[MIParser] Set RegClassOrRegBank during instruction parsing

[llvm-complete.git] / lib / CodeGen / GlobalISel / IRTranslator.cpp

//===- llvm/CodeGen/GlobalISel/IRTranslator.cpp - IRTranslator ---*- 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
//
//===----------------------------------------------------------------------===//
/// \file
/// This file implements the IRTranslator class.
//===----------------------------------------------------------------------===//

#include "llvm/CodeGen/GlobalISel/IRTranslator.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/ScopeExit.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/CodeGen/FunctionLoweringInfo.h"
#include "llvm/CodeGen/GlobalISel/CallLowering.h"
#include "llvm/CodeGen/GlobalISel/GISelChangeObserver.h"
#include "llvm/CodeGen/LowLevelType.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/StackProtector.h"
#include "llvm/CodeGen/TargetFrameLowering.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/MC/MCContext.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/LowLevelTypeImpl.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetIntrinsicInfo.h"
#include "llvm/Target/TargetMachine.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <iterator>
#include <string>
#include <utility>
#include <vector>

#define DEBUG_TYPE "irtranslator"

using namespace llvm;

static cl::opt<bool>
    EnableCSEInIRTranslator("enable-cse-in-irtranslator",
                            cl::desc("Should enable CSE in irtranslator"),
                            cl::Optional, cl::init(false));
char IRTranslator::ID = 0;

INITIALIZE_PASS_BEGIN(IRTranslator, DEBUG_TYPE, "IRTranslator LLVM IR -> MI",
                false, false)
INITIALIZE_PASS_DEPENDENCY(TargetPassConfig)
INITIALIZE_PASS_DEPENDENCY(GISelCSEAnalysisWrapperPass)
INITIALIZE_PASS_END(IRTranslator, DEBUG_TYPE, "IRTranslator LLVM IR -> MI",
                false, false)

static void reportTranslationError(MachineFunction &MF,
                                   const TargetPassConfig &TPC,
                                   OptimizationRemarkEmitter &ORE,
                                   OptimizationRemarkMissed &R) {
  MF.getProperties().set(MachineFunctionProperties::Property::FailedISel);

  // Print the function name explicitly if we don't have a debug location (which
  // makes the diagnostic less useful) or if we're going to emit a raw error.
  if (!R.getLocation().isValid() || TPC.isGlobalISelAbortEnabled())
    R << (" (in function: " + MF.getName() + ")").str();

  if (TPC.isGlobalISelAbortEnabled())
    report_fatal_error(R.getMsg());
  else
    ORE.emit(R);
}

IRTranslator::IRTranslator() : MachineFunctionPass(ID) { }

#ifndef NDEBUG
namespace {
/// Verify that every instruction created has the same DILocation as the
/// instruction being translated.
class DILocationVerifier : public GISelChangeObserver {
  const Instruction *CurrInst = nullptr;

public:
  DILocationVerifier() = default;
  ~DILocationVerifier() = default;

  const Instruction *getCurrentInst() const { return CurrInst; }
  void setCurrentInst(const Instruction *Inst) { CurrInst = Inst; }

  void erasingInstr(MachineInstr &MI) override {}
  void changingInstr(MachineInstr &MI) override {}
  void changedInstr(MachineInstr &MI) override {}

  void createdInstr(MachineInstr &MI) override {
    assert(getCurrentInst() && "Inserted instruction without a current MI");

    // Only print the check message if we're actually checking it.
#ifndef NDEBUG
    LLVM_DEBUG(dbgs() << "Checking DILocation from " << *CurrInst
                      << " was copied to " << MI);
#endif
    // We allow insts in the entry block to have a debug loc line of 0 because
    // they could have originated from constants, and we don't want a jumpy
    // debug experience.
    assert((CurrInst->getDebugLoc() == MI.getDebugLoc() ||
            MI.getDebugLoc().getLine() == 0) &&
           "Line info was not transferred to all instructions");
  }
};
} // namespace
#endif // ifndef NDEBUG


void IRTranslator::getAnalysisUsage(AnalysisUsage &AU) const {
  AU.addRequired<StackProtector>();
  AU.addRequired<TargetPassConfig>();
  AU.addRequired<GISelCSEAnalysisWrapperPass>();
  getSelectionDAGFallbackAnalysisUsage(AU);
  MachineFunctionPass::getAnalysisUsage(AU);
}

IRTranslator::ValueToVRegInfo::VRegListT &
IRTranslator::allocateVRegs(const Value &Val) {
  assert(!VMap.contains(Val) && "Value already allocated in VMap");
  auto *Regs = VMap.getVRegs(Val);
  auto *Offsets = VMap.getOffsets(Val);
  SmallVector<LLT, 4> SplitTys;
  computeValueLLTs(*DL, *Val.getType(), SplitTys,
                   Offsets->empty() ? Offsets : nullptr);
  for (unsigned i = 0; i < SplitTys.size(); ++i)
    Regs->push_back(0);
  return *Regs;
}

ArrayRef<Register> IRTranslator::getOrCreateVRegs(const Value &Val) {
  auto VRegsIt = VMap.findVRegs(Val);
  if (VRegsIt != VMap.vregs_end())
    return *VRegsIt->second;

  if (Val.getType()->isVoidTy())
    return *VMap.getVRegs(Val);

  // Create entry for this type.
  auto *VRegs = VMap.getVRegs(Val);
  auto *Offsets = VMap.getOffsets(Val);

  assert(Val.getType()->isSized() &&
         "Don't know how to create an empty vreg");

  SmallVector<LLT, 4> SplitTys;
  computeValueLLTs(*DL, *Val.getType(), SplitTys,
                   Offsets->empty() ? Offsets : nullptr);

  if (!isa<Constant>(Val)) {
    for (auto Ty : SplitTys)
      VRegs->push_back(MRI->createGenericVirtualRegister(Ty));
    return *VRegs;
  }

  if (Val.getType()->isAggregateType()) {
    // UndefValue, ConstantAggregateZero
    auto &C = cast<Constant>(Val);
    unsigned Idx = 0;
    while (auto Elt = C.getAggregateElement(Idx++)) {
      auto EltRegs = getOrCreateVRegs(*Elt);
      llvm::copy(EltRegs, std::back_inserter(*VRegs));
    }
  } else {
    assert(SplitTys.size() == 1 && "unexpectedly split LLT");
    VRegs->push_back(MRI->createGenericVirtualRegister(SplitTys[0]));
    bool Success = translate(cast<Constant>(Val), VRegs->front());
    if (!Success) {
      OptimizationRemarkMissed R("gisel-irtranslator", "GISelFailure",
                                 MF->getFunction().getSubprogram(),
                                 &MF->getFunction().getEntryBlock());
      R << "unable to translate constant: " << ore::NV("Type", Val.getType());
      reportTranslationError(*MF, *TPC, *ORE, R);
      return *VRegs;
    }
  }

  return *VRegs;
}

int IRTranslator::getOrCreateFrameIndex(const AllocaInst &AI) {
  if (FrameIndices.find(&AI) != FrameIndices.end())
    return FrameIndices[&AI];

  unsigned ElementSize = DL->getTypeAllocSize(AI.getAllocatedType());
  unsigned Size =
      ElementSize * cast<ConstantInt>(AI.getArraySize())->getZExtValue();

  // Always allocate at least one byte.
  Size = std::max(Size, 1u);

  unsigned Alignment = AI.getAlignment();
  if (!Alignment)
    Alignment = DL->getABITypeAlignment(AI.getAllocatedType());

  int &FI = FrameIndices[&AI];
  FI = MF->getFrameInfo().CreateStackObject(Size, Alignment, false, &AI);
  return FI;
}

unsigned IRTranslator::getMemOpAlignment(const Instruction &I) {
  unsigned Alignment = 0;
  Type *ValTy = nullptr;
  if (const StoreInst *SI = dyn_cast<StoreInst>(&I)) {
    Alignment = SI->getAlignment();
    ValTy = SI->getValueOperand()->getType();
  } else if (const LoadInst *LI = dyn_cast<LoadInst>(&I)) {
    Alignment = LI->getAlignment();
    ValTy = LI->getType();
  } else if (const AtomicCmpXchgInst *AI = dyn_cast<AtomicCmpXchgInst>(&I)) {
    // TODO(PR27168): This instruction has no alignment attribute, but unlike
    // the default alignment for load/store, the default here is to assume
    // it has NATURAL alignment, not DataLayout-specified alignment.
    const DataLayout &DL = AI->getModule()->getDataLayout();
    Alignment = DL.getTypeStoreSize(AI->getCompareOperand()->getType());
    ValTy = AI->getCompareOperand()->getType();
  } else if (const AtomicRMWInst *AI = dyn_cast<AtomicRMWInst>(&I)) {
    // TODO(PR27168): This instruction has no alignment attribute, but unlike
    // the default alignment for load/store, the default here is to assume
    // it has NATURAL alignment, not DataLayout-specified alignment.
    const DataLayout &DL = AI->getModule()->getDataLayout();
    Alignment = DL.getTypeStoreSize(AI->getValOperand()->getType());
    ValTy = AI->getType();
  } else {
    OptimizationRemarkMissed R("gisel-irtranslator", "", &I);
    R << "unable to translate memop: " << ore::NV("Opcode", &I);
    reportTranslationError(*MF, *TPC, *ORE, R);
    return 1;
  }

  return Alignment ? Alignment : DL->getABITypeAlignment(ValTy);
}

MachineBasicBlock &IRTranslator::getMBB(const BasicBlock &BB) {
  MachineBasicBlock *&MBB = BBToMBB[&BB];
  assert(MBB && "BasicBlock was not encountered before");
  return *MBB;
}

void IRTranslator::addMachineCFGPred(CFGEdge Edge, MachineBasicBlock *NewPred) {
  assert(NewPred && "new predecessor must be a real MachineBasicBlock");
  MachinePreds[Edge].push_back(NewPred);
}

bool IRTranslator::translateBinaryOp(unsigned Opcode, const User &U,
                                     MachineIRBuilder &MIRBuilder) {
  // Get or create a virtual register for each value.
  // Unless the value is a Constant => loadimm cst?
  // or inline constant each time?
  // Creation of a virtual register needs to have a size.
  Register Op0 = getOrCreateVReg(*U.getOperand(0));
  Register Op1 = getOrCreateVReg(*U.getOperand(1));
  Register Res = getOrCreateVReg(U);
  uint16_t Flags = 0;
  if (isa<Instruction>(U)) {
    const Instruction &I = cast<Instruction>(U);
    Flags = MachineInstr::copyFlagsFromInstruction(I);
  }

  MIRBuilder.buildInstr(Opcode, {Res}, {Op0, Op1}, Flags);
  return true;
}

bool IRTranslator::translateFSub(const User &U, MachineIRBuilder &MIRBuilder) {
  // -0.0 - X --> G_FNEG
  if (isa<Constant>(U.getOperand(0)) &&
      U.getOperand(0) == ConstantFP::getZeroValueForNegation(U.getType())) {
    Register Op1 = getOrCreateVReg(*U.getOperand(1));
    Register Res = getOrCreateVReg(U);
    uint16_t Flags = 0;
    if (isa<Instruction>(U)) {
      const Instruction &I = cast<Instruction>(U);
      Flags = MachineInstr::copyFlagsFromInstruction(I);
    }
    // Negate the last operand of the FSUB
    MIRBuilder.buildInstr(TargetOpcode::G_FNEG, {Res}, {Op1}, Flags);
    return true;
  }
  return translateBinaryOp(TargetOpcode::G_FSUB, U, MIRBuilder);
}

bool IRTranslator::translateFNeg(const User &U, MachineIRBuilder &MIRBuilder) {
  Register Op0 = getOrCreateVReg(*U.getOperand(0));
  Register Res = getOrCreateVReg(U);
  uint16_t Flags = 0;
  if (isa<Instruction>(U)) {
    const Instruction &I = cast<Instruction>(U);
    Flags = MachineInstr::copyFlagsFromInstruction(I);
  }
  MIRBuilder.buildInstr(TargetOpcode::G_FNEG, {Res}, {Op0}, Flags);
  return true;
}

bool IRTranslator::translateCompare(const User &U,
                                    MachineIRBuilder &MIRBuilder) {
  auto *CI = dyn_cast<CmpInst>(&U);
  Register Op0 = getOrCreateVReg(*U.getOperand(0));
  Register Op1 = getOrCreateVReg(*U.getOperand(1));
  Register Res = getOrCreateVReg(U);
  CmpInst::Predicate Pred =
      CI ? CI->getPredicate() : static_cast<CmpInst::Predicate>(
                                    cast<ConstantExpr>(U).getPredicate());
  if (CmpInst::isIntPredicate(Pred))
    MIRBuilder.buildICmp(Pred, Res, Op0, Op1);
  else if (Pred == CmpInst::FCMP_FALSE)
    MIRBuilder.buildCopy(
        Res, getOrCreateVReg(*Constant::getNullValue(U.getType())));
  else if (Pred == CmpInst::FCMP_TRUE)
    MIRBuilder.buildCopy(
        Res, getOrCreateVReg(*Constant::getAllOnesValue(U.getType())));
  else {
    assert(CI && "Instruction should be CmpInst");
    MIRBuilder.buildInstr(TargetOpcode::G_FCMP, {Res}, {Pred, Op0, Op1},
                          MachineInstr::copyFlagsFromInstruction(*CI));
  }

  return true;
}

bool IRTranslator::translateRet(const User &U, MachineIRBuilder &MIRBuilder) {
  const ReturnInst &RI = cast<ReturnInst>(U);
  const Value *Ret = RI.getReturnValue();
  if (Ret && DL->getTypeStoreSize(Ret->getType()) == 0)
    Ret = nullptr;

