X86ISelDAGToDAG.cpp

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//===- X86ISelDAGToDAG.cpp - A DAG pattern matching inst selector for X86 -===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines a DAG pattern matching instruction selector for X86,
// converting from a legalized dag to a X86 dag.
//
//===----------------------------------------------------------------------===//

#include "X86.h"
#include "X86InstrBuilder.h"
#include "X86MachineFunctionInfo.h"
#include "X86RegisterInfo.h"
#include "X86Subtarget.h"
#include "X86TargetMachine.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SelectionDAGISel.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Type.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
using namespace llvm;

#define DEBUG_TYPE "x86-isel"

STATISTIC(NumLoadMoved, "Number of loads moved below TokenFactor");

//===----------------------------------------------------------------------===//
//                      Pattern Matcher Implementation
//===----------------------------------------------------------------------===//

namespace {
  /// X86ISelAddressMode - This corresponds to X86AddressMode, but uses
  /// SDValue's instead of register numbers for the leaves of the matched
  /// tree.
  struct X86ISelAddressMode {
    enum {
      RegBase,
      FrameIndexBase
    } BaseType;

    // This is really a union, discriminated by BaseType!
    SDValue Base_Reg;
    int Base_FrameIndex;

    unsigned Scale;
    SDValue IndexReg;
    int32_t Disp;
    SDValue Segment;
    const GlobalValue *GV;
    const Constant *CP;
    const BlockAddress *BlockAddr;
    const char *ES;
    int JT;
    unsigned Align;    // CP alignment.
    unsigned char SymbolFlags;  // X86II::MO_*

    X86ISelAddressMode()
      : BaseType(RegBase), Base_FrameIndex(0), Scale(1), IndexReg(), Disp(0),
        Segment(), GV(nullptr), CP(nullptr), BlockAddr(nullptr), ES(nullptr),
        JT(-1), Align(0), SymbolFlags(X86II::MO_NO_FLAG) {
    }

    bool hasSymbolicDisplacement() const {
      return GV != nullptr || CP != nullptr || ES != nullptr ||
             JT != -1 || BlockAddr != nullptr;
    }

    bool hasBaseOrIndexReg() const {
      return BaseType == FrameIndexBase ||
             IndexReg.getNode() != nullptr || Base_Reg.getNode() != nullptr;
    }

    /// isRIPRelative - Return true if this addressing mode is already RIP
    /// relative.
    bool isRIPRelative() const {
      if (BaseType != RegBase) return false;
      if (RegisterSDNode *RegNode =
            dyn_cast_or_null<RegisterSDNode>(Base_Reg.getNode()))
        return RegNode->getReg() == X86::RIP;
      return false;
    }

    void setBaseReg(SDValue Reg) {
      BaseType = RegBase;
      Base_Reg = Reg;
    }

#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
    void dump() {
      dbgs() << "X86ISelAddressMode " << this << '\n';
      dbgs() << "Base_Reg ";
      if (Base_Reg.getNode())
        Base_Reg.getNode()->dump();
      else
        dbgs() << "nul";
      dbgs() << " Base.FrameIndex " << Base_FrameIndex << '\n'
             << " Scale" << Scale << '\n'
             << "IndexReg ";
      if (IndexReg.getNode())
        IndexReg.getNode()->dump();
      else
        dbgs() << "nul";
      dbgs() << " Disp " << Disp << '\n'
             << "GV ";
      if (GV)
        GV->dump();
      else
        dbgs() << "nul";
      dbgs() << " CP ";
      if (CP)
        CP->dump();
      else
        dbgs() << "nul";
      dbgs() << '\n'
             << "ES ";
      if (ES)
        dbgs() << ES;
      else
        dbgs() << "nul";
      dbgs() << " JT" << JT << " Align" << Align << '\n';
    }
#endif
  };
}

namespace {
  //===--------------------------------------------------------------------===//
  /// ISel - X86 specific code to select X86 machine instructions for
  /// SelectionDAG operations.
  ///
  class X86DAGToDAGISel final : public SelectionDAGISel {
    /// Subtarget - Keep a pointer to the X86Subtarget around so that we can
    /// make the right decision when generating code for different targets.
    const X86Subtarget *Subtarget;

    /// OptForSize - If true, selector should try to optimize for code size
    /// instead of performance.
    bool OptForSize;

  public:
    explicit X86DAGToDAGISel(X86TargetMachine &tm, CodeGenOpt::Level OptLevel)
      : SelectionDAGISel(tm, OptLevel),
        Subtarget(&tm.getSubtarget<X86Subtarget>()),
        OptForSize(false) {}

    const char *getPassName() const override {
      return "X86 DAG->DAG Instruction Selection";
    }

    bool runOnMachineFunction(MachineFunction &MF) override {
      // Reset the subtarget each time through.
      Subtarget = &TM.getSubtarget<X86Subtarget>();
      SelectionDAGISel::runOnMachineFunction(MF);
      return true;
    }

    void EmitFunctionEntryCode() override;

    bool IsProfitableToFold(SDValue N, SDNode *U, SDNode *Root) const override;

    void PreprocessISelDAG() override;

    inline bool immSext8(SDNode *N) const {
      return isInt<8>(cast<ConstantSDNode>(N)->getSExtValue());
    }

    // i64immSExt32 predicate - True if the 64-bit immediate fits in a 32-bit
    // sign extended field.
    inline bool i64immSExt32(SDNode *N) const {
      uint64_t v = cast<ConstantSDNode>(N)->getZExtValue();
      return (int64_t)v == (int32_t)v;
    }

// Include the pieces autogenerated from the target description.
#include "X86GenDAGISel.inc"

  private:
    SDNode *Select(SDNode *N) override;
    SDNode *SelectGather(SDNode *N, unsigned Opc);
    SDNode *SelectAtomicLoadArith(SDNode *Node, MVT NVT);

    bool FoldOffsetIntoAddress(uint64_t Offset, X86ISelAddressMode &AM);
    bool MatchLoadInAddress(LoadSDNode *N, X86ISelAddressMode &AM);
    bool MatchWrapper(SDValue N, X86ISelAddressMode &AM);
    bool MatchAddress(SDValue N, X86ISelAddressMode &AM);
    bool MatchAddressRecursively(SDValue N, X86ISelAddressMode &AM,
                                 unsigned Depth);
    bool MatchAddressBase(SDValue N, X86ISelAddressMode &AM);
    bool SelectAddr(SDNode *Parent, SDValue N, SDValue &Base,
                    SDValue &Scale, SDValue &Index, SDValue &Disp,
                    SDValue &Segment);
    bool SelectMOV64Imm32(SDValue N, SDValue &Imm);
    bool SelectLEAAddr(SDValue N, SDValue &Base,
                       SDValue &Scale, SDValue &Index, SDValue &Disp,
                       SDValue &Segment);
    bool SelectLEA64_32Addr(SDValue N, SDValue &Base,
                            SDValue &Scale, SDValue &Index, SDValue &Disp,
                            SDValue &Segment);
    bool SelectTLSADDRAddr(SDValue N, SDValue &Base,
                           SDValue &Scale, SDValue &Index, SDValue &Disp,
                           SDValue &Segment);
    bool SelectScalarSSELoad(SDNode *Root, SDValue N,
                             SDValue &Base, SDValue &Scale,
                             SDValue &Index, SDValue &Disp,
                             SDValue &Segment,
                             SDValue &NodeWithChain);

    bool TryFoldLoad(SDNode *P, SDValue N,
                     SDValue &Base, SDValue &Scale,
                     SDValue &Index, SDValue &Disp,
                     SDValue &Segment);

    /// SelectInlineAsmMemoryOperand - Implement addressing mode selection for
    /// inline asm expressions.
    bool SelectInlineAsmMemoryOperand(const SDValue &Op,
                                      char ConstraintCode,
                                      std::vector<SDValue> &OutOps) override;

    void EmitSpecialCodeForMain(MachineBasicBlock *BB, MachineFrameInfo *MFI);

    inline void getAddressOperands(X86ISelAddressMode &AM, SDValue &Base,
                                   SDValue &Scale, SDValue &Index,
                                   SDValue &Disp, SDValue &Segment) {
      Base  = (AM.BaseType == X86ISelAddressMode::FrameIndexBase) ?
        CurDAG->getTargetFrameIndex(AM.Base_FrameIndex,
                                    getTargetLowering()->getPointerTy()) :
        AM.Base_Reg;
      Scale = getI8Imm(AM.Scale);
      Index = AM.IndexReg;
      // These are 32-bit even in 64-bit mode since RIP relative offset
      // is 32-bit.
      if (AM.GV)
        Disp = CurDAG->getTargetGlobalAddress(AM.GV, SDLoc(),
                                              MVT::i32, AM.Disp,
                                              AM.SymbolFlags);
      else if (AM.CP)
        Disp = CurDAG->getTargetConstantPool(AM.CP, MVT::i32,
                                             AM.Align, AM.Disp, AM.SymbolFlags);
      else if (AM.ES) {
        assert(!AM.Disp && "Non-zero displacement is ignored with ES.");
        Disp = CurDAG->getTargetExternalSymbol(AM.ES, MVT::i32, AM.SymbolFlags);
      } else if (AM.JT != -1) {
        assert(!AM.Disp && "Non-zero displacement is ignored with JT.");
        Disp = CurDAG->getTargetJumpTable(AM.JT, MVT::i32, AM.SymbolFlags);
      } else if (AM.BlockAddr)
        Disp = CurDAG->getTargetBlockAddress(AM.BlockAddr, MVT::i32, AM.Disp,
                                             AM.SymbolFlags);
      else
        Disp = CurDAG->getTargetConstant(AM.Disp, MVT::i32);

      if (AM.Segment.getNode())
        Segment = AM.Segment;
      else
        Segment = CurDAG->getRegister(0, MVT::i32);
    }

    /// getI8Imm - Return a target constant with the specified value, of type
    /// i8.
    inline SDValue getI8Imm(unsigned Imm) {
      return CurDAG->getTargetConstant(Imm, MVT::i8);
    }

    /// getI32Imm - Return a target constant with the specified value, of type
    /// i32.
    inline SDValue getI32Imm(unsigned Imm) {
      return CurDAG->getTargetConstant(Imm, MVT::i32);
    }

    /// getGlobalBaseReg - Return an SDNode that returns the value of
    /// the global base register. Output instructions required to
    /// initialize the global base register, if necessary.
    ///
    SDNode *getGlobalBaseReg();

    /// getTargetMachine - Return a reference to the TargetMachine, casted
    /// to the target-specific type.
    const X86TargetMachine &getTargetMachine() const {
      return static_cast<const X86TargetMachine &>(TM);
    }

    /// getInstrInfo - Return a reference to the TargetInstrInfo, casted
    /// to the target-specific type.
    const X86InstrInfo *getInstrInfo() const {
      return getTargetMachine().getSubtargetImpl()->getInstrInfo();
    }
  };
}


bool
X86DAGToDAGISel::IsProfitableToFold(SDValue N, SDNode *U, SDNode *Root) const {
  if (OptLevel == CodeGenOpt::None) return false;

  if (!N.hasOneUse())
    return false;

  if (N.getOpcode() != ISD::LOAD)
    return true;

  // If N is a load, do additional profitability checks.
  if (U == Root) {
    switch (U->getOpcode()) {
    default: break;
    case X86ISD::ADD:
    case X86ISD::SUB:
    case X86ISD::AND:
    case X86ISD::XOR:
    case X86ISD::OR:
    case ISD::ADD:
    case ISD::ADDC:
    case ISD::ADDE:
    case ISD::AND:
    case ISD::OR:
    case ISD::XOR: {
      SDValue Op1 = U->getOperand(1);

      // If the other operand is a 8-bit immediate we should fold the immediate
      // instead. This reduces code size.
      // e.g.
      // movl 4(%esp), %eax
      // addl $4, %eax
      // vs.
      // movl $4, %eax
      // addl 4(%esp), %eax
      // The former is 2 bytes shorter. In case where the increment is 1, then
      // the saving can be 4 bytes (by using incl %eax).
      if (ConstantSDNode *Imm = dyn_cast<ConstantSDNode>(Op1))
        if (Imm->getAPIntValue().isSignedIntN(8))
          return false;

      // If the other operand is a TLS address, we should fold it instead.
      // This produces
      // movl    %gs:0, %eax
      // leal    i@NTPOFF(%eax), %eax
      // instead of
      // movl    $i@NTPOFF, %eax
      // addl    %gs:0, %eax
      // if the block also has an access to a second TLS address this will save
      // a load.
      // FIXME: This is probably also true for non-TLS addresses.
      if (Op1.getOpcode() == X86ISD::Wrapper) {
        SDValue Val = Op1.getOperand(0);
        if (Val.getOpcode() == ISD::TargetGlobalTLSAddress)
          return false;
      }
    }
    }
  }

  return true;
}

/// MoveBelowCallOrigChain - Replace the original chain operand of the call with
/// load's chain operand and move load below the call's chain operand.
static void MoveBelowOrigChain(SelectionDAG *CurDAG, SDValue Load,
                               SDValue Call, SDValue OrigChain) {
  SmallVector<SDValue, 8> Ops;
  SDValue Chain = OrigChain.getOperand(0);
  if (Chain.getNode() == Load.getNode())
    Ops.push_back(Load.getOperand(0));
  else {
    assert(Chain.getOpcode() == ISD::TokenFactor &&
           "Unexpected chain operand");
    for (unsigned i = 0, e = Chain.getNumOperands(); i != e; ++i)
      if (Chain.getOperand(i).getNode() == Load.getNode())
        Ops.push_back(Load.getOperand(0));
      else
        Ops.push_back(Chain.getOperand(i));
    SDValue NewChain =
      CurDAG->getNode(ISD::TokenFactor, SDLoc(Load), MVT::Other, Ops);
    Ops.clear();
    Ops.push_back(NewChain);
  }
  for (unsigned i = 1, e = OrigChain.getNumOperands(); i != e; ++i)
    Ops.push_back(OrigChain.getOperand(i));
  CurDAG->UpdateNodeOperands(OrigChain.getNode(), Ops);
  CurDAG->UpdateNodeOperands(Load.getNode(), Call.getOperand(0),
                             Load.getOperand(1), Load.getOperand(2));

  unsigned NumOps = Call.getNode()->getNumOperands();
  Ops.clear();
  Ops.push_back(SDValue(Load.getNode(), 1));
  for (unsigned i = 1, e = NumOps; i != e; ++i)
    Ops.push_back(Call.getOperand(i));
  CurDAG->UpdateNodeOperands(Call.getNode(), Ops);
}

/// isCalleeLoad - Return true if call address is a load and it can be
/// moved below CALLSEQ_START and the chains leading up to the call.
/// Return the CALLSEQ_START by reference as a second output.
/// In the case of a tail call, there isn't a callseq node between the call
/// chain and the load.
static bool isCalleeLoad(SDValue Callee, SDValue &Chain, bool HasCallSeq) {
  // The transformation is somewhat dangerous if the call's chain was glued to
  // the call. After MoveBelowOrigChain the load is moved between the call and
  // the chain, this can create a cycle if the load is not folded. So it is
  // *really* important that we are sure the load will be folded.
  if (Callee.getNode() == Chain.getNode() || !Callee.hasOneUse())
    return false;
  LoadSDNode *LD = dyn_cast<LoadSDNode>(Callee.getNode());
  if (!LD ||
      LD->isVolatile() ||
      LD->getAddressingMode() != ISD::UNINDEXED ||
      LD->getExtensionType() != ISD::NON_EXTLOAD)
    return false;

