//===- SPIRVInstructionSelector.cpp ------------------------------*- C++ -*-==//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the targeting of the InstructionSelector class for
// SPIRV.
// TODO: This should be generated by TableGen.
//
//===----------------------------------------------------------------------===//

#include "SPIRV.h"
#include "SPIRVGlobalRegistry.h"
#include "SPIRVInstrInfo.h"
#include "SPIRVRegisterBankInfo.h"
#include "SPIRVRegisterInfo.h"
#include "SPIRVTargetMachine.h"
#include "SPIRVUtils.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/CodeGen/GlobalISel/InstructionSelector.h"
#include "llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/IR/IntrinsicsSPIRV.h"
#include "llvm/Support/Debug.h"

#define DEBUG_TYPE "spirv-isel"

using namespace llvm;

namespace {

#define GET_GLOBALISEL_PREDICATE_BITSET
#include "SPIRVGenGlobalISel.inc"
#undef GET_GLOBALISEL_PREDICATE_BITSET

class SPIRVInstructionSelector : public InstructionSelector {
  const SPIRVSubtarget &STI;
  const SPIRVInstrInfo &TII;
  const SPIRVRegisterInfo &TRI;
  const RegisterBankInfo &RBI;
  SPIRVGlobalRegistry &GR;
  MachineRegisterInfo *MRI;

public:
  SPIRVInstructionSelector(const SPIRVTargetMachine &TM,
                           const SPIRVSubtarget &ST,
                           const RegisterBankInfo &RBI);
  void setupMF(MachineFunction &MF, GISelKnownBits *KB,
               CodeGenCoverage &CoverageInfo, ProfileSummaryInfo *PSI,
               BlockFrequencyInfo *BFI) override;
  // Common selection code. Instruction-specific selection occurs in spvSelect.
  bool select(MachineInstr &I) override;
  static const char *getName() { return DEBUG_TYPE; }

#define GET_GLOBALISEL_PREDICATES_DECL
#include "SPIRVGenGlobalISel.inc"
#undef GET_GLOBALISEL_PREDICATES_DECL

#define GET_GLOBALISEL_TEMPORARIES_DECL
#include "SPIRVGenGlobalISel.inc"
#undef GET_GLOBALISEL_TEMPORARIES_DECL

private:
  // tblgen-erated 'select' implementation, used as the initial selector for
  // the patterns that don't require complex C++.
  bool selectImpl(MachineInstr &I, CodeGenCoverage &CoverageInfo) const;

  // All instruction-specific selection that didn't happen in "select()".
  // Is basically a large Switch/Case delegating to all other select method.
  bool spvSelect(Register ResVReg, const SPIRVType *ResType,
                 MachineInstr &I) const;

  bool selectGlobalValue(Register ResVReg, MachineInstr &I,
                         const MachineInstr *Init = nullptr) const;

  bool selectUnOpWithSrc(Register ResVReg, const SPIRVType *ResType,
                         MachineInstr &I, Register SrcReg,
                         unsigned Opcode) const;
  bool selectUnOp(Register ResVReg, const SPIRVType *ResType, MachineInstr &I,
                  unsigned Opcode) const;

  bool selectLoad(Register ResVReg, const SPIRVType *ResType,
                  MachineInstr &I) const;
  bool selectStore(MachineInstr &I) const;

  bool selectMemOperation(Register ResVReg, MachineInstr &I) const;

  bool selectAtomicRMW(Register ResVReg, const SPIRVType *ResType,
                       MachineInstr &I, unsigned NewOpcode) const;

  bool selectAtomicCmpXchg(Register ResVReg, const SPIRVType *ResType,
                           MachineInstr &I) const;

  bool selectFence(MachineInstr &I) const;

  bool selectAddrSpaceCast(Register ResVReg, const SPIRVType *ResType,
                           MachineInstr &I) const;

  bool selectBitreverse(Register ResVReg, const SPIRVType *ResType,
                        MachineInstr &I) const;

  bool selectConstVector(Register ResVReg, const SPIRVType *ResType,
                         MachineInstr &I) const;

  bool selectCmp(Register ResVReg, const SPIRVType *ResType,
                 unsigned comparisonOpcode, MachineInstr &I) const;

  bool selectICmp(Register ResVReg, const SPIRVType *ResType,
                  MachineInstr &I) const;
  bool selectFCmp(Register ResVReg, const SPIRVType *ResType,
                  MachineInstr &I) const;

  void renderImm32(MachineInstrBuilder &MIB, const MachineInstr &I,
                   int OpIdx) const;
  void renderFImm32(MachineInstrBuilder &MIB, const MachineInstr &I,
                    int OpIdx) const;

  bool selectConst(Register ResVReg, const SPIRVType *ResType, const APInt &Imm,
                   MachineInstr &I) const;

  bool selectSelect(Register ResVReg, const SPIRVType *ResType, MachineInstr &I,
                    bool IsSigned) const;
  bool selectIToF(Register ResVReg, const SPIRVType *ResType, MachineInstr &I,
                  bool IsSigned, unsigned Opcode) const;
  bool selectExt(Register ResVReg, const SPIRVType *ResType, MachineInstr &I,
                 bool IsSigned) const;

  bool selectTrunc(Register ResVReg, const SPIRVType *ResType,
                   MachineInstr &I) const;

  bool selectIntToBool(Register IntReg, Register ResVReg,
                       const SPIRVType *intTy, const SPIRVType *boolTy,
                       MachineInstr &I) const;

  bool selectOpUndef(Register ResVReg, const SPIRVType *ResType,
                     MachineInstr &I) const;
  bool selectIntrinsic(Register ResVReg, const SPIRVType *ResType,
                       MachineInstr &I) const;
  bool selectExtractVal(Register ResVReg, const SPIRVType *ResType,
                        MachineInstr &I) const;
  bool selectInsertVal(Register ResVReg, const SPIRVType *ResType,
                       MachineInstr &I) const;
  bool selectExtractElt(Register ResVReg, const SPIRVType *ResType,
                        MachineInstr &I) const;
  bool selectInsertElt(Register ResVReg, const SPIRVType *ResType,
                       MachineInstr &I) const;
  bool selectGEP(Register ResVReg, const SPIRVType *ResType,
                 MachineInstr &I) const;

  bool selectFrameIndex(Register ResVReg, const SPIRVType *ResType,
                        MachineInstr &I) const;

  bool selectBranch(MachineInstr &I) const;
  bool selectBranchCond(MachineInstr &I) const;

  bool selectPhi(Register ResVReg, const SPIRVType *ResType,
                 MachineInstr &I) const;

  Register buildI32Constant(uint32_t Val, MachineInstr &I,
                            const SPIRVType *ResType = nullptr) const;

  Register buildZerosVal(const SPIRVType *ResType, MachineInstr &I) const;
  Register buildOnesVal(bool AllOnes, const SPIRVType *ResType,
                        MachineInstr &I) const;
};

} // end anonymous namespace

#define GET_GLOBALISEL_IMPL
#include "SPIRVGenGlobalISel.inc"
#undef GET_GLOBALISEL_IMPL

SPIRVInstructionSelector::SPIRVInstructionSelector(const SPIRVTargetMachine &TM,
                                                   const SPIRVSubtarget &ST,
                                                   const RegisterBankInfo &RBI)
    : InstructionSelector(), STI(ST), TII(*ST.getInstrInfo()),
      TRI(*ST.getRegisterInfo()), RBI(RBI), GR(*ST.getSPIRVGlobalRegistry()),
#define GET_GLOBALISEL_PREDICATES_INIT
#include "SPIRVGenGlobalISel.inc"
#undef GET_GLOBALISEL_PREDICATES_INIT
#define GET_GLOBALISEL_TEMPORARIES_INIT
#include "SPIRVGenGlobalISel.inc"
#undef GET_GLOBALISEL_TEMPORARIES_INIT
{
}

void SPIRVInstructionSelector::setupMF(MachineFunction &MF, GISelKnownBits *KB,
                                       CodeGenCoverage &CoverageInfo,
                                       ProfileSummaryInfo *PSI,
                                       BlockFrequencyInfo *BFI) {
  MRI = &MF.getRegInfo();
  GR.setCurrentFunc(MF);
  InstructionSelector::setupMF(MF, KB, CoverageInfo, PSI, BFI);
}

static bool isImm(const MachineOperand &MO, MachineRegisterInfo *MRI);