  ArrayRef<Register> VRegs;
  if (Ret)
    VRegs = getOrCreateVRegs(*Ret);

  Register SwiftErrorVReg = 0;
  if (CLI->supportSwiftError() && SwiftError.getFunctionArg()) {
    SwiftErrorVReg = SwiftError.getOrCreateVRegUseAt(
        &RI, &MIRBuilder.getMBB(), SwiftError.getFunctionArg());
  }

  // The target may mess up with the insertion point, but
  // this is not important as a return is the last instruction
  // of the block anyway.
  return CLI->lowerReturn(MIRBuilder, Ret, VRegs, SwiftErrorVReg);
}

bool IRTranslator::translateBr(const User &U, MachineIRBuilder &MIRBuilder) {
  const BranchInst &BrInst = cast<BranchInst>(U);
  unsigned Succ = 0;
  if (!BrInst.isUnconditional()) {
    // We want a G_BRCOND to the true BB followed by an unconditional branch.
    Register Tst = getOrCreateVReg(*BrInst.getCondition());
    const BasicBlock &TrueTgt = *cast<BasicBlock>(BrInst.getSuccessor(Succ++));
    MachineBasicBlock &TrueBB = getMBB(TrueTgt);
    MIRBuilder.buildBrCond(Tst, TrueBB);
  }

  const BasicBlock &BrTgt = *cast<BasicBlock>(BrInst.getSuccessor(Succ));
  MachineBasicBlock &TgtBB = getMBB(BrTgt);
  MachineBasicBlock &CurBB = MIRBuilder.getMBB();

  // If the unconditional target is the layout successor, fallthrough.
  if (!CurBB.isLayoutSuccessor(&TgtBB))
    MIRBuilder.buildBr(TgtBB);

  // Link successors.
  for (const BasicBlock *Succ : successors(&BrInst))
    CurBB.addSuccessor(&getMBB(*Succ));
  return true;
}

void IRTranslator::addSuccessorWithProb(MachineBasicBlock *Src,
                                        MachineBasicBlock *Dst,
                                        BranchProbability Prob) {
  if (!FuncInfo.BPI) {
    Src->addSuccessorWithoutProb(Dst);
    return;
  }
  if (Prob.isUnknown())
    Prob = getEdgeProbability(Src, Dst);
  Src->addSuccessor(Dst, Prob);
}

BranchProbability
IRTranslator::getEdgeProbability(const MachineBasicBlock *Src,
                                 const MachineBasicBlock *Dst) const {
  const BasicBlock *SrcBB = Src->getBasicBlock();
  const BasicBlock *DstBB = Dst->getBasicBlock();
  if (!FuncInfo.BPI) {
    // If BPI is not available, set the default probability as 1 / N, where N is
    // the number of successors.
    auto SuccSize = std::max<uint32_t>(succ_size(SrcBB), 1);
    return BranchProbability(1, SuccSize);
  }
  return FuncInfo.BPI->getEdgeProbability(SrcBB, DstBB);
}

bool IRTranslator::translateSwitch(const User &U, MachineIRBuilder &MIB) {
  using namespace SwitchCG;
  // Extract cases from the switch.
  const SwitchInst &SI = cast<SwitchInst>(U);
  BranchProbabilityInfo *BPI = FuncInfo.BPI;
  CaseClusterVector Clusters;
  Clusters.reserve(SI.getNumCases());
  for (auto &I : SI.cases()) {
    MachineBasicBlock *Succ = &getMBB(*I.getCaseSuccessor());
    assert(Succ && "Could not find successor mbb in mapping");
    const ConstantInt *CaseVal = I.getCaseValue();
    BranchProbability Prob =
        BPI ? BPI->getEdgeProbability(SI.getParent(), I.getSuccessorIndex())
            : BranchProbability(1, SI.getNumCases() + 1);
    Clusters.push_back(CaseCluster::range(CaseVal, CaseVal, Succ, Prob));
  }

  MachineBasicBlock *DefaultMBB = &getMBB(*SI.getDefaultDest());

  // Cluster adjacent cases with the same destination. We do this at all
  // optimization levels because it's cheap to do and will make codegen faster
  // if there are many clusters.
  sortAndRangeify(Clusters);

  MachineBasicBlock *SwitchMBB = &getMBB(*SI.getParent());

  // If there is only the default destination, jump there directly.
  if (Clusters.empty()) {
    SwitchMBB->addSuccessor(DefaultMBB);
    if (DefaultMBB != SwitchMBB->getNextNode())
      MIB.buildBr(*DefaultMBB);
    return true;
  }

  SL->findJumpTables(Clusters, &SI, DefaultMBB);

  LLVM_DEBUG({
    dbgs() << "Case clusters: ";
    for (const CaseCluster &C : Clusters) {
      if (C.Kind == CC_JumpTable)
        dbgs() << "JT:";
      if (C.Kind == CC_BitTests)
        dbgs() << "BT:";

      C.Low->getValue().print(dbgs(), true);
      if (C.Low != C.High) {
        dbgs() << '-';
        C.High->getValue().print(dbgs(), true);
      }
      dbgs() << ' ';
    }
    dbgs() << '\n';
  });

  assert(!Clusters.empty());
  SwitchWorkList WorkList;
  CaseClusterIt First = Clusters.begin();
  CaseClusterIt Last = Clusters.end() - 1;
  auto DefaultProb = getEdgeProbability(SwitchMBB, DefaultMBB);
  WorkList.push_back({SwitchMBB, First, Last, nullptr, nullptr, DefaultProb});

  // FIXME: At the moment we don't do any splitting optimizations here like
  // SelectionDAG does, so this worklist only has one entry.
  while (!WorkList.empty()) {
    SwitchWorkListItem W = WorkList.back();
    WorkList.pop_back();
    if (!lowerSwitchWorkItem(W, SI.getCondition(), SwitchMBB, DefaultMBB, MIB))
      return false;
  }
  return true;
}

void IRTranslator::emitJumpTable(SwitchCG::JumpTable &JT,
                                 MachineBasicBlock *MBB) {
  // Emit the code for the jump table
  assert(JT.Reg != -1U && "Should lower JT Header first!");
  MachineIRBuilder MIB(*MBB->getParent());
  MIB.setMBB(*MBB);
  MIB.setDebugLoc(CurBuilder->getDebugLoc());

  Type *PtrIRTy = Type::getInt8PtrTy(MF->getFunction().getContext());
  const LLT PtrTy = getLLTForType(*PtrIRTy, *DL);

  auto Table = MIB.buildJumpTable(PtrTy, JT.JTI);
  MIB.buildBrJT(Table.getReg(0), JT.JTI, JT.Reg);
}

bool IRTranslator::emitJumpTableHeader(SwitchCG::JumpTable &JT,
                                       SwitchCG::JumpTableHeader &JTH,
                                       MachineBasicBlock *HeaderBB) {
  MachineIRBuilder MIB(*HeaderBB->getParent());
  MIB.setMBB(*HeaderBB);
  MIB.setDebugLoc(CurBuilder->getDebugLoc());

  const Value &SValue = *JTH.SValue;
  // Subtract the lowest switch case value from the value being switched on.
  const LLT SwitchTy = getLLTForType(*SValue.getType(), *DL);
  Register SwitchOpReg = getOrCreateVReg(SValue);
  auto FirstCst = MIB.buildConstant(SwitchTy, JTH.First);
  auto Sub = MIB.buildSub({SwitchTy}, SwitchOpReg, FirstCst);

  // This value may be smaller or larger than the target's pointer type, and
  // therefore require extension or truncating.
  Type *PtrIRTy = SValue.getType()->getPointerTo();
  const LLT PtrScalarTy = LLT::scalar(DL->getTypeSizeInBits(PtrIRTy));
  Sub = MIB.buildZExtOrTrunc(PtrScalarTy, Sub);

  JT.Reg = Sub.getReg(0);

  if (JTH.OmitRangeCheck) {
    if (JT.MBB != HeaderBB->getNextNode())
      MIB.buildBr(*JT.MBB);
    return true;
  }

  // Emit the range check for the jump table, and branch to the default block
  // for the switch statement if the value being switched on exceeds the
  // largest case in the switch.
  auto Cst = getOrCreateVReg(
      *ConstantInt::get(SValue.getType(), JTH.Last - JTH.First));
  Cst = MIB.buildZExtOrTrunc(PtrScalarTy, Cst).getReg(0);
  auto Cmp = MIB.buildICmp(CmpInst::ICMP_UGT, LLT::scalar(1), Sub, Cst);

  auto BrCond = MIB.buildBrCond(Cmp.getReg(0), *JT.Default);

  // Avoid emitting unnecessary branches to the next block.
  if (JT.MBB != HeaderBB->getNextNode())
    BrCond = MIB.buildBr(*JT.MBB);
  return true;
}

void IRTranslator::emitSwitchCase(SwitchCG::CaseBlock &CB,
                                  MachineBasicBlock *SwitchBB,
                                  MachineIRBuilder &MIB) {
  Register CondLHS = getOrCreateVReg(*CB.CmpLHS);
  Register Cond;
  DebugLoc OldDbgLoc = MIB.getDebugLoc();
  MIB.setDebugLoc(CB.DbgLoc);
  MIB.setMBB(*CB.ThisBB);

  if (CB.PredInfo.NoCmp) {
    // Branch or fall through to TrueBB.
    addSuccessorWithProb(CB.ThisBB, CB.TrueBB, CB.TrueProb);
    addMachineCFGPred({SwitchBB->getBasicBlock(), CB.TrueBB->getBasicBlock()},
                      CB.ThisBB);
    CB.ThisBB->normalizeSuccProbs();
    if (CB.TrueBB != CB.ThisBB->getNextNode())
      MIB.buildBr(*CB.TrueBB);
    MIB.setDebugLoc(OldDbgLoc);
    return;
  }

  const LLT i1Ty = LLT::scalar(1);
  // Build the compare.
  if (!CB.CmpMHS) {
    Register CondRHS = getOrCreateVReg(*CB.CmpRHS);
    Cond = MIB.buildICmp(CB.PredInfo.Pred, i1Ty, CondLHS, CondRHS).getReg(0);
  } else {
    assert(CB.PredInfo.Pred == CmpInst::ICMP_SLE &&
           "Can only handle SLE ranges");

    const APInt& Low = cast<ConstantInt>(CB.CmpLHS)->getValue();
    const APInt& High = cast<ConstantInt>(CB.CmpRHS)->getValue();

    Register CmpOpReg = getOrCreateVReg(*CB.CmpMHS);
    if (cast<ConstantInt>(CB.CmpLHS)->isMinValue(true)) {
      Register CondRHS = getOrCreateVReg(*CB.CmpRHS);
      Cond =
          MIB.buildICmp(CmpInst::ICMP_SLE, i1Ty, CmpOpReg, CondRHS).getReg(0);
    } else {
      const LLT &CmpTy = MRI->getType(CmpOpReg);
      auto Sub = MIB.buildSub({CmpTy}, CmpOpReg, CondLHS);
      auto Diff = MIB.buildConstant(CmpTy, High - Low);
      Cond = MIB.buildICmp(CmpInst::ICMP_ULE, i1Ty, Sub, Diff).getReg(0);
    }
  }

  // Update successor info
  addSuccessorWithProb(CB.ThisBB, CB.TrueBB, CB.TrueProb);

  addMachineCFGPred({SwitchBB->getBasicBlock(), CB.TrueBB->getBasicBlock()},
                    CB.ThisBB);

  // TrueBB and FalseBB are always different unless the incoming IR is
  // degenerate. This only happens when running llc on weird IR.
  if (CB.TrueBB != CB.FalseBB)
    addSuccessorWithProb(CB.ThisBB, CB.FalseBB, CB.FalseProb);
  CB.ThisBB->normalizeSuccProbs();

  //  if (SwitchBB->getBasicBlock() != CB.FalseBB->getBasicBlock())
    addMachineCFGPred({SwitchBB->getBasicBlock(), CB.FalseBB->getBasicBlock()},
                      CB.ThisBB);