  // Now let's find the callseq_start.
  while (HasCallSeq && Chain.getOpcode() != ISD::CALLSEQ_START) {
    if (!Chain.hasOneUse())
      return false;
    Chain = Chain.getOperand(0);
  }

  if (!Chain.getNumOperands())
    return false;
  // Since we are not checking for AA here, conservatively abort if the chain
  // writes to memory. It's not safe to move the callee (a load) across a store.
  if (isa<MemSDNode>(Chain.getNode()) &&
      cast<MemSDNode>(Chain.getNode())->writeMem())
    return false;
  if (Chain.getOperand(0).getNode() == Callee.getNode())
    return true;
  if (Chain.getOperand(0).getOpcode() == ISD::TokenFactor &&
      Callee.getValue(1).isOperandOf(Chain.getOperand(0).getNode()) &&
      Callee.getValue(1).hasOneUse())
    return true;
  return false;
}

void X86DAGToDAGISel::PreprocessISelDAG() {
  // OptForSize is used in pattern predicates that isel is matching.
  OptForSize = MF->getFunction()->getAttributes().
    hasAttribute(AttributeSet::FunctionIndex, Attribute::OptimizeForSize);

  for (SelectionDAG::allnodes_iterator I = CurDAG->allnodes_begin(),
       E = CurDAG->allnodes_end(); I != E; ) {
    SDNode *N = I++;  // Preincrement iterator to avoid invalidation issues.

    if (OptLevel != CodeGenOpt::None &&
        // Only does this when target favors doesn't favor register indirect
        // call.
        ((N->getOpcode() == X86ISD::CALL && !Subtarget->callRegIndirect()) ||
         (N->getOpcode() == X86ISD::TC_RETURN &&
          // Only does this if load can be folded into TC_RETURN.
          (Subtarget->is64Bit() ||
           getTargetMachine().getRelocationModel() != Reloc::PIC_)))) {
      /// Also try moving call address load from outside callseq_start to just
      /// before the call to allow it to be folded.
      ///
      ///     [Load chain]
      ///         ^
      ///         |
      ///       [Load]
      ///       ^    ^
      ///       |    |
      ///      /      \--
      ///     /          |
      ///[CALLSEQ_START] |
      ///     ^          |
      ///     |          |
      /// [LOAD/C2Reg]   |
      ///     |          |
      ///      \        /
      ///       \      /
      ///       [CALL]
      bool HasCallSeq = N->getOpcode() == X86ISD::CALL;
      SDValue Chain = N->getOperand(0);
      SDValue Load  = N->getOperand(1);
      if (!isCalleeLoad(Load, Chain, HasCallSeq))
        continue;
      MoveBelowOrigChain(CurDAG, Load, SDValue(N, 0), Chain);
      ++NumLoadMoved;
      continue;
    }

    // Lower fpround and fpextend nodes that target the FP stack to be store and
    // load to the stack.  This is a gross hack.  We would like to simply mark
    // these as being illegal, but when we do that, legalize produces these when
    // it expands calls, then expands these in the same legalize pass.  We would
    // like dag combine to be able to hack on these between the call expansion
    // and the node legalization.  As such this pass basically does "really
    // late" legalization of these inline with the X86 isel pass.
    // FIXME: This should only happen when not compiled with -O0.
    if (N->getOpcode() != ISD::FP_ROUND && N->getOpcode() != ISD::FP_EXTEND)
      continue;

    MVT SrcVT = N->getOperand(0).getSimpleValueType();
    MVT DstVT = N->getSimpleValueType(0);

    // If any of the sources are vectors, no fp stack involved.
    if (SrcVT.isVector() || DstVT.isVector())
      continue;

    // If the source and destination are SSE registers, then this is a legal
    // conversion that should not be lowered.
    const X86TargetLowering *X86Lowering =
        static_cast<const X86TargetLowering *>(getTargetLowering());
    bool SrcIsSSE = X86Lowering->isScalarFPTypeInSSEReg(SrcVT);
    bool DstIsSSE = X86Lowering->isScalarFPTypeInSSEReg(DstVT);
    if (SrcIsSSE && DstIsSSE)
      continue;

    if (!SrcIsSSE && !DstIsSSE) {
      // If this is an FPStack extension, it is a noop.
      if (N->getOpcode() == ISD::FP_EXTEND)
        continue;
      // If this is a value-preserving FPStack truncation, it is a noop.
      if (N->getConstantOperandVal(1))
        continue;
    }

    // Here we could have an FP stack truncation or an FPStack <-> SSE convert.
    // FPStack has extload and truncstore.  SSE can fold direct loads into other
    // operations.  Based on this, decide what we want to do.
    MVT MemVT;
    if (N->getOpcode() == ISD::FP_ROUND)
      MemVT = DstVT;  // FP_ROUND must use DstVT, we can't do a 'trunc load'.
    else
      MemVT = SrcIsSSE ? SrcVT : DstVT;

    SDValue MemTmp = CurDAG->CreateStackTemporary(MemVT);
    SDLoc dl(N);

    // FIXME: optimize the case where the src/dest is a load or store?
    SDValue Store = CurDAG->getTruncStore(CurDAG->getEntryNode(), dl,
                                          N->getOperand(0),
                                          MemTmp, MachinePointerInfo(), MemVT,
                                          false, false, 0);
    SDValue Result = CurDAG->getExtLoad(ISD::EXTLOAD, dl, DstVT, Store, MemTmp,
                                        MachinePointerInfo(),
                                        MemVT, false, false, false, 0);

    // We're about to replace all uses of the FP_ROUND/FP_EXTEND with the
    // extload we created.  This will cause general havok on the dag because
    // anything below the conversion could be folded into other existing nodes.
    // To avoid invalidating 'I', back it up to the convert node.
    --I;
    CurDAG->ReplaceAllUsesOfValueWith(SDValue(N, 0), Result);

    // Now that we did that, the node is dead.  Increment the iterator to the
    // next node to process, then delete N.
    ++I;
    CurDAG->DeleteNode(N);
  }
}


/// EmitSpecialCodeForMain - Emit any code that needs to be executed only in
/// the main function.
void X86DAGToDAGISel::EmitSpecialCodeForMain(MachineBasicBlock *BB,
                                             MachineFrameInfo *MFI) {
  const TargetInstrInfo *TII = TM.getSubtargetImpl()->getInstrInfo();
  if (Subtarget->isTargetCygMing()) {
    unsigned CallOp =
      Subtarget->is64Bit() ? X86::CALL64pcrel32 : X86::CALLpcrel32;
    BuildMI(BB, DebugLoc(),
            TII->get(CallOp)).addExternalSymbol("__main");
  }
}

void X86DAGToDAGISel::EmitFunctionEntryCode() {
  // If this is main, emit special code for main.
  if (const Function *Fn = MF->getFunction())
    if (Fn->hasExternalLinkage() && Fn->getName() == "main")
      EmitSpecialCodeForMain(MF->begin(), MF->getFrameInfo());
}

static bool isDispSafeForFrameIndex(int64_t Val) {
  // On 64-bit platforms, we can run into an issue where a frame index
  // includes a displacement that, when added to the explicit displacement,
  // will overflow the displacement field. Assuming that the frame index
  // displacement fits into a 31-bit integer  (which is only slightly more
  // aggressive than the current fundamental assumption that it fits into
  // a 32-bit integer), a 31-bit disp should always be safe.
  return isInt<31>(Val);
}

bool X86DAGToDAGISel::FoldOffsetIntoAddress(uint64_t Offset,
                                            X86ISelAddressMode &AM) {
  int64_t Val = AM.Disp + Offset;
  CodeModel::Model M = TM.getCodeModel();
  if (Subtarget->is64Bit()) {
    if (!X86::isOffsetSuitableForCodeModel(Val, M,
                                           AM.hasSymbolicDisplacement()))
      return true;
    // In addition to the checks required for a register base, check that
    // we do not try to use an unsafe Disp with a frame index.
    if (AM.BaseType == X86ISelAddressMode::FrameIndexBase &&
        !isDispSafeForFrameIndex(Val))
      return true;
  }
  AM.Disp = Val;
  return false;

}

bool X86DAGToDAGISel::MatchLoadInAddress(LoadSDNode *N, X86ISelAddressMode &AM){
  SDValue Address = N->getOperand(1);

  // load gs:0 -> GS segment register.
  // load fs:0 -> FS segment register.
  //
  // This optimization is valid because the GNU TLS model defines that
  // gs:0 (or fs:0 on X86-64) contains its own address.
  // For more information see http://people.redhat.com/drepper/tls.pdf
  if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Address))
    if (C->getSExtValue() == 0 && AM.Segment.getNode() == nullptr &&
        Subtarget->isTargetLinux())
      switch (N->getPointerInfo().getAddrSpace()) {
      case 256:
        AM.Segment = CurDAG->getRegister(X86::GS, MVT::i16);
        return false;
      case 257:
        AM.Segment = CurDAG->getRegister(X86::FS, MVT::i16);
        return false;
      }

  return true;
}

/// MatchWrapper - Try to match X86ISD::Wrapper and X86ISD::WrapperRIP nodes
/// into an addressing mode.  These wrap things that will resolve down into a
/// symbol reference.  If no match is possible, this returns true, otherwise it
/// returns false.
bool X86DAGToDAGISel::MatchWrapper(SDValue N, X86ISelAddressMode &AM) {
  // If the addressing mode already has a symbol as the displacement, we can
  // never match another symbol.
  if (AM.hasSymbolicDisplacement())
    return true;

  SDValue N0 = N.getOperand(0);
  CodeModel::Model M = TM.getCodeModel();

  // Handle X86-64 rip-relative addresses.  We check this before checking direct
  // folding because RIP is preferable to non-RIP accesses.
  if (Subtarget->is64Bit() && N.getOpcode() == X86ISD::WrapperRIP &&
      // Under X86-64 non-small code model, GV (and friends) are 64-bits, so
      // they cannot be folded into immediate fields.
      // FIXME: This can be improved for kernel and other models?
      (M == CodeModel::Small || M == CodeModel::Kernel)) {
    // Base and index reg must be 0 in order to use %rip as base.
    if (AM.hasBaseOrIndexReg())
      return true;
    if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(N0)) {
      X86ISelAddressMode Backup = AM;
      AM.GV = G->getGlobal();
      AM.SymbolFlags = G->getTargetFlags();
      if (FoldOffsetIntoAddress(G->getOffset(), AM)) {
        AM = Backup;
        return true;
      }
    } else if (ConstantPoolSDNode *CP = dyn_cast<ConstantPoolSDNode>(N0)) {
      X86ISelAddressMode Backup = AM;
      AM.CP = CP->getConstVal();
      AM.Align = CP->getAlignment();
      AM.SymbolFlags = CP->getTargetFlags();
      if (FoldOffsetIntoAddress(CP->getOffset(), AM)) {
        AM = Backup;
        return true;
      }
    } else if (ExternalSymbolSDNode *S = dyn_cast<ExternalSymbolSDNode>(N0)) {
      AM.ES = S->getSymbol();
      AM.SymbolFlags = S->getTargetFlags();
    } else if (JumpTableSDNode *J = dyn_cast<JumpTableSDNode>(N0)) {
      AM.JT = J->getIndex();
      AM.SymbolFlags = J->getTargetFlags();
    } else if (BlockAddressSDNode *BA = dyn_cast<BlockAddressSDNode>(N0)) {
      X86ISelAddressMode Backup = AM;
      AM.BlockAddr = BA->getBlockAddress();
      AM.SymbolFlags = BA->getTargetFlags();
      if (FoldOffsetIntoAddress(BA->getOffset(), AM)) {
        AM = Backup;
        return true;
      }
    } else
      llvm_unreachable("Unhandled symbol reference node.");

    if (N.getOpcode() == X86ISD::WrapperRIP)
      AM.setBaseReg(CurDAG->getRegister(X86::RIP, MVT::i64));
    return false;
  }

  // Handle the case when globals fit in our immediate field: This is true for
  // X86-32 always and X86-64 when in -mcmodel=small mode.  In 64-bit
  // mode, this only applies to a non-RIP-relative computation.
  if (!Subtarget->is64Bit() ||
      M == CodeModel::Small || M == CodeModel::Kernel) {
    assert(N.getOpcode() != X86ISD::WrapperRIP &&
           "RIP-relative addressing already handled");
    if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(N0)) {
      AM.GV = G->getGlobal();
      AM.Disp += G->getOffset();
      AM.SymbolFlags = G->getTargetFlags();
    } else if (ConstantPoolSDNode *CP = dyn_cast<ConstantPoolSDNode>(N0)) {
      AM.CP = CP->getConstVal();
      AM.Align = CP->getAlignment();
      AM.Disp += CP->getOffset();
      AM.SymbolFlags = CP->getTargetFlags();
    } else if (ExternalSymbolSDNode *S = dyn_cast<ExternalSymbolSDNode>(N0)) {
      AM.ES = S->getSymbol();
      AM.SymbolFlags = S->getTargetFlags();
    } else if (JumpTableSDNode *J = dyn_cast<JumpTableSDNode>(N0)) {
      AM.JT = J->getIndex();
      AM.SymbolFlags = J->getTargetFlags();
    } else if (BlockAddressSDNode *BA = dyn_cast<BlockAddressSDNode>(N0)) {
      AM.BlockAddr = BA->getBlockAddress();
      AM.Disp += BA->getOffset();
      AM.SymbolFlags = BA->getTargetFlags();
    } else
      llvm_unreachable("Unhandled symbol reference node.");
    return false;
  }

  return true;
}

/// MatchAddress - Add the specified node to the specified addressing mode,
/// returning true if it cannot be done.  This just pattern matches for the
/// addressing mode.
bool X86DAGToDAGISel::MatchAddress(SDValue N, X86ISelAddressMode &AM) {
  if (MatchAddressRecursively(N, AM, 0))
    return true;

  // Post-processing: Convert lea(,%reg,2) to lea(%reg,%reg), which has
  // a smaller encoding and avoids a scaled-index.
  if (AM.Scale == 2 &&
      AM.BaseType == X86ISelAddressMode::RegBase &&
      AM.Base_Reg.getNode() == nullptr) {
    AM.Base_Reg = AM.IndexReg;
    AM.Scale = 1;
  }

