text: //===- ConstantFold.cpp - LLVM constant folder ----------------------------===//
  //
  // 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 implements folding of constants for LLVM.  This implements the
  // (internal) ConstantFold.h interface, which is used by the
  // ConstantExpr::get* methods to automatically fold constants when possible.
  //
  // The current constant folding implementation is implemented in two pieces: the
  // pieces that don't need DataLayout, and the pieces that do. This is to avoid
  // a dependence in IR on Target.
  //
  //===----------------------------------------------------------------------===//
  
  #include "ConstantFold.h"
  #include "llvm/ADT/APSInt.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/IR/Constants.h"
  #include "llvm/IR/DerivedTypes.h"
  #include "llvm/IR/Function.h"
  #include "llvm/IR/GetElementPtrTypeIterator.h"
  #include "llvm/IR/GlobalAlias.h"
  #include "llvm/IR/GlobalVariable.h"
  #include "llvm/IR/Instructions.h"
  #include "llvm/IR/Module.h"
  #include "llvm/IR/Operator.h"
  #include "llvm/IR/PatternMatch.h"
  #include "llvm/Support/ErrorHandling.h"
  using namespace llvm;
  using namespace llvm::PatternMatch;
  
  //===----------------------------------------------------------------------===//
  //                ConstantFold*Instruction Implementations
  //===----------------------------------------------------------------------===//
  
  /// Convert the specified vector Constant node to the specified vector type.
  /// At this point, we know that the elements of the input vector constant are
  /// all simple integer or FP values.
  static Constant *BitCastConstantVector(Constant *CV, VectorType *DstTy) {
  
    if (CV->isAllOnesValue()) return Constant::getAllOnesValue(DstTy);
    if (CV->isNullValue()) return Constant::getNullValue(DstTy);
  
    // Do not iterate on scalable vector. The num of elements is unknown at
    // compile-time.
    if (isa<ScalableVectorType>(DstTy))
      return nullptr;
  
    // If this cast changes element count then we can't handle it here:
    // doing so requires endianness information.  This should be handled by
    // Analysis/ConstantFolding.cpp
    unsigned NumElts = cast<FixedVectorType>(DstTy)->getNumElements();
    if (NumElts != cast<FixedVectorType>(CV->getType())->getNumElements())
      return nullptr;
  
    Type *DstEltTy = DstTy->getElementType();
    // Fast path for splatted constants.
    if (Constant *Splat = CV->getSplatValue()) {
      return ConstantVector::getSplat(DstTy->getElementCount(),
                                      ConstantExpr::getBitCast(Splat, DstEltTy));
    }
  
    SmallVector<Constant*, 16> Result;
    Type *Ty = IntegerType::get(CV->getContext(), 32);
    for (unsigned i = 0; i != NumElts; ++i) {
      Constant *C =
        ConstantExpr::getExtractElement(CV, ConstantInt::get(Ty, i));
      C = ConstantExpr::getBitCast(C, DstEltTy);
      Result.push_back(C);
    }
  
    return ConstantVector::get(Result);
  }
  
  /// This function determines which opcode to use to fold two constant cast
  /// expressions together. It uses CastInst::isEliminableCastPair to determine
  /// the opcode. Consequently its just a wrapper around that function.
  /// Determine if it is valid to fold a cast of a cast
  static unsigned
  foldConstantCastPair(
    unsigned opc,          ///< opcode of the second cast constant expression
    ConstantExpr *Op,      ///< the first cast constant expression
    Type *DstTy            ///< destination type of the first cast
  ) {
    assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!");
    assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type");
    assert(CastInst::isCast(opc) && "Invalid cast opcode");
  
    // The types and opcodes for the two Cast constant expressions
    Type *SrcTy = Op->getOperand(0)->getType();
    Type *MidTy = Op->getType();
    Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode());
    Instruction::CastOps secondOp = Instruction::CastOps(opc);
  
    // Assume that pointers are never more than 64 bits wide, and only use this
    // for the middle type. Otherwise we could end up folding away illegal
    // bitcasts between address spaces with different sizes.
    IntegerType *FakeIntPtrTy = Type::getInt64Ty(DstTy->getContext());
  
    // Let CastInst::isEliminableCastPair do the heavy lifting.
    return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy,
                                          nullptr, FakeIntPtrTy, nullptr);
  }
  
  static Constant *FoldBitCast(Constant *V, Type *DestTy) {
    Type *SrcTy = V->getType();
    if (SrcTy == DestTy)
      return V; // no-op cast
  
    // Check to see if we are casting a pointer to an aggregate to a pointer to
    // the first element.  If so, return the appropriate GEP instruction.
    if (PointerType *PTy = dyn_cast<PointerType>(V->getType()))
      if (PointerType *DPTy = dyn_cast<PointerType>(DestTy))
        if (PTy->getAddressSpace() == DPTy->getAddressSpace() &&
            !PTy->isOpaque() && !DPTy->isOpaque() &&
            PTy->getNonOpaquePointerElementType()->isSized()) {
          SmallVector<Value*, 8> IdxList;
          Value *Zero =
            Constant::getNullValue(Type::getInt32Ty(DPTy->getContext()));
          IdxList.push_back(Zero);
          Type *ElTy = PTy->getNonOpaquePointerElementType();
          while (ElTy && ElTy != DPTy->getNonOpaquePointerElementType()) {
            ElTy = GetElementPtrInst::getTypeAtIndex(ElTy, (uint64_t)0);
            IdxList.push_back(Zero);
          }
  
          if (ElTy == DPTy->getNonOpaquePointerElementType())
            // This GEP is inbounds because all indices are zero.
            return ConstantExpr::getInBoundsGetElementPtr(
                PTy->getNonOpaquePointerElementType(), V, IdxList);
        }
  
    // Handle casts from one vector constant to another.  We know that the src
    // and dest type have the same size (otherwise its an illegal cast).
    if (VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
      if (VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) {
        assert(DestPTy->getPrimitiveSizeInBits() ==
                   SrcTy->getPrimitiveSizeInBits() &&
               "Not cast between same sized vectors!");
        SrcTy = nullptr;
        // First, check for null.  Undef is already handled.
        if (isa<ConstantAggregateZero>(V))
          return Constant::getNullValue(DestTy);
  
        // Handle ConstantVector and ConstantAggregateVector.
        return BitCastConstantVector(V, DestPTy);
      }
  
      // Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts
      // This allows for other simplifications (although some of them
      // can only be handled by Analysis/ConstantFolding.cpp).
      if (isa<ConstantInt>(V) || isa<ConstantFP>(V))
        return ConstantExpr::getBitCast(ConstantVector::get(V), DestPTy);
    }
  
    // Finally, implement bitcast folding now.   The code below doesn't handle
    // bitcast right.
    if (isa<ConstantPointerNull>(V))  // ptr->ptr cast.
      return ConstantPointerNull::get(cast<PointerType>(DestTy));
  
    // Handle integral constant input.
    if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
      if (DestTy->isIntegerTy())
        // Integral -> Integral. This is a no-op because the bit widths must
        // be the same. Consequently, we just fold to V.
        return V;
  
      // See note below regarding the PPC_FP128 restriction.
      if (DestTy->isFloatingPointTy() && !DestTy->isPPC_FP128Ty())
        return ConstantFP::get(DestTy->getContext(),
                               APFloat(DestTy->getFltSemantics(),
                                       CI->getValue()));
  
      // Otherwise, can't fold this (vector?)
      return nullptr;
    }
  
    // Handle ConstantFP input: FP -> Integral.
    if (ConstantFP *FP = dyn_cast<ConstantFP>(V)) {
      // PPC_FP128 is really the sum of two consecutive doubles, where the first
      // double is always stored first in memory, regardless of the target
      // endianness. The memory layout of i128, however, depends on the target
      // endianness, and so we can't fold this without target endianness
      // information. This should instead be handled by
      // Analysis/ConstantFolding.cpp
      if (FP->getType()->isPPC_FP128Ty())
        return nullptr;
  
      // Make sure dest type is compatible with the folded integer constant.
      if (!DestTy->isIntegerTy())
        return nullptr;
  
      return ConstantInt::get(FP->getContext(),
                              FP->getValueAPF().bitcastToAPInt());
    }
  
    return nullptr;
  }
  
  
  /// V is an integer constant which only has a subset of its bytes used.
  /// The bytes used are indicated by ByteStart (which is the first byte used,
  /// counting from the least significant byte) and ByteSize, which is the number
  /// of bytes used.
  ///
  /// This function analyzes the specified constant to see if the specified byte
  /// range can be returned as a simplified constant.  If so, the constant is
  /// returned, otherwise null is returned.
  static Constant *ExtractConstantBytes(Constant *C, unsigned ByteStart,
                                        unsigned ByteSize) {
    assert(C->getType()->isIntegerTy() &&
           (cast<IntegerType>(C->getType())->getBitWidth() & 7) == 0 &&
           "Non-byte sized integer input");
    unsigned CSize = cast<IntegerType>(C->getType())->getBitWidth()/8;
    assert(ByteSize && "Must be accessing some piece");
    assert(ByteStart+ByteSize <= CSize && "Extracting invalid piece from input");
    assert(ByteSize != CSize && "Should not extract everything");
  
    // Constant Integers are simple.
    if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
      APInt V = CI->getValue();
      if (ByteStart)
        V.lshrInPlace(ByteStart*8);
      V = V.trunc(ByteSize*8);
      return ConstantInt::get(CI->getContext(), V);
    }
  
    // In the input is a constant expr, we might be able to recursively simplify.
    // If not, we definitely can't do anything.
    ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
    if (!CE) return nullptr;
  
    switch (CE->getOpcode()) {
    default: return nullptr;
    case Instruction::Or: {
      Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize);
      if (!RHS)
        return nullptr;
  
      // X | -1 -> -1.
      if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS))
        if (RHSC->isMinusOne())
          return RHSC;
  
      Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize);
      if (!LHS)
        return nullptr;
      return ConstantExpr::getOr(LHS, RHS);
    }
    case Instruction::And: {
      Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize);
      if (!RHS)
        return nullptr;
  
      // X & 0 -> 0.
      if (RHS->isNullValue())
        return RHS;
  
      Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize);
      if (!LHS)
        return nullptr;
      return ConstantExpr::getAnd(LHS, RHS);
    }
    case Instruction::LShr: {
      ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1));
      if (!Amt)
        return nullptr;
      APInt ShAmt = Amt->getValue();
      // Cannot analyze non-byte shifts.
      if ((ShAmt & 7) != 0)
        return nullptr;
      ShAmt.lshrInPlace(3);
  
      // If the extract is known to be all zeros, return zero.
      if (ShAmt.uge(CSize - ByteStart))
        return Constant::getNullValue(
            IntegerType::get(CE->getContext(), ByteSize * 8));
      // If the extract is known to be fully in the input, extract it.
      if (ShAmt.ule(CSize - (ByteStart + ByteSize)))
        return ExtractConstantBytes(CE->getOperand(0),
                                    ByteStart + ShAmt.getZExtValue(), ByteSize);
  
