text: //===--- CGExprScalar.cpp - Emit LLVM Code for Scalar Exprs ---------------===//
  //
  // 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 contains code to emit Expr nodes with scalar LLVM types as LLVM code.
  //
  //===----------------------------------------------------------------------===//
  
  #include "CGCXXABI.h"
  #include "CGCleanup.h"
  #include "CGDebugInfo.h"
  #include "CGObjCRuntime.h"
  #include "CodeGenFunction.h"
  #include "CodeGenModule.h"
  #include "ConstantEmitter.h"
  #include "TargetInfo.h"
  #include "clang/AST/ASTContext.h"
  #include "clang/AST/DeclObjC.h"
  #include "clang/AST/Expr.h"
  #include "clang/AST/RecordLayout.h"
  #include "clang/AST/StmtVisitor.h"
  #include "clang/Basic/CodeGenOptions.h"
  #include "clang/Basic/FixedPoint.h"
  #include "clang/Basic/TargetInfo.h"
  #include "llvm/ADT/Optional.h"
  #include "llvm/IR/CFG.h"
  #include "llvm/IR/Constants.h"
  #include "llvm/IR/DataLayout.h"
  #include "llvm/IR/Function.h"
  #include "llvm/IR/GetElementPtrTypeIterator.h"
  #include "llvm/IR/GlobalVariable.h"
  #include "llvm/IR/Intrinsics.h"
  #include "llvm/IR/Module.h"
  #include <cstdarg>
  
  using namespace clang;
  using namespace CodeGen;
  using llvm::Value;
  
  //===----------------------------------------------------------------------===//
  //                         Scalar Expression Emitter
  //===----------------------------------------------------------------------===//
  
  namespace {
  
  /// Determine whether the given binary operation may overflow.
  /// Sets \p Result to the value of the operation for BO_Add, BO_Sub, BO_Mul,
  /// and signed BO_{Div,Rem}. For these opcodes, and for unsigned BO_{Div,Rem},
  /// the returned overflow check is precise. The returned value is 'true' for
  /// all other opcodes, to be conservative.
  bool mayHaveIntegerOverflow(llvm::ConstantInt *LHS, llvm::ConstantInt *RHS,
                               BinaryOperator::Opcode Opcode, bool Signed,
                               llvm::APInt &Result) {
    // Assume overflow is possible, unless we can prove otherwise.
    bool Overflow = true;
    const auto &LHSAP = LHS->getValue();
    const auto &RHSAP = RHS->getValue();
    if (Opcode == BO_Add) {
      if (Signed)
        Result = LHSAP.sadd_ov(RHSAP, Overflow);
      else
        Result = LHSAP.uadd_ov(RHSAP, Overflow);
    } else if (Opcode == BO_Sub) {
      if (Signed)
        Result = LHSAP.ssub_ov(RHSAP, Overflow);
      else
        Result = LHSAP.usub_ov(RHSAP, Overflow);
    } else if (Opcode == BO_Mul) {
      if (Signed)
        Result = LHSAP.smul_ov(RHSAP, Overflow);
      else
        Result = LHSAP.umul_ov(RHSAP, Overflow);
    } else if (Opcode == BO_Div || Opcode == BO_Rem) {
      if (Signed && !RHS->isZero())
        Result = LHSAP.sdiv_ov(RHSAP, Overflow);
      else
        return false;
    }
    return Overflow;
  }
  
  struct BinOpInfo {
    Value *LHS;
    Value *RHS;
    QualType Ty;  // Computation Type.
    BinaryOperator::Opcode Opcode; // Opcode of BinOp to perform
    FPOptions FPFeatures;
    const Expr *E;      // Entire expr, for error unsupported.  May not be binop.
  
    /// Check if the binop can result in integer overflow.
    bool mayHaveIntegerOverflow() const {
      // Without constant input, we can't rule out overflow.
      auto *LHSCI = dyn_cast<llvm::ConstantInt>(LHS);
      auto *RHSCI = dyn_cast<llvm::ConstantInt>(RHS);
      if (!LHSCI || !RHSCI)
        return true;
  
      llvm::APInt Result;
      return ::mayHaveIntegerOverflow(
          LHSCI, RHSCI, Opcode, Ty->hasSignedIntegerRepresentation(), Result);
    }
  
    /// Check if the binop computes a division or a remainder.
    bool isDivremOp() const {
      return Opcode == BO_Div || Opcode == BO_Rem || Opcode == BO_DivAssign ||
             Opcode == BO_RemAssign;
    }
  
    /// Check if the binop can result in an integer division by zero.
    bool mayHaveIntegerDivisionByZero() const {
      if (isDivremOp())
        if (auto *CI = dyn_cast<llvm::ConstantInt>(RHS))
          return CI->isZero();
      return true;
    }
  
    /// Check if the binop can result in a float division by zero.
    bool mayHaveFloatDivisionByZero() const {
      if (isDivremOp())
        if (auto *CFP = dyn_cast<llvm::ConstantFP>(RHS))
          return CFP->isZero();
      return true;
    }
  
    /// Check if either operand is a fixed point type or integer type, with at
    /// least one being a fixed point type. In any case, this
    /// operation did not follow usual arithmetic conversion and both operands may
    /// not be the same.
    bool isFixedPointBinOp() const {
      // We cannot simply check the result type since comparison operations return
      // an int.
      if (const auto *BinOp = dyn_cast<BinaryOperator>(E)) {
        QualType LHSType = BinOp->getLHS()->getType();
        QualType RHSType = BinOp->getRHS()->getType();
        return LHSType->isFixedPointType() || RHSType->isFixedPointType();
      }
      return false;
    }
  };
  
  static bool MustVisitNullValue(const Expr *E) {
    // If a null pointer expression's type is the C++0x nullptr_t, then
    // it's not necessarily a simple constant and it must be evaluated
    // for its potential side effects.
    return E->getType()->isNullPtrType();
  }
  
  /// If \p E is a widened promoted integer, get its base (unpromoted) type.
  static llvm::Optional<QualType> getUnwidenedIntegerType(const ASTContext &Ctx,
                                                          const Expr *E) {
    const Expr *Base = E->IgnoreImpCasts();
    if (E == Base)
      return llvm::None;
  
    QualType BaseTy = Base->getType();
    if (!BaseTy->isPromotableIntegerType() ||
        Ctx.getTypeSize(BaseTy) >= Ctx.getTypeSize(E->getType()))
      return llvm::None;
  
    return BaseTy;
  }
  
  /// Check if \p E is a widened promoted integer.
  static bool IsWidenedIntegerOp(const ASTContext &Ctx, const Expr *E) {
    return getUnwidenedIntegerType(Ctx, E).hasValue();
  }
  
  /// Check if we can skip the overflow check for \p Op.
  static bool CanElideOverflowCheck(const ASTContext &Ctx, const BinOpInfo &Op) {
    assert((isa<UnaryOperator>(Op.E) || isa<BinaryOperator>(Op.E)) &&
           "Expected a unary or binary operator");
  
    // If the binop has constant inputs and we can prove there is no overflow,
    // we can elide the overflow check.
    if (!Op.mayHaveIntegerOverflow())
      return true;
  
    // If a unary op has a widened operand, the op cannot overflow.
    if (const auto *UO = dyn_cast<UnaryOperator>(Op.E))
      return !UO->canOverflow();
  
    // We usually don't need overflow checks for binops with widened operands.
    // Multiplication with promoted unsigned operands is a special case.
    const auto *BO = cast<BinaryOperator>(Op.E);
    auto OptionalLHSTy = getUnwidenedIntegerType(Ctx, BO->getLHS());
    if (!OptionalLHSTy)
      return false;
  
    auto OptionalRHSTy = getUnwidenedIntegerType(Ctx, BO->getRHS());
    if (!OptionalRHSTy)
      return false;
  
    QualType LHSTy = *OptionalLHSTy;
    QualType RHSTy = *OptionalRHSTy;
  
    // This is the simple case: binops without unsigned multiplication, and with
    // widened operands. No overflow check is needed here.
    if ((Op.Opcode != BO_Mul && Op.Opcode != BO_MulAssign) ||
        !LHSTy->isUnsignedIntegerType() || !RHSTy->isUnsignedIntegerType())
      return true;
  
    // For unsigned multiplication the overflow check can be elided if either one
    // of the unpromoted types are less than half the size of the promoted type.
    unsigned PromotedSize = Ctx.getTypeSize(Op.E->getType());
    return (2 * Ctx.getTypeSize(LHSTy)) < PromotedSize ||
           (2 * Ctx.getTypeSize(RHSTy)) < PromotedSize;
  }
  
  /// Update the FastMathFlags of LLVM IR from the FPOptions in LangOptions.
  static void updateFastMathFlags(llvm::FastMathFlags &FMF,
                                  FPOptions FPFeatures) {
    FMF.setAllowContract(FPFeatures.allowFPContractAcrossStatement());
  }
  
  /// Propagate fast-math flags from \p Op to the instruction in \p V.
  static Value *propagateFMFlags(Value *V, const BinOpInfo &Op) {
    if (auto *I = dyn_cast<llvm::Instruction>(V)) {
      llvm::FastMathFlags FMF = I->getFastMathFlags();
      updateFastMathFlags(FMF, Op.FPFeatures);
      I->setFastMathFlags(FMF);
    }
    return V;
  }
  
  class ScalarExprEmitter
    : public StmtVisitor<ScalarExprEmitter, Value*> {
    CodeGenFunction &CGF;
    CGBuilderTy &Builder;
    bool IgnoreResultAssign;
    llvm::LLVMContext &VMContext;
  public:
  
    ScalarExprEmitter(CodeGenFunction &cgf, bool ira=false)
      : CGF(cgf), Builder(CGF.Builder), IgnoreResultAssign(ira),
        VMContext(cgf.getLLVMContext()) {
    }
  
    //===--------------------------------------------------------------------===//
    //                               Utilities
    //===--------------------------------------------------------------------===//
  
    bool TestAndClearIgnoreResultAssign() {
      bool I = IgnoreResultAssign;
      IgnoreResultAssign = false;
      return I;
    }
  
    llvm::Type *ConvertType(QualType T) { return CGF.ConvertType(T); }
    LValue EmitLValue(const Expr *E) { return CGF.EmitLValue(E); }
    LValue EmitCheckedLValue(const Expr *E, CodeGenFunction::TypeCheckKind TCK) {
      return CGF.EmitCheckedLValue(E, TCK);
    }
  
    void EmitBinOpCheck(ArrayRef<std::pair<Value *, SanitizerMask>> Checks,
                        const BinOpInfo &Info);
  
    Value *EmitLoadOfLValue(LValue LV, SourceLocation Loc) {
      return CGF.EmitLoadOfLValue(LV, Loc).getScalarVal();
    }
  
    void EmitLValueAlignmentAssumption(const Expr *E, Value *V) {
      const AlignValueAttr *AVAttr = nullptr;
      if (const auto *DRE = dyn_cast<DeclRefExpr>(E)) {
        const ValueDecl *VD = DRE->getDecl();
  
        if (VD->getType()->isReferenceType()) {
          if (const auto *TTy =
              dyn_cast<TypedefType>(VD->getType().getNonReferenceType()))
            AVAttr = TTy->getDecl()->getAttr<AlignValueAttr>();
        } else {
          // Assumptions for function parameters are emitted at the start of the
          // function, so there is no need to repeat that here,
          // unless the alignment-assumption sanitizer is enabled,
          // then we prefer the assumption over alignment attribute
          // on IR function param.
          if (isa<ParmVarDecl>(VD) && !CGF.SanOpts.has(SanitizerKind::Alignment))
            return;
  
          AVAttr = VD->getAttr<AlignValueAttr>();
        }
      }
  
      if (!AVAttr)
        if (const auto *TTy =
            dyn_cast<TypedefType>(E->getType()))
          AVAttr = TTy->getDecl()->getAttr<AlignValueAttr>();
  
      if (!AVAttr)
        return;
  
      Value *AlignmentValue = CGF.EmitScalarExpr(AVAttr->getAlignment());
      llvm::ConstantInt *AlignmentCI = cast<llvm::ConstantInt>(AlignmentValue);
      CGF.EmitAlignmentAssumption(V, E, AVAttr->getLocation(),
                                  AlignmentCI->getZExtValue());
    }
  
    /// EmitLoadOfLValue - Given an expression with complex type that represents a
    /// value l-value, this method emits the address of the l-value, then loads
    /// and returns the result.
    Value *EmitLoadOfLValue(const Expr *E) {
      Value *V = EmitLoadOfLValue(EmitCheckedLValue(E, CodeGenFunction::TCK_Load),
                                  E->getExprLoc());
  
      EmitLValueAlignmentAssumption(E, V);
      return V;
    }
  
    /// EmitConversionToBool - Convert the specified expression value to a
    /// boolean (i1) truth value.  This is equivalent to "Val != 0".
    Value *EmitConversionToBool(Value *Src, QualType DstTy);
  
    /// Emit a check that a conversion from a floating-point type does not
    /// overflow.
    void EmitFloatConversionCheck(Value *OrigSrc, QualType OrigSrcType,
                                  Value *Src, QualType SrcType, QualType DstType,
                                  llvm::Type *DstTy, SourceLocation Loc);
  
    /// Known implicit conversion check kinds.
    /// Keep in sync with the enum of the same name in ubsan_handlers.h
    enum ImplicitConversionCheckKind : unsigned char {
      ICCK_IntegerTruncation = 0, // Legacy, was only used by clang 7.
      ICCK_UnsignedIntegerTruncation = 1,
      ICCK_SignedIntegerTruncation = 2,
      ICCK_IntegerSignChange = 3,
      ICCK_SignedIntegerTruncationOrSignChange = 4,
    };
  
    /// Emit a check that an [implicit] truncation of an integer  does not
    /// discard any bits. It is not UB, so we use the value after truncation.
    void EmitIntegerTruncationCheck(Value *Src, QualType SrcType, Value *Dst,
                                    QualType DstType, SourceLocation Loc);
  
    /// Emit a check that an [implicit] conversion of an integer does not change
    /// the sign of the value. It is not UB, so we use the value after conversion.
    /// NOTE: Src and Dst may be the exact same value! (point to the same thing)
    void EmitIntegerSignChangeCheck(Value *Src, QualType SrcType, Value *Dst,
                                    QualType DstType, SourceLocation Loc);
  
    /// Emit a conversion from the specified type to the specified destination
    /// type, both of which are LLVM scalar types.
    struct ScalarConversionOpts {
      bool TreatBooleanAsSigned;
      bool EmitImplicitIntegerTruncationChecks;
      bool EmitImplicitIntegerSignChangeChecks;
  
      ScalarConversionOpts()
          : TreatBooleanAsSigned(false),
            EmitImplicitIntegerTruncationChecks(false),
            EmitImplicitIntegerSignChangeChecks(false) {}
  
      ScalarConversionOpts(clang::SanitizerSet SanOpts)
          : TreatBooleanAsSigned(false),
            EmitImplicitIntegerTruncationChecks(
                SanOpts.hasOneOf(SanitizerKind::ImplicitIntegerTruncation)),
            EmitImplicitIntegerSignChangeChecks(
                SanOpts.has(SanitizerKind::ImplicitIntegerSignChange)) {}
    };
    Value *
    EmitScalarConversion(Value *Src, QualType SrcTy, QualType DstTy,
                         SourceLocation Loc,
                         ScalarConversionOpts Opts = ScalarConversionOpts());
  
    /// Convert between either a fixed point and other fixed point or fixed point
    /// and an integer.
    Value *EmitFixedPointConversion(Value *Src, QualType SrcTy, QualType DstTy,
                                    SourceLocation Loc);
    Value *EmitFixedPointConversion(Value *Src, FixedPointSemantics &SrcFixedSema,
                                    FixedPointSemantics &DstFixedSema,
                                    SourceLocation Loc,
                                    bool DstIsInteger = false);
  
    /// Emit a conversion from the specified complex type to the specified
    /// destination type, where the destination type is an LLVM scalar type.
    Value *EmitComplexToScalarConversion(CodeGenFunction::ComplexPairTy Src,
                                         QualType SrcTy, QualType DstTy,
                                         SourceLocation Loc);
  
    /// EmitNullValue - Emit a value that corresponds to null for the given type.
    Value *EmitNullValue(QualType Ty);
  
    /// EmitFloatToBoolConversion - Perform an FP to boolean conversion.
    Value *EmitFloatToBoolConversion(Value *V) {
      // Compare against 0.0 for fp scalars.
      llvm::Value *Zero = llvm::Constant::getNullValue(V->getType());
      return Builder.CreateFCmpUNE(V, Zero, "tobool");
    }
  
    /// EmitPointerToBoolConversion - Perform a pointer to boolean conversion.
    Value *EmitPointerToBoolConversion(Value *V, QualType QT) {
      Value *Zero = CGF.CGM.getNullPointer(cast<llvm::PointerType>(V->getType()), QT);
  
      return Builder.CreateICmpNE(V, Zero, "tobool");
    }
  
    Value *EmitIntToBoolConversion(Value *V) {
      // Because of the type rules of C, we often end up computing a
      // logical value, then zero extending it to int, then wanting it
      // as a logical value again.  Optimize this common case.
      if (llvm::ZExtInst *ZI = dyn_cast<llvm::ZExtInst>(V)) {
        if (ZI->getOperand(0)->getType() == Builder.getInt1Ty()) {
          Value *Result = ZI->getOperand(0);
          // If there aren't any more uses, zap the instruction to save space.
          // Note that there can be more uses, for example if this
          // is the result of an assignment.
          if (ZI->use_empty())
            ZI->eraseFromParent();
          return Result;
        }
      }
  
      return Builder.CreateIsNotNull(V, "tobool");
    }
  
    //===--------------------------------------------------------------------===//
    //                            Visitor Methods
    //===--------------------------------------------------------------------===//
  
    Value *Visit(Expr *E) {
      if (getenv("DBG_CG_SCALAR_EXPR")) {
        llvm::errs() << "Expr: "; E->dump();
      }
      ApplyDebugLocation DL(CGF, E);
      auto Res = StmtVisitor<ScalarExprEmitter, Value*>::Visit(E);
      if (getenv("DBG_CG_SCALAR_EXPR")) {
        llvm::errs() << " => " << *Res << '\n';
      }
      return Res;
    }
  
    Value *VisitStmt(Stmt *S) {
      S->dump(CGF.getContext().getSourceManager());
      llvm_unreachable("Stmt can't have complex result type!");
    }
    Value *VisitExpr(Expr *S);
  
    Value *VisitConstantExpr(ConstantExpr *E) {
      return Visit(E->getSubExpr());
    }
    Value *VisitParenExpr(ParenExpr *PE) {
      return Visit(PE->getSubExpr());
    }
    Value *VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *E) {
      return Visit(E->getReplacement());
    }
    Value *VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
      return Visit(GE->getResultExpr());
    }
    Value *VisitCoawaitExpr(CoawaitExpr *S) {
      return CGF.EmitCoawaitExpr(*S).getScalarVal();
    }
    Value *VisitCoyieldExpr(CoyieldExpr *S) {
      return CGF.EmitCoyieldExpr(*S).getScalarVal();
    }
    Value *VisitUnaryCoawait(const UnaryOperator *E) {
      return Visit(E->getSubExpr());
    }
  
    // Leaves.
    Value *VisitIntegerLiteral(const IntegerLiteral *E) {
      return Builder.getInt(E->getValue());
    }
    Value *VisitFixedPointLiteral(const FixedPointLiteral *E) {
      return Builder.getInt(E->getValue());
    }
    Value *VisitFloatingLiteral(const FloatingLiteral *E) {
      return llvm::ConstantFP::get(VMContext, E->getValue());
    }
    Value *VisitCharacterLiteral(const CharacterLiteral *E) {
      return llvm::ConstantInt::get(ConvertType(E->getType()), E->getValue());
    }
    Value *VisitObjCBoolLiteralExpr(const ObjCBoolLiteralExpr *E) {
      return llvm::ConstantInt::get(ConvertType(E->getType()), E->getValue());
    }
    Value *VisitCXXBoolLiteralExpr(const CXXBoolLiteralExpr *E) {
      return llvm::ConstantInt::get(ConvertType(E->getType()), E->getValue());
    }
    Value *VisitCXXScalarValueInitExpr(const CXXScalarValueInitExpr *E) {
      return EmitNullValue(E->getType());
    }
    Value *VisitGNUNullExpr(const GNUNullExpr *E) {
      return EmitNullValue(E->getType());
    }
    Value *VisitOffsetOfExpr(OffsetOfExpr *E);
    Value *VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *E);
    Value *VisitAddrLabelExpr(const AddrLabelExpr *E) {
      llvm::Value *V = CGF.GetAddrOfLabel(E->getLabel());
      return Builder.CreateBitCast(V, ConvertType(E->getType()));
    }
  
    Value *VisitSizeOfPackExpr(SizeOfPackExpr *E) {
      return llvm::ConstantInt::get(ConvertType(E->getType()),E->getPackLength());
    }
  
    Value *VisitPseudoObjectExpr(PseudoObjectExpr *E) {
      return CGF.EmitPseudoObjectRValue(E).getScalarVal();
    }
  
    Value *VisitOpaqueValueExpr(OpaqueValueExpr *E) {
      if (E->isGLValue())
        return EmitLoadOfLValue(CGF.getOrCreateOpaqueLValueMapping(E),
                                E->getExprLoc());
  
      // Otherwise, assume the mapping is the scalar directly.
      return CGF.getOrCreateOpaqueRValueMapping(E).getScalarVal();
    }
  
    // l-values.
    Value *VisitDeclRefExpr(DeclRefExpr *E) {
      if (CodeGenFunction::ConstantEmission Constant = CGF.tryEmitAsConstant(E))
        return CGF.emitScalarConstant(Constant, E);
      return EmitLoadOfLValue(E);
    }
  
    Value *VisitObjCSelectorExpr(ObjCSelectorExpr *E) {
      return CGF.EmitObjCSelectorExpr(E);
    }
    Value *VisitObjCProtocolExpr(ObjCProtocolExpr *E) {
      return CGF.EmitObjCProtocolExpr(E);
    }
    Value *VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
      return EmitLoadOfLValue(E);
    }
    Value *VisitObjCMessageExpr(ObjCMessageExpr *E) {
      if (E->getMethodDecl() &&
          E->getMethodDecl()->getReturnType()->isReferenceType())
        return EmitLoadOfLValue(E);
      return CGF.EmitObjCMessageExpr(E).getScalarVal();
    }
  
    Value *VisitObjCIsaExpr(ObjCIsaExpr *E) {
      LValue LV = CGF.EmitObjCIsaExpr(E);
      Value *V = CGF.EmitLoadOfLValue(LV, E->getExprLoc()).getScalarVal();
      return V;
    }
  
    Value *VisitObjCAvailabilityCheckExpr(ObjCAvailabilityCheckExpr *E) {
      VersionTuple Version = E->getVersion();
  
      // If we're checking for a platform older than our minimum deployment
      // target, we can fold the check away.
      if (Version <= CGF.CGM.getTarget().getPlatformMinVersion())
        return llvm::ConstantInt::get(Builder.getInt1Ty(), 1);
  
      Optional<unsigned> Min = Version.getMinor(), SMin = Version.getSubminor();
      llvm::Value *Args[] = {
          llvm::ConstantInt::get(CGF.CGM.Int32Ty, Version.getMajor()),
          llvm::ConstantInt::get(CGF.CGM.Int32Ty, Min ? *Min : 0),
          llvm::ConstantInt::get(CGF.CGM.Int32Ty, SMin ? *SMin : 0),
      };
  
      return CGF.EmitBuiltinAvailable(Args);
    }
  
    Value *VisitArraySubscriptExpr(ArraySubscriptExpr *E);
    Value *VisitShuffleVectorExpr(ShuffleVectorExpr *E);
    Value *VisitConvertVectorExpr(ConvertVectorExpr *E);
    Value *VisitMemberExpr(MemberExpr *E);
    Value *VisitExtVectorElementExpr(Expr *E) { return EmitLoadOfLValue(E); }
    Value *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
      return EmitLoadOfLValue(E);
    }
  
    Value *VisitInitListExpr(InitListExpr *E);
  
    Value *VisitArrayInitIndexExpr(ArrayInitIndexExpr *E) {
      assert(CGF.getArrayInitIndex() &&
             "ArrayInitIndexExpr not inside an ArrayInitLoopExpr?");
      return CGF.getArrayInitIndex();
    }
  
    Value *VisitImplicitValueInitExpr(const ImplicitValueInitExpr *E) {
      return EmitNullValue(E->getType());
    }
    Value *VisitExplicitCastExpr(ExplicitCastExpr *E) {
      CGF.CGM.EmitExplicitCastExprType(E, &CGF);
      return VisitCastExpr(E);
    }
    Value *VisitCastExpr(CastExpr *E);
  
    Value *VisitCallExpr(const CallExpr *E) {
      if (E->getCallReturnType(CGF.getContext())->isReferenceType())
        return EmitLoadOfLValue(E);
  
      Value *V = CGF.EmitCallExpr(E).getScalarVal();
  
      EmitLValueAlignmentAssumption(E, V);
      return V;
    }
  
    Value *VisitStmtExpr(const StmtExpr *E);
  
    // Unary Operators.
    Value *VisitUnaryPostDec(const UnaryOperator *E) {
      LValue LV = EmitLValue(E->getSubExpr());
      return EmitScalarPrePostIncDec(E, LV, false, false);
    }
    Value *VisitUnaryPostInc(const UnaryOperator *E) {
      LValue LV = EmitLValue(E->getSubExpr());
      return EmitScalarPrePostIncDec(E, LV, true, false);
    }
    Value *VisitUnaryPreDec(const UnaryOperator *E) {
      LValue LV = EmitLValue(E->getSubExpr());
      return EmitScalarPrePostIncDec(E, LV, false, true);
    }
    Value *VisitUnaryPreInc(const UnaryOperator *E) {
      LValue LV = EmitLValue(E->getSubExpr());
      return EmitScalarPrePostIncDec(E, LV, true, true);
    }
  
    llvm::Value *EmitIncDecConsiderOverflowBehavior(const UnaryOperator *E,
                                                    llvm::Value *InVal,
                                                    bool IsInc);
  
    llvm::Value *EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
                                         bool isInc, bool isPre);
  
