text: //===-- ConstantFolding.cpp - Fold instructions into constants ------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  // This file defines routines for folding instructions into constants.
  //
  // Also, to supplement the basic IR ConstantExpr simplifications,
  // this file defines some additional folding routines that can make use of
  // DataLayout information. These functions cannot go in IR due to library
  // dependency issues.
  //
  //===----------------------------------------------------------------------===//
  
  #include "llvm/Analysis/ConstantFolding.h"
  #include "llvm/ADT/APFloat.h"
  #include "llvm/ADT/APInt.h"
  #include "llvm/ADT/ArrayRef.h"
  #include "llvm/ADT/DenseMap.h"
  #include "llvm/ADT/STLExtras.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/StringRef.h"
  #include "llvm/Analysis/TargetLibraryInfo.h"
  #include "llvm/Analysis/ValueTracking.h"
  #include "llvm/Config/config.h"
  #include "llvm/IR/Constant.h"
  #include "llvm/IR/Constants.h"
  #include "llvm/IR/DataLayout.h"
  #include "llvm/IR/DerivedTypes.h"
  #include "llvm/IR/Function.h"
  #include "llvm/IR/GlobalValue.h"
  #include "llvm/IR/GlobalVariable.h"
  #include "llvm/IR/InstrTypes.h"
  #include "llvm/IR/Instruction.h"
  #include "llvm/IR/Instructions.h"
  #include "llvm/IR/Operator.h"
  #include "llvm/IR/Type.h"
  #include "llvm/IR/Value.h"
  #include "llvm/Support/Casting.h"
  #include "llvm/Support/ErrorHandling.h"
  #include "llvm/Support/KnownBits.h"
  #include "llvm/Support/MathExtras.h"
  #include <cassert>
  #include <cerrno>
  #include <cfenv>
  #include <cmath>
  #include <cstddef>
  #include <cstdint>
  
  using namespace llvm;
  
  namespace {
  
  //===----------------------------------------------------------------------===//
  // Constant Folding internal helper functions
  //===----------------------------------------------------------------------===//
  
  static Constant *foldConstVectorToAPInt(APInt &Result, Type *DestTy,
                                          Constant *C, Type *SrcEltTy,
                                          unsigned NumSrcElts,
                                          const DataLayout &DL) {
    // Now that we know that the input value is a vector of integers, just shift
    // and insert them into our result.
    unsigned BitShift = DL.getTypeSizeInBits(SrcEltTy);
    for (unsigned i = 0; i != NumSrcElts; ++i) {
      Constant *Element;
      if (DL.isLittleEndian())
        Element = C->getAggregateElement(NumSrcElts - i - 1);
      else
        Element = C->getAggregateElement(i);
  
      if (Element && isa<UndefValue>(Element)) {
        Result <<= BitShift;
        continue;
      }
  
      auto *ElementCI = dyn_cast_or_null<ConstantInt>(Element);
      if (!ElementCI)
        return ConstantExpr::getBitCast(C, DestTy);
  
      Result <<= BitShift;
      Result |= ElementCI->getValue().zextOrSelf(Result.getBitWidth());
    }
  
    return nullptr;
  }
  
  /// Constant fold bitcast, symbolically evaluating it with DataLayout.
  /// This always returns a non-null constant, but it may be a
  /// ConstantExpr if unfoldable.
  Constant *FoldBitCast(Constant *C, Type *DestTy, const DataLayout &DL) {
    // Catch the obvious splat cases.
    if (C->isNullValue() && !DestTy->isX86_MMXTy())
      return Constant::getNullValue(DestTy);
    if (C->isAllOnesValue() && !DestTy->isX86_MMXTy() &&
        !DestTy->isPtrOrPtrVectorTy()) // Don't get ones for ptr types!
      return Constant::getAllOnesValue(DestTy);
  
    if (auto *VTy = dyn_cast<VectorType>(C->getType())) {
      // Handle a vector->scalar integer/fp cast.
      if (isa<IntegerType>(DestTy) || DestTy->isFloatingPointTy()) {
        unsigned NumSrcElts = VTy->getNumElements();
        Type *SrcEltTy = VTy->getElementType();
  
        // If the vector is a vector of floating point, convert it to vector of int
        // to simplify things.
        if (SrcEltTy->isFloatingPointTy()) {
          unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
          Type *SrcIVTy =
            VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumSrcElts);
          // Ask IR to do the conversion now that #elts line up.
          C = ConstantExpr::getBitCast(C, SrcIVTy);
        }
  
        APInt Result(DL.getTypeSizeInBits(DestTy), 0);
        if (Constant *CE = foldConstVectorToAPInt(Result, DestTy, C,
                                                  SrcEltTy, NumSrcElts, DL))
          return CE;
  
        if (isa<IntegerType>(DestTy))
          return ConstantInt::get(DestTy, Result);
  
        APFloat FP(DestTy->getFltSemantics(), Result);
        return ConstantFP::get(DestTy->getContext(), FP);
      }
    }
  
    // The code below only handles casts to vectors currently.
    auto *DestVTy = dyn_cast<VectorType>(DestTy);
    if (!DestVTy)
      return ConstantExpr::getBitCast(C, DestTy);
  
    // If this is a scalar -> vector cast, convert the input into a <1 x scalar>
    // vector so the code below can handle it uniformly.
    if (isa<ConstantFP>(C) || isa<ConstantInt>(C)) {
      Constant *Ops = C; // don't take the address of C!
      return FoldBitCast(ConstantVector::get(Ops), DestTy, DL);
    }
  
    // If this is a bitcast from constant vector -> vector, fold it.
    if (!isa<ConstantDataVector>(C) && !isa<ConstantVector>(C))
      return ConstantExpr::getBitCast(C, DestTy);
  
    // If the element types match, IR can fold it.
    unsigned NumDstElt = DestVTy->getNumElements();
    unsigned NumSrcElt = C->getType()->getVectorNumElements();
    if (NumDstElt == NumSrcElt)
      return ConstantExpr::getBitCast(C, DestTy);
  
    Type *SrcEltTy = C->getType()->getVectorElementType();
    Type *DstEltTy = DestVTy->getElementType();
  
    // Otherwise, we're changing the number of elements in a vector, which
    // requires endianness information to do the right thing.  For example,
    //    bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
    // folds to (little endian):
    //    <4 x i32> <i32 0, i32 0, i32 1, i32 0>
    // and to (big endian):
    //    <4 x i32> <i32 0, i32 0, i32 0, i32 1>
  
    // First thing is first.  We only want to think about integer here, so if
    // we have something in FP form, recast it as integer.
    if (DstEltTy->isFloatingPointTy()) {
      // Fold to an vector of integers with same size as our FP type.
      unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
      Type *DestIVTy =
        VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumDstElt);
      // Recursively handle this integer conversion, if possible.
      C = FoldBitCast(C, DestIVTy, DL);
  
      // Finally, IR can handle this now that #elts line up.
      return ConstantExpr::getBitCast(C, DestTy);
    }
  
    // Okay, we know the destination is integer, if the input is FP, convert
    // it to integer first.
    if (SrcEltTy->isFloatingPointTy()) {
      unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
      Type *SrcIVTy =
        VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumSrcElt);
      // Ask IR to do the conversion now that #elts line up.
      C = ConstantExpr::getBitCast(C, SrcIVTy);
      // If IR wasn't able to fold it, bail out.
      if (!isa<ConstantVector>(C) &&  // FIXME: Remove ConstantVector.
          !isa<ConstantDataVector>(C))
        return C;
    }
  
    // Now we know that the input and output vectors are both integer vectors
    // of the same size, and that their #elements is not the same.  Do the
    // conversion here, which depends on whether the input or output has
    // more elements.
    bool isLittleEndian = DL.isLittleEndian();
  
    SmallVector<Constant*, 32> Result;
    if (NumDstElt < NumSrcElt) {
      // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
      Constant *Zero = Constant::getNullValue(DstEltTy);
      unsigned Ratio = NumSrcElt/NumDstElt;
      unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
      unsigned SrcElt = 0;
      for (unsigned i = 0; i != NumDstElt; ++i) {
        // Build each element of the result.
        Constant *Elt = Zero;
        unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
        for (unsigned j = 0; j != Ratio; ++j) {
          Constant *Src = C->getAggregateElement(SrcElt++);
          if (Src && isa<UndefValue>(Src))
            Src = Constant::getNullValue(C->getType()->getVectorElementType());
          else
            Src = dyn_cast_or_null<ConstantInt>(Src);
          if (!Src)  // Reject constantexpr elements.
            return ConstantExpr::getBitCast(C, DestTy);
  
          // Zero extend the element to the right size.
          Src = ConstantExpr::getZExt(Src, Elt->getType());
  
          // Shift it to the right place, depending on endianness.
          Src = ConstantExpr::getShl(Src,
                                     ConstantInt::get(Src->getType(), ShiftAmt));
          ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
  
          // Mix it in.
          Elt = ConstantExpr::getOr(Elt, Src);
        }
        Result.push_back(Elt);
      }
      return ConstantVector::get(Result);
    }
  
    // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
    unsigned Ratio = NumDstElt/NumSrcElt;
    unsigned DstBitSize = DL.getTypeSizeInBits(DstEltTy);
  
    // Loop over each source value, expanding into multiple results.
    for (unsigned i = 0; i != NumSrcElt; ++i) {
      auto *Element = C->getAggregateElement(i);
  
      if (!Element) // Reject constantexpr elements.
        return ConstantExpr::getBitCast(C, DestTy);
  
      if (isa<UndefValue>(Element)) {
        // Correctly Propagate undef values.
        Result.append(Ratio, UndefValue::get(DstEltTy));
        continue;
      }
  
      auto *Src = dyn_cast<ConstantInt>(Element);
      if (!Src)
        return ConstantExpr::getBitCast(C, DestTy);
  
      unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
      for (unsigned j = 0; j != Ratio; ++j) {
        // Shift the piece of the value into the right place, depending on
        // endianness.
        Constant *Elt = ConstantExpr::getLShr(Src,
                                    ConstantInt::get(Src->getType(), ShiftAmt));
        ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
  
        // Truncate the element to an integer with the same pointer size and
        // convert the element back to a pointer using a inttoptr.
        if (DstEltTy->isPointerTy()) {
          IntegerType *DstIntTy = Type::getIntNTy(C->getContext(), DstBitSize);
          Constant *CE = ConstantExpr::getTrunc(Elt, DstIntTy);
          Result.push_back(ConstantExpr::getIntToPtr(CE, DstEltTy));
          continue;
        }
  
        // Truncate and remember this piece.
        Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
      }
    }
  
    return ConstantVector::get(Result);
  }
  
  } // end anonymous namespace
  
  /// If this constant is a constant offset from a global, return the global and
  /// the constant. Because of constantexprs, this function is recursive.
  bool llvm::IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV,
                                        APInt &Offset, const DataLayout &DL) {
    // Trivial case, constant is the global.
    if ((GV = dyn_cast<GlobalValue>(C))) {
      unsigned BitWidth = DL.getIndexTypeSizeInBits(GV->getType());
      Offset = APInt(BitWidth, 0);
      return true;
    }
  
    // Otherwise, if this isn't a constant expr, bail out.
    auto *CE = dyn_cast<ConstantExpr>(C);
    if (!CE) return false;
  
    // Look through ptr->int and ptr->ptr casts.
    if (CE->getOpcode() == Instruction::PtrToInt ||
        CE->getOpcode() == Instruction::BitCast)
      return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, DL);
  
    // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5)
    auto *GEP = dyn_cast<GEPOperator>(CE);
    if (!GEP)
      return false;
  
    unsigned BitWidth = DL.getIndexTypeSizeInBits(GEP->getType());
    APInt TmpOffset(BitWidth, 0);
  
    // If the base isn't a global+constant, we aren't either.
    if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, TmpOffset, DL))
      return false;
  
    // Otherwise, add any offset that our operands provide.
    if (!GEP->accumulateConstantOffset(DL, TmpOffset))
      return false;
  
    Offset = TmpOffset;
    return true;
  }
  
  Constant *llvm::ConstantFoldLoadThroughBitcast(Constant *C, Type *DestTy,
                                           const DataLayout &DL) {
    do {
      Type *SrcTy = C->getType();
  
      // If the type sizes are the same and a cast is legal, just directly
      // cast the constant.
      if (DL.getTypeSizeInBits(DestTy) == DL.getTypeSizeInBits(SrcTy)) {
        Instruction::CastOps Cast = Instruction::BitCast;
        // If we are going from a pointer to int or vice versa, we spell the cast
        // differently.
        if (SrcTy->isIntegerTy() && DestTy->isPointerTy())
          Cast = Instruction::IntToPtr;
        else if (SrcTy->isPointerTy() && DestTy->isIntegerTy())
          Cast = Instruction::PtrToInt;
  
        if (CastInst::castIsValid(Cast, C, DestTy))
          return ConstantExpr::getCast(Cast, C, DestTy);
      }
  