  // Post-processing: Convert foo to foo(%rip), even in non-PIC mode,
  // because it has a smaller encoding.
  // TODO: Which other code models can use this?
  if (TM.getCodeModel() == CodeModel::Small &&
      Subtarget->is64Bit() &&
      AM.Scale == 1 &&
      AM.BaseType == X86ISelAddressMode::RegBase &&
      AM.Base_Reg.getNode() == nullptr &&
      AM.IndexReg.getNode() == nullptr &&
      AM.SymbolFlags == X86II::MO_NO_FLAG &&
      AM.hasSymbolicDisplacement())
    AM.Base_Reg = CurDAG->getRegister(X86::RIP, MVT::i64);

  return false;
}

// Insert a node into the DAG at least before the Pos node's position. This
// will reposition the node as needed, and will assign it a node ID that is <=
// the Pos node's ID. Note that this does *not* preserve the uniqueness of node
// IDs! The selection DAG must no longer depend on their uniqueness when this
// is used.
static void InsertDAGNode(SelectionDAG &DAG, SDValue Pos, SDValue N) {
  if (N.getNode()->getNodeId() == -1 ||
      N.getNode()->getNodeId() > Pos.getNode()->getNodeId()) {
    DAG.RepositionNode(Pos.getNode(), N.getNode());
    N.getNode()->setNodeId(Pos.getNode()->getNodeId());
  }
}

// Transform "(X >> (8-C1)) & (0xff << C1)" to "((X >> 8) & 0xff) << C1" if
// safe. This allows us to convert the shift and and into an h-register
// extract and a scaled index. Returns false if the simplification is
// performed.
static bool FoldMaskAndShiftToExtract(SelectionDAG &DAG, SDValue N,
                                      uint64_t Mask,
                                      SDValue Shift, SDValue X,
                                      X86ISelAddressMode &AM) {
  if (Shift.getOpcode() != ISD::SRL ||
      !isa<ConstantSDNode>(Shift.getOperand(1)) ||
      !Shift.hasOneUse())
    return true;

  int ScaleLog = 8 - Shift.getConstantOperandVal(1);
  if (ScaleLog <= 0 || ScaleLog >= 4 ||
      Mask != (0xffu << ScaleLog))
    return true;

  MVT VT = N.getSimpleValueType();
  SDLoc DL(N);
  SDValue Eight = DAG.getConstant(8, MVT::i8);
  SDValue NewMask = DAG.getConstant(0xff, VT);
  SDValue Srl = DAG.getNode(ISD::SRL, DL, VT, X, Eight);
  SDValue And = DAG.getNode(ISD::AND, DL, VT, Srl, NewMask);
  SDValue ShlCount = DAG.getConstant(ScaleLog, MVT::i8);
  SDValue Shl = DAG.getNode(ISD::SHL, DL, VT, And, ShlCount);

  // Insert the new nodes into the topological ordering. We must do this in
  // a valid topological ordering as nothing is going to go back and re-sort
  // these nodes. We continually insert before 'N' in sequence as this is
  // essentially a pre-flattened and pre-sorted sequence of nodes. There is no
  // hierarchy left to express.
  InsertDAGNode(DAG, N, Eight);
  InsertDAGNode(DAG, N, Srl);
  InsertDAGNode(DAG, N, NewMask);
  InsertDAGNode(DAG, N, And);
  InsertDAGNode(DAG, N, ShlCount);
  InsertDAGNode(DAG, N, Shl);
  DAG.ReplaceAllUsesWith(N, Shl);
  AM.IndexReg = And;
  AM.Scale = (1 << ScaleLog);
  return false;
}

// Transforms "(X << C1) & C2" to "(X & (C2>>C1)) << C1" if safe and if this
// allows us to fold the shift into this addressing mode. Returns false if the
// transform succeeded.
static bool FoldMaskedShiftToScaledMask(SelectionDAG &DAG, SDValue N,
                                        uint64_t Mask,
                                        SDValue Shift, SDValue X,
                                        X86ISelAddressMode &AM) {
  if (Shift.getOpcode() != ISD::SHL ||
      !isa<ConstantSDNode>(Shift.getOperand(1)))
    return true;

  // Not likely to be profitable if either the AND or SHIFT node has more
  // than one use (unless all uses are for address computation). Besides,
  // isel mechanism requires their node ids to be reused.
  if (!N.hasOneUse() || !Shift.hasOneUse())
    return true;

  // Verify that the shift amount is something we can fold.
  unsigned ShiftAmt = Shift.getConstantOperandVal(1);
  if (ShiftAmt != 1 && ShiftAmt != 2 && ShiftAmt != 3)
    return true;

  MVT VT = N.getSimpleValueType();
  SDLoc DL(N);
  SDValue NewMask = DAG.getConstant(Mask >> ShiftAmt, VT);
  SDValue NewAnd = DAG.getNode(ISD::AND, DL, VT, X, NewMask);
  SDValue NewShift = DAG.getNode(ISD::SHL, DL, VT, NewAnd, Shift.getOperand(1));

  // Insert the new nodes into the topological ordering. We must do this in
  // a valid topological ordering as nothing is going to go back and re-sort
  // these nodes. We continually insert before 'N' in sequence as this is
  // essentially a pre-flattened and pre-sorted sequence of nodes. There is no
  // hierarchy left to express.
  InsertDAGNode(DAG, N, NewMask);
  InsertDAGNode(DAG, N, NewAnd);
  InsertDAGNode(DAG, N, NewShift);
  DAG.ReplaceAllUsesWith(N, NewShift);

  AM.Scale = 1 << ShiftAmt;
  AM.IndexReg = NewAnd;
  return false;
}

// Implement some heroics to detect shifts of masked values where the mask can
// be replaced by extending the shift and undoing that in the addressing mode
// scale. Patterns such as (shl (srl x, c1), c2) are canonicalized into (and
// (srl x, SHIFT), MASK) by DAGCombines that don't know the shl can be done in
// the addressing mode. This results in code such as:
//
//   int f(short *y, int *lookup_table) {
//     ...
//     return *y + lookup_table[*y >> 11];
//   }
//
// Turning into:
//   movzwl (%rdi), %eax
//   movl %eax, %ecx
//   shrl $11, %ecx
//   addl (%rsi,%rcx,4), %eax
//
// Instead of:
//   movzwl (%rdi), %eax
//   movl %eax, %ecx
//   shrl $9, %ecx
//   andl $124, %rcx
//   addl (%rsi,%rcx), %eax
//
// Note that this function assumes the mask is provided as a mask *after* the
// value is shifted. The input chain may or may not match that, but computing
// such a mask is trivial.
static bool FoldMaskAndShiftToScale(SelectionDAG &DAG, SDValue N,
                                    uint64_t Mask,
                                    SDValue Shift, SDValue X,
                                    X86ISelAddressMode &AM) {
  if (Shift.getOpcode() != ISD::SRL || !Shift.hasOneUse() ||
      !isa<ConstantSDNode>(Shift.getOperand(1)))
    return true;

  unsigned ShiftAmt = Shift.getConstantOperandVal(1);
  unsigned MaskLZ = countLeadingZeros(Mask);
  unsigned MaskTZ = countTrailingZeros(Mask);

  // The amount of shift we're trying to fit into the addressing mode is taken
  // from the trailing zeros of the mask.
  unsigned AMShiftAmt = MaskTZ;

  // There is nothing we can do here unless the mask is removing some bits.
  // Also, the addressing mode can only represent shifts of 1, 2, or 3 bits.
  if (AMShiftAmt <= 0 || AMShiftAmt > 3) return true;

  // We also need to ensure that mask is a continuous run of bits.
  if (CountTrailingOnes_64(Mask >> MaskTZ) + MaskTZ + MaskLZ != 64) return true;

  // Scale the leading zero count down based on the actual size of the value.
  // Also scale it down based on the size of the shift.
  MaskLZ -= (64 - X.getSimpleValueType().getSizeInBits()) + ShiftAmt;

  // The final check is to ensure that any masked out high bits of X are
  // already known to be zero. Otherwise, the mask has a semantic impact
  // other than masking out a couple of low bits. Unfortunately, because of
  // the mask, zero extensions will be removed from operands in some cases.
  // This code works extra hard to look through extensions because we can
  // replace them with zero extensions cheaply if necessary.
  bool ReplacingAnyExtend = false;
  if (X.getOpcode() == ISD::ANY_EXTEND) {
    unsigned ExtendBits = X.getSimpleValueType().getSizeInBits() -
                          X.getOperand(0).getSimpleValueType().getSizeInBits();
    // Assume that we'll replace the any-extend with a zero-extend, and
    // narrow the search to the extended value.
    X = X.getOperand(0);
    MaskLZ = ExtendBits > MaskLZ ? 0 : MaskLZ - ExtendBits;
    ReplacingAnyExtend = true;
  }
  APInt MaskedHighBits =
    APInt::getHighBitsSet(X.getSimpleValueType().getSizeInBits(), MaskLZ);
  APInt KnownZero, KnownOne;
  DAG.computeKnownBits(X, KnownZero, KnownOne);
  if (MaskedHighBits != KnownZero) return true;

  // We've identified a pattern that can be transformed into a single shift
  // and an addressing mode. Make it so.
  MVT VT = N.getSimpleValueType();
  if (ReplacingAnyExtend) {
    assert(X.getValueType() != VT);
    // We looked through an ANY_EXTEND node, insert a ZERO_EXTEND.
    SDValue NewX = DAG.getNode(ISD::ZERO_EXTEND, SDLoc(X), VT, X);
    InsertDAGNode(DAG, N, NewX);
    X = NewX;
  }
  SDLoc DL(N);
  SDValue NewSRLAmt = DAG.getConstant(ShiftAmt + AMShiftAmt, MVT::i8);
  SDValue NewSRL = DAG.getNode(ISD::SRL, DL, VT, X, NewSRLAmt);
  SDValue NewSHLAmt = DAG.getConstant(AMShiftAmt, MVT::i8);
  SDValue NewSHL = DAG.getNode(ISD::SHL, DL, VT, NewSRL, NewSHLAmt);

  // Insert the new nodes into the topological ordering. We must do this in
  // a valid topological ordering as nothing is going to go back and re-sort
  // these nodes. We continually insert before 'N' in sequence as this is
  // essentially a pre-flattened and pre-sorted sequence of nodes. There is no
  // hierarchy left to express.
  InsertDAGNode(DAG, N, NewSRLAmt);
  InsertDAGNode(DAG, N, NewSRL);
  InsertDAGNode(DAG, N, NewSHLAmt);
  InsertDAGNode(DAG, N, NewSHL);
  DAG.ReplaceAllUsesWith(N, NewSHL);

  AM.Scale = 1 << AMShiftAmt;
  AM.IndexReg = NewSRL;
  return false;
}

bool X86DAGToDAGISel::MatchAddressRecursively(SDValue N, X86ISelAddressMode &AM,
                                              unsigned Depth) {
  SDLoc dl(N);
  DEBUG({
      dbgs() << "MatchAddress: ";
      AM.dump();
    });
  // Limit recursion.
  if (Depth > 5)
    return MatchAddressBase(N, AM);

  // If this is already a %rip relative address, we can only merge immediates
  // into it.  Instead of handling this in every case, we handle it here.
  // RIP relative addressing: %rip + 32-bit displacement!
  if (AM.isRIPRelative()) {
    // FIXME: JumpTable and ExternalSymbol address currently don't like
    // displacements.  It isn't very important, but this should be fixed for
    // consistency.
    if (!AM.ES && AM.JT != -1) return true;

    if (ConstantSDNode *Cst = dyn_cast<ConstantSDNode>(N))
      if (!FoldOffsetIntoAddress(Cst->getSExtValue(), AM))
        return false;
    return true;
  }

  switch (N.getOpcode()) {
  default: break;
  case ISD::Constant: {
    uint64_t Val = cast<ConstantSDNode>(N)->getSExtValue();
    if (!FoldOffsetIntoAddress(Val, AM))
      return false;
    break;
  }

  case X86ISD::Wrapper:
  case X86ISD::WrapperRIP:
    if (!MatchWrapper(N, AM))
      return false;
    break;

  case ISD::LOAD:
    if (!MatchLoadInAddress(cast<LoadSDNode>(N), AM))
      return false;
    break;

  case ISD::FrameIndex:
    if (AM.BaseType == X86ISelAddressMode::RegBase &&
        AM.Base_Reg.getNode() == nullptr &&
        (!Subtarget->is64Bit() || isDispSafeForFrameIndex(AM.Disp))) {
      AM.BaseType = X86ISelAddressMode::FrameIndexBase;
      AM.Base_FrameIndex = cast<FrameIndexSDNode>(N)->getIndex();
      return false;
    }
    break;

  case ISD::SHL:
    if (AM.IndexReg.getNode() != nullptr || AM.Scale != 1)
      break;

    if (ConstantSDNode
          *CN = dyn_cast<ConstantSDNode>(N.getNode()->getOperand(1))) {
      unsigned Val = CN->getZExtValue();
      // Note that we handle x<<1 as (,x,2) rather than (x,x) here so
      // that the base operand remains free for further matching. If
      // the base doesn't end up getting used, a post-processing step
      // in MatchAddress turns (,x,2) into (x,x), which is cheaper.
      if (Val == 1 || Val == 2 || Val == 3) {
        AM.Scale = 1 << Val;
        SDValue ShVal = N.getNode()->getOperand(0);

        // Okay, we know that we have a scale by now.  However, if the scaled
        // value is an add of something and a constant, we can fold the
        // constant into the disp field here.
        if (CurDAG->isBaseWithConstantOffset(ShVal)) {
          AM.IndexReg = ShVal.getNode()->getOperand(0);
          ConstantSDNode *AddVal =
            cast<ConstantSDNode>(ShVal.getNode()->getOperand(1));
          uint64_t Disp = (uint64_t)AddVal->getSExtValue() << Val;
          if (!FoldOffsetIntoAddress(Disp, AM))
            return false;
        }

        AM.IndexReg = ShVal;
        return false;
      }
    }
    break;

  case ISD::SRL: {
    // Scale must not be used already.
    if (AM.IndexReg.getNode() != nullptr || AM.Scale != 1) break;

    SDValue And = N.getOperand(0);
    if (And.getOpcode() != ISD::AND) break;
    SDValue X = And.getOperand(0);

    // We only handle up to 64-bit values here as those are what matter for
    // addressing mode optimizations.
    if (X.getSimpleValueType().getSizeInBits() > 64) break;

    // The mask used for the transform is expected to be post-shift, but we
    // found the shift first so just apply the shift to the mask before passing
    // it down.
    if (!isa<ConstantSDNode>(N.getOperand(1)) ||
        !isa<ConstantSDNode>(And.getOperand(1)))
      break;
    uint64_t Mask = And.getConstantOperandVal(1) >> N.getConstantOperandVal(1);

    // Try to fold the mask and shift into the scale, and return false if we
    // succeed.
    if (!FoldMaskAndShiftToScale(*CurDAG, N, Mask, N, X, AM))
      return false;
    break;
  }

  case ISD::SMUL_LOHI:
  case ISD::UMUL_LOHI:
    // A mul_lohi where we need the low part can be folded as a plain multiply.
    if (N.getResNo() != 0) break;
    // FALL THROUGH
  case ISD::MUL:
  case X86ISD::MUL_IMM:
    // X*[3,5,9] -> X+X*[2,4,8]
    if (AM.BaseType == X86ISelAddressMode::RegBase &&
        AM.Base_Reg.getNode() == nullptr &&
        AM.IndexReg.getNode() == nullptr) {
      if (ConstantSDNode
            *CN = dyn_cast<ConstantSDNode>(N.getNode()->getOperand(1)))
        if (CN->getZExtValue() == 3 || CN->getZExtValue() == 5 ||
            CN->getZExtValue() == 9) {
          AM.Scale = unsigned(CN->getZExtValue())-1;

          SDValue MulVal = N.getNode()->getOperand(0);
          SDValue Reg;

          // Okay, we know that we have a scale by now.  However, if the scaled
          // value is an add of something and a constant, we can fold the
          // constant into the disp field here.
          if (MulVal.getNode()->getOpcode() == ISD::ADD && MulVal.hasOneUse() &&
              isa<ConstantSDNode>(MulVal.getNode()->getOperand(1))) {
            Reg = MulVal.getNode()->getOperand(0);
            ConstantSDNode *AddVal =
              cast<ConstantSDNode>(MulVal.getNode()->getOperand(1));
            uint64_t Disp = AddVal->getSExtValue() * CN->getZExtValue();
            if (FoldOffsetIntoAddress(Disp, AM))
              Reg = N.getNode()->getOperand(0);
          } else {
            Reg = N.getNode()->getOperand(0);
          }

          AM.IndexReg = AM.Base_Reg = Reg;
          return false;
        }
    }
    break;

  case ISD::SUB: {
    // Given A-B, if A can be completely folded into the address and
    // the index field with the index field unused, use -B as the index.
    // This is a win if a has multiple parts that can be folded into
    // the address. Also, this saves a mov if the base register has
    // other uses, since it avoids a two-address sub instruction, however
    // it costs an additional mov if the index register has other uses.