      // TODO: Handle the 'partially zero' case.
      return nullptr;
    }
  
    case Instruction::Shl: {
      ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1));
      if (!Amt)
        return nullptr;
      APInt ShAmt = Amt->getValue();
      // Cannot analyze non-byte shifts.
      if ((ShAmt & 7) != 0)
        return nullptr;
      ShAmt.lshrInPlace(3);
  
      // If the extract is known to be all zeros, return zero.
      if (ShAmt.uge(ByteStart + ByteSize))
        return Constant::getNullValue(
            IntegerType::get(CE->getContext(), ByteSize * 8));
      // If the extract is known to be fully in the input, extract it.
      if (ShAmt.ule(ByteStart))
        return ExtractConstantBytes(CE->getOperand(0),
                                    ByteStart - ShAmt.getZExtValue(), ByteSize);
  
      // TODO: Handle the 'partially zero' case.
      return nullptr;
    }
  
    case Instruction::ZExt: {
      unsigned SrcBitSize =
        cast<IntegerType>(CE->getOperand(0)->getType())->getBitWidth();
  
      // If extracting something that is completely zero, return 0.
      if (ByteStart*8 >= SrcBitSize)
        return Constant::getNullValue(IntegerType::get(CE->getContext(),
                                                       ByteSize*8));
  
      // If exactly extracting the input, return it.
      if (ByteStart == 0 && ByteSize*8 == SrcBitSize)
        return CE->getOperand(0);
  
      // If extracting something completely in the input, if the input is a
      // multiple of 8 bits, recurse.
      if ((SrcBitSize&7) == 0 && (ByteStart+ByteSize)*8 <= SrcBitSize)
        return ExtractConstantBytes(CE->getOperand(0), ByteStart, ByteSize);
  
      // Otherwise, if extracting a subset of the input, which is not multiple of
      // 8 bits, do a shift and trunc to get the bits.
      if ((ByteStart+ByteSize)*8 < SrcBitSize) {
        assert((SrcBitSize&7) && "Shouldn't get byte sized case here");
        Constant *Res = CE->getOperand(0);
        if (ByteStart)
          Res = ConstantExpr::getLShr(Res,
                                   ConstantInt::get(Res->getType(), ByteStart*8));
        return ConstantExpr::getTrunc(Res, IntegerType::get(C->getContext(),
                                                            ByteSize*8));
      }
  
      // TODO: Handle the 'partially zero' case.
      return nullptr;
    }
    }
  }
  
  Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V,
                                              Type *DestTy) {
    if (isa<PoisonValue>(V))
      return PoisonValue::get(DestTy);
  
    if (isa<UndefValue>(V)) {
      // zext(undef) = 0, because the top bits will be zero.
      // sext(undef) = 0, because the top bits will all be the same.
      // [us]itofp(undef) = 0, because the result value is bounded.
      if (opc == Instruction::ZExt || opc == Instruction::SExt ||
          opc == Instruction::UIToFP || opc == Instruction::SIToFP)
        return Constant::getNullValue(DestTy);
      return UndefValue::get(DestTy);
    }
  
    if (V->isNullValue() && !DestTy->isX86_MMXTy() && !DestTy->isX86_AMXTy() &&
        opc != Instruction::AddrSpaceCast)
      return Constant::getNullValue(DestTy);
  
    // If the cast operand is a constant expression, there's a few things we can
    // do to try to simplify it.
    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
      if (CE->isCast()) {
        // Try hard to fold cast of cast because they are often eliminable.
        if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
          return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
      } else if (CE->getOpcode() == Instruction::GetElementPtr &&
                 // Do not fold addrspacecast (gep 0, .., 0). It might make the
                 // addrspacecast uncanonicalized.
                 opc != Instruction::AddrSpaceCast &&
                 // Do not fold bitcast (gep) with inrange index, as this loses
                 // information.
                 !cast<GEPOperator>(CE)->getInRangeIndex().hasValue() &&
                 // Do not fold if the gep type is a vector, as bitcasting
                 // operand 0 of a vector gep will result in a bitcast between
                 // different sizes.
                 !CE->getType()->isVectorTy()) {
        // If all of the indexes in the GEP are null values, there is no pointer
        // adjustment going on.  We might as well cast the source pointer.
        bool isAllNull = true;
        for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
          if (!CE->getOperand(i)->isNullValue()) {
            isAllNull = false;
            break;
          }
        if (isAllNull)
          // This is casting one pointer type to another, always BitCast
          return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
      }
    }
  
    // If the cast operand is a constant vector, perform the cast by
    // operating on each element. In the cast of bitcasts, the element
    // count may be mismatched; don't attempt to handle that here.
    if ((isa<ConstantVector>(V) || isa<ConstantDataVector>(V)) &&
        DestTy->isVectorTy() &&
        cast<FixedVectorType>(DestTy)->getNumElements() ==
            cast<FixedVectorType>(V->getType())->getNumElements()) {
      VectorType *DestVecTy = cast<VectorType>(DestTy);
      Type *DstEltTy = DestVecTy->getElementType();
      // Fast path for splatted constants.
      if (Constant *Splat = V->getSplatValue()) {
        return ConstantVector::getSplat(
            cast<VectorType>(DestTy)->getElementCount(),
            ConstantExpr::getCast(opc, Splat, DstEltTy));
      }
      SmallVector<Constant *, 16> res;
      Type *Ty = IntegerType::get(V->getContext(), 32);
      for (unsigned i = 0,
                    e = cast<FixedVectorType>(V->getType())->getNumElements();
           i != e; ++i) {
        Constant *C =
          ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i));
        res.push_back(ConstantExpr::getCast(opc, C, DstEltTy));
      }
      return ConstantVector::get(res);
    }
  
    // We actually have to do a cast now. Perform the cast according to the
    // opcode specified.
    switch (opc) {
    default:
      llvm_unreachable("Failed to cast constant expression");
    case Instruction::FPTrunc:
    case Instruction::FPExt:
      if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
        bool ignored;
        APFloat Val = FPC->getValueAPF();
        Val.convert(DestTy->isHalfTy() ? APFloat::IEEEhalf() :
                    DestTy->isFloatTy() ? APFloat::IEEEsingle() :
                    DestTy->isDoubleTy() ? APFloat::IEEEdouble() :
                    DestTy->isX86_FP80Ty() ? APFloat::x87DoubleExtended() :
                    DestTy->isFP128Ty() ? APFloat::IEEEquad() :
                    DestTy->isPPC_FP128Ty() ? APFloat::PPCDoubleDouble() :
                    APFloat::Bogus(),
                    APFloat::rmNearestTiesToEven, &ignored);
        return ConstantFP::get(V->getContext(), Val);
      }
      return nullptr; // Can't fold.
    case Instruction::FPToUI:
    case Instruction::FPToSI:
      if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
        const APFloat &V = FPC->getValueAPF();
        bool ignored;
        uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
        APSInt IntVal(DestBitWidth, opc == Instruction::FPToUI);
        if (APFloat::opInvalidOp ==
            V.convertToInteger(IntVal, APFloat::rmTowardZero, &ignored)) {
          // Undefined behavior invoked - the destination type can't represent
          // the input constant.
          return PoisonValue::get(DestTy);
        }
        return ConstantInt::get(FPC->getContext(), IntVal);
      }
      return nullptr; // Can't fold.
    case Instruction::IntToPtr:   //always treated as unsigned
      if (V->isNullValue())       // Is it an integral null value?
        return ConstantPointerNull::get(cast<PointerType>(DestTy));
      return nullptr;                   // Other pointer types cannot be casted
    case Instruction::PtrToInt:   // always treated as unsigned
      // Is it a null pointer value?
      if (V->isNullValue())
        return ConstantInt::get(DestTy, 0);
      // Other pointer types cannot be casted
      return nullptr;
    case Instruction::UIToFP:
    case Instruction::SIToFP:
      if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
        const APInt &api = CI->getValue();
        APFloat apf(DestTy->getFltSemantics(),
                    APInt::getZero(DestTy->getPrimitiveSizeInBits()));
        apf.convertFromAPInt(api, opc==Instruction::SIToFP,
                             APFloat::rmNearestTiesToEven);
        return ConstantFP::get(V->getContext(), apf);
      }
      return nullptr;
    case Instruction::ZExt:
      if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
        uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
        return ConstantInt::get(V->getContext(),
                                CI->getValue().zext(BitWidth));
      }
      return nullptr;
    case Instruction::SExt:
      if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
        uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
        return ConstantInt::get(V->getContext(),
                                CI->getValue().sext(BitWidth));
      }
      return nullptr;
    case Instruction::Trunc: {
      if (V->getType()->isVectorTy())
        return nullptr;
  
      uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
      if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
        return ConstantInt::get(V->getContext(),
                                CI->getValue().trunc(DestBitWidth));
      }
  
      // The input must be a constantexpr.  See if we can simplify this based on
      // the bytes we are demanding.  Only do this if the source and dest are an
      // even multiple of a byte.
      if ((DestBitWidth & 7) == 0 &&
          (cast<IntegerType>(V->getType())->getBitWidth() & 7) == 0)
        if (Constant *Res = ExtractConstantBytes(V, 0, DestBitWidth / 8))
          return Res;
  
      return nullptr;
    }
    case Instruction::BitCast:
      return FoldBitCast(V, DestTy);
    case Instruction::AddrSpaceCast:
      return nullptr;
    }
  }
  
  Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond,
                                                Constant *V1, Constant *V2) {
    // Check for i1 and vector true/false conditions.
    if (Cond->isNullValue()) return V2;
    if (Cond->isAllOnesValue()) return V1;
  
    // If the condition is a vector constant, fold the result elementwise.
    if (ConstantVector *CondV = dyn_cast<ConstantVector>(Cond)) {
      auto *V1VTy = CondV->getType();
      SmallVector<Constant*, 16> Result;
      Type *Ty = IntegerType::get(CondV->getContext(), 32);
      for (unsigned i = 0, e = V1VTy->getNumElements(); i != e; ++i) {
        Constant *V;
        Constant *V1Element = ConstantExpr::getExtractElement(V1,
                                                      ConstantInt::get(Ty, i));
        Constant *V2Element = ConstantExpr::getExtractElement(V2,
                                                      ConstantInt::get(Ty, i));
        auto *Cond = cast<Constant>(CondV->getOperand(i));
        if (isa<PoisonValue>(Cond)) {
          V = PoisonValue::get(V1Element->getType());
        } else if (V1Element == V2Element) {
          V = V1Element;
        } else if (isa<UndefValue>(Cond)) {
          V = isa<UndefValue>(V1Element) ? V1Element : V2Element;
        } else {
          if (!isa<ConstantInt>(Cond)) break;
          V = Cond->isNullValue() ? V2Element : V1Element;
        }
        Result.push_back(V);
      }
  
      // If we were able to build the vector, return it.
      if (Result.size() == V1VTy->getNumElements())
        return ConstantVector::get(Result);
    }
  
    if (isa<PoisonValue>(Cond))
      return PoisonValue::get(V1->getType());
  
    if (isa<UndefValue>(Cond)) {
      if (isa<UndefValue>(V1)) return V1;
      return V2;
    }
  
    if (V1 == V2) return V1;
  
    if (isa<PoisonValue>(V1))
      return V2;
    if (isa<PoisonValue>(V2))
      return V1;
  