// Defined in SPIRVLegalizerInfo.cpp.
extern bool isTypeFoldingSupported(unsigned Opcode);

bool SPIRVInstructionSelector::select(MachineInstr &I) {
  assert(I.getParent() && "Instruction should be in a basic block!");
  assert(I.getParent()->getParent() && "Instruction should be in a function!");

  Register Opcode = I.getOpcode();
  // If it's not a GMIR instruction, we've selected it already.
  if (!isPreISelGenericOpcode(Opcode)) {
    if (Opcode == SPIRV::ASSIGN_TYPE) { // These pseudos aren't needed any more.
      auto *Def = MRI->getVRegDef(I.getOperand(1).getReg());
      if (isTypeFoldingSupported(Def->getOpcode())) {
        auto Res = selectImpl(I, *CoverageInfo);
        assert(Res || Def->getOpcode() == TargetOpcode::G_CONSTANT);
        if (Res)
          return Res;
      }
      MRI->replaceRegWith(I.getOperand(1).getReg(), I.getOperand(0).getReg());
      I.removeFromParent();
    } else if (I.getNumDefs() == 1) {
      // Make all vregs 32 bits (for SPIR-V IDs).
      MRI->setType(I.getOperand(0).getReg(), LLT::scalar(32));
    }
    return true;
  }

  if (I.getNumOperands() != I.getNumExplicitOperands()) {
    LLVM_DEBUG(errs() << "Generic instr has unexpected implicit operands\n");
    return false;
  }

  // Common code for getting return reg+type, and removing selected instr
  // from parent occurs here. Instr-specific selection happens in spvSelect().
  bool HasDefs = I.getNumDefs() > 0;
  Register ResVReg = HasDefs ? I.getOperand(0).getReg() : Register(0);
  SPIRVType *ResType = HasDefs ? GR.getSPIRVTypeForVReg(ResVReg) : nullptr;
  assert(!HasDefs || ResType || I.getOpcode() == TargetOpcode::G_GLOBAL_VALUE);
  if (spvSelect(ResVReg, ResType, I)) {
    if (HasDefs) // Make all vregs 32 bits (for SPIR-V IDs).
      MRI->setType(ResVReg, LLT::scalar(32));
    I.removeFromParent();
    return true;
  }
  return false;
}

bool SPIRVInstructionSelector::spvSelect(Register ResVReg,
                                         const SPIRVType *ResType,
                                         MachineInstr &I) const {
  assert(!isTypeFoldingSupported(I.getOpcode()) ||
         I.getOpcode() == TargetOpcode::G_CONSTANT);
  const unsigned Opcode = I.getOpcode();
  switch (Opcode) {
  case TargetOpcode::G_CONSTANT:
    return selectConst(ResVReg, ResType, I.getOperand(1).getCImm()->getValue(),
                       I);
  case TargetOpcode::G_GLOBAL_VALUE:
    return selectGlobalValue(ResVReg, I);
  case TargetOpcode::G_IMPLICIT_DEF:
    return selectOpUndef(ResVReg, ResType, I);

  case TargetOpcode::G_INTRINSIC_W_SIDE_EFFECTS:
    return selectIntrinsic(ResVReg, ResType, I);
  case TargetOpcode::G_BITREVERSE:
    return selectBitreverse(ResVReg, ResType, I);

  case TargetOpcode::G_BUILD_VECTOR:
    return selectConstVector(ResVReg, ResType, I);

  case TargetOpcode::G_SHUFFLE_VECTOR: {
    MachineBasicBlock &BB = *I.getParent();
    auto MIB = BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpVectorShuffle))
                   .addDef(ResVReg)
                   .addUse(GR.getSPIRVTypeID(ResType))
                   .addUse(I.getOperand(1).getReg())
                   .addUse(I.getOperand(2).getReg());
    for (auto V : I.getOperand(3).getShuffleMask())
      MIB.addImm(V);
    return MIB.constrainAllUses(TII, TRI, RBI);
  }
  case TargetOpcode::G_MEMMOVE:
  case TargetOpcode::G_MEMCPY:
    return selectMemOperation(ResVReg, I);

  case TargetOpcode::G_ICMP:
    return selectICmp(ResVReg, ResType, I);
  case TargetOpcode::G_FCMP:
    return selectFCmp(ResVReg, ResType, I);

  case TargetOpcode::G_FRAME_INDEX:
    return selectFrameIndex(ResVReg, ResType, I);

  case TargetOpcode::G_LOAD:
    return selectLoad(ResVReg, ResType, I);
  case TargetOpcode::G_STORE:
    return selectStore(I);

  case TargetOpcode::G_BR:
    return selectBranch(I);
  case TargetOpcode::G_BRCOND:
    return selectBranchCond(I);

  case TargetOpcode::G_PHI:
    return selectPhi(ResVReg, ResType, I);

  case TargetOpcode::G_FPTOSI:
    return selectUnOp(ResVReg, ResType, I, SPIRV::OpConvertFToS);
  case TargetOpcode::G_FPTOUI:
    return selectUnOp(ResVReg, ResType, I, SPIRV::OpConvertFToU);

  case TargetOpcode::G_SITOFP:
    return selectIToF(ResVReg, ResType, I, true, SPIRV::OpConvertSToF);
  case TargetOpcode::G_UITOFP:
    return selectIToF(ResVReg, ResType, I, false, SPIRV::OpConvertUToF);

  case TargetOpcode::G_CTPOP:
    return selectUnOp(ResVReg, ResType, I, SPIRV::OpBitCount);

  case TargetOpcode::G_SEXT:
    return selectExt(ResVReg, ResType, I, true);
  case TargetOpcode::G_ANYEXT:
  case TargetOpcode::G_ZEXT:
    return selectExt(ResVReg, ResType, I, false);
  case TargetOpcode::G_TRUNC:
    return selectTrunc(ResVReg, ResType, I);
  case TargetOpcode::G_FPTRUNC:
  case TargetOpcode::G_FPEXT:
    return selectUnOp(ResVReg, ResType, I, SPIRV::OpFConvert);

  case TargetOpcode::G_PTRTOINT:
    return selectUnOp(ResVReg, ResType, I, SPIRV::OpConvertPtrToU);
  case TargetOpcode::G_INTTOPTR:
    return selectUnOp(ResVReg, ResType, I, SPIRV::OpConvertUToPtr);
  case TargetOpcode::G_BITCAST:
    return selectUnOp(ResVReg, ResType, I, SPIRV::OpBitcast);
  case TargetOpcode::G_ADDRSPACE_CAST:
    return selectAddrSpaceCast(ResVReg, ResType, I);
  case TargetOpcode::G_PTR_ADD: {
    // Currently, we get G_PTR_ADD only as a result of translating
    // global variables, initialized with constant expressions like GV + Const
    // (see test opencl/basic/progvar_prog_scope_init.ll).
    // TODO: extend the handler once we have other cases.
    assert(I.getOperand(1).isReg() && I.getOperand(2).isReg());
    Register GV = I.getOperand(1).getReg();
    MachineRegisterInfo::def_instr_iterator II = MRI->def_instr_begin(GV);
    assert(((*II).getOpcode() == TargetOpcode::G_GLOBAL_VALUE ||
            (*II).getOpcode() == TargetOpcode::COPY ||
            (*II).getOpcode() == SPIRV::OpVariable) &&
           isImm(I.getOperand(2), MRI));
    Register Idx = buildZerosVal(GR.getOrCreateSPIRVIntegerType(32, I, TII), I);
    MachineBasicBlock &BB = *I.getParent();
    auto MIB = BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpSpecConstantOp))
                   .addDef(ResVReg)
                   .addUse(GR.getSPIRVTypeID(ResType))
                   .addImm(static_cast<uint32_t>(
                       SPIRV::Opcode::InBoundsPtrAccessChain))
                   .addUse(GV)
                   .addUse(Idx)
                   .addUse(I.getOperand(2).getReg());
    return MIB.constrainAllUses(TII, TRI, RBI);
  }

