text: //===- InstCombineCalls.cpp -----------------------------------------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file implements the visitCall and visitInvoke functions.
  //
  //===----------------------------------------------------------------------===//
  
  #include "InstCombineInternal.h"
  #include "llvm/ADT/Statistic.h"
  #include "llvm/Analysis/InstructionSimplify.h"
  #include "llvm/Analysis/MemoryBuiltins.h"
  #include "llvm/IR/CallSite.h"
  #include "llvm/IR/Dominators.h"
  #include "llvm/IR/PatternMatch.h"
  #include "llvm/IR/Statepoint.h"
  #include "llvm/Transforms/Utils/BuildLibCalls.h"
  #include "llvm/Transforms/Utils/Local.h"
  #include "llvm/Transforms/Utils/SimplifyLibCalls.h"
  using namespace llvm;
  using namespace PatternMatch;
  
  #define DEBUG_TYPE "instcombine"
  
  STATISTIC(NumSimplified, "Number of library calls simplified");
  
  /// getPromotedType - Return the specified type promoted as it would be to pass
  /// though a va_arg area.
  static Type *getPromotedType(Type *Ty) {
    if (IntegerType* ITy = dyn_cast<IntegerType>(Ty)) {
      if (ITy->getBitWidth() < 32)
        return Type::getInt32Ty(Ty->getContext());
    }
    return Ty;
  }
  
  /// reduceToSingleValueType - Given an aggregate type which ultimately holds a
  /// single scalar element, like {{{type}}} or [1 x type], return type.
  static Type *reduceToSingleValueType(Type *T) {
    while (!T->isSingleValueType()) {
      if (StructType *STy = dyn_cast<StructType>(T)) {
        if (STy->getNumElements() == 1)
          T = STy->getElementType(0);
        else
          break;
      } else if (ArrayType *ATy = dyn_cast<ArrayType>(T)) {
        if (ATy->getNumElements() == 1)
          T = ATy->getElementType();
        else
          break;
      } else
        break;
    }
  
    return T;
  }
  
  Instruction *InstCombiner::SimplifyMemTransfer(MemIntrinsic *MI) {
    unsigned DstAlign = getKnownAlignment(MI->getArgOperand(0), DL, MI, AC, DT);
    unsigned SrcAlign = getKnownAlignment(MI->getArgOperand(1), DL, MI, AC, DT);
    unsigned MinAlign = std::min(DstAlign, SrcAlign);
    unsigned CopyAlign = MI->getAlignment();
  
    if (CopyAlign < MinAlign) {
      MI->setAlignment(ConstantInt::get(MI->getAlignmentType(), MinAlign, false));
      return MI;
    }
  
    // If MemCpyInst length is 1/2/4/8 bytes then replace memcpy with
    // load/store.
    ConstantInt *MemOpLength = dyn_cast<ConstantInt>(MI->getArgOperand(2));
    if (!MemOpLength) return nullptr;
  
    // Source and destination pointer types are always "i8*" for intrinsic.  See
    // if the size is something we can handle with a single primitive load/store.
    // A single load+store correctly handles overlapping memory in the memmove
    // case.
    uint64_t Size = MemOpLength->getLimitedValue();
    assert(Size && "0-sized memory transferring should be removed already.");
  
    if (Size > 8 || (Size&(Size-1)))
      return nullptr;  // If not 1/2/4/8 bytes, exit.
  
    // Use an integer load+store unless we can find something better.
    unsigned SrcAddrSp =
      cast<PointerType>(MI->getArgOperand(1)->getType())->getAddressSpace();
    unsigned DstAddrSp =
      cast<PointerType>(MI->getArgOperand(0)->getType())->getAddressSpace();
  
    IntegerType* IntType = IntegerType::get(MI->getContext(), Size<<3);
    Type *NewSrcPtrTy = PointerType::get(IntType, SrcAddrSp);
    Type *NewDstPtrTy = PointerType::get(IntType, DstAddrSp);
  
    // Memcpy forces the use of i8* for the source and destination.  That means
    // that if you're using memcpy to move one double around, you'll get a cast
    // from double* to i8*.  We'd much rather use a double load+store rather than
    // an i64 load+store, here because this improves the odds that the source or
    // dest address will be promotable.  See if we can find a better type than the
    // integer datatype.
    Value *StrippedDest = MI->getArgOperand(0)->stripPointerCasts();
    MDNode *CopyMD = nullptr;
    if (StrippedDest != MI->getArgOperand(0)) {
      Type *SrcETy = cast<PointerType>(StrippedDest->getType())
                                      ->getElementType();
      if (SrcETy->isSized() && DL.getTypeStoreSize(SrcETy) == Size) {
        // The SrcETy might be something like {{{double}}} or [1 x double].  Rip
        // down through these levels if so.
        SrcETy = reduceToSingleValueType(SrcETy);
  
        if (SrcETy->isSingleValueType()) {
          NewSrcPtrTy = PointerType::get(SrcETy, SrcAddrSp);
          NewDstPtrTy = PointerType::get(SrcETy, DstAddrSp);
  
          // If the memcpy has metadata describing the members, see if we can
          // get the TBAA tag describing our copy.
          if (MDNode *M = MI->getMetadata(LLVMContext::MD_tbaa_struct)) {
            if (M->getNumOperands() == 3 && M->getOperand(0) &&
                mdconst::hasa<ConstantInt>(M->getOperand(0)) &&
                mdconst::extract<ConstantInt>(M->getOperand(0))->isNullValue() &&
                M->getOperand(1) &&
                mdconst::hasa<ConstantInt>(M->getOperand(1)) &&
                mdconst::extract<ConstantInt>(M->getOperand(1))->getValue() ==
                    Size &&
                M->getOperand(2) && isa<MDNode>(M->getOperand(2)))
              CopyMD = cast<MDNode>(M->getOperand(2));
          }
        }
      }
    }
  
    // If the memcpy/memmove provides better alignment info than we can
    // infer, use it.
    SrcAlign = std::max(SrcAlign, CopyAlign);
    DstAlign = std::max(DstAlign, CopyAlign);
  
    Value *Src = Builder->CreateBitCast(MI->getArgOperand(1), NewSrcPtrTy);
    Value *Dest = Builder->CreateBitCast(MI->getArgOperand(0), NewDstPtrTy);
    LoadInst *L = Builder->CreateLoad(Src, MI->isVolatile());
    L->setAlignment(SrcAlign);
    if (CopyMD)
      L->setMetadata(LLVMContext::MD_tbaa, CopyMD);
    StoreInst *S = Builder->CreateStore(L, Dest, MI->isVolatile());
    S->setAlignment(DstAlign);
    if (CopyMD)
      S->setMetadata(LLVMContext::MD_tbaa, CopyMD);
  
    // Set the size of the copy to 0, it will be deleted on the next iteration.
    MI->setArgOperand(2, Constant::getNullValue(MemOpLength->getType()));
    return MI;
  }
  
  Instruction *InstCombiner::SimplifyMemSet(MemSetInst *MI) {
    unsigned Alignment = getKnownAlignment(MI->getDest(), DL, MI, AC, DT);
    if (MI->getAlignment() < Alignment) {
      MI->setAlignment(ConstantInt::get(MI->getAlignmentType(),
                                               Alignment, false));
      return MI;
    }
  
    // Extract the length and alignment and fill if they are constant.
    ConstantInt *LenC = dyn_cast<ConstantInt>(MI->getLength());
    ConstantInt *FillC = dyn_cast<ConstantInt>(MI->getValue());
    if (!LenC || !FillC || !FillC->getType()->isIntegerTy(8))
      return nullptr;
    uint64_t Len = LenC->getLimitedValue();
    Alignment = MI->getAlignment();
    assert(Len && "0-sized memory setting should be removed already.");
  
    // memset(s,c,n) -> store s, c (for n=1,2,4,8)
    if (Len <= 8 && isPowerOf2_32((uint32_t)Len)) {
      Type *ITy = IntegerType::get(MI->getContext(), Len*8);  // n=1 -> i8.
  
      Value *Dest = MI->getDest();
      unsigned DstAddrSp = cast<PointerType>(Dest->getType())->getAddressSpace();
      Type *NewDstPtrTy = PointerType::get(ITy, DstAddrSp);
      Dest = Builder->CreateBitCast(Dest, NewDstPtrTy);
  
      // Alignment 0 is identity for alignment 1 for memset, but not store.
      if (Alignment == 0) Alignment = 1;
  
      // Extract the fill value and store.
      uint64_t Fill = FillC->getZExtValue()*0x0101010101010101ULL;
      StoreInst *S = Builder->CreateStore(ConstantInt::get(ITy, Fill), Dest,
                                          MI->isVolatile());
      S->setAlignment(Alignment);
  
      // Set the size of the copy to 0, it will be deleted on the next iteration.
      MI->setLength(Constant::getNullValue(LenC->getType()));
      return MI;
    }
  
    return nullptr;
  }
  
  static Value *SimplifyX86immshift(const IntrinsicInst &II,
                                    InstCombiner::BuilderTy &Builder) {
    bool LogicalShift = false;
    bool ShiftLeft = false;
  
    switch (II.getIntrinsicID()) {
    default:
      return nullptr;
    case Intrinsic::x86_sse2_psra_d:
    case Intrinsic::x86_sse2_psra_w:
    case Intrinsic::x86_sse2_psrai_d:
    case Intrinsic::x86_sse2_psrai_w:
    case Intrinsic::x86_avx2_psra_d:
    case Intrinsic::x86_avx2_psra_w:
    case Intrinsic::x86_avx2_psrai_d:
    case Intrinsic::x86_avx2_psrai_w:
      LogicalShift = false; ShiftLeft = false;
      break;
    case Intrinsic::x86_sse2_psrl_d:
    case Intrinsic::x86_sse2_psrl_q:
    case Intrinsic::x86_sse2_psrl_w:
    case Intrinsic::x86_sse2_psrli_d:
    case Intrinsic::x86_sse2_psrli_q:
    case Intrinsic::x86_sse2_psrli_w:
    case Intrinsic::x86_avx2_psrl_d:
    case Intrinsic::x86_avx2_psrl_q:
    case Intrinsic::x86_avx2_psrl_w:
    case Intrinsic::x86_avx2_psrli_d:
    case Intrinsic::x86_avx2_psrli_q:
    case Intrinsic::x86_avx2_psrli_w:
      LogicalShift = true; ShiftLeft = false;
      break;
    case Intrinsic::x86_sse2_psll_d:
    case Intrinsic::x86_sse2_psll_q:
    case Intrinsic::x86_sse2_psll_w:
    case Intrinsic::x86_sse2_pslli_d:
    case Intrinsic::x86_sse2_pslli_q:
    case Intrinsic::x86_sse2_pslli_w:
    case Intrinsic::x86_avx2_psll_d:
    case Intrinsic::x86_avx2_psll_q:
    case Intrinsic::x86_avx2_psll_w:
    case Intrinsic::x86_avx2_pslli_d:
    case Intrinsic::x86_avx2_pslli_q:
    case Intrinsic::x86_avx2_pslli_w:
      LogicalShift = true; ShiftLeft = true;
      break;
    }
    assert((LogicalShift || !ShiftLeft) && "Only logical shifts can shift left");
  
    // Simplify if count is constant.
    auto Arg1 = II.getArgOperand(1);
    auto CAZ = dyn_cast<ConstantAggregateZero>(Arg1);
    auto CDV = dyn_cast<ConstantDataVector>(Arg1);
    auto CInt = dyn_cast<ConstantInt>(Arg1);
    if (!CAZ && !CDV && !CInt)
      return nullptr;
  
    APInt Count(64, 0);
    if (CDV) {
      // SSE2/AVX2 uses all the first 64-bits of the 128-bit vector
      // operand to compute the shift amount.
      auto VT = cast<VectorType>(CDV->getType());
      unsigned BitWidth = VT->getElementType()->getPrimitiveSizeInBits();
      assert((64 % BitWidth) == 0 && "Unexpected packed shift size");
      unsigned NumSubElts = 64 / BitWidth;
  
