llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

//===- 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/Loads.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");

/// 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;
}

/// 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;
}

/// Return a constant boolean vector that has true elements in all positions
/// where the input constant data vector has an element with the sign bit set.
static Constant *getNegativeIsTrueBoolVec(ConstantDataVector *V) {
  SmallVector<Constant *, 32> BoolVec;
  IntegerType *BoolTy = Type::getInt1Ty(V->getContext());
  for (unsigned I = 0, E = V->getNumElements(); I != E; ++I) {
    Constant *Elt = V->getElementAsConstant(I);
    assert((isa<ConstantInt>(Elt) || isa<ConstantFP>(Elt)) &&
           "Unexpected constant data vector element type");
    bool Sign = V->getElementType()->isIntegerTy()
                    ? cast<ConstantInt>(Elt)->isNegative()
                    : cast<ConstantFP>(Elt)->isNegative();
    BoolVec.push_back(ConstantInt::get(BoolTy, Sign));
  }
  return ConstantVector::get(BoolVec);
}

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);
}

// Attempt to simplify AVX2 per-element shift intrinsics to a generic IR shift.
// Unlike the generic IR shifts, the intrinsics have defined behaviour for out
// of range shift amounts (logical - set to zero, arithmetic - splat sign bit).
static Value *simplifyX86varShift(const IntrinsicInst &II,
                                  InstCombiner::BuilderTy &Builder) {
  bool LogicalShift = false;
  bool ShiftLeft = false;

  switch (II.getIntrinsicID()) {
  default:
    return nullptr;
  case Intrinsic::x86_avx2_psrav_d:
  case Intrinsic::x86_avx2_psrav_d_256:
    LogicalShift = false;
    ShiftLeft = false;
    break;
  case Intrinsic::x86_avx2_psrlv_d:
  case Intrinsic::x86_avx2_psrlv_d_256:
  case Intrinsic::x86_avx2_psrlv_q:
  case Intrinsic::x86_avx2_psrlv_q_256:
    LogicalShift = true;
    ShiftLeft = false;
    break;
  case Intrinsic::x86_avx2_psllv_d:
  case Intrinsic::x86_avx2_psllv_d_256:
  case Intrinsic::x86_avx2_psllv_q:
  case Intrinsic::x86_avx2_psllv_q_256:
    LogicalShift = true;
    ShiftLeft = true;
    break;
  }
  assert((LogicalShift || !ShiftLeft) && "Only logical shifts can shift left");

  // Simplify if all shift amounts are constant/undef.
  auto *CShift = dyn_cast<Constant>(II.getArgOperand(1));
  if (!CShift)
    return nullptr;

  auto Vec = II.getArgOperand(0);
  auto VT = cast<VectorType>(II.getType());
  auto SVT = VT->getVectorElementType();
  int NumElts = VT->getNumElements();
  int BitWidth = SVT->getIntegerBitWidth();

  // Collect each element's shift amount.
  // We also collect special cases: UNDEF = -1, OUT-OF-RANGE = BitWidth.
  bool AnyOutOfRange = false;
  SmallVector<int, 8> ShiftAmts;
  for (int I = 0; I < NumElts; ++I) {
    auto *CElt = CShift->getAggregateElement(I);
    if (CElt && isa<UndefValue>(CElt)) {
      ShiftAmts.push_back(-1);
      continue;
    }

    auto *COp = dyn_cast_or_null<ConstantInt>(CElt);
    if (!COp)
      return nullptr;

    // Handle out of range shifts.
    // If LogicalShift - set to BitWidth (special case).
    // If ArithmeticShift - set to (BitWidth - 1) (sign splat).
    APInt ShiftVal = COp->getValue();
    if (ShiftVal.uge(BitWidth)) {
      AnyOutOfRange = LogicalShift;
      ShiftAmts.push_back(LogicalShift ? BitWidth : BitWidth - 1);
      continue;
    }

    ShiftAmts.push_back((int)ShiftVal.getZExtValue());
  }

  // If all elements out of range or UNDEF, return vector of zeros/undefs.
  // ArithmeticShift should only hit this if they are all UNDEF.
  auto OutOfRange = [&](int Idx) { return (Idx < 0) || (BitWidth <= Idx); };
  if (llvm::all_of(ShiftAmts, OutOfRange)) {
    SmallVector<Constant *, 8> ConstantVec;
    for (int Idx : ShiftAmts) {
      if (Idx < 0) {
        ConstantVec.push_back(UndefValue::get(SVT));
      } else {
        assert(LogicalShift && "Logical shift expected");
        ConstantVec.push_back(ConstantInt::getNullValue(SVT));
      }
    }
    return ConstantVector::get(ConstantVec);
  }

  // We can't handle only some out of range values with generic logical shifts.
  if (AnyOutOfRange)
    return nullptr;

  // Build the shift amount constant vector.
  SmallVector<Constant *, 8> ShiftVecAmts;
  for (int Idx : ShiftAmts) {
    if (Idx < 0)
      ShiftVecAmts.push_back(UndefValue::get(SVT));
    else
      ShiftVecAmts.push_back(ConstantInt::get(SVT, Idx));
  }
  auto ShiftVec = ConstantVector::get(ShiftVecAmts);

  if (ShiftLeft)
    return Builder.CreateShl(Vec, ShiftVec);

  if (LogicalShift)
    return Builder.CreateLShr(Vec, ShiftVec);

  return Builder.CreateAShr(Vec, ShiftVec);
}

static Value *simplifyX86movmsk(const IntrinsicInst &II,
                                InstCombiner::BuilderTy &Builder) {
  Value *Arg = II.getArgOperand(0);
  Type *ResTy = II.getType();
  Type *ArgTy = Arg->getType();

  // movmsk(undef) -> zero as we must ensure the upper bits are zero.
  if (isa<UndefValue>(Arg))
    return Constant::getNullValue(ResTy);

  // We can't easily peek through x86_mmx types.
  if (!ArgTy->isVectorTy())
    return nullptr;

  auto *C = dyn_cast<Constant>(Arg);
  if (!C)
    return nullptr;

  // Extract signbits of the vector input and pack into integer result.
  APInt Result(ResTy->getPrimitiveSizeInBits(), 0);
  for (unsigned I = 0, E = ArgTy->getVectorNumElements(); I != E; ++I) {
    auto *COp = C->getAggregateElement(I);
    if (!COp)
      return nullptr;
    if (isa<UndefValue>(COp))
      continue;

    auto *CInt = dyn_cast<ConstantInt>(COp);
    auto *CFp = dyn_cast<ConstantFP>(COp);
    if (!CInt && !CFp)
      return nullptr;

    if ((CInt && CInt->isNegative()) || (CFp && CFp->isNegative()))
      Result.setBit(I);
  }

  return Constant::getIntegerValue(ResTy, Result);
}

static Value *simplifyX86insertps(const IntrinsicInst &II,
                                  InstCombiner::BuilderTy &Builder) {
  auto *CInt = dyn_cast<ConstantInt>(II.getArgOperand(2));
  if (!CInt)
    return nullptr;

