llvm/lib/Target/X86/X86MCInstLower.cpp

//===-- X86MCInstLower.cpp - Convert X86 MachineInstr to an MCInst --------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains code to lower X86 MachineInstrs to their corresponding
// MCInst records.
//
//===----------------------------------------------------------------------===//

#include "X86AsmPrinter.h"
#include "X86RegisterInfo.h"
#include "InstPrinter/X86ATTInstPrinter.h"
#include "MCTargetDesc/X86BaseInfo.h"
#include "Utils/X86ShuffleDecode.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineModuleInfoImpls.h"
#include "llvm/CodeGen/StackMaps.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/Mangler.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCFixup.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstBuilder.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/TargetRegistry.h"
using namespace llvm;

namespace {

/// X86MCInstLower - This class is used to lower an MachineInstr into an MCInst.
class X86MCInstLower {
  MCContext &Ctx;
  const MachineFunction &MF;
  const TargetMachine &TM;
  const MCAsmInfo &MAI;
  X86AsmPrinter &AsmPrinter;
public:
  X86MCInstLower(const MachineFunction &MF, X86AsmPrinter &asmprinter);

  void Lower(const MachineInstr *MI, MCInst &OutMI) const;

  MCSymbol *GetSymbolFromOperand(const MachineOperand &MO) const;
  MCOperand LowerSymbolOperand(const MachineOperand &MO, MCSymbol *Sym) const;

private:
  MachineModuleInfoMachO &getMachOMMI() const;
  Mangler *getMang() const {
    return AsmPrinter.Mang;
  }
};

} // end anonymous namespace

// Emit a minimal sequence of nops spanning NumBytes bytes.
static void EmitNops(MCStreamer &OS, unsigned NumBytes, bool Is64Bit,
                     const MCSubtargetInfo &STI);

namespace llvm {
   X86AsmPrinter::StackMapShadowTracker::StackMapShadowTracker(TargetMachine &TM)
     : TM(TM), InShadow(false), RequiredShadowSize(0), CurrentShadowSize(0) {}

  X86AsmPrinter::StackMapShadowTracker::~StackMapShadowTracker() {}

  void
  X86AsmPrinter::StackMapShadowTracker::startFunction(MachineFunction &F) {
    MF = &F;
    CodeEmitter.reset(TM.getTarget().createMCCodeEmitter(
        *MF->getSubtarget().getInstrInfo(),
        *MF->getSubtarget().getRegisterInfo(), MF->getContext()));
  }

  void X86AsmPrinter::StackMapShadowTracker::count(MCInst &Inst,
                                                   const MCSubtargetInfo &STI) {
    if (InShadow) {
      SmallString<256> Code;
      SmallVector<MCFixup, 4> Fixups;
      raw_svector_ostream VecOS(Code);
      CodeEmitter->encodeInstruction(Inst, VecOS, Fixups, STI);
      VecOS.flush();
      CurrentShadowSize += Code.size();
      if (CurrentShadowSize >= RequiredShadowSize)
        InShadow = false; // The shadow is big enough. Stop counting.
    }
  }

  void X86AsmPrinter::StackMapShadowTracker::emitShadowPadding(
    MCStreamer &OutStreamer, const MCSubtargetInfo &STI) {
    if (InShadow && CurrentShadowSize < RequiredShadowSize) {
      InShadow = false;
      EmitNops(OutStreamer, RequiredShadowSize - CurrentShadowSize,
               MF->getSubtarget<X86Subtarget>().is64Bit(), STI);
    }
  }

  void X86AsmPrinter::EmitAndCountInstruction(MCInst &Inst) {
    OutStreamer->EmitInstruction(Inst, getSubtargetInfo());
    SMShadowTracker.count(Inst, getSubtargetInfo());
  }
} // end llvm namespace

X86MCInstLower::X86MCInstLower(const MachineFunction &mf,
                               X86AsmPrinter &asmprinter)
    : Ctx(mf.getContext()), MF(mf), TM(mf.getTarget()), MAI(*TM.getMCAsmInfo()),
      AsmPrinter(asmprinter) {}

MachineModuleInfoMachO &X86MCInstLower::getMachOMMI() const {
  return MF.getMMI().getObjFileInfo<MachineModuleInfoMachO>();
}


/// GetSymbolFromOperand - Lower an MO_GlobalAddress or MO_ExternalSymbol
/// operand to an MCSymbol.
MCSymbol *X86MCInstLower::
GetSymbolFromOperand(const MachineOperand &MO) const {
  const DataLayout *DL = TM.getDataLayout();
  assert((MO.isGlobal() || MO.isSymbol() || MO.isMBB()) && "Isn't a symbol reference");

  MCSymbol *Sym = nullptr;
  SmallString<128> Name;
  StringRef Suffix;

  switch (MO.getTargetFlags()) {
  case X86II::MO_DLLIMPORT:
    // Handle dllimport linkage.
    Name += "__imp_";
    break;
  case X86II::MO_DARWIN_STUB:
    Suffix = "$stub";
    break;
  case X86II::MO_DARWIN_NONLAZY:
  case X86II::MO_DARWIN_NONLAZY_PIC_BASE:
  case X86II::MO_DARWIN_HIDDEN_NONLAZY_PIC_BASE:
    Suffix = "$non_lazy_ptr";
    break;
  }

  if (!Suffix.empty())
    Name += DL->getPrivateGlobalPrefix();

  unsigned PrefixLen = Name.size();

  if (MO.isGlobal()) {
    const GlobalValue *GV = MO.getGlobal();
    AsmPrinter.getNameWithPrefix(Name, GV);
  } else if (MO.isSymbol()) {
    if (MO.getTargetFlags() == X86II::MO_NOPREFIX)
      Name += MO.getSymbolName();
    else
      getMang()->getNameWithPrefix(Name, MO.getSymbolName());
  } else if (MO.isMBB()) {
    assert(Suffix.empty());
    Sym = MO.getMBB()->getSymbol();
  }
  unsigned OrigLen = Name.size() - PrefixLen;

  Name += Suffix;
  if (!Sym)
    Sym = Ctx.getOrCreateSymbol(Name);

  StringRef OrigName = StringRef(Name).substr(PrefixLen, OrigLen);

  // If the target flags on the operand changes the name of the symbol, do that
  // before we return the symbol.
  switch (MO.getTargetFlags()) {
  default: break;
  case X86II::MO_DARWIN_NONLAZY:
  case X86II::MO_DARWIN_NONLAZY_PIC_BASE: {
    MachineModuleInfoImpl::StubValueTy &StubSym =
      getMachOMMI().getGVStubEntry(Sym);
    if (!StubSym.getPointer()) {
      assert(MO.isGlobal() && "Extern symbol not handled yet");
      StubSym =
        MachineModuleInfoImpl::
        StubValueTy(AsmPrinter.getSymbol(MO.getGlobal()),
                    !MO.getGlobal()->hasInternalLinkage());
    }
    break;
  }
  case X86II::MO_DARWIN_HIDDEN_NONLAZY_PIC_BASE: {
    MachineModuleInfoImpl::StubValueTy &StubSym =
      getMachOMMI().getHiddenGVStubEntry(Sym);
    if (!StubSym.getPointer()) {
      assert(MO.isGlobal() && "Extern symbol not handled yet");
      StubSym =
        MachineModuleInfoImpl::
        StubValueTy(AsmPrinter.getSymbol(MO.getGlobal()),
                    !MO.getGlobal()->hasInternalLinkage());
    }
    break;
  }
  case X86II::MO_DARWIN_STUB: {
    MachineModuleInfoImpl::StubValueTy &StubSym =
      getMachOMMI().getFnStubEntry(Sym);
    if (StubSym.getPointer())
      return Sym;

