SPIRVPreLegalizer.cpp

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//===-- SPIRVPreLegalizer.cpp - prepare IR for legalization -----*- 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
//
//===----------------------------------------------------------------------===//
//
// The pass prepares IR for legalization: it assigns SPIR-V types to registers
// and removes intrinsics which holded these types during IR translation.
// Also it processes constants and registers them in GR to avoid duplication.
//
//===----------------------------------------------------------------------===//
 
#include "SPIRV.h"
#include "SPIRVSubtarget.h"
#include "SPIRVUtils.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/IntrinsicsSPIRV.h"
#include "llvm/Target/TargetIntrinsicInfo.h"
 
#define DEBUG_TYPE "spirv-prelegalizer"
 
using namespace llvm;
 
namespace {
class SPIRVPreLegalizer : public MachineFunctionPass {
public:
  static char ID;
  SPIRVPreLegalizer() : MachineFunctionPass(ID) {
    initializeSPIRVPreLegalizerPass(*PassRegistry::getPassRegistry());
  }
  bool runOnMachineFunction(MachineFunction &MF) override;
};
} // namespace
 
static void
addConstantsToTrack(MachineFunction &MF, SPIRVGlobalRegistry *GR,
                    const SPIRVSubtarget &STI,
                    DenseMap<MachineInstr *, Type *> &TargetExtConstTypes,
                    SmallSet<Register, 4> &TrackedConstRegs) {
  MachineRegisterInfo &MRI = MF.getRegInfo();
  DenseMap<MachineInstr *, Register> RegsAlreadyAddedToDT;
  SmallVector<MachineInstr *, 10> ToErase, ToEraseComposites;
  for (MachineBasicBlock &MBB : MF) {
    for (MachineInstr &MI : MBB) {
      if (!isSpvIntrinsic(MI, Intrinsic::spv_track_constant))
        continue;
      ToErase.push_back(&MI);
      Register SrcReg = MI.getOperand(2).getReg();
      auto *Const =
          cast<Constant>(cast<ConstantAsMetadata>(
                             MI.getOperand(3).getMetadata()->getOperand(0))
                             ->getValue());
      if (auto *GV = dyn_cast<GlobalValue>(Const)) {
        Register Reg = GR->find(GV, &MF);
        if (!Reg.isValid())
          GR->add(GV, &MF, SrcReg);
        else
          RegsAlreadyAddedToDT[&MI] = Reg;
      } else {
        Register Reg = GR->find(Const, &MF);
        if (!Reg.isValid()) {
          if (auto *ConstVec = dyn_cast<ConstantDataVector>(Const)) {
            auto *BuildVec = MRI.getVRegDef(SrcReg);
            assert(BuildVec &&
                   BuildVec->getOpcode() == TargetOpcode::G_BUILD_VECTOR);
            for (unsigned i = 0; i < ConstVec->getNumElements(); ++i) {
              // Ensure that OpConstantComposite reuses a constant when it's
              // already created and available in the same machine function.
              Constant *ElemConst = ConstVec->getElementAsConstant(i);
              Register ElemReg = GR->find(ElemConst, &MF);
              if (!ElemReg.isValid())
                GR->add(ElemConst, &MF, BuildVec->getOperand(1 + i).getReg());
              else
                BuildVec->getOperand(1 + i).setReg(ElemReg);
            }
          }
          GR->add(Const, &MF, SrcReg);
          TrackedConstRegs.insert(SrcReg);
          if (Const->getType()->isTargetExtTy()) {
            // remember association so that we can restore it when assign types
            MachineInstr *SrcMI = MRI.getVRegDef(SrcReg);
            if (SrcMI && (SrcMI->getOpcode() == TargetOpcode::G_CONSTANT ||
                          SrcMI->getOpcode() == TargetOpcode::G_IMPLICIT_DEF))
              TargetExtConstTypes[SrcMI] = Const->getType();
            if (Const->isNullValue()) {
              MachineIRBuilder MIB(MF);
              SPIRVType *ExtType =
                  GR->getOrCreateSPIRVType(Const->getType(), MIB);
              SrcMI->setDesc(STI.getInstrInfo()->get(SPIRV::OpConstantNull));
              SrcMI->addOperand(MachineOperand::CreateReg(
                  GR->getSPIRVTypeID(ExtType), false));
            }
          }
        } else {
          RegsAlreadyAddedToDT[&MI] = Reg;
          // This MI is unused and will be removed. If the MI uses
          // const_composite, it will be unused and should be removed too.
          assert(MI.getOperand(2).isReg() && "Reg operand is expected");
          MachineInstr *SrcMI = MRI.getVRegDef(MI.getOperand(2).getReg());
          if (SrcMI && isSpvIntrinsic(*SrcMI, Intrinsic::spv_const_composite))
            ToEraseComposites.push_back(SrcMI);
        }
      }
    }
  }
  for (MachineInstr *MI : ToErase) {
    Register Reg = MI->getOperand(2).getReg();
    if (RegsAlreadyAddedToDT.contains(MI))
      Reg = RegsAlreadyAddedToDT[MI];
    auto *RC = MRI.getRegClassOrNull(MI->getOperand(0).getReg());
    if (!MRI.getRegClassOrNull(Reg) && RC)
      MRI.setRegClass(Reg, RC);
    MRI.replaceRegWith(MI->getOperand(0).getReg(), Reg);
    MI->eraseFromParent();
  }
  for (MachineInstr *MI : ToEraseComposites)
    MI->eraseFromParent();
}
 