  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.
  uint32_t 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);
}

/// Attempt to simplify SSE4A EXTRQ/EXTRQI instructions using constant folding
/// or conversion to a shuffle vector.
static Value *simplifyX86extrq(IntrinsicInst &II, Value *Op0,
                               ConstantInt *CILength, ConstantInt *CIIndex,
                               InstCombiner::BuilderTy &Builder) {
  auto LowConstantHighUndef = [&](uint64_t Val) {
    Type *IntTy64 = Type::getInt64Ty(II.getContext());
    Constant *Args[] = {ConstantInt::get(IntTy64, Val),
                        UndefValue::get(IntTy64)};
    return ConstantVector::get(Args);
  };

  // See if we're dealing with constant values.
  Constant *C0 = dyn_cast<Constant>(Op0);
  ConstantInt *CI0 =
      C0 ? dyn_cast<ConstantInt>(C0->getAggregateElement((unsigned)0))
         : nullptr;

  // Attempt to constant fold.
  if (CILength && CIIndex) {
    // From AMD documentation: "The bit index and field length are each six
    // bits in length other bits of the field are ignored."
    APInt APIndex = CIIndex->getValue().zextOrTrunc(6);
    APInt APLength = CILength->getValue().zextOrTrunc(6);

    unsigned Index = APIndex.getZExtValue();

    // From AMD documentation: "a value of zero in the field length is
    // defined as length of 64".
    unsigned Length = APLength == 0 ? 64 : APLength.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 UndefValue::get(II.getType());

    // If we are inserting whole bytes, we can convert this to a shuffle.
    // Lowering can recognize EXTRQI shuffle masks.
    if ((Length % 8) == 0 && (Index % 8) == 0) {
      // Convert bit indices to byte indices.
      Length /= 8;
      Index /= 8;

      Type *IntTy8 = Type::getInt8Ty(II.getContext());
      Type *IntTy32 = Type::getInt32Ty(II.getContext());
      VectorType *ShufTy = VectorType::get(IntTy8, 16);

      SmallVector<Constant *, 16> ShuffleMask;
      for (int i = 0; i != (int)Length; ++i)
        ShuffleMask.push_back(
            Constant::getIntegerValue(IntTy32, APInt(32, i + Index)));
      for (int i = Length; i != 8; ++i)
        ShuffleMask.push_back(
            Constant::getIntegerValue(IntTy32, APInt(32, i + 16)));
      for (int i = 8; i != 16; ++i)
        ShuffleMask.push_back(UndefValue::get(IntTy32));

      Value *SV = Builder.CreateShuffleVector(
          Builder.CreateBitCast(Op0, ShufTy),
          ConstantAggregateZero::get(ShufTy), ConstantVector::get(ShuffleMask));
      return Builder.CreateBitCast(SV, II.getType());
    }

    // Constant Fold - shift Index'th bit to lowest position and mask off
    // Length bits.
    if (CI0) {
      APInt Elt = CI0->getValue();
      Elt = Elt.lshr(Index).zextOrTrunc(Length);
      return LowConstantHighUndef(Elt.getZExtValue());
    }

    // If we were an EXTRQ call, we'll save registers if we convert to EXTRQI.
    if (II.getIntrinsicID() == Intrinsic::x86_sse4a_extrq) {
      Value *Args[] = {Op0, CILength, CIIndex};
      Module *M = II.getModule();
      Value *F = Intrinsic::getDeclaration(M, Intrinsic::x86_sse4a_extrqi);
      return Builder.CreateCall(F, Args);
    }
  }

  // Constant Fold - extraction from zero is always {zero, undef}.
  if (CI0 && CI0->equalsInt(0))
    return LowConstantHighUndef(0);

  return nullptr;
}

/// Attempt to simplify SSE4A INSERTQ/INSERTQI instructions using constant
/// folding or conversion to a shuffle vector.
static Value *simplifyX86insertq(IntrinsicInst &II, Value *Op0, Value *Op1,
                                 APInt APLength, APInt APIndex,
                                 InstCombiner::BuilderTy &Builder) {

  // From AMD documentation: "The bit index and field length are each six bits
  // in length other bits of the field are ignored."
  APIndex = APIndex.zextOrTrunc(6);
  APLength = APLength.zextOrTrunc(6);

  // Attempt to constant fold.
  unsigned Index = APIndex.getZExtValue();

  // From AMD documentation: "a value of zero in the field length is
  // defined as length of 64".
  unsigned Length = APLength == 0 ? 64 : APLength.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 UndefValue::get(II.getType());

  // If we are inserting whole bytes, we can convert this to a shuffle.
  // Lowering can recognize INSERTQI shuffle masks.
  if ((Length % 8) == 0 && (Index % 8) == 0) {
    // Convert bit indices to byte indices.
    Length /= 8;
    Index /= 8;

    Type *IntTy8 = Type::getInt8Ty(II.getContext());
    Type *IntTy32 = Type::getInt32Ty(II.getContext());
    VectorType *ShufTy = VectorType::get(IntTy8, 16);

    SmallVector<Constant *, 16> ShuffleMask;
    for (int i = 0; i != (int)Index; ++i)
      ShuffleMask.push_back(Constant::getIntegerValue(IntTy32, APInt(32, i)));
    for (int i = 0; i != (int)Length; ++i)
      ShuffleMask.push_back(
          Constant::getIntegerValue(IntTy32, APInt(32, i + 16)));
    for (int i = Index + Length; i != 8; ++i)
      ShuffleMask.push_back(Constant::getIntegerValue(IntTy32, APInt(32, i)));
    for (int i = 8; i != 16; ++i)
      ShuffleMask.push_back(UndefValue::get(IntTy32));

    Value *SV = Builder.CreateShuffleVector(Builder.CreateBitCast(Op0, ShufTy),
                                            Builder.CreateBitCast(Op1, ShufTy),
                                            ConstantVector::get(ShuffleMask));
    return Builder.CreateBitCast(SV, II.getType());
  }

  // See if we're dealing with constant values.
  Constant *C0 = dyn_cast<Constant>(Op0);
  Constant *C1 = dyn_cast<Constant>(Op1);
  ConstantInt *CI00 =
      C0 ? dyn_cast<ConstantInt>(C0->getAggregateElement((unsigned)0))
         : nullptr;
  ConstantInt *CI10 =
      C1 ? dyn_cast<ConstantInt>(C1->getAggregateElement((unsigned)0))
         : nullptr;