      // If this isn't an aggregate type, there is nothing we can do to drill down
      // and find a bitcastable constant.
      if (!SrcTy->isAggregateType())
        return nullptr;
  
      // We're simulating a load through a pointer that was bitcast to point to
      // a different type, so we can try to walk down through the initial
      // elements of an aggregate to see if some part of the aggregate is
      // castable to implement the "load" semantic model.
      if (SrcTy->isStructTy()) {
        // Struct types might have leading zero-length elements like [0 x i32],
        // which are certainly not what we are looking for, so skip them.
        unsigned Elem = 0;
        Constant *ElemC;
        do {
          ElemC = C->getAggregateElement(Elem++);
        } while (ElemC && DL.getTypeSizeInBits(ElemC->getType()) == 0);
        C = ElemC;
      } else {
        C = C->getAggregateElement(0u);
      }
    } while (C);
  
    return nullptr;
  }
  
  namespace {
  
  /// Recursive helper to read bits out of global. C is the constant being copied
  /// out of. ByteOffset is an offset into C. CurPtr is the pointer to copy
  /// results into and BytesLeft is the number of bytes left in
  /// the CurPtr buffer. DL is the DataLayout.
  bool ReadDataFromGlobal(Constant *C, uint64_t ByteOffset, unsigned char *CurPtr,
                          unsigned BytesLeft, const DataLayout &DL) {
    assert(ByteOffset <= DL.getTypeAllocSize(C->getType()) &&
           "Out of range access");
  
    // If this element is zero or undefined, we can just return since *CurPtr is
    // zero initialized.
    if (isa<ConstantAggregateZero>(C) || isa<UndefValue>(C))
      return true;
  
    if (auto *CI = dyn_cast<ConstantInt>(C)) {
      if (CI->getBitWidth() > 64 ||
          (CI->getBitWidth() & 7) != 0)
        return false;
  
      uint64_t Val = CI->getZExtValue();
      unsigned IntBytes = unsigned(CI->getBitWidth()/8);
  
      for (unsigned i = 0; i != BytesLeft && ByteOffset != IntBytes; ++i) {
        int n = ByteOffset;
        if (!DL.isLittleEndian())
          n = IntBytes - n - 1;
        CurPtr[i] = (unsigned char)(Val >> (n * 8));
        ++ByteOffset;
      }
      return true;
    }
  
    if (auto *CFP = dyn_cast<ConstantFP>(C)) {
      if (CFP->getType()->isDoubleTy()) {
        C = FoldBitCast(C, Type::getInt64Ty(C->getContext()), DL);
        return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, DL);
      }
      if (CFP->getType()->isFloatTy()){
        C = FoldBitCast(C, Type::getInt32Ty(C->getContext()), DL);
        return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, DL);
      }
      if (CFP->getType()->isHalfTy()){
        C = FoldBitCast(C, Type::getInt16Ty(C->getContext()), DL);
        return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, DL);
      }
      return false;
    }
  
    if (auto *CS = dyn_cast<ConstantStruct>(C)) {
      const StructLayout *SL = DL.getStructLayout(CS->getType());
      unsigned Index = SL->getElementContainingOffset(ByteOffset);
      uint64_t CurEltOffset = SL->getElementOffset(Index);
      ByteOffset -= CurEltOffset;
  
      while (true) {
        // If the element access is to the element itself and not to tail padding,
        // read the bytes from the element.
        uint64_t EltSize = DL.getTypeAllocSize(CS->getOperand(Index)->getType());
  
        if (ByteOffset < EltSize &&
            !ReadDataFromGlobal(CS->getOperand(Index), ByteOffset, CurPtr,
                                BytesLeft, DL))
          return false;
  
        ++Index;
  
        // Check to see if we read from the last struct element, if so we're done.
        if (Index == CS->getType()->getNumElements())
          return true;
  
        // If we read all of the bytes we needed from this element we're done.
        uint64_t NextEltOffset = SL->getElementOffset(Index);
  
        if (BytesLeft <= NextEltOffset - CurEltOffset - ByteOffset)
          return true;
  
        // Move to the next element of the struct.
        CurPtr += NextEltOffset - CurEltOffset - ByteOffset;
        BytesLeft -= NextEltOffset - CurEltOffset - ByteOffset;
        ByteOffset = 0;
        CurEltOffset = NextEltOffset;
      }
      // not reached.
    }
  
    if (isa<ConstantArray>(C) || isa<ConstantVector>(C) ||
        isa<ConstantDataSequential>(C)) {
      Type *EltTy = C->getType()->getSequentialElementType();
      uint64_t EltSize = DL.getTypeAllocSize(EltTy);
      uint64_t Index = ByteOffset / EltSize;
      uint64_t Offset = ByteOffset - Index * EltSize;
      uint64_t NumElts;
      if (auto *AT = dyn_cast<ArrayType>(C->getType()))
        NumElts = AT->getNumElements();
      else
        NumElts = C->getType()->getVectorNumElements();
  
      for (; Index != NumElts; ++Index) {
        if (!ReadDataFromGlobal(C->getAggregateElement(Index), Offset, CurPtr,
                                BytesLeft, DL))
          return false;
  
        uint64_t BytesWritten = EltSize - Offset;
        assert(BytesWritten <= EltSize && "Not indexing into this element?");
        if (BytesWritten >= BytesLeft)
          return true;
  
        Offset = 0;
        BytesLeft -= BytesWritten;
        CurPtr += BytesWritten;
      }
      return true;
    }
  
    if (auto *CE = dyn_cast<ConstantExpr>(C)) {
      if (CE->getOpcode() == Instruction::IntToPtr &&
          CE->getOperand(0)->getType() == DL.getIntPtrType(CE->getType())) {
        return ReadDataFromGlobal(CE->getOperand(0), ByteOffset, CurPtr,
                                  BytesLeft, DL);
      }
    }
  
    // Otherwise, unknown initializer type.
    return false;
  }
  
  Constant *FoldReinterpretLoadFromConstPtr(Constant *C, Type *LoadTy,
                                            const DataLayout &DL) {
    auto *PTy = cast<PointerType>(C->getType());
    auto *IntType = dyn_cast<IntegerType>(LoadTy);
  
    // If this isn't an integer load we can't fold it directly.
    if (!IntType) {
      unsigned AS = PTy->getAddressSpace();
  
      // If this is a float/double load, we can try folding it as an int32/64 load
      // and then bitcast the result.  This can be useful for union cases.  Note
      // that address spaces don't matter here since we're not going to result in
      // an actual new load.
      Type *MapTy;
      if (LoadTy->isHalfTy())
        MapTy = Type::getInt16Ty(C->getContext());
      else if (LoadTy->isFloatTy())
        MapTy = Type::getInt32Ty(C->getContext());
      else if (LoadTy->isDoubleTy())
        MapTy = Type::getInt64Ty(C->getContext());
      else if (LoadTy->isVectorTy()) {
        MapTy = PointerType::getIntNTy(C->getContext(),
                                       DL.getTypeSizeInBits(LoadTy));
      } else
        return nullptr;
  
      C = FoldBitCast(C, MapTy->getPointerTo(AS), DL);
      if (Constant *Res = FoldReinterpretLoadFromConstPtr(C, MapTy, DL))
        return FoldBitCast(Res, LoadTy, DL);
      return nullptr;
    }
  
    unsigned BytesLoaded = (IntType->getBitWidth() + 7) / 8;
    if (BytesLoaded > 32 || BytesLoaded == 0)
      return nullptr;
  
    GlobalValue *GVal;
    APInt OffsetAI;
    if (!IsConstantOffsetFromGlobal(C, GVal, OffsetAI, DL))
      return nullptr;
  
    auto *GV = dyn_cast<GlobalVariable>(GVal);
    if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
        !GV->getInitializer()->getType()->isSized())
      return nullptr;
  
    int64_t Offset = OffsetAI.getSExtValue();
    int64_t InitializerSize = DL.getTypeAllocSize(GV->getInitializer()->getType());
  
    // If we're not accessing anything in this constant, the result is undefined.
    if (Offset + BytesLoaded <= 0)
      return UndefValue::get(IntType);
  
    // If we're not accessing anything in this constant, the result is undefined.
    if (Offset >= InitializerSize)
      return UndefValue::get(IntType);
  
    unsigned char RawBytes[32] = {0};
    unsigned char *CurPtr = RawBytes;
    unsigned BytesLeft = BytesLoaded;
  
    // If we're loading off the beginning of the global, some bytes may be valid.
    if (Offset < 0) {
      CurPtr += -Offset;
      BytesLeft += Offset;
      Offset = 0;
    }
  
    if (!ReadDataFromGlobal(GV->getInitializer(), Offset, CurPtr, BytesLeft, DL))
      return nullptr;
  
    APInt ResultVal = APInt(IntType->getBitWidth(), 0);
    if (DL.isLittleEndian()) {
      ResultVal = RawBytes[BytesLoaded - 1];
      for (unsigned i = 1; i != BytesLoaded; ++i) {
        ResultVal <<= 8;
        ResultVal |= RawBytes[BytesLoaded - 1 - i];
      }
    } else {
      ResultVal = RawBytes[0];
      for (unsigned i = 1; i != BytesLoaded; ++i) {
        ResultVal <<= 8;
        ResultVal |= RawBytes[i];
      }
    }
  
    return ConstantInt::get(IntType->getContext(), ResultVal);
  }
  
  Constant *ConstantFoldLoadThroughBitcastExpr(ConstantExpr *CE, Type *DestTy,
                                               const DataLayout &DL) {
    auto *SrcPtr = CE->getOperand(0);
    auto *SrcPtrTy = dyn_cast<PointerType>(SrcPtr->getType());
    if (!SrcPtrTy)
      return nullptr;
    Type *SrcTy = SrcPtrTy->getPointerElementType();
  
    Constant *C = ConstantFoldLoadFromConstPtr(SrcPtr, SrcTy, DL);
    if (!C)
      return nullptr;
  
    return llvm::ConstantFoldLoadThroughBitcast(C, DestTy, DL);
  }
  
  } // end anonymous namespace
  
  Constant *llvm::ConstantFoldLoadFromConstPtr(Constant *C, Type *Ty,
                                               const DataLayout &DL) {
    // First, try the easy cases:
    if (auto *GV = dyn_cast<GlobalVariable>(C))
      if (GV->isConstant() && GV->hasDefinitiveInitializer())
        return GV->getInitializer();
  
    if (auto *GA = dyn_cast<GlobalAlias>(C))
      if (GA->getAliasee() && !GA->isInterposable())
        return ConstantFoldLoadFromConstPtr(GA->getAliasee(), Ty, DL);
  
    // If the loaded value isn't a constant expr, we can't handle it.
    auto *CE = dyn_cast<ConstantExpr>(C);
    if (!CE)
      return nullptr;
  
    if (CE->getOpcode() == Instruction::GetElementPtr) {
      if (auto *GV = dyn_cast<GlobalVariable>(CE->getOperand(0))) {
        if (GV->isConstant() && GV->hasDefinitiveInitializer()) {
          if (Constant *V =
               ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE))
            return V;
        }
      }
    }
  
    if (CE->getOpcode() == Instruction::BitCast)
      if (Constant *LoadedC = ConstantFoldLoadThroughBitcastExpr(CE, Ty, DL))
        return LoadedC;
  
    // Instead of loading constant c string, use corresponding integer value
    // directly if string length is small enough.
    StringRef Str;
    if (getConstantStringInfo(CE, Str) && !Str.empty()) {
      size_t StrLen = Str.size();
      unsigned NumBits = Ty->getPrimitiveSizeInBits();
      // Replace load with immediate integer if the result is an integer or fp
      // value.
      if ((NumBits >> 3) == StrLen + 1 && (NumBits & 7) == 0 &&
          (isa<IntegerType>(Ty) || Ty->isFloatingPointTy())) {
        APInt StrVal(NumBits, 0);
        APInt SingleChar(NumBits, 0);
        if (DL.isLittleEndian()) {
          for (unsigned char C : reverse(Str.bytes())) {
            SingleChar = static_cast<uint64_t>(C);
            StrVal = (StrVal << 8) | SingleChar;
          }
        } else {
          for (unsigned char C : Str.bytes()) {
            SingleChar = static_cast<uint64_t>(C);
            StrVal = (StrVal << 8) | SingleChar;
          }
          // Append NULL at the end.
          SingleChar = 0;
          StrVal = (StrVal << 8) | SingleChar;
        }
  
        Constant *Res = ConstantInt::get(CE->getContext(), StrVal);
        if (Ty->isFloatingPointTy())
          Res = ConstantExpr::getBitCast(Res, Ty);
        return Res;
      }
    }
  
    // If this load comes from anywhere in a constant global, and if the global
    // is all undef or zero, we know what it loads.
    if (auto *GV = dyn_cast<GlobalVariable>(GetUnderlyingObject(CE, DL))) {
      if (GV->isConstant() && GV->hasDefinitiveInitializer()) {
        if (GV->getInitializer()->isNullValue())
          return Constant::getNullValue(Ty);
        if (isa<UndefValue>(GV->getInitializer()))
          return UndefValue::get(Ty);
      }
    }
  