static void
foldConstantsIntoIntrinsics(MachineFunction &MF,
                            const SmallSet<Register, 4> &TrackedConstRegs) {
  SmallVector<MachineInstr *, 10> ToErase;
  MachineRegisterInfo &MRI = MF.getRegInfo();
  const unsigned AssignNameOperandShift = 2;
  for (MachineBasicBlock &MBB : MF) {
    for (MachineInstr &MI : MBB) {
      if (!isSpvIntrinsic(MI, Intrinsic::spv_assign_name))
        continue;
      unsigned NumOp = MI.getNumExplicitDefs() + AssignNameOperandShift;
      while (MI.getOperand(NumOp).isReg()) {
        MachineOperand &MOp = MI.getOperand(NumOp);
        MachineInstr *ConstMI = MRI.getVRegDef(MOp.getReg());
        assert(ConstMI->getOpcode() == TargetOpcode::G_CONSTANT);
        MI.removeOperand(NumOp);
        MI.addOperand(MachineOperand::CreateImm(
            ConstMI->getOperand(1).getCImm()->getZExtValue()));
        Register DefReg = ConstMI->getOperand(0).getReg();
        if (MRI.use_empty(DefReg) && !TrackedConstRegs.contains(DefReg))
          ToErase.push_back(ConstMI);
      }
    }
  }
  for (MachineInstr *MI : ToErase)
    MI->eraseFromParent();
}
 
static MachineInstr *findAssignTypeInstr(Register Reg,
                                         MachineRegisterInfo *MRI) {
  for (MachineRegisterInfo::use_instr_iterator I = MRI->use_instr_begin(Reg),
                                               IE = MRI->use_instr_end();
       I != IE; ++I) {
    MachineInstr *UseMI = &*I;
    if ((isSpvIntrinsic(*UseMI, Intrinsic::spv_assign_ptr_type) ||
         isSpvIntrinsic(*UseMI, Intrinsic::spv_assign_type)) &&
        UseMI->getOperand(1).getReg() == Reg)
      return UseMI;
  }
  return nullptr;
}
 
static void insertBitcasts(MachineFunction &MF, SPIRVGlobalRegistry *GR,
                           MachineIRBuilder MIB) {
  // Get access to information about available extensions
  const SPIRVSubtarget *ST =
      static_cast<const SPIRVSubtarget *>(&MIB.getMF().getSubtarget());
  SmallVector<MachineInstr *, 10> ToErase;
  for (MachineBasicBlock &MBB : MF) {
    for (MachineInstr &MI : MBB) {
      if (!isSpvIntrinsic(MI, Intrinsic::spv_bitcast) &&
          !isSpvIntrinsic(MI, Intrinsic::spv_ptrcast))
        continue;
      assert(MI.getOperand(2).isReg());
      MIB.setInsertPt(*MI.getParent(), MI);
      ToErase.push_back(&MI);
      if (isSpvIntrinsic(MI, Intrinsic::spv_bitcast)) {
        MIB.buildBitcast(MI.getOperand(0).getReg(), MI.getOperand(2).getReg());
        continue;
      }
      Register Def = MI.getOperand(0).getReg();
      Register Source = MI.getOperand(2).getReg();
      Type *ElemTy = getMDOperandAsType(MI.getOperand(3).getMetadata(), 0);
      SPIRVType *BaseTy = GR->getOrCreateSPIRVType(ElemTy, MIB);
      SPIRVType *AssignedPtrType = GR->getOrCreateSPIRVPointerType(
          BaseTy, MI, *MF.getSubtarget<SPIRVSubtarget>().getInstrInfo(),
          addressSpaceToStorageClass(MI.getOperand(4).getImm(), *ST));
 
      // If the ptrcast would be redundant, replace all uses with the source
      // register.
      MachineRegisterInfo *MRI = MIB.getMRI();
      if (GR->getSPIRVTypeForVReg(Source) == AssignedPtrType) {
        // Erase Def's assign type instruction if we are going to replace Def.
        if (MachineInstr *AssignMI = findAssignTypeInstr(Def, MRI))
          ToErase.push_back(AssignMI);
        MRI->replaceRegWith(Def, Source);
      } else {
        GR->assignSPIRVTypeToVReg(AssignedPtrType, Def, MF);
        MIB.buildBitcast(Def, Source);
        // MachineVerifier requires that bitcast must change the type.
        // Change AddressSpace if needed to hint that Def and Source points to
        // different types: this doesn't change actual code generation.
        LLT DefType = MRI->getType(Def);
        if (DefType == MRI->getType(Source))
          MRI->setType(Def,
                       LLT::pointer((DefType.getAddressSpace() + 1) %
                                        SPIRVSubtarget::MaxLegalAddressSpace,
                                    GR->getPointerSize()));
      }
    }
  }
  for (MachineInstr *MI : ToErase)
    MI->eraseFromParent();
}
 