    // Add an artificial use to this node so that we can keep track of
    // it if it gets CSE'd with a different node.
    HandleSDNode Handle(N);

    // Test if the LHS of the sub can be folded.
    X86ISelAddressMode Backup = AM;
    if (MatchAddressRecursively(N.getNode()->getOperand(0), AM, Depth+1)) {
      AM = Backup;
      break;
    }
    // Test if the index field is free for use.
    if (AM.IndexReg.getNode() || AM.isRIPRelative()) {
      AM = Backup;
      break;
    }

    int Cost = 0;
    SDValue RHS = Handle.getValue().getNode()->getOperand(1);
    // If the RHS involves a register with multiple uses, this
    // transformation incurs an extra mov, due to the neg instruction
    // clobbering its operand.
    if (!RHS.getNode()->hasOneUse() ||
        RHS.getNode()->getOpcode() == ISD::CopyFromReg ||
        RHS.getNode()->getOpcode() == ISD::TRUNCATE ||
        RHS.getNode()->getOpcode() == ISD::ANY_EXTEND ||
        (RHS.getNode()->getOpcode() == ISD::ZERO_EXTEND &&
         RHS.getNode()->getOperand(0).getValueType() == MVT::i32))
      ++Cost;
    // If the base is a register with multiple uses, this
    // transformation may save a mov.
    if ((AM.BaseType == X86ISelAddressMode::RegBase &&
         AM.Base_Reg.getNode() &&
         !AM.Base_Reg.getNode()->hasOneUse()) ||
        AM.BaseType == X86ISelAddressMode::FrameIndexBase)
      --Cost;
    // If the folded LHS was interesting, this transformation saves
    // address arithmetic.
    if ((AM.hasSymbolicDisplacement() && !Backup.hasSymbolicDisplacement()) +
        ((AM.Disp != 0) && (Backup.Disp == 0)) +
        (AM.Segment.getNode() && !Backup.Segment.getNode()) >= 2)
      --Cost;
    // If it doesn't look like it may be an overall win, don't do it.
    if (Cost >= 0) {
      AM = Backup;
      break;
    }

    // Ok, the transformation is legal and appears profitable. Go for it.
    SDValue Zero = CurDAG->getConstant(0, N.getValueType());
    SDValue Neg = CurDAG->getNode(ISD::SUB, dl, N.getValueType(), Zero, RHS);
    AM.IndexReg = Neg;
    AM.Scale = 1;

    // Insert the new nodes into the topological ordering.
    InsertDAGNode(*CurDAG, N, Zero);
    InsertDAGNode(*CurDAG, N, Neg);
    return false;
  }

  case ISD::ADD: {
    // Add an artificial use to this node so that we can keep track of
    // it if it gets CSE'd with a different node.
    HandleSDNode Handle(N);

    X86ISelAddressMode Backup = AM;
    if (!MatchAddressRecursively(N.getOperand(0), AM, Depth+1) &&
        !MatchAddressRecursively(Handle.getValue().getOperand(1), AM, Depth+1))
      return false;
    AM = Backup;

    // Try again after commuting the operands.
    if (!MatchAddressRecursively(Handle.getValue().getOperand(1), AM, Depth+1)&&
        !MatchAddressRecursively(Handle.getValue().getOperand(0), AM, Depth+1))
      return false;
    AM = Backup;

    // If we couldn't fold both operands into the address at the same time,
    // see if we can just put each operand into a register and fold at least
    // the add.
    if (AM.BaseType == X86ISelAddressMode::RegBase &&
        !AM.Base_Reg.getNode() &&
        !AM.IndexReg.getNode()) {
      N = Handle.getValue();
      AM.Base_Reg = N.getOperand(0);
      AM.IndexReg = N.getOperand(1);
      AM.Scale = 1;
      return false;
    }
    N = Handle.getValue();
    break;
  }

  case ISD::OR:
    // Handle "X | C" as "X + C" iff X is known to have C bits clear.
    if (CurDAG->isBaseWithConstantOffset(N)) {
      X86ISelAddressMode Backup = AM;
      ConstantSDNode *CN = cast<ConstantSDNode>(N.getOperand(1));

      // Start with the LHS as an addr mode.
      if (!MatchAddressRecursively(N.getOperand(0), AM, Depth+1) &&
          !FoldOffsetIntoAddress(CN->getSExtValue(), AM))
        return false;
      AM = Backup;
    }
    break;

  case ISD::AND: {
    // Perform some heroic transforms on an and of a constant-count shift
    // with a constant to enable use of the scaled offset field.

    // Scale must not be used already.
    if (AM.IndexReg.getNode() != nullptr || AM.Scale != 1) break;

    SDValue Shift = N.getOperand(0);
    if (Shift.getOpcode() != ISD::SRL && Shift.getOpcode() != ISD::SHL) break;
    SDValue X = Shift.getOperand(0);

    // We only handle up to 64-bit values here as those are what matter for
    // addressing mode optimizations.
    if (X.getSimpleValueType().getSizeInBits() > 64) break;

    if (!isa<ConstantSDNode>(N.getOperand(1)))
      break;
    uint64_t Mask = N.getConstantOperandVal(1);

    // Try to fold the mask and shift into an extract and scale.
    if (!FoldMaskAndShiftToExtract(*CurDAG, N, Mask, Shift, X, AM))
      return false;

    // Try to fold the mask and shift directly into the scale.
    if (!FoldMaskAndShiftToScale(*CurDAG, N, Mask, Shift, X, AM))
      return false;

    // Try to swap the mask and shift to place shifts which can be done as
    // a scale on the outside of the mask.
    if (!FoldMaskedShiftToScaledMask(*CurDAG, N, Mask, Shift, X, AM))
      return false;
    break;
  }
  }

  return MatchAddressBase(N, AM);
}

/// MatchAddressBase - Helper for MatchAddress. Add the specified node to the
/// specified addressing mode without any further recursion.
bool X86DAGToDAGISel::MatchAddressBase(SDValue N, X86ISelAddressMode &AM) {
  // Is the base register already occupied?
  if (AM.BaseType != X86ISelAddressMode::RegBase || AM.Base_Reg.getNode()) {
    // If so, check to see if the scale index register is set.
    if (!AM.IndexReg.getNode()) {
      AM.IndexReg = N;
      AM.Scale = 1;
      return false;
    }

    // Otherwise, we cannot select it.
    return true;
  }

  // Default, generate it as a register.
  AM.BaseType = X86ISelAddressMode::RegBase;
  AM.Base_Reg = N;
  return false;
}

/// SelectAddr - returns true if it is able pattern match an addressing mode.
/// It returns the operands which make up the maximal addressing mode it can
/// match by reference.
///
/// Parent is the parent node of the addr operand that is being matched.  It
/// is always a load, store, atomic node, or null.  It is only null when
/// checking memory operands for inline asm nodes.
bool X86DAGToDAGISel::SelectAddr(SDNode *Parent, SDValue N, SDValue &Base,
                                 SDValue &Scale, SDValue &Index,
                                 SDValue &Disp, SDValue &Segment) {
  X86ISelAddressMode AM;

  if (Parent &&
      // This list of opcodes are all the nodes that have an "addr:$ptr" operand
      // that are not a MemSDNode, and thus don't have proper addrspace info.
      Parent->getOpcode() != ISD::INTRINSIC_W_CHAIN && // unaligned loads, fixme
      Parent->getOpcode() != ISD::INTRINSIC_VOID && // nontemporal stores
      Parent->getOpcode() != X86ISD::TLSCALL && // Fixme
      Parent->getOpcode() != X86ISD::EH_SJLJ_SETJMP && // setjmp
      Parent->getOpcode() != X86ISD::EH_SJLJ_LONGJMP) { // longjmp
    unsigned AddrSpace =
      cast<MemSDNode>(Parent)->getPointerInfo().getAddrSpace();
    // AddrSpace 256 -> GS, 257 -> FS.
    if (AddrSpace == 256)
      AM.Segment = CurDAG->getRegister(X86::GS, MVT::i16);
    if (AddrSpace == 257)
      AM.Segment = CurDAG->getRegister(X86::FS, MVT::i16);
  }

  if (MatchAddress(N, AM))
    return false;

  MVT VT = N.getSimpleValueType();
  if (AM.BaseType == X86ISelAddressMode::RegBase) {
    if (!AM.Base_Reg.getNode())
      AM.Base_Reg = CurDAG->getRegister(0, VT);
  }

  if (!AM.IndexReg.getNode())
    AM.IndexReg = CurDAG->getRegister(0, VT);

  getAddressOperands(AM, Base, Scale, Index, Disp, Segment);
  return true;
}

/// SelectScalarSSELoad - Match a scalar SSE load.  In particular, we want to
/// match a load whose top elements are either undef or zeros.  The load flavor
/// is derived from the type of N, which is either v4f32 or v2f64.
///
/// We also return:
///   PatternChainNode: this is the matched node that has a chain input and
///   output.
bool X86DAGToDAGISel::SelectScalarSSELoad(SDNode *Root,
                                          SDValue N, SDValue &Base,
                                          SDValue &Scale, SDValue &Index,
                                          SDValue &Disp, SDValue &Segment,
                                          SDValue &PatternNodeWithChain) {
  if (N.getOpcode() == ISD::SCALAR_TO_VECTOR) {
    PatternNodeWithChain = N.getOperand(0);
    if (ISD::isNON_EXTLoad(PatternNodeWithChain.getNode()) &&
        PatternNodeWithChain.hasOneUse() &&
        IsProfitableToFold(N.getOperand(0), N.getNode(), Root) &&
        IsLegalToFold(N.getOperand(0), N.getNode(), Root, OptLevel)) {
      LoadSDNode *LD = cast<LoadSDNode>(PatternNodeWithChain);
      if (!SelectAddr(LD, LD->getBasePtr(), Base, Scale, Index, Disp, Segment))
        return false;
      return true;
    }
  }

  // Also handle the case where we explicitly require zeros in the top
  // elements.  This is a vector shuffle from the zero vector.
  if (N.getOpcode() == X86ISD::VZEXT_MOVL && N.getNode()->hasOneUse() &&
      // Check to see if the top elements are all zeros (or bitcast of zeros).
      N.getOperand(0).getOpcode() == ISD::SCALAR_TO_VECTOR &&
      N.getOperand(0).getNode()->hasOneUse() &&
      ISD::isNON_EXTLoad(N.getOperand(0).getOperand(0).getNode()) &&
      N.getOperand(0).getOperand(0).hasOneUse() &&
      IsProfitableToFold(N.getOperand(0), N.getNode(), Root) &&
      IsLegalToFold(N.getOperand(0), N.getNode(), Root, OptLevel)) {
    // Okay, this is a zero extending load.  Fold it.
    LoadSDNode *LD = cast<LoadSDNode>(N.getOperand(0).getOperand(0));
    if (!SelectAddr(LD, LD->getBasePtr(), Base, Scale, Index, Disp, Segment))
      return false;
    PatternNodeWithChain = SDValue(LD, 0);
    return true;
  }
  return false;
}


bool X86DAGToDAGISel::SelectMOV64Imm32(SDValue N, SDValue &Imm) {
  if (const ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N)) {
    uint64_t ImmVal = CN->getZExtValue();
    if ((uint32_t)ImmVal != (uint64_t)ImmVal)
      return false;

    Imm = CurDAG->getTargetConstant(ImmVal, MVT::i64);
    return true;
  }

  // In static codegen with small code model, we can get the address of a label
  // into a register with 'movl'. TableGen has already made sure we're looking
  // at a label of some kind.
  assert(N->getOpcode() == X86ISD::Wrapper &&
         "Unexpected node type for MOV32ri64");
  N = N.getOperand(0);

  if (N->getOpcode() != ISD::TargetConstantPool &&
      N->getOpcode() != ISD::TargetJumpTable &&
      N->getOpcode() != ISD::TargetGlobalAddress &&
      N->getOpcode() != ISD::TargetExternalSymbol &&
      N->getOpcode() != ISD::TargetBlockAddress)
    return false;

  Imm = N;
  return TM.getCodeModel() == CodeModel::Small;
}

bool X86DAGToDAGISel::SelectLEA64_32Addr(SDValue N, SDValue &Base,
                                         SDValue &Scale, SDValue &Index,
                                         SDValue &Disp, SDValue &Segment) {
  if (!SelectLEAAddr(N, Base, Scale, Index, Disp, Segment))
    return false;

  SDLoc DL(N);
  RegisterSDNode *RN = dyn_cast<RegisterSDNode>(Base);
  if (RN && RN->getReg() == 0)
    Base = CurDAG->getRegister(0, MVT::i64);
  else if (Base.getValueType() == MVT::i32 && !dyn_cast<FrameIndexSDNode>(Base)) {
    // Base could already be %rip, particularly in the x32 ABI.
    Base = SDValue(CurDAG->getMachineNode(
                       TargetOpcode::SUBREG_TO_REG, DL, MVT::i64,
                       CurDAG->getTargetConstant(0, MVT::i64),
                       Base,
                       CurDAG->getTargetConstant(X86::sub_32bit, MVT::i32)),
                   0);
  }