    if (MO.isGlobal()) {
      StubSym =
        MachineModuleInfoImpl::
        StubValueTy(AsmPrinter.getSymbol(MO.getGlobal()),
                    !MO.getGlobal()->hasInternalLinkage());
    } else {
      StubSym =
        MachineModuleInfoImpl::
        StubValueTy(Ctx.getOrCreateSymbol(OrigName), false);
    }
    break;
  }
  }

  return Sym;
}

MCOperand X86MCInstLower::LowerSymbolOperand(const MachineOperand &MO,
                                             MCSymbol *Sym) const {
  // FIXME: We would like an efficient form for this, so we don't have to do a
  // lot of extra uniquing.
  const MCExpr *Expr = nullptr;
  MCSymbolRefExpr::VariantKind RefKind = MCSymbolRefExpr::VK_None;

  switch (MO.getTargetFlags()) {
  default: llvm_unreachable("Unknown target flag on GV operand");
  case X86II::MO_NO_FLAG:    // No flag.
  // These affect the name of the symbol, not any suffix.
  case X86II::MO_DARWIN_NONLAZY:
  case X86II::MO_DLLIMPORT:
  case X86II::MO_DARWIN_STUB:
  case X86II::MO_NOPREFIX:
    break;

  case X86II::MO_TLVP:      RefKind = MCSymbolRefExpr::VK_TLVP; break;
  case X86II::MO_TLVP_PIC_BASE:
    Expr = MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_TLVP, Ctx);
    // Subtract the pic base.
    Expr = MCBinaryExpr::createSub(Expr,
                                  MCSymbolRefExpr::create(MF.getPICBaseSymbol(),
                                                           Ctx),
                                   Ctx);
    break;
  case X86II::MO_SECREL:    RefKind = MCSymbolRefExpr::VK_SECREL; break;
  case X86II::MO_TLSGD:     RefKind = MCSymbolRefExpr::VK_TLSGD; break;
  case X86II::MO_TLSLD:     RefKind = MCSymbolRefExpr::VK_TLSLD; break;
  case X86II::MO_TLSLDM:    RefKind = MCSymbolRefExpr::VK_TLSLDM; break;
  case X86II::MO_GOTTPOFF:  RefKind = MCSymbolRefExpr::VK_GOTTPOFF; break;
  case X86II::MO_INDNTPOFF: RefKind = MCSymbolRefExpr::VK_INDNTPOFF; break;
  case X86II::MO_TPOFF:     RefKind = MCSymbolRefExpr::VK_TPOFF; break;
  case X86II::MO_DTPOFF:    RefKind = MCSymbolRefExpr::VK_DTPOFF; break;
  case X86II::MO_NTPOFF:    RefKind = MCSymbolRefExpr::VK_NTPOFF; break;
  case X86II::MO_GOTNTPOFF: RefKind = MCSymbolRefExpr::VK_GOTNTPOFF; break;
  case X86II::MO_GOTPCREL:  RefKind = MCSymbolRefExpr::VK_GOTPCREL; break;
  case X86II::MO_GOT:       RefKind = MCSymbolRefExpr::VK_GOT; break;
  case X86II::MO_GOTOFF:    RefKind = MCSymbolRefExpr::VK_GOTOFF; break;
  case X86II::MO_PLT:       RefKind = MCSymbolRefExpr::VK_PLT; break;
  case X86II::MO_PIC_BASE_OFFSET:
  case X86II::MO_DARWIN_NONLAZY_PIC_BASE:
  case X86II::MO_DARWIN_HIDDEN_NONLAZY_PIC_BASE:
    Expr = MCSymbolRefExpr::create(Sym, Ctx);
    // Subtract the pic base.
    Expr = MCBinaryExpr::createSub(Expr,
                            MCSymbolRefExpr::create(MF.getPICBaseSymbol(), Ctx),
                                   Ctx);
    if (MO.isJTI()) {
      assert(MAI.doesSetDirectiveSuppressesReloc());
      // If .set directive is supported, use it to reduce the number of
      // relocations the assembler will generate for differences between
      // local labels. This is only safe when the symbols are in the same
      // section so we are restricting it to jumptable references.
      MCSymbol *Label = Ctx.createTempSymbol();
      AsmPrinter.OutStreamer->EmitAssignment(Label, Expr);
      Expr = MCSymbolRefExpr::create(Label, Ctx);
    }
    break;
  }

  if (!Expr)
    Expr = MCSymbolRefExpr::create(Sym, RefKind, Ctx);

  if (!MO.isJTI() && !MO.isMBB() && MO.getOffset())
    Expr = MCBinaryExpr::createAdd(Expr,
                                   MCConstantExpr::create(MO.getOffset(), Ctx),
                                   Ctx);
  return MCOperand::createExpr(Expr);
}


/// \brief Simplify FOO $imm, %{al,ax,eax,rax} to FOO $imm, for instruction with
/// a short fixed-register form.
static void SimplifyShortImmForm(MCInst &Inst, unsigned Opcode) {
  unsigned ImmOp = Inst.getNumOperands() - 1;
  assert(Inst.getOperand(0).isReg() &&
         (Inst.getOperand(ImmOp).isImm() || Inst.getOperand(ImmOp).isExpr()) &&
         ((Inst.getNumOperands() == 3 && Inst.getOperand(1).isReg() &&
           Inst.getOperand(0).getReg() == Inst.getOperand(1).getReg()) ||
          Inst.getNumOperands() == 2) && "Unexpected instruction!");

  // Check whether the destination register can be fixed.
  unsigned Reg = Inst.getOperand(0).getReg();
  if (Reg != X86::AL && Reg != X86::AX && Reg != X86::EAX && Reg != X86::RAX)
    return;

  // If so, rewrite the instruction.
  MCOperand Saved = Inst.getOperand(ImmOp);
  Inst = MCInst();
  Inst.setOpcode(Opcode);
  Inst.addOperand(Saved);
}

/// \brief If a movsx instruction has a shorter encoding for the used register
/// simplify the instruction to use it instead.
static void SimplifyMOVSX(MCInst &Inst) {
  unsigned NewOpcode = 0;
  unsigned Op0 = Inst.getOperand(0).getReg(), Op1 = Inst.getOperand(1).getReg();
  switch (Inst.getOpcode()) {
  default:
    llvm_unreachable("Unexpected instruction!");
  case X86::MOVSX16rr8:  // movsbw %al, %ax   --> cbtw
    if (Op0 == X86::AX && Op1 == X86::AL)
      NewOpcode = X86::CBW;
    break;
  case X86::MOVSX32rr16: // movswl %ax, %eax  --> cwtl
    if (Op0 == X86::EAX && Op1 == X86::AX)
      NewOpcode = X86::CWDE;
    break;
  case X86::MOVSX64rr32: // movslq %eax, %rax --> cltq
    if (Op0 == X86::RAX && Op1 == X86::EAX)
      NewOpcode = X86::CDQE;
    break;
  }

  if (NewOpcode != 0) {
    Inst = MCInst();
    Inst.setOpcode(NewOpcode);
  }
}

/// \brief Simplify things like MOV32rm to MOV32o32a.
static void SimplifyShortMoveForm(X86AsmPrinter &Printer, MCInst &Inst,
                                  unsigned Opcode) {
  // Don't make these simplifications in 64-bit mode; other assemblers don't
  // perform them because they make the code larger.
  if (Printer.getSubtarget().is64Bit())
    return;

  bool IsStore = Inst.getOperand(0).isReg() && Inst.getOperand(1).isReg();
  unsigned AddrBase = IsStore;
  unsigned RegOp = IsStore ? 0 : 5;
  unsigned AddrOp = AddrBase + 3;
  assert(Inst.getNumOperands() == 6 && Inst.getOperand(RegOp).isReg() &&
         Inst.getOperand(AddrBase + X86::AddrBaseReg).isReg() &&
         Inst.getOperand(AddrBase + X86::AddrScaleAmt).isImm() &&
         Inst.getOperand(AddrBase + X86::AddrIndexReg).isReg() &&
         Inst.getOperand(AddrBase + X86::AddrSegmentReg).isReg() &&
         (Inst.getOperand(AddrOp).isExpr() ||
          Inst.getOperand(AddrOp).isImm()) &&
         "Unexpected instruction!");