// Translating GV, IRTranslator sometimes generates following IR:
//   %1 = G_GLOBAL_VALUE
//   %2 = COPY %1
//   %3 = G_ADDRSPACE_CAST %2
//
// or
//
//  %1 = G_ZEXT %2
//  G_MEMCPY ... %2 ...
//
// New registers have no SPIRVType and no register class info.
//
// Set SPIRVType for GV, propagate it from GV to other instructions,
// also set register classes.
static SPIRVType *propagateSPIRVType(MachineInstr *MI, SPIRVGlobalRegistry *GR,
                                     MachineRegisterInfo &MRI,
                                     MachineIRBuilder &MIB) {
  SPIRVType *SpvType = nullptr;
  assert(MI && "Machine instr is expected");
  if (MI->getOperand(0).isReg()) {
    Register Reg = MI->getOperand(0).getReg();
    SpvType = GR->getSPIRVTypeForVReg(Reg);
    if (!SpvType) {
      switch (MI->getOpcode()) {
      case TargetOpcode::G_CONSTANT: {
        MIB.setInsertPt(*MI->getParent(), MI);
        Type *Ty = MI->getOperand(1).getCImm()->getType();
        SpvType = GR->getOrCreateSPIRVType(Ty, MIB);
        break;
      }
      case TargetOpcode::G_GLOBAL_VALUE: {
        MIB.setInsertPt(*MI->getParent(), MI);
        const GlobalValue *Global = MI->getOperand(1).getGlobal();
        Type *ElementTy = toTypedPointer(GR->getDeducedGlobalValueType(Global));
        auto *Ty = TypedPointerType::get(ElementTy,
                                         Global->getType()->getAddressSpace());
        SpvType = GR->getOrCreateSPIRVType(Ty, MIB);
        break;
      }
      case TargetOpcode::G_ANYEXT:
      case TargetOpcode::G_SEXT:
      case TargetOpcode::G_ZEXT: {
        if (MI->getOperand(1).isReg()) {
          if (MachineInstr *DefInstr =
                  MRI.getVRegDef(MI->getOperand(1).getReg())) {
            if (SPIRVType *Def = propagateSPIRVType(DefInstr, GR, MRI, MIB)) {
              unsigned CurrentBW = GR->getScalarOrVectorBitWidth(Def);
              unsigned ExpectedBW =
                  std::max(MRI.getType(Reg).getScalarSizeInBits(), CurrentBW);
              unsigned NumElements = GR->getScalarOrVectorComponentCount(Def);
              SpvType = GR->getOrCreateSPIRVIntegerType(ExpectedBW, MIB);
              if (NumElements > 1)
                SpvType =
                    GR->getOrCreateSPIRVVectorType(SpvType, NumElements, MIB);
            }
          }
        }
        break;
      }
      case TargetOpcode::G_PTRTOINT:
        SpvType = GR->getOrCreateSPIRVIntegerType(
            MRI.getType(Reg).getScalarSizeInBits(), MIB);
        break;
      case TargetOpcode::G_TRUNC:
      case TargetOpcode::G_ADDRSPACE_CAST:
      case TargetOpcode::G_PTR_ADD:
      case TargetOpcode::COPY: {
        MachineOperand &Op = MI->getOperand(1);
        MachineInstr *Def = Op.isReg() ? MRI.getVRegDef(Op.getReg()) : nullptr;
        if (Def)
          SpvType = propagateSPIRVType(Def, GR, MRI, MIB);
        break;
      }
      default:
        break;
      }
      if (SpvType)
        GR->assignSPIRVTypeToVReg(SpvType, Reg, MIB.getMF());
      if (!MRI.getRegClassOrNull(Reg))
        MRI.setRegClass(Reg, SpvType ? GR->getRegClass(SpvType)
                                     : &SPIRV::iIDRegClass);
    }
  }
  return SpvType;
}
 
// To support current approach and limitations wrt. bit width here we widen a
// scalar register with a bit width greater than 1 to valid sizes and cap it to
// 64 width.
static void widenScalarLLTNextPow2(Register Reg, MachineRegisterInfo &MRI) {
  LLT RegType = MRI.getType(Reg);
  if (!RegType.isScalar())
    return;
  unsigned Sz = RegType.getScalarSizeInBits();
  if (Sz == 1)
    return;
  unsigned NewSz = std::min(std::max(1u << Log2_32_Ceil(Sz), 8u), 64u);
  if (NewSz != Sz)
    MRI.setType(Reg, LLT::scalar(NewSz));
}
 
static std::pair<Register, unsigned>
createNewIdReg(SPIRVType *SpvType, Register SrcReg, MachineRegisterInfo &MRI,
               const SPIRVGlobalRegistry &GR) {
  if (!SpvType)
    SpvType = GR.getSPIRVTypeForVReg(SrcReg);
  const TargetRegisterClass *RC = GR.getRegClass(SpvType);
  Register Reg = MRI.createGenericVirtualRegister(GR.getRegType(SpvType));
  MRI.setRegClass(Reg, RC);
  unsigned GetIdOp = SPIRV::GET_ID;
  if (RC == &SPIRV::fIDRegClass)
    GetIdOp = SPIRV::GET_fID;
  else if (RC == &SPIRV::pIDRegClass)
    GetIdOp = SPIRV::GET_pID;
  else if (RC == &SPIRV::vfIDRegClass)
    GetIdOp = SPIRV::GET_vfID;
  else if (RC == &SPIRV::vpIDRegClass)
    GetIdOp = SPIRV::GET_vpID;
  else if (RC == &SPIRV::vIDRegClass)
    GetIdOp = SPIRV::GET_vID;
  return {Reg, GetIdOp};
}
 