  // Constant Fold - insert bottom Length bits starting at the Index'th bit.
  if (CI00 && CI10) {
    APInt V00 = CI00->getValue();
    APInt V10 = CI10->getValue();
    APInt Mask = APInt::getLowBitsSet(64, Length).shl(Index);
    V00 = V00 & ~Mask;
    V10 = V10.zextOrTrunc(Length).zextOrTrunc(64).shl(Index);
    APInt Val = V00 | V10;
    Type *IntTy64 = Type::getInt64Ty(II.getContext());
    Constant *Args[] = {ConstantInt::get(IntTy64, Val.getZExtValue()),
                        UndefValue::get(IntTy64)};
    return ConstantVector::get(Args);
  }

  // If we were an INSERTQ call, we'll save demanded elements if we convert to
  // INSERTQI.
  if (II.getIntrinsicID() == Intrinsic::x86_sse4a_insertq) {
    Type *IntTy8 = Type::getInt8Ty(II.getContext());
    Constant *CILength = ConstantInt::get(IntTy8, Length, false);
    Constant *CIIndex = ConstantInt::get(IntTy8, Index, false);

    Value *Args[] = {Op0, Op1, CILength, CIIndex};
    Module *M = II.getModule();
    Value *F = Intrinsic::getDeclaration(M, Intrinsic::x86_sse4a_insertqi);
    return Builder.CreateCall(F, Args);
  }

  return nullptr;
}

/// Attempt to convert pshufb* to shufflevector if the mask is constant.
static Value *simplifyX86pshufb(const IntrinsicInst &II,
                                InstCombiner::BuilderTy &Builder) {
  Constant *V = dyn_cast<Constant>(II.getArgOperand(1));
  if (!V)
    return nullptr;

  auto *VecTy = cast<VectorType>(II.getType());
  auto *MaskEltTy = Type::getInt32Ty(II.getContext());
  unsigned NumElts = VecTy->getNumElements();
  assert((NumElts == 16 || NumElts == 32) &&
         "Unexpected number of elements in shuffle mask!");

  // Construct a shuffle mask from constant integers or UNDEFs.
  Constant *Indexes[32] = {NULL};

  // Each byte in the shuffle control mask forms an index to permute the
  // corresponding byte in the destination operand.
  for (unsigned I = 0; I < NumElts; ++I) {
    Constant *COp = V->getAggregateElement(I);
    if (!COp || (!isa<UndefValue>(COp) && !isa<ConstantInt>(COp)))
      return nullptr;

    if (isa<UndefValue>(COp)) {
      Indexes[I] = UndefValue::get(MaskEltTy);
      continue;
    }

    int8_t Index = cast<ConstantInt>(COp)->getValue().getZExtValue();

    // If the most significant bit (bit[7]) of each byte of the shuffle
    // control mask is set, then zero is written in the result byte.
    // The zero vector is in the right-hand side of the resulting
    // shufflevector.

    // The value of each index for the high 128-bit lane is the least
    // significant 4 bits of the respective shuffle control byte.
    Index = ((Index < 0) ? NumElts : Index & 0x0F) + (I & 0xF0);
    Indexes[I] = ConstantInt::get(MaskEltTy, Index);
  }

  auto ShuffleMask = ConstantVector::get(makeArrayRef(Indexes, NumElts));
  auto V1 = II.getArgOperand(0);
  auto V2 = Constant::getNullValue(VecTy);
  return Builder.CreateShuffleVector(V1, V2, ShuffleMask);
}

/// Attempt to convert vpermilvar* to shufflevector if the mask is constant.
static Value *simplifyX86vpermilvar(const IntrinsicInst &II,
                                    InstCombiner::BuilderTy &Builder) {
  Constant *V = dyn_cast<Constant>(II.getArgOperand(1));
  if (!V)
    return nullptr;

  auto *MaskEltTy = Type::getInt32Ty(II.getContext());
  unsigned NumElts = cast<VectorType>(V->getType())->getNumElements();
  assert(NumElts == 8 || NumElts == 4 || NumElts == 2);

  // Construct a shuffle mask from constant integers or UNDEFs.
  Constant *Indexes[8] = {NULL};

  // The intrinsics only read one or two bits, clear the rest.
  for (unsigned I = 0; I < NumElts; ++I) {
    Constant *COp = V->getAggregateElement(I);
    if (!COp || (!isa<UndefValue>(COp) && !isa<ConstantInt>(COp)))
      return nullptr;

    if (isa<UndefValue>(COp)) {
      Indexes[I] = UndefValue::get(MaskEltTy);
      continue;
    }

    APInt Index = cast<ConstantInt>(COp)->getValue();
    Index = Index.zextOrTrunc(32).getLoBits(2);

    // The PD variants uses bit 1 to select per-lane element index, so
    // shift down to convert to generic shuffle mask index.
    if (II.getIntrinsicID() == Intrinsic::x86_avx_vpermilvar_pd ||
        II.getIntrinsicID() == Intrinsic::x86_avx_vpermilvar_pd_256)
      Index = Index.lshr(1);

    // 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) &&
        ((NumElts / 2) <= I)) {
      Index += APInt(32, NumElts / 2);
    }

    Indexes[I] = ConstantInt::get(MaskEltTy, Index);
  }

  auto ShuffleMask = ConstantVector::get(makeArrayRef(Indexes, NumElts));
  auto V1 = II.getArgOperand(0);
  auto V2 = UndefValue::get(V1->getType());
  return Builder.CreateShuffleVector(V1, V2, ShuffleMask);
}

/// Attempt to convert vpermd/vpermps to shufflevector if the mask is constant.
static Value *simplifyX86vpermv(const IntrinsicInst &II,
                                InstCombiner::BuilderTy &Builder) {
  auto *V = dyn_cast<Constant>(II.getArgOperand(1));
  if (!V)
    return nullptr;

  auto *VecTy = cast<VectorType>(II.getType());
  auto *MaskEltTy = Type::getInt32Ty(II.getContext());
  unsigned Size = VecTy->getNumElements();
  assert(Size == 8 && "Unexpected shuffle mask size");

  // Construct a shuffle mask from constant integers or UNDEFs.
  Constant *Indexes[8] = {NULL};

  for (unsigned I = 0; I < Size; ++I) {
    Constant *COp = V->getAggregateElement(I);
    if (!COp || (!isa<UndefValue>(COp) && !isa<ConstantInt>(COp)))
      return nullptr;

    if (isa<UndefValue>(COp)) {
      Indexes[I] = UndefValue::get(MaskEltTy);
      continue;
    }