  case TargetOpcode::G_ATOMICRMW_OR:
    return selectAtomicRMW(ResVReg, ResType, I, SPIRV::OpAtomicOr);
  case TargetOpcode::G_ATOMICRMW_ADD:
    return selectAtomicRMW(ResVReg, ResType, I, SPIRV::OpAtomicIAdd);
  case TargetOpcode::G_ATOMICRMW_AND:
    return selectAtomicRMW(ResVReg, ResType, I, SPIRV::OpAtomicAnd);
  case TargetOpcode::G_ATOMICRMW_MAX:
    return selectAtomicRMW(ResVReg, ResType, I, SPIRV::OpAtomicSMax);
  case TargetOpcode::G_ATOMICRMW_MIN:
    return selectAtomicRMW(ResVReg, ResType, I, SPIRV::OpAtomicSMin);
  case TargetOpcode::G_ATOMICRMW_SUB:
    return selectAtomicRMW(ResVReg, ResType, I, SPIRV::OpAtomicISub);
  case TargetOpcode::G_ATOMICRMW_XOR:
    return selectAtomicRMW(ResVReg, ResType, I, SPIRV::OpAtomicXor);
  case TargetOpcode::G_ATOMICRMW_UMAX:
    return selectAtomicRMW(ResVReg, ResType, I, SPIRV::OpAtomicUMax);
  case TargetOpcode::G_ATOMICRMW_UMIN:
    return selectAtomicRMW(ResVReg, ResType, I, SPIRV::OpAtomicUMin);
  case TargetOpcode::G_ATOMICRMW_XCHG:
    return selectAtomicRMW(ResVReg, ResType, I, SPIRV::OpAtomicExchange);
  case TargetOpcode::G_ATOMIC_CMPXCHG:
    return selectAtomicCmpXchg(ResVReg, ResType, I);

  case TargetOpcode::G_FENCE:
    return selectFence(I);

  default:
    return false;
  }
}

bool SPIRVInstructionSelector::selectUnOpWithSrc(Register ResVReg,
                                                 const SPIRVType *ResType,
                                                 MachineInstr &I,
                                                 Register SrcReg,
                                                 unsigned Opcode) const {
  return BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(Opcode))
      .addDef(ResVReg)
      .addUse(GR.getSPIRVTypeID(ResType))
      .addUse(SrcReg)
      .constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectUnOp(Register ResVReg,
                                          const SPIRVType *ResType,
                                          MachineInstr &I,
                                          unsigned Opcode) const {
  return selectUnOpWithSrc(ResVReg, ResType, I, I.getOperand(1).getReg(),
                           Opcode);
}

static SPIRV::Scope getScope(SyncScope::ID Ord) {
  switch (Ord) {
  case SyncScope::SingleThread:
    return SPIRV::Scope::Invocation;
  case SyncScope::System:
    return SPIRV::Scope::Device;
  default:
    llvm_unreachable("Unsupported synchronization Scope ID.");
  }
}

static void addMemoryOperands(MachineMemOperand *MemOp,
                              MachineInstrBuilder &MIB) {
  uint32_t SpvMemOp = static_cast<uint32_t>(SPIRV::MemoryOperand::None);
  if (MemOp->isVolatile())
    SpvMemOp |= static_cast<uint32_t>(SPIRV::MemoryOperand::Volatile);
  if (MemOp->isNonTemporal())
    SpvMemOp |= static_cast<uint32_t>(SPIRV::MemoryOperand::Nontemporal);
  if (MemOp->getAlign().value())
    SpvMemOp |= static_cast<uint32_t>(SPIRV::MemoryOperand::Aligned);

  if (SpvMemOp != static_cast<uint32_t>(SPIRV::MemoryOperand::None)) {
    MIB.addImm(SpvMemOp);
    if (SpvMemOp & static_cast<uint32_t>(SPIRV::MemoryOperand::Aligned))
      MIB.addImm(MemOp->getAlign().value());
  }
}

static void addMemoryOperands(uint64_t Flags, MachineInstrBuilder &MIB) {
  uint32_t SpvMemOp = static_cast<uint32_t>(SPIRV::MemoryOperand::None);
  if (Flags & MachineMemOperand::Flags::MOVolatile)
    SpvMemOp |= static_cast<uint32_t>(SPIRV::MemoryOperand::Volatile);
  if (Flags & MachineMemOperand::Flags::MONonTemporal)
    SpvMemOp |= static_cast<uint32_t>(SPIRV::MemoryOperand::Nontemporal);

  if (SpvMemOp != static_cast<uint32_t>(SPIRV::MemoryOperand::None))
    MIB.addImm(SpvMemOp);
}

bool SPIRVInstructionSelector::selectLoad(Register ResVReg,
                                          const SPIRVType *ResType,
                                          MachineInstr &I) const {
  unsigned OpOffset =
      I.getOpcode() == TargetOpcode::G_INTRINSIC_W_SIDE_EFFECTS ? 1 : 0;
  Register Ptr = I.getOperand(1 + OpOffset).getReg();
  auto MIB = BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(SPIRV::OpLoad))
                 .addDef(ResVReg)
                 .addUse(GR.getSPIRVTypeID(ResType))
                 .addUse(Ptr);
  if (!I.getNumMemOperands()) {
    assert(I.getOpcode() == TargetOpcode::G_INTRINSIC_W_SIDE_EFFECTS);
    addMemoryOperands(I.getOperand(2 + OpOffset).getImm(), MIB);
  } else {
    addMemoryOperands(*I.memoperands_begin(), MIB);
  }
  return MIB.constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectStore(MachineInstr &I) const {
  unsigned OpOffset =
      I.getOpcode() == TargetOpcode::G_INTRINSIC_W_SIDE_EFFECTS ? 1 : 0;
  Register StoreVal = I.getOperand(0 + OpOffset).getReg();
  Register Ptr = I.getOperand(1 + OpOffset).getReg();
  MachineBasicBlock &BB = *I.getParent();
  auto MIB = BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpStore))
                 .addUse(Ptr)
                 .addUse(StoreVal);
  if (!I.getNumMemOperands()) {
    assert(I.getOpcode() == TargetOpcode::G_INTRINSIC_W_SIDE_EFFECTS);
    addMemoryOperands(I.getOperand(2 + OpOffset).getImm(), MIB);
  } else {
    addMemoryOperands(*I.memoperands_begin(), MIB);
  }
  return MIB.constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectMemOperation(Register ResVReg,
                                                  MachineInstr &I) const {
  MachineBasicBlock &BB = *I.getParent();
  auto MIB = BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpCopyMemorySized))
                 .addUse(I.getOperand(0).getReg())
                 .addUse(I.getOperand(1).getReg())
                 .addUse(I.getOperand(2).getReg());
  if (I.getNumMemOperands())
    addMemoryOperands(*I.memoperands_begin(), MIB);
  bool Result = MIB.constrainAllUses(TII, TRI, RBI);
  if (ResVReg.isValid() && ResVReg != MIB->getOperand(0).getReg())
    BuildMI(BB, I, I.getDebugLoc(), TII.get(TargetOpcode::COPY), ResVReg)
        .addUse(MIB->getOperand(0).getReg());
  return Result;
}

bool SPIRVInstructionSelector::selectAtomicRMW(Register ResVReg,
                                               const SPIRVType *ResType,
                                               MachineInstr &I,
                                               unsigned NewOpcode) const {
  assert(I.hasOneMemOperand());
  const MachineMemOperand *MemOp = *I.memoperands_begin();
  uint32_t Scope = static_cast<uint32_t>(getScope(MemOp->getSyncScopeID()));
  Register ScopeReg = buildI32Constant(Scope, I);