  // Check whether the destination register can be fixed.
  unsigned Reg = Inst.getOperand(RegOp).getReg();
  if (Reg != X86::AL && Reg != X86::AX && Reg != X86::EAX && Reg != X86::RAX)
    return;

  // Check whether this is an absolute address.
  // FIXME: We know TLVP symbol refs aren't, but there should be a better way
  // to do this here.
  bool Absolute = true;
  if (Inst.getOperand(AddrOp).isExpr()) {
    const MCExpr *MCE = Inst.getOperand(AddrOp).getExpr();
    if (const MCSymbolRefExpr *SRE = dyn_cast<MCSymbolRefExpr>(MCE))
      if (SRE->getKind() == MCSymbolRefExpr::VK_TLVP)
        Absolute = false;
  }

  if (Absolute &&
      (Inst.getOperand(AddrBase + X86::AddrBaseReg).getReg() != 0 ||
       Inst.getOperand(AddrBase + X86::AddrScaleAmt).getImm() != 1 ||
       Inst.getOperand(AddrBase + X86::AddrIndexReg).getReg() != 0))
    return;

  // If so, rewrite the instruction.
  MCOperand Saved = Inst.getOperand(AddrOp);
  MCOperand Seg = Inst.getOperand(AddrBase + X86::AddrSegmentReg);
  Inst = MCInst();
  Inst.setOpcode(Opcode);
  Inst.addOperand(Saved);
  Inst.addOperand(Seg);
}

static unsigned getRetOpcode(const X86Subtarget &Subtarget) {
  return Subtarget.is64Bit() ? X86::RETQ : X86::RETL;
}

void X86MCInstLower::Lower(const MachineInstr *MI, MCInst &OutMI) const {
  OutMI.setOpcode(MI->getOpcode());

  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
    const MachineOperand &MO = MI->getOperand(i);

    MCOperand MCOp;
    switch (MO.getType()) {
    default:
      MI->dump();
      llvm_unreachable("unknown operand type");
    case MachineOperand::MO_Register:
      // Ignore all implicit register operands.
      if (MO.isImplicit()) continue;
      MCOp = MCOperand::createReg(MO.getReg());
      break;
    case MachineOperand::MO_Immediate:
      MCOp = MCOperand::createImm(MO.getImm());
      break;
    case MachineOperand::MO_MachineBasicBlock:
    case MachineOperand::MO_GlobalAddress:
    case MachineOperand::MO_ExternalSymbol:
      MCOp = LowerSymbolOperand(MO, GetSymbolFromOperand(MO));
      break;
    case MachineOperand::MO_JumpTableIndex:
      MCOp = LowerSymbolOperand(MO, AsmPrinter.GetJTISymbol(MO.getIndex()));
      break;
    case MachineOperand::MO_ConstantPoolIndex:
      MCOp = LowerSymbolOperand(MO, AsmPrinter.GetCPISymbol(MO.getIndex()));
      break;
    case MachineOperand::MO_BlockAddress:
      MCOp = LowerSymbolOperand(MO,
                     AsmPrinter.GetBlockAddressSymbol(MO.getBlockAddress()));
      break;
    case MachineOperand::MO_RegisterMask:
      // Ignore call clobbers.
      continue;
    }

    OutMI.addOperand(MCOp);
  }

  // Handle a few special cases to eliminate operand modifiers.
ReSimplify:
  switch (OutMI.getOpcode()) {
  case X86::LEA64_32r:
  case X86::LEA64r:
  case X86::LEA16r:
  case X86::LEA32r:
    // LEA should have a segment register, but it must be empty.
    assert(OutMI.getNumOperands() == 1+X86::AddrNumOperands &&
           "Unexpected # of LEA operands");
    assert(OutMI.getOperand(1+X86::AddrSegmentReg).getReg() == 0 &&
           "LEA has segment specified!");
    break;

  case X86::MOV32ri64:
    OutMI.setOpcode(X86::MOV32ri);
    break;

  // Commute operands to get a smaller encoding by using VEX.R instead of VEX.B
  // if one of the registers is extended, but other isn't.
  case X86::VMOVAPDrr:
  case X86::VMOVAPDYrr:
  case X86::VMOVAPSrr:
  case X86::VMOVAPSYrr:
  case X86::VMOVDQArr:
  case X86::VMOVDQAYrr:
  case X86::VMOVDQUrr:
  case X86::VMOVDQUYrr:
  case X86::VMOVUPDrr:
  case X86::VMOVUPDYrr:
  case X86::VMOVUPSrr:
  case X86::VMOVUPSYrr: {
    if (!X86II::isX86_64ExtendedReg(OutMI.getOperand(0).getReg()) &&
        X86II::isX86_64ExtendedReg(OutMI.getOperand(1).getReg())) {
      unsigned NewOpc;
      switch (OutMI.getOpcode()) {
      default: llvm_unreachable("Invalid opcode");
      case X86::VMOVAPDrr:  NewOpc = X86::VMOVAPDrr_REV;  break;
      case X86::VMOVAPDYrr: NewOpc = X86::VMOVAPDYrr_REV; break;
      case X86::VMOVAPSrr:  NewOpc = X86::VMOVAPSrr_REV;  break;
      case X86::VMOVAPSYrr: NewOpc = X86::VMOVAPSYrr_REV; break;
      case X86::VMOVDQArr:  NewOpc = X86::VMOVDQArr_REV;  break;
      case X86::VMOVDQAYrr: NewOpc = X86::VMOVDQAYrr_REV; break;
      case X86::VMOVDQUrr:  NewOpc = X86::VMOVDQUrr_REV;  break;
      case X86::VMOVDQUYrr: NewOpc = X86::VMOVDQUYrr_REV; break;
      case X86::VMOVUPDrr:  NewOpc = X86::VMOVUPDrr_REV;  break;
      case X86::VMOVUPDYrr: NewOpc = X86::VMOVUPDYrr_REV; break;
      case X86::VMOVUPSrr:  NewOpc = X86::VMOVUPSrr_REV;  break;
      case X86::VMOVUPSYrr: NewOpc = X86::VMOVUPSYrr_REV; break;
      }
      OutMI.setOpcode(NewOpc);
    }
    break;
  }
  case X86::VMOVSDrr:
  case X86::VMOVSSrr: {
    if (!X86II::isX86_64ExtendedReg(OutMI.getOperand(0).getReg()) &&
        X86II::isX86_64ExtendedReg(OutMI.getOperand(2).getReg())) {
      unsigned NewOpc;
      switch (OutMI.getOpcode()) {
      default: llvm_unreachable("Invalid opcode");
      case X86::VMOVSDrr:   NewOpc = X86::VMOVSDrr_REV;   break;
      case X86::VMOVSSrr:   NewOpc = X86::VMOVSSrr_REV;   break;
      }
      OutMI.setOpcode(NewOpc);
    }
    break;
  }

  // TAILJMPr64, CALL64r, CALL64pcrel32 - These instructions have register
  // inputs modeled as normal uses instead of implicit uses.  As such, truncate
  // off all but the first operand (the callee).  FIXME: Change isel.
  case X86::TAILJMPr64:
  case X86::TAILJMPr64_REX:
  case X86::CALL64r:
  case X86::CALL64pcrel32: {
    unsigned Opcode = OutMI.getOpcode();
    MCOperand Saved = OutMI.getOperand(0);
    OutMI = MCInst();
    OutMI.setOpcode(Opcode);
    OutMI.addOperand(Saved);
    break;
  }

  case X86::EH_RETURN:
  case X86::EH_RETURN64: {
    OutMI = MCInst();
    OutMI.setOpcode(getRetOpcode(AsmPrinter.getSubtarget()));
    break;
  }