    APInt Index = cast<ConstantInt>(COp)->getValue();
    Index = Index.zextOrTrunc(32).getLoBits(3);
    Indexes[I] = ConstantInt::get(MaskEltTy, Index);
  }

  auto ShuffleMask = ConstantVector::get(makeArrayRef(Indexes, Size));
  auto V1 = II.getArgOperand(0);
  auto V2 = UndefValue::get(VecTy);
  return Builder.CreateShuffleVector(V1, V2, ShuffleMask);
}

/// 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) {
  auto *CInt = dyn_cast<ConstantInt>(II.getArgOperand(2));
  if (!CInt)
    return nullptr;

  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<uint32_t, 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);
}

/// Decode XOP integer vector comparison intrinsics.
static Value *simplifyX86vpcom(const IntrinsicInst &II,
                               InstCombiner::BuilderTy &Builder,
                               bool IsSigned) {
  if (auto *CInt = dyn_cast<ConstantInt>(II.getArgOperand(2))) {
    uint64_t Imm = CInt->getZExtValue() & 0x7;
    VectorType *VecTy = cast<VectorType>(II.getType());
    CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;

    switch (Imm) {
    case 0x0:
      Pred = IsSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
      break;
    case 0x1:
      Pred = IsSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
      break;
    case 0x2:
      Pred = IsSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
      break;
    case 0x3:
      Pred = IsSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
      break;
    case 0x4:
      Pred = ICmpInst::ICMP_EQ; break;
    case 0x5:
      Pred = ICmpInst::ICMP_NE; break;
    case 0x6:
      return ConstantInt::getSigned(VecTy, 0); // FALSE
    case 0x7:
      return ConstantInt::getSigned(VecTy, -1); // TRUE
    }

    if (Value *Cmp = Builder.CreateICmp(Pred, II.getArgOperand(0),
                                        II.getArgOperand(1)))
      return Builder.CreateSExtOrTrunc(Cmp, VecTy);
  }
  return nullptr;
}

static Value *simplifyMinnumMaxnum(const IntrinsicInst &II) {
  Value *Arg0 = II.getArgOperand(0);
  Value *Arg1 = II.getArgOperand(1);

  // fmin(x, x) -> x
  if (Arg0 == Arg1)
    return Arg0;

  const auto *C1 = dyn_cast<ConstantFP>(Arg1);

  // fmin(x, nan) -> x
  if (C1 && C1->isNaN())
    return 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 Arg1;

  // fmin(x, undef) -> x
  if (isa<UndefValue>(Arg1))
    return 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 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 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 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 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 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 Arg1;
    }
  }
  return nullptr;
}

static bool maskIsAllOneOrUndef(Value *Mask) {
  auto *ConstMask = dyn_cast<Constant>(Mask);
  if (!ConstMask)
    return false;
  if (ConstMask->isAllOnesValue() || isa<UndefValue>(ConstMask))
    return true;
  for (unsigned I = 0, E = ConstMask->getType()->getVectorNumElements(); I != E;
       ++I) {
    if (auto *MaskElt = ConstMask->getAggregateElement(I))
      if (MaskElt->isAllOnesValue() || isa<UndefValue>(MaskElt))
        continue;
    return false;
  }
  return true;
}

static Value *simplifyMaskedLoad(const IntrinsicInst &II,
                                 InstCombiner::BuilderTy &Builder) {
  // If the mask is all ones or undefs, this is a plain vector load of the 1st
  // argument.
  if (maskIsAllOneOrUndef(II.getArgOperand(2))) {
    Value *LoadPtr = II.getArgOperand(0);
    unsigned Alignment = cast<ConstantInt>(II.getArgOperand(1))->getZExtValue();
    return Builder.CreateAlignedLoad(LoadPtr, Alignment, "unmaskedload");
  }

  return nullptr;
}

static Instruction *simplifyMaskedStore(IntrinsicInst &II, InstCombiner &IC) {
  auto *ConstMask = dyn_cast<Constant>(II.getArgOperand(3));
  if (!ConstMask)
    return nullptr;

  // If the mask is all zeros, this instruction does nothing.
  if (ConstMask->isNullValue())
    return IC.eraseInstFromFunction(II);

  // If the mask is all ones, this is a plain vector store of the 1st argument.
  if (ConstMask->isAllOnesValue()) {
    Value *StorePtr = II.getArgOperand(1);
    unsigned Alignment = cast<ConstantInt>(II.getArgOperand(2))->getZExtValue();
    return new StoreInst(II.getArgOperand(0), StorePtr, false, Alignment);
  }

  return nullptr;
}

static Instruction *simplifyMaskedGather(IntrinsicInst &II, InstCombiner &IC) {
  // If the mask is all zeros, return the "passthru" argument of the gather.
  auto *ConstMask = dyn_cast<Constant>(II.getArgOperand(2));
  if (ConstMask && ConstMask->isNullValue())
    return IC.replaceInstUsesWith(II, II.getArgOperand(3));

  return nullptr;
}

static Instruction *simplifyMaskedScatter(IntrinsicInst &II, InstCombiner &IC) {
  // If the mask is all zeros, a scatter does nothing.
  auto *ConstMask = dyn_cast<Constant>(II.getArgOperand(3));
  if (ConstMask && ConstMask->isNullValue())
    return IC.eraseInstFromFunction(II);

  return nullptr;
}

// TODO: If the x86 backend knew how to convert a bool vector mask back to an
// XMM register mask efficiently, we could transform all x86 masked intrinsics
// to LLVM masked intrinsics and remove the x86 masked intrinsic defs.
static Instruction *simplifyX86MaskedLoad(IntrinsicInst &II, InstCombiner &IC) {
  Value *Ptr = II.getOperand(0);
  Value *Mask = II.getOperand(1);
  Constant *ZeroVec = Constant::getNullValue(II.getType());

  // Special case a zero mask since that's not a ConstantDataVector.
  // This masked load instruction creates a zero vector.
  if (isa<ConstantAggregateZero>(Mask))
    return IC.replaceInstUsesWith(II, ZeroVec);

  auto *ConstMask = dyn_cast<ConstantDataVector>(Mask);
  if (!ConstMask)
    return nullptr;

  // The mask is constant. Convert this x86 intrinsic to the LLVM instrinsic
  // to allow target-independent optimizations.