// Insert ASSIGN_TYPE instuction between Reg and its definition, set NewReg as
// a dst of the definition, assign SPIRVType to both registers. If SpvType is
// provided, use it as SPIRVType in ASSIGN_TYPE, otherwise create it from Ty.
// It's used also in SPIRVBuiltins.cpp.
// TODO: maybe move to SPIRVUtils.
namespace llvm {
Register insertAssignInstr(Register Reg, Type *Ty, SPIRVType *SpvType,
                           SPIRVGlobalRegistry *GR, MachineIRBuilder &MIB,
                           MachineRegisterInfo &MRI) {
  MachineInstr *Def = MRI.getVRegDef(Reg);
  assert((Ty || SpvType) && "Either LLVM or SPIRV type is expected.");
  MIB.setInsertPt(*Def->getParent(),
                  (Def->getNextNode() ? Def->getNextNode()->getIterator()
                                      : Def->getParent()->end()));
  SpvType = SpvType ? SpvType : GR->getOrCreateSPIRVType(Ty, MIB);
  Register NewReg = MRI.createGenericVirtualRegister(MRI.getType(Reg));
  if (auto *RC = MRI.getRegClassOrNull(Reg)) {
    MRI.setRegClass(NewReg, RC);
  } else {
    auto RegClass = GR->getRegClass(SpvType);
    MRI.setRegClass(NewReg, RegClass);
    MRI.setRegClass(Reg, RegClass);
  }
  GR->assignSPIRVTypeToVReg(SpvType, Reg, MIB.getMF());
  // This is to make it convenient for Legalizer to get the SPIRVType
  // when processing the actual MI (i.e. not pseudo one).
  GR->assignSPIRVTypeToVReg(SpvType, NewReg, MIB.getMF());
  // Copy MIFlags from Def to ASSIGN_TYPE instruction. It's required to keep
  // the flags after instruction selection.
  const uint32_t Flags = Def->getFlags();
  MIB.buildInstr(SPIRV::ASSIGN_TYPE)
      .addDef(Reg)
      .addUse(NewReg)
      .addUse(GR->getSPIRVTypeID(SpvType))
      .setMIFlags(Flags);
  Def->getOperand(0).setReg(NewReg);
  return NewReg;
}
 
void processInstr(MachineInstr &MI, MachineIRBuilder &MIB,
                  MachineRegisterInfo &MRI, SPIRVGlobalRegistry *GR) {
  assert(MI.getNumDefs() > 0 && MRI.hasOneUse(MI.getOperand(0).getReg()));
  MachineInstr &AssignTypeInst =
      *(MRI.use_instr_begin(MI.getOperand(0).getReg()));
  auto NewReg =
      createNewIdReg(nullptr, MI.getOperand(0).getReg(), MRI, *GR).first;
  AssignTypeInst.getOperand(1).setReg(NewReg);
  MI.getOperand(0).setReg(NewReg);
  MIB.setInsertPt(*MI.getParent(),
                  (MI.getNextNode() ? MI.getNextNode()->getIterator()
                                    : MI.getParent()->end()));
  for (auto &Op : MI.operands()) {
    if (!Op.isReg() || Op.isDef())
      continue;
    auto IdOpInfo = createNewIdReg(nullptr, Op.getReg(), MRI, *GR);
    MIB.buildInstr(IdOpInfo.second).addDef(IdOpInfo.first).addUse(Op.getReg());
    Op.setReg(IdOpInfo.first);
  }
}
} // namespace llvm
 
static void
generateAssignInstrs(MachineFunction &MF, SPIRVGlobalRegistry *GR,
                     MachineIRBuilder MIB,
                     DenseMap<MachineInstr *, Type *> &TargetExtConstTypes) {
  // Get access to information about available extensions
  const SPIRVSubtarget *ST =
      static_cast<const SPIRVSubtarget *>(&MIB.getMF().getSubtarget());
 
  MachineRegisterInfo &MRI = MF.getRegInfo();
  SmallVector<MachineInstr *, 10> ToErase;
  DenseMap<MachineInstr *, Register> RegsAlreadyAddedToDT;
 
  bool IsExtendedInts =
      ST->canUseExtension(
          SPIRV::Extension::SPV_INTEL_arbitrary_precision_integers) ||
      ST->canUseExtension(SPIRV::Extension::SPV_KHR_bit_instructions);
 
  for (MachineBasicBlock *MBB : post_order(&MF)) {
    if (MBB->empty())
      continue;
 
    bool ReachedBegin = false;
    for (auto MII = std::prev(MBB->end()), Begin = MBB->begin();
         !ReachedBegin;) {
      MachineInstr &MI = *MII;
      unsigned MIOp = MI.getOpcode();
 
      if (!IsExtendedInts) {
        // validate bit width of scalar registers
        for (const auto &MOP : MI.operands())
          if (MOP.isReg())
            widenScalarLLTNextPow2(MOP.getReg(), MRI);
      }
 