  // TAILJMPd, TAILJMPd64 - Lower to the correct jump instructions.
  case X86::TAILJMPr:
  case X86::TAILJMPd:
  case X86::TAILJMPd64: {
    unsigned Opcode;
    switch (OutMI.getOpcode()) {
    default: llvm_unreachable("Invalid opcode");
    case X86::TAILJMPr: Opcode = X86::JMP32r; break;
    case X86::TAILJMPd:
    case X86::TAILJMPd64: Opcode = X86::JMP_1; break;
    }

    MCOperand Saved = OutMI.getOperand(0);
    OutMI = MCInst();
    OutMI.setOpcode(Opcode);
    OutMI.addOperand(Saved);
    break;
  }

  case X86::DEC16r:
  case X86::DEC32r:
  case X86::INC16r:
  case X86::INC32r:
    // If we aren't in 64-bit mode we can use the 1-byte inc/dec instructions.
    if (!AsmPrinter.getSubtarget().is64Bit()) {
      unsigned Opcode;
      switch (OutMI.getOpcode()) {
      default: llvm_unreachable("Invalid opcode");
      case X86::DEC16r: Opcode = X86::DEC16r_alt; break;
      case X86::DEC32r: Opcode = X86::DEC32r_alt; break;
      case X86::INC16r: Opcode = X86::INC16r_alt; break;
      case X86::INC32r: Opcode = X86::INC32r_alt; break;
      }
      OutMI.setOpcode(Opcode);
    }
    break;

  // These are pseudo-ops for OR to help with the OR->ADD transformation.  We do
  // this with an ugly goto in case the resultant OR uses EAX and needs the
  // short form.
  case X86::ADD16rr_DB:   OutMI.setOpcode(X86::OR16rr); goto ReSimplify;
  case X86::ADD32rr_DB:   OutMI.setOpcode(X86::OR32rr); goto ReSimplify;
  case X86::ADD64rr_DB:   OutMI.setOpcode(X86::OR64rr); goto ReSimplify;
  case X86::ADD16ri_DB:   OutMI.setOpcode(X86::OR16ri); goto ReSimplify;
  case X86::ADD32ri_DB:   OutMI.setOpcode(X86::OR32ri); goto ReSimplify;
  case X86::ADD64ri32_DB: OutMI.setOpcode(X86::OR64ri32); goto ReSimplify;
  case X86::ADD16ri8_DB:  OutMI.setOpcode(X86::OR16ri8); goto ReSimplify;
  case X86::ADD32ri8_DB:  OutMI.setOpcode(X86::OR32ri8); goto ReSimplify;
  case X86::ADD64ri8_DB:  OutMI.setOpcode(X86::OR64ri8); goto ReSimplify;

  // Atomic load and store require a separate pseudo-inst because Acquire
  // implies mayStore and Release implies mayLoad; fix these to regular MOV
  // instructions here
  case X86::ACQUIRE_MOV8rm:    OutMI.setOpcode(X86::MOV8rm); goto ReSimplify;
  case X86::ACQUIRE_MOV16rm:   OutMI.setOpcode(X86::MOV16rm); goto ReSimplify;
  case X86::ACQUIRE_MOV32rm:   OutMI.setOpcode(X86::MOV32rm); goto ReSimplify;
  case X86::ACQUIRE_MOV64rm:   OutMI.setOpcode(X86::MOV64rm); goto ReSimplify;
  case X86::RELEASE_MOV8mr:    OutMI.setOpcode(X86::MOV8mr); goto ReSimplify;
  case X86::RELEASE_MOV16mr:   OutMI.setOpcode(X86::MOV16mr); goto ReSimplify;
  case X86::RELEASE_MOV32mr:   OutMI.setOpcode(X86::MOV32mr); goto ReSimplify;
  case X86::RELEASE_MOV64mr:   OutMI.setOpcode(X86::MOV64mr); goto ReSimplify;
  case X86::RELEASE_MOV8mi:    OutMI.setOpcode(X86::MOV8mi); goto ReSimplify;
  case X86::RELEASE_MOV16mi:   OutMI.setOpcode(X86::MOV16mi); goto ReSimplify;
  case X86::RELEASE_MOV32mi:   OutMI.setOpcode(X86::MOV32mi); goto ReSimplify;
  case X86::RELEASE_MOV64mi32: OutMI.setOpcode(X86::MOV64mi32); goto ReSimplify;
  case X86::RELEASE_ADD8mi:    OutMI.setOpcode(X86::ADD8mi); goto ReSimplify;
  case X86::RELEASE_ADD32mi:   OutMI.setOpcode(X86::ADD32mi); goto ReSimplify;
  case X86::RELEASE_ADD64mi32: OutMI.setOpcode(X86::ADD64mi32); goto ReSimplify;
  case X86::RELEASE_AND8mi:    OutMI.setOpcode(X86::AND8mi); goto ReSimplify;
  case X86::RELEASE_AND32mi:   OutMI.setOpcode(X86::AND32mi); goto ReSimplify;
  case X86::RELEASE_AND64mi32: OutMI.setOpcode(X86::AND64mi32); goto ReSimplify;
  case X86::RELEASE_OR8mi:     OutMI.setOpcode(X86::OR8mi); goto ReSimplify;
  case X86::RELEASE_OR32mi:    OutMI.setOpcode(X86::OR32mi); goto ReSimplify;
  case X86::RELEASE_OR64mi32:  OutMI.setOpcode(X86::OR64mi32); goto ReSimplify;
  case X86::RELEASE_XOR8mi:    OutMI.setOpcode(X86::XOR8mi); goto ReSimplify;
  case X86::RELEASE_XOR32mi:   OutMI.setOpcode(X86::XOR32mi); goto ReSimplify;
  case X86::RELEASE_XOR64mi32: OutMI.setOpcode(X86::XOR64mi32); goto ReSimplify;
  case X86::RELEASE_INC8m:     OutMI.setOpcode(X86::INC8m); goto ReSimplify;
  case X86::RELEASE_INC16m:    OutMI.setOpcode(X86::INC16m); goto ReSimplify;
  case X86::RELEASE_INC32m:    OutMI.setOpcode(X86::INC32m); goto ReSimplify;
  case X86::RELEASE_INC64m:    OutMI.setOpcode(X86::INC64m); goto ReSimplify;
  case X86::RELEASE_DEC8m:     OutMI.setOpcode(X86::DEC8m); goto ReSimplify;
  case X86::RELEASE_DEC16m:    OutMI.setOpcode(X86::DEC16m); goto ReSimplify;
  case X86::RELEASE_DEC32m:    OutMI.setOpcode(X86::DEC32m); goto ReSimplify;
  case X86::RELEASE_DEC64m:    OutMI.setOpcode(X86::DEC64m); goto ReSimplify;