  Register Ptr = I.getOperand(1).getReg();
  // TODO: Changed as it's implemented in the translator. See test/atomicrmw.ll
  // auto ScSem =
  // getMemSemanticsForStorageClass(GR.getPointerStorageClass(Ptr));
  AtomicOrdering AO = MemOp->getSuccessOrdering();
  uint32_t MemSem = static_cast<uint32_t>(getMemSemantics(AO));
  Register MemSemReg = buildI32Constant(MemSem /*| ScSem*/, I);

  return BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(NewOpcode))
      .addDef(ResVReg)
      .addUse(GR.getSPIRVTypeID(ResType))
      .addUse(Ptr)
      .addUse(ScopeReg)
      .addUse(MemSemReg)
      .addUse(I.getOperand(2).getReg())
      .constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectFence(MachineInstr &I) const {
  AtomicOrdering AO = AtomicOrdering(I.getOperand(0).getImm());
  uint32_t MemSem = static_cast<uint32_t>(getMemSemantics(AO));
  Register MemSemReg = buildI32Constant(MemSem, I);
  SyncScope::ID Ord = SyncScope::ID(I.getOperand(1).getImm());
  uint32_t Scope = static_cast<uint32_t>(getScope(Ord));
  Register ScopeReg = buildI32Constant(Scope, I);
  MachineBasicBlock &BB = *I.getParent();
  return BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpMemoryBarrier))
      .addUse(ScopeReg)
      .addUse(MemSemReg)
      .constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectAtomicCmpXchg(Register ResVReg,
                                                   const SPIRVType *ResType,
                                                   MachineInstr &I) const {
  Register ScopeReg;
  Register MemSemEqReg;
  Register MemSemNeqReg;
  Register Ptr = I.getOperand(2).getReg();
  if (I.getOpcode() != TargetOpcode::G_INTRINSIC_W_SIDE_EFFECTS) {
    assert(I.hasOneMemOperand());
    const MachineMemOperand *MemOp = *I.memoperands_begin();
    unsigned Scope = static_cast<uint32_t>(getScope(MemOp->getSyncScopeID()));
    ScopeReg = buildI32Constant(Scope, I);

    unsigned ScSem = static_cast<uint32_t>(
        getMemSemanticsForStorageClass(GR.getPointerStorageClass(Ptr)));
    AtomicOrdering AO = MemOp->getSuccessOrdering();
    unsigned MemSemEq = static_cast<uint32_t>(getMemSemantics(AO)) | ScSem;
    MemSemEqReg = buildI32Constant(MemSemEq, I);
    AtomicOrdering FO = MemOp->getFailureOrdering();
    unsigned MemSemNeq = static_cast<uint32_t>(getMemSemantics(FO)) | ScSem;
    MemSemNeqReg =
        MemSemEq == MemSemNeq ? MemSemEqReg : buildI32Constant(MemSemNeq, I);
  } else {
    ScopeReg = I.getOperand(5).getReg();
    MemSemEqReg = I.getOperand(6).getReg();
    MemSemNeqReg = I.getOperand(7).getReg();
  }

  Register Cmp = I.getOperand(3).getReg();
  Register Val = I.getOperand(4).getReg();
  SPIRVType *SpvValTy = GR.getSPIRVTypeForVReg(Val);
  Register ACmpRes = MRI->createVirtualRegister(&SPIRV::IDRegClass);
  const DebugLoc &DL = I.getDebugLoc();
  bool Result =
      BuildMI(*I.getParent(), I, DL, TII.get(SPIRV::OpAtomicCompareExchange))
          .addDef(ACmpRes)
          .addUse(GR.getSPIRVTypeID(SpvValTy))
          .addUse(Ptr)
          .addUse(ScopeReg)
          .addUse(MemSemEqReg)
          .addUse(MemSemNeqReg)
          .addUse(Val)
          .addUse(Cmp)
          .constrainAllUses(TII, TRI, RBI);
  Register CmpSuccReg = MRI->createVirtualRegister(&SPIRV::IDRegClass);
  SPIRVType *BoolTy = GR.getOrCreateSPIRVBoolType(I, TII);
  Result |= BuildMI(*I.getParent(), I, DL, TII.get(SPIRV::OpIEqual))
                .addDef(CmpSuccReg)
                .addUse(GR.getSPIRVTypeID(BoolTy))
                .addUse(ACmpRes)
                .addUse(Cmp)
                .constrainAllUses(TII, TRI, RBI);
  Register TmpReg = MRI->createVirtualRegister(&SPIRV::IDRegClass);
  Result |= BuildMI(*I.getParent(), I, DL, TII.get(SPIRV::OpCompositeInsert))
                .addDef(TmpReg)
                .addUse(GR.getSPIRVTypeID(ResType))
                .addUse(ACmpRes)
                .addUse(GR.getOrCreateUndef(I, ResType, TII))
                .addImm(0)
                .constrainAllUses(TII, TRI, RBI);
  Result |= BuildMI(*I.getParent(), I, DL, TII.get(SPIRV::OpCompositeInsert))
                .addDef(ResVReg)
                .addUse(GR.getSPIRVTypeID(ResType))
                .addUse(CmpSuccReg)
                .addUse(TmpReg)
                .addImm(1)
                .constrainAllUses(TII, TRI, RBI);
  return Result;
}

static bool isGenericCastablePtr(SPIRV::StorageClass SC) {
  switch (SC) {
  case SPIRV::StorageClass::Workgroup:
  case SPIRV::StorageClass::CrossWorkgroup:
  case SPIRV::StorageClass::Function:
    return true;
  default:
    return false;
  }
}

// In SPIR-V address space casting can only happen to and from the Generic
// storage class. We can also only case Workgroup, CrossWorkgroup, or Function
// pointers to and from Generic pointers. As such, we can convert e.g. from
// Workgroup to Function by going via a Generic pointer as an intermediary. All
// other combinations can only be done by a bitcast, and are probably not safe.
bool SPIRVInstructionSelector::selectAddrSpaceCast(Register ResVReg,
                                                   const SPIRVType *ResType,
                                                   MachineInstr &I) const {
  // If the AddrSpaceCast user is single and in OpConstantComposite or
  // OpVariable, we should select OpSpecConstantOp.
  auto UIs = MRI->use_instructions(ResVReg);
  if (!UIs.empty() && ++UIs.begin() == UIs.end() &&
      (UIs.begin()->getOpcode() == SPIRV::OpConstantComposite ||
       UIs.begin()->getOpcode() == SPIRV::OpVariable ||
       isSpvIntrinsic(*UIs.begin(), Intrinsic::spv_init_global))) {
    Register NewReg = I.getOperand(1).getReg();
    MachineBasicBlock &BB = *I.getParent();
    SPIRVType *SpvBaseTy = GR.getOrCreateSPIRVIntegerType(8, I, TII);
    ResType = GR.getOrCreateSPIRVPointerType(SpvBaseTy, I, TII,
                                             SPIRV::StorageClass::Generic);
    bool Result =
        BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpSpecConstantOp))
            .addDef(ResVReg)
            .addUse(GR.getSPIRVTypeID(ResType))
            .addImm(static_cast<uint32_t>(SPIRV::Opcode::PtrCastToGeneric))
            .addUse(NewReg)
            .constrainAllUses(TII, TRI, RBI);
    return Result;
  }
  Register SrcPtr = I.getOperand(1).getReg();
  SPIRVType *SrcPtrTy = GR.getSPIRVTypeForVReg(SrcPtr);
  SPIRV::StorageClass SrcSC = GR.getPointerStorageClass(SrcPtr);
  SPIRV::StorageClass DstSC = GR.getPointerStorageClass(ResVReg);