  
    Value *VisitUnaryAddrOf(const UnaryOperator *E) {
      if (isa<MemberPointerType>(E->getType())) // never sugared
        return CGF.CGM.getMemberPointerConstant(E);
  
      return EmitLValue(E->getSubExpr()).getPointer();
    }
    Value *VisitUnaryDeref(const UnaryOperator *E) {
      if (E->getType()->isVoidType())
        return Visit(E->getSubExpr()); // the actual value should be unused
      return EmitLoadOfLValue(E);
    }
    Value *VisitUnaryPlus(const UnaryOperator *E) {
      // This differs from gcc, though, most likely due to a bug in gcc.
      TestAndClearIgnoreResultAssign();
      return Visit(E->getSubExpr());
    }
    Value *VisitUnaryMinus    (const UnaryOperator *E);
    Value *VisitUnaryNot      (const UnaryOperator *E);
    Value *VisitUnaryLNot     (const UnaryOperator *E);
    Value *VisitUnaryReal     (const UnaryOperator *E);
    Value *VisitUnaryImag     (const UnaryOperator *E);
    Value *VisitUnaryExtension(const UnaryOperator *E) {
      return Visit(E->getSubExpr());
    }
  
    // C++
    Value *VisitMaterializeTemporaryExpr(const MaterializeTemporaryExpr *E) {
      return EmitLoadOfLValue(E);
    }
    Value *VisitSourceLocExpr(SourceLocExpr *SLE) {
      auto &Ctx = CGF.getContext();
      APValue Evaluated =
          SLE->EvaluateInContext(Ctx, CGF.CurSourceLocExprScope.getDefaultExpr());
      return ConstantEmitter(CGF.CGM, &CGF)
          .emitAbstract(SLE->getLocation(), Evaluated, SLE->getType());
    }
  
    Value *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
      CodeGenFunction::CXXDefaultArgExprScope Scope(CGF, DAE);
      return Visit(DAE->getExpr());
    }
    Value *VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE) {
      CodeGenFunction::CXXDefaultInitExprScope Scope(CGF, DIE);
      return Visit(DIE->getExpr());
    }
    Value *VisitCXXThisExpr(CXXThisExpr *TE) {
      return CGF.LoadCXXThis();
    }
  
    Value *VisitExprWithCleanups(ExprWithCleanups *E);
    Value *VisitCXXNewExpr(const CXXNewExpr *E) {
      return CGF.EmitCXXNewExpr(E);
    }
    Value *VisitCXXDeleteExpr(const CXXDeleteExpr *E) {
      CGF.EmitCXXDeleteExpr(E);
      return nullptr;
    }
  
    Value *VisitTypeTraitExpr(const TypeTraitExpr *E) {
      return llvm::ConstantInt::get(ConvertType(E->getType()), E->getValue());
    }
  
    Value *VisitArrayTypeTraitExpr(const ArrayTypeTraitExpr *E) {
      return llvm::ConstantInt::get(Builder.getInt32Ty(), E->getValue());
    }
  
    Value *VisitExpressionTraitExpr(const ExpressionTraitExpr *E) {
      return llvm::ConstantInt::get(Builder.getInt1Ty(), E->getValue());
    }
  
    Value *VisitCXXPseudoDestructorExpr(const CXXPseudoDestructorExpr *E) {
      // C++ [expr.pseudo]p1:
      //   The result shall only be used as the operand for the function call
      //   operator (), and the result of such a call has type void. The only
      //   effect is the evaluation of the postfix-expression before the dot or
      //   arrow.
      CGF.EmitScalarExpr(E->getBase());
      return nullptr;
    }
  
    Value *VisitCXXNullPtrLiteralExpr(const CXXNullPtrLiteralExpr *E) {
      return EmitNullValue(E->getType());
    }
  
    Value *VisitCXXThrowExpr(const CXXThrowExpr *E) {
      CGF.EmitCXXThrowExpr(E);
      return nullptr;
    }
  
    Value *VisitCXXNoexceptExpr(const CXXNoexceptExpr *E) {
      return Builder.getInt1(E->getValue());
    }
  
    // Binary Operators.
    Value *EmitMul(const BinOpInfo &Ops) {
      if (Ops.Ty->isSignedIntegerOrEnumerationType()) {
        switch (CGF.getLangOpts().getSignedOverflowBehavior()) {
        case LangOptions::SOB_Defined:
          return Builder.CreateMul(Ops.LHS, Ops.RHS, "mul");
        case LangOptions::SOB_Undefined:
          if (!CGF.SanOpts.has(SanitizerKind::SignedIntegerOverflow))
            return Builder.CreateNSWMul(Ops.LHS, Ops.RHS, "mul");
          LLVM_FALLTHROUGH;
        case LangOptions::SOB_Trapping:
          if (CanElideOverflowCheck(CGF.getContext(), Ops))
            return Builder.CreateNSWMul(Ops.LHS, Ops.RHS, "mul");
          return EmitOverflowCheckedBinOp(Ops);
        }
      }
  
      if (Ops.Ty->isUnsignedIntegerType() &&
          CGF.SanOpts.has(SanitizerKind::UnsignedIntegerOverflow) &&
          !CanElideOverflowCheck(CGF.getContext(), Ops))
        return EmitOverflowCheckedBinOp(Ops);
  
      if (Ops.LHS->getType()->isFPOrFPVectorTy()) {
        Value *V = Builder.CreateFMul(Ops.LHS, Ops.RHS, "mul");
        return propagateFMFlags(V, Ops);
      }
      return Builder.CreateMul(Ops.LHS, Ops.RHS, "mul");
    }
    /// Create a binary op that checks for overflow.
    /// Currently only supports +, - and *.
    Value *EmitOverflowCheckedBinOp(const BinOpInfo &Ops);
  
    // Check for undefined division and modulus behaviors.
    void EmitUndefinedBehaviorIntegerDivAndRemCheck(const BinOpInfo &Ops,
                                                    llvm::Value *Zero,bool isDiv);
    // Common helper for getting how wide LHS of shift is.
    static Value *GetWidthMinusOneValue(Value* LHS,Value* RHS);
    Value *EmitDiv(const BinOpInfo &Ops);
    Value *EmitRem(const BinOpInfo &Ops);
    Value *EmitAdd(const BinOpInfo &Ops);
    Value *EmitSub(const BinOpInfo &Ops);
    Value *EmitShl(const BinOpInfo &Ops);
    Value *EmitShr(const BinOpInfo &Ops);
    Value *EmitAnd(const BinOpInfo &Ops) {
      return Builder.CreateAnd(Ops.LHS, Ops.RHS, "and");
    }
    Value *EmitXor(const BinOpInfo &Ops) {
      return Builder.CreateXor(Ops.LHS, Ops.RHS, "xor");
    }
    Value *EmitOr (const BinOpInfo &Ops) {
      return Builder.CreateOr(Ops.LHS, Ops.RHS, "or");
    }
  
    // Helper functions for fixed point binary operations.
    Value *EmitFixedPointBinOp(const BinOpInfo &Ops);
  
    BinOpInfo EmitBinOps(const BinaryOperator *E);
    LValue EmitCompoundAssignLValue(const CompoundAssignOperator *E,
                              Value *(ScalarExprEmitter::*F)(const BinOpInfo &),
                                    Value *&Result);
  
    Value *EmitCompoundAssign(const CompoundAssignOperator *E,
                              Value *(ScalarExprEmitter::*F)(const BinOpInfo &));
  
    // Binary operators and binary compound assignment operators.
  #define HANDLEBINOP(OP) \
    Value *VisitBin ## OP(const BinaryOperator *E) {                         \
      return Emit ## OP(EmitBinOps(E));                                      \
    }                                                                        \
    Value *VisitBin ## OP ## Assign(const CompoundAssignOperator *E) {       \
      return EmitCompoundAssign(E, &ScalarExprEmitter::Emit ## OP);          \
    }
    HANDLEBINOP(Mul)
    HANDLEBINOP(Div)
    HANDLEBINOP(Rem)
    HANDLEBINOP(Add)
    HANDLEBINOP(Sub)
    HANDLEBINOP(Shl)
    HANDLEBINOP(Shr)
    HANDLEBINOP(And)
    HANDLEBINOP(Xor)
    HANDLEBINOP(Or)
  #undef HANDLEBINOP
  
    // Comparisons.
    Value *EmitCompare(const BinaryOperator *E, llvm::CmpInst::Predicate UICmpOpc,
                       llvm::CmpInst::Predicate SICmpOpc,
                       llvm::CmpInst::Predicate FCmpOpc);
  #define VISITCOMP(CODE, UI, SI, FP) \
      Value *VisitBin##CODE(const BinaryOperator *E) { \
        return EmitCompare(E, llvm::ICmpInst::UI, llvm::ICmpInst::SI, \
                           llvm::FCmpInst::FP); }
    VISITCOMP(LT, ICMP_ULT, ICMP_SLT, FCMP_OLT)
    VISITCOMP(GT, ICMP_UGT, ICMP_SGT, FCMP_OGT)
    VISITCOMP(LE, ICMP_ULE, ICMP_SLE, FCMP_OLE)
    VISITCOMP(GE, ICMP_UGE, ICMP_SGE, FCMP_OGE)
    VISITCOMP(EQ, ICMP_EQ , ICMP_EQ , FCMP_OEQ)
    VISITCOMP(NE, ICMP_NE , ICMP_NE , FCMP_UNE)
  #undef VISITCOMP
  
    Value *VisitBinAssign     (const BinaryOperator *E);
  
    Value *VisitBinLAnd       (const BinaryOperator *E);
    Value *VisitBinLOr        (const BinaryOperator *E);
    Value *VisitBinComma      (const BinaryOperator *E);
  
    Value *VisitBinPtrMemD(const Expr *E) { return EmitLoadOfLValue(E); }
    Value *VisitBinPtrMemI(const Expr *E) { return EmitLoadOfLValue(E); }
  
    // Other Operators.
    Value *VisitBlockExpr(const BlockExpr *BE);
    Value *VisitAbstractConditionalOperator(const AbstractConditionalOperator *);
    Value *VisitChooseExpr(ChooseExpr *CE);
    Value *VisitVAArgExpr(VAArgExpr *VE);
    Value *VisitObjCStringLiteral(const ObjCStringLiteral *E) {
      return CGF.EmitObjCStringLiteral(E);
    }
    Value *VisitObjCBoxedExpr(ObjCBoxedExpr *E) {
      return CGF.EmitObjCBoxedExpr(E);
    }
    Value *VisitObjCArrayLiteral(ObjCArrayLiteral *E) {
      return CGF.EmitObjCArrayLiteral(E);
    }
    Value *VisitObjCDictionaryLiteral(ObjCDictionaryLiteral *E) {
      return CGF.EmitObjCDictionaryLiteral(E);
    }
    Value *VisitAsTypeExpr(AsTypeExpr *CE);
    Value *VisitAtomicExpr(AtomicExpr *AE);
  };
  }  // end anonymous namespace.
  
  //===----------------------------------------------------------------------===//
  //                                Utilities
  //===----------------------------------------------------------------------===//
  
  /// EmitConversionToBool - Convert the specified expression value to a
  /// boolean (i1) truth value.  This is equivalent to "Val != 0".
  Value *ScalarExprEmitter::EmitConversionToBool(Value *Src, QualType SrcType) {
    assert(SrcType.isCanonical() && "EmitScalarConversion strips typedefs");
  
    if (SrcType->isRealFloatingType())
      return EmitFloatToBoolConversion(Src);
  
    if (const MemberPointerType *MPT = dyn_cast<MemberPointerType>(SrcType))
      return CGF.CGM.getCXXABI().EmitMemberPointerIsNotNull(CGF, Src, MPT);
  
    assert((SrcType->isIntegerType() || isa<llvm::PointerType>(Src->getType())) &&
           "Unknown scalar type to convert");
  
    if (isa<llvm::IntegerType>(Src->getType()))
      return EmitIntToBoolConversion(Src);
  
    assert(isa<llvm::PointerType>(Src->getType()));
    return EmitPointerToBoolConversion(Src, SrcType);
  }
  
  void ScalarExprEmitter::EmitFloatConversionCheck(
      Value *OrigSrc, QualType OrigSrcType, Value *Src, QualType SrcType,
      QualType DstType, llvm::Type *DstTy, SourceLocation Loc) {
    assert(SrcType->isFloatingType() && "not a conversion from floating point");
    if (!isa<llvm::IntegerType>(DstTy))
      return;
  
    CodeGenFunction::SanitizerScope SanScope(&CGF);
    using llvm::APFloat;
    using llvm::APSInt;
  
    llvm::Value *Check = nullptr;
    const llvm::fltSemantics &SrcSema =
      CGF.getContext().getFloatTypeSemantics(OrigSrcType);
  
    // Floating-point to integer. This has undefined behavior if the source is
    // +-Inf, NaN, or doesn't fit into the destination type (after truncation
    // to an integer).
    unsigned Width = CGF.getContext().getIntWidth(DstType);
    bool Unsigned = DstType->isUnsignedIntegerOrEnumerationType();
  
    APSInt Min = APSInt::getMinValue(Width, Unsigned);
    APFloat MinSrc(SrcSema, APFloat::uninitialized);
    if (MinSrc.convertFromAPInt(Min, !Unsigned, APFloat::rmTowardZero) &
        APFloat::opOverflow)
      // Don't need an overflow check for lower bound. Just check for
      // -Inf/NaN.
      MinSrc = APFloat::getInf(SrcSema, true);
    else
      // Find the largest value which is too small to represent (before
      // truncation toward zero).
      MinSrc.subtract(APFloat(SrcSema, 1), APFloat::rmTowardNegative);
  
    APSInt Max = APSInt::getMaxValue(Width, Unsigned);
    APFloat MaxSrc(SrcSema, APFloat::uninitialized);
    if (MaxSrc.convertFromAPInt(Max, !Unsigned, APFloat::rmTowardZero) &
        APFloat::opOverflow)
      // Don't need an overflow check for upper bound. Just check for
      // +Inf/NaN.
      MaxSrc = APFloat::getInf(SrcSema, false);
    else
      // Find the smallest value which is too large to represent (before
      // truncation toward zero).
      MaxSrc.add(APFloat(SrcSema, 1), APFloat::rmTowardPositive);
  
    // If we're converting from __half, convert the range to float to match
    // the type of src.
    if (OrigSrcType->isHalfType()) {
      const llvm::fltSemantics &Sema =
        CGF.getContext().getFloatTypeSemantics(SrcType);
      bool IsInexact;
      MinSrc.convert(Sema, APFloat::rmTowardZero, &IsInexact);
      MaxSrc.convert(Sema, APFloat::rmTowardZero, &IsInexact);
    }
  
    llvm::Value *GE =
      Builder.CreateFCmpOGT(Src, llvm::ConstantFP::get(VMContext, MinSrc));
    llvm::Value *LE =
      Builder.CreateFCmpOLT(Src, llvm::ConstantFP::get(VMContext, MaxSrc));
    Check = Builder.CreateAnd(GE, LE);
  
    llvm::Constant *StaticArgs[] = {CGF.EmitCheckSourceLocation(Loc),
                                    CGF.EmitCheckTypeDescriptor(OrigSrcType),
                                    CGF.EmitCheckTypeDescriptor(DstType)};
    CGF.EmitCheck(std::make_pair(Check, SanitizerKind::FloatCastOverflow),
                  SanitizerHandler::FloatCastOverflow, StaticArgs, OrigSrc);
  }
  
  // Should be called within CodeGenFunction::SanitizerScope RAII scope.
  // Returns 'i1 false' when the truncation Src -> Dst was lossy.
  static std::pair<ScalarExprEmitter::ImplicitConversionCheckKind,
                   std::pair<llvm::Value *, SanitizerMask>>
  EmitIntegerTruncationCheckHelper(Value *Src, QualType SrcType, Value *Dst,
                                   QualType DstType, CGBuilderTy &Builder) {
    llvm::Type *SrcTy = Src->getType();
    llvm::Type *DstTy = Dst->getType();
    (void)DstTy; // Only used in assert()
  
    // This should be truncation of integral types.
    assert(Src != Dst);
    assert(SrcTy->getScalarSizeInBits() > Dst->getType()->getScalarSizeInBits());
    assert(isa<llvm::IntegerType>(SrcTy) && isa<llvm::IntegerType>(DstTy) &&
           "non-integer llvm type");
  
    bool SrcSigned = SrcType->isSignedIntegerOrEnumerationType();
    bool DstSigned = DstType->isSignedIntegerOrEnumerationType();
  
    // If both (src and dst) types are unsigned, then it's an unsigned truncation.
    // Else, it is a signed truncation.
    ScalarExprEmitter::ImplicitConversionCheckKind Kind;
    SanitizerMask Mask;
    if (!SrcSigned && !DstSigned) {
      Kind = ScalarExprEmitter::ICCK_UnsignedIntegerTruncation;
      Mask = SanitizerKind::ImplicitUnsignedIntegerTruncation;
    } else {
      Kind = ScalarExprEmitter::ICCK_SignedIntegerTruncation;
      Mask = SanitizerKind::ImplicitSignedIntegerTruncation;
    }
  
    llvm::Value *Check = nullptr;
    // 1. Extend the truncated value back to the same width as the Src.
    Check = Builder.CreateIntCast(Dst, SrcTy, DstSigned, "anyext");
    // 2. Equality-compare with the original source value
    Check = Builder.CreateICmpEQ(Check, Src, "truncheck");
    // If the comparison result is 'i1 false', then the truncation was lossy.
    return std::make_pair(Kind, std::make_pair(Check, Mask));
  }
  
  void ScalarExprEmitter::EmitIntegerTruncationCheck(Value *Src, QualType SrcType,
                                                     Value *Dst, QualType DstType,
                                                     SourceLocation Loc) {
    if (!CGF.SanOpts.hasOneOf(SanitizerKind::ImplicitIntegerTruncation))
      return;
  
    // We only care about int->int conversions here.
    // We ignore conversions to/from pointer and/or bool.
    if (!(SrcType->isIntegerType() && DstType->isIntegerType()))
      return;
  
    unsigned SrcBits = Src->getType()->getScalarSizeInBits();
    unsigned DstBits = Dst->getType()->getScalarSizeInBits();
    // This must be truncation. Else we do not care.
    if (SrcBits <= DstBits)
      return;
  
    assert(!DstType->isBooleanType() && "we should not get here with booleans.");
  
    // If the integer sign change sanitizer is enabled,
    // and we are truncating from larger unsigned type to smaller signed type,
    // let that next sanitizer deal with it.
    bool SrcSigned = SrcType->isSignedIntegerOrEnumerationType();
    bool DstSigned = DstType->isSignedIntegerOrEnumerationType();
    if (CGF.SanOpts.has(SanitizerKind::ImplicitIntegerSignChange) &&
        (!SrcSigned && DstSigned))
      return;
  
    CodeGenFunction::SanitizerScope SanScope(&CGF);
  
    std::pair<ScalarExprEmitter::ImplicitConversionCheckKind,
              std::pair<llvm::Value *, SanitizerMask>>
        Check =
            EmitIntegerTruncationCheckHelper(Src, SrcType, Dst, DstType, Builder);
    // If the comparison result is 'i1 false', then the truncation was lossy.
  
    // Do we care about this type of truncation?
    if (!CGF.SanOpts.has(Check.second.second))
      return;
  
    llvm::Constant *StaticArgs[] = {
        CGF.EmitCheckSourceLocation(Loc), CGF.EmitCheckTypeDescriptor(SrcType),
        CGF.EmitCheckTypeDescriptor(DstType),
        llvm::ConstantInt::get(Builder.getInt8Ty(), Check.first)};
    CGF.EmitCheck(Check.second, SanitizerHandler::ImplicitConversion, StaticArgs,
                  {Src, Dst});
  }
  
  // Should be called within CodeGenFunction::SanitizerScope RAII scope.
  // Returns 'i1 false' when the conversion Src -> Dst changed the sign.
  static std::pair<ScalarExprEmitter::ImplicitConversionCheckKind,
                   std::pair<llvm::Value *, SanitizerMask>>
  EmitIntegerSignChangeCheckHelper(Value *Src, QualType SrcType, Value *Dst,
                                   QualType DstType, CGBuilderTy &Builder) {
    llvm::Type *SrcTy = Src->getType();
    llvm::Type *DstTy = Dst->getType();
  
    assert(isa<llvm::IntegerType>(SrcTy) && isa<llvm::IntegerType>(DstTy) &&
           "non-integer llvm type");
  
    bool SrcSigned = SrcType->isSignedIntegerOrEnumerationType();
    bool DstSigned = DstType->isSignedIntegerOrEnumerationType();
    (void)SrcSigned; // Only used in assert()
    (void)DstSigned; // Only used in assert()
    unsigned SrcBits = SrcTy->getScalarSizeInBits();
    unsigned DstBits = DstTy->getScalarSizeInBits();
    (void)SrcBits; // Only used in assert()
    (void)DstBits; // Only used in assert()
  
    assert(((SrcBits != DstBits) || (SrcSigned != DstSigned)) &&
           "either the widths should be different, or the signednesses.");
  
    // NOTE: zero value is considered to be non-negative.
    auto EmitIsNegativeTest = [&Builder](Value *V, QualType VType,
                                         const char *Name) -> Value * {
      // Is this value a signed type?
      bool VSigned = VType->isSignedIntegerOrEnumerationType();
      llvm::Type *VTy = V->getType();
      if (!VSigned) {
        // If the value is unsigned, then it is never negative.
        // FIXME: can we encounter non-scalar VTy here?
        return llvm::ConstantInt::getFalse(VTy->getContext());
      }
      // Get the zero of the same type with which we will be comparing.
      llvm::Constant *Zero = llvm::ConstantInt::get(VTy, 0);
      // %V.isnegative = icmp slt %V, 0
      // I.e is %V *strictly* less than zero, does it have negative value?
      return Builder.CreateICmp(llvm::ICmpInst::ICMP_SLT, V, Zero,
                                llvm::Twine(Name) + "." + V->getName() +
                                    ".negativitycheck");
    };
  
    // 1. Was the old Value negative?
    llvm::Value *SrcIsNegative = EmitIsNegativeTest(Src, SrcType, "src");
    // 2. Is the new Value negative?
    llvm::Value *DstIsNegative = EmitIsNegativeTest(Dst, DstType, "dst");
    // 3. Now, was the 'negativity status' preserved during the conversion?
    //    NOTE: conversion from negative to zero is considered to change the sign.
    //    (We want to get 'false' when the conversion changed the sign)
    //    So we should just equality-compare the negativity statuses.
    llvm::Value *Check = nullptr;
    Check = Builder.CreateICmpEQ(SrcIsNegative, DstIsNegative, "signchangecheck");
    // If the comparison result is 'false', then the conversion changed the sign.
    return std::make_pair(
        ScalarExprEmitter::ICCK_IntegerSignChange,
        std::make_pair(Check, SanitizerKind::ImplicitIntegerSignChange));
  }
  
  void ScalarExprEmitter::EmitIntegerSignChangeCheck(Value *Src, QualType SrcType,
                                                     Value *Dst, QualType DstType,
                                                     SourceLocation Loc) {
    if (!CGF.SanOpts.has(SanitizerKind::ImplicitIntegerSignChange))
      return;
  
    llvm::Type *SrcTy = Src->getType();
    llvm::Type *DstTy = Dst->getType();
  
    // We only care about int->int conversions here.
    // We ignore conversions to/from pointer and/or bool.
    if (!(SrcType->isIntegerType() && DstType->isIntegerType()))
      return;
  
    bool SrcSigned = SrcType->isSignedIntegerOrEnumerationType();
    bool DstSigned = DstType->isSignedIntegerOrEnumerationType();
    unsigned SrcBits = SrcTy->getScalarSizeInBits();
    unsigned DstBits = DstTy->getScalarSizeInBits();
  
    // Now, we do not need to emit the check in *all* of the cases.
    // We can avoid emitting it in some obvious cases where it would have been
    // dropped by the opt passes (instcombine) always anyways.
    // If it's a cast between effectively the same type, no check.
    // NOTE: this is *not* equivalent to checking the canonical types.
    if (SrcSigned == DstSigned && SrcBits == DstBits)
      return;
    // At least one of the values needs to have signed type.
    // If both are unsigned, then obviously, neither of them can be negative.
    if (!SrcSigned && !DstSigned)
      return;
    // If the conversion is to *larger* *signed* type, then no check is needed.
    // Because either sign-extension happens (so the sign will remain),
    // or zero-extension will happen (the sign bit will be zero.)
    if ((DstBits > SrcBits) && DstSigned)
      return;
    if (CGF.SanOpts.has(SanitizerKind::ImplicitSignedIntegerTruncation) &&
        (SrcBits > DstBits) && SrcSigned) {
      // If the signed integer truncation sanitizer is enabled,
      // and this is a truncation from signed type, then no check is needed.
      // Because here sign change check is interchangeable with truncation check.
      return;
    }
    // That's it. We can't rule out any more cases with the data we have.
  
    CodeGenFunction::SanitizerScope SanScope(&CGF);
  
    std::pair<ScalarExprEmitter::ImplicitConversionCheckKind,
              std::pair<llvm::Value *, SanitizerMask>>
        Check;
  
    // Each of these checks needs to return 'false' when an issue was detected.
    ImplicitConversionCheckKind CheckKind;
    llvm::SmallVector<std::pair<llvm::Value *, SanitizerMask>, 2> Checks;
    // So we can 'and' all the checks together, and still get 'false',
    // if at least one of the checks detected an issue.
  