  // If the lhs block is the next block, invert the condition so that we can
  // fall through to the lhs instead of the rhs block.
  if (CB.TrueBB == CB.ThisBB->getNextNode()) {
    std::swap(CB.TrueBB, CB.FalseBB);
    auto True = MIB.buildConstant(i1Ty, 1);
    Cond = MIB.buildInstr(TargetOpcode::G_XOR, {i1Ty}, {Cond, True}, None)
               .getReg(0);
  }

  MIB.buildBrCond(Cond, *CB.TrueBB);
  MIB.buildBr(*CB.FalseBB);
  MIB.setDebugLoc(OldDbgLoc);
}

bool IRTranslator::lowerJumpTableWorkItem(SwitchCG::SwitchWorkListItem W,
                                          MachineBasicBlock *SwitchMBB,
                                          MachineBasicBlock *CurMBB,
                                          MachineBasicBlock *DefaultMBB,
                                          MachineIRBuilder &MIB,
                                          MachineFunction::iterator BBI,
                                          BranchProbability UnhandledProbs,
                                          SwitchCG::CaseClusterIt I,
                                          MachineBasicBlock *Fallthrough,
                                          bool FallthroughUnreachable) {
  using namespace SwitchCG;
  MachineFunction *CurMF = SwitchMBB->getParent();
  // FIXME: Optimize away range check based on pivot comparisons.
  JumpTableHeader *JTH = &SL->JTCases[I->JTCasesIndex].first;
  SwitchCG::JumpTable *JT = &SL->JTCases[I->JTCasesIndex].second;
  BranchProbability DefaultProb = W.DefaultProb;

  // The jump block hasn't been inserted yet; insert it here.
  MachineBasicBlock *JumpMBB = JT->MBB;
  CurMF->insert(BBI, JumpMBB);

  // Since the jump table block is separate from the switch block, we need
  // to keep track of it as a machine predecessor to the default block,
  // otherwise we lose the phi edges.
  addMachineCFGPred({SwitchMBB->getBasicBlock(), DefaultMBB->getBasicBlock()},
                    CurMBB);
  addMachineCFGPred({SwitchMBB->getBasicBlock(), DefaultMBB->getBasicBlock()},
                    JumpMBB);

  auto JumpProb = I->Prob;
  auto FallthroughProb = UnhandledProbs;

  // If the default statement is a target of the jump table, we evenly
  // distribute the default probability to successors of CurMBB. Also
  // update the probability on the edge from JumpMBB to Fallthrough.
  for (MachineBasicBlock::succ_iterator SI = JumpMBB->succ_begin(),
                                        SE = JumpMBB->succ_end();
       SI != SE; ++SI) {
    if (*SI == DefaultMBB) {
      JumpProb += DefaultProb / 2;
      FallthroughProb -= DefaultProb / 2;
      JumpMBB->setSuccProbability(SI, DefaultProb / 2);
      JumpMBB->normalizeSuccProbs();
    } else {
      // Also record edges from the jump table block to it's successors.
      addMachineCFGPred({SwitchMBB->getBasicBlock(), (*SI)->getBasicBlock()},
                        JumpMBB);
    }
  }

  // Skip the range check if the fallthrough block is unreachable.
  if (FallthroughUnreachable)
    JTH->OmitRangeCheck = true;

  if (!JTH->OmitRangeCheck)
    addSuccessorWithProb(CurMBB, Fallthrough, FallthroughProb);
  addSuccessorWithProb(CurMBB, JumpMBB, JumpProb);
  CurMBB->normalizeSuccProbs();

  // The jump table header will be inserted in our current block, do the
  // range check, and fall through to our fallthrough block.
  JTH->HeaderBB = CurMBB;
  JT->Default = Fallthrough; // FIXME: Move Default to JumpTableHeader.

  // If we're in the right place, emit the jump table header right now.
  if (CurMBB == SwitchMBB) {
    if (!emitJumpTableHeader(*JT, *JTH, CurMBB))
      return false;
    JTH->Emitted = true;
  }
  return true;
}
bool IRTranslator::lowerSwitchRangeWorkItem(SwitchCG::CaseClusterIt I,
                                            Value *Cond,
                                            MachineBasicBlock *Fallthrough,
                                            bool FallthroughUnreachable,
                                            BranchProbability UnhandledProbs,
                                            MachineBasicBlock *CurMBB,
                                            MachineIRBuilder &MIB,
                                            MachineBasicBlock *SwitchMBB) {
  using namespace SwitchCG;
  const Value *RHS, *LHS, *MHS;
  CmpInst::Predicate Pred;
  if (I->Low == I->High) {
    // Check Cond == I->Low.
    Pred = CmpInst::ICMP_EQ;
    LHS = Cond;
    RHS = I->Low;
    MHS = nullptr;
  } else {
    // Check I->Low <= Cond <= I->High.
    Pred = CmpInst::ICMP_SLE;
    LHS = I->Low;
    MHS = Cond;
    RHS = I->High;
  }

  // If Fallthrough is unreachable, fold away the comparison.
  // The false probability is the sum of all unhandled cases.
  CaseBlock CB(Pred, FallthroughUnreachable, LHS, RHS, MHS, I->MBB, Fallthrough,
               CurMBB, MIB.getDebugLoc(), I->Prob, UnhandledProbs);

  emitSwitchCase(CB, SwitchMBB, MIB);
  return true;
}

bool IRTranslator::lowerSwitchWorkItem(SwitchCG::SwitchWorkListItem W,
                                       Value *Cond,
                                       MachineBasicBlock *SwitchMBB,
                                       MachineBasicBlock *DefaultMBB,
                                       MachineIRBuilder &MIB) {
  using namespace SwitchCG;
  MachineFunction *CurMF = FuncInfo.MF;
  MachineBasicBlock *NextMBB = nullptr;
  MachineFunction::iterator BBI(W.MBB);
  if (++BBI != FuncInfo.MF->end())
    NextMBB = &*BBI;

  if (EnableOpts) {
    // Here, we order cases by probability so the most likely case will be
    // checked first. However, two clusters can have the same probability in
    // which case their relative ordering is non-deterministic. So we use Low
    // as a tie-breaker as clusters are guaranteed to never overlap.
    llvm::sort(W.FirstCluster, W.LastCluster + 1,
               [](const CaseCluster &a, const CaseCluster &b) {
                 return a.Prob != b.Prob
                            ? a.Prob > b.Prob
                            : a.Low->getValue().slt(b.Low->getValue());
               });

    // Rearrange the case blocks so that the last one falls through if possible
    // without changing the order of probabilities.
    for (CaseClusterIt I = W.LastCluster; I > W.FirstCluster;) {
      --I;
      if (I->Prob > W.LastCluster->Prob)
        break;
      if (I->Kind == CC_Range && I->MBB == NextMBB) {
        std::swap(*I, *W.LastCluster);
        break;
      }
    }
  }

  // Compute total probability.
  BranchProbability DefaultProb = W.DefaultProb;
  BranchProbability UnhandledProbs = DefaultProb;
  for (CaseClusterIt I = W.FirstCluster; I <= W.LastCluster; ++I)
    UnhandledProbs += I->Prob;

  MachineBasicBlock *CurMBB = W.MBB;
  for (CaseClusterIt I = W.FirstCluster, E = W.LastCluster; I <= E; ++I) {
    bool FallthroughUnreachable = false;
    MachineBasicBlock *Fallthrough;
    if (I == W.LastCluster) {
      // For the last cluster, fall through to the default destination.
      Fallthrough = DefaultMBB;
      FallthroughUnreachable = isa<UnreachableInst>(
          DefaultMBB->getBasicBlock()->getFirstNonPHIOrDbg());
    } else {
      Fallthrough = CurMF->CreateMachineBasicBlock(CurMBB->getBasicBlock());
      CurMF->insert(BBI, Fallthrough);
    }
    UnhandledProbs -= I->Prob;

    switch (I->Kind) {
    case CC_BitTests: {
      LLVM_DEBUG(dbgs() << "Switch to bit test optimization unimplemented");
      return false; // Bit tests currently unimplemented.
    }
    case CC_JumpTable: {
      if (!lowerJumpTableWorkItem(W, SwitchMBB, CurMBB, DefaultMBB, MIB, BBI,
                                  UnhandledProbs, I, Fallthrough,
                                  FallthroughUnreachable)) {
        LLVM_DEBUG(dbgs() << "Failed to lower jump table");
        return false;
      }
      break;
    }
    case CC_Range: {
      if (!lowerSwitchRangeWorkItem(I, Cond, Fallthrough,
                                    FallthroughUnreachable, UnhandledProbs,
                                    CurMBB, MIB, SwitchMBB)) {
        LLVM_DEBUG(dbgs() << "Failed to lower switch range");
        return false;
      }
      break;
    }
    }
    CurMBB = Fallthrough;
  }

  return true;
}

bool IRTranslator::translateIndirectBr(const User &U,
                                       MachineIRBuilder &MIRBuilder) {
  const IndirectBrInst &BrInst = cast<IndirectBrInst>(U);

  const Register Tgt = getOrCreateVReg(*BrInst.getAddress());
  MIRBuilder.buildBrIndirect(Tgt);

  // Link successors.
  MachineBasicBlock &CurBB = MIRBuilder.getMBB();
  for (const BasicBlock *Succ : successors(&BrInst))
    CurBB.addSuccessor(&getMBB(*Succ));

  return true;
}

static bool isSwiftError(const Value *V) {
  if (auto Arg = dyn_cast<Argument>(V))
    return Arg->hasSwiftErrorAttr();
  if (auto AI = dyn_cast<AllocaInst>(V))
    return AI->isSwiftError();
  return false;
}

bool IRTranslator::translateLoad(const User &U, MachineIRBuilder &MIRBuilder) {
  const LoadInst &LI = cast<LoadInst>(U);

  auto Flags = LI.isVolatile() ? MachineMemOperand::MOVolatile
                               : MachineMemOperand::MONone;
  Flags |= MachineMemOperand::MOLoad;

  if (DL->getTypeStoreSize(LI.getType()) == 0)
    return true;

  ArrayRef<Register> Regs = getOrCreateVRegs(LI);
  ArrayRef<uint64_t> Offsets = *VMap.getOffsets(LI);
  Register Base = getOrCreateVReg(*LI.getPointerOperand());

  Type *OffsetIRTy = DL->getIntPtrType(LI.getPointerOperandType());
  LLT OffsetTy = getLLTForType(*OffsetIRTy, *DL);

  if (CLI->supportSwiftError() && isSwiftError(LI.getPointerOperand())) {
    assert(Regs.size() == 1 && "swifterror should be single pointer");
    Register VReg = SwiftError.getOrCreateVRegUseAt(&LI, &MIRBuilder.getMBB(),
                                                    LI.getPointerOperand());
    MIRBuilder.buildCopy(Regs[0], VReg);
    return true;
  }

  const MDNode *Ranges =
      Regs.size() == 1 ? LI.getMetadata(LLVMContext::MD_range) : nullptr;
  for (unsigned i = 0; i < Regs.size(); ++i) {
    Register Addr;
    MIRBuilder.materializeGEP(Addr, Base, OffsetTy, Offsets[i] / 8);

    MachinePointerInfo Ptr(LI.getPointerOperand(), Offsets[i] / 8);
    unsigned BaseAlign = getMemOpAlignment(LI);
    auto MMO = MF->getMachineMemOperand(
        Ptr, Flags, (MRI->getType(Regs[i]).getSizeInBits() + 7) / 8,
        MinAlign(BaseAlign, Offsets[i] / 8), AAMDNodes(), Ranges,
        LI.getSyncScopeID(), LI.getOrdering());
    MIRBuilder.buildLoad(Regs[i], Addr, *MMO);
  }

  return true;
}

bool IRTranslator::translateStore(const User &U, MachineIRBuilder &MIRBuilder) {
  const StoreInst &SI = cast<StoreInst>(U);
  auto Flags = SI.isVolatile() ? MachineMemOperand::MOVolatile
                               : MachineMemOperand::MONone;
  Flags |= MachineMemOperand::MOStore;

  if (DL->getTypeStoreSize(SI.getValueOperand()->getType()) == 0)
    return true;

  ArrayRef<Register> Vals = getOrCreateVRegs(*SI.getValueOperand());
  ArrayRef<uint64_t> Offsets = *VMap.getOffsets(*SI.getValueOperand());
  Register Base = getOrCreateVReg(*SI.getPointerOperand());

  Type *OffsetIRTy = DL->getIntPtrType(SI.getPointerOperandType());
  LLT OffsetTy = getLLTForType(*OffsetIRTy, *DL);

  if (CLI->supportSwiftError() && isSwiftError(SI.getPointerOperand())) {
    assert(Vals.size() == 1 && "swifterror should be single pointer");