    // If the true or false value is undef, we can fold to the other value as
    // long as the other value isn't poison.
    auto NotPoison = [](Constant *C) {
      if (isa<PoisonValue>(C))
        return false;
  
      // TODO: We can analyze ConstExpr by opcode to determine if there is any
      //       possibility of poison.
      if (isa<ConstantExpr>(C))
        return false;
  
      if (isa<ConstantInt>(C) || isa<GlobalVariable>(C) || isa<ConstantFP>(C) ||
          isa<ConstantPointerNull>(C) || isa<Function>(C))
        return true;
  
      if (C->getType()->isVectorTy())
        return !C->containsPoisonElement() && !C->containsConstantExpression();
  
      // TODO: Recursively analyze aggregates or other constants.
      return false;
    };
    if (isa<UndefValue>(V1) && NotPoison(V2)) return V2;
    if (isa<UndefValue>(V2) && NotPoison(V1)) return V1;
  
    if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) {
      if (TrueVal->getOpcode() == Instruction::Select)
        if (TrueVal->getOperand(0) == Cond)
          return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2);
    }
    if (ConstantExpr *FalseVal = dyn_cast<ConstantExpr>(V2)) {
      if (FalseVal->getOpcode() == Instruction::Select)
        if (FalseVal->getOperand(0) == Cond)
          return ConstantExpr::getSelect(Cond, V1, FalseVal->getOperand(2));
    }
  
    return nullptr;
  }
  
  Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val,
                                                        Constant *Idx) {
    auto *ValVTy = cast<VectorType>(Val->getType());
  
    // extractelt poison, C -> poison
    // extractelt C, undef -> poison
    if (isa<PoisonValue>(Val) || isa<UndefValue>(Idx))
      return PoisonValue::get(ValVTy->getElementType());
  
    // extractelt undef, C -> undef
    if (isa<UndefValue>(Val))
      return UndefValue::get(ValVTy->getElementType());
  
    auto *CIdx = dyn_cast<ConstantInt>(Idx);
    if (!CIdx)
      return nullptr;
  
    if (auto *ValFVTy = dyn_cast<FixedVectorType>(Val->getType())) {
      // ee({w,x,y,z}, wrong_value) -> poison
      if (CIdx->uge(ValFVTy->getNumElements()))
        return PoisonValue::get(ValFVTy->getElementType());
    }
  
    // ee (gep (ptr, idx0, ...), idx) -> gep (ee (ptr, idx), ee (idx0, idx), ...)
    if (auto *CE = dyn_cast<ConstantExpr>(Val)) {
      if (auto *GEP = dyn_cast<GEPOperator>(CE)) {
        SmallVector<Constant *, 8> Ops;
        Ops.reserve(CE->getNumOperands());
        for (unsigned i = 0, e = CE->getNumOperands(); i != e; ++i) {
          Constant *Op = CE->getOperand(i);
          if (Op->getType()->isVectorTy()) {
            Constant *ScalarOp = ConstantExpr::getExtractElement(Op, Idx);
            if (!ScalarOp)
              return nullptr;
            Ops.push_back(ScalarOp);
          } else
            Ops.push_back(Op);
        }
        return CE->getWithOperands(Ops, ValVTy->getElementType(), false,
                                   GEP->getSourceElementType());
      } else if (CE->getOpcode() == Instruction::InsertElement) {
        if (const auto *IEIdx = dyn_cast<ConstantInt>(CE->getOperand(2))) {
          if (APSInt::isSameValue(APSInt(IEIdx->getValue()),
                                  APSInt(CIdx->getValue()))) {
            return CE->getOperand(1);
          } else {
            return ConstantExpr::getExtractElement(CE->getOperand(0), CIdx);
          }
        }
      }
    }
  
    if (Constant *C = Val->getAggregateElement(CIdx))
      return C;
  
    // Lane < Splat minimum vector width => extractelt Splat(x), Lane -> x
    if (CIdx->getValue().ult(ValVTy->getElementCount().getKnownMinValue())) {
      if (Constant *SplatVal = Val->getSplatValue())
        return SplatVal;
    }
  
    return nullptr;
  }
  
  Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val,
                                                       Constant *Elt,
                                                       Constant *Idx) {
    if (isa<UndefValue>(Idx))
      return PoisonValue::get(Val->getType());
  
    ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
    if (!CIdx) return nullptr;
  
    // Do not iterate on scalable vector. The num of elements is unknown at
    // compile-time.
    if (isa<ScalableVectorType>(Val->getType()))
      return nullptr;
  
    auto *ValTy = cast<FixedVectorType>(Val->getType());
  
    unsigned NumElts = ValTy->getNumElements();
    if (CIdx->uge(NumElts))
      return PoisonValue::get(Val->getType());
  
    SmallVector<Constant*, 16> Result;
    Result.reserve(NumElts);
    auto *Ty = Type::getInt32Ty(Val->getContext());
    uint64_t IdxVal = CIdx->getZExtValue();
    for (unsigned i = 0; i != NumElts; ++i) {
      if (i == IdxVal) {
        Result.push_back(Elt);
        continue;
      }
  
      Constant *C = ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i));
      Result.push_back(C);
    }
  
    return ConstantVector::get(Result);
  }
  
  Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1, Constant *V2,
                                                       ArrayRef<int> Mask) {
    auto *V1VTy = cast<VectorType>(V1->getType());
    unsigned MaskNumElts = Mask.size();
    auto MaskEltCount =
        ElementCount::get(MaskNumElts, isa<ScalableVectorType>(V1VTy));
    Type *EltTy = V1VTy->getElementType();
  
    // Undefined shuffle mask -> undefined value.
    if (all_of(Mask, [](int Elt) { return Elt == UndefMaskElem; })) {
      return UndefValue::get(FixedVectorType::get(EltTy, MaskNumElts));
    }
  
    // If the mask is all zeros this is a splat, no need to go through all
    // elements.
    if (all_of(Mask, [](int Elt) { return Elt == 0; })) {
      Type *Ty = IntegerType::get(V1->getContext(), 32);
      Constant *Elt =
          ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, 0));
  
      if (Elt->isNullValue()) {
        auto *VTy = VectorType::get(EltTy, MaskEltCount);
        return ConstantAggregateZero::get(VTy);
      } else if (!MaskEltCount.isScalable())
        return ConstantVector::getSplat(MaskEltCount, Elt);
    }
    // Do not iterate on scalable vector. The num of elements is unknown at
    // compile-time.
    if (isa<ScalableVectorType>(V1VTy))
      return nullptr;
  
    unsigned SrcNumElts = V1VTy->getElementCount().getKnownMinValue();
  
    // Loop over the shuffle mask, evaluating each element.
    SmallVector<Constant*, 32> Result;
    for (unsigned i = 0; i != MaskNumElts; ++i) {
      int Elt = Mask[i];
      if (Elt == -1) {
        Result.push_back(UndefValue::get(EltTy));
        continue;
      }
      Constant *InElt;
      if (unsigned(Elt) >= SrcNumElts*2)
        InElt = UndefValue::get(EltTy);
      else if (unsigned(Elt) >= SrcNumElts) {
        Type *Ty = IntegerType::get(V2->getContext(), 32);
        InElt =
          ConstantExpr::getExtractElement(V2,
                                          ConstantInt::get(Ty, Elt - SrcNumElts));
      } else {
        Type *Ty = IntegerType::get(V1->getContext(), 32);
        InElt = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, Elt));
      }
      Result.push_back(InElt);
    }
  
    return ConstantVector::get(Result);
  }
  
  Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg,
                                                      ArrayRef<unsigned> Idxs) {
    // Base case: no indices, so return the entire value.
    if (Idxs.empty())
      return Agg;
  
    if (Constant *C = Agg->getAggregateElement(Idxs[0]))
      return ConstantFoldExtractValueInstruction(C, Idxs.slice(1));
  
    return nullptr;
  }
  
  Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg,
                                                     Constant *Val,
                                                     ArrayRef<unsigned> Idxs) {
    // Base case: no indices, so replace the entire value.
    if (Idxs.empty())
      return Val;
  
    unsigned NumElts;
    if (StructType *ST = dyn_cast<StructType>(Agg->getType()))
      NumElts = ST->getNumElements();
    else
      NumElts = cast<ArrayType>(Agg->getType())->getNumElements();
  
    SmallVector<Constant*, 32> Result;
    for (unsigned i = 0; i != NumElts; ++i) {
      Constant *C = Agg->getAggregateElement(i);
      if (!C) return nullptr;
  
      if (Idxs[0] == i)
        C = ConstantFoldInsertValueInstruction(C, Val, Idxs.slice(1));
  
      Result.push_back(C);
    }
  
    if (StructType *ST = dyn_cast<StructType>(Agg->getType()))
      return ConstantStruct::get(ST, Result);
    return ConstantArray::get(cast<ArrayType>(Agg->getType()), Result);
  }
  
  Constant *llvm::ConstantFoldUnaryInstruction(unsigned Opcode, Constant *C) {
    assert(Instruction::isUnaryOp(Opcode) && "Non-unary instruction detected");
  
    // Handle scalar UndefValue and scalable vector UndefValue. Fixed-length
    // vectors are always evaluated per element.
    bool IsScalableVector = isa<ScalableVectorType>(C->getType());
    bool HasScalarUndefOrScalableVectorUndef =
        (!C->getType()->isVectorTy() || IsScalableVector) && isa<UndefValue>(C);
  
    if (HasScalarUndefOrScalableVectorUndef) {
      switch (static_cast<Instruction::UnaryOps>(Opcode)) {
      case Instruction::FNeg:
        return C; // -undef -> undef
      case Instruction::UnaryOpsEnd:
        llvm_unreachable("Invalid UnaryOp");
      }
    }
  
    // Constant should not be UndefValue, unless these are vector constants.
    assert(!HasScalarUndefOrScalableVectorUndef && "Unexpected UndefValue");
    // We only have FP UnaryOps right now.
    assert(!isa<ConstantInt>(C) && "Unexpected Integer UnaryOp");
  
    if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) {
      const APFloat &CV = CFP->getValueAPF();
      switch (Opcode) {
      default:
        break;
      case Instruction::FNeg:
        return ConstantFP::get(C->getContext(), neg(CV));
      }
    } else if (auto *VTy = dyn_cast<FixedVectorType>(C->getType())) {
  
      Type *Ty = IntegerType::get(VTy->getContext(), 32);
      // Fast path for splatted constants.
      if (Constant *Splat = C->getSplatValue()) {
        Constant *Elt = ConstantExpr::get(Opcode, Splat);
        return ConstantVector::getSplat(VTy->getElementCount(), Elt);
      }
  
      // Fold each element and create a vector constant from those constants.
      SmallVector<Constant *, 16> Result;
      for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
        Constant *ExtractIdx = ConstantInt::get(Ty, i);
        Constant *Elt = ConstantExpr::getExtractElement(C, ExtractIdx);
  
        Result.push_back(ConstantExpr::get(Opcode, Elt));
      }
  
      return ConstantVector::get(Result);
    }
  
    // We don't know how to fold this.
    return nullptr;
  }
  
  Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, Constant *C1,
                                                Constant *C2) {
    assert(Instruction::isBinaryOp(Opcode) && "Non-binary instruction detected");
  