  // First, cast the x86 intrinsic scalar pointer to a vector pointer to match
  // the LLVM intrinsic definition for the pointer argument.
  unsigned AddrSpace = cast<PointerType>(Ptr->getType())->getAddressSpace();
  PointerType *VecPtrTy = PointerType::get(II.getType(), AddrSpace);
  Value *PtrCast = IC.Builder->CreateBitCast(Ptr, VecPtrTy, "castvec");

  // Second, convert the x86 XMM integer vector mask to a vector of bools based
  // on each element's most significant bit (the sign bit).
  Constant *BoolMask = getNegativeIsTrueBoolVec(ConstMask);

  // The pass-through vector for an x86 masked load is a zero vector.
  CallInst *NewMaskedLoad =
      IC.Builder->CreateMaskedLoad(PtrCast, 1, BoolMask, ZeroVec);
  return IC.replaceInstUsesWith(II, NewMaskedLoad);
}

// TODO: If the x86 backend knew how to convert a bool vector mask back to an
// XMM register mask efficiently, we could transform all x86 masked intrinsics
// to LLVM masked intrinsics and remove the x86 masked intrinsic defs.
static bool simplifyX86MaskedStore(IntrinsicInst &II, InstCombiner &IC) {
  Value *Ptr = II.getOperand(0);
  Value *Mask = II.getOperand(1);
  Value *Vec = II.getOperand(2);

  // Special case a zero mask since that's not a ConstantDataVector:
  // this masked store instruction does nothing.
  if (isa<ConstantAggregateZero>(Mask)) {
    IC.eraseInstFromFunction(II);
    return true;
  }

  // The SSE2 version is too weird (eg, unaligned but non-temporal) to do
  // anything else at this level.
  if (II.getIntrinsicID() == Intrinsic::x86_sse2_maskmov_dqu)
    return false;

  auto *ConstMask = dyn_cast<ConstantDataVector>(Mask);
  if (!ConstMask)
    return false;

  // The mask is constant. Convert this x86 intrinsic to the LLVM instrinsic
  // to allow target-independent optimizations.

  // First, cast the x86 intrinsic scalar pointer to a vector pointer to match
  // the LLVM intrinsic definition for the pointer argument.
  unsigned AddrSpace = cast<PointerType>(Ptr->getType())->getAddressSpace();
  PointerType *VecPtrTy = PointerType::get(Vec->getType(), AddrSpace);
  Value *PtrCast = IC.Builder->CreateBitCast(Ptr, VecPtrTy, "castvec");

  // Second, convert the x86 XMM integer vector mask to a vector of bools based
  // on each element's most significant bit (the sign bit).
  Constant *BoolMask = getNegativeIsTrueBoolVec(ConstMask);

  IC.Builder->CreateMaskedStore(Vec, PtrCast, 1, BoolMask);

  // 'Replace uses' doesn't work for stores. Erase the original masked store.
  IC.eraseInstFromFunction(II);
  return true;
}

// Returns true iff the 2 intrinsics have the same operands, limiting the
// comparison to the first NumOperands.
static bool haveSameOperands(const IntrinsicInst &I, const IntrinsicInst &E,
                             unsigned NumOperands) {
  assert(I.getNumArgOperands() >= NumOperands && "Not enough operands");
  assert(E.getNumArgOperands() >= NumOperands && "Not enough operands");
  for (unsigned i = 0; i < NumOperands; i++)
    if (I.getArgOperand(i) != E.getArgOperand(i))
      return false;
  return true;
}

// Remove trivially empty start/end intrinsic ranges, i.e. a start
// immediately followed by an end (ignoring debuginfo or other
// start/end intrinsics in between). As this handles only the most trivial
// cases, tracking the nesting level is not needed:
//
//   call @llvm.foo.start(i1 0) ; &I
//   call @llvm.foo.start(i1 0)
//   call @llvm.foo.end(i1 0) ; This one will not be skipped: it will be removed
//   call @llvm.foo.end(i1 0)
static bool removeTriviallyEmptyRange(IntrinsicInst &I, unsigned StartID,
                                      unsigned EndID, InstCombiner &IC) {
  assert(I.getIntrinsicID() == StartID &&
         "Start intrinsic does not have expected ID");
  BasicBlock::iterator BI(I), BE(I.getParent()->end());
  for (++BI; BI != BE; ++BI) {
    if (auto *E = dyn_cast<IntrinsicInst>(BI)) {
      if (isa<DbgInfoIntrinsic>(E) || E->getIntrinsicID() == StartID)
        continue;
      if (E->getIntrinsicID() == EndID &&
          haveSameOperands(I, *E, E->getNumArgOperands())) {
        IC.eraseInstFromFunction(*E);
        IC.eraseInstFromFunction(I);
        return true;
      }
    }
    break;
  }

  return false;
}

Instruction *InstCombiner::visitVAStartInst(VAStartInst &I) {
  removeTriviallyEmptyRange(I, Intrinsic::vastart, Intrinsic::vaend, *this);
  return nullptr;
}

Instruction *InstCombiner::visitVACopyInst(VACopyInst &I) {
  removeTriviallyEmptyRange(I, Intrinsic::vacopy, Intrinsic::vaend, *this);
  return nullptr;
}

/// 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.getModule();
          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);
  };
  auto SimplifyDemandedVectorEltsHigh = [this](Value *Op, unsigned Width,
                                              unsigned DemandedWidth) {
    APInt UndefElts(Width, 0);
    APInt DemandedElts = APInt::getHighBitsSet(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)) {
      APInt APSize(II->getType()->getIntegerBitWidth(), Size);
      // Equality check to be sure that `Size` can fit in a value of type
      // `II->getType()`
      if (APSize == Size)
        return replaceInstUsesWith(CI, ConstantInt::get(II->getType(), APSize));
    }
    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::bitreverse: {
    Value *IIOperand = II->getArgOperand(0);
    Value *X = nullptr;

    // bitreverse(bitreverse(x)) -> x
    if (match(IIOperand, m_Intrinsic<Intrinsic::bitreverse>(m_Value(X))))
      return replaceInstUsesWith(CI, X);
    break;
  }

  case Intrinsic::masked_load:
    if (Value *SimplifiedMaskedOp = simplifyMaskedLoad(*II, *Builder))
      return replaceInstUsesWith(CI, SimplifiedMaskedOp);
    break;
  case Intrinsic::masked_store:
    return simplifyMaskedStore(*II, *this);
  case Intrinsic::masked_gather:
    return simplifyMaskedGather(*II, *this);
  case Intrinsic::masked_scatter:
    return simplifyMaskedScatter(*II, *this);

