ByteCodeExprGen.cpp

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//===--- ByteCodeExprGen.cpp - Code generator for expressions ---*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
 
#include "ByteCodeExprGen.h"
#include "ByteCodeEmitter.h"
#include "ByteCodeStmtGen.h"
#include "Context.h"
#include "Floating.h"
#include "Function.h"
#include "InterpShared.h"
#include "PrimType.h"
#include "Program.h"
#include "clang/AST/Attr.h"
 
using namespace clang;
using namespace clang::interp;
 
using APSInt = llvm::APSInt;
 
namespace clang {
namespace interp {
 
/// Scope used to handle temporaries in toplevel variable declarations.
template <class Emitter> class DeclScope final : public VariableScope<Emitter> {
public:
  DeclScope(ByteCodeExprGen<Emitter> *Ctx, const ValueDecl *VD)
      : VariableScope<Emitter>(Ctx, nullptr), Scope(Ctx->P, VD),
        OldGlobalDecl(Ctx->GlobalDecl) {
    Ctx->GlobalDecl = Context::shouldBeGloballyIndexed(VD);
  }
 
  ~DeclScope() { this->Ctx->GlobalDecl = OldGlobalDecl; }
 
private:
  Program::DeclScope Scope;
  bool OldGlobalDecl;
};
 
/// Scope used to handle initialization methods.
template <class Emitter> class OptionScope final {
public:
  /// Root constructor, compiling or discarding primitives.
  OptionScope(ByteCodeExprGen<Emitter> *Ctx, bool NewDiscardResult,
              bool NewInitializing)
      : Ctx(Ctx), OldDiscardResult(Ctx->DiscardResult),
        OldInitializing(Ctx->Initializing) {
    Ctx->DiscardResult = NewDiscardResult;
    Ctx->Initializing = NewInitializing;
  }
 
  ~OptionScope() {
    Ctx->DiscardResult = OldDiscardResult;
    Ctx->Initializing = OldInitializing;
  }
 
private:
  /// Parent context.
  ByteCodeExprGen<Emitter> *Ctx;
  /// Old discard flag to restore.
  bool OldDiscardResult;
  bool OldInitializing;
};
 
} // namespace interp
} // namespace clang
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCastExpr(const CastExpr *CE) {
  const Expr *SubExpr = CE->getSubExpr();
  switch (CE->getCastKind()) {
 
  case CK_LValueToRValue: {
    if (DiscardResult)
      return this->discard(SubExpr);
 
    std::optional<PrimType> SubExprT = classify(SubExpr->getType());
    // Prepare storage for the result.
    if (!Initializing && !SubExprT) {
      std::optional<unsigned> LocalIndex = allocateLocal(SubExpr);
      if (!LocalIndex)
        return false;
      if (!this->emitGetPtrLocal(*LocalIndex, CE))
        return false;
    }
 
    if (!this->visit(SubExpr))
      return false;
 
    if (SubExprT)
      return this->emitLoadPop(*SubExprT, CE);
 
    // If the subexpr type is not primitive, we need to perform a copy here.
    // This happens for example in C when dereferencing a pointer of struct
    // type.
    return this->emitMemcpy(CE);
  }
 
  case CK_UncheckedDerivedToBase:
  case CK_DerivedToBase: {
    if (!this->visit(SubExpr))
      return false;
 
    const auto extractRecordDecl = [](QualType Ty) -> const CXXRecordDecl * {
      if (const auto *PT = dyn_cast<PointerType>(Ty))
        return PT->getPointeeType()->getAsCXXRecordDecl();
      return Ty->getAsCXXRecordDecl();
    };
 
    // FIXME: We can express a series of non-virtual casts as a single
    // GetPtrBasePop op.
    QualType CurType = SubExpr->getType();
    for (const CXXBaseSpecifier *B : CE->path()) {
      if (B->isVirtual()) {
        if (!this->emitGetPtrVirtBasePop(extractRecordDecl(B->getType()), CE))
          return false;
        CurType = B->getType();
      } else {
        unsigned DerivedOffset = collectBaseOffset(B->getType(), CurType);
        if (!this->emitGetPtrBasePop(DerivedOffset, CE))
          return false;
        CurType = B->getType();
      }
    }
 
    return true;
  }
 
  case CK_BaseToDerived: {
    if (!this->visit(SubExpr))
      return false;
 
    unsigned DerivedOffset =
        collectBaseOffset(SubExpr->getType(), CE->getType());
 
    return this->emitGetPtrDerivedPop(DerivedOffset, CE);
  }
 
  case CK_FloatingCast: {
    if (DiscardResult)
      return this->discard(SubExpr);
    if (!this->visit(SubExpr))
      return false;
    const auto *TargetSemantics = &Ctx.getFloatSemantics(CE->getType());
    return this->emitCastFP(TargetSemantics, getRoundingMode(CE), CE);
  }
 
  case CK_IntegralToFloating: {
    if (DiscardResult)
      return this->discard(SubExpr);
    std::optional<PrimType> FromT = classify(SubExpr->getType());
    if (!FromT)
      return false;
 
    if (!this->visit(SubExpr))
      return false;
 
    const auto *TargetSemantics = &Ctx.getFloatSemantics(CE->getType());
    llvm::RoundingMode RM = getRoundingMode(CE);
    return this->emitCastIntegralFloating(*FromT, TargetSemantics, RM, CE);
  }
 
  case CK_FloatingToBoolean:
  case CK_FloatingToIntegral: {
    if (DiscardResult)
      return this->discard(SubExpr);
 
    std::optional<PrimType> ToT = classify(CE->getType());
 
    if (!ToT)
      return false;
 
    if (!this->visit(SubExpr))
      return false;
 
    if (ToT == PT_IntAP)
      return this->emitCastFloatingIntegralAP(Ctx.getBitWidth(CE->getType()),
                                              CE);
    if (ToT == PT_IntAPS)
      return this->emitCastFloatingIntegralAPS(Ctx.getBitWidth(CE->getType()),
                                               CE);
 
    return this->emitCastFloatingIntegral(*ToT, CE);
  }
 
  case CK_NullToPointer: {
    if (DiscardResult)
      return true;
 
    const Descriptor *Desc = nullptr;
    const QualType PointeeType = CE->getType()->getPointeeType();
    if (!PointeeType.isNull()) {
      if (std::optional<PrimType> T = classify(PointeeType))
        Desc = P.createDescriptor(SubExpr, *T);
    }
    return this->emitNull(classifyPrim(CE->getType()), Desc, CE);
  }
 
  case CK_PointerToIntegral: {
    if (DiscardResult)
      return this->discard(SubExpr);
 
    if (!this->visit(SubExpr))
      return false;
 
    // If SubExpr doesn't result in a pointer, make it one.
    if (PrimType FromT = classifyPrim(SubExpr->getType()); FromT != PT_Ptr) {
      assert(isPtrType(FromT));
      if (!this->emitDecayPtr(FromT, PT_Ptr, CE))
        return false;
    }
 
    PrimType T = classifyPrim(CE->getType());
    if (T == PT_IntAP)
      return this->emitCastPointerIntegralAP(Ctx.getBitWidth(CE->getType()),
                                             CE);
    if (T == PT_IntAPS)
      return this->emitCastPointerIntegralAPS(Ctx.getBitWidth(CE->getType()),
                                              CE);
    return this->emitCastPointerIntegral(T, CE);
  }
 
  case CK_ArrayToPointerDecay: {
    if (!this->visit(SubExpr))
      return false;
    if (!this->emitArrayDecay(CE))
      return false;
    if (DiscardResult)
      return this->emitPopPtr(CE);
    return true;
  }
 
  case CK_IntegralToPointer: {
    QualType IntType = SubExpr->getType();
    assert(IntType->isIntegralOrEnumerationType());
    if (!this->visit(SubExpr))
      return false;
    // FIXME: I think the discard is wrong since the int->ptr cast might cause a
    // diagnostic.
    PrimType T = classifyPrim(IntType);
    if (DiscardResult)
      return this->emitPop(T, CE);
 
    QualType PtrType = CE->getType();
    assert(PtrType->isPointerType());
 
    const Descriptor *Desc;
    if (std::optional<PrimType> T = classify(PtrType->getPointeeType()))
      Desc = P.createDescriptor(SubExpr, *T);
    else if (PtrType->getPointeeType()->isVoidType())
      Desc = nullptr;
    else
      Desc = P.createDescriptor(CE, PtrType->getPointeeType().getTypePtr(),
                                Descriptor::InlineDescMD, true, false,
                                /*IsMutable=*/false, nullptr);
 
    if (!this->emitGetIntPtr(T, Desc, CE))
      return false;
 
    PrimType DestPtrT = classifyPrim(PtrType);
    if (DestPtrT == PT_Ptr)
      return true;
 
    // In case we're converting the integer to a non-Pointer.
    return this->emitDecayPtr(PT_Ptr, DestPtrT, CE);
  }
 
  case CK_AtomicToNonAtomic:
  case CK_ConstructorConversion:
  case CK_FunctionToPointerDecay:
  case CK_NonAtomicToAtomic:
  case CK_NoOp:
  case CK_UserDefinedConversion:
    return this->delegate(SubExpr);
 
  case CK_BitCast: {
    // Reject bitcasts to atomic types.
    if (CE->getType()->isAtomicType()) {
      if (!this->discard(SubExpr))
        return false;
      return this->emitInvalidCast(CastKind::Reinterpret, CE);
    }
 
    if (DiscardResult)
      return this->discard(SubExpr);
 
    std::optional<PrimType> FromT = classify(SubExpr->getType());
    std::optional<PrimType> ToT = classify(CE->getType());
    if (!FromT || !ToT)
      return false;
 
    assert(isPtrType(*FromT));
    assert(isPtrType(*ToT));
    if (FromT == ToT)
      return this->delegate(SubExpr);
 
    if (!this->visit(SubExpr))
      return false;
    return this->emitDecayPtr(*FromT, *ToT, CE);
  }
 
  case CK_IntegralToBoolean:
  case CK_IntegralCast: {
    if (DiscardResult)
      return this->discard(SubExpr);
    std::optional<PrimType> FromT = classify(SubExpr->getType());
    std::optional<PrimType> ToT = classify(CE->getType());
 
    if (!FromT || !ToT)
      return false;
 
    if (!this->visit(SubExpr))
      return false;
 
    if (ToT == PT_IntAP)
      return this->emitCastAP(*FromT, Ctx.getBitWidth(CE->getType()), CE);
    if (ToT == PT_IntAPS)
      return this->emitCastAPS(*FromT, Ctx.getBitWidth(CE->getType()), CE);
 
    if (FromT == ToT)
      return true;
    return this->emitCast(*FromT, *ToT, CE);
  }
 
  case CK_PointerToBoolean: {
    PrimType PtrT = classifyPrim(SubExpr->getType());
 
    // Just emit p != nullptr for this.
    if (!this->visit(SubExpr))
      return false;
 
    if (!this->emitNull(PtrT, nullptr, CE))
      return false;
 
    return this->emitNE(PtrT, CE);
  }
 
  case CK_IntegralComplexToBoolean:
  case CK_FloatingComplexToBoolean: {
    if (DiscardResult)
      return this->discard(SubExpr);
    if (!this->visit(SubExpr))
      return false;
    return this->emitComplexBoolCast(SubExpr);
  }
 
  case CK_IntegralComplexToReal:
  case CK_FloatingComplexToReal:
    return this->emitComplexReal(SubExpr);
 
  case CK_IntegralRealToComplex:
  case CK_FloatingRealToComplex: {
    // We're creating a complex value here, so we need to
    // allocate storage for it.
    if (!Initializing) {
      std::optional<unsigned> LocalIndex = allocateLocal(CE);
      if (!LocalIndex)
        return false;
      if (!this->emitGetPtrLocal(*LocalIndex, CE))
        return false;
    }
 
    // Init the complex value to {SubExpr, 0}.
    if (!this->visitArrayElemInit(0, SubExpr))
      return false;
    // Zero-init the second element.
    PrimType T = classifyPrim(SubExpr->getType());
    if (!this->visitZeroInitializer(T, SubExpr->getType(), SubExpr))
      return false;
    return this->emitInitElem(T, 1, SubExpr);
  }
 
  case CK_IntegralComplexCast:
  case CK_FloatingComplexCast:
  case CK_IntegralComplexToFloatingComplex:
  case CK_FloatingComplexToIntegralComplex: {
    assert(CE->getType()->isAnyComplexType());
    assert(SubExpr->getType()->isAnyComplexType());
    if (DiscardResult)
      return this->discard(SubExpr);
 
    if (!Initializing) {
      std::optional<unsigned> LocalIndex = allocateLocal(CE);
      if (!LocalIndex)
        return false;
      if (!this->emitGetPtrLocal(*LocalIndex, CE))
        return false;
    }
 
    // Location for the SubExpr.
    // Since SubExpr is of complex type, visiting it results in a pointer
    // anyway, so we just create a temporary pointer variable.
    unsigned SubExprOffset = allocateLocalPrimitive(
        SubExpr, PT_Ptr, /*IsConst=*/true, /*IsExtended=*/false);
    if (!this->visit(SubExpr))
      return false;
    if (!this->emitSetLocal(PT_Ptr, SubExprOffset, CE))
      return false;
 
    PrimType SourceElemT = classifyComplexElementType(SubExpr->getType());
    QualType DestElemType =
        CE->getType()->getAs<ComplexType>()->getElementType();
    PrimType DestElemT = classifyPrim(DestElemType);
    // Cast both elements individually.
    for (unsigned I = 0; I != 2; ++I) {
      if (!this->emitGetLocal(PT_Ptr, SubExprOffset, CE))
        return false;
      if (!this->emitArrayElemPop(SourceElemT, I, CE))
        return false;
 
      // Do the cast.
      if (!this->emitPrimCast(SourceElemT, DestElemT, DestElemType, CE))
        return false;
 
      // Save the value.
      if (!this->emitInitElem(DestElemT, I, CE))
        return false;
    }
    return true;
  }
 
  case CK_VectorSplat: {
    assert(!classify(CE->getType()));
    assert(classify(SubExpr->getType()));
    assert(CE->getType()->isVectorType());
 
    if (DiscardResult)
      return this->discard(SubExpr);
 
    assert(Initializing); // FIXME: Not always correct.
    const auto *VT = CE->getType()->getAs<VectorType>();
    PrimType ElemT = classifyPrim(SubExpr);
    unsigned ElemOffset = allocateLocalPrimitive(
        SubExpr, ElemT, /*IsConst=*/true, /*IsExtended=*/false);
 
    if (!this->visit(SubExpr))
      return false;
    if (!this->emitSetLocal(ElemT, ElemOffset, CE))
      return false;
 
    for (unsigned I = 0; I != VT->getNumElements(); ++I) {
      if (!this->emitGetLocal(ElemT, ElemOffset, CE))
        return false;
      if (!this->emitInitElem(ElemT, I, CE))
        return false;
    }
 
    return true;
  }
 
  case CK_ToVoid:
    return discard(SubExpr);
 
  default:
    return this->emitInvalid(CE);
  }
  llvm_unreachable("Unhandled clang::CastKind enum");
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitIntegerLiteral(const IntegerLiteral *LE) {
  if (DiscardResult)
    return true;
 
  return this->emitConst(LE->getValue(), LE);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitFloatingLiteral(const FloatingLiteral *E) {
  if (DiscardResult)
    return true;
 
  return this->emitConstFloat(E->getValue(), E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitImaginaryLiteral(
    const ImaginaryLiteral *E) {
  assert(E->getType()->isAnyComplexType());
  if (DiscardResult)
    return true;
 
  if (!Initializing) {
    std::optional<unsigned> LocalIndex = allocateLocal(E);
    if (!LocalIndex)
      return false;
    if (!this->emitGetPtrLocal(*LocalIndex, E))
      return false;
  }
 
  const Expr *SubExpr = E->getSubExpr();
  PrimType SubExprT = classifyPrim(SubExpr->getType());
 
  if (!this->visitZeroInitializer(SubExprT, SubExpr->getType(), SubExpr))
    return false;
  if (!this->emitInitElem(SubExprT, 0, SubExpr))
    return false;
  return this->visitArrayElemInit(1, SubExpr);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitParenExpr(const ParenExpr *E) {
  return this->delegate(E->getSubExpr());
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitBinaryOperator(const BinaryOperator *BO) {
  // Need short-circuiting for these.
  if (BO->isLogicalOp())
    return this->VisitLogicalBinOp(BO);
 
  const Expr *LHS = BO->getLHS();
  const Expr *RHS = BO->getRHS();
 