    // Simplify BinOps with their identity values first. They are no-ops and we
    // can always return the other value, including undef or poison values.
    // FIXME: remove unnecessary duplicated identity patterns below.
    // FIXME: Use AllowRHSConstant with getBinOpIdentity to handle additional ops,
    //        like X << 0 = X.
    Constant *Identity = ConstantExpr::getBinOpIdentity(Opcode, C1->getType());
    if (Identity) {
      if (C1 == Identity)
        return C2;
      if (C2 == Identity)
        return C1;
    }
  
    // Binary operations propagate poison.
    if (isa<PoisonValue>(C1) || isa<PoisonValue>(C2))
      return PoisonValue::get(C1->getType());
  
    // Handle scalar UndefValue and scalable vector UndefValue. Fixed-length
    // vectors are always evaluated per element.
    bool IsScalableVector = isa<ScalableVectorType>(C1->getType());
    bool HasScalarUndefOrScalableVectorUndef =
        (!C1->getType()->isVectorTy() || IsScalableVector) &&
        (isa<UndefValue>(C1) || isa<UndefValue>(C2));
    if (HasScalarUndefOrScalableVectorUndef) {
      switch (static_cast<Instruction::BinaryOps>(Opcode)) {
      case Instruction::Xor:
        if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
          // Handle undef ^ undef -> 0 special case. This is a common
          // idiom (misuse).
          return Constant::getNullValue(C1->getType());
        LLVM_FALLTHROUGH;
      case Instruction::Add:
      case Instruction::Sub:
        return UndefValue::get(C1->getType());
      case Instruction::And:
        if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef & undef -> undef
          return C1;
        return Constant::getNullValue(C1->getType());   // undef & X -> 0
      case Instruction::Mul: {
        // undef * undef -> undef
        if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
          return C1;
        const APInt *CV;
        // X * undef -> undef   if X is odd
        if (match(C1, m_APInt(CV)) || match(C2, m_APInt(CV)))
          if ((*CV)[0])
            return UndefValue::get(C1->getType());
  
        // X * undef -> 0       otherwise
        return Constant::getNullValue(C1->getType());
      }
      case Instruction::SDiv:
      case Instruction::UDiv:
        // X / undef -> poison
        // X / 0 -> poison
        if (match(C2, m_CombineOr(m_Undef(), m_Zero())))
          return PoisonValue::get(C2->getType());
        // undef / 1 -> undef
        if (match(C2, m_One()))
          return C1;
        // undef / X -> 0       otherwise
        return Constant::getNullValue(C1->getType());
      case Instruction::URem:
      case Instruction::SRem:
        // X % undef -> poison
        // X % 0 -> poison
        if (match(C2, m_CombineOr(m_Undef(), m_Zero())))
          return PoisonValue::get(C2->getType());
        // undef % X -> 0       otherwise
        return Constant::getNullValue(C1->getType());
      case Instruction::Or:                          // X | undef -> -1
        if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef | undef -> undef
          return C1;
        return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0
      case Instruction::LShr:
        // X >>l undef -> poison
        if (isa<UndefValue>(C2))
          return PoisonValue::get(C2->getType());
        // undef >>l 0 -> undef
        if (match(C2, m_Zero()))
          return C1;
        // undef >>l X -> 0
        return Constant::getNullValue(C1->getType());
      case Instruction::AShr:
        // X >>a undef -> poison
        if (isa<UndefValue>(C2))
          return PoisonValue::get(C2->getType());
        // undef >>a 0 -> undef
        if (match(C2, m_Zero()))
          return C1;
        // TODO: undef >>a X -> poison if the shift is exact
        // undef >>a X -> 0
        return Constant::getNullValue(C1->getType());
      case Instruction::Shl:
        // X << undef -> undef
        if (isa<UndefValue>(C2))
          return PoisonValue::get(C2->getType());
        // undef << 0 -> undef
        if (match(C2, m_Zero()))
          return C1;
        // undef << X -> 0
        return Constant::getNullValue(C1->getType());
      case Instruction::FSub:
        // -0.0 - undef --> undef (consistent with "fneg undef")
        if (match(C1, m_NegZeroFP()) && isa<UndefValue>(C2))
          return C2;
        LLVM_FALLTHROUGH;
      case Instruction::FAdd:
      case Instruction::FMul:
      case Instruction::FDiv:
      case Instruction::FRem:
        // [any flop] undef, undef -> undef
        if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
          return C1;
        // [any flop] C, undef -> NaN
        // [any flop] undef, C -> NaN
        // We could potentially specialize NaN/Inf constants vs. 'normal'
        // constants (possibly differently depending on opcode and operand). This
        // would allow returning undef sometimes. But it is always safe to fold to
        // NaN because we can choose the undef operand as NaN, and any FP opcode
        // with a NaN operand will propagate NaN.
        return ConstantFP::getNaN(C1->getType());
      case Instruction::BinaryOpsEnd:
        llvm_unreachable("Invalid BinaryOp");
      }
    }
  
    // Neither constant should be UndefValue, unless these are vector constants.
    assert((!HasScalarUndefOrScalableVectorUndef) && "Unexpected UndefValue");
  
    // Handle simplifications when the RHS is a constant int.
    if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
      switch (Opcode) {
      case Instruction::Add:
        if (CI2->isZero()) return C1;                             // X + 0 == X
        break;
      case Instruction::Sub:
        if (CI2->isZero()) return C1;                             // X - 0 == X
        break;
      case Instruction::Mul:
        if (CI2->isZero()) return C2;                             // X * 0 == 0
        if (CI2->isOne())
          return C1;                                              // X * 1 == X
        break;
      case Instruction::UDiv:
      case Instruction::SDiv:
        if (CI2->isOne())
          return C1;                                            // X / 1 == X
        if (CI2->isZero())
          return PoisonValue::get(CI2->getType());              // X / 0 == poison
        break;
      case Instruction::URem:
      case Instruction::SRem:
        if (CI2->isOne())
          return Constant::getNullValue(CI2->getType());        // X % 1 == 0
        if (CI2->isZero())
          return PoisonValue::get(CI2->getType());              // X % 0 == poison
        break;
      case Instruction::And:
        if (CI2->isZero()) return C2;                           // X & 0 == 0
        if (CI2->isMinusOne())
          return C1;                                            // X & -1 == X
  
        if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
          // (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
          if (CE1->getOpcode() == Instruction::ZExt) {
            unsigned DstWidth = CI2->getType()->getBitWidth();
            unsigned SrcWidth =
              CE1->getOperand(0)->getType()->getPrimitiveSizeInBits();
            APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth));
            if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits)
              return C1;
          }
  
          // If and'ing the address of a global with a constant, fold it.
          if (CE1->getOpcode() == Instruction::PtrToInt &&
              isa<GlobalValue>(CE1->getOperand(0))) {
            GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0));
  
            MaybeAlign GVAlign;
  
            if (Module *TheModule = GV->getParent()) {
              const DataLayout &DL = TheModule->getDataLayout();
              GVAlign = GV->getPointerAlignment(DL);
  
              // If the function alignment is not specified then assume that it
              // is 4.
              // This is dangerous; on x86, the alignment of the pointer
              // corresponds to the alignment of the function, but might be less
              // than 4 if it isn't explicitly specified.
              // However, a fix for this behaviour was reverted because it
              // increased code size (see https://reviews.llvm.org/D55115)
              // FIXME: This code should be deleted once existing targets have
              // appropriate defaults
              if (isa<Function>(GV) && !DL.getFunctionPtrAlign())
                GVAlign = Align(4);
            } else if (isa<Function>(GV)) {
              // Without a datalayout we have to assume the worst case: that the
              // function pointer isn't aligned at all.
              GVAlign = llvm::None;
            } else if (isa<GlobalVariable>(GV)) {
              GVAlign = cast<GlobalVariable>(GV)->getAlign();
            }
  
            if (GVAlign && *GVAlign > 1) {
              unsigned DstWidth = CI2->getType()->getBitWidth();
              unsigned SrcWidth = std::min(DstWidth, Log2(*GVAlign));
              APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth));
  
              // If checking bits we know are clear, return zero.
              if ((CI2->getValue() & BitsNotSet) == CI2->getValue())
                return Constant::getNullValue(CI2->getType());
            }
          }
        }
        break;
      case Instruction::Or:
        if (CI2->isZero()) return C1;        // X | 0 == X
        if (CI2->isMinusOne())
          return C2;                         // X | -1 == -1
        break;
      case Instruction::Xor:
        if (CI2->isZero()) return C1;        // X ^ 0 == X
  
        if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
          switch (CE1->getOpcode()) {
          default: break;
          case Instruction::ICmp:
          case Instruction::FCmp:
            // cmp pred ^ true -> cmp !pred
            assert(CI2->isOne());
            CmpInst::Predicate pred = (CmpInst::Predicate)CE1->getPredicate();
            pred = CmpInst::getInversePredicate(pred);
            return ConstantExpr::getCompare(pred, CE1->getOperand(0),
                                            CE1->getOperand(1));
          }
        }
        break;
      case Instruction::AShr:
        // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
        if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1))
          if (CE1->getOpcode() == Instruction::ZExt)  // Top bits known zero.
            return ConstantExpr::getLShr(C1, C2);
        break;
      }
    } else if (isa<ConstantInt>(C1)) {
      // If C1 is a ConstantInt and C2 is not, swap the operands.
      if (Instruction::isCommutative(Opcode))
        return ConstantExpr::get(Opcode, C2, C1);
    }
  
    if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
      if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
        const APInt &C1V = CI1->getValue();
        const APInt &C2V = CI2->getValue();
        switch (Opcode) {
        default:
          break;
        case Instruction::Add:
          return ConstantInt::get(CI1->getContext(), C1V + C2V);
        case Instruction::Sub:
          return ConstantInt::get(CI1->getContext(), C1V - C2V);
        case Instruction::Mul:
          return ConstantInt::get(CI1->getContext(), C1V * C2V);
        case Instruction::UDiv:
          assert(!CI2->isZero() && "Div by zero handled above");
          return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V));
        case Instruction::SDiv:
          assert(!CI2->isZero() && "Div by zero handled above");
          if (C2V.isAllOnes() && C1V.isMinSignedValue())
            return PoisonValue::get(CI1->getType());   // MIN_INT / -1 -> poison
          return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V));
        case Instruction::URem:
          assert(!CI2->isZero() && "Div by zero handled above");
          return ConstantInt::get(CI1->getContext(), C1V.urem(C2V));
        case Instruction::SRem:
          assert(!CI2->isZero() && "Div by zero handled above");
          if (C2V.isAllOnes() && C1V.isMinSignedValue())
            return PoisonValue::get(CI1->getType());   // MIN_INT % -1 -> poison
          return ConstantInt::get(CI1->getContext(), C1V.srem(C2V));
        case Instruction::And:
          return ConstantInt::get(CI1->getContext(), C1V & C2V);
        case Instruction::Or:
          return ConstantInt::get(CI1->getContext(), C1V | C2V);
        case Instruction::Xor:
          return ConstantInt::get(CI1->getContext(), C1V ^ C2V);
        case Instruction::Shl:
          if (C2V.ult(C1V.getBitWidth()))
            return ConstantInt::get(CI1->getContext(), C1V.shl(C2V));
          return PoisonValue::get(C1->getType()); // too big shift is poison
        case Instruction::LShr:
          if (C2V.ult(C1V.getBitWidth()))
            return ConstantInt::get(CI1->getContext(), C1V.lshr(C2V));
          return PoisonValue::get(C1->getType()); // too big shift is poison
        case Instruction::AShr:
          if (C2V.ult(C1V.getBitWidth()))
            return ConstantInt::get(CI1->getContext(), C1V.ashr(C2V));
          return PoisonValue::get(C1->getType()); // too big shift is poison
        }
      }
  