  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);
    // Canonicalize constants to the RHS.
    if (isa<ConstantFP>(Arg0) && !isa<ConstantFP>(Arg1)) {
      II->setArgOperand(0, Arg1);
      II->setArgOperand(1, Arg0);
      return II;
    }
    if (Value *V = simplifyMinnumMaxnum(*II))
      return replaceInstUsesWith(*II, V);
    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_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<uint32_t, 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.
    if (Value *V = SimplifyDemandedVectorEltsLow(Arg, ArgWidth, RetWidth)) {
      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.
    Value *Arg = II->getArgOperand(0);
    unsigned VWidth = Arg->getType()->getVectorNumElements();
    if (Value *V = SimplifyDemandedVectorEltsLow(Arg, VWidth, 1)) {
      II->setArgOperand(0, V);
      return II;
    }
    break;
  }

  case Intrinsic::x86_mmx_pmovmskb:
  case Intrinsic::x86_sse_movmsk_ps:
  case Intrinsic::x86_sse2_movmsk_pd:
  case Intrinsic::x86_sse2_pmovmskb_128:
  case Intrinsic::x86_avx_movmsk_pd_256:
  case Intrinsic::x86_avx_movmsk_ps_256:
  case Intrinsic::x86_avx2_pmovmskb: {
    if (Value *V = simplifyX86movmsk(*II, *Builder))
      return replaceInstUsesWith(*II, V);
    break;
  }

  case Intrinsic::x86_sse_comieq_ss:
  case Intrinsic::x86_sse_comige_ss:
  case Intrinsic::x86_sse_comigt_ss:
  case Intrinsic::x86_sse_comile_ss:
  case Intrinsic::x86_sse_comilt_ss:
  case Intrinsic::x86_sse_comineq_ss:
  case Intrinsic::x86_sse_ucomieq_ss:
  case Intrinsic::x86_sse_ucomige_ss:
  case Intrinsic::x86_sse_ucomigt_ss:
  case Intrinsic::x86_sse_ucomile_ss:
  case Intrinsic::x86_sse_ucomilt_ss:
  case Intrinsic::x86_sse_ucomineq_ss:
  case Intrinsic::x86_sse2_comieq_sd:
  case Intrinsic::x86_sse2_comige_sd:
  case Intrinsic::x86_sse2_comigt_sd:
  case Intrinsic::x86_sse2_comile_sd:
  case Intrinsic::x86_sse2_comilt_sd:
  case Intrinsic::x86_sse2_comineq_sd:
  case Intrinsic::x86_sse2_ucomieq_sd:
  case Intrinsic::x86_sse2_ucomige_sd:
  case Intrinsic::x86_sse2_ucomigt_sd:
  case Intrinsic::x86_sse2_ucomile_sd:
  case Intrinsic::x86_sse2_ucomilt_sd:
  case Intrinsic::x86_sse2_ucomineq_sd: {
    // These intrinsics only demand the 0th element of their input vectors. If
    // we can simplify the input based on that, do so now.
    bool MadeChange = false;
    Value *Arg0 = II->getArgOperand(0);
    Value *Arg1 = II->getArgOperand(1);
    unsigned VWidth = Arg0->getType()->getVectorNumElements();
    if (Value *V = SimplifyDemandedVectorEltsLow(Arg0, VWidth, 1)) {
      II->setArgOperand(0, V);
      MadeChange = true;
    }
    if (Value *V = SimplifyDemandedVectorEltsLow(Arg1, VWidth, 1)) {
      II->setArgOperand(1, V);
      MadeChange = true;
    }
    if (MadeChange)
      return II;
    break;
  }

  case Intrinsic::x86_sse_add_ss:
  case Intrinsic::x86_sse_sub_ss:
  case Intrinsic::x86_sse_mul_ss:
  case Intrinsic::x86_sse_div_ss:
  case Intrinsic::x86_sse_min_ss:
  case Intrinsic::x86_sse_max_ss:
  case Intrinsic::x86_sse_cmp_ss:
  case Intrinsic::x86_sse2_add_sd:
  case Intrinsic::x86_sse2_sub_sd:
  case Intrinsic::x86_sse2_mul_sd:
  case Intrinsic::x86_sse2_div_sd:
  case Intrinsic::x86_sse2_min_sd:
  case Intrinsic::x86_sse2_max_sd:
  case Intrinsic::x86_sse2_cmp_sd: {
    // These intrinsics only demand the lowest element of the second input
    // vector.
    Value *Arg1 = II->getArgOperand(1);
    unsigned VWidth = Arg1->getType()->getVectorNumElements();
    if (Value *V = SimplifyDemandedVectorEltsLow(Arg1, VWidth, 1)) {
      II->setArgOperand(1, V);
      return II;
    }
    break;
  }

  case Intrinsic::x86_sse41_round_ss:
  case Intrinsic::x86_sse41_round_sd: {
    // These intrinsics demand the upper elements of the first input vector and
    // the lowest element of the second input vector.
    bool MadeChange = false;
    Value *Arg0 = II->getArgOperand(0);
    Value *Arg1 = II->getArgOperand(1);
    unsigned VWidth = Arg0->getType()->getVectorNumElements();
    if (Value *V = SimplifyDemandedVectorEltsHigh(Arg0, VWidth, VWidth - 1)) {
      II->setArgOperand(0, V);
      MadeChange = true;
    }
    if (Value *V = SimplifyDemandedVectorEltsLow(Arg1, VWidth, 1)) {
      II->setArgOperand(1, V);
      MadeChange = true;
    }
    if (MadeChange)
      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.
    Value *Arg1 = II->getArgOperand(1);
    assert(Arg1->getType()->getPrimitiveSizeInBits() == 128 &&
           "Unexpected packed shift size");
    unsigned VWidth = Arg1->getType()->getVectorNumElements();

    if (Value *V = SimplifyDemandedVectorEltsLow(Arg1, VWidth, VWidth / 2)) {
      II->setArgOperand(1, V);
      return II;
    }
    break;
  }

  case Intrinsic::x86_avx2_psllv_d:
  case Intrinsic::x86_avx2_psllv_d_256:
  case Intrinsic::x86_avx2_psllv_q:
  case Intrinsic::x86_avx2_psllv_q_256:
  case Intrinsic::x86_avx2_psrav_d:
  case Intrinsic::x86_avx2_psrav_d_256:
  case Intrinsic::x86_avx2_psrlv_d:
  case Intrinsic::x86_avx2_psrlv_d_256:
  case Intrinsic::x86_avx2_psrlv_q:
  case Intrinsic::x86_avx2_psrlv_q_256:
    if (Value *V = simplifyX86varShift(*II, *Builder))
      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: {
    Value *Op0 = II->getArgOperand(0);
    Value *Op1 = II->getArgOperand(1);
    unsigned VWidth0 = Op0->getType()->getVectorNumElements();
    unsigned VWidth1 = Op1->getType()->getVectorNumElements();
    assert(Op0->getType()->getPrimitiveSizeInBits() == 128 &&
           Op1->getType()->getPrimitiveSizeInBits() == 128 && VWidth0 == 2 &&
           VWidth1 == 16 && "Unexpected operand sizes");

    // See if we're dealing with constant values.
    Constant *C1 = dyn_cast<Constant>(Op1);
    ConstantInt *CILength =
        C1 ? dyn_cast<ConstantInt>(C1->getAggregateElement((unsigned)0))
           : nullptr;
    ConstantInt *CIIndex =
        C1 ? dyn_cast<ConstantInt>(C1->getAggregateElement((unsigned)1))
           : nullptr;