      // Concatenate the sub-elements to create the 64-bit value.
      for (unsigned i = 0; i != NumSubElts; ++i) {
        unsigned SubEltIdx = (NumSubElts - 1) - i;
        auto SubElt = cast<ConstantInt>(CDV->getElementAsConstant(SubEltIdx));
        Count = Count.shl(BitWidth);
        Count |= SubElt->getValue().zextOrTrunc(64);
      }
    }
    else if (CInt)
      Count = CInt->getValue();
  
    auto Vec = II.getArgOperand(0);
    auto VT = cast<VectorType>(Vec->getType());
    auto SVT = VT->getElementType();
    unsigned VWidth = VT->getNumElements();
    unsigned BitWidth = SVT->getPrimitiveSizeInBits();
  
    // If shift-by-zero then just return the original value.
    if (Count == 0)
      return Vec;
  
    // Handle cases when Shift >= BitWidth.
    if (Count.uge(BitWidth)) {
      // If LogicalShift - just return zero.
      if (LogicalShift)
        return ConstantAggregateZero::get(VT);
  
      // If ArithmeticShift - clamp Shift to (BitWidth - 1).
      Count = APInt(64, BitWidth - 1);
    }
  
    // Get a constant vector of the same type as the first operand.
    auto ShiftAmt = ConstantInt::get(SVT, Count.zextOrTrunc(BitWidth));
    auto ShiftVec = Builder.CreateVectorSplat(VWidth, ShiftAmt);
  
    if (ShiftLeft)
      return Builder.CreateShl(Vec, ShiftVec);
  
    if (LogicalShift)
      return Builder.CreateLShr(Vec, ShiftVec);
  
    return Builder.CreateAShr(Vec, ShiftVec);
  }
  
  static Value *SimplifyX86extend(const IntrinsicInst &II,
                                  InstCombiner::BuilderTy &Builder,
                                  bool SignExtend) {
    VectorType *SrcTy = cast<VectorType>(II.getArgOperand(0)->getType());
    VectorType *DstTy = cast<VectorType>(II.getType());
    unsigned NumDstElts = DstTy->getNumElements();
  
    // Extract a subvector of the first NumDstElts lanes and sign/zero extend.
    SmallVector<int, 8> ShuffleMask;
    for (int i = 0; i != (int)NumDstElts; ++i)
      ShuffleMask.push_back(i);
  
    Value *SV = Builder.CreateShuffleVector(II.getArgOperand(0),
                                            UndefValue::get(SrcTy), ShuffleMask);
    return SignExtend ? Builder.CreateSExt(SV, DstTy)
                      : Builder.CreateZExt(SV, DstTy);
  }
  
  static Value *SimplifyX86insertps(const IntrinsicInst &II,
                                    InstCombiner::BuilderTy &Builder) {
    if (auto *CInt = dyn_cast<ConstantInt>(II.getArgOperand(2))) {
      VectorType *VecTy = cast<VectorType>(II.getType());
      assert(VecTy->getNumElements() == 4 && "insertps with wrong vector type");
  
      // The immediate permute control byte looks like this:
      //    [3:0] - zero mask for each 32-bit lane
      //    [5:4] - select one 32-bit destination lane
      //    [7:6] - select one 32-bit source lane
  
      uint8_t Imm = CInt->getZExtValue();
      uint8_t ZMask = Imm & 0xf;
      uint8_t DestLane = (Imm >> 4) & 0x3;
      uint8_t SourceLane = (Imm >> 6) & 0x3;
  
      ConstantAggregateZero *ZeroVector = ConstantAggregateZero::get(VecTy);
  
      // If all zero mask bits are set, this was just a weird way to
      // generate a zero vector.
      if (ZMask == 0xf)
        return ZeroVector;
  
      // Initialize by passing all of the first source bits through.
      int ShuffleMask[4] = { 0, 1, 2, 3 };
  
      // We may replace the second operand with the zero vector.
      Value *V1 = II.getArgOperand(1);
  
      if (ZMask) {
        // If the zero mask is being used with a single input or the zero mask
        // overrides the destination lane, this is a shuffle with the zero vector.
        if ((II.getArgOperand(0) == II.getArgOperand(1)) ||
            (ZMask & (1 << DestLane))) {
          V1 = ZeroVector;
          // We may still move 32-bits of the first source vector from one lane
          // to another.
          ShuffleMask[DestLane] = SourceLane;
          // The zero mask may override the previous insert operation.
          for (unsigned i = 0; i < 4; ++i)
            if ((ZMask >> i) & 0x1)
              ShuffleMask[i] = i + 4;
        } else {
          // TODO: Model this case as 2 shuffles or a 'logical and' plus shuffle?
          return nullptr;
        }
      } else {
        // Replace the selected destination lane with the selected source lane.
        ShuffleMask[DestLane] = SourceLane + 4;
      }
  
      return Builder.CreateShuffleVector(II.getArgOperand(0), V1, ShuffleMask);
    }
    return nullptr;
  }
  
  /// The shuffle mask for a perm2*128 selects any two halves of two 256-bit
  /// source vectors, unless a zero bit is set. If a zero bit is set,
  /// then ignore that half of the mask and clear that half of the vector.
  static Value *SimplifyX86vperm2(const IntrinsicInst &II,
                                  InstCombiner::BuilderTy &Builder) {
    if (auto *CInt = dyn_cast<ConstantInt>(II.getArgOperand(2))) {
      VectorType *VecTy = cast<VectorType>(II.getType());
      ConstantAggregateZero *ZeroVector = ConstantAggregateZero::get(VecTy);
  
      // The immediate permute control byte looks like this:
      //    [1:0] - select 128 bits from sources for low half of destination
      //    [2]   - ignore
      //    [3]   - zero low half of destination
      //    [5:4] - select 128 bits from sources for high half of destination
      //    [6]   - ignore
      //    [7]   - zero high half of destination
  
      uint8_t Imm = CInt->getZExtValue();
  
      bool LowHalfZero = Imm & 0x08;
      bool HighHalfZero = Imm & 0x80;
  
      // If both zero mask bits are set, this was just a weird way to
      // generate a zero vector.
      if (LowHalfZero && HighHalfZero)
        return ZeroVector;
  
      // If 0 or 1 zero mask bits are set, this is a simple shuffle.
      unsigned NumElts = VecTy->getNumElements();
      unsigned HalfSize = NumElts / 2;
      SmallVector<int, 8> ShuffleMask(NumElts);
  
      // The high bit of the selection field chooses the 1st or 2nd operand.
      bool LowInputSelect = Imm & 0x02;
      bool HighInputSelect = Imm & 0x20;
  
      // The low bit of the selection field chooses the low or high half
      // of the selected operand.
      bool LowHalfSelect = Imm & 0x01;
      bool HighHalfSelect = Imm & 0x10;
  
      // Determine which operand(s) are actually in use for this instruction.
      Value *V0 = LowInputSelect ? II.getArgOperand(1) : II.getArgOperand(0);
      Value *V1 = HighInputSelect ? II.getArgOperand(1) : II.getArgOperand(0);
  
      // If needed, replace operands based on zero mask.
      V0 = LowHalfZero ? ZeroVector : V0;
      V1 = HighHalfZero ? ZeroVector : V1;
  
      // Permute low half of result.
      unsigned StartIndex = LowHalfSelect ? HalfSize : 0;
      for (unsigned i = 0; i < HalfSize; ++i)
        ShuffleMask[i] = StartIndex + i;
  
      // Permute high half of result.
      StartIndex = HighHalfSelect ? HalfSize : 0;
      StartIndex += NumElts;
      for (unsigned i = 0; i < HalfSize; ++i)
        ShuffleMask[i + HalfSize] = StartIndex + i;
  
      return Builder.CreateShuffleVector(V0, V1, ShuffleMask);
    }
    return nullptr;
  }
  
  /// visitCallInst - CallInst simplification.  This mostly only handles folding
  /// of intrinsic instructions.  For normal calls, it allows visitCallSite to do
  /// the heavy lifting.
  ///
  Instruction *InstCombiner::visitCallInst(CallInst &CI) {
    auto Args = CI.arg_operands();
    if (Value *V = SimplifyCall(CI.getCalledValue(), Args.begin(), Args.end(), DL,
                                TLI, DT, AC))
      return ReplaceInstUsesWith(CI, V);
  
    if (isFreeCall(&CI, TLI))
      return visitFree(CI);
  
    // If the caller function is nounwind, mark the call as nounwind, even if the
    // callee isn't.
    if (CI.getParent()->getParent()->doesNotThrow() &&
        !CI.doesNotThrow()) {
      CI.setDoesNotThrow();
      return &CI;
    }
  
    IntrinsicInst *II = dyn_cast<IntrinsicInst>(&CI);
    if (!II) return visitCallSite(&CI);
  
    // Intrinsics cannot occur in an invoke, so handle them here instead of in
    // visitCallSite.
    if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(II)) {
      bool Changed = false;
  
      // memmove/cpy/set of zero bytes is a noop.
      if (Constant *NumBytes = dyn_cast<Constant>(MI->getLength())) {
        if (NumBytes->isNullValue())
          return EraseInstFromFunction(CI);
  
        if (ConstantInt *CI = dyn_cast<ConstantInt>(NumBytes))
          if (CI->getZExtValue() == 1) {
            // Replace the instruction with just byte operations.  We would
            // transform other cases to loads/stores, but we don't know if
            // alignment is sufficient.
          }
      }
  
      // No other transformations apply to volatile transfers.
      if (MI->isVolatile())
        return nullptr;
  
      // If we have a memmove and the source operation is a constant global,
      // then the source and dest pointers can't alias, so we can change this
      // into a call to memcpy.
      if (MemMoveInst *MMI = dyn_cast<MemMoveInst>(MI)) {
        if (GlobalVariable *GVSrc = dyn_cast<GlobalVariable>(MMI->getSource()))
          if (GVSrc->isConstant()) {
            Module *M = CI.getParent()->getParent()->getParent();
            Intrinsic::ID MemCpyID = Intrinsic::memcpy;
            Type *Tys[3] = { CI.getArgOperand(0)->getType(),
                             CI.getArgOperand(1)->getType(),
                             CI.getArgOperand(2)->getType() };
            CI.setCalledFunction(Intrinsic::getDeclaration(M, MemCpyID, Tys));
            Changed = true;
          }
      }
  
      if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) {
        // memmove(x,x,size) -> noop.
        if (MTI->getSource() == MTI->getDest())
          return EraseInstFromFunction(CI);
      }
  
      // If we can determine a pointer alignment that is bigger than currently
      // set, update the alignment.
      if (isa<MemTransferInst>(MI)) {
        if (Instruction *I = SimplifyMemTransfer(MI))
          return I;
      } else if (MemSetInst *MSI = dyn_cast<MemSetInst>(MI)) {
        if (Instruction *I = SimplifyMemSet(MSI))
          return I;
      }
  
      if (Changed) return II;
    }
  
    auto SimplifyDemandedVectorEltsLow = [this](Value *Op, unsigned Width, unsigned DemandedWidth)
    {
      APInt UndefElts(Width, 0);
      APInt DemandedElts = APInt::getLowBitsSet(Width, DemandedWidth);
      return SimplifyDemandedVectorElts(Op, DemandedElts, UndefElts);
    };
  
    switch (II->getIntrinsicID()) {
    default: break;
    case Intrinsic::objectsize: {
      uint64_t Size;
      if (getObjectSize(II->getArgOperand(0), Size, DL, TLI))
        return ReplaceInstUsesWith(CI, ConstantInt::get(CI.getType(), Size));
      return nullptr;
    }
    case Intrinsic::bswap: {
      Value *IIOperand = II->getArgOperand(0);
      Value *X = nullptr;
  
      // bswap(bswap(x)) -> x
      if (match(IIOperand, m_BSwap(m_Value(X))))
          return ReplaceInstUsesWith(CI, X);
  