  // Casting from an eligable pointer to Generic.
  if (DstSC == SPIRV::StorageClass::Generic && isGenericCastablePtr(SrcSC))
    return selectUnOp(ResVReg, ResType, I, SPIRV::OpPtrCastToGeneric);
  // Casting from Generic to an eligable pointer.
  if (SrcSC == SPIRV::StorageClass::Generic && isGenericCastablePtr(DstSC))
    return selectUnOp(ResVReg, ResType, I, SPIRV::OpGenericCastToPtr);
  // Casting between 2 eligable pointers using Generic as an intermediary.
  if (isGenericCastablePtr(SrcSC) && isGenericCastablePtr(DstSC)) {
    Register Tmp = MRI->createVirtualRegister(&SPIRV::IDRegClass);
    SPIRVType *GenericPtrTy = GR.getOrCreateSPIRVPointerType(
        SrcPtrTy, I, TII, SPIRV::StorageClass::Generic);
    MachineBasicBlock &BB = *I.getParent();
    const DebugLoc &DL = I.getDebugLoc();
    bool Success = BuildMI(BB, I, DL, TII.get(SPIRV::OpPtrCastToGeneric))
                       .addDef(Tmp)
                       .addUse(GR.getSPIRVTypeID(GenericPtrTy))
                       .addUse(SrcPtr)
                       .constrainAllUses(TII, TRI, RBI);
    return Success && BuildMI(BB, I, DL, TII.get(SPIRV::OpGenericCastToPtr))
                          .addDef(ResVReg)
                          .addUse(GR.getSPIRVTypeID(ResType))
                          .addUse(Tmp)
                          .constrainAllUses(TII, TRI, RBI);
  }
  // TODO Should this case just be disallowed completely?
  // We're casting 2 other arbitrary address spaces, so have to bitcast.
  return selectUnOp(ResVReg, ResType, I, SPIRV::OpBitcast);
}

static unsigned getFCmpOpcode(unsigned PredNum) {
  auto Pred = static_cast<CmpInst::Predicate>(PredNum);
  switch (Pred) {
  case CmpInst::FCMP_OEQ:
    return SPIRV::OpFOrdEqual;
  case CmpInst::FCMP_OGE:
    return SPIRV::OpFOrdGreaterThanEqual;
  case CmpInst::FCMP_OGT:
    return SPIRV::OpFOrdGreaterThan;
  case CmpInst::FCMP_OLE:
    return SPIRV::OpFOrdLessThanEqual;
  case CmpInst::FCMP_OLT:
    return SPIRV::OpFOrdLessThan;
  case CmpInst::FCMP_ONE:
    return SPIRV::OpFOrdNotEqual;
  case CmpInst::FCMP_ORD:
    return SPIRV::OpOrdered;
  case CmpInst::FCMP_UEQ:
    return SPIRV::OpFUnordEqual;
  case CmpInst::FCMP_UGE:
    return SPIRV::OpFUnordGreaterThanEqual;
  case CmpInst::FCMP_UGT:
    return SPIRV::OpFUnordGreaterThan;
  case CmpInst::FCMP_ULE:
    return SPIRV::OpFUnordLessThanEqual;
  case CmpInst::FCMP_ULT:
    return SPIRV::OpFUnordLessThan;
  case CmpInst::FCMP_UNE:
    return SPIRV::OpFUnordNotEqual;
  case CmpInst::FCMP_UNO:
    return SPIRV::OpUnordered;
  default:
    llvm_unreachable("Unknown predicate type for FCmp");
  }
}

static unsigned getICmpOpcode(unsigned PredNum) {
  auto Pred = static_cast<CmpInst::Predicate>(PredNum);
  switch (Pred) {
  case CmpInst::ICMP_EQ:
    return SPIRV::OpIEqual;
  case CmpInst::ICMP_NE:
    return SPIRV::OpINotEqual;
  case CmpInst::ICMP_SGE:
    return SPIRV::OpSGreaterThanEqual;
  case CmpInst::ICMP_SGT:
    return SPIRV::OpSGreaterThan;
  case CmpInst::ICMP_SLE:
    return SPIRV::OpSLessThanEqual;
  case CmpInst::ICMP_SLT:
    return SPIRV::OpSLessThan;
  case CmpInst::ICMP_UGE:
    return SPIRV::OpUGreaterThanEqual;
  case CmpInst::ICMP_UGT:
    return SPIRV::OpUGreaterThan;
  case CmpInst::ICMP_ULE:
    return SPIRV::OpULessThanEqual;
  case CmpInst::ICMP_ULT:
    return SPIRV::OpULessThan;
  default:
    llvm_unreachable("Unknown predicate type for ICmp");
  }
}

static unsigned getPtrCmpOpcode(unsigned Pred) {
  switch (static_cast<CmpInst::Predicate>(Pred)) {
  case CmpInst::ICMP_EQ:
    return SPIRV::OpPtrEqual;
  case CmpInst::ICMP_NE:
    return SPIRV::OpPtrNotEqual;
  default:
    llvm_unreachable("Unknown predicate type for pointer comparison");
  }
}

// Return the logical operation, or abort if none exists.
static unsigned getBoolCmpOpcode(unsigned PredNum) {
  auto Pred = static_cast<CmpInst::Predicate>(PredNum);
  switch (Pred) {
  case CmpInst::ICMP_EQ:
    return SPIRV::OpLogicalEqual;
  case CmpInst::ICMP_NE:
    return SPIRV::OpLogicalNotEqual;
  default:
    llvm_unreachable("Unknown predicate type for Bool comparison");
  }
}

bool SPIRVInstructionSelector::selectBitreverse(Register ResVReg,
                                                const SPIRVType *ResType,
                                                MachineInstr &I) const {
  MachineBasicBlock &BB = *I.getParent();
  return BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpBitReverse))
      .addDef(ResVReg)
      .addUse(GR.getSPIRVTypeID(ResType))
      .addUse(I.getOperand(1).getReg())
      .constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectConstVector(Register ResVReg,
                                                 const SPIRVType *ResType,
                                                 MachineInstr &I) const {
  // TODO: only const case is supported for now.
  assert(std::all_of(
      I.operands_begin(), I.operands_end(), [this](const MachineOperand &MO) {
        if (MO.isDef())
          return true;
        if (!MO.isReg())
          return false;
        SPIRVType *ConstTy = this->MRI->getVRegDef(MO.getReg());
        assert(ConstTy && ConstTy->getOpcode() == SPIRV::ASSIGN_TYPE &&
               ConstTy->getOperand(1).isReg());
        Register ConstReg = ConstTy->getOperand(1).getReg();
        const MachineInstr *Const = this->MRI->getVRegDef(ConstReg);
        assert(Const);
        return (Const->getOpcode() == TargetOpcode::G_CONSTANT ||
                Const->getOpcode() == TargetOpcode::G_FCONSTANT);
      }));

  auto MIB = BuildMI(*I.getParent(), I, I.getDebugLoc(),
                     TII.get(SPIRV::OpConstantComposite))
                 .addDef(ResVReg)
                 .addUse(GR.getSPIRVTypeID(ResType));
  for (unsigned i = I.getNumExplicitDefs(); i < I.getNumExplicitOperands(); ++i)
    MIB.addUse(I.getOperand(i).getReg());
  return MIB.constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectCmp(Register ResVReg,
                                         const SPIRVType *ResType,
                                         unsigned CmpOpc,
                                         MachineInstr &I) const {
  Register Cmp0 = I.getOperand(2).getReg();
  Register Cmp1 = I.getOperand(3).getReg();
  assert(GR.getSPIRVTypeForVReg(Cmp0)->getOpcode() ==
             GR.getSPIRVTypeForVReg(Cmp1)->getOpcode() &&
         "CMP operands should have the same type");
  return BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(CmpOpc))
      .addDef(ResVReg)
      .addUse(GR.getSPIRVTypeID(ResType))
      .addUse(Cmp0)
      .addUse(Cmp1)
      .constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectICmp(Register ResVReg,
                                          const SPIRVType *ResType,
                                          MachineInstr &I) const {
  auto Pred = I.getOperand(1).getPredicate();
  unsigned CmpOpc;

  Register CmpOperand = I.getOperand(2).getReg();
  if (GR.isScalarOfType(CmpOperand, SPIRV::OpTypePointer))
    CmpOpc = getPtrCmpOpcode(Pred);
  else if (GR.isScalarOrVectorOfType(CmpOperand, SPIRV::OpTypeBool))
    CmpOpc = getBoolCmpOpcode(Pred);
  else
    CmpOpc = getICmpOpcode(Pred);
  return selectCmp(ResVReg, ResType, CmpOpc, I);
}

void SPIRVInstructionSelector::renderFImm32(MachineInstrBuilder &MIB,
                                            const MachineInstr &I,
                                            int OpIdx) const {
  assert(I.getOpcode() == TargetOpcode::G_FCONSTANT && OpIdx == -1 &&
         "Expected G_FCONSTANT");
  const ConstantFP *FPImm = I.getOperand(1).getFPImm();
  addNumImm(FPImm->getValueAPF().bitcastToAPInt(), MIB);
}

void SPIRVInstructionSelector::renderImm32(MachineInstrBuilder &MIB,
                                           const MachineInstr &I,
                                           int OpIdx) const {
  assert(I.getOpcode() == TargetOpcode::G_CONSTANT && OpIdx == -1 &&
         "Expected G_CONSTANT");
  addNumImm(I.getOperand(1).getCImm()->getValue(), MIB);
}