    // Attempt to simplify to a constant, shuffle vector or EXTRQI call.
    if (Value *V = simplifyX86extrq(*II, Op0, CILength, CIIndex, *Builder))
      return replaceInstUsesWith(*II, V);

    // EXTRQ only uses the lowest 64-bits of the first 128-bit vector
    // operands and the lowest 16-bits of the second.
    bool MadeChange = false;
    if (Value *V = SimplifyDemandedVectorEltsLow(Op0, VWidth0, 1)) {
      II->setArgOperand(0, V);
      MadeChange = true;
    }
    if (Value *V = SimplifyDemandedVectorEltsLow(Op1, VWidth1, 2)) {
      II->setArgOperand(1, V);
      MadeChange = true;
    }
    if (MadeChange)
      return II;
    break;
  }

  case Intrinsic::x86_sse4a_extrqi: {
    // EXTRQI: Extract Length bits starting from Index. Zero pad the remaining
    // bits of the lower 64-bits. The upper 64-bits are undefined.
    Value *Op0 = II->getArgOperand(0);
    unsigned VWidth = Op0->getType()->getVectorNumElements();
    assert(Op0->getType()->getPrimitiveSizeInBits() == 128 && VWidth == 2 &&
           "Unexpected operand size");

    // See if we're dealing with constant values.
    ConstantInt *CILength = dyn_cast<ConstantInt>(II->getArgOperand(1));
    ConstantInt *CIIndex = dyn_cast<ConstantInt>(II->getArgOperand(2));

    // Attempt to simplify to a constant or shuffle vector.
    if (Value *V = simplifyX86extrq(*II, Op0, CILength, CIIndex, *Builder))
      return replaceInstUsesWith(*II, V);

    // EXTRQI only uses the lowest 64-bits of the first 128-bit vector
    // operand.
    if (Value *V = SimplifyDemandedVectorEltsLow(Op0, VWidth, 1)) {
      II->setArgOperand(0, V);
      return II;
    }
    break;
  }

  case Intrinsic::x86_sse4a_insertq: {
    Value *Op0 = II->getArgOperand(0);
    Value *Op1 = II->getArgOperand(1);
    unsigned VWidth = Op0->getType()->getVectorNumElements();
    assert(Op0->getType()->getPrimitiveSizeInBits() == 128 &&
           Op1->getType()->getPrimitiveSizeInBits() == 128 && VWidth == 2 &&
           Op1->getType()->getVectorNumElements() == 2 &&
           "Unexpected operand size");

    // See if we're dealing with constant values.
    Constant *C1 = dyn_cast<Constant>(Op1);
    ConstantInt *CI11 =
        C1 ? dyn_cast<ConstantInt>(C1->getAggregateElement((unsigned)1))
           : nullptr;

    // Attempt to simplify to a constant, shuffle vector or INSERTQI call.
    if (CI11) {
      const APInt &V11 = CI11->getValue();
      APInt Len = V11.zextOrTrunc(6);
      APInt Idx = V11.lshr(8).zextOrTrunc(6);
      if (Value *V = simplifyX86insertq(*II, Op0, Op1, Len, Idx, *Builder))
        return replaceInstUsesWith(*II, V);
    }

    // INSERTQ only uses the lowest 64-bits of the first 128-bit vector
    // operand.
    if (Value *V = SimplifyDemandedVectorEltsLow(Op0, VWidth, 1)) {
      II->setArgOperand(0, V);
      return II;
    }
    break;
  }

  case Intrinsic::x86_sse4a_insertqi: {
    // INSERTQI: Extract lowest Length bits from lower half of second source and
    // insert over first source starting at Index bit. The upper 64-bits are
    // undefined.
    Value *Op0 = II->getArgOperand(0);
    Value *Op1 = II->getArgOperand(1);
    unsigned VWidth0 = Op0->getType()->getVectorNumElements();
    unsigned VWidth1 = Op1->getType()->getVectorNumElements();
    assert(Op0->getType()->getPrimitiveSizeInBits() == 128 &&
           Op1->getType()->getPrimitiveSizeInBits() == 128 && VWidth0 == 2 &&
           VWidth1 == 2 && "Unexpected operand sizes");

    // See if we're dealing with constant values.
    ConstantInt *CILength = dyn_cast<ConstantInt>(II->getArgOperand(2));
    ConstantInt *CIIndex = dyn_cast<ConstantInt>(II->getArgOperand(3));

    // Attempt to simplify to a constant or shuffle vector.
    if (CILength && CIIndex) {
      APInt Len = CILength->getValue().zextOrTrunc(6);
      APInt Idx = CIIndex->getValue().zextOrTrunc(6);
      if (Value *V = simplifyX86insertq(*II, Op0, Op1, Len, Idx, *Builder))
        return replaceInstUsesWith(*II, V);
    }

    // INSERTQI only uses the lowest 64-bits of the first two 128-bit vector
    // operands.
    bool MadeChange = false;
    if (Value *V = SimplifyDemandedVectorEltsLow(Op0, VWidth0, 1)) {
      II->setArgOperand(0, V);
      MadeChange = true;
    }
    if (Value *V = SimplifyDemandedVectorEltsLow(Op1, VWidth1, 1)) {
      II->setArgOperand(1, V);
      MadeChange = true;
    }
    if (MadeChange)
      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 *ConstantMask = dyn_cast<ConstantDataVector>(Mask)) {
      Constant *NewSelector = getNegativeIsTrueBoolVec(ConstantMask);
      return SelectInst::Create(NewSelector, Op1, Op0, "blendv");
    }
    break;
  }

  case Intrinsic::x86_ssse3_pshuf_b_128:
  case Intrinsic::x86_avx2_pshuf_b:
    if (Value *V = simplifyX86pshufb(*II, *Builder))
      return replaceInstUsesWith(*II, V);
    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:
    if (Value *V = simplifyX86vpermilvar(*II, *Builder))
      return replaceInstUsesWith(*II, V);
    break;

  case Intrinsic::x86_avx2_permd:
  case Intrinsic::x86_avx2_permps:
    if (Value *V = simplifyX86vpermv(*II, *Builder))
      return replaceInstUsesWith(*II, V);
    break;

