C++ ConstantSDNode::isNullValue方法代码示例

SDValue ARM64SelectionDAGInfo::EmitTargetCodeForMemset(
    SelectionDAG &DAG, SDLoc dl, SDValue Chain, SDValue Dst, SDValue Src,
    SDValue Size, unsigned Align, bool isVolatile,
    MachinePointerInfo DstPtrInfo) const {
  // Check to see if there is a specialized entry-point for memory zeroing.
  ConstantSDNode *V = dyn_cast<ConstantSDNode>(Src);
  ConstantSDNode *SizeValue = dyn_cast<ConstantSDNode>(Size);
  const char *bzeroEntry =
      (V && V->isNullValue()) ? Subtarget->getBZeroEntry() : 0;
  // For small size (< 256), it is not beneficial to use bzero
  // instead of memset.
  if (bzeroEntry && (!SizeValue || SizeValue->getZExtValue() > 256)) {
    const ARM64TargetLowering &TLI = *static_cast<const ARM64TargetLowering *>(
                                          DAG.getTarget().getTargetLowering());

    EVT IntPtr = TLI.getPointerTy();
    Type *IntPtrTy = getDataLayout()->getIntPtrType(*DAG.getContext());
    TargetLowering::ArgListTy Args;
    TargetLowering::ArgListEntry Entry;
    Entry.Node = Dst;
    Entry.Ty = IntPtrTy;
    Args.push_back(Entry);
    Entry.Node = Size;
    Args.push_back(Entry);
    TargetLowering::CallLoweringInfo CLI(
        Chain, Type::getVoidTy(*DAG.getContext()), false, false, false, false,
        0, CallingConv::C, /*isTailCall=*/false,
        /*doesNotRet=*/false, /*isReturnValueUsed=*/false,
        DAG.getExternalSymbol(bzeroEntry, IntPtr), Args, DAG, dl);
    std::pair<SDValue, SDValue> CallResult = TLI.LowerCallTo(CLI);
    return CallResult.second;
  }
  return SDValue();
}

SDValue
X86SelectionDAGInfo::EmitTargetCodeForMemset(SelectionDAG &DAG, SDLoc dl,
                                             SDValue Chain,
                                             SDValue Dst, SDValue Src,
                                             SDValue Size, unsigned Align,
                                             bool isVolatile,
                                         MachinePointerInfo DstPtrInfo) const {
  ConstantSDNode *ConstantSize = dyn_cast<ConstantSDNode>(Size);

  // If to a segment-relative address space, use the default lowering.
  if (DstPtrInfo.getAddrSpace() >= 256)
    return SDValue();

  // If not DWORD aligned or size is more than the threshold, call the library.
  // The libc version is likely to be faster for these cases. It can use the
  // address value and run time information about the CPU.
  if ((Align & 3) != 0 ||
      !ConstantSize ||
      ConstantSize->getZExtValue() >
        Subtarget->getMaxInlineSizeThreshold()) {
    // Check to see if there is a specialized entry-point for memory zeroing.
    ConstantSDNode *V = dyn_cast<ConstantSDNode>(Src);

    if (const char *bzeroEntry =  V &&
        V->isNullValue() ? Subtarget->getBZeroEntry() : nullptr) {
      EVT IntPtr = TLI.getPointerTy();
      Type *IntPtrTy = getDataLayout()->getIntPtrType(*DAG.getContext());
      TargetLowering::ArgListTy Args;
      TargetLowering::ArgListEntry Entry;
      Entry.Node = Dst;
      Entry.Ty = IntPtrTy;
      Args.push_back(Entry);
      Entry.Node = Size;
      Args.push_back(Entry);

      TargetLowering::CallLoweringInfo CLI(DAG);
      CLI.setDebugLoc(dl).setChain(Chain)
        .setCallee(CallingConv::C, Type::getVoidTy(*DAG.getContext()),
                   DAG.getExternalSymbol(bzeroEntry, IntPtr), &Args, 0)
        .setDiscardResult();

      std::pair<SDValue,SDValue> CallResult = TLI.LowerCallTo(CLI);
      return CallResult.second;
    }

    // Otherwise have the target-independent code call memset.
    return SDValue();
  }

  uint64_t SizeVal = ConstantSize->getZExtValue();
  SDValue InFlag;
  EVT AVT;
  SDValue Count;
  ConstantSDNode *ValC = dyn_cast<ConstantSDNode>(Src);
  unsigned BytesLeft = 0;
  bool TwoRepStos = false;
  if (ValC) {
    unsigned ValReg;
    uint64_t Val = ValC->getZExtValue() & 255;

    // If the value is a constant, then we can potentially use larger sets.
    switch (Align & 3) {
    case 2:   // WORD aligned
      AVT = MVT::i16;
      ValReg = X86::AX;
      Val = (Val << 8) | Val;
      break;
    case 0:  // DWORD aligned
      AVT = MVT::i32;
      ValReg = X86::EAX;
      Val = (Val << 8)  | Val;
      Val = (Val << 16) | Val;
      if (Subtarget->is64Bit() && ((Align & 0x7) == 0)) {  // QWORD aligned
        AVT = MVT::i64;
        ValReg = X86::RAX;
        Val = (Val << 32) | Val;
      }
      break;
    default:  // Byte aligned
      AVT = MVT::i8;
      ValReg = X86::AL;
      Count = DAG.getIntPtrConstant(SizeVal);
      break;
    }

    if (AVT.bitsGT(MVT::i8)) {
      unsigned UBytes = AVT.getSizeInBits() / 8;
      Count = DAG.getIntPtrConstant(SizeVal / UBytes);
      BytesLeft = SizeVal % UBytes;
    }