      switch (Opcode) {
      case Instruction::SDiv:
      case Instruction::UDiv:
      case Instruction::URem:
      case Instruction::SRem:
      case Instruction::LShr:
      case Instruction::AShr:
      case Instruction::Shl:
        if (CI1->isZero()) return C1;
        break;
      default:
        break;
      }
    } else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
      if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
        const APFloat &C1V = CFP1->getValueAPF();
        const APFloat &C2V = CFP2->getValueAPF();
        APFloat C3V = C1V;  // copy for modification
        switch (Opcode) {
        default:
          break;
        case Instruction::FAdd:
          (void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
          return ConstantFP::get(C1->getContext(), C3V);
        case Instruction::FSub:
          (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
          return ConstantFP::get(C1->getContext(), C3V);
        case Instruction::FMul:
          (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
          return ConstantFP::get(C1->getContext(), C3V);
        case Instruction::FDiv:
          (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
          return ConstantFP::get(C1->getContext(), C3V);
        case Instruction::FRem:
          (void)C3V.mod(C2V);
          return ConstantFP::get(C1->getContext(), C3V);
        }
      }
    } else if (auto *VTy = dyn_cast<VectorType>(C1->getType())) {
      // Fast path for splatted constants.
      if (Constant *C2Splat = C2->getSplatValue()) {
        if (Instruction::isIntDivRem(Opcode) && C2Splat->isNullValue())
          return PoisonValue::get(VTy);
        if (Constant *C1Splat = C1->getSplatValue()) {
          return ConstantVector::getSplat(
              VTy->getElementCount(),
              ConstantExpr::get(Opcode, C1Splat, C2Splat));
        }
      }
  
      if (auto *FVTy = dyn_cast<FixedVectorType>(VTy)) {
        // Fold each element and create a vector constant from those constants.
        SmallVector<Constant*, 16> Result;
        Type *Ty = IntegerType::get(FVTy->getContext(), 32);
        for (unsigned i = 0, e = FVTy->getNumElements(); i != e; ++i) {
          Constant *ExtractIdx = ConstantInt::get(Ty, i);
          Constant *LHS = ConstantExpr::getExtractElement(C1, ExtractIdx);
          Constant *RHS = ConstantExpr::getExtractElement(C2, ExtractIdx);
  
          // If any element of a divisor vector is zero, the whole op is poison.
          if (Instruction::isIntDivRem(Opcode) && RHS->isNullValue())
            return PoisonValue::get(VTy);
  
          Result.push_back(ConstantExpr::get(Opcode, LHS, RHS));
        }
  
        return ConstantVector::get(Result);
      }
    }
  
    if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
      // There are many possible foldings we could do here.  We should probably
      // at least fold add of a pointer with an integer into the appropriate
      // getelementptr.  This will improve alias analysis a bit.
  
      // Given ((a + b) + c), if (b + c) folds to something interesting, return
      // (a + (b + c)).
      if (Instruction::isAssociative(Opcode) && CE1->getOpcode() == Opcode) {
        Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2);
        if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode)
          return ConstantExpr::get(Opcode, CE1->getOperand(0), T);
      }
    } else if (isa<ConstantExpr>(C2)) {
      // If C2 is a constant expr and C1 isn't, flop them around and fold the
      // other way if possible.
      if (Instruction::isCommutative(Opcode))
        return ConstantFoldBinaryInstruction(Opcode, C2, C1);
    }
  
    // i1 can be simplified in many cases.
    if (C1->getType()->isIntegerTy(1)) {
      switch (Opcode) {
      case Instruction::Add:
      case Instruction::Sub:
        return ConstantExpr::getXor(C1, C2);
      case Instruction::Mul:
        return ConstantExpr::getAnd(C1, C2);
      case Instruction::Shl:
      case Instruction::LShr:
      case Instruction::AShr:
        // We can assume that C2 == 0.  If it were one the result would be
        // undefined because the shift value is as large as the bitwidth.
        return C1;
      case Instruction::SDiv:
      case Instruction::UDiv:
        // We can assume that C2 == 1.  If it were zero the result would be
        // undefined through division by zero.
        return C1;
      case Instruction::URem:
      case Instruction::SRem:
        // We can assume that C2 == 1.  If it were zero the result would be
        // undefined through division by zero.
        return ConstantInt::getFalse(C1->getContext());
      default:
        break;
      }
    }
  
    // We don't know how to fold this.
    return nullptr;
  }
  
  /// This function determines if there is anything we can decide about the two
  /// constants provided. This doesn't need to handle simple things like
  /// ConstantFP comparisons, but should instead handle ConstantExprs.
  /// If we can determine that the two constants have a particular relation to
  /// each other, we should return the corresponding FCmpInst predicate,
  /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
  /// ConstantFoldCompareInstruction.
  ///
  /// To simplify this code we canonicalize the relation so that the first
  /// operand is always the most "complex" of the two.  We consider ConstantFP
  /// to be the simplest, and ConstantExprs to be the most complex.
  static FCmpInst::Predicate evaluateFCmpRelation(Constant *V1, Constant *V2) {
    assert(V1->getType() == V2->getType() &&
           "Cannot compare values of different types!");
  
    // We do not know if a constant expression will evaluate to a number or NaN.
    // Therefore, we can only say that the relation is unordered or equal.
    if (V1 == V2) return FCmpInst::FCMP_UEQ;
  
    if (!isa<ConstantExpr>(V1)) {
      if (!isa<ConstantExpr>(V2)) {
        // Simple case, use the standard constant folder.
        ConstantInt *R = nullptr;
        R = dyn_cast<ConstantInt>(
                        ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2));
        if (R && !R->isZero())
          return FCmpInst::FCMP_OEQ;
        R = dyn_cast<ConstantInt>(
                        ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2));
        if (R && !R->isZero())
          return FCmpInst::FCMP_OLT;
        R = dyn_cast<ConstantInt>(
                        ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, V1, V2));
        if (R && !R->isZero())
          return FCmpInst::FCMP_OGT;
  
        // Nothing more we can do
        return FCmpInst::BAD_FCMP_PREDICATE;
      }
  
      // If the first operand is simple and second is ConstantExpr, swap operands.
      FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1);
      if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
        return FCmpInst::getSwappedPredicate(SwappedRelation);
    } else {
      // Ok, the LHS is known to be a constantexpr.  The RHS can be any of a
      // constantexpr or a simple constant.
      ConstantExpr *CE1 = cast<ConstantExpr>(V1);
      switch (CE1->getOpcode()) {
      case Instruction::FPTrunc:
      case Instruction::FPExt:
      case Instruction::UIToFP:
      case Instruction::SIToFP:
        // We might be able to do something with these but we don't right now.
        break;
      default:
        break;
      }
    }
    // There are MANY other foldings that we could perform here.  They will
    // probably be added on demand, as they seem needed.
    return FCmpInst::BAD_FCMP_PREDICATE;
  }
  
  static ICmpInst::Predicate areGlobalsPotentiallyEqual(const GlobalValue *GV1,
                                                        const GlobalValue *GV2) {
    auto isGlobalUnsafeForEquality = [](const GlobalValue *GV) {
      if (GV->isInterposable() || GV->hasGlobalUnnamedAddr())
        return true;
      if (const auto *GVar = dyn_cast<GlobalVariable>(GV)) {
        Type *Ty = GVar->getValueType();
        // A global with opaque type might end up being zero sized.
        if (!Ty->isSized())
          return true;
        // A global with an empty type might lie at the address of any other
        // global.
        if (Ty->isEmptyTy())
          return true;
      }
      return false;
    };
    // Don't try to decide equality of aliases.
    if (!isa<GlobalAlias>(GV1) && !isa<GlobalAlias>(GV2))
      if (!isGlobalUnsafeForEquality(GV1) && !isGlobalUnsafeForEquality(GV2))
        return ICmpInst::ICMP_NE;
    return ICmpInst::BAD_ICMP_PREDICATE;
  }
  
  /// This function determines if there is anything we can decide about the two
  /// constants provided. This doesn't need to handle simple things like integer
  /// comparisons, but should instead handle ConstantExprs and GlobalValues.
  /// If we can determine that the two constants have a particular relation to
  /// each other, we should return the corresponding ICmp predicate, otherwise
  /// return ICmpInst::BAD_ICMP_PREDICATE.
  ///
  /// To simplify this code we canonicalize the relation so that the first
  /// operand is always the most "complex" of the two.  We consider simple
  /// constants (like ConstantInt) to be the simplest, followed by
  /// GlobalValues, followed by ConstantExpr's (the most complex).
  ///
  static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2,
                                                  bool isSigned) {
    assert(V1->getType() == V2->getType() &&
           "Cannot compare different types of values!");
    if (V1 == V2) return ICmpInst::ICMP_EQ;
  
    if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1) &&
        !isa<BlockAddress>(V1)) {
      if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2) &&
          !isa<BlockAddress>(V2)) {
        // We distilled this down to a simple case, use the standard constant
        // folder.
        ConstantInt *R = nullptr;
        ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
        R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
        if (R && !R->isZero())
          return pred;
        pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
        R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
        if (R && !R->isZero())
          return pred;
        pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
        R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
        if (R && !R->isZero())
          return pred;
  
        // If we couldn't figure it out, bail.
        return ICmpInst::BAD_ICMP_PREDICATE;
      }
  
      // If the first operand is simple, swap operands.
      ICmpInst::Predicate SwappedRelation =
        evaluateICmpRelation(V2, V1, isSigned);
      if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
        return ICmpInst::getSwappedPredicate(SwappedRelation);
  
    } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V1)) {
      if (isa<ConstantExpr>(V2)) {  // Swap as necessary.
        ICmpInst::Predicate SwappedRelation =
          evaluateICmpRelation(V2, V1, isSigned);
        if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
          return ICmpInst::getSwappedPredicate(SwappedRelation);
        return ICmpInst::BAD_ICMP_PREDICATE;
      }
  
      // Now we know that the RHS is a GlobalValue, BlockAddress or simple
      // constant (which, since the types must match, means that it's a
      // ConstantPointerNull).
      if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
        return areGlobalsPotentiallyEqual(GV, GV2);
      } else if (isa<BlockAddress>(V2)) {
        return ICmpInst::ICMP_NE; // Globals never equal labels.
      } else {
        assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
        // GlobalVals can never be null unless they have external weak linkage.
        // We don't try to evaluate aliases here.
        // NOTE: We should not be doing this constant folding if null pointer
        // is considered valid for the function. But currently there is no way to
        // query it from the Constant type.
        if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV) &&
            !NullPointerIsDefined(nullptr /* F */,
                                  GV->getType()->getAddressSpace()))
          return ICmpInst::ICMP_UGT;
      }
    } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) {
      if (isa<ConstantExpr>(V2)) {  // Swap as necessary.
        ICmpInst::Predicate SwappedRelation =
          evaluateICmpRelation(V2, V1, isSigned);
        if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
          return ICmpInst::getSwappedPredicate(SwappedRelation);
        return ICmpInst::BAD_ICMP_PREDICATE;
      }
  