  // Handle comma operators. Just discard the LHS
  // and delegate to RHS.
  if (BO->isCommaOp()) {
    if (!this->discard(LHS))
      return false;
    if (RHS->getType()->isVoidType())
      return this->discard(RHS);
 
    return this->delegate(RHS);
  }
 
  if (BO->getType()->isAnyComplexType())
    return this->VisitComplexBinOp(BO);
  if ((LHS->getType()->isAnyComplexType() ||
       RHS->getType()->isAnyComplexType()) &&
      BO->isComparisonOp())
    return this->emitComplexComparison(LHS, RHS, BO);
 
  if (BO->isPtrMemOp())
    return this->visit(RHS);
 
  // Typecheck the args.
  std::optional<PrimType> LT = classify(LHS->getType());
  std::optional<PrimType> RT = classify(RHS->getType());
  std::optional<PrimType> T = classify(BO->getType());
 
  // Special case for C++'s three-way/spaceship operator <=>, which
  // returns a std::{strong,weak,partial}_ordering (which is a class, so doesn't
  // have a PrimType).
  if (!T && BO->getOpcode() == BO_Cmp) {
    if (DiscardResult)
      return true;
    const ComparisonCategoryInfo *CmpInfo =
        Ctx.getASTContext().CompCategories.lookupInfoForType(BO->getType());
    assert(CmpInfo);
 
    // We need a temporary variable holding our return value.
    if (!Initializing) {
      std::optional<unsigned> ResultIndex = this->allocateLocal(BO);
      if (!this->emitGetPtrLocal(*ResultIndex, BO))
        return false;
    }
 
    if (!visit(LHS) || !visit(RHS))
      return false;
 
    return this->emitCMP3(*LT, CmpInfo, BO);
  }
 
  if (!LT || !RT || !T)
    return false;
 
  // Pointer arithmetic special case.
  if (BO->getOpcode() == BO_Add || BO->getOpcode() == BO_Sub) {
    if (isPtrType(*T) || (isPtrType(*LT) && isPtrType(*RT)))
      return this->VisitPointerArithBinOp(BO);
  }
 
  if (!visit(LHS) || !visit(RHS))
    return false;
 
  // For languages such as C, cast the result of one
  // of our comparision opcodes to T (which is usually int).
  auto MaybeCastToBool = [this, T, BO](bool Result) {
    if (!Result)
      return false;
    if (DiscardResult)
      return this->emitPop(*T, BO);
    if (T != PT_Bool)
      return this->emitCast(PT_Bool, *T, BO);
    return true;
  };
 
  auto Discard = [this, T, BO](bool Result) {
    if (!Result)
      return false;
    return DiscardResult ? this->emitPop(*T, BO) : true;
  };
 
  switch (BO->getOpcode()) {
  case BO_EQ:
    return MaybeCastToBool(this->emitEQ(*LT, BO));
  case BO_NE:
    return MaybeCastToBool(this->emitNE(*LT, BO));
  case BO_LT:
    return MaybeCastToBool(this->emitLT(*LT, BO));
  case BO_LE:
    return MaybeCastToBool(this->emitLE(*LT, BO));
  case BO_GT:
    return MaybeCastToBool(this->emitGT(*LT, BO));
  case BO_GE:
    return MaybeCastToBool(this->emitGE(*LT, BO));
  case BO_Sub:
    if (BO->getType()->isFloatingType())
      return Discard(this->emitSubf(getRoundingMode(BO), BO));
    return Discard(this->emitSub(*T, BO));
  case BO_Add:
    if (BO->getType()->isFloatingType())
      return Discard(this->emitAddf(getRoundingMode(BO), BO));
    return Discard(this->emitAdd(*T, BO));
  case BO_Mul:
    if (BO->getType()->isFloatingType())
      return Discard(this->emitMulf(getRoundingMode(BO), BO));
    return Discard(this->emitMul(*T, BO));
  case BO_Rem:
    return Discard(this->emitRem(*T, BO));
  case BO_Div:
    if (BO->getType()->isFloatingType())
      return Discard(this->emitDivf(getRoundingMode(BO), BO));
    return Discard(this->emitDiv(*T, BO));
  case BO_Assign:
    if (DiscardResult)
      return LHS->refersToBitField() ? this->emitStoreBitFieldPop(*T, BO)
                                     : this->emitStorePop(*T, BO);
    if (LHS->refersToBitField()) {
      if (!this->emitStoreBitField(*T, BO))
        return false;
    } else {
      if (!this->emitStore(*T, BO))
        return false;
    }
    // Assignments aren't necessarily lvalues in C.
    // Load from them in that case.
    if (!BO->isLValue())
      return this->emitLoadPop(*T, BO);
    return true;
  case BO_And:
    return Discard(this->emitBitAnd(*T, BO));
  case BO_Or:
    return Discard(this->emitBitOr(*T, BO));
  case BO_Shl:
    return Discard(this->emitShl(*LT, *RT, BO));
  case BO_Shr:
    return Discard(this->emitShr(*LT, *RT, BO));
  case BO_Xor:
    return Discard(this->emitBitXor(*T, BO));
  case BO_LOr:
  case BO_LAnd:
    llvm_unreachable("Already handled earlier");
  default:
    return false;
  }
 
  llvm_unreachable("Unhandled binary op");
}
 
/// Perform addition/subtraction of a pointer and an integer or
/// subtraction of two pointers.
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitPointerArithBinOp(const BinaryOperator *E) {
  BinaryOperatorKind Op = E->getOpcode();
  const Expr *LHS = E->getLHS();
  const Expr *RHS = E->getRHS();
 
  if ((Op != BO_Add && Op != BO_Sub) ||
      (!LHS->getType()->isPointerType() && !RHS->getType()->isPointerType()))
    return false;
 
  std::optional<PrimType> LT = classify(LHS);
  std::optional<PrimType> RT = classify(RHS);
 
  if (!LT || !RT)
    return false;
 
  if (LHS->getType()->isPointerType() && RHS->getType()->isPointerType()) {
    if (Op != BO_Sub)
      return false;
 
    assert(E->getType()->isIntegerType());
    if (!visit(RHS) || !visit(LHS))
      return false;
 
    return this->emitSubPtr(classifyPrim(E->getType()), E);
  }
 
  PrimType OffsetType;
  if (LHS->getType()->isIntegerType()) {
    if (!visit(RHS) || !visit(LHS))
      return false;
    OffsetType = *LT;
  } else if (RHS->getType()->isIntegerType()) {
    if (!visit(LHS) || !visit(RHS))
      return false;
    OffsetType = *RT;
  } else {
    return false;
  }
 
  if (Op == BO_Add)
    return this->emitAddOffset(OffsetType, E);
  else if (Op == BO_Sub)
    return this->emitSubOffset(OffsetType, E);
 
  return false;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitLogicalBinOp(const BinaryOperator *E) {
  assert(E->isLogicalOp());
  BinaryOperatorKind Op = E->getOpcode();
  const Expr *LHS = E->getLHS();
  const Expr *RHS = E->getRHS();
  std::optional<PrimType> T = classify(E->getType());
 
  if (Op == BO_LOr) {
    // Logical OR. Visit LHS and only evaluate RHS if LHS was FALSE.
    LabelTy LabelTrue = this->getLabel();
    LabelTy LabelEnd = this->getLabel();
 
    if (!this->visitBool(LHS))
      return false;
    if (!this->jumpTrue(LabelTrue))
      return false;
 
    if (!this->visitBool(RHS))
      return false;
    if (!this->jump(LabelEnd))
      return false;
 
    this->emitLabel(LabelTrue);
    this->emitConstBool(true, E);
    this->fallthrough(LabelEnd);
    this->emitLabel(LabelEnd);
 
  } else {
    assert(Op == BO_LAnd);
    // Logical AND.
    // Visit LHS. Only visit RHS if LHS was TRUE.
    LabelTy LabelFalse = this->getLabel();
    LabelTy LabelEnd = this->getLabel();
 
    if (!this->visitBool(LHS))
      return false;
    if (!this->jumpFalse(LabelFalse))
      return false;
 
    if (!this->visitBool(RHS))
      return false;
    if (!this->jump(LabelEnd))
      return false;
 
    this->emitLabel(LabelFalse);
    this->emitConstBool(false, E);
    this->fallthrough(LabelEnd);
    this->emitLabel(LabelEnd);
  }
 
  if (DiscardResult)
    return this->emitPopBool(E);
 
  // For C, cast back to integer type.
  assert(T);
  if (T != PT_Bool)
    return this->emitCast(PT_Bool, *T, E);
  return true;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitComplexBinOp(const BinaryOperator *E) {
  // Prepare storage for result.
  if (!Initializing) {
    std::optional<unsigned> LocalIndex = allocateLocal(E);
    if (!LocalIndex)
      return false;
    if (!this->emitGetPtrLocal(*LocalIndex, E))
      return false;
  }
 
  // Both LHS and RHS might _not_ be of complex type, but one of them
  // needs to be.
  const Expr *LHS = E->getLHS();
  const Expr *RHS = E->getRHS();
 
  PrimType ResultElemT = this->classifyComplexElementType(E->getType());
  unsigned ResultOffset = ~0u;
  if (!DiscardResult)
    ResultOffset = this->allocateLocalPrimitive(E, PT_Ptr, true, false);
 
  // Save result pointer in ResultOffset
  if (!this->DiscardResult) {
    if (!this->emitDupPtr(E))
      return false;
    if (!this->emitSetLocal(PT_Ptr, ResultOffset, E))
      return false;
  }
  QualType LHSType = LHS->getType();
  if (const auto *AT = LHSType->getAs<AtomicType>())
    LHSType = AT->getValueType();
  QualType RHSType = RHS->getType();
  if (const auto *AT = RHSType->getAs<AtomicType>())
    RHSType = AT->getValueType();
 
  // Evaluate LHS and save value to LHSOffset.
  bool LHSIsComplex;
  unsigned LHSOffset;
  if (LHSType->isAnyComplexType()) {
    LHSIsComplex = true;
    LHSOffset = this->allocateLocalPrimitive(LHS, PT_Ptr, true, false);
    if (!this->visit(LHS))
      return false;
    if (!this->emitSetLocal(PT_Ptr, LHSOffset, E))
      return false;
  } else {
    LHSIsComplex = false;
    PrimType LHST = classifyPrim(LHSType);
    LHSOffset = this->allocateLocalPrimitive(LHS, LHST, true, false);
    if (!this->visit(LHS))
      return false;
    if (!this->emitSetLocal(LHST, LHSOffset, E))
      return false;
  }
 
  // Same with RHS.
  bool RHSIsComplex;
  unsigned RHSOffset;
  if (RHSType->isAnyComplexType()) {
    RHSIsComplex = true;
    RHSOffset = this->allocateLocalPrimitive(RHS, PT_Ptr, true, false);
    if (!this->visit(RHS))
      return false;
    if (!this->emitSetLocal(PT_Ptr, RHSOffset, E))
      return false;
  } else {
    RHSIsComplex = false;
    PrimType RHST = classifyPrim(RHSType);
    RHSOffset = this->allocateLocalPrimitive(RHS, RHST, true, false);
    if (!this->visit(RHS))
      return false;
    if (!this->emitSetLocal(RHST, RHSOffset, E))
      return false;
  }
 
  // For both LHS and RHS, either load the value from the complex pointer, or
  // directly from the local variable. For index 1 (i.e. the imaginary part),
  // just load 0 and do the operation anyway.
  auto loadComplexValue = [this](bool IsComplex, unsigned ElemIndex,
                                 unsigned Offset, const Expr *E) -> bool {
    if (IsComplex) {
      if (!this->emitGetLocal(PT_Ptr, Offset, E))
        return false;
      return this->emitArrayElemPop(classifyComplexElementType(E->getType()),
                                    ElemIndex, E);
    }
    if (ElemIndex == 0)
      return this->emitGetLocal(classifyPrim(E->getType()), Offset, E);
    return this->visitZeroInitializer(classifyPrim(E->getType()), E->getType(),
                                      E);
  };
 
  // Now we can get pointers to the LHS and RHS from the offsets above.
  BinaryOperatorKind Op = E->getOpcode();
  for (unsigned ElemIndex = 0; ElemIndex != 2; ++ElemIndex) {
    // Result pointer for the store later.
    if (!this->DiscardResult) {
      if (!this->emitGetLocal(PT_Ptr, ResultOffset, E))
        return false;
    }
 
    if (!loadComplexValue(LHSIsComplex, ElemIndex, LHSOffset, LHS))
      return false;
 
    if (!loadComplexValue(RHSIsComplex, ElemIndex, RHSOffset, RHS))
      return false;
 
    // The actual operation.
    switch (Op) {
    case BO_Add:
      if (ResultElemT == PT_Float) {
        if (!this->emitAddf(getRoundingMode(E), E))
          return false;
      } else {
        if (!this->emitAdd(ResultElemT, E))
          return false;
      }
      break;
    case BO_Sub:
      if (ResultElemT == PT_Float) {
        if (!this->emitSubf(getRoundingMode(E), E))
          return false;
      } else {
        if (!this->emitSub(ResultElemT, E))
          return false;
      }
      break;
 
    default:
      return false;
    }
 
    if (!this->DiscardResult) {
      // Initialize array element with the value we just computed.
      if (!this->emitInitElemPop(ResultElemT, ElemIndex, E))
        return false;
    } else {
      if (!this->emitPop(ResultElemT, E))
        return false;
    }
  }
  return true;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitImplicitValueInitExpr(const ImplicitValueInitExpr *E) {
  QualType QT = E->getType();
 
  if (std::optional<PrimType> T = classify(QT))
    return this->visitZeroInitializer(*T, QT, E);
 
  if (QT->isRecordType()) {
    const RecordDecl *RD = QT->getAsRecordDecl();
    assert(RD);
    if (RD->isInvalidDecl())
      return false;
    if (RD->isUnion()) {
      // C++11 [dcl.init]p5: If T is a (possibly cv-qualified) union type, the
      // object's first non-static named data member is zero-initialized
      // FIXME
      return false;
    }
 
    if (const auto *CXXRD = dyn_cast<CXXRecordDecl>(RD);
        CXXRD && CXXRD->getNumVBases() > 0) {
      // TODO: Diagnose.
      return false;
    }
 
    const Record *R = getRecord(QT);
    if (!R)
      return false;
 
    assert(Initializing);
    return this->visitZeroRecordInitializer(R, E);
  }
 
  if (QT->isIncompleteArrayType())
    return true;
 
  if (QT->isArrayType()) {
    const ArrayType *AT = QT->getAsArrayTypeUnsafe();
    assert(AT);
    const auto *CAT = cast<ConstantArrayType>(AT);
    size_t NumElems = CAT->getZExtSize();
    PrimType ElemT = classifyPrim(CAT->getElementType());
 
    for (size_t I = 0; I != NumElems; ++I) {
      if (!this->visitZeroInitializer(ElemT, CAT->getElementType(), E))
        return false;
      if (!this->emitInitElem(ElemT, I, E))
        return false;
    }
 
    return true;
  }
 
  if (const auto *ComplexTy = E->getType()->getAs<ComplexType>()) {
    assert(Initializing);
    QualType ElemQT = ComplexTy->getElementType();
    PrimType ElemT = classifyPrim(ElemQT);
    for (unsigned I = 0; I < 2; ++I) {
      if (!this->visitZeroInitializer(ElemT, ElemQT, E))
        return false;
      if (!this->emitInitElem(ElemT, I, E))
        return false;
    }
    return true;
  }
 
  if (const auto *VecT = E->getType()->getAs<VectorType>()) {
    unsigned NumVecElements = VecT->getNumElements();
    QualType ElemQT = VecT->getElementType();
    PrimType ElemT = classifyPrim(ElemQT);
 
    for (unsigned I = 0; I < NumVecElements; ++I) {
      if (!this->visitZeroInitializer(ElemT, ElemQT, E))
        return false;
      if (!this->emitInitElem(ElemT, I, E))
        return false;
    }
    return true;
  }
 
  return false;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitArraySubscriptExpr(
    const ArraySubscriptExpr *E) {
  const Expr *Base = E->getBase();
  const Expr *Index = E->getIdx();
 
  if (DiscardResult)
    return this->discard(Base) && this->discard(Index);
 