    // Try hard to fold loads from bitcasted strange and non-type-safe things.
    return FoldReinterpretLoadFromConstPtr(CE, Ty, DL);
  }
  
  namespace {
  
  Constant *ConstantFoldLoadInst(const LoadInst *LI, const DataLayout &DL) {
    if (LI->isVolatile()) return nullptr;
  
    if (auto *C = dyn_cast<Constant>(LI->getOperand(0)))
      return ConstantFoldLoadFromConstPtr(C, LI->getType(), DL);
  
    return nullptr;
  }
  
  /// One of Op0/Op1 is a constant expression.
  /// Attempt to symbolically evaluate the result of a binary operator merging
  /// these together.  If target data info is available, it is provided as DL,
  /// otherwise DL is null.
  Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0, Constant *Op1,
                                      const DataLayout &DL) {
    // SROA
  
    // Fold (and 0xffffffff00000000, (shl x, 32)) -> shl.
    // Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute
    // bits.
  
    if (Opc == Instruction::And) {
      KnownBits Known0 = computeKnownBits(Op0, DL);
      KnownBits Known1 = computeKnownBits(Op1, DL);
      if ((Known1.One | Known0.Zero).isAllOnesValue()) {
        // All the bits of Op0 that the 'and' could be masking are already zero.
        return Op0;
      }
      if ((Known0.One | Known1.Zero).isAllOnesValue()) {
        // All the bits of Op1 that the 'and' could be masking are already zero.
        return Op1;
      }
  
      Known0.Zero |= Known1.Zero;
      Known0.One &= Known1.One;
      if (Known0.isConstant())
        return ConstantInt::get(Op0->getType(), Known0.getConstant());
    }
  
    // If the constant expr is something like &A[123] - &A[4].f, fold this into a
    // constant.  This happens frequently when iterating over a global array.
    if (Opc == Instruction::Sub) {
      GlobalValue *GV1, *GV2;
      APInt Offs1, Offs2;
  
      if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, DL))
        if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, DL) && GV1 == GV2) {
          unsigned OpSize = DL.getTypeSizeInBits(Op0->getType());
  
          // (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow.
          // PtrToInt may change the bitwidth so we have convert to the right size
          // first.
          return ConstantInt::get(Op0->getType(), Offs1.zextOrTrunc(OpSize) -
                                                  Offs2.zextOrTrunc(OpSize));
        }
    }
  
    return nullptr;
  }
  
  /// If array indices are not pointer-sized integers, explicitly cast them so
  /// that they aren't implicitly casted by the getelementptr.
  Constant *CastGEPIndices(Type *SrcElemTy, ArrayRef<Constant *> Ops,
                           Type *ResultTy, Optional<unsigned> InRangeIndex,
                           const DataLayout &DL, const TargetLibraryInfo *TLI) {
    Type *IntPtrTy = DL.getIntPtrType(ResultTy);
    Type *IntPtrScalarTy = IntPtrTy->getScalarType();
  
    bool Any = false;
    SmallVector<Constant*, 32> NewIdxs;
    for (unsigned i = 1, e = Ops.size(); i != e; ++i) {
      if ((i == 1 ||
           !isa<StructType>(GetElementPtrInst::getIndexedType(
               SrcElemTy, Ops.slice(1, i - 1)))) &&
          Ops[i]->getType()->getScalarType() != IntPtrScalarTy) {
        Any = true;
        Type *NewType = Ops[i]->getType()->isVectorTy()
                            ? IntPtrTy
                            : IntPtrTy->getScalarType();
        NewIdxs.push_back(ConstantExpr::getCast(CastInst::getCastOpcode(Ops[i],
                                                                        true,
                                                                        NewType,
                                                                        true),
                                                Ops[i], NewType));
      } else
        NewIdxs.push_back(Ops[i]);
    }
  
    if (!Any)
      return nullptr;
  
    Constant *C = ConstantExpr::getGetElementPtr(
        SrcElemTy, Ops[0], NewIdxs, /*InBounds=*/false, InRangeIndex);
    if (Constant *Folded = ConstantFoldConstant(C, DL, TLI))
      C = Folded;
  
    return C;
  }
  
  /// Strip the pointer casts, but preserve the address space information.
  Constant* StripPtrCastKeepAS(Constant* Ptr, Type *&ElemTy) {
    assert(Ptr->getType()->isPointerTy() && "Not a pointer type");
    auto *OldPtrTy = cast<PointerType>(Ptr->getType());
    Ptr = Ptr->stripPointerCasts();
    auto *NewPtrTy = cast<PointerType>(Ptr->getType());
  
    ElemTy = NewPtrTy->getPointerElementType();
  
    // Preserve the address space number of the pointer.
    if (NewPtrTy->getAddressSpace() != OldPtrTy->getAddressSpace()) {
      NewPtrTy = ElemTy->getPointerTo(OldPtrTy->getAddressSpace());
      Ptr = ConstantExpr::getPointerCast(Ptr, NewPtrTy);
    }
    return Ptr;
  }
  
  /// If we can symbolically evaluate the GEP constant expression, do so.
  Constant *SymbolicallyEvaluateGEP(const GEPOperator *GEP,
                                    ArrayRef<Constant *> Ops,
                                    const DataLayout &DL,
                                    const TargetLibraryInfo *TLI) {
    const GEPOperator *InnermostGEP = GEP;
    bool InBounds = GEP->isInBounds();
  
    Type *SrcElemTy = GEP->getSourceElementType();
    Type *ResElemTy = GEP->getResultElementType();
    Type *ResTy = GEP->getType();
    if (!SrcElemTy->isSized())
      return nullptr;
  
    if (Constant *C = CastGEPIndices(SrcElemTy, Ops, ResTy,
                                     GEP->getInRangeIndex(), DL, TLI))
      return C;
  
    Constant *Ptr = Ops[0];
    if (!Ptr->getType()->isPointerTy())
      return nullptr;
  
    Type *IntPtrTy = DL.getIntPtrType(Ptr->getType());
  
    // If this is a constant expr gep that is effectively computing an
    // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
    for (unsigned i = 1, e = Ops.size(); i != e; ++i)
        if (!isa<ConstantInt>(Ops[i])) {
  
          // If this is "gep i8* Ptr, (sub 0, V)", fold this as:
          // "inttoptr (sub (ptrtoint Ptr), V)"
          if (Ops.size() == 2 && ResElemTy->isIntegerTy(8)) {
            auto *CE = dyn_cast<ConstantExpr>(Ops[1]);
            assert((!CE || CE->getType() == IntPtrTy) &&
                   "CastGEPIndices didn't canonicalize index types!");
            if (CE && CE->getOpcode() == Instruction::Sub &&
                CE->getOperand(0)->isNullValue()) {
              Constant *Res = ConstantExpr::getPtrToInt(Ptr, CE->getType());
              Res = ConstantExpr::getSub(Res, CE->getOperand(1));
              Res = ConstantExpr::getIntToPtr(Res, ResTy);
              if (auto *FoldedRes = ConstantFoldConstant(Res, DL, TLI))
                Res = FoldedRes;
              return Res;
            }
          }
          return nullptr;
        }
  
    unsigned BitWidth = DL.getTypeSizeInBits(IntPtrTy);
    APInt Offset =
        APInt(BitWidth,
              DL.getIndexedOffsetInType(
                  SrcElemTy,
                  makeArrayRef((Value * const *)Ops.data() + 1, Ops.size() - 1)));
    Ptr = StripPtrCastKeepAS(Ptr, SrcElemTy);
  
    // If this is a GEP of a GEP, fold it all into a single GEP.
    while (auto *GEP = dyn_cast<GEPOperator>(Ptr)) {
      InnermostGEP = GEP;
      InBounds &= GEP->isInBounds();
  
      SmallVector<Value *, 4> NestedOps(GEP->op_begin() + 1, GEP->op_end());
  
      // Do not try the incorporate the sub-GEP if some index is not a number.
      bool AllConstantInt = true;
      for (Value *NestedOp : NestedOps)
        if (!isa<ConstantInt>(NestedOp)) {
          AllConstantInt = false;
          break;
        }
      if (!AllConstantInt)
        break;
  
      Ptr = cast<Constant>(GEP->getOperand(0));
      SrcElemTy = GEP->getSourceElementType();
      Offset += APInt(BitWidth, DL.getIndexedOffsetInType(SrcElemTy, NestedOps));
      Ptr = StripPtrCastKeepAS(Ptr, SrcElemTy);
    }
  
    // If the base value for this address is a literal integer value, fold the
    // getelementptr to the resulting integer value casted to the pointer type.
    APInt BasePtr(BitWidth, 0);
    if (auto *CE = dyn_cast<ConstantExpr>(Ptr)) {
      if (CE->getOpcode() == Instruction::IntToPtr) {
        if (auto *Base = dyn_cast<ConstantInt>(CE->getOperand(0)))
          BasePtr = Base->getValue().zextOrTrunc(BitWidth);
      }
    }
  
    auto *PTy = cast<PointerType>(Ptr->getType());
    if ((Ptr->isNullValue() || BasePtr != 0) &&
        !DL.isNonIntegralPointerType(PTy)) {
      Constant *C = ConstantInt::get(Ptr->getContext(), Offset + BasePtr);
      return ConstantExpr::getIntToPtr(C, ResTy);
    }
  
    // Otherwise form a regular getelementptr. Recompute the indices so that
    // we eliminate over-indexing of the notional static type array bounds.
    // This makes it easy to determine if the getelementptr is "inbounds".
    // Also, this helps GlobalOpt do SROA on GlobalVariables.
    Type *Ty = PTy;
    SmallVector<Constant *, 32> NewIdxs;
  
    do {
      if (!Ty->isStructTy()) {
        if (Ty->isPointerTy()) {
          // The only pointer indexing we'll do is on the first index of the GEP.
          if (!NewIdxs.empty())
            break;
  
          Ty = SrcElemTy;
  
          // Only handle pointers to sized types, not pointers to functions.
          if (!Ty->isSized())
            return nullptr;
        } else if (auto *ATy = dyn_cast<SequentialType>(Ty)) {
          Ty = ATy->getElementType();
        } else {
          // We've reached some non-indexable type.
          break;
        }
  
        // Determine which element of the array the offset points into.
        APInt ElemSize(BitWidth, DL.getTypeAllocSize(Ty));
        if (ElemSize == 0) {
          // The element size is 0. This may be [0 x Ty]*, so just use a zero
          // index for this level and proceed to the next level to see if it can
          // accommodate the offset.
          NewIdxs.push_back(ConstantInt::get(IntPtrTy, 0));
        } else {
          // The element size is non-zero divide the offset by the element
          // size (rounding down), to compute the index at this level.
          bool Overflow;
          APInt NewIdx = Offset.sdiv_ov(ElemSize, Overflow);
          if (Overflow)
            break;
          Offset -= NewIdx * ElemSize;
          NewIdxs.push_back(ConstantInt::get(IntPtrTy, NewIdx));
        }
      } else {
        auto *STy = cast<StructType>(Ty);
        // If we end up with an offset that isn't valid for this struct type, we
        // can't re-form this GEP in a regular form, so bail out. The pointer
        // operand likely went through casts that are necessary to make the GEP
        // sensible.
        const StructLayout &SL = *DL.getStructLayout(STy);
        if (Offset.isNegative() || Offset.uge(SL.getSizeInBytes()))
          break;
  
        // Determine which field of the struct the offset points into. The
        // getZExtValue is fine as we've already ensured that the offset is
        // within the range representable by the StructLayout API.
        unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue());
        NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()),
                                           ElIdx));
        Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx));
        Ty = STy->getTypeAtIndex(ElIdx);
      }
    } while (Ty != ResElemTy);
  
    // If we haven't used up the entire offset by descending the static
    // type, then the offset is pointing into the middle of an indivisible
    // member, so we can't simplify it.
    if (Offset != 0)
      return nullptr;
  
    // Preserve the inrange index from the innermost GEP if possible. We must
    // have calculated the same indices up to and including the inrange index.
    Optional<unsigned> InRangeIndex;
    if (Optional<unsigned> LastIRIndex = InnermostGEP->getInRangeIndex())
      if (SrcElemTy == InnermostGEP->getSourceElementType() &&
          NewIdxs.size() > *LastIRIndex) {
        InRangeIndex = LastIRIndex;
        for (unsigned I = 0; I <= *LastIRIndex; ++I)
          if (NewIdxs[I] != InnermostGEP->getOperand(I + 1))
            return nullptr;
      }
  
    // Create a GEP.
    Constant *C = ConstantExpr::getGetElementPtr(SrcElemTy, Ptr, NewIdxs,
                                                 InBounds, InRangeIndex);
    assert(C->getType()->getPointerElementType() == Ty &&
           "Computed GetElementPtr has unexpected type!");
  