    Register VReg = SwiftError.getOrCreateVRegDefAt(&SI, &MIRBuilder.getMBB(),
                                                    SI.getPointerOperand());
    MIRBuilder.buildCopy(VReg, Vals[0]);
    return true;
  }

  for (unsigned i = 0; i < Vals.size(); ++i) {
    Register Addr;
    MIRBuilder.materializeGEP(Addr, Base, OffsetTy, Offsets[i] / 8);

    MachinePointerInfo Ptr(SI.getPointerOperand(), Offsets[i] / 8);
    unsigned BaseAlign = getMemOpAlignment(SI);
    auto MMO = MF->getMachineMemOperand(
        Ptr, Flags, (MRI->getType(Vals[i]).getSizeInBits() + 7) / 8,
        MinAlign(BaseAlign, Offsets[i] / 8), AAMDNodes(), nullptr,
        SI.getSyncScopeID(), SI.getOrdering());
    MIRBuilder.buildStore(Vals[i], Addr, *MMO);
  }
  return true;
}

static uint64_t getOffsetFromIndices(const User &U, const DataLayout &DL) {
  const Value *Src = U.getOperand(0);
  Type *Int32Ty = Type::getInt32Ty(U.getContext());

  // getIndexedOffsetInType is designed for GEPs, so the first index is the
  // usual array element rather than looking into the actual aggregate.
  SmallVector<Value *, 1> Indices;
  Indices.push_back(ConstantInt::get(Int32Ty, 0));

  if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(&U)) {
    for (auto Idx : EVI->indices())
      Indices.push_back(ConstantInt::get(Int32Ty, Idx));
  } else if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(&U)) {
    for (auto Idx : IVI->indices())
      Indices.push_back(ConstantInt::get(Int32Ty, Idx));
  } else {
    for (unsigned i = 1; i < U.getNumOperands(); ++i)
      Indices.push_back(U.getOperand(i));
  }

  return 8 * static_cast<uint64_t>(
                 DL.getIndexedOffsetInType(Src->getType(), Indices));
}

bool IRTranslator::translateExtractValue(const User &U,
                                         MachineIRBuilder &MIRBuilder) {
  const Value *Src = U.getOperand(0);
  uint64_t Offset = getOffsetFromIndices(U, *DL);
  ArrayRef<Register> SrcRegs = getOrCreateVRegs(*Src);
  ArrayRef<uint64_t> Offsets = *VMap.getOffsets(*Src);
  unsigned Idx = llvm::lower_bound(Offsets, Offset) - Offsets.begin();
  auto &DstRegs = allocateVRegs(U);

  for (unsigned i = 0; i < DstRegs.size(); ++i)
    DstRegs[i] = SrcRegs[Idx++];

  return true;
}

bool IRTranslator::translateInsertValue(const User &U,
                                        MachineIRBuilder &MIRBuilder) {
  const Value *Src = U.getOperand(0);
  uint64_t Offset = getOffsetFromIndices(U, *DL);
  auto &DstRegs = allocateVRegs(U);
  ArrayRef<uint64_t> DstOffsets = *VMap.getOffsets(U);
  ArrayRef<Register> SrcRegs = getOrCreateVRegs(*Src);
  ArrayRef<Register> InsertedRegs = getOrCreateVRegs(*U.getOperand(1));
  auto InsertedIt = InsertedRegs.begin();

  for (unsigned i = 0; i < DstRegs.size(); ++i) {
    if (DstOffsets[i] >= Offset && InsertedIt != InsertedRegs.end())
      DstRegs[i] = *InsertedIt++;
    else
      DstRegs[i] = SrcRegs[i];
  }

  return true;
}

bool IRTranslator::translateSelect(const User &U,
                                   MachineIRBuilder &MIRBuilder) {
  Register Tst = getOrCreateVReg(*U.getOperand(0));
  ArrayRef<Register> ResRegs = getOrCreateVRegs(U);
  ArrayRef<Register> Op0Regs = getOrCreateVRegs(*U.getOperand(1));
  ArrayRef<Register> Op1Regs = getOrCreateVRegs(*U.getOperand(2));

  const SelectInst &SI = cast<SelectInst>(U);
  uint16_t Flags = 0;
  if (const CmpInst *Cmp = dyn_cast<CmpInst>(SI.getCondition()))
    Flags = MachineInstr::copyFlagsFromInstruction(*Cmp);

  for (unsigned i = 0; i < ResRegs.size(); ++i) {
    MIRBuilder.buildInstr(TargetOpcode::G_SELECT, {ResRegs[i]},
                          {Tst, Op0Regs[i], Op1Regs[i]}, Flags);
  }

  return true;
}

bool IRTranslator::translateBitCast(const User &U,
                                    MachineIRBuilder &MIRBuilder) {
  // If we're bitcasting to the source type, we can reuse the source vreg.
  if (getLLTForType(*U.getOperand(0)->getType(), *DL) ==
      getLLTForType(*U.getType(), *DL)) {
    Register SrcReg = getOrCreateVReg(*U.getOperand(0));
    auto &Regs = *VMap.getVRegs(U);
    // If we already assigned a vreg for this bitcast, we can't change that.
    // Emit a copy to satisfy the users we already emitted.
    if (!Regs.empty())
      MIRBuilder.buildCopy(Regs[0], SrcReg);
    else {
      Regs.push_back(SrcReg);
      VMap.getOffsets(U)->push_back(0);
    }
    return true;
  }
  return translateCast(TargetOpcode::G_BITCAST, U, MIRBuilder);
}

bool IRTranslator::translateCast(unsigned Opcode, const User &U,
                                 MachineIRBuilder &MIRBuilder) {
  Register Op = getOrCreateVReg(*U.getOperand(0));
  Register Res = getOrCreateVReg(U);
  MIRBuilder.buildInstr(Opcode, {Res}, {Op});
  return true;
}

bool IRTranslator::translateGetElementPtr(const User &U,
                                          MachineIRBuilder &MIRBuilder) {
  // FIXME: support vector GEPs.
  if (U.getType()->isVectorTy())
    return false;

  Value &Op0 = *U.getOperand(0);
  Register BaseReg = getOrCreateVReg(Op0);
  Type *PtrIRTy = Op0.getType();
  LLT PtrTy = getLLTForType(*PtrIRTy, *DL);
  Type *OffsetIRTy = DL->getIntPtrType(PtrIRTy);
  LLT OffsetTy = getLLTForType(*OffsetIRTy, *DL);

  int64_t Offset = 0;
  for (gep_type_iterator GTI = gep_type_begin(&U), E = gep_type_end(&U);
       GTI != E; ++GTI) {
    const Value *Idx = GTI.getOperand();
    if (StructType *StTy = GTI.getStructTypeOrNull()) {
      unsigned Field = cast<Constant>(Idx)->getUniqueInteger().getZExtValue();
      Offset += DL->getStructLayout(StTy)->getElementOffset(Field);
      continue;
    } else {
      uint64_t ElementSize = DL->getTypeAllocSize(GTI.getIndexedType());

      // If this is a scalar constant or a splat vector of constants,
      // handle it quickly.
      if (const auto *CI = dyn_cast<ConstantInt>(Idx)) {
        Offset += ElementSize * CI->getSExtValue();
        continue;
      }

      if (Offset != 0) {
        LLT OffsetTy = getLLTForType(*OffsetIRTy, *DL);
        auto OffsetMIB = MIRBuilder.buildConstant({OffsetTy}, Offset);
        BaseReg =
            MIRBuilder.buildGEP(PtrTy, BaseReg, OffsetMIB.getReg(0)).getReg(0);
        Offset = 0;
      }

      Register IdxReg = getOrCreateVReg(*Idx);
      if (MRI->getType(IdxReg) != OffsetTy)
        IdxReg = MIRBuilder.buildSExtOrTrunc(OffsetTy, IdxReg).getReg(0);

      // N = N + Idx * ElementSize;
      // Avoid doing it for ElementSize of 1.
      Register GepOffsetReg;
      if (ElementSize != 1) {
        auto ElementSizeMIB = MIRBuilder.buildConstant(
            getLLTForType(*OffsetIRTy, *DL), ElementSize);
        GepOffsetReg =
            MIRBuilder.buildMul(OffsetTy, ElementSizeMIB, IdxReg).getReg(0);
      } else
        GepOffsetReg = IdxReg;

      BaseReg = MIRBuilder.buildGEP(PtrTy, BaseReg, GepOffsetReg).getReg(0);
    }
  }

  if (Offset != 0) {
    auto OffsetMIB =
        MIRBuilder.buildConstant(getLLTForType(*OffsetIRTy, *DL), Offset);
    MIRBuilder.buildGEP(getOrCreateVReg(U), BaseReg, OffsetMIB.getReg(0));
    return true;
  }

  MIRBuilder.buildCopy(getOrCreateVReg(U), BaseReg);
  return true;
}

bool IRTranslator::translateMemFunc(const CallInst &CI,
                                    MachineIRBuilder &MIRBuilder,
                                    Intrinsic::ID ID) {

  // If the source is undef, then just emit a nop.
  if (isa<UndefValue>(CI.getArgOperand(1)))
    return true;

  ArrayRef<Register> Res;
  auto ICall = MIRBuilder.buildIntrinsic(ID, Res, true);
  for (auto AI = CI.arg_begin(), AE = CI.arg_end(); std::next(AI) != AE; ++AI)
    ICall.addUse(getOrCreateVReg(**AI));

  unsigned DstAlign = 0, SrcAlign = 0;
  unsigned IsVol =
      cast<ConstantInt>(CI.getArgOperand(CI.getNumArgOperands() - 1))
          ->getZExtValue();

  if (auto *MCI = dyn_cast<MemCpyInst>(&CI)) {
    DstAlign = std::max<unsigned>(MCI->getDestAlignment(), 1);
    SrcAlign = std::max<unsigned>(MCI->getSourceAlignment(), 1);
  } else if (auto *MMI = dyn_cast<MemMoveInst>(&CI)) {
    DstAlign = std::max<unsigned>(MMI->getDestAlignment(), 1);
    SrcAlign = std::max<unsigned>(MMI->getSourceAlignment(), 1);
  } else {
    auto *MSI = cast<MemSetInst>(&CI);
    DstAlign = std::max<unsigned>(MSI->getDestAlignment(), 1);
  }

  // We need to propagate the tail call flag from the IR inst as an argument.
  // Otherwise, we have to pessimize and assume later that we cannot tail call
  // any memory intrinsics.
  ICall.addImm(CI.isTailCall() ? 1 : 0);

  // Create mem operands to store the alignment and volatile info.
  auto VolFlag = IsVol ? MachineMemOperand::MOVolatile : MachineMemOperand::MONone;
  ICall.addMemOperand(MF->getMachineMemOperand(
      MachinePointerInfo(CI.getArgOperand(0)),
      MachineMemOperand::MOStore | VolFlag, 1, DstAlign));
  if (ID != Intrinsic::memset)
    ICall.addMemOperand(MF->getMachineMemOperand(
        MachinePointerInfo(CI.getArgOperand(1)),
        MachineMemOperand::MOLoad | VolFlag, 1, SrcAlign));

  return true;
}

void IRTranslator::getStackGuard(Register DstReg,
                                 MachineIRBuilder &MIRBuilder) {
  const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
  MRI->setRegClass(DstReg, TRI->getPointerRegClass(*MF));
  auto MIB = MIRBuilder.buildInstr(TargetOpcode::LOAD_STACK_GUARD);
  MIB.addDef(DstReg);

  auto &TLI = *MF->getSubtarget().getTargetLowering();
  Value *Global = TLI.getSDagStackGuard(*MF->getFunction().getParent());
  if (!Global)
    return;