    Chain  = DAG.getCopyToReg(Chain, dl, ValReg, DAG.getConstant(Val, AVT),
                              InFlag);
    InFlag = Chain.getValue(1);
  } else {
    AVT = MVT::i8;
    Count  = DAG.getIntPtrConstant(SizeVal);
    Chain  = DAG.getCopyToReg(Chain, dl, X86::AL, Src, InFlag);
    InFlag = Chain.getValue(1);
  }
//.........这里部分代码省略.........

static bool isZero(SDValue V) 
{
  ConstantSDNode *C = dyn_cast<ConstantSDNode>(V);
  return C && C->isNullValue();
}

SDValue X86SelectionDAGInfo::EmitTargetCodeForMemset(
    SelectionDAG &DAG, const SDLoc &dl, SDValue Chain, SDValue Dst, SDValue Val,
    SDValue Size, unsigned Align, bool isVolatile,
    MachinePointerInfo DstPtrInfo) const {
  ConstantSDNode *ConstantSize = dyn_cast<ConstantSDNode>(Size);
  const X86Subtarget &Subtarget =
      DAG.getMachineFunction().getSubtarget<X86Subtarget>();

#ifndef NDEBUG
  // If the base register might conflict with our physical registers, bail out.
  const MCPhysReg ClobberSet[] = {X86::RCX, X86::RAX, X86::RDI,
                                  X86::ECX, X86::EAX, X86::EDI};
  assert(!isBaseRegConflictPossible(DAG, ClobberSet));
#endif

  // If to a segment-relative address space, use the default lowering.
  if (DstPtrInfo.getAddrSpace() >= 256)
    return SDValue();

  // If not DWORD aligned or size is more than the threshold, call the library.
  // The libc version is likely to be faster for these cases. It can use the
  // address value and run time information about the CPU.
  if ((Align & 3) != 0 || !ConstantSize ||
      ConstantSize->getZExtValue() > Subtarget.getMaxInlineSizeThreshold()) {
    // Check to see if there is a specialized entry-point for memory zeroing.
    ConstantSDNode *ValC = dyn_cast<ConstantSDNode>(Val);

    if (const char *bzeroName = (ValC && ValC->isNullValue())
        ? DAG.getTargetLoweringInfo().getLibcallName(RTLIB::BZERO)
        : nullptr) {
      const TargetLowering &TLI = DAG.getTargetLoweringInfo();
      EVT IntPtr = TLI.getPointerTy(DAG.getDataLayout());
      Type *IntPtrTy = DAG.getDataLayout().getIntPtrType(*DAG.getContext());
      TargetLowering::ArgListTy Args;
      TargetLowering::ArgListEntry Entry;
      Entry.Node = Dst;
      Entry.Ty = IntPtrTy;
      Args.push_back(Entry);
      Entry.Node = Size;
      Args.push_back(Entry);

      TargetLowering::CallLoweringInfo CLI(DAG);
      CLI.setDebugLoc(dl)
          .setChain(Chain)
          .setLibCallee(CallingConv::C, Type::getVoidTy(*DAG.getContext()),
                        DAG.getExternalSymbol(bzeroName, IntPtr),
                        std::move(Args))
          .setDiscardResult();

      std::pair<SDValue,SDValue> CallResult = TLI.LowerCallTo(CLI);
      return CallResult.second;
    }

    // Otherwise have the target-independent code call memset.
    return SDValue();
  }

  uint64_t SizeVal = ConstantSize->getZExtValue();
  SDValue InFlag;
  EVT AVT;
  SDValue Count;
  ConstantSDNode *ValC = dyn_cast<ConstantSDNode>(Val);
  unsigned BytesLeft = 0;
  if (ValC) {
    unsigned ValReg;
    uint64_t Val = ValC->getZExtValue() & 255;

    // If the value is a constant, then we can potentially use larger sets.
    switch (Align & 3) {
    case 2:   // WORD aligned
      AVT = MVT::i16;
      ValReg = X86::AX;
      Val = (Val << 8) | Val;
      break;
    case 0:  // DWORD aligned
      AVT = MVT::i32;
      ValReg = X86::EAX;
      Val = (Val << 8)  | Val;
      Val = (Val << 16) | Val;
      if (Subtarget.is64Bit() && ((Align & 0x7) == 0)) {  // QWORD aligned
        AVT = MVT::i64;
        ValReg = X86::RAX;
        Val = (Val << 32) | Val;
      }
      break;
    default:  // Byte aligned
      AVT = MVT::i8;
      ValReg = X86::AL;
      Count = DAG.getIntPtrConstant(SizeVal, dl);
      break;
    }

    if (AVT.bitsGT(MVT::i8)) {
      unsigned UBytes = AVT.getSizeInBits() / 8;
      Count = DAG.getIntPtrConstant(SizeVal / UBytes, dl);
      BytesLeft = SizeVal % UBytes;
    }

    Chain = DAG.getCopyToReg(Chain, dl, ValReg, DAG.getConstant(Val, dl, AVT),
                             InFlag);
//.........这里部分代码省略.........