    // If we ended up indexing a member with a type that doesn't match
    // the type of what the original indices indexed, add a cast.
    if (Ty != ResElemTy)
      C = FoldBitCast(C, ResTy, DL);
  
    return C;
  }
  
  /// Attempt to constant fold an instruction with the
  /// specified opcode and operands.  If successful, the constant result is
  /// returned, if not, null is returned.  Note that this function can fail when
  /// attempting to fold instructions like loads and stores, which have no
  /// constant expression form.
  Constant *ConstantFoldInstOperandsImpl(const Value *InstOrCE, unsigned Opcode,
                                         ArrayRef<Constant *> Ops,
                                         const DataLayout &DL,
                                         const TargetLibraryInfo *TLI) {
    Type *DestTy = InstOrCE->getType();
  
    if (Instruction::isUnaryOp(Opcode))
      return ConstantFoldUnaryOpOperand(Opcode, Ops[0], DL);
  
    if (Instruction::isBinaryOp(Opcode))
      return ConstantFoldBinaryOpOperands(Opcode, Ops[0], Ops[1], DL);
  
    if (Instruction::isCast(Opcode))
      return ConstantFoldCastOperand(Opcode, Ops[0], DestTy, DL);
  
    if (auto *GEP = dyn_cast<GEPOperator>(InstOrCE)) {
      if (Constant *C = SymbolicallyEvaluateGEP(GEP, Ops, DL, TLI))
        return C;
  
      return ConstantExpr::getGetElementPtr(GEP->getSourceElementType(), Ops[0],
                                            Ops.slice(1), GEP->isInBounds(),
                                            GEP->getInRangeIndex());
    }
  
    if (auto *CE = dyn_cast<ConstantExpr>(InstOrCE))
      return CE->getWithOperands(Ops);
  
    switch (Opcode) {
    default: return nullptr;
    case Instruction::ICmp:
    case Instruction::FCmp: llvm_unreachable("Invalid for compares");
    case Instruction::Call:
      if (auto *F = dyn_cast<Function>(Ops.back())) {
        const auto *Call = cast<CallBase>(InstOrCE);
        if (canConstantFoldCallTo(Call, F))
          return ConstantFoldCall(Call, F, Ops.slice(0, Ops.size() - 1), TLI);
      }
      return nullptr;
    case Instruction::Select:
      return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
    case Instruction::ExtractElement:
      return ConstantExpr::getExtractElement(Ops[0], Ops[1]);
    case Instruction::InsertElement:
      return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]);
    case Instruction::ShuffleVector:
      return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]);
    }
  }
  
  } // end anonymous namespace
  
  //===----------------------------------------------------------------------===//
  // Constant Folding public APIs
  //===----------------------------------------------------------------------===//
  
  namespace {
  
  Constant *
  ConstantFoldConstantImpl(const Constant *C, const DataLayout &DL,
                           const TargetLibraryInfo *TLI,
                           SmallDenseMap<Constant *, Constant *> &FoldedOps) {
    if (!isa<ConstantVector>(C) && !isa<ConstantExpr>(C))
      return nullptr;
  
    SmallVector<Constant *, 8> Ops;
    for (const Use &NewU : C->operands()) {
      auto *NewC = cast<Constant>(&NewU);
      // Recursively fold the ConstantExpr's operands. If we have already folded
      // a ConstantExpr, we don't have to process it again.
      if (isa<ConstantVector>(NewC) || isa<ConstantExpr>(NewC)) {
        auto It = FoldedOps.find(NewC);
        if (It == FoldedOps.end()) {
          if (auto *FoldedC =
                  ConstantFoldConstantImpl(NewC, DL, TLI, FoldedOps)) {
            FoldedOps.insert({NewC, FoldedC});
            NewC = FoldedC;
          } else {
            FoldedOps.insert({NewC, NewC});
          }
        } else {
          NewC = It->second;
        }
      }
      Ops.push_back(NewC);
    }
  
    if (auto *CE = dyn_cast<ConstantExpr>(C)) {
      if (CE->isCompare())
        return ConstantFoldCompareInstOperands(CE->getPredicate(), Ops[0], Ops[1],
                                               DL, TLI);
  
      return ConstantFoldInstOperandsImpl(CE, CE->getOpcode(), Ops, DL, TLI);
    }
  
    assert(isa<ConstantVector>(C));
    return ConstantVector::get(Ops);
  }
  
  } // end anonymous namespace
  
  Constant *llvm::ConstantFoldInstruction(Instruction *I, const DataLayout &DL,
                                          const TargetLibraryInfo *TLI) {
    // Handle PHI nodes quickly here...
    if (auto *PN = dyn_cast<PHINode>(I)) {
      Constant *CommonValue = nullptr;
  
      SmallDenseMap<Constant *, Constant *> FoldedOps;
      for (Value *Incoming : PN->incoming_values()) {
        // If the incoming value is undef then skip it.  Note that while we could
        // skip the value if it is equal to the phi node itself we choose not to
        // because that would break the rule that constant folding only applies if
        // all operands are constants.
        if (isa<UndefValue>(Incoming))
          continue;
        // If the incoming value is not a constant, then give up.
        auto *C = dyn_cast<Constant>(Incoming);
        if (!C)
          return nullptr;
        // Fold the PHI's operands.
        if (auto *FoldedC = ConstantFoldConstantImpl(C, DL, TLI, FoldedOps))
          C = FoldedC;
        // If the incoming value is a different constant to
        // the one we saw previously, then give up.
        if (CommonValue && C != CommonValue)
          return nullptr;
        CommonValue = C;
      }
  
      // If we reach here, all incoming values are the same constant or undef.
      return CommonValue ? CommonValue : UndefValue::get(PN->getType());
    }
  
    // Scan the operand list, checking to see if they are all constants, if so,
    // hand off to ConstantFoldInstOperandsImpl.
    if (!all_of(I->operands(), [](Use &U) { return isa<Constant>(U); }))
      return nullptr;
  
    SmallDenseMap<Constant *, Constant *> FoldedOps;
    SmallVector<Constant *, 8> Ops;
    for (const Use &OpU : I->operands()) {
      auto *Op = cast<Constant>(&OpU);
      // Fold the Instruction's operands.
      if (auto *FoldedOp = ConstantFoldConstantImpl(Op, DL, TLI, FoldedOps))
        Op = FoldedOp;
  
      Ops.push_back(Op);
    }
  
    if (const auto *CI = dyn_cast<CmpInst>(I))
      return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1],
                                             DL, TLI);
  
    if (const auto *LI = dyn_cast<LoadInst>(I))
      return ConstantFoldLoadInst(LI, DL);
  
    if (auto *IVI = dyn_cast<InsertValueInst>(I)) {
      return ConstantExpr::getInsertValue(
                                  cast<Constant>(IVI->getAggregateOperand()),
                                  cast<Constant>(IVI->getInsertedValueOperand()),
                                  IVI->getIndices());
    }
  
    if (auto *EVI = dyn_cast<ExtractValueInst>(I)) {
      return ConstantExpr::getExtractValue(
                                      cast<Constant>(EVI->getAggregateOperand()),
                                      EVI->getIndices());
    }
  
    return ConstantFoldInstOperands(I, Ops, DL, TLI);
  }
  
  Constant *llvm::ConstantFoldConstant(const Constant *C, const DataLayout &DL,
                                       const TargetLibraryInfo *TLI) {
    SmallDenseMap<Constant *, Constant *> FoldedOps;
    return ConstantFoldConstantImpl(C, DL, TLI, FoldedOps);
  }
  
  Constant *llvm::ConstantFoldInstOperands(Instruction *I,
                                           ArrayRef<Constant *> Ops,
                                           const DataLayout &DL,
                                           const TargetLibraryInfo *TLI) {
    return ConstantFoldInstOperandsImpl(I, I->getOpcode(), Ops, DL, TLI);
  }
  
  Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
                                                  Constant *Ops0, Constant *Ops1,
                                                  const DataLayout &DL,
                                                  const TargetLibraryInfo *TLI) {
    // fold: icmp (inttoptr x), null         -> icmp x, 0
    // fold: icmp null, (inttoptr x)         -> icmp 0, x
    // fold: icmp (ptrtoint x), 0            -> icmp x, null
    // fold: icmp 0, (ptrtoint x)            -> icmp null, x
    // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
    // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
    //
    // FIXME: The following comment is out of data and the DataLayout is here now.
    // ConstantExpr::getCompare cannot do this, because it doesn't have DL
    // around to know if bit truncation is happening.
    if (auto *CE0 = dyn_cast<ConstantExpr>(Ops0)) {
      if (Ops1->isNullValue()) {
        if (CE0->getOpcode() == Instruction::IntToPtr) {
          Type *IntPtrTy = DL.getIntPtrType(CE0->getType());
          // Convert the integer value to the right size to ensure we get the
          // proper extension or truncation.
          Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0),
                                                     IntPtrTy, false);
          Constant *Null = Constant::getNullValue(C->getType());
          return ConstantFoldCompareInstOperands(Predicate, C, Null, DL, TLI);
        }
  
        // Only do this transformation if the int is intptrty in size, otherwise
        // there is a truncation or extension that we aren't modeling.
        if (CE0->getOpcode() == Instruction::PtrToInt) {
          Type *IntPtrTy = DL.getIntPtrType(CE0->getOperand(0)->getType());
          if (CE0->getType() == IntPtrTy) {
            Constant *C = CE0->getOperand(0);
            Constant *Null = Constant::getNullValue(C->getType());
            return ConstantFoldCompareInstOperands(Predicate, C, Null, DL, TLI);
          }
        }
      }
  
      if (auto *CE1 = dyn_cast<ConstantExpr>(Ops1)) {
        if (CE0->getOpcode() == CE1->getOpcode()) {
          if (CE0->getOpcode() == Instruction::IntToPtr) {
            Type *IntPtrTy = DL.getIntPtrType(CE0->getType());
  
            // Convert the integer value to the right size to ensure we get the
            // proper extension or truncation.
            Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0),
                                                        IntPtrTy, false);
            Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0),
                                                        IntPtrTy, false);
            return ConstantFoldCompareInstOperands(Predicate, C0, C1, DL, TLI);
          }
  
          // Only do this transformation if the int is intptrty in size, otherwise
          // there is a truncation or extension that we aren't modeling.
          if (CE0->getOpcode() == Instruction::PtrToInt) {
            Type *IntPtrTy = DL.getIntPtrType(CE0->getOperand(0)->getType());
            if (CE0->getType() == IntPtrTy &&
                CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType()) {
              return ConstantFoldCompareInstOperands(
                  Predicate, CE0->getOperand(0), CE1->getOperand(0), DL, TLI);
            }
          }
        }
      }
  
      // icmp eq (or x, y), 0 -> (icmp eq x, 0) & (icmp eq y, 0)
      // icmp ne (or x, y), 0 -> (icmp ne x, 0) | (icmp ne y, 0)
      if ((Predicate == ICmpInst::ICMP_EQ || Predicate == ICmpInst::ICMP_NE) &&
          CE0->getOpcode() == Instruction::Or && Ops1->isNullValue()) {
        Constant *LHS = ConstantFoldCompareInstOperands(
            Predicate, CE0->getOperand(0), Ops1, DL, TLI);
        Constant *RHS = ConstantFoldCompareInstOperands(
            Predicate, CE0->getOperand(1), Ops1, DL, TLI);
        unsigned OpC =
          Predicate == ICmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
        return ConstantFoldBinaryOpOperands(OpC, LHS, RHS, DL);
      }
    } else if (isa<ConstantExpr>(Ops1)) {
      // If RHS is a constant expression, but the left side isn't, swap the
      // operands and try again.
      Predicate = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)Predicate);
      return ConstantFoldCompareInstOperands(Predicate, Ops1, Ops0, DL, TLI);
    }
  
    return ConstantExpr::getCompare(Predicate, Ops0, Ops1);
  }
  
  Constant *llvm::ConstantFoldUnaryOpOperand(unsigned Opcode, Constant *Op,
                                             const DataLayout &DL) {
    assert(Instruction::isUnaryOp(Opcode));
  
    return ConstantExpr::get(Opcode, Op);
  }
  
  Constant *llvm::ConstantFoldBinaryOpOperands(unsigned Opcode, Constant *LHS,
                                               Constant *RHS,
                                               const DataLayout &DL) {
    assert(Instruction::isBinaryOp(Opcode));
    if (isa<ConstantExpr>(LHS) || isa<ConstantExpr>(RHS))
      if (Constant *C = SymbolicallyEvaluateBinop(Opcode, LHS, RHS, DL))
        return C;
  