      if (isSpvIntrinsic(MI, Intrinsic::spv_assign_ptr_type)) {
        Register Reg = MI.getOperand(1).getReg();
        MIB.setInsertPt(*MI.getParent(), MI.getIterator());
        Type *ElementTy = getMDOperandAsType(MI.getOperand(2).getMetadata(), 0);
        SPIRVType *BaseTy = GR->getOrCreateSPIRVType(ElementTy, MIB);
        SPIRVType *AssignedPtrType = GR->getOrCreateSPIRVPointerType(
            BaseTy, MI, *MF.getSubtarget<SPIRVSubtarget>().getInstrInfo(),
            addressSpaceToStorageClass(MI.getOperand(3).getImm(), *ST));
        MachineInstr *Def = MRI.getVRegDef(Reg);
        assert(Def && "Expecting an instruction that defines the register");
        // G_GLOBAL_VALUE already has type info.
        if (Def->getOpcode() != TargetOpcode::G_GLOBAL_VALUE &&
            Def->getOpcode() != SPIRV::ASSIGN_TYPE)
          insertAssignInstr(Reg, nullptr, AssignedPtrType, GR, MIB,
                            MF.getRegInfo());
        ToErase.push_back(&MI);
      } else if (isSpvIntrinsic(MI, Intrinsic::spv_assign_type)) {
        Register Reg = MI.getOperand(1).getReg();
        Type *Ty = getMDOperandAsType(MI.getOperand(2).getMetadata(), 0);
        MachineInstr *Def = MRI.getVRegDef(Reg);
        assert(Def && "Expecting an instruction that defines the register");
        // G_GLOBAL_VALUE already has type info.
        if (Def->getOpcode() != TargetOpcode::G_GLOBAL_VALUE &&
            Def->getOpcode() != SPIRV::ASSIGN_TYPE)
          insertAssignInstr(Reg, Ty, nullptr, GR, MIB, MF.getRegInfo());
        ToErase.push_back(&MI);
      } else if (MIOp == TargetOpcode::G_CONSTANT ||
                 MIOp == TargetOpcode::G_FCONSTANT ||
                 MIOp == TargetOpcode::G_BUILD_VECTOR) {
        // %rc = G_CONSTANT ty Val
        // ===>
        // %cty = OpType* ty
        // %rctmp = G_CONSTANT ty Val
        // %rc = ASSIGN_TYPE %rctmp, %cty
        Register Reg = MI.getOperand(0).getReg();
        bool NeedAssignType = true;
        if (MRI.hasOneUse(Reg)) {
          MachineInstr &UseMI = *MRI.use_instr_begin(Reg);
          if (isSpvIntrinsic(UseMI, Intrinsic::spv_assign_type) ||
              isSpvIntrinsic(UseMI, Intrinsic::spv_assign_name))
            continue;
          if (UseMI.getOpcode() == SPIRV::ASSIGN_TYPE)
            NeedAssignType = false;
        }
        Type *Ty = nullptr;
        if (MIOp == TargetOpcode::G_CONSTANT) {
          auto TargetExtIt = TargetExtConstTypes.find(&MI);
          Ty = TargetExtIt == TargetExtConstTypes.end()
                   ? MI.getOperand(1).getCImm()->getType()
                   : TargetExtIt->second;
          const ConstantInt *OpCI = MI.getOperand(1).getCImm();
          Register PrimaryReg = GR->find(OpCI, &MF);
          if (!PrimaryReg.isValid()) {
            GR->add(OpCI, &MF, Reg);
          } else if (PrimaryReg != Reg &&
                     MRI.getType(Reg) == MRI.getType(PrimaryReg)) {
            auto *RCReg = MRI.getRegClassOrNull(Reg);
            auto *RCPrimary = MRI.getRegClassOrNull(PrimaryReg);
            if (!RCReg || RCPrimary == RCReg) {
              RegsAlreadyAddedToDT[&MI] = PrimaryReg;
              ToErase.push_back(&MI);
              NeedAssignType = false;
            }
          }
        } else if (MIOp == TargetOpcode::G_FCONSTANT) {
          Ty = MI.getOperand(1).getFPImm()->getType();
        } else {
          assert(MIOp == TargetOpcode::G_BUILD_VECTOR);
          Type *ElemTy = nullptr;
          MachineInstr *ElemMI = MRI.getVRegDef(MI.getOperand(1).getReg());
          assert(ElemMI);
 
          if (ElemMI->getOpcode() == TargetOpcode::G_CONSTANT) {
            ElemTy = ElemMI->getOperand(1).getCImm()->getType();
          } else if (ElemMI->getOpcode() == TargetOpcode::G_FCONSTANT) {
            ElemTy = ElemMI->getOperand(1).getFPImm()->getType();
          } else {
            // There may be a case when we already know Reg's type.
            MachineInstr *NextMI = MI.getNextNode();
            if (!NextMI || NextMI->getOpcode() != SPIRV::ASSIGN_TYPE ||
                NextMI->getOperand(1).getReg() != Reg)
              llvm_unreachable("Unexpected opcode");
          }
          if (ElemTy)
            Ty = VectorType::get(
                ElemTy, MI.getNumExplicitOperands() - MI.getNumExplicitDefs(),
                false);
          else
            NeedAssignType = false;
        }
        if (NeedAssignType)
          insertAssignInstr(Reg, Ty, nullptr, GR, MIB, MRI);
      } else if (MIOp == TargetOpcode::G_GLOBAL_VALUE) {
        propagateSPIRVType(&MI, GR, MRI, MIB);
      }
 
      if (MII == Begin)
        ReachedBegin = true;
      else
        --MII;
    }
  }
  for (MachineInstr *MI : ToErase) {
    auto It = RegsAlreadyAddedToDT.find(MI);
    if (RegsAlreadyAddedToDT.contains(MI))
      MRI.replaceRegWith(MI->getOperand(0).getReg(), It->second);
    MI->eraseFromParent();
  }
 
  // Address the case when IRTranslator introduces instructions with new
  // registers without SPIRVType associated.
  for (MachineBasicBlock &MBB : MF) {
    for (MachineInstr &MI : MBB) {
      switch (MI.getOpcode()) {
      case TargetOpcode::G_TRUNC:
      case TargetOpcode::G_ANYEXT:
      case TargetOpcode::G_SEXT:
      case TargetOpcode::G_ZEXT:
      case TargetOpcode::G_PTRTOINT:
      case TargetOpcode::COPY:
      case TargetOpcode::G_ADDRSPACE_CAST:
        propagateSPIRVType(&MI, GR, MRI, MIB);
        break;
      }
    }
  }
}
 