      // Now we know that the RHS is a GlobalValue, BlockAddress or simple
      // constant (which, since the types must match, means that it is a
      // ConstantPointerNull).
      if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) {
        // Block address in another function can't equal this one, but block
        // addresses in the current function might be the same if blocks are
        // empty.
        if (BA2->getFunction() != BA->getFunction())
          return ICmpInst::ICMP_NE;
      } else {
        // Block addresses aren't null, don't equal the address of globals.
        assert((isa<ConstantPointerNull>(V2) || isa<GlobalValue>(V2)) &&
               "Canonicalization guarantee!");
        return ICmpInst::ICMP_NE;
      }
    } else {
      // Ok, the LHS is known to be a constantexpr.  The RHS can be any of a
      // constantexpr, a global, block address, or a simple constant.
      ConstantExpr *CE1 = cast<ConstantExpr>(V1);
      Constant *CE1Op0 = CE1->getOperand(0);
  
      switch (CE1->getOpcode()) {
      case Instruction::Trunc:
      case Instruction::FPTrunc:
      case Instruction::FPExt:
      case Instruction::FPToUI:
      case Instruction::FPToSI:
        break; // We can't evaluate floating point casts or truncations.
  
      case Instruction::BitCast:
        // If this is a global value cast, check to see if the RHS is also a
        // GlobalValue.
        if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0))
          if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2))
            return areGlobalsPotentiallyEqual(GV, GV2);
        LLVM_FALLTHROUGH;
      case Instruction::UIToFP:
      case Instruction::SIToFP:
      case Instruction::ZExt:
      case Instruction::SExt:
        // We can't evaluate floating point casts or truncations.
        if (CE1Op0->getType()->isFPOrFPVectorTy())
          break;
  
        // If the cast is not actually changing bits, and the second operand is a
        // null pointer, do the comparison with the pre-casted value.
        if (V2->isNullValue() && CE1->getType()->isIntOrPtrTy()) {
          if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
          if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
          return evaluateICmpRelation(CE1Op0,
                                      Constant::getNullValue(CE1Op0->getType()),
                                      isSigned);
        }
        break;
  
      case Instruction::GetElementPtr: {
        GEPOperator *CE1GEP = cast<GEPOperator>(CE1);
        // Ok, since this is a getelementptr, we know that the constant has a
        // pointer type.  Check the various cases.
        if (isa<ConstantPointerNull>(V2)) {
          // If we are comparing a GEP to a null pointer, check to see if the base
          // of the GEP equals the null pointer.
          if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
            // If its not weak linkage, the GVal must have a non-zero address
            // so the result is greater-than
            if (!GV->hasExternalWeakLinkage() && CE1GEP->isInBounds())
              return ICmpInst::ICMP_UGT;
          }
        } else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
          if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
            if (GV != GV2) {
              if (CE1GEP->hasAllZeroIndices())
                return areGlobalsPotentiallyEqual(GV, GV2);
              return ICmpInst::BAD_ICMP_PREDICATE;
            }
          }
        } else if (const auto *CE2GEP = dyn_cast<GEPOperator>(V2)) {
          // By far the most common case to handle is when the base pointers are
          // obviously to the same global.
          const Constant *CE2Op0 = cast<Constant>(CE2GEP->getPointerOperand());
          if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
            // Don't know relative ordering, but check for inequality.
            if (CE1Op0 != CE2Op0) {
              if (CE1GEP->hasAllZeroIndices() && CE2GEP->hasAllZeroIndices())
                return areGlobalsPotentiallyEqual(cast<GlobalValue>(CE1Op0),
                                                  cast<GlobalValue>(CE2Op0));
              return ICmpInst::BAD_ICMP_PREDICATE;
            }
          }
        }
        break;
      }
      default:
        break;
      }
    }
  
    return ICmpInst::BAD_ICMP_PREDICATE;
  }
  
  Constant *llvm::ConstantFoldCompareInstruction(CmpInst::Predicate Predicate,
                                                 Constant *C1, Constant *C2) {
    Type *ResultTy;
    if (VectorType *VT = dyn_cast<VectorType>(C1->getType()))
      ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()),
                                 VT->getElementCount());
    else
      ResultTy = Type::getInt1Ty(C1->getContext());
  
    // Fold FCMP_FALSE/FCMP_TRUE unconditionally.
    if (Predicate == FCmpInst::FCMP_FALSE)
      return Constant::getNullValue(ResultTy);
  
    if (Predicate == FCmpInst::FCMP_TRUE)
      return Constant::getAllOnesValue(ResultTy);
  
    // Handle some degenerate cases first
    if (isa<PoisonValue>(C1) || isa<PoisonValue>(C2))
      return PoisonValue::get(ResultTy);
  
    if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
      bool isIntegerPredicate = ICmpInst::isIntPredicate(Predicate);
      // For EQ and NE, we can always pick a value for the undef to make the
      // predicate pass or fail, so we can return undef.
      // Also, if both operands are undef, we can return undef for int comparison.
      if (ICmpInst::isEquality(Predicate) || (isIntegerPredicate && C1 == C2))
        return UndefValue::get(ResultTy);
  
      // Otherwise, for integer compare, pick the same value as the non-undef
      // operand, and fold it to true or false.
      if (isIntegerPredicate)
        return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(Predicate));
  
      // Choosing NaN for the undef will always make unordered comparison succeed
      // and ordered comparison fails.
      return ConstantInt::get(ResultTy, CmpInst::isUnordered(Predicate));
    }
  
    // icmp eq/ne(null,GV) -> false/true
    if (C1->isNullValue()) {
      if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
        // Don't try to evaluate aliases.  External weak GV can be null.
        if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage() &&
            !NullPointerIsDefined(nullptr /* F */,
                                  GV->getType()->getAddressSpace())) {
          if (Predicate == ICmpInst::ICMP_EQ)
            return ConstantInt::getFalse(C1->getContext());
          else if (Predicate == ICmpInst::ICMP_NE)
            return ConstantInt::getTrue(C1->getContext());
        }
    // icmp eq/ne(GV,null) -> false/true
    } else if (C2->isNullValue()) {
      if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1)) {
        // Don't try to evaluate aliases.  External weak GV can be null.
        if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage() &&
            !NullPointerIsDefined(nullptr /* F */,
                                  GV->getType()->getAddressSpace())) {
          if (Predicate == ICmpInst::ICMP_EQ)
            return ConstantInt::getFalse(C1->getContext());
          else if (Predicate == ICmpInst::ICMP_NE)
            return ConstantInt::getTrue(C1->getContext());
        }
      }
  
      // The caller is expected to commute the operands if the constant expression
      // is C2.
      // C1 >= 0 --> true
      if (Predicate == ICmpInst::ICMP_UGE)
        return Constant::getAllOnesValue(ResultTy);
      // C1 < 0 --> false
      if (Predicate == ICmpInst::ICMP_ULT)
        return Constant::getNullValue(ResultTy);
    }
  
    // If the comparison is a comparison between two i1's, simplify it.
    if (C1->getType()->isIntegerTy(1)) {
      switch (Predicate) {
      case ICmpInst::ICMP_EQ:
        if (isa<ConstantInt>(C2))
          return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2));
        return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2);
      case ICmpInst::ICMP_NE:
        return ConstantExpr::getXor(C1, C2);
      default:
        break;
      }
    }
  
    if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
      const APInt &V1 = cast<ConstantInt>(C1)->getValue();
      const APInt &V2 = cast<ConstantInt>(C2)->getValue();
      return ConstantInt::get(ResultTy, ICmpInst::compare(V1, V2, Predicate));
    } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
      const APFloat &C1V = cast<ConstantFP>(C1)->getValueAPF();
      const APFloat &C2V = cast<ConstantFP>(C2)->getValueAPF();
      return ConstantInt::get(ResultTy, FCmpInst::compare(C1V, C2V, Predicate));
    } else if (auto *C1VTy = dyn_cast<VectorType>(C1->getType())) {
  
      // Fast path for splatted constants.
      if (Constant *C1Splat = C1->getSplatValue())
        if (Constant *C2Splat = C2->getSplatValue())
          return ConstantVector::getSplat(
              C1VTy->getElementCount(),
              ConstantExpr::getCompare(Predicate, C1Splat, C2Splat));
  
      // Do not iterate on scalable vector. The number of elements is unknown at
      // compile-time.
      if (isa<ScalableVectorType>(C1VTy))
        return nullptr;
  
      // If we can constant fold the comparison of each element, constant fold
      // the whole vector comparison.
      SmallVector<Constant*, 4> ResElts;
      Type *Ty = IntegerType::get(C1->getContext(), 32);
      // Compare the elements, producing an i1 result or constant expr.
      for (unsigned I = 0, E = C1VTy->getElementCount().getKnownMinValue();
           I != E; ++I) {
        Constant *C1E =
            ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, I));
        Constant *C2E =
            ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, I));
  
        ResElts.push_back(ConstantExpr::getCompare(Predicate, C1E, C2E));
      }
  
      return ConstantVector::get(ResElts);
    }
  
    if (C1->getType()->isFloatingPointTy() &&
        // Only call evaluateFCmpRelation if we have a constant expr to avoid
        // infinite recursive loop
        (isa<ConstantExpr>(C1) || isa<ConstantExpr>(C2))) {
      int Result = -1;  // -1 = unknown, 0 = known false, 1 = known true.
      switch (evaluateFCmpRelation(C1, C2)) {
      default: llvm_unreachable("Unknown relation!");
      case FCmpInst::FCMP_UNO:
      case FCmpInst::FCMP_ORD:
      case FCmpInst::FCMP_UNE:
      case FCmpInst::FCMP_ULT:
      case FCmpInst::FCMP_UGT:
      case FCmpInst::FCMP_ULE:
      case FCmpInst::FCMP_UGE:
      case FCmpInst::FCMP_TRUE:
      case FCmpInst::FCMP_FALSE:
      case FCmpInst::BAD_FCMP_PREDICATE:
        break; // Couldn't determine anything about these constants.
      case FCmpInst::FCMP_OEQ: // We know that C1 == C2
        Result =
            (Predicate == FCmpInst::FCMP_UEQ || Predicate == FCmpInst::FCMP_OEQ ||
             Predicate == FCmpInst::FCMP_ULE || Predicate == FCmpInst::FCMP_OLE ||
             Predicate == FCmpInst::FCMP_UGE || Predicate == FCmpInst::FCMP_OGE);
        break;
      case FCmpInst::FCMP_OLT: // We know that C1 < C2
        Result =
            (Predicate == FCmpInst::FCMP_UNE || Predicate == FCmpInst::FCMP_ONE ||
             Predicate == FCmpInst::FCMP_ULT || Predicate == FCmpInst::FCMP_OLT ||
             Predicate == FCmpInst::FCMP_ULE || Predicate == FCmpInst::FCMP_OLE);
        break;
      case FCmpInst::FCMP_OGT: // We know that C1 > C2
        Result =
            (Predicate == FCmpInst::FCMP_UNE || Predicate == FCmpInst::FCMP_ONE ||
             Predicate == FCmpInst::FCMP_UGT || Predicate == FCmpInst::FCMP_OGT ||
             Predicate == FCmpInst::FCMP_UGE || Predicate == FCmpInst::FCMP_OGE);
        break;
      case FCmpInst::FCMP_OLE: // We know that C1 <= C2
        // We can only partially decide this relation.
        if (Predicate == FCmpInst::FCMP_UGT || Predicate == FCmpInst::FCMP_OGT)
          Result = 0;
        else if (Predicate == FCmpInst::FCMP_ULT ||
                 Predicate == FCmpInst::FCMP_OLT)
          Result = 1;
        break;
      case FCmpInst::FCMP_OGE: // We known that C1 >= C2
        // We can only partially decide this relation.
        if (Predicate == FCmpInst::FCMP_ULT || Predicate == FCmpInst::FCMP_OLT)
          Result = 0;
        else if (Predicate == FCmpInst::FCMP_UGT ||
                 Predicate == FCmpInst::FCMP_OGT)
          Result = 1;
        break;
      case FCmpInst::FCMP_ONE: // We know that C1 != C2
        // We can only partially decide this relation.
        if (Predicate == FCmpInst::FCMP_OEQ || Predicate == FCmpInst::FCMP_UEQ)
          Result = 0;
        else if (Predicate == FCmpInst::FCMP_ONE ||
                 Predicate == FCmpInst::FCMP_UNE)
          Result = 1;
        break;
      case FCmpInst::FCMP_UEQ: // We know that C1 == C2 || isUnordered(C1, C2).
        // We can only partially decide this relation.
        if (Predicate == FCmpInst::FCMP_ONE)
          Result = 0;
        else if (Predicate == FCmpInst::FCMP_UEQ)
          Result = 1;
        break;
      }
  