Register
SPIRVInstructionSelector::buildI32Constant(uint32_t Val, MachineInstr &I,
                                           const SPIRVType *ResType) const {
  Type *LLVMTy = IntegerType::get(GR.CurMF->getFunction().getContext(), 32);
  const SPIRVType *SpvI32Ty =
      ResType ? ResType : GR.getOrCreateSPIRVIntegerType(32, I, TII);
  // Find a constant in DT or build a new one.
  auto ConstInt = ConstantInt::get(LLVMTy, Val);
  Register NewReg = GR.find(ConstInt, GR.CurMF);
  if (!NewReg.isValid()) {
    NewReg = MRI->createGenericVirtualRegister(LLT::scalar(32));
    GR.add(ConstInt, GR.CurMF, NewReg);
    MachineInstr *MI;
    MachineBasicBlock &BB = *I.getParent();
    if (Val == 0) {
      MI = BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpConstantNull))
               .addDef(NewReg)
               .addUse(GR.getSPIRVTypeID(SpvI32Ty));
    } else {
      MI = BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpConstantI))
               .addDef(NewReg)
               .addUse(GR.getSPIRVTypeID(SpvI32Ty))
               .addImm(APInt(32, Val).getZExtValue());
    }
    constrainSelectedInstRegOperands(*MI, TII, TRI, RBI);
  }
  return NewReg;
}

bool SPIRVInstructionSelector::selectFCmp(Register ResVReg,
                                          const SPIRVType *ResType,
                                          MachineInstr &I) const {
  unsigned CmpOp = getFCmpOpcode(I.getOperand(1).getPredicate());
  return selectCmp(ResVReg, ResType, CmpOp, I);
}

Register SPIRVInstructionSelector::buildZerosVal(const SPIRVType *ResType,
                                                 MachineInstr &I) const {
  if (ResType->getOpcode() == SPIRV::OpTypeVector)
    return GR.getOrCreateConsIntVector(0, I, ResType, TII);
  return GR.getOrCreateConstInt(0, I, ResType, TII);
}

Register SPIRVInstructionSelector::buildOnesVal(bool AllOnes,
                                                const SPIRVType *ResType,
                                                MachineInstr &I) const {
  unsigned BitWidth = GR.getScalarOrVectorBitWidth(ResType);
  APInt One = AllOnes ? APInt::getAllOnesValue(BitWidth)
                      : APInt::getOneBitSet(BitWidth, 0);
  if (ResType->getOpcode() == SPIRV::OpTypeVector)
    return GR.getOrCreateConsIntVector(One.getZExtValue(), I, ResType, TII);
  return GR.getOrCreateConstInt(One.getZExtValue(), I, ResType, TII);
}

bool SPIRVInstructionSelector::selectSelect(Register ResVReg,
                                            const SPIRVType *ResType,
                                            MachineInstr &I,
                                            bool IsSigned) const {
  // To extend a bool, we need to use OpSelect between constants.
  Register ZeroReg = buildZerosVal(ResType, I);
  Register OneReg = buildOnesVal(IsSigned, ResType, I);
  bool IsScalarBool =
      GR.isScalarOfType(I.getOperand(1).getReg(), SPIRV::OpTypeBool);
  unsigned Opcode =
      IsScalarBool ? SPIRV::OpSelectSISCond : SPIRV::OpSelectSIVCond;
  return BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(Opcode))
      .addDef(ResVReg)
      .addUse(GR.getSPIRVTypeID(ResType))
      .addUse(I.getOperand(1).getReg())
      .addUse(OneReg)
      .addUse(ZeroReg)
      .constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectIToF(Register ResVReg,
                                          const SPIRVType *ResType,
                                          MachineInstr &I, bool IsSigned,
                                          unsigned Opcode) const {
  Register SrcReg = I.getOperand(1).getReg();
  // We can convert bool value directly to float type without OpConvert*ToF,
  // however the translator generates OpSelect+OpConvert*ToF, so we do the same.
  if (GR.isScalarOrVectorOfType(I.getOperand(1).getReg(), SPIRV::OpTypeBool)) {
    unsigned BitWidth = GR.getScalarOrVectorBitWidth(ResType);
    SPIRVType *TmpType = GR.getOrCreateSPIRVIntegerType(BitWidth, I, TII);
    if (ResType->getOpcode() == SPIRV::OpTypeVector) {
      const unsigned NumElts = ResType->getOperand(2).getImm();
      TmpType = GR.getOrCreateSPIRVVectorType(TmpType, NumElts, I, TII);
    }
    SrcReg = MRI->createVirtualRegister(&SPIRV::IDRegClass);
    selectSelect(SrcReg, TmpType, I, false);
  }
  return selectUnOpWithSrc(ResVReg, ResType, I, SrcReg, Opcode);
}

bool SPIRVInstructionSelector::selectExt(Register ResVReg,
                                         const SPIRVType *ResType,
                                         MachineInstr &I, bool IsSigned) const {
  if (GR.isScalarOrVectorOfType(I.getOperand(1).getReg(), SPIRV::OpTypeBool))
    return selectSelect(ResVReg, ResType, I, IsSigned);
  unsigned Opcode = IsSigned ? SPIRV::OpSConvert : SPIRV::OpUConvert;
  return selectUnOp(ResVReg, ResType, I, Opcode);
}

bool SPIRVInstructionSelector::selectIntToBool(Register IntReg,
                                               Register ResVReg,
                                               const SPIRVType *IntTy,
                                               const SPIRVType *BoolTy,
                                               MachineInstr &I) const {
  // To truncate to a bool, we use OpBitwiseAnd 1 and OpINotEqual to zero.
  Register BitIntReg = MRI->createVirtualRegister(&SPIRV::IDRegClass);
  bool IsVectorTy = IntTy->getOpcode() == SPIRV::OpTypeVector;
  unsigned Opcode = IsVectorTy ? SPIRV::OpBitwiseAndV : SPIRV::OpBitwiseAndS;
  Register Zero = buildZerosVal(IntTy, I);
  Register One = buildOnesVal(false, IntTy, I);
  MachineBasicBlock &BB = *I.getParent();
  BuildMI(BB, I, I.getDebugLoc(), TII.get(Opcode))
      .addDef(BitIntReg)
      .addUse(GR.getSPIRVTypeID(IntTy))
      .addUse(IntReg)
      .addUse(One)
      .constrainAllUses(TII, TRI, RBI);
  return BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpINotEqual))
      .addDef(ResVReg)
      .addUse(GR.getSPIRVTypeID(BoolTy))
      .addUse(BitIntReg)
      .addUse(Zero)
      .constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectTrunc(Register ResVReg,
                                           const SPIRVType *ResType,
                                           MachineInstr &I) const {
  if (GR.isScalarOrVectorOfType(ResVReg, SPIRV::OpTypeBool)) {
    Register IntReg = I.getOperand(1).getReg();
    const SPIRVType *ArgType = GR.getSPIRVTypeForVReg(IntReg);
    return selectIntToBool(IntReg, ResVReg, ArgType, ResType, I);
  }
  bool IsSigned = GR.isScalarOrVectorSigned(ResType);
  unsigned Opcode = IsSigned ? SPIRV::OpSConvert : SPIRV::OpUConvert;
  return selectUnOp(ResVReg, ResType, I, Opcode);
}