  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::x86_avx_maskload_ps:
  case Intrinsic::x86_avx_maskload_pd:
  case Intrinsic::x86_avx_maskload_ps_256:
  case Intrinsic::x86_avx_maskload_pd_256:
  case Intrinsic::x86_avx2_maskload_d:
  case Intrinsic::x86_avx2_maskload_q:
  case Intrinsic::x86_avx2_maskload_d_256:
  case Intrinsic::x86_avx2_maskload_q_256:
    if (Instruction *I = simplifyX86MaskedLoad(*II, *this))
      return I;
    break;

  case Intrinsic::x86_sse2_maskmov_dqu:
  case Intrinsic::x86_avx_maskstore_ps:
  case Intrinsic::x86_avx_maskstore_pd:
  case Intrinsic::x86_avx_maskstore_ps_256:
  case Intrinsic::x86_avx_maskstore_pd_256:
  case Intrinsic::x86_avx2_maskstore_d:
  case Intrinsic::x86_avx2_maskstore_q:
  case Intrinsic::x86_avx2_maskstore_d_256:
  case Intrinsic::x86_avx2_maskstore_q_256:
    if (simplifyX86MaskedStore(*II, *this))
      return nullptr;
    break;

  case Intrinsic::x86_xop_vpcomb:
  case Intrinsic::x86_xop_vpcomd:
  case Intrinsic::x86_xop_vpcomq:
  case Intrinsic::x86_xop_vpcomw:
    if (Value *V = simplifyX86vpcom(*II, *Builder, true))
      return replaceInstUsesWith(*II, V);
    break;

  case Intrinsic::x86_xop_vpcomub:
  case Intrinsic::x86_xop_vpcomud:
  case Intrinsic::x86_xop_vpcomuq:
  case Intrinsic::x86_xop_vpcomuw:
    if (Value *V = simplifyX86vpcom(*II, *Builder, false))
      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::amdgcn_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::amdgcn_frexp_mant:
  case Intrinsic::amdgcn_frexp_exp: {
    Value *Src = II->getArgOperand(0);
    if (const ConstantFP *C = dyn_cast<ConstantFP>(Src)) {
      int Exp;
      APFloat Significand = frexp(C->getValueAPF(), Exp,
                                  APFloat::rmNearestTiesToEven);

      if (II->getIntrinsicID() == Intrinsic::amdgcn_frexp_mant) {
        return replaceInstUsesWith(CI, ConstantFP::get(II->getContext(),
                                                       Significand));
      }

      // Match instruction special case behavior.
      if (Exp == APFloat::IEK_NaN || Exp == APFloat::IEK_Inf)
        Exp = 0;

      return replaceInstUsesWith(CI, ConstantInt::get(II->getType(), Exp));
    }

    if (isa<UndefValue>(Src))
      return replaceInstUsesWith(CI, UndefValue::get(II->getType()));

    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) {
        if (&*++SS->getIterator() == 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);

          // Bail if we cross over an intrinsic with side effects, such as
          // llvm.stacksave, llvm.read_register, or llvm.setjmp.
          if (II->mayHaveSideEffects()) {
            CannotRemove = true;
            break;
          }
        } 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::lifetime_start:
    // Asan needs to poison memory to detect invalid access which is possible
    // even for empty lifetime range.
    if (II->getFunction()->hasFnAttribute(Attribute::SanitizeAddress))
      break;

    if (removeTriviallyEmptyRange(*II, Intrinsic::lifetime_start,
                                  Intrinsic::lifetime_end, *this))
      return nullptr;
    break;
  case Intrinsic::assume: {
    Value *IIOperand = II->getArgOperand(0);
    // Remove an assume if it is immediately followed by an identical assume.
    if (match(II->getNextNode(),
              m_Intrinsic<Intrinsic::assume>(m_Specific(IIOperand))))
      return eraseInstFromFunction(CI);

    // Canonicalize assume(a && b) -> assume(a); assume(b);
    // Note: New assumption intrinsics created here are registered by
    // the InstCombineIRInserter object.
    Value *AssumeIntrinsic = II->getCalledValue(), *A, *B;
    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.
    Value *DerivedPtr = cast<GCRelocateInst>(II)->getDerivedPtr();

    // 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))
      // Use undef of gc_relocate's type to replace it.
      return replaceInstUsesWith(*II, UndefValue::get(II->getType()));

    if (auto *PT = dyn_cast<PointerType>(II->getType())) {
      // 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))
        // Use null-pointer of gc_relocate's type to replace it.
        return replaceInstUsesWith(*II, ConstantPointerNull::get(PT));

      // isKnownNonNull -> nonnull attribute
      if (isKnownNonNullAt(DerivedPtr, II, &DT))
        II->addAttribute(AttributeSet::ReturnIndex, Attribute::NonNull);
    }

    // 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, ...)
    break;
  }
  }

  return visitCallSite(II);
}

// InvokeInst simplification
//
Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
  return visitCallSite(&II);
}

/// 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;
}

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->getIterator(),
                            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;
}

/// 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.
  SmallVector<unsigned, 4> Indices;
  unsigned ArgNo = 0;

  for (Value *V : CS.args()) {
    if (V->getType()->isPointerTy() &&
        !CS.paramHasAttr(ArgNo + 1, Attribute::NonNull) &&
        isKnownNonNullAt(V, CS.getInstruction(), &DT))
      Indices.push_back(ArgNo + 1);
    ArgNo++;
  }

  assert(ArgNo == CS.arg_size() && "sanity check");

  if (!Indices.empty()) {
    AttributeSet AS = CS.getAttributes();
    LLVMContext &Ctx = CS.getInstruction()->getContext();
    AS = AS.addAttribute(Ctx, Indices,
                         Attribute::get(Ctx, Attribute::NonNull));
    CS.setAttributes(AS);
    Changed = true;
  }

  // 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)) {
    // Remove the convergent attr on calls when the callee is not convergent.
    if (CS.isConvergent() && !CalleeF->isConvergent() &&
        !CalleeF->isIntrinsic()) {
      DEBUG(dbgs() << "Removing convergent attr from instr "
                   << CS.getInstruction() << "\n");
      CS.setNotConvergent();
      return CS.getInstruction();
    }

    // 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;
}

/// 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);

  SmallVector<OperandBundleDef, 1> OpBundles;
  CS.getOperandBundlesAsDefs(OpBundles);

  Instruction *NC;
  if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
    NC = Builder->CreateInvoke(Callee, II->getNormalDest(), II->getUnwindDest(),
                               Args, OpBundles);
    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, OpBundles);
    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;
}

/// 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());
  FunctionType *NestFTy = cast<FunctionType>(NestF->getValueType());

  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);

      SmallVector<OperandBundleDef, 1> OpBundles;
      CS.getOperandBundlesAsDefs(OpBundles);

      Instruction *NewCaller;
      if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
        NewCaller = InvokeInst::Create(NewCallee,
                                       II->getNormalDest(), II->getUnwindDest(),
                                       NewArgs, OpBundles);
        cast<InvokeInst>(NewCaller)->setCallingConv(II->getCallingConv());
        cast<InvokeInst>(NewCaller)->setAttributes(NewPAL);
      } else {
        NewCaller = CallInst::Create(NewCallee, NewArgs, OpBundles);
        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();
}