      // bswap(trunc(bswap(x))) -> trunc(lshr(x, c))
      if (match(IIOperand, m_Trunc(m_BSwap(m_Value(X))))) {
        unsigned C = X->getType()->getPrimitiveSizeInBits() -
          IIOperand->getType()->getPrimitiveSizeInBits();
        Value *CV = ConstantInt::get(X->getType(), C);
        Value *V = Builder->CreateLShr(X, CV);
        return new TruncInst(V, IIOperand->getType());
      }
      break;
    }
  
    case Intrinsic::powi:
      if (ConstantInt *Power = dyn_cast<ConstantInt>(II->getArgOperand(1))) {
        // powi(x, 0) -> 1.0
        if (Power->isZero())
          return ReplaceInstUsesWith(CI, ConstantFP::get(CI.getType(), 1.0));
        // powi(x, 1) -> x
        if (Power->isOne())
          return ReplaceInstUsesWith(CI, II->getArgOperand(0));
        // powi(x, -1) -> 1/x
        if (Power->isAllOnesValue())
          return BinaryOperator::CreateFDiv(ConstantFP::get(CI.getType(), 1.0),
                                            II->getArgOperand(0));
      }
      break;
    case Intrinsic::cttz: {
      // If all bits below the first known one are known zero,
      // this value is constant.
      IntegerType *IT = dyn_cast<IntegerType>(II->getArgOperand(0)->getType());
      // FIXME: Try to simplify vectors of integers.
      if (!IT) break;
      uint32_t BitWidth = IT->getBitWidth();
      APInt KnownZero(BitWidth, 0);
      APInt KnownOne(BitWidth, 0);
      computeKnownBits(II->getArgOperand(0), KnownZero, KnownOne, 0, II);
      unsigned TrailingZeros = KnownOne.countTrailingZeros();
      APInt Mask(APInt::getLowBitsSet(BitWidth, TrailingZeros));
      if ((Mask & KnownZero) == Mask)
        return ReplaceInstUsesWith(CI, ConstantInt::get(IT,
                                   APInt(BitWidth, TrailingZeros)));
  
      }
      break;
    case Intrinsic::ctlz: {
      // If all bits above the first known one are known zero,
      // this value is constant.
      IntegerType *IT = dyn_cast<IntegerType>(II->getArgOperand(0)->getType());
      // FIXME: Try to simplify vectors of integers.
      if (!IT) break;
      uint32_t BitWidth = IT->getBitWidth();
      APInt KnownZero(BitWidth, 0);
      APInt KnownOne(BitWidth, 0);
      computeKnownBits(II->getArgOperand(0), KnownZero, KnownOne, 0, II);
      unsigned LeadingZeros = KnownOne.countLeadingZeros();
      APInt Mask(APInt::getHighBitsSet(BitWidth, LeadingZeros));
      if ((Mask & KnownZero) == Mask)
        return ReplaceInstUsesWith(CI, ConstantInt::get(IT,
                                   APInt(BitWidth, LeadingZeros)));
  
      }
      break;
  
    case Intrinsic::uadd_with_overflow:
    case Intrinsic::sadd_with_overflow:
    case Intrinsic::umul_with_overflow:
    case Intrinsic::smul_with_overflow:
      if (isa<Constant>(II->getArgOperand(0)) &&
          !isa<Constant>(II->getArgOperand(1))) {
        // Canonicalize constants into the RHS.
        Value *LHS = II->getArgOperand(0);
        II->setArgOperand(0, II->getArgOperand(1));
        II->setArgOperand(1, LHS);
        return II;
      }
      // fall through
  
    case Intrinsic::usub_with_overflow:
    case Intrinsic::ssub_with_overflow: {
      OverflowCheckFlavor OCF =
          IntrinsicIDToOverflowCheckFlavor(II->getIntrinsicID());
      assert(OCF != OCF_INVALID && "unexpected!");
  
      Value *OperationResult = nullptr;
      Constant *OverflowResult = nullptr;
      if (OptimizeOverflowCheck(OCF, II->getArgOperand(0), II->getArgOperand(1),
                                *II, OperationResult, OverflowResult))
        return CreateOverflowTuple(II, OperationResult, OverflowResult);
  
      break;
    }
  
    case Intrinsic::minnum:
    case Intrinsic::maxnum: {
      Value *Arg0 = II->getArgOperand(0);
      Value *Arg1 = II->getArgOperand(1);
  
      // fmin(x, x) -> x
      if (Arg0 == Arg1)
        return ReplaceInstUsesWith(CI, Arg0);
  
      const ConstantFP *C0 = dyn_cast<ConstantFP>(Arg0);
      const ConstantFP *C1 = dyn_cast<ConstantFP>(Arg1);
  
      // Canonicalize constants into the RHS.
      if (C0 && !C1) {
        II->setArgOperand(0, Arg1);
        II->setArgOperand(1, Arg0);
        return II;
      }
  
      // fmin(x, nan) -> x
      if (C1 && C1->isNaN())
        return ReplaceInstUsesWith(CI, Arg0);
  
      // This is the value because if undef were NaN, we would return the other
      // value and cannot return a NaN unless both operands are.
      //
      // fmin(undef, x) -> x
      if (isa<UndefValue>(Arg0))
        return ReplaceInstUsesWith(CI, Arg1);
  
      // fmin(x, undef) -> x
      if (isa<UndefValue>(Arg1))
        return ReplaceInstUsesWith(CI, Arg0);
  
      Value *X = nullptr;
      Value *Y = nullptr;
      if (II->getIntrinsicID() == Intrinsic::minnum) {
        // fmin(x, fmin(x, y)) -> fmin(x, y)
        // fmin(y, fmin(x, y)) -> fmin(x, y)
        if (match(Arg1, m_FMin(m_Value(X), m_Value(Y)))) {
          if (Arg0 == X || Arg0 == Y)
            return ReplaceInstUsesWith(CI, Arg1);
        }
  
        // fmin(fmin(x, y), x) -> fmin(x, y)
        // fmin(fmin(x, y), y) -> fmin(x, y)
        if (match(Arg0, m_FMin(m_Value(X), m_Value(Y)))) {
          if (Arg1 == X || Arg1 == Y)
            return ReplaceInstUsesWith(CI, Arg0);
        }
  
        // TODO: fmin(nnan x, inf) -> x
        // TODO: fmin(nnan ninf x, flt_max) -> x
        if (C1 && C1->isInfinity()) {
          // fmin(x, -inf) -> -inf
          if (C1->isNegative())
            return ReplaceInstUsesWith(CI, Arg1);
        }
      } else {
        assert(II->getIntrinsicID() == Intrinsic::maxnum);
        // fmax(x, fmax(x, y)) -> fmax(x, y)
        // fmax(y, fmax(x, y)) -> fmax(x, y)
        if (match(Arg1, m_FMax(m_Value(X), m_Value(Y)))) {
          if (Arg0 == X || Arg0 == Y)
            return ReplaceInstUsesWith(CI, Arg1);
        }
  
        // fmax(fmax(x, y), x) -> fmax(x, y)
        // fmax(fmax(x, y), y) -> fmax(x, y)
        if (match(Arg0, m_FMax(m_Value(X), m_Value(Y)))) {
          if (Arg1 == X || Arg1 == Y)
            return ReplaceInstUsesWith(CI, Arg0);
        }
  
        // TODO: fmax(nnan x, -inf) -> x
        // TODO: fmax(nnan ninf x, -flt_max) -> x
        if (C1 && C1->isInfinity()) {
          // fmax(x, inf) -> inf
          if (!C1->isNegative())
            return ReplaceInstUsesWith(CI, Arg1);
        }
      }
      break;
    }
    case Intrinsic::ppc_altivec_lvx:
    case Intrinsic::ppc_altivec_lvxl:
      // Turn PPC lvx -> load if the pointer is known aligned.
      if (getOrEnforceKnownAlignment(II->getArgOperand(0), 16, DL, II, AC, DT) >=
          16) {
        Value *Ptr = Builder->CreateBitCast(II->getArgOperand(0),
                                           PointerType::getUnqual(II->getType()));
        return new LoadInst(Ptr);
      }
      break;
    case Intrinsic::ppc_vsx_lxvw4x:
    case Intrinsic::ppc_vsx_lxvd2x: {
      // Turn PPC VSX loads into normal loads.
      Value *Ptr = Builder->CreateBitCast(II->getArgOperand(0),
                                          PointerType::getUnqual(II->getType()));
      return new LoadInst(Ptr, Twine(""), false, 1);
    }
    case Intrinsic::ppc_altivec_stvx:
    case Intrinsic::ppc_altivec_stvxl:
      // Turn stvx -> store if the pointer is known aligned.
      if (getOrEnforceKnownAlignment(II->getArgOperand(1), 16, DL, II, AC, DT) >=
          16) {
        Type *OpPtrTy =
          PointerType::getUnqual(II->getArgOperand(0)->getType());
        Value *Ptr = Builder->CreateBitCast(II->getArgOperand(1), OpPtrTy);
        return new StoreInst(II->getArgOperand(0), Ptr);
      }
      break;
    case Intrinsic::ppc_vsx_stxvw4x:
    case Intrinsic::ppc_vsx_stxvd2x: {
      // Turn PPC VSX stores into normal stores.
      Type *OpPtrTy = PointerType::getUnqual(II->getArgOperand(0)->getType());
      Value *Ptr = Builder->CreateBitCast(II->getArgOperand(1), OpPtrTy);
      return new StoreInst(II->getArgOperand(0), Ptr, false, 1);
    }
    case Intrinsic::ppc_qpx_qvlfs:
      // Turn PPC QPX qvlfs -> load if the pointer is known aligned.
      if (getOrEnforceKnownAlignment(II->getArgOperand(0), 16, DL, II, AC, DT) >=
          16) {
        Type *VTy = VectorType::get(Builder->getFloatTy(),
                                    II->getType()->getVectorNumElements());
        Value *Ptr = Builder->CreateBitCast(II->getArgOperand(0),
                                           PointerType::getUnqual(VTy));
        Value *Load = Builder->CreateLoad(Ptr);
        return new FPExtInst(Load, II->getType());
      }
      break;
    case Intrinsic::ppc_qpx_qvlfd:
      // Turn PPC QPX qvlfd -> load if the pointer is known aligned.
      if (getOrEnforceKnownAlignment(II->getArgOperand(0), 32, DL, II, AC, DT) >=
          32) {
        Value *Ptr = Builder->CreateBitCast(II->getArgOperand(0),
                                           PointerType::getUnqual(II->getType()));
        return new LoadInst(Ptr);
      }
      break;
    case Intrinsic::ppc_qpx_qvstfs:
      // Turn PPC QPX qvstfs -> store if the pointer is known aligned.
      if (getOrEnforceKnownAlignment(II->getArgOperand(1), 16, DL, II, AC, DT) >=
          16) {
        Type *VTy = VectorType::get(Builder->getFloatTy(),
            II->getArgOperand(0)->getType()->getVectorNumElements());
        Value *TOp = Builder->CreateFPTrunc(II->getArgOperand(0), VTy);
        Type *OpPtrTy = PointerType::getUnqual(VTy);
        Value *Ptr = Builder->CreateBitCast(II->getArgOperand(1), OpPtrTy);
        return new StoreInst(TOp, Ptr);
      }
      break;
    case Intrinsic::ppc_qpx_qvstfd:
      // Turn PPC QPX qvstfd -> store if the pointer is known aligned.
      if (getOrEnforceKnownAlignment(II->getArgOperand(1), 32, DL, II, AC, DT) >=
          32) {
        Type *OpPtrTy =
          PointerType::getUnqual(II->getArgOperand(0)->getType());
        Value *Ptr = Builder->CreateBitCast(II->getArgOperand(1), OpPtrTy);
        return new StoreInst(II->getArgOperand(0), Ptr);
      }
      break;
  
    case Intrinsic::x86_sse_storeu_ps:
    case Intrinsic::x86_sse2_storeu_pd:
    case Intrinsic::x86_sse2_storeu_dq:
      // Turn X86 storeu -> store if the pointer is known aligned.
      if (getOrEnforceKnownAlignment(II->getArgOperand(0), 16, DL, II, AC, DT) >=
          16) {
        Type *OpPtrTy =
          PointerType::getUnqual(II->getArgOperand(1)->getType());
        Value *Ptr = Builder->CreateBitCast(II->getArgOperand(0), OpPtrTy);
        return new StoreInst(II->getArgOperand(1), Ptr);
      }
      break;
  
    case Intrinsic::x86_vcvtph2ps_128:
    case Intrinsic::x86_vcvtph2ps_256: {
      auto Arg = II->getArgOperand(0);
      auto ArgType = cast<VectorType>(Arg->getType());
      auto RetType = cast<VectorType>(II->getType());
      unsigned ArgWidth = ArgType->getNumElements();
      unsigned RetWidth = RetType->getNumElements();
      assert(RetWidth <= ArgWidth && "Unexpected input/return vector widths");
      assert(ArgType->isIntOrIntVectorTy() &&
             ArgType->getScalarSizeInBits() == 16 &&
             "CVTPH2PS input type should be 16-bit integer vector");
      assert(RetType->getScalarType()->isFloatTy() &&
             "CVTPH2PS output type should be 32-bit float vector");
  