  // We don't currently select the correct instruction form for instructions
  // which have a short %eax, etc. form. Handle this by custom lowering, for
  // now.
  //
  // Note, we are currently not handling the following instructions:
  // MOV64ao8, MOV64o8a
  // XCHG16ar, XCHG32ar, XCHG64ar
  case X86::MOV8mr_NOREX:
  case X86::MOV8mr:     SimplifyShortMoveForm(AsmPrinter, OutMI, X86::MOV8o32a); break;
  case X86::MOV8rm_NOREX:
  case X86::MOV8rm:     SimplifyShortMoveForm(AsmPrinter, OutMI, X86::MOV8ao32); break;
  case X86::MOV16mr:    SimplifyShortMoveForm(AsmPrinter, OutMI, X86::MOV16o32a); break;
  case X86::MOV16rm:    SimplifyShortMoveForm(AsmPrinter, OutMI, X86::MOV16ao32); break;
  case X86::MOV32mr:    SimplifyShortMoveForm(AsmPrinter, OutMI, X86::MOV32o32a); break;
  case X86::MOV32rm:    SimplifyShortMoveForm(AsmPrinter, OutMI, X86::MOV32ao32); break;

  case X86::ADC8ri:     SimplifyShortImmForm(OutMI, X86::ADC8i8);    break;
  case X86::ADC16ri:    SimplifyShortImmForm(OutMI, X86::ADC16i16);  break;
  case X86::ADC32ri:    SimplifyShortImmForm(OutMI, X86::ADC32i32);  break;
  case X86::ADC64ri32:  SimplifyShortImmForm(OutMI, X86::ADC64i32);  break;
  case X86::ADD8ri:     SimplifyShortImmForm(OutMI, X86::ADD8i8);    break;
  case X86::ADD16ri:    SimplifyShortImmForm(OutMI, X86::ADD16i16);  break;
  case X86::ADD32ri:    SimplifyShortImmForm(OutMI, X86::ADD32i32);  break;
  case X86::ADD64ri32:  SimplifyShortImmForm(OutMI, X86::ADD64i32);  break;
  case X86::AND8ri:     SimplifyShortImmForm(OutMI, X86::AND8i8);    break;
  case X86::AND16ri:    SimplifyShortImmForm(OutMI, X86::AND16i16);  break;
  case X86::AND32ri:    SimplifyShortImmForm(OutMI, X86::AND32i32);  break;
  case X86::AND64ri32:  SimplifyShortImmForm(OutMI, X86::AND64i32);  break;
  case X86::CMP8ri:     SimplifyShortImmForm(OutMI, X86::CMP8i8);    break;
  case X86::CMP16ri:    SimplifyShortImmForm(OutMI, X86::CMP16i16);  break;
  case X86::CMP32ri:    SimplifyShortImmForm(OutMI, X86::CMP32i32);  break;
  case X86::CMP64ri32:  SimplifyShortImmForm(OutMI, X86::CMP64i32);  break;
  case X86::OR8ri:      SimplifyShortImmForm(OutMI, X86::OR8i8);     break;
  case X86::OR16ri:     SimplifyShortImmForm(OutMI, X86::OR16i16);   break;
  case X86::OR32ri:     SimplifyShortImmForm(OutMI, X86::OR32i32);   break;
  case X86::OR64ri32:   SimplifyShortImmForm(OutMI, X86::OR64i32);   break;
  case X86::SBB8ri:     SimplifyShortImmForm(OutMI, X86::SBB8i8);    break;
  case X86::SBB16ri:    SimplifyShortImmForm(OutMI, X86::SBB16i16);  break;
  case X86::SBB32ri:    SimplifyShortImmForm(OutMI, X86::SBB32i32);  break;
  case X86::SBB64ri32:  SimplifyShortImmForm(OutMI, X86::SBB64i32);  break;
  case X86::SUB8ri:     SimplifyShortImmForm(OutMI, X86::SUB8i8);    break;
  case X86::SUB16ri:    SimplifyShortImmForm(OutMI, X86::SUB16i16);  break;
  case X86::SUB32ri:    SimplifyShortImmForm(OutMI, X86::SUB32i32);  break;
  case X86::SUB64ri32:  SimplifyShortImmForm(OutMI, X86::SUB64i32);  break;
  case X86::TEST8ri:    SimplifyShortImmForm(OutMI, X86::TEST8i8);   break;
  case X86::TEST16ri:   SimplifyShortImmForm(OutMI, X86::TEST16i16); break;
  case X86::TEST32ri:   SimplifyShortImmForm(OutMI, X86::TEST32i32); break;
  case X86::TEST64ri32: SimplifyShortImmForm(OutMI, X86::TEST64i32); break;
  case X86::XOR8ri:     SimplifyShortImmForm(OutMI, X86::XOR8i8);    break;
  case X86::XOR16ri:    SimplifyShortImmForm(OutMI, X86::XOR16i16);  break;
  case X86::XOR32ri:    SimplifyShortImmForm(OutMI, X86::XOR32i32);  break;
  case X86::XOR64ri32:  SimplifyShortImmForm(OutMI, X86::XOR64i32);  break;

  // Try to shrink some forms of movsx.
  case X86::MOVSX16rr8:
  case X86::MOVSX32rr16:
  case X86::MOVSX64rr32:
    SimplifyMOVSX(OutMI);
    break;
  }
}

void X86AsmPrinter::LowerTlsAddr(X86MCInstLower &MCInstLowering,
                                 const MachineInstr &MI) {

  bool is64Bits = MI.getOpcode() == X86::TLS_addr64 ||
                  MI.getOpcode() == X86::TLS_base_addr64;

  bool needsPadding = MI.getOpcode() == X86::TLS_addr64;

  MCContext &context = OutStreamer->getContext();

  if (needsPadding)
    EmitAndCountInstruction(MCInstBuilder(X86::DATA16_PREFIX));

  MCSymbolRefExpr::VariantKind SRVK;
  switch (MI.getOpcode()) {
    case X86::TLS_addr32:
    case X86::TLS_addr64:
      SRVK = MCSymbolRefExpr::VK_TLSGD;
      break;
    case X86::TLS_base_addr32:
      SRVK = MCSymbolRefExpr::VK_TLSLDM;
      break;
    case X86::TLS_base_addr64:
      SRVK = MCSymbolRefExpr::VK_TLSLD;
      break;
    default:
      llvm_unreachable("unexpected opcode");
  }

  MCSymbol *sym = MCInstLowering.GetSymbolFromOperand(MI.getOperand(3));
  const MCSymbolRefExpr *symRef = MCSymbolRefExpr::create(sym, SRVK, context);

  MCInst LEA;
  if (is64Bits) {
    LEA.setOpcode(X86::LEA64r);
    LEA.addOperand(MCOperand::createReg(X86::RDI)); // dest
    LEA.addOperand(MCOperand::createReg(X86::RIP)); // base
    LEA.addOperand(MCOperand::createImm(1));        // scale
    LEA.addOperand(MCOperand::createReg(0));        // index
    LEA.addOperand(MCOperand::createExpr(symRef));  // disp
    LEA.addOperand(MCOperand::createReg(0));        // seg
  } else if (SRVK == MCSymbolRefExpr::VK_TLSLDM) {
    LEA.setOpcode(X86::LEA32r);
    LEA.addOperand(MCOperand::createReg(X86::EAX)); // dest
    LEA.addOperand(MCOperand::createReg(X86::EBX)); // base
    LEA.addOperand(MCOperand::createImm(1));        // scale
    LEA.addOperand(MCOperand::createReg(0));        // index
    LEA.addOperand(MCOperand::createExpr(symRef));  // disp
    LEA.addOperand(MCOperand::createReg(0));        // seg
  } else {
    LEA.setOpcode(X86::LEA32r);
    LEA.addOperand(MCOperand::createReg(X86::EAX)); // dest
    LEA.addOperand(MCOperand::createReg(0));        // base
    LEA.addOperand(MCOperand::createImm(1));        // scale
    LEA.addOperand(MCOperand::createReg(X86::EBX)); // index
    LEA.addOperand(MCOperand::createExpr(symRef));  // disp
    LEA.addOperand(MCOperand::createReg(0));        // seg
  }
  EmitAndCountInstruction(LEA);

  if (needsPadding) {
    EmitAndCountInstruction(MCInstBuilder(X86::DATA16_PREFIX));
    EmitAndCountInstruction(MCInstBuilder(X86::DATA16_PREFIX));
    EmitAndCountInstruction(MCInstBuilder(X86::REX64_PREFIX));
  }