    Check = EmitIntegerSignChangeCheckHelper(Src, SrcType, Dst, DstType, Builder);
    CheckKind = Check.first;
    Checks.emplace_back(Check.second);
  
    if (CGF.SanOpts.has(SanitizerKind::ImplicitSignedIntegerTruncation) &&
        (SrcBits > DstBits) && !SrcSigned && DstSigned) {
      // If the signed integer truncation sanitizer was enabled,
      // and we are truncating from larger unsigned type to smaller signed type,
      // let's handle the case we skipped in that check.
      Check =
          EmitIntegerTruncationCheckHelper(Src, SrcType, Dst, DstType, Builder);
      CheckKind = ICCK_SignedIntegerTruncationOrSignChange;
      Checks.emplace_back(Check.second);
      // If the comparison result is 'i1 false', then the truncation was lossy.
    }
  
    llvm::Constant *StaticArgs[] = {
        CGF.EmitCheckSourceLocation(Loc), CGF.EmitCheckTypeDescriptor(SrcType),
        CGF.EmitCheckTypeDescriptor(DstType),
        llvm::ConstantInt::get(Builder.getInt8Ty(), CheckKind)};
    // EmitCheck() will 'and' all the checks together.
    CGF.EmitCheck(Checks, SanitizerHandler::ImplicitConversion, StaticArgs,
                  {Src, Dst});
  }
  
  /// Emit a conversion from the specified type to the specified destination type,
  /// both of which are LLVM scalar types.
  Value *ScalarExprEmitter::EmitScalarConversion(Value *Src, QualType SrcType,
                                                 QualType DstType,
                                                 SourceLocation Loc,
                                                 ScalarConversionOpts Opts) {
    // All conversions involving fixed point types should be handled by the
    // EmitFixedPoint family functions. This is done to prevent bloating up this
    // function more, and although fixed point numbers are represented by
    // integers, we do not want to follow any logic that assumes they should be
    // treated as integers.
    // TODO(leonardchan): When necessary, add another if statement checking for
    // conversions to fixed point types from other types.
    if (SrcType->isFixedPointType()) {
      if (DstType->isBooleanType())
        // It is important that we check this before checking if the dest type is
        // an integer because booleans are technically integer types.
        // We do not need to check the padding bit on unsigned types if unsigned
        // padding is enabled because overflow into this bit is undefined
        // behavior.
        return Builder.CreateIsNotNull(Src, "tobool");
      if (DstType->isFixedPointType() || DstType->isIntegerType())
        return EmitFixedPointConversion(Src, SrcType, DstType, Loc);
  
      llvm_unreachable(
          "Unhandled scalar conversion from a fixed point type to another type.");
    } else if (DstType->isFixedPointType()) {
      if (SrcType->isIntegerType())
        // This also includes converting booleans and enums to fixed point types.
        return EmitFixedPointConversion(Src, SrcType, DstType, Loc);
  
      llvm_unreachable(
          "Unhandled scalar conversion to a fixed point type from another type.");
    }
  
    QualType NoncanonicalSrcType = SrcType;
    QualType NoncanonicalDstType = DstType;
  
    SrcType = CGF.getContext().getCanonicalType(SrcType);
    DstType = CGF.getContext().getCanonicalType(DstType);
    if (SrcType == DstType) return Src;
  
    if (DstType->isVoidType()) return nullptr;
  
    llvm::Value *OrigSrc = Src;
    QualType OrigSrcType = SrcType;
    llvm::Type *SrcTy = Src->getType();
  
    // Handle conversions to bool first, they are special: comparisons against 0.
    if (DstType->isBooleanType())
      return EmitConversionToBool(Src, SrcType);
  
    llvm::Type *DstTy = ConvertType(DstType);
  
    // Cast from half through float if half isn't a native type.
    if (SrcType->isHalfType() && !CGF.getContext().getLangOpts().NativeHalfType) {
      // Cast to FP using the intrinsic if the half type itself isn't supported.
      if (DstTy->isFloatingPointTy()) {
        if (CGF.getContext().getTargetInfo().useFP16ConversionIntrinsics())
          return Builder.CreateCall(
              CGF.CGM.getIntrinsic(llvm::Intrinsic::convert_from_fp16, DstTy),
              Src);
      } else {
        // Cast to other types through float, using either the intrinsic or FPExt,
        // depending on whether the half type itself is supported
        // (as opposed to operations on half, available with NativeHalfType).
        if (CGF.getContext().getTargetInfo().useFP16ConversionIntrinsics()) {
          Src = Builder.CreateCall(
              CGF.CGM.getIntrinsic(llvm::Intrinsic::convert_from_fp16,
                                   CGF.CGM.FloatTy),
              Src);
        } else {
          Src = Builder.CreateFPExt(Src, CGF.CGM.FloatTy, "conv");
        }
        SrcType = CGF.getContext().FloatTy;
        SrcTy = CGF.FloatTy;
      }
    }
  
    // Ignore conversions like int -> uint.
    if (SrcTy == DstTy) {
      if (Opts.EmitImplicitIntegerSignChangeChecks)
        EmitIntegerSignChangeCheck(Src, NoncanonicalSrcType, Src,
                                   NoncanonicalDstType, Loc);
  
      return Src;
    }
  
    // Handle pointer conversions next: pointers can only be converted to/from
    // other pointers and integers. Check for pointer types in terms of LLVM, as
    // some native types (like Obj-C id) may map to a pointer type.
    if (auto DstPT = dyn_cast<llvm::PointerType>(DstTy)) {
      // The source value may be an integer, or a pointer.
      if (isa<llvm::PointerType>(SrcTy))
        return Builder.CreateBitCast(Src, DstTy, "conv");
  
      assert(SrcType->isIntegerType() && "Not ptr->ptr or int->ptr conversion?");
      // First, convert to the correct width so that we control the kind of
      // extension.
      llvm::Type *MiddleTy = CGF.CGM.getDataLayout().getIntPtrType(DstPT);
      bool InputSigned = SrcType->isSignedIntegerOrEnumerationType();
      llvm::Value* IntResult =
          Builder.CreateIntCast(Src, MiddleTy, InputSigned, "conv");
      // Then, cast to pointer.
      return Builder.CreateIntToPtr(IntResult, DstTy, "conv");
    }
  
    if (isa<llvm::PointerType>(SrcTy)) {
      // Must be an ptr to int cast.
      assert(isa<llvm::IntegerType>(DstTy) && "not ptr->int?");
      return Builder.CreatePtrToInt(Src, DstTy, "conv");
    }
  
    // A scalar can be splatted to an extended vector of the same element type
    if (DstType->isExtVectorType() && !SrcType->isVectorType()) {
      // Sema should add casts to make sure that the source expression's type is
      // the same as the vector's element type (sans qualifiers)
      assert(DstType->castAs<ExtVectorType>()->getElementType().getTypePtr() ==
                 SrcType.getTypePtr() &&
             "Splatted expr doesn't match with vector element type?");
  
      // Splat the element across to all elements
      unsigned NumElements = DstTy->getVectorNumElements();
      return Builder.CreateVectorSplat(NumElements, Src, "splat");
    }
  
    if (isa<llvm::VectorType>(SrcTy) || isa<llvm::VectorType>(DstTy)) {
      // Allow bitcast from vector to integer/fp of the same size.
      unsigned SrcSize = SrcTy->getPrimitiveSizeInBits();
      unsigned DstSize = DstTy->getPrimitiveSizeInBits();
      if (SrcSize == DstSize)
        return Builder.CreateBitCast(Src, DstTy, "conv");
  
      // Conversions between vectors of different sizes are not allowed except
      // when vectors of half are involved. Operations on storage-only half
      // vectors require promoting half vector operands to float vectors and
      // truncating the result, which is either an int or float vector, to a
      // short or half vector.
  
      // Source and destination are both expected to be vectors.
      llvm::Type *SrcElementTy = SrcTy->getVectorElementType();
      llvm::Type *DstElementTy = DstTy->getVectorElementType();
      (void)DstElementTy;
  
      assert(((SrcElementTy->isIntegerTy() &&
               DstElementTy->isIntegerTy()) ||
              (SrcElementTy->isFloatingPointTy() &&
               DstElementTy->isFloatingPointTy())) &&
             "unexpected conversion between a floating-point vector and an "
             "integer vector");
  
      // Truncate an i32 vector to an i16 vector.
      if (SrcElementTy->isIntegerTy())
        return Builder.CreateIntCast(Src, DstTy, false, "conv");
  
      // Truncate a float vector to a half vector.
      if (SrcSize > DstSize)
        return Builder.CreateFPTrunc(Src, DstTy, "conv");
  
      // Promote a half vector to a float vector.
      return Builder.CreateFPExt(Src, DstTy, "conv");
    }
  
    // Finally, we have the arithmetic types: real int/float.
    Value *Res = nullptr;
    llvm::Type *ResTy = DstTy;
  
    // An overflowing conversion has undefined behavior if either the source type
    // or the destination type is a floating-point type. However, we consider the
    // range of representable values for all floating-point types to be
    // [-inf,+inf], so no overflow can ever happen when the destination type is a
    // floating-point type.
    if (CGF.SanOpts.has(SanitizerKind::FloatCastOverflow) &&
        OrigSrcType->isFloatingType())
      EmitFloatConversionCheck(OrigSrc, OrigSrcType, Src, SrcType, DstType, DstTy,
                               Loc);
  
    // Cast to half through float if half isn't a native type.
    if (DstType->isHalfType() && !CGF.getContext().getLangOpts().NativeHalfType) {
      // Make sure we cast in a single step if from another FP type.
      if (SrcTy->isFloatingPointTy()) {
        // Use the intrinsic if the half type itself isn't supported
        // (as opposed to operations on half, available with NativeHalfType).
        if (CGF.getContext().getTargetInfo().useFP16ConversionIntrinsics())
          return Builder.CreateCall(
              CGF.CGM.getIntrinsic(llvm::Intrinsic::convert_to_fp16, SrcTy), Src);
        // If the half type is supported, just use an fptrunc.
        return Builder.CreateFPTrunc(Src, DstTy);
      }
      DstTy = CGF.FloatTy;
    }
  
    if (isa<llvm::IntegerType>(SrcTy)) {
      bool InputSigned = SrcType->isSignedIntegerOrEnumerationType();
      if (SrcType->isBooleanType() && Opts.TreatBooleanAsSigned) {
        InputSigned = true;
      }
      if (isa<llvm::IntegerType>(DstTy))
        Res = Builder.CreateIntCast(Src, DstTy, InputSigned, "conv");
      else if (InputSigned)
        Res = Builder.CreateSIToFP(Src, DstTy, "conv");
      else
        Res = Builder.CreateUIToFP(Src, DstTy, "conv");
    } else if (isa<llvm::IntegerType>(DstTy)) {
      assert(SrcTy->isFloatingPointTy() && "Unknown real conversion");
      if (DstType->isSignedIntegerOrEnumerationType())
        Res = Builder.CreateFPToSI(Src, DstTy, "conv");
      else
        Res = Builder.CreateFPToUI(Src, DstTy, "conv");
    } else {
      assert(SrcTy->isFloatingPointTy() && DstTy->isFloatingPointTy() &&
             "Unknown real conversion");
      if (DstTy->getTypeID() < SrcTy->getTypeID())
        Res = Builder.CreateFPTrunc(Src, DstTy, "conv");
      else
        Res = Builder.CreateFPExt(Src, DstTy, "conv");
    }
  
    if (DstTy != ResTy) {
      if (CGF.getContext().getTargetInfo().useFP16ConversionIntrinsics()) {
        assert(ResTy->isIntegerTy(16) && "Only half FP requires extra conversion");
        Res = Builder.CreateCall(
          CGF.CGM.getIntrinsic(llvm::Intrinsic::convert_to_fp16, CGF.CGM.FloatTy),
          Res);
      } else {
        Res = Builder.CreateFPTrunc(Res, ResTy, "conv");
      }
    }
  
    if (Opts.EmitImplicitIntegerTruncationChecks)
      EmitIntegerTruncationCheck(Src, NoncanonicalSrcType, Res,
                                 NoncanonicalDstType, Loc);
  
    if (Opts.EmitImplicitIntegerSignChangeChecks)
      EmitIntegerSignChangeCheck(Src, NoncanonicalSrcType, Res,
                                 NoncanonicalDstType, Loc);
  
    return Res;
  }
  
  Value *ScalarExprEmitter::EmitFixedPointConversion(Value *Src, QualType SrcTy,
                                                     QualType DstTy,
                                                     SourceLocation Loc) {
    FixedPointSemantics SrcFPSema =
        CGF.getContext().getFixedPointSemantics(SrcTy);
    FixedPointSemantics DstFPSema =
        CGF.getContext().getFixedPointSemantics(DstTy);
    return EmitFixedPointConversion(Src, SrcFPSema, DstFPSema, Loc,
                                    DstTy->isIntegerType());
  }
  
  Value *ScalarExprEmitter::EmitFixedPointConversion(
      Value *Src, FixedPointSemantics &SrcFPSema, FixedPointSemantics &DstFPSema,
      SourceLocation Loc, bool DstIsInteger) {
    using llvm::APInt;
    using llvm::ConstantInt;
    using llvm::Value;
  
    unsigned SrcWidth = SrcFPSema.getWidth();
    unsigned DstWidth = DstFPSema.getWidth();
    unsigned SrcScale = SrcFPSema.getScale();
    unsigned DstScale = DstFPSema.getScale();
    bool SrcIsSigned = SrcFPSema.isSigned();
    bool DstIsSigned = DstFPSema.isSigned();
  
    llvm::Type *DstIntTy = Builder.getIntNTy(DstWidth);
  
    Value *Result = Src;
    unsigned ResultWidth = SrcWidth;
  
    // Downscale.
    if (DstScale < SrcScale) {
      // When converting to integers, we round towards zero. For negative numbers,
      // right shifting rounds towards negative infinity. In this case, we can
      // just round up before shifting.
      if (DstIsInteger && SrcIsSigned) {
        Value *Zero = llvm::Constant::getNullValue(Result->getType());
        Value *IsNegative = Builder.CreateICmpSLT(Result, Zero);
        Value *LowBits = ConstantInt::get(
            CGF.getLLVMContext(), APInt::getLowBitsSet(ResultWidth, SrcScale));
        Value *Rounded = Builder.CreateAdd(Result, LowBits);
        Result = Builder.CreateSelect(IsNegative, Rounded, Result);
      }
  
      Result = SrcIsSigned
                   ? Builder.CreateAShr(Result, SrcScale - DstScale, "downscale")
                   : Builder.CreateLShr(Result, SrcScale - DstScale, "downscale");
    }
  
    if (!DstFPSema.isSaturated()) {
      // Resize.
      Result = Builder.CreateIntCast(Result, DstIntTy, SrcIsSigned, "resize");
  
      // Upscale.
      if (DstScale > SrcScale)
        Result = Builder.CreateShl(Result, DstScale - SrcScale, "upscale");
    } else {
      // Adjust the number of fractional bits.
      if (DstScale > SrcScale) {
        // Compare to DstWidth to prevent resizing twice.
        ResultWidth = std::max(SrcWidth + DstScale - SrcScale, DstWidth);
        llvm::Type *UpscaledTy = Builder.getIntNTy(ResultWidth);
        Result = Builder.CreateIntCast(Result, UpscaledTy, SrcIsSigned, "resize");
        Result = Builder.CreateShl(Result, DstScale - SrcScale, "upscale");
      }
  
      // Handle saturation.
      bool LessIntBits = DstFPSema.getIntegralBits() < SrcFPSema.getIntegralBits();
      if (LessIntBits) {
        Value *Max = ConstantInt::get(
            CGF.getLLVMContext(),
            APFixedPoint::getMax(DstFPSema).getValue().extOrTrunc(ResultWidth));
        Value *TooHigh = SrcIsSigned ? Builder.CreateICmpSGT(Result, Max)
                                     : Builder.CreateICmpUGT(Result, Max);
        Result = Builder.CreateSelect(TooHigh, Max, Result, "satmax");
      }
      // Cannot overflow min to dest type if src is unsigned since all fixed
      // point types can cover the unsigned min of 0.
      if (SrcIsSigned && (LessIntBits || !DstIsSigned)) {
        Value *Min = ConstantInt::get(
            CGF.getLLVMContext(),
            APFixedPoint::getMin(DstFPSema).getValue().extOrTrunc(ResultWidth));
        Value *TooLow = Builder.CreateICmpSLT(Result, Min);
        Result = Builder.CreateSelect(TooLow, Min, Result, "satmin");
      }
  
      // Resize the integer part to get the final destination size.
      if (ResultWidth != DstWidth)
        Result = Builder.CreateIntCast(Result, DstIntTy, SrcIsSigned, "resize");
    }
    return Result;
  }
  
  /// Emit a conversion from the specified complex type to the specified
  /// destination type, where the destination type is an LLVM scalar type.
  Value *ScalarExprEmitter::EmitComplexToScalarConversion(
      CodeGenFunction::ComplexPairTy Src, QualType SrcTy, QualType DstTy,
      SourceLocation Loc) {
    // Get the source element type.
    SrcTy = SrcTy->castAs<ComplexType>()->getElementType();
  
    // Handle conversions to bool first, they are special: comparisons against 0.
    if (DstTy->isBooleanType()) {
      //  Complex != 0  -> (Real != 0) | (Imag != 0)
      Src.first = EmitScalarConversion(Src.first, SrcTy, DstTy, Loc);
      Src.second = EmitScalarConversion(Src.second, SrcTy, DstTy, Loc);
      return Builder.CreateOr(Src.first, Src.second, "tobool");
    }
  
    // C99 6.3.1.7p2: "When a value of complex type is converted to a real type,
    // the imaginary part of the complex value is discarded and the value of the
    // real part is converted according to the conversion rules for the
    // corresponding real type.
    return EmitScalarConversion(Src.first, SrcTy, DstTy, Loc);
  }
  
  Value *ScalarExprEmitter::EmitNullValue(QualType Ty) {
    return CGF.EmitFromMemory(CGF.CGM.EmitNullConstant(Ty), Ty);
  }
  
  /// Emit a sanitization check for the given "binary" operation (which
  /// might actually be a unary increment which has been lowered to a binary
  /// operation). The check passes if all values in \p Checks (which are \c i1),
  /// are \c true.
  void ScalarExprEmitter::EmitBinOpCheck(
      ArrayRef<std::pair<Value *, SanitizerMask>> Checks, const BinOpInfo &Info) {
    assert(CGF.IsSanitizerScope);
    SanitizerHandler Check;
    SmallVector<llvm::Constant *, 4> StaticData;
    SmallVector<llvm::Value *, 2> DynamicData;
  
    BinaryOperatorKind Opcode = Info.Opcode;
    if (BinaryOperator::isCompoundAssignmentOp(Opcode))
      Opcode = BinaryOperator::getOpForCompoundAssignment(Opcode);
  
    StaticData.push_back(CGF.EmitCheckSourceLocation(Info.E->getExprLoc()));
    const UnaryOperator *UO = dyn_cast<UnaryOperator>(Info.E);
    if (UO && UO->getOpcode() == UO_Minus) {
      Check = SanitizerHandler::NegateOverflow;
      StaticData.push_back(CGF.EmitCheckTypeDescriptor(UO->getType()));
      DynamicData.push_back(Info.RHS);
    } else {
      if (BinaryOperator::isShiftOp(Opcode)) {
        // Shift LHS negative or too large, or RHS out of bounds.
        Check = SanitizerHandler::ShiftOutOfBounds;
        const BinaryOperator *BO = cast<BinaryOperator>(Info.E);
        StaticData.push_back(
          CGF.EmitCheckTypeDescriptor(BO->getLHS()->getType()));
        StaticData.push_back(
          CGF.EmitCheckTypeDescriptor(BO->getRHS()->getType()));
      } else if (Opcode == BO_Div || Opcode == BO_Rem) {
        // Divide or modulo by zero, or signed overflow (eg INT_MAX / -1).
        Check = SanitizerHandler::DivremOverflow;
        StaticData.push_back(CGF.EmitCheckTypeDescriptor(Info.Ty));
      } else {
        // Arithmetic overflow (+, -, *).
        switch (Opcode) {
        case BO_Add: Check = SanitizerHandler::AddOverflow; break;
        case BO_Sub: Check = SanitizerHandler::SubOverflow; break;
        case BO_Mul: Check = SanitizerHandler::MulOverflow; break;
        default: llvm_unreachable("unexpected opcode for bin op check");
        }
        StaticData.push_back(CGF.EmitCheckTypeDescriptor(Info.Ty));
      }
      DynamicData.push_back(Info.LHS);
      DynamicData.push_back(Info.RHS);
    }
  
    CGF.EmitCheck(Checks, Check, StaticData, DynamicData);
  }
  
  //===----------------------------------------------------------------------===//
  //                            Visitor Methods
  //===----------------------------------------------------------------------===//
  
  Value *ScalarExprEmitter::VisitExpr(Expr *E) {
    CGF.ErrorUnsupported(E, "scalar expression");
    if (E->getType()->isVoidType())
      return nullptr;
    return llvm::UndefValue::get(CGF.ConvertType(E->getType()));
  }
  
  Value *ScalarExprEmitter::VisitShuffleVectorExpr(ShuffleVectorExpr *E) {
    // Vector Mask Case
    if (E->getNumSubExprs() == 2) {
      Value *LHS = CGF.EmitScalarExpr(E->getExpr(0));
      Value *RHS = CGF.EmitScalarExpr(E->getExpr(1));
      Value *Mask;
  
      llvm::VectorType *LTy = cast<llvm::VectorType>(LHS->getType());
      unsigned LHSElts = LTy->getNumElements();
  
      Mask = RHS;
  
      llvm::VectorType *MTy = cast<llvm::VectorType>(Mask->getType());
  
      // Mask off the high bits of each shuffle index.
      Value *MaskBits =
          llvm::ConstantInt::get(MTy, llvm::NextPowerOf2(LHSElts - 1) - 1);
      Mask = Builder.CreateAnd(Mask, MaskBits, "mask");
  
      // newv = undef
      // mask = mask & maskbits
      // for each elt
      //   n = extract mask i
      //   x = extract val n
      //   newv = insert newv, x, i
      llvm::VectorType *RTy = llvm::VectorType::get(LTy->getElementType(),
                                                    MTy->getNumElements());
      Value* NewV = llvm::UndefValue::get(RTy);
      for (unsigned i = 0, e = MTy->getNumElements(); i != e; ++i) {
        Value *IIndx = llvm::ConstantInt::get(CGF.SizeTy, i);
        Value *Indx = Builder.CreateExtractElement(Mask, IIndx, "shuf_idx");
  
        Value *VExt = Builder.CreateExtractElement(LHS, Indx, "shuf_elt");
        NewV = Builder.CreateInsertElement(NewV, VExt, IIndx, "shuf_ins");
      }
      return NewV;
    }
  
    Value* V1 = CGF.EmitScalarExpr(E->getExpr(0));
    Value* V2 = CGF.EmitScalarExpr(E->getExpr(1));
  
    SmallVector<llvm::Constant*, 32> indices;
    for (unsigned i = 2; i < E->getNumSubExprs(); ++i) {
      llvm::APSInt Idx = E->getShuffleMaskIdx(CGF.getContext(), i-2);
      // Check for -1 and output it as undef in the IR.
      if (Idx.isSigned() && Idx.isAllOnesValue())
        indices.push_back(llvm::UndefValue::get(CGF.Int32Ty));
      else
        indices.push_back(Builder.getInt32(Idx.getZExtValue()));
    }
  
    Value *SV = llvm::ConstantVector::get(indices);
    return Builder.CreateShuffleVector(V1, V2, SV, "shuffle");
  }
  
  Value *ScalarExprEmitter::VisitConvertVectorExpr(ConvertVectorExpr *E) {
    QualType SrcType = E->getSrcExpr()->getType(),
             DstType = E->getType();
  
    Value *Src  = CGF.EmitScalarExpr(E->getSrcExpr());
  
    SrcType = CGF.getContext().getCanonicalType(SrcType);
    DstType = CGF.getContext().getCanonicalType(DstType);
    if (SrcType == DstType) return Src;
  
    assert(SrcType->isVectorType() &&
           "ConvertVector source type must be a vector");
    assert(DstType->isVectorType() &&
           "ConvertVector destination type must be a vector");
  
    llvm::Type *SrcTy = Src->getType();
    llvm::Type *DstTy = ConvertType(DstType);
  
    // Ignore conversions like int -> uint.
    if (SrcTy == DstTy)
      return Src;
  
    QualType SrcEltType = SrcType->getAs<VectorType>()->getElementType(),
             DstEltType = DstType->getAs<VectorType>()->getElementType();
  
    assert(SrcTy->isVectorTy() &&
           "ConvertVector source IR type must be a vector");
    assert(DstTy->isVectorTy() &&
           "ConvertVector destination IR type must be a vector");
  
    llvm::Type *SrcEltTy = SrcTy->getVectorElementType(),
               *DstEltTy = DstTy->getVectorElementType();
  
    if (DstEltType->isBooleanType()) {
      assert((SrcEltTy->isFloatingPointTy() ||
              isa<llvm::IntegerType>(SrcEltTy)) && "Unknown boolean conversion");
  
      llvm::Value *Zero = llvm::Constant::getNullValue(SrcTy);
      if (SrcEltTy->isFloatingPointTy()) {
        return Builder.CreateFCmpUNE(Src, Zero, "tobool");
      } else {
        return Builder.CreateICmpNE(Src, Zero, "tobool");
      }
    }
  
    // We have the arithmetic types: real int/float.
    Value *Res = nullptr;
  
    if (isa<llvm::IntegerType>(SrcEltTy)) {
      bool InputSigned = SrcEltType->isSignedIntegerOrEnumerationType();
      if (isa<llvm::IntegerType>(DstEltTy))
        Res = Builder.CreateIntCast(Src, DstTy, InputSigned, "conv");
      else if (InputSigned)
        Res = Builder.CreateSIToFP(Src, DstTy, "conv");
      else
        Res = Builder.CreateUIToFP(Src, DstTy, "conv");
    } else if (isa<llvm::IntegerType>(DstEltTy)) {
      assert(SrcEltTy->isFloatingPointTy() && "Unknown real conversion");
      if (DstEltType->isSignedIntegerOrEnumerationType())
        Res = Builder.CreateFPToSI(Src, DstTy, "conv");
      else
        Res = Builder.CreateFPToUI(Src, DstTy, "conv");
    } else {
      assert(SrcEltTy->isFloatingPointTy() && DstEltTy->isFloatingPointTy() &&
             "Unknown real conversion");
      if (DstEltTy->getTypeID() < SrcEltTy->getTypeID())
        Res = Builder.CreateFPTrunc(Src, DstTy, "conv");
      else
        Res = Builder.CreateFPExt(Src, DstTy, "conv");
    }
  
    return Res;
  }
  
  Value *ScalarExprEmitter::VisitMemberExpr(MemberExpr *E) {
    if (CodeGenFunction::ConstantEmission Constant = CGF.tryEmitAsConstant(E)) {
      CGF.EmitIgnoredExpr(E->getBase());
      return CGF.emitScalarConstant(Constant, E);
    } else {
      Expr::EvalResult Result;
      if (E->EvaluateAsInt(Result, CGF.getContext(), Expr::SE_AllowSideEffects)) {
        llvm::APSInt Value = Result.Val.getInt();
        CGF.EmitIgnoredExpr(E->getBase());
        return Builder.getInt(Value);
      }
    }
  
    return EmitLoadOfLValue(E);
  }
  
  Value *ScalarExprEmitter::VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
    TestAndClearIgnoreResultAssign();
  
    // Emit subscript expressions in rvalue context's.  For most cases, this just
    // loads the lvalue formed by the subscript expr.  However, we have to be
    // careful, because the base of a vector subscript is occasionally an rvalue,
    // so we can't get it as an lvalue.
    if (!E->getBase()->getType()->isVectorType())
      return EmitLoadOfLValue(E);
  