      // Constant folding: Convert to generic half to single conversion.
      if (isa<ConstantAggregateZero>(Arg))
        return ReplaceInstUsesWith(*II, ConstantAggregateZero::get(RetType));
  
      if (isa<ConstantDataVector>(Arg)) {
        auto VectorHalfAsShorts = Arg;
        if (RetWidth < ArgWidth) {
          SmallVector<int, 8> SubVecMask;
          for (unsigned i = 0; i != RetWidth; ++i)
            SubVecMask.push_back((int)i);
          VectorHalfAsShorts = Builder->CreateShuffleVector(
              Arg, UndefValue::get(ArgType), SubVecMask);
        }
  
        auto VectorHalfType =
            VectorType::get(Type::getHalfTy(II->getContext()), RetWidth);
        auto VectorHalfs =
            Builder->CreateBitCast(VectorHalfAsShorts, VectorHalfType);
        auto VectorFloats = Builder->CreateFPExt(VectorHalfs, RetType);
        return ReplaceInstUsesWith(*II, VectorFloats);
      }
  
      // We only use the lowest lanes of the argument.
      APInt DemandedElts = APInt::getLowBitsSet(ArgWidth, RetWidth);
      APInt UndefElts(ArgWidth, 0);
      if (Value *V = SimplifyDemandedVectorElts(Arg, DemandedElts, UndefElts)) {
        II->setArgOperand(0, V);
        return II;
      }
      break;
    }
  
    case Intrinsic::x86_sse_cvtss2si:
    case Intrinsic::x86_sse_cvtss2si64:
    case Intrinsic::x86_sse_cvttss2si:
    case Intrinsic::x86_sse_cvttss2si64:
    case Intrinsic::x86_sse2_cvtsd2si:
    case Intrinsic::x86_sse2_cvtsd2si64:
    case Intrinsic::x86_sse2_cvttsd2si:
    case Intrinsic::x86_sse2_cvttsd2si64: {
      // These intrinsics only demand the 0th element of their input vectors. If
      // we can simplify the input based on that, do so now.
      unsigned VWidth =
        cast<VectorType>(II->getArgOperand(0)->getType())->getNumElements();
      APInt DemandedElts(VWidth, 1);
      APInt UndefElts(VWidth, 0);
      if (Value *V = SimplifyDemandedVectorElts(II->getArgOperand(0),
                                                DemandedElts, UndefElts)) {
        II->setArgOperand(0, V);
        return II;
      }
      break;
    }
  
    // Constant fold ashr( <A x Bi>, Ci ).
    // Constant fold lshr( <A x Bi>, Ci ).
    // Constant fold shl( <A x Bi>, Ci ).
    case Intrinsic::x86_sse2_psrai_d:
    case Intrinsic::x86_sse2_psrai_w:
    case Intrinsic::x86_avx2_psrai_d:
    case Intrinsic::x86_avx2_psrai_w:
    case Intrinsic::x86_sse2_psrli_d:
    case Intrinsic::x86_sse2_psrli_q:
    case Intrinsic::x86_sse2_psrli_w:
    case Intrinsic::x86_avx2_psrli_d:
    case Intrinsic::x86_avx2_psrli_q:
    case Intrinsic::x86_avx2_psrli_w:
    case Intrinsic::x86_sse2_pslli_d:
    case Intrinsic::x86_sse2_pslli_q:
    case Intrinsic::x86_sse2_pslli_w:
    case Intrinsic::x86_avx2_pslli_d:
    case Intrinsic::x86_avx2_pslli_q:
    case Intrinsic::x86_avx2_pslli_w:
      if (Value *V = SimplifyX86immshift(*II, *Builder))
        return ReplaceInstUsesWith(*II, V);
      break;
  
    case Intrinsic::x86_sse2_psra_d:
    case Intrinsic::x86_sse2_psra_w:
    case Intrinsic::x86_avx2_psra_d:
    case Intrinsic::x86_avx2_psra_w:
    case Intrinsic::x86_sse2_psrl_d:
    case Intrinsic::x86_sse2_psrl_q:
    case Intrinsic::x86_sse2_psrl_w:
    case Intrinsic::x86_avx2_psrl_d:
    case Intrinsic::x86_avx2_psrl_q:
    case Intrinsic::x86_avx2_psrl_w:
    case Intrinsic::x86_sse2_psll_d:
    case Intrinsic::x86_sse2_psll_q:
    case Intrinsic::x86_sse2_psll_w:
    case Intrinsic::x86_avx2_psll_d:
    case Intrinsic::x86_avx2_psll_q:
    case Intrinsic::x86_avx2_psll_w: {
      if (Value *V = SimplifyX86immshift(*II, *Builder))
        return ReplaceInstUsesWith(*II, V);
  
      // SSE2/AVX2 uses only the first 64-bits of the 128-bit vector
      // operand to compute the shift amount.
      auto ShiftAmt = II->getArgOperand(1);
      auto ShiftType = cast<VectorType>(ShiftAmt->getType());
      assert(ShiftType->getPrimitiveSizeInBits() == 128 &&
             "Unexpected packed shift size");
      unsigned VWidth = ShiftType->getNumElements();
  
      APInt DemandedElts = APInt::getLowBitsSet(VWidth, VWidth / 2);
      APInt UndefElts(VWidth, 0);
      if (Value *V =
              SimplifyDemandedVectorElts(ShiftAmt, DemandedElts, UndefElts)) {
        II->setArgOperand(1, V);
        return II;
      }
      break;
    }
  
    case Intrinsic::x86_sse41_pmovsxbd:
    case Intrinsic::x86_sse41_pmovsxbq:
    case Intrinsic::x86_sse41_pmovsxbw:
    case Intrinsic::x86_sse41_pmovsxdq:
    case Intrinsic::x86_sse41_pmovsxwd:
    case Intrinsic::x86_sse41_pmovsxwq:
    case Intrinsic::x86_avx2_pmovsxbd:
    case Intrinsic::x86_avx2_pmovsxbq:
    case Intrinsic::x86_avx2_pmovsxbw:
    case Intrinsic::x86_avx2_pmovsxdq:
    case Intrinsic::x86_avx2_pmovsxwd:
    case Intrinsic::x86_avx2_pmovsxwq:
      if (Value *V = SimplifyX86extend(*II, *Builder, true))
        return ReplaceInstUsesWith(*II, V);
      break;
  
    case Intrinsic::x86_sse41_pmovzxbd:
    case Intrinsic::x86_sse41_pmovzxbq:
    case Intrinsic::x86_sse41_pmovzxbw:
    case Intrinsic::x86_sse41_pmovzxdq:
    case Intrinsic::x86_sse41_pmovzxwd:
    case Intrinsic::x86_sse41_pmovzxwq:
    case Intrinsic::x86_avx2_pmovzxbd:
    case Intrinsic::x86_avx2_pmovzxbq:
    case Intrinsic::x86_avx2_pmovzxbw:
    case Intrinsic::x86_avx2_pmovzxdq:
    case Intrinsic::x86_avx2_pmovzxwd:
    case Intrinsic::x86_avx2_pmovzxwq:
      if (Value *V = SimplifyX86extend(*II, *Builder, false))
        return ReplaceInstUsesWith(*II, V);
      break;
  
    case Intrinsic::x86_sse41_insertps:
      if (Value *V = SimplifyX86insertps(*II, *Builder))
        return ReplaceInstUsesWith(*II, V);
      break;
  
    case Intrinsic::x86_sse4a_extrq: {
      // EXTRQ uses only the lowest 64-bits of the first 128-bit vector
      // operands and the lowest 16-bits of the second.
      Value *Op0 = II->getArgOperand(0);
      Value *Op1 = II->getArgOperand(1);
      unsigned VWidth0 = Op0->getType()->getVectorNumElements();
      unsigned VWidth1 = Op1->getType()->getVectorNumElements();
      assert(VWidth0 == 2 && VWidth1 == 16 && "Unexpected operand sizes");
  
      if (Value *V = SimplifyDemandedVectorEltsLow(Op0, VWidth0, 1)) {
        II->setArgOperand(0, V);
        return II;
      }
      if (Value *V = SimplifyDemandedVectorEltsLow(Op1, VWidth1, 2)) {
        II->setArgOperand(1, V);
        return II;
      }
      break;
    }
  
    case Intrinsic::x86_sse4a_extrqi: {
      // EXTRQI uses only the lowest 64-bits of the first 128-bit vector
      // operand.
      Value *Op = II->getArgOperand(0);
      unsigned VWidth = Op->getType()->getVectorNumElements();
      assert(VWidth == 2 && "Unexpected operand size");
  
      if (Value *V = SimplifyDemandedVectorEltsLow(Op, VWidth, 1)) {
        II->setArgOperand(0, V);
        return II;
      }
      break;
    }
  
    case Intrinsic::x86_sse4a_insertq: {
      // INSERTQ uses only the lowest 64-bits of the first 128-bit vector
      // operand.
      Value *Op = II->getArgOperand(0);
      unsigned VWidth = Op->getType()->getVectorNumElements();
      assert(VWidth == 2 && "Unexpected operand size");
  
      if (Value *V = SimplifyDemandedVectorEltsLow(Op, VWidth, 1)) {
        II->setArgOperand(0, V);
        return II;
      }
      break;
    }
  
    case Intrinsic::x86_sse4a_insertqi: {
      // insertqi x, y, 64, 0 can just copy y's lower bits and leave the top
      // ones undef
      // TODO: eventually we should lower this intrinsic to IR
      if (auto CILength = dyn_cast<ConstantInt>(II->getArgOperand(2))) {
        if (auto CIIndex = dyn_cast<ConstantInt>(II->getArgOperand(3))) {
          unsigned Index = CIIndex->getZExtValue();
          // From AMD documentation: "a value of zero in the field length is
          // defined as length of 64".
          unsigned Length = CILength->equalsInt(0) ? 64 : CILength->getZExtValue();
  
          // From AMD documentation: "If the sum of the bit index + length field
          // is greater than 64, the results are undefined".
          unsigned End = Index + Length;
  