    return ConstantExpr::get(Opcode, LHS, RHS);
  }
  
  Constant *llvm::ConstantFoldCastOperand(unsigned Opcode, Constant *C,
                                          Type *DestTy, const DataLayout &DL) {
    assert(Instruction::isCast(Opcode));
    switch (Opcode) {
    default:
      llvm_unreachable("Missing case");
    case Instruction::PtrToInt:
      // If the input is a inttoptr, eliminate the pair.  This requires knowing
      // the width of a pointer, so it can't be done in ConstantExpr::getCast.
      if (auto *CE = dyn_cast<ConstantExpr>(C)) {
        if (CE->getOpcode() == Instruction::IntToPtr) {
          Constant *Input = CE->getOperand(0);
          unsigned InWidth = Input->getType()->getScalarSizeInBits();
          unsigned PtrWidth = DL.getPointerTypeSizeInBits(CE->getType());
          if (PtrWidth < InWidth) {
            Constant *Mask =
              ConstantInt::get(CE->getContext(),
                               APInt::getLowBitsSet(InWidth, PtrWidth));
            Input = ConstantExpr::getAnd(Input, Mask);
          }
          // Do a zext or trunc to get to the dest size.
          return ConstantExpr::getIntegerCast(Input, DestTy, false);
        }
      }
      return ConstantExpr::getCast(Opcode, C, DestTy);
    case Instruction::IntToPtr:
      // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if
      // the int size is >= the ptr size and the address spaces are the same.
      // This requires knowing the width of a pointer, so it can't be done in
      // ConstantExpr::getCast.
      if (auto *CE = dyn_cast<ConstantExpr>(C)) {
        if (CE->getOpcode() == Instruction::PtrToInt) {
          Constant *SrcPtr = CE->getOperand(0);
          unsigned SrcPtrSize = DL.getPointerTypeSizeInBits(SrcPtr->getType());
          unsigned MidIntSize = CE->getType()->getScalarSizeInBits();
  
          if (MidIntSize >= SrcPtrSize) {
            unsigned SrcAS = SrcPtr->getType()->getPointerAddressSpace();
            if (SrcAS == DestTy->getPointerAddressSpace())
              return FoldBitCast(CE->getOperand(0), DestTy, DL);
          }
        }
      }
  
      return ConstantExpr::getCast(Opcode, C, DestTy);
    case Instruction::Trunc:
    case Instruction::ZExt:
    case Instruction::SExt:
    case Instruction::FPTrunc:
    case Instruction::FPExt:
    case Instruction::UIToFP:
    case Instruction::SIToFP:
    case Instruction::FPToUI:
    case Instruction::FPToSI:
    case Instruction::AddrSpaceCast:
        return ConstantExpr::getCast(Opcode, C, DestTy);
    case Instruction::BitCast:
      return FoldBitCast(C, DestTy, DL);
    }
  }
  
  Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C,
                                                         ConstantExpr *CE) {
    if (!CE->getOperand(1)->isNullValue())
      return nullptr;  // Do not allow stepping over the value!
  
    // Loop over all of the operands, tracking down which value we are
    // addressing.
    for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i) {
      C = C->getAggregateElement(CE->getOperand(i));
      if (!C)
        return nullptr;
    }
    return C;
  }
  
  Constant *
  llvm::ConstantFoldLoadThroughGEPIndices(Constant *C,
                                          ArrayRef<Constant *> Indices) {
    // Loop over all of the operands, tracking down which value we are
    // addressing.
    for (Constant *Index : Indices) {
      C = C->getAggregateElement(Index);
      if (!C)
        return nullptr;
    }
    return C;
  }
  
  //===----------------------------------------------------------------------===//
  //  Constant Folding for Calls
  //
  
  bool llvm::canConstantFoldCallTo(const CallBase *Call, const Function *F) {
    if (Call->isNoBuiltin() || Call->isStrictFP())
      return false;
    switch (F->getIntrinsicID()) {
    case Intrinsic::fabs:
    case Intrinsic::minnum:
    case Intrinsic::maxnum:
    case Intrinsic::minimum:
    case Intrinsic::maximum:
    case Intrinsic::log:
    case Intrinsic::log2:
    case Intrinsic::log10:
    case Intrinsic::exp:
    case Intrinsic::exp2:
    case Intrinsic::floor:
    case Intrinsic::ceil:
    case Intrinsic::sqrt:
    case Intrinsic::sin:
    case Intrinsic::cos:
    case Intrinsic::trunc:
    case Intrinsic::rint:
    case Intrinsic::nearbyint:
    case Intrinsic::pow:
    case Intrinsic::powi:
    case Intrinsic::bswap:
    case Intrinsic::ctpop:
    case Intrinsic::ctlz:
    case Intrinsic::cttz:
    case Intrinsic::fshl:
    case Intrinsic::fshr:
    case Intrinsic::fma:
    case Intrinsic::fmuladd:
    case Intrinsic::copysign:
    case Intrinsic::launder_invariant_group:
    case Intrinsic::strip_invariant_group:
    case Intrinsic::round:
    case Intrinsic::masked_load:
    case Intrinsic::sadd_with_overflow:
    case Intrinsic::uadd_with_overflow:
    case Intrinsic::ssub_with_overflow:
    case Intrinsic::usub_with_overflow:
    case Intrinsic::smul_with_overflow:
    case Intrinsic::umul_with_overflow:
    case Intrinsic::sadd_sat:
    case Intrinsic::uadd_sat:
    case Intrinsic::ssub_sat:
    case Intrinsic::usub_sat:
    case Intrinsic::smul_fix:
    case Intrinsic::smul_fix_sat:
    case Intrinsic::convert_from_fp16:
    case Intrinsic::convert_to_fp16:
    case Intrinsic::bitreverse:
    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:
    case Intrinsic::x86_avx512_vcvtss2si32:
    case Intrinsic::x86_avx512_vcvtss2si64:
    case Intrinsic::x86_avx512_cvttss2si:
    case Intrinsic::x86_avx512_cvttss2si64:
    case Intrinsic::x86_avx512_vcvtsd2si32:
    case Intrinsic::x86_avx512_vcvtsd2si64:
    case Intrinsic::x86_avx512_cvttsd2si:
    case Intrinsic::x86_avx512_cvttsd2si64:
    case Intrinsic::x86_avx512_vcvtss2usi32:
    case Intrinsic::x86_avx512_vcvtss2usi64:
    case Intrinsic::x86_avx512_cvttss2usi:
    case Intrinsic::x86_avx512_cvttss2usi64:
    case Intrinsic::x86_avx512_vcvtsd2usi32:
    case Intrinsic::x86_avx512_vcvtsd2usi64:
    case Intrinsic::x86_avx512_cvttsd2usi:
    case Intrinsic::x86_avx512_cvttsd2usi64:
    case Intrinsic::is_constant:
      return true;
    default:
      return false;
    case Intrinsic::not_intrinsic: break;
    }
  
    if (!F->hasName())
      return false;
    StringRef Name = F->getName();
  
    // In these cases, the check of the length is required.  We don't want to
    // return true for a name like "cos\0blah" which strcmp would return equal to
    // "cos", but has length 8.
    switch (Name[0]) {
    default:
      return false;
    case 'a':
      return Name == "acos" || Name == "asin" || Name == "atan" ||
             Name == "atan2" || Name == "acosf" || Name == "asinf" ||
             Name == "atanf" || Name == "atan2f";
    case 'c':
      return Name == "ceil" || Name == "cos" || Name == "cosh" ||
             Name == "ceilf" || Name == "cosf" || Name == "coshf";
    case 'e':
      return Name == "exp" || Name == "exp2" || Name == "expf" || Name == "exp2f";
    case 'f':
      return Name == "fabs" || Name == "floor" || Name == "fmod" ||
             Name == "fabsf" || Name == "floorf" || Name == "fmodf";
    case 'l':
      return Name == "log" || Name == "log10" || Name == "logf" ||
             Name == "log10f";
    case 'p':
      return Name == "pow" || Name == "powf";
    case 'r':
      return Name == "round" || Name == "roundf";
    case 's':
      return Name == "sin" || Name == "sinh" || Name == "sqrt" ||
             Name == "sinf" || Name == "sinhf" || Name == "sqrtf";
    case 't':
      return Name == "tan" || Name == "tanh" || Name == "tanf" || Name == "tanhf";
    case '_':
  
      // Check for various function names that get used for the math functions
      // when the header files are preprocessed with the macro
      // __FINITE_MATH_ONLY__ enabled.
      // The '12' here is the length of the shortest name that can match.
      // We need to check the size before looking at Name[1] and Name[2]
      // so we may as well check a limit that will eliminate mismatches.
      if (Name.size() < 12 || Name[1] != '_')
        return false;
      switch (Name[2]) {
      default:
        return false;
      case 'a':
        return Name == "__acos_finite" || Name == "__acosf_finite" ||
               Name == "__asin_finite" || Name == "__asinf_finite" ||
               Name == "__atan2_finite" || Name == "__atan2f_finite";
      case 'c':
        return Name == "__cosh_finite" || Name == "__coshf_finite";
      case 'e':
        return Name == "__exp_finite" || Name == "__expf_finite" ||
               Name == "__exp2_finite" || Name == "__exp2f_finite";
      case 'l':
        return Name == "__log_finite" || Name == "__logf_finite" ||
               Name == "__log10_finite" || Name == "__log10f_finite";
      case 'p':
        return Name == "__pow_finite" || Name == "__powf_finite";
      case 's':
        return Name == "__sinh_finite" || Name == "__sinhf_finite";
      }
    }
  }
  
  namespace {
  
  Constant *GetConstantFoldFPValue(double V, Type *Ty) {
    if (Ty->isHalfTy() || Ty->isFloatTy()) {
      APFloat APF(V);
      bool unused;
      APF.convert(Ty->getFltSemantics(), APFloat::rmNearestTiesToEven, &unused);
      return ConstantFP::get(Ty->getContext(), APF);
    }
    if (Ty->isDoubleTy())
      return ConstantFP::get(Ty->getContext(), APFloat(V));
    llvm_unreachable("Can only constant fold half/float/double");
  }
  
  /// Clear the floating-point exception state.
  inline void llvm_fenv_clearexcept() {
  #if defined(HAVE_FENV_H) && HAVE_DECL_FE_ALL_EXCEPT
    feclearexcept(FE_ALL_EXCEPT);
  #endif
    errno = 0;
  }
  
  /// Test if a floating-point exception was raised.
  inline bool llvm_fenv_testexcept() {
    int errno_val = errno;
    if (errno_val == ERANGE || errno_val == EDOM)
      return true;
  #if defined(HAVE_FENV_H) && HAVE_DECL_FE_ALL_EXCEPT && HAVE_DECL_FE_INEXACT
    if (fetestexcept(FE_ALL_EXCEPT & ~FE_INEXACT))
      return true;
  #endif
    return false;
  }
  
  Constant *ConstantFoldFP(double (*NativeFP)(double), double V, Type *Ty) {
    llvm_fenv_clearexcept();
    V = NativeFP(V);
    if (llvm_fenv_testexcept()) {
      llvm_fenv_clearexcept();
      return nullptr;
    }
  
    return GetConstantFoldFPValue(V, Ty);
  }
  
  Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double), double V,
                                 double W, Type *Ty) {
    llvm_fenv_clearexcept();
    V = NativeFP(V, W);
    if (llvm_fenv_testexcept()) {
      llvm_fenv_clearexcept();
      return nullptr;
    }
  
    return GetConstantFoldFPValue(V, Ty);
  }
  
  /// Attempt to fold an SSE floating point to integer conversion of a constant
  /// floating point. If roundTowardZero is false, the default IEEE rounding is
  /// used (toward nearest, ties to even). This matches the behavior of the
  /// non-truncating SSE instructions in the default rounding mode. The desired
  /// integer type Ty is used to select how many bits are available for the
  /// result. Returns null if the conversion cannot be performed, otherwise
  /// returns the Constant value resulting from the conversion.
  Constant *ConstantFoldSSEConvertToInt(const APFloat &Val, bool roundTowardZero,
                                        Type *Ty, bool IsSigned) {
    // All of these conversion intrinsics form an integer of at most 64bits.
    unsigned ResultWidth = Ty->getIntegerBitWidth();
    assert(ResultWidth <= 64 &&
           "Can only constant fold conversions to 64 and 32 bit ints");
  
    uint64_t UIntVal;
    bool isExact = false;
    APFloat::roundingMode mode = roundTowardZero? APFloat::rmTowardZero
                                                : APFloat::rmNearestTiesToEven;
    APFloat::opStatus status =
        Val.convertToInteger(makeMutableArrayRef(UIntVal), ResultWidth,
                             IsSigned, mode, &isExact);
    if (status != APFloat::opOK &&
        (!roundTowardZero || status != APFloat::opInexact))
      return nullptr;
    return ConstantInt::get(Ty, UIntVal, IsSigned);
  }
  
  double getValueAsDouble(ConstantFP *Op) {
    Type *Ty = Op->getType();
  
    if (Ty->isFloatTy())
      return Op->getValueAPF().convertToFloat();
  
    if (Ty->isDoubleTy())
      return Op->getValueAPF().convertToDouble();
  
    bool unused;
    APFloat APF = Op->getValueAPF();
    APF.convert(APFloat::IEEEdouble(), APFloat::rmNearestTiesToEven, &unused);
    return APF.convertToDouble();
  }
  