    // Handle the vector case.  The base must be a vector, the index must be an
    // integer value.
    Value *Base = Visit(E->getBase());
    Value *Idx  = Visit(E->getIdx());
    QualType IdxTy = E->getIdx()->getType();
  
    if (CGF.SanOpts.has(SanitizerKind::ArrayBounds))
      CGF.EmitBoundsCheck(E, E->getBase(), Idx, IdxTy, /*Accessed*/true);
  
    return Builder.CreateExtractElement(Base, Idx, "vecext");
  }
  
  static llvm::Constant *getMaskElt(llvm::ShuffleVectorInst *SVI, unsigned Idx,
                                    unsigned Off, llvm::Type *I32Ty) {
    int MV = SVI->getMaskValue(Idx);
    if (MV == -1)
      return llvm::UndefValue::get(I32Ty);
    return llvm::ConstantInt::get(I32Ty, Off+MV);
  }
  
  static llvm::Constant *getAsInt32(llvm::ConstantInt *C, llvm::Type *I32Ty) {
    if (C->getBitWidth() != 32) {
        assert(llvm::ConstantInt::isValueValidForType(I32Ty,
                                                      C->getZExtValue()) &&
               "Index operand too large for shufflevector mask!");
        return llvm::ConstantInt::get(I32Ty, C->getZExtValue());
    }
    return C;
  }
  
  Value *ScalarExprEmitter::VisitInitListExpr(InitListExpr *E) {
    bool Ignore = TestAndClearIgnoreResultAssign();
    (void)Ignore;
    assert (Ignore == false && "init list ignored");
    unsigned NumInitElements = E->getNumInits();
  
    if (E->hadArrayRangeDesignator())
      CGF.ErrorUnsupported(E, "GNU array range designator extension");
  
    llvm::VectorType *VType =
      dyn_cast<llvm::VectorType>(ConvertType(E->getType()));
  
    if (!VType) {
      if (NumInitElements == 0) {
        // C++11 value-initialization for the scalar.
        return EmitNullValue(E->getType());
      }
      // We have a scalar in braces. Just use the first element.
      return Visit(E->getInit(0));
    }
  
    unsigned ResElts = VType->getNumElements();
  
    // Loop over initializers collecting the Value for each, and remembering
    // whether the source was swizzle (ExtVectorElementExpr).  This will allow
    // us to fold the shuffle for the swizzle into the shuffle for the vector
    // initializer, since LLVM optimizers generally do not want to touch
    // shuffles.
    unsigned CurIdx = 0;
    bool VIsUndefShuffle = false;
    llvm::Value *V = llvm::UndefValue::get(VType);
    for (unsigned i = 0; i != NumInitElements; ++i) {
      Expr *IE = E->getInit(i);
      Value *Init = Visit(IE);
      SmallVector<llvm::Constant*, 16> Args;
  
      llvm::VectorType *VVT = dyn_cast<llvm::VectorType>(Init->getType());
  
      // Handle scalar elements.  If the scalar initializer is actually one
      // element of a different vector of the same width, use shuffle instead of
      // extract+insert.
      if (!VVT) {
        if (isa<ExtVectorElementExpr>(IE)) {
          llvm::ExtractElementInst *EI = cast<llvm::ExtractElementInst>(Init);
  
          if (EI->getVectorOperandType()->getNumElements() == ResElts) {
            llvm::ConstantInt *C = cast<llvm::ConstantInt>(EI->getIndexOperand());
            Value *LHS = nullptr, *RHS = nullptr;
            if (CurIdx == 0) {
              // insert into undef -> shuffle (src, undef)
              // shufflemask must use an i32
              Args.push_back(getAsInt32(C, CGF.Int32Ty));
              Args.resize(ResElts, llvm::UndefValue::get(CGF.Int32Ty));
  
              LHS = EI->getVectorOperand();
              RHS = V;
              VIsUndefShuffle = true;
            } else if (VIsUndefShuffle) {
              // insert into undefshuffle && size match -> shuffle (v, src)
              llvm::ShuffleVectorInst *SVV = cast<llvm::ShuffleVectorInst>(V);
              for (unsigned j = 0; j != CurIdx; ++j)
                Args.push_back(getMaskElt(SVV, j, 0, CGF.Int32Ty));
              Args.push_back(Builder.getInt32(ResElts + C->getZExtValue()));
              Args.resize(ResElts, llvm::UndefValue::get(CGF.Int32Ty));
  
              LHS = cast<llvm::ShuffleVectorInst>(V)->getOperand(0);
              RHS = EI->getVectorOperand();
              VIsUndefShuffle = false;
            }
            if (!Args.empty()) {
              llvm::Constant *Mask = llvm::ConstantVector::get(Args);
              V = Builder.CreateShuffleVector(LHS, RHS, Mask);
              ++CurIdx;
              continue;
            }
          }
        }
        V = Builder.CreateInsertElement(V, Init, Builder.getInt32(CurIdx),
                                        "vecinit");
        VIsUndefShuffle = false;
        ++CurIdx;
        continue;
      }
  
      unsigned InitElts = VVT->getNumElements();
  
      // If the initializer is an ExtVecEltExpr (a swizzle), and the swizzle's
      // input is the same width as the vector being constructed, generate an
      // optimized shuffle of the swizzle input into the result.
      unsigned Offset = (CurIdx == 0) ? 0 : ResElts;
      if (isa<ExtVectorElementExpr>(IE)) {
        llvm::ShuffleVectorInst *SVI = cast<llvm::ShuffleVectorInst>(Init);
        Value *SVOp = SVI->getOperand(0);
        llvm::VectorType *OpTy = cast<llvm::VectorType>(SVOp->getType());
  
        if (OpTy->getNumElements() == ResElts) {
          for (unsigned j = 0; j != CurIdx; ++j) {
            // If the current vector initializer is a shuffle with undef, merge
            // this shuffle directly into it.
            if (VIsUndefShuffle) {
              Args.push_back(getMaskElt(cast<llvm::ShuffleVectorInst>(V), j, 0,
                                        CGF.Int32Ty));
            } else {
              Args.push_back(Builder.getInt32(j));
            }
          }
          for (unsigned j = 0, je = InitElts; j != je; ++j)
            Args.push_back(getMaskElt(SVI, j, Offset, CGF.Int32Ty));
          Args.resize(ResElts, llvm::UndefValue::get(CGF.Int32Ty));
  
          if (VIsUndefShuffle)
            V = cast<llvm::ShuffleVectorInst>(V)->getOperand(0);
  
          Init = SVOp;
        }
      }
  
      // Extend init to result vector length, and then shuffle its contribution
      // to the vector initializer into V.
      if (Args.empty()) {
        for (unsigned j = 0; j != InitElts; ++j)
          Args.push_back(Builder.getInt32(j));
        Args.resize(ResElts, llvm::UndefValue::get(CGF.Int32Ty));
        llvm::Constant *Mask = llvm::ConstantVector::get(Args);
        Init = Builder.CreateShuffleVector(Init, llvm::UndefValue::get(VVT),
                                           Mask, "vext");
  
        Args.clear();
        for (unsigned j = 0; j != CurIdx; ++j)
          Args.push_back(Builder.getInt32(j));
        for (unsigned j = 0; j != InitElts; ++j)
          Args.push_back(Builder.getInt32(j+Offset));
        Args.resize(ResElts, llvm::UndefValue::get(CGF.Int32Ty));
      }
  
      // If V is undef, make sure it ends up on the RHS of the shuffle to aid
      // merging subsequent shuffles into this one.
      if (CurIdx == 0)
        std::swap(V, Init);
      llvm::Constant *Mask = llvm::ConstantVector::get(Args);
      V = Builder.CreateShuffleVector(V, Init, Mask, "vecinit");
      VIsUndefShuffle = isa<llvm::UndefValue>(Init);
      CurIdx += InitElts;
    }
  
    // FIXME: evaluate codegen vs. shuffling against constant null vector.
    // Emit remaining default initializers.
    llvm::Type *EltTy = VType->getElementType();
  
    // Emit remaining default initializers
    for (/* Do not initialize i*/; CurIdx < ResElts; ++CurIdx) {
      Value *Idx = Builder.getInt32(CurIdx);
      llvm::Value *Init = llvm::Constant::getNullValue(EltTy);
      V = Builder.CreateInsertElement(V, Init, Idx, "vecinit");
    }
    return V;
  }
  
  bool CodeGenFunction::ShouldNullCheckClassCastValue(const CastExpr *CE) {
    const Expr *E = CE->getSubExpr();
  
    if (CE->getCastKind() == CK_UncheckedDerivedToBase)
      return false;
  
    if (isa<CXXThisExpr>(E->IgnoreParens())) {
      // We always assume that 'this' is never null.
      return false;
    }
  
    if (const ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(CE)) {
      // And that glvalue casts are never null.
      if (ICE->getValueKind() != VK_RValue)
        return false;
    }
  
    return true;
  }
  
  // VisitCastExpr - Emit code for an explicit or implicit cast.  Implicit casts
  // have to handle a more broad range of conversions than explicit casts, as they
  // handle things like function to ptr-to-function decay etc.
  Value *ScalarExprEmitter::VisitCastExpr(CastExpr *CE) {
    Expr *E = CE->getSubExpr();
    QualType DestTy = CE->getType();
    CastKind Kind = CE->getCastKind();
  
    // These cases are generally not written to ignore the result of
    // evaluating their sub-expressions, so we clear this now.
    bool Ignored = TestAndClearIgnoreResultAssign();
  
    // Since almost all cast kinds apply to scalars, this switch doesn't have
    // a default case, so the compiler will warn on a missing case.  The cases
    // are in the same order as in the CastKind enum.
    switch (Kind) {
    case CK_Dependent: llvm_unreachable("dependent cast kind in IR gen!");
    case CK_BuiltinFnToFnPtr:
      llvm_unreachable("builtin functions are handled elsewhere");
  
    case CK_LValueBitCast:
    case CK_ObjCObjectLValueCast: {
      Address Addr = EmitLValue(E).getAddress();
      Addr = Builder.CreateElementBitCast(Addr, CGF.ConvertTypeForMem(DestTy));
      LValue LV = CGF.MakeAddrLValue(Addr, DestTy);
      return EmitLoadOfLValue(LV, CE->getExprLoc());
    }
  
    case CK_LValueToRValueBitCast: {
      LValue SourceLVal = CGF.EmitLValue(E);
      Address Addr = Builder.CreateElementBitCast(SourceLVal.getAddress(),
                                                  CGF.ConvertTypeForMem(DestTy));
      LValue DestLV = CGF.MakeAddrLValue(Addr, DestTy);
      DestLV.setTBAAInfo(TBAAAccessInfo::getMayAliasInfo());
      return EmitLoadOfLValue(DestLV, CE->getExprLoc());
    }
  
    case CK_CPointerToObjCPointerCast:
    case CK_BlockPointerToObjCPointerCast:
    case CK_AnyPointerToBlockPointerCast:
    case CK_BitCast: {
      Value *Src = Visit(const_cast<Expr*>(E));
      llvm::Type *SrcTy = Src->getType();
      llvm::Type *DstTy = ConvertType(DestTy);
      if (SrcTy->isPtrOrPtrVectorTy() && DstTy->isPtrOrPtrVectorTy() &&
          SrcTy->getPointerAddressSpace() != DstTy->getPointerAddressSpace()) {
        llvm_unreachable("wrong cast for pointers in different address spaces"
                         "(must be an address space cast)!");
      }
  
      if (CGF.SanOpts.has(SanitizerKind::CFIUnrelatedCast)) {
        if (auto PT = DestTy->getAs<PointerType>())
          CGF.EmitVTablePtrCheckForCast(PT->getPointeeType(), Src,
                                        /*MayBeNull=*/true,
                                        CodeGenFunction::CFITCK_UnrelatedCast,
                                        CE->getBeginLoc());
      }
  
      if (CGF.CGM.getCodeGenOpts().StrictVTablePointers) {
        const QualType SrcType = E->getType();
  
        if (SrcType.mayBeNotDynamicClass() && DestTy.mayBeDynamicClass()) {
          // Casting to pointer that could carry dynamic information (provided by
          // invariant.group) requires launder.
          Src = Builder.CreateLaunderInvariantGroup(Src);
        } else if (SrcType.mayBeDynamicClass() && DestTy.mayBeNotDynamicClass()) {
          // Casting to pointer that does not carry dynamic information (provided
          // by invariant.group) requires stripping it.  Note that we don't do it
          // if the source could not be dynamic type and destination could be
          // dynamic because dynamic information is already laundered.  It is
          // because launder(strip(src)) == launder(src), so there is no need to
          // add extra strip before launder.
          Src = Builder.CreateStripInvariantGroup(Src);
        }
      }
  
      // Update heapallocsite metadata when there is an explicit cast.
      if (llvm::CallInst *CI = dyn_cast<llvm::CallInst>(Src))
        if (CI->getMetadata("heapallocsite") && isa<ExplicitCastExpr>(CE))
            CGF.getDebugInfo()->
                addHeapAllocSiteMetadata(CI, CE->getType(), CE->getExprLoc());
  
      return Builder.CreateBitCast(Src, DstTy);
    }
    case CK_AddressSpaceConversion: {
      Expr::EvalResult Result;
      if (E->EvaluateAsRValue(Result, CGF.getContext()) &&
          Result.Val.isNullPointer()) {
        // If E has side effect, it is emitted even if its final result is a
        // null pointer. In that case, a DCE pass should be able to
        // eliminate the useless instructions emitted during translating E.
        if (Result.HasSideEffects)
          Visit(E);
        return CGF.CGM.getNullPointer(cast<llvm::PointerType>(
            ConvertType(DestTy)), DestTy);
      }
      // Since target may map different address spaces in AST to the same address
      // space, an address space conversion may end up as a bitcast.
      return CGF.CGM.getTargetCodeGenInfo().performAddrSpaceCast(
          CGF, Visit(E), E->getType()->getPointeeType().getAddressSpace(),
          DestTy->getPointeeType().getAddressSpace(), ConvertType(DestTy));
    }
    case CK_AtomicToNonAtomic:
    case CK_NonAtomicToAtomic:
    case CK_NoOp:
    case CK_UserDefinedConversion:
      return Visit(const_cast<Expr*>(E));
  
    case CK_BaseToDerived: {
      const CXXRecordDecl *DerivedClassDecl = DestTy->getPointeeCXXRecordDecl();
      assert(DerivedClassDecl && "BaseToDerived arg isn't a C++ object pointer!");
  
      Address Base = CGF.EmitPointerWithAlignment(E);
      Address Derived =
        CGF.GetAddressOfDerivedClass(Base, DerivedClassDecl,
                                     CE->path_begin(), CE->path_end(),
                                     CGF.ShouldNullCheckClassCastValue(CE));
  
      // C++11 [expr.static.cast]p11: Behavior is undefined if a downcast is
      // performed and the object is not of the derived type.
      if (CGF.sanitizePerformTypeCheck())
        CGF.EmitTypeCheck(CodeGenFunction::TCK_DowncastPointer, CE->getExprLoc(),
                          Derived.getPointer(), DestTy->getPointeeType());
  
      if (CGF.SanOpts.has(SanitizerKind::CFIDerivedCast))
        CGF.EmitVTablePtrCheckForCast(
            DestTy->getPointeeType(), Derived.getPointer(),
            /*MayBeNull=*/true, CodeGenFunction::CFITCK_DerivedCast,
            CE->getBeginLoc());
  
      return Derived.getPointer();
    }
    case CK_UncheckedDerivedToBase:
    case CK_DerivedToBase: {
      // The EmitPointerWithAlignment path does this fine; just discard
      // the alignment.
      return CGF.EmitPointerWithAlignment(CE).getPointer();
    }
  
    case CK_Dynamic: {
      Address V = CGF.EmitPointerWithAlignment(E);
      const CXXDynamicCastExpr *DCE = cast<CXXDynamicCastExpr>(CE);
      return CGF.EmitDynamicCast(V, DCE);
    }
  
    case CK_ArrayToPointerDecay:
      return CGF.EmitArrayToPointerDecay(E).getPointer();
    case CK_FunctionToPointerDecay:
      return EmitLValue(E).getPointer();
  
    case CK_NullToPointer:
      if (MustVisitNullValue(E))
        CGF.EmitIgnoredExpr(E);
  
      return CGF.CGM.getNullPointer(cast<llvm::PointerType>(ConvertType(DestTy)),
                                DestTy);
  
    case CK_NullToMemberPointer: {
      if (MustVisitNullValue(E))
        CGF.EmitIgnoredExpr(E);
  
      const MemberPointerType *MPT = CE->getType()->getAs<MemberPointerType>();
      return CGF.CGM.getCXXABI().EmitNullMemberPointer(MPT);
    }
  
    case CK_ReinterpretMemberPointer:
    case CK_BaseToDerivedMemberPointer:
    case CK_DerivedToBaseMemberPointer: {
      Value *Src = Visit(E);
  
      // Note that the AST doesn't distinguish between checked and
      // unchecked member pointer conversions, so we always have to
      // implement checked conversions here.  This is inefficient when
      // actual control flow may be required in order to perform the
      // check, which it is for data member pointers (but not member
      // function pointers on Itanium and ARM).
      return CGF.CGM.getCXXABI().EmitMemberPointerConversion(CGF, CE, Src);
    }
  
    case CK_ARCProduceObject:
      return CGF.EmitARCRetainScalarExpr(E);
    case CK_ARCConsumeObject:
      return CGF.EmitObjCConsumeObject(E->getType(), Visit(E));
    case CK_ARCReclaimReturnedObject:
      return CGF.EmitARCReclaimReturnedObject(E, /*allowUnsafe*/ Ignored);
    case CK_ARCExtendBlockObject:
      return CGF.EmitARCExtendBlockObject(E);
  
    case CK_CopyAndAutoreleaseBlockObject:
      return CGF.EmitBlockCopyAndAutorelease(Visit(E), E->getType());
  
    case CK_FloatingRealToComplex:
    case CK_FloatingComplexCast:
    case CK_IntegralRealToComplex:
    case CK_IntegralComplexCast:
    case CK_IntegralComplexToFloatingComplex:
    case CK_FloatingComplexToIntegralComplex:
    case CK_ConstructorConversion:
    case CK_ToUnion:
      llvm_unreachable("scalar cast to non-scalar value");
  
    case CK_LValueToRValue:
      assert(CGF.getContext().hasSameUnqualifiedType(E->getType(), DestTy));
      assert(E->isGLValue() && "lvalue-to-rvalue applied to r-value!");
      return Visit(const_cast<Expr*>(E));
  
    case CK_IntegralToPointer: {
      Value *Src = Visit(const_cast<Expr*>(E));
  
      // First, convert to the correct width so that we control the kind of
      // extension.
      auto DestLLVMTy = ConvertType(DestTy);
      llvm::Type *MiddleTy = CGF.CGM.getDataLayout().getIntPtrType(DestLLVMTy);
      bool InputSigned = E->getType()->isSignedIntegerOrEnumerationType();
      llvm::Value* IntResult =
        Builder.CreateIntCast(Src, MiddleTy, InputSigned, "conv");
  
      auto *IntToPtr = Builder.CreateIntToPtr(IntResult, DestLLVMTy);
  
      if (CGF.CGM.getCodeGenOpts().StrictVTablePointers) {
        // Going from integer to pointer that could be dynamic requires reloading
        // dynamic information from invariant.group.
        if (DestTy.mayBeDynamicClass())
          IntToPtr = Builder.CreateLaunderInvariantGroup(IntToPtr);
      }
      return IntToPtr;
    }
    case CK_PointerToIntegral: {
      assert(!DestTy->isBooleanType() && "bool should use PointerToBool");
      auto *PtrExpr = Visit(E);
  
      if (CGF.CGM.getCodeGenOpts().StrictVTablePointers) {
        const QualType SrcType = E->getType();
  
        // Casting to integer requires stripping dynamic information as it does
        // not carries it.
        if (SrcType.mayBeDynamicClass())
          PtrExpr = Builder.CreateStripInvariantGroup(PtrExpr);
      }
  
      return Builder.CreatePtrToInt(PtrExpr, ConvertType(DestTy));
    }
    case CK_ToVoid: {
      CGF.EmitIgnoredExpr(E);
      return nullptr;
    }
    case CK_VectorSplat: {
      llvm::Type *DstTy = ConvertType(DestTy);
      Value *Elt = Visit(const_cast<Expr*>(E));
      // Splat the element across to all elements
      unsigned NumElements = DstTy->getVectorNumElements();
      return Builder.CreateVectorSplat(NumElements, Elt, "splat");
    }
  
    case CK_FixedPointCast:
      return EmitScalarConversion(Visit(E), E->getType(), DestTy,
                                  CE->getExprLoc());
  
    case CK_FixedPointToBoolean:
      assert(E->getType()->isFixedPointType() &&
             "Expected src type to be fixed point type");
      assert(DestTy->isBooleanType() && "Expected dest type to be boolean type");
      return EmitScalarConversion(Visit(E), E->getType(), DestTy,
                                  CE->getExprLoc());
  
    case CK_FixedPointToIntegral:
      assert(E->getType()->isFixedPointType() &&
             "Expected src type to be fixed point type");
      assert(DestTy->isIntegerType() && "Expected dest type to be an integer");
      return EmitScalarConversion(Visit(E), E->getType(), DestTy,
                                  CE->getExprLoc());
  
    case CK_IntegralToFixedPoint:
      assert(E->getType()->isIntegerType() &&
             "Expected src type to be an integer");
      assert(DestTy->isFixedPointType() &&
             "Expected dest type to be fixed point type");
      return EmitScalarConversion(Visit(E), E->getType(), DestTy,
                                  CE->getExprLoc());
  
    case CK_IntegralCast: {
      ScalarConversionOpts Opts;
      if (auto *ICE = dyn_cast<ImplicitCastExpr>(CE)) {
        if (!ICE->isPartOfExplicitCast())
          Opts = ScalarConversionOpts(CGF.SanOpts);
      }
      return EmitScalarConversion(Visit(E), E->getType(), DestTy,
                                  CE->getExprLoc(), Opts);
    }
    case CK_IntegralToFloating:
    case CK_FloatingToIntegral:
    case CK_FloatingCast:
      return EmitScalarConversion(Visit(E), E->getType(), DestTy,
                                  CE->getExprLoc());
    case CK_BooleanToSignedIntegral: {
      ScalarConversionOpts Opts;
      Opts.TreatBooleanAsSigned = true;
      return EmitScalarConversion(Visit(E), E->getType(), DestTy,
                                  CE->getExprLoc(), Opts);
    }
    case CK_IntegralToBoolean:
      return EmitIntToBoolConversion(Visit(E));
    case CK_PointerToBoolean:
      return EmitPointerToBoolConversion(Visit(E), E->getType());
    case CK_FloatingToBoolean:
      return EmitFloatToBoolConversion(Visit(E));
    case CK_MemberPointerToBoolean: {
      llvm::Value *MemPtr = Visit(E);
      const MemberPointerType *MPT = E->getType()->getAs<MemberPointerType>();
      return CGF.CGM.getCXXABI().EmitMemberPointerIsNotNull(CGF, MemPtr, MPT);
    }
  
    case CK_FloatingComplexToReal:
    case CK_IntegralComplexToReal:
      return CGF.EmitComplexExpr(E, false, true).first;
  
    case CK_FloatingComplexToBoolean:
    case CK_IntegralComplexToBoolean: {
      CodeGenFunction::ComplexPairTy V = CGF.EmitComplexExpr(E);
  
      // TODO: kill this function off, inline appropriate case here
      return EmitComplexToScalarConversion(V, E->getType(), DestTy,
                                           CE->getExprLoc());
    }
  
    case CK_ZeroToOCLOpaqueType: {
      assert((DestTy->isEventT() || DestTy->isQueueT() ||
              DestTy->isOCLIntelSubgroupAVCType()) &&
             "CK_ZeroToOCLEvent cast on non-event type");
      return llvm::Constant::getNullValue(ConvertType(DestTy));
    }
  
    case CK_IntToOCLSampler:
      return CGF.CGM.createOpenCLIntToSamplerConversion(E, CGF);
  
    } // end of switch
  
    llvm_unreachable("unknown scalar cast");
  }
  
  Value *ScalarExprEmitter::VisitStmtExpr(const StmtExpr *E) {
    CodeGenFunction::StmtExprEvaluation eval(CGF);
    Address RetAlloca = CGF.EmitCompoundStmt(*E->getSubStmt(),
                                             !E->getType()->isVoidType());
    if (!RetAlloca.isValid())
      return nullptr;
    return CGF.EmitLoadOfScalar(CGF.MakeAddrLValue(RetAlloca, E->getType()),
                                E->getExprLoc());
  }
  
  Value *ScalarExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
    CGF.enterFullExpression(E);
    CodeGenFunction::RunCleanupsScope Scope(CGF);
    Value *V = Visit(E->getSubExpr());
    // Defend against dominance problems caused by jumps out of expression
    // evaluation through the shared cleanup block.
    Scope.ForceCleanup({&V});
    return V;
  }
  
  //===----------------------------------------------------------------------===//
  //                             Unary Operators
  //===----------------------------------------------------------------------===//
  
  static BinOpInfo createBinOpInfoFromIncDec(const UnaryOperator *E,
                                             llvm::Value *InVal, bool IsInc) {
    BinOpInfo BinOp;
    BinOp.LHS = InVal;
    BinOp.RHS = llvm::ConstantInt::get(InVal->getType(), 1, false);
    BinOp.Ty = E->getType();
    BinOp.Opcode = IsInc ? BO_Add : BO_Sub;
    // FIXME: once UnaryOperator carries FPFeatures, copy it here.
    BinOp.E = E;
    return BinOp;
  }
  
  llvm::Value *ScalarExprEmitter::EmitIncDecConsiderOverflowBehavior(
      const UnaryOperator *E, llvm::Value *InVal, bool IsInc) {
    llvm::Value *Amount =
        llvm::ConstantInt::get(InVal->getType(), IsInc ? 1 : -1, true);
    StringRef Name = IsInc ? "inc" : "dec";
    switch (CGF.getLangOpts().getSignedOverflowBehavior()) {
    case LangOptions::SOB_Defined:
      return Builder.CreateAdd(InVal, Amount, Name);
    case LangOptions::SOB_Undefined:
      if (!CGF.SanOpts.has(SanitizerKind::SignedIntegerOverflow))
        return Builder.CreateNSWAdd(InVal, Amount, Name);
      LLVM_FALLTHROUGH;
    case LangOptions::SOB_Trapping:
      if (!E->canOverflow())
        return Builder.CreateNSWAdd(InVal, Amount, Name);
      return EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(E, InVal, IsInc));
    }
    llvm_unreachable("Unknown SignedOverflowBehaviorTy");
  }
  
  llvm::Value *
  ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
                                             bool isInc, bool isPre) {
  