  StringRef name = is64Bits ? "__tls_get_addr" : "___tls_get_addr";
  MCSymbol *tlsGetAddr = context.getOrCreateSymbol(name);
  const MCSymbolRefExpr *tlsRef =
    MCSymbolRefExpr::create(tlsGetAddr,
                            MCSymbolRefExpr::VK_PLT,
                            context);

  EmitAndCountInstruction(MCInstBuilder(is64Bits ? X86::CALL64pcrel32
                                                 : X86::CALLpcrel32)
                            .addExpr(tlsRef));
}

/// \brief Emit the optimal amount of multi-byte nops on X86.
static void EmitNops(MCStreamer &OS, unsigned NumBytes, bool Is64Bit, const MCSubtargetInfo &STI) {
  // This works only for 64bit. For 32bit we have to do additional checking if
  // the CPU supports multi-byte nops.
  assert(Is64Bit && "EmitNops only supports X86-64");
  while (NumBytes) {
    unsigned Opc, BaseReg, ScaleVal, IndexReg, Displacement, SegmentReg;
    Opc = IndexReg = Displacement = SegmentReg = 0;
    BaseReg = X86::RAX; ScaleVal = 1;
    switch (NumBytes) {
    case  0: llvm_unreachable("Zero nops?"); break;
    case  1: NumBytes -=  1; Opc = X86::NOOP; break;
    case  2: NumBytes -=  2; Opc = X86::XCHG16ar; break;
    case  3: NumBytes -=  3; Opc = X86::NOOPL; break;
    case  4: NumBytes -=  4; Opc = X86::NOOPL; Displacement = 8; break;
    case  5: NumBytes -=  5; Opc = X86::NOOPL; Displacement = 8;
             IndexReg = X86::RAX; break;
    case  6: NumBytes -=  6; Opc = X86::NOOPW; Displacement = 8;
             IndexReg = X86::RAX; break;
    case  7: NumBytes -=  7; Opc = X86::NOOPL; Displacement = 512; break;
    case  8: NumBytes -=  8; Opc = X86::NOOPL; Displacement = 512;
             IndexReg = X86::RAX; break;
    case  9: NumBytes -=  9; Opc = X86::NOOPW; Displacement = 512;
             IndexReg = X86::RAX; break;
    default: NumBytes -= 10; Opc = X86::NOOPW; Displacement = 512;
             IndexReg = X86::RAX; SegmentReg = X86::CS; break;
    }

    unsigned NumPrefixes = std::min(NumBytes, 5U);
    NumBytes -= NumPrefixes;
    for (unsigned i = 0; i != NumPrefixes; ++i)
      OS.EmitBytes("\x66");

    switch (Opc) {
    default: llvm_unreachable("Unexpected opcode"); break;
    case X86::NOOP:
      OS.EmitInstruction(MCInstBuilder(Opc), STI);
      break;
    case X86::XCHG16ar:
      OS.EmitInstruction(MCInstBuilder(Opc).addReg(X86::AX), STI);
      break;
    case X86::NOOPL:
    case X86::NOOPW:
      OS.EmitInstruction(MCInstBuilder(Opc).addReg(BaseReg)
                         .addImm(ScaleVal).addReg(IndexReg)
                         .addImm(Displacement).addReg(SegmentReg), STI);
      break;
    }
  } // while (NumBytes)
}

void X86AsmPrinter::LowerSTATEPOINT(const MachineInstr &MI,
                                    X86MCInstLower &MCIL) {
  assert(Subtarget->is64Bit() && "Statepoint currently only supports X86-64");

  StatepointOpers SOpers(&MI);
  if (unsigned PatchBytes = SOpers.getNumPatchBytes()) {
    EmitNops(*OutStreamer, PatchBytes, Subtarget->is64Bit(),
             getSubtargetInfo());
  } else {
    // Lower call target and choose correct opcode
    const MachineOperand &CallTarget = SOpers.getCallTarget();
    MCOperand CallTargetMCOp;
    unsigned CallOpcode;
    switch (CallTarget.getType()) {
    case MachineOperand::MO_GlobalAddress:
    case MachineOperand::MO_ExternalSymbol:
      CallTargetMCOp = MCIL.LowerSymbolOperand(
          CallTarget, MCIL.GetSymbolFromOperand(CallTarget));
      CallOpcode = X86::CALL64pcrel32;
      // Currently, we only support relative addressing with statepoints.
      // Otherwise, we'll need a scratch register to hold the target
      // address.  You'll fail asserts during load & relocation if this
      // symbol is to far away. (TODO: support non-relative addressing)
      break;
    case MachineOperand::MO_Immediate:
      CallTargetMCOp = MCOperand::createImm(CallTarget.getImm());
      CallOpcode = X86::CALL64pcrel32;
      // Currently, we only support relative addressing with statepoints.
      // Otherwise, we'll need a scratch register to hold the target
      // immediate.  You'll fail asserts during load & relocation if this
      // address is to far away. (TODO: support non-relative addressing)
      break;
    case MachineOperand::MO_Register:
      CallTargetMCOp = MCOperand::createReg(CallTarget.getReg());
      CallOpcode = X86::CALL64r;
      break;
    default:
      llvm_unreachable("Unsupported operand type in statepoint call target");
      break;
    }

    // Emit call
    MCInst CallInst;
    CallInst.setOpcode(CallOpcode);
    CallInst.addOperand(CallTargetMCOp);
    OutStreamer->EmitInstruction(CallInst, getSubtargetInfo());
  }

  // Record our statepoint node in the same section used by STACKMAP
  // and PATCHPOINT
  SM.recordStatepoint(MI);
}


// Lower a stackmap of the form:
// <id>, <shadowBytes>, ...
void X86AsmPrinter::LowerSTACKMAP(const MachineInstr &MI) {
  SMShadowTracker.emitShadowPadding(*OutStreamer, getSubtargetInfo());
  SM.recordStackMap(MI);
  unsigned NumShadowBytes = MI.getOperand(1).getImm();
  SMShadowTracker.reset(NumShadowBytes);
}

// Lower a patchpoint of the form:
// [<def>], <id>, <numBytes>, <target>, <numArgs>, <cc>, ...
void X86AsmPrinter::LowerPATCHPOINT(const MachineInstr &MI,
                                    X86MCInstLower &MCIL) {
  assert(Subtarget->is64Bit() && "Patchpoint currently only supports X86-64");

  SMShadowTracker.emitShadowPadding(*OutStreamer, getSubtargetInfo());

  SM.recordPatchPoint(MI);

  PatchPointOpers opers(&MI);
  unsigned ScratchIdx = opers.getNextScratchIdx();
  unsigned EncodedBytes = 0;
  const MachineOperand &CalleeMO =
    opers.getMetaOper(PatchPointOpers::TargetPos);

  // Check for null target. If target is non-null (i.e. is non-zero or is
  // symbolic) then emit a call.
  if (!(CalleeMO.isImm() && !CalleeMO.getImm())) {
    MCOperand CalleeMCOp;
    switch (CalleeMO.getType()) {
    default:
      /// FIXME: Add a verifier check for bad callee types.
      llvm_unreachable("Unrecognized callee operand type.");
    case MachineOperand::MO_Immediate:
      if (CalleeMO.getImm())
        CalleeMCOp = MCOperand::createImm(CalleeMO.getImm());
      break;
    case MachineOperand::MO_ExternalSymbol:
    case MachineOperand::MO_GlobalAddress:
      CalleeMCOp =
        MCIL.LowerSymbolOperand(CalleeMO,
                                MCIL.GetSymbolFromOperand(CalleeMO));
      break;
    }