          // Note that both field index and field length are 8-bit quantities.
          // Since variables 'Index' and 'Length' are unsigned values
          // obtained from zero-extending field index and field length
          // respectively, their sum should never wrap around.
          if (End > 64)
            return ReplaceInstUsesWith(CI, UndefValue::get(II->getType()));
  
          if (Length == 64 && Index == 0) {
            Value *Vec = II->getArgOperand(1);
            Value *Undef = UndefValue::get(Vec->getType());
            const uint32_t Mask[] = { 0, 2 };
            return ReplaceInstUsesWith(
                CI,
                Builder->CreateShuffleVector(
                    Vec, Undef, ConstantDataVector::get(
                                    II->getContext(), makeArrayRef(Mask))));
          } else if (auto Source =
                         dyn_cast<IntrinsicInst>(II->getArgOperand(0))) {
            if (Source->hasOneUse() &&
                Source->getArgOperand(1) == II->getArgOperand(1)) {
              // If the source of the insert has only one use and it's another
              // insert (and they're both inserting from the same vector), try to
              // bundle both together.
              auto CISourceLength =
                  dyn_cast<ConstantInt>(Source->getArgOperand(2));
              auto CISourceIndex =
                  dyn_cast<ConstantInt>(Source->getArgOperand(3));
              if (CISourceIndex && CISourceLength) {
                unsigned SourceIndex = CISourceIndex->getZExtValue();
                unsigned SourceLength = CISourceLength->getZExtValue();
                unsigned SourceEnd = SourceIndex + SourceLength;
                unsigned NewIndex, NewLength;
                bool ShouldReplace = false;
                if (Index <= SourceIndex && SourceIndex <= End) {
                  NewIndex = Index;
                  NewLength = std::max(End, SourceEnd) - NewIndex;
                  ShouldReplace = true;
                } else if (SourceIndex <= Index && Index <= SourceEnd) {
                  NewIndex = SourceIndex;
                  NewLength = std::max(SourceEnd, End) - NewIndex;
                  ShouldReplace = true;
                }
  
                if (ShouldReplace) {
                  Constant *ConstantLength = ConstantInt::get(
                      II->getArgOperand(2)->getType(), NewLength, false);
                  Constant *ConstantIndex = ConstantInt::get(
                      II->getArgOperand(3)->getType(), NewIndex, false);
                  Value *Args[4] = { Source->getArgOperand(0),
                                     II->getArgOperand(1), ConstantLength,
                                     ConstantIndex };
                  Module *M = CI.getParent()->getParent()->getParent();
                  Value *F =
                      Intrinsic::getDeclaration(M, Intrinsic::x86_sse4a_insertqi);
                  return ReplaceInstUsesWith(CI, Builder->CreateCall(F, Args));
                }
              }
            }
          }
        }
      }
  
      // INSERTQI uses only the lowest 64-bits of the first two 128-bit vector
      // operands.
      Value *Op0 = II->getArgOperand(0);
      Value *Op1 = II->getArgOperand(1);
      unsigned VWidth0 = Op0->getType()->getVectorNumElements();
      unsigned VWidth1 = Op1->getType()->getVectorNumElements();
      assert(VWidth0 == 2 && VWidth1 == 2 && "Unexpected operand sizes");
  
      if (Value *V = SimplifyDemandedVectorEltsLow(Op0, VWidth0, 1)) {
        II->setArgOperand(0, V);
        return II;
      }
  
      if (Value *V = SimplifyDemandedVectorEltsLow(Op1, VWidth1, 1)) {
        II->setArgOperand(1, V);
        return II;
      }
      break;
    }
  
    case Intrinsic::x86_sse41_pblendvb:
    case Intrinsic::x86_sse41_blendvps:
    case Intrinsic::x86_sse41_blendvpd:
    case Intrinsic::x86_avx_blendv_ps_256:
    case Intrinsic::x86_avx_blendv_pd_256:
    case Intrinsic::x86_avx2_pblendvb: {
      // Convert blendv* to vector selects if the mask is constant.
      // This optimization is convoluted because the intrinsic is defined as
      // getting a vector of floats or doubles for the ps and pd versions.
      // FIXME: That should be changed.
  
      Value *Op0 = II->getArgOperand(0);
      Value *Op1 = II->getArgOperand(1);
      Value *Mask = II->getArgOperand(2);
  
      // fold (blend A, A, Mask) -> A
      if (Op0 == Op1)
        return ReplaceInstUsesWith(CI, Op0);
  
      // Zero Mask - select 1st argument.
      if (isa<ConstantAggregateZero>(Mask))
        return ReplaceInstUsesWith(CI, Op0);
  
      // Constant Mask - select 1st/2nd argument lane based on top bit of mask.
      if (auto C = dyn_cast<ConstantDataVector>(Mask)) {
        auto Tyi1 = Builder->getInt1Ty();
        auto SelectorType = cast<VectorType>(Mask->getType());
        auto EltTy = SelectorType->getElementType();
        unsigned Size = SelectorType->getNumElements();
        unsigned BitWidth =
            EltTy->isFloatTy()
                ? 32
                : (EltTy->isDoubleTy() ? 64 : EltTy->getIntegerBitWidth());
        assert((BitWidth == 64 || BitWidth == 32 || BitWidth == 8) &&
               "Wrong arguments for variable blend intrinsic");
        SmallVector<Constant *, 32> Selectors;
        for (unsigned I = 0; I < Size; ++I) {
          // The intrinsics only read the top bit
          uint64_t Selector;
          if (BitWidth == 8)
            Selector = C->getElementAsInteger(I);
          else
            Selector = C->getElementAsAPFloat(I).bitcastToAPInt().getZExtValue();
          Selectors.push_back(ConstantInt::get(Tyi1, Selector >> (BitWidth - 1)));
        }
        auto NewSelector = ConstantVector::get(Selectors);
        return SelectInst::Create(NewSelector, Op1, Op0, "blendv");
      }
      break;
    }
  
    case Intrinsic::x86_avx_vpermilvar_ps:
    case Intrinsic::x86_avx_vpermilvar_ps_256:
    case Intrinsic::x86_avx_vpermilvar_pd:
    case Intrinsic::x86_avx_vpermilvar_pd_256: {
      // Convert vpermil* to shufflevector if the mask is constant.
      Value *V = II->getArgOperand(1);
      unsigned Size = cast<VectorType>(V->getType())->getNumElements();
      assert(Size == 8 || Size == 4 || Size == 2);
      uint32_t Indexes[8];
      if (auto C = dyn_cast<ConstantDataVector>(V)) {
        // The intrinsics only read one or two bits, clear the rest.
        for (unsigned I = 0; I < Size; ++I) {
          uint32_t Index = C->getElementAsInteger(I) & 0x3;
          if (II->getIntrinsicID() == Intrinsic::x86_avx_vpermilvar_pd ||
              II->getIntrinsicID() == Intrinsic::x86_avx_vpermilvar_pd_256)
            Index >>= 1;
          Indexes[I] = Index;
        }
      } else if (isa<ConstantAggregateZero>(V)) {
        for (unsigned I = 0; I < Size; ++I)
          Indexes[I] = 0;
      } else {
        break;
      }
      // The _256 variants are a bit trickier since the mask bits always index
      // into the corresponding 128 half. In order to convert to a generic
      // shuffle, we have to make that explicit.
      if (II->getIntrinsicID() == Intrinsic::x86_avx_vpermilvar_ps_256 ||
          II->getIntrinsicID() == Intrinsic::x86_avx_vpermilvar_pd_256) {
        for (unsigned I = Size / 2; I < Size; ++I)
          Indexes[I] += Size / 2;
      }
      auto NewC =
          ConstantDataVector::get(V->getContext(), makeArrayRef(Indexes, Size));
      auto V1 = II->getArgOperand(0);
      auto V2 = UndefValue::get(V1->getType());
      auto Shuffle = Builder->CreateShuffleVector(V1, V2, NewC);
      return ReplaceInstUsesWith(CI, Shuffle);
    }
  
    case Intrinsic::x86_avx_vperm2f128_pd_256:
    case Intrinsic::x86_avx_vperm2f128_ps_256:
    case Intrinsic::x86_avx_vperm2f128_si_256:
    case Intrinsic::x86_avx2_vperm2i128:
      if (Value *V = SimplifyX86vperm2(*II, *Builder))
        return ReplaceInstUsesWith(*II, V);
      break;
  
    case Intrinsic::ppc_altivec_vperm:
      // Turn vperm(V1,V2,mask) -> shuffle(V1,V2,mask) if mask is a constant.
      // Note that ppc_altivec_vperm has a big-endian bias, so when creating
      // a vectorshuffle for little endian, we must undo the transformation
      // performed on vec_perm in altivec.h.  That is, we must complement
      // the permutation mask with respect to 31 and reverse the order of
      // V1 and V2.
      if (Constant *Mask = dyn_cast<Constant>(II->getArgOperand(2))) {
        assert(Mask->getType()->getVectorNumElements() == 16 &&
               "Bad type for intrinsic!");
  
        // Check that all of the elements are integer constants or undefs.
        bool AllEltsOk = true;
        for (unsigned i = 0; i != 16; ++i) {
          Constant *Elt = Mask->getAggregateElement(i);
          if (!Elt || !(isa<ConstantInt>(Elt) || isa<UndefValue>(Elt))) {
            AllEltsOk = false;
            break;
          }
        }
  
        if (AllEltsOk) {
          // Cast the input vectors to byte vectors.
          Value *Op0 = Builder->CreateBitCast(II->getArgOperand(0),
                                              Mask->getType());
          Value *Op1 = Builder->CreateBitCast(II->getArgOperand(1),
                                              Mask->getType());
          Value *Result = UndefValue::get(Op0->getType());
  
          // Only extract each element once.
          Value *ExtractedElts[32];
          memset(ExtractedElts, 0, sizeof(ExtractedElts));
  
          for (unsigned i = 0; i != 16; ++i) {
            if (isa<UndefValue>(Mask->getAggregateElement(i)))
              continue;
            unsigned Idx =
              cast<ConstantInt>(Mask->getAggregateElement(i))->getZExtValue();
            Idx &= 31;  // Match the hardware behavior.
            if (DL.isLittleEndian())
              Idx = 31 - Idx;
  
            if (!ExtractedElts[Idx]) {
              Value *Op0ToUse = (DL.isLittleEndian()) ? Op1 : Op0;
              Value *Op1ToUse = (DL.isLittleEndian()) ? Op0 : Op1;
              ExtractedElts[Idx] =
                Builder->CreateExtractElement(Idx < 16 ? Op0ToUse : Op1ToUse,
                                              Builder->getInt32(Idx&15));
            }
  
            // Insert this value into the result vector.
            Result = Builder->CreateInsertElement(Result, ExtractedElts[Idx],
                                                  Builder->getInt32(i));
          }
          return CastInst::Create(Instruction::BitCast, Result, CI.getType());
        }
      }
      break;
  
    case Intrinsic::arm_neon_vld1:
    case Intrinsic::arm_neon_vld2:
    case Intrinsic::arm_neon_vld3:
    case Intrinsic::arm_neon_vld4:
    case Intrinsic::arm_neon_vld2lane:
    case Intrinsic::arm_neon_vld3lane:
    case Intrinsic::arm_neon_vld4lane:
    case Intrinsic::arm_neon_vst1:
    case Intrinsic::arm_neon_vst2:
    case Intrinsic::arm_neon_vst3:
    case Intrinsic::arm_neon_vst4:
    case Intrinsic::arm_neon_vst2lane:
    case Intrinsic::arm_neon_vst3lane:
    case Intrinsic::arm_neon_vst4lane: {
      unsigned MemAlign = getKnownAlignment(II->getArgOperand(0), DL, II, AC, DT);
      unsigned AlignArg = II->getNumArgOperands() - 1;
      ConstantInt *IntrAlign = dyn_cast<ConstantInt>(II->getArgOperand(AlignArg));
      if (IntrAlign && IntrAlign->getZExtValue() < MemAlign) {
        II->setArgOperand(AlignArg,
                          ConstantInt::get(Type::getInt32Ty(II->getContext()),
                                           MemAlign, false));
        return II;
      }
      break;
    }
  
    case Intrinsic::arm_neon_vmulls:
    case Intrinsic::arm_neon_vmullu:
    case Intrinsic::aarch64_neon_smull:
    case Intrinsic::aarch64_neon_umull: {
      Value *Arg0 = II->getArgOperand(0);
      Value *Arg1 = II->getArgOperand(1);
  