    QualType type = E->getSubExpr()->getType();
    llvm::PHINode *atomicPHI = nullptr;
    llvm::Value *value;
    llvm::Value *input;
  
    int amount = (isInc ? 1 : -1);
    bool isSubtraction = !isInc;
  
    if (const AtomicType *atomicTy = type->getAs<AtomicType>()) {
      type = atomicTy->getValueType();
      if (isInc && type->isBooleanType()) {
        llvm::Value *True = CGF.EmitToMemory(Builder.getTrue(), type);
        if (isPre) {
          Builder.CreateStore(True, LV.getAddress(), LV.isVolatileQualified())
            ->setAtomic(llvm::AtomicOrdering::SequentiallyConsistent);
          return Builder.getTrue();
        }
        // For atomic bool increment, we just store true and return it for
        // preincrement, do an atomic swap with true for postincrement
        return Builder.CreateAtomicRMW(
            llvm::AtomicRMWInst::Xchg, LV.getPointer(), True,
            llvm::AtomicOrdering::SequentiallyConsistent);
      }
      // Special case for atomic increment / decrement on integers, emit
      // atomicrmw instructions.  We skip this if we want to be doing overflow
      // checking, and fall into the slow path with the atomic cmpxchg loop.
      if (!type->isBooleanType() && type->isIntegerType() &&
          !(type->isUnsignedIntegerType() &&
            CGF.SanOpts.has(SanitizerKind::UnsignedIntegerOverflow)) &&
          CGF.getLangOpts().getSignedOverflowBehavior() !=
              LangOptions::SOB_Trapping) {
        llvm::AtomicRMWInst::BinOp aop = isInc ? llvm::AtomicRMWInst::Add :
          llvm::AtomicRMWInst::Sub;
        llvm::Instruction::BinaryOps op = isInc ? llvm::Instruction::Add :
          llvm::Instruction::Sub;
        llvm::Value *amt = CGF.EmitToMemory(
            llvm::ConstantInt::get(ConvertType(type), 1, true), type);
        llvm::Value *old = Builder.CreateAtomicRMW(aop,
            LV.getPointer(), amt, llvm::AtomicOrdering::SequentiallyConsistent);
        return isPre ? Builder.CreateBinOp(op, old, amt) : old;
      }
      value = EmitLoadOfLValue(LV, E->getExprLoc());
      input = value;
      // For every other atomic operation, we need to emit a load-op-cmpxchg loop
      llvm::BasicBlock *startBB = Builder.GetInsertBlock();
      llvm::BasicBlock *opBB = CGF.createBasicBlock("atomic_op", CGF.CurFn);
      value = CGF.EmitToMemory(value, type);
      Builder.CreateBr(opBB);
      Builder.SetInsertPoint(opBB);
      atomicPHI = Builder.CreatePHI(value->getType(), 2);
      atomicPHI->addIncoming(value, startBB);
      value = atomicPHI;
    } else {
      value = EmitLoadOfLValue(LV, E->getExprLoc());
      input = value;
    }
  
    // Special case of integer increment that we have to check first: bool++.
    // Due to promotion rules, we get:
    //   bool++ -> bool = bool + 1
    //          -> bool = (int)bool + 1
    //          -> bool = ((int)bool + 1 != 0)
    // An interesting aspect of this is that increment is always true.
    // Decrement does not have this property.
    if (isInc && type->isBooleanType()) {
      value = Builder.getTrue();
  
    // Most common case by far: integer increment.
    } else if (type->isIntegerType()) {
      // Note that signed integer inc/dec with width less than int can't
      // overflow because of promotion rules; we're just eliding a few steps here.
      if (E->canOverflow() && type->isSignedIntegerOrEnumerationType()) {
        value = EmitIncDecConsiderOverflowBehavior(E, value, isInc);
      } else if (E->canOverflow() && type->isUnsignedIntegerType() &&
                 CGF.SanOpts.has(SanitizerKind::UnsignedIntegerOverflow)) {
        value =
            EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(E, value, isInc));
      } else {
        llvm::Value *amt = llvm::ConstantInt::get(value->getType(), amount, true);
        value = Builder.CreateAdd(value, amt, isInc ? "inc" : "dec");
      }
  
    // Next most common: pointer increment.
    } else if (const PointerType *ptr = type->getAs<PointerType>()) {
      QualType type = ptr->getPointeeType();
  
      // VLA types don't have constant size.
      if (const VariableArrayType *vla
            = CGF.getContext().getAsVariableArrayType(type)) {
        llvm::Value *numElts = CGF.getVLASize(vla).NumElts;
        if (!isInc) numElts = Builder.CreateNSWNeg(numElts, "vla.negsize");
        if (CGF.getLangOpts().isSignedOverflowDefined())
          value = Builder.CreateGEP(value, numElts, "vla.inc");
        else
          value = CGF.EmitCheckedInBoundsGEP(
              value, numElts, /*SignedIndices=*/false, isSubtraction,
              E->getExprLoc(), "vla.inc");
  
      // Arithmetic on function pointers (!) is just +-1.
      } else if (type->isFunctionType()) {
        llvm::Value *amt = Builder.getInt32(amount);
  
        value = CGF.EmitCastToVoidPtr(value);
        if (CGF.getLangOpts().isSignedOverflowDefined())
          value = Builder.CreateGEP(value, amt, "incdec.funcptr");
        else
          value = CGF.EmitCheckedInBoundsGEP(value, amt, /*SignedIndices=*/false,
                                             isSubtraction, E->getExprLoc(),
                                             "incdec.funcptr");
        value = Builder.CreateBitCast(value, input->getType());
  
      // For everything else, we can just do a simple increment.
      } else {
        llvm::Value *amt = Builder.getInt32(amount);
        if (CGF.getLangOpts().isSignedOverflowDefined())
          value = Builder.CreateGEP(value, amt, "incdec.ptr");
        else
          value = CGF.EmitCheckedInBoundsGEP(value, amt, /*SignedIndices=*/false,
                                             isSubtraction, E->getExprLoc(),
                                             "incdec.ptr");
      }
  
    // Vector increment/decrement.
    } else if (type->isVectorType()) {
      if (type->hasIntegerRepresentation()) {
        llvm::Value *amt = llvm::ConstantInt::get(value->getType(), amount);
  
        value = Builder.CreateAdd(value, amt, isInc ? "inc" : "dec");
      } else {
        value = Builder.CreateFAdd(
                    value,
                    llvm::ConstantFP::get(value->getType(), amount),
                    isInc ? "inc" : "dec");
      }
  
    // Floating point.
    } else if (type->isRealFloatingType()) {
      // Add the inc/dec to the real part.
      llvm::Value *amt;
  
      if (type->isHalfType() && !CGF.getContext().getLangOpts().NativeHalfType) {
        // Another special case: half FP increment should be done via float
        if (CGF.getContext().getTargetInfo().useFP16ConversionIntrinsics()) {
          value = Builder.CreateCall(
              CGF.CGM.getIntrinsic(llvm::Intrinsic::convert_from_fp16,
                                   CGF.CGM.FloatTy),
              input, "incdec.conv");
        } else {
          value = Builder.CreateFPExt(input, CGF.CGM.FloatTy, "incdec.conv");
        }
      }
  
      if (value->getType()->isFloatTy())
        amt = llvm::ConstantFP::get(VMContext,
                                    llvm::APFloat(static_cast<float>(amount)));
      else if (value->getType()->isDoubleTy())
        amt = llvm::ConstantFP::get(VMContext,
                                    llvm::APFloat(static_cast<double>(amount)));
      else {
        // Remaining types are Half, LongDouble or __float128. Convert from float.
        llvm::APFloat F(static_cast<float>(amount));
        bool ignored;
        const llvm::fltSemantics *FS;
        // Don't use getFloatTypeSemantics because Half isn't
        // necessarily represented using the "half" LLVM type.
        if (value->getType()->isFP128Ty())
          FS = &CGF.getTarget().getFloat128Format();
        else if (value->getType()->isHalfTy())
          FS = &CGF.getTarget().getHalfFormat();
        else
          FS = &CGF.getTarget().getLongDoubleFormat();
        F.convert(*FS, llvm::APFloat::rmTowardZero, &ignored);
        amt = llvm::ConstantFP::get(VMContext, F);
      }
      value = Builder.CreateFAdd(value, amt, isInc ? "inc" : "dec");
  
      if (type->isHalfType() && !CGF.getContext().getLangOpts().NativeHalfType) {
        if (CGF.getContext().getTargetInfo().useFP16ConversionIntrinsics()) {
          value = Builder.CreateCall(
              CGF.CGM.getIntrinsic(llvm::Intrinsic::convert_to_fp16,
                                   CGF.CGM.FloatTy),
              value, "incdec.conv");
        } else {
          value = Builder.CreateFPTrunc(value, input->getType(), "incdec.conv");
        }
      }
  
    // Objective-C pointer types.
    } else {
      const ObjCObjectPointerType *OPT = type->castAs<ObjCObjectPointerType>();
      value = CGF.EmitCastToVoidPtr(value);
  
      CharUnits size = CGF.getContext().getTypeSizeInChars(OPT->getObjectType());
      if (!isInc) size = -size;
      llvm::Value *sizeValue =
        llvm::ConstantInt::get(CGF.SizeTy, size.getQuantity());
  
      if (CGF.getLangOpts().isSignedOverflowDefined())
        value = Builder.CreateGEP(value, sizeValue, "incdec.objptr");
      else
        value = CGF.EmitCheckedInBoundsGEP(value, sizeValue,
                                           /*SignedIndices=*/false, isSubtraction,
                                           E->getExprLoc(), "incdec.objptr");
      value = Builder.CreateBitCast(value, input->getType());
    }
  
    if (atomicPHI) {
      llvm::BasicBlock *curBlock = Builder.GetInsertBlock();
      llvm::BasicBlock *contBB = CGF.createBasicBlock("atomic_cont", CGF.CurFn);
      auto Pair = CGF.EmitAtomicCompareExchange(
          LV, RValue::get(atomicPHI), RValue::get(value), E->getExprLoc());
      llvm::Value *old = CGF.EmitToMemory(Pair.first.getScalarVal(), type);
      llvm::Value *success = Pair.second;
      atomicPHI->addIncoming(old, curBlock);
      Builder.CreateCondBr(success, contBB, atomicPHI->getParent());
      Builder.SetInsertPoint(contBB);
      return isPre ? value : input;
    }
  
    // Store the updated result through the lvalue.
    if (LV.isBitField())
      CGF.EmitStoreThroughBitfieldLValue(RValue::get(value), LV, &value);
    else
      CGF.EmitStoreThroughLValue(RValue::get(value), LV);
  
    // If this is a postinc, return the value read from memory, otherwise use the
    // updated value.
    return isPre ? value : input;
  }
  
  
  
  Value *ScalarExprEmitter::VisitUnaryMinus(const UnaryOperator *E) {
    TestAndClearIgnoreResultAssign();
    // Emit unary minus with EmitSub so we handle overflow cases etc.
    BinOpInfo BinOp;
    BinOp.RHS = Visit(E->getSubExpr());
  
    if (BinOp.RHS->getType()->isFPOrFPVectorTy())
      BinOp.LHS = llvm::ConstantFP::getZeroValueForNegation(BinOp.RHS->getType());
    else
      BinOp.LHS = llvm::Constant::getNullValue(BinOp.RHS->getType());
    BinOp.Ty = E->getType();
    BinOp.Opcode = BO_Sub;
    // FIXME: once UnaryOperator carries FPFeatures, copy it here.
    BinOp.E = E;
    return EmitSub(BinOp);
  }
  
  Value *ScalarExprEmitter::VisitUnaryNot(const UnaryOperator *E) {
    TestAndClearIgnoreResultAssign();
    Value *Op = Visit(E->getSubExpr());
    return Builder.CreateNot(Op, "neg");
  }
  
  Value *ScalarExprEmitter::VisitUnaryLNot(const UnaryOperator *E) {
    // Perform vector logical not on comparison with zero vector.
    if (E->getType()->isExtVectorType()) {
      Value *Oper = Visit(E->getSubExpr());
      Value *Zero = llvm::Constant::getNullValue(Oper->getType());
      Value *Result;
      if (Oper->getType()->isFPOrFPVectorTy())
        Result = Builder.CreateFCmp(llvm::CmpInst::FCMP_OEQ, Oper, Zero, "cmp");
      else
        Result = Builder.CreateICmp(llvm::CmpInst::ICMP_EQ, Oper, Zero, "cmp");
      return Builder.CreateSExt(Result, ConvertType(E->getType()), "sext");
    }
  
    // Compare operand to zero.
    Value *BoolVal = CGF.EvaluateExprAsBool(E->getSubExpr());
  
    // Invert value.
    // TODO: Could dynamically modify easy computations here.  For example, if
    // the operand is an icmp ne, turn into icmp eq.
    BoolVal = Builder.CreateNot(BoolVal, "lnot");
  
    // ZExt result to the expr type.
    return Builder.CreateZExt(BoolVal, ConvertType(E->getType()), "lnot.ext");
  }
  
  Value *ScalarExprEmitter::VisitOffsetOfExpr(OffsetOfExpr *E) {
    // Try folding the offsetof to a constant.
    Expr::EvalResult EVResult;
    if (E->EvaluateAsInt(EVResult, CGF.getContext())) {
      llvm::APSInt Value = EVResult.Val.getInt();
      return Builder.getInt(Value);
    }
  
    // Loop over the components of the offsetof to compute the value.
    unsigned n = E->getNumComponents();
    llvm::Type* ResultType = ConvertType(E->getType());
    llvm::Value* Result = llvm::Constant::getNullValue(ResultType);
    QualType CurrentType = E->getTypeSourceInfo()->getType();
    for (unsigned i = 0; i != n; ++i) {
      OffsetOfNode ON = E->getComponent(i);
      llvm::Value *Offset = nullptr;
      switch (ON.getKind()) {
      case OffsetOfNode::Array: {
        // Compute the index
        Expr *IdxExpr = E->getIndexExpr(ON.getArrayExprIndex());
        llvm::Value* Idx = CGF.EmitScalarExpr(IdxExpr);
        bool IdxSigned = IdxExpr->getType()->isSignedIntegerOrEnumerationType();
        Idx = Builder.CreateIntCast(Idx, ResultType, IdxSigned, "conv");
  
        // Save the element type
        CurrentType =
            CGF.getContext().getAsArrayType(CurrentType)->getElementType();
  
        // Compute the element size
        llvm::Value* ElemSize = llvm::ConstantInt::get(ResultType,
            CGF.getContext().getTypeSizeInChars(CurrentType).getQuantity());
  
        // Multiply out to compute the result
        Offset = Builder.CreateMul(Idx, ElemSize);
        break;
      }
  
      case OffsetOfNode::Field: {
        FieldDecl *MemberDecl = ON.getField();
        RecordDecl *RD = CurrentType->getAs<RecordType>()->getDecl();
        const ASTRecordLayout &RL = CGF.getContext().getASTRecordLayout(RD);
  
        // Compute the index of the field in its parent.
        unsigned i = 0;
        // FIXME: It would be nice if we didn't have to loop here!
        for (RecordDecl::field_iterator Field = RD->field_begin(),
                                        FieldEnd = RD->field_end();
             Field != FieldEnd; ++Field, ++i) {
          if (*Field == MemberDecl)
            break;
        }
        assert(i < RL.getFieldCount() && "offsetof field in wrong type");
  
        // Compute the offset to the field
        int64_t OffsetInt = RL.getFieldOffset(i) /
                            CGF.getContext().getCharWidth();
        Offset = llvm::ConstantInt::get(ResultType, OffsetInt);
  
        // Save the element type.
        CurrentType = MemberDecl->getType();
        break;
      }
  
      case OffsetOfNode::Identifier:
        llvm_unreachable("dependent __builtin_offsetof");
  
      case OffsetOfNode::Base: {
        if (ON.getBase()->isVirtual()) {
          CGF.ErrorUnsupported(E, "virtual base in offsetof");
          continue;
        }
  
        RecordDecl *RD = CurrentType->getAs<RecordType>()->getDecl();
        const ASTRecordLayout &RL = CGF.getContext().getASTRecordLayout(RD);
  
        // Save the element type.
        CurrentType = ON.getBase()->getType();
  
        // Compute the offset to the base.
        const RecordType *BaseRT = CurrentType->getAs<RecordType>();
        CXXRecordDecl *BaseRD = cast<CXXRecordDecl>(BaseRT->getDecl());
        CharUnits OffsetInt = RL.getBaseClassOffset(BaseRD);
        Offset = llvm::ConstantInt::get(ResultType, OffsetInt.getQuantity());
        break;
      }
      }
      Result = Builder.CreateAdd(Result, Offset);
    }
    return Result;
  }
  
  /// VisitUnaryExprOrTypeTraitExpr - Return the size or alignment of the type of
  /// argument of the sizeof expression as an integer.
  Value *
  ScalarExprEmitter::VisitUnaryExprOrTypeTraitExpr(
                                const UnaryExprOrTypeTraitExpr *E) {
    QualType TypeToSize = E->getTypeOfArgument();
    if (E->getKind() == UETT_SizeOf) {
      if (const VariableArrayType *VAT =
            CGF.getContext().getAsVariableArrayType(TypeToSize)) {
        if (E->isArgumentType()) {
          // sizeof(type) - make sure to emit the VLA size.
          CGF.EmitVariablyModifiedType(TypeToSize);
        } else {
          // C99 6.5.3.4p2: If the argument is an expression of type
          // VLA, it is evaluated.
          CGF.EmitIgnoredExpr(E->getArgumentExpr());
        }
  
        auto VlaSize = CGF.getVLASize(VAT);
        llvm::Value *size = VlaSize.NumElts;
  
        // Scale the number of non-VLA elements by the non-VLA element size.
        CharUnits eltSize = CGF.getContext().getTypeSizeInChars(VlaSize.Type);
        if (!eltSize.isOne())
          size = CGF.Builder.CreateNUWMul(CGF.CGM.getSize(eltSize), size);
  
        return size;
      }
    } else if (E->getKind() == UETT_OpenMPRequiredSimdAlign) {
      auto Alignment =
          CGF.getContext()
              .toCharUnitsFromBits(CGF.getContext().getOpenMPDefaultSimdAlign(
                  E->getTypeOfArgument()->getPointeeType()))
              .getQuantity();
      return llvm::ConstantInt::get(CGF.SizeTy, Alignment);
    }
  
    // If this isn't sizeof(vla), the result must be constant; use the constant
    // folding logic so we don't have to duplicate it here.
    return Builder.getInt(E->EvaluateKnownConstInt(CGF.getContext()));
  }
  
  Value *ScalarExprEmitter::VisitUnaryReal(const UnaryOperator *E) {
    Expr *Op = E->getSubExpr();
    if (Op->getType()->isAnyComplexType()) {
      // If it's an l-value, load through the appropriate subobject l-value.
      // Note that we have to ask E because Op might be an l-value that
      // this won't work for, e.g. an Obj-C property.
      if (E->isGLValue())
        return CGF.EmitLoadOfLValue(CGF.EmitLValue(E),
                                    E->getExprLoc()).getScalarVal();
  
      // Otherwise, calculate and project.
      return CGF.EmitComplexExpr(Op, false, true).first;
    }
  
    return Visit(Op);
  }
  
  Value *ScalarExprEmitter::VisitUnaryImag(const UnaryOperator *E) {
    Expr *Op = E->getSubExpr();
    if (Op->getType()->isAnyComplexType()) {
      // If it's an l-value, load through the appropriate subobject l-value.
      // Note that we have to ask E because Op might be an l-value that
      // this won't work for, e.g. an Obj-C property.
      if (Op->isGLValue())
        return CGF.EmitLoadOfLValue(CGF.EmitLValue(E),
                                    E->getExprLoc()).getScalarVal();
  
      // Otherwise, calculate and project.
      return CGF.EmitComplexExpr(Op, true, false).second;
    }
  
    // __imag on a scalar returns zero.  Emit the subexpr to ensure side
    // effects are evaluated, but not the actual value.
    if (Op->isGLValue())
      CGF.EmitLValue(Op);
    else
      CGF.EmitScalarExpr(Op, true);
    return llvm::Constant::getNullValue(ConvertType(E->getType()));
  }
  
  //===----------------------------------------------------------------------===//
  //                           Binary Operators
  //===----------------------------------------------------------------------===//
  
  BinOpInfo ScalarExprEmitter::EmitBinOps(const BinaryOperator *E) {
    TestAndClearIgnoreResultAssign();
    BinOpInfo Result;
    Result.LHS = Visit(E->getLHS());
    Result.RHS = Visit(E->getRHS());
    Result.Ty  = E->getType();
    Result.Opcode = E->getOpcode();
    Result.FPFeatures = E->getFPFeatures();
    Result.E = E;
    return Result;
  }
  
  LValue ScalarExprEmitter::EmitCompoundAssignLValue(
                                                const CompoundAssignOperator *E,
                          Value *(ScalarExprEmitter::*Func)(const BinOpInfo &),
                                                     Value *&Result) {
    QualType LHSTy = E->getLHS()->getType();
    BinOpInfo OpInfo;
  
    if (E->getComputationResultType()->isAnyComplexType())
      return CGF.EmitScalarCompoundAssignWithComplex(E, Result);
  
    // Emit the RHS first.  __block variables need to have the rhs evaluated
    // first, plus this should improve codegen a little.
    OpInfo.RHS = Visit(E->getRHS());
    OpInfo.Ty = E->getComputationResultType();
    OpInfo.Opcode = E->getOpcode();
    OpInfo.FPFeatures = E->getFPFeatures();
    OpInfo.E = E;
    // Load/convert the LHS.
    LValue LHSLV = EmitCheckedLValue(E->getLHS(), CodeGenFunction::TCK_Store);
  
    llvm::PHINode *atomicPHI = nullptr;
    if (const AtomicType *atomicTy = LHSTy->getAs<AtomicType>()) {
      QualType type = atomicTy->getValueType();
      if (!type->isBooleanType() && type->isIntegerType() &&
          !(type->isUnsignedIntegerType() &&
            CGF.SanOpts.has(SanitizerKind::UnsignedIntegerOverflow)) &&
          CGF.getLangOpts().getSignedOverflowBehavior() !=
              LangOptions::SOB_Trapping) {
        llvm::AtomicRMWInst::BinOp aop = llvm::AtomicRMWInst::BAD_BINOP;
        switch (OpInfo.Opcode) {
          // We don't have atomicrmw operands for *, %, /, <<, >>
          case BO_MulAssign: case BO_DivAssign:
          case BO_RemAssign:
          case BO_ShlAssign:
          case BO_ShrAssign:
            break;
          case BO_AddAssign:
            aop = llvm::AtomicRMWInst::Add;
            break;
          case BO_SubAssign:
            aop = llvm::AtomicRMWInst::Sub;
            break;
          case BO_AndAssign:
            aop = llvm::AtomicRMWInst::And;
            break;
          case BO_XorAssign:
            aop = llvm::AtomicRMWInst::Xor;
            break;
          case BO_OrAssign:
            aop = llvm::AtomicRMWInst::Or;
            break;
          default:
            llvm_unreachable("Invalid compound assignment type");
        }
        if (aop != llvm::AtomicRMWInst::BAD_BINOP) {
          llvm::Value *amt = CGF.EmitToMemory(
              EmitScalarConversion(OpInfo.RHS, E->getRHS()->getType(), LHSTy,
                                   E->getExprLoc()),
              LHSTy);
          Builder.CreateAtomicRMW(aop, LHSLV.getPointer(), amt,
              llvm::AtomicOrdering::SequentiallyConsistent);
          return LHSLV;
        }
      }
      // FIXME: For floating point types, we should be saving and restoring the
      // floating point environment in the loop.
      llvm::BasicBlock *startBB = Builder.GetInsertBlock();
      llvm::BasicBlock *opBB = CGF.createBasicBlock("atomic_op", CGF.CurFn);
      OpInfo.LHS = EmitLoadOfLValue(LHSLV, E->getExprLoc());
      OpInfo.LHS = CGF.EmitToMemory(OpInfo.LHS, type);
      Builder.CreateBr(opBB);
      Builder.SetInsertPoint(opBB);
      atomicPHI = Builder.CreatePHI(OpInfo.LHS->getType(), 2);
      atomicPHI->addIncoming(OpInfo.LHS, startBB);
      OpInfo.LHS = atomicPHI;
    }
    else
      OpInfo.LHS = EmitLoadOfLValue(LHSLV, E->getExprLoc());
  
    SourceLocation Loc = E->getExprLoc();
    OpInfo.LHS =
        EmitScalarConversion(OpInfo.LHS, LHSTy, E->getComputationLHSType(), Loc);
  
    // Expand the binary operator.
    Result = (this->*Func)(OpInfo);
  
    // Convert the result back to the LHS type,
    // potentially with Implicit Conversion sanitizer check.
    Result = EmitScalarConversion(Result, E->getComputationResultType(), LHSTy,
                                  Loc, ScalarConversionOpts(CGF.SanOpts));
  
    if (atomicPHI) {
      llvm::BasicBlock *curBlock = Builder.GetInsertBlock();
      llvm::BasicBlock *contBB = CGF.createBasicBlock("atomic_cont", CGF.CurFn);
      auto Pair = CGF.EmitAtomicCompareExchange(
          LHSLV, RValue::get(atomicPHI), RValue::get(Result), E->getExprLoc());
      llvm::Value *old = CGF.EmitToMemory(Pair.first.getScalarVal(), LHSTy);
      llvm::Value *success = Pair.second;
      atomicPHI->addIncoming(old, curBlock);
      Builder.CreateCondBr(success, contBB, atomicPHI->getParent());
      Builder.SetInsertPoint(contBB);
      return LHSLV;
    }
  
    // Store the result value into the LHS lvalue. Bit-fields are handled
    // specially because the result is altered by the store, i.e., [C99 6.5.16p1]
    // 'An assignment expression has the value of the left operand after the
    // assignment...'.
    if (LHSLV.isBitField())
      CGF.EmitStoreThroughBitfieldLValue(RValue::get(Result), LHSLV, &Result);
    else
      CGF.EmitStoreThroughLValue(RValue::get(Result), LHSLV);
  
    return LHSLV;
  }
  
  Value *ScalarExprEmitter::EmitCompoundAssign(const CompoundAssignOperator *E,
                        Value *(ScalarExprEmitter::*Func)(const BinOpInfo &)) {
    bool Ignore = TestAndClearIgnoreResultAssign();
    Value *RHS = nullptr;
    LValue LHS = EmitCompoundAssignLValue(E, Func, RHS);
  
    // If the result is clearly ignored, return now.
    if (Ignore)
      return nullptr;
  
    // The result of an assignment in C is the assigned r-value.
    if (!CGF.getLangOpts().CPlusPlus)
      return RHS;
  
    // If the lvalue is non-volatile, return the computed value of the assignment.
    if (!LHS.isVolatileQualified())
      return RHS;
  