  RN = dyn_cast<RegisterSDNode>(Index);
  if (RN && RN->getReg() == 0)
    Index = CurDAG->getRegister(0, MVT::i64);
  else {
    assert(Index.getValueType() == MVT::i32 &&
           "Expect to be extending 32-bit registers for use in LEA");
    Index = SDValue(CurDAG->getMachineNode(
                        TargetOpcode::SUBREG_TO_REG, DL, MVT::i64,
                        CurDAG->getTargetConstant(0, MVT::i64),
                        Index,
                        CurDAG->getTargetConstant(X86::sub_32bit, MVT::i32)),
                    0);
  }

  return true;
}

/// SelectLEAAddr - it calls SelectAddr and determines if the maximal addressing
/// mode it matches can be cost effectively emitted as an LEA instruction.
bool X86DAGToDAGISel::SelectLEAAddr(SDValue N,
                                    SDValue &Base, SDValue &Scale,
                                    SDValue &Index, SDValue &Disp,
                                    SDValue &Segment) {
  X86ISelAddressMode AM;

  // Set AM.Segment to prevent MatchAddress from using one. LEA doesn't support
  // segments.
  SDValue Copy = AM.Segment;
  SDValue T = CurDAG->getRegister(0, MVT::i32);
  AM.Segment = T;
  if (MatchAddress(N, AM))
    return false;
  assert (T == AM.Segment);
  AM.Segment = Copy;

  MVT VT = N.getSimpleValueType();
  unsigned Complexity = 0;
  if (AM.BaseType == X86ISelAddressMode::RegBase)
    if (AM.Base_Reg.getNode())
      Complexity = 1;
    else
      AM.Base_Reg = CurDAG->getRegister(0, VT);
  else if (AM.BaseType == X86ISelAddressMode::FrameIndexBase)
    Complexity = 4;

  if (AM.IndexReg.getNode())
    Complexity++;
  else
    AM.IndexReg = CurDAG->getRegister(0, VT);

  // Don't match just leal(,%reg,2). It's cheaper to do addl %reg, %reg, or with
  // a simple shift.
  if (AM.Scale > 1)
    Complexity++;

  // FIXME: We are artificially lowering the criteria to turn ADD %reg, $GA
  // to a LEA. This is determined with some expermentation but is by no means
  // optimal (especially for code size consideration). LEA is nice because of
  // its three-address nature. Tweak the cost function again when we can run
  // convertToThreeAddress() at register allocation time.
  if (AM.hasSymbolicDisplacement()) {
    // For X86-64, we should always use lea to materialize RIP relative
    // addresses.
    if (Subtarget->is64Bit())
      Complexity = 4;
    else
      Complexity += 2;
  }

  if (AM.Disp && (AM.Base_Reg.getNode() || AM.IndexReg.getNode()))
    Complexity++;

  // If it isn't worth using an LEA, reject it.
  if (Complexity <= 2)
    return false;

  getAddressOperands(AM, Base, Scale, Index, Disp, Segment);
  return true;
}

/// SelectTLSADDRAddr - This is only run on TargetGlobalTLSAddress nodes.
bool X86DAGToDAGISel::SelectTLSADDRAddr(SDValue N, SDValue &Base,
                                        SDValue &Scale, SDValue &Index,
                                        SDValue &Disp, SDValue &Segment) {
  assert(N.getOpcode() == ISD::TargetGlobalTLSAddress);
  const GlobalAddressSDNode *GA = cast<GlobalAddressSDNode>(N);

  X86ISelAddressMode AM;
  AM.GV = GA->getGlobal();
  AM.Disp += GA->getOffset();
  AM.Base_Reg = CurDAG->getRegister(0, N.getValueType());
  AM.SymbolFlags = GA->getTargetFlags();

  if (N.getValueType() == MVT::i32) {
    AM.Scale = 1;
    AM.IndexReg = CurDAG->getRegister(X86::EBX, MVT::i32);
  } else {
    AM.IndexReg = CurDAG->getRegister(0, MVT::i64);
  }

  getAddressOperands(AM, Base, Scale, Index, Disp, Segment);
  return true;
}


bool X86DAGToDAGISel::TryFoldLoad(SDNode *P, SDValue N,
                                  SDValue &Base, SDValue &Scale,
                                  SDValue &Index, SDValue &Disp,
                                  SDValue &Segment) {
  if (!ISD::isNON_EXTLoad(N.getNode()) ||
      !IsProfitableToFold(N, P, P) ||
      !IsLegalToFold(N, P, P, OptLevel))
    return false;

  return SelectAddr(N.getNode(),
                    N.getOperand(1), Base, Scale, Index, Disp, Segment);
}

/// getGlobalBaseReg - Return an SDNode that returns the value of
/// the global base register. Output instructions required to
/// initialize the global base register, if necessary.
///
SDNode *X86DAGToDAGISel::getGlobalBaseReg() {
  unsigned GlobalBaseReg = getInstrInfo()->getGlobalBaseReg(MF);
  return CurDAG->getRegister(GlobalBaseReg,
                             getTargetLowering()->getPointerTy()).getNode();
}

/// Atomic opcode table
///
enum AtomicOpc {
  ADD,
  SUB,
  INC,
  DEC,
  OR,
  AND,
  XOR,
  AtomicOpcEnd
};

enum AtomicSz {
  ConstantI8,
  I8,
  SextConstantI16,
  ConstantI16,
  I16,
  SextConstantI32,
  ConstantI32,
  I32,
  SextConstantI64,
  ConstantI64,
  I64,
  AtomicSzEnd
};

static const uint16_t AtomicOpcTbl[AtomicOpcEnd][AtomicSzEnd] = {
  {
    X86::LOCK_ADD8mi,
    X86::LOCK_ADD8mr,
    X86::LOCK_ADD16mi8,
    X86::LOCK_ADD16mi,
    X86::LOCK_ADD16mr,
    X86::LOCK_ADD32mi8,
    X86::LOCK_ADD32mi,
    X86::LOCK_ADD32mr,
    X86::LOCK_ADD64mi8,
    X86::LOCK_ADD64mi32,
    X86::LOCK_ADD64mr,
  },
  {
    X86::LOCK_SUB8mi,
    X86::LOCK_SUB8mr,
    X86::LOCK_SUB16mi8,
    X86::LOCK_SUB16mi,
    X86::LOCK_SUB16mr,
    X86::LOCK_SUB32mi8,
    X86::LOCK_SUB32mi,
    X86::LOCK_SUB32mr,
    X86::LOCK_SUB64mi8,
    X86::LOCK_SUB64mi32,
    X86::LOCK_SUB64mr,
  },
  {
    0,
    X86::LOCK_INC8m,
    0,
    0,
    X86::LOCK_INC16m,
    0,
    0,
    X86::LOCK_INC32m,
    0,
    0,
    X86::LOCK_INC64m,
  },
  {
    0,
    X86::LOCK_DEC8m,
    0,
    0,
    X86::LOCK_DEC16m,
    0,
    0,
    X86::LOCK_DEC32m,
    0,
    0,
    X86::LOCK_DEC64m,
  },
  {
    X86::LOCK_OR8mi,
    X86::LOCK_OR8mr,
    X86::LOCK_OR16mi8,
    X86::LOCK_OR16mi,
    X86::LOCK_OR16mr,
    X86::LOCK_OR32mi8,
    X86::LOCK_OR32mi,
    X86::LOCK_OR32mr,
    X86::LOCK_OR64mi8,
    X86::LOCK_OR64mi32,
    X86::LOCK_OR64mr,
  },
  {
    X86::LOCK_AND8mi,
    X86::LOCK_AND8mr,
    X86::LOCK_AND16mi8,
    X86::LOCK_AND16mi,
    X86::LOCK_AND16mr,
    X86::LOCK_AND32mi8,
    X86::LOCK_AND32mi,
    X86::LOCK_AND32mr,
    X86::LOCK_AND64mi8,
    X86::LOCK_AND64mi32,
    X86::LOCK_AND64mr,
  },
  {
    X86::LOCK_XOR8mi,
    X86::LOCK_XOR8mr,
    X86::LOCK_XOR16mi8,
    X86::LOCK_XOR16mi,
    X86::LOCK_XOR16mr,
    X86::LOCK_XOR32mi8,
    X86::LOCK_XOR32mi,
    X86::LOCK_XOR32mr,
    X86::LOCK_XOR64mi8,
    X86::LOCK_XOR64mi32,
    X86::LOCK_XOR64mr,
  }
};

// Return the target constant operand for atomic-load-op and do simple
// translations, such as from atomic-load-add to lock-sub. The return value is
// one of the following 3 cases:
// + target-constant, the operand could be supported as a target constant.
// + empty, the operand is not needed any more with the new op selected.
// + non-empty, otherwise.
static SDValue getAtomicLoadArithTargetConstant(SelectionDAG *CurDAG,
                                                SDLoc dl,
                                                enum AtomicOpc &Op, MVT NVT,
                                                SDValue Val) {
  if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(Val)) {
    int64_t CNVal = CN->getSExtValue();
    // Quit if not 32-bit imm.
    if ((int32_t)CNVal != CNVal)
      return Val;
    // For atomic-load-add, we could do some optimizations.
    if (Op == ADD) {
      // Translate to INC/DEC if ADD by 1 or -1.
      if ((CNVal == 1) || (CNVal == -1)) {
        Op = (CNVal == 1) ? INC : DEC;
        // No more constant operand after being translated into INC/DEC.
        return SDValue();
      }
      // Translate to SUB if ADD by negative value.
      if (CNVal < 0) {
        Op = SUB;
        CNVal = -CNVal;
      }
    }
    return CurDAG->getTargetConstant(CNVal, NVT);
  }

  // If the value operand is single-used, try to optimize it.
  if (Op == ADD && Val.hasOneUse()) {
    // Translate (atomic-load-add ptr (sub 0 x)) back to (lock-sub x).
    if (Val.getOpcode() == ISD::SUB && X86::isZeroNode(Val.getOperand(0))) {
      Op = SUB;
      return Val.getOperand(1);
    }
    // A special case for i16, which needs truncating as, in most cases, it's
    // promoted to i32. We will translate
    // (atomic-load-add (truncate (sub 0 x))) to (lock-sub (EXTRACT_SUBREG x))
    if (Val.getOpcode() == ISD::TRUNCATE && NVT == MVT::i16 &&
        Val.getOperand(0).getOpcode() == ISD::SUB &&
        X86::isZeroNode(Val.getOperand(0).getOperand(0))) {
      Op = SUB;
      Val = Val.getOperand(0);
      return CurDAG->getTargetExtractSubreg(X86::sub_16bit, dl, NVT,
                                            Val.getOperand(1));
    }
  }

  return Val;
}

SDNode *X86DAGToDAGISel::SelectAtomicLoadArith(SDNode *Node, MVT NVT) {
  if (Node->hasAnyUseOfValue(0))
    return nullptr;

  SDLoc dl(Node);

  // Optimize common patterns for __sync_or_and_fetch and similar arith
  // operations where the result is not used. This allows us to use the "lock"
  // version of the arithmetic instruction.
  SDValue Chain = Node->getOperand(0);
  SDValue Ptr = Node->getOperand(1);
  SDValue Val = Node->getOperand(2);
  SDValue Base, Scale, Index, Disp, Segment;
  if (!SelectAddr(Node, Ptr, Base, Scale, Index, Disp, Segment))
    return nullptr;

  // Which index into the table.
  enum AtomicOpc Op;
  switch (Node->getOpcode()) {
    default:
      return nullptr;
    case ISD::ATOMIC_LOAD_OR:
      Op = OR;
      break;
    case ISD::ATOMIC_LOAD_AND:
      Op = AND;
      break;
    case ISD::ATOMIC_LOAD_XOR:
      Op = XOR;
      break;
    case ISD::ATOMIC_LOAD_ADD:
      Op = ADD;
      break;
  }

  Val = getAtomicLoadArithTargetConstant(CurDAG, dl, Op, NVT, Val);
  bool isUnOp = !Val.getNode();
  bool isCN = Val.getNode() && (Val.getOpcode() == ISD::TargetConstant);

  unsigned Opc = 0;
  switch (NVT.SimpleTy) {
    default: return nullptr;
    case MVT::i8:
      if (isCN)
        Opc = AtomicOpcTbl[Op][ConstantI8];
      else
        Opc = AtomicOpcTbl[Op][I8];
      break;
    case MVT::i16:
      if (isCN) {
        if (immSext8(Val.getNode()))
          Opc = AtomicOpcTbl[Op][SextConstantI16];
        else
          Opc = AtomicOpcTbl[Op][ConstantI16];
      } else
        Opc = AtomicOpcTbl[Op][I16];
      break;
    case MVT::i32:
      if (isCN) {
        if (immSext8(Val.getNode()))
          Opc = AtomicOpcTbl[Op][SextConstantI32];
        else
          Opc = AtomicOpcTbl[Op][ConstantI32];
      } else
        Opc = AtomicOpcTbl[Op][I32];
      break;
    case MVT::i64:
      if (isCN) {
        if (immSext8(Val.getNode()))
          Opc = AtomicOpcTbl[Op][SextConstantI64];
        else if (i64immSExt32(Val.getNode()))
          Opc = AtomicOpcTbl[Op][ConstantI64];
      } else
        Opc = AtomicOpcTbl[Op][I64];
      break;
  }

  assert(Opc != 0 && "Invalid arith lock transform!");

  // Building the new node.
  SDValue Ret;
  if (isUnOp) {
    SDValue Ops[] = { Base, Scale, Index, Disp, Segment, Chain };
    Ret = SDValue(CurDAG->getMachineNode(Opc, dl, MVT::Other, Ops), 0);
  } else {
    SDValue Ops[] = { Base, Scale, Index, Disp, Segment, Val, Chain };
    Ret = SDValue(CurDAG->getMachineNode(Opc, dl, MVT::Other, Ops), 0);
  }

  // Copying the MachineMemOperand.
  MachineSDNode::mmo_iterator MemOp = MF->allocateMemRefsArray(1);
  MemOp[0] = cast<MemSDNode>(Node)->getMemOperand();
  cast<MachineSDNode>(Ret)->setMemRefs(MemOp, MemOp + 1);

  // We need to have two outputs as that is what the original instruction had.
  // So we add a dummy, undefined output. This is safe as we checked first
  // that no-one uses our output anyway.
  SDValue Undef = SDValue(CurDAG->getMachineNode(TargetOpcode::IMPLICIT_DEF,
                                                 dl, NVT), 0);
  SDValue RetVals[] = { Undef, Ret };
  return CurDAG->getMergeValues(RetVals, dl).getNode();
}