      // Handle mul by zero first:
      if (isa<ConstantAggregateZero>(Arg0) || isa<ConstantAggregateZero>(Arg1)) {
        return ReplaceInstUsesWith(CI, ConstantAggregateZero::get(II->getType()));
      }
  
      // Check for constant LHS & RHS - in this case we just simplify.
      bool Zext = (II->getIntrinsicID() == Intrinsic::arm_neon_vmullu ||
                   II->getIntrinsicID() == Intrinsic::aarch64_neon_umull);
      VectorType *NewVT = cast<VectorType>(II->getType());
      if (Constant *CV0 = dyn_cast<Constant>(Arg0)) {
        if (Constant *CV1 = dyn_cast<Constant>(Arg1)) {
          CV0 = ConstantExpr::getIntegerCast(CV0, NewVT, /*isSigned=*/!Zext);
          CV1 = ConstantExpr::getIntegerCast(CV1, NewVT, /*isSigned=*/!Zext);
  
          return ReplaceInstUsesWith(CI, ConstantExpr::getMul(CV0, CV1));
        }
  
        // Couldn't simplify - canonicalize constant to the RHS.
        std::swap(Arg0, Arg1);
      }
  
      // Handle mul by one:
      if (Constant *CV1 = dyn_cast<Constant>(Arg1))
        if (ConstantInt *Splat =
                dyn_cast_or_null<ConstantInt>(CV1->getSplatValue()))
          if (Splat->isOne())
            return CastInst::CreateIntegerCast(Arg0, II->getType(),
                                               /*isSigned=*/!Zext);
  
      break;
    }
  
    case Intrinsic::AMDGPU_rcp: {
      if (const ConstantFP *C = dyn_cast<ConstantFP>(II->getArgOperand(0))) {
        const APFloat &ArgVal = C->getValueAPF();
        APFloat Val(ArgVal.getSemantics(), 1.0);
        APFloat::opStatus Status = Val.divide(ArgVal,
                                              APFloat::rmNearestTiesToEven);
        // Only do this if it was exact and therefore not dependent on the
        // rounding mode.
        if (Status == APFloat::opOK)
          return ReplaceInstUsesWith(CI, ConstantFP::get(II->getContext(), Val));
      }
  
      break;
    }
    case Intrinsic::stackrestore: {
      // If the save is right next to the restore, remove the restore.  This can
      // happen when variable allocas are DCE'd.
      if (IntrinsicInst *SS = dyn_cast<IntrinsicInst>(II->getArgOperand(0))) {
        if (SS->getIntrinsicID() == Intrinsic::stacksave) {
          BasicBlock::iterator BI = SS;
          if (&*++BI == II)
            return EraseInstFromFunction(CI);
        }
      }
  
      // Scan down this block to see if there is another stack restore in the
      // same block without an intervening call/alloca.
      BasicBlock::iterator BI = II;
      TerminatorInst *TI = II->getParent()->getTerminator();
      bool CannotRemove = false;
      for (++BI; &*BI != TI; ++BI) {
        if (isa<AllocaInst>(BI)) {
          CannotRemove = true;
          break;
        }
        if (CallInst *BCI = dyn_cast<CallInst>(BI)) {
          if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(BCI)) {
            // If there is a stackrestore below this one, remove this one.
            if (II->getIntrinsicID() == Intrinsic::stackrestore)
              return EraseInstFromFunction(CI);
            // Otherwise, ignore the intrinsic.
          } else {
            // If we found a non-intrinsic call, we can't remove the stack
            // restore.
            CannotRemove = true;
            break;
          }
        }
      }
  
      // If the stack restore is in a return, resume, or unwind block and if there
      // are no allocas or calls between the restore and the return, nuke the
      // restore.
      if (!CannotRemove && (isa<ReturnInst>(TI) || isa<ResumeInst>(TI)))
        return EraseInstFromFunction(CI);
      break;
    }
    case Intrinsic::assume: {
      // Canonicalize assume(a && b) -> assume(a); assume(b);
      // Note: New assumption intrinsics created here are registered by
      // the InstCombineIRInserter object.
      Value *IIOperand = II->getArgOperand(0), *A, *B,
            *AssumeIntrinsic = II->getCalledValue();
      if (match(IIOperand, m_And(m_Value(A), m_Value(B)))) {
        Builder->CreateCall(AssumeIntrinsic, A, II->getName());
        Builder->CreateCall(AssumeIntrinsic, B, II->getName());
        return EraseInstFromFunction(*II);
      }
      // assume(!(a || b)) -> assume(!a); assume(!b);
      if (match(IIOperand, m_Not(m_Or(m_Value(A), m_Value(B))))) {
        Builder->CreateCall(AssumeIntrinsic, Builder->CreateNot(A),
                            II->getName());
        Builder->CreateCall(AssumeIntrinsic, Builder->CreateNot(B),
                            II->getName());
        return EraseInstFromFunction(*II);
      }
  
      // assume( (load addr) != null ) -> add 'nonnull' metadata to load
      // (if assume is valid at the load)
      if (ICmpInst* ICmp = dyn_cast<ICmpInst>(IIOperand)) {
        Value *LHS = ICmp->getOperand(0);
        Value *RHS = ICmp->getOperand(1);
        if (ICmpInst::ICMP_NE == ICmp->getPredicate() &&
            isa<LoadInst>(LHS) &&
            isa<Constant>(RHS) &&
            RHS->getType()->isPointerTy() &&
            cast<Constant>(RHS)->isNullValue()) {
          LoadInst* LI = cast<LoadInst>(LHS);
          if (isValidAssumeForContext(II, LI, DT)) {
            MDNode *MD = MDNode::get(II->getContext(), None);
            LI->setMetadata(LLVMContext::MD_nonnull, MD);
            return EraseInstFromFunction(*II);
          }
        }
        // TODO: apply nonnull return attributes to calls and invokes
        // TODO: apply range metadata for range check patterns?
      }
      // If there is a dominating assume with the same condition as this one,
      // then this one is redundant, and should be removed.
      APInt KnownZero(1, 0), KnownOne(1, 0);
      computeKnownBits(IIOperand, KnownZero, KnownOne, 0, II);
      if (KnownOne.isAllOnesValue())
        return EraseInstFromFunction(*II);
  
      break;
    }
    case Intrinsic::experimental_gc_relocate: {
      // Translate facts known about a pointer before relocating into
      // facts about the relocate value, while being careful to
      // preserve relocation semantics.
      GCRelocateOperands Operands(II);
      Value *DerivedPtr = Operands.getDerivedPtr();
      auto *GCRelocateType = cast<PointerType>(II->getType());
  
      // Remove the relocation if unused, note that this check is required
      // to prevent the cases below from looping forever.
      if (II->use_empty())
        return EraseInstFromFunction(*II);
  
      // Undef is undef, even after relocation.
      // TODO: provide a hook for this in GCStrategy.  This is clearly legal for
      // most practical collectors, but there was discussion in the review thread
      // about whether it was legal for all possible collectors.
      if (isa<UndefValue>(DerivedPtr)) {
        // gc_relocate is uncasted. Use undef of gc_relocate's type to replace it.
        return ReplaceInstUsesWith(*II, UndefValue::get(GCRelocateType));
      }
  
      // The relocation of null will be null for most any collector.
      // TODO: provide a hook for this in GCStrategy.  There might be some weird
      // collector this property does not hold for.
      if (isa<ConstantPointerNull>(DerivedPtr)) {
        // gc_relocate is uncasted. Use null-pointer of gc_relocate's type to replace it.
        return ReplaceInstUsesWith(*II, ConstantPointerNull::get(GCRelocateType));
      }
  
      // isKnownNonNull -> nonnull attribute
      if (isKnownNonNullAt(DerivedPtr, II, DT, TLI))
        II->addAttribute(AttributeSet::ReturnIndex, Attribute::NonNull);
  
      // isDereferenceablePointer -> deref attribute
      if (isDereferenceablePointer(DerivedPtr, DL)) {
        if (Argument *A = dyn_cast<Argument>(DerivedPtr)) {
          uint64_t Bytes = A->getDereferenceableBytes();
          II->addDereferenceableAttr(AttributeSet::ReturnIndex, Bytes);
        }
      }
  
      // TODO: bitcast(relocate(p)) -> relocate(bitcast(p))
      // Canonicalize on the type from the uses to the defs
  
      // TODO: relocate((gep p, C, C2, ...)) -> gep(relocate(p), C, C2, ...)
    }
    }
  
    return visitCallSite(II);
  }
  
  // InvokeInst simplification
  //
  Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
    return visitCallSite(&II);
  }
  
  /// isSafeToEliminateVarargsCast - If this cast does not affect the value
  /// passed through the varargs area, we can eliminate the use of the cast.
  static bool isSafeToEliminateVarargsCast(const CallSite CS,
                                           const DataLayout &DL,
                                           const CastInst *const CI,
                                           const int ix) {
    if (!CI->isLosslessCast())
      return false;
  
    // If this is a GC intrinsic, avoid munging types.  We need types for
    // statepoint reconstruction in SelectionDAG.
    // TODO: This is probably something which should be expanded to all
    // intrinsics since the entire point of intrinsics is that
    // they are understandable by the optimizer.
    if (isStatepoint(CS) || isGCRelocate(CS) || isGCResult(CS))
      return false;
  
    // The size of ByVal or InAlloca arguments is derived from the type, so we
    // can't change to a type with a different size.  If the size were
    // passed explicitly we could avoid this check.
    if (!CS.isByValOrInAllocaArgument(ix))
      return true;
  
    Type* SrcTy =
              cast<PointerType>(CI->getOperand(0)->getType())->getElementType();
    Type* DstTy = cast<PointerType>(CI->getType())->getElementType();
    if (!SrcTy->isSized() || !DstTy->isSized())
      return false;
    if (DL.getTypeAllocSize(SrcTy) != DL.getTypeAllocSize(DstTy))
      return false;
    return true;
  }
  
  // Try to fold some different type of calls here.
  // Currently we're only working with the checking functions, memcpy_chk,
  // mempcpy_chk, memmove_chk, memset_chk, strcpy_chk, stpcpy_chk, strncpy_chk,
  // strcat_chk and strncat_chk.
  Instruction *InstCombiner::tryOptimizeCall(CallInst *CI) {
    if (!CI->getCalledFunction()) return nullptr;
  
    auto InstCombineRAUW = [this](Instruction *From, Value *With) {
      ReplaceInstUsesWith(*From, With);
    };
    LibCallSimplifier Simplifier(DL, TLI, InstCombineRAUW);
    if (Value *With = Simplifier.optimizeCall(CI)) {
      ++NumSimplified;
      return CI->use_empty() ? CI : ReplaceInstUsesWith(*CI, With);
    }
  
    return nullptr;
  }
  
  static IntrinsicInst *FindInitTrampolineFromAlloca(Value *TrampMem) {
    // Strip off at most one level of pointer casts, looking for an alloca.  This
    // is good enough in practice and simpler than handling any number of casts.
    Value *Underlying = TrampMem->stripPointerCasts();
    if (Underlying != TrampMem &&
        (!Underlying->hasOneUse() || Underlying->user_back() != TrampMem))
      return nullptr;
    if (!isa<AllocaInst>(Underlying))
      return nullptr;
  
    IntrinsicInst *InitTrampoline = nullptr;
    for (User *U : TrampMem->users()) {
      IntrinsicInst *II = dyn_cast<IntrinsicInst>(U);
      if (!II)
        return nullptr;
      if (II->getIntrinsicID() == Intrinsic::init_trampoline) {
        if (InitTrampoline)
          // More than one init_trampoline writes to this value.  Give up.
          return nullptr;
        InitTrampoline = II;
        continue;
      }
      if (II->getIntrinsicID() == Intrinsic::adjust_trampoline)
        // Allow any number of calls to adjust.trampoline.
        continue;
      return nullptr;
    }
  
    // No call to init.trampoline found.
    if (!InitTrampoline)
      return nullptr;
  