  // Take pointer of LHS, add offset from RHS.
  // What's left on the stack after this is a pointer.
  if (!this->visit(Base))
    return false;
 
  if (!this->visit(Index))
    return false;
 
  PrimType IndexT = classifyPrim(Index->getType());
  return this->emitArrayElemPtrPop(IndexT, E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::visitInitList(ArrayRef<const Expr *> Inits,
                                             const Expr *ArrayFiller,
                                             const Expr *E) {
  if (E->getType()->isVoidType())
    return this->emitInvalid(E);
 
  // Handle discarding first.
  if (DiscardResult) {
    for (const Expr *Init : Inits) {
      if (!this->discard(Init))
        return false;
    }
    return true;
  }
 
  // Primitive values.
  if (std::optional<PrimType> T = classify(E->getType())) {
    assert(!DiscardResult);
    if (Inits.size() == 0)
      return this->visitZeroInitializer(*T, E->getType(), E);
    assert(Inits.size() == 1);
    return this->delegate(Inits[0]);
  }
 
  QualType T = E->getType();
  if (T->isRecordType()) {
    const Record *R = getRecord(E->getType());
 
    if (Inits.size() == 1 && E->getType() == Inits[0]->getType()) {
      return this->visitInitializer(Inits[0]);
    }
 
    unsigned InitIndex = 0;
    for (const Expr *Init : Inits) {
      // Skip unnamed bitfields.
      while (InitIndex < R->getNumFields() &&
             R->getField(InitIndex)->Decl->isUnnamedBitField())
        ++InitIndex;
 
      if (!this->emitDupPtr(E))
        return false;
 
      if (std::optional<PrimType> T = classify(Init)) {
        const Record::Field *FieldToInit = R->getField(InitIndex);
        if (!this->visit(Init))
          return false;
 
        if (FieldToInit->isBitField()) {
          if (!this->emitInitBitField(*T, FieldToInit, E))
            return false;
        } else {
          if (!this->emitInitField(*T, FieldToInit->Offset, E))
            return false;
        }
 
        if (!this->emitPopPtr(E))
          return false;
        ++InitIndex;
      } else {
        // Initializer for a direct base class.
        if (const Record::Base *B = R->getBase(Init->getType())) {
          if (!this->emitGetPtrBasePop(B->Offset, Init))
            return false;
 
          if (!this->visitInitializer(Init))
            return false;
 
          if (!this->emitFinishInitPop(E))
            return false;
          // Base initializers don't increase InitIndex, since they don't count
          // into the Record's fields.
        } else {
          const Record::Field *FieldToInit = R->getField(InitIndex);
          // Non-primitive case. Get a pointer to the field-to-initialize
          // on the stack and recurse into visitInitializer().
          if (!this->emitGetPtrField(FieldToInit->Offset, Init))
            return false;
 
          if (!this->visitInitializer(Init))
            return false;
 
          if (!this->emitPopPtr(E))
            return false;
          ++InitIndex;
        }
      }
    }
    return true;
  }
 
  if (T->isArrayType()) {
    unsigned ElementIndex = 0;
    for (const Expr *Init : Inits) {
      if (!this->visitArrayElemInit(ElementIndex, Init))
        return false;
      ++ElementIndex;
    }
 
    // Expand the filler expression.
    // FIXME: This should go away.
    if (ArrayFiller) {
      const ConstantArrayType *CAT =
          Ctx.getASTContext().getAsConstantArrayType(E->getType());
      uint64_t NumElems = CAT->getZExtSize();
 
      for (; ElementIndex != NumElems; ++ElementIndex) {
        if (!this->visitArrayElemInit(ElementIndex, ArrayFiller))
          return false;
      }
    }
 
    return true;
  }
 
  if (const auto *ComplexTy = E->getType()->getAs<ComplexType>()) {
    unsigned NumInits = Inits.size();
 
    if (NumInits == 1)
      return this->delegate(Inits[0]);
 
    QualType ElemQT = ComplexTy->getElementType();
    PrimType ElemT = classifyPrim(ElemQT);
    if (NumInits == 0) {
      // Zero-initialize both elements.
      for (unsigned I = 0; I < 2; ++I) {
        if (!this->visitZeroInitializer(ElemT, ElemQT, E))
          return false;
        if (!this->emitInitElem(ElemT, I, E))
          return false;
      }
    } else if (NumInits == 2) {
      unsigned InitIndex = 0;
      for (const Expr *Init : Inits) {
        if (!this->visit(Init))
          return false;
 
        if (!this->emitInitElem(ElemT, InitIndex, E))
          return false;
        ++InitIndex;
      }
    }
    return true;
  }
 
  if (const auto *VecT = E->getType()->getAs<VectorType>()) {
    unsigned NumVecElements = VecT->getNumElements();
    assert(NumVecElements >= Inits.size());
 
    QualType ElemQT = VecT->getElementType();
    PrimType ElemT = classifyPrim(ElemQT);
 
    // All initializer elements.
    unsigned InitIndex = 0;
    for (const Expr *Init : Inits) {
      if (!this->visit(Init))
        return false;
 
      // If the initializer is of vector type itself, we have to deconstruct
      // that and initialize all the target fields from the initializer fields.
      if (const auto *InitVecT = Init->getType()->getAs<VectorType>()) {
        if (!this->emitCopyArray(ElemT, 0, InitIndex, InitVecT->getNumElements(), E))
          return false;
        InitIndex += InitVecT->getNumElements();
      } else {
        if (!this->emitInitElem(ElemT, InitIndex, E))
          return false;
        ++InitIndex;
      }
    }
 
    assert(InitIndex <= NumVecElements);
 
    // Fill the rest with zeroes.
    for (; InitIndex != NumVecElements; ++InitIndex) {
      if (!this->visitZeroInitializer(ElemT, ElemQT, E))
        return false;
      if (!this->emitInitElem(ElemT, InitIndex, E))
        return false;
    }
    return true;
  }
 
  return false;
}
 
/// Pointer to the array(not the element!) must be on the stack when calling
/// this.
template <class Emitter>
bool ByteCodeExprGen<Emitter>::visitArrayElemInit(unsigned ElemIndex,
                                                  const Expr *Init) {
  if (std::optional<PrimType> T = classify(Init->getType())) {
    // Visit the primitive element like normal.
    if (!this->visit(Init))
      return false;
    return this->emitInitElem(*T, ElemIndex, Init);
  }
 
  // Advance the pointer currently on the stack to the given
  // dimension.
  if (!this->emitConstUint32(ElemIndex, Init))
    return false;
  if (!this->emitArrayElemPtrUint32(Init))
    return false;
  if (!this->visitInitializer(Init))
    return false;
  return this->emitFinishInitPop(Init);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitInitListExpr(const InitListExpr *E) {
  return this->visitInitList(E->inits(), E->getArrayFiller(), E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCXXParenListInitExpr(
    const CXXParenListInitExpr *E) {
  return this->visitInitList(E->getInitExprs(), E->getArrayFiller(), E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitSubstNonTypeTemplateParmExpr(
    const SubstNonTypeTemplateParmExpr *E) {
  return this->delegate(E->getReplacement());
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitConstantExpr(const ConstantExpr *E) {
  std::optional<PrimType> T = classify(E->getType());
  if (T && E->hasAPValueResult()) {
    // Try to emit the APValue directly, without visiting the subexpr.
    // This will only fail if we can't emit the APValue, so won't emit any
    // diagnostics or any double values.
    if (DiscardResult)
      return true;
 
    if (this->visitAPValue(E->getAPValueResult(), *T, E))
      return true;
  }
  return this->delegate(E->getSubExpr());
}
 
static CharUnits AlignOfType(QualType T, const ASTContext &ASTCtx,
                             UnaryExprOrTypeTrait Kind) {
  bool AlignOfReturnsPreferred =
      ASTCtx.getLangOpts().getClangABICompat() <= LangOptions::ClangABI::Ver7;
 
  // C++ [expr.alignof]p3:
  //     When alignof is applied to a reference type, the result is the
  //     alignment of the referenced type.
  if (const auto *Ref = T->getAs<ReferenceType>())
    T = Ref->getPointeeType();
 
  if (T.getQualifiers().hasUnaligned())
    return CharUnits::One();
 
  // __alignof is defined to return the preferred alignment.
  // Before 8, clang returned the preferred alignment for alignof and
  // _Alignof as well.
  if (Kind == UETT_PreferredAlignOf || AlignOfReturnsPreferred)
    return ASTCtx.toCharUnitsFromBits(ASTCtx.getPreferredTypeAlign(T));
 
  return ASTCtx.getTypeAlignInChars(T);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitUnaryExprOrTypeTraitExpr(
    const UnaryExprOrTypeTraitExpr *E) {
  UnaryExprOrTypeTrait Kind = E->getKind();
  const ASTContext &ASTCtx = Ctx.getASTContext();
 
  if (Kind == UETT_SizeOf || Kind == UETT_DataSizeOf) {
    QualType ArgType = E->getTypeOfArgument();
 
    // C++ [expr.sizeof]p2: "When applied to a reference or a reference type,
    //   the result is the size of the referenced type."
    if (const auto *Ref = ArgType->getAs<ReferenceType>())
      ArgType = Ref->getPointeeType();
 
    CharUnits Size;
    if (ArgType->isVoidType() || ArgType->isFunctionType())
      Size = CharUnits::One();
    else {
      if (ArgType->isDependentType() || !ArgType->isConstantSizeType())
        return false;
 
      if (Kind == UETT_SizeOf)
        Size = ASTCtx.getTypeSizeInChars(ArgType);
      else
        Size = ASTCtx.getTypeInfoDataSizeInChars(ArgType).Width;
    }
 
    if (DiscardResult)
      return true;
 
    return this->emitConst(Size.getQuantity(), E);
  }
 
  if (Kind == UETT_AlignOf || Kind == UETT_PreferredAlignOf) {
    CharUnits Size;
 
    if (E->isArgumentType()) {
      QualType ArgType = E->getTypeOfArgument();
 
      Size = AlignOfType(ArgType, ASTCtx, Kind);
    } else {
      // Argument is an expression, not a type.
      const Expr *Arg = E->getArgumentExpr()->IgnoreParens();
 
      // The kinds of expressions that we have special-case logic here for
      // should be kept up to date with the special checks for those
      // expressions in Sema.
 
      // alignof decl is always accepted, even if it doesn't make sense: we
      // default to 1 in those cases.
      if (const auto *DRE = dyn_cast<DeclRefExpr>(Arg))
        Size = ASTCtx.getDeclAlign(DRE->getDecl(),
                                   /*RefAsPointee*/ true);
      else if (const auto *ME = dyn_cast<MemberExpr>(Arg))
        Size = ASTCtx.getDeclAlign(ME->getMemberDecl(),
                                   /*RefAsPointee*/ true);
      else
        Size = AlignOfType(Arg->getType(), ASTCtx, Kind);
    }
 
    if (DiscardResult)
      return true;
 
    return this->emitConst(Size.getQuantity(), E);
  }
 
  if (Kind == UETT_VectorElements) {
    if (const auto *VT = E->getTypeOfArgument()->getAs<VectorType>())
      return this->emitConst(VT->getNumElements(), E);
 
    // FIXME: Apparently we need to catch the fact that a sizeless vector type
    // has been passed and diagnose that (at run time).
    assert(E->getTypeOfArgument()->isSizelessVectorType());
  }
 
  if (Kind == UETT_VecStep) {
    if (const auto *VT = E->getTypeOfArgument()->getAs<VectorType>()) {
      unsigned N = VT->getNumElements();
 
      // The vec_step built-in functions that take a 3-component
      // vector return 4. (OpenCL 1.1 spec 6.11.12)
      if (N == 3)
        N = 4;
 
      return this->emitConst(N, E);
    }
    return this->emitConst(1, E);
  }
 
  return false;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitMemberExpr(const MemberExpr *E) {
  // 'Base.Member'
  const Expr *Base = E->getBase();
  const ValueDecl *Member = E->getMemberDecl();
 
  if (DiscardResult)
    return this->discard(Base);
 
  // MemberExprs are almost always lvalues, in which case we don't need to
  // do the load. But sometimes they aren't.
  const auto maybeLoadValue = [&]() -> bool {
    if (E->isGLValue())
      return true;
    if (std::optional<PrimType> T = classify(E))
      return this->emitLoadPop(*T, E);
    return false;
  };
 
  if (const auto *VD = dyn_cast<VarDecl>(Member)) {
    // I am almost confident in saying that a var decl must be static
    // and therefore registered as a global variable. But this will probably
    // turn out to be wrong some time in the future, as always.
    if (auto GlobalIndex = P.getGlobal(VD))
      return this->emitGetPtrGlobal(*GlobalIndex, E) && maybeLoadValue();
    return false;
  }
 
  if (Initializing) {
    if (!this->delegate(Base))
      return false;
  } else {
    if (!this->visit(Base))
      return false;
  }
 
  // Base above gives us a pointer on the stack.
  if (const auto *FD = dyn_cast<FieldDecl>(Member)) {
    const RecordDecl *RD = FD->getParent();
    const Record *R = getRecord(RD);
    if (!R)
      return false;
    const Record::Field *F = R->getField(FD);
    // Leave a pointer to the field on the stack.
    if (F->Decl->getType()->isReferenceType())
      return this->emitGetFieldPop(PT_Ptr, F->Offset, E) && maybeLoadValue();
    return this->emitGetPtrField(F->Offset, E) && maybeLoadValue();
  }
 
  return false;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitArrayInitIndexExpr(
    const ArrayInitIndexExpr *E) {
  // ArrayIndex might not be set if a ArrayInitIndexExpr is being evaluated
  // stand-alone, e.g. via EvaluateAsInt().
  if (!ArrayIndex)
    return false;
  return this->emitConst(*ArrayIndex, E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitArrayInitLoopExpr(
    const ArrayInitLoopExpr *E) {
  assert(Initializing);
  assert(!DiscardResult);
 
  // We visit the common opaque expression here once so we have its value
  // cached.
  if (!this->discard(E->getCommonExpr()))
    return false;
 
  // TODO: This compiles to quite a lot of bytecode if the array is larger.
  //   Investigate compiling this to a loop.
  const Expr *SubExpr = E->getSubExpr();
  size_t Size = E->getArraySize().getZExtValue();
 
  // So, every iteration, we execute an assignment here
  // where the LHS is on the stack (the target array)
  // and the RHS is our SubExpr.
  for (size_t I = 0; I != Size; ++I) {
    ArrayIndexScope<Emitter> IndexScope(this, I);
    BlockScope<Emitter> BS(this);
 
    if (!this->visitArrayElemInit(I, SubExpr))
      return false;
  }
  return true;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitOpaqueValueExpr(const OpaqueValueExpr *E) {
  const Expr *SourceExpr = E->getSourceExpr();
  if (!SourceExpr)
    return false;
 
  if (Initializing)
    return this->visitInitializer(SourceExpr);
 
  PrimType SubExprT = classify(SourceExpr).value_or(PT_Ptr);
  if (auto It = OpaqueExprs.find(E); It != OpaqueExprs.end())
    return this->emitGetLocal(SubExprT, It->second, E);
 
  if (!this->visit(SourceExpr))
    return false;
 
  // At this point we either have the evaluated source expression or a pointer
  // to an object on the stack. We want to create a local variable that stores
  // this value.
  unsigned LocalIndex = allocateLocalPrimitive(E, SubExprT, /*IsConst=*/true);
  if (!this->emitSetLocal(SubExprT, LocalIndex, E))
    return false;
 
  // Here the local variable is created but the value is removed from the stack,
  // so we put it back if the caller needs it.
  if (!DiscardResult) {
    if (!this->emitGetLocal(SubExprT, LocalIndex, E))
      return false;
  }
 