bool SPIRVInstructionSelector::selectConst(Register ResVReg,
                                           const SPIRVType *ResType,
                                           const APInt &Imm,
                                           MachineInstr &I) const {
  unsigned TyOpcode = ResType->getOpcode();
  assert(TyOpcode != SPIRV::OpTypePointer || Imm.isNullValue());
  MachineBasicBlock &BB = *I.getParent();
  if ((TyOpcode == SPIRV::OpTypePointer || TyOpcode == SPIRV::OpTypeEvent) &&
      Imm.isNullValue())
    return BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpConstantNull))
        .addDef(ResVReg)
        .addUse(GR.getSPIRVTypeID(ResType))
        .constrainAllUses(TII, TRI, RBI);
  if (TyOpcode == SPIRV::OpTypeInt) {
    Register Reg = GR.getOrCreateConstInt(Imm.getZExtValue(), I, ResType, TII);
    if (Reg == ResVReg)
      return true;
    return BuildMI(BB, I, I.getDebugLoc(), TII.get(TargetOpcode::COPY))
        .addDef(ResVReg)
        .addUse(Reg)
        .constrainAllUses(TII, TRI, RBI);
  }
  auto MIB = BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpConstantI))
                 .addDef(ResVReg)
                 .addUse(GR.getSPIRVTypeID(ResType));
  // <=32-bit integers should be caught by the sdag pattern.
  assert(Imm.getBitWidth() > 32);
  addNumImm(Imm, MIB);
  return MIB.constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectOpUndef(Register ResVReg,
                                             const SPIRVType *ResType,
                                             MachineInstr &I) const {
  return BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(SPIRV::OpUndef))
      .addDef(ResVReg)
      .addUse(GR.getSPIRVTypeID(ResType))
      .constrainAllUses(TII, TRI, RBI);
}

static bool isImm(const MachineOperand &MO, MachineRegisterInfo *MRI) {
  assert(MO.isReg());
  const SPIRVType *TypeInst = MRI->getVRegDef(MO.getReg());
  if (TypeInst->getOpcode() != SPIRV::ASSIGN_TYPE)
    return false;
  assert(TypeInst->getOperand(1).isReg());
  MachineInstr *ImmInst = MRI->getVRegDef(TypeInst->getOperand(1).getReg());
  return ImmInst->getOpcode() == TargetOpcode::G_CONSTANT;
}

static int64_t foldImm(const MachineOperand &MO, MachineRegisterInfo *MRI) {
  const SPIRVType *TypeInst = MRI->getVRegDef(MO.getReg());
  MachineInstr *ImmInst = MRI->getVRegDef(TypeInst->getOperand(1).getReg());
  assert(ImmInst->getOpcode() == TargetOpcode::G_CONSTANT);
  return ImmInst->getOperand(1).getCImm()->getZExtValue();
}

bool SPIRVInstructionSelector::selectInsertVal(Register ResVReg,
                                               const SPIRVType *ResType,
                                               MachineInstr &I) const {
  MachineBasicBlock &BB = *I.getParent();
  auto MIB = BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpCompositeInsert))
                 .addDef(ResVReg)
                 .addUse(GR.getSPIRVTypeID(ResType))
                 // object to insert
                 .addUse(I.getOperand(3).getReg())
                 // composite to insert into
                 .addUse(I.getOperand(2).getReg());
  for (unsigned i = 4; i < I.getNumOperands(); i++)
    MIB.addImm(foldImm(I.getOperand(i), MRI));
  return MIB.constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectExtractVal(Register ResVReg,
                                                const SPIRVType *ResType,
                                                MachineInstr &I) const {
  MachineBasicBlock &BB = *I.getParent();
  auto MIB = BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpCompositeExtract))
                 .addDef(ResVReg)
                 .addUse(GR.getSPIRVTypeID(ResType))
                 .addUse(I.getOperand(2).getReg());
  for (unsigned i = 3; i < I.getNumOperands(); i++)
    MIB.addImm(foldImm(I.getOperand(i), MRI));
  return MIB.constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectInsertElt(Register ResVReg,
                                               const SPIRVType *ResType,
                                               MachineInstr &I) const {
  if (isImm(I.getOperand(4), MRI))
    return selectInsertVal(ResVReg, ResType, I);
  MachineBasicBlock &BB = *I.getParent();
  return BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpVectorInsertDynamic))
      .addDef(ResVReg)
      .addUse(GR.getSPIRVTypeID(ResType))
      .addUse(I.getOperand(2).getReg())
      .addUse(I.getOperand(3).getReg())
      .addUse(I.getOperand(4).getReg())
      .constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectExtractElt(Register ResVReg,
                                                const SPIRVType *ResType,
                                                MachineInstr &I) const {
  if (isImm(I.getOperand(3), MRI))
    return selectExtractVal(ResVReg, ResType, I);
  MachineBasicBlock &BB = *I.getParent();
  return BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpVectorExtractDynamic))
      .addDef(ResVReg)
      .addUse(GR.getSPIRVTypeID(ResType))
      .addUse(I.getOperand(2).getReg())
      .addUse(I.getOperand(3).getReg())
      .constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectGEP(Register ResVReg,
                                         const SPIRVType *ResType,
                                         MachineInstr &I) const {
  // In general we should also support OpAccessChain instrs here (i.e. not
  // PtrAccessChain) but SPIRV-LLVM Translator doesn't emit them at all and so
  // do we to stay compliant with its test and more importantly consumers.
  unsigned Opcode = I.getOperand(2).getImm() ? SPIRV::OpInBoundsPtrAccessChain
                                             : SPIRV::OpPtrAccessChain;
  auto Res = BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(Opcode))
                 .addDef(ResVReg)
                 .addUse(GR.getSPIRVTypeID(ResType))
                 // Object to get a pointer to.
                 .addUse(I.getOperand(3).getReg());
  // Adding indices.
  for (unsigned i = 4; i < I.getNumExplicitOperands(); ++i)
    Res.addUse(I.getOperand(i).getReg());
  return Res.constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectIntrinsic(Register ResVReg,
                                               const SPIRVType *ResType,
                                               MachineInstr &I) const {
  MachineBasicBlock &BB = *I.getParent();
  switch (I.getIntrinsicID()) {
  case Intrinsic::spv_load:
    return selectLoad(ResVReg, ResType, I);
    break;
  case Intrinsic::spv_store:
    return selectStore(I);
    break;
  case Intrinsic::spv_extractv:
    return selectExtractVal(ResVReg, ResType, I);
    break;
  case Intrinsic::spv_insertv:
    return selectInsertVal(ResVReg, ResType, I);
    break;
  case Intrinsic::spv_extractelt:
    return selectExtractElt(ResVReg, ResType, I);
    break;
  case Intrinsic::spv_insertelt:
    return selectInsertElt(ResVReg, ResType, I);
    break;
  case Intrinsic::spv_gep:
    return selectGEP(ResVReg, ResType, I);
    break;
  case Intrinsic::spv_unref_global:
  case Intrinsic::spv_init_global: {
    MachineInstr *MI = MRI->getVRegDef(I.getOperand(1).getReg());
    MachineInstr *Init = I.getNumExplicitOperands() > 2
                             ? MRI->getVRegDef(I.getOperand(2).getReg())
                             : nullptr;
    assert(MI);
    return selectGlobalValue(MI->getOperand(0).getReg(), *MI, Init);
  } break;
  case Intrinsic::spv_const_composite: {
    // If no values are attached, the composite is null constant.
    bool IsNull = I.getNumExplicitDefs() + 1 == I.getNumExplicitOperands();
    unsigned Opcode =
        IsNull ? SPIRV::OpConstantNull : SPIRV::OpConstantComposite;
    auto MIB = BuildMI(BB, I, I.getDebugLoc(), TII.get(Opcode))
                   .addDef(ResVReg)
                   .addUse(GR.getSPIRVTypeID(ResType));
    // skip type MD node we already used when generated assign.type for this
    if (!IsNull) {
      for (unsigned i = I.getNumExplicitDefs() + 1;
           i < I.getNumExplicitOperands(); ++i) {
        MIB.addUse(I.getOperand(i).getReg());
      }
    }
    return MIB.constrainAllUses(TII, TRI, RBI);
  } break;
  case Intrinsic::spv_assign_name: {
    auto MIB = BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpName));
    MIB.addUse(I.getOperand(I.getNumExplicitDefs() + 1).getReg());
    for (unsigned i = I.getNumExplicitDefs() + 2;
         i < I.getNumExplicitOperands(); ++i) {
      MIB.addImm(I.getOperand(i).getImm());
    }
    return MIB.constrainAllUses(TII, TRI, RBI);
  } break;
  case Intrinsic::spv_switch: {
    auto MIB = BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpSwitch));
    for (unsigned i = 1; i < I.getNumExplicitOperands(); ++i) {
      if (I.getOperand(i).isReg())
        MIB.addReg(I.getOperand(i).getReg());
      else if (I.getOperand(i).isCImm())
        addNumImm(I.getOperand(i).getCImm()->getValue(), MIB);
      else if (I.getOperand(i).isMBB())
        MIB.addMBB(I.getOperand(i).getMBB());
      else
        llvm_unreachable("Unexpected OpSwitch operand");
    }
    return MIB.constrainAllUses(TII, TRI, RBI);
  } break;
  case Intrinsic::spv_cmpxchg:
    return selectAtomicCmpXchg(ResVReg, ResType, I);
    break;
  default:
    llvm_unreachable("Intrinsic selection not implemented");
  }
  return true;
}