    // Otherwise, reload the value.
    return EmitLoadOfLValue(LHS, E->getExprLoc());
  }
  
  void ScalarExprEmitter::EmitUndefinedBehaviorIntegerDivAndRemCheck(
      const BinOpInfo &Ops, llvm::Value *Zero, bool isDiv) {
    SmallVector<std::pair<llvm::Value *, SanitizerMask>, 2> Checks;
  
    if (CGF.SanOpts.has(SanitizerKind::IntegerDivideByZero)) {
      Checks.push_back(std::make_pair(Builder.CreateICmpNE(Ops.RHS, Zero),
                                      SanitizerKind::IntegerDivideByZero));
    }
  
    const auto *BO = cast<BinaryOperator>(Ops.E);
    if (CGF.SanOpts.has(SanitizerKind::SignedIntegerOverflow) &&
        Ops.Ty->hasSignedIntegerRepresentation() &&
        !IsWidenedIntegerOp(CGF.getContext(), BO->getLHS()) &&
        Ops.mayHaveIntegerOverflow()) {
      llvm::IntegerType *Ty = cast<llvm::IntegerType>(Zero->getType());
  
      llvm::Value *IntMin =
        Builder.getInt(llvm::APInt::getSignedMinValue(Ty->getBitWidth()));
      llvm::Value *NegOne = llvm::ConstantInt::get(Ty, -1ULL);
  
      llvm::Value *LHSCmp = Builder.CreateICmpNE(Ops.LHS, IntMin);
      llvm::Value *RHSCmp = Builder.CreateICmpNE(Ops.RHS, NegOne);
      llvm::Value *NotOverflow = Builder.CreateOr(LHSCmp, RHSCmp, "or");
      Checks.push_back(
          std::make_pair(NotOverflow, SanitizerKind::SignedIntegerOverflow));
    }
  
    if (Checks.size() > 0)
      EmitBinOpCheck(Checks, Ops);
  }
  
  Value *ScalarExprEmitter::EmitDiv(const BinOpInfo &Ops) {
    {
      CodeGenFunction::SanitizerScope SanScope(&CGF);
      if ((CGF.SanOpts.has(SanitizerKind::IntegerDivideByZero) ||
           CGF.SanOpts.has(SanitizerKind::SignedIntegerOverflow)) &&
          Ops.Ty->isIntegerType() &&
          (Ops.mayHaveIntegerDivisionByZero() || Ops.mayHaveIntegerOverflow())) {
        llvm::Value *Zero = llvm::Constant::getNullValue(ConvertType(Ops.Ty));
        EmitUndefinedBehaviorIntegerDivAndRemCheck(Ops, Zero, true);
      } else if (CGF.SanOpts.has(SanitizerKind::FloatDivideByZero) &&
                 Ops.Ty->isRealFloatingType() &&
                 Ops.mayHaveFloatDivisionByZero()) {
        llvm::Value *Zero = llvm::Constant::getNullValue(ConvertType(Ops.Ty));
        llvm::Value *NonZero = Builder.CreateFCmpUNE(Ops.RHS, Zero);
        EmitBinOpCheck(std::make_pair(NonZero, SanitizerKind::FloatDivideByZero),
                       Ops);
      }
    }
  
    if (Ops.LHS->getType()->isFPOrFPVectorTy()) {
      llvm::Value *Val = Builder.CreateFDiv(Ops.LHS, Ops.RHS, "div");
      if (CGF.getLangOpts().OpenCL &&
          !CGF.CGM.getCodeGenOpts().CorrectlyRoundedDivSqrt) {
        // OpenCL v1.1 s7.4: minimum accuracy of single precision / is 2.5ulp
        // OpenCL v1.2 s5.6.4.2: The -cl-fp32-correctly-rounded-divide-sqrt
        // build option allows an application to specify that single precision
        // floating-point divide (x/y and 1/x) and sqrt used in the program
        // source are correctly rounded.
        llvm::Type *ValTy = Val->getType();
        if (ValTy->isFloatTy() ||
            (isa<llvm::VectorType>(ValTy) &&
             cast<llvm::VectorType>(ValTy)->getElementType()->isFloatTy()))
          CGF.SetFPAccuracy(Val, 2.5);
      }
      return Val;
    }
    else if (Ops.Ty->hasUnsignedIntegerRepresentation())
      return Builder.CreateUDiv(Ops.LHS, Ops.RHS, "div");
    else
      return Builder.CreateSDiv(Ops.LHS, Ops.RHS, "div");
  }
  
  Value *ScalarExprEmitter::EmitRem(const BinOpInfo &Ops) {
    // Rem in C can't be a floating point type: C99 6.5.5p2.
    if ((CGF.SanOpts.has(SanitizerKind::IntegerDivideByZero) ||
         CGF.SanOpts.has(SanitizerKind::SignedIntegerOverflow)) &&
        Ops.Ty->isIntegerType() &&
        (Ops.mayHaveIntegerDivisionByZero() || Ops.mayHaveIntegerOverflow())) {
      CodeGenFunction::SanitizerScope SanScope(&CGF);
      llvm::Value *Zero = llvm::Constant::getNullValue(ConvertType(Ops.Ty));
      EmitUndefinedBehaviorIntegerDivAndRemCheck(Ops, Zero, false);
    }
  
    if (Ops.Ty->hasUnsignedIntegerRepresentation())
      return Builder.CreateURem(Ops.LHS, Ops.RHS, "rem");
    else
      return Builder.CreateSRem(Ops.LHS, Ops.RHS, "rem");
  }
  
  Value *ScalarExprEmitter::EmitOverflowCheckedBinOp(const BinOpInfo &Ops) {
    unsigned IID;
    unsigned OpID = 0;
  
    bool isSigned = Ops.Ty->isSignedIntegerOrEnumerationType();
    switch (Ops.Opcode) {
    case BO_Add:
    case BO_AddAssign:
      OpID = 1;
      IID = isSigned ? llvm::Intrinsic::sadd_with_overflow :
                       llvm::Intrinsic::uadd_with_overflow;
      break;
    case BO_Sub:
    case BO_SubAssign:
      OpID = 2;
      IID = isSigned ? llvm::Intrinsic::ssub_with_overflow :
                       llvm::Intrinsic::usub_with_overflow;
      break;
    case BO_Mul:
    case BO_MulAssign:
      OpID = 3;
      IID = isSigned ? llvm::Intrinsic::smul_with_overflow :
                       llvm::Intrinsic::umul_with_overflow;
      break;
    default:
      llvm_unreachable("Unsupported operation for overflow detection");
    }
    OpID <<= 1;
    if (isSigned)
      OpID |= 1;
  
    CodeGenFunction::SanitizerScope SanScope(&CGF);
    llvm::Type *opTy = CGF.CGM.getTypes().ConvertType(Ops.Ty);
  
    llvm::Function *intrinsic = CGF.CGM.getIntrinsic(IID, opTy);
  
    Value *resultAndOverflow = Builder.CreateCall(intrinsic, {Ops.LHS, Ops.RHS});
    Value *result = Builder.CreateExtractValue(resultAndOverflow, 0);
    Value *overflow = Builder.CreateExtractValue(resultAndOverflow, 1);
  
    // Handle overflow with llvm.trap if no custom handler has been specified.
    const std::string *handlerName =
      &CGF.getLangOpts().OverflowHandler;
    if (handlerName->empty()) {
      // If the signed-integer-overflow sanitizer is enabled, emit a call to its
      // runtime. Otherwise, this is a -ftrapv check, so just emit a trap.
      if (!isSigned || CGF.SanOpts.has(SanitizerKind::SignedIntegerOverflow)) {
        llvm::Value *NotOverflow = Builder.CreateNot(overflow);
        SanitizerMask Kind = isSigned ? SanitizerKind::SignedIntegerOverflow
                                : SanitizerKind::UnsignedIntegerOverflow;
        EmitBinOpCheck(std::make_pair(NotOverflow, Kind), Ops);
      } else
        CGF.EmitTrapCheck(Builder.CreateNot(overflow));
      return result;
    }
  
    // Branch in case of overflow.
    llvm::BasicBlock *initialBB = Builder.GetInsertBlock();
    llvm::BasicBlock *continueBB =
        CGF.createBasicBlock("nooverflow", CGF.CurFn, initialBB->getNextNode());
    llvm::BasicBlock *overflowBB = CGF.createBasicBlock("overflow", CGF.CurFn);
  
    Builder.CreateCondBr(overflow, overflowBB, continueBB);
  
    // If an overflow handler is set, then we want to call it and then use its
    // result, if it returns.
    Builder.SetInsertPoint(overflowBB);
  
    // Get the overflow handler.
    llvm::Type *Int8Ty = CGF.Int8Ty;
    llvm::Type *argTypes[] = { CGF.Int64Ty, CGF.Int64Ty, Int8Ty, Int8Ty };
    llvm::FunctionType *handlerTy =
        llvm::FunctionType::get(CGF.Int64Ty, argTypes, true);
    llvm::FunctionCallee handler =
        CGF.CGM.CreateRuntimeFunction(handlerTy, *handlerName);
  
    // Sign extend the args to 64-bit, so that we can use the same handler for
    // all types of overflow.
    llvm::Value *lhs = Builder.CreateSExt(Ops.LHS, CGF.Int64Ty);
    llvm::Value *rhs = Builder.CreateSExt(Ops.RHS, CGF.Int64Ty);
  
    // Call the handler with the two arguments, the operation, and the size of
    // the result.
    llvm::Value *handlerArgs[] = {
      lhs,
      rhs,
      Builder.getInt8(OpID),
      Builder.getInt8(cast<llvm::IntegerType>(opTy)->getBitWidth())
    };
    llvm::Value *handlerResult =
      CGF.EmitNounwindRuntimeCall(handler, handlerArgs);
  
    // Truncate the result back to the desired size.
    handlerResult = Builder.CreateTrunc(handlerResult, opTy);
    Builder.CreateBr(continueBB);
  
    Builder.SetInsertPoint(continueBB);
    llvm::PHINode *phi = Builder.CreatePHI(opTy, 2);
    phi->addIncoming(result, initialBB);
    phi->addIncoming(handlerResult, overflowBB);
  
    return phi;
  }
  
  /// Emit pointer + index arithmetic.
  static Value *emitPointerArithmetic(CodeGenFunction &CGF,
                                      const BinOpInfo &op,
                                      bool isSubtraction) {
    // Must have binary (not unary) expr here.  Unary pointer
    // increment/decrement doesn't use this path.
    const BinaryOperator *expr = cast<BinaryOperator>(op.E);
  
    Value *pointer = op.LHS;
    Expr *pointerOperand = expr->getLHS();
    Value *index = op.RHS;
    Expr *indexOperand = expr->getRHS();
  
    // In a subtraction, the LHS is always the pointer.
    if (!isSubtraction && !pointer->getType()->isPointerTy()) {
      std::swap(pointer, index);
      std::swap(pointerOperand, indexOperand);
    }
  
    bool isSigned = indexOperand->getType()->isSignedIntegerOrEnumerationType();
  
    unsigned width = cast<llvm::IntegerType>(index->getType())->getBitWidth();
    auto &DL = CGF.CGM.getDataLayout();
    auto PtrTy = cast<llvm::PointerType>(pointer->getType());
  
    // Some versions of glibc and gcc use idioms (particularly in their malloc
    // routines) that add a pointer-sized integer (known to be a pointer value)
    // to a null pointer in order to cast the value back to an integer or as
    // part of a pointer alignment algorithm.  This is undefined behavior, but
    // we'd like to be able to compile programs that use it.
    //
    // Normally, we'd generate a GEP with a null-pointer base here in response
    // to that code, but it's also UB to dereference a pointer created that
    // way.  Instead (as an acknowledged hack to tolerate the idiom) we will
    // generate a direct cast of the integer value to a pointer.
    //
    // The idiom (p = nullptr + N) is not met if any of the following are true:
    //
    //   The operation is subtraction.
    //   The index is not pointer-sized.
    //   The pointer type is not byte-sized.
    //
    if (BinaryOperator::isNullPointerArithmeticExtension(CGF.getContext(),
                                                         op.Opcode,
                                                         expr->getLHS(),
                                                         expr->getRHS()))
      return CGF.Builder.CreateIntToPtr(index, pointer->getType());
  
    if (width != DL.getTypeSizeInBits(PtrTy)) {
      // Zero-extend or sign-extend the pointer value according to
      // whether the index is signed or not.
      index = CGF.Builder.CreateIntCast(index, DL.getIntPtrType(PtrTy), isSigned,
                                        "idx.ext");
    }
  
    // If this is subtraction, negate the index.
    if (isSubtraction)
      index = CGF.Builder.CreateNeg(index, "idx.neg");
  
    if (CGF.SanOpts.has(SanitizerKind::ArrayBounds))
      CGF.EmitBoundsCheck(op.E, pointerOperand, index, indexOperand->getType(),
                          /*Accessed*/ false);
  
    const PointerType *pointerType
      = pointerOperand->getType()->getAs<PointerType>();
    if (!pointerType) {
      QualType objectType = pointerOperand->getType()
                                          ->castAs<ObjCObjectPointerType>()
                                          ->getPointeeType();
      llvm::Value *objectSize
        = CGF.CGM.getSize(CGF.getContext().getTypeSizeInChars(objectType));
  
      index = CGF.Builder.CreateMul(index, objectSize);
  
      Value *result = CGF.Builder.CreateBitCast(pointer, CGF.VoidPtrTy);
      result = CGF.Builder.CreateGEP(result, index, "add.ptr");
      return CGF.Builder.CreateBitCast(result, pointer->getType());
    }
  
    QualType elementType = pointerType->getPointeeType();
    if (const VariableArrayType *vla
          = CGF.getContext().getAsVariableArrayType(elementType)) {
      // The element count here is the total number of non-VLA elements.
      llvm::Value *numElements = CGF.getVLASize(vla).NumElts;
  
      // Effectively, the multiply by the VLA size is part of the GEP.
      // GEP indexes are signed, and scaling an index isn't permitted to
      // signed-overflow, so we use the same semantics for our explicit
      // multiply.  We suppress this if overflow is not undefined behavior.
      if (CGF.getLangOpts().isSignedOverflowDefined()) {
        index = CGF.Builder.CreateMul(index, numElements, "vla.index");
        pointer = CGF.Builder.CreateGEP(pointer, index, "add.ptr");
      } else {
        index = CGF.Builder.CreateNSWMul(index, numElements, "vla.index");
        pointer =
            CGF.EmitCheckedInBoundsGEP(pointer, index, isSigned, isSubtraction,
                                       op.E->getExprLoc(), "add.ptr");
      }
      return pointer;
    }
  
    // Explicitly handle GNU void* and function pointer arithmetic extensions. The
    // GNU void* casts amount to no-ops since our void* type is i8*, but this is
    // future proof.
    if (elementType->isVoidType() || elementType->isFunctionType()) {
      Value *result = CGF.Builder.CreateBitCast(pointer, CGF.VoidPtrTy);
      result = CGF.Builder.CreateGEP(result, index, "add.ptr");
      return CGF.Builder.CreateBitCast(result, pointer->getType());
    }
  
    if (CGF.getLangOpts().isSignedOverflowDefined())
      return CGF.Builder.CreateGEP(pointer, index, "add.ptr");
  
    return CGF.EmitCheckedInBoundsGEP(pointer, index, isSigned, isSubtraction,
                                      op.E->getExprLoc(), "add.ptr");
  }
  
  // Construct an fmuladd intrinsic to represent a fused mul-add of MulOp and
  // Addend. Use negMul and negAdd to negate the first operand of the Mul or
  // the add operand respectively. This allows fmuladd to represent a*b-c, or
  // c-a*b. Patterns in LLVM should catch the negated forms and translate them to
  // efficient operations.
  static Value* buildFMulAdd(llvm::BinaryOperator *MulOp, Value *Addend,
                             const CodeGenFunction &CGF, CGBuilderTy &Builder,
                             bool negMul, bool negAdd) {
    assert(!(negMul && negAdd) && "Only one of negMul and negAdd should be set.");
  
    Value *MulOp0 = MulOp->getOperand(0);
    Value *MulOp1 = MulOp->getOperand(1);
    if (negMul) {
      MulOp0 =
        Builder.CreateFSub(
          llvm::ConstantFP::getZeroValueForNegation(MulOp0->getType()), MulOp0,
          "neg");
    } else if (negAdd) {
      Addend =
        Builder.CreateFSub(
          llvm::ConstantFP::getZeroValueForNegation(Addend->getType()), Addend,
          "neg");
    }
  
    Value *FMulAdd = Builder.CreateCall(
        CGF.CGM.getIntrinsic(llvm::Intrinsic::fmuladd, Addend->getType()),
        {MulOp0, MulOp1, Addend});
     MulOp->eraseFromParent();
  
     return FMulAdd;
  }
  
  // Check whether it would be legal to emit an fmuladd intrinsic call to
  // represent op and if so, build the fmuladd.
  //
  // Checks that (a) the operation is fusable, and (b) -ffp-contract=on.
  // Does NOT check the type of the operation - it's assumed that this function
  // will be called from contexts where it's known that the type is contractable.
  static Value* tryEmitFMulAdd(const BinOpInfo &op,
                           const CodeGenFunction &CGF, CGBuilderTy &Builder,
                           bool isSub=false) {
  
    assert((op.Opcode == BO_Add || op.Opcode == BO_AddAssign ||
            op.Opcode == BO_Sub || op.Opcode == BO_SubAssign) &&
           "Only fadd/fsub can be the root of an fmuladd.");
  
    // Check whether this op is marked as fusable.
    if (!op.FPFeatures.allowFPContractWithinStatement())
      return nullptr;
  
    // We have a potentially fusable op. Look for a mul on one of the operands.
    // Also, make sure that the mul result isn't used directly. In that case,
    // there's no point creating a muladd operation.
    if (auto *LHSBinOp = dyn_cast<llvm::BinaryOperator>(op.LHS)) {
      if (LHSBinOp->getOpcode() == llvm::Instruction::FMul &&
          LHSBinOp->use_empty())
        return buildFMulAdd(LHSBinOp, op.RHS, CGF, Builder, false, isSub);
    }
    if (auto *RHSBinOp = dyn_cast<llvm::BinaryOperator>(op.RHS)) {
      if (RHSBinOp->getOpcode() == llvm::Instruction::FMul &&
          RHSBinOp->use_empty())
        return buildFMulAdd(RHSBinOp, op.LHS, CGF, Builder, isSub, false);
    }
  
    return nullptr;
  }
  
  Value *ScalarExprEmitter::EmitAdd(const BinOpInfo &op) {
    if (op.LHS->getType()->isPointerTy() ||
        op.RHS->getType()->isPointerTy())
      return emitPointerArithmetic(CGF, op, CodeGenFunction::NotSubtraction);
  
    if (op.Ty->isSignedIntegerOrEnumerationType()) {
      switch (CGF.getLangOpts().getSignedOverflowBehavior()) {
      case LangOptions::SOB_Defined:
        return Builder.CreateAdd(op.LHS, op.RHS, "add");
      case LangOptions::SOB_Undefined:
        if (!CGF.SanOpts.has(SanitizerKind::SignedIntegerOverflow))
          return Builder.CreateNSWAdd(op.LHS, op.RHS, "add");
        LLVM_FALLTHROUGH;
      case LangOptions::SOB_Trapping:
        if (CanElideOverflowCheck(CGF.getContext(), op))
          return Builder.CreateNSWAdd(op.LHS, op.RHS, "add");
        return EmitOverflowCheckedBinOp(op);
      }
    }
  
    if (op.Ty->isUnsignedIntegerType() &&
        CGF.SanOpts.has(SanitizerKind::UnsignedIntegerOverflow) &&
        !CanElideOverflowCheck(CGF.getContext(), op))
      return EmitOverflowCheckedBinOp(op);
  
    if (op.LHS->getType()->isFPOrFPVectorTy()) {
      // Try to form an fmuladd.
      if (Value *FMulAdd = tryEmitFMulAdd(op, CGF, Builder))
        return FMulAdd;
  
      Value *V = Builder.CreateFAdd(op.LHS, op.RHS, "add");
      return propagateFMFlags(V, op);
    }
  
    if (op.isFixedPointBinOp())
      return EmitFixedPointBinOp(op);
  
    return Builder.CreateAdd(op.LHS, op.RHS, "add");
  }
  
  /// The resulting value must be calculated with exact precision, so the operands
  /// may not be the same type.
  Value *ScalarExprEmitter::EmitFixedPointBinOp(const BinOpInfo &op) {
    using llvm::APSInt;
    using llvm::ConstantInt;
  
    const auto *BinOp = cast<BinaryOperator>(op.E);
  
    // The result is a fixed point type and at least one of the operands is fixed
    // point while the other is either fixed point or an int. This resulting type
    // should be determined by Sema::handleFixedPointConversions().
    QualType ResultTy = op.Ty;
    QualType LHSTy = BinOp->getLHS()->getType();
    QualType RHSTy = BinOp->getRHS()->getType();
    ASTContext &Ctx = CGF.getContext();
    Value *LHS = op.LHS;
    Value *RHS = op.RHS;
  
    auto LHSFixedSema = Ctx.getFixedPointSemantics(LHSTy);
    auto RHSFixedSema = Ctx.getFixedPointSemantics(RHSTy);
    auto ResultFixedSema = Ctx.getFixedPointSemantics(ResultTy);
    auto CommonFixedSema = LHSFixedSema.getCommonSemantics(RHSFixedSema);
  
    // Convert the operands to the full precision type.
    Value *FullLHS = EmitFixedPointConversion(LHS, LHSFixedSema, CommonFixedSema,
                                              BinOp->getExprLoc());
    Value *FullRHS = EmitFixedPointConversion(RHS, RHSFixedSema, CommonFixedSema,
                                              BinOp->getExprLoc());
  
    // Perform the actual addition.
    Value *Result;
    switch (BinOp->getOpcode()) {
    case BO_Add: {
      if (ResultFixedSema.isSaturated()) {
        llvm::Intrinsic::ID IID = ResultFixedSema.isSigned()
                                      ? llvm::Intrinsic::sadd_sat
                                      : llvm::Intrinsic::uadd_sat;
        Result = Builder.CreateBinaryIntrinsic(IID, FullLHS, FullRHS);
      } else {
        Result = Builder.CreateAdd(FullLHS, FullRHS);
      }
      break;
    }
    case BO_Sub: {
      if (ResultFixedSema.isSaturated()) {
        llvm::Intrinsic::ID IID = ResultFixedSema.isSigned()
                                      ? llvm::Intrinsic::ssub_sat
                                      : llvm::Intrinsic::usub_sat;
        Result = Builder.CreateBinaryIntrinsic(IID, FullLHS, FullRHS);
      } else {
        Result = Builder.CreateSub(FullLHS, FullRHS);
      }
      break;
    }
    case BO_LT:
      return CommonFixedSema.isSigned() ? Builder.CreateICmpSLT(FullLHS, FullRHS)
                                        : Builder.CreateICmpULT(FullLHS, FullRHS);
    case BO_GT:
      return CommonFixedSema.isSigned() ? Builder.CreateICmpSGT(FullLHS, FullRHS)
                                        : Builder.CreateICmpUGT(FullLHS, FullRHS);
    case BO_LE:
      return CommonFixedSema.isSigned() ? Builder.CreateICmpSLE(FullLHS, FullRHS)
                                        : Builder.CreateICmpULE(FullLHS, FullRHS);
    case BO_GE:
      return CommonFixedSema.isSigned() ? Builder.CreateICmpSGE(FullLHS, FullRHS)
                                        : Builder.CreateICmpUGE(FullLHS, FullRHS);
    case BO_EQ:
      // For equality operations, we assume any padding bits on unsigned types are
      // zero'd out. They could be overwritten through non-saturating operations
      // that cause overflow, but this leads to undefined behavior.
      return Builder.CreateICmpEQ(FullLHS, FullRHS);
    case BO_NE:
      return Builder.CreateICmpNE(FullLHS, FullRHS);
    case BO_Mul:
    case BO_Div:
    case BO_Shl:
    case BO_Shr:
    case BO_Cmp:
    case BO_LAnd:
    case BO_LOr:
    case BO_MulAssign:
    case BO_DivAssign:
    case BO_AddAssign:
    case BO_SubAssign:
    case BO_ShlAssign:
    case BO_ShrAssign:
      llvm_unreachable("Found unimplemented fixed point binary operation");
    case BO_PtrMemD:
    case BO_PtrMemI:
    case BO_Rem:
    case BO_Xor:
    case BO_And:
    case BO_Or:
    case BO_Assign:
    case BO_RemAssign:
    case BO_AndAssign:
    case BO_XorAssign:
    case BO_OrAssign:
    case BO_Comma:
      llvm_unreachable("Found unsupported binary operation for fixed point types.");
    }
  
    // Convert to the result type.
    return EmitFixedPointConversion(Result, CommonFixedSema, ResultFixedSema,
                                    BinOp->getExprLoc());
  }
  
  Value *ScalarExprEmitter::EmitSub(const BinOpInfo &op) {
    // The LHS is always a pointer if either side is.
    if (!op.LHS->getType()->isPointerTy()) {
      if (op.Ty->isSignedIntegerOrEnumerationType()) {
        switch (CGF.getLangOpts().getSignedOverflowBehavior()) {
        case LangOptions::SOB_Defined:
          return Builder.CreateSub(op.LHS, op.RHS, "sub");
        case LangOptions::SOB_Undefined:
          if (!CGF.SanOpts.has(SanitizerKind::SignedIntegerOverflow))
            return Builder.CreateNSWSub(op.LHS, op.RHS, "sub");
          LLVM_FALLTHROUGH;
        case LangOptions::SOB_Trapping:
          if (CanElideOverflowCheck(CGF.getContext(), op))
            return Builder.CreateNSWSub(op.LHS, op.RHS, "sub");
          return EmitOverflowCheckedBinOp(op);
        }
      }
  
      if (op.Ty->isUnsignedIntegerType() &&
          CGF.SanOpts.has(SanitizerKind::UnsignedIntegerOverflow) &&
          !CanElideOverflowCheck(CGF.getContext(), op))
        return EmitOverflowCheckedBinOp(op);
  
      if (op.LHS->getType()->isFPOrFPVectorTy()) {
        // Try to form an fmuladd.
        if (Value *FMulAdd = tryEmitFMulAdd(op, CGF, Builder, true))
          return FMulAdd;
        Value *V = Builder.CreateFSub(op.LHS, op.RHS, "sub");
        return propagateFMFlags(V, op);
      }
  
      if (op.isFixedPointBinOp())
        return EmitFixedPointBinOp(op);
  
      return Builder.CreateSub(op.LHS, op.RHS, "sub");
    }
  
    // If the RHS is not a pointer, then we have normal pointer
    // arithmetic.
    if (!op.RHS->getType()->isPointerTy())
      return emitPointerArithmetic(CGF, op, CodeGenFunction::IsSubtraction);
  
    // Otherwise, this is a pointer subtraction.
  