  // This is cleaned up when the local variable is destroyed.
  OpaqueExprs.insert({E, LocalIndex});
 
  return true;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitAbstractConditionalOperator(
    const AbstractConditionalOperator *E) {
  const Expr *Condition = E->getCond();
  const Expr *TrueExpr = E->getTrueExpr();
  const Expr *FalseExpr = E->getFalseExpr();
 
  LabelTy LabelEnd = this->getLabel();   // Label after the operator.
  LabelTy LabelFalse = this->getLabel(); // Label for the false expr.
 
  if (!this->visitBool(Condition))
    return false;
 
  if (!this->jumpFalse(LabelFalse))
    return false;
 
  if (!this->delegate(TrueExpr))
    return false;
  if (!this->jump(LabelEnd))
    return false;
 
  this->emitLabel(LabelFalse);
 
  if (!this->delegate(FalseExpr))
    return false;
 
  this->fallthrough(LabelEnd);
  this->emitLabel(LabelEnd);
 
  return true;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitStringLiteral(const StringLiteral *E) {
  if (DiscardResult)
    return true;
 
  if (!Initializing) {
    unsigned StringIndex = P.createGlobalString(E);
    return this->emitGetPtrGlobal(StringIndex, E);
  }
 
  // We are initializing an array on the stack.
  const ConstantArrayType *CAT =
      Ctx.getASTContext().getAsConstantArrayType(E->getType());
  assert(CAT && "a string literal that's not a constant array?");
 
  // If the initializer string is too long, a diagnostic has already been
  // emitted. Read only the array length from the string literal.
  unsigned ArraySize = CAT->getZExtSize();
  unsigned N = std::min(ArraySize, E->getLength());
  size_t CharWidth = E->getCharByteWidth();
 
  for (unsigned I = 0; I != N; ++I) {
    uint32_t CodeUnit = E->getCodeUnit(I);
 
    if (CharWidth == 1) {
      this->emitConstSint8(CodeUnit, E);
      this->emitInitElemSint8(I, E);
    } else if (CharWidth == 2) {
      this->emitConstUint16(CodeUnit, E);
      this->emitInitElemUint16(I, E);
    } else if (CharWidth == 4) {
      this->emitConstUint32(CodeUnit, E);
      this->emitInitElemUint32(I, E);
    } else {
      llvm_unreachable("unsupported character width");
    }
  }
 
  // Fill up the rest of the char array with NUL bytes.
  for (unsigned I = N; I != ArraySize; ++I) {
    if (CharWidth == 1) {
      this->emitConstSint8(0, E);
      this->emitInitElemSint8(I, E);
    } else if (CharWidth == 2) {
      this->emitConstUint16(0, E);
      this->emitInitElemUint16(I, E);
    } else if (CharWidth == 4) {
      this->emitConstUint32(0, E);
      this->emitInitElemUint32(I, E);
    } else {
      llvm_unreachable("unsupported character width");
    }
  }
 
  return true;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCharacterLiteral(
    const CharacterLiteral *E) {
  if (DiscardResult)
    return true;
  return this->emitConst(E->getValue(), E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitFloatCompoundAssignOperator(
    const CompoundAssignOperator *E) {
 
  const Expr *LHS = E->getLHS();
  const Expr *RHS = E->getRHS();
  QualType LHSType = LHS->getType();
  QualType LHSComputationType = E->getComputationLHSType();
  QualType ResultType = E->getComputationResultType();
  std::optional<PrimType> LT = classify(LHSComputationType);
  std::optional<PrimType> RT = classify(ResultType);
 
  assert(ResultType->isFloatingType());
 
  if (!LT || !RT)
    return false;
 
  PrimType LHST = classifyPrim(LHSType);
 
  // C++17 onwards require that we evaluate the RHS first.
  // Compute RHS and save it in a temporary variable so we can
  // load it again later.
  if (!visit(RHS))
    return false;
 
  unsigned TempOffset = this->allocateLocalPrimitive(E, *RT, /*IsConst=*/true);
  if (!this->emitSetLocal(*RT, TempOffset, E))
    return false;
 
  // First, visit LHS.
  if (!visit(LHS))
    return false;
  if (!this->emitLoad(LHST, E))
    return false;
 
  // If necessary, convert LHS to its computation type.
  if (!this->emitPrimCast(LHST, classifyPrim(LHSComputationType),
                          LHSComputationType, E))
    return false;
 
  // Now load RHS.
  if (!this->emitGetLocal(*RT, TempOffset, E))
    return false;
 
  llvm::RoundingMode RM = getRoundingMode(E);
  switch (E->getOpcode()) {
  case BO_AddAssign:
    if (!this->emitAddf(RM, E))
      return false;
    break;
  case BO_SubAssign:
    if (!this->emitSubf(RM, E))
      return false;
    break;
  case BO_MulAssign:
    if (!this->emitMulf(RM, E))
      return false;
    break;
  case BO_DivAssign:
    if (!this->emitDivf(RM, E))
      return false;
    break;
  default:
    return false;
  }
 
  if (!this->emitPrimCast(classifyPrim(ResultType), LHST, LHS->getType(), E))
    return false;
 
  if (DiscardResult)
    return this->emitStorePop(LHST, E);
  return this->emitStore(LHST, E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitPointerCompoundAssignOperator(
    const CompoundAssignOperator *E) {
  BinaryOperatorKind Op = E->getOpcode();
  const Expr *LHS = E->getLHS();
  const Expr *RHS = E->getRHS();
  std::optional<PrimType> LT = classify(LHS->getType());
  std::optional<PrimType> RT = classify(RHS->getType());
 
  if (Op != BO_AddAssign && Op != BO_SubAssign)
    return false;
 
  if (!LT || !RT)
    return false;
 
  if (!visit(LHS))
    return false;
 
  if (!this->emitLoad(*LT, LHS))
    return false;
 
  if (!visit(RHS))
    return false;
 
  if (Op == BO_AddAssign) {
    if (!this->emitAddOffset(*RT, E))
      return false;
  } else {
    if (!this->emitSubOffset(*RT, E))
      return false;
  }
 
  if (DiscardResult)
    return this->emitStorePopPtr(E);
  return this->emitStorePtr(E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCompoundAssignOperator(
    const CompoundAssignOperator *E) {
 
  const Expr *LHS = E->getLHS();
  const Expr *RHS = E->getRHS();
  std::optional<PrimType> LHSComputationT =
      classify(E->getComputationLHSType());
  std::optional<PrimType> LT = classify(LHS->getType());
  std::optional<PrimType> RT = classify(RHS->getType());
  std::optional<PrimType> ResultT = classify(E->getType());
 
  if (!LT || !RT || !ResultT || !LHSComputationT)
    return false;
 
  // Handle floating point operations separately here, since they
  // require special care.
 
  if (ResultT == PT_Float || RT == PT_Float)
    return VisitFloatCompoundAssignOperator(E);
 
  if (E->getType()->isPointerType())
    return VisitPointerCompoundAssignOperator(E);
 
  assert(!E->getType()->isPointerType() && "Handled above");
  assert(!E->getType()->isFloatingType() && "Handled above");
 
  // C++17 onwards require that we evaluate the RHS first.
  // Compute RHS and save it in a temporary variable so we can
  // load it again later.
  // FIXME: Compound assignments are unsequenced in C, so we might
  //   have to figure out how to reject them.
  if (!visit(RHS))
    return false;
 
  unsigned TempOffset = this->allocateLocalPrimitive(E, *RT, /*IsConst=*/true);
 
  if (!this->emitSetLocal(*RT, TempOffset, E))
    return false;
 
  // Get LHS pointer, load its value and cast it to the
  // computation type if necessary.
  if (!visit(LHS))
    return false;
  if (!this->emitLoad(*LT, E))
    return false;
  if (LT != LHSComputationT) {
    if (!this->emitCast(*LT, *LHSComputationT, E))
      return false;
  }
 
  // Get the RHS value on the stack.
  if (!this->emitGetLocal(*RT, TempOffset, E))
    return false;
 
  // Perform operation.
  switch (E->getOpcode()) {
  case BO_AddAssign:
    if (!this->emitAdd(*LHSComputationT, E))
      return false;
    break;
  case BO_SubAssign:
    if (!this->emitSub(*LHSComputationT, E))
      return false;
    break;
  case BO_MulAssign:
    if (!this->emitMul(*LHSComputationT, E))
      return false;
    break;
  case BO_DivAssign:
    if (!this->emitDiv(*LHSComputationT, E))
      return false;
    break;
  case BO_RemAssign:
    if (!this->emitRem(*LHSComputationT, E))
      return false;
    break;
  case BO_ShlAssign:
    if (!this->emitShl(*LHSComputationT, *RT, E))
      return false;
    break;
  case BO_ShrAssign:
    if (!this->emitShr(*LHSComputationT, *RT, E))
      return false;
    break;
  case BO_AndAssign:
    if (!this->emitBitAnd(*LHSComputationT, E))
      return false;
    break;
  case BO_XorAssign:
    if (!this->emitBitXor(*LHSComputationT, E))
      return false;
    break;
  case BO_OrAssign:
    if (!this->emitBitOr(*LHSComputationT, E))
      return false;
    break;
  default:
    llvm_unreachable("Unimplemented compound assign operator");
  }
 
  // And now cast from LHSComputationT to ResultT.
  if (ResultT != LHSComputationT) {
    if (!this->emitCast(*LHSComputationT, *ResultT, E))
      return false;
  }
 
  // And store the result in LHS.
  if (DiscardResult) {
    if (LHS->refersToBitField())
      return this->emitStoreBitFieldPop(*ResultT, E);
    return this->emitStorePop(*ResultT, E);
  }
  if (LHS->refersToBitField())
    return this->emitStoreBitField(*ResultT, E);
  return this->emitStore(*ResultT, E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitExprWithCleanups(
    const ExprWithCleanups *E) {
  ExprScope<Emitter> ES(this);
  const Expr *SubExpr = E->getSubExpr();
 
  assert(E->getNumObjects() == 0 && "TODO: Implement cleanups");
 
  return this->delegate(SubExpr) && ES.destroyLocals();
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitMaterializeTemporaryExpr(
    const MaterializeTemporaryExpr *E) {
  const Expr *SubExpr = E->getSubExpr();
 
  if (Initializing) {
    // We already have a value, just initialize that.
    return this->visitInitializer(SubExpr);
  }
  // If we don't end up using the materialized temporary anyway, don't
  // bother creating it.
  if (DiscardResult)
    return this->discard(SubExpr);
 
  // When we're initializing a global variable *or* the storage duration of
  // the temporary is explicitly static, create a global variable.
  std::optional<PrimType> SubExprT = classify(SubExpr);
  bool IsStatic = E->getStorageDuration() == SD_Static;
  if (GlobalDecl || IsStatic) {
    std::optional<unsigned> GlobalIndex = P.createGlobal(E);
    if (!GlobalIndex)
      return false;
 
    const LifetimeExtendedTemporaryDecl *TempDecl =
        E->getLifetimeExtendedTemporaryDecl();
    if (IsStatic)
      assert(TempDecl);
 
    if (SubExprT) {
      if (!this->visit(SubExpr))
        return false;
      if (IsStatic) {
        if (!this->emitInitGlobalTemp(*SubExprT, *GlobalIndex, TempDecl, E))
          return false;
      } else {
        if (!this->emitInitGlobal(*SubExprT, *GlobalIndex, E))
          return false;
      }
      return this->emitGetPtrGlobal(*GlobalIndex, E);
    }
 
    // Non-primitive values.
    if (!this->emitGetPtrGlobal(*GlobalIndex, E))
      return false;
    if (!this->visitInitializer(SubExpr))
      return false;
    if (IsStatic)
      return this->emitInitGlobalTempComp(TempDecl, E);
    return true;
  }
 
  // For everyhing else, use local variables.
  if (SubExprT) {
    unsigned LocalIndex = allocateLocalPrimitive(
        SubExpr, *SubExprT, /*IsConst=*/true, /*IsExtended=*/true);
    if (!this->visit(SubExpr))
      return false;
    if (!this->emitSetLocal(*SubExprT, LocalIndex, E))
      return false;
    return this->emitGetPtrLocal(LocalIndex, E);
  } else {
    const Expr *Inner = E->getSubExpr()->skipRValueSubobjectAdjustments();
    if (std::optional<unsigned> LocalIndex =
            allocateLocal(Inner, E->getExtendingDecl())) {
      if (!this->emitGetPtrLocal(*LocalIndex, E))
        return false;
      return this->visitInitializer(SubExpr);
    }
  }
  return false;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCXXBindTemporaryExpr(
    const CXXBindTemporaryExpr *E) {
  return this->delegate(E->getSubExpr());
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCompoundLiteralExpr(
    const CompoundLiteralExpr *E) {
  const Expr *Init = E->getInitializer();
  if (Initializing) {
    // We already have a value, just initialize that.
    return this->visitInitializer(Init) && this->emitFinishInit(E);
  }
 
  std::optional<PrimType> T = classify(E->getType());
  if (E->isFileScope()) {
    // Avoid creating a variable if this is a primitive RValue anyway.
    if (T && !E->isLValue())
      return this->delegate(Init);
 
    if (std::optional<unsigned> GlobalIndex = P.createGlobal(E)) {
      if (!this->emitGetPtrGlobal(*GlobalIndex, E))
        return false;
 
      if (T) {
        if (!this->visit(Init))
          return false;
        return this->emitInitGlobal(*T, *GlobalIndex, E);
      }
 
      return this->visitInitializer(Init) && this->emitFinishInit(E);
    }
 
    return false;
  }
 
  // Otherwise, use a local variable.
  if (T && !E->isLValue()) {
    // For primitive types, we just visit the initializer.
    return this->delegate(Init);
  } else {
    unsigned LocalIndex;
 
    if (T)
      LocalIndex = this->allocateLocalPrimitive(Init, *T, false, false);
    else if (std::optional<unsigned> MaybeIndex = this->allocateLocal(Init))
      LocalIndex = *MaybeIndex;
    else
      return false;
 
    if (!this->emitGetPtrLocal(LocalIndex, E))
      return false;
 
    if (T) {
      if (!this->visit(Init)) {
        return false;
      }
      return this->emitInit(*T, E);
    } else {
      if (!this->visitInitializer(Init) || !this->emitFinishInit(E))
        return false;
    }
 
    if (DiscardResult)
      return this->emitPopPtr(E);
    return true;
  }
 
  return false;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitTypeTraitExpr(const TypeTraitExpr *E) {
  if (DiscardResult)
    return true;
  if (E->getType()->isBooleanType())
    return this->emitConstBool(E->getValue(), E);
  return this->emitConst(E->getValue(), E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitArrayTypeTraitExpr(
    const ArrayTypeTraitExpr *E) {
  if (DiscardResult)
    return true;
  return this->emitConst(E->getValue(), E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitLambdaExpr(const LambdaExpr *E) {
  if (DiscardResult)
    return true;
 
  assert(Initializing);
  const Record *R = P.getOrCreateRecord(E->getLambdaClass());
 
  auto *CaptureInitIt = E->capture_init_begin();
  // Initialize all fields (which represent lambda captures) of the
  // record with their initializers.
  for (const Record::Field &F : R->fields()) {
    const Expr *Init = *CaptureInitIt;
    ++CaptureInitIt;
 
    if (!Init)
      continue;
 
    if (std::optional<PrimType> T = classify(Init)) {
      if (!this->visit(Init))
        return false;
 
      if (!this->emitInitField(*T, F.Offset, E))
        return false;
    } else {
      if (!this->emitDupPtr(E))
        return false;
 
      if (!this->emitGetPtrField(F.Offset, E))
        return false;
 
      if (!this->visitInitializer(Init))
        return false;
 
      if (!this->emitPopPtr(E))
        return false;
    }
  }
 
  return true;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitPredefinedExpr(const PredefinedExpr *E) {
  if (DiscardResult)
    return true;
 
  return this->delegate(E->getFunctionName());
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCXXThrowExpr(const CXXThrowExpr *E) {
  if (E->getSubExpr() && !this->discard(E->getSubExpr()))
    return false;
 
  return this->emitInvalid(E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCXXReinterpretCastExpr(
    const CXXReinterpretCastExpr *E) {
  if (!this->discard(E->getSubExpr()))
    return false;
 
  return this->emitInvalidCast(CastKind::Reinterpret, E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCXXNoexceptExpr(const CXXNoexceptExpr *E) {
  assert(E->getType()->isBooleanType());
 
  if (DiscardResult)
    return true;
  return this->emitConstBool(E->getValue(), E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCXXConstructExpr(
    const CXXConstructExpr *E) {
  QualType T = E->getType();
  assert(!classify(T));
 
  if (T->isRecordType()) {
    const CXXConstructorDecl *Ctor = E->getConstructor();
 
