
    if (MRI.getType(MI.getOperand(0).getReg()).isVector())
      break;
    OpRegBankIdx = {PMI_FirstGPR, PMI_FirstFPR};
    break;
  case TargetOpcode::G_FCMP: {
    // If the result is a vector, it must use a FPR.
    AArch64GenRegisterBankInfo::PartialMappingIdx Idx0 =
        MRI.getType(MI.getOperand(0).getReg()).isVector() ? PMI_FirstFPR
                                                          : PMI_FirstGPR;
    OpRegBankIdx = {Idx0,
                    /* Predicate */ PMI_None, PMI_FirstFPR, PMI_FirstFPR};
    break;
  }
  case TargetOpcode::G_BITCAST:
    // This is going to be a cross register bank copy and this is expensive.
    if (OpRegBankIdx[0] != OpRegBankIdx[1])
      Cost = copyCost(
          *AArch64GenRegisterBankInfo::PartMappings[OpRegBankIdx[0]].RegBank,
          *AArch64GenRegisterBankInfo::PartMappings[OpRegBankIdx[1]].RegBank,
          TypeSize::getFixed(OpSize[0]));
    break;
  case TargetOpcode::G_LOAD: {
    // Loading in vector unit is slightly more expensive.
    // This is actually only true for the LD1R and co instructions,
    // but anyway for the fast mode this number does not matter and
    // for the greedy mode the cost of the cross bank copy will
    // offset this number.
    // FIXME: Should be derived from the scheduling model.
    if (OpRegBankIdx[0] != PMI_FirstGPR) {
      Cost = 2;
      break;
    }
 
    if (cast<GLoad>(MI).isAtomic()) {
      // Atomics always use GPR destinations. Don't refine any further.
      OpRegBankIdx[0] = PMI_FirstGPR;
      break;
    }
 
    // Try to guess the type of the load from the MMO.
    if (isLoadFromFPType(MI)) {
      OpRegBankIdx[0] = PMI_FirstFPR;
      break;
    }
 
    // Check if that load feeds fp instructions.
    // In that case, we want the default mapping to be on FPR
    // instead of blind map every scalar to GPR.
    if (any_of(MRI.use_nodbg_instructions(MI.getOperand(0).getReg()),
               [&](const MachineInstr &UseMI) {
                 // If we have at least one direct or indirect use
                 // in a FP instruction,
                 // assume this was a floating point load in the IR. If it was
                 // not, we would have had a bitcast before reaching that
                 // instruction.
                 //
                 // Int->FP conversion operations are also captured in
                 // prefersFPUse().
 
                 if (isPHIWithFPConstraints(UseMI, MRI, TRI))
                   return true;
 
                 return onlyUsesFP(UseMI, MRI, TRI) ||
                        prefersFPUse(UseMI, MRI, TRI);
               }))
      OpRegBankIdx[0] = PMI_FirstFPR;
    break;
  }
  case TargetOpcode::G_STORE:
    // Check if that store is fed by fp instructions.
    if (OpRegBankIdx[0] == PMI_FirstGPR) {
      Register VReg = MI.getOperand(0).getReg();
      if (!VReg)
        break;
      MachineInstr *DefMI = MRI.getVRegDef(VReg);
      if (onlyDefinesFP(*DefMI, MRI, TRI))
        OpRegBankIdx[0] = PMI_FirstFPR;
      break;
    }
    break;
  case TargetOpcode::G_INDEXED_STORE:
    if (OpRegBankIdx[1] == PMI_FirstGPR) {
      Register VReg = MI.getOperand(1).getReg();
      if (!VReg)
        break;
      MachineInstr *DefMI = MRI.getVRegDef(VReg);
      if (onlyDefinesFP(*DefMI, MRI, TRI))
        OpRegBankIdx[1] = PMI_FirstFPR;
      break;
    }
    break;
  case TargetOpcode::G_INDEXED_SEXTLOAD:
  case TargetOpcode::G_INDEXED_ZEXTLOAD:
    // These should always be GPR.
    OpRegBankIdx[0] = PMI_FirstGPR;
    break;
  case TargetOpcode::G_INDEXED_LOAD: {
    if (isLoadFromFPType(MI))
      OpRegBankIdx[0] = PMI_FirstFPR;
    break;
  }
  case TargetOpcode::G_SELECT: {
    // If the destination is FPR, preserve that.
    if (OpRegBankIdx[0] != PMI_FirstGPR)
      break;
 