// Defined in SPIRVLegalizerInfo.cpp.
extern bool isTypeFoldingSupported(unsigned Opcode);
 
static void processInstrsWithTypeFolding(MachineFunction &MF,
                                         SPIRVGlobalRegistry *GR,
                                         MachineIRBuilder MIB) {
  MachineRegisterInfo &MRI = MF.getRegInfo();
  for (MachineBasicBlock &MBB : MF) {
    for (MachineInstr &MI : MBB) {
      if (isTypeFoldingSupported(MI.getOpcode()))
        processInstr(MI, MIB, MRI, GR);
    }
  }
 
  for (MachineBasicBlock &MBB : MF) {
    for (MachineInstr &MI : MBB) {
      // We need to rewrite dst types for ASSIGN_TYPE instrs to be able
      // to perform tblgen'erated selection and we can't do that on Legalizer
      // as it operates on gMIR only.
      if (MI.getOpcode() != SPIRV::ASSIGN_TYPE)
        continue;
      Register SrcReg = MI.getOperand(1).getReg();
      unsigned Opcode = MRI.getVRegDef(SrcReg)->getOpcode();
      if (!isTypeFoldingSupported(Opcode))
        continue;
      Register DstReg = MI.getOperand(0).getReg();
      // Don't need to reset type of register holding constant and used in
      // G_ADDRSPACE_CAST, since it breaks legalizer.
      if (Opcode == TargetOpcode::G_CONSTANT && MRI.hasOneUse(DstReg)) {
        MachineInstr &UseMI = *MRI.use_instr_begin(DstReg);
        if (UseMI.getOpcode() == TargetOpcode::G_ADDRSPACE_CAST)
          continue;
      }
    }
  }
}
 
static Register
collectInlineAsmInstrOperands(MachineInstr *MI,
                              SmallVector<unsigned, 4> *Ops = nullptr) {
  Register DefReg;
  unsigned StartOp = InlineAsm::MIOp_FirstOperand,
           AsmDescOp = InlineAsm::MIOp_FirstOperand;
  for (unsigned Idx = StartOp, MISz = MI->getNumOperands(); Idx != MISz;
       ++Idx) {
    const MachineOperand &MO = MI->getOperand(Idx);
    if (MO.isMetadata())
      continue;
    if (Idx == AsmDescOp && MO.isImm()) {
      // compute the index of the next operand descriptor
      const InlineAsm::Flag F(MO.getImm());
      AsmDescOp += 1 + F.getNumOperandRegisters();
      continue;
    }
    if (MO.isReg() && MO.isDef()) {
      if (!Ops)
        return MO.getReg();
      else
        DefReg = MO.getReg();
    } else if (Ops) {
      Ops->push_back(Idx);
    }
  }
  return DefReg;
}
 
static void
insertInlineAsmProcess(MachineFunction &MF, SPIRVGlobalRegistry *GR,
                       const SPIRVSubtarget &ST, MachineIRBuilder MIRBuilder,
                       const SmallVector<MachineInstr *> &ToProcess) {
  MachineRegisterInfo &MRI = MF.getRegInfo();
  Register AsmTargetReg;
  for (unsigned i = 0, Sz = ToProcess.size(); i + 1 < Sz; i += 2) {
    MachineInstr *I1 = ToProcess[i], *I2 = ToProcess[i + 1];
    assert(isSpvIntrinsic(*I1, Intrinsic::spv_inline_asm) && I2->isInlineAsm());
    MIRBuilder.setInsertPt(*I2->getParent(), *I2);
 
    if (!AsmTargetReg.isValid()) {
      // define vendor specific assembly target or dialect
      AsmTargetReg = MRI.createGenericVirtualRegister(LLT::scalar(32));
      MRI.setRegClass(AsmTargetReg, &SPIRV::iIDRegClass);
      auto AsmTargetMIB =
          MIRBuilder.buildInstr(SPIRV::OpAsmTargetINTEL).addDef(AsmTargetReg);
      addStringImm(ST.getTargetTripleAsStr(), AsmTargetMIB);
      GR->add(AsmTargetMIB.getInstr(), &MF, AsmTargetReg);
    }
 
    // create types
    const MDNode *IAMD = I1->getOperand(1).getMetadata();
    FunctionType *FTy = cast<FunctionType>(getMDOperandAsType(IAMD, 0));
    SmallVector<SPIRVType *, 4> ArgTypes;
    for (const auto &ArgTy : FTy->params())
      ArgTypes.push_back(GR->getOrCreateSPIRVType(ArgTy, MIRBuilder));
    SPIRVType *RetType =
        GR->getOrCreateSPIRVType(FTy->getReturnType(), MIRBuilder);
    SPIRVType *FuncType = GR->getOrCreateOpTypeFunctionWithArgs(
        FTy, RetType, ArgTypes, MIRBuilder);
 