    // Zero initialization.
    if (E->requiresZeroInitialization()) {
      const Record *R = getRecord(E->getType());
 
      if (!this->visitZeroRecordInitializer(R, E))
        return false;
 
      // If the constructor is trivial anyway, we're done.
      if (Ctor->isTrivial())
        return true;
    }
 
    const Function *Func = getFunction(Ctor);
 
    if (!Func)
      return false;
 
    assert(Func->hasThisPointer());
    assert(!Func->hasRVO());
 
    // If we're discarding a construct expression, we still need
    // to allocate a variable and call the constructor and destructor.
    if (DiscardResult) {
      assert(!Initializing);
      std::optional<unsigned> LocalIndex = allocateLocal(E);
 
      if (!LocalIndex)
        return false;
 
      if (!this->emitGetPtrLocal(*LocalIndex, E))
        return false;
    }
 
    //  The This pointer is already on the stack because this is an initializer,
    //  but we need to dup() so the call() below has its own copy.
    if (!this->emitDupPtr(E))
      return false;
 
    // Constructor arguments.
    for (const auto *Arg : E->arguments()) {
      if (!this->visit(Arg))
        return false;
    }
 
    if (Func->isVariadic()) {
      uint32_t VarArgSize = 0;
      unsigned NumParams = Func->getNumWrittenParams();
      for (unsigned I = NumParams, N = E->getNumArgs(); I != N; ++I) {
        VarArgSize +=
            align(primSize(classify(E->getArg(I)->getType()).value_or(PT_Ptr)));
      }
      if (!this->emitCallVar(Func, VarArgSize, E))
        return false;
    } else {
      if (!this->emitCall(Func, 0, E))
        return false;
    }
 
    // Immediately call the destructor if we have to.
    if (DiscardResult) {
      if (!this->emitRecordDestruction(getRecord(E->getType())))
        return false;
      if (!this->emitPopPtr(E))
        return false;
    }
    return true;
  }
 
  if (T->isArrayType()) {
    const ConstantArrayType *CAT =
        Ctx.getASTContext().getAsConstantArrayType(E->getType());
    if (!CAT)
      return false;
 
    size_t NumElems = CAT->getZExtSize();
    const Function *Func = getFunction(E->getConstructor());
    if (!Func || !Func->isConstexpr())
      return false;
 
    // FIXME(perf): We're calling the constructor once per array element here,
    //   in the old intepreter we had a special-case for trivial constructors.
    for (size_t I = 0; I != NumElems; ++I) {
      if (!this->emitConstUint64(I, E))
        return false;
      if (!this->emitArrayElemPtrUint64(E))
        return false;
 
      // Constructor arguments.
      for (const auto *Arg : E->arguments()) {
        if (!this->visit(Arg))
          return false;
      }
 
      if (!this->emitCall(Func, 0, E))
        return false;
    }
    return true;
  }
 
  return false;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitSourceLocExpr(const SourceLocExpr *E) {
  if (DiscardResult)
    return true;
 
  const APValue Val =
      E->EvaluateInContext(Ctx.getASTContext(), SourceLocDefaultExpr);
 
  // Things like __builtin_LINE().
  if (E->getType()->isIntegerType()) {
    assert(Val.isInt());
    const APSInt &I = Val.getInt();
    return this->emitConst(I, E);
  }
  // Otherwise, the APValue is an LValue, with only one element.
  // Theoretically, we don't need the APValue at all of course.
  assert(E->getType()->isPointerType());
  assert(Val.isLValue());
  const APValue::LValueBase &Base = Val.getLValueBase();
  if (const Expr *LValueExpr = Base.dyn_cast<const Expr *>())
    return this->visit(LValueExpr);
 
  // Otherwise, we have a decl (which is the case for
  // __builtin_source_location).
  assert(Base.is<const ValueDecl *>());
  assert(Val.getLValuePath().size() == 0);
  const auto *BaseDecl = Base.dyn_cast<const ValueDecl *>();
  assert(BaseDecl);
 
  auto *UGCD = cast<UnnamedGlobalConstantDecl>(BaseDecl);
 
  std::optional<unsigned> GlobalIndex = P.getOrCreateGlobal(UGCD);
  if (!GlobalIndex)
    return false;
 
  if (!this->emitGetPtrGlobal(*GlobalIndex, E))
    return false;
 
  const Record *R = getRecord(E->getType());
  const APValue &V = UGCD->getValue();
  for (unsigned I = 0, N = R->getNumFields(); I != N; ++I) {
    const Record::Field *F = R->getField(I);
    const APValue &FieldValue = V.getStructField(I);
 
    PrimType FieldT = classifyPrim(F->Decl->getType());
 
    if (!this->visitAPValue(FieldValue, FieldT, E))
      return false;
    if (!this->emitInitField(FieldT, F->Offset, E))
      return false;
  }
 
  // Leave the pointer to the global on the stack.
  return true;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitOffsetOfExpr(const OffsetOfExpr *E) {
  unsigned N = E->getNumComponents();
  if (N == 0)
    return false;
 
  for (unsigned I = 0; I != N; ++I) {
    const OffsetOfNode &Node = E->getComponent(I);
    if (Node.getKind() == OffsetOfNode::Array) {
      const Expr *ArrayIndexExpr = E->getIndexExpr(Node.getArrayExprIndex());
      PrimType IndexT = classifyPrim(ArrayIndexExpr->getType());
 
      if (DiscardResult) {
        if (!this->discard(ArrayIndexExpr))
          return false;
        continue;
      }
 
      if (!this->visit(ArrayIndexExpr))
        return false;
      // Cast to Sint64.
      if (IndexT != PT_Sint64) {
        if (!this->emitCast(IndexT, PT_Sint64, E))
          return false;
      }
    }
  }
 
  if (DiscardResult)
    return true;
 
  PrimType T = classifyPrim(E->getType());
  return this->emitOffsetOf(T, E, E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCXXScalarValueInitExpr(
    const CXXScalarValueInitExpr *E) {
  QualType Ty = E->getType();
 
  if (DiscardResult || Ty->isVoidType())
    return true;
 
  if (std::optional<PrimType> T = classify(Ty))
    return this->visitZeroInitializer(*T, Ty, E);
 
  if (const auto *CT = Ty->getAs<ComplexType>()) {
    if (!Initializing) {
      std::optional<unsigned> LocalIndex = allocateLocal(E);
      if (!LocalIndex)
        return false;
      if (!this->emitGetPtrLocal(*LocalIndex, E))
        return false;
    }
 
    // Initialize both fields to 0.
    QualType ElemQT = CT->getElementType();
    PrimType ElemT = classifyPrim(ElemQT);
 
    for (unsigned I = 0; I != 2; ++I) {
      if (!this->visitZeroInitializer(ElemT, ElemQT, E))
        return false;
      if (!this->emitInitElem(ElemT, I, E))
        return false;
    }
    return true;
  }
 
  if (const auto *VT = Ty->getAs<VectorType>()) {
    // FIXME: Code duplication with the _Complex case above.
    if (!Initializing) {
      std::optional<unsigned> LocalIndex = allocateLocal(E);
      if (!LocalIndex)
        return false;
      if (!this->emitGetPtrLocal(*LocalIndex, E))
        return false;
    }
 
    // Initialize all fields to 0.
    QualType ElemQT = VT->getElementType();
    PrimType ElemT = classifyPrim(ElemQT);
 
    for (unsigned I = 0, N = VT->getNumElements(); I != N; ++I) {
      if (!this->visitZeroInitializer(ElemT, ElemQT, E))
        return false;
      if (!this->emitInitElem(ElemT, I, E))
        return false;
    }
    return true;
  }
 
  return false;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitSizeOfPackExpr(const SizeOfPackExpr *E) {
  return this->emitConst(E->getPackLength(), E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitGenericSelectionExpr(
    const GenericSelectionExpr *E) {
  return this->delegate(E->getResultExpr());
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitChooseExpr(const ChooseExpr *E) {
  return this->delegate(E->getChosenSubExpr());
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitObjCBoolLiteralExpr(
    const ObjCBoolLiteralExpr *E) {
  if (DiscardResult)
    return true;
 
  return this->emitConst(E->getValue(), E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCXXInheritedCtorInitExpr(
    const CXXInheritedCtorInitExpr *E) {
  const CXXConstructorDecl *Ctor = E->getConstructor();
  assert(!Ctor->isTrivial() &&
         "Trivial CXXInheritedCtorInitExpr, implement. (possible?)");
  const Function *F = this->getFunction(Ctor);
  assert(F);
  assert(!F->hasRVO());
  assert(F->hasThisPointer());
 
  if (!this->emitDupPtr(SourceInfo{}))
    return false;
 
  // Forward all arguments of the current function (which should be a
  // constructor itself) to the inherited ctor.
  // This is necessary because the calling code has pushed the pointer
  // of the correct base for  us already, but the arguments need
  // to come after.
  unsigned Offset = align(primSize(PT_Ptr)); // instance pointer.
  for (const ParmVarDecl *PD : Ctor->parameters()) {
    PrimType PT = this->classify(PD->getType()).value_or(PT_Ptr);
 
    if (!this->emitGetParam(PT, Offset, E))
      return false;
    Offset += align(primSize(PT));
  }
 
  return this->emitCall(F, 0, E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitExpressionTraitExpr(
    const ExpressionTraitExpr *E) {
  assert(Ctx.getLangOpts().CPlusPlus);
  return this->emitConstBool(E->getValue(), E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCXXUuidofExpr(const CXXUuidofExpr *E) {
  if (DiscardResult)
    return true;
  assert(!Initializing);
 
  std::optional<unsigned> GlobalIndex = P.getOrCreateGlobal(E->getGuidDecl());
  if (!GlobalIndex)
    return false;
  if (!this->emitGetPtrGlobal(*GlobalIndex, E))
    return false;
 
  assert(this->getRecord(E->getType()));
 
  const APValue &V = E->getGuidDecl()->getAsAPValue();
  if (V.getKind() == APValue::None)
    return true;
 
  assert(V.isStruct());
  assert(V.getStructNumBases() == 0);
  if (!this->visitAPValueInitializer(V, E))
    return false;
 
  return this->emitFinishInit(E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitRequiresExpr(const RequiresExpr *E) {
  assert(classifyPrim(E->getType()) == PT_Bool);
  if (DiscardResult)
    return true;
  return this->emitConstBool(E->isSatisfied(), E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitConceptSpecializationExpr(
    const ConceptSpecializationExpr *E) {
  assert(classifyPrim(E->getType()) == PT_Bool);
  if (DiscardResult)
    return true;
  return this->emitConstBool(E->isSatisfied(), E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCXXRewrittenBinaryOperator(
    const CXXRewrittenBinaryOperator *E) {
  return this->delegate(E->getSemanticForm());
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitPseudoObjectExpr(
    const PseudoObjectExpr *E) {
 
  for (const Expr *SemE : E->semantics()) {
    if (auto *OVE = dyn_cast<OpaqueValueExpr>(SemE)) {
      if (SemE == E->getResultExpr())
        return false;
 
      if (OVE->isUnique())
        continue;
 
      if (!this->discard(OVE))
        return false;
    } else if (SemE == E->getResultExpr()) {
      if (!this->delegate(SemE))
        return false;
    } else {
      if (!this->discard(SemE))
        return false;
    }
  }
  return true;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitPackIndexingExpr(
    const PackIndexingExpr *E) {
  return this->delegate(E->getSelectedExpr());
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitRecoveryExpr(const RecoveryExpr *E) {
  return this->emitError(E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitAddrLabelExpr(const AddrLabelExpr *E) {
  assert(E->getType()->isVoidPointerType());
 
  unsigned Offset = allocateLocalPrimitive(
      E->getLabel(), PT_Ptr, /*IsConst=*/true, /*IsExtended=*/false);
 
  return this->emitGetLocal(PT_Ptr, Offset, E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitConvertVectorExpr(
    const ConvertVectorExpr *E) {
  assert(Initializing);
  const auto *VT = E->getType()->castAs<VectorType>();
  QualType ElemType = VT->getElementType();
  PrimType ElemT = classifyPrim(ElemType);
  const Expr *Src = E->getSrcExpr();
  PrimType SrcElemT =
      classifyPrim(Src->getType()->castAs<VectorType>()->getElementType());
 
  unsigned SrcOffset = this->allocateLocalPrimitive(Src, PT_Ptr, true, false);
  if (!this->visit(Src))
    return false;
  if (!this->emitSetLocal(PT_Ptr, SrcOffset, E))
    return false;
 
  for (unsigned I = 0; I != VT->getNumElements(); ++I) {
    if (!this->emitGetLocal(PT_Ptr, SrcOffset, E))
      return false;
    if (!this->emitArrayElemPop(SrcElemT, I, E))
      return false;
    if (SrcElemT != ElemT) {
      if (!this->emitPrimCast(SrcElemT, ElemT, ElemType, E))
        return false;
    }
    if (!this->emitInitElem(ElemT, I, E))
      return false;
  }
 
  return true;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitShuffleVectorExpr(
    const ShuffleVectorExpr *E) {
  assert(Initializing);
  assert(E->getNumSubExprs() > 2);
 
  const Expr *Vecs[] = {E->getExpr(0), E->getExpr(1)};
  assert(Vecs[0]->getType() == Vecs[1]->getType());
 
  const VectorType *VT = Vecs[0]->getType()->castAs<VectorType>();
  PrimType ElemT = classifyPrim(VT->getElementType());
  unsigned NumInputElems = VT->getNumElements();
  unsigned NumOutputElems = E->getNumSubExprs() - 2;
  assert(NumOutputElems > 0);
 
  // Save both input vectors to a local variable.
  unsigned VectorOffsets[2];
  for (unsigned I = 0; I != 2; ++I) {
    VectorOffsets[I] = this->allocateLocalPrimitive(
        Vecs[I], PT_Ptr, /*IsConst=*/true, /*IsExtended=*/false);
    if (!this->visit(Vecs[I]))
      return false;
    if (!this->emitSetLocal(PT_Ptr, VectorOffsets[I], E))
      return false;
  }
  for (unsigned I = 0; I != NumOutputElems; ++I) {
    APSInt ShuffleIndex = E->getShuffleMaskIdx(Ctx.getASTContext(), I);
    if (ShuffleIndex == -1)
      return this->emitInvalid(E); // FIXME: Better diagnostic.
 
    assert(ShuffleIndex < (NumInputElems * 2));
    if (!this->emitGetLocal(PT_Ptr,
                            VectorOffsets[ShuffleIndex >= NumInputElems], E))
      return false;
    unsigned InputVectorIndex = ShuffleIndex.getZExtValue() % NumInputElems;
    if (!this->emitArrayElemPop(ElemT, InputVectorIndex, E))
      return false;
 
    if (!this->emitInitElem(ElemT, I, E))
      return false;
  }
 
  return true;
}
 
template <class Emitter> bool ByteCodeExprGen<Emitter>::discard(const Expr *E) {
  OptionScope<Emitter> Scope(this, /*NewDiscardResult=*/true,
                             /*NewInitializing=*/false);
  return this->Visit(E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::delegate(const Expr *E) {
  // We're basically doing:
  // OptionScope<Emitter> Scope(this, DicardResult, Initializing);
  // but that's unnecessary of course.
  return this->Visit(E);
}
 
template <class Emitter> bool ByteCodeExprGen<Emitter>::visit(const Expr *E) {
  if (E->getType()->isVoidType())
    return this->discard(E);
 