    // If we're taking in vectors, we have no choice but to put everything on
    // FPRs, except for the condition. The condition must always be on a GPR.
    LLT SrcTy = MRI.getType(MI.getOperand(2).getReg());
    if (SrcTy.isVector()) {
      OpRegBankIdx = {PMI_FirstFPR, PMI_FirstGPR, PMI_FirstFPR, PMI_FirstFPR};
      break;
    }
 
    // Try to minimize the number of copies. If we have more floating point
    // constrained values than not, then we'll put everything on FPR. Otherwise,
    // everything has to be on GPR.
    unsigned NumFP = 0;
 
    // Check if the uses of the result always produce floating point values.
    //
    // For example:
    //
    // %z = G_SELECT %cond %x %y
    // fpr = G_FOO %z ...
    if (any_of(MRI.use_nodbg_instructions(MI.getOperand(0).getReg()),
               [&](MachineInstr &MI) { return onlyUsesFP(MI, MRI, TRI); }))
      ++NumFP;
 
    // Check if the defs of the source values always produce floating point
    // values.
    //
    // For example:
    //
    // %x = G_SOMETHING_ALWAYS_FLOAT %a ...
    // %z = G_SELECT %cond %x %y
    //
    // Also check whether or not the sources have already been decided to be
    // FPR. Keep track of this.
    //
    // This doesn't check the condition, since it's just whatever is in NZCV.
    // This isn't passed explicitly in a register to fcsel/csel.
    for (unsigned Idx = 2; Idx < 4; ++Idx) {
      Register VReg = MI.getOperand(Idx).getReg();
      MachineInstr *DefMI = MRI.getVRegDef(VReg);
      if (getRegBank(VReg, MRI, TRI) == &AArch64::FPRRegBank ||
          onlyDefinesFP(*DefMI, MRI, TRI))
        ++NumFP;
    }
 
    // If we have more FP constraints than not, then move everything over to
    // FPR.
    if (NumFP >= 2)
      OpRegBankIdx = {PMI_FirstFPR, PMI_FirstGPR, PMI_FirstFPR, PMI_FirstFPR};
 
    break;
  }
  case TargetOpcode::G_UNMERGE_VALUES: {
    // If the first operand belongs to a FPR register bank, then make sure that
    // we preserve that.
    if (OpRegBankIdx[0] != PMI_FirstGPR)
      break;
 
    LLT SrcTy = MRI.getType(MI.getOperand(MI.getNumOperands()-1).getReg());
    // UNMERGE into scalars from a vector should always use FPR.
    // Likewise if any of the uses are FP instructions.
    if (SrcTy.isVector() || SrcTy == LLT::scalar(128) ||
        any_of(MRI.use_nodbg_instructions(MI.getOperand(0).getReg()),
               [&](MachineInstr &MI) { return onlyUsesFP(MI, MRI, TRI); })) {
      // Set the register bank of every operand to FPR.
      for (unsigned Idx = 0, NumOperands = MI.getNumOperands();
           Idx < NumOperands; ++Idx)
        OpRegBankIdx[Idx] = PMI_FirstFPR;
    }
    break;
  }
  case TargetOpcode::G_EXTRACT_VECTOR_ELT:
    // Destination and source need to be FPRs.
    OpRegBankIdx[0] = PMI_FirstFPR;
    OpRegBankIdx[1] = PMI_FirstFPR;
 
    // Index needs to be a GPR.
    OpRegBankIdx[2] = PMI_FirstGPR;
    break;
  case TargetOpcode::G_INSERT_VECTOR_ELT:
    OpRegBankIdx[0] = PMI_FirstFPR;
    OpRegBankIdx[1] = PMI_FirstFPR;
 
    // The element may be either a GPR or FPR. Preserve that behaviour.
    if (getRegBank(MI.getOperand(2).getReg(), MRI, TRI) == &AArch64::FPRRegBank)
      OpRegBankIdx[2] = PMI_FirstFPR;
    else {
      // If the type is i8/i16, and the regank will be GPR, then we change the
      // type to i32 in applyMappingImpl.
      LLT Ty = MRI.getType(MI.getOperand(2).getReg());
      if (Ty.getSizeInBits() == 8 || Ty.getSizeInBits() == 16) {
        // Calls applyMappingImpl()
        MappingID = CustomMappingID;
      }
      OpRegBankIdx[2] = PMI_FirstGPR;
    }
 