/// HasNoSignedComparisonUses - Test whether the given X86ISD::CMP node has
/// any uses which require the SF or OF bits to be accurate.
static bool HasNoSignedComparisonUses(SDNode *N) {
  // Examine each user of the node.
  for (SDNode::use_iterator UI = N->use_begin(),
         UE = N->use_end(); UI != UE; ++UI) {
    // Only examine CopyToReg uses.
    if (UI->getOpcode() != ISD::CopyToReg)
      return false;
    // Only examine CopyToReg uses that copy to EFLAGS.
    if (cast<RegisterSDNode>(UI->getOperand(1))->getReg() !=
          X86::EFLAGS)
      return false;
    // Examine each user of the CopyToReg use.
    for (SDNode::use_iterator FlagUI = UI->use_begin(),
           FlagUE = UI->use_end(); FlagUI != FlagUE; ++FlagUI) {
      // Only examine the Flag result.
      if (FlagUI.getUse().getResNo() != 1) continue;
      // Anything unusual: assume conservatively.
      if (!FlagUI->isMachineOpcode()) return false;
      // Examine the opcode of the user.
      switch (FlagUI->getMachineOpcode()) {
      // These comparisons don't treat the most significant bit specially.
      case X86::SETAr: case X86::SETAEr: case X86::SETBr: case X86::SETBEr:
      case X86::SETEr: case X86::SETNEr: case X86::SETPr: case X86::SETNPr:
      case X86::SETAm: case X86::SETAEm: case X86::SETBm: case X86::SETBEm:
      case X86::SETEm: case X86::SETNEm: case X86::SETPm: case X86::SETNPm:
      case X86::JA_4: case X86::JAE_4: case X86::JB_4: case X86::JBE_4:
      case X86::JE_4: case X86::JNE_4: case X86::JP_4: case X86::JNP_4:
      case X86::CMOVA16rr: case X86::CMOVA16rm:
      case X86::CMOVA32rr: case X86::CMOVA32rm:
      case X86::CMOVA64rr: case X86::CMOVA64rm:
      case X86::CMOVAE16rr: case X86::CMOVAE16rm:
      case X86::CMOVAE32rr: case X86::CMOVAE32rm:
      case X86::CMOVAE64rr: case X86::CMOVAE64rm:
      case X86::CMOVB16rr: case X86::CMOVB16rm:
      case X86::CMOVB32rr: case X86::CMOVB32rm:
      case X86::CMOVB64rr: case X86::CMOVB64rm:
      case X86::CMOVBE16rr: case X86::CMOVBE16rm:
      case X86::CMOVBE32rr: case X86::CMOVBE32rm:
      case X86::CMOVBE64rr: case X86::CMOVBE64rm:
      case X86::CMOVE16rr: case X86::CMOVE16rm:
      case X86::CMOVE32rr: case X86::CMOVE32rm:
      case X86::CMOVE64rr: case X86::CMOVE64rm:
      case X86::CMOVNE16rr: case X86::CMOVNE16rm:
      case X86::CMOVNE32rr: case X86::CMOVNE32rm:
      case X86::CMOVNE64rr: case X86::CMOVNE64rm:
      case X86::CMOVNP16rr: case X86::CMOVNP16rm:
      case X86::CMOVNP32rr: case X86::CMOVNP32rm:
      case X86::CMOVNP64rr: case X86::CMOVNP64rm:
      case X86::CMOVP16rr: case X86::CMOVP16rm:
      case X86::CMOVP32rr: case X86::CMOVP32rm:
      case X86::CMOVP64rr: case X86::CMOVP64rm:
        continue;
      // Anything else: assume conservatively.
      default: return false;
      }
    }
  }
  return true;
}

/// isLoadIncOrDecStore - Check whether or not the chain ending in StoreNode
/// is suitable for doing the {load; increment or decrement; store} to modify
/// transformation.
static bool isLoadIncOrDecStore(StoreSDNode *StoreNode, unsigned Opc,
                                SDValue StoredVal, SelectionDAG *CurDAG,
                                LoadSDNode* &LoadNode, SDValue &InputChain) {

  // is the value stored the result of a DEC or INC?
  if (!(Opc == X86ISD::DEC || Opc == X86ISD::INC)) return false;

  // is the stored value result 0 of the load?
  if (StoredVal.getResNo() != 0) return false;

  // are there other uses of the loaded value than the inc or dec?
  if (!StoredVal.getNode()->hasNUsesOfValue(1, 0)) return false;

  // is the store non-extending and non-indexed?
  if (!ISD::isNormalStore(StoreNode) || StoreNode->isNonTemporal())
    return false;

  SDValue Load = StoredVal->getOperand(0);
  // Is the stored value a non-extending and non-indexed load?
  if (!ISD::isNormalLoad(Load.getNode())) return false;

  // Return LoadNode by reference.
  LoadNode = cast<LoadSDNode>(Load);
  // is the size of the value one that we can handle? (i.e. 64, 32, 16, or 8)
  EVT LdVT = LoadNode->getMemoryVT();
  if (LdVT != MVT::i64 && LdVT != MVT::i32 && LdVT != MVT::i16 &&
      LdVT != MVT::i8)
    return false;

  // Is store the only read of the loaded value?
  if (!Load.hasOneUse())
    return false;

  // Is the address of the store the same as the load?
  if (LoadNode->getBasePtr() != StoreNode->getBasePtr() ||
      LoadNode->getOffset() != StoreNode->getOffset())
    return false;

  // Check if the chain is produced by the load or is a TokenFactor with
  // the load output chain as an operand. Return InputChain by reference.
  SDValue Chain = StoreNode->getChain();

  bool ChainCheck = false;
  if (Chain == Load.getValue(1)) {
    ChainCheck = true;
    InputChain = LoadNode->getChain();
  } else if (Chain.getOpcode() == ISD::TokenFactor) {
    SmallVector<SDValue, 4> ChainOps;
    for (unsigned i = 0, e = Chain.getNumOperands(); i != e; ++i) {
      SDValue Op = Chain.getOperand(i);
      if (Op == Load.getValue(1)) {
        ChainCheck = true;
        continue;
      }

      // Make sure using Op as part of the chain would not cause a cycle here.
      // In theory, we could check whether the chain node is a predecessor of
      // the load. But that can be very expensive. Instead visit the uses and
      // make sure they all have smaller node id than the load.
      int LoadId = LoadNode->getNodeId();
      for (SDNode::use_iterator UI = Op.getNode()->use_begin(),
             UE = UI->use_end(); UI != UE; ++UI) {
        if (UI.getUse().getResNo() != 0)
          continue;
        if (UI->getNodeId() > LoadId)
          return false;
      }

      ChainOps.push_back(Op);
    }

    if (ChainCheck)
      // Make a new TokenFactor with all the other input chains except
      // for the load.
      InputChain = CurDAG->getNode(ISD::TokenFactor, SDLoc(Chain),
                                   MVT::Other, ChainOps);
  }
  if (!ChainCheck)
    return false;

  return true;
}

/// getFusedLdStOpcode - Get the appropriate X86 opcode for an in memory
/// increment or decrement. Opc should be X86ISD::DEC or X86ISD::INC.
static unsigned getFusedLdStOpcode(EVT &LdVT, unsigned Opc) {
  if (Opc == X86ISD::DEC) {
    if (LdVT == MVT::i64) return X86::DEC64m;
    if (LdVT == MVT::i32) return X86::DEC32m;
    if (LdVT == MVT::i16) return X86::DEC16m;
    if (LdVT == MVT::i8)  return X86::DEC8m;
  } else {
    assert(Opc == X86ISD::INC && "unrecognized opcode");
    if (LdVT == MVT::i64) return X86::INC64m;
    if (LdVT == MVT::i32) return X86::INC32m;
    if (LdVT == MVT::i16) return X86::INC16m;
    if (LdVT == MVT::i8)  return X86::INC8m;
  }
  llvm_unreachable("unrecognized size for LdVT");
}

/// SelectGather - Customized ISel for GATHER operations.
///
SDNode *X86DAGToDAGISel::SelectGather(SDNode *Node, unsigned Opc) {
  // Operands of Gather: VSrc, Base, VIdx, VMask, Scale
  SDValue Chain = Node->getOperand(0);
  SDValue VSrc = Node->getOperand(2);
  SDValue Base = Node->getOperand(3);
  SDValue VIdx = Node->getOperand(4);
  SDValue VMask = Node->getOperand(5);
  ConstantSDNode *Scale = dyn_cast<ConstantSDNode>(Node->getOperand(6));
  if (!Scale)
    return nullptr;

  SDVTList VTs = CurDAG->getVTList(VSrc.getValueType(), VSrc.getValueType(),
                                   MVT::Other);

  // Memory Operands: Base, Scale, Index, Disp, Segment
  SDValue Disp = CurDAG->getTargetConstant(0, MVT::i32);
  SDValue Segment = CurDAG->getRegister(0, MVT::i32);
  const SDValue Ops[] = { VSrc, Base, getI8Imm(Scale->getSExtValue()), VIdx,
                          Disp, Segment, VMask, Chain};
  SDNode *ResNode = CurDAG->getMachineNode(Opc, SDLoc(Node), VTs, Ops);
  // Node has 2 outputs: VDst and MVT::Other.
  // ResNode has 3 outputs: VDst, VMask_wb, and MVT::Other.
  // We replace VDst of Node with VDst of ResNode, and Other of Node with Other
  // of ResNode.
  ReplaceUses(SDValue(Node, 0), SDValue(ResNode, 0));
  ReplaceUses(SDValue(Node, 1), SDValue(ResNode, 2));
  return ResNode;
}

SDNode *X86DAGToDAGISel::Select(SDNode *Node) {
  MVT NVT = Node->getSimpleValueType(0);
  unsigned Opc, MOpc;
  unsigned Opcode = Node->getOpcode();
  SDLoc dl(Node);

  DEBUG(dbgs() << "Selecting: "; Node->dump(CurDAG); dbgs() << '\n');

  if (Node->isMachineOpcode()) {
    DEBUG(dbgs() << "== ";  Node->dump(CurDAG); dbgs() << '\n');
    Node->setNodeId(-1);
    return nullptr;   // Already selected.
  }

  switch (Opcode) {
  default: break;
  case ISD::INTRINSIC_W_CHAIN: {
    unsigned IntNo = cast<ConstantSDNode>(Node->getOperand(1))->getZExtValue();
    switch (IntNo) {
    default: break;
    case Intrinsic::x86_avx2_gather_d_pd:
    case Intrinsic::x86_avx2_gather_d_pd_256:
    case Intrinsic::x86_avx2_gather_q_pd:
    case Intrinsic::x86_avx2_gather_q_pd_256:
    case Intrinsic::x86_avx2_gather_d_ps:
    case Intrinsic::x86_avx2_gather_d_ps_256:
    case Intrinsic::x86_avx2_gather_q_ps:
    case Intrinsic::x86_avx2_gather_q_ps_256:
    case Intrinsic::x86_avx2_gather_d_q:
    case Intrinsic::x86_avx2_gather_d_q_256:
    case Intrinsic::x86_avx2_gather_q_q:
    case Intrinsic::x86_avx2_gather_q_q_256:
    case Intrinsic::x86_avx2_gather_d_d:
    case Intrinsic::x86_avx2_gather_d_d_256:
    case Intrinsic::x86_avx2_gather_q_d:
    case Intrinsic::x86_avx2_gather_q_d_256: {
      if (!Subtarget->hasAVX2())
        break;
      unsigned Opc;
      switch (IntNo) {
      default: llvm_unreachable("Impossible intrinsic");
      case Intrinsic::x86_avx2_gather_d_pd:     Opc = X86::VGATHERDPDrm;  break;
      case Intrinsic::x86_avx2_gather_d_pd_256: Opc = X86::VGATHERDPDYrm; break;
      case Intrinsic::x86_avx2_gather_q_pd:     Opc = X86::VGATHERQPDrm;  break;
      case Intrinsic::x86_avx2_gather_q_pd_256: Opc = X86::VGATHERQPDYrm; break;
      case Intrinsic::x86_avx2_gather_d_ps:     Opc = X86::VGATHERDPSrm;  break;
      case Intrinsic::x86_avx2_gather_d_ps_256: Opc = X86::VGATHERDPSYrm; break;
      case Intrinsic::x86_avx2_gather_q_ps:     Opc = X86::VGATHERQPSrm;  break;
      case Intrinsic::x86_avx2_gather_q_ps_256: Opc = X86::VGATHERQPSYrm; break;
      case Intrinsic::x86_avx2_gather_d_q:      Opc = X86::VPGATHERDQrm;  break;
      case Intrinsic::x86_avx2_gather_d_q_256:  Opc = X86::VPGATHERDQYrm; break;
      case Intrinsic::x86_avx2_gather_q_q:      Opc = X86::VPGATHERQQrm;  break;
      case Intrinsic::x86_avx2_gather_q_q_256:  Opc = X86::VPGATHERQQYrm; break;
      case Intrinsic::x86_avx2_gather_d_d:      Opc = X86::VPGATHERDDrm;  break;
      case Intrinsic::x86_avx2_gather_d_d_256:  Opc = X86::VPGATHERDDYrm; break;
      case Intrinsic::x86_avx2_gather_q_d:      Opc = X86::VPGATHERQDrm;  break;
      case Intrinsic::x86_avx2_gather_q_d_256:  Opc = X86::VPGATHERQDYrm; break;
      }
      SDNode *RetVal = SelectGather(Node, Opc);
      if (RetVal)
        // We already called ReplaceUses inside SelectGather.
        return nullptr;
      break;
    }
    }
    break;
  }
  case X86ISD::GlobalBaseReg:
    return getGlobalBaseReg();


  case ISD::ATOMIC_LOAD_XOR:
  case ISD::ATOMIC_LOAD_AND:
  case ISD::ATOMIC_LOAD_OR:
  case ISD::ATOMIC_LOAD_ADD: {
    SDNode *RetVal = SelectAtomicLoadArith(Node, NVT);
    if (RetVal)
      return RetVal;
    break;
  }
  case ISD::AND:
  case ISD::OR:
  case ISD::XOR: {
    // For operations of the form (x << C1) op C2, check if we can use a smaller
    // encoding for C2 by transforming it into (x op (C2>>C1)) << C1.
    SDValue N0 = Node->getOperand(0);
    SDValue N1 = Node->getOperand(1);

    if (N0->getOpcode() != ISD::SHL || !N0->hasOneUse())
      break;

    // i8 is unshrinkable, i16 should be promoted to i32.
    if (NVT != MVT::i32 && NVT != MVT::i64)
      break;

    ConstantSDNode *Cst = dyn_cast<ConstantSDNode>(N1);
    ConstantSDNode *ShlCst = dyn_cast<ConstantSDNode>(N0->getOperand(1));
    if (!Cst || !ShlCst)
      break;

    int64_t Val = Cst->getSExtValue();
    uint64_t ShlVal = ShlCst->getZExtValue();

    // Make sure that we don't change the operation by removing bits.
    // This only matters for OR and XOR, AND is unaffected.
    uint64_t RemovedBitsMask = (1ULL << ShlVal) - 1;
    if (Opcode != ISD::AND && (Val & RemovedBitsMask) != 0)
      break;

    unsigned ShlOp, Op;
    MVT CstVT = NVT;

    // Check the minimum bitwidth for the new constant.
    // TODO: AND32ri is the same as AND64ri32 with zext imm.
    // TODO: MOV32ri+OR64r is cheaper than MOV64ri64+OR64rr
    // TODO: Using 16 and 8 bit operations is also possible for or32 & xor32.
    if (!isInt<8>(Val) && isInt<8>(Val >> ShlVal))
      CstVT = MVT::i8;
    else if (!isInt<32>(Val) && isInt<32>(Val >> ShlVal))
      CstVT = MVT::i32;