  // Create local variable to hold the return value.
  if (!E->isGLValue() && !E->getType()->isAnyComplexType() &&
      !classify(E->getType())) {
    std::optional<unsigned> LocalIndex = allocateLocal(E);
    if (!LocalIndex)
      return false;
 
    if (!this->emitGetPtrLocal(*LocalIndex, E))
      return false;
    return this->visitInitializer(E);
  }
 
  //  Otherwise,we have a primitive return value, produce the value directly
  //  and push it on the stack.
  OptionScope<Emitter> Scope(this, /*NewDiscardResult=*/false,
                             /*NewInitializing=*/false);
  return this->Visit(E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::visitInitializer(const Expr *E) {
  assert(!classify(E->getType()));
 
  if (E->containsErrors())
    return this->emitError(E);
 
  OptionScope<Emitter> Scope(this, /*NewDiscardResult=*/false,
                             /*NewInitializing=*/true);
  return this->Visit(E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::visitBool(const Expr *E) {
  std::optional<PrimType> T = classify(E->getType());
  if (!T) {
    // Convert complex values to bool.
    if (E->getType()->isAnyComplexType()) {
      if (!this->visit(E))
        return false;
      return this->emitComplexBoolCast(E);
    }
    return false;
  }
 
  if (!this->visit(E))
    return false;
 
  if (T == PT_Bool)
    return true;
 
  // Convert pointers to bool.
  if (T == PT_Ptr || T == PT_FnPtr) {
    if (!this->emitNull(*T, nullptr, E))
      return false;
    return this->emitNE(*T, E);
  }
 
  // Or Floats.
  if (T == PT_Float)
    return this->emitCastFloatingIntegralBool(E);
 
  // Or anything else we can.
  return this->emitCast(*T, PT_Bool, E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::visitZeroInitializer(PrimType T, QualType QT,
                                                    const Expr *E) {
  switch (T) {
  case PT_Bool:
    return this->emitZeroBool(E);
  case PT_Sint8:
    return this->emitZeroSint8(E);
  case PT_Uint8:
    return this->emitZeroUint8(E);
  case PT_Sint16:
    return this->emitZeroSint16(E);
  case PT_Uint16:
    return this->emitZeroUint16(E);
  case PT_Sint32:
    return this->emitZeroSint32(E);
  case PT_Uint32:
    return this->emitZeroUint32(E);
  case PT_Sint64:
    return this->emitZeroSint64(E);
  case PT_Uint64:
    return this->emitZeroUint64(E);
  case PT_IntAP:
    return this->emitZeroIntAP(Ctx.getBitWidth(QT), E);
  case PT_IntAPS:
    return this->emitZeroIntAPS(Ctx.getBitWidth(QT), E);
  case PT_Ptr:
    return this->emitNullPtr(nullptr, E);
  case PT_FnPtr:
    return this->emitNullFnPtr(nullptr, E);
  case PT_Float: {
    return this->emitConstFloat(APFloat::getZero(Ctx.getFloatSemantics(QT)), E);
  }
  }
  llvm_unreachable("unknown primitive type");
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::visitZeroRecordInitializer(const Record *R,
                                                          const Expr *E) {
  assert(E);
  assert(R);
  // Fields
  for (const Record::Field &Field : R->fields()) {
    const Descriptor *D = Field.Desc;
    if (D->isPrimitive()) {
      QualType QT = D->getType();
      PrimType T = classifyPrim(D->getType());
      if (!this->visitZeroInitializer(T, QT, E))
        return false;
      if (!this->emitInitField(T, Field.Offset, E))
        return false;
      continue;
    }
 
    // TODO: Add GetPtrFieldPop and get rid of this dup.
    if (!this->emitDupPtr(E))
      return false;
    if (!this->emitGetPtrField(Field.Offset, E))
      return false;
 
    if (D->isPrimitiveArray()) {
      QualType ET = D->getElemQualType();
      PrimType T = classifyPrim(ET);
      for (uint32_t I = 0, N = D->getNumElems(); I != N; ++I) {
        if (!this->visitZeroInitializer(T, ET, E))
          return false;
        if (!this->emitInitElem(T, I, E))
          return false;
      }
    } else if (D->isCompositeArray()) {
      const Record *ElemRecord = D->ElemDesc->ElemRecord;
      assert(D->ElemDesc->ElemRecord);
      for (uint32_t I = 0, N = D->getNumElems(); I != N; ++I) {
        if (!this->emitConstUint32(I, E))
          return false;
        if (!this->emitArrayElemPtr(PT_Uint32, E))
          return false;
        if (!this->visitZeroRecordInitializer(ElemRecord, E))
          return false;
        if (!this->emitPopPtr(E))
          return false;
      }
    } else if (D->isRecord()) {
      if (!this->visitZeroRecordInitializer(D->ElemRecord, E))
        return false;
    } else {
      assert(false);
    }
 
    if (!this->emitPopPtr(E))
      return false;
  }
 
  for (const Record::Base &B : R->bases()) {
    if (!this->emitGetPtrBase(B.Offset, E))
      return false;
    if (!this->visitZeroRecordInitializer(B.R, E))
      return false;
    if (!this->emitFinishInitPop(E))
      return false;
  }
 
  // FIXME: Virtual bases.
 
  return true;
}
 
template <class Emitter>
template <typename T>
bool ByteCodeExprGen<Emitter>::emitConst(T Value, PrimType Ty, const Expr *E) {
  switch (Ty) {
  case PT_Sint8:
    return this->emitConstSint8(Value, E);
  case PT_Uint8:
    return this->emitConstUint8(Value, E);
  case PT_Sint16:
    return this->emitConstSint16(Value, E);
  case PT_Uint16:
    return this->emitConstUint16(Value, E);
  case PT_Sint32:
    return this->emitConstSint32(Value, E);
  case PT_Uint32:
    return this->emitConstUint32(Value, E);
  case PT_Sint64:
    return this->emitConstSint64(Value, E);
  case PT_Uint64:
    return this->emitConstUint64(Value, E);
  case PT_Bool:
    return this->emitConstBool(Value, E);
  case PT_Ptr:
  case PT_FnPtr:
  case PT_Float:
  case PT_IntAP:
  case PT_IntAPS:
    llvm_unreachable("Invalid integral type");
    break;
  }
  llvm_unreachable("unknown primitive type");
}
 
template <class Emitter>
template <typename T>
bool ByteCodeExprGen<Emitter>::emitConst(T Value, const Expr *E) {
  return this->emitConst(Value, classifyPrim(E->getType()), E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::emitConst(const APSInt &Value, PrimType Ty,
                                         const Expr *E) {
  if (Ty == PT_IntAPS)
    return this->emitConstIntAPS(Value, E);
  if (Ty == PT_IntAP)
    return this->emitConstIntAP(Value, E);
 
  if (Value.isSigned())
    return this->emitConst(Value.getSExtValue(), Ty, E);
  return this->emitConst(Value.getZExtValue(), Ty, E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::emitConst(const APSInt &Value, const Expr *E) {
  return this->emitConst(Value, classifyPrim(E->getType()), E);
}
 
template <class Emitter>
unsigned ByteCodeExprGen<Emitter>::allocateLocalPrimitive(DeclTy &&Src,
                                                          PrimType Ty,
                                                          bool IsConst,
                                                          bool IsExtended) {
  // Make sure we don't accidentally register the same decl twice.
  if (const auto *VD =
          dyn_cast_if_present<ValueDecl>(Src.dyn_cast<const Decl *>())) {
    assert(!P.getGlobal(VD));
    assert(!Locals.contains(VD));
    (void)VD;
  }
 
  // FIXME: There are cases where Src.is<Expr*>() is wrong, e.g.
  //   (int){12} in C. Consider using Expr::isTemporaryObject() instead
  //   or isa<MaterializeTemporaryExpr>().
  Descriptor *D = P.createDescriptor(Src, Ty, Descriptor::InlineDescMD, IsConst,
                                     Src.is<const Expr *>());
  Scope::Local Local = this->createLocal(D);
  if (auto *VD = dyn_cast_if_present<ValueDecl>(Src.dyn_cast<const Decl *>()))
    Locals.insert({VD, Local});
  VarScope->add(Local, IsExtended);
  return Local.Offset;
}
 
template <class Emitter>
std::optional<unsigned>
ByteCodeExprGen<Emitter>::allocateLocal(DeclTy &&Src,
                                        const ValueDecl *ExtendingDecl) {
  // Make sure we don't accidentally register the same decl twice.
  if ([[maybe_unused]]  const auto *VD =
          dyn_cast_if_present<ValueDecl>(Src.dyn_cast<const Decl *>())) {
    assert(!P.getGlobal(VD));
    assert(!Locals.contains(VD));
  }
 
  QualType Ty;
  const ValueDecl *Key = nullptr;
  const Expr *Init = nullptr;
  bool IsTemporary = false;
  if (auto *VD = dyn_cast_if_present<ValueDecl>(Src.dyn_cast<const Decl *>())) {
    Key = VD;
    Ty = VD->getType();
 
    if (const auto *VarD = dyn_cast<VarDecl>(VD))
      Init = VarD->getInit();
  }
  if (auto *E = Src.dyn_cast<const Expr *>()) {
    IsTemporary = true;
    Ty = E->getType();
  }
 
  Descriptor *D = P.createDescriptor(
      Src, Ty.getTypePtr(), Descriptor::InlineDescMD, Ty.isConstQualified(),
      IsTemporary, /*IsMutable=*/false, Init);
  if (!D)
    return std::nullopt;
 
  Scope::Local Local = this->createLocal(D);
  if (Key)
    Locals.insert({Key, Local});
  if (ExtendingDecl)
    VarScope->addExtended(Local, ExtendingDecl);
  else
    VarScope->add(Local, false);
  return Local.Offset;
}
 
template <class Emitter>
const RecordType *ByteCodeExprGen<Emitter>::getRecordTy(QualType Ty) {
  if (const PointerType *PT = dyn_cast<PointerType>(Ty))
    return PT->getPointeeType()->getAs<RecordType>();
  return Ty->getAs<RecordType>();
}
 
template <class Emitter>
Record *ByteCodeExprGen<Emitter>::getRecord(QualType Ty) {
  if (const auto *RecordTy = getRecordTy(Ty))
    return getRecord(RecordTy->getDecl());
  return nullptr;
}
 
template <class Emitter>
Record *ByteCodeExprGen<Emitter>::getRecord(const RecordDecl *RD) {
  return P.getOrCreateRecord(RD);
}
 
template <class Emitter>
const Function *ByteCodeExprGen<Emitter>::getFunction(const FunctionDecl *FD) {
  return Ctx.getOrCreateFunction(FD);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::visitExpr(const Expr *E) {
  ExprScope<Emitter> RootScope(this);
  // Void expressions.
  if (E->getType()->isVoidType()) {
    if (!visit(E))
      return false;
    return this->emitRetVoid(E) && RootScope.destroyLocals();
  }
 
  // Expressions with a primitive return type.
  if (std::optional<PrimType> T = classify(E)) {
    if (!visit(E))
      return false;
    return this->emitRet(*T, E) && RootScope.destroyLocals();
  }
 
  // Expressions with a composite return type.
  // For us, that means everything we don't
  // have a PrimType for.
  if (std::optional<unsigned> LocalOffset = this->allocateLocal(E)) {
    if (!this->emitGetPtrLocal(*LocalOffset, E))
      return false;
 
    if (!visitInitializer(E))
      return false;
 
    if (!this->emitFinishInit(E))
      return false;
    // We are destroying the locals AFTER the Ret op.
    // The Ret op needs to copy the (alive) values, but the
    // destructors may still turn the entire expression invalid.
    return this->emitRetValue(E) && RootScope.destroyLocals();
  }
 
  RootScope.destroyLocals();
  return false;
}
 
/// Toplevel visitDecl().
/// We get here from evaluateAsInitializer().
/// We need to evaluate the initializer and return its value.
template <class Emitter>
bool ByteCodeExprGen<Emitter>::visitDecl(const VarDecl *VD) {
  assert(!VD->isInvalidDecl() && "Trying to constant evaluate an invalid decl");
 
  // Global variable we've already seen but that's uninitialized means
  // evaluating the initializer failed. Just return failure.
  if (std::optional<unsigned> Index = P.getGlobal(VD);
      Index && !P.getPtrGlobal(*Index).isInitialized())
    return false;
 
  // Create and initialize the variable.
  if (!this->visitVarDecl(VD))
    return false;
 
  std::optional<PrimType> VarT = classify(VD->getType());
  // Get a pointer to the variable
  if (Context::shouldBeGloballyIndexed(VD)) {
    auto GlobalIndex = P.getGlobal(VD);
    assert(GlobalIndex); // visitVarDecl() didn't return false.
    if (VarT) {
      if (!this->emitGetGlobalUnchecked(*VarT, *GlobalIndex, VD))
        return false;
    } else {
      if (!this->emitGetPtrGlobal(*GlobalIndex, VD))
        return false;
    }
  } else {
    auto Local = Locals.find(VD);
    assert(Local != Locals.end()); // Same here.
    if (VarT) {
      if (!this->emitGetLocal(*VarT, Local->second.Offset, VD))
        return false;
    } else {
      if (!this->emitGetPtrLocal(Local->second.Offset, VD))
        return false;
    }
  }
 
  // Return the value
  if (VarT)
    return this->emitRet(*VarT, VD);
 
  // Return non-primitive values as pointers here.
  return this->emitRet(PT_Ptr, VD);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::visitVarDecl(const VarDecl *VD) {
  // We don't know what to do with these, so just return false.
  if (VD->getType().isNull())
    return false;
 
  const Expr *Init = VD->getInit();
  std::optional<PrimType> VarT = classify(VD->getType());
 
  if (Context::shouldBeGloballyIndexed(VD)) {
    auto initGlobal = [&](unsigned GlobalIndex) -> bool {
      assert(Init);
      DeclScope<Emitter> LocalScope(this, VD);
 
      if (VarT) {
        if (!this->visit(Init))
          return false;
        return this->emitInitGlobal(*VarT, GlobalIndex, VD);
      }
      return this->visitGlobalInitializer(Init, GlobalIndex);
    };
 
    // We've already seen and initialized this global.
    if (std::optional<unsigned> GlobalIndex = P.getGlobal(VD)) {
      if (P.getPtrGlobal(*GlobalIndex).isInitialized())
        return true;
 
      // The previous attempt at initialization might've been unsuccessful,
      // so let's try this one.
      return Init && initGlobal(*GlobalIndex);
    }
 
    std::optional<unsigned> GlobalIndex = P.createGlobal(VD, Init);
 
    if (!GlobalIndex)
      return false;
 
    return !Init || initGlobal(*GlobalIndex);
  } else {
    VariableScope<Emitter> LocalScope(this, VD);
    if (VarT) {
      unsigned Offset = this->allocateLocalPrimitive(
          VD, *VarT, VD->getType().isConstQualified());
      if (Init) {
        // Compile the initializer in its own scope.
        ExprScope<Emitter> Scope(this);
        if (!this->visit(Init))
          return false;
 
        return this->emitSetLocal(*VarT, Offset, VD);
      }
    } else {
      if (std::optional<unsigned> Offset = this->allocateLocal(VD))
        return !Init || this->visitLocalInitializer(Init, *Offset);
      return false;
    }
 
    return true;
  }
 
  return false;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::visitAPValue(const APValue &Val,
                                            PrimType ValType, const Expr *E) {
  assert(!DiscardResult);
  if (Val.isInt())
    return this->emitConst(Val.getInt(), ValType, E);
 
  if (Val.isLValue()) {
    APValue::LValueBase Base = Val.getLValueBase();
    if (const Expr *BaseExpr = Base.dyn_cast<const Expr *>())
      return this->visit(BaseExpr);
  }
 
  return false;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::visitAPValueInitializer(const APValue &Val,
                                                       const Expr *E) {
  if (Val.isStruct()) {
    const Record *R = this->getRecord(E->getType());
    assert(R);
 
    for (unsigned I = 0, N = Val.getStructNumFields(); I != N; ++I) {
      const APValue &F = Val.getStructField(I);
      const Record::Field *RF = R->getField(I);
 
      if (F.isInt()) {
        PrimType T = classifyPrim(RF->Decl->getType());
        if (!this->visitAPValue(F, T, E))
          return false;
        if (!this->emitInitField(T, RF->Offset, E))
          return false;
      } else if (F.isArray()) {
        assert(RF->Desc->isPrimitiveArray());
        const auto *ArrType = RF->Decl->getType()->getAsArrayTypeUnsafe();
        PrimType ElemT = classifyPrim(ArrType->getElementType());
        assert(ArrType);
 
        if (!this->emitDupPtr(E))
          return false;
        if (!this->emitGetPtrField(RF->Offset, E))
          return false;
 
        for (unsigned A = 0, AN = F.getArraySize(); A != AN; ++A) {
          if (!this->visitAPValue(F.getArrayInitializedElt(A), ElemT, E))
            return false;
          if (!this->emitInitElem(ElemT, A, E))
            return false;
        }
 
        if (!this->emitPopPtr(E))
          return false;
      } else {
        assert(false && "I don't think this should be possible");
      }
    }
    return true;
  }
  // TODO: Other types.
 