    // Do the raw subtraction part.
    llvm::Value *LHS
      = Builder.CreatePtrToInt(op.LHS, CGF.PtrDiffTy, "sub.ptr.lhs.cast");
    llvm::Value *RHS
      = Builder.CreatePtrToInt(op.RHS, CGF.PtrDiffTy, "sub.ptr.rhs.cast");
    Value *diffInChars = Builder.CreateSub(LHS, RHS, "sub.ptr.sub");
  
    // Okay, figure out the element size.
    const BinaryOperator *expr = cast<BinaryOperator>(op.E);
    QualType elementType = expr->getLHS()->getType()->getPointeeType();
  
    llvm::Value *divisor = nullptr;
  
    // For a variable-length array, this is going to be non-constant.
    if (const VariableArrayType *vla
          = CGF.getContext().getAsVariableArrayType(elementType)) {
      auto VlaSize = CGF.getVLASize(vla);
      elementType = VlaSize.Type;
      divisor = VlaSize.NumElts;
  
      // Scale the number of non-VLA elements by the non-VLA element size.
      CharUnits eltSize = CGF.getContext().getTypeSizeInChars(elementType);
      if (!eltSize.isOne())
        divisor = CGF.Builder.CreateNUWMul(CGF.CGM.getSize(eltSize), divisor);
  
    // For everything elese, we can just compute it, safe in the
    // assumption that Sema won't let anything through that we can't
    // safely compute the size of.
    } else {
      CharUnits elementSize;
      // Handle GCC extension for pointer arithmetic on void* and
      // function pointer types.
      if (elementType->isVoidType() || elementType->isFunctionType())
        elementSize = CharUnits::One();
      else
        elementSize = CGF.getContext().getTypeSizeInChars(elementType);
  
      // Don't even emit the divide for element size of 1.
      if (elementSize.isOne())
        return diffInChars;
  
      divisor = CGF.CGM.getSize(elementSize);
    }
  
    // Otherwise, do a full sdiv. This uses the "exact" form of sdiv, since
    // pointer difference in C is only defined in the case where both operands
    // are pointing to elements of an array.
    return Builder.CreateExactSDiv(diffInChars, divisor, "sub.ptr.div");
  }
  
  Value *ScalarExprEmitter::GetWidthMinusOneValue(Value* LHS,Value* RHS) {
    llvm::IntegerType *Ty;
    if (llvm::VectorType *VT = dyn_cast<llvm::VectorType>(LHS->getType()))
      Ty = cast<llvm::IntegerType>(VT->getElementType());
    else
      Ty = cast<llvm::IntegerType>(LHS->getType());
    return llvm::ConstantInt::get(RHS->getType(), Ty->getBitWidth() - 1);
  }
  
  Value *ScalarExprEmitter::EmitShl(const BinOpInfo &Ops) {
    // LLVM requires the LHS and RHS to be the same type: promote or truncate the
    // RHS to the same size as the LHS.
    Value *RHS = Ops.RHS;
    if (Ops.LHS->getType() != RHS->getType())
      RHS = Builder.CreateIntCast(RHS, Ops.LHS->getType(), false, "sh_prom");
  
    bool SanitizeBase = CGF.SanOpts.has(SanitizerKind::ShiftBase) &&
                        Ops.Ty->hasSignedIntegerRepresentation() &&
                        !CGF.getLangOpts().isSignedOverflowDefined() &&
                        !CGF.getLangOpts().CPlusPlus2a;
    bool SanitizeExponent = CGF.SanOpts.has(SanitizerKind::ShiftExponent);
    // OpenCL 6.3j: shift values are effectively % word size of LHS.
    if (CGF.getLangOpts().OpenCL)
      RHS =
          Builder.CreateAnd(RHS, GetWidthMinusOneValue(Ops.LHS, RHS), "shl.mask");
    else if ((SanitizeBase || SanitizeExponent) &&
             isa<llvm::IntegerType>(Ops.LHS->getType())) {
      CodeGenFunction::SanitizerScope SanScope(&CGF);
      SmallVector<std::pair<Value *, SanitizerMask>, 2> Checks;
      llvm::Value *WidthMinusOne = GetWidthMinusOneValue(Ops.LHS, Ops.RHS);
      llvm::Value *ValidExponent = Builder.CreateICmpULE(Ops.RHS, WidthMinusOne);
  
      if (SanitizeExponent) {
        Checks.push_back(
            std::make_pair(ValidExponent, SanitizerKind::ShiftExponent));
      }
  
      if (SanitizeBase) {
        // Check whether we are shifting any non-zero bits off the top of the
        // integer. We only emit this check if exponent is valid - otherwise
        // instructions below will have undefined behavior themselves.
        llvm::BasicBlock *Orig = Builder.GetInsertBlock();
        llvm::BasicBlock *Cont = CGF.createBasicBlock("cont");
        llvm::BasicBlock *CheckShiftBase = CGF.createBasicBlock("check");
        Builder.CreateCondBr(ValidExponent, CheckShiftBase, Cont);
        llvm::Value *PromotedWidthMinusOne =
            (RHS == Ops.RHS) ? WidthMinusOne
                             : GetWidthMinusOneValue(Ops.LHS, RHS);
        CGF.EmitBlock(CheckShiftBase);
        llvm::Value *BitsShiftedOff = Builder.CreateLShr(
            Ops.LHS, Builder.CreateSub(PromotedWidthMinusOne, RHS, "shl.zeros",
                                       /*NUW*/ true, /*NSW*/ true),
            "shl.check");
        if (CGF.getLangOpts().CPlusPlus) {
          // In C99, we are not permitted to shift a 1 bit into the sign bit.
          // Under C++11's rules, shifting a 1 bit into the sign bit is
          // OK, but shifting a 1 bit out of it is not. (C89 and C++03 don't
          // define signed left shifts, so we use the C99 and C++11 rules there).
          llvm::Value *One = llvm::ConstantInt::get(BitsShiftedOff->getType(), 1);
          BitsShiftedOff = Builder.CreateLShr(BitsShiftedOff, One);
        }
        llvm::Value *Zero = llvm::ConstantInt::get(BitsShiftedOff->getType(), 0);
        llvm::Value *ValidBase = Builder.CreateICmpEQ(BitsShiftedOff, Zero);
        CGF.EmitBlock(Cont);
        llvm::PHINode *BaseCheck = Builder.CreatePHI(ValidBase->getType(), 2);
        BaseCheck->addIncoming(Builder.getTrue(), Orig);
        BaseCheck->addIncoming(ValidBase, CheckShiftBase);
        Checks.push_back(std::make_pair(BaseCheck, SanitizerKind::ShiftBase));
      }
  
      assert(!Checks.empty());
      EmitBinOpCheck(Checks, Ops);
    }
  
    return Builder.CreateShl(Ops.LHS, RHS, "shl");
  }
  
  Value *ScalarExprEmitter::EmitShr(const BinOpInfo &Ops) {
    // LLVM requires the LHS and RHS to be the same type: promote or truncate the
    // RHS to the same size as the LHS.
    Value *RHS = Ops.RHS;
    if (Ops.LHS->getType() != RHS->getType())
      RHS = Builder.CreateIntCast(RHS, Ops.LHS->getType(), false, "sh_prom");
  
    // OpenCL 6.3j: shift values are effectively % word size of LHS.
    if (CGF.getLangOpts().OpenCL)
      RHS =
          Builder.CreateAnd(RHS, GetWidthMinusOneValue(Ops.LHS, RHS), "shr.mask");
    else if (CGF.SanOpts.has(SanitizerKind::ShiftExponent) &&
             isa<llvm::IntegerType>(Ops.LHS->getType())) {
      CodeGenFunction::SanitizerScope SanScope(&CGF);
      llvm::Value *Valid =
          Builder.CreateICmpULE(RHS, GetWidthMinusOneValue(Ops.LHS, RHS));
      EmitBinOpCheck(std::make_pair(Valid, SanitizerKind::ShiftExponent), Ops);
    }
  
    if (Ops.Ty->hasUnsignedIntegerRepresentation())
      return Builder.CreateLShr(Ops.LHS, RHS, "shr");
    return Builder.CreateAShr(Ops.LHS, RHS, "shr");
  }
  
  enum IntrinsicType { VCMPEQ, VCMPGT };
  // return corresponding comparison intrinsic for given vector type
  static llvm::Intrinsic::ID GetIntrinsic(IntrinsicType IT,
                                          BuiltinType::Kind ElemKind) {
    switch (ElemKind) {
    default: llvm_unreachable("unexpected element type");
    case BuiltinType::Char_U:
    case BuiltinType::UChar:
      return (IT == VCMPEQ) ? llvm::Intrinsic::ppc_altivec_vcmpequb_p :
                              llvm::Intrinsic::ppc_altivec_vcmpgtub_p;
    case BuiltinType::Char_S:
    case BuiltinType::SChar:
      return (IT == VCMPEQ) ? llvm::Intrinsic::ppc_altivec_vcmpequb_p :
                              llvm::Intrinsic::ppc_altivec_vcmpgtsb_p;
    case BuiltinType::UShort:
      return (IT == VCMPEQ) ? llvm::Intrinsic::ppc_altivec_vcmpequh_p :
                              llvm::Intrinsic::ppc_altivec_vcmpgtuh_p;
    case BuiltinType::Short:
      return (IT == VCMPEQ) ? llvm::Intrinsic::ppc_altivec_vcmpequh_p :
                              llvm::Intrinsic::ppc_altivec_vcmpgtsh_p;
    case BuiltinType::UInt:
      return (IT == VCMPEQ) ? llvm::Intrinsic::ppc_altivec_vcmpequw_p :
                              llvm::Intrinsic::ppc_altivec_vcmpgtuw_p;
    case BuiltinType::Int:
      return (IT == VCMPEQ) ? llvm::Intrinsic::ppc_altivec_vcmpequw_p :
                              llvm::Intrinsic::ppc_altivec_vcmpgtsw_p;
    case BuiltinType::ULong:
    case BuiltinType::ULongLong:
      return (IT == VCMPEQ) ? llvm::Intrinsic::ppc_altivec_vcmpequd_p :
                              llvm::Intrinsic::ppc_altivec_vcmpgtud_p;
    case BuiltinType::Long:
    case BuiltinType::LongLong:
      return (IT == VCMPEQ) ? llvm::Intrinsic::ppc_altivec_vcmpequd_p :
                              llvm::Intrinsic::ppc_altivec_vcmpgtsd_p;
    case BuiltinType::Float:
      return (IT == VCMPEQ) ? llvm::Intrinsic::ppc_altivec_vcmpeqfp_p :
                              llvm::Intrinsic::ppc_altivec_vcmpgtfp_p;
    case BuiltinType::Double:
      return (IT == VCMPEQ) ? llvm::Intrinsic::ppc_vsx_xvcmpeqdp_p :
                              llvm::Intrinsic::ppc_vsx_xvcmpgtdp_p;
    }
  }
  
  Value *ScalarExprEmitter::EmitCompare(const BinaryOperator *E,
                                        llvm::CmpInst::Predicate UICmpOpc,
                                        llvm::CmpInst::Predicate SICmpOpc,
                                        llvm::CmpInst::Predicate FCmpOpc) {
    TestAndClearIgnoreResultAssign();
    Value *Result;
    QualType LHSTy = E->getLHS()->getType();
    QualType RHSTy = E->getRHS()->getType();
    if (const MemberPointerType *MPT = LHSTy->getAs<MemberPointerType>()) {
      assert(E->getOpcode() == BO_EQ ||
             E->getOpcode() == BO_NE);
      Value *LHS = CGF.EmitScalarExpr(E->getLHS());
      Value *RHS = CGF.EmitScalarExpr(E->getRHS());
      Result = CGF.CGM.getCXXABI().EmitMemberPointerComparison(
                     CGF, LHS, RHS, MPT, E->getOpcode() == BO_NE);
    } else if (!LHSTy->isAnyComplexType() && !RHSTy->isAnyComplexType()) {
      BinOpInfo BOInfo = EmitBinOps(E);
      Value *LHS = BOInfo.LHS;
      Value *RHS = BOInfo.RHS;
  
      // If AltiVec, the comparison results in a numeric type, so we use
      // intrinsics comparing vectors and giving 0 or 1 as a result
      if (LHSTy->isVectorType() && !E->getType()->isVectorType()) {
        // constants for mapping CR6 register bits to predicate result
        enum { CR6_EQ=0, CR6_EQ_REV, CR6_LT, CR6_LT_REV } CR6;
  
        llvm::Intrinsic::ID ID = llvm::Intrinsic::not_intrinsic;
  
        // in several cases vector arguments order will be reversed
        Value *FirstVecArg = LHS,
              *SecondVecArg = RHS;
  
        QualType ElTy = LHSTy->getAs<VectorType>()->getElementType();
        const BuiltinType *BTy = ElTy->getAs<BuiltinType>();
        BuiltinType::Kind ElementKind = BTy->getKind();
  
        switch(E->getOpcode()) {
        default: llvm_unreachable("is not a comparison operation");
        case BO_EQ:
          CR6 = CR6_LT;
          ID = GetIntrinsic(VCMPEQ, ElementKind);
          break;
        case BO_NE:
          CR6 = CR6_EQ;
          ID = GetIntrinsic(VCMPEQ, ElementKind);
          break;
        case BO_LT:
          CR6 = CR6_LT;
          ID = GetIntrinsic(VCMPGT, ElementKind);
          std::swap(FirstVecArg, SecondVecArg);
          break;
        case BO_GT:
          CR6 = CR6_LT;
          ID = GetIntrinsic(VCMPGT, ElementKind);
          break;
        case BO_LE:
          if (ElementKind == BuiltinType::Float) {
            CR6 = CR6_LT;
            ID = llvm::Intrinsic::ppc_altivec_vcmpgefp_p;
            std::swap(FirstVecArg, SecondVecArg);
          }
          else {
            CR6 = CR6_EQ;
            ID = GetIntrinsic(VCMPGT, ElementKind);
          }
          break;
        case BO_GE:
          if (ElementKind == BuiltinType::Float) {
            CR6 = CR6_LT;
            ID = llvm::Intrinsic::ppc_altivec_vcmpgefp_p;
          }
          else {
            CR6 = CR6_EQ;
            ID = GetIntrinsic(VCMPGT, ElementKind);
            std::swap(FirstVecArg, SecondVecArg);
          }
          break;
        }
  
        Value *CR6Param = Builder.getInt32(CR6);
        llvm::Function *F = CGF.CGM.getIntrinsic(ID);
        Result = Builder.CreateCall(F, {CR6Param, FirstVecArg, SecondVecArg});
  
        // The result type of intrinsic may not be same as E->getType().
        // If E->getType() is not BoolTy, EmitScalarConversion will do the
        // conversion work. If E->getType() is BoolTy, EmitScalarConversion will
        // do nothing, if ResultTy is not i1 at the same time, it will cause
        // crash later.
        llvm::IntegerType *ResultTy = cast<llvm::IntegerType>(Result->getType());
        if (ResultTy->getBitWidth() > 1 &&
            E->getType() == CGF.getContext().BoolTy)
          Result = Builder.CreateTrunc(Result, Builder.getInt1Ty());
        return EmitScalarConversion(Result, CGF.getContext().BoolTy, E->getType(),
                                    E->getExprLoc());
      }
  
      if (BOInfo.isFixedPointBinOp()) {
        Result = EmitFixedPointBinOp(BOInfo);
      } else if (LHS->getType()->isFPOrFPVectorTy()) {
        Result = Builder.CreateFCmp(FCmpOpc, LHS, RHS, "cmp");
      } else if (LHSTy->hasSignedIntegerRepresentation()) {
        Result = Builder.CreateICmp(SICmpOpc, LHS, RHS, "cmp");
      } else {
        // Unsigned integers and pointers.
  
        if (CGF.CGM.getCodeGenOpts().StrictVTablePointers &&
            !isa<llvm::ConstantPointerNull>(LHS) &&
            !isa<llvm::ConstantPointerNull>(RHS)) {
  
          // Dynamic information is required to be stripped for comparisons,
          // because it could leak the dynamic information.  Based on comparisons
          // of pointers to dynamic objects, the optimizer can replace one pointer
          // with another, which might be incorrect in presence of invariant
          // groups. Comparison with null is safe because null does not carry any
          // dynamic information.
          if (LHSTy.mayBeDynamicClass())
            LHS = Builder.CreateStripInvariantGroup(LHS);
          if (RHSTy.mayBeDynamicClass())
            RHS = Builder.CreateStripInvariantGroup(RHS);
        }
  
        Result = Builder.CreateICmp(UICmpOpc, LHS, RHS, "cmp");
      }
  
      // If this is a vector comparison, sign extend the result to the appropriate
      // vector integer type and return it (don't convert to bool).
      if (LHSTy->isVectorType())
        return Builder.CreateSExt(Result, ConvertType(E->getType()), "sext");
  
    } else {
      // Complex Comparison: can only be an equality comparison.
      CodeGenFunction::ComplexPairTy LHS, RHS;
      QualType CETy;
      if (auto *CTy = LHSTy->getAs<ComplexType>()) {
        LHS = CGF.EmitComplexExpr(E->getLHS());
        CETy = CTy->getElementType();
      } else {
        LHS.first = Visit(E->getLHS());
        LHS.second = llvm::Constant::getNullValue(LHS.first->getType());
        CETy = LHSTy;
      }
      if (auto *CTy = RHSTy->getAs<ComplexType>()) {
        RHS = CGF.EmitComplexExpr(E->getRHS());
        assert(CGF.getContext().hasSameUnqualifiedType(CETy,
                                                       CTy->getElementType()) &&
               "The element types must always match.");
        (void)CTy;
      } else {
        RHS.first = Visit(E->getRHS());
        RHS.second = llvm::Constant::getNullValue(RHS.first->getType());
        assert(CGF.getContext().hasSameUnqualifiedType(CETy, RHSTy) &&
               "The element types must always match.");
      }
  
      Value *ResultR, *ResultI;
      if (CETy->isRealFloatingType()) {
        ResultR = Builder.CreateFCmp(FCmpOpc, LHS.first, RHS.first, "cmp.r");
        ResultI = Builder.CreateFCmp(FCmpOpc, LHS.second, RHS.second, "cmp.i");
      } else {
        // Complex comparisons can only be equality comparisons.  As such, signed
        // and unsigned opcodes are the same.
        ResultR = Builder.CreateICmp(UICmpOpc, LHS.first, RHS.first, "cmp.r");
        ResultI = Builder.CreateICmp(UICmpOpc, LHS.second, RHS.second, "cmp.i");
      }
  
      if (E->getOpcode() == BO_EQ) {
        Result = Builder.CreateAnd(ResultR, ResultI, "and.ri");
      } else {
        assert(E->getOpcode() == BO_NE &&
               "Complex comparison other than == or != ?");
        Result = Builder.CreateOr(ResultR, ResultI, "or.ri");
      }
    }
  
    return EmitScalarConversion(Result, CGF.getContext().BoolTy, E->getType(),
                                E->getExprLoc());
  }
  
  Value *ScalarExprEmitter::VisitBinAssign(const BinaryOperator *E) {
    bool Ignore = TestAndClearIgnoreResultAssign();
  
    Value *RHS;
    LValue LHS;
  
    switch (E->getLHS()->getType().getObjCLifetime()) {
    case Qualifiers::OCL_Strong:
      std::tie(LHS, RHS) = CGF.EmitARCStoreStrong(E, Ignore);
      break;
  
    case Qualifiers::OCL_Autoreleasing:
      std::tie(LHS, RHS) = CGF.EmitARCStoreAutoreleasing(E);
      break;
  
    case Qualifiers::OCL_ExplicitNone:
      std::tie(LHS, RHS) = CGF.EmitARCStoreUnsafeUnretained(E, Ignore);
      break;
  
    case Qualifiers::OCL_Weak:
      RHS = Visit(E->getRHS());
      LHS = EmitCheckedLValue(E->getLHS(), CodeGenFunction::TCK_Store);
      RHS = CGF.EmitARCStoreWeak(LHS.getAddress(), RHS, Ignore);
      break;
  
    case Qualifiers::OCL_None:
      // __block variables need to have the rhs evaluated first, plus
      // this should improve codegen just a little.
      RHS = Visit(E->getRHS());
      LHS = EmitCheckedLValue(E->getLHS(), CodeGenFunction::TCK_Store);
  
      // Store the value into the LHS.  Bit-fields are handled specially
      // because the result is altered by the store, i.e., [C99 6.5.16p1]
      // 'An assignment expression has the value of the left operand after
      // the assignment...'.
      if (LHS.isBitField()) {
        CGF.EmitStoreThroughBitfieldLValue(RValue::get(RHS), LHS, &RHS);
      } else {
        CGF.EmitNullabilityCheck(LHS, RHS, E->getExprLoc());
        CGF.EmitStoreThroughLValue(RValue::get(RHS), LHS);
      }
    }
  
    // If the result is clearly ignored, return now.
    if (Ignore)
      return nullptr;
  
    // The result of an assignment in C is the assigned r-value.
    if (!CGF.getLangOpts().CPlusPlus)
      return RHS;
  
    // If the lvalue is non-volatile, return the computed value of the assignment.
    if (!LHS.isVolatileQualified())
      return RHS;
  
    // Otherwise, reload the value.
    return EmitLoadOfLValue(LHS, E->getExprLoc());
  }
  
  Value *ScalarExprEmitter::VisitBinLAnd(const BinaryOperator *E) {
    // Perform vector logical and on comparisons with zero vectors.
    if (E->getType()->isVectorType()) {
      CGF.incrementProfileCounter(E);
  
      Value *LHS = Visit(E->getLHS());
      Value *RHS = Visit(E->getRHS());
      Value *Zero = llvm::ConstantAggregateZero::get(LHS->getType());
      if (LHS->getType()->isFPOrFPVectorTy()) {
        LHS = Builder.CreateFCmp(llvm::CmpInst::FCMP_UNE, LHS, Zero, "cmp");
        RHS = Builder.CreateFCmp(llvm::CmpInst::FCMP_UNE, RHS, Zero, "cmp");
      } else {
        LHS = Builder.CreateICmp(llvm::CmpInst::ICMP_NE, LHS, Zero, "cmp");
        RHS = Builder.CreateICmp(llvm::CmpInst::ICMP_NE, RHS, Zero, "cmp");
      }
      Value *And = Builder.CreateAnd(LHS, RHS);
      return Builder.CreateSExt(And, ConvertType(E->getType()), "sext");
    }
  
    llvm::Type *ResTy = ConvertType(E->getType());
  
    // If we have 0 && RHS, see if we can elide RHS, if so, just return 0.
    // If we have 1 && X, just emit X without inserting the control flow.
    bool LHSCondVal;
    if (CGF.ConstantFoldsToSimpleInteger(E->getLHS(), LHSCondVal)) {
      if (LHSCondVal) { // If we have 1 && X, just emit X.
        CGF.incrementProfileCounter(E);
  
        Value *RHSCond = CGF.EvaluateExprAsBool(E->getRHS());
        // ZExt result to int or bool.
        return Builder.CreateZExtOrBitCast(RHSCond, ResTy, "land.ext");
      }
  
      // 0 && RHS: If it is safe, just elide the RHS, and return 0/false.
      if (!CGF.ContainsLabel(E->getRHS()))
        return llvm::Constant::getNullValue(ResTy);
    }
  
    llvm::BasicBlock *ContBlock = CGF.createBasicBlock("land.end");
    llvm::BasicBlock *RHSBlock  = CGF.createBasicBlock("land.rhs");
  
    CodeGenFunction::ConditionalEvaluation eval(CGF);
  
    // Branch on the LHS first.  If it is false, go to the failure (cont) block.
    CGF.EmitBranchOnBoolExpr(E->getLHS(), RHSBlock, ContBlock,
                             CGF.getProfileCount(E->getRHS()));
  
    // Any edges into the ContBlock are now from an (indeterminate number of)
    // edges from this first condition.  All of these values will be false.  Start
    // setting up the PHI node in the Cont Block for this.
    llvm::PHINode *PN = llvm::PHINode::Create(llvm::Type::getInt1Ty(VMContext), 2,
                                              "", ContBlock);
    for (llvm::pred_iterator PI = pred_begin(ContBlock), PE = pred_end(ContBlock);
         PI != PE; ++PI)
      PN->addIncoming(llvm::ConstantInt::getFalse(VMContext), *PI);
  
    eval.begin(CGF);
    CGF.EmitBlock(RHSBlock);
    CGF.incrementProfileCounter(E);
    Value *RHSCond = CGF.EvaluateExprAsBool(E->getRHS());
    eval.end(CGF);
  
    // Reaquire the RHS block, as there may be subblocks inserted.
    RHSBlock = Builder.GetInsertBlock();
  
    // Emit an unconditional branch from this block to ContBlock.
    {
      // There is no need to emit line number for unconditional branch.
      auto NL = ApplyDebugLocation::CreateEmpty(CGF);
      CGF.EmitBlock(ContBlock);
    }
    // Insert an entry into the phi node for the edge with the value of RHSCond.
    PN->addIncoming(RHSCond, RHSBlock);
  
    // Artificial location to preserve the scope information
    {
      auto NL = ApplyDebugLocation::CreateArtificial(CGF);
      PN->setDebugLoc(Builder.getCurrentDebugLocation());
    }
  
    // ZExt result to int.
    return Builder.CreateZExtOrBitCast(PN, ResTy, "land.ext");
  }
  
  Value *ScalarExprEmitter::VisitBinLOr(const BinaryOperator *E) {
    // Perform vector logical or on comparisons with zero vectors.
    if (E->getType()->isVectorType()) {
      CGF.incrementProfileCounter(E);
  
      Value *LHS = Visit(E->getLHS());
      Value *RHS = Visit(E->getRHS());
      Value *Zero = llvm::ConstantAggregateZero::get(LHS->getType());
      if (LHS->getType()->isFPOrFPVectorTy()) {
        LHS = Builder.CreateFCmp(llvm::CmpInst::FCMP_UNE, LHS, Zero, "cmp");
        RHS = Builder.CreateFCmp(llvm::CmpInst::FCMP_UNE, RHS, Zero, "cmp");
      } else {
        LHS = Builder.CreateICmp(llvm::CmpInst::ICMP_NE, LHS, Zero, "cmp");
        RHS = Builder.CreateICmp(llvm::CmpInst::ICMP_NE, RHS, Zero, "cmp");
      }
      Value *Or = Builder.CreateOr(LHS, RHS);
      return Builder.CreateSExt(Or, ConvertType(E->getType()), "sext");
    }
  
    llvm::Type *ResTy = ConvertType(E->getType());
  