    // define vendor specific assembly instructions string
    Register AsmReg = MRI.createGenericVirtualRegister(LLT::scalar(32));
    MRI.setRegClass(AsmReg, &SPIRV::iIDRegClass);
    auto AsmMIB = MIRBuilder.buildInstr(SPIRV::OpAsmINTEL)
                      .addDef(AsmReg)
                      .addUse(GR->getSPIRVTypeID(RetType))
                      .addUse(GR->getSPIRVTypeID(FuncType))
                      .addUse(AsmTargetReg);
    // inline asm string:
    addStringImm(I2->getOperand(InlineAsm::MIOp_AsmString).getSymbolName(),
                 AsmMIB);
    // inline asm constraint string:
    addStringImm(cast<MDString>(I1->getOperand(2).getMetadata()->getOperand(0))
                     ->getString(),
                 AsmMIB);
    GR->add(AsmMIB.getInstr(), &MF, AsmReg);
 
    // calls the inline assembly instruction
    unsigned ExtraInfo = I2->getOperand(InlineAsm::MIOp_ExtraInfo).getImm();
    if (ExtraInfo & InlineAsm::Extra_HasSideEffects)
      MIRBuilder.buildInstr(SPIRV::OpDecorate)
          .addUse(AsmReg)
          .addImm(static_cast<uint32_t>(SPIRV::Decoration::SideEffectsINTEL));
 
    Register DefReg = collectInlineAsmInstrOperands(I2);
    if (!DefReg.isValid()) {
      DefReg = MRI.createGenericVirtualRegister(LLT::scalar(32));
      MRI.setRegClass(DefReg, &SPIRV::iIDRegClass);
      SPIRVType *VoidType = GR->getOrCreateSPIRVType(
          Type::getVoidTy(MF.getFunction().getContext()), MIRBuilder);
      GR->assignSPIRVTypeToVReg(VoidType, DefReg, MF);
    }
 
    auto AsmCall = MIRBuilder.buildInstr(SPIRV::OpAsmCallINTEL)
                       .addDef(DefReg)
                       .addUse(GR->getSPIRVTypeID(RetType))
                       .addUse(AsmReg);
    for (unsigned IntrIdx = 3; IntrIdx < I1->getNumOperands(); ++IntrIdx)
      AsmCall.addUse(I1->getOperand(IntrIdx).getReg());
  }
  for (MachineInstr *MI : ToProcess)
    MI->eraseFromParent();
}
 
static void insertInlineAsm(MachineFunction &MF, SPIRVGlobalRegistry *GR,
                            const SPIRVSubtarget &ST,
                            MachineIRBuilder MIRBuilder) {
  SmallVector<MachineInstr *> ToProcess;
  for (MachineBasicBlock &MBB : MF) {
    for (MachineInstr &MI : MBB) {
      if (isSpvIntrinsic(MI, Intrinsic::spv_inline_asm) ||
          MI.getOpcode() == TargetOpcode::INLINEASM)
        ToProcess.push_back(&MI);
    }
  }
  if (ToProcess.size() == 0)
    return;
 
  if (!ST.canUseExtension(SPIRV::Extension::SPV_INTEL_inline_assembly))
    report_fatal_error("Inline assembly instructions require the "
                       "following SPIR-V extension: SPV_INTEL_inline_assembly",
                       false);
 
  insertInlineAsmProcess(MF, GR, ST, MIRBuilder, ToProcess);
}
 
static void insertSpirvDecorations(MachineFunction &MF, MachineIRBuilder MIB) {
  SmallVector<MachineInstr *, 10> ToErase;
  for (MachineBasicBlock &MBB : MF) {
    for (MachineInstr &MI : MBB) {
      if (!isSpvIntrinsic(MI, Intrinsic::spv_assign_decoration))
        continue;
      MIB.setInsertPt(*MI.getParent(), MI);
      buildOpSpirvDecorations(MI.getOperand(1).getReg(), MIB,
                              MI.getOperand(2).getMetadata());
      ToErase.push_back(&MI);
    }
  }
  for (MachineInstr *MI : ToErase)
    MI->eraseFromParent();
}
 
// Find basic blocks of the switch and replace registers in spv_switch() by its
// MBB equivalent.
static void processSwitches(MachineFunction &MF, SPIRVGlobalRegistry *GR,
                            MachineIRBuilder MIB) {
  DenseMap<const BasicBlock *, MachineBasicBlock *> BB2MBB;
  SmallVector<std::pair<MachineInstr *, SmallVector<MachineInstr *, 8>>>
      Switches;
  for (MachineBasicBlock &MBB : MF) {
    MachineRegisterInfo &MRI = MF.getRegInfo();
    BB2MBB[MBB.getBasicBlock()] = &MBB;
    for (MachineInstr &MI : MBB) {
      if (!isSpvIntrinsic(MI, Intrinsic::spv_switch))
        continue;
      // Calls to spv_switch intrinsics representing IR switches.
      SmallVector<MachineInstr *, 8> NewOps;
      for (unsigned i = 2; i < MI.getNumOperands(); ++i) {
        Register Reg = MI.getOperand(i).getReg();
        if (i % 2 == 1) {
          MachineInstr *ConstInstr = getDefInstrMaybeConstant(Reg, &MRI);
          NewOps.push_back(ConstInstr);
        } else {
          MachineInstr *BuildMBB = MRI.getVRegDef(Reg);
          assert(BuildMBB &&
                 BuildMBB->getOpcode() == TargetOpcode::G_BLOCK_ADDR &&
                 BuildMBB->getOperand(1).isBlockAddress() &&
                 BuildMBB->getOperand(1).getBlockAddress());
          NewOps.push_back(BuildMBB);
        }
      }
      Switches.push_back(std::make_pair(&MI, NewOps));
    }
  }
 