  return false;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitBuiltinCallExpr(const CallExpr *E) {
  const Function *Func = getFunction(E->getDirectCallee());
  if (!Func)
    return false;
 
  QualType ReturnType = E->getType();
  std::optional<PrimType> ReturnT = classify(E);
 
  // Non-primitive return type. Prepare storage.
  if (!Initializing && !ReturnT && !ReturnType->isVoidType()) {
    std::optional<unsigned> LocalIndex = allocateLocal(E);
    if (!LocalIndex)
      return false;
    if (!this->emitGetPtrLocal(*LocalIndex, E))
      return false;
  }
 
  if (!Func->isUnevaluatedBuiltin()) {
    // Put arguments on the stack.
    for (const auto *Arg : E->arguments()) {
      if (!this->visit(Arg))
        return false;
    }
  }
 
  if (!this->emitCallBI(Func, E, E))
    return false;
 
  if (DiscardResult && !ReturnType->isVoidType()) {
    assert(ReturnT);
    return this->emitPop(*ReturnT, E);
  }
 
  return true;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCallExpr(const CallExpr *E) {
  if (E->getBuiltinCallee())
    return VisitBuiltinCallExpr(E);
 
  QualType ReturnType = E->getCallReturnType(Ctx.getASTContext());
  std::optional<PrimType> T = classify(ReturnType);
  bool HasRVO = !ReturnType->isVoidType() && !T;
  const FunctionDecl *FuncDecl = E->getDirectCallee();
 
  if (HasRVO) {
    if (DiscardResult) {
      // If we need to discard the return value but the function returns its
      // value via an RVO pointer, we need to create one such pointer just
      // for this call.
      if (std::optional<unsigned> LocalIndex = allocateLocal(E)) {
        if (!this->emitGetPtrLocal(*LocalIndex, E))
          return false;
      }
    } else {
      // We need the result. Prepare a pointer to return or
      // dup the current one.
      if (!Initializing) {
        if (std::optional<unsigned> LocalIndex = allocateLocal(E)) {
          if (!this->emitGetPtrLocal(*LocalIndex, E))
            return false;
        }
      }
      if (!this->emitDupPtr(E))
        return false;
    }
  }
 
  auto Args = llvm::ArrayRef(E->getArgs(), E->getNumArgs());
  // Calling a static operator will still
  // pass the instance, but we don't need it.
  // Discard it here.
  if (isa<CXXOperatorCallExpr>(E)) {
    if (const auto *MD = dyn_cast_if_present<CXXMethodDecl>(FuncDecl);
        MD && MD->isStatic()) {
      if (!this->discard(E->getArg(0)))
        return false;
      Args = Args.drop_front();
    }
  }
 
  // Add the (optional, implicit) This pointer.
  if (const auto *MC = dyn_cast<CXXMemberCallExpr>(E)) {
    if (!this->visit(MC->getImplicitObjectArgument()))
      return false;
  }
 
  llvm::BitVector NonNullArgs = collectNonNullArgs(FuncDecl, Args);
  // Put arguments on the stack.
  unsigned ArgIndex = 0;
  for (const auto *Arg : Args) {
    if (!this->visit(Arg))
      return false;
 
    // If we know the callee already, check the known parametrs for nullability.
    if (FuncDecl && NonNullArgs[ArgIndex]) {
      PrimType ArgT = classify(Arg).value_or(PT_Ptr);
      if (ArgT == PT_Ptr || ArgT == PT_FnPtr) {
        if (!this->emitCheckNonNullArg(ArgT, Arg))
          return false;
      }
    }
    ++ArgIndex;
  }
 
  if (FuncDecl) {
    const Function *Func = getFunction(FuncDecl);
    if (!Func)
      return false;
    assert(HasRVO == Func->hasRVO());
 
    bool HasQualifier = false;
    if (const auto *ME = dyn_cast<MemberExpr>(E->getCallee()))
      HasQualifier = ME->hasQualifier();
 
    bool IsVirtual = false;
    if (const auto *MD = dyn_cast<CXXMethodDecl>(FuncDecl))
      IsVirtual = MD->isVirtual();
 
    // In any case call the function. The return value will end up on the stack
    // and if the function has RVO, we already have the pointer on the stack to
    // write the result into.
    if (IsVirtual && !HasQualifier) {
      uint32_t VarArgSize = 0;
      unsigned NumParams = Func->getNumWrittenParams();
      for (unsigned I = NumParams, N = E->getNumArgs(); I != N; ++I)
        VarArgSize += align(primSize(classify(E->getArg(I)).value_or(PT_Ptr)));
 
      if (!this->emitCallVirt(Func, VarArgSize, E))
        return false;
    } else if (Func->isVariadic()) {
      uint32_t VarArgSize = 0;
      unsigned NumParams =
          Func->getNumWrittenParams() + isa<CXXOperatorCallExpr>(E);
      for (unsigned I = NumParams, N = E->getNumArgs(); I != N; ++I)
        VarArgSize += align(primSize(classify(E->getArg(I)).value_or(PT_Ptr)));
      if (!this->emitCallVar(Func, VarArgSize, E))
        return false;
    } else {
      if (!this->emitCall(Func, 0, E))
        return false;
    }
  } else {
    // Indirect call. Visit the callee, which will leave a FunctionPointer on
    // the stack. Cleanup of the returned value if necessary will be done after
    // the function call completed.
 
    // Sum the size of all args from the call expr.
    uint32_t ArgSize = 0;
    for (unsigned I = 0, N = E->getNumArgs(); I != N; ++I)
      ArgSize += align(primSize(classify(E->getArg(I)).value_or(PT_Ptr)));
 
    if (!this->visit(E->getCallee()))
      return false;
 
    if (!this->emitCallPtr(ArgSize, E, E))
      return false;
  }
 
  // Cleanup for discarded return values.
  if (DiscardResult && !ReturnType->isVoidType() && T)
    return this->emitPop(*T, E);
 
  return true;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCXXDefaultInitExpr(
    const CXXDefaultInitExpr *E) {
  SourceLocScope<Emitter> SLS(this, E);
  return this->delegate(E->getExpr());
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCXXDefaultArgExpr(
    const CXXDefaultArgExpr *E) {
  SourceLocScope<Emitter> SLS(this, E);
 
  const Expr *SubExpr = E->getExpr();
  if (std::optional<PrimType> T = classify(E->getExpr()))
    return this->visit(SubExpr);
 
  assert(Initializing);
  return this->visitInitializer(SubExpr);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCXXBoolLiteralExpr(
    const CXXBoolLiteralExpr *E) {
  if (DiscardResult)
    return true;
 
  return this->emitConstBool(E->getValue(), E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCXXNullPtrLiteralExpr(
    const CXXNullPtrLiteralExpr *E) {
  if (DiscardResult)
    return true;
 
  return this->emitNullPtr(nullptr, E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitGNUNullExpr(const GNUNullExpr *E) {
  if (DiscardResult)
    return true;
 
  assert(E->getType()->isIntegerType());
 
  PrimType T = classifyPrim(E->getType());
  return this->emitZero(T, E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitCXXThisExpr(const CXXThisExpr *E) {
  if (DiscardResult)
    return true;
 
  if (this->LambdaThisCapture.Offset > 0) {
    if (this->LambdaThisCapture.IsPtr)
      return this->emitGetThisFieldPtr(this->LambdaThisCapture.Offset, E);
    return this->emitGetPtrThisField(this->LambdaThisCapture.Offset, E);
  }
 
  return this->emitThis(E);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitUnaryOperator(const UnaryOperator *E) {
  const Expr *SubExpr = E->getSubExpr();
  if (SubExpr->getType()->isAnyComplexType())
    return this->VisitComplexUnaryOperator(E);
  std::optional<PrimType> T = classify(SubExpr->getType());
 
  switch (E->getOpcode()) {
  case UO_PostInc: { // x++
    if (!this->visit(SubExpr))
      return false;
 
    if (T == PT_Ptr || T == PT_FnPtr) {
      if (!this->emitIncPtr(E))
        return false;
 
      return DiscardResult ? this->emitPopPtr(E) : true;
    }
 
    if (T == PT_Float) {
      return DiscardResult ? this->emitIncfPop(getRoundingMode(E), E)
                           : this->emitIncf(getRoundingMode(E), E);
    }
 
    return DiscardResult ? this->emitIncPop(*T, E) : this->emitInc(*T, E);
  }
  case UO_PostDec: { // x--
    if (!this->visit(SubExpr))
      return false;
 
    if (T == PT_Ptr || T == PT_FnPtr) {
      if (!this->emitDecPtr(E))
        return false;
 
      return DiscardResult ? this->emitPopPtr(E) : true;
    }
 
    if (T == PT_Float) {
      return DiscardResult ? this->emitDecfPop(getRoundingMode(E), E)
                           : this->emitDecf(getRoundingMode(E), E);
    }
 
    return DiscardResult ? this->emitDecPop(*T, E) : this->emitDec(*T, E);
  }
  case UO_PreInc: { // ++x
    if (!this->visit(SubExpr))
      return false;
 
    if (T == PT_Ptr || T == PT_FnPtr) {
      if (!this->emitLoadPtr(E))
        return false;
      if (!this->emitConstUint8(1, E))
        return false;
      if (!this->emitAddOffsetUint8(E))
        return false;
      return DiscardResult ? this->emitStorePopPtr(E) : this->emitStorePtr(E);
    }
 
    // Post-inc and pre-inc are the same if the value is to be discarded.
    if (DiscardResult) {
      if (T == PT_Float)
        return this->emitIncfPop(getRoundingMode(E), E);
      return this->emitIncPop(*T, E);
    }
 
    if (T == PT_Float) {
      const auto &TargetSemantics = Ctx.getFloatSemantics(E->getType());
      if (!this->emitLoadFloat(E))
        return false;
      if (!this->emitConstFloat(llvm::APFloat(TargetSemantics, 1), E))
        return false;
      if (!this->emitAddf(getRoundingMode(E), E))
        return false;
      if (!this->emitStoreFloat(E))
        return false;
    } else {
      assert(isIntegralType(*T));
      if (!this->emitLoad(*T, E))
        return false;
      if (!this->emitConst(1, E))
        return false;
      if (!this->emitAdd(*T, E))
        return false;
      if (!this->emitStore(*T, E))
        return false;
    }
    return E->isGLValue() || this->emitLoadPop(*T, E);
  }
  case UO_PreDec: { // --x
    if (!this->visit(SubExpr))
      return false;
 
    if (T == PT_Ptr || T == PT_FnPtr) {
      if (!this->emitLoadPtr(E))
        return false;
      if (!this->emitConstUint8(1, E))
        return false;
      if (!this->emitSubOffsetUint8(E))
        return false;
      return DiscardResult ? this->emitStorePopPtr(E) : this->emitStorePtr(E);
    }
 
    // Post-dec and pre-dec are the same if the value is to be discarded.
    if (DiscardResult) {
      if (T == PT_Float)
        return this->emitDecfPop(getRoundingMode(E), E);
      return this->emitDecPop(*T, E);
    }
 
    if (T == PT_Float) {
      const auto &TargetSemantics = Ctx.getFloatSemantics(E->getType());
      if (!this->emitLoadFloat(E))
        return false;
      if (!this->emitConstFloat(llvm::APFloat(TargetSemantics, 1), E))
        return false;
      if (!this->emitSubf(getRoundingMode(E), E))
        return false;
      if (!this->emitStoreFloat(E))
        return false;
    } else {
      assert(isIntegralType(*T));
      if (!this->emitLoad(*T, E))
        return false;
      if (!this->emitConst(1, E))
        return false;
      if (!this->emitSub(*T, E))
        return false;
      if (!this->emitStore(*T, E))
        return false;
    }
    return E->isGLValue() || this->emitLoadPop(*T, E);
  }
  case UO_LNot: // !x
    if (DiscardResult)
      return this->discard(SubExpr);
 
    if (!this->visitBool(SubExpr))
      return false;
 
    if (!this->emitInvBool(E))
      return false;
 
    if (PrimType ET = classifyPrim(E->getType()); ET != PT_Bool)
      return this->emitCast(PT_Bool, ET, E);
    return true;
  case UO_Minus: // -x
    if (!this->visit(SubExpr))
      return false;
    return DiscardResult ? this->emitPop(*T, E) : this->emitNeg(*T, E);
  case UO_Plus:  // +x
    if (!this->visit(SubExpr)) // noop
      return false;
    return DiscardResult ? this->emitPop(*T, E) : true;
  case UO_AddrOf: // &x
    // We should already have a pointer when we get here.
    return this->delegate(SubExpr);
  case UO_Deref:  // *x
    if (DiscardResult)
      return this->discard(SubExpr);
    return this->visit(SubExpr);
  case UO_Not:    // ~x
    if (!this->visit(SubExpr))
      return false;
    return DiscardResult ? this->emitPop(*T, E) : this->emitComp(*T, E);
  case UO_Real: // __real x
    assert(T);
    return this->delegate(SubExpr);
  case UO_Imag: { // __imag x
    assert(T);
    if (!this->discard(SubExpr))
      return false;
    return this->visitZeroInitializer(*T, SubExpr->getType(), SubExpr);
  }
  case UO_Extension:
    return this->delegate(SubExpr);
  case UO_Coawait:
    assert(false && "Unhandled opcode");
  }
 
  return false;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitComplexUnaryOperator(
    const UnaryOperator *E) {
  const Expr *SubExpr = E->getSubExpr();
  assert(SubExpr->getType()->isAnyComplexType());
 
  if (DiscardResult)
    return this->discard(SubExpr);
 
  std::optional<PrimType> ResT = classify(E);
  auto prepareResult = [=]() -> bool {
    if (!ResT && !Initializing) {
      std::optional<unsigned> LocalIndex = allocateLocal(SubExpr);
      if (!LocalIndex)
        return false;
      return this->emitGetPtrLocal(*LocalIndex, E);
    }
 
    return true;
  };
 
  // The offset of the temporary, if we created one.
  unsigned SubExprOffset = ~0u;
  auto createTemp = [=, &SubExprOffset]() -> bool {
    SubExprOffset = this->allocateLocalPrimitive(SubExpr, PT_Ptr, true, false);
    if (!this->visit(SubExpr))
      return false;
    return this->emitSetLocal(PT_Ptr, SubExprOffset, E);
  };
 
  PrimType ElemT = classifyComplexElementType(SubExpr->getType());
  auto getElem = [=](unsigned Offset, unsigned Index) -> bool {
    if (!this->emitGetLocal(PT_Ptr, Offset, E))
      return false;
    return this->emitArrayElemPop(ElemT, Index, E);
  };
 
  switch (E->getOpcode()) {
  case UO_Minus:
    if (!prepareResult())
      return false;
    if (!createTemp())
      return false;
    for (unsigned I = 0; I != 2; ++I) {
      if (!getElem(SubExprOffset, I))
        return false;
      if (!this->emitNeg(ElemT, E))
        return false;
      if (!this->emitInitElem(ElemT, I, E))
        return false;
    }
    break;
 
  case UO_Plus:   // +x
  case UO_AddrOf: // &x
  case UO_Deref:  // *x
    return this->delegate(SubExpr);
 
  case UO_LNot:
    if (!this->visit(SubExpr))
      return false;
    if (!this->emitComplexBoolCast(SubExpr))
      return false;
    if (!this->emitInvBool(E))
      return false;
    if (PrimType ET = classifyPrim(E->getType()); ET != PT_Bool)
      return this->emitCast(PT_Bool, ET, E);
    return true;
 
  case UO_Real:
    return this->emitComplexReal(SubExpr);
 
  case UO_Imag:
    if (!this->visit(SubExpr))
      return false;
 
    if (SubExpr->isLValue()) {
      if (!this->emitConstUint8(1, E))
        return false;
      return this->emitArrayElemPtrPopUint8(E);
    }
 