  static bool isManifestConstant(const Constant *c) {
    if (isa<ConstantData>(c)) {
      return true;
    } else if (isa<ConstantAggregate>(c) || isa<ConstantExpr>(c)) {
      for (const Value *subc : c->operand_values()) {
        if (!isManifestConstant(cast<Constant>(subc)))
          return false;
      }
      return true;
    }
    return false;
  }
  
  static bool getConstIntOrUndef(Value *Op, const APInt *&C) {
    if (auto *CI = dyn_cast<ConstantInt>(Op)) {
      C = &CI->getValue();
      return true;
    }
    if (isa<UndefValue>(Op)) {
      C = nullptr;
      return true;
    }
    return false;
  }
  
  static Constant *ConstantFoldScalarCall1(StringRef Name, unsigned IntrinsicID,
                                           Type *Ty,
                                           ArrayRef<Constant *> Operands,
                                           const TargetLibraryInfo *TLI,
                                           const CallBase *Call) {
    assert(Operands.size() == 1 && "Wrong number of operands.");
  
    if (IntrinsicID == Intrinsic::is_constant) {
      // We know we have a "Constant" argument. But we want to only
      // return true for manifest constants, not those that depend on
      // constants with unknowable values, e.g. GlobalValue or BlockAddress.
      if (isManifestConstant(Operands[0]))
        return ConstantInt::getTrue(Ty->getContext());
      return nullptr;
    }
    if (isa<UndefValue>(Operands[0])) {
      // cosine(arg) is between -1 and 1. cosine(invalid arg) is NaN.
      // ctpop() is between 0 and bitwidth, pick 0 for undef.
      if (IntrinsicID == Intrinsic::cos ||
          IntrinsicID == Intrinsic::ctpop)
        return Constant::getNullValue(Ty);
      if (IntrinsicID == Intrinsic::bswap ||
          IntrinsicID == Intrinsic::bitreverse ||
          IntrinsicID == Intrinsic::launder_invariant_group ||
          IntrinsicID == Intrinsic::strip_invariant_group)
        return Operands[0];
    }
  
    if (isa<ConstantPointerNull>(Operands[0])) {
      // launder(null) == null == strip(null) iff in addrspace 0
      if (IntrinsicID == Intrinsic::launder_invariant_group ||
          IntrinsicID == Intrinsic::strip_invariant_group) {
        // If instruction is not yet put in a basic block (e.g. when cloning
        // a function during inlining), Call's caller may not be available.
        // So check Call's BB first before querying Call->getCaller.
        const Function *Caller =
            Call->getParent() ? Call->getCaller() : nullptr;
        if (Caller &&
            !NullPointerIsDefined(
                Caller, Operands[0]->getType()->getPointerAddressSpace())) {
          return Operands[0];
        }
        return nullptr;
      }
    }
  
    if (auto *Op = dyn_cast<ConstantFP>(Operands[0])) {
      if (IntrinsicID == Intrinsic::convert_to_fp16) {
        APFloat Val(Op->getValueAPF());
  
        bool lost = false;
        Val.convert(APFloat::IEEEhalf(), APFloat::rmNearestTiesToEven, &lost);
  
        return ConstantInt::get(Ty->getContext(), Val.bitcastToAPInt());
      }
  
      if (!Ty->isHalfTy() && !Ty->isFloatTy() && !Ty->isDoubleTy())
        return nullptr;
  
      if (IntrinsicID == Intrinsic::round) {
        APFloat V = Op->getValueAPF();
        V.roundToIntegral(APFloat::rmNearestTiesToAway);
        return ConstantFP::get(Ty->getContext(), V);
      }
  
      if (IntrinsicID == Intrinsic::floor) {
        APFloat V = Op->getValueAPF();
        V.roundToIntegral(APFloat::rmTowardNegative);
        return ConstantFP::get(Ty->getContext(), V);
      }
  
      if (IntrinsicID == Intrinsic::ceil) {
        APFloat V = Op->getValueAPF();
        V.roundToIntegral(APFloat::rmTowardPositive);
        return ConstantFP::get(Ty->getContext(), V);
      }
  
      if (IntrinsicID == Intrinsic::trunc) {
        APFloat V = Op->getValueAPF();
        V.roundToIntegral(APFloat::rmTowardZero);
        return ConstantFP::get(Ty->getContext(), V);
      }
  
      if (IntrinsicID == Intrinsic::rint) {
        APFloat V = Op->getValueAPF();
        V.roundToIntegral(APFloat::rmNearestTiesToEven);
        return ConstantFP::get(Ty->getContext(), V);
      }
  
      if (IntrinsicID == Intrinsic::nearbyint) {
        APFloat V = Op->getValueAPF();
        V.roundToIntegral(APFloat::rmNearestTiesToEven);
        return ConstantFP::get(Ty->getContext(), V);
      }
  
      /// We only fold functions with finite arguments. Folding NaN and inf is
      /// likely to be aborted with an exception anyway, and some host libms
      /// have known errors raising exceptions.
      if (Op->getValueAPF().isNaN() || Op->getValueAPF().isInfinity())
        return nullptr;
  
      /// Currently APFloat versions of these functions do not exist, so we use
      /// the host native double versions.  Float versions are not called
      /// directly but for all these it is true (float)(f((double)arg)) ==
      /// f(arg).  Long double not supported yet.
      double V = getValueAsDouble(Op);
  
      switch (IntrinsicID) {
        default: break;
        case Intrinsic::fabs:
          return ConstantFoldFP(fabs, V, Ty);
        case Intrinsic::log2:
          return ConstantFoldFP(Log2, V, Ty);
        case Intrinsic::log:
          return ConstantFoldFP(log, V, Ty);
        case Intrinsic::log10:
          return ConstantFoldFP(log10, V, Ty);
        case Intrinsic::exp:
          return ConstantFoldFP(exp, V, Ty);
        case Intrinsic::exp2:
          return ConstantFoldFP(exp2, V, Ty);
        case Intrinsic::sin:
          return ConstantFoldFP(sin, V, Ty);
        case Intrinsic::cos:
          return ConstantFoldFP(cos, V, Ty);
        case Intrinsic::sqrt:
          return ConstantFoldFP(sqrt, V, Ty);
      }
  
      if (!TLI)
        return nullptr;
  
      char NameKeyChar = Name[0];
      if (Name[0] == '_' && Name.size() > 2 && Name[1] == '_')
        NameKeyChar = Name[2];
  
      switch (NameKeyChar) {
      case 'a':
        if ((Name == "acos" && TLI->has(LibFunc_acos)) ||
            (Name == "acosf" && TLI->has(LibFunc_acosf)) ||
            (Name == "__acos_finite" && TLI->has(LibFunc_acos_finite)) ||
            (Name == "__acosf_finite" && TLI->has(LibFunc_acosf_finite)))
          return ConstantFoldFP(acos, V, Ty);
        else if ((Name == "asin" && TLI->has(LibFunc_asin)) ||
                 (Name == "asinf" && TLI->has(LibFunc_asinf)) ||
                 (Name == "__asin_finite" && TLI->has(LibFunc_asin_finite)) ||
                 (Name == "__asinf_finite" && TLI->has(LibFunc_asinf_finite)))
          return ConstantFoldFP(asin, V, Ty);
        else if ((Name == "atan" && TLI->has(LibFunc_atan)) ||
                 (Name == "atanf" && TLI->has(LibFunc_atanf)))
          return ConstantFoldFP(atan, V, Ty);
        break;
      case 'c':
        if ((Name == "ceil" && TLI->has(LibFunc_ceil)) ||
            (Name == "ceilf" && TLI->has(LibFunc_ceilf)))
          return ConstantFoldFP(ceil, V, Ty);
        else if ((Name == "cos" && TLI->has(LibFunc_cos)) ||
                 (Name == "cosf" && TLI->has(LibFunc_cosf)))
          return ConstantFoldFP(cos, V, Ty);
        else if ((Name == "cosh" && TLI->has(LibFunc_cosh)) ||
                 (Name == "coshf" && TLI->has(LibFunc_coshf)) ||
                 (Name == "__cosh_finite" && TLI->has(LibFunc_cosh_finite)) ||
                 (Name == "__coshf_finite" && TLI->has(LibFunc_coshf_finite)))
          return ConstantFoldFP(cosh, V, Ty);
        break;
      case 'e':
        if ((Name == "exp" && TLI->has(LibFunc_exp)) ||
            (Name == "expf" && TLI->has(LibFunc_expf)) ||
            (Name == "__exp_finite" && TLI->has(LibFunc_exp_finite)) ||
            (Name == "__expf_finite" && TLI->has(LibFunc_expf_finite)))
          return ConstantFoldFP(exp, V, Ty);
        if ((Name == "exp2" && TLI->has(LibFunc_exp2)) ||
            (Name == "exp2f" && TLI->has(LibFunc_exp2f)) ||
            (Name == "__exp2_finite" && TLI->has(LibFunc_exp2_finite)) ||
            (Name == "__exp2f_finite" && TLI->has(LibFunc_exp2f_finite)))
          // Constant fold exp2(x) as pow(2,x) in case the host doesn't have a
          // C99 library.
          return ConstantFoldBinaryFP(pow, 2.0, V, Ty);
        break;
      case 'f':
        if ((Name == "fabs" && TLI->has(LibFunc_fabs)) ||
            (Name == "fabsf" && TLI->has(LibFunc_fabsf)))
          return ConstantFoldFP(fabs, V, Ty);
        else if ((Name == "floor" && TLI->has(LibFunc_floor)) ||
                 (Name == "floorf" && TLI->has(LibFunc_floorf)))
          return ConstantFoldFP(floor, V, Ty);
        break;
      case 'l':
        if ((Name == "log" && V > 0 && TLI->has(LibFunc_log)) ||
            (Name == "logf" && V > 0 && TLI->has(LibFunc_logf)) ||
            (Name == "__log_finite" && V > 0 &&
              TLI->has(LibFunc_log_finite)) ||
            (Name == "__logf_finite" && V > 0 &&
              TLI->has(LibFunc_logf_finite)))
          return ConstantFoldFP(log, V, Ty);
        else if ((Name == "log10" && V > 0 && TLI->has(LibFunc_log10)) ||
                 (Name == "log10f" && V > 0 && TLI->has(LibFunc_log10f)) ||
                 (Name == "__log10_finite" && V > 0 &&
                   TLI->has(LibFunc_log10_finite)) ||
                 (Name == "__log10f_finite" && V > 0 &&
                   TLI->has(LibFunc_log10f_finite)))
          return ConstantFoldFP(log10, V, Ty);
        break;
      case 'r':
        if ((Name == "round" && TLI->has(LibFunc_round)) ||
            (Name == "roundf" && TLI->has(LibFunc_roundf)))
          return ConstantFoldFP(round, V, Ty);
        break;
      case 's':
        if ((Name == "sin" && TLI->has(LibFunc_sin)) ||
            (Name == "sinf" && TLI->has(LibFunc_sinf)))
          return ConstantFoldFP(sin, V, Ty);
        else if ((Name == "sinh" && TLI->has(LibFunc_sinh)) ||
                 (Name == "sinhf" && TLI->has(LibFunc_sinhf)) ||
                 (Name == "__sinh_finite" && TLI->has(LibFunc_sinh_finite)) ||
                 (Name == "__sinhf_finite" && TLI->has(LibFunc_sinhf_finite)))
          return ConstantFoldFP(sinh, V, Ty);
        else if ((Name == "sqrt" && V >= 0 && TLI->has(LibFunc_sqrt)) ||
                 (Name == "sqrtf" && V >= 0 && TLI->has(LibFunc_sqrtf)))
          return ConstantFoldFP(sqrt, V, Ty);
        break;
      case 't':
        if ((Name == "tan" && TLI->has(LibFunc_tan)) ||
            (Name == "tanf" && TLI->has(LibFunc_tanf)))
          return ConstantFoldFP(tan, V, Ty);
        else if ((Name == "tanh" && TLI->has(LibFunc_tanh)) ||
                 (Name == "tanhf" && TLI->has(LibFunc_tanhf)))
          return ConstantFoldFP(tanh, V, Ty);
        break;
      default:
        break;
      }
      return nullptr;
    }
  
    if (auto *Op = dyn_cast<ConstantInt>(Operands[0])) {
      switch (IntrinsicID) {
      case Intrinsic::bswap:
        return ConstantInt::get(Ty->getContext(), Op->getValue().byteSwap());
      case Intrinsic::ctpop:
        return ConstantInt::get(Ty, Op->getValue().countPopulation());
      case Intrinsic::bitreverse:
        return ConstantInt::get(Ty->getContext(), Op->getValue().reverseBits());
      case Intrinsic::convert_from_fp16: {
        APFloat Val(APFloat::IEEEhalf(), Op->getValue());
  
        bool lost = false;
        APFloat::opStatus status = Val.convert(
            Ty->getFltSemantics(), APFloat::rmNearestTiesToEven, &lost);
  
        // Conversion is always precise.
        (void)status;
        assert(status == APFloat::opOK && !lost &&
               "Precision lost during fp16 constfolding");
  
        return ConstantFP::get(Ty->getContext(), Val);
      }
      default:
        return nullptr;
      }
    }
  