  MachinePointerInfo MPInfo(Global);
  auto Flags = MachineMemOperand::MOLoad | MachineMemOperand::MOInvariant |
               MachineMemOperand::MODereferenceable;
  MachineMemOperand *MemRef =
      MF->getMachineMemOperand(MPInfo, Flags, DL->getPointerSizeInBits() / 8,
                               DL->getPointerABIAlignment(0).value());
  MIB.setMemRefs({MemRef});
}

bool IRTranslator::translateOverflowIntrinsic(const CallInst &CI, unsigned Op,
                                              MachineIRBuilder &MIRBuilder) {
  ArrayRef<Register> ResRegs = getOrCreateVRegs(CI);
  MIRBuilder.buildInstr(Op)
      .addDef(ResRegs[0])
      .addDef(ResRegs[1])
      .addUse(getOrCreateVReg(*CI.getOperand(0)))
      .addUse(getOrCreateVReg(*CI.getOperand(1)));

  return true;
}

unsigned IRTranslator::getSimpleIntrinsicOpcode(Intrinsic::ID ID) {
  switch (ID) {
    default:
      break;
    case Intrinsic::bswap:
      return TargetOpcode::G_BSWAP;
  case Intrinsic::bitreverse:
      return TargetOpcode::G_BITREVERSE;
    case Intrinsic::ceil:
      return TargetOpcode::G_FCEIL;
    case Intrinsic::cos:
      return TargetOpcode::G_FCOS;
    case Intrinsic::ctpop:
      return TargetOpcode::G_CTPOP;
    case Intrinsic::exp:
      return TargetOpcode::G_FEXP;
    case Intrinsic::exp2:
      return TargetOpcode::G_FEXP2;
    case Intrinsic::fabs:
      return TargetOpcode::G_FABS;
    case Intrinsic::copysign:
      return TargetOpcode::G_FCOPYSIGN;
    case Intrinsic::minnum:
      return TargetOpcode::G_FMINNUM;
    case Intrinsic::maxnum:
      return TargetOpcode::G_FMAXNUM;
    case Intrinsic::minimum:
      return TargetOpcode::G_FMINIMUM;
    case Intrinsic::maximum:
      return TargetOpcode::G_FMAXIMUM;
    case Intrinsic::canonicalize:
      return TargetOpcode::G_FCANONICALIZE;
    case Intrinsic::floor:
      return TargetOpcode::G_FFLOOR;
    case Intrinsic::fma:
      return TargetOpcode::G_FMA;
    case Intrinsic::log:
      return TargetOpcode::G_FLOG;
    case Intrinsic::log2:
      return TargetOpcode::G_FLOG2;
    case Intrinsic::log10:
      return TargetOpcode::G_FLOG10;
    case Intrinsic::nearbyint:
      return TargetOpcode::G_FNEARBYINT;
    case Intrinsic::pow:
      return TargetOpcode::G_FPOW;
    case Intrinsic::rint:
      return TargetOpcode::G_FRINT;
    case Intrinsic::round:
      return TargetOpcode::G_INTRINSIC_ROUND;
    case Intrinsic::sin:
      return TargetOpcode::G_FSIN;
    case Intrinsic::sqrt:
      return TargetOpcode::G_FSQRT;
    case Intrinsic::trunc:
      return TargetOpcode::G_INTRINSIC_TRUNC;
  }
  return Intrinsic::not_intrinsic;
}

bool IRTranslator::translateSimpleIntrinsic(const CallInst &CI,
                                            Intrinsic::ID ID,
                                            MachineIRBuilder &MIRBuilder) {

  unsigned Op = getSimpleIntrinsicOpcode(ID);

  // Is this a simple intrinsic?
  if (Op == Intrinsic::not_intrinsic)
    return false;

  // Yes. Let's translate it.
  SmallVector<llvm::SrcOp, 4> VRegs;
  for (auto &Arg : CI.arg_operands())
    VRegs.push_back(getOrCreateVReg(*Arg));

  MIRBuilder.buildInstr(Op, {getOrCreateVReg(CI)}, VRegs,
                        MachineInstr::copyFlagsFromInstruction(CI));
  return true;
}

bool IRTranslator::translateKnownIntrinsic(const CallInst &CI, Intrinsic::ID ID,
                                           MachineIRBuilder &MIRBuilder) {

  // If this is a simple intrinsic (that is, we just need to add a def of
  // a vreg, and uses for each arg operand, then translate it.
  if (translateSimpleIntrinsic(CI, ID, MIRBuilder))
    return true;

  switch (ID) {
  default:
    break;
  case Intrinsic::lifetime_start:
  case Intrinsic::lifetime_end: {
    // No stack colouring in O0, discard region information.
    if (MF->getTarget().getOptLevel() == CodeGenOpt::None)
      return true;

    unsigned Op = ID == Intrinsic::lifetime_start ? TargetOpcode::LIFETIME_START
                                                  : TargetOpcode::LIFETIME_END;

    // Get the underlying objects for the location passed on the lifetime
    // marker.
    SmallVector<const Value *, 4> Allocas;
    GetUnderlyingObjects(CI.getArgOperand(1), Allocas, *DL);

    // Iterate over each underlying object, creating lifetime markers for each
    // static alloca. Quit if we find a non-static alloca.
    for (const Value *V : Allocas) {
      const AllocaInst *AI = dyn_cast<AllocaInst>(V);
      if (!AI)
        continue;

      if (!AI->isStaticAlloca())
        return true;

      MIRBuilder.buildInstr(Op).addFrameIndex(getOrCreateFrameIndex(*AI));
    }
    return true;
  }
  case Intrinsic::dbg_declare: {
    const DbgDeclareInst &DI = cast<DbgDeclareInst>(CI);
    assert(DI.getVariable() && "Missing variable");

    const Value *Address = DI.getAddress();
    if (!Address || isa<UndefValue>(Address)) {
      LLVM_DEBUG(dbgs() << "Dropping debug info for " << DI << "\n");
      return true;
    }

    assert(DI.getVariable()->isValidLocationForIntrinsic(
               MIRBuilder.getDebugLoc()) &&
           "Expected inlined-at fields to agree");
    auto AI = dyn_cast<AllocaInst>(Address);
    if (AI && AI->isStaticAlloca()) {
      // Static allocas are tracked at the MF level, no need for DBG_VALUE
      // instructions (in fact, they get ignored if they *do* exist).
      MF->setVariableDbgInfo(DI.getVariable(), DI.getExpression(),
                             getOrCreateFrameIndex(*AI), DI.getDebugLoc());
    } else {
      // A dbg.declare describes the address of a source variable, so lower it
      // into an indirect DBG_VALUE.
      MIRBuilder.buildIndirectDbgValue(getOrCreateVReg(*Address),
                                       DI.getVariable(), DI.getExpression());
    }
    return true;
  }
  case Intrinsic::dbg_label: {
    const DbgLabelInst &DI = cast<DbgLabelInst>(CI);
    assert(DI.getLabel() && "Missing label");

    assert(DI.getLabel()->isValidLocationForIntrinsic(
               MIRBuilder.getDebugLoc()) &&
           "Expected inlined-at fields to agree");

    MIRBuilder.buildDbgLabel(DI.getLabel());
    return true;
  }
  case Intrinsic::vaend:
    // No target I know of cares about va_end. Certainly no in-tree target
    // does. Simplest intrinsic ever!
    return true;
  case Intrinsic::vastart: {
    auto &TLI = *MF->getSubtarget().getTargetLowering();
    Value *Ptr = CI.getArgOperand(0);
    unsigned ListSize = TLI.getVaListSizeInBits(*DL) / 8;

    // FIXME: Get alignment
    MIRBuilder.buildInstr(TargetOpcode::G_VASTART)
        .addUse(getOrCreateVReg(*Ptr))
        .addMemOperand(MF->getMachineMemOperand(
            MachinePointerInfo(Ptr), MachineMemOperand::MOStore, ListSize, 1));
    return true;
  }
  case Intrinsic::dbg_value: {
    // This form of DBG_VALUE is target-independent.
    const DbgValueInst &DI = cast<DbgValueInst>(CI);
    const Value *V = DI.getValue();
    assert(DI.getVariable()->isValidLocationForIntrinsic(
               MIRBuilder.getDebugLoc()) &&
           "Expected inlined-at fields to agree");
    if (!V) {
      // Currently the optimizer can produce this; insert an undef to
      // help debugging.  Probably the optimizer should not do this.
      MIRBuilder.buildDirectDbgValue(0, DI.getVariable(), DI.getExpression());
    } else if (const auto *CI = dyn_cast<Constant>(V)) {
      MIRBuilder.buildConstDbgValue(*CI, DI.getVariable(), DI.getExpression());
    } else {
      for (Register Reg : getOrCreateVRegs(*V)) {
        // FIXME: This does not handle register-indirect values at offset 0. The
        // direct/indirect thing shouldn't really be handled by something as
        // implicit as reg+noreg vs reg+imm in the first place, but it seems
        // pretty baked in right now.
        MIRBuilder.buildDirectDbgValue(Reg, DI.getVariable(), DI.getExpression());
      }
    }
    return true;
  }
  case Intrinsic::uadd_with_overflow:
    return translateOverflowIntrinsic(CI, TargetOpcode::G_UADDO, MIRBuilder);
  case Intrinsic::sadd_with_overflow:
    return translateOverflowIntrinsic(CI, TargetOpcode::G_SADDO, MIRBuilder);
  case Intrinsic::usub_with_overflow:
    return translateOverflowIntrinsic(CI, TargetOpcode::G_USUBO, MIRBuilder);
  case Intrinsic::ssub_with_overflow:
    return translateOverflowIntrinsic(CI, TargetOpcode::G_SSUBO, MIRBuilder);
  case Intrinsic::umul_with_overflow:
    return translateOverflowIntrinsic(CI, TargetOpcode::G_UMULO, MIRBuilder);
  case Intrinsic::smul_with_overflow:
    return translateOverflowIntrinsic(CI, TargetOpcode::G_SMULO, MIRBuilder);
  case Intrinsic::fmuladd: {
    const TargetMachine &TM = MF->getTarget();
    const TargetLowering &TLI = *MF->getSubtarget().getTargetLowering();
    Register Dst = getOrCreateVReg(CI);
    Register Op0 = getOrCreateVReg(*CI.getArgOperand(0));
    Register Op1 = getOrCreateVReg(*CI.getArgOperand(1));
    Register Op2 = getOrCreateVReg(*CI.getArgOperand(2));
    if (TM.Options.AllowFPOpFusion != FPOpFusion::Strict &&
        TLI.isFMAFasterThanFMulAndFAdd(TLI.getValueType(*DL, CI.getType()))) {
      // TODO: Revisit this to see if we should move this part of the
      // lowering to the combiner.
      MIRBuilder.buildInstr(TargetOpcode::G_FMA, {Dst}, {Op0, Op1, Op2},
                            MachineInstr::copyFlagsFromInstruction(CI));
    } else {
      LLT Ty = getLLTForType(*CI.getType(), *DL);
      auto FMul = MIRBuilder.buildInstr(TargetOpcode::G_FMUL, {Ty}, {Op0, Op1},
                                        MachineInstr::copyFlagsFromInstruction(CI));
      MIRBuilder.buildInstr(TargetOpcode::G_FADD, {Dst}, {FMul, Op2},
                            MachineInstr::copyFlagsFromInstruction(CI));
    }
    return true;
  }
  case Intrinsic::memcpy:
  case Intrinsic::memmove:
  case Intrinsic::memset:
    return translateMemFunc(CI, MIRBuilder, ID);
  case Intrinsic::eh_typeid_for: {
    GlobalValue *GV = ExtractTypeInfo(CI.getArgOperand(0));
    Register Reg = getOrCreateVReg(CI);
    unsigned TypeID = MF->getTypeIDFor(GV);
    MIRBuilder.buildConstant(Reg, TypeID);
    return true;
  }
  case Intrinsic::objectsize:
    llvm_unreachable("llvm.objectsize.* should have been lowered already");

  case Intrinsic::is_constant:
    llvm_unreachable("llvm.is.constant.* should have been lowered already");

  case Intrinsic::stackguard:
    getStackGuard(getOrCreateVReg(CI), MIRBuilder);
    return true;
  case Intrinsic::stackprotector: {
    LLT PtrTy = getLLTForType(*CI.getArgOperand(0)->getType(), *DL);
    Register GuardVal = MRI->createGenericVirtualRegister(PtrTy);
    getStackGuard(GuardVal, MIRBuilder);

    AllocaInst *Slot = cast<AllocaInst>(CI.getArgOperand(1));
    int FI = getOrCreateFrameIndex(*Slot);
    MF->getFrameInfo().setStackProtectorIndex(FI);

    MIRBuilder.buildStore(
        GuardVal, getOrCreateVReg(*Slot),
        *MF->getMachineMemOperand(MachinePointerInfo::getFixedStack(*MF, FI),
                                  MachineMemOperand::MOStore |
                                      MachineMemOperand::MOVolatile,
                                  PtrTy.getSizeInBits() / 8, 8));
    return true;
  }
  case Intrinsic::stacksave: {
    // Save the stack pointer to the location provided by the intrinsic.
    Register Reg = getOrCreateVReg(CI);
    Register StackPtr = MF->getSubtarget()
                            .getTargetLowering()
                            ->getStackPointerRegisterToSaveRestore();

    // If the target doesn't specify a stack pointer, then fall back.
    if (!StackPtr)
      return false;

    MIRBuilder.buildCopy(Reg, StackPtr);
    return true;
  }
  case Intrinsic::stackrestore: {
    // Restore the stack pointer from the location provided by the intrinsic.
    Register Reg = getOrCreateVReg(*CI.getArgOperand(0));
    Register StackPtr = MF->getSubtarget()
                            .getTargetLowering()
                            ->getStackPointerRegisterToSaveRestore();

    // If the target doesn't specify a stack pointer, then fall back.
    if (!StackPtr)
      return false;