    // Since our _Complex implementation does not map to a primitive type,
    // we sometimes have to do the lvalue-to-rvalue conversion here manually.
    return this->emitArrayElemPop(classifyPrim(E->getType()), 1, E);
 
  default:
    return this->emitInvalid(E);
  }
 
  return true;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::VisitDeclRefExpr(const DeclRefExpr *E) {
  if (DiscardResult)
    return true;
 
  const auto *D = E->getDecl();
 
  if (const auto *ECD = dyn_cast<EnumConstantDecl>(D)) {
    return this->emitConst(ECD->getInitVal(), E);
  } else if (const auto *BD = dyn_cast<BindingDecl>(D)) {
    return this->visit(BD->getBinding());
  } else if (const auto *FuncDecl = dyn_cast<FunctionDecl>(D)) {
    const Function *F = getFunction(FuncDecl);
    return F && this->emitGetFnPtr(F, E);
  } else if (const auto *TPOD = dyn_cast<TemplateParamObjectDecl>(D)) {
    if (std::optional<unsigned> Index = P.getOrCreateGlobal(D)) {
      if (!this->emitGetPtrGlobal(*Index, E))
        return false;
      if (std::optional<PrimType> T = classify(E->getType())) {
        if (!this->visitAPValue(TPOD->getValue(), *T, E))
          return false;
        return this->emitInitGlobal(*T, *Index, E);
      }
      return this->visitAPValueInitializer(TPOD->getValue(), E);
    }
    return false;
  }
 
  // References are implemented via pointers, so when we see a DeclRefExpr
  // pointing to a reference, we need to get its value directly (i.e. the
  // pointer to the actual value) instead of a pointer to the pointer to the
  // value.
  bool IsReference = D->getType()->isReferenceType();
 
  // Check for local/global variables and parameters.
  if (auto It = Locals.find(D); It != Locals.end()) {
    const unsigned Offset = It->second.Offset;
    if (IsReference)
      return this->emitGetLocal(PT_Ptr, Offset, E);
    return this->emitGetPtrLocal(Offset, E);
  } else if (auto GlobalIndex = P.getGlobal(D)) {
    if (IsReference)
      return this->emitGetGlobalPtr(*GlobalIndex, E);
 
    return this->emitGetPtrGlobal(*GlobalIndex, E);
  } else if (const auto *PVD = dyn_cast<ParmVarDecl>(D)) {
    if (auto It = this->Params.find(PVD); It != this->Params.end()) {
      if (IsReference || !It->second.IsPtr)
        return this->emitGetParamPtr(It->second.Offset, E);
 
      return this->emitGetPtrParam(It->second.Offset, E);
    }
  }
 
  // Handle lambda captures.
  if (auto It = this->LambdaCaptures.find(D);
      It != this->LambdaCaptures.end()) {
    auto [Offset, IsPtr] = It->second;
 
    if (IsPtr)
      return this->emitGetThisFieldPtr(Offset, E);
    return this->emitGetPtrThisField(Offset, E);
  }
 
  // Try to lazily visit (or emit dummy pointers for) declarations
  // we haven't seen yet.
  if (Ctx.getLangOpts().CPlusPlus) {
    if (const auto *VD = dyn_cast<VarDecl>(D)) {
      // Visit local const variables like normal.
      if ((VD->isLocalVarDecl() || VD->isStaticDataMember()) &&
          VD->getType().isConstQualified()) {
        if (!this->visitVarDecl(VD))
          return false;
        // Retry.
        return this->VisitDeclRefExpr(E);
      }
    }
  } else {
    if (const auto *VD = dyn_cast<VarDecl>(D);
        VD && VD->getAnyInitializer() && VD->getType().isConstQualified()) {
      if (!this->visitVarDecl(VD))
        return false;
      // Retry.
      return this->VisitDeclRefExpr(E);
    }
  }
 
  if (std::optional<unsigned> I = P.getOrCreateDummy(D))
    return this->emitGetPtrGlobal(*I, E);
 
  return this->emitInvalidDeclRef(E, E);
}
 
template <class Emitter>
void ByteCodeExprGen<Emitter>::emitCleanup() {
  for (VariableScope<Emitter> *C = VarScope; C; C = C->getParent())
    C->emitDestruction();
}
 
template <class Emitter>
unsigned
ByteCodeExprGen<Emitter>::collectBaseOffset(const QualType BaseType,
                                            const QualType DerivedType) {
  const auto extractRecordDecl = [](QualType Ty) -> const CXXRecordDecl * {
    if (const auto *PT = dyn_cast<PointerType>(Ty))
      return PT->getPointeeType()->getAsCXXRecordDecl();
    return Ty->getAsCXXRecordDecl();
  };
  const CXXRecordDecl *BaseDecl = extractRecordDecl(BaseType);
  const CXXRecordDecl *DerivedDecl = extractRecordDecl(DerivedType);
 
  return Ctx.collectBaseOffset(BaseDecl, DerivedDecl);
}
 
/// Emit casts from a PrimType to another PrimType.
template <class Emitter>
bool ByteCodeExprGen<Emitter>::emitPrimCast(PrimType FromT, PrimType ToT,
                                            QualType ToQT, const Expr *E) {
 
  if (FromT == PT_Float) {
    // Floating to floating.
    if (ToT == PT_Float) {
      const llvm::fltSemantics *ToSem = &Ctx.getFloatSemantics(ToQT);
      return this->emitCastFP(ToSem, getRoundingMode(E), E);
    }
 
    if (ToT == PT_IntAP)
      return this->emitCastFloatingIntegralAP(Ctx.getBitWidth(ToQT), E);
    if (ToT == PT_IntAPS)
      return this->emitCastFloatingIntegralAPS(Ctx.getBitWidth(ToQT), E);
 
    // Float to integral.
    if (isIntegralType(ToT) || ToT == PT_Bool)
      return this->emitCastFloatingIntegral(ToT, E);
  }
 
  if (isIntegralType(FromT) || FromT == PT_Bool) {
    if (ToT == PT_IntAP)
      return this->emitCastAP(FromT, Ctx.getBitWidth(ToQT), E);
    if (ToT == PT_IntAPS)
      return this->emitCastAPS(FromT, Ctx.getBitWidth(ToQT), E);
 
    // Integral to integral.
    if (isIntegralType(ToT) || ToT == PT_Bool)
      return FromT != ToT ? this->emitCast(FromT, ToT, E) : true;
 
    if (ToT == PT_Float) {
      // Integral to floating.
      const llvm::fltSemantics *ToSem = &Ctx.getFloatSemantics(ToQT);
      return this->emitCastIntegralFloating(FromT, ToSem, getRoundingMode(E),
                                            E);
    }
  }
 
  return false;
}
 
/// Emits __real(SubExpr)
template <class Emitter>
bool ByteCodeExprGen<Emitter>::emitComplexReal(const Expr *SubExpr) {
  assert(SubExpr->getType()->isAnyComplexType());
 
  if (DiscardResult)
    return this->discard(SubExpr);
 
  if (!this->visit(SubExpr))
    return false;
  if (SubExpr->isLValue()) {
    if (!this->emitConstUint8(0, SubExpr))
      return false;
    return this->emitArrayElemPtrPopUint8(SubExpr);
  }
 
  // Rvalue, load the actual element.
  return this->emitArrayElemPop(classifyComplexElementType(SubExpr->getType()),
                                0, SubExpr);
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::emitComplexBoolCast(const Expr *E) {
  assert(!DiscardResult);
  PrimType ElemT = classifyComplexElementType(E->getType());
  // We emit the expression (__real(E) != 0 || __imag(E) != 0)
  // for us, that means (bool)E[0] || (bool)E[1]
  if (!this->emitArrayElem(ElemT, 0, E))
    return false;
  if (ElemT == PT_Float) {
    if (!this->emitCastFloatingIntegral(PT_Bool, E))
      return false;
  } else {
    if (!this->emitCast(ElemT, PT_Bool, E))
      return false;
  }
 
  // We now have the bool value of E[0] on the stack.
  LabelTy LabelTrue = this->getLabel();
  if (!this->jumpTrue(LabelTrue))
    return false;
 
  if (!this->emitArrayElemPop(ElemT, 1, E))
    return false;
  if (ElemT == PT_Float) {
    if (!this->emitCastFloatingIntegral(PT_Bool, E))
      return false;
  } else {
    if (!this->emitCast(ElemT, PT_Bool, E))
      return false;
  }
  // Leave the boolean value of E[1] on the stack.
  LabelTy EndLabel = this->getLabel();
  this->jump(EndLabel);
 
  this->emitLabel(LabelTrue);
  if (!this->emitPopPtr(E))
    return false;
  if (!this->emitConstBool(true, E))
    return false;
 
  this->fallthrough(EndLabel);
  this->emitLabel(EndLabel);
 
  return true;
}
 
template <class Emitter>
bool ByteCodeExprGen<Emitter>::emitComplexComparison(const Expr *LHS,
                                                     const Expr *RHS,
                                                     const BinaryOperator *E) {
  assert(E->isComparisonOp());
  assert(!Initializing);
  assert(!DiscardResult);
 
  PrimType ElemT;
  bool LHSIsComplex;
  unsigned LHSOffset;
  if (LHS->getType()->isAnyComplexType()) {
    LHSIsComplex = true;
    ElemT = classifyComplexElementType(LHS->getType());
    LHSOffset = allocateLocalPrimitive(LHS, PT_Ptr, /*IsConst=*/true,
                                       /*IsExtended=*/false);
    if (!this->visit(LHS))
      return false;
    if (!this->emitSetLocal(PT_Ptr, LHSOffset, E))
      return false;
  } else {
    LHSIsComplex = false;
    PrimType LHST = classifyPrim(LHS->getType());
    LHSOffset = this->allocateLocalPrimitive(LHS, LHST, true, false);
    if (!this->visit(LHS))
      return false;
    if (!this->emitSetLocal(LHST, LHSOffset, E))
      return false;
  }
 
  bool RHSIsComplex;
  unsigned RHSOffset;
  if (RHS->getType()->isAnyComplexType()) {
    RHSIsComplex = true;
    ElemT = classifyComplexElementType(RHS->getType());
    RHSOffset = allocateLocalPrimitive(RHS, PT_Ptr, /*IsConst=*/true,
                                       /*IsExtended=*/false);
    if (!this->visit(RHS))
      return false;
    if (!this->emitSetLocal(PT_Ptr, RHSOffset, E))
      return false;
  } else {
    RHSIsComplex = false;
    PrimType RHST = classifyPrim(RHS->getType());
    RHSOffset = this->allocateLocalPrimitive(RHS, RHST, true, false);
    if (!this->visit(RHS))
      return false;
    if (!this->emitSetLocal(RHST, RHSOffset, E))
      return false;
  }
 
  auto getElem = [&](unsigned LocalOffset, unsigned Index,
                     bool IsComplex) -> bool {
    if (IsComplex) {
      if (!this->emitGetLocal(PT_Ptr, LocalOffset, E))
        return false;
      return this->emitArrayElemPop(ElemT, Index, E);
    }
    return this->emitGetLocal(ElemT, LocalOffset, E);
  };
 
  for (unsigned I = 0; I != 2; ++I) {
    // Get both values.
    if (!getElem(LHSOffset, I, LHSIsComplex))
      return false;
    if (!getElem(RHSOffset, I, RHSIsComplex))
      return false;
    // And compare them.
    if (!this->emitEQ(ElemT, E))
      return false;
 
    if (!this->emitCastBoolUint8(E))
      return false;
  }
 
  // We now have two bool values on the stack. Compare those.
  if (!this->emitAddUint8(E))
    return false;
  if (!this->emitConstUint8(2, E))
    return false;
 
  if (E->getOpcode() == BO_EQ) {
    if (!this->emitEQUint8(E))
      return false;
  } else if (E->getOpcode() == BO_NE) {
    if (!this->emitNEUint8(E))
      return false;
  } else
    return false;
 
  // In C, this returns an int.
  if (PrimType ResT = classifyPrim(E->getType()); ResT != PT_Bool)
    return this->emitCast(PT_Bool, ResT, E);
  return true;
}
 
/// When calling this, we have a pointer of the local-to-destroy
/// on the stack.
/// Emit destruction of record types (or arrays of record types).
template <class Emitter>
bool ByteCodeExprGen<Emitter>::emitRecordDestruction(const Record *R) {
  assert(R);
  // First, destroy all fields.
  for (const Record::Field &Field : llvm::reverse(R->fields())) {
    const Descriptor *D = Field.Desc;
    if (!D->isPrimitive() && !D->isPrimitiveArray()) {
      if (!this->emitDupPtr(SourceInfo{}))
        return false;
      if (!this->emitGetPtrField(Field.Offset, SourceInfo{}))
        return false;
      if (!this->emitDestruction(D))
        return false;
      if (!this->emitPopPtr(SourceInfo{}))
        return false;
    }
  }
 
  // FIXME: Unions need to be handled differently here. We don't want to
  //   call the destructor of its members.
 
  // Now emit the destructor and recurse into base classes.
  if (const CXXDestructorDecl *Dtor = R->getDestructor();
      Dtor && !Dtor->isTrivial()) {
    const Function *DtorFunc = getFunction(Dtor);
    if (!DtorFunc)
      return false;
    assert(DtorFunc->hasThisPointer());
    assert(DtorFunc->getNumParams() == 1);
    if (!this->emitDupPtr(SourceInfo{}))
      return false;
    if (!this->emitCall(DtorFunc, 0, SourceInfo{}))
      return false;
  }
 
  for (const Record::Base &Base : llvm::reverse(R->bases())) {
    if (!this->emitGetPtrBase(Base.Offset, SourceInfo{}))
      return false;
    if (!this->emitRecordDestruction(Base.R))
      return false;
    if (!this->emitPopPtr(SourceInfo{}))
      return false;
  }
 
  // FIXME: Virtual bases.
  return true;
}
/// When calling this, we have a pointer of the local-to-destroy
/// on the stack.
/// Emit destruction of record types (or arrays of record types).
template <class Emitter>
bool ByteCodeExprGen<Emitter>::emitDestruction(const Descriptor *Desc) {
  assert(Desc);
  assert(!Desc->isPrimitive());
  assert(!Desc->isPrimitiveArray());
 
  // Arrays.
  if (Desc->isArray()) {
    const Descriptor *ElemDesc = Desc->ElemDesc;
    assert(ElemDesc);
 
    // Don't need to do anything for these.
    if (ElemDesc->isPrimitiveArray())
      return true;
 
    // If this is an array of record types, check if we need
    // to call the element destructors at all. If not, try
    // to save the work.
    if (const Record *ElemRecord = ElemDesc->ElemRecord) {
      if (const CXXDestructorDecl *Dtor = ElemRecord->getDestructor();
          !Dtor || Dtor->isTrivial())
        return true;
    }
 
    for (ssize_t I = Desc->getNumElems() - 1; I >= 0; --I) {
      if (!this->emitConstUint64(I, SourceInfo{}))
        return false;
      if (!this->emitArrayElemPtrUint64(SourceInfo{}))
        return false;
      if (!this->emitDestruction(ElemDesc))
        return false;
      if (!this->emitPopPtr(SourceInfo{}))
        return false;
    }
    return true;
  }
 
  assert(Desc->ElemRecord);
  return this->emitRecordDestruction(Desc->ElemRecord);
}
 
namespace clang {
namespace interp {
 
template class ByteCodeExprGen<ByteCodeEmitter>;
template class ByteCodeExprGen<EvalEmitter>;
 
} // namespace interp
} // namespace clang