  SmallPtrSet<MachineInstr *, 8> ToEraseMI;
  for (auto &SwIt : Switches) {
    MachineInstr &MI = *SwIt.first;
    SmallVector<MachineInstr *, 8> &Ins = SwIt.second;
    SmallVector<MachineOperand, 8> NewOps;
    for (unsigned i = 0; i < Ins.size(); ++i) {
      if (Ins[i]->getOpcode() == TargetOpcode::G_BLOCK_ADDR) {
        BasicBlock *CaseBB =
            Ins[i]->getOperand(1).getBlockAddress()->getBasicBlock();
        auto It = BB2MBB.find(CaseBB);
        if (It == BB2MBB.end())
          report_fatal_error("cannot find a machine basic block by a basic "
                             "block in a switch statement");
        NewOps.push_back(MachineOperand::CreateMBB(It->second));
        MI.getParent()->addSuccessor(It->second);
        ToEraseMI.insert(Ins[i]);
      } else {
        NewOps.push_back(
            MachineOperand::CreateCImm(Ins[i]->getOperand(1).getCImm()));
      }
    }
    for (unsigned i = MI.getNumOperands() - 1; i > 1; --i)
      MI.removeOperand(i);
    for (auto &MO : NewOps)
      MI.addOperand(MO);
    if (MachineInstr *Next = MI.getNextNode()) {
      if (isSpvIntrinsic(*Next, Intrinsic::spv_track_constant)) {
        ToEraseMI.insert(Next);
        Next = MI.getNextNode();
      }
      if (Next && Next->getOpcode() == TargetOpcode::G_BRINDIRECT)
        ToEraseMI.insert(Next);
    }
  }
 
  // If we just delete G_BLOCK_ADDR instructions with BlockAddress operands,
  // this leaves their BasicBlock counterparts in a "address taken" status. This
  // would make AsmPrinter to generate a series of unneeded labels of a "Address
  // of block that was removed by CodeGen" kind. Let's first ensure that we
  // don't have a dangling BlockAddress constants by zapping the BlockAddress
  // nodes, and only after that proceed with erasing G_BLOCK_ADDR instructions.
  Constant *Replacement =
      ConstantInt::get(Type::getInt32Ty(MF.getFunction().getContext()), 1);
  for (MachineInstr *BlockAddrI : ToEraseMI) {
    if (BlockAddrI->getOpcode() == TargetOpcode::G_BLOCK_ADDR) {
      BlockAddress *BA = const_cast<BlockAddress *>(
          BlockAddrI->getOperand(1).getBlockAddress());
      BA->replaceAllUsesWith(
          ConstantExpr::getIntToPtr(Replacement, BA->getType()));
      BA->destroyConstant();
    }
    BlockAddrI->eraseFromParent();
  }
}
 
static bool isImplicitFallthrough(MachineBasicBlock &MBB) {
  if (MBB.empty())
    return true;
 
  // Branching SPIR-V intrinsics are not detected by this generic method.
  // Thus, we can only trust negative result.
  if (!MBB.canFallThrough())
    return false;
 
  // Otherwise, we must manually check if we have a SPIR-V intrinsic which
  // prevent an implicit fallthrough.
  for (MachineBasicBlock::reverse_iterator It = MBB.rbegin(), E = MBB.rend();
       It != E; ++It) {
    if (isSpvIntrinsic(*It, Intrinsic::spv_switch))
      return false;
  }
  return true;
}
 
static void removeImplicitFallthroughs(MachineFunction &MF,
                                       MachineIRBuilder MIB) {
  // It is valid for MachineBasicBlocks to not finish with a branch instruction.
  // In such cases, they will simply fallthrough their immediate successor.
  for (MachineBasicBlock &MBB : MF) {
    if (!isImplicitFallthrough(MBB))
      continue;
 
    assert(std::distance(MBB.successors().begin(), MBB.successors().end()) ==
           1);
    MIB.setInsertPt(MBB, MBB.end());
    MIB.buildBr(**MBB.successors().begin());
  }
}
 
bool SPIRVPreLegalizer::runOnMachineFunction(MachineFunction &MF) {
  // Initialize the type registry.
  const SPIRVSubtarget &ST = MF.getSubtarget<SPIRVSubtarget>();
  SPIRVGlobalRegistry *GR = ST.getSPIRVGlobalRegistry();
  GR->setCurrentFunc(MF);
  MachineIRBuilder MIB(MF);
  // a registry of target extension constants
  DenseMap<MachineInstr *, Type *> TargetExtConstTypes;
  // to keep record of tracked constants
  SmallSet<Register, 4> TrackedConstRegs;
  addConstantsToTrack(MF, GR, ST, TargetExtConstTypes, TrackedConstRegs);
  foldConstantsIntoIntrinsics(MF, TrackedConstRegs);
  insertBitcasts(MF, GR, MIB);
  generateAssignInstrs(MF, GR, MIB, TargetExtConstTypes);
  processSwitches(MF, GR, MIB);
  processInstrsWithTypeFolding(MF, GR, MIB);
  removeImplicitFallthroughs(MF, MIB);
  insertSpirvDecorations(MF, MIB);
  insertInlineAsm(MF, GR, ST, MIB);
 
  return true;
}
 
INITIALIZE_PASS(SPIRVPreLegalizer, DEBUG_TYPE, "SPIRV pre legalizer", false,
                false)
 
char SPIRVPreLegalizer::ID = 0;
 
FunctionPass *llvm::createSPIRVPreLegalizerPass() {
  return new SPIRVPreLegalizer();
}