    // Bail if there is no smaller encoding.
    if (NVT == CstVT)
      break;

    switch (NVT.SimpleTy) {
    default: llvm_unreachable("Unsupported VT!");
    case MVT::i32:
      assert(CstVT == MVT::i8);
      ShlOp = X86::SHL32ri;

      switch (Opcode) {
      default: llvm_unreachable("Impossible opcode");
      case ISD::AND: Op = X86::AND32ri8; break;
      case ISD::OR:  Op =  X86::OR32ri8; break;
      case ISD::XOR: Op = X86::XOR32ri8; break;
      }
      break;
    case MVT::i64:
      assert(CstVT == MVT::i8 || CstVT == MVT::i32);
      ShlOp = X86::SHL64ri;

      switch (Opcode) {
      default: llvm_unreachable("Impossible opcode");
      case ISD::AND: Op = CstVT==MVT::i8? X86::AND64ri8 : X86::AND64ri32; break;
      case ISD::OR:  Op = CstVT==MVT::i8?  X86::OR64ri8 :  X86::OR64ri32; break;
      case ISD::XOR: Op = CstVT==MVT::i8? X86::XOR64ri8 : X86::XOR64ri32; break;
      }
      break;
    }

    // Emit the smaller op and the shift.
    SDValue NewCst = CurDAG->getTargetConstant(Val >> ShlVal, CstVT);
    SDNode *New = CurDAG->getMachineNode(Op, dl, NVT, N0->getOperand(0),NewCst);
    return CurDAG->SelectNodeTo(Node, ShlOp, NVT, SDValue(New, 0),
                                getI8Imm(ShlVal));
  }
  case X86ISD::UMUL: {
    SDValue N0 = Node->getOperand(0);
    SDValue N1 = Node->getOperand(1);

    unsigned LoReg;
    switch (NVT.SimpleTy) {
    default: llvm_unreachable("Unsupported VT!");
    case MVT::i8:  LoReg = X86::AL;  Opc = X86::MUL8r; break;
    case MVT::i16: LoReg = X86::AX;  Opc = X86::MUL16r; break;
    case MVT::i32: LoReg = X86::EAX; Opc = X86::MUL32r; break;
    case MVT::i64: LoReg = X86::RAX; Opc = X86::MUL64r; break;
    }

    SDValue InFlag = CurDAG->getCopyToReg(CurDAG->getEntryNode(), dl, LoReg,
                                          N0, SDValue()).getValue(1);

    SDVTList VTs = CurDAG->getVTList(NVT, NVT, MVT::i32);
    SDValue Ops[] = {N1, InFlag};
    SDNode *CNode = CurDAG->getMachineNode(Opc, dl, VTs, Ops);

    ReplaceUses(SDValue(Node, 0), SDValue(CNode, 0));
    ReplaceUses(SDValue(Node, 1), SDValue(CNode, 1));
    ReplaceUses(SDValue(Node, 2), SDValue(CNode, 2));
    return nullptr;
  }

  case ISD::SMUL_LOHI:
  case ISD::UMUL_LOHI: {
    SDValue N0 = Node->getOperand(0);
    SDValue N1 = Node->getOperand(1);

    bool isSigned = Opcode == ISD::SMUL_LOHI;
    bool hasBMI2 = Subtarget->hasBMI2();
    if (!isSigned) {
      switch (NVT.SimpleTy) {
      default: llvm_unreachable("Unsupported VT!");
      case MVT::i8:  Opc = X86::MUL8r;  MOpc = X86::MUL8m;  break;
      case MVT::i16: Opc = X86::MUL16r; MOpc = X86::MUL16m; break;
      case MVT::i32: Opc = hasBMI2 ? X86::MULX32rr : X86::MUL32r;
                     MOpc = hasBMI2 ? X86::MULX32rm : X86::MUL32m; break;
      case MVT::i64: Opc = hasBMI2 ? X86::MULX64rr : X86::MUL64r;
                     MOpc = hasBMI2 ? X86::MULX64rm : X86::MUL64m; break;
      }
    } else {
      switch (NVT.SimpleTy) {
      default: llvm_unreachable("Unsupported VT!");
      case MVT::i8:  Opc = X86::IMUL8r;  MOpc = X86::IMUL8m;  break;
      case MVT::i16: Opc = X86::IMUL16r; MOpc = X86::IMUL16m; break;
      case MVT::i32: Opc = X86::IMUL32r; MOpc = X86::IMUL32m; break;
      case MVT::i64: Opc = X86::IMUL64r; MOpc = X86::IMUL64m; break;
      }
    }

    unsigned SrcReg, LoReg, HiReg;
    switch (Opc) {
    default: llvm_unreachable("Unknown MUL opcode!");
    case X86::IMUL8r:
    case X86::MUL8r:
      SrcReg = LoReg = X86::AL; HiReg = X86::AH;
      break;
    case X86::IMUL16r:
    case X86::MUL16r:
      SrcReg = LoReg = X86::AX; HiReg = X86::DX;
      break;
    case X86::IMUL32r:
    case X86::MUL32r:
      SrcReg = LoReg = X86::EAX; HiReg = X86::EDX;
      break;
    case X86::IMUL64r:
    case X86::MUL64r:
      SrcReg = LoReg = X86::RAX; HiReg = X86::RDX;
      break;
    case X86::MULX32rr:
      SrcReg = X86::EDX; LoReg = HiReg = 0;
      break;
    case X86::MULX64rr:
      SrcReg = X86::RDX; LoReg = HiReg = 0;
      break;
    }

    SDValue Tmp0, Tmp1, Tmp2, Tmp3, Tmp4;
    bool foldedLoad = TryFoldLoad(Node, N1, Tmp0, Tmp1, Tmp2, Tmp3, Tmp4);
    // Multiply is commmutative.
    if (!foldedLoad) {
      foldedLoad = TryFoldLoad(Node, N0, Tmp0, Tmp1, Tmp2, Tmp3, Tmp4);
      if (foldedLoad)
        std::swap(N0, N1);
    }

    SDValue InFlag = CurDAG->getCopyToReg(CurDAG->getEntryNode(), dl, SrcReg,
                                          N0, SDValue()).getValue(1);
    SDValue ResHi, ResLo;

    if (foldedLoad) {
      SDValue Chain;
      SDValue Ops[] = { Tmp0, Tmp1, Tmp2, Tmp3, Tmp4, N1.getOperand(0),
                        InFlag };
      if (MOpc == X86::MULX32rm || MOpc == X86::MULX64rm) {
        SDVTList VTs = CurDAG->getVTList(NVT, NVT, MVT::Other, MVT::Glue);
        SDNode *CNode = CurDAG->getMachineNode(MOpc, dl, VTs, Ops);
        ResHi = SDValue(CNode, 0);
        ResLo = SDValue(CNode, 1);
        Chain = SDValue(CNode, 2);
        InFlag = SDValue(CNode, 3);
      } else {
        SDVTList VTs = CurDAG->getVTList(MVT::Other, MVT::Glue);
        SDNode *CNode = CurDAG->getMachineNode(MOpc, dl, VTs, Ops);
        Chain = SDValue(CNode, 0);
        InFlag = SDValue(CNode, 1);
      }

      // Update the chain.
      ReplaceUses(N1.getValue(1), Chain);
    } else {
      SDValue Ops[] = { N1, InFlag };
      if (Opc == X86::MULX32rr || Opc == X86::MULX64rr) {
        SDVTList VTs = CurDAG->getVTList(NVT, NVT, MVT::Glue);
        SDNode *CNode = CurDAG->getMachineNode(Opc, dl, VTs, Ops);
        ResHi = SDValue(CNode, 0);
        ResLo = SDValue(CNode, 1);
        InFlag = SDValue(CNode, 2);
      } else {
        SDVTList VTs = CurDAG->getVTList(MVT::Glue);
        SDNode *CNode = CurDAG->getMachineNode(Opc, dl, VTs, Ops);
        InFlag = SDValue(CNode, 0);
      }
    }

    // Prevent use of AH in a REX instruction by referencing AX instead.
    if (HiReg == X86::AH && Subtarget->is64Bit() &&
        !SDValue(Node, 1).use_empty()) {
      SDValue Result = CurDAG->getCopyFromReg(CurDAG->getEntryNode(), dl,
                                              X86::AX, MVT::i16, InFlag);
      InFlag = Result.getValue(2);
      // Get the low part if needed. Don't use getCopyFromReg for aliasing
      // registers.
      if (!SDValue(Node, 0).use_empty())
        ReplaceUses(SDValue(Node, 1),
          CurDAG->getTargetExtractSubreg(X86::sub_8bit, dl, MVT::i8, Result));

      // Shift AX down 8 bits.
      Result = SDValue(CurDAG->getMachineNode(X86::SHR16ri, dl, MVT::i16,
                                              Result,
                                     CurDAG->getTargetConstant(8, MVT::i8)), 0);
      // Then truncate it down to i8.
      ReplaceUses(SDValue(Node, 1),
        CurDAG->getTargetExtractSubreg(X86::sub_8bit, dl, MVT::i8, Result));
    }
    // Copy the low half of the result, if it is needed.
    if (!SDValue(Node, 0).use_empty()) {
      if (!ResLo.getNode()) {
        assert(LoReg && "Register for low half is not defined!");
        ResLo = CurDAG->getCopyFromReg(CurDAG->getEntryNode(), dl, LoReg, NVT,
                                       InFlag);
        InFlag = ResLo.getValue(2);
      }
      ReplaceUses(SDValue(Node, 0), ResLo);
      DEBUG(dbgs() << "=> "; ResLo.getNode()->dump(CurDAG); dbgs() << '\n');
    }
    // Copy the high half of the result, if it is needed.
    if (!SDValue(Node, 1).use_empty()) {
      if (!ResHi.getNode()) {
        assert(HiReg && "Register for high half is not defined!");
        ResHi = CurDAG->getCopyFromReg(CurDAG->getEntryNode(), dl, HiReg, NVT,
                                       InFlag);
        InFlag = ResHi.getValue(2);
      }
      ReplaceUses(SDValue(Node, 1), ResHi);
      DEBUG(dbgs() << "=> "; ResHi.getNode()->dump(CurDAG); dbgs() << '\n');
    }

    return nullptr;
  }

  case ISD::SDIVREM:
  case ISD::UDIVREM: {
    SDValue N0 = Node->getOperand(0);
    SDValue N1 = Node->getOperand(1);

    bool isSigned = Opcode == ISD::SDIVREM;
    if (!isSigned) {
      switch (NVT.SimpleTy) {
      default: llvm_unreachable("Unsupported VT!");
      case MVT::i8:  Opc = X86::DIV8r;  MOpc = X86::DIV8m;  break;
      case MVT::i16: Opc = X86::DIV16r; MOpc = X86::DIV16m; break;
      case MVT::i32: Opc = X86::DIV32r; MOpc = X86::DIV32m; break;
      case MVT::i64: Opc = X86::DIV64r; MOpc = X86::DIV64m; break;
      }
    } else {
      switch (NVT.SimpleTy) {
      default: llvm_unreachable("Unsupported VT!");
      case MVT::i8:  Opc = X86::IDIV8r;  MOpc = X86::IDIV8m;  break;
      case MVT::i16: Opc = X86::IDIV16r; MOpc = X86::IDIV16m; break;
      case MVT::i32: Opc = X86::IDIV32r; MOpc = X86::IDIV32m; break;
      case MVT::i64: Opc = X86::IDIV64r; MOpc = X86::IDIV64m; break;
      }
    }

    unsigned LoReg, HiReg, ClrReg;
    unsigned SExtOpcode;
    switch (NVT.SimpleTy) {
    default: llvm_unreachable("Unsupported VT!");
    case MVT::i8:
      LoReg = X86::AL;  ClrReg = HiReg = X86::AH;
      SExtOpcode = X86::CBW;
      break;
    case MVT::i16:
      LoReg = X86::AX;  HiReg = X86::DX;
      ClrReg = X86::DX;
      SExtOpcode = X86::CWD;
      break;
    case MVT::i32:
      LoReg = X86::EAX; ClrReg = HiReg = X86::EDX;
      SExtOpcode = X86::CDQ;
      break;
    case MVT::i64:
      LoReg = X86::RAX; ClrReg = HiReg = X86::RDX;
      SExtOpcode = X86::CQO;
      break;
    }

    SDValue Tmp0, Tmp1, Tmp2, Tmp3, Tmp4;
    bool foldedLoad = TryFoldLoad(Node, N1, Tmp0, Tmp1, Tmp2, Tmp3, Tmp4);
    bool signBitIsZero = CurDAG->SignBitIsZero(N0);

    SDValue InFlag;
    if (NVT == MVT::i8 && (!isSigned || signBitIsZero)) {
      // Special case for div8, just use a move with zero extension to AX to
      // clear the upper 8 bits (AH).
      SDValue Tmp0, Tmp1, Tmp2, Tmp3, Tmp4, Move, Chain;
      if (TryFoldLoad(Node, N0, Tmp0, Tmp1, Tmp2, Tmp3, Tmp4)) {
        SDValue Ops[] = { Tmp0, Tmp1, Tmp2, Tmp3, Tmp4, N0.getOperand(0) };
        Move =
          SDValue(CurDAG->getMachineNode(X86::MOVZX32rm8, dl, MVT::i32,
                                         MVT::Other, Ops), 0);
        Chain = Move.getValue(1);
        ReplaceUses(N0.getValue(1), Chain);
      } else {
        Move =
          SDValue(CurDAG->getMachineNode(X86::MOVZX32rr8, dl, MVT::i32, N0),0);
        Chain = CurDAG->getEntryNode();
      }
      Chain  = CurDAG->getCopyToReg(Chain, dl, X86::EAX, Move, SDValue());
      InFlag = Chain.getValue(1);
    } else {
      InFlag =
        CurDAG->getCopyToReg(CurDAG->getEntryNode(), dl,
                             LoReg, N0, SDValue()).getValue(1);
      if (isSigned && !signBitIsZero) {
        // Sign extend the low part into the high part.
        InFlag =
          SDValue(CurDAG->getMachineNode(SExtOpcode, dl, MVT::Glue, InFlag),0);
      } else {
        // Zero out the high part, effectively zero extending the input.
        SDValue ClrNode = SDValue(CurDAG->getMachineNode(X86::MOV32r0, dl, NVT), 0);       
        switch (NVT.SimpleTy) {
        case MVT::i16:
          ClrNode =
              SDValue(CurDAG->getMachineNode(
                          TargetOpcode::EXTRACT_SUBREG, dl, MVT::i16, ClrNode,
                          CurDAG->getTargetConstant(X86::sub_16bit, MVT::i32)),
                      0);
          break;
        case MVT::i32:
          break;
        case MVT::i64:
          ClrNode =
              SDValue(CurDAG->getMachineNode(
                          TargetOpcode::SUBREG_TO_REG, dl, MVT::i64,
                          CurDAG->getTargetConstant(0, MVT::i64), ClrNode,
                          CurDAG->getTargetConstant(X86::sub_32bit, MVT::i32)),
                      0);
          break;
        default:
          llvm_unreachable("Unexpected division source");
        }