    // Support ConstantVector in case we have an Undef in the top.
    if (isa<ConstantVector>(Operands[0]) ||
        isa<ConstantDataVector>(Operands[0])) {
      auto *Op = cast<Constant>(Operands[0]);
      switch (IntrinsicID) {
      default: break;
      case Intrinsic::x86_sse_cvtss2si:
      case Intrinsic::x86_sse_cvtss2si64:
      case Intrinsic::x86_sse2_cvtsd2si:
      case Intrinsic::x86_sse2_cvtsd2si64:
        if (ConstantFP *FPOp =
                dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U)))
          return ConstantFoldSSEConvertToInt(FPOp->getValueAPF(),
                                             /*roundTowardZero=*/false, Ty,
                                             /*IsSigned*/true);
        break;
      case Intrinsic::x86_sse_cvttss2si:
      case Intrinsic::x86_sse_cvttss2si64:
      case Intrinsic::x86_sse2_cvttsd2si:
      case Intrinsic::x86_sse2_cvttsd2si64:
        if (ConstantFP *FPOp =
                dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U)))
          return ConstantFoldSSEConvertToInt(FPOp->getValueAPF(),
                                             /*roundTowardZero=*/true, Ty,
                                             /*IsSigned*/true);
        break;
      }
    }
  
    return nullptr;
  }
  
  static Constant *ConstantFoldScalarCall2(StringRef Name, unsigned IntrinsicID,
                                           Type *Ty,
                                           ArrayRef<Constant *> Operands,
                                           const TargetLibraryInfo *TLI,
                                           const CallBase *Call) {
    assert(Operands.size() == 2 && "Wrong number of operands.");
  
    if (auto *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
      if (!Ty->isHalfTy() && !Ty->isFloatTy() && !Ty->isDoubleTy())
        return nullptr;
      double Op1V = getValueAsDouble(Op1);
  
      if (auto *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
        if (Op2->getType() != Op1->getType())
          return nullptr;
  
        double Op2V = getValueAsDouble(Op2);
        if (IntrinsicID == Intrinsic::pow) {
          return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty);
        }
        if (IntrinsicID == Intrinsic::copysign) {
          APFloat V1 = Op1->getValueAPF();
          const APFloat &V2 = Op2->getValueAPF();
          V1.copySign(V2);
          return ConstantFP::get(Ty->getContext(), V1);
        }
  
        if (IntrinsicID == Intrinsic::minnum) {
          const APFloat &C1 = Op1->getValueAPF();
          const APFloat &C2 = Op2->getValueAPF();
          return ConstantFP::get(Ty->getContext(), minnum(C1, C2));
        }
  
        if (IntrinsicID == Intrinsic::maxnum) {
          const APFloat &C1 = Op1->getValueAPF();
          const APFloat &C2 = Op2->getValueAPF();
          return ConstantFP::get(Ty->getContext(), maxnum(C1, C2));
        }
  
        if (IntrinsicID == Intrinsic::minimum) {
          const APFloat &C1 = Op1->getValueAPF();
          const APFloat &C2 = Op2->getValueAPF();
          return ConstantFP::get(Ty->getContext(), minimum(C1, C2));
        }
  
        if (IntrinsicID == Intrinsic::maximum) {
          const APFloat &C1 = Op1->getValueAPF();
          const APFloat &C2 = Op2->getValueAPF();
          return ConstantFP::get(Ty->getContext(), maximum(C1, C2));
        }
  
        if (!TLI)
          return nullptr;
        if ((Name == "pow" && TLI->has(LibFunc_pow)) ||
            (Name == "powf" && TLI->has(LibFunc_powf)) ||
            (Name == "__pow_finite" && TLI->has(LibFunc_pow_finite)) ||
            (Name == "__powf_finite" && TLI->has(LibFunc_powf_finite)))
          return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty);
        if ((Name == "fmod" && TLI->has(LibFunc_fmod)) ||
            (Name == "fmodf" && TLI->has(LibFunc_fmodf)))
          return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty);
        if ((Name == "atan2" && TLI->has(LibFunc_atan2)) ||
            (Name == "atan2f" && TLI->has(LibFunc_atan2f)) ||
            (Name == "__atan2_finite" && TLI->has(LibFunc_atan2_finite)) ||
            (Name == "__atan2f_finite" && TLI->has(LibFunc_atan2f_finite)))
          return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty);
      } else if (auto *Op2C = dyn_cast<ConstantInt>(Operands[1])) {
        if (IntrinsicID == Intrinsic::powi && Ty->isHalfTy())
          return ConstantFP::get(Ty->getContext(),
                                 APFloat((float)std::pow((float)Op1V,
                                                 (int)Op2C->getZExtValue())));
        if (IntrinsicID == Intrinsic::powi && Ty->isFloatTy())
          return ConstantFP::get(Ty->getContext(),
                                 APFloat((float)std::pow((float)Op1V,
                                                 (int)Op2C->getZExtValue())));
        if (IntrinsicID == Intrinsic::powi && Ty->isDoubleTy())
          return ConstantFP::get(Ty->getContext(),
                                 APFloat((double)std::pow((double)Op1V,
                                                   (int)Op2C->getZExtValue())));
      }
      return nullptr;
    }
  
    if (Operands[0]->getType()->isIntegerTy() &&
        Operands[1]->getType()->isIntegerTy()) {
      const APInt *C0, *C1;
      if (!getConstIntOrUndef(Operands[0], C0) ||
          !getConstIntOrUndef(Operands[1], C1))
        return nullptr;
  
      switch (IntrinsicID) {
      default: break;
      case Intrinsic::smul_with_overflow:
      case Intrinsic::umul_with_overflow:
        // Even if both operands are undef, we cannot fold muls to undef
        // in the general case. For example, on i2 there are no inputs
        // that would produce { i2 -1, i1 true } as the result.
        if (!C0 || !C1)
          return Constant::getNullValue(Ty);
        LLVM_FALLTHROUGH;
      case Intrinsic::sadd_with_overflow:
      case Intrinsic::uadd_with_overflow:
      case Intrinsic::ssub_with_overflow:
      case Intrinsic::usub_with_overflow: {
        if (!C0 || !C1)
          return UndefValue::get(Ty);
  
        APInt Res;
        bool Overflow;
        switch (IntrinsicID) {
        default: llvm_unreachable("Invalid case");
        case Intrinsic::sadd_with_overflow:
          Res = C0->sadd_ov(*C1, Overflow);
          break;
        case Intrinsic::uadd_with_overflow:
          Res = C0->uadd_ov(*C1, Overflow);
          break;
        case Intrinsic::ssub_with_overflow:
          Res = C0->ssub_ov(*C1, Overflow);
          break;
        case Intrinsic::usub_with_overflow:
          Res = C0->usub_ov(*C1, Overflow);
          break;
        case Intrinsic::smul_with_overflow:
          Res = C0->smul_ov(*C1, Overflow);
          break;
        case Intrinsic::umul_with_overflow:
          Res = C0->umul_ov(*C1, Overflow);
          break;
        }
        Constant *Ops[] = {
          ConstantInt::get(Ty->getContext(), Res),
          ConstantInt::get(Type::getInt1Ty(Ty->getContext()), Overflow)
        };
        return ConstantStruct::get(cast<StructType>(Ty), Ops);
      }
      case Intrinsic::uadd_sat:
      case Intrinsic::sadd_sat:
        if (!C0 && !C1)
          return UndefValue::get(Ty);
        if (!C0 || !C1)
          return Constant::getAllOnesValue(Ty);
        if (IntrinsicID == Intrinsic::uadd_sat)
          return ConstantInt::get(Ty, C0->uadd_sat(*C1));
        else
          return ConstantInt::get(Ty, C0->sadd_sat(*C1));
      case Intrinsic::usub_sat:
      case Intrinsic::ssub_sat:
        if (!C0 && !C1)
          return UndefValue::get(Ty);
        if (!C0 || !C1)
          return Constant::getNullValue(Ty);
        if (IntrinsicID == Intrinsic::usub_sat)
          return ConstantInt::get(Ty, C0->usub_sat(*C1));
        else
          return ConstantInt::get(Ty, C0->ssub_sat(*C1));
      case Intrinsic::cttz:
      case Intrinsic::ctlz:
        assert(C1 && "Must be constant int");
  
        // cttz(0, 1) and ctlz(0, 1) are undef.
        if (C1->isOneValue() && (!C0 || C0->isNullValue()))
          return UndefValue::get(Ty);
        if (!C0)
          return Constant::getNullValue(Ty);
        if (IntrinsicID == Intrinsic::cttz)
          return ConstantInt::get(Ty, C0->countTrailingZeros());
        else
          return ConstantInt::get(Ty, C0->countLeadingZeros());
      }
  
      return nullptr;
    }
  
    // Support ConstantVector in case we have an Undef in the top.
    if ((isa<ConstantVector>(Operands[0]) ||
         isa<ConstantDataVector>(Operands[0])) &&
        // Check for default rounding mode.
        // FIXME: Support other rounding modes?
        isa<ConstantInt>(Operands[1]) &&
        cast<ConstantInt>(Operands[1])->getValue() == 4) {
      auto *Op = cast<Constant>(Operands[0]);
      switch (IntrinsicID) {
      default: break;
      case Intrinsic::x86_avx512_vcvtss2si32:
      case Intrinsic::x86_avx512_vcvtss2si64:
      case Intrinsic::x86_avx512_vcvtsd2si32:
      case Intrinsic::x86_avx512_vcvtsd2si64:
        if (ConstantFP *FPOp =
                dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U)))
          return ConstantFoldSSEConvertToInt(FPOp->getValueAPF(),
                                             /*roundTowardZero=*/false, Ty,
                                             /*IsSigned*/true);
        break;
      case Intrinsic::x86_avx512_vcvtss2usi32:
      case Intrinsic::x86_avx512_vcvtss2usi64:
      case Intrinsic::x86_avx512_vcvtsd2usi32:
      case Intrinsic::x86_avx512_vcvtsd2usi64:
        if (ConstantFP *FPOp =
                dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U)))
          return ConstantFoldSSEConvertToInt(FPOp->getValueAPF(),
                                             /*roundTowardZero=*/false, Ty,
                                             /*IsSigned*/false);
        break;
      case Intrinsic::x86_avx512_cvttss2si:
      case Intrinsic::x86_avx512_cvttss2si64:
      case Intrinsic::x86_avx512_cvttsd2si:
      case Intrinsic::x86_avx512_cvttsd2si64:
        if (ConstantFP *FPOp =
                dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U)))
          return ConstantFoldSSEConvertToInt(FPOp->getValueAPF(),
                                             /*roundTowardZero=*/true, Ty,
                                             /*IsSigned*/true);
        break;
      case Intrinsic::x86_avx512_cvttss2usi:
      case Intrinsic::x86_avx512_cvttss2usi64:
      case Intrinsic::x86_avx512_cvttsd2usi:
      case Intrinsic::x86_avx512_cvttsd2usi64:
        if (ConstantFP *FPOp =
                dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U)))
          return ConstantFoldSSEConvertToInt(FPOp->getValueAPF(),
                                             /*roundTowardZero=*/true, Ty,
                                             /*IsSigned*/false);
        break;
      }
    }
    return nullptr;
  }
  
  static Constant *ConstantFoldScalarCall3(StringRef Name, unsigned IntrinsicID,
                                           Type *Ty,
                                           ArrayRef<Constant *> Operands,
                                           const TargetLibraryInfo *TLI,
                                           const CallBase *Call) {
    assert(Operands.size() == 3 && "Wrong number of operands.");
  
    if (const auto *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
      if (const auto *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
        if (const auto *Op3 = dyn_cast<ConstantFP>(Operands[2])) {
          switch (IntrinsicID) {
          default: break;
          case Intrinsic::fma:
          case Intrinsic::fmuladd: {
            APFloat V = Op1->getValueAPF();
            APFloat::opStatus s = V.fusedMultiplyAdd(Op2->getValueAPF(),
                                                     Op3->getValueAPF(),
                                                     APFloat::rmNearestTiesToEven);
            if (s != APFloat::opInvalidOp)
              return ConstantFP::get(Ty->getContext(), V);
  
            return nullptr;
          }
          }
        }
      }
    }
  
    if (const auto *Op1 = dyn_cast<ConstantInt>(Operands[0])) {
      if (const auto *Op2 = dyn_cast<ConstantInt>(Operands[1])) {
        if (const auto *Op3 = dyn_cast<ConstantInt>(Operands[2])) {
          switch (IntrinsicID) {
          default: break;
          case Intrinsic::smul_fix:
          case Intrinsic::smul_fix_sat: {
            // This code performs rounding towards negative infinity in case the
            // result cannot be represented exactly for the given scale. Targets
            // that do care about rounding should use a target hook for specifying
            // how rounding should be done, and provide their own folding to be
            // consistent with rounding. This is the same approach as used by
            // DAGTypeLegalizer::ExpandIntRes_MULFIX.
            APInt Lhs = Op1->getValue();
            APInt Rhs = Op2->getValue();
            unsigned Scale = Op3->getValue().getZExtValue();
            unsigned Width = Lhs.getBitWidth();
            assert(Scale < Width && "Illegal scale.");
            unsigned ExtendedWidth = Width * 2;
            APInt Product = (Lhs.sextOrSelf(ExtendedWidth) *
                             Rhs.sextOrSelf(ExtendedWidth)).ashr(Scale);
            if (IntrinsicID == Intrinsic::smul_fix_sat) {
              APInt MaxValue =
                APInt::getSignedMaxValue(Width).sextOrSelf(ExtendedWidth);
              APInt MinValue =
                APInt::getSignedMinValue(Width).sextOrSelf(ExtendedWidth);
              Product = APIntOps::smin(Product, MaxValue);
              Product = APIntOps::smax(Product, MinValue);
            }
            return ConstantInt::get(Ty->getContext(),
                                    Product.sextOrTrunc(Width));
          }
          }
        }
      }
    }
  
    if (IntrinsicID == Intrinsic::fshl || IntrinsicID == Intrinsic::fshr) {
      const APInt *C0, *C1, *C2;
      if (!getConstIntOrUndef(Operands[0], C0) ||
          !getConstIntOrUndef(Operands[1], C1) ||
          !getConstIntOrUndef(Operands[2], C2))
        return nullptr;
  
      bool IsRight = IntrinsicID == Intrinsic::fshr;
      if (!C2)
        return Operands[IsRight ? 1 : 0];
      if (!C0 && !C1)
        return UndefValue::get(Ty);
  