    // Emit MOV to materialize the target address and the CALL to target.
    // This is encoded with 12-13 bytes, depending on which register is used.
    unsigned ScratchReg = MI.getOperand(ScratchIdx).getReg();
    if (X86II::isX86_64ExtendedReg(ScratchReg))
      EncodedBytes = 13;
    else
      EncodedBytes = 12;

    EmitAndCountInstruction(
        MCInstBuilder(X86::MOV64ri).addReg(ScratchReg).addOperand(CalleeMCOp));
    EmitAndCountInstruction(MCInstBuilder(X86::CALL64r).addReg(ScratchReg));
  }

  // Emit padding.
  unsigned NumBytes = opers.getMetaOper(PatchPointOpers::NBytesPos).getImm();
  assert(NumBytes >= EncodedBytes &&
         "Patchpoint can't request size less than the length of a call.");

  EmitNops(*OutStreamer, NumBytes - EncodedBytes, Subtarget->is64Bit(),
           getSubtargetInfo());
}

// Returns instruction preceding MBBI in MachineFunction.
// If MBBI is the first instruction of the first basic block, returns null.
static MachineBasicBlock::const_iterator
PrevCrossBBInst(MachineBasicBlock::const_iterator MBBI) {
  const MachineBasicBlock *MBB = MBBI->getParent();
  while (MBBI == MBB->begin()) {
    if (MBB == MBB->getParent()->begin())
      return nullptr;
    MBB = MBB->getPrevNode();
    MBBI = MBB->end();
  }
  return --MBBI;
}

static const Constant *getConstantFromPool(const MachineInstr &MI,
                                           const MachineOperand &Op) {
  if (!Op.isCPI())
    return nullptr;

  ArrayRef<MachineConstantPoolEntry> Constants =
      MI.getParent()->getParent()->getConstantPool()->getConstants();
  const MachineConstantPoolEntry &ConstantEntry =
      Constants[Op.getIndex()];

  // Bail if this is a machine constant pool entry, we won't be able to dig out
  // anything useful.
  if (ConstantEntry.isMachineConstantPoolEntry())
    return nullptr;

  auto *C = dyn_cast<Constant>(ConstantEntry.Val.ConstVal);
  assert((!C || ConstantEntry.getType() == C->getType()) &&
         "Expected a constant of the same type!");
  return C;
}

static std::string getShuffleComment(const MachineOperand &DstOp,
                                     const MachineOperand &SrcOp,
                                     ArrayRef<int> Mask) {
  std::string Comment;

  // Compute the name for a register. This is really goofy because we have
  // multiple instruction printers that could (in theory) use different
  // names. Fortunately most people use the ATT style (outside of Windows)
  // and they actually agree on register naming here. Ultimately, this is
  // a comment, and so its OK if it isn't perfect.
  auto GetRegisterName = [](unsigned RegNum) -> StringRef {
    return X86ATTInstPrinter::getRegisterName(RegNum);
  };

  StringRef DstName = DstOp.isReg() ? GetRegisterName(DstOp.getReg()) : "mem";
  StringRef SrcName = SrcOp.isReg() ? GetRegisterName(SrcOp.getReg()) : "mem";

  raw_string_ostream CS(Comment);
  CS << DstName << " = ";
  bool NeedComma = false;
  bool InSrc = false;
  for (int M : Mask) {
    // Wrap up any prior entry...
    if (M == SM_SentinelZero && InSrc) {
      InSrc = false;
      CS << "]";
    }
    if (NeedComma)
      CS << ",";
    else
      NeedComma = true;

    // Print this shuffle...
    if (M == SM_SentinelZero) {
      CS << "zero";
    } else {
      if (!InSrc) {
        InSrc = true;
        CS << SrcName << "[";
      }
      if (M == SM_SentinelUndef)
        CS << "u";
      else
        CS << M;
    }
  }
  if (InSrc)
    CS << "]";
  CS.flush();

  return Comment;
}

void X86AsmPrinter::EmitInstruction(const MachineInstr *MI) {
  X86MCInstLower MCInstLowering(*MF, *this);
  const X86RegisterInfo *RI = MF->getSubtarget<X86Subtarget>().getRegisterInfo();

  switch (MI->getOpcode()) {
  case TargetOpcode::DBG_VALUE:
    llvm_unreachable("Should be handled target independently");

  // Emit nothing here but a comment if we can.
  case X86::Int_MemBarrier:
    OutStreamer->emitRawComment("MEMBARRIER");
    return;


  case X86::EH_RETURN:
  case X86::EH_RETURN64: {
    // Lower these as normal, but add some comments.
    unsigned Reg = MI->getOperand(0).getReg();
    OutStreamer->AddComment(StringRef("eh_return, addr: %") +
                            X86ATTInstPrinter::getRegisterName(Reg));
    break;
  }
  case X86::TAILJMPr:
  case X86::TAILJMPm:
  case X86::TAILJMPd:
  case X86::TAILJMPr64:
  case X86::TAILJMPm64:
  case X86::TAILJMPd64:
  case X86::TAILJMPr64_REX:
  case X86::TAILJMPm64_REX:
  case X86::TAILJMPd64_REX:
    // Lower these as normal, but add some comments.
    OutStreamer->AddComment("TAILCALL");
    break;

  case X86::TLS_addr32:
  case X86::TLS_addr64:
  case X86::TLS_base_addr32:
  case X86::TLS_base_addr64:
    return LowerTlsAddr(MCInstLowering, *MI);

  case X86::MOVPC32r: {
    // This is a pseudo op for a two instruction sequence with a label, which
    // looks like:
    //     call "L1$pb"
    // "L1$pb":
    //     popl %esi

    // Emit the call.
    MCSymbol *PICBase = MF->getPICBaseSymbol();
    // FIXME: We would like an efficient form for this, so we don't have to do a
    // lot of extra uniquing.
    EmitAndCountInstruction(MCInstBuilder(X86::CALLpcrel32)
      .addExpr(MCSymbolRefExpr::create(PICBase, OutContext)));

    // Emit the label.
    OutStreamer->EmitLabel(PICBase);

    // popl $reg
    EmitAndCountInstruction(MCInstBuilder(X86::POP32r)
                            .addReg(MI->getOperand(0).getReg()));
    return;
  }

  case X86::ADD32ri: {
    // Lower the MO_GOT_ABSOLUTE_ADDRESS form of ADD32ri.
    if (MI->getOperand(2).getTargetFlags() != X86II::MO_GOT_ABSOLUTE_ADDRESS)
      break;

    // Okay, we have something like:
    //  EAX = ADD32ri EAX, MO_GOT_ABSOLUTE_ADDRESS(@MYGLOBAL)

    // For this, we want to print something like:
    //   MYGLOBAL + (. - PICBASE)
    // However, we can't generate a ".", so just emit a new label here and refer
    // to it.
    MCSymbol *DotSym = OutContext.createTempSymbol();
    OutStreamer->EmitLabel(DotSym);

    // Now that we have emitted the label, lower the complex operand expression.
    MCSymbol *OpSym = MCInstLowering.GetSymbolFromOperand(MI->getOperand(2));

    const MCExpr *DotExpr = MCSymbolRefExpr::create(DotSym, OutContext);
    const MCExpr *PICBase =
      MCSymbolRefExpr::create(MF->getPICBaseSymbol(), OutContext);
    DotExpr = MCBinaryExpr::createSub(DotExpr, PICBase, OutContext);

    DotExpr = MCBinaryExpr::createAdd(MCSymbolRefExpr::create(OpSym,OutContext),
                                      DotExpr, OutContext);