        InFlag = CurDAG->getCopyToReg(CurDAG->getEntryNode(), dl, ClrReg,
                                      ClrNode, InFlag).getValue(1);
      }
    }

    if (foldedLoad) {
      SDValue Ops[] = { Tmp0, Tmp1, Tmp2, Tmp3, Tmp4, N1.getOperand(0),
                        InFlag };
      SDNode *CNode =
        CurDAG->getMachineNode(MOpc, dl, MVT::Other, MVT::Glue, Ops);
      InFlag = SDValue(CNode, 1);
      // Update the chain.
      ReplaceUses(N1.getValue(1), SDValue(CNode, 0));
    } else {
      InFlag =
        SDValue(CurDAG->getMachineNode(Opc, dl, MVT::Glue, N1, InFlag), 0);
    }

    // Prevent use of AH in a REX instruction by referencing AX instead.
    // Shift it down 8 bits.
    //
    // The current assumption of the register allocator is that isel
    // won't generate explicit references to the GPR8_NOREX registers. If
    // the allocator and/or the backend get enhanced to be more robust in
    // that regard, this can be, and should be, removed.
    if (HiReg == X86::AH && Subtarget->is64Bit() &&
        !SDValue(Node, 1).use_empty()) {
      SDValue Result = CurDAG->getCopyFromReg(CurDAG->getEntryNode(), dl,
                                              X86::AX, MVT::i16, InFlag);
      InFlag = Result.getValue(2);

      // If we also need AL (the quotient), get it by extracting a subreg from
      // Result. The fast register allocator does not like multiple CopyFromReg
      // nodes using aliasing registers.
      if (!SDValue(Node, 0).use_empty())
        ReplaceUses(SDValue(Node, 0),
          CurDAG->getTargetExtractSubreg(X86::sub_8bit, dl, MVT::i8, Result));

      // Shift AX right by 8 bits instead of using AH.
      Result = SDValue(CurDAG->getMachineNode(X86::SHR16ri, dl, MVT::i16,
                                         Result,
                                         CurDAG->getTargetConstant(8, MVT::i8)),
                       0);
      ReplaceUses(SDValue(Node, 1),
        CurDAG->getTargetExtractSubreg(X86::sub_8bit, dl, MVT::i8, Result));
    }
    // Copy the division (low) result, if it is needed.
    if (!SDValue(Node, 0).use_empty()) {
      SDValue Result = CurDAG->getCopyFromReg(CurDAG->getEntryNode(), dl,
                                                LoReg, NVT, InFlag);
      InFlag = Result.getValue(2);
      ReplaceUses(SDValue(Node, 0), Result);
      DEBUG(dbgs() << "=> "; Result.getNode()->dump(CurDAG); dbgs() << '\n');
    }
    // Copy the remainder (high) result, if it is needed.
    if (!SDValue(Node, 1).use_empty()) {
      SDValue Result = CurDAG->getCopyFromReg(CurDAG->getEntryNode(), dl,
                                              HiReg, NVT, InFlag);
      InFlag = Result.getValue(2);
      ReplaceUses(SDValue(Node, 1), Result);
      DEBUG(dbgs() << "=> "; Result.getNode()->dump(CurDAG); dbgs() << '\n');
    }
    return nullptr;
  }

  case X86ISD::CMP:
  case X86ISD::SUB: {
    // Sometimes a SUB is used to perform comparison.
    if (Opcode == X86ISD::SUB && Node->hasAnyUseOfValue(0))
      // This node is not a CMP.
      break;
    SDValue N0 = Node->getOperand(0);
    SDValue N1 = Node->getOperand(1);

    if (N0.getOpcode() == ISD::TRUNCATE && N0.hasOneUse() &&
        HasNoSignedComparisonUses(Node)) {
      // Look for (X86cmp (truncate $op, i1), 0) and try to convert to a
      // smaller encoding
      if (Opcode == X86ISD::CMP && N0.getValueType() == MVT::i1 &&
          X86::isZeroNode(N1)) {
        SDValue Reg = N0.getOperand(0);
        SDValue Imm = CurDAG->getTargetConstant(1, MVT::i8);

        // Emit testb
        if (Reg.getScalarValueSizeInBits() > 8)
          Reg = CurDAG->getTargetExtractSubreg(X86::sub_8bit, dl, MVT::i8, Reg);
        // Emit a testb.
        SDNode *NewNode = CurDAG->getMachineNode(X86::TEST8ri, dl, MVT::i32,
                                                Reg, Imm);
        ReplaceUses(SDValue(Node, 0), SDValue(NewNode, 0));
        return nullptr;
      }

      N0 = N0.getOperand(0);
    }
    // Look for (X86cmp (and $op, $imm), 0) and see if we can convert it to
    // use a smaller encoding.
    // Look past the truncate if CMP is the only use of it.
    if ((N0.getNode()->getOpcode() == ISD::AND ||
         (N0.getResNo() == 0 && N0.getNode()->getOpcode() == X86ISD::AND)) &&
        N0.getNode()->hasOneUse() &&
        N0.getValueType() != MVT::i8 &&
        X86::isZeroNode(N1)) {
      ConstantSDNode *C = dyn_cast<ConstantSDNode>(N0.getNode()->getOperand(1));
      if (!C) break;

      // For example, convert "testl %eax, $8" to "testb %al, $8"
      if ((C->getZExtValue() & ~UINT64_C(0xff)) == 0 &&
          (!(C->getZExtValue() & 0x80) ||
           HasNoSignedComparisonUses(Node))) {
        SDValue Imm = CurDAG->getTargetConstant(C->getZExtValue(), MVT::i8);
        SDValue Reg = N0.getNode()->getOperand(0);

        // On x86-32, only the ABCD registers have 8-bit subregisters.
        if (!Subtarget->is64Bit()) {
          const TargetRegisterClass *TRC;
          switch (N0.getSimpleValueType().SimpleTy) {
          case MVT::i32: TRC = &X86::GR32_ABCDRegClass; break;
          case MVT::i16: TRC = &X86::GR16_ABCDRegClass; break;
          default: llvm_unreachable("Unsupported TEST operand type!");
          }
          SDValue RC = CurDAG->getTargetConstant(TRC->getID(), MVT::i32);
          Reg = SDValue(CurDAG->getMachineNode(X86::COPY_TO_REGCLASS, dl,
                                               Reg.getValueType(), Reg, RC), 0);
        }

        // Extract the l-register.
        SDValue Subreg = CurDAG->getTargetExtractSubreg(X86::sub_8bit, dl,
                                                        MVT::i8, Reg);

        // Emit a testb.
        SDNode *NewNode = CurDAG->getMachineNode(X86::TEST8ri, dl, MVT::i32,
                                                 Subreg, Imm);
        // Replace SUB|CMP with TEST, since SUB has two outputs while TEST has
        // one, do not call ReplaceAllUsesWith.
        ReplaceUses(SDValue(Node, (Opcode == X86ISD::SUB ? 1 : 0)),
                    SDValue(NewNode, 0));
        return nullptr;
      }

      // For example, "testl %eax, $2048" to "testb %ah, $8".
      if ((C->getZExtValue() & ~UINT64_C(0xff00)) == 0 &&
          (!(C->getZExtValue() & 0x8000) ||
           HasNoSignedComparisonUses(Node))) {
        // Shift the immediate right by 8 bits.
        SDValue ShiftedImm = CurDAG->getTargetConstant(C->getZExtValue() >> 8,
                                                       MVT::i8);
        SDValue Reg = N0.getNode()->getOperand(0);

        // Put the value in an ABCD register.
        const TargetRegisterClass *TRC;
        switch (N0.getSimpleValueType().SimpleTy) {
        case MVT::i64: TRC = &X86::GR64_ABCDRegClass; break;
        case MVT::i32: TRC = &X86::GR32_ABCDRegClass; break;
        case MVT::i16: TRC = &X86::GR16_ABCDRegClass; break;
        default: llvm_unreachable("Unsupported TEST operand type!");
        }
        SDValue RC = CurDAG->getTargetConstant(TRC->getID(), MVT::i32);
        Reg = SDValue(CurDAG->getMachineNode(X86::COPY_TO_REGCLASS, dl,
                                             Reg.getValueType(), Reg, RC), 0);

        // Extract the h-register.
        SDValue Subreg = CurDAG->getTargetExtractSubreg(X86::sub_8bit_hi, dl,
                                                        MVT::i8, Reg);

        // Emit a testb.  The EXTRACT_SUBREG becomes a COPY that can only
        // target GR8_NOREX registers, so make sure the register class is
        // forced.
        SDNode *NewNode = CurDAG->getMachineNode(X86::TEST8ri_NOREX, dl,
                                                 MVT::i32, Subreg, ShiftedImm);
        // Replace SUB|CMP with TEST, since SUB has two outputs while TEST has
        // one, do not call ReplaceAllUsesWith.
        ReplaceUses(SDValue(Node, (Opcode == X86ISD::SUB ? 1 : 0)),
                    SDValue(NewNode, 0));
        return nullptr;
      }

      // For example, "testl %eax, $32776" to "testw %ax, $32776".
      if ((C->getZExtValue() & ~UINT64_C(0xffff)) == 0 &&
          N0.getValueType() != MVT::i16 &&
          (!(C->getZExtValue() & 0x8000) ||
           HasNoSignedComparisonUses(Node))) {
        SDValue Imm = CurDAG->getTargetConstant(C->getZExtValue(), MVT::i16);
        SDValue Reg = N0.getNode()->getOperand(0);

        // Extract the 16-bit subregister.
        SDValue Subreg = CurDAG->getTargetExtractSubreg(X86::sub_16bit, dl,
                                                        MVT::i16, Reg);

        // Emit a testw.
        SDNode *NewNode = CurDAG->getMachineNode(X86::TEST16ri, dl, MVT::i32,
                                                 Subreg, Imm);
        // Replace SUB|CMP with TEST, since SUB has two outputs while TEST has
        // one, do not call ReplaceAllUsesWith.
        ReplaceUses(SDValue(Node, (Opcode == X86ISD::SUB ? 1 : 0)),
                    SDValue(NewNode, 0));
        return nullptr;
      }

      // For example, "testq %rax, $268468232" to "testl %eax, $268468232".
      if ((C->getZExtValue() & ~UINT64_C(0xffffffff)) == 0 &&
          N0.getValueType() == MVT::i64 &&
          (!(C->getZExtValue() & 0x80000000) ||
           HasNoSignedComparisonUses(Node))) {
        SDValue Imm = CurDAG->getTargetConstant(C->getZExtValue(), MVT::i32);
        SDValue Reg = N0.getNode()->getOperand(0);

        // Extract the 32-bit subregister.
        SDValue Subreg = CurDAG->getTargetExtractSubreg(X86::sub_32bit, dl,
                                                        MVT::i32, Reg);

        // Emit a testl.
        SDNode *NewNode = CurDAG->getMachineNode(X86::TEST32ri, dl, MVT::i32,
                                                 Subreg, Imm);
        // Replace SUB|CMP with TEST, since SUB has two outputs while TEST has
        // one, do not call ReplaceAllUsesWith.
        ReplaceUses(SDValue(Node, (Opcode == X86ISD::SUB ? 1 : 0)),
                    SDValue(NewNode, 0));
        return nullptr;
      }
    }
    break;
  }
  case ISD::STORE: {
    // Change a chain of {load; incr or dec; store} of the same value into
    // a simple increment or decrement through memory of that value, if the
    // uses of the modified value and its address are suitable.
    // The DEC64m tablegen pattern is currently not able to match the case where
    // the EFLAGS on the original DEC are used. (This also applies to
    // {INC,DEC}X{64,32,16,8}.)
    // We'll need to improve tablegen to allow flags to be transferred from a
    // node in the pattern to the result node.  probably with a new keyword
    // for example, we have this
    // def DEC64m : RI<0xFF, MRM1m, (outs), (ins i64mem:$dst), "dec{q}\t$dst",
    //  [(store (add (loadi64 addr:$dst), -1), addr:$dst),
    //   (implicit EFLAGS)]>;
    // but maybe need something like this
    // def DEC64m : RI<0xFF, MRM1m, (outs), (ins i64mem:$dst), "dec{q}\t$dst",
    //  [(store (add (loadi64 addr:$dst), -1), addr:$dst),
    //   (transferrable EFLAGS)]>;

    StoreSDNode *StoreNode = cast<StoreSDNode>(Node);
    SDValue StoredVal = StoreNode->getOperand(1);
    unsigned Opc = StoredVal->getOpcode();

    LoadSDNode *LoadNode = nullptr;
    SDValue InputChain;
    if (!isLoadIncOrDecStore(StoreNode, Opc, StoredVal, CurDAG,
                             LoadNode, InputChain))
      break;

    SDValue Base, Scale, Index, Disp, Segment;
    if (!SelectAddr(LoadNode, LoadNode->getBasePtr(),
                    Base, Scale, Index, Disp, Segment))
      break;

    MachineSDNode::mmo_iterator MemOp = MF->allocateMemRefsArray(2);
    MemOp[0] = StoreNode->getMemOperand();
    MemOp[1] = LoadNode->getMemOperand();
    const SDValue Ops[] = { Base, Scale, Index, Disp, Segment, InputChain };
    EVT LdVT = LoadNode->getMemoryVT();
    unsigned newOpc = getFusedLdStOpcode(LdVT, Opc);
    MachineSDNode *Result = CurDAG->getMachineNode(newOpc,
                                                   SDLoc(Node),
                                                   MVT::i32, MVT::Other, Ops);
    Result->setMemRefs(MemOp, MemOp + 2);

    ReplaceUses(SDValue(StoreNode, 0), SDValue(Result, 1));
    ReplaceUses(SDValue(StoredVal.getNode(), 1), SDValue(Result, 0));

    return Result;
  }
  }

  SDNode *ResNode = SelectCode(Node);

  DEBUG(dbgs() << "=> ";
        if (ResNode == nullptr || ResNode == Node)
          Node->dump(CurDAG);
        else
          ResNode->dump(CurDAG);
        dbgs() << '\n');

  return ResNode;
}

bool X86DAGToDAGISel::
SelectInlineAsmMemoryOperand(const SDValue &Op, char ConstraintCode,
                             std::vector<SDValue> &OutOps) {
  SDValue Op0, Op1, Op2, Op3, Op4;
  switch (ConstraintCode) {
  case 'o':   // offsetable        ??
  case 'v':   // not offsetable    ??
  default: return true;
  case 'm':   // memory
    if (!SelectAddr(nullptr, Op, Op0, Op1, Op2, Op3, Op4))
      return true;
    break;
  }

  OutOps.push_back(Op0);
  OutOps.push_back(Op1);
  OutOps.push_back(Op2);
  OutOps.push_back(Op3);
  OutOps.push_back(Op4);
  return false;
}

/// createX86ISelDag - This pass converts a legalized DAG into a
/// X86-specific DAG, ready for instruction scheduling.
///
FunctionPass *llvm::createX86ISelDag(X86TargetMachine &TM,
                                     CodeGenOpt::Level OptLevel) {
  return new X86DAGToDAGISel(TM, OptLevel);
}