    MIRBuilder.buildCopy(StackPtr, Reg);
    return true;
  }
  case Intrinsic::cttz:
  case Intrinsic::ctlz: {
    ConstantInt *Cst = cast<ConstantInt>(CI.getArgOperand(1));
    bool isTrailing = ID == Intrinsic::cttz;
    unsigned Opcode = isTrailing
                          ? Cst->isZero() ? TargetOpcode::G_CTTZ
                                          : TargetOpcode::G_CTTZ_ZERO_UNDEF
                          : Cst->isZero() ? TargetOpcode::G_CTLZ
                                          : TargetOpcode::G_CTLZ_ZERO_UNDEF;
    MIRBuilder.buildInstr(Opcode)
        .addDef(getOrCreateVReg(CI))
        .addUse(getOrCreateVReg(*CI.getArgOperand(0)));
    return true;
  }
  case Intrinsic::invariant_start: {
    LLT PtrTy = getLLTForType(*CI.getArgOperand(0)->getType(), *DL);
    Register Undef = MRI->createGenericVirtualRegister(PtrTy);
    MIRBuilder.buildUndef(Undef);
    return true;
  }
  case Intrinsic::invariant_end:
    return true;
  case Intrinsic::assume:
  case Intrinsic::var_annotation:
  case Intrinsic::sideeffect:
    // Discard annotate attributes, assumptions, and artificial side-effects.
    return true;
  }
  return false;
}

bool IRTranslator::translateInlineAsm(const CallInst &CI,
                                      MachineIRBuilder &MIRBuilder) {
  const InlineAsm &IA = cast<InlineAsm>(*CI.getCalledValue());
  if (!IA.getConstraintString().empty())
    return false;

  unsigned ExtraInfo = 0;
  if (IA.hasSideEffects())
    ExtraInfo |= InlineAsm::Extra_HasSideEffects;
  if (IA.getDialect() == InlineAsm::AD_Intel)
    ExtraInfo |= InlineAsm::Extra_AsmDialect;

  MIRBuilder.buildInstr(TargetOpcode::INLINEASM)
    .addExternalSymbol(IA.getAsmString().c_str())
    .addImm(ExtraInfo);

  return true;
}

bool IRTranslator::translateCallSite(const ImmutableCallSite &CS,
                                     MachineIRBuilder &MIRBuilder) {
  const Instruction &I = *CS.getInstruction();
  ArrayRef<Register> Res = getOrCreateVRegs(I);

  SmallVector<ArrayRef<Register>, 8> Args;
  Register SwiftInVReg = 0;
  Register SwiftErrorVReg = 0;
  for (auto &Arg : CS.args()) {
    if (CLI->supportSwiftError() && isSwiftError(Arg)) {
      assert(SwiftInVReg == 0 && "Expected only one swift error argument");
      LLT Ty = getLLTForType(*Arg->getType(), *DL);
      SwiftInVReg = MRI->createGenericVirtualRegister(Ty);
      MIRBuilder.buildCopy(SwiftInVReg, SwiftError.getOrCreateVRegUseAt(
                                            &I, &MIRBuilder.getMBB(), Arg));
      Args.emplace_back(makeArrayRef(SwiftInVReg));
      SwiftErrorVReg =
          SwiftError.getOrCreateVRegDefAt(&I, &MIRBuilder.getMBB(), Arg);
      continue;
    }
    Args.push_back(getOrCreateVRegs(*Arg));
  }

  // We don't set HasCalls on MFI here yet because call lowering may decide to
  // optimize into tail calls. Instead, we defer that to selection where a final
  // scan is done to check if any instructions are calls.
  bool Success =
      CLI->lowerCall(MIRBuilder, CS, Res, Args, SwiftErrorVReg,
                     [&]() { return getOrCreateVReg(*CS.getCalledValue()); });

  // Check if we just inserted a tail call.
  if (Success) {
    assert(!HasTailCall && "Can't tail call return twice from block?");
    const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
    HasTailCall = TII->isTailCall(*std::prev(MIRBuilder.getInsertPt()));
  }

  return Success;
}

bool IRTranslator::translateCall(const User &U, MachineIRBuilder &MIRBuilder) {
  const CallInst &CI = cast<CallInst>(U);
  auto TII = MF->getTarget().getIntrinsicInfo();
  const Function *F = CI.getCalledFunction();

  // FIXME: support Windows dllimport function calls.
  if (F && F->hasDLLImportStorageClass())
    return false;

  if (CI.isInlineAsm())
    return translateInlineAsm(CI, MIRBuilder);

  Intrinsic::ID ID = Intrinsic::not_intrinsic;
  if (F && F->isIntrinsic()) {
    ID = F->getIntrinsicID();
    if (TII && ID == Intrinsic::not_intrinsic)
      ID = static_cast<Intrinsic::ID>(TII->getIntrinsicID(F));
  }

  if (!F || !F->isIntrinsic() || ID == Intrinsic::not_intrinsic)
    return translateCallSite(&CI, MIRBuilder);

  assert(ID != Intrinsic::not_intrinsic && "unknown intrinsic");

  if (translateKnownIntrinsic(CI, ID, MIRBuilder))
    return true;

  ArrayRef<Register> ResultRegs;
  if (!CI.getType()->isVoidTy())
    ResultRegs = getOrCreateVRegs(CI);

  // Ignore the callsite attributes. Backend code is most likely not expecting
  // an intrinsic to sometimes have side effects and sometimes not.
  MachineInstrBuilder MIB =
      MIRBuilder.buildIntrinsic(ID, ResultRegs, !F->doesNotAccessMemory());
  if (isa<FPMathOperator>(CI))
    MIB->copyIRFlags(CI);

  for (auto &Arg : enumerate(CI.arg_operands())) {
    // Some intrinsics take metadata parameters. Reject them.
    if (isa<MetadataAsValue>(Arg.value()))
      return false;

    // If this is required to be an immediate, don't materialize it in a
    // register.
    if (CI.paramHasAttr(Arg.index(), Attribute::ImmArg)) {
      if (ConstantInt *CI = dyn_cast<ConstantInt>(Arg.value())) {
        // imm arguments are more convenient than cimm (and realistically
        // probably sufficient), so use them.
        assert(CI->getBitWidth() <= 64 &&
               "large intrinsic immediates not handled");
        MIB.addImm(CI->getSExtValue());
      } else {
        MIB.addFPImm(cast<ConstantFP>(Arg.value()));
      }
    } else {
      ArrayRef<Register> VRegs = getOrCreateVRegs(*Arg.value());
      if (VRegs.size() > 1)
        return false;
      MIB.addUse(VRegs[0]);
    }
  }

  // Add a MachineMemOperand if it is a target mem intrinsic.
  const TargetLowering &TLI = *MF->getSubtarget().getTargetLowering();
  TargetLowering::IntrinsicInfo Info;
  // TODO: Add a GlobalISel version of getTgtMemIntrinsic.
  if (TLI.getTgtMemIntrinsic(Info, CI, *MF, ID)) {
    MaybeAlign Align = Info.align;
    if (!Align)
      Align = MaybeAlign(
          DL->getABITypeAlignment(Info.memVT.getTypeForEVT(F->getContext())));

    uint64_t Size = Info.memVT.getStoreSize();
    MIB.addMemOperand(MF->getMachineMemOperand(
        MachinePointerInfo(Info.ptrVal), Info.flags, Size, Align->value()));
  }

  return true;
}

bool IRTranslator::translateInvoke(const User &U,
                                   MachineIRBuilder &MIRBuilder) {
  const InvokeInst &I = cast<InvokeInst>(U);
  MCContext &Context = MF->getContext();

  const BasicBlock *ReturnBB = I.getSuccessor(0);
  const BasicBlock *EHPadBB = I.getSuccessor(1);

  const Value *Callee = I.getCalledValue();
  const Function *Fn = dyn_cast<Function>(Callee);
  if (isa<InlineAsm>(Callee))
    return false;

  // FIXME: support invoking patchpoint and statepoint intrinsics.
  if (Fn && Fn->isIntrinsic())
    return false;

  // FIXME: support whatever these are.
  if (I.countOperandBundlesOfType(LLVMContext::OB_deopt))
    return false;

  // FIXME: support Windows exception handling.
  if (!isa<LandingPadInst>(EHPadBB->front()))
    return false;

  // Emit the actual call, bracketed by EH_LABELs so that the MF knows about
  // the region covered by the try.
  MCSymbol *BeginSymbol = Context.createTempSymbol();
  MIRBuilder.buildInstr(TargetOpcode::EH_LABEL).addSym(BeginSymbol);

  if (!translateCallSite(&I, MIRBuilder))
    return false;

  MCSymbol *EndSymbol = Context.createTempSymbol();
  MIRBuilder.buildInstr(TargetOpcode::EH_LABEL).addSym(EndSymbol);

  // FIXME: track probabilities.
  MachineBasicBlock &EHPadMBB = getMBB(*EHPadBB),
                    &ReturnMBB = getMBB(*ReturnBB);
  MF->addInvoke(&EHPadMBB, BeginSymbol, EndSymbol);
  MIRBuilder.getMBB().addSuccessor(&ReturnMBB);
  MIRBuilder.getMBB().addSuccessor(&EHPadMBB);
  MIRBuilder.buildBr(ReturnMBB);

  return true;
}

bool IRTranslator::translateCallBr(const User &U,
                                   MachineIRBuilder &MIRBuilder) {
  // FIXME: Implement this.
  return false;
}

bool IRTranslator::translateLandingPad(const User &U,
                                       MachineIRBuilder &MIRBuilder) {
  const LandingPadInst &LP = cast<LandingPadInst>(U);

  MachineBasicBlock &MBB = MIRBuilder.getMBB();

  MBB.setIsEHPad();

  // If there aren't registers to copy the values into (e.g., during SjLj
  // exceptions), then don't bother.
  auto &TLI = *MF->getSubtarget().getTargetLowering();
  const Constant *PersonalityFn = MF->getFunction().getPersonalityFn();
  if (TLI.getExceptionPointerRegister(PersonalityFn) == 0 &&
      TLI.getExceptionSelectorRegister(PersonalityFn) == 0)
    return true;

  // If landingpad's return type is token type, we don't create DAG nodes
  // for its exception pointer and selector value. The extraction of exception
  // pointer or selector value from token type landingpads is not currently
  // supported.
  if (LP.getType()->isTokenTy())
    return true;

  // Add a label to mark the beginning of the landing pad.  Deletion of the
  // landing pad can thus be detected via the MachineModuleInfo.
  MIRBuilder.buildInstr(TargetOpcode::EH_LABEL)
    .addSym(MF->addLandingPad(&MBB));

  LLT Ty = getLLTForType(*LP.getType(), *DL);
  Register Undef = MRI->createGenericVirtualRegister(Ty);
  MIRBuilder.buildUndef(Undef);

  SmallVector<LLT, 2> Tys;
  for (Type *Ty : cast<StructType>(LP.getType())->elements())
    Tys.push_back(getLLTForType(*Ty, *DL));
  assert(Tys.size() == 2 && "Only two-valued landingpads are supported");

  // Mark exception register as live in.
  Register ExceptionReg = TLI.getExceptionPointerRegister(PersonalityFn);
  if (!ExceptionReg)
    return false;

  MBB.addLiveIn(ExceptionReg);
  ArrayRef<Register> ResRegs = getOrCreateVRegs(LP);
  MIRBuilder.buildCopy(ResRegs[0], ExceptionReg);

  Register SelectorReg = TLI.getExceptionSelectorRegister(PersonalityFn);
  if (!SelectorReg)
    return false;

  MBB.addLiveIn(SelectorReg);
  Register PtrVReg = MRI->createGenericVirtualRegister(Tys[0]);
  MIRBuilder.buildCopy(PtrVReg, SelectorReg);
  MIRBuilder.buildCast(ResRegs[1], PtrVReg);

  return true;
}

bool IRTranslator::translateAlloca(const User &U,
                                   MachineIRBuilder &MIRBuilder) {
  auto &AI = cast<AllocaInst>(U);

  if (AI.isSwiftError())
    return true;

  if (AI.isStaticAlloca()) {
    Register Res = getOrCreateVReg(AI);
    int FI = getOrCreateFrameIndex(AI);
    MIRBuilder.buildFrameIndex(Res, FI);
    return true;
  }

  // FIXME: support stack probing for Windows.
  if (MF->getTarget().getTargetTriple().isOSWindows())
    return false;

  // Now we're in the harder dynamic case.
  Type *Ty = AI.getAllocatedType();
  unsigned Align =
      std::max((unsigned)DL->getPrefTypeAlignment(Ty), AI.getAlignment());

  Register NumElts = getOrCreateVReg(*AI.getArraySize());

  Type *IntPtrIRTy = DL->getIntPtrType(AI.getType());
  LLT IntPtrTy = getLLTForType(*IntPtrIRTy, *DL);
  if (MRI->getType(NumElts) != IntPtrTy) {
    Register ExtElts = MRI->createGenericVirtualRegister(IntPtrTy);
    MIRBuilder.buildZExtOrTrunc(ExtElts, NumElts);
    NumElts = ExtElts;
  }