bool SPIRVInstructionSelector::selectFrameIndex(Register ResVReg,
                                                const SPIRVType *ResType,
                                                MachineInstr &I) const {
  return BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(SPIRV::OpVariable))
      .addDef(ResVReg)
      .addUse(GR.getSPIRVTypeID(ResType))
      .addImm(static_cast<uint32_t>(SPIRV::StorageClass::Function))
      .constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectBranch(MachineInstr &I) const {
  // InstructionSelector walks backwards through the instructions. We can use
  // both a G_BR and a G_BRCOND to create an OpBranchConditional. We hit G_BR
  // first, so can generate an OpBranchConditional here. If there is no
  // G_BRCOND, we just use OpBranch for a regular unconditional branch.
  const MachineInstr *PrevI = I.getPrevNode();
  MachineBasicBlock &MBB = *I.getParent();
  if (PrevI != nullptr && PrevI->getOpcode() == TargetOpcode::G_BRCOND) {
    return BuildMI(MBB, I, I.getDebugLoc(), TII.get(SPIRV::OpBranchConditional))
        .addUse(PrevI->getOperand(0).getReg())
        .addMBB(PrevI->getOperand(1).getMBB())
        .addMBB(I.getOperand(0).getMBB())
        .constrainAllUses(TII, TRI, RBI);
  }
  return BuildMI(MBB, I, I.getDebugLoc(), TII.get(SPIRV::OpBranch))
      .addMBB(I.getOperand(0).getMBB())
      .constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectBranchCond(MachineInstr &I) const {
  // InstructionSelector walks backwards through the instructions. For an
  // explicit conditional branch with no fallthrough, we use both a G_BR and a
  // G_BRCOND to create an OpBranchConditional. We should hit G_BR first, and
  // generate the OpBranchConditional in selectBranch above.
  //
  // If an OpBranchConditional has been generated, we simply return, as the work
  // is alread done. If there is no OpBranchConditional, LLVM must be relying on
  // implicit fallthrough to the next basic block, so we need to create an
  // OpBranchConditional with an explicit "false" argument pointing to the next
  // basic block that LLVM would fall through to.
  const MachineInstr *NextI = I.getNextNode();
  // Check if this has already been successfully selected.
  if (NextI != nullptr && NextI->getOpcode() == SPIRV::OpBranchConditional)
    return true;
  // Must be relying on implicit block fallthrough, so generate an
  // OpBranchConditional with the "next" basic block as the "false" target.
  MachineBasicBlock &MBB = *I.getParent();
  unsigned NextMBBNum = MBB.getNextNode()->getNumber();
  MachineBasicBlock *NextMBB = I.getMF()->getBlockNumbered(NextMBBNum);
  return BuildMI(MBB, I, I.getDebugLoc(), TII.get(SPIRV::OpBranchConditional))
      .addUse(I.getOperand(0).getReg())
      .addMBB(I.getOperand(1).getMBB())
      .addMBB(NextMBB)
      .constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectPhi(Register ResVReg,
                                         const SPIRVType *ResType,
                                         MachineInstr &I) const {
  auto MIB = BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(SPIRV::OpPhi))
                 .addDef(ResVReg)
                 .addUse(GR.getSPIRVTypeID(ResType));
  const unsigned NumOps = I.getNumOperands();
  for (unsigned i = 1; i < NumOps; i += 2) {
    MIB.addUse(I.getOperand(i + 0).getReg());
    MIB.addMBB(I.getOperand(i + 1).getMBB());
  }
  return MIB.constrainAllUses(TII, TRI, RBI);
}

bool SPIRVInstructionSelector::selectGlobalValue(
    Register ResVReg, MachineInstr &I, const MachineInstr *Init) const {
  // FIXME: don't use MachineIRBuilder here, replace it with BuildMI.
  MachineIRBuilder MIRBuilder(I);
  const GlobalValue *GV = I.getOperand(1).getGlobal();
  SPIRVType *ResType = GR.getOrCreateSPIRVType(
      GV->getType(), MIRBuilder, SPIRV::AccessQualifier::ReadWrite, false);

  std::string GlobalIdent = GV->getGlobalIdentifier();
  // We have functions as operands in tests with blocks of instruction e.g. in
  // transcoding/global_block.ll. These operands are not used and should be
  // substituted by zero constants. Their type is expected to be always
  // OpTypePointer Function %uchar.
  if (isa<Function>(GV)) {
    const Constant *ConstVal = GV;
    MachineBasicBlock &BB = *I.getParent();
    Register NewReg = GR.find(ConstVal, GR.CurMF);
    if (!NewReg.isValid()) {
      SPIRVType *SpvBaseTy = GR.getOrCreateSPIRVIntegerType(8, I, TII);
      ResType = GR.getOrCreateSPIRVPointerType(SpvBaseTy, I, TII);
      Register NewReg = ResVReg;
      GR.add(ConstVal, GR.CurMF, NewReg);
      return BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpConstantNull))
          .addDef(NewReg)
          .addUse(GR.getSPIRVTypeID(ResType))
          .constrainAllUses(TII, TRI, RBI);
    }
    assert(NewReg != ResVReg);
    return BuildMI(BB, I, I.getDebugLoc(), TII.get(TargetOpcode::COPY))
        .addDef(ResVReg)
        .addUse(NewReg)
        .constrainAllUses(TII, TRI, RBI);
  }
  auto GlobalVar = cast<GlobalVariable>(GV);
  assert(GlobalVar->getName() != "llvm.global.annotations");

  bool HasInit = GlobalVar->hasInitializer() &&
                 !isa<UndefValue>(GlobalVar->getInitializer());
  // Skip empty declaration for GVs with initilaizers till we get the decl with
  // passed initializer.
  if (HasInit && !Init)
    return true;

  unsigned AddrSpace = GV->getAddressSpace();
  SPIRV::StorageClass Storage = addressSpaceToStorageClass(AddrSpace);
  bool HasLnkTy = GV->getLinkage() != GlobalValue::InternalLinkage &&
                  Storage != SPIRV::StorageClass::Function;
  SPIRV::LinkageType LnkType =
      (GV->isDeclaration() || GV->hasAvailableExternallyLinkage())
          ? SPIRV::LinkageType::Import
          : SPIRV::LinkageType::Export;

  Register Reg = GR.buildGlobalVariable(ResVReg, ResType, GlobalIdent, GV,
                                        Storage, Init, GlobalVar->isConstant(),
                                        HasLnkTy, LnkType, MIRBuilder, true);
  return Reg.isValid();
}

namespace llvm {
InstructionSelector *
createSPIRVInstructionSelector(const SPIRVTargetMachine &TM,
                               const SPIRVSubtarget &Subtarget,
                               const RegisterBankInfo &RBI) {
  return new SPIRVInstructionSelector(TM, Subtarget, RBI);
}
} // namespace llvm