      // The shift amount is interpreted as modulo the bitwidth. If the shift
      // amount is effectively 0, avoid UB due to oversized inverse shift below.
      unsigned BitWidth = C2->getBitWidth();
      unsigned ShAmt = C2->urem(BitWidth);
      if (!ShAmt)
        return Operands[IsRight ? 1 : 0];
  
      // (C0 << ShlAmt) | (C1 >> LshrAmt)
      unsigned LshrAmt = IsRight ? ShAmt : BitWidth - ShAmt;
      unsigned ShlAmt = !IsRight ? ShAmt : BitWidth - ShAmt;
      if (!C0)
        return ConstantInt::get(Ty, C1->lshr(LshrAmt));
      if (!C1)
        return ConstantInt::get(Ty, C0->shl(ShlAmt));
      return ConstantInt::get(Ty, C0->shl(ShlAmt) | C1->lshr(LshrAmt));
    }
  
    return nullptr;
  }
  
  static Constant *ConstantFoldScalarCall(StringRef Name, unsigned IntrinsicID,
                                          Type *Ty,
                                          ArrayRef<Constant *> Operands,
                                          const TargetLibraryInfo *TLI,
                                          const CallBase *Call) {
    if (Operands.size() == 1)
      return ConstantFoldScalarCall1(Name, IntrinsicID, Ty, Operands, TLI, Call);
  
    if (Operands.size() == 2)
      return ConstantFoldScalarCall2(Name, IntrinsicID, Ty, Operands, TLI, Call);
  
    if (Operands.size() == 3)
      return ConstantFoldScalarCall3(Name, IntrinsicID, Ty, Operands, TLI, Call);
  
    return nullptr;
  }
  
  static Constant *ConstantFoldVectorCall(StringRef Name, unsigned IntrinsicID,
                                          VectorType *VTy,
                                          ArrayRef<Constant *> Operands,
                                          const DataLayout &DL,
                                          const TargetLibraryInfo *TLI,
                                          const CallBase *Call) {
    SmallVector<Constant *, 4> Result(VTy->getNumElements());
    SmallVector<Constant *, 4> Lane(Operands.size());
    Type *Ty = VTy->getElementType();
  
    if (IntrinsicID == Intrinsic::masked_load) {
      auto *SrcPtr = Operands[0];
      auto *Mask = Operands[2];
      auto *Passthru = Operands[3];
  
      Constant *VecData = ConstantFoldLoadFromConstPtr(SrcPtr, VTy, DL);
  
      SmallVector<Constant *, 32> NewElements;
      for (unsigned I = 0, E = VTy->getNumElements(); I != E; ++I) {
        auto *MaskElt = Mask->getAggregateElement(I);
        if (!MaskElt)
          break;
        auto *PassthruElt = Passthru->getAggregateElement(I);
        auto *VecElt = VecData ? VecData->getAggregateElement(I) : nullptr;
        if (isa<UndefValue>(MaskElt)) {
          if (PassthruElt)
            NewElements.push_back(PassthruElt);
          else if (VecElt)
            NewElements.push_back(VecElt);
          else
            return nullptr;
        }
        if (MaskElt->isNullValue()) {
          if (!PassthruElt)
            return nullptr;
          NewElements.push_back(PassthruElt);
        } else if (MaskElt->isOneValue()) {
          if (!VecElt)
            return nullptr;
          NewElements.push_back(VecElt);
        } else {
          return nullptr;
        }
      }
      if (NewElements.size() != VTy->getNumElements())
        return nullptr;
      return ConstantVector::get(NewElements);
    }
  
    for (unsigned I = 0, E = VTy->getNumElements(); I != E; ++I) {
      // Gather a column of constants.
      for (unsigned J = 0, JE = Operands.size(); J != JE; ++J) {
        // These intrinsics use a scalar type for their second argument.
        if (J == 1 &&
            (IntrinsicID == Intrinsic::cttz || IntrinsicID == Intrinsic::ctlz ||
             IntrinsicID == Intrinsic::powi)) {
          Lane[J] = Operands[J];
          continue;
        }
        // These intrinsics use a scalar type for their third argument.
        if (J == 2 &&
            (IntrinsicID == Intrinsic::smul_fix ||
             IntrinsicID == Intrinsic::smul_fix_sat)) {
          Lane[J] = Operands[J];
          continue;
        }
  
        Constant *Agg = Operands[J]->getAggregateElement(I);
        if (!Agg)
          return nullptr;
  
        Lane[J] = Agg;
      }
  
      // Use the regular scalar folding to simplify this column.
      Constant *Folded =
          ConstantFoldScalarCall(Name, IntrinsicID, Ty, Lane, TLI, Call);
      if (!Folded)
        return nullptr;
      Result[I] = Folded;
    }
  
    return ConstantVector::get(Result);
  }
  
  } // end anonymous namespace
  
  Constant *llvm::ConstantFoldCall(const CallBase *Call, Function *F,
                                   ArrayRef<Constant *> Operands,
                                   const TargetLibraryInfo *TLI) {
    if (Call->isNoBuiltin() || Call->isStrictFP())
      return nullptr;
    if (!F->hasName())
      return nullptr;
    StringRef Name = F->getName();
  
    Type *Ty = F->getReturnType();
  
    if (auto *VTy = dyn_cast<VectorType>(Ty))
      return ConstantFoldVectorCall(Name, F->getIntrinsicID(), VTy, Operands,
                                    F->getParent()->getDataLayout(), TLI, Call);
  
    return ConstantFoldScalarCall(Name, F->getIntrinsicID(), Ty, Operands, TLI,
                                  Call);
  }
  
  bool llvm::isMathLibCallNoop(const CallBase *Call,
                               const TargetLibraryInfo *TLI) {
    // FIXME: Refactor this code; this duplicates logic in LibCallsShrinkWrap
    // (and to some extent ConstantFoldScalarCall).
    if (Call->isNoBuiltin() || Call->isStrictFP())
      return false;
    Function *F = Call->getCalledFunction();
    if (!F)
      return false;
  
    LibFunc Func;
    if (!TLI || !TLI->getLibFunc(*F, Func))
      return false;
  
    if (Call->getNumArgOperands() == 1) {
      if (ConstantFP *OpC = dyn_cast<ConstantFP>(Call->getArgOperand(0))) {
        const APFloat &Op = OpC->getValueAPF();
        switch (Func) {
        case LibFunc_logl:
        case LibFunc_log:
        case LibFunc_logf:
        case LibFunc_log2l:
        case LibFunc_log2:
        case LibFunc_log2f:
        case LibFunc_log10l:
        case LibFunc_log10:
        case LibFunc_log10f:
          return Op.isNaN() || (!Op.isZero() && !Op.isNegative());
  
        case LibFunc_expl:
        case LibFunc_exp:
        case LibFunc_expf:
          // FIXME: These boundaries are slightly conservative.
          if (OpC->getType()->isDoubleTy())
            return Op.compare(APFloat(-745.0)) != APFloat::cmpLessThan &&
                   Op.compare(APFloat(709.0)) != APFloat::cmpGreaterThan;
          if (OpC->getType()->isFloatTy())
            return Op.compare(APFloat(-103.0f)) != APFloat::cmpLessThan &&
                   Op.compare(APFloat(88.0f)) != APFloat::cmpGreaterThan;
          break;
  
        case LibFunc_exp2l:
        case LibFunc_exp2:
        case LibFunc_exp2f:
          // FIXME: These boundaries are slightly conservative.
          if (OpC->getType()->isDoubleTy())
            return Op.compare(APFloat(-1074.0)) != APFloat::cmpLessThan &&
                   Op.compare(APFloat(1023.0)) != APFloat::cmpGreaterThan;
          if (OpC->getType()->isFloatTy())
            return Op.compare(APFloat(-149.0f)) != APFloat::cmpLessThan &&
                   Op.compare(APFloat(127.0f)) != APFloat::cmpGreaterThan;
          break;
  
        case LibFunc_sinl:
        case LibFunc_sin:
        case LibFunc_sinf:
        case LibFunc_cosl:
        case LibFunc_cos:
        case LibFunc_cosf:
          return !Op.isInfinity();
  
        case LibFunc_tanl:
        case LibFunc_tan:
        case LibFunc_tanf: {
          // FIXME: Stop using the host math library.
          // FIXME: The computation isn't done in the right precision.
          Type *Ty = OpC->getType();
          if (Ty->isDoubleTy() || Ty->isFloatTy() || Ty->isHalfTy()) {
            double OpV = getValueAsDouble(OpC);
            return ConstantFoldFP(tan, OpV, Ty) != nullptr;
          }
          break;
        }
  
        case LibFunc_asinl:
        case LibFunc_asin:
        case LibFunc_asinf:
        case LibFunc_acosl:
        case LibFunc_acos:
        case LibFunc_acosf:
          return Op.compare(APFloat(Op.getSemantics(), "-1")) !=
                     APFloat::cmpLessThan &&
                 Op.compare(APFloat(Op.getSemantics(), "1")) !=
                     APFloat::cmpGreaterThan;
  
        case LibFunc_sinh:
        case LibFunc_cosh:
        case LibFunc_sinhf:
        case LibFunc_coshf:
        case LibFunc_sinhl:
        case LibFunc_coshl:
          // FIXME: These boundaries are slightly conservative.
          if (OpC->getType()->isDoubleTy())
            return Op.compare(APFloat(-710.0)) != APFloat::cmpLessThan &&
                   Op.compare(APFloat(710.0)) != APFloat::cmpGreaterThan;
          if (OpC->getType()->isFloatTy())
            return Op.compare(APFloat(-89.0f)) != APFloat::cmpLessThan &&
                   Op.compare(APFloat(89.0f)) != APFloat::cmpGreaterThan;
          break;
  
        case LibFunc_sqrtl:
        case LibFunc_sqrt:
        case LibFunc_sqrtf:
          return Op.isNaN() || Op.isZero() || !Op.isNegative();
  
        // FIXME: Add more functions: sqrt_finite, atanh, expm1, log1p,
        // maybe others?
        default:
          break;
        }
      }
    }
  
    if (Call->getNumArgOperands() == 2) {
      ConstantFP *Op0C = dyn_cast<ConstantFP>(Call->getArgOperand(0));
      ConstantFP *Op1C = dyn_cast<ConstantFP>(Call->getArgOperand(1));
      if (Op0C && Op1C) {
        const APFloat &Op0 = Op0C->getValueAPF();
        const APFloat &Op1 = Op1C->getValueAPF();
  
        switch (Func) {
        case LibFunc_powl:
        case LibFunc_pow:
        case LibFunc_powf: {
          // FIXME: Stop using the host math library.
          // FIXME: The computation isn't done in the right precision.
          Type *Ty = Op0C->getType();
          if (Ty->isDoubleTy() || Ty->isFloatTy() || Ty->isHalfTy()) {
            if (Ty == Op1C->getType()) {
              double Op0V = getValueAsDouble(Op0C);
              double Op1V = getValueAsDouble(Op1C);
              return ConstantFoldBinaryFP(pow, Op0V, Op1V, Ty) != nullptr;
            }
          }
          break;
        }
  
        case LibFunc_fmodl:
        case LibFunc_fmod:
        case LibFunc_fmodf:
          return Op0.isNaN() || Op1.isNaN() ||
                 (!Op0.isInfinity() && !Op1.isZero());
  
        default:
          break;
        }
      }
    }
  
    return false;
  }
  