      // If we evaluated the result, return it now.
      if (Result != -1)
        return ConstantInt::get(ResultTy, Result);
  
    } else {
      // Evaluate the relation between the two constants, per the predicate.
      int Result = -1;  // -1 = unknown, 0 = known false, 1 = known true.
      switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(Predicate))) {
      default: llvm_unreachable("Unknown relational!");
      case ICmpInst::BAD_ICMP_PREDICATE:
        break;  // Couldn't determine anything about these constants.
      case ICmpInst::ICMP_EQ:   // We know the constants are equal!
        // If we know the constants are equal, we can decide the result of this
        // computation precisely.
        Result = ICmpInst::isTrueWhenEqual(Predicate);
        break;
      case ICmpInst::ICMP_ULT:
        switch (Predicate) {
        case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE:
          Result = 1; break;
        case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE:
          Result = 0; break;
        default:
          break;
        }
        break;
      case ICmpInst::ICMP_SLT:
        switch (Predicate) {
        case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE:
          Result = 1; break;
        case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE:
          Result = 0; break;
        default:
          break;
        }
        break;
      case ICmpInst::ICMP_UGT:
        switch (Predicate) {
        case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE:
          Result = 1; break;
        case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE:
          Result = 0; break;
        default:
          break;
        }
        break;
      case ICmpInst::ICMP_SGT:
        switch (Predicate) {
        case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE:
          Result = 1; break;
        case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE:
          Result = 0; break;
        default:
          break;
        }
        break;
      case ICmpInst::ICMP_ULE:
        if (Predicate == ICmpInst::ICMP_UGT)
          Result = 0;
        if (Predicate == ICmpInst::ICMP_ULT || Predicate == ICmpInst::ICMP_ULE)
          Result = 1;
        break;
      case ICmpInst::ICMP_SLE:
        if (Predicate == ICmpInst::ICMP_SGT)
          Result = 0;
        if (Predicate == ICmpInst::ICMP_SLT || Predicate == ICmpInst::ICMP_SLE)
          Result = 1;
        break;
      case ICmpInst::ICMP_UGE:
        if (Predicate == ICmpInst::ICMP_ULT)
          Result = 0;
        if (Predicate == ICmpInst::ICMP_UGT || Predicate == ICmpInst::ICMP_UGE)
          Result = 1;
        break;
      case ICmpInst::ICMP_SGE:
        if (Predicate == ICmpInst::ICMP_SLT)
          Result = 0;
        if (Predicate == ICmpInst::ICMP_SGT || Predicate == ICmpInst::ICMP_SGE)
          Result = 1;
        break;
      case ICmpInst::ICMP_NE:
        if (Predicate == ICmpInst::ICMP_EQ)
          Result = 0;
        if (Predicate == ICmpInst::ICMP_NE)
          Result = 1;
        break;
      }
  
      // If we evaluated the result, return it now.
      if (Result != -1)
        return ConstantInt::get(ResultTy, Result);
  
      // If the right hand side is a bitcast, try using its inverse to simplify
      // it by moving it to the left hand side.  We can't do this if it would turn
      // a vector compare into a scalar compare or visa versa, or if it would turn
      // the operands into FP values.
      if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) {
        Constant *CE2Op0 = CE2->getOperand(0);
        if (CE2->getOpcode() == Instruction::BitCast &&
            CE2->getType()->isVectorTy() == CE2Op0->getType()->isVectorTy() &&
            !CE2Op0->getType()->isFPOrFPVectorTy()) {
          Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType());
          return ConstantExpr::getICmp(Predicate, Inverse, CE2Op0);
        }
      }
  
      // If the left hand side is an extension, try eliminating it.
      if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
        if ((CE1->getOpcode() == Instruction::SExt &&
             ICmpInst::isSigned(Predicate)) ||
            (CE1->getOpcode() == Instruction::ZExt &&
             !ICmpInst::isSigned(Predicate))) {
          Constant *CE1Op0 = CE1->getOperand(0);
          Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType());
          if (CE1Inverse == CE1Op0) {
            // Check whether we can safely truncate the right hand side.
            Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType());
            if (ConstantExpr::getCast(CE1->getOpcode(), C2Inverse,
                                      C2->getType()) == C2)
              return ConstantExpr::getICmp(Predicate, CE1Inverse, C2Inverse);
          }
        }
      }
  
      if ((!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) ||
          (C1->isNullValue() && !C2->isNullValue())) {
        // If C2 is a constant expr and C1 isn't, flip them around and fold the
        // other way if possible.
        // Also, if C1 is null and C2 isn't, flip them around.
        Predicate = ICmpInst::getSwappedPredicate(Predicate);
        return ConstantExpr::getICmp(Predicate, C2, C1);
      }
    }
    return nullptr;
  }
  
  /// Test whether the given sequence of *normalized* indices is "inbounds".
  template<typename IndexTy>
  static bool isInBoundsIndices(ArrayRef<IndexTy> Idxs) {
    // No indices means nothing that could be out of bounds.
    if (Idxs.empty()) return true;
  
    // If the first index is zero, it's in bounds.
    if (cast<Constant>(Idxs[0])->isNullValue()) return true;
  
    // If the first index is one and all the rest are zero, it's in bounds,
    // by the one-past-the-end rule.
    if (auto *CI = dyn_cast<ConstantInt>(Idxs[0])) {
      if (!CI->isOne())
        return false;
    } else {
      auto *CV = cast<ConstantDataVector>(Idxs[0]);
      CI = dyn_cast_or_null<ConstantInt>(CV->getSplatValue());
      if (!CI || !CI->isOne())
        return false;
    }
  
    for (unsigned i = 1, e = Idxs.size(); i != e; ++i)
      if (!cast<Constant>(Idxs[i])->isNullValue())
        return false;
    return true;
  }
  
  /// Test whether a given ConstantInt is in-range for a SequentialType.
  static bool isIndexInRangeOfArrayType(uint64_t NumElements,
                                        const ConstantInt *CI) {
    // We cannot bounds check the index if it doesn't fit in an int64_t.
    if (CI->getValue().getMinSignedBits() > 64)
      return false;
  
    // A negative index or an index past the end of our sequential type is
    // considered out-of-range.
    int64_t IndexVal = CI->getSExtValue();
    if (IndexVal < 0 || (NumElements > 0 && (uint64_t)IndexVal >= NumElements))
      return false;
  
    // Otherwise, it is in-range.
    return true;
  }
  
  // Combine Indices - If the source pointer to this getelementptr instruction
  // is a getelementptr instruction, combine the indices of the two
  // getelementptr instructions into a single instruction.
  static Constant *foldGEPOfGEP(GEPOperator *GEP, Type *PointeeTy, bool InBounds,
                                ArrayRef<Value *> Idxs) {
    if (PointeeTy != GEP->getResultElementType())
      return nullptr;
  
    Constant *Idx0 = cast<Constant>(Idxs[0]);
    if (Idx0->isNullValue()) {
      // Handle the simple case of a zero index.
      SmallVector<Value*, 16> NewIndices;
      NewIndices.reserve(Idxs.size() + GEP->getNumIndices());
      NewIndices.append(GEP->idx_begin(), GEP->idx_end());
      NewIndices.append(Idxs.begin() + 1, Idxs.end());
      return ConstantExpr::getGetElementPtr(
          GEP->getSourceElementType(), cast<Constant>(GEP->getPointerOperand()),
          NewIndices, InBounds && GEP->isInBounds(), GEP->getInRangeIndex());
    }
  
    gep_type_iterator LastI = gep_type_end(GEP);
    for (gep_type_iterator I = gep_type_begin(GEP), E = gep_type_end(GEP);
         I != E; ++I)
      LastI = I;
  
    // We can't combine GEPs if the last index is a struct type.
    if (!LastI.isSequential())
      return nullptr;
    // We could perform the transform with non-constant index, but prefer leaving
    // it as GEP of GEP rather than GEP of add for now.
    ConstantInt *CI = dyn_cast<ConstantInt>(Idx0);
    if (!CI)
      return nullptr;
  
    // TODO: This code may be extended to handle vectors as well.
    auto *LastIdx = cast<Constant>(GEP->getOperand(GEP->getNumOperands()-1));
    Type *LastIdxTy = LastIdx->getType();
    if (LastIdxTy->isVectorTy())
      return nullptr;
  
    SmallVector<Value*, 16> NewIndices;
    NewIndices.reserve(Idxs.size() + GEP->getNumIndices());
    NewIndices.append(GEP->idx_begin(), GEP->idx_end() - 1);
  
    // Add the last index of the source with the first index of the new GEP.
    // Make sure to handle the case when they are actually different types.
    if (LastIdxTy != Idx0->getType()) {
      unsigned CommonExtendedWidth =
          std::max(LastIdxTy->getIntegerBitWidth(),
                   Idx0->getType()->getIntegerBitWidth());
      CommonExtendedWidth = std::max(CommonExtendedWidth, 64U);
  
      Type *CommonTy =
          Type::getIntNTy(LastIdxTy->getContext(), CommonExtendedWidth);
      Idx0 = ConstantExpr::getSExtOrBitCast(Idx0, CommonTy);
      LastIdx = ConstantExpr::getSExtOrBitCast(LastIdx, CommonTy);
    }
  
    NewIndices.push_back(ConstantExpr::get(Instruction::Add, Idx0, LastIdx));
    NewIndices.append(Idxs.begin() + 1, Idxs.end());
  