    // Index needs to be a GPR.
    OpRegBankIdx[3] = PMI_FirstGPR;
    break;
  case TargetOpcode::G_EXTRACT: {
    // For s128 sources we have to use fpr unless we know otherwise.
    auto Src = MI.getOperand(1).getReg();
    LLT SrcTy = MRI.getType(MI.getOperand(1).getReg());
    if (SrcTy.getSizeInBits() != 128)
      break;
    auto Idx = MRI.getRegClassOrNull(Src) == &AArch64::XSeqPairsClassRegClass
                   ? PMI_FirstGPR
                   : PMI_FirstFPR;
    OpRegBankIdx[0] = Idx;
    OpRegBankIdx[1] = Idx;
    break;
  }
  case TargetOpcode::G_BUILD_VECTOR: {
    // If the first source operand belongs to a FPR register bank, then make
    // sure that we preserve that.
    if (OpRegBankIdx[1] != PMI_FirstGPR)
      break;
    Register VReg = MI.getOperand(1).getReg();
    if (!VReg)
      break;
 
    // Get the instruction that defined the source operand reg, and check if
    // it's a floating point operation. Or, if it's a type like s16 which
    // doesn't have a exact size gpr register class. The exception is if the
    // build_vector has all constant operands, which may be better to leave as
    // gpr without copies, so it can be matched in imported patterns.
    MachineInstr *DefMI = MRI.getVRegDef(VReg);
    unsigned DefOpc = DefMI->getOpcode();
    const LLT SrcTy = MRI.getType(VReg);
    if (all_of(MI.operands(), [&](const MachineOperand &Op) {
          return Op.isDef() || MRI.getVRegDef(Op.getReg())->getOpcode() ==
                                   TargetOpcode::G_CONSTANT;
        }))
      break;
    if (isPreISelGenericFloatingPointOpcode(DefOpc) ||
        SrcTy.getSizeInBits() < 32 ||
        getRegBank(VReg, MRI, TRI) == &AArch64::FPRRegBank) {
      // Have a floating point op.
      // Make sure every operand gets mapped to a FPR register class.
      unsigned NumOperands = MI.getNumOperands();
      for (unsigned Idx = 0; Idx < NumOperands; ++Idx)
        OpRegBankIdx[Idx] = PMI_FirstFPR;
    }
    break;
  }
  case TargetOpcode::G_VECREDUCE_FADD:
  case TargetOpcode::G_VECREDUCE_FMUL:
  case TargetOpcode::G_VECREDUCE_FMAX:
  case TargetOpcode::G_VECREDUCE_FMIN:
  case TargetOpcode::G_VECREDUCE_FMAXIMUM:
  case TargetOpcode::G_VECREDUCE_FMINIMUM:
  case TargetOpcode::G_VECREDUCE_ADD:
  case TargetOpcode::G_VECREDUCE_MUL:
  case TargetOpcode::G_VECREDUCE_AND:
  case TargetOpcode::G_VECREDUCE_OR:
  case TargetOpcode::G_VECREDUCE_XOR:
  case TargetOpcode::G_VECREDUCE_SMAX:
  case TargetOpcode::G_VECREDUCE_SMIN:
  case TargetOpcode::G_VECREDUCE_UMAX:
  case TargetOpcode::G_VECREDUCE_UMIN:
    // Reductions produce a scalar value from a vector, the scalar should be on
    // FPR bank.
    OpRegBankIdx = {PMI_FirstFPR, PMI_FirstFPR};
    break;
  case TargetOpcode::G_VECREDUCE_SEQ_FADD:
  case TargetOpcode::G_VECREDUCE_SEQ_FMUL:
    // These reductions also take a scalar accumulator input.
    // Assign them FPR for now.
    OpRegBankIdx = {PMI_FirstFPR, PMI_FirstFPR, PMI_FirstFPR};
    break;
  case TargetOpcode::G_INTRINSIC:
  case TargetOpcode::G_INTRINSIC_W_SIDE_EFFECTS: {
    switch (cast<GIntrinsic>(MI).getIntrinsicID()) {
    case Intrinsic::aarch64_neon_fcvtas:
    case Intrinsic::aarch64_neon_fcvtau:
    case Intrinsic::aarch64_neon_fcvtzs:
    case Intrinsic::aarch64_neon_fcvtzu:
    case Intrinsic::aarch64_neon_fcvtms:
    case Intrinsic::aarch64_neon_fcvtmu:
    case Intrinsic::aarch64_neon_fcvtns:
    case Intrinsic::aarch64_neon_fcvtnu:
    case Intrinsic::aarch64_neon_fcvtps:
    case Intrinsic::aarch64_neon_fcvtpu: {
      OpRegBankIdx[2] = PMI_FirstFPR;
      if (MRI.getType(MI.getOperand(0).getReg()).isVector()) {
        OpRegBankIdx[0] = PMI_FirstFPR;
        break;
      }
      TypeSize DstSize = getSizeInBits(MI.getOperand(0).getReg(), MRI, TRI);
      TypeSize SrcSize = getSizeInBits(MI.getOperand(2).getReg(), MRI, TRI);
      if (((DstSize == SrcSize) || STI.hasFeature(AArch64::FeatureFPRCVT)) &&
          all_of(MRI.use_nodbg_instructions(MI.getOperand(0).getReg()),
                 [&](const MachineInstr &UseMI) {
                   return onlyUsesFP(UseMI, MRI, TRI) ||
                          prefersFPUse(UseMI, MRI, TRI);
                 }))
        OpRegBankIdx[0] = PMI_FirstFPR;
      else
        OpRegBankIdx[0] = PMI_FirstGPR;
      break;
    }
    case Intrinsic::aarch64_neon_vcvtfxs2fp:
    case Intrinsic::aarch64_neon_vcvtfxu2fp:
    case Intrinsic::aarch64_neon_vcvtfp2fxs:
    case Intrinsic::aarch64_neon_vcvtfp2fxu:
      // Override these intrinsics, because they would have a partial
      // mapping. This is needed for 'half' types, which otherwise don't
      // get legalised correctly.
      OpRegBankIdx[0] = PMI_FirstFPR;
      OpRegBankIdx[2] = PMI_FirstFPR;
      // OpRegBankIdx[1] is the intrinsic ID.
      // OpRegBankIdx[3] is an integer immediate.
      break;
    default: {
      // Check if we know that the intrinsic has any constraints on its register
      // banks. If it does, then update the mapping accordingly.
      unsigned Idx = 0;
      if (onlyDefinesFP(MI, MRI, TRI))
        for (const auto &Op : MI.defs()) {
          if (Op.isReg())
            OpRegBankIdx[Idx] = PMI_FirstFPR;
          ++Idx;
        }
      else
        Idx += MI.getNumExplicitDefs();
 