    // If we have 1 || RHS, see if we can elide RHS, if so, just return 1.
    // If we have 0 || X, just emit X without inserting the control flow.
    bool LHSCondVal;
    if (CGF.ConstantFoldsToSimpleInteger(E->getLHS(), LHSCondVal)) {
      if (!LHSCondVal) { // If we have 0 || X, just emit X.
        CGF.incrementProfileCounter(E);
  
        Value *RHSCond = CGF.EvaluateExprAsBool(E->getRHS());
        // ZExt result to int or bool.
        return Builder.CreateZExtOrBitCast(RHSCond, ResTy, "lor.ext");
      }
  
      // 1 || RHS: If it is safe, just elide the RHS, and return 1/true.
      if (!CGF.ContainsLabel(E->getRHS()))
        return llvm::ConstantInt::get(ResTy, 1);
    }
  
    llvm::BasicBlock *ContBlock = CGF.createBasicBlock("lor.end");
    llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("lor.rhs");
  
    CodeGenFunction::ConditionalEvaluation eval(CGF);
  
    // Branch on the LHS first.  If it is true, go to the success (cont) block.
    CGF.EmitBranchOnBoolExpr(E->getLHS(), ContBlock, RHSBlock,
                             CGF.getCurrentProfileCount() -
                                 CGF.getProfileCount(E->getRHS()));
  
    // Any edges into the ContBlock are now from an (indeterminate number of)
    // edges from this first condition.  All of these values will be true.  Start
    // setting up the PHI node in the Cont Block for this.
    llvm::PHINode *PN = llvm::PHINode::Create(llvm::Type::getInt1Ty(VMContext), 2,
                                              "", ContBlock);
    for (llvm::pred_iterator PI = pred_begin(ContBlock), PE = pred_end(ContBlock);
         PI != PE; ++PI)
      PN->addIncoming(llvm::ConstantInt::getTrue(VMContext), *PI);
  
    eval.begin(CGF);
  
    // Emit the RHS condition as a bool value.
    CGF.EmitBlock(RHSBlock);
    CGF.incrementProfileCounter(E);
    Value *RHSCond = CGF.EvaluateExprAsBool(E->getRHS());
  
    eval.end(CGF);
  
    // Reaquire the RHS block, as there may be subblocks inserted.
    RHSBlock = Builder.GetInsertBlock();
  
    // Emit an unconditional branch from this block to ContBlock.  Insert an entry
    // into the phi node for the edge with the value of RHSCond.
    CGF.EmitBlock(ContBlock);
    PN->addIncoming(RHSCond, RHSBlock);
  
    // ZExt result to int.
    return Builder.CreateZExtOrBitCast(PN, ResTy, "lor.ext");
  }
  
  Value *ScalarExprEmitter::VisitBinComma(const BinaryOperator *E) {
    CGF.EmitIgnoredExpr(E->getLHS());
    CGF.EnsureInsertPoint();
    return Visit(E->getRHS());
  }
  
  //===----------------------------------------------------------------------===//
  //                             Other Operators
  //===----------------------------------------------------------------------===//
  
  /// isCheapEnoughToEvaluateUnconditionally - Return true if the specified
  /// expression is cheap enough and side-effect-free enough to evaluate
  /// unconditionally instead of conditionally.  This is used to convert control
  /// flow into selects in some cases.
  static bool isCheapEnoughToEvaluateUnconditionally(const Expr *E,
                                                     CodeGenFunction &CGF) {
    // Anything that is an integer or floating point constant is fine.
    return E->IgnoreParens()->isEvaluatable(CGF.getContext());
  
    // Even non-volatile automatic variables can't be evaluated unconditionally.
    // Referencing a thread_local may cause non-trivial initialization work to
    // occur. If we're inside a lambda and one of the variables is from the scope
    // outside the lambda, that function may have returned already. Reading its
    // locals is a bad idea. Also, these reads may introduce races there didn't
    // exist in the source-level program.
  }
  
  
  Value *ScalarExprEmitter::
  VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
    TestAndClearIgnoreResultAssign();
  
    // Bind the common expression if necessary.
    CodeGenFunction::OpaqueValueMapping binding(CGF, E);
  
    Expr *condExpr = E->getCond();
    Expr *lhsExpr = E->getTrueExpr();
    Expr *rhsExpr = E->getFalseExpr();
  
    // If the condition constant folds and can be elided, try to avoid emitting
    // the condition and the dead arm.
    bool CondExprBool;
    if (CGF.ConstantFoldsToSimpleInteger(condExpr, CondExprBool)) {
      Expr *live = lhsExpr, *dead = rhsExpr;
      if (!CondExprBool) std::swap(live, dead);
  
      // If the dead side doesn't have labels we need, just emit the Live part.
      if (!CGF.ContainsLabel(dead)) {
        if (CondExprBool)
          CGF.incrementProfileCounter(E);
        Value *Result = Visit(live);
  
        // If the live part is a throw expression, it acts like it has a void
        // type, so evaluating it returns a null Value*.  However, a conditional
        // with non-void type must return a non-null Value*.
        if (!Result && !E->getType()->isVoidType())
          Result = llvm::UndefValue::get(CGF.ConvertType(E->getType()));
  
        return Result;
      }
    }
  
    // OpenCL: If the condition is a vector, we can treat this condition like
    // the select function.
    if (CGF.getLangOpts().OpenCL
        && condExpr->getType()->isVectorType()) {
      CGF.incrementProfileCounter(E);
  
      llvm::Value *CondV = CGF.EmitScalarExpr(condExpr);
      llvm::Value *LHS = Visit(lhsExpr);
      llvm::Value *RHS = Visit(rhsExpr);
  
      llvm::Type *condType = ConvertType(condExpr->getType());
      llvm::VectorType *vecTy = cast<llvm::VectorType>(condType);
  
      unsigned numElem = vecTy->getNumElements();
      llvm::Type *elemType = vecTy->getElementType();
  
      llvm::Value *zeroVec = llvm::Constant::getNullValue(vecTy);
      llvm::Value *TestMSB = Builder.CreateICmpSLT(CondV, zeroVec);
      llvm::Value *tmp = Builder.CreateSExt(TestMSB,
                                            llvm::VectorType::get(elemType,
                                                                  numElem),
                                            "sext");
      llvm::Value *tmp2 = Builder.CreateNot(tmp);
  
      // Cast float to int to perform ANDs if necessary.
      llvm::Value *RHSTmp = RHS;
      llvm::Value *LHSTmp = LHS;
      bool wasCast = false;
      llvm::VectorType *rhsVTy = cast<llvm::VectorType>(RHS->getType());
      if (rhsVTy->getElementType()->isFloatingPointTy()) {
        RHSTmp = Builder.CreateBitCast(RHS, tmp2->getType());
        LHSTmp = Builder.CreateBitCast(LHS, tmp->getType());
        wasCast = true;
      }
  
      llvm::Value *tmp3 = Builder.CreateAnd(RHSTmp, tmp2);
      llvm::Value *tmp4 = Builder.CreateAnd(LHSTmp, tmp);
      llvm::Value *tmp5 = Builder.CreateOr(tmp3, tmp4, "cond");
      if (wasCast)
        tmp5 = Builder.CreateBitCast(tmp5, RHS->getType());
  
      return tmp5;
    }
  
    // If this is a really simple expression (like x ? 4 : 5), emit this as a
    // select instead of as control flow.  We can only do this if it is cheap and
    // safe to evaluate the LHS and RHS unconditionally.
    if (isCheapEnoughToEvaluateUnconditionally(lhsExpr, CGF) &&
        isCheapEnoughToEvaluateUnconditionally(rhsExpr, CGF)) {
      llvm::Value *CondV = CGF.EvaluateExprAsBool(condExpr);
      llvm::Value *StepV = Builder.CreateZExtOrBitCast(CondV, CGF.Int64Ty);
  
      CGF.incrementProfileCounter(E, StepV);
  
      llvm::Value *LHS = Visit(lhsExpr);
      llvm::Value *RHS = Visit(rhsExpr);
      if (!LHS) {
        // If the conditional has void type, make sure we return a null Value*.
        assert(!RHS && "LHS and RHS types must match");
        return nullptr;
      }
      return Builder.CreateSelect(CondV, LHS, RHS, "cond");
    }
  
    llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
    llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
    llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
  
    CodeGenFunction::ConditionalEvaluation eval(CGF);
    CGF.EmitBranchOnBoolExpr(condExpr, LHSBlock, RHSBlock,
                             CGF.getProfileCount(lhsExpr));
  
    CGF.EmitBlock(LHSBlock);
    CGF.incrementProfileCounter(E);
    eval.begin(CGF);
    Value *LHS = Visit(lhsExpr);
    eval.end(CGF);
  
    LHSBlock = Builder.GetInsertBlock();
    Builder.CreateBr(ContBlock);
  
    CGF.EmitBlock(RHSBlock);
    eval.begin(CGF);
    Value *RHS = Visit(rhsExpr);
    eval.end(CGF);
  
    RHSBlock = Builder.GetInsertBlock();
    CGF.EmitBlock(ContBlock);
  
    // If the LHS or RHS is a throw expression, it will be legitimately null.
    if (!LHS)
      return RHS;
    if (!RHS)
      return LHS;
  
    // Create a PHI node for the real part.
    llvm::PHINode *PN = Builder.CreatePHI(LHS->getType(), 2, "cond");
    PN->addIncoming(LHS, LHSBlock);
    PN->addIncoming(RHS, RHSBlock);
    return PN;
  }
  
  Value *ScalarExprEmitter::VisitChooseExpr(ChooseExpr *E) {
    return Visit(E->getChosenSubExpr());
  }
  
  Value *ScalarExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
    QualType Ty = VE->getType();
  
    if (Ty->isVariablyModifiedType())
      CGF.EmitVariablyModifiedType(Ty);
  
    Address ArgValue = Address::invalid();
    Address ArgPtr = CGF.EmitVAArg(VE, ArgValue);
  
    llvm::Type *ArgTy = ConvertType(VE->getType());
  
    // If EmitVAArg fails, emit an error.
    if (!ArgPtr.isValid()) {
      CGF.ErrorUnsupported(VE, "va_arg expression");
      return llvm::UndefValue::get(ArgTy);
    }
  
    // FIXME Volatility.
    llvm::Value *Val = Builder.CreateLoad(ArgPtr);
  
    // If EmitVAArg promoted the type, we must truncate it.
    if (ArgTy != Val->getType()) {
      if (ArgTy->isPointerTy() && !Val->getType()->isPointerTy())
        Val = Builder.CreateIntToPtr(Val, ArgTy);
      else
        Val = Builder.CreateTrunc(Val, ArgTy);
    }
  
    return Val;
  }
  
  Value *ScalarExprEmitter::VisitBlockExpr(const BlockExpr *block) {
    return CGF.EmitBlockLiteral(block);
  }
  
  // Convert a vec3 to vec4, or vice versa.
  static Value *ConvertVec3AndVec4(CGBuilderTy &Builder, CodeGenFunction &CGF,
                                   Value *Src, unsigned NumElementsDst) {
    llvm::Value *UnV = llvm::UndefValue::get(Src->getType());
    SmallVector<llvm::Constant*, 4> Args;
    Args.push_back(Builder.getInt32(0));
    Args.push_back(Builder.getInt32(1));
    Args.push_back(Builder.getInt32(2));
    if (NumElementsDst == 4)
      Args.push_back(llvm::UndefValue::get(CGF.Int32Ty));
    llvm::Constant *Mask = llvm::ConstantVector::get(Args);
    return Builder.CreateShuffleVector(Src, UnV, Mask);
  }
  
  // Create cast instructions for converting LLVM value \p Src to LLVM type \p
  // DstTy. \p Src has the same size as \p DstTy. Both are single value types
  // but could be scalar or vectors of different lengths, and either can be
  // pointer.
  // There are 4 cases:
  // 1. non-pointer -> non-pointer  : needs 1 bitcast
  // 2. pointer -> pointer          : needs 1 bitcast or addrspacecast
  // 3. pointer -> non-pointer
  //   a) pointer -> intptr_t       : needs 1 ptrtoint
  //   b) pointer -> non-intptr_t   : needs 1 ptrtoint then 1 bitcast
  // 4. non-pointer -> pointer
  //   a) intptr_t -> pointer       : needs 1 inttoptr
  //   b) non-intptr_t -> pointer   : needs 1 bitcast then 1 inttoptr
  // Note: for cases 3b and 4b two casts are required since LLVM casts do not
  // allow casting directly between pointer types and non-integer non-pointer
  // types.
  static Value *createCastsForTypeOfSameSize(CGBuilderTy &Builder,
                                             const llvm::DataLayout &DL,
                                             Value *Src, llvm::Type *DstTy,
                                             StringRef Name = "") {
    auto SrcTy = Src->getType();
  
    // Case 1.
    if (!SrcTy->isPointerTy() && !DstTy->isPointerTy())
      return Builder.CreateBitCast(Src, DstTy, Name);
  
    // Case 2.
    if (SrcTy->isPointerTy() && DstTy->isPointerTy())
      return Builder.CreatePointerBitCastOrAddrSpaceCast(Src, DstTy, Name);
  
    // Case 3.
    if (SrcTy->isPointerTy() && !DstTy->isPointerTy()) {
      // Case 3b.
      if (!DstTy->isIntegerTy())
        Src = Builder.CreatePtrToInt(Src, DL.getIntPtrType(SrcTy));
      // Cases 3a and 3b.
      return Builder.CreateBitOrPointerCast(Src, DstTy, Name);
    }
  
    // Case 4b.
    if (!SrcTy->isIntegerTy())
      Src = Builder.CreateBitCast(Src, DL.getIntPtrType(DstTy));
    // Cases 4a and 4b.
    return Builder.CreateIntToPtr(Src, DstTy, Name);
  }
  
  Value *ScalarExprEmitter::VisitAsTypeExpr(AsTypeExpr *E) {
    Value *Src  = CGF.EmitScalarExpr(E->getSrcExpr());
    llvm::Type *DstTy = ConvertType(E->getType());
  
    llvm::Type *SrcTy = Src->getType();
    unsigned NumElementsSrc = isa<llvm::VectorType>(SrcTy) ?
      cast<llvm::VectorType>(SrcTy)->getNumElements() : 0;
    unsigned NumElementsDst = isa<llvm::VectorType>(DstTy) ?
      cast<llvm::VectorType>(DstTy)->getNumElements() : 0;
  
    // Going from vec3 to non-vec3 is a special case and requires a shuffle
    // vector to get a vec4, then a bitcast if the target type is different.
    if (NumElementsSrc == 3 && NumElementsDst != 3) {
      Src = ConvertVec3AndVec4(Builder, CGF, Src, 4);
  
      if (!CGF.CGM.getCodeGenOpts().PreserveVec3Type) {
        Src = createCastsForTypeOfSameSize(Builder, CGF.CGM.getDataLayout(), Src,
                                           DstTy);
      }
  
      Src->setName("astype");
      return Src;
    }
  
    // Going from non-vec3 to vec3 is a special case and requires a bitcast
    // to vec4 if the original type is not vec4, then a shuffle vector to
    // get a vec3.
    if (NumElementsSrc != 3 && NumElementsDst == 3) {
      if (!CGF.CGM.getCodeGenOpts().PreserveVec3Type) {
        auto Vec4Ty = llvm::VectorType::get(DstTy->getVectorElementType(), 4);
        Src = createCastsForTypeOfSameSize(Builder, CGF.CGM.getDataLayout(), Src,
                                           Vec4Ty);
      }
  
      Src = ConvertVec3AndVec4(Builder, CGF, Src, 3);
      Src->setName("astype");
      return Src;
    }
  
    return Src = createCastsForTypeOfSameSize(Builder, CGF.CGM.getDataLayout(),
                                              Src, DstTy, "astype");
  }
  
  Value *ScalarExprEmitter::VisitAtomicExpr(AtomicExpr *E) {
    return CGF.EmitAtomicExpr(E).getScalarVal();
  }
  
  //===----------------------------------------------------------------------===//
  //                         Entry Point into this File
  //===----------------------------------------------------------------------===//
  
  /// Emit the computation of the specified expression of scalar type, ignoring
  /// the result.
  Value *CodeGenFunction::EmitScalarExpr(const Expr *E, bool IgnoreResultAssign) {
    assert(E && hasScalarEvaluationKind(E->getType()) &&
           "Invalid scalar expression to emit");
  
    return ScalarExprEmitter(*this, IgnoreResultAssign)
        .Visit(const_cast<Expr *>(E));
  }
  
  /// Emit a conversion from the specified type to the specified destination type,
  /// both of which are LLVM scalar types.
  Value *CodeGenFunction::EmitScalarConversion(Value *Src, QualType SrcTy,
                                               QualType DstTy,
                                               SourceLocation Loc) {
    assert(hasScalarEvaluationKind(SrcTy) && hasScalarEvaluationKind(DstTy) &&
           "Invalid scalar expression to emit");
    return ScalarExprEmitter(*this).EmitScalarConversion(Src, SrcTy, DstTy, Loc);
  }
  
  /// Emit a conversion from the specified complex type to the specified
  /// destination type, where the destination type is an LLVM scalar type.
  Value *CodeGenFunction::EmitComplexToScalarConversion(ComplexPairTy Src,
                                                        QualType SrcTy,
                                                        QualType DstTy,
                                                        SourceLocation Loc) {
    assert(SrcTy->isAnyComplexType() && hasScalarEvaluationKind(DstTy) &&
           "Invalid complex -> scalar conversion");
    return ScalarExprEmitter(*this)
        .EmitComplexToScalarConversion(Src, SrcTy, DstTy, Loc);
  }
  
  
  llvm::Value *CodeGenFunction::
  EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
                          bool isInc, bool isPre) {
    return ScalarExprEmitter(*this).EmitScalarPrePostIncDec(E, LV, isInc, isPre);
  }
  
  LValue CodeGenFunction::EmitObjCIsaExpr(const ObjCIsaExpr *E) {
    // object->isa or (*object).isa
    // Generate code as for: *(Class*)object
  
    Expr *BaseExpr = E->getBase();
    Address Addr = Address::invalid();
    if (BaseExpr->isRValue()) {
      Addr = Address(EmitScalarExpr(BaseExpr), getPointerAlign());
    } else {
      Addr = EmitLValue(BaseExpr).getAddress();
    }
  
    // Cast the address to Class*.
    Addr = Builder.CreateElementBitCast(Addr, ConvertType(E->getType()));
    return MakeAddrLValue(Addr, E->getType());
  }
  
  
  LValue CodeGenFunction::EmitCompoundAssignmentLValue(
                                              const CompoundAssignOperator *E) {
    ScalarExprEmitter Scalar(*this);
    Value *Result = nullptr;
    switch (E->getOpcode()) {
  #define COMPOUND_OP(Op)                                                       \
      case BO_##Op##Assign:                                                     \
        return Scalar.EmitCompoundAssignLValue(E, &ScalarExprEmitter::Emit##Op, \
                                               Result)
    COMPOUND_OP(Mul);
    COMPOUND_OP(Div);
    COMPOUND_OP(Rem);
    COMPOUND_OP(Add);
    COMPOUND_OP(Sub);
    COMPOUND_OP(Shl);
    COMPOUND_OP(Shr);
    COMPOUND_OP(And);
    COMPOUND_OP(Xor);
    COMPOUND_OP(Or);
  #undef COMPOUND_OP
  
    case BO_PtrMemD:
    case BO_PtrMemI:
    case BO_Mul:
    case BO_Div:
    case BO_Rem:
    case BO_Add:
    case BO_Sub:
    case BO_Shl:
    case BO_Shr:
    case BO_LT:
    case BO_GT:
    case BO_LE:
    case BO_GE:
    case BO_EQ:
    case BO_NE:
    case BO_Cmp:
    case BO_And:
    case BO_Xor:
    case BO_Or:
    case BO_LAnd:
    case BO_LOr:
    case BO_Assign:
    case BO_Comma:
      llvm_unreachable("Not valid compound assignment operators");
    }
  
    llvm_unreachable("Unhandled compound assignment operator");
  }
  
  Value *CodeGenFunction::EmitCheckedInBoundsGEP(Value *Ptr,
                                                 ArrayRef<Value *> IdxList,
                                                 bool SignedIndices,
                                                 bool IsSubtraction,
                                                 SourceLocation Loc,
                                                 const Twine &Name) {
    Value *GEPVal = Builder.CreateInBoundsGEP(Ptr, IdxList, Name);
  
    // If the pointer overflow sanitizer isn't enabled, do nothing.
    if (!SanOpts.has(SanitizerKind::PointerOverflow))
      return GEPVal;
  
    // If the GEP has already been reduced to a constant, leave it be.
    if (isa<llvm::Constant>(GEPVal))
      return GEPVal;
  
    // Only check for overflows in the default address space.
    if (GEPVal->getType()->getPointerAddressSpace())
      return GEPVal;
  
    auto *GEP = cast<llvm::GEPOperator>(GEPVal);
    assert(GEP->isInBounds() && "Expected inbounds GEP");
  
    SanitizerScope SanScope(this);
    auto &VMContext = getLLVMContext();
    const auto &DL = CGM.getDataLayout();
    auto *IntPtrTy = DL.getIntPtrType(GEP->getPointerOperandType());
  
    // Grab references to the signed add/mul overflow intrinsics for intptr_t.
    auto *Zero = llvm::ConstantInt::getNullValue(IntPtrTy);
    auto *SAddIntrinsic =
        CGM.getIntrinsic(llvm::Intrinsic::sadd_with_overflow, IntPtrTy);
    auto *SMulIntrinsic =
        CGM.getIntrinsic(llvm::Intrinsic::smul_with_overflow, IntPtrTy);
  
    // The total (signed) byte offset for the GEP.
    llvm::Value *TotalOffset = nullptr;
    // The offset overflow flag - true if the total offset overflows.
    llvm::Value *OffsetOverflows = Builder.getFalse();
  
    /// Return the result of the given binary operation.
    auto eval = [&](BinaryOperator::Opcode Opcode, llvm::Value *LHS,
                    llvm::Value *RHS) -> llvm::Value * {
      assert((Opcode == BO_Add || Opcode == BO_Mul) && "Can't eval binop");
  
      // If the operands are constants, return a constant result.
      if (auto *LHSCI = dyn_cast<llvm::ConstantInt>(LHS)) {
        if (auto *RHSCI = dyn_cast<llvm::ConstantInt>(RHS)) {
          llvm::APInt N;
          bool HasOverflow = mayHaveIntegerOverflow(LHSCI, RHSCI, Opcode,
                                                    /*Signed=*/true, N);
          if (HasOverflow)
            OffsetOverflows = Builder.getTrue();
          return llvm::ConstantInt::get(VMContext, N);
        }
      }
  
      // Otherwise, compute the result with checked arithmetic.
      auto *ResultAndOverflow = Builder.CreateCall(
          (Opcode == BO_Add) ? SAddIntrinsic : SMulIntrinsic, {LHS, RHS});
      OffsetOverflows = Builder.CreateOr(
          Builder.CreateExtractValue(ResultAndOverflow, 1), OffsetOverflows);
      return Builder.CreateExtractValue(ResultAndOverflow, 0);
    };
  
    // Determine the total byte offset by looking at each GEP operand.
    for (auto GTI = llvm::gep_type_begin(GEP), GTE = llvm::gep_type_end(GEP);
         GTI != GTE; ++GTI) {
      llvm::Value *LocalOffset;
      auto *Index = GTI.getOperand();
      // Compute the local offset contributed by this indexing step:
      if (auto *STy = GTI.getStructTypeOrNull()) {
        // For struct indexing, the local offset is the byte position of the
        // specified field.
        unsigned FieldNo = cast<llvm::ConstantInt>(Index)->getZExtValue();
        LocalOffset = llvm::ConstantInt::get(
            IntPtrTy, DL.getStructLayout(STy)->getElementOffset(FieldNo));
      } else {
        // Otherwise this is array-like indexing. The local offset is the index
        // multiplied by the element size.
        auto *ElementSize = llvm::ConstantInt::get(
            IntPtrTy, DL.getTypeAllocSize(GTI.getIndexedType()));
        auto *IndexS = Builder.CreateIntCast(Index, IntPtrTy, /*isSigned=*/true);
        LocalOffset = eval(BO_Mul, ElementSize, IndexS);
      }
  
      // If this is the first offset, set it as the total offset. Otherwise, add
      // the local offset into the running total.
      if (!TotalOffset || TotalOffset == Zero)
        TotalOffset = LocalOffset;
      else
        TotalOffset = eval(BO_Add, TotalOffset, LocalOffset);
    }
  
    // Common case: if the total offset is zero, don't emit a check.
    if (TotalOffset == Zero)
      return GEPVal;
  
    // Now that we've computed the total offset, add it to the base pointer (with
    // wrapping semantics).
    auto *IntPtr = Builder.CreatePtrToInt(GEP->getPointerOperand(), IntPtrTy);
    auto *ComputedGEP = Builder.CreateAdd(IntPtr, TotalOffset);
  
    // The GEP is valid if:
    // 1) The total offset doesn't overflow, and
    // 2) The sign of the difference between the computed address and the base
    // pointer matches the sign of the total offset.
    llvm::Value *ValidGEP;
    auto *NoOffsetOverflow = Builder.CreateNot(OffsetOverflows);
    if (SignedIndices) {
      auto *PosOrZeroValid = Builder.CreateICmpUGE(ComputedGEP, IntPtr);
      auto *PosOrZeroOffset = Builder.CreateICmpSGE(TotalOffset, Zero);
      llvm::Value *NegValid = Builder.CreateICmpULT(ComputedGEP, IntPtr);
      ValidGEP = Builder.CreateAnd(
          Builder.CreateSelect(PosOrZeroOffset, PosOrZeroValid, NegValid),
          NoOffsetOverflow);
    } else if (!SignedIndices && !IsSubtraction) {
      auto *PosOrZeroValid = Builder.CreateICmpUGE(ComputedGEP, IntPtr);
      ValidGEP = Builder.CreateAnd(PosOrZeroValid, NoOffsetOverflow);
    } else {
      auto *NegOrZeroValid = Builder.CreateICmpULE(ComputedGEP, IntPtr);
      ValidGEP = Builder.CreateAnd(NegOrZeroValid, NoOffsetOverflow);
    }
  
    llvm::Constant *StaticArgs[] = {EmitCheckSourceLocation(Loc)};
    // Pass the computed GEP to the runtime to avoid emitting poisoned arguments.
    llvm::Value *DynamicArgs[] = {IntPtr, ComputedGEP};
    EmitCheck(std::make_pair(ValidGEP, SanitizerKind::PointerOverflow),
              SanitizerHandler::PointerOverflow, StaticArgs, DynamicArgs);
  
    return GEPVal;
  }
  