    // Check that the alloca is being used in the expected way.
    if (InitTrampoline->getOperand(0) != TrampMem)
      return nullptr;
  
    return InitTrampoline;
  }
  
  static IntrinsicInst *FindInitTrampolineFromBB(IntrinsicInst *AdjustTramp,
                                                 Value *TrampMem) {
    // Visit all the previous instructions in the basic block, and try to find a
    // init.trampoline which has a direct path to the adjust.trampoline.
    for (BasicBlock::iterator I = AdjustTramp,
         E = AdjustTramp->getParent()->begin(); I != E; ) {
      Instruction *Inst = --I;
      if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
        if (II->getIntrinsicID() == Intrinsic::init_trampoline &&
            II->getOperand(0) == TrampMem)
          return II;
      if (Inst->mayWriteToMemory())
        return nullptr;
    }
    return nullptr;
  }
  
  // Given a call to llvm.adjust.trampoline, find and return the corresponding
  // call to llvm.init.trampoline if the call to the trampoline can be optimized
  // to a direct call to a function.  Otherwise return NULL.
  //
  static IntrinsicInst *FindInitTrampoline(Value *Callee) {
    Callee = Callee->stripPointerCasts();
    IntrinsicInst *AdjustTramp = dyn_cast<IntrinsicInst>(Callee);
    if (!AdjustTramp ||
        AdjustTramp->getIntrinsicID() != Intrinsic::adjust_trampoline)
      return nullptr;
  
    Value *TrampMem = AdjustTramp->getOperand(0);
  
    if (IntrinsicInst *IT = FindInitTrampolineFromAlloca(TrampMem))
      return IT;
    if (IntrinsicInst *IT = FindInitTrampolineFromBB(AdjustTramp, TrampMem))
      return IT;
    return nullptr;
  }
  
  // visitCallSite - Improvements for call and invoke instructions.
  //
  Instruction *InstCombiner::visitCallSite(CallSite CS) {
  
    if (isAllocLikeFn(CS.getInstruction(), TLI))
      return visitAllocSite(*CS.getInstruction());
  
    bool Changed = false;
  
    // Mark any parameters that are known to be non-null with the nonnull
    // attribute.  This is helpful for inlining calls to functions with null
    // checks on their arguments.
    unsigned ArgNo = 0;
    for (Value *V : CS.args()) {
      if (V->getType()->isPointerTy() && !CS.paramHasAttr(ArgNo+1, Attribute::NonNull) &&
          isKnownNonNullAt(V, CS.getInstruction(), DT, TLI)) {
        AttributeSet AS = CS.getAttributes();
        AS = AS.addAttribute(CS.getInstruction()->getContext(), ArgNo+1,
                             Attribute::NonNull);
        CS.setAttributes(AS);
        Changed = true;
      }
      ArgNo++;
    }
    assert(ArgNo == CS.arg_size() && "sanity check");
  
    // If the callee is a pointer to a function, attempt to move any casts to the
    // arguments of the call/invoke.
    Value *Callee = CS.getCalledValue();
    if (!isa<Function>(Callee) && transformConstExprCastCall(CS))
      return nullptr;
  
    if (Function *CalleeF = dyn_cast<Function>(Callee))
      // If the call and callee calling conventions don't match, this call must
      // be unreachable, as the call is undefined.
      if (CalleeF->getCallingConv() != CS.getCallingConv() &&
          // Only do this for calls to a function with a body.  A prototype may
          // not actually end up matching the implementation's calling conv for a
          // variety of reasons (e.g. it may be written in assembly).
          !CalleeF->isDeclaration()) {
        Instruction *OldCall = CS.getInstruction();
        new StoreInst(ConstantInt::getTrue(Callee->getContext()),
                  UndefValue::get(Type::getInt1PtrTy(Callee->getContext())),
                                    OldCall);
        // If OldCall does not return void then replaceAllUsesWith undef.
        // This allows ValueHandlers and custom metadata to adjust itself.
        if (!OldCall->getType()->isVoidTy())
          ReplaceInstUsesWith(*OldCall, UndefValue::get(OldCall->getType()));
        if (isa<CallInst>(OldCall))
          return EraseInstFromFunction(*OldCall);
  
        // We cannot remove an invoke, because it would change the CFG, just
        // change the callee to a null pointer.
        cast<InvokeInst>(OldCall)->setCalledFunction(
                                      Constant::getNullValue(CalleeF->getType()));
        return nullptr;
      }
  
    if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
      // If CS does not return void then replaceAllUsesWith undef.
      // This allows ValueHandlers and custom metadata to adjust itself.
      if (!CS.getInstruction()->getType()->isVoidTy())
        ReplaceInstUsesWith(*CS.getInstruction(),
                            UndefValue::get(CS.getInstruction()->getType()));
  
      if (isa<InvokeInst>(CS.getInstruction())) {
        // Can't remove an invoke because we cannot change the CFG.
        return nullptr;
      }
  
      // This instruction is not reachable, just remove it.  We insert a store to
      // undef so that we know that this code is not reachable, despite the fact
      // that we can't modify the CFG here.
      new StoreInst(ConstantInt::getTrue(Callee->getContext()),
                    UndefValue::get(Type::getInt1PtrTy(Callee->getContext())),
                    CS.getInstruction());
  
      return EraseInstFromFunction(*CS.getInstruction());
    }
  
    if (IntrinsicInst *II = FindInitTrampoline(Callee))
      return transformCallThroughTrampoline(CS, II);
  
    PointerType *PTy = cast<PointerType>(Callee->getType());
    FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
    if (FTy->isVarArg()) {
      int ix = FTy->getNumParams();
      // See if we can optimize any arguments passed through the varargs area of
      // the call.
      for (CallSite::arg_iterator I = CS.arg_begin() + FTy->getNumParams(),
             E = CS.arg_end(); I != E; ++I, ++ix) {
        CastInst *CI = dyn_cast<CastInst>(*I);
        if (CI && isSafeToEliminateVarargsCast(CS, DL, CI, ix)) {
          *I = CI->getOperand(0);
          Changed = true;
        }
      }
    }
  
    if (isa<InlineAsm>(Callee) && !CS.doesNotThrow()) {
      // Inline asm calls cannot throw - mark them 'nounwind'.
      CS.setDoesNotThrow();
      Changed = true;
    }
  
    // Try to optimize the call if possible, we require DataLayout for most of
    // this.  None of these calls are seen as possibly dead so go ahead and
    // delete the instruction now.
    if (CallInst *CI = dyn_cast<CallInst>(CS.getInstruction())) {
      Instruction *I = tryOptimizeCall(CI);
      // If we changed something return the result, etc. Otherwise let
      // the fallthrough check.
      if (I) return EraseInstFromFunction(*I);
    }
  
    return Changed ? CS.getInstruction() : nullptr;
  }
  
  // transformConstExprCastCall - If the callee is a constexpr cast of a function,
  // attempt to move the cast to the arguments of the call/invoke.
  //
  bool InstCombiner::transformConstExprCastCall(CallSite CS) {
    Function *Callee =
      dyn_cast<Function>(CS.getCalledValue()->stripPointerCasts());
    if (!Callee)
      return false;
    // The prototype of thunks are a lie, don't try to directly call such
    // functions.
    if (Callee->hasFnAttribute("thunk"))
      return false;
    Instruction *Caller = CS.getInstruction();
    const AttributeSet &CallerPAL = CS.getAttributes();
  
    // Okay, this is a cast from a function to a different type.  Unless doing so
    // would cause a type conversion of one of our arguments, change this call to
    // be a direct call with arguments casted to the appropriate types.
    //
    FunctionType *FT = Callee->getFunctionType();
    Type *OldRetTy = Caller->getType();
    Type *NewRetTy = FT->getReturnType();
  
    // Check to see if we are changing the return type...
    if (OldRetTy != NewRetTy) {
  
      if (NewRetTy->isStructTy())
        return false; // TODO: Handle multiple return values.
  
      if (!CastInst::isBitOrNoopPointerCastable(NewRetTy, OldRetTy, DL)) {
        if (Callee->isDeclaration())
          return false;   // Cannot transform this return value.
  
        if (!Caller->use_empty() &&
            // void -> non-void is handled specially
            !NewRetTy->isVoidTy())
          return false;   // Cannot transform this return value.
      }
  
      if (!CallerPAL.isEmpty() && !Caller->use_empty()) {
        AttrBuilder RAttrs(CallerPAL, AttributeSet::ReturnIndex);
        if (RAttrs.overlaps(AttributeFuncs::typeIncompatible(NewRetTy)))
          return false;   // Attribute not compatible with transformed value.
      }
  
      // If the callsite is an invoke instruction, and the return value is used by
      // a PHI node in a successor, we cannot change the return type of the call
      // because there is no place to put the cast instruction (without breaking
      // the critical edge).  Bail out in this case.
      if (!Caller->use_empty())
        if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
          for (User *U : II->users())
            if (PHINode *PN = dyn_cast<PHINode>(U))
              if (PN->getParent() == II->getNormalDest() ||
                  PN->getParent() == II->getUnwindDest())
                return false;
    }
  
    unsigned NumActualArgs = CS.arg_size();
    unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
  
    // Prevent us turning:
    // declare void @takes_i32_inalloca(i32* inalloca)
    //  call void bitcast (void (i32*)* @takes_i32_inalloca to void (i32)*)(i32 0)
    //
    // into:
    //  call void @takes_i32_inalloca(i32* null)
    //
    //  Similarly, avoid folding away bitcasts of byval calls.
    if (Callee->getAttributes().hasAttrSomewhere(Attribute::InAlloca) ||
        Callee->getAttributes().hasAttrSomewhere(Attribute::ByVal))
      return false;
  
    CallSite::arg_iterator AI = CS.arg_begin();
    for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
      Type *ParamTy = FT->getParamType(i);
      Type *ActTy = (*AI)->getType();
  
      if (!CastInst::isBitOrNoopPointerCastable(ActTy, ParamTy, DL))
        return false;   // Cannot transform this parameter value.
  
      if (AttrBuilder(CallerPAL.getParamAttributes(i + 1), i + 1).
            overlaps(AttributeFuncs::typeIncompatible(ParamTy)))
        return false;   // Attribute not compatible with transformed value.
  
      if (CS.isInAllocaArgument(i))
        return false;   // Cannot transform to and from inalloca.
  