  Register AllocSize = MRI->createGenericVirtualRegister(IntPtrTy);
  Register TySize =
      getOrCreateVReg(*ConstantInt::get(IntPtrIRTy, DL->getTypeAllocSize(Ty)));
  MIRBuilder.buildMul(AllocSize, NumElts, TySize);

  unsigned StackAlign =
      MF->getSubtarget().getFrameLowering()->getStackAlignment();
  if (Align <= StackAlign)
    Align = 0;

  // Round the size of the allocation up to the stack alignment size
  // by add SA-1 to the size. This doesn't overflow because we're computing
  // an address inside an alloca.
  auto SAMinusOne = MIRBuilder.buildConstant(IntPtrTy, StackAlign - 1);
  auto AllocAdd = MIRBuilder.buildAdd(IntPtrTy, AllocSize, SAMinusOne,
                                      MachineInstr::NoUWrap);
  auto AlignCst =
      MIRBuilder.buildConstant(IntPtrTy, ~(uint64_t)(StackAlign - 1));
  auto AlignedAlloc = MIRBuilder.buildAnd(IntPtrTy, AllocAdd, AlignCst);

  MIRBuilder.buildDynStackAlloc(getOrCreateVReg(AI), AlignedAlloc, Align);

  MF->getFrameInfo().CreateVariableSizedObject(Align ? Align : 1, &AI);
  assert(MF->getFrameInfo().hasVarSizedObjects());
  return true;
}

bool IRTranslator::translateVAArg(const User &U, MachineIRBuilder &MIRBuilder) {
  // FIXME: We may need more info about the type. Because of how LLT works,
  // we're completely discarding the i64/double distinction here (amongst
  // others). Fortunately the ABIs I know of where that matters don't use va_arg
  // anyway but that's not guaranteed.
  MIRBuilder.buildInstr(TargetOpcode::G_VAARG)
    .addDef(getOrCreateVReg(U))
    .addUse(getOrCreateVReg(*U.getOperand(0)))
    .addImm(DL->getABITypeAlignment(U.getType()));
  return true;
}

bool IRTranslator::translateInsertElement(const User &U,
                                          MachineIRBuilder &MIRBuilder) {
  // If it is a <1 x Ty> vector, use the scalar as it is
  // not a legal vector type in LLT.
  if (U.getType()->getVectorNumElements() == 1) {
    Register Elt = getOrCreateVReg(*U.getOperand(1));
    auto &Regs = *VMap.getVRegs(U);
    if (Regs.empty()) {
      Regs.push_back(Elt);
      VMap.getOffsets(U)->push_back(0);
    } else {
      MIRBuilder.buildCopy(Regs[0], Elt);
    }
    return true;
  }

  Register Res = getOrCreateVReg(U);
  Register Val = getOrCreateVReg(*U.getOperand(0));
  Register Elt = getOrCreateVReg(*U.getOperand(1));
  Register Idx = getOrCreateVReg(*U.getOperand(2));
  MIRBuilder.buildInsertVectorElement(Res, Val, Elt, Idx);
  return true;
}

bool IRTranslator::translateExtractElement(const User &U,
                                           MachineIRBuilder &MIRBuilder) {
  // If it is a <1 x Ty> vector, use the scalar as it is
  // not a legal vector type in LLT.
  if (U.getOperand(0)->getType()->getVectorNumElements() == 1) {
    Register Elt = getOrCreateVReg(*U.getOperand(0));
    auto &Regs = *VMap.getVRegs(U);
    if (Regs.empty()) {
      Regs.push_back(Elt);
      VMap.getOffsets(U)->push_back(0);
    } else {
      MIRBuilder.buildCopy(Regs[0], Elt);
    }
    return true;
  }
  Register Res = getOrCreateVReg(U);
  Register Val = getOrCreateVReg(*U.getOperand(0));
  const auto &TLI = *MF->getSubtarget().getTargetLowering();
  unsigned PreferredVecIdxWidth = TLI.getVectorIdxTy(*DL).getSizeInBits();
  Register Idx;
  if (auto *CI = dyn_cast<ConstantInt>(U.getOperand(1))) {
    if (CI->getBitWidth() != PreferredVecIdxWidth) {
      APInt NewIdx = CI->getValue().sextOrTrunc(PreferredVecIdxWidth);
      auto *NewIdxCI = ConstantInt::get(CI->getContext(), NewIdx);
      Idx = getOrCreateVReg(*NewIdxCI);
    }
  }
  if (!Idx)
    Idx = getOrCreateVReg(*U.getOperand(1));
  if (MRI->getType(Idx).getSizeInBits() != PreferredVecIdxWidth) {
    const LLT &VecIdxTy = LLT::scalar(PreferredVecIdxWidth);
    Idx = MIRBuilder.buildSExtOrTrunc(VecIdxTy, Idx)->getOperand(0).getReg();
  }
  MIRBuilder.buildExtractVectorElement(Res, Val, Idx);
  return true;
}

bool IRTranslator::translateShuffleVector(const User &U,
                                          MachineIRBuilder &MIRBuilder) {
  MIRBuilder.buildInstr(TargetOpcode::G_SHUFFLE_VECTOR)
      .addDef(getOrCreateVReg(U))
      .addUse(getOrCreateVReg(*U.getOperand(0)))
      .addUse(getOrCreateVReg(*U.getOperand(1)))
      .addShuffleMask(cast<Constant>(U.getOperand(2)));
  return true;
}

bool IRTranslator::translatePHI(const User &U, MachineIRBuilder &MIRBuilder) {
  const PHINode &PI = cast<PHINode>(U);

  SmallVector<MachineInstr *, 4> Insts;
  for (auto Reg : getOrCreateVRegs(PI)) {
    auto MIB = MIRBuilder.buildInstr(TargetOpcode::G_PHI, {Reg}, {});
    Insts.push_back(MIB.getInstr());
  }

  PendingPHIs.emplace_back(&PI, std::move(Insts));
  return true;
}

bool IRTranslator::translateAtomicCmpXchg(const User &U,
                                          MachineIRBuilder &MIRBuilder) {
  const AtomicCmpXchgInst &I = cast<AtomicCmpXchgInst>(U);

  if (I.isWeak())
    return false;

  auto Flags = I.isVolatile() ? MachineMemOperand::MOVolatile
                              : MachineMemOperand::MONone;
  Flags |= MachineMemOperand::MOLoad | MachineMemOperand::MOStore;

  Type *ResType = I.getType();
  Type *ValType = ResType->Type::getStructElementType(0);

  auto Res = getOrCreateVRegs(I);
  Register OldValRes = Res[0];
  Register SuccessRes = Res[1];
  Register Addr = getOrCreateVReg(*I.getPointerOperand());
  Register Cmp = getOrCreateVReg(*I.getCompareOperand());
  Register NewVal = getOrCreateVReg(*I.getNewValOperand());

  MIRBuilder.buildAtomicCmpXchgWithSuccess(
      OldValRes, SuccessRes, Addr, Cmp, NewVal,
      *MF->getMachineMemOperand(MachinePointerInfo(I.getPointerOperand()),
                                Flags, DL->getTypeStoreSize(ValType),
                                getMemOpAlignment(I), AAMDNodes(), nullptr,
                                I.getSyncScopeID(), I.getSuccessOrdering(),
                                I.getFailureOrdering()));
  return true;
}

bool IRTranslator::translateAtomicRMW(const User &U,
                                      MachineIRBuilder &MIRBuilder) {
  const AtomicRMWInst &I = cast<AtomicRMWInst>(U);

  auto Flags = I.isVolatile() ? MachineMemOperand::MOVolatile
                              : MachineMemOperand::MONone;
  Flags |= MachineMemOperand::MOLoad | MachineMemOperand::MOStore;

  Type *ResType = I.getType();

  Register Res = getOrCreateVReg(I);
  Register Addr = getOrCreateVReg(*I.getPointerOperand());
  Register Val = getOrCreateVReg(*I.getValOperand());

  unsigned Opcode = 0;
  switch (I.getOperation()) {
  default:
    return false;
  case AtomicRMWInst::Xchg:
    Opcode = TargetOpcode::G_ATOMICRMW_XCHG;
    break;
  case AtomicRMWInst::Add:
    Opcode = TargetOpcode::G_ATOMICRMW_ADD;
    break;
  case AtomicRMWInst::Sub:
    Opcode = TargetOpcode::G_ATOMICRMW_SUB;
    break;
  case AtomicRMWInst::And:
    Opcode = TargetOpcode::G_ATOMICRMW_AND;
    break;
  case AtomicRMWInst::Nand:
    Opcode = TargetOpcode::G_ATOMICRMW_NAND;
    break;
  case AtomicRMWInst::Or:
    Opcode = TargetOpcode::G_ATOMICRMW_OR;
    break;
  case AtomicRMWInst::Xor:
    Opcode = TargetOpcode::G_ATOMICRMW_XOR;
    break;
  case AtomicRMWInst::Max:
    Opcode = TargetOpcode::G_ATOMICRMW_MAX;
    break;
  case AtomicRMWInst::Min:
    Opcode = TargetOpcode::G_ATOMICRMW_MIN;
    break;
  case AtomicRMWInst::UMax:
    Opcode = TargetOpcode::G_ATOMICRMW_UMAX;
    break;
  case AtomicRMWInst::UMin:
    Opcode = TargetOpcode::G_ATOMICRMW_UMIN;
    break;
  case AtomicRMWInst::FAdd:
    Opcode = TargetOpcode::G_ATOMICRMW_FADD;
    break;
  case AtomicRMWInst::FSub:
    Opcode = TargetOpcode::G_ATOMICRMW_FSUB;
    break;
  }

  MIRBuilder.buildAtomicRMW(
      Opcode, Res, Addr, Val,
      *MF->getMachineMemOperand(MachinePointerInfo(I.getPointerOperand()),
                                Flags, DL->getTypeStoreSize(ResType),
                                getMemOpAlignment(I), AAMDNodes(), nullptr,
                                I.getSyncScopeID(), I.getOrdering()));
  return true;
}

bool IRTranslator::translateFence(const User &U,
                                  MachineIRBuilder &MIRBuilder) {
  const FenceInst &Fence = cast<FenceInst>(U);
  MIRBuilder.buildFence(static_cast<unsigned>(Fence.getOrdering()),
                        Fence.getSyncScopeID());
  return true;
}

void IRTranslator::finishPendingPhis() {
#ifndef NDEBUG
  DILocationVerifier Verifier;
  GISelObserverWrapper WrapperObserver(&Verifier);
  RAIIDelegateInstaller DelInstall(*MF, &WrapperObserver);
#endif // ifndef NDEBUG
  for (auto &Phi : PendingPHIs) {
    const PHINode *PI = Phi.first;
    ArrayRef<MachineInstr *> ComponentPHIs = Phi.second;
    MachineBasicBlock *PhiMBB = ComponentPHIs[0]->getParent();
    EntryBuilder->setDebugLoc(PI->getDebugLoc());
#ifndef NDEBUG
    Verifier.setCurrentInst(PI);
#endif // ifndef NDEBUG

    SmallSet<const MachineBasicBlock *, 16> SeenPreds;
    for (unsigned i = 0; i < PI->getNumIncomingValues(); ++i) {
      auto IRPred = PI->getIncomingBlock(i);
      ArrayRef<Register> ValRegs = getOrCreateVRegs(*PI->getIncomingValue(i));
      for (auto Pred : getMachinePredBBs({IRPred, PI->getParent()})) {
        if (SeenPreds.count(Pred) || !PhiMBB->isPredecessor(Pred))
          continue;
        SeenPreds.insert(Pred);
        for (unsigned j = 0; j < ValRegs.size(); ++j) {
          MachineInstrBuilder MIB(*MF, ComponentPHIs[j]);
          MIB.addUse(ValRegs[j]);
          MIB.addMBB(Pred);
        }
      }
    }
  }
}

bool IRTranslator::valueIsSplit(const Value &V,
                                SmallVectorImpl<uint64_t> *Offsets) {
  SmallVector<LLT, 4> SplitTys;
  if (Offsets && !Offsets->empty())
    Offsets->clear();
  computeValueLLTs(*DL, *V.getType(), SplitTys, Offsets);
  return SplitTys.size() > 1;
}

bool IRTranslator::translate(const Instruction &Inst) {
  CurBuilder->setDebugLoc(Inst.getDebugLoc());
  // We only emit constants into the entry block from here. To prevent jumpy
  // debug behaviour set the line to 0.
  if (const DebugLoc &DL = Inst.getDebugLoc())
    EntryBuilder->setDebugLoc(
        DebugLoc::get(0, 0, DL.getScope(), DL.getInlinedAt()));
  else
    EntryBuilder->setDebugLoc(DebugLoc());

  switch (Inst.getOpcode()) {
#define HANDLE_INST(NUM, OPCODE, CLASS)                                        \
  case Instruction::OPCODE:                                                    \
    return translate##OPCODE(Inst, *CurBuilder.get());
#include "llvm/IR/Instruction.def"
  default:
    return false;
  }
}