    // The combined GEP normally inherits its index inrange attribute from
    // the inner GEP, but if the inner GEP's last index was adjusted by the
    // outer GEP, any inbounds attribute on that index is invalidated.
    Optional<unsigned> IRIndex = GEP->getInRangeIndex();
    if (IRIndex && *IRIndex == GEP->getNumIndices() - 1)
      IRIndex = None;
  
    return ConstantExpr::getGetElementPtr(
        GEP->getSourceElementType(), cast<Constant>(GEP->getPointerOperand()),
        NewIndices, InBounds && GEP->isInBounds(), IRIndex);
  }
  
  Constant *llvm::ConstantFoldGetElementPtr(Type *PointeeTy, Constant *C,
                                            bool InBounds,
                                            Optional<unsigned> InRangeIndex,
                                            ArrayRef<Value *> Idxs) {
    if (Idxs.empty()) return C;
  
    Type *GEPTy = GetElementPtrInst::getGEPReturnType(
        PointeeTy, C, makeArrayRef((Value *const *)Idxs.data(), Idxs.size()));
  
    if (isa<PoisonValue>(C))
      return PoisonValue::get(GEPTy);
  
    if (isa<UndefValue>(C))
      // If inbounds, we can choose an out-of-bounds pointer as a base pointer.
      return InBounds ? PoisonValue::get(GEPTy) : UndefValue::get(GEPTy);
  
    Constant *Idx0 = cast<Constant>(Idxs[0]);
    if (Idxs.size() == 1 && (Idx0->isNullValue() || isa<UndefValue>(Idx0)))
      return GEPTy->isVectorTy() && !C->getType()->isVectorTy()
                 ? ConstantVector::getSplat(
                       cast<VectorType>(GEPTy)->getElementCount(), C)
                 : C;
  
    if (C->isNullValue()) {
      bool isNull = true;
      for (Value *Idx : Idxs)
        if (!isa<UndefValue>(Idx) && !cast<Constant>(Idx)->isNullValue()) {
          isNull = false;
          break;
        }
      if (isNull) {
        PointerType *PtrTy = cast<PointerType>(C->getType()->getScalarType());
        Type *Ty = GetElementPtrInst::getIndexedType(PointeeTy, Idxs);
  
        assert(Ty && "Invalid indices for GEP!");
        Type *OrigGEPTy = PointerType::get(Ty, PtrTy->getAddressSpace());
        Type *GEPTy = PointerType::get(Ty, PtrTy->getAddressSpace());
        if (VectorType *VT = dyn_cast<VectorType>(C->getType()))
          GEPTy = VectorType::get(OrigGEPTy, VT->getElementCount());
  
        // The GEP returns a vector of pointers when one of more of
        // its arguments is a vector.
        for (Value *Idx : Idxs) {
          if (auto *VT = dyn_cast<VectorType>(Idx->getType())) {
            assert((!isa<VectorType>(GEPTy) || isa<ScalableVectorType>(GEPTy) ==
                                                   isa<ScalableVectorType>(VT)) &&
                   "Mismatched GEPTy vector types");
            GEPTy = VectorType::get(OrigGEPTy, VT->getElementCount());
            break;
          }
        }
  
        return Constant::getNullValue(GEPTy);
      }
    }
  
    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
      if (auto *GEP = dyn_cast<GEPOperator>(CE))
        if (Constant *C = foldGEPOfGEP(GEP, PointeeTy, InBounds, Idxs))
          return C;
  
      // Attempt to fold casts to the same type away.  For example, folding:
      //
      //   i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*),
      //                       i64 0, i64 0)
      // into:
      //
      //   i32* getelementptr ([3 x i32]* %X, i64 0, i64 0)
      //
      // Don't fold if the cast is changing address spaces.
      if (CE->isCast() && Idxs.size() > 1 && Idx0->isNullValue()) {
        PointerType *SrcPtrTy =
          dyn_cast<PointerType>(CE->getOperand(0)->getType());
        PointerType *DstPtrTy = dyn_cast<PointerType>(CE->getType());
        if (SrcPtrTy && DstPtrTy && !SrcPtrTy->isOpaque() &&
            !DstPtrTy->isOpaque()) {
          ArrayType *SrcArrayTy =
            dyn_cast<ArrayType>(SrcPtrTy->getNonOpaquePointerElementType());
          ArrayType *DstArrayTy =
            dyn_cast<ArrayType>(DstPtrTy->getNonOpaquePointerElementType());
          if (SrcArrayTy && DstArrayTy
              && SrcArrayTy->getElementType() == DstArrayTy->getElementType()
              && SrcPtrTy->getAddressSpace() == DstPtrTy->getAddressSpace())
            return ConstantExpr::getGetElementPtr(SrcArrayTy,
                                                  (Constant *)CE->getOperand(0),
                                                  Idxs, InBounds, InRangeIndex);
        }
      }
    }
  
    // Check to see if any array indices are not within the corresponding
    // notional array or vector bounds. If so, try to determine if they can be
    // factored out into preceding dimensions.
    SmallVector<Constant *, 8> NewIdxs;
    Type *Ty = PointeeTy;
    Type *Prev = C->getType();
    auto GEPIter = gep_type_begin(PointeeTy, Idxs);
    bool Unknown =
        !isa<ConstantInt>(Idxs[0]) && !isa<ConstantDataVector>(Idxs[0]);
    for (unsigned i = 1, e = Idxs.size(); i != e;
         Prev = Ty, Ty = (++GEPIter).getIndexedType(), ++i) {
      if (!isa<ConstantInt>(Idxs[i]) && !isa<ConstantDataVector>(Idxs[i])) {
        // We don't know if it's in range or not.
        Unknown = true;
        continue;
      }
      if (!isa<ConstantInt>(Idxs[i - 1]) && !isa<ConstantDataVector>(Idxs[i - 1]))
        // Skip if the type of the previous index is not supported.
        continue;
      if (InRangeIndex && i == *InRangeIndex + 1) {
        // If an index is marked inrange, we cannot apply this canonicalization to
        // the following index, as that will cause the inrange index to point to
        // the wrong element.
        continue;
      }
      if (isa<StructType>(Ty)) {
        // The verify makes sure that GEPs into a struct are in range.
        continue;
      }
      if (isa<VectorType>(Ty)) {
        // There can be awkward padding in after a non-power of two vector.
        Unknown = true;
        continue;
      }
      auto *STy = cast<ArrayType>(Ty);
      if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) {
        if (isIndexInRangeOfArrayType(STy->getNumElements(), CI))
          // It's in range, skip to the next index.
          continue;
        if (CI->isNegative()) {
          // It's out of range and negative, don't try to factor it.
          Unknown = true;
          continue;
        }
      } else {
        auto *CV = cast<ConstantDataVector>(Idxs[i]);
        bool InRange = true;
        for (unsigned I = 0, E = CV->getNumElements(); I != E; ++I) {
          auto *CI = cast<ConstantInt>(CV->getElementAsConstant(I));
          InRange &= isIndexInRangeOfArrayType(STy->getNumElements(), CI);
          if (CI->isNegative()) {
            Unknown = true;
            break;
          }
        }
        if (InRange || Unknown)
          // It's in range, skip to the next index.
          // It's out of range and negative, don't try to factor it.
          continue;
      }
      if (isa<StructType>(Prev)) {
        // It's out of range, but the prior dimension is a struct
        // so we can't do anything about it.
        Unknown = true;
        continue;
      }
      // It's out of range, but we can factor it into the prior
      // dimension.
      NewIdxs.resize(Idxs.size());
      // Determine the number of elements in our sequential type.
      uint64_t NumElements = STy->getArrayNumElements();
  
      // Expand the current index or the previous index to a vector from a scalar
      // if necessary.
      Constant *CurrIdx = cast<Constant>(Idxs[i]);
      auto *PrevIdx =
          NewIdxs[i - 1] ? NewIdxs[i - 1] : cast<Constant>(Idxs[i - 1]);
      bool IsCurrIdxVector = CurrIdx->getType()->isVectorTy();
      bool IsPrevIdxVector = PrevIdx->getType()->isVectorTy();
      bool UseVector = IsCurrIdxVector || IsPrevIdxVector;
  
      if (!IsCurrIdxVector && IsPrevIdxVector)
        CurrIdx = ConstantDataVector::getSplat(
            cast<FixedVectorType>(PrevIdx->getType())->getNumElements(), CurrIdx);
  
      if (!IsPrevIdxVector && IsCurrIdxVector)
        PrevIdx = ConstantDataVector::getSplat(
            cast<FixedVectorType>(CurrIdx->getType())->getNumElements(), PrevIdx);
  
      Constant *Factor =
          ConstantInt::get(CurrIdx->getType()->getScalarType(), NumElements);
      if (UseVector)
        Factor = ConstantDataVector::getSplat(
            IsPrevIdxVector
                ? cast<FixedVectorType>(PrevIdx->getType())->getNumElements()
                : cast<FixedVectorType>(CurrIdx->getType())->getNumElements(),
            Factor);
  
      NewIdxs[i] = ConstantExpr::getSRem(CurrIdx, Factor);
  
      Constant *Div = ConstantExpr::getSDiv(CurrIdx, Factor);
  
      unsigned CommonExtendedWidth =
          std::max(PrevIdx->getType()->getScalarSizeInBits(),
                   Div->getType()->getScalarSizeInBits());
      CommonExtendedWidth = std::max(CommonExtendedWidth, 64U);
  
      // Before adding, extend both operands to i64 to avoid
      // overflow trouble.
      Type *ExtendedTy = Type::getIntNTy(Div->getContext(), CommonExtendedWidth);
      if (UseVector)
        ExtendedTy = FixedVectorType::get(
            ExtendedTy,
            IsPrevIdxVector
                ? cast<FixedVectorType>(PrevIdx->getType())->getNumElements()
                : cast<FixedVectorType>(CurrIdx->getType())->getNumElements());
  
      if (!PrevIdx->getType()->isIntOrIntVectorTy(CommonExtendedWidth))
        PrevIdx = ConstantExpr::getSExt(PrevIdx, ExtendedTy);
  
      if (!Div->getType()->isIntOrIntVectorTy(CommonExtendedWidth))
        Div = ConstantExpr::getSExt(Div, ExtendedTy);
  
      NewIdxs[i - 1] = ConstantExpr::getAdd(PrevIdx, Div);
    }
  
    // If we did any factoring, start over with the adjusted indices.
    if (!NewIdxs.empty()) {
      for (unsigned i = 0, e = Idxs.size(); i != e; ++i)
        if (!NewIdxs[i]) NewIdxs[i] = cast<Constant>(Idxs[i]);
      return ConstantExpr::getGetElementPtr(PointeeTy, C, NewIdxs, InBounds,
                                            InRangeIndex);
    }
  
    // If all indices are known integers and normalized, we can do a simple
    // check for the "inbounds" property.
    if (!Unknown && !InBounds)
      if (auto *GV = dyn_cast<GlobalVariable>(C))
        if (!GV->hasExternalWeakLinkage() && isInBoundsIndices(Idxs))
          return ConstantExpr::getGetElementPtr(PointeeTy, C, Idxs,
                                                /*InBounds=*/true, InRangeIndex);
  
    return nullptr;
  }
  