    EmitAndCountInstruction(MCInstBuilder(X86::ADD32ri)
      .addReg(MI->getOperand(0).getReg())
      .addReg(MI->getOperand(1).getReg())
      .addExpr(DotExpr));
    return;
  }
  case TargetOpcode::STATEPOINT:
    return LowerSTATEPOINT(*MI, MCInstLowering);

  case TargetOpcode::STACKMAP:
    return LowerSTACKMAP(*MI);

  case TargetOpcode::PATCHPOINT:
    return LowerPATCHPOINT(*MI, MCInstLowering);

  case X86::MORESTACK_RET:
    EmitAndCountInstruction(MCInstBuilder(getRetOpcode(*Subtarget)));
    return;

  case X86::MORESTACK_RET_RESTORE_R10:
    // Return, then restore R10.
    EmitAndCountInstruction(MCInstBuilder(getRetOpcode(*Subtarget)));
    EmitAndCountInstruction(MCInstBuilder(X86::MOV64rr)
                            .addReg(X86::R10)
                            .addReg(X86::RAX));
    return;

  case X86::SEH_PushReg:
    OutStreamer->EmitWinCFIPushReg(RI->getSEHRegNum(MI->getOperand(0).getImm()));
    return;

  case X86::SEH_SaveReg:
    OutStreamer->EmitWinCFISaveReg(RI->getSEHRegNum(MI->getOperand(0).getImm()),
                                   MI->getOperand(1).getImm());
    return;

  case X86::SEH_SaveXMM:
    OutStreamer->EmitWinCFISaveXMM(RI->getSEHRegNum(MI->getOperand(0).getImm()),
                                   MI->getOperand(1).getImm());
    return;

  case X86::SEH_StackAlloc:
    OutStreamer->EmitWinCFIAllocStack(MI->getOperand(0).getImm());
    return;

  case X86::SEH_SetFrame:
    OutStreamer->EmitWinCFISetFrame(RI->getSEHRegNum(MI->getOperand(0).getImm()),
                                    MI->getOperand(1).getImm());
    return;

  case X86::SEH_PushFrame:
    OutStreamer->EmitWinCFIPushFrame(MI->getOperand(0).getImm());
    return;

  case X86::SEH_EndPrologue:
    OutStreamer->EmitWinCFIEndProlog();
    return;

  case X86::SEH_Epilogue: {
    MachineBasicBlock::const_iterator MBBI(MI);
    // Check if preceded by a call and emit nop if so.
    for (MBBI = PrevCrossBBInst(MBBI); MBBI; MBBI = PrevCrossBBInst(MBBI)) {
      // Conservatively assume that pseudo instructions don't emit code and keep
      // looking for a call. We may emit an unnecessary nop in some cases.
      if (!MBBI->isPseudo()) {
        if (MBBI->isCall())
          EmitAndCountInstruction(MCInstBuilder(X86::NOOP));
        break;
      }
    }
    return;
  }

    // Lower PSHUFB and VPERMILP normally but add a comment if we can find
    // a constant shuffle mask. We won't be able to do this at the MC layer
    // because the mask isn't an immediate.
  case X86::PSHUFBrm:
  case X86::VPSHUFBrm:
  case X86::VPSHUFBYrm: {
    if (!OutStreamer->isVerboseAsm())
      break;
    assert(MI->getNumOperands() > 5 &&
           "We should always have at least 5 operands!");
    const MachineOperand &DstOp = MI->getOperand(0);
    const MachineOperand &SrcOp = MI->getOperand(1);
    const MachineOperand &MaskOp = MI->getOperand(5);

    if (auto *C = getConstantFromPool(*MI, MaskOp)) {
      SmallVector<int, 16> Mask;
      DecodePSHUFBMask(C, Mask);
      if (!Mask.empty())
        OutStreamer->AddComment(getShuffleComment(DstOp, SrcOp, Mask));
    }
    break;
  }
  case X86::VPERMILPSrm:
  case X86::VPERMILPDrm:
  case X86::VPERMILPSYrm:
  case X86::VPERMILPDYrm: {
    if (!OutStreamer->isVerboseAsm())
      break;
    assert(MI->getNumOperands() > 5 &&
           "We should always have at least 5 operands!");
    const MachineOperand &DstOp = MI->getOperand(0);
    const MachineOperand &SrcOp = MI->getOperand(1);
    const MachineOperand &MaskOp = MI->getOperand(5);

    if (auto *C = getConstantFromPool(*MI, MaskOp)) {
      SmallVector<int, 16> Mask;
      DecodeVPERMILPMask(C, Mask);
      if (!Mask.empty())
        OutStreamer->AddComment(getShuffleComment(DstOp, SrcOp, Mask));
    }
    break;
  }

    // For loads from a constant pool to a vector register, print the constant
    // loaded.
  case X86::MOVAPDrm:
  case X86::VMOVAPDrm:
  case X86::VMOVAPDYrm:
  case X86::MOVUPDrm:
  case X86::VMOVUPDrm:
  case X86::VMOVUPDYrm:
  case X86::MOVAPSrm:
  case X86::VMOVAPSrm:
  case X86::VMOVAPSYrm:
  case X86::MOVUPSrm:
  case X86::VMOVUPSrm:
  case X86::VMOVUPSYrm:
  case X86::MOVDQArm:
  case X86::VMOVDQArm:
  case X86::VMOVDQAYrm:
  case X86::MOVDQUrm:
  case X86::VMOVDQUrm:
  case X86::VMOVDQUYrm:
    if (!OutStreamer->isVerboseAsm())
      break;
    if (MI->getNumOperands() > 4)
    if (auto *C = getConstantFromPool(*MI, MI->getOperand(4))) {
      std::string Comment;
      raw_string_ostream CS(Comment);
      const MachineOperand &DstOp = MI->getOperand(0);
      CS << X86ATTInstPrinter::getRegisterName(DstOp.getReg()) << " = ";
      if (auto *CDS = dyn_cast<ConstantDataSequential>(C)) {
        CS << "[";
        for (int i = 0, NumElements = CDS->getNumElements(); i < NumElements; ++i) {
          if (i != 0)
            CS << ",";
          if (CDS->getElementType()->isIntegerTy())
            CS << CDS->getElementAsInteger(i);
          else if (CDS->getElementType()->isFloatTy())
            CS << CDS->getElementAsFloat(i);
          else if (CDS->getElementType()->isDoubleTy())
            CS << CDS->getElementAsDouble(i);
          else
            CS << "?";
        }
        CS << "]";
        OutStreamer->AddComment(CS.str());
      } else if (auto *CV = dyn_cast<ConstantVector>(C)) {
        CS << "<";
        for (int i = 0, NumOperands = CV->getNumOperands(); i < NumOperands; ++i) {
          if (i != 0)
            CS << ",";
          Constant *COp = CV->getOperand(i);
          if (isa<UndefValue>(COp)) {
            CS << "u";
          } else if (auto *CI = dyn_cast<ConstantInt>(COp)) {
            CS << CI->getZExtValue();
          } else if (auto *CF = dyn_cast<ConstantFP>(COp)) {
            SmallString<32> Str;
            CF->getValueAPF().toString(Str);
            CS << Str;
          } else {
            CS << "?";
          }
        }
        CS << ">";
        OutStreamer->AddComment(CS.str());
      }
    }
    break;
  }

  MCInst TmpInst;
  MCInstLowering.Lower(MI, TmpInst);

  // Stackmap shadows cannot include branch targets, so we can count the bytes
  // in a call towards the shadow, but must ensure that the no thread returns
  // in to the stackmap shadow.  The only way to achieve this is if the call
  // is at the end of the shadow.
  if (MI->isCall()) {
    // Count then size of the call towards the shadow
    SMShadowTracker.count(TmpInst, getSubtargetInfo());
    // Then flush the shadow so that we fill with nops before the call, not
    // after it.
    SMShadowTracker.emitShadowPadding(*OutStreamer, getSubtargetInfo());
    // Then emit the call
    OutStreamer->EmitInstruction(TmpInst, getSubtargetInfo());
    return;
  }

  EmitAndCountInstruction(TmpInst);
}