      if (onlyUsesFP(MI, MRI, TRI))
        for (const auto &Op : MI.explicit_uses()) {
          if (Op.isReg())
            OpRegBankIdx[Idx] = PMI_FirstFPR;
          ++Idx;
        }
      break;
    }
    }
    break;
  }
  case TargetOpcode::G_LROUND:
  case TargetOpcode::G_LLROUND: {
    // Source is always floating point and destination is always integer.
    OpRegBankIdx = {PMI_FirstGPR, PMI_FirstFPR};
    break;
  }
  }
 
  // Finally construct the computed mapping.
  SmallVector<const ValueMapping *, 8> OpdsMapping(NumOperands);
  for (unsigned Idx = 0; Idx < NumOperands; ++Idx) {
    if (MI.getOperand(Idx).isReg() && MI.getOperand(Idx).getReg()) {
      LLT Ty = MRI.getType(MI.getOperand(Idx).getReg());
      if (!Ty.isValid())
        continue;
      auto Mapping =
          getValueMapping(OpRegBankIdx[Idx], TypeSize::getFixed(OpSize[Idx]));
      if (!Mapping->isValid())
        return getInvalidInstructionMapping();
 
      OpdsMapping[Idx] = Mapping;
    }
  }
 
  return getInstructionMapping(MappingID, Cost, getOperandsMapping(OpdsMapping),
                               NumOperands);
}