bool IRTranslator::translate(const Constant &C, Register Reg) {
  if (auto CI = dyn_cast<ConstantInt>(&C))
    EntryBuilder->buildConstant(Reg, *CI);
  else if (auto CF = dyn_cast<ConstantFP>(&C))
    EntryBuilder->buildFConstant(Reg, *CF);
  else if (isa<UndefValue>(C))
    EntryBuilder->buildUndef(Reg);
  else if (isa<ConstantPointerNull>(C)) {
    // As we are trying to build a constant val of 0 into a pointer,
    // insert a cast to make them correct with respect to types.
    unsigned NullSize = DL->getTypeSizeInBits(C.getType());
    auto *ZeroTy = Type::getIntNTy(C.getContext(), NullSize);
    auto *ZeroVal = ConstantInt::get(ZeroTy, 0);
    Register ZeroReg = getOrCreateVReg(*ZeroVal);
    EntryBuilder->buildCast(Reg, ZeroReg);
  } else if (auto GV = dyn_cast<GlobalValue>(&C))
    EntryBuilder->buildGlobalValue(Reg, GV);
  else if (auto CAZ = dyn_cast<ConstantAggregateZero>(&C)) {
    if (!CAZ->getType()->isVectorTy())
      return false;
    // Return the scalar if it is a <1 x Ty> vector.
    if (CAZ->getNumElements() == 1)
      return translate(*CAZ->getElementValue(0u), Reg);
    SmallVector<Register, 4> Ops;
    for (unsigned i = 0; i < CAZ->getNumElements(); ++i) {
      Constant &Elt = *CAZ->getElementValue(i);
      Ops.push_back(getOrCreateVReg(Elt));
    }
    EntryBuilder->buildBuildVector(Reg, Ops);
  } else if (auto CV = dyn_cast<ConstantDataVector>(&C)) {
    // Return the scalar if it is a <1 x Ty> vector.
    if (CV->getNumElements() == 1)
      return translate(*CV->getElementAsConstant(0), Reg);
    SmallVector<Register, 4> Ops;
    for (unsigned i = 0; i < CV->getNumElements(); ++i) {
      Constant &Elt = *CV->getElementAsConstant(i);
      Ops.push_back(getOrCreateVReg(Elt));
    }
    EntryBuilder->buildBuildVector(Reg, Ops);
  } else if (auto CE = dyn_cast<ConstantExpr>(&C)) {
    switch(CE->getOpcode()) {
#define HANDLE_INST(NUM, OPCODE, CLASS)                                        \
  case Instruction::OPCODE:                                                    \
    return translate##OPCODE(*CE, *EntryBuilder.get());
#include "llvm/IR/Instruction.def"
    default:
      return false;
    }
  } else if (auto CV = dyn_cast<ConstantVector>(&C)) {
    if (CV->getNumOperands() == 1)
      return translate(*CV->getOperand(0), Reg);
    SmallVector<Register, 4> Ops;
    for (unsigned i = 0; i < CV->getNumOperands(); ++i) {
      Ops.push_back(getOrCreateVReg(*CV->getOperand(i)));
    }
    EntryBuilder->buildBuildVector(Reg, Ops);
  } else if (auto *BA = dyn_cast<BlockAddress>(&C)) {
    EntryBuilder->buildBlockAddress(Reg, BA);
  } else
    return false;

  return true;
}

void IRTranslator::finalizeBasicBlock() {
  for (auto &JTCase : SL->JTCases) {
    // Emit header first, if it wasn't already emitted.
    if (!JTCase.first.Emitted)
      emitJumpTableHeader(JTCase.second, JTCase.first, JTCase.first.HeaderBB);

    emitJumpTable(JTCase.second, JTCase.second.MBB);
  }
  SL->JTCases.clear();
}

void IRTranslator::finalizeFunction() {
  // Release the memory used by the different maps we
  // needed during the translation.
  PendingPHIs.clear();
  VMap.reset();
  FrameIndices.clear();
  MachinePreds.clear();
  // MachineIRBuilder::DebugLoc can outlive the DILocation it holds. Clear it
  // to avoid accessing free’d memory (in runOnMachineFunction) and to avoid
  // destroying it twice (in ~IRTranslator() and ~LLVMContext())
  EntryBuilder.reset();
  CurBuilder.reset();
  FuncInfo.clear();
}

/// Returns true if a BasicBlock \p BB within a variadic function contains a
/// variadic musttail call.
static bool checkForMustTailInVarArgFn(bool IsVarArg, const BasicBlock &BB) {
  if (!IsVarArg)
    return false;

  // Walk the block backwards, because tail calls usually only appear at the end
  // of a block.
  return std::any_of(BB.rbegin(), BB.rend(), [](const Instruction &I) {
    const auto *CI = dyn_cast<CallInst>(&I);
    return CI && CI->isMustTailCall();
  });
}

bool IRTranslator::runOnMachineFunction(MachineFunction &CurMF) {
  MF = &CurMF;
  const Function &F = MF->getFunction();
  if (F.empty())
    return false;
  GISelCSEAnalysisWrapper &Wrapper =
      getAnalysis<GISelCSEAnalysisWrapperPass>().getCSEWrapper();
  // Set the CSEConfig and run the analysis.
  GISelCSEInfo *CSEInfo = nullptr;
  TPC = &getAnalysis<TargetPassConfig>();
  bool EnableCSE = EnableCSEInIRTranslator.getNumOccurrences()
                       ? EnableCSEInIRTranslator
                       : TPC->isGISelCSEEnabled();

  if (EnableCSE) {
    EntryBuilder = std::make_unique<CSEMIRBuilder>(CurMF);
    CSEInfo = &Wrapper.get(TPC->getCSEConfig());
    EntryBuilder->setCSEInfo(CSEInfo);
    CurBuilder = std::make_unique<CSEMIRBuilder>(CurMF);
    CurBuilder->setCSEInfo(CSEInfo);
  } else {
    EntryBuilder = std::make_unique<MachineIRBuilder>();
    CurBuilder = std::make_unique<MachineIRBuilder>();
  }
  CLI = MF->getSubtarget().getCallLowering();
  CurBuilder->setMF(*MF);
  EntryBuilder->setMF(*MF);
  MRI = &MF->getRegInfo();
  DL = &F.getParent()->getDataLayout();
  ORE = std::make_unique<OptimizationRemarkEmitter>(&F);
  FuncInfo.MF = MF;
  FuncInfo.BPI = nullptr;
  const auto &TLI = *MF->getSubtarget().getTargetLowering();
  const TargetMachine &TM = MF->getTarget();
  SL = std::make_unique<GISelSwitchLowering>(this, FuncInfo);
  SL->init(TLI, TM, *DL);

  EnableOpts = TM.getOptLevel() != CodeGenOpt::None && !skipFunction(F);

  assert(PendingPHIs.empty() && "stale PHIs");

  if (!DL->isLittleEndian()) {
    // Currently we don't properly handle big endian code.
    OptimizationRemarkMissed R("gisel-irtranslator", "GISelFailure",
                               F.getSubprogram(), &F.getEntryBlock());
    R << "unable to translate in big endian mode";
    reportTranslationError(*MF, *TPC, *ORE, R);
  }

  // Release the per-function state when we return, whether we succeeded or not.
  auto FinalizeOnReturn = make_scope_exit([this]() { finalizeFunction(); });

  // Setup a separate basic-block for the arguments and constants
  MachineBasicBlock *EntryBB = MF->CreateMachineBasicBlock();
  MF->push_back(EntryBB);
  EntryBuilder->setMBB(*EntryBB);

  DebugLoc DbgLoc = F.getEntryBlock().getFirstNonPHI()->getDebugLoc();
  SwiftError.setFunction(CurMF);
  SwiftError.createEntriesInEntryBlock(DbgLoc);

  bool IsVarArg = F.isVarArg();
  bool HasMustTailInVarArgFn = false;

  // Create all blocks, in IR order, to preserve the layout.
  for (const BasicBlock &BB: F) {
    auto *&MBB = BBToMBB[&BB];

    MBB = MF->CreateMachineBasicBlock(&BB);
    MF->push_back(MBB);

    if (BB.hasAddressTaken())
      MBB->setHasAddressTaken();

    if (!HasMustTailInVarArgFn)
      HasMustTailInVarArgFn = checkForMustTailInVarArgFn(IsVarArg, BB);
  }

  MF->getFrameInfo().setHasMustTailInVarArgFunc(HasMustTailInVarArgFn);

  // Make our arguments/constants entry block fallthrough to the IR entry block.
  EntryBB->addSuccessor(&getMBB(F.front()));

  // Lower the actual args into this basic block.
  SmallVector<ArrayRef<Register>, 8> VRegArgs;
  for (const Argument &Arg: F.args()) {
    if (DL->getTypeStoreSize(Arg.getType()) == 0)
      continue; // Don't handle zero sized types.
    ArrayRef<Register> VRegs = getOrCreateVRegs(Arg);
    VRegArgs.push_back(VRegs);

    if (Arg.hasSwiftErrorAttr()) {
      assert(VRegs.size() == 1 && "Too many vregs for Swift error");
      SwiftError.setCurrentVReg(EntryBB, SwiftError.getFunctionArg(), VRegs[0]);
    }
  }

  if (!CLI->lowerFormalArguments(*EntryBuilder.get(), F, VRegArgs)) {
    OptimizationRemarkMissed R("gisel-irtranslator", "GISelFailure",
                               F.getSubprogram(), &F.getEntryBlock());
    R << "unable to lower arguments: " << ore::NV("Prototype", F.getType());
    reportTranslationError(*MF, *TPC, *ORE, R);
    return false;
  }

  // Need to visit defs before uses when translating instructions.
  GISelObserverWrapper WrapperObserver;
  if (EnableCSE && CSEInfo)
    WrapperObserver.addObserver(CSEInfo);
  {
    ReversePostOrderTraversal<const Function *> RPOT(&F);
#ifndef NDEBUG
    DILocationVerifier Verifier;
    WrapperObserver.addObserver(&Verifier);
#endif // ifndef NDEBUG
    RAIIDelegateInstaller DelInstall(*MF, &WrapperObserver);
    for (const BasicBlock *BB : RPOT) {
      MachineBasicBlock &MBB = getMBB(*BB);
      // Set the insertion point of all the following translations to
      // the end of this basic block.
      CurBuilder->setMBB(MBB);
      HasTailCall = false;
      for (const Instruction &Inst : *BB) {
        // If we translated a tail call in the last step, then we know
        // everything after the call is either a return, or something that is
        // handled by the call itself. (E.g. a lifetime marker or assume
        // intrinsic.) In this case, we should stop translating the block and
        // move on.
        if (HasTailCall)
          break;
#ifndef NDEBUG
        Verifier.setCurrentInst(&Inst);
#endif // ifndef NDEBUG
        if (translate(Inst))
          continue;

        OptimizationRemarkMissed R("gisel-irtranslator", "GISelFailure",
                                   Inst.getDebugLoc(), BB);
        R << "unable to translate instruction: " << ore::NV("Opcode", &Inst);

        if (ORE->allowExtraAnalysis("gisel-irtranslator")) {
          std::string InstStrStorage;
          raw_string_ostream InstStr(InstStrStorage);
          InstStr << Inst;

          R << ": '" << InstStr.str() << "'";
        }

        reportTranslationError(*MF, *TPC, *ORE, R);
        return false;
      }

      finalizeBasicBlock();
    }
#ifndef NDEBUG
    WrapperObserver.removeObserver(&Verifier);
#endif
  }

  finishPendingPhis();

  SwiftError.propagateVRegs();

  // Merge the argument lowering and constants block with its single
  // successor, the LLVM-IR entry block.  We want the basic block to
  // be maximal.
  assert(EntryBB->succ_size() == 1 &&
         "Custom BB used for lowering should have only one successor");
  // Get the successor of the current entry block.
  MachineBasicBlock &NewEntryBB = **EntryBB->succ_begin();
  assert(NewEntryBB.pred_size() == 1 &&
         "LLVM-IR entry block has a predecessor!?");
  // Move all the instruction from the current entry block to the
  // new entry block.
  NewEntryBB.splice(NewEntryBB.begin(), EntryBB, EntryBB->begin(),
                    EntryBB->end());

  // Update the live-in information for the new entry block.
  for (const MachineBasicBlock::RegisterMaskPair &LiveIn : EntryBB->liveins())
    NewEntryBB.addLiveIn(LiveIn);
  NewEntryBB.sortUniqueLiveIns();

  // Get rid of the now empty basic block.
  EntryBB->removeSuccessor(&NewEntryBB);
  MF->remove(EntryBB);
  MF->DeleteMachineBasicBlock(EntryBB);

  assert(&MF->front() == &NewEntryBB &&
         "New entry wasn't next in the list of basic block!");

  // Initialize stack protector information.
  StackProtector &SP = getAnalysis<StackProtector>();
  SP.copyToMachineFrameInfo(MF->getFrameInfo());

  return false;
}