      // If the parameter is passed as a byval argument, then we have to have a
      // sized type and the sized type has to have the same size as the old type.
      if (ParamTy != ActTy &&
          CallerPAL.getParamAttributes(i + 1).hasAttribute(i + 1,
                                                           Attribute::ByVal)) {
        PointerType *ParamPTy = dyn_cast<PointerType>(ParamTy);
        if (!ParamPTy || !ParamPTy->getElementType()->isSized())
          return false;
  
        Type *CurElTy = ActTy->getPointerElementType();
        if (DL.getTypeAllocSize(CurElTy) !=
            DL.getTypeAllocSize(ParamPTy->getElementType()))
          return false;
      }
    }
  
    if (Callee->isDeclaration()) {
      // Do not delete arguments unless we have a function body.
      if (FT->getNumParams() < NumActualArgs && !FT->isVarArg())
        return false;
  
      // If the callee is just a declaration, don't change the varargsness of the
      // call.  We don't want to introduce a varargs call where one doesn't
      // already exist.
      PointerType *APTy = cast<PointerType>(CS.getCalledValue()->getType());
      if (FT->isVarArg()!=cast<FunctionType>(APTy->getElementType())->isVarArg())
        return false;
  
      // If both the callee and the cast type are varargs, we still have to make
      // sure the number of fixed parameters are the same or we have the same
      // ABI issues as if we introduce a varargs call.
      if (FT->isVarArg() &&
          cast<FunctionType>(APTy->getElementType())->isVarArg() &&
          FT->getNumParams() !=
          cast<FunctionType>(APTy->getElementType())->getNumParams())
        return false;
    }
  
    if (FT->getNumParams() < NumActualArgs && FT->isVarArg() &&
        !CallerPAL.isEmpty())
      // In this case we have more arguments than the new function type, but we
      // won't be dropping them.  Check that these extra arguments have attributes
      // that are compatible with being a vararg call argument.
      for (unsigned i = CallerPAL.getNumSlots(); i; --i) {
        unsigned Index = CallerPAL.getSlotIndex(i - 1);
        if (Index <= FT->getNumParams())
          break;
  
        // Check if it has an attribute that's incompatible with varargs.
        AttributeSet PAttrs = CallerPAL.getSlotAttributes(i - 1);
        if (PAttrs.hasAttribute(Index, Attribute::StructRet))
          return false;
      }
  
  
    // Okay, we decided that this is a safe thing to do: go ahead and start
    // inserting cast instructions as necessary.
    std::vector<Value*> Args;
    Args.reserve(NumActualArgs);
    SmallVector<AttributeSet, 8> attrVec;
    attrVec.reserve(NumCommonArgs);
  
    // Get any return attributes.
    AttrBuilder RAttrs(CallerPAL, AttributeSet::ReturnIndex);
  
    // If the return value is not being used, the type may not be compatible
    // with the existing attributes.  Wipe out any problematic attributes.
    RAttrs.remove(AttributeFuncs::typeIncompatible(NewRetTy));
  
    // Add the new return attributes.
    if (RAttrs.hasAttributes())
      attrVec.push_back(AttributeSet::get(Caller->getContext(),
                                          AttributeSet::ReturnIndex, RAttrs));
  
    AI = CS.arg_begin();
    for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
      Type *ParamTy = FT->getParamType(i);
  
      if ((*AI)->getType() == ParamTy) {
        Args.push_back(*AI);
      } else {
        Args.push_back(Builder->CreateBitOrPointerCast(*AI, ParamTy));
      }
  
      // Add any parameter attributes.
      AttrBuilder PAttrs(CallerPAL.getParamAttributes(i + 1), i + 1);
      if (PAttrs.hasAttributes())
        attrVec.push_back(AttributeSet::get(Caller->getContext(), i + 1,
                                            PAttrs));
    }
  
    // If the function takes more arguments than the call was taking, add them
    // now.
    for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
      Args.push_back(Constant::getNullValue(FT->getParamType(i)));
  
    // If we are removing arguments to the function, emit an obnoxious warning.
    if (FT->getNumParams() < NumActualArgs) {
      // TODO: if (!FT->isVarArg()) this call may be unreachable. PR14722
      if (FT->isVarArg()) {
        // Add all of the arguments in their promoted form to the arg list.
        for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
          Type *PTy = getPromotedType((*AI)->getType());
          if (PTy != (*AI)->getType()) {
            // Must promote to pass through va_arg area!
            Instruction::CastOps opcode =
              CastInst::getCastOpcode(*AI, false, PTy, false);
            Args.push_back(Builder->CreateCast(opcode, *AI, PTy));
          } else {
            Args.push_back(*AI);
          }
  
          // Add any parameter attributes.
          AttrBuilder PAttrs(CallerPAL.getParamAttributes(i + 1), i + 1);
          if (PAttrs.hasAttributes())
            attrVec.push_back(AttributeSet::get(FT->getContext(), i + 1,
                                                PAttrs));
        }
      }
    }
  
    AttributeSet FnAttrs = CallerPAL.getFnAttributes();
    if (CallerPAL.hasAttributes(AttributeSet::FunctionIndex))
      attrVec.push_back(AttributeSet::get(Callee->getContext(), FnAttrs));
  
    if (NewRetTy->isVoidTy())
      Caller->setName("");   // Void type should not have a name.
  
    const AttributeSet &NewCallerPAL = AttributeSet::get(Callee->getContext(),
                                                         attrVec);
  
    Instruction *NC;
    if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
      NC = Builder->CreateInvoke(Callee, II->getNormalDest(),
                                 II->getUnwindDest(), Args);
      NC->takeName(II);
      cast<InvokeInst>(NC)->setCallingConv(II->getCallingConv());
      cast<InvokeInst>(NC)->setAttributes(NewCallerPAL);
    } else {
      CallInst *CI = cast<CallInst>(Caller);
      NC = Builder->CreateCall(Callee, Args);
      NC->takeName(CI);
      if (CI->isTailCall())
        cast<CallInst>(NC)->setTailCall();
      cast<CallInst>(NC)->setCallingConv(CI->getCallingConv());
      cast<CallInst>(NC)->setAttributes(NewCallerPAL);
    }
  
    // Insert a cast of the return type as necessary.
    Value *NV = NC;
    if (OldRetTy != NV->getType() && !Caller->use_empty()) {
      if (!NV->getType()->isVoidTy()) {
        NV = NC = CastInst::CreateBitOrPointerCast(NC, OldRetTy);
        NC->setDebugLoc(Caller->getDebugLoc());
  
        // If this is an invoke instruction, we should insert it after the first
        // non-phi, instruction in the normal successor block.
        if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
          BasicBlock::iterator I = II->getNormalDest()->getFirstInsertionPt();
          InsertNewInstBefore(NC, *I);
        } else {
          // Otherwise, it's a call, just insert cast right after the call.
          InsertNewInstBefore(NC, *Caller);
        }
        Worklist.AddUsersToWorkList(*Caller);
      } else {
        NV = UndefValue::get(Caller->getType());
      }
    }
  
    if (!Caller->use_empty())
      ReplaceInstUsesWith(*Caller, NV);
    else if (Caller->hasValueHandle()) {
      if (OldRetTy == NV->getType())
        ValueHandleBase::ValueIsRAUWd(Caller, NV);
      else
        // We cannot call ValueIsRAUWd with a different type, and the
        // actual tracked value will disappear.
        ValueHandleBase::ValueIsDeleted(Caller);
    }
  
    EraseInstFromFunction(*Caller);
    return true;
  }
  
  // transformCallThroughTrampoline - Turn a call to a function created by
  // init_trampoline / adjust_trampoline intrinsic pair into a direct call to the
  // underlying function.
  //
  Instruction *
  InstCombiner::transformCallThroughTrampoline(CallSite CS,
                                               IntrinsicInst *Tramp) {
    Value *Callee = CS.getCalledValue();
    PointerType *PTy = cast<PointerType>(Callee->getType());
    FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
    const AttributeSet &Attrs = CS.getAttributes();
  
    // If the call already has the 'nest' attribute somewhere then give up -
    // otherwise 'nest' would occur twice after splicing in the chain.
    if (Attrs.hasAttrSomewhere(Attribute::Nest))
      return nullptr;
  
    assert(Tramp &&
           "transformCallThroughTrampoline called with incorrect CallSite.");
  
    Function *NestF =cast<Function>(Tramp->getArgOperand(1)->stripPointerCasts());
    PointerType *NestFPTy = cast<PointerType>(NestF->getType());
    FunctionType *NestFTy = cast<FunctionType>(NestFPTy->getElementType());
  
    const AttributeSet &NestAttrs = NestF->getAttributes();
    if (!NestAttrs.isEmpty()) {
      unsigned NestIdx = 1;
      Type *NestTy = nullptr;
      AttributeSet NestAttr;
  
      // Look for a parameter marked with the 'nest' attribute.
      for (FunctionType::param_iterator I = NestFTy->param_begin(),
           E = NestFTy->param_end(); I != E; ++NestIdx, ++I)
        if (NestAttrs.hasAttribute(NestIdx, Attribute::Nest)) {
          // Record the parameter type and any other attributes.
          NestTy = *I;
          NestAttr = NestAttrs.getParamAttributes(NestIdx);
          break;
        }
  
      if (NestTy) {
        Instruction *Caller = CS.getInstruction();
        std::vector<Value*> NewArgs;
        NewArgs.reserve(CS.arg_size() + 1);
  
        SmallVector<AttributeSet, 8> NewAttrs;
        NewAttrs.reserve(Attrs.getNumSlots() + 1);
  
        // Insert the nest argument into the call argument list, which may
        // mean appending it.  Likewise for attributes.
  
        // Add any result attributes.
        if (Attrs.hasAttributes(AttributeSet::ReturnIndex))
          NewAttrs.push_back(AttributeSet::get(Caller->getContext(),
                                               Attrs.getRetAttributes()));
  
        {
          unsigned Idx = 1;
          CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
          do {
            if (Idx == NestIdx) {
              // Add the chain argument and attributes.
              Value *NestVal = Tramp->getArgOperand(2);
              if (NestVal->getType() != NestTy)
                NestVal = Builder->CreateBitCast(NestVal, NestTy, "nest");
              NewArgs.push_back(NestVal);
              NewAttrs.push_back(AttributeSet::get(Caller->getContext(),
                                                   NestAttr));
            }
  
            if (I == E)
              break;
  
            // Add the original argument and attributes.
            NewArgs.push_back(*I);
            AttributeSet Attr = Attrs.getParamAttributes(Idx);
            if (Attr.hasAttributes(Idx)) {
              AttrBuilder B(Attr, Idx);
              NewAttrs.push_back(AttributeSet::get(Caller->getContext(),
                                                   Idx + (Idx >= NestIdx), B));
            }
  
            ++Idx, ++I;
          } while (1);
        }
  
        // Add any function attributes.
        if (Attrs.hasAttributes(AttributeSet::FunctionIndex))
          NewAttrs.push_back(AttributeSet::get(FTy->getContext(),
                                               Attrs.getFnAttributes()));
  
        // The trampoline may have been bitcast to a bogus type (FTy).
        // Handle this by synthesizing a new function type, equal to FTy
        // with the chain parameter inserted.
  
        std::vector<Type*> NewTypes;
        NewTypes.reserve(FTy->getNumParams()+1);
  
        // Insert the chain's type into the list of parameter types, which may
        // mean appending it.
        {
          unsigned Idx = 1;
          FunctionType::param_iterator I = FTy->param_begin(),
            E = FTy->param_end();
  
          do {
            if (Idx == NestIdx)
              // Add the chain's type.
              NewTypes.push_back(NestTy);
  
            if (I == E)
              break;
  
            // Add the original type.
            NewTypes.push_back(*I);
  
            ++Idx, ++I;
          } while (1);
        }
  
        // Replace the trampoline call with a direct call.  Let the generic
        // code sort out any function type mismatches.
        FunctionType *NewFTy = FunctionType::get(FTy->getReturnType(), NewTypes,
                                                  FTy->isVarArg());
        Constant *NewCallee =
          NestF->getType() == PointerType::getUnqual(NewFTy) ?
          NestF : ConstantExpr::getBitCast(NestF,
                                           PointerType::getUnqual(NewFTy));
        const AttributeSet &NewPAL =
            AttributeSet::get(FTy->getContext(), NewAttrs);
  
        Instruction *NewCaller;
        if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
          NewCaller = InvokeInst::Create(NewCallee,
                                         II->getNormalDest(), II->getUnwindDest(),
                                         NewArgs);
          cast<InvokeInst>(NewCaller)->setCallingConv(II->getCallingConv());
          cast<InvokeInst>(NewCaller)->setAttributes(NewPAL);
        } else {
          NewCaller = CallInst::Create(NewCallee, NewArgs);
          if (cast<CallInst>(Caller)->isTailCall())
            cast<CallInst>(NewCaller)->setTailCall();
          cast<CallInst>(NewCaller)->
            setCallingConv(cast<CallInst>(Caller)->getCallingConv());
          cast<CallInst>(NewCaller)->setAttributes(NewPAL);
        }
  
        return NewCaller;
      }
    }
  
    // Replace the trampoline call with a direct call.  Since there is no 'nest'
    // parameter, there is no need to adjust the argument list.  Let the generic
    // code sort out any function type mismatches.
    Constant *NewCallee =
      NestF->getType() == PTy ? NestF :
                                ConstantExpr::getBitCast(NestF, PTy);
    CS.setCalledFunction(NewCallee);
    return CS